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  • 301.
    Lundell, Marie
    et al.
    Karolinska University Hospital, Sweden; Karolinska Institute, Sweden.
    Karlsson, Mattias
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Karolinska University Hospital, Sweden.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Karolinska University Hospital, Sweden.
    New dosimetry for childhood skin hemangioma treatments with Ra-226 needles or tubes2015In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 116, no 1, p. 139-142Article in journal (Refereed)
    Abstract [en]

    Background: The Stockholm Hemangioma Cohort is important for evaluation of late effects after exposure to ionizing radiation during childhood. Dose estimates in this cohort were based on both measurements and calculations using an old treatment planning system. Methods: We compare previously published and calculated dose estimates with new ones, obtained by Monte Carlo simulations, which mimic the hemangioma treatments with Ra-226 needles and tubes. The distances between the Ra-226 sources and the thyroid and breasts, respectively, were reassessed. Result:. The Monte Carlo calculations showed significantly lower dose values than those obtained earlier. The differences depended both on the modeling of the sources and on further individualized distances from the sources. The mean value of the new calculated doses was 25% of the old breast doses and 46% of the old thyroid doses. Conclusion: New dosimetry for hemangioma treatments gives significantly lower organ doses for the few cases receiving the highest absorbed dose values. This implies that radiation risk estimates will increase and have to be recalculated. For retrospective studies it is now possible to calculate organ doses from radium treatments using modern treatment planning systems by modeling the source geometry carefully and apply the TG-43 formalism. It is important to be aware of the large uncertainties in calculated absorbed dose values.

  • 302. Order onlineBuy this publication >>
    Lundengård, Karin
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Mechanistic modelling - a BOLD response to the fMRI information loss problem2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Functional Magnetic Resonance Imaging (fMRI) is a common technique for imaging brain activity in humans. However, the fMRI signal stems from local changes in oxygen level rather than from neuronal excitation. The change in oxygen level is referred to as the Blood Oxygen Level Dependent (BOLD) response, and is connected to neuronal excitation and the BOLD response are connected by the neurovascular coupling. The neurons affect the oxygen metabolism, blood volume and blood flow, and this in turn controls the shape of the BOLD response. This interplay is complex, and therefore fMRI analysis often relies on models. However, none of the previously existing models are based on the intracellular mechanisms of the neurovascular coupling. Systems biology is a relatively new field where mechanistic models are used to integrate data from many different parts of a system in order to holistically analyze and predict system properties. This thesis presents a new framework for analysis of fMRI data, based on mechanistic modelling of the neurovascular coupling, using systems biology methods.

     Paper I presents the development of the first intracellular signaling model of the neurovascular coupling. Using models, a feed-forward and a feedback hypothesis are tested against each other. The resulting model can mechanistically explain both the initial dip, the main response and the post-peak undershoot of the BOLD response. It is also fitted to estimation data from the visual cortex and validated against variations in frequency and intensity of the stimulus. In Paper II, I present a framework for separating activity from noise by investigating the influence of the astrocytes on the blood vessels via release of vasoactive sub- stances, using observability analysis. This new method can recognize activity in both measured and simulated data, and separate differences in stimulus strength in simulated data. Paper III investigates the effects of the positive allosteric GABA modulator diazepam on working memory in healthy adults. Both positive and negative BOLD was measured during a working memory task, and activation in the cingulate cortex was negatively correlated to the plasma concentration of diazepam. In this area, the BOLD response had decreased below baseline in test subjects with >0.01 mg/L diazepam in the blood. Paper IV expands the model presented in Paper I with a GABA mechanism so that it can describe neuronal inhibition and the negative BOLD response. Sensitization of the GABA receptors by diazepam was added, which enabled the model to explain how changes to the BOLD response described in Paper III could occur without a change in the balance between the GABA and glutamate concentrations.

    The framework presented herein may serve as the basis for a new method for identification of both brain activity and useful potential biomarkers for brain diseases and disorders, which will bring us a deeper understanding of the functioning of the human brain.

    List of papers
    1. Mechanistic Mathematical Modeling Tests Hypotheses of the Neurovascular Coupling in fMRI
    Open this publication in new window or tab >>Mechanistic Mathematical Modeling Tests Hypotheses of the Neurovascular Coupling in fMRI
    Show others...
    2016 (English)In: PloS Computational Biology, ISSN 1553-734X, E-ISSN 1553-7358, Vol. 12, no 6, article id e1004971Article in journal (Refereed) Published
    Abstract [en]

    Functional magnetic resonance imaging (fMRI) measures brain activity by detecting the blood-oxygen-level dependent (BOLD) response to neural activity. The BOLD response depends on the neurovascular coupling, which connects cerebral blood flow, cerebral blood volume, and deoxyhemoglobin level to neuronal activity. The exact mechanisms behind this neurovascular coupling are not yet fully investigated. There are at least three different ways in which these mechanisms are being discussed. Firstly, mathematical models involving the so-called Balloon model describes the relation between oxygen metabolism, cerebral blood volume, and cerebral blood flow. However, the Balloon model does not describe cellular and biochemical mechanisms. Secondly, the metabolic feedback hypothesis, which is based on experimental findings on metabolism associated with brain activation, and thirdly, the neurotransmitter feed-forward hypothesis which describes intracellular pathways leading to vasoactive substance release. Both the metabolic feedback and the neurotransmitter feed-forward hypotheses have been extensively studied, but only experimentally. These two hypotheses have never been implemented as mathematical models. Here we investigate these two hypotheses by mechanistic mathematical modeling using a systems biology approach; these methods have been used in biological research for many years but never been applied to the BOLD response in fMRI. In the current work, model structures describing the metabolic feedback and the neurotransmitter feed-forward hypotheses were applied to measured BOLD responses in the visual cortex of 12 healthy volunteers. Evaluating each hypothesis separately shows that neither hypothesis alone can describe the data in a biologically plausible way. However, by adding metabolism to the neurotransmitter feed-forward model structure, we obtained a new model structure which is able to fit the estimation data and successfully predict new, independent validation data. These results open the door to a new type of fMRI analysis that more accurately reflects the true neuronal activity.

    Place, publisher, year, edition, pages
    PUBLIC LIBRARY SCIENCE, 2016
    National Category
    Bioinformatics (Computational Biology)
    Identifiers
    urn:nbn:se:liu:diva-130437 (URN)10.1371/journal.pcbi.1004971 (DOI)000379349700045 ()27310017 (PubMedID)
    Note

    Funding Agencies|Swedish Research council [2014-6249]; Knut and Alice Wallenbergs foundation, KAW [2013.0076]; Research council of Southeast Sweden [FORSS-481691]; Linkoping University

    Available from: 2016-08-06 Created: 2016-08-05 Last updated: 2018-03-19
    2. Positive Allosteric Modulator of GABA Lowers BOLD Responses in the Cingulate Cortex
    Open this publication in new window or tab >>Positive Allosteric Modulator of GABA Lowers BOLD Responses in the Cingulate Cortex
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    2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 3Article in journal (Refereed) Published
    Abstract [en]

    Knowledge about the neural underpinnings of the negative blood oxygen level dependent (BOLD) responses in functional magnetic resonance imaging (fMRI) is still limited. We hypothesized that pharmacological GABAergic modulation attenuates BOLD responses, and that blood concentrations of a positive allosteric modulator of GABA correlate inversely with BOLD responses in the cingulate cortex. We investigated whether or not pure task-related negative BOLD responses were co-localized with pharmacologically modulated BOLD responses. Twenty healthy adults received either 5 mg diazepam or placebo in a double blind, randomized design. During fMRI the subjects performed a working memory task. Results showed that BOLD responses in the cingulate cortex were inversely correlated with diazepam blood concentrations; that is, the higher the blood diazepam concentration, the lower the BOLD response. This inverse correlation was most pronounced in the pregenual anterior cingulate cortex and the anterior mid-cingulate cortex. For subjects with diazepam plasma concentration > 0.1 mg/L we observed negative BOLD responses with respect to fixation baseline. There was minor overlap between cingulate regions with task-related negative BOLD responses and regions where the BOLD responses were inversely correlated with diazepam concentration. We interpret that the inverse correlation between the BOLD response and diazepam was caused by GABA-related neural inhibition. Thus, this study supports the hypothesis that GABA attenuates BOLD responses in fMRI. The minimal overlap between task-related negative BOLD responses and responses attenuated by diazepam suggests that these responses might be caused by different mechanisms.

    Place, publisher, year, edition, pages
    San Francisco, CA, United States: Public Library of Science, 2016
    Keywords
    quantitative magnetic resonance imaging; brain tissue modeling; myelin; edema; T-1 relaxation; T-2 relaxation; proton density
    National Category
    Neurosciences
    Identifiers
    urn:nbn:se:liu:diva-126192 (URN)10.1371/journal.pone.0148737 (DOI)000371434500011 ()26930498 (PubMedID)
    Note

    Funding agencies: Linkoping University; County Council of Ostergotland

    Available from: 2016-03-18 Created: 2016-03-18 Last updated: 2018-01-10Bibliographically approved
    3. Neural inhibition can explain negative BOLD responses: A mechanistic modelling and fMRI study
    Open this publication in new window or tab >>Neural inhibition can explain negative BOLD responses: A mechanistic modelling and fMRI study
    Show others...
    2017 (English)In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 158, p. 219-231Article in journal (Refereed) Published
    Abstract [en]

    Functional magnetic resonance imaging (fMRI) of hemodynamic changes captured in the blood oxygen level-dependent (BOLD) response contains information of brain activity. The BOLD response is the result of a complex neurovascular coupling and comes in at least two fundamentally different forms: a positive and a negative deflection. Because of the complexity of the signaling, mathematical modelling can provide vital help in the data analysis. For the positive BOLD response, there are plenty of mathematical models, both physiological and phenomenological. However, for the negative BOLD response, no physiologically based model exists. Here, we expand our previously developed physiological model with the most prominent mechanistic hypothesis for the negative BOLD response: the neural inhibition hypothesis. The model was trained and tested on experimental data containing both negative and positive BOLD responses from two studies: 1) a visual-motor task and 2) a workin-gmemory task in conjunction with administration of the tranquilizer diazepam. Our model was able to predict independent validation data not used for training and provides a mechanistic underpinning for previously observed effects of diazepam. The new model moves our understanding of the negative BOLD response from qualitative reasoning to a quantitative systems-biology level, which can be useful both in basic research and in clinical use.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    fMRI; Neurovascular coupling; GABA; glutamate; Cerebral blood flow; Blood oxygen level dependent response; Hemodynamic response; Systems biology
    National Category
    Bioinformatics (Computational Biology)
    Identifiers
    urn:nbn:se:liu:diva-141844 (URN)10.1016/j.neuroimage.2017.07.002 (DOI)000411450600021 ()28687518 (PubMedID)2-s2.0-85022231713 (Scopus ID)
    Note

    Funding Agencies|Swedish Research Council [20146249]; Knut and Alice Wallenbergs foundation, KAW [2013.0076]; Research council of Southeast Sweden [FORSS-481691]; Linkoping University local funds

    Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2018-01-25Bibliographically approved
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  • 303.
    Lundengård, Karin
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Cedersund, Gunnar
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Elinder, Fredrik
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Mechanistic Modelling Investigates the Neural Basis behind the Hemodynamic Response in fMRI2015In: 16TH NORDIC-BALTIC CONFERENCE ON BIOMEDICAL ENGINEERING, Springer Science Business Media , 2015, Vol. 48, p. 86-87Conference paper (Refereed)
    Abstract [en]

    This work serves as a basis for a new type of fMRI analysis, which is based on a mechanistic interpretation of the hemodynamic response to synaptic activity. Activation was measured in the visual cortex of 12 healthy controls and ordinary differential equation models were fitted to the time series of the hemodynamic response. This allowed us to reject or refine previously proposed mechanistic hypotheses. This is the first attempt to describe the hemodynamic response quantitatively based on recent neurobiological findings. This mechanistic approach stands in contrast to the standard phenomenological description using the gamma variate function.

  • 304.
    Lundengård, Karin
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Cedersund, Gunnar
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology.
    Sten, Sebastian
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Leong, Felix
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Smedberg, Alexander
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Elinder, Fredrik
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Mechanistic Mathematical Modeling Tests Hypotheses of the Neurovascular Coupling in fMRI2016In: PloS Computational Biology, ISSN 1553-734X, E-ISSN 1553-7358, Vol. 12, no 6, article id e1004971Article in journal (Refereed)
    Abstract [en]

    Functional magnetic resonance imaging (fMRI) measures brain activity by detecting the blood-oxygen-level dependent (BOLD) response to neural activity. The BOLD response depends on the neurovascular coupling, which connects cerebral blood flow, cerebral blood volume, and deoxyhemoglobin level to neuronal activity. The exact mechanisms behind this neurovascular coupling are not yet fully investigated. There are at least three different ways in which these mechanisms are being discussed. Firstly, mathematical models involving the so-called Balloon model describes the relation between oxygen metabolism, cerebral blood volume, and cerebral blood flow. However, the Balloon model does not describe cellular and biochemical mechanisms. Secondly, the metabolic feedback hypothesis, which is based on experimental findings on metabolism associated with brain activation, and thirdly, the neurotransmitter feed-forward hypothesis which describes intracellular pathways leading to vasoactive substance release. Both the metabolic feedback and the neurotransmitter feed-forward hypotheses have been extensively studied, but only experimentally. These two hypotheses have never been implemented as mathematical models. Here we investigate these two hypotheses by mechanistic mathematical modeling using a systems biology approach; these methods have been used in biological research for many years but never been applied to the BOLD response in fMRI. In the current work, model structures describing the metabolic feedback and the neurotransmitter feed-forward hypotheses were applied to measured BOLD responses in the visual cortex of 12 healthy volunteers. Evaluating each hypothesis separately shows that neither hypothesis alone can describe the data in a biologically plausible way. However, by adding metabolism to the neurotransmitter feed-forward model structure, we obtained a new model structure which is able to fit the estimation data and successfully predict new, independent validation data. These results open the door to a new type of fMRI analysis that more accurately reflects the true neuronal activity.

