liu.seSearch for publications in DiVA
Change search
Refine search result
1234567 51 - 100 of 511
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51.
    Blystad, Ida
    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). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Håkansson, I
    Tisell, Anders
    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). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Ernerudh, J
    Smedby, Örjan
    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). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    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). 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.
    Larsson, EM
    Quantitative MRI for the evaluation of active MS-lesions without gadolinium based contrast agent.2014Conference paper (Other academic)
  • 52.
    Blystad, Ida
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Håkansson, Irene
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
    Tisell, Anders
    Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    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.
    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).
    Lundberg, Peter
    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).
    Larsson, Elna-Marie
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Uppsala University, Sweden.
    Quantitative MRI for Analysis of Active Multiple Sclerosis Lesions without Gadolinium-Based Contrast Agent2016In: American Journal of Neuroradiology, ISSN 0195-6108, E-ISSN 1936-959X, Vol. 37, no 1, p. 94-100Article in journal (Refereed)
    Abstract [en]

    BACKGROUND AND PURPOSE: Contrast-enhancing MS lesions are important markers of active inflammation in the diagnostic work-up of MS and in disease monitoring with MR imaging. Because intravenous contrast agents involve an expense and a potential risk of adverse events, it would be desirable to identify active lesions without using a contrast agent. The purpose of this study was to evaluate whether pre-contrast injection tissue-relaxation rates and proton density of MS lesions, by using a new quantitative MR imaging sequence, can identify active lesions. MATERIALS AND METHODS: Forty-four patients with a clinical suspicion of MS were studied. MR imaging with a standard clinical MS protocol and a quantitative MR imaging sequence was performed at inclusion (baseline) and after 1 year. ROIs were placed in MS lesions, classified as nonenhancing or enhancing. Longitudinal and transverse relaxation rates, as well as proton density were obtained from the quantitative MR imaging sequence. Statistical analyses of ROI values were performed by using a mixed linear model, logistic regression, and receiver operating characteristic analysis. RESULTS: Enhancing lesions had a significantly (P < .001) higher mean longitudinal relaxation rate (1.22 0.36 versus 0.89 +/- 0.24), a higher mean transverse relaxation rate (9.8 +/- 2.6 versus 7.4 +/- 1.9), and a lower mean proton density (77 +/- 11.2 versus 90 +/- 8.4) than nonenhancing lesions. An area under the receiver operating characteristic curve value of 0.832 was obtained. CONCLUSIONS: Contrast-enhancing MS lesions often have proton density and relaxation times that differ from those in nonenhancing lesions, with lower proton density and shorter relaxation times in enhancing lesions compared with nonenhancing lesions.

  • 53.
    Blystad, Ida
    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). Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Warntjes, Marcel Jan Bertus
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    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). KTH Royal Institute Technology, Sweden.
    Lundberg, Peter
    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).
    Larsson, Elna-Marie
    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). Uppsala University, Sweden.
    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).
    Quantitative MRI for analysis of peritumoral edema in malignant gliomas2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 5, article id e0177135Article in journal (Refereed)
    Abstract [en]

    Background and purpose Damage to the blood-brain barrier with subsequent contrast enhancement is a hallmark of glioblastoma. Non-enhancing tumor invasion into the peritumoral edema is, however, not usually visible on conventional magnetic resonance imaging. New quantitative techniques using relaxometry offer additional information about tissue properties. The aim of this study was to evaluate longitudinal relaxation R-1, transverse relaxation R-2, and proton density in the peritumoral edema in a group of patients with malignant glioma before surgery to assess whether relaxometry can detect changes not visible on conventional images. Methods In a prospective study, 24 patients with suspected malignant glioma were examined before surgery. A standard MRI protocol was used with the addition of a quantitative MR method (MAGIC), which measured R-1, R-2, and proton density. The diagnosis of malignant glioma was confirmed after biopsy/surgery. In 19 patients synthetic MR images were then created from the MAGIC scan, and ROIs were placed in the peritumoral edema to obtain the quantitative values. Dynamic susceptibility contrast perfusion was used to obtain cerebral blood volume (rCBV) data of the peritumoral edema. Voxel-based statistical analysis was performed using a mixed linear model. Results R-1, R-2, and rCBV decrease with increasing distance from the contrast-enhancing part of the tumor. There is a significant increase in R1 gradient after contrast agent injection (Pamp;lt;.0001). There is a heterogeneous pattern of relaxation values in the peritumoral edema adjacent to the contrast-enhancing part of the tumor. Conclusion Quantitative analysis with relaxometry of peritumoral edema in malignant gliomas detects tissue changes not visualized on conventional MR images. The finding of decreasing R-1 and R-2 means shorter relaxation times closer to the tumor, which could reflect tumor invasion into the peritumoral edema. However, these findings need to be validated in the future.

    Download full text (pdf)
    fulltext
  • 54.
    Bonzon, Jerome
    et al.
    University of Bern, Switzerland.
    Schoen, Corinna A.
    University of Bern, Switzerland.
    Schwendener, Nicole
    University of Bern, Switzerland.
    Zech, Wolf-Dieter
    University of Bern, Switzerland.
    Kara, Levent
    Triemli Hospital, Switzerland.
    Persson, 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 Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Jackowski, Christian
    University of Bern, Switzerland.
    Rigor mortis at the myocardium investigated by post-mortem magnetic resonance imaging2015In: Forensic Science International, ISSN 0379-0738, E-ISSN 1872-6283, Vol. 257, p. 93-97Article in journal (Refereed)
    Abstract [en]

    Introduction: Post-mortem cardiac MR exams present with different contraction appearances of the left ventricle in cardiac short axis images. It was hypothesized that the grade of post-mortem contraction may be related to the post-mortem interval (PMI) or cause of death and a phenomenon caused by internal rigor mortis that may give further insights in the circumstances of death. Method and materials: The cardiac contraction grade was investigated in 71 post-mortem cardiac MR exams (mean age at death 52 y, range 12-89 y; 48 males, 23 females). In cardiac short axis images the left ventricular lumen volume as well as the left ventricular myocardial volume were assessed by manual segmentation. The quotient of both (LVQ) represents the grade of myocardial contraction. LVQ was correlated to the PMI, sex, age, cardiac weight, body mass and height, cause of death and pericardial tamponade when present. In cardiac causes of death a separate correlation was investigated for acute myocardial infarction cases and arrhythmic deaths. Results: LVQ values ranged from 1.99 (maximum dilatation) to 42.91 (maximum contraction) with a mean of 15.13. LVQ decreased slightly with increasing PMI, however without significant correlation. Pericardial tamponade positively correlated with higher LVQ values. Variables such as sex, age, body mass and height, cardiac weight and cause of death did not correlate with LVQ values. There was no difference in LVQ values for myocardial infarction without tamponade and arrhythmic deaths. Conclusion: Based on the observation in our investigated cases, the phenomenon of post-mortem myocardial contraction cannot be explained by the influence of the investigated variables, except for pericardial tamponade cases. Further research addressing post-mortem myocardial contraction has to focus on other, less obvious factors, which may influence the early post-mortem phase too. (C) 2015 Elsevier Ireland Ltd. All rights reserved.

  • 55.
    Borga, Magnus
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Andersson, Thord
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    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.
    Semi-Supervised Learning of Anatomical Manifolds for Atlas-Based Segmentation of Medical Images2016In: Proceedings of the 23rd International Conference on Pattern Recognition (ICPR), IEEE Computer Society, 2016, p. 3146-3149Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel method for atlas-based segmentation of medical images. The method uses semi- supervised learning of a graph describing a manifold of anatom- ical variations of whole-body images, where unlabelled data are used to find a path with small deformations from the labelled atlas to the target image. The method is evaluated on 36 whole-body magnetic resonance images with manually segmented livers as ground truth. Significant improvement (p < 0.001) was obtained compared to direct atlas-based registration. 

  • 56.
    Borga, Magnus
    et al.
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Dahlqvist, Leinhard Olof
    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). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    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). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Improvement in Magnetic Resonance Imaging Relating to Correction of Chemical Shift Artifact and Intensity Inhomogeneity2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Present invention discloses systems and methods for improvement of magnetic resonance images. Correction of a chemical shift artefact in an image acquired from a magnetic resonance imaging system is obtained by a system and a method involving iterative - compensation for the misregistration effect in an image domain. Correction of an intensity inhomogeneity in such images is obtained by a system and a method involving locating voxels corresponding to pure adipose tissue and estimating correction field from these points.