    Download full text (pdf)
    fulltext
  • 305.
    Lundengård, Karin
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Elinder, Fredrik
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    A mechanistic model for blood flow regulation in response to neuronal activity2013Conference paper (Other academic)
  • 306.
    Lundin, Fredrik
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Tisell, Anders
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Leijon, Göran
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Davidsson, Leif
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences.
    Grönqvist, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Medical radiation physics.
    Wikkelso, Carsten
    University of Gothenburg, Sweden .
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Preoperative and postoperative H-1-MR spectroscopy changes in frontal deep white matter and the thalamus in idiopathic normal pressure hydrocephalus2013In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 84, no 2, p. 188-193Article in journal (Refereed)
    Abstract [en]

    Background In a previous study we found significantly decreased N-acetyl aspartate (NAA) and total N-acetyl (tNA) groups in the thalamus of patients with idiopathic normal pressure hydrocephalus (iNPH) compared with healthy individuals (HI). No significant difference between the groups could be found in the frontal deep white matter (FDWM). less thanbrgreater than less thanbrgreater thanObjective The primary aim of this study was to investigate if these metabolites in the thalamus were normalised after shunt surgery. The secondary aim was to investigate postoperative metabolic changes in FDWM. less thanbrgreater than less thanbrgreater thanSubjects and methods Fourteen patients with iNPH, mean age 74 years, and 15 HI, also mean age 74 years, were examined. Assessment of a motor score (MOSs) was performed before and after shunt surgery. Absolute quantitative H-1-MR spectroscopy (1.5 T, volumes of interest 2.5-3 ml) was performed on the patients in the FDWM and in the thalamus, before and 3 months after shunt surgery, and also once on the HI. The following metabolites were analysed: tNA, NAA, total creatine, total choline (tCho), myo-inositol (mIns), glutamate and lactate concentrations. MRI volumetric calculations of the lateral ventricles were also performed. less thanbrgreater than less thanbrgreater thanResults At 3 months postoperatively, we found no significant changes of tNA or NAA in the thalamus. In contrast, in the FDWM, there was a significant increase of tCho (p=0.01) and a borderline significant decrease of mIns (p=0.06). 12/14 patients were shunt responders (motor function). Median reduction of the lateral ventricle was 16%. A weak correlation between MOS and ventricular reduction was seen. less thanbrgreater than less thanbrgreater thanConclusions Normalisation of thalamic tNA and NAA could not be detected postoperatively. The increased tCho and decreased mIns in the FDWM postoperatively might relate to clinical improvement.

  • 307.
    Lundström, Claes
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Science & Engineering. Sectra AB.
    Thorstenson, Sten
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
    Waltersson, Marie
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Persson, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Treanor, Darren
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. St. James University Hospital, Leeds, England.
    Summary of 2nd Nordic symposium on digital pathology2015In: Journal of Pathology Informatics, ISSN 2229-5089, E-ISSN 2153-3539, Vol. 6Article in journal (Refereed)
    Abstract [en]

    Techniques for digital pathology are envisioned to provide great benefits in clinical practice, but experiences also show that solutions must be carefully crafted. The Nordic countries are far along the path toward the use of whole-slide imaging in clinical routine. The Nordic Symposium on Digital Pathology (NDP) was created to promote knowledge exchange in this area, between stakeholders in health care, industry, and academia. This article is a summary of the NDP 2014 symposium, including conclusions from a workshop on clinical adoption of digital pathology among the 144 attendees.

  • 308.
    Lundström, Claes
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Waltersson, Marie
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Persson, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Treanor, Darren
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Department of Cellular Pathology, St. James University Hospital, Leeds, UK.
    Summary of third Nordic symposium on digital pathology2016In: Journal of Pathology Informatics, ISSN 2229-5089, E-ISSN 2153-3539, Vol. 7, no 12Article in journal (Other academic)
    Abstract [en]

    Cross-disciplinary and cross-sectorial collaboration is a key success factor for turning the promise of digital pathology into actual clinical benefits. The Nordic symposium on digital pathology (NDP) was created to promote knowledge exchange in this area, among stakeholders in health care, industry, and academia. This article is a summary of the third NDP symposium in Linkφping, Sweden. The Nordic experiences, including several hospitals using whole-slide imaging for substantial parts of their primary reviews, formed a fertile base for discussions among the 190 NDP attendees originating from 15 different countries. This summary also contains results from a survey on adoption and validation aspects of clinical digital pathology use.

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    fulltext
  • 309. Order onlineBuy this publication >>
    Lundvall, Lise-Lott
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Radiographers’ professional practice: a Swedish perspective2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The general aim of this thesis was to empirically describe the radiographers’ professional scope in diagnostic imaging from the viewpoint of the practitioners and investigate how technical development affects the relations and actions in this practice.

    Data was collected by interviews and observations to both studies at the same time with two different aims. Eight radiographers (n=8) were interviewed. The interviews were open in character, were recorded with a digital voice recorder, and transcribed verbatim by the interviewer. The interview guide consisted of four interview questions. The observations of radiographers during their work with Computer Tomography (CT) and Magnetic Resonance Imaging (MRI) were conducted in a middle-sized radiology department in the southern part of Sweden. The observations were ten (n=10) in total.

    Two different theoretical perspectives were used: phenomenology (Study I) and practice theory perspective (Study II). Data was analysed with a phenomenological method in Study I. In Study II data was firstly analysed inductively, which resulted in seven codes. Secondly, abduction was made by interpretation of these codes from a practice theory perspective. This led to four themes.

    The findings in Study I display the main aspect of the radiographers’ work with image production. Their general tasks and responsibilities can be viewed as a process with the goal of producing images that can be used for diagnosis purposes. The process has three different phases: planning the examination, production of images, and evaluation of the image quality. The radiographers experience the production of images as their autonomous professional area.

    The findings in Study II report how technology development affects the relations between different actors and their actions in the practice of Computer Tomography. Four themes were identified; 1) Changed materiality makes the practical action easier. Radiographers’ practica work with image production has become easier when working with CT  compared to conventional techniques because the CT usually performs the image production in one scan. 2) Changed machines cause conflict between the arrangements of the work and the patients` needs. It is difficult to plan the examination individually for each patient because of the arrangements of the CT practice, i.e. they have little information about the patient before the examination. 3) Changing materiality prefigures learning. The radiographers describe a need for constant learning activities because of the changing procedures for image production and new modalities for image production. If not achieved it may affect their relations with the patients. 4) How the connections between different practices lead to times when practical reasoning is required in the radiography process with CT. The connections between the different professions in CT practice mainly occur through material arrangements because physically they work in different areas. The external arrangements in CT practice pre-figure actions for securing accurate radiation level and image quality. But the radiographers, who meet the patients, have to critically judge the intended actions in relation to clinical observed data to ensure patient safety.

    List of papers
    1. Professionals' experiences of imaging in the radiography process – A phenomenological approach
    Open this publication in new window or tab >>Professionals' experiences of imaging in the radiography process – A phenomenological approach
    2014 (English)In: Radiography, ISSN 1078-8174, E-ISSN 1532-2831, Vol. 20, no 1, p. 48-52Article in journal (Refereed) Published
    Abstract [en]

    Introduction

    Previous studies on radiographers' professional work have shown that this practice covers both technology and patient care. How these two competence areas blend together in practice needs to be investigated. The professionals' experiences of their work have not been studied in depth, and there is a need to focus on their experiences of the main features of their practice.

    The aim

    To explore, from the perspective of the radiographer, the general tasks and responsibilities of their work.

    Method

    Data were generated through a combination of open interviews with radiographers and observations of their work with Computer Tomography (CT) and Magnetic Resonance Imaging (MRI). The interviews and observations were analysed using an interpretative phenomenological method.

    Result

    Radiographers' professional work with diagnostic imaging, in a Swedish context, can be viewed as a problem-solving process involving judgments and responsibility for obtaining images that can be used for diagnosis. The examination process comprises three phases; planning, producing the images, and evaluation. In the first phase the radiographer makes judgments on adapting the method to the individual patient, and the second phase involves responsibilities and practical skills for image production. In the third phase, the quality of the images is judged in relation to the actual patient and the imaging process itself.

    Conclusions

    Radiographers consider that the main features of their professional work are patient safety aspects and their knowledge and skills regarding how to produce images of optimal quality, in the actual circumstances of each examination.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Radiography process, Radiographer, Phenomenology, Diagnostic radiography
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-103181 (URN)10.1016/j.radi.2013.10.002 (DOI)2-s2.0-84891740515 (Scopus ID)
    Available from: 2014-01-14 Created: 2014-01-14 Last updated: 2019-03-06Bibliographically approved
    2. How do technical improvements change radiographers’ practice: a practice theory perspective
    Open this publication in new window or tab >>How do technical improvements change radiographers’ practice: a practice theory perspective
    2015 (English)In: Radiography, ISSN 1078-8174, E-ISSN 1532-2831, Vol. 21, no 3, p. 231-235Article in journal (Refereed) Published
    Abstract [en]

    Introduction: Technical improvements in medical imaging have led to the replacement of two-plane imaging techniques by multidimensional imaging. How this affects radiographers’ professional practice has not been investigated.

    Aim: To explore how technical development affects the relations between different actors and their actions in the practice of computed tomography.

    Method: A qualitative design was used with data collection by open interviews (n=8) and open observations (n=10) of radiographers during their work with computed tomography. Data was first analysed inductively, resulting in seven preliminary codes. The initial analysis was followed by a phase of abduction, in which the preliminary codes were interpreted theoretically through the lens of practice theory. This resulted in four final themes.

    Result: First theme: Changed materiality makes practical action easier. The actual image production has become practically easier. Second theme: New machines cause conflict between the structural arrangements of the work and the patient’s needs. The time required for the scanner to carry out image production is easy to foresee, but information about the patient’s individual status and needs is missing and this leads to difficulties in giving individual planned care. Third theme: Changing materiality prefigures learning. The different apparatus in use and the continuously changing methods of image production are coconstitutive of the practitioner’s activities and learning. Fourth theme: How the connections between different practices lead to moments of practical reasoning in the radiography process with CT. The practice of image production with computed tomography takes account of patient safety in relation to radiation doses and medical security risks. The different professions in CT practice are interconnected through common material objects such as computers and machines. However, the radiographers, who meet the patients, have to check the accuracy of the planned examination in relation to the clinical observed information about patient safety risks during the examination.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keywords
    Practice, Radiographer, Radiography, Practice theory
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:liu:diva-111721 (URN)10.1016/j.radi.2014.12.002 (DOI)
    Note

    When defending the Ph.D. thesis the status of this article was Manuscript.

    Available from: 2014-10-29 Created: 2014-10-29 Last updated: 2019-03-06Bibliographically approved
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    Radiographers’ professional practice: a Swedish perspective
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  • 310.
    Lundvall, Lise-Lott
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Radiography in Practice: Work and Learning in Medical Imaging2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Those following the profession of radiographer mainly work in the healthcare sector, with image production in medical imaging or with radiotherapy treatments. Radiographers are responsible for patient care and handling technology in this profession al field. Radiographers’ practice is interesting to study in relation to technical developments and changing conditions for performing professional work.

    The general aim of this thesis was to empirically explore the main features of radiographers’ work, how advances in tech n ology affect radiographers’ practice, interconnections with other practices and students learn in g in practice on the way to becoming professionals.

    Methods: Data was collected using interviews and observations (Papers I, II & IV). For Paper III, individual interviews were conducted. Data was analysed using a phenomenological interpretative method (Paper I) and practice theory perspective (Papers II–IV).

    Findings: Radiographers’ professional work with image production was seen as a process comprising three phases: planning the examination, producing the images, and evaluating the images. During this process, radiographers make judgements to ensure patient safety and adapt the technology in use to the individual patient. When conventional imaging techniques are converted into examinations performed by Computer Tomography, the planning phase of radiographers’ work process becomes more important. Technology improvements also mean that the technical aspects of radiographers’ work with image production are easier to foresee in scheduling examinations. The caring aspects however are difficult to plan for because of little information about the patient before the examination. The professional practices involved in medical imaging interconnect to ensure patient safety through materiality and common tasks and/ or projects. The content and quality of two artefacts, the referral and the image, in these interconnections are important in collaborative work to ensure patient safety within medical imaging. Radiography students learn professional knowing in practice i.e. practice-as-work, practice-as language and practice-as-morality, during their clinical placements through alternating between two modes of participation: either observing and listening or acting by themselves. The students developed knowing in practice if the other practitioners allowed them to alternate between these two modes of participation.

    Implications: The description of radiographers’ general tasks an d responsibilities in a work process can be used for both educational and professionalization purposes. The identified interconnections between involved professions are useful for quality improvement to secure patient safety. The findings about development of knowing in practice can be used in the planning and evaluation of clinical placements for students.

    List of papers
    1. Professionals' experiences of imaging in the radiography process – A phenomenological approach
    Open this publication in new window or tab >>Professionals' experiences of imaging in the radiography process – A phenomenological approach
    2014 (English)In: Radiography, ISSN 1078-8174, E-ISSN 1532-2831, Vol. 20, no 1, p. 48-52Article in journal (Refereed) Published
    Abstract [en]

    Introduction

    Previous studies on radiographers' professional work have shown that this practice covers both technology and patient care. How these two competence areas blend together in practice needs to be investigated. The professionals' experiences of their work have not been studied in depth, and there is a need to focus on their experiences of the main features of their practice.

    The aim

    To explore, from the perspective of the radiographer, the general tasks and responsibilities of their work.

    Method

    Data were generated through a combination of open interviews with radiographers and observations of their work with Computer Tomography (CT) and Magnetic Resonance Imaging (MRI). The interviews and observations were analysed using an interpretative phenomenological method.

    Result

    Radiographers' professional work with diagnostic imaging, in a Swedish context, can be viewed as a problem-solving process involving judgments and responsibility for obtaining images that can be used for diagnosis. The examination process comprises three phases; planning, producing the images, and evaluation. In the first phase the radiographer makes judgments on adapting the method to the individual patient, and the second phase involves responsibilities and practical skills for image production. In the third phase, the quality of the images is judged in relation to the actual patient and the imaging process itself.

    Conclusions

    Radiographers consider that the main features of their professional work are patient safety aspects and their knowledge and skills regarding how to produce images of optimal quality, in the actual circumstances of each examination.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keywords
    Radiography process, Radiographer, Phenomenology, Diagnostic radiography
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-103181 (URN)10.1016/j.radi.2013.10.002 (DOI)2-s2.0-84891740515 (Scopus ID)
    Available from: 2014-01-14 Created: 2014-01-14 Last updated: 2019-03-06Bibliographically approved
    2. How do technical improvements change radiographers’ practice: a practice theory perspective
    Open this publication in new window or tab >>How do technical improvements change radiographers’ practice: a practice theory perspective
    2015 (English)In: Radiography, ISSN 1078-8174, E-ISSN 1532-2831, Vol. 21, no 3, p. 231-235Article in journal (Refereed) Published
    Abstract [en]

    Introduction: Technical improvements in medical imaging have led to the replacement of two-plane imaging techniques by multidimensional imaging. How this affects radiographers’ professional practice has not been investigated.

    Aim: To explore how technical development affects the relations between different actors and their actions in the practice of computed tomography.

    Method: A qualitative design was used with data collection by open interviews (n=8) and open observations (n=10) of radiographers during their work with computed tomography. Data was first analysed inductively, resulting in seven preliminary codes. The initial analysis was followed by a phase of abduction, in which the preliminary codes were interpreted theoretically through the lens of practice theory. This resulted in four final themes.

    Result: First theme: Changed materiality makes practical action easier. The actual image production has become practically easier. Second theme: New machines cause conflict between the structural arrangements of the work and the patient’s needs. The time required for the scanner to carry out image production is easy to foresee, but information about the patient’s individual status and needs is missing and this leads to difficulties in giving individual planned care. Third theme: Changing materiality prefigures learning. The different apparatus in use and the continuously changing methods of image production are coconstitutive of the practitioner’s activities and learning. Fourth theme: How the connections between different practices lead to moments of practical reasoning in the radiography process with CT. The practice of image production with computed tomography takes account of patient safety in relation to radiation doses and medical security risks. The different professions in CT practice are interconnected through common material objects such as computers and machines. However, the radiographers, who meet the patients, have to check the accuracy of the planned examination in relation to the clinical observed information about patient safety risks during the examination.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keywords
    Practice, Radiographer, Radiography, Practice theory
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:liu:diva-111721 (URN)10.1016/j.radi.2014.12.002 (DOI)
    Note

    When defending the Ph.D. thesis the status of this article was Manuscript.

    Available from: 2014-10-29 Created: 2014-10-29 Last updated: 2019-03-06Bibliographically approved
    Download full text (pdf)
    Radiography in Practice: Work and Learning in Medical Imaging
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  • 311.
    Lundvall, Lise-Lott
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Abrandt Dahlgren, Madeleine
    Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Health Sciences.
    Wirell, Staffan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    How do technical improvements change radiographers’ practice: a practice theory perspective2015In: Radiography, ISSN 1078-8174, E-ISSN 1532-2831, Vol. 21, no 3, p. 231-235Article in journal (Refereed)
    Abstract [en]

    Introduction: Technical improvements in medical imaging have led to the replacement of two-plane imaging techniques by multidimensional imaging. How this affects radiographers’ professional practice has not been investigated.

    Aim: To explore how technical development affects the relations between different actors and their actions in the practice of computed tomography.

    Method: A qualitative design was used with data collection by open interviews (n=8) and open observations (n=10) of radiographers during their work with computed tomography. Data was first analysed inductively, resulting in seven preliminary codes. The initial analysis was followed by a phase of abduction, in which the preliminary codes were interpreted theoretically through the lens of practice theory. This resulted in four final themes.

    Result: First theme: Changed materiality makes practical action easier. The actual image production has become practically easier. Second theme: New machines cause conflict between the structural arrangements of the work and the patient’s needs. The time required for the scanner to carry out image production is easy to foresee, but information about the patient’s individual status and needs is missing and this leads to difficulties in giving individual planned care. Third theme: Changing materiality prefigures learning. The different apparatus in use and the continuously changing methods of image production are coconstitutive of the practitioner’s activities and learning. Fourth theme: How the connections between different practices lead to moments of practical reasoning in the radiography process with CT. The practice of image production with computed tomography takes account of patient safety in relation to radiation doses and medical security risks. The different professions in CT practice are interconnected through common material objects such as computers and machines. However, the radiographers, who meet the patients, have to check the accuracy of the planned examination in relation to the clinical observed information about patient safety risks during the examination.

  • 312.
    Lundvall, Lise-Lott
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Abrandt Dahlgren, Madeleine
    Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Health Sciences.
    Wirell, Staffan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Professionals' experiences of imaging in the radiography process – A phenomenological approach2014In: Radiography, ISSN 1078-8174, E-ISSN 1532-2831, Vol. 20, no 1, p. 48-52Article in journal (Refereed)
    Abstract [en]

    Introduction

    Previous studies on radiographers' professional work have shown that this practice covers both technology and patient care. How these two competence areas blend together in practice needs to be investigated. The professionals' experiences of their work have not been studied in depth, and there is a need to focus on their experiences of the main features of their practice.

    The aim

    To explore, from the perspective of the radiographer, the general tasks and responsibilities of their work.

    Method

    Data were generated through a combination of open interviews with radiographers and observations of their work with Computer Tomography (CT) and Magnetic Resonance Imaging (MRI). The interviews and observations were analysed using an interpretative phenomenological method.

    Result

    Radiographers' professional work with diagnostic imaging, in a Swedish context, can be viewed as a problem-solving process involving judgments and responsibility for obtaining images that can be used for diagnosis. The examination process comprises three phases; planning, producing the images, and evaluation. In the first phase the radiographer makes judgments on adapting the method to the individual patient, and the second phase involves responsibilities and practical skills for image production. In the third phase, the quality of the images is judged in relation to the actual patient and the imaging process itself.

    Conclusions

    Radiographers consider that the main features of their professional work are patient safety aspects and their knowledge and skills regarding how to produce images of optimal quality, in the actual circumstances of each examination.

    Download full text (pdf)
    fulltext
  • 313.
    Ma, Yunzhi
    et al.
    CHU Quebec, Canada; University of Laval, Canada; University of Laval, Canada.
    Vijande, Javier
    University of Valencia, Spain; IFIC, Spain.
    Ballester, Facundo
    University of Valencia, Spain.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Karolinska University Hospital, Sweden.
    Granero, Domingo
    Hospital Gen University, Spain.
    Haworth, Annette
    University of Sydney, Australia.
    Mourtada, Firas
    Christiana Care Health Syst, DE 19713 USA; Christiana Care Health Syst, DE 19713 USA.
    Paiva Fonseca, Gabriel
    Maastricht University, Netherlands.
    Zourari, Kyveli
    University of Athens, Greece.
    Papagiannis, Panagiotis
    University of Athens, Greece.
    Rivard, Mark J.
    Tufts University, MA 02111 USA.
    Siebert, Frank-Andre
    University Hospital Schleswig Holstein, Germany.
    Sloboda, Ron S.
    Cross Cancer Institute, Canada; University of Alberta, Canada.
    Smith, Ryan
    Alfred Hospital, Australia.
    Chamberland, Marc J. P.
    Carleton University, Canada.
    Thomson, Rowan M.
    Carleton University, Canada.
    Verhaegen, Frank
    Maastricht University, Netherlands.
    Beaulieu, Luc
    CHU Quebec, Canada; University of Laval, Canada; University of Laval, Canada.
    A generic TG-186 shielded applicator for commissioning model-based dose calculation algorithms for high-dose-rate Ir-192 brachytherapy2017In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 44, no 11, p. 5961-5976Article in journal (Refereed)
    Abstract [en]

    PurposeA joint working group was created by the American Association of Physicists in Medicine (AAPM), the European Society for Radiotherapy and Oncology (ESTRO), and the Australasian Brachytherapy Group (ABG) with the charge, among others, to develop a set of well-defined test case plans and perform calculations and comparisons with model-based dose calculation algorithms (MBDCAs). Its main goal is to facilitate a smooth transition from the AAPM Task Group No. 43 (TG-43) dose calculation formalism, widely being used in clinical practice for brachytherapy, to the one proposed by Task Group No. 186 (TG-186) for MBDCAs. To do so, in this work a hypothetical, generic high-dose rate (HDR) Ir-192 shielded applicator has been designed and benchmarked. MethodsA generic HDR Ir-192 shielded applicator was designed based on three commercially available gynecological applicators as well as a virtual cubic water phantom that can be imported into any DICOM-RT compatible treatment planning system (TPS). The absorbed dose distribution around the applicator with the TG-186 Ir-192 source located at one dwell position at its center was computed using two commercial TPSs incorporating MBDCAs (Oncentra((R)) Brachy with Advanced Collapsed-cone Engine, ACE, and BrachyVision ACUROS) and state-of-the-art Monte Carlo (MC) codes, including ALGEBRA, BrachyDose, egs_brachy, Geant4, MCNP6, and Penelope2008. TPS-based volumetric dose distributions for the previously reported source centered in water and source displaced test cases, and the new source centered in applicator test case, were analyzed here using the MCNP6 dose distribution as a reference. Volumetric dose comparisons of TPS results against results for the other MC codes were also performed. Distributions of local and global dose difference ratios are reported. ResultsThe local dose differences among MC codes are comparable to the statistical uncertainties of the reference datasets for the source centered in water and source displaced test cases and for the clinically relevant part of the unshielded volume in the source centered in applicator case. Larger local differences appear in the shielded volume or at large distances. Considering clinically relevant regions, global dose differences are smaller than the local ones. The most disadvantageous case for the MBDCAs is the one including the shielded applicator. In this case, ACUROS agrees with MC within [-4.2%, +4.2%] for the majority of voxels (95%) while presenting dose differences within [-0.12%, +0.12%] of the dose at a clinically relevant reference point. For ACE, 95% of the total volume presents differences with respect to MC in the range [-1.7%, +0.4%] of the dose at the reference point. ConclusionsThe combination of the generic source and generic shielded applicator, together with the previously developed test cases and reference datasets (available in the Brachytherapy Source Registry), lay a solid foundation in supporting uniform commissioning procedures and direct comparisons among treatment planning systems for HDR Ir-192 brachytherapy.

  • 314.
    Magnusson, Amanda
    et al.
    Univ Gothenburg, Sweden.
    Ahle, Margareta
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Andersson, Roland
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Cty Hosp Ryhov, Sweden.
    Swolin-Eide, Diana
    Univ Gothenburg, Sweden; Sahlgrens Univ Hosp, Sweden.
    Elfvin, Anders
    Univ Gothenburg, Sweden; Sahlgrens Univ Hosp, Sweden.
    Increased risk of rickets but not fractures during childhood and adolescence following necrotizing enterocolitis among children born preterm in Sweden2019In: Pediatric Research, ISSN 0031-3998, E-ISSN 1530-0447, Vol. 86, no 1, p. 100-106Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The aim was to clarify whether children born preterm with a history of necrotizing enterocolitis (NEC) had an increased risk of rickets, fractures, and/or vitamin D deficiency during childhood and adolescence compared to controls without NEC, matched for gestational age. METHODS: All infants born in Sweden between 1987 and 2009 with a gestational age amp;lt;32 + 0 weeks and a diagnosis of NEC were identified. Totally, 465 children with a history of NEC and 2127 controls were included. International Classification of Diseases codes for all categories of fractures, rickets, vitamin D deficiency, and malnutrition were analyzed. RESULTS: In total, 94 of the 465 children with NEC died within 28 days. Of the 2127 controls, 288 died within 28 days. Among the remaining 371 NEC cases, 39 fracture occasions were identified. The 1839 controls had 204 fracture occasions. There was no significant difference in fractures. Rickets was diagnosed in 11 (3%) of the children with a history of NEC compared to 21 (1%) of the controls (odds ratio 2.65, 95% CI 1.26-5.53, p = 0.007). CONCLUSIONS: This study showed an increased risk of rickets but not fractures during childhood and adolescence in children born preterm and with a history of NEC, compared to matched controls.