  • 57.
    Borga, Magnus
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Thomas, E. Louise
    Department of Life Sciences Faculty of Science and Technology University of Westminster, London, United Kingdom.
    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).
    Rosander, Johannes
    Advanced MR Analytics AB, Linköping, Sweden.
    Fitzpatrick, Julie
    Department of Life Sciences Faculty of Science and Technology University of Westminster, London, United Kingdom.
    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.
    Bell, Jimmy D
    Department of Life Sciences Faculty of Science and Technology University of Westminster, London, United Kingdom.
    Validation of a Fast Method for Quantification of Intra-abdominal and Subcutaneous Adipose Tissue for Large Scale Human Studies2015In: NMR in Biomedicine, ISSN 1099-1492, Vol. 28, no 12, p. 1747-1753Article in journal (Refereed)
    Abstract [en]

    Central obesity is the hallmark of a number of non-inheritable disorders. The advent of imaging techniques such as magnetic resonance imaging (MRI) has allowed for a fast and accurate assessment of body fat content and distribution. However, image analysis continues to be one of the major obstacles for the use of MRI in large scale studies. In this study we assess the validity of the recently proposed fat-muscle-quantitation-system (AMRATM Profiler) for the quantification of intra-abdominal adipose tissue (IAAT) and abdominal subcutaneous adipose tissue (ASAT) from abdominal MR images.  Abdominal MR images were acquired from 23 volunteers with a broad range of BMIs and analysed using SliceOmatic, the current gold-standard, and the AMRATM Profiler based on a non-rigid image registration of a library of segmented atlases. The results show that there was a highly significant correlation between the fat volumes generated by both analysis methods, (Pearson correlation r = 0.97 p<0.001), with the AMRATM Profiler analysis being significantly faster (~3 mins) than the conventional SliceOmatic approach (~40 mins). There was also excellent agreement between the methods for the quantification of IAAT (AMRA 4.73 ± 1.99 vs SliceOmatic 4.73 ± 1.75 litres, p=0.97). For the AMRATM Profiler analysis, the intra-observer coefficient of variation was 1.6 % for IAAT and 1.1 % for ASAT, the inter-observer coefficient of variation was 1.4 % for IAAT and 1.2 % for ASAT, the intra-observer correlation was 0.998 for IAAT and 0.999 for ASAT, and the inter-observer correlation was 0.999 for both IAAT and ASAT. These results indicate that precise and accurate measures of body fat content and distribution can be obtained in a fast and reliable form by the AMRATM Profiler, opening up the possibility of large-scale human phenotypic studies.

  • 58.
    Borga, Magnus
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Virtanen, Kirsi A.
    Turku PET Centre, University of Turku, Finland.
    Romu, Thobias
    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). 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.
    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 Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Nuutila, Pirjo
    Turku PET Centre, University of Turku, Finland.
    Enerbäck, Sven
    Department of Biomedicine, University of Gothenburg, Sweden.
    Brown adipose tissue in humans: detection and functional analysis using PET (Positron Emission Tomography), MRI (Magnetic Resonance Imaging), and DECT (Dual Energy Computed Tomography)2014In: Methods in Enzymology: Methods of Adipose Tissue Biology / [ed] Ormond MacDougald, Elsevier, 2014, 1, p. 141-159Chapter in book (Other academic)
    Abstract [en]

    Research with the aim to translate findings of the beneficial effects induced by brown adipose tissue (BAT) on metabolism, as seen in various non-human experimental systems to also include human metabolism requires tools that accurately measure how BAT influences human metabolism. This review sets out to discuss such techniques, how they can be used, what they can measure and also some of their limitations. The focus is on detection and functional analysis of human BAT and how this can be facilitated by applying advanced imaging technology such as:  PET (Positron Emission Tomography), MRI (Magnetic Resonance Imaging), and DECT (Dual Energy Computed Tomography).

    Download full text (pdf)
    fulltext
  • 59.
    Borga, Magnus
    et al.
    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).
    West, Janne
    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.
    Bell, Jimmy
    Westminster University, London, UK.
    Harvey, Nicholas
    University of Southampton, IK.
    Romu, Thobias
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Heymsfield, Steven
    Pennington Biomedical Research Center, Baton Rouge, LA, US.
    Dahlqvist Leinhard, Olof
    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. Advanced MR Analytics AB, Linköping, Sweden.
    Advanced body composition assessment: From body mass index to body composition profiling2018In: Journal of Investigative Medicine, ISSN 1081-5589, E-ISSN 1708-8267, Vol. 66, p. 887-895Article, review/survey (Refereed)
    Abstract [en]

    This paper gives a brief overview of common non-invasive techniques for body composition analysis and a more in-depth review of a body composition assessment method based on fat-referenced quantitative magnetic resonance imaging (MRI). Earlier published studies of this method are summarized, and a previously un-published validation study, based on 4.753 subjects from the UK Biobank imaging cohort, comparing the quantitative MRI method with dual-energy x-ray absorptiometry (DXA) is presented. For whole-body measurements of adipose tissue (AT) or fat and lean tissue (LT), DXA and quantitative MRI show excellent agreement with linear correlation of 0.99 and 0.97, and coefficient of variation (CV) of 4.5 % and 4.6 % for fat (computed from AT) and lean tissue respectively, but the agreement was found significantly lower for visceral adipose tissue, with a CV of more than 20 %. The additional ability of MRI to also measure muscle volumes, muscle AT infiltration and ectopic fat in combination with rapid scanning protocols and efficient image analysis tools make quantitative MRI a powerful tool for advanced body composition assessment. 

    Download full text (pdf)
    Advanced body composition assessment: From body mass index to body composition profiling
  • 60.
    Brismar, T. B.
    et al.
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Shams, S.
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Berinder, K.
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Berlin, M.
    Karolinska University Hospital, Sweden.
    Udden, J.
    Karolinska University Hospital, Sweden.
    Brismar, K.
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Ringertz, Hans
    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).
    GLUCOCORTICOIDS AND SARCOIDOSIS: A LONGITUDINAL STUDY ON THE EFFECTS ON CORTICAL AND TRABECULAR BONE2015In: Sarcoidosis Vasculitis and Diffuse Lung Diseases, ISSN 1124-0490, Vol. 32, no 1, p. 63-69Article in journal (Refereed)
    Abstract [en]

    Background: Glucocorticoid induced osteoporosis is a well-known side effect of glucocorticoid treatment. In sarcoidosis the impact on bone by glucocorticoid treatment is complex due to hormonal disturbances of calcium and vitamin-D, which by itself may cause bone loss. In this study we aimed to investigate the longitudinal impact of glucocorticoids on cortical and trabecular bone in patients with mild, recently diagnosed sarcoidosis.

    Methods: Ten patients (8 females; mean age 44 (+/- 13)) were studied during one year of glucocorticoid treatment. The assessment of mainly cortical to purely trabecular bone was made by dual X-ray absorptiometry (DXA) of the spine and hip, quantitative ultrasound of the calcaneus, and magnetic resonance relaxometry of the spine and calcaneus. Bone and hormonal measurements were performed at baseline, after 3, 6, and 12 months, and baseline, 3 weeks and 3 months, respectively.

    Results: DXA of the spine, decreased from baseline at 6 months (P=0.01). R2 of the calcaneus decreased with time (B: -3.6; P=0.03). In the females (n=8) there was a significant decrease in DXA of the spine when comparing 3 months and 6 months (P=0.03), and 3 months and 12 months (P=0.02) and a decrease in R2 of the calcaneus from baseline to 12 months (P=0.01). There was no change in hormonal levels.

    Conclusion: Treatment of initial mild sarcoidosis with dose tapered glucocorticoid therapy only mildly affects the final trabecular and cortical bone and hormone levels. Dose tapering is an important part in glucocorticoid therapy, likely contributing to the mild effects on bone observed in this study.

  • 61.
    Brolin, Gustav
    et al.
    Lund University, Sweden.
    Edenbrandt, Lars
    EQUALIS AB, Sweden; Lund University, Sweden.
    Granerus, Göran
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Olsson, Anna
    Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Afzelius, David
    EQUALIS AB, Sweden.
    Gustafsson, Agneta
    EQUALIS AB, Sweden; Karolinska University Hospital, Sweden.
    Jonsson, Cathrine
    EQUALIS AB, Sweden; Karolinska University Hospital, Sweden.
    Hagerman, Jessica
    EQUALIS AB, Sweden; Skåne University Hospital, Sweden.
    Johansson, Lena
    EQUALIS AB, Sweden; Central Hospital Karlstad, Sweden.
    Riklund, Katrine
    EQUALIS AB, Sweden; Umeå University, Sweden.
    Ljungberg, Michael
    Lund University, Sweden.
    The accuracy of quantitative parameters in Tc-99m-MAG3 dynamic renography: a national audit based on virtual image data2016In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 36, no 2, p. 146-154Article in journal (Refereed)
    Abstract [en]

    Assessment of image analysis methods and computer software used in Tc-99m-MAG3 dynamic renography is important to ensure reliable study results and ultimately the best possible care for patients. In this work, we present a national multicentre study of the quantification accuracy in Tc-99m-MAG3 renography, utilizing virtual dynamic scintigraphic data obtained by Monte Carlo-simulated scintillation camera imaging of digital phantoms with time-varying activity distributions. Three digital phantom studies were distributed to the participating departments, and quantitative evaluation was performed with standard clinical software according to local routines. The differential renal function (DRF) and time to maximum renal activity (T-max) were reported by 21 of the 28 Swedish departments performing Tc-99m-MAG3 studies as of 2012. The reported DRF estimates showed a significantly lower precision for the phantom with impaired renal uptake than for the phantom with normal uptake. The T-max estimates showed a similar trend, but the difference was only significant for the right kidney. There was a significant bias in the measured DRF for all phantoms caused by different positions of the left and right kidney in the anterior-posterior direction. In conclusion, this study shows that virtual scintigraphic studies are applicable for quality assurance and that there is a considerable uncertainty associated with standard quantitative parameters in dynamic Tc-99m-MAG3 renography, especially for patients with impaired renal function.