  • 315.
    Magnusson, Amanda
    et al.
    University of Gothenburg, Sweden.
    Ahle, Margareta
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Swolin-Eide, Diana
    University of Gothenburg, Sweden.
    Elfvin, Anders
    University of Gothenburg, Sweden.
    Andersson, Roland E.
    County Hospital Ryhov, Sweden.
    Population-based study showed that necrotising enterocolitis occurred in space-time clusters with a decreasing secular trend in Sweden2017In: Acta Paediatrica, ISSN 0803-5253, E-ISSN 1651-2227, Vol. 106, no 7, p. 1097-1102Article in journal (Refereed)
    Abstract [en]

    Aim: This study investigated space-time clustering of neonatal necrotising enterocolitis over three decades. Methods: Space-time clustering analyses objects that are grouped by a specific place and time. The Knox test and Kulldorffs scan statistic were used to analyse space-time clusters in 808 children diagnosed with necrotising enterocolitis in a national cohort of 2 389 681 children born between 1987 and 2009 in Sweden. The municipality the mother lived in and the delivery hospital defined closeness in space and the time between when the cases were born - seven, 14 and 21 days - defined closeness in time. Results: The Knox test showed no indication of space-time clustering at the residential level, but clear indications at the hospital level in all the time windows: seven days (p = 0.026), 14 days (p = 0.010) and 21 days (p = 0.004). Significant clustering at the hospital level was found during 1987-1997, but not during 1998-2009. Kulldorffs scan statistic found seven significant clusters at the hospital level. Conclusion: Space-time clustering was found at the hospital but not residential level, suggesting a contagious environmental effect after delivery, but not in the prenatal period. The decrease in clustering over time may reflect improved routines to minimise the risk of contagion between patients receiving neonatal care.

  • 316.
    Magnusson, Maria
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV). Region Östergötland, Center for Diagnostics, Medical radiation physics.
    Björnfot, Magnus
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Medical radiation physics.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Medical radiation physics. Karolinska Univ, Sweden.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Medical radiation physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Malusek, Alexandr
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    DIRA-3D-a model-based iterative algorithm for accurate dual-energy dual-source 3D helical CT2019In: BIOMEDICAL PHYSICS and ENGINEERING EXPRESS, ISSN 2057-1976, Vol. 5, no 6, article id UNSP 065005Article in journal (Refereed)
    Abstract [en]

    Quantitative dual-energy computed tomography may improve the accuracy of treatment planning in radiation therapy. Of special interest are algorithms that can estimate material composition of the imaged object. One example of such an algorithm is the 2D model-based iterative reconstruction algorithm DIRA. The aim of this work is to extend this algorithm to 3D so that it can be used with cone-beams and helical scanning. In the new algorithm, the parallel FBP method was replaced with the approximate 3D FBP-based PI-method. Its performance was tested using a mathematical phantom consisting of six ellipsoids. The algorithm substantially reduced the beam-hardening artefact and the artefacts caused by approximate reconstruction after six iterations. Compared to Alvarez-Macovskis base material decomposition, DIRA-3D does not require geometrically consistent projections and hence can be used in dual-source CT scanners. Also, it can use several tissue-specific material bases at the same time to represent the imaged object.

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  • 317.
    Malusek, Alexandr
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Helmrot, Ebba
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Grindborg, J-E
    Swedish Radiat Protect Author, Sweden.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    In-situ calibration of clinical built-in KAP meters with traceability to a primary standard using a reference KAP meter2014In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 59, no 23, p. 7195-7210Article in journal (Refereed)
    Abstract [en]

    The air kerma-area product (KAP) is used for settings of diagnostic reference levels. The International Atomic Energy Agency (IAEA) recommends that doses in diagnostic radiology (including the KAP values) be estimated with an accuracy of at least +/- 7% (k = 2). Industry standards defined by the International Electrotechnical Commission (IEC) specify that the uncertainty of KAP meter measurements should be less than +/- 25% (k = 2). Medical physicists willing to comply with the IAEAs recommendation need to apply correction factors to KAP values reported by x-ray units. The aim of this work is to present and evaluate a calibration method for built-in KAP meters on clinical x-ray units. The method is based on (i) a tandem calibration method, which uses a reference KAP meter calibrated to measure the incident radiation, (ii) measurements using an energy-independent ionization chamber to correct for the energy dependence of the reference KAP meter, and (iii) Monte Carlo simulations of the beam quality correction factors that correct for differences between beam qualities at a standard laboratory and the clinic. The method was applied to the KAP meter in a Siemens Aristos FX plus unit. It was found that values reported by the built-in KAP meter differed from the more accurate values measured by the reference KAP meter by more than 25% for high tube voltages (more than 140 kV) and heavily filtered beams (0.3 mm Cu). Associated uncertainties were too high to claim that the IECs limit of 25% was exceeded. Nevertheless the differences were high enough to justify the need for a more accurate calibration of built-in KAP meters.

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  • 318.
    Malusek, Alexandr
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Karlsson, Mattias
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Magnusson, Maria
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    The potential of dual-energy computed tomography for quantitative decomposition of soft tissues to water, protein and lipid in brachytherapy2013In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 58, no 4, p. 771-785Article in journal (Refereed)
    Abstract [en]

    Dosimetric accuracy of radiation treatment planning in brachytherapy depends on knowledge of tissue composition. It has been speculated that soft tissues can be decomposed to water, lipid and protein. The aim of our work is to evaluate the accuracy of such tissue decomposition. Selected abdominal soft tissues, whose average elemental compositions were taken from literature, were decomposed using dual energy computed tomography to water, lipid and protein via the three-material decomposition method. The quality of the decomposition was assessed using relative differences between (i) mass energy absorption and (ii) mass energy attenuation coefficients of the analyzed and approximated tissues. It was found that the relative differences were less than 2% for photon energies larger than 10 keV. The differences were notably smaller than the ones for water as the transport and dose scoring medium. The choice of the water, protein and lipid triplet resulted in negative elemental mass fractions for some analyzed tissues. As negative elemental mass fractions cannot be used in general purpose particle transport computer codes using the Monte Carlo method, other triplets should be used for the decomposition. These triplets may further improve the accuracy of the approximation as the differences were mainly caused by the lack of high-Z materials in the water, protein and lipid triplet.

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  • 319.
    Malusek, Alexandr
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Magnusson, Maria
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    A model-based iterative reconstruction algorithm DIRA using patient-specific tissue classification via DECT for improved quantitative CT in dose planning2017In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 44, no 6, p. 2345-2357Article in journal (Refereed)
    Abstract [en]

    Purpose: To develop and evaluate-in a proof-of-concept configuration-a novel iterative reconstruction algorithm (DIRA) for quantitative determination of elemental composition of patient tissues for application to brachytherapy with low energy (amp;lt; 50 keV) photons and proton therapy. Methods: DIRA was designed as a model-based iterative reconstruction algorithm, which uses filtered backprojection, automatic segmentation and multimaterial tissue decomposition. The evaluation was done for a phantom derived from the voxelized ICRP 110 male phantom. Soft tissues were decomposed to the lipid, protein and water triplet, bones were decomposed to the compact bone and bone marrow doublet. Projections were derived using the Drasim simulation code for an axial scanning configuration resembling a typical DECT (dual-energy CT) scanner with 80 kV and Sn140 kV x-ray spectra. The iterative loop produced mono-energetic images at 50 and 88 keV without beam hardening artifacts. Different noise levels were considered: no noise, a typical noise level in diagnostic imaging and reduced noise level corresponding to tenfold higher doses. An uncertainty analysis of the results was performed using type A and B evaluations. The two approaches were compared. Results: Linear attenuation coefficients averaged over a region were obtained with relative errors less than 0.5% for all evaluated regions. Errors in average mass fractions of the three-material decomposition were less than 0.04 for no noise and reduced noise levels and less than 0.11 for the typical noise level. Mass fractions of individual pixels were strongly affected by noise, which slightly increased after the first iteration but subsequently stabilized. Estimates of uncertainties in mass fractions provided by the type B evaluation differed from the type A estimates by less than 1.5% for most cases. The algorithm was fast, the results converged after 5 iterations. The algorithmic complexity of forward polyenergetic projection calculation was much reduced by using material doublets and triplets. Conclusions: The simulations indicated that DIRA is capable of determining elemental composition of tissues, which are needed in brachytherapy with low energy (amp;lt; 50 keV) photons and proton therapy. The algorithm provided quantitative monoenergetic images with beam hardening artifacts removed. Its convergence was fast, image sharpness expressed via the modulation transfer function was maintained, and image noise did not increase with the number of iterations. c 2017 American Association of Physicists in Medicine

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  • 320.
    Malusek, Alexandr
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Magnusson, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Sandborg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Westin, Robin
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Prostate tissue decomposition via DECT using the modelbased iterative image reconstruction algorithm DIRA2014In: Medical Imaging 2014: Physics of Medical Imaging / [ed] Bruce R. Whiting; Christoph Hoeschen; Despina Kontos, SPIE - International Society for Optical Engineering, 2014, Vol. 9033, no 90333H, p. Art.nr. 90333H-Conference paper (Refereed)
    Abstract [en]

    Better knowledge of elemental composition of patient tissues may improve the accuracy of absorbed dose delivery in brachytherapy. Deficiencies of water-based protocols have been recognized and work is ongoing to implement patient-specific radiation treatment protocols. A model based iterative image reconstruction algorithm DIRA has been developed by the authors to automatically decompose patient tissues to two or three base components via dual-energy computed tomography. Performance of an updated version of DIRA was evaluated for the determination of prostate calcification. A computer simulation using an anthropomorphic phantom showed that the mass fraction of calcium in the prostate tissue was determined with accuracy better than 9%. The calculated mass fraction was little affected by the choice of the material triplet for the surrounding soft tissue. Relative differences between true and approximated values of linear attenuation coefficient and mass energy absorption coefficient for the prostate tissue were less than 6% for photon energies from 1 keV to 2 MeV. The results indicate that DIRA has the potential to improve the accuracy of dose delivery in brachytherapy despite the fact that base material triplets only approximate surrounding soft tissues.

  • 321.
    Malusek, Alexandr
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Sandborg, Michael
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Alm Carlsson, Gudrun
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Medicine and Health Sciences.
    ACCURATE KAP METER CALIBRATION AS A PREREQUISITE FOR OPTIMISATION IN PROJECTION RADIOGRAPHY2016In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 353-359Article in journal (Refereed)
    Abstract [en]

    Modern X-ray units register the air kerma–area product, PKA, with a built-in KAP meter. Some KAP meters show an energydependent bias comparable with the maximum uncertainty articulated by the IEC (25 %), adversely affecting dose-optimisation processes. To correct for the bias, a reference KAP meter calibrated at a standards laboratory and two calibration methods described here can be used to achieve an uncertainty of <7 % as recommended by IAEA. A computational model of the reference KAP meter is used to calculate beam quality correction factors for transfer of the calibration coefficient at the standards laboratory, Q0, to any beam quality, Q, in the clinic. Alternatively, beam quality corrections are measured with an energy-independent dosemeter via a reference beam quality in the clinic, Q1, to beam quality, Q. Biases up to 35 % of built-in KAP meter readings were noted. Energy-dependent calibration factors are needed for unbiased PKA. Accurate KAP meter calibration as a prerequisite for optimisation in projection radiography.

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  • 322.
    Marcu, Loredana G.
    et al.
    University of Oradea, Romania and University of Adelaide, Australia.
    Bezak, Eva
    Royal Adelaide Hospital, Australia.
    Toma-Dasu, Iuliana
    Stockholm University and Karolinska Institutet, Sweden.
    Dasu, Alexandru
    Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Predictive models of tumour response to treatment using functional imaging techniques2015In: Computational & Mathematical Methods in Medicine, ISSN 1748-670X, E-ISSN 1748-6718, Vol. 2015, p. Article ID 571351-Article in journal (Other academic)
  • 323.
    Marcu, Loredana G.
    et al.
    University of Oradea, Romania and University of Adelaide, Australia.
    Toma-Dasu, Iuliana
    Stockholm University and Karolinska Institutet.
    Dasu, Alexandru
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    The six Rs of head and neck cancer radiotherapy2015In: Contemporary Issues in Head and Neck Cancer Management / [ed] Loredana G. Marcu, Rijeka: InTech , 2015, p. 35-58Chapter in book (Refereed)
    Abstract [en]

    While the management of head and neck cancer has evolved over the last few decades, there are still several challenges and unanswered questions that need solutions. This book is a small compilation of some topical aspects regarding head and neck cancer treatment, including the etiology of HPV-positive oropharyngeal cancers and risk factors in the young population, the challenge of surgical margin definition and the perennial problem of systemic treatment due to distant metastases. Radiobiological aspects are also covered through the Rs of radiotherapy, with a couple of chapters being dedicated to radioresistance and tumour microenvironment. Contemporary Issues in Head and Neck Cancer Management comes as an addition to the existing literature that aims to tackle this radiobiologically challenging tumour.

  • 324. Order onlineBuy this publication >>
    Maria Marreiros, Filipe Miguel
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Science & Engineering.
    Guidance and Visualization for Brain Tumor Surgery2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Image guidance and visualization play an important role in modern surgery to help surgeons perform their surgical procedures. Here, the focus is on neurosurgery applications, in particular brain tumor surgery where a craniotomy (opening of the skull) is performed to access directly the brain region to be treated. In this type of surgery, once the skull is opened the brain can change its shape, and this deformation is known as brain shift. Moreover, the boundaries of many types of tumors are difficult to identify by the naked eye from healthy tissue. The main goal of this work was to study and develop image guidance and visualization methods for tumor surgery in order to overcome the problems faced in this type of surgery.