  • 62.
    Candela-Juan, C.
    et al.
    La Fe University of and Polytech Hospital, Spain; University of Valencia, Spain.
    Karlsson, Mattias
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Lundell, M.
    Karolinska University Hospital, Sweden; Karolinska Institute, Sweden.
    Ballester, F.
    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. Swedish Radiat Safety Author, Sweden.
    Dosimetric characterization of two radium sources for retrospective dosimetry studies2015In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 42, no 5, p. 2132-2142Article in journal (Refereed)
    Abstract [en]

    Purpose: During the first part of the 20th century, Ra-226 was the most used radionuclide for brachytherapy. Retrospective accurate dosimetry, coupled with patient follow up, is important for advancing knowledge on long-term radiation effects. The purpose of this work was to dosimetrically characterize two Ra-226 sources, commonly used in Sweden during the first half of the 20th century, for retrospective dose-effect studies. Methods: An 8 mg Ra-226 tube and a 10 mg Ra-226 needle, used at Radiumhemmet (Karolinska University Hospital, Stockholm, Sweden), from 1925 to the 1960s, were modeled in two independent Monte Carlo (MC) radiation transport codes: GEANT4 and MCNP5. Absorbed dose and collision kerma around the two sources were obtained, from which the TG-43 parameters were derived for the secular equilibrium state. Furthermore, results from this dosimetric formalism were compared with results from a MC simulation with a superficial mould constituted by five needles inside a glass casing, placed over a water phantom, trying to mimic a typical clinical setup. Calculated absorbed doses using the TG-43 formalism were also compared with previously reported measurements and calculations based on the Sievert integral. Finally, the dose rate at large distances from a Ra-226 point-like-source placed in the center of 1 m radius water sphere was calculated with GEANT4. Results: TG-43 parameters [including gL(r), F(r,theta), Lambda, and s(K)] have been uploaded in spreadsheets as additional material, and the fitting parameters of a mathematical curve that provides the dose rate between 10 and 60 cm from the source have been provided. Results from TG-43 formalism are consistent within the treatment volume with those of a MC simulation of a typical clinical scenario. Comparisons with reported measurements made with thermoluminescent dosimeters show differences up to 13% along the transverse axis of the radium needle. It has been estimated that the uncertainty associated to the absorbed dose within the treatment volume is 10%-15%, whereas uncertainty of absorbed dose to distant organs is roughly 20%-25%. Conclusions: The results provided here facilitate retrospective dosimetry studies of Ra-226 using modern treatment planning systems, which may be used to improve knowledge on long term radiation effects. It is surely important for the epidemiologic studies to be aware of the estimated uncertainty provided here before extracting their conclusions.

  • 63. Order onlineBuy this publication >>
    Carina, Stenman
    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).
    Standardized ultrasonography with cine-loop documentation: diagnostic variability in liver and kidney examinations2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Ultrasound examination of the abdomen is often a first choice at radiology departments due to the lack of ionizing radiation. For diagnostic accuracy and economic benefits there has been a need for new routines in this area that incorporate the benefits of an radiographer or sonographer performing a multitude of ultrasound examinations following strictly standardized examination protocols and documentation forms made by cine-loops that will give the radiologist access to all relevant information needed for an accurate postexamination diagnosis.

    Aim: The overall objective of this thesis was to evaluate the diagnostic variability in examinations of the kidneys and liver that use a standardized ultrasound method along with video documentation of the entire examination and off-line review by radiologists. More specifically, we wanted to compare the agreement between readers and between operators.

    Design and method: This thesis is based on four quantitative studies using standardized protocols for kidney, liver and gallbladder examinations. In paper I, including 64 patients, and paper IV, including 98 patients, the patients were prospectively enrolled and the  examinations were retrospectively reviewed. The patients in papers I and IV were examined by one radiographer (sonographer) and one radiologist during the same session. In paper I, findings using the standardized ultrasound method were compared with traditional bedside assessments by a radiologist. In paper IV, the patients were examined using only the standardized method. In paper II, including 98 patients, and in paper III, including 115 patients, the patients were examined by one sonographer using the standardized method and the examinations were reviewed by two or three radiologists.

    Results: In paper I, no significant systematic differences were found between the findings using the standardized method and the traditional bedside assessment.

    Paper II showed good intra- and inter-observer agreement between three experienced radiologists when reviewing examinations conducted using the standardized method.

    In paper III we verified good inter-observer agreement between two radiologists reviewing ultrasound examinations using the standardized technique in patients who had undergone surgery for colorectal cancer. Intravenous contrast was used and the injection of contrast medium increased the visibility of liver lesions.

    In paper IV, we observed that using a standardized cine-loop technique, there was a slightly better inter-operator agreement than inter-reader agreement.

    Conclusion: The satisfactory agreement shown in all four studies suggests that the new workflow method using standardized ultrasound examinations and stored cine-loops, performed by a radiographer or sonographer and analyzed off-line by a radiologist, is a promising technique. The results are less affected when a radiologist examiner is replaced by a radiographer or sonographer than when the reviewer is replaced by a different radiologist.

    List of papers
    1. Radiographer-acquired and radiologist-reviewed ultrasound examination: agreement with radiologist’s bedside evaluation
    Open this publication in new window or tab >>Radiographer-acquired and radiologist-reviewed ultrasound examination: agreement with radiologist’s bedside evaluation
    2011 (English)In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 52, no 1, p. 70-74Article in journal (Refereed) Published
    Abstract [en]

    Background: Growing demand for ultrasound examinations and higher quality requirements motivate searching for routines combining the diagnostic accuracy of radiologist-performed examinations with the economical advantages of sonographer-performed examinations. One possible approach is to use strictly standardized acquisition and documentation schemes that give the radiologist access to all relevant information after the examination.

    Purpose: To compare a recently introduced routine, combining acquisition by a radiographer, documentation as standardized cine-loops, and review by a radiologist (‘standardized method’), with the formerly used routine where the diagnosis is made bedside by the radiologist (‘traditional  method’).

    Material and Methods: In 64 policlinic patients, the kidneys (n ¼ 27) or the gallbladder (n ¼ 37) were examined with both the standardized and the traditional method. The radiologists’ findings of hydronephrosis, tumors, cysts, echogenicity changes, and cortical thickness (in the kidneys), and wall thickness, concrements, and polyps (in the gallbladder) were compared between the methods with respect to agreement (proportion of agreement and kappa coefficient) as well as systematic differences (McNemar’s test).

    Results: The findings at the gallbladder examination showed a median agreement of 97% (86–100%; kappa ¼ 0.64–1.00), and those at the kidney examination, an agreement of 90% (78–100%; kappa ¼ 0.69–1.00). There were no significant systematic differences between the methods.

    Conclusion: The satisfactory agreement in this preliminary study indicates that the new workflow with ultrasound examinations performed by a radiographer and analyzed off-line by a radiologist is promising, and motivates further studies.

    Place, publisher, year, edition, pages
    Informa Healthcare, 2011
    Keywords
    Ultrasound, radiographer, radiologist, comparison, diagnostic
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-67047 (URN)10.1258/ar.2010.090260 (DOI)000290498800013 ()
    Available from: 2011-03-25 Created: 2011-03-25 Last updated: 2017-12-11Bibliographically approved
    2. Do Radiologists Agree on Findings in Radiographer-Acquired Sonographic Examinations?
    Open this publication in new window or tab >>Do Radiologists Agree on Findings in Radiographer-Acquired Sonographic Examinations?
    Show others...
    2013 (English)In: Journal of ultrasound in medicine, ISSN 0278-4297, E-ISSN 1550-9613, Vol. 32, no 3, p. 513-518Article in journal (Refereed) Published
    Abstract [en]

    OBJECTIVES:

    Sonographic examinations are usually regarded as observer dependent, but a recently introduced method using documentation with cine loops acquired in a standardized way attempts to address this problem. The aim of this study was to evaluate the intraobserver and interobserver agreement of sonographic liver examinations using strictly standardized examination protocols with cine loop documentation.

    METHODS:

    Ninety-eight outpatients were examined by a radiographer using the standardized method. Three radiologists, each with 10 to 20 years of experience in sonography, reviewed the cine loops retrospectively. After 4 weeks, the review was repeated; the 3 radiologists were blinded to the initial reading. The κ coefficient was used to analyze intraobserver and interobserver agreement, and agreement in percent was also calculated.

    RESULTS:

    The intraobserver agreement was highest for concrements in the gallbladder (κ= 0.91-0.96) and lowest when assessing the need for further examination (κ = 0.38-0.64). For increased liver echogenicity, κ varied between 0.73 and 0.92 and for skip areas between 0.73 and 0.90. The interobserver agreement was also highest for concrements in the gallbladder (κ = 0.84-1.00) and lowest for the need for further examination (κ = -0.12-0.46). For most other findings, substantial intraobserver agreement was found.

    CONCLUSIONS:

    For sonographic examinations performed according to a standardized examination protocol by a radiographer and viewed by an experienced radiologist, good interobserver agreement was found, except for judgments of the need for further examinations.

    Place, publisher, year, edition, pages
    American Institute of Ultrasound in Medicine, 2013
    Keywords
    agreement, liver examination, observer, radiologist, sonography
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-90759 (URN)10.7863/jum.2013.32.3.513 (DOI)000315835900016 ()23443192 (PubMedID)
    Note

    On the day of the defence date of the Ph.D. Thesis the status of this artilce was Manuscript and the title was Do radiologists agree on findings in radiographer-acquired ultrasound liver examinations?

    Available from: 2013-04-05 Created: 2013-04-05 Last updated: 2017-12-06
    3. Visualization of liver lesions in standardized video-documented ultrasonography - inter-observer agreement and effect of contrast injection
    Open this publication in new window or tab >>Visualization of liver lesions in standardized video-documented ultrasonography - inter-observer agreement and effect of contrast injection
    Show others...
    2015 (English)In: Medical ultrasonography, ISSN 1844-4172, E-ISSN 2066-8643, Vol. 17, no 4, p. 437-443Article in journal (Refereed) Published
    Abstract [en]

    The aim of this study was to evaluate the inter-observer agreement and effect of contrast injection on the visibility of liver lesions by radiologists reviewing ultrasound examinations acquired by a radiographer using a standardized examination protocol. Material and method: A retrospective review was conducted by two radiologists, independently of each other, of 115 ultrasound examinations of the liver with standardized examination protocols between January 2008 and December 2012. All patients included in the study had undergone surgery for colorectal cancer. Patients attending the two-year follow-up were included. Results: Focal findings, the most common of which were cysts, were seen in 42-43 out of the 115 patients before intravenous contrast and in 46-47 patients after intravenous contrast (p=0.012). The inter-observer agreement for focal findings was 86.1% before contrast, and 90.4% after contrast (n.s.), and the corresponding kappa values were 0.72 and 0.84, respectively. Conclusion: A good inter-observer agreement between two radiologists reviewing ultrasound examinations (standardized ultrasound cine-loop method acquired by a radiographer) after surgery for colorectal cancer was obtained. Injection of contrast medium increased the visibility of liver lesions.

    Place, publisher, year, edition, pages
    Cluj-Napoca, Romania: Societatea Romana de Ultrasonografie in Medicina si Biologie, 2015
    Keywords
    liver; contrast-enhanced ultrasound; inter-observer agreement; standardized examination
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:liu:diva-123790 (URN)10.11152/mu.2013.2066.174.vis (DOI)000365549400004 ()26649336 (PubMedID)
    Available from: 2016-01-11 Created: 2016-01-11 Last updated: 2017-11-30Bibliographically approved
    4. Do radiologists agree when reviewing ultrasound examinations performed by a sonographer and a radiologist?
    Open this publication in new window or tab >>Do radiologists agree when reviewing ultrasound examinations performed by a sonographer and a radiologist?
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Background: Ultrasound examinations are usually performed by a radiologist or, in suitable cases, by a sonographer or radiographer. Standardized scanning protocols and cine-loop documentation may permit the transfer of tasks from a radiologist to a sonographer or radiographer.

    Purpose: To study the diagnostic variability in standardized ultrasound examinations of the kidney by comparing inter-reader agreement between two radiologists who reviewed examinations acquired by a sonographer and a radiologist, as well as inter-operator agreement between the sonographer and the radiologist.

    Material and methods: After approval by the local research ethics committee, 98 adult patients, aged from 18 to 92, referred for diagnostic renal sonographic examination and were prospectively enrolled. Both kidneys were imaged using standardized scanning protocols, and the entire examination was documented with cine-loops. Two radiologists reviewed the examinations for different types of pathology, including tumors, cysts, decreased cortical thickness, increased echogenicity and hydronephrosis. Inter-reader and inter-operator agreement was evaluated with kappa coefficient and intra-class correlation.

    Results: The most common finding was cysts, which were found in 32 to 40 cases. Tumors were found in three to 10 cases. With one exception, the kappa values for inter-operator agreement (0.65–1.00) were higher than those for inter-reader agreement (0.31–1.00). With two exceptions, no systematic differences between operators or between observers were found.

    Conclusion: Using a standardized cine-loop technique, we found slightly better interoperator agreement than inter-reader agreement. This suggests that it may be easier to exchange an operator than to exchange a reader.

    Keywords
    Cine-loop imaging, renal sonography, agreement
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:liu:diva-124674 (URN)
    Available from: 2016-02-09 Created: 2016-02-09 Last updated: 2016-02-10Bibliographically approved
    Download full text (pdf)
    fulltext
    Download (pdf)
    omslag
    Download (jpg)
    presentationsbild
  • 64.
    Carlsson Tedgren, Åsa
    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. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Swedish Radiation Safety Authority, Stockholm, Sweden.
    Bjerke, Hans
    Norwegian Radiation Protection Authority, Österås, Norway.
    Grindborg, Jan-Erik
    Swedish Radiation Safety Authority, Stockholm, Sweden.
    Hetland, Per-Otto
    Norwegian Radiation Protection Authority, Österås, Norway.
    Kosunen, Antti
    STUK-Radiation and Nuclear Safety Authority, Helsinki, Finland.
    Paulsen Hellebust, Taran
    Oslo University Hospital, Norway; University of Oslo, Norway .
    Persson, Linda
    Swedish Radiation Safety Authority, Stockholm, Sweden.
    Sipila, Petri
    TUK-Radiation and Nuclear Safety Authority, Helsinki, Finland.
    Comparison of high-dose-rate Ir-192 source strength measurements using equipment with traceability to different standards2014In: Brachytherapy, ISSN 1538-4721, E-ISSN 1873-1449, Vol. 13, no 4, p. 420-423Article in journal (Refereed)
    Abstract [en]

    PURPOSE:

    According to the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism used for dose calculation in brachytherapy treatment planning systems, the absolute level of absorbed dose is determined through coupling with the measurable quantity air-kerma strength or the numerically equal reference air-kerma rate (RAKR). Traceability to established standards is important for accurate dosimetry in laying the ground for reliable comparisons of results and safety in adoption of new treatment protocols. The purpose of this work was to compare the source strength for a high-dose rate (HDR) (192)Ir source as measured using equipment traceable to different standard laboratories in Europe and the United States.

    METHODS AND MATERIALS:

    Source strength was determined for one HDR (192)Ir source using four independent systems, all with traceability to different primary or interim standards in the United States and Europe.

    RESULTS:

    The measured HDR (192)Ir source strengths varied by 0.8% and differed on average from the vendor value by 0.3%. Measurements with the well chambers were 0.5% ± 0.1% higher than the vendor-provided source strength. Measurements with the Farmer chamber were 0.7% lower than the average well chamber results and 0.2% lower than the vendor-provided source strength. All of these results were less than the reported source calibration uncertainties (k=2) of each measurement system.

    CONCLUSIONS:

    In view of the uncertainties in ion chamber calibration factors, the maximum difference in source strength found in this study is small and confirms the consistency between calibration standards in use for HDR (192)Ir brachytherapy.

  • 65.
    Carlsson Tedgren, Åsa
    et al.
    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.
    Plamondon, Mathieu
    CHU Quebec, Canada; CHU Quebec, Canada; University of Laval, Canada; University of Laval, Canada.
    Beaulieu, Luc
    CHU Quebec, Canada; CHU Quebec, Canada; University of Laval, Canada; University of Laval, Canada.
    The collapsed cone algorithm for Ir-192 dosimetry using phantom-size adaptive multiple-scatter point kernels2015In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 60, no 13, p. 5313-5323Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to investigate how dose distributions calculated with the collapsed cone (CC) algorithm depend on the size of the water phantom used in deriving the point kernel for multiple scatter. A research version of the CC algorithm equipped with a set of selectable point kernels for multiple-scatter dose that had initially been derived in water phantoms of various dimensions was used. The new point kernels were generated using EGSnrc in spherical water phantoms of radii 5 cm, 7.5 cm, 10 cm, 15 cm, 20 cm, 30 cm and 50 cm. Dose distributions derived with CC in water phantoms of different dimensions and in a CT-based clinical breast geometry were compared to Monte Carlo (MC) simulations using the Geant4-based brachytherapy specific MC code Algebra. Agreement with MC within 1% was obtained when the dimensions of the phantom used to derive the multiple-scatter kernel were similar to those of the calculation phantom. Doses are overestimated at phantom edges when kernels are derived in larger phantoms and underestimated when derived in smaller phantoms (by around 2% to 7% depending on distance from source and phantom dimensions). CC agrees well with MC in the high dose region of a breast implant and is superior to TG43 in determining skin doses for all multiple-scatter point kernel sizes. Increased agreement between CC and MC is achieved when the point kernel is comparable to breast dimensions. The investigated approximation in multiple scatter dose depends on the choice of point kernel in relation to phantom size and yields a significant fraction of the total dose only at distances of several centimeters from a source/implant which correspond to volumes of low doses. The current implementation of the CC algorithm utilizes a point kernel derived in a comparatively large (radius 20 cm) water phantom. A fixed point kernel leads to predictable behaviour of the algorithm with the worst case being a source/implant located well within a patient/phantom for which low doses at phantom edges can be overestimated by 2-5 %. It would be possible to improve the situation by using a point kernel for multiple-scatter dose adapted to the patient/phantom dimensions at hand.