    Due to brain shift the magnetic resonance dataset acquired before the operation (preoperatively) no longer corresponds to the anatomy of the patient during the operation (intraoperatively). For this reason, in this work methods were studied and developed to compensate for this deformation. To guide the deformation methods, information of the superficial vessel centerlines of the brain was used. A method for accurate (approximately 1 mm) reconstruction of the vessel centerlines using a multiview camera system was developed. It uses geometrical constraints, relaxation labeling, thin plate spline filtering and finally mean shift to find the correct correspondences between the camera images.

    A complete non-rigid deformation pipeline was initially proposed and evaluated with an animal model. From these experiments it was observed that although the traditional non-rigid registration methods (in our case coherent point drift) were able to produce satisfactory vessel correspondences between preoperative and intraoperative vessels, in some specific areas the results were suboptimal. For this reason a new method was proposed that combined the coherent point drift and thin plate spline semilandmarks. This combination resulted in an accurate (below 1 mm) non-rigid registration method, evaluated with simulated data where artificial deformations were performed.

    Besides the non-rigid registration methods, a new rigid registration method to obtain the rigid transformation between the magnetic resonance dataset and the neuronavigation coordinate systems was also developed.

    Once the rigid transformation and the vessel correspondences are known, the thin plate spline can be used to perform the brain shift deformation. To do so, we have used two approaches: a direct and an indirect. With the direct approach, an image is created that represents the deformed data, and with the indirect approach, a new volume is first constructed and only after that can the deformed image be created. A comparison of these two approaches, implemented for the graphics processing units, in terms of performance and image quality, was performed. The indirect method was superior in terms of performance if the sampling along the ray is high, in comparison to the voxel grid, while the direct was superior otherwise. The image quality analysis seemed to indicate that the direct method is superior.

    Furthermore, visualization studies were performed to understand how different rendering methods and parameters influence the perception of the spatial position of enclosed objects (typical situation of a tumor enclosed in the brain). To test these methods a new single-monitor-mirror stereoscopic display was constructed. Using this display, stereo images simulating a tumor inside the brain were presented to the users with two rendering methods (illustrative rendering and simple alpha blending) and different levels of opacity. For the simple alpha blending method an optimal opacity level was found, while for the illustrative rendering method all the opacity levels used seemed to perform similarly.

    In conclusion, this work developed and evaluated 3D reconstruction, registration (rigid and non-rigid) and deformation methods with the purpose of minimizing the brain shift problem. Stereoscopic perception of the spatial position of enclosed objects was also studied using different rendering methods and parameter values.

    List of papers
    1. Superficial vessel reconstruction with a multiview camera system
    Open this publication in new window or tab >>Superficial vessel reconstruction with a multiview camera system
    Show others...
    2016 (English)In: Journal of Medical Imaging, ISSN 2329-4302, E-ISSN 2329-4310, Vol. 3, no 1, p. 015001-1-015001-13Article in journal (Refereed) Published
    Abstract [en]

    We aim at reconstructing superficial vessels of the brain. Ultimately, they will serve to guide the deformationmethods to compensate for the brain shift. A pipeline for three-dimensional (3-D) vessel reconstructionusing three mono-complementary metal-oxide semiconductor cameras has been developed. Vessel centerlinesare manually selected in the images. Using the properties of the Hessian matrix, the centerline points areassigned direction information. For correspondence matching, a combination of methods was used. The processstarts with epipolar and spatial coherence constraints (geometrical constraints), followed by relaxation labelingand an iterative filtering where the 3-D points are compared to surfaces obtained using the thin-plate spline withdecreasing relaxation parameter. Finally, the points are shifted to their local centroid position. Evaluation invirtual, phantom, and experimental images, including intraoperative data from patient experiments, showsthat, with appropriate camera positions, the error estimates (root-mean square error and mean error) are∼1 mm.

    Place, publisher, year, edition, pages
    SPIE - International Society for Optical Engineering, 2016
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-123661 (URN)10.1117/1.JMI.3.1.015001 (DOI)
    Projects
    ARIOR
    Funder
    Swedish Childhood Cancer Foundation, MT2013-0036
    Available from: 2016-01-05 Created: 2016-01-05 Last updated: 2018-01-10Bibliographically approved
    2. Non-rigid Deformation Pipeline for Compensation of Superficial Brain Shift
    Open this publication in new window or tab >>Non-rigid Deformation Pipeline for Compensation of Superficial Brain Shift
    2013 (English)In: Medical Image Computing and Computer-Assisted Intervention, MICCAI 2013: 16th International Conference, Nagoya, Japan, September 22-26, 2013, Proceedings, Part II, Springer Berlin/Heidelberg, 2013, p. 141-148Conference paper, Published paper (Refereed)
    Abstract [en]

    The correct visualization of anatomical structures is a critical component of neurosurgical navigation systems, to guide the surgeon to the areas of interest as well as to avoid brain damage. A major challenge for neuronavigation systems is the brain shift, or deformation of the exposed brain in comparison to preoperative Magnetic Resonance (MR) image sets. In this work paper, a non-rigid deformation pipeline is proposed for brain shift compensation of preoperative imaging datasets using superficial blood vessels as landmarks. The input was preoperative and intraoperative 3D image sets of superficial vessel centerlines. The intraoperative vessels (obtained using 3 Near-Infrared cameras) were registered and aligned with preoperative Magnetic Resonance Angiography vessel centerlines using manual interaction for the rigid transformation and, for the non-rigid transformation, the non-rigid point set registration method Coherent Point Drift. The rigid registration transforms the intraoperative points from the camera coordinate system to the preoperative MR coordinate system, and the non-rigid registration deals with local transformations in the MR coordinate system. Finally, the generation of a new deformed volume is achieved with the Thin-Plate Spline (TPS) method using as control points the matches in the MR coordinate system found in the previous step. The method was tested in a rabbit brain exposed via craniotomy, where deformations were produced by a balloon inserted into the brain. There was a good correlation between the real state of the brain and the deformed volume obtained using the pipeline. Maximum displacements were approximately 4.0 mm for the exposed brain alone, and 6.7 mm after balloon inflation.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2013
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 8150
    National Category
    Engineering and Technology Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-106901 (URN)10.1007/978-3-642-40763-5_18 (DOI)000342835100018 ()978-3-642-40762-8 (ISBN)978-3-642-40763-5 (ISBN)
    Conference
    16th International Conference on Medical Image Computing and Computer-Assisted Intervention (MICCAI 2013), Nagoya, Japan, September 22-26, 2013
    Available from: 2014-05-23 Created: 2014-05-23 Last updated: 2018-01-23Bibliographically approved
    3. Non-rigid point set registration of curves: registration of the superficial vessel centerlines of the brain
    Open this publication in new window or tab >>Non-rigid point set registration of curves: registration of the superficial vessel centerlines of the brain
    2016 (English)In: Medical Imaging 2016: Image-Guided Procedures, Robotic Interventions, and Modeling, SPIE - International Society for Optical Engineering, 2016, Vol. 9786, p. 8p. 978611-1-978611-8Conference paper, Published paper (Refereed)
    Abstract [en]

    In this study we present a non-rigid point set registration for 3D curves (composed by 3D set of points). Themethod was evaluated in the task of registration of 3D superficial vessels of the brain where it was used to matchvessel centerline points. It consists of a combination of the Coherent Point Drift (CPD) and the Thin-PlateSpline (TPS) semilandmarks. The CPD is used to perform the initial matching of centerline 3D points, whilethe semilandmark method iteratively relaxes/slides the points.

    For the evaluation, a Magnetic Resonance Angiography (MRA) dataset was used. Deformations were appliedto the extracted vessels centerlines to simulate brain bulging and sinking, using a TPS deformation where afew control points were manipulated to obtain the desired transformation (T1). Once the correspondences areknown, the corresponding points are used to define a new TPS deformation(T2). The errors are measured in thedeformed space, by transforming the original points using T1 and T2 and measuring the distance between them.To simulate cases where the deformed vessel data is incomplete, parts of the reference vessels were cut and thendeformed. Furthermore, anisotropic normally distributed noise was added.

    The results show that the error estimates (root mean square error and mean error) are below 1 mm, even inthe presence of noise and incomplete data.

    Place, publisher, year, edition, pages
    SPIE - International Society for Optical Engineering, 2016. p. 8
    Series
    Progress in Biomedical Optics, ISSN 1605-7422 ; 9786
    Keywords
    Non-rigid registration, brain shift correction, vessel registration
    National Category
    Medical Image Processing
    Identifiers
    urn:nbn:se:liu:diva-126347 (URN)10.1117/12.2208421 (DOI)000382315800036 ()978-1-5106-0021-8 (ISBN)
    Conference
    Medical Imaging 2016: Image-Guided Procedures, Robotic Interventions, and Modeling, San Diego, California, United States, February 27, 2016
    Projects
    ARIOR
    Funder
    Swedish Childhood Cancer Foundation, MT2013-0036
    Available from: 2016-03-22 Created: 2016-03-22 Last updated: 2016-09-27Bibliographically approved
    4. GPU-based ray-casting of non-rigid deformations: a comparison between direct and indirect approaches
    Open this publication in new window or tab >>GPU-based ray-casting of non-rigid deformations: a comparison between direct and indirect approaches
    2014 (English)In: Proceedings of SIGRAD 2014, Visual Computing, June 12-13, 2014, Göteborg, Sweden / [ed] Mohammad Obaid; Daniel Sjölie; Erik Sintorn; Morten Fjeld, Linköping University Electronic Press, 2014, p. 67-74Conference paper, Published paper (Refereed)
    Abstract [en]

    For ray-casting of non-rigid deformations, the direct approach (as opposed to the traditional indirect approach) does not require the computation of an intermediate volume to be used for the rendering step. The aim of this study was to compare the two approaches in terms of performance (speed) and accuracy (image quality).

    The direct and the indirect approach were carefully implemented to benefit of the massive GPU parallel power, using CUDA. They were then tested with Computed Tomography (CT) datasets of varying sizes and with a synthetic image, the Marschner-Lobb function.

    The results show that the direct approach is dependent on the ray sampling steps, number of landmarks and image resolution. The indirect approach is mainly affected by the number of landmarks, if the volume is large enough.

    These results exclude extreme cases, i.e. if the sampling steps are much smaller than the voxel size and if the image resolution is much higher than the ones used here. For a volume of size 512×512×512, using 100 landmarks and image resolution of 1280×960, the direct method performs better if the ray sampling steps are approximately above 1 voxel. Regarding accuracy, the direct method provides better results for multiple frequencies using the Marschner-Lobb function.

    The conclusion is that the indirect method is superior in terms of performance, if the sampling along the rays is high, in comparison to the voxel grid, while the direct is superior otherwise. The accuracy analysis seems to point out that the direct method is superior, in particular when the implicit function is used.

    Place, publisher, year, edition, pages
    Linköping University Electronic Press, 2014
    Series
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 106
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-107553 (URN)9789175192123 (ISBN)
    Conference
    Swedish Computer Graphics Association (SIGRAD), Göteborg, Sweden, June 12-13, 2014
    Available from: 2014-06-16 Created: 2014-06-16 Last updated: 2018-02-19Bibliographically approved
    5. Single-Monitor-Mirror Stereoscopic Display
    Open this publication in new window or tab >>Single-Monitor-Mirror Stereoscopic Display
    2013 (English)In: Journal of Graphics Tools, ISSN 2165-347X, Vol. 17, no 3, p. 85-97Article in journal (Refereed) Published
    Abstract [en]

    A new single-monitor-mirror stereoscopic display is presented. The stereoscopic display system is composed of one monitor and one acrylic first-surface mirror. The mirror reflects one image for one of the eyes. The geometrical transformations to compute correctly the stereo pair are derived and presented. System considerations such as mirror placement and implications are also discussed.

    In contrast to other similar solutions that use fixed configurations, we try to optimize the display area by controlling the mirror placement. Consequently, one of the images needs to be skewed. Advantages of the system include absence of ghosting and flickering.

    We also developed the rendering engine for direct volume rendering (DVR) of volumetric datasets mostly for medical imaging visualization and using OpenGL for polygonal datasets and stereoscopic digital photography. The skewing process in this case is integrated into the ray-casting of DVR. Using geometrical transformations, we can compute precisely the directions of the rays, producing accurate stereo pairs. A similar operation is also performed using OpenGL.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2013
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-120584 (URN)10.1080/2165347X.2015.1028690 (DOI)
    Projects
    arior
    Funder
    Swedish Childhood Cancer Foundation, MT2013-0036Swedish Foundation for Strategic Research VINNOVAVårdal Foundation
    Available from: 2015-08-17 Created: 2015-08-17 Last updated: 2018-01-11Bibliographically approved
    6. Stereoscopic static depth perception of enclosed 3D objects
    Open this publication in new window or tab >>Stereoscopic static depth perception of enclosed 3D objects
    2013 (English)In: SAP '13 Proceedings of the ACM Symposium on Applied Perception, New York, USA: Association for Computing Machinery (ACM), 2013, p. 15-22Conference paper, Published paper (Refereed)
    Abstract [en]

    Depth perception of semi-transparent virtual objects and the visu-alization of their spatial layout are crucial in many applications, in particular medical applications. Depth cues for opaque objects have been extensively studied, but this is not the case for stereo-scopic semi-transparent objects, in particular in the case when one 3D object is enclosed within a larger exterior object.