  • 66. Cedefamn, J
    et al.
    Friman, O
    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). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Borga, M
    Knutsson, H
    Novel method for true spatio-temporal analysis of fMRI data2000Conference paper (Other academic)
  • 67.
    Chowdhury, Manish
    et al.
    KTH, School of Technology and Health, Sweden.
    Klintström, Benjamin
    Linköping University, Center for Medical Image Science and Visualization (CMIV). KTH, School of Technology and Health, Sweden.
    Klintström, Eva
    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 Diagnostics, Department of Radiology in Linköping.
    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. KTH, School of Technology and Health, Sweden.
    Moreno, Rodrigo
    KTH, School of Technology and Health, Sweden.
    Granulometry-Based Trabecular Bone Segmentation2017In: Image Analysis - 20th Scandinavian Conference on Image Analysis, SCIA 2017, Proceedings / [ed] Sharma P., Bianchi F., Springer, 2017, Vol. 10270, p. 100-108Conference paper (Refereed)
    Abstract [en]

    The accuracy of the analyses for studying the three dimensionaltrabecular bone microstructure rely on the quality of the segmentationbetween trabecular bone and bone marrow. Such segmentationis challenging for images from computed tomography modalities thatcan be used in vivo due to their low contrast and resolution. For thispurpose, we propose in this paper a granulometry-based segmentationmethod. In a first step, the trabecular thickness is estimated by usingthe granulometry in gray scale, which is generated by applying the openingmorphological operation with ball-shaped structuring elements ofdifferent diameters. This process mimics the traditional sphere-fittingmethod used for estimating trabecular thickness in segmented images.The residual obtained after computing the granulometry is comparedto the original gray scale value in order to obtain a measurement ofhow likely a voxel belongs to trabecular bone. A threshold is applied toobtain the final segmentation. Six histomorphometric parameters werecomputed on 14 segmented bone specimens imaged with cone-beam computedtomography (CBCT), considering micro-computed tomography(micro-CT) as the ground truth. Otsu’s thresholding and AutomatedRegion Growing (ARG) segmentation methods were used for comparison.For three parameters (Tb.N, Tb.Th and BV/TV), the proposedsegmentation algorithm yielded the highest correlations with micro-CT,while for the remaining three (Tb.Nd, Tb.Tm and Tb.Sp), its performancewas comparable to ARG. The method also yielded the strongestaverage correlation (0.89). When Tb.Th was computed directly fromthe gray scale images, the correlation was superior to the binary-basedmethods. The results suggest that the proposed algorithm can be usedfor studying trabecular bone in vivo through CBCT.

  • 68.
    Christensen, Michael
    et al.
    Aarhus Univ, Denmark.
    Schiffer, Tomas A.
    Uppsala Univ, Sweden.
    Gustafsson, Håkan
    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 Norrköping/Finspång.
    Palmelund Krag, Soren
    Aarhus Univ Hosp, Denmark.
    Norregaard, Rikke
    Aarhus Univ, Denmark.
    Palm, Fredrik
    Uppsala Univ, Sweden.
    Metformin attenuates renal medullary hypoxia in diabetic nephropathy through inhibition uncoupling protein-22019In: Diabetes/Metabolism Research Reviews, ISSN 1520-7552, E-ISSN 1520-7560, Vol. 35, no 2, article id e3091Article in journal (Refereed)
    Abstract [en]

    Background The purpose of the study is to examine the effect of metformin on oxygen metabolism and mitochondrial function in the kidney of an animal model of insulinopenic diabetes in order to isolate any renoprotective effect from any concomitant effect on blood glucose homeostasis. Methods Sprague-Dawley rats were injected with streptozotocin (STZ) (50 mg kg(-1)) and when stable started on metformin treatment (250 mg kg(-1)) in the drinking water. Rats were prepared for in vivo measurements 25 to 30 days after STZ injection, where renal function, including glomerular filtration rate and sodium transport, was estimated in anesthetized rats. Intrarenal oxygen tension was measured using oxygen sensors. Furthermore, mitochondrial function was assessed in mitochondria isolated from kidney cortex and medulla analysed by high-resolution respirometry, and superoxide production was evaluated using electron paramagnetic resonance. Results Insulinopenic rats chronically treated with metformin for 4 weeks displayed improved medullary tissue oxygen tension despite of no effect of metformin on blood glucose homeostasis. Metformin reduced UCP2-dependent LEAK and differentially affected medullary mitochondrial superoxide radical production in control and diabetic rats. Conclusions Metformin attenuates diabetes-induced renal medullary tissue hypoxia in an animal model of insulinopenic type 1 diabetes. The results suggest that the mechanistic pathway to attenuate the diabetes-induced medullary hypoxia is independent of blood glucose homeostasis and includes reduced UCP2-mediated mitochondrial proton LEAK.

  • 69.
    Cibis, Merih
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Bustamante, Mariana
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Eriksson, Jonatan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Carlhäll, Carljohan
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ebbers, Tino
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Creating Hemodynamic Atlases of Cardiac 4D Flow MRI2017In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 46, no 5, p. 1389-1399Article in journal (Refereed)
    Abstract [en]

    Purpose: Hemodynamic atlases can add to the pathophysiological understanding of cardiac diseases. This study proposes a method to create hemodynamic atlases using 4D Flow magnetic resonance imaging (MRI). The method is demonstrated for kinetic energy (KE) and helicity density (Hd). Materials and Methods: Thirteen healthy subjects underwent 4D Flow MRI at 3T. Phase-contrast magnetic resonance cardioangiographies (PC-MRCAs) and an average heart were created and segmented. The PC-MRCAs, KE, and Hd were nonrigidly registered to the average heart to create atlases. The method was compared with 1) rigid, 2) affine registration of the PC-MRCAs, and 3) affine registration of segmentations. The peak and mean KE and Hd before and after registration were calculated to evaluate interpolation error due to nonrigid registration. Results: The segmentations deformed using nonrigid registration overlapped (median: 92.3%) more than rigid (23.1%, P amp;lt; 0.001), and affine registration of PC-MRCAs (38.5%, P amp;lt; 0.001) and affine registration of segmentations (61.5%, P amp;lt; 0.001). The peak KE was 4.9 mJ using the proposed method and affine registration of segmentations (P50.91), 3.5 mJ using rigid registration (P amp;lt; 0.001), and 4.2 mJ using affine registration of the PC-MRCAs (P amp;lt; 0.001). The mean KE was 1.1 mJ using the proposed method, 0.8 mJ using rigid registration (P amp;lt; 0.001), 0.9 mJ using affine registration of the PC-MRCAs (P amp;lt; 0.001), and 1.0 mJ using affine registration of segmentations (P50.028). The interpolation error was 5.262.6% at mid-systole, 2.863.8% at early diastole for peak KE; 9.669.3% at mid-systole, 4.064.6% at early diastole, and 4.964.6% at late diastole for peak Hd. The mean KE and Hd were not affected by interpolation. Conclusion: Hemodynamic atlases can be obtained with minimal user interaction using nonrigid registration of 4D Flow MRI. Level of Evidence: 2 Technical Efficacy: Stage 1

    Download full text (pdf)
    fulltext
  • 70.
    Coenen, Adriaan
    et al.
    Erasmus Univ, Netherlands.
    Kim, Young-Hak
    Univ Ulsan, South Korea.
    Kruk, Mariusz
    Inst Cardiol, Poland.
    Tesche, Christian
    Med Univ South Carolina, SC 29425 USA.
    De Geer, Jakob
    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 Diagnostics, Department of Radiology in Linköping.
    Kurata, Akira
    Ehime Univ, Japan.
    Lubbers, Marisa L.
    Erasmus Univ, Netherlands.
    Daemen, Joost
    Erasmus Univ, Netherlands.
    Itu, Lucian
    Siemens SRL, Romania.
    Rapaka, Saikiran
    Siemens Healthcare, NJ USA.
    Sharma, Puneet
    Siemens Healthcare, NJ USA.
    Schwemmer, Chris
    Siemens Healthcare GmbH, Germany.
    Persson, 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 Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Schoepf, U. Joseph
    Med Univ South Carolina, SC 29425 USA.
    Kepka, Cezary
    Inst Cardiol, Poland.
    Yang, Dong Hyun
    Univ Ulsan, South Korea.
    Nieman, Koen
    Erasmus Univ, Netherlands; Stanford Univ, CA 94305 USA.
    Diagnostic Accuracy of a Machine-Learning Approach to Coronary Computed Tomographic Angiography-Based Fractional Flow Reserve Result From the MACHINE Consortium2018In: Circulation Cardiovascular Imaging, ISSN 1941-9651, E-ISSN 1942-0080, Vol. 11, no 6, article id e007217Article in journal (Refereed)
    Abstract [en]

    Background: Coronary computed tomographic angiography (CTA) is a reliable modality to detect coronary artery disease. However, CTA generally overestimates stenosis severity compared with invasive angiography, and angiographic stenosis does not necessarily imply hemodynamic relevance when fractional flow reserve (FFR) is used as reference. CTA-based FFR (CT-FFR), using computational fluid dynamics (CFD), improves the correlation with invasive FFR results but is computationally demanding. More recently, a new machine-learning (ML) CT-FFR algorithm has been developed based on a deep learning model, which can be performed on a regular workstation. In this large multicenter cohort, the diagnostic performance ML-based CT-FFR was compared with CTA and CFD-based CT-FFR for detection of functionally obstructive coronary artery disease. Methods and Results: At 5 centers in Europe, Asia, and the United States, 351 patients, including 525 vessels with invasive FFR comparison, were included. ML-based and CFD-based CT-FFR were performed on the CTA data, and diagnostic performance was evaluated using invasive FFR as reference. Correlation between ML-based and CFD-based CT-FFR was excellent (R=0.997). ML-based (area under curve, 0.84) and CFD-based CT-FFR (0.84) outperformed visual CTA (0.69; Pamp;lt;0.0001). On a per-vessel basis, diagnostic accuracy improved from 58% (95% confidence interval, 54%-63%) by CTA to 78% (75%-82%) by ML-based CT-FFR. The per-patient accuracy improved from 71% (66%-76%) by CTA to 85% (81%-89%) by adding ML-based CT-FFR as 62 of 85 (73%) false-positive CTA results could be correctly reclassified by adding ML-based CT-FFR. Conclusions: On-site CT-FFR based on ML improves the performance of CTA by correctly reclassifying hemodynamically nonsignificant stenosis and performs equally well as CFD-based CT-FFR.

  • 71.
    Concheiro, Marta
    et al.
    NIDA, MD 21224 USA.
    Castaneto, Marisol
    NIDA, MD 21224 USA; University of Maryland Baltimore County, MD 21228 USA.
    Kronstrand, Robert
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. National Board Forens Med, Department Forens Genet and Forens Toxicol, Linkoping, Sweden.
    Huestis, Marilyn A.
    NIDA, MD 21224 USA.
    Simultaneous determination of 40 novel psychoactive stimulants in urine by liquid chromatography-high resolution mass spectrometry and library matching2015In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1397, p. 32-42Article in journal (Refereed)
    Abstract [en]

    The emergence of novel psychoactive substances is an ongoing challenge for analytical toxicologists. Different analogs are continuously introduced in the market to circumvent legislation and to enhance their pharmacological activity. Although detection of drugs in blood indicates recent exposure and link intoxication to the causative agent, urine is still the most preferred testing matrix in clinical and forensic settings. We developed a method for the simultaneous quantification of 8 piperazines, 4 designer amphetamines and 28 synthetic cathinones and 4 metabolites, in urine by liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). Data were acquired in full scan and data dependent MS2 mode. Compounds were quantified by precursor ion exact mass, and confirmed by product ion spectra library matching, taking into account product ions exact mass and intensities. One-hundred pi, urine was subjected to solid phase cation exchange extraction (SOLA SCX). The chromatographic reverse-phase separation was achieved with gradient mobile phase of 0.1% formic acid in water and in acetonitrile in 20 min. The assay was linear from 2.5 or 5 to 500 mu g/L. Imprecision (n = 15) was less than15.4%, and accuracy (n = 15) 84.2-118.5%. Extraction efficiency was 51.2-111.2%, process efficiency 57.7-104.9% and matrix effect ranged from -41.9% to 238.5% (CV less than 23.3%, except MDBZP CV less than 34%). Authentic urine specimens (n = 62) were analyzed with the method that provides a comprehensive confirmation for 40 new stimulant drugs with specificity and sensitivity.

  • 72.
    Costa, Tatiana
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Adolfsson, Emelie
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Fager, M.
    Karolinska Univ Hosp, Sweden.
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    CHARACTERIZATION OF A LITHIUM FORMATE EPR-DOSIMETRY SYSTEM FOR PROTON RADIATION THERAPY2019In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 186, no 1, p. 83-87Article in journal (Refereed)
    Abstract [en]

    The specific aim for the characterization of the lithium formate dosimetry system is to determine response and stability in a proton beam. The long-term goal for this investigation is an audit system for proton therapy like the end-to-end dose determinations performed for radiotherapy with photons. For a 150-MeV proton beam, the dose response was found to be linear in the dose interval 0-8.8 Gy. The accuracy of dose reconstruction was controlled in a blind test, in which the dose of 6.63 Gy was measured in samples irradiated with a real dose of 6.70 Gy. The stability was determined by irradiations of sets of four dosimeters every week during 1 month and analyzed at the same day thereafter. The fitting of the fading curve was done with a second-order polynomial resulting in a 6.6% lower value compared to the reference after 31 d.

  • 73.
    Covarrubias, Yesenia
    et al.
    Univ Calif San Diego, CA 92093 USA.
    Fowler, Kathryn J.
    Univ Calif San Diego, CA 92093 USA.
    Mamidipalli, Adrija
    Univ Calif San Diego, CA 92093 USA.
    Hamilton, Gavin
    Univ Calif San Diego, CA 92093 USA.
    Wolfson, Tanya
    Univ Calif San Diego, CA 92093 USA.
    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.
    Jacobsen, Garth
    Univ Calif San Diego, CA 92093 USA.
    Horgan, Santiago
    Univ Calif San Diego, CA 92093 USA.
    Schwimmer, Jeffrey B.
    Univ Calif San Diego, CA 92093 USA; Rady Childrens Hosp San Diego, CA USA.
    Reeder, Scott B.
    Univ Wisconsin, WI 53706 USA; Univ Wisconsin, WI 53706 USA; Univ Wisconsin, WI USA; Univ Wisconsin, WI USA.
    Sirlin, Claude B.
    Univ Calif San Diego, CA 92093 USA.
    Pilot study on longitudinal change in pancreatic proton density fat fraction during a weight-loss surgery program in adults with obesity2019In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 50, no 4, p. 1092-1102Article in journal (Refereed)
    Abstract [en]

    Background Quantitative-chemical-shift-encoded (CSE)-MRI methods have been applied to the liver. The feasibility and potential utility CSE-MRI in monitoring changes in pancreatic proton density fat fraction (PDFF) have not yet been demonstrated. Purpose To use quantitative CSE-MRI to estimate pancreatic fat changes during a weight-loss program in adults with severe obesity and nonalcoholic fatty liver disease (NAFLD). To explore the relationship of reduction in pancreatic PDFF with reductions in anthropometric indices. Study Type Prospective/longitudinal. Population Nine adults with severe obesity and NAFLD enrolled in a weight-loss program. Field Strength/Sequence CSE-MRI fat quantification techniques and multistation-volumetric fat/water separation techniques were performed at 3 T. Assessment PDFF values were recorded from parametric maps colocalized across timepoints. Statistical Tests Rates of change of log-transformed variables across time were determined (linear-regression), and their significance assessed compared with no change (Wilcoxon test). Rates of change were correlated pairwise (Spearmans correlation). Results Mean pancreatic PDFF decreased by 5.7% (range 0.7-17.7%) from 14.3 to 8.6%, hepatic PDFF by 11.4% (2.6-22.0%) from 14.8 to 3.4%, weight by 30.9 kg (17.3-64.2 kg) from 119.0 to 88.1 kg, body mass index by 11.0 kg/m(2) (6.3-19.1 kg/m(2)) from 44.1 to 32.9 kg/m(2), waist circumference (WC) by 25.2 cm (4.0-41.0 cm) from 133.1 to 107.9 cm, HC by 23.5 cm (4.5-47.0 cm) from 135.8 to 112.3 cm, visceral adipose tissue (VAT) by 2.9 L (1.7-5.7 L) from 7.1 to 4.2 L, subcutaneous adipose tissue (SCAT) by 4.0 L (2.9-7.4 L) from 15.0 to 11.0 L. Log-transformed rate of change for pancreatic PDFF was moderately correlated with log-transformed rates for hepatic PDFF, VAT, SCAT, and WC (rho = 0.5, 0.47, 0.45, and 0.48, respectively), although not statistically significant. Data Conclusion Changes in pancreatic PDFF can be estimated by quantitative CSE-MRI in adults undergoing a weight-loss surgery program. Pancreatic and hepatic PDFF and anthropometric indices decreased significantly. Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019;50:1092-1102.

  • 74.
    Daghighi, Abtin
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences.
    Tropp, Hans
    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 Surgery, Orthopaedics and Cancer Treatment, Department of Spinal Surgery.
    Dahlström, Nils
    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).
    Klarbring, Anders
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    F.E.M. Stress-Investigation of Scolios Apex2018In: Open Biomedical Engineering Journal, ISSN 1874-1207, E-ISSN 1874-1207, Vol. 12, p. 51-71Article in journal (Refereed)
    Abstract [en]

    In scoliosis, kypholordos and wedge properties of the vertebrae should be involved in determining how stress is distributed in the vertebral column. The impact is logically expected to be maximal at the apex.