    In this work we explored different stereoscopic rendering methodsto analyze their impact on depth perception accuracy of an enclosed3D object. Two experiments were performed: the first tested the hypotheses that depth perception is dependent on the color blending of objects (opacity - alpha) for each rendering method and that one of two rendering methods used is superior. The second experiment was performed to corroborate the results of the first experiment and to test an extra hypothesis: is depth perception improved if an auxiliary object that provides a relationship between the enclosed objectand the exterior is used?

    The first rendering method used is simple alpha blending with Blinn-Phong shading model, where a segmented brain (exterior object) and a synthetic tumor (enclosed object) were blended. The second rendering method also uses Blinn-Phong, but the shading was modified to preserve silhouettes and to provide an illustrative rendering. Comparing both rendering methods, the brighter regionsof the first rendering method will become more transparent in the second rendering method, thus preserving silhouette areas.

    The results show that depth perception accuracy of an enclosed object rendered with a stereoscopic system is dependent on opacity for some rendering methods (simple alpha blending), but this effect is less pronounced than the dependence on object position in relation to the exterior object. The illustrative rendering method is less dependent on opacity. The different rendering methods also perform slightly differently; an illustrative rendering method was superior and the use of an auxiliary object seems to facilitate depth perception.

    Place, publisher, year, edition, pages
    New York, USA: Association for Computing Machinery (ACM), 2013
    Keywords
    depth perception, stereoscopy, enclosed 3D objects
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-106896 (URN)10.1145/2492494.2492501 (DOI)978-1-4503-2262-1 (ISBN)
    Conference
    2013 ACM Symposium on Applied Perception, SAP 2013; Dublin, Ireland, August 22 - 23, 2013
    Funder
    VINNOVA
    Available from: 2014-05-23 Created: 2014-05-23 Last updated: 2018-01-11Bibliographically approved
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    Guidance and Visualization for Brain Tumor Surgery
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  • 325.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology.
    Heuzé, Yann
    Université de Bordeaux, Allée Geoffroy de Saint Hilaire Bat. B8, CS 50023, 33615, Pessac Cedex, France.
    Verius, Michael
    Department of Radiology, Innsbruck Medical University, Innrain 52, Christoph-Probst-Platz, 6020, Innsbruck, Austria.
    Unterhofer, Claudia
    Innsbruck Medical University, Innrain 52, Christoph-Probst-Platz, 6020, Innsbruck, Austria.
    Freysinger, Wolfgang
    Innsbruck Medical University, Innrain 52, Christoph-Probst-Platz, 6020, Innsbruck, Austria.
    Recheis, Wolfgang
    Innsbruck Medical University, Innrain 52, Christoph-Probst-Platz, 6020, Innsbruck, Austria.
    Custom implant design for large cranial defects2016In: International Journal of Computer Assisted Radiology and Surgery, ISSN 1861-6410, E-ISSN 1861-6429, Vol. 11, no 12, p. 2217-2230Article in journal (Refereed)
    Abstract [en]

    Purpose

    The aim of this work was to introduce a Computer Aided Design (CAD)tool that enables the design of large skull defects (> 100cm2) implants. Functional and aesthetically correct custom implants are extremely important for patients with large cranial defects. For these cases pre-operative fabrication of implants is recommended to avoid problems of donor site morbidity, sufficiencyof donor material and quality. Finally, crafting the correct shape is a non-trivial task increasingly complicated by defect size.

    Methods

    We present a Computer Aided Design (CAD) tool to design such implants for the neurocranium. A combination of Geometric Morphometrics (GM) and Radial Basis Functions (RBF), namely Thin Plate Splines (TPS), allows semiautomatic implant generation. The method uses symmetry and the best fitting shape to estimate missing data directly within the radiologic volume data. In addition, this approach delivers correct implant fitting via a boundary fitting approach.

    Results

    This method generates a smooth implant surface, free of sharp edges that follows the main contours of the boundary, enabling accurate implant placementin the defect site intraoperatively. The present approach is evaluated and compared to existing methods. A mean error of 89.29% (72.64% - 100%)missing landmarks with an error less or equal to 1 mm was obtained.

    Conclusion

    In conclusion, the results show that our Computer Aided Design (CAD)tool can generate patient specific implants with high accuracy.

  • 326.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Rossitti, Sandro
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Gustafsson, Torbjörn
    XM Reality Research AB, Linköping, Sweden.
    Carleberg, Per
    XM Reality Research AB, Linköping, Sweden.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Multi-view 3D vessel tracking using near-infrared cameras2014In: Proceedings of the 27th International Congress and Exhibition on Computer Assisted Radiology and Surgery: Image Processing and Visualization, Springer, 2014, p. S165-S165Conference paper (Other academic)
  • 327.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Rossitti, Sandro
    Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery. Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
    Karlsson, Per
    Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Wang, Chunliang
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Royal Institute of Technology, School of Technology and Health, Alfred Nobels Allé 10, Huddinge.
    Gustafsson, Torbjörn
    XM Reality AB, Linköping, Sweden.
    Carleberg, Per
    XM Reality AB, Linköping, Sweden.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping. Royal Institute of Technology, School of Technology and Health, Alfred Nobels Allé 10, Huddinge .
    Superficial vessel reconstruction with a multiview camera system2016In: Journal of Medical Imaging, ISSN 2329-4302, E-ISSN 2329-4310, Vol. 3, no 1, p. 015001-1-015001-13Article in journal (Refereed)
    Abstract [en]

    We aim at reconstructing superficial vessels of the brain. Ultimately, they will serve to guide the deformationmethods to compensate for the brain shift. A pipeline for three-dimensional (3-D) vessel reconstructionusing three mono-complementary metal-oxide semiconductor cameras has been developed. Vessel centerlinesare manually selected in the images. Using the properties of the Hessian matrix, the centerline points areassigned direction information. For correspondence matching, a combination of methods was used. The processstarts with epipolar and spatial coherence constraints (geometrical constraints), followed by relaxation labelingand an iterative filtering where the 3-D points are compared to surfaces obtained using the thin-plate spline withdecreasing relaxation parameter. Finally, the points are shifted to their local centroid position. Evaluation invirtual, phantom, and experimental images, including intraoperative data from patient experiments, showsthat, with appropriate camera positions, the error estimates (root-mean square error and mean error) are∼1 mm.

  • 328.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Rossitti, Sandro
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Wang, Chunliang
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Non-rigid Deformation Pipeline for Compensation of Superficial Brain Shift2013In: Medical Image Computing and Computer-Assisted Intervention, MICCAI 2013: 16th International Conference, Nagoya, Japan, September 22-26, 2013, Proceedings, Part II, Springer Berlin/Heidelberg, 2013, p. 141-148Conference paper (Refereed)
    Abstract [en]

    The correct visualization of anatomical structures is a critical component of neurosurgical navigation systems, to guide the surgeon to the areas of interest as well as to avoid brain damage. A major challenge for neuronavigation systems is the brain shift, or deformation of the exposed brain in comparison to preoperative Magnetic Resonance (MR) image sets. In this work paper, a non-rigid deformation pipeline is proposed for brain shift compensation of preoperative imaging datasets using superficial blood vessels as landmarks. The input was preoperative and intraoperative 3D image sets of superficial vessel centerlines. The intraoperative vessels (obtained using 3 Near-Infrared cameras) were registered and aligned with preoperative Magnetic Resonance Angiography vessel centerlines using manual interaction for the rigid transformation and, for the non-rigid transformation, the non-rigid point set registration method Coherent Point Drift. The rigid registration transforms the intraoperative points from the camera coordinate system to the preoperative MR coordinate system, and the non-rigid registration deals with local transformations in the MR coordinate system. Finally, the generation of a new deformed volume is achieved with the Thin-Plate Spline (TPS) method using as control points the matches in the MR coordinate system found in the previous step. The method was tested in a rabbit brain exposed via craniotomy, where deformations were produced by a balloon inserted into the brain. There was a good correlation between the real state of the brain and the deformed volume obtained using the pipeline. Maximum displacements were approximately 4.0 mm for the exposed brain alone, and 6.7 mm after balloon inflation.

  • 329.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    GPU-based ray-casting of non-rigid deformations: a comparison between direct and indirect approaches2014In: Proceedings of SIGRAD 2014, Visual Computing, June 12-13, 2014, Göteborg, Sweden / [ed] Mohammad Obaid; Daniel Sjölie; Erik Sintorn; Morten Fjeld, Linköping University Electronic Press, 2014, p. 67-74Conference paper (Refereed)
    Abstract [en]

    For ray-casting of non-rigid deformations, the direct approach (as opposed to the traditional indirect approach) does not require the computation of an intermediate volume to be used for the rendering step. The aim of this study was to compare the two approaches in terms of performance (speed) and accuracy (image quality).

    The direct and the indirect approach were carefully implemented to benefit of the massive GPU parallel power, using CUDA. They were then tested with Computed Tomography (CT) datasets of varying sizes and with a synthetic image, the Marschner-Lobb function.

    The results show that the direct approach is dependent on the ray sampling steps, number of landmarks and image resolution. The indirect approach is mainly affected by the number of landmarks, if the volume is large enough.

    These results exclude extreme cases, i.e. if the sampling steps are much smaller than the voxel size and if the image resolution is much higher than the ones used here. For a volume of size 512×512×512, using 100 landmarks and image resolution of 1280×960, the direct method performs better if the ray sampling steps are approximately above 1 voxel. Regarding accuracy, the direct method provides better results for multiple frequencies using the Marschner-Lobb function.

    The conclusion is that the indirect method is superior in terms of performance, if the sampling along the rays is high, in comparison to the voxel grid, while the direct is superior otherwise. The accuracy analysis seems to point out that the direct method is superior, in particular when the implicit function is used.

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  • 330.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Mirror Stereoscopic Display for Direct Volume Rendering2014In: Proceedings of SIGRAD 2014, Visual Computing, June 12-13, 2014, Göteborg, Sweden / [ed] Mohammad Obaid; Daniel Sjölie; Erik Sintorn; Morten Fjeld, Linköping University Electronic Press, 2014, p. 75-82Conference paper (Refereed)
    Abstract [en]

    A new mirror stereoscopic display for Direct Volume Rendering (DVR) is presented. The stereoscopic display system is composed of one monitor and one acrylic first surface mirror. The mirror reflects one image for one of the eyes. The geometrical transformations to compute correctly the stereo pair is presented and is the core of this paper. System considerations such as mirror placement and implications are also discussed.

    In contrast to other similar solutions, we do not use two monitors, but just one. Consequently one of the images needs to be skewed. Advantages of the system include absence of ghosting and of flickering.

    We also developed the rendering engine for DVR of volumetric datasets mostly for medical imaging visualization. The skewing process in this case is integrated into the ray casting of DVR. Using geometrical transformations, we can compute precisely the directions of the rays, producing accurate stereo pairs.

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  • 331.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Single-Monitor-Mirror Stereoscopic Display2013In: Journal of Graphics Tools, ISSN 2165-347X, Vol. 17, no 3, p. 85-97Article in journal (Refereed)
    Abstract [en]

    A new single-monitor-mirror stereoscopic display is presented. The stereoscopic display system is composed of one monitor and one acrylic first-surface mirror. The mirror reflects one image for one of the eyes. The geometrical transformations to compute correctly the stereo pair are derived and presented. System considerations such as mirror placement and implications are also discussed.

    In contrast to other similar solutions that use fixed configurations, we try to optimize the display area by controlling the mirror placement. Consequently, one of the images needs to be skewed. Advantages of the system include absence of ghosting and flickering.

    We also developed the rendering engine for direct volume rendering (DVR) of volumetric datasets mostly for medical imaging visualization and using OpenGL for polygonal datasets and stereoscopic digital photography. The skewing process in this case is integrated into the ray-casting of DVR. Using geometrical transformations, we can compute precisely the directions of the rays, producing accurate stereo pairs. A similar operation is also performed using OpenGL.

  • 332.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Stereoscopic static depth perception of enclosed 3D objects2013In: SAP '13 Proceedings of the ACM Symposium on Applied Perception, New York, USA: Association for Computing Machinery (ACM), 2013, p. 15-22Conference paper (Refereed)
    Abstract [en]

    Depth perception of semi-transparent virtual objects and the visu-alization of their spatial layout are crucial in many applications, in particular medical applications. Depth cues for opaque objects have been extensively studied, but this is not the case for stereo-scopic semi-transparent objects, in particular in the case when one 3D object is enclosed within a larger exterior object.

    In this work we explored different stereoscopic rendering methodsto analyze their impact on depth perception accuracy of an enclosed3D object. Two experiments were performed: the first tested the hypotheses that depth perception is dependent on the color blending of objects (opacity - alpha) for each rendering method and that one of two rendering methods used is superior. The second experiment was performed to corroborate the results of the first experiment and to test an extra hypothesis: is depth perception improved if an auxiliary object that provides a relationship between the enclosed objectand the exterior is used?

    The first rendering method used is simple alpha blending with Blinn-Phong shading model, where a segmented brain (exterior object) and a synthetic tumor (enclosed object) were blended. The second rendering method also uses Blinn-Phong, but the shading was modified to preserve silhouettes and to provide an illustrative rendering. Comparing both rendering methods, the brighter regionsof the first rendering method will become more transparent in the second rendering method, thus preserving silhouette areas.