    Download full text (pdf)
    fulltext
  • 75.
    Dahl, Sara
    et al.
    Karolinska Inst, Sweden.
    Kristoffersen Wiberg, Maria
    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. Karolinska Inst, Sweden; Karolinska Univ Hosp, Sweden.
    Fahnehjelm, Kristina Tear
    Karolinska Inst, Sweden; St Erik Eye Hosp, Sweden; Univ Gothenburg, Sweden.
    Savendahl, Lars
    Karolinska Inst, Sweden.
    Wickstrom, Ronny
    Karolinska Inst, Sweden.
    High prevalence of pituitary hormone deficiency in both unilateral and bilateral optic nerve hypoplasia2019In: Acta Paediatrica, ISSN 0803-5253, E-ISSN 1651-2227, Vol. 108, no 9, p. 1677-1685Article in journal (Refereed)
    Abstract [en]

    Aim This study examined the prevalence of neurological impairment and pituitary hormone deficiency (PHD) in patients with unilateral and bilateral optic nerve hypoplasia (ONH). Methods A population-based cross-sectional cohort study of 65 patients (51% female) with ONH was conducted in Stockholm. Of these were 35 bilateral and 30 unilateral. The patients were below 20 years of age, living in Stockholm in December 2009 and found through database searching. The median age at the analysis of the results in January 2018 was 16.1 years (range 8.1-27.5 years). Neurological assessments and blood sampling were conducted, neuroradiology was reviewed and growth curves were analysed. Diagnoses of PHDs were based on clinical and biochemical evidence of hormone deficiency. Results Neurological impairments were identified in 47% of the patients and impairments in gross and fine motor function were more prevalent in bilateral ONH (p amp;lt; 0.001). In addition, 9% had cerebral palsy and 14% had epilepsy. The prevalence of PHD was 29 and 19% had multiple PHD. Conclusion Children with ONH had a high risk of neurological impairment, especially in bilateral disease. Both unilateral and bilateral ONH signified an increased prevalence of PHD and all these children should be endocrinologically followed up until completed puberty.

  • 76.
    Dahlqvist Leinhard, Olof
    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. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Linge, Jennifer
    Advanced MR Analytics AB, Linköping, Sweden.
    West, Janne
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Bell, Jimmy
    Westminster University, London, UK.
    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.
    Body Composition Profiling using MRI - Normative Data for Subjects with Cardiovascular Disease Extracted from the UK Biobank Imaging Cohort2016Conference paper (Other academic)
    Abstract [en]

    PURPOSE

    To describe the distribution of MRI-derived body composition measurements in subjects with cardiovascular disease (CVD) compared to subjects without any history of CVD.

    METHOD AND MATERIALS

    1864 males and 2036 females with an age range from 45 to 78 years from the UK Biobank imaging study were included in the study. Visceral adipose tissue volume normalized with height2 (VATi), total abdominal adipose tissue volume normalized with height2 (ATATi), total lean thigh muscle volume normalized with body weight (muscle ratio) and liver proton density fat fraction (PDFF) were measured with a 2-point Dixon imaging protocol covering neck to knee and a 10-point Dixon single slice protocol positioned within the liver using a 1.5T MR-scanner (Siemens, Germany). The MR-images were analyzed using AMRA® Profiler research (AMRA, Sweden). 213 subjects with history of cardiovascular events (angina, heart attack, or stroke) (event group) were age and gender matched to subjects with high blood pressure (HBP group), and subjects without CVD (controls).Kruskal-Wallis and Mann-Whitney U tests were used to test the observed differences for each measurement and group without correction for multiple comparisons.

    RESULTS

    VATi in the event group was 1.73 (1.13 - 2.32) l/m2 (median, 25%-75% percentile) compared to 1.68 (1.19 - 2.23) in the HBP group, and 1.30 (0.82-1.87) in the controls. ATATi in the event group was 4.31 (2.90-5.39) l/m2 compared to 4.05 (3.07-5.12) in the HBP group, and 3.48 (2.48-4.61) in the controls. Muscle ratio in the event group was 0.13 (0.12 - 0.15) l/kg as well as in the HBP group, compared to 0.14 (0.12 - 0.15) in the controls. Liver PDFF in the event group was 2.88 (1.77 - 7.72) % compared to 3.44 (2.04-6.18) in the HBP group, and 2.50 (1.58 - 5.15) in the controls. Kruskal-Wallis test showed significant differences for all variables and group comparisons (p<0.007). The post hoc test showed significant differences comparing the controls to both the event group and the HBP group. These were more significant for VATi and ATATi (p<10-4) than for muscle ratio and PDFF (p<0.03). No significant differences were detected between the event group and the HBP group.

    CONCLUSION

    Cardiovascular disease is strongly associated with high VATi, liver fat, and ATATi, and with low muscle ratio.

    CLINICAL RELEVANCE/APPLICATION

    The metabolic syndrome component in CVD can be effectively described using MRI-based body composition profiling.

  • 77.
    Dahlqvist Leinhard, Olof
    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. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Linge, Jennifer
    Advanced MR Analytics AB, Linköping, Sweden.
    West, Janne
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Bell, Jimmy
    Westminster University, London, UK.
    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.
    Body Composition Profiling using MRI - Normative Data for Subjects with Diabetes Extracted from the UK Biobank Imaging Cohort2016Conference paper (Other academic)
    Abstract [en]

    PURPOSE

    To describe the distribution of MRI derived body composition measurements in subjects with diabetes mellitus (DM) compared to subjects without diabetes.

    METHOD AND MATERIALS

    3900 subjects (1864 males and 2036 females) from the UK Biobank imaging study were included in the study. The age range was 45 to 78 years. Visceral adipose tissue volume normalized with height2 (VATi), total abdominal adipose tissue volume normalized with height2 (ATATi), total lean thigh muscle volume normalized with body weight (muscle ratio) and liver proton density fat fraction (PDFF) were measured with a 6 minutes 2-point Dixon imaging protocol covering neck to knee and a 10-point Dixon single axial slice protocol positioned within the liver using a 1.5T MR-scanner (Siemens, Germany). The MR-images were analyzed using AMRA® Profiler research (AMRA, Sweden). 194 subjects with clinically diagnosed DM (DM group) were age and gender matched to subjects without DM (control group). For each variable and group, the median, 25%-percentile and 75%-percentile was calculated. Mann-Whitney U test was used to test the observed differences.

    RESULTS

    VATi in the DM group was 2.13 (1.43-2.62) l/m2 (median, 25% - 75% percentile) compared to 1.32 (0.86 - 1.79) l/m2 in the control group. ATATi in the DM group was 4.94 (3.86-6.19) l/m2 compared to 3.40 (2.56 - 4.70) l/m2 in the control group. Muscle ratio in the DM group was 0.13 (0.11 - 0.14) l/kg compared to 0.14 (0.12 - 0.15) l/kg in the control group. Liver PDFF in the DM group was 7.23 (2.68 - 13.26) % compared to 2.49 (1.53 - 4.73) % in the control group. Mann-Whitney U test detected significant differences between the DM group and the control group for all variables (p<10-5).

    CONCLUSION

    DM is strongly associated with high visceral fat, liver fat, and total abdominal fat, and low muscle ratio.

    CLINICAL RELEVANCE/APPLICATION

    Body composition profiling shows high potential to provide direct biomarkers to improve characterization and early diagnosis of DM.

  • 78.
    Dahlqvist Leinhard, Olof
    et al.
    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.
    Motsch, Johann
    Clinical Research, University of Heidelberg, Heidelberg, Germany.
    van der Meulen, Jan
    Clinical Epidemiology, Department of Health Services Research and Policy, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London,UK.
    Clinical News: Body composition study reveals link between specific fat distributions and metabolic diseases2018In: British Journal of Hospital Medicine, ISSN 1750-8460, Vol. 79, no 6, p. 308-308Article in journal (Other academic)
  • 79.
    Darras, Kathryn E.
    et al.
    Univ British Columbia, Canada; Maastricht Univ, Netherlands.
    de Bruin, Anique B. H.
    Maastricht Univ, Netherlands.
    Nicolaou, Savvas
    Univ British Columbia, Canada.
    Dahlström, Nils
    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.
    Persson, 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 Diagnostics, Department of Radiology in Linköping.
    van Merrienboer, Jeroen
    Maastricht Univ, Netherlands.
    Forster, Bruce B.
    Univ British Columbia, Canada.
    Is there a superior simulator for human anatomy education? How virtual dissection can overcome the anatomic and pedagogic limitations of cadaveric dissection2018In: Medical teacher, ISSN 0142-159X, E-ISSN 1466-187X, Vol. 40, no 7, p. 752-753Article in journal (Refereed)
    Abstract [en]

    Educators must select the best tools to teach anatomy to future physicians and traditionally, cadavers have always been considered the "gold standard" simulator for living anatomy. However, new advances in technology and radiology have created new teaching tools, such as virtual dissection, which provide students with new learning opportunities. Virtual dissection is a novel way of studying human anatomy through patient computed tomography (CT) scans. Through touchscreen technology, students can work together in groups to "virtually dissect" the CT scans to better understand complex anatomic relationships. This article presents the anatomic and pedagogic limitations of cadaveric dissection and explains what virtual dissection is and how this new technology may be used to overcome these limitations.