    The results show that depth perception accuracy of an enclosed object rendered with a stereoscopic system is dependent on opacity for some rendering methods (simple alpha blending), but this effect is less pronounced than the dependence on object position in relation to the exterior object. The illustrative rendering method is less dependent on opacity. The different rendering methods also perform slightly differently; an illustrative rendering method was superior and the use of an auxiliary object seems to facilitate depth perception.

  • 333.
    Maria Marreiros, Filipe Miguel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Wang, Chunliang
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Royal Institute of Technology (KTH), School of Technology and Health, Huddinge, Sweden.
    Rossitti, Sandro
    Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping. Royal Institute of Technology (KTH), School of Technology and Health, Huddinge, Sweden.
    Non-rigid point set registration of curves: registration of the superficial vessel centerlines of the brain2016In: Medical Imaging 2016: Image-Guided Procedures, Robotic Interventions, and Modeling, SPIE - International Society for Optical Engineering, 2016, Vol. 9786, p. 8p. 978611-1-978611-8Conference paper (Refereed)
    Abstract [en]

    In this study we present a non-rigid point set registration for 3D curves (composed by 3D set of points). Themethod was evaluated in the task of registration of 3D superficial vessels of the brain where it was used to matchvessel centerline points. It consists of a combination of the Coherent Point Drift (CPD) and the Thin-PlateSpline (TPS) semilandmarks. The CPD is used to perform the initial matching of centerline 3D points, whilethe semilandmark method iteratively relaxes/slides the points.

    For the evaluation, a Magnetic Resonance Angiography (MRA) dataset was used. Deformations were appliedto the extracted vessels centerlines to simulate brain bulging and sinking, using a TPS deformation where afew control points were manipulated to obtain the desired transformation (T1). Once the correspondences areknown, the corresponding points are used to define a new TPS deformation(T2). The errors are measured in thedeformed space, by transforming the original points using T1 and T2 and measuring the distance between them.To simulate cases where the deformed vessel data is incomplete, parts of the reference vessels were cut and thendeformed. Furthermore, anisotropic normally distributed noise was added.

    The results show that the error estimates (root mean square error and mean error) are below 1 mm, even inthe presence of noise and incomplete data.

  • 334.
    McIntyre, Deane D.
    et al.
    Departments of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
    Apblett, Allen W.
    Department of Chemistry, University of Calgary, Calgary, Alberta, Canada.
    Lundberg, Peter
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Departments of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
    Schmidt, Kenneth J.
    Department of Chemistry, University of Calgary, Calgary, Alberta, Canada .
    Vogel, Hans J.
    Departments of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
    Nitrogen-14 NMR relaxation, and reorientation behavior of dissolved dinitrogen1989In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 83, no 2, p. 377-382Article in journal (Refereed)
    Abstract [en]

    In recent years, nitrogen- 14 and - 15 NMR spectroscopy has become an important technique in organic chemistry and in biochemistry ( Z-4). A frequent occurrence in the NMR spectra of both nuclei is the presence of a signal at approximately -7 1.5ppm (referred to neat nitromethane; -66 ppm referred to aqueous nitrate). This resonance, which has been observed in water (4) and a range of organic solvents (.5-7), has been the subject of some confusion in the literature. In the case of nitrogen-14 NMR spectra, the signal for the quadrupolar nucleus has a remarkably narrow linewidth (about 25 Hz) compared to those recorded for a wide variety of other substances. This indicates a fairly high degree of electronic symmetry about the nitrogenatom and/or a very short correlation time ( 7,). In a recent report (8)) this signal has been assigned to dissolved dinitrogen on the basis that it could be removed by degassing´the solution; however, no reference was made to the fact that it had a remarkably narrow linewidth compared to other 14N NMR resonances. When detected in the 15NCIDNP spectra of the decomposition products of diazonium ions (5, 6) as well as azo compounds ( 7)) the signal has been assigned either to dinitrogen (6, 7) or to a terminal diazonium nitrogen (5). This work is in general agreement with our own observations over a period of years which indicate that the signal arises from dissolved dinitrogen. We have measured the 14N chemical shift of dissolved N2 in a number of solvents at 25°C and have also determined the T, and T2 relaxation times under a variety of conditions in solvents of different viscosity. This Note is concerned with a discussion of these 14N NMR observations and with the determination of the correlation time of dissolved dinitrogen which permits the determination of both the enthalpy and the entropy of activation via the Eyring equation. These results will be compared with earlier reported data regarding the chemical shift and relaxation of liquid nitrogen obtained under a variety of conditions ( 9-12). All spectra were obtained on a Bruker AM-400 wide-bore NMR spectrometer operating in the FT mode at a frequency of 28.9 MHz for 14N and 40.5 MHz for 15N, using a 10 mm broadband probe. Typical conditions for the acquisition of 14N spectra

  • 335.
    Medrano-Gracia, Pau
    et al.
    Dept. Anatomy with Radiology, University of Auckland, New Zealand.
    Ormiston, John
    Auckland Heart Group, Auckland, New Zealand.
    Webster, Mark
    Auckland City Hospital, Auckland, New Zealand.
    Beier, Susann
    Dept. Anatomy with Radiology, University of Auckland, New Zealand.
    Ellis, Chris
    Auckland Heart Group, Auckland, New Zealand.
    Wang, Chunliang
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Young, Alistair A
    Dept. Anatomy with Radiology, University of Auckland, New Zealand.
    Cowan, Brett R
    Dept. Anatomy with Radiology, University of Auckland, New Zealand.
    Construction of a coronary artery atlas from CT angiography.2014In: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2014, Springer, 2014, Vol. 8674, no 2014, p. 513-520Conference paper (Refereed)
    Abstract [en]

    Describing the detailed statistical anatomy of the coronary artery tree is important for determining the aetiology of heart disease. A number of studies have investigated geometrical features and have found that these correlate with clinical outcomes, e.g. bifurcation angle with major adverse cardiac events. These methodologies were mainly two-dimensional, manual and prone to inter-observer variability, and the data commonly relates to cases already with pathology. We propose a hybrid atlasing methodology to build a population of computational models of the coronary arteries to comprehensively and accurately assess anatomy including 3D size, geometry and shape descriptors. A random sample of 122 cardiac CT scans with a calcium score of zero was segmented and analysed using a standardised protocol. The resulting atlas includes, but is not limited to, the distributions of the coronary tree in terms of angles, diameters, centrelines, principal component shape analysis and cross-sectional contours. This novel resource will facilitate the improvement of stent design and provide a reference for hemodynamic simulations, and provides a basis for large normal and pathological databases.

  • 336.
    Mellergård, Johan
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Neurology.
    Tisell, Anders
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Blystad, Ida
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Grönqvist, Anders
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Blennow,, K.
    Clinical Neurochemistry Laboratory, Institution of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, Sahlgrenska Academy, University of Gothenburg, Sweden.
    Olsson,, B.
    Clinical Neurochemistry Laboratory, Institution of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, Sahlgrenska Academy, University of Gothenburg.
    Dahle, Charlotte
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Immunology and Transfusion Medicine.
    Vrethem, Magnus
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Neurology. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Clinical Neurophysiology.
    Lundberg, Peter
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Ernerudh, Jan
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Immunology and Transfusion Medicine.
    Cerebrospinal fluid levels of neurofilament and tau correlate with brain atrophy in natalizumab-treated multiple sclerosis2017In: European Journal of Neurology, ISSN 1351-5101, E-ISSN 1468-1331, Vol. 24, no 1, p. 112-121Article in journal (Refereed)
    Abstract [en]

    Background and purpose

    Brain atrophy is related to clinical deterioration in multiple sclerosis (MS) but its association with intrathecal markers of inflammation or neurodegeneration is unclear. Our aim was to investigate whether cerebrospinal fluid (CSF) markers of inflammation or neurodegeneration are associated with brain volume change in natalizumab-treated MS and whether this change is reflected in non-lesional white matter metabolites.

    Methods

    About 25 patients with natalizumab-treated MS were followed for 3 years with assessment of percentage brain volume change (PBVC) and absolute quantification of metabolites with proton magnetic resonance spectroscopy (1H MRS). Analyses of inflammatory [interleukin 1β (IL-1β), IL-6, C-X-C motif chemokine 8 (CXCL8), CXCL10, CXCL11, C-C motif chemokine 22] and neurodegenerative [neurofilament light protein (NFL), glial fibrillary acidic protein, myelin basic protein, tau proteins] markers were done at baseline and 1-year follow-up.

    Results

    The mean decline in PBVC was 3% at the 3-year follow-up, although mean 1H MRS metabolite levels in non-lesional white matter were unchanged. CSF levels of NFL and tau at baseline correlated negatively with PBVC over 3 years (r = −0.564, P = 0.012, and r = −0.592, P = 0.010, respectively).

    Conclusions

    A significant 3-year whole-brain atrophy was not reflected in mean metabolite change of non-lesional white matter. In addition, our results suggest that CSF levels of NFL and tau correlate with brain atrophy development and may be used for evaluating treatment response in inflammatory active MS.

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  • 337.
    Mendrik, Adrienne M.
    et al.
    University of Medical Centre Utrecht, Netherlands.
    Vincken, Koen L.
    University of Medical Centre Utrecht, Netherlands.
    Kuijf, Hugo J.
    University of Medical Centre Utrecht, Netherlands.
    Breeuwer, Marcel
    Philips Healthcare, Netherlands; Eindhoven University of Technology, Netherlands.
    Bouvy, Willem H.
    University of Medical Centre Utrecht, Netherlands.
    de Bresser, Jeroen
    University of Medical Centre Utrecht, Netherlands.
    Alansary, Amir
    University of Louisville, KY 40292 USA.
    de Bruijne, Marleen
    Erasmus MC, Netherlands; Erasmus MC, Netherlands; University of Copenhagen, Denmark.
    Carass, Aaron
    Johns Hopkins University, MD 21218 USA.
    El-Baz, Ayman
    University of Louisville, KY 40292 USA.
    Jog, Amod
    Johns Hopkins University, MD 21218 USA.
    Katyal, Ranveer
    LNM Institute Informat Technology, India.
    Khan, Ali R.
    Robarts Research Institute, Canada; University of Western Ontario, Canada.
    van der Lijn, Fedde
    Erasmus MC, Netherlands; Erasmus MC, Netherlands.
    Mahmood, Qaiser
    Chalmers, Sweden.
    Mukherjee, Ryan
    Johns Hopkins University, MD 20723 USA.
    van Opbroek, Annegreet
    Erasmus MC, Netherlands; Erasmus MC, Netherlands.
    Paneri, Sahil
    LNM Institute Informat Technology, India.
    Pereira, Sergio
    University of Minho, Portugal.
    Persson, Mikael
    Chalmers, Sweden.
    Rajchl, Martin
    Robarts Research Institute, Canada; University of London Imperial Coll Science Technology and Med, England.
    Sarikaya, Duygu
    SUNY Buffalo, NY 14260 USA.
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Silva, Carlos A.
    University of Minho, Portugal.
    Vrooman, Henri A.
    Erasmus MC, Netherlands; Erasmus MC, Netherlands.
    Vyas, Saurabh
    Johns Hopkins University, MD 20723 USA.
    Wang, Chunliang
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Zhao, Liang
    SUNY Buffalo, NY 14260 USA.
    Jan Biessels, Geert
    University of Medical Centre Utrecht, Netherlands.
    Viergever, Max A.
    University of Medical Centre Utrecht, Netherlands.
    MRBrainS Challenge: Online Evaluation Framework for Brain Image Segmentation in 3T MRI Scans2015In: Computational Intelligence and Neuroscience, ISSN 1687-5265, E-ISSN 1687-5273, article id 813696Article in journal (Refereed)
    Abstract [en]

    Many methods have been proposed for tissue segmentation in brain MRI scans. The multitude of methods proposed complicates the choice of one method above others. We have therefore established the MRBrainS online evaluation framework for evaluating (semi) automatic algorithms that segment gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) on 3T brain MRI scans of elderly subjects (65-80 y). Participants apply their algorithms to the provided data, after which their results are evaluated and ranked. Full manual segmentations of GM, WM, and CSF are available for all scans and used as the reference standard. Five datasets are provided for training and fifteen for testing. The evaluated methods are ranked based on their overall performance to segment GM, WM, and CSF and evaluated using three evaluation metrics (Dice, H95, and AVD) and the results are published on the MRBrainS13 website. We present the results of eleven segmentation algorithms that participated in the MRBrainS13 challenge workshop at MICCAI, where the framework was launched, and three commonly used freeware packages: FreeSurfer, FSL, and SPM. The MRBrainS evaluation framework provides an objective and direct comparison of all evaluated algorithms and can aid in selecting the best performing method for the segmentation goal at hand.

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  • 338.
    Middleton, Michael
    et al.
    Department of Radiology, University of California, San Diego, CA, USA.
    Haufe, William
    Department of Radiology, University of California, San Diego, CA, USA.
    Hooker, Jonathan
    Department of Radiology, University of California, San Diego, CA, USA.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Romu, Thobias
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Tunón, Patrik
    Advanced MR Analytics AB, Linköping.
    Hamilton, Gavin
    Department of Radiology, University of California, San Diego, CA.
    Wolfson, Tanya
    Computational and Applied Statistics Laboratory (CASL), San Diego Supercomputing Center (SDSC), University of California, San Diego, CA.
    Gamst, Anthony
    Computational and Applied Statistics Laboratory (CASL), San Diego Supercomputing Center (SDSC), University of California, San Diego, CA.
    Loomba, Rohit
    3Department of Medicine (Division of Gastroenterology and Hepatology), University of California, San Diego, CA.
    Sirlin, Claude
    Department of Radiology, University of California, San Diego, CA.
    Quantifying Abdominal Adipose Tissue and Thigh Muscle Volume and Hepatic Proton Density Fat Fraction: Repeatability and Accuracy of an MR Imaging–based, Semiautomated Analysis Method2017In: Radiology, ISSN 0033-8419, E-ISSN 1527-1315, Vol. 283, no 2, p. 438-449Article in journal (Refereed)
    Abstract [en]

    Purpose

    The purpose of this study was to determine the repeatability and accuracy of an   commercially available (Advanced MR Analytics [AMRA®]; Linköping, Sweden) magnetic resonance imaging (MRI)-based, semi-automated method to quantify abdominal adipose tissue and thigh muscle volume as well as hepatic proton density fat fraction (PDFF)

    Materials and Methods

    This prospective study was approved by an institutional review board (IRB) and was Health Insurance Portability and Accountability Act (HIPAA) compliant. All subjects provided written informed consent. Inclusion criteria were age ≥ 18 years, and willingness to participate. Exclusion criteria were contraindication to MRI. Three-dimensional, T1-weighted, dual-echo body-coil images were acquired from base of skull to knees at 3T, twice before and once after taking subjects off the scanner table (total of three acquisitions). Source images were reconstructed offline to generate water, and calibrated fat images where pure adipose tissue has unit value and absence of adipose tissue has zero value. Abdominal adipose tissues and thigh muscles were segmented, and their volumes estimated using AMRA  a semi-automated analysis method and, as a reference standard, manually. Hepatic PDFF was estimated using a confounder-corrected chemical-shift encoded MRI method with hybrid complex-magnitude reconstruction., and, as a reference standard, with magnetic resonance spectroscopy (MRS). Tissue volume and hepatic PDFF intra- and inter-examination repeatability was assessed by intraclass correlation (ICC) and coefficient of variation (CV) analysis. Tissue volume and hepatic PDFF accuracies were assessed by linear regression using their respective reference standards.

    Results

    Twenty adult subjects were enrolled (18 female, age range 25 - 76 yrs, body mass index range 19.3 to 43.9 kg/m2). Adipose and thigh muscle tissue volumes estimated using the semi-automated analysis method had intra-and inter-examination ICCs between 0.996 and 0.998, and CVs between 1.5 and 3.6%. For hepatic MRI PDFF, intra- and inter-examination ICCs were ≥ 0.994 and CVs, ≤ 7.3%. Agreement between semi-automated and manual volume estimates, and between MRI and MRS hepatic PDFF estimates, was high, with regression slopes and intercepts not significantly different from the identity line (all p’s > 0.05), and R2’s between 0.744 and 0.994.

    Conclusions

    This MRI-based, semi-automated method provides high repeatability, and high accuracy for estimating abdominal adipose tissue and thigh muscle volumes, and hepatic PDFF.

  • 339.
    Middleton, Michael
    et al.
    Department of Radiology, University of California, San Diego, San Diego, CA, United States.
    Haufe, William
    Department of Radiology, University of California, San Diego, San Diego, CA, United States.
    Hooker, Jonathan
    Department of Radiology, University of California, San Diego, San Diego, CA, United States.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Faculty of Science & Engineering. Advanced MR Analytics AB, Linköping, Sweden.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Advanced MR Analytics AB, Linköping, Sweden.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Faculty of Science & Engineering. Advanced MR Analytics AB, Linköping, Sweden.
    Tunón, Patrik
    Advanced MR Analytics AB, Linköping, Sweden.
    Szeverenyi, Nick
    Department of Radiology, University of California, San Diego, San Diego, CA, United States.
    Hamilton, Gavin
    Department of Radiology, University of California, San Diego, San Diego, CA, United States.
    Wolfson, Tanya
    Department of Radiology, University of California, San Diego, San Diego, CA, United States; Computational and Applied Statistics Laboratory (CASL), University of California, San Diego, San Diego, CA, United States.
    Gamst, Anthony
    Department of Radiology, University of California, San Diego, San Diego, CA, United States; Computational and Applied Statistics Laboratory (CASL), University of California, San Diego, San Diego, CA, United States.
    Loomba, Rohit
    Department of Medicine, University of California, San Diego, San Diego, CA, United States.
    Sirlin, Claude B.
    Department of Radiology, University of California, San Diego, San Diego, CA, United States.
    Repeatability and accuracy of a novel, MRI-based, semi-automated analysis method for quantifying abdominal adipose tissue and thigh muscle volumes2016Conference paper (Other academic)
    Abstract [en]

    Current MRI methods to estimate body tissue compartment volumes rely on manual segmentation, which is laborious, expensive, not widely available outside specialized centers, and not standardized. To address these concerns, a novel, semi-automated image analysis method has been developed. Image acquisition takes about six minutes, and uses widely available MRI pulse sequences. We found that this method permits comprehensive body compartment analysis and provides high repeatability and accuracy. Current and future clinical and drug development studies may benefit from this methodology, as may clinical settings where monitoring change in these measures is desired.

  • 340.
    Mirdell, Robin
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in West Östergötland.
    Farnebo, Simon
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Hand and Plastic Surgery.
    Sjöberg, Folke
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Hand and Plastic Surgery.
    Tesselaar, Erik
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Medical radiation physics. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Accuracy of laser speckle contrast imaging in the assessment of pediatric scald wounds2018In: Burns, ISSN 0305-4179, E-ISSN 1879-1409, Vol. 44, no 1, p. 90-98Article in journal (Refereed)
    Abstract [en]

    Background: Changes in microvascular perfusion in scalds in children during the first four days, measured with laser speckle contrast imaging (LSCI), are related to the time to healing and need for surgical intervention. The aim of this study was to determine the accuracy (sensitivity and specificity) of LSCI on different days after injury in the prediction of healing outcome and if the accuracy can be improved by combining an early and a late measurement. Also, the accuracy of LSCI was compared with that of clinical assessment. Methods: Perfusion was measured between 0-24h and between 72-96h using LSCI in 45 children with scalds. On the same occasions, burn surgeons assessed the burns as healing amp;lt; 14days or healing amp;gt; 14days/surgery. Receiver operating characteristic (ROC) curves were constructed for the early and late measurement and for the double measurement (DM) using two different methods. Results: Sensitivity and specificity were 92.3% (95% CI: 64.0-99.8%) and 78.3% (95% CI: 69.985.3%) between 0-24h, 100% (95% CI: 84.6-100%) and 90.4% (95% CI: 83.8-94.9%) between 72-96h, and was 100% (95% CI: 59.0-100%) and 100% (95% CI: 95.1-100%) when combining the two measurements into a modified perfusion trend. Clinical assessment had an accuracy of 67%, Cohens k=0.23. Conclusion: The perfusion in scalds between 72-96h after injury, as measured using LSCI, is highly predictive of healing outcome in scalds when measured. The predictive value can be further improved by incorporating an early perfusion measurement within 24h after injury. (C) 2017 Elsevier Ltd and ISBI. All rights reserved.

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  • 341.
    Mirdell, Robin
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Hand and Plastic Surgery.
    Lemstra-Idsardi, Aukje Nienke
    University of Twente, Enschede, Netherlands.
    Farnebo, Simon
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Hand and Plastic Surgery.
    Tesselaar, Erik
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Medical radiation physics. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Data on microcirculatory perfusion dips in the resting nail bed2018In: Data in Brief, E-ISSN 2352-3409, Vol. 21, p. 1232-1235Article in journal (Refereed)
    Abstract [en]

    This article contains the raw data from the article entitled: "The presence of synchronized perfusion dips in the microcirculation of the resting nail bed" Mirdell et al. (in press). A laser speckle contrast imager (LSCI) was used to make a total of 21 recordings of the perfusion in the resting nail bed of 10 healthy test subjects. The first 10 recordings were acquired after 5?min of acclimatization. An additional 10 recordings were acquired in the same test subjects, after 20?min of acclimatization. In the last recording, a digital nerve block was applied to the left dig III. The data show the presence of highly irregular perfusion variations, a phenomenon we like to call perfusion dips. The data also show how the perfusion dips can be abolished through a digital nerve block. An algorithm for the quantification of the perfusion dips is included in the data.

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  • 342.
    Moberg, A. B.
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Primary Health Care in Central County. Kärna Vårdcent, Linkoping, Sweden.
    Taleus, U.
    Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Primary Health Care in Central County. Ljungsbro Vårdcent, Sweden.
    Garvin, Peter
    Linköping University, Department of Medical and Health Sciences. Region Östergötland, Local Health Care Services in West Östergötland, Research & Development Unit in Local Health Care. Linköping University, Faculty of Medicine and Health Sciences.
    Fransson, Sven Göran
    Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Falk, Magnus
    Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in West Östergötland, Research & Development Unit in Local Health Care.
    Community-acquired pneumonia in primary care: clinical assessment and the usability of chest radiography2016In: Scandinavian Journal of Primary Health Care, ISSN 0281-3432, E-ISSN 1502-7724, Vol. 34, no 1, p. 21-27Article in journal (Refereed)
    Abstract [en]

    Objectives: To investigate the diagnostic value of different clinical and laboratory findings in pneumonia and to explore the association between the doctors degree of suspicion and chest X-ray (CXR) result and to evaluate whether or not CXR should be used routinely in primary care, when available. Design: A three-year prospective study was conducted between September 2011 and December 2014. Setting: Two primary care settings in Linkoping, Sweden. Subjects: A total of 103 adult patients with suspected pneumonia in primary care. Main outcome measures: The physicians recorded results of a standardized medical physical examination, including laboratory results, and rated their suspicion into three degrees. The outcome of the diagnostic variables and the degree of suspicion was compared with the result of CXR. Results: Radiographic pneumonia was reported in 45% of patients. When the physicians were sure of the diagnosis radiographic pneumonia was found in 88% of cases (p&lt;0.001), when quite sure the frequency of positive CXR was 45%, and when not sure 28%. Elevated levels of C-reactive protein (CRP)50mg/L were associated with the presence of radiographic pneumonia when the diagnosis was suspected (p&lt;0.001). Conclusion: This study indicates that CXR can be useful if the physician is not sure of the diagnosis, but when sure one can rely on ones judgement without ordering CXR.

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  • 343.
    Morales Drissi, Natasha
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Romu, Thobias
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV). AMRA Med AB, Linkoping, Sweden.
    Landtblom, Anne-Marie
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Neurology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Uppsala Univ, Sweden.
    Szakacs, Attila
    Univ Gothenburg, Sweden.
    Hallbook, Tove
    Univ Gothenburg, Sweden.
    Darin, Niklas
    Univ Gothenburg, Sweden.
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV). AMRA Med AB, Linkoping, Sweden.
    Dahlqvist Leinhard, Olof
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV). AMRA Med AB, Linkoping, Sweden.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Unexpected Fat Distribution in Adolescents With Narcolepsy2018In: Frontiers in Endocrinology, ISSN 1664-2392, E-ISSN 1664-2392, Vol. 9, article id 728Article in journal (Refereed)
    Abstract [en]

    Narcolepsy type 1 is a chronic sleep disorder with significantly higher BMI reported in more than 50% of adolescent patients, putting them at a higher risk for metabolic syndrome in adulthood. Although well-documented, the body fat distribution and mechanisms behind weight gain in narcolepsy are still not fully understood but may be related to the loss of orexin associated with the disease. Orexin has been linked to the regulation of brown adipose tissue (BAT), a metabolically active fat involved in energy homeostasis. Previous studies have used BMI and waist circumference to characterize adipose tissue increases in narcolepsy but none have investigated its specific distribution. Here, we examine adipose tissue distribution in 19 adolescent patients with narcolepsy type 1 and compare them to 17 of their healthy peers using full body magnetic resonance imaging (MRI). In line with previous findings we saw that the narcolepsy patients had more overall fat than the healthy controls, but contrary to our expectations there were no group differences in supraclavicular BAT, suggesting that orexin may have no effect at all on BAT, at least under thermoneutral conditions. Also, in line with previous reports, we observed that patients had more total abdominal adipose tissue (TAAT), however, we found that they had a lower ratio between visceral adipose tissue (VAT) and TAAT indicating a relative increase of subcutaneous abdominal adipose tissue (ASAT). This relationship between VAT and ASAT has been associated with a lower risk for metabolic disease. We conclude that while weight gain in adolescents with narcolepsy matches that of central obesity, the lower VAT ratio may suggest a lower risk of developing metabolic disease.

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  • 344.
    Morales Drissi, Natasha
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Szakacs, Attila
    Univ Gothenburg, Sweden.
    Witt, Suzanne Tyson
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Wretman, Anna
    Linköping University, Department of Behavioural Sciences and Learning, Disability Research. Linköping University, Faculty of Arts and Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Neurology in Linköping.
    Ulander, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Clinical Neurophysiology.
    Stahlbrandt, Henriettae
    Highland Hosp, Sweden.
    Darin, Niklas
    Univ Gothenburg, Sweden.
    Hallbook, Tove
    Univ Gothenburg, Sweden.
    Landtblom, Anne-Marie
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Neurology in Linköping. Uppsala Univ, Sweden.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).