  • 80.
    Dasu, Alexandru
    Östergötlands Läns Landsting, 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.
    Radiobiology of prostate cancer2012In: Robotic Radiosurgery. Treating Prostate Cancer and Related Genitourinary Applications / [ed] Ponsky LE, Fuller DB, Meier RM, Ma C-MC, Springer Berlin/Heidelberg, 2012, p. 79-101Chapter in book (Refereed)
    Abstract [en]

    The 1999 proposal of Brenner and Hall of an alpha/beta value of 1.5 Gy for prostate tumors has rekindled the interest in the traditional radiobiological aspects of time, dose, and fractionation as effective means of modulating the therapeutic window in radiation therapy. It is well established that, depending on the fractionation sensitivity of normal and tumor tissues, one could depart from the usual fractionation pattern and devise schedules that lead to the same tumor results with less complications, or better tumor control with the same level of complications. Nevertheless, radiobiology experience indicates that the success of any fractionation schedule depends on the temporal pattern of dose delivery. From this perspective, the present chapter aims to review the radiobiological aspects that may be relevant for the design of treatment schedules for prostate tumors.

  • 81.
    Dasu, Alexandru
    et al.
    Östergötlands Läns Landsting, 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.
    Toma-Dasu, Iuliana
    Stockholm University and Karolinska Institutet.
    Dose painting by numbers - do the practical limitations of the technique decrease or increase the probability of controlling tumours?2013In: IFMBE Proceedings / [ed] Long Mian, Springer, 2013, Vol. 39, p. 1731-1734Conference paper (Refereed)
    Abstract [en]

    One of the important questions regarding the feasibility of dose-painting-by-numbers approaches for treatment planning concerns the influence of the averaging of the imaging techniques used and the resolution of the planned and achieved dose distributions. This study investigates the impact of these aspects on the probability of controlling dynamic tumours. The effectiveness of dose painting approaches to target tumour hypoxia has been investigated in terms of the predicted tumour control probabilities (TCP) for tumours with dynamic oxygenations. Several levels of resolution for the resistance of the tumour or the planned dose distributions have been investigated. A very fine heterogeneous dose distribution ideally calculated at voxel level for a high target TCP would fail to control a tumour with dynamic oxygenation during the course of fractionated radiotherapy as mismatches between hotspots in the dose distribution and resistant hypoxic foci would lead to a significant loss in TCP. Only adaptive treatment would lead to reasonably high TCP. A coarse resolution for imaging or for dose distributions might compensate microscale mismatches in dynamic tumours, but the resulting tumour control could still be below the target levels. These results indicate that there is a complex relationship between the resolution of the dose-painting-by-numbers approaches and the dynamics of tumour oxygenation. Furthermore, the clinical success of hypoxia targeting strategies in the absence of adaptive approaches might be explained by changes in tumour radiation resistance through reoxygenation.

  • 82.
    Dasu, Alexandru
    et al.
    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.
    Toma-Dasu, Iuliana
    Stockholm University, Sweden.
    Impact of increasing irradiation time on the treatment of prostate cancers2015In: World Congress on Medical Physics and Biomedical Engineering, June 7-12, 2015, Toronto, Canada / [ed] Jaffray David A., Springer, 2015, Vol. 51, p. 490-493Conference paper (Refereed)
    Abstract [en]

    This study aimed to investigate the expected impact of intrafraction repair during increasing irradiation times for the treatment of prostate cancers. Lengthy sessions are indeed expected for some advanced irradiation techniques capable to deliver the large fractional doses required by the increased fractionation sensitivity of the prostates. For this purpose, clinically-derived parameters characterizing repair rates and dose response curves for prostate tumors have been used to calculate the expected loss of effectiveness when increasing the irradiation time. The results have shown that treatment sessions lasting more than about 20 to 40 minutes could reduce the probability of biochemical control of prostate tumors by more than 20 to 30 percentage points. These results are in agreement with some observed clinical results and therefore they suggest that treatment durations in prostate radiation therapy should be carefully recorded in order to explicitly account for intrafraction repair, especially when irradiation techniques make use of multiple beams and imaging sessions. Failure to do so might overestimate the expected effectiveness of the treatment and could lead to disappointing clinical results precisely from the demanding treatment modalities expected to increase the therapeutic gain in prostate radiotherapy.

  • 83.
    Dasu, Alexandru
    et al.
    Östergötlands Läns Landsting, 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.
    Toma-Dasu, Iuliana
    Stockholm University and Karolinska Institutet.
    Impact of variable RBE on proton fractionation2013In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 40, no 1, p. Article ID 011705-Article in journal (Refereed)
    Abstract [en]

    Purpose: To explore the impact of variable proton RBE on dose fractionation for clinically-relevant situations. A generic RBE=1.1 is generally used for isoeffect calculations, while experimental studies showed that proton RBE varies with tissue type, dose and LET.

    Material and methods: An analytical expression for the LET and α/β dependence of the LQ model has been used for proton simulations in parallel with the assumption of a generic RBE=1.1. Calculations have been performed for ranges of LET values and fractionation sensitivities to describe clinically-relevant cases, like the treatment of H&N and prostate tumors. Isoeffect calculations were compared with predictions from a generic RBE value and reported clinical results.

    Results: The generic RBE=1.1 appears to be a reasonable estimate for the proton RBE of rapidly growing tissues irradiated with low LET radiation. However, the use of a variable RBE predicts larger differences for tissues with low α/β (both tumor and normal) and at low doses per fraction. In some situations these differences may appear in contrast to the findings from photon studies highlighting the importance of accurate accounting for the radiobiological effectiveness of protons. Furthermore, the use of variable RBE leads to closer predictions to clinical results.

    Conclusions: The LET dependence of the RBE has a strong impact on the predicted effectiveness of fractionated proton radiotherapy. The magnitude of the effect is modulated by the fractionation sensitivity and the fractional dose indicating the need for accurate analyses both in the target and around it. Care should therefore be employed for changing clinical fractionation patterns or when analyzing results from clinical studies for this type of radiation.

  • 84.
    Dasu, Alexandru
    et al.
    Östergötlands Läns Landsting, 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.
    Toma-Dasu, Iuliana
    Stockholm University and Karolinska Institutet, Stockholm, Sweden.
    Long-term effects and secondary tumors2014In: Comprehensive Biomedical Physics, Volume 9: Radiation Therapy Physics and Treatment Optimization / [ed] Anders Brahme, Amsterdam: Elsevier, 2014, p. 223-233Chapter in book (Refereed)
    Abstract [en]

    The issue of secondary tumours as long-term effects of radiation therapy has gained increased importance as the life expectancy of cancer patients has increased due to improvements in detecting and treating their primary tumours. Current knowledge indicates that radiotherapy leads to a small but significant risk of inducing cancers which is often referred to as the price to pay for the effectiveness of this treatment modality. Nevertheless, the levels of incidence for the long-term effects of radiation therapy may be influenced by many factors that could be both treatment-related and patient-related and therefore proposals have been made to include risk estimations in the process of treatment optimisation. This chapter summarises the current knowledge concerning the induction of secondary cancers after radiotherapy and discusses their consequences for the therapeutic use of ionising radiation.

  • 85.
    Dasu, Alexandru
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. The Skandion Clinic, Uppsala, Sweden.
    Toma-Dasu, Iuliana
    Stockholm University, Sweden; Karolinska Institutet, Sweden .
    Models for the risk of secondary cancers from radiation therapy2017In: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 42, p. 232-238Article in journal (Refereed)
    Abstract [en]

    The interest in the induction of secondary tumours following radiotherapy has greatly increased as developments in detecting and treating the primary tumours have improved the life expectancy of cancer patients. However, most of the knowledge on the current levels of risk comes from patients treated many decades ago. As developments of irradiation techniques take place at a much faster pace than the progression of the carcinogenesis process, the earlier results could not be easily extrapolated to modern treatments. Indeed, the patterns of irradiation from historically-used orthovoltage radiotherapy and from contemporary techniques like conformal radiotherapy with megavoltage radiation, intensity modulated radiation therapy with photons or with particles are quite different. Furthermore, the increased interest in individualised treatment options raises the question of evaluating and ranking the different treatment plan options from the point of view of the risk for cancer induction, in parallel with the quantification of other long-term effects. It is therefore inevitable that models for risk assessment will have to be used to complement the knowledge from epidemiological studies and to make predictions for newer forms of treatment for which clinical evidence is not yet available. This work reviews the mathematical models that could be used to predict the risk of secondary cancers from radiotherapy-relevant dose levels, as well as the approaches and factors that have to be taken into account when including these models in the clinical evaluation process. These include the effects of heterogeneous irradiation, secondary particles production, imaging techniques, interpatient variability and other confounding factors.

  • 86.
    Dasu, Alexandru
    et al.
    Östergötlands Läns Landsting, 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.
    Toma-Dasu, Iuliana
    Stockholm University and Karolinska Institutet.
    Prostate alpha/beta revisited – an analysis of clinical results from 14168 patients2012In: Acta Oncologica, ISSN 0284-186X, E-ISSN 1651-226X, Vol. 51, no 8, p. 963-974Article, review/survey (Refereed)
    Abstract [en]

    Purpose: To determine the dose response parameters and the fractionation sensitivity of prostate tumours from clinical results of patients treated with external beam radiotherapy.

    Material and methods: The study was based on 5-year biochemical results from 14168 patients treated with external beam radiotherapy. Treatment data from 11330 patients treated with conventional fractionation have been corrected for overall treatment time and fitted with a logit equation. The results have been used to determine the optimum α/β values that minimise differences in predictions from 2838 patients treated with hypofractionated schedules.

    Results: Conventional fractionation data yielded logit dose response parameters for all risk groups and for all definitions of biochemical failures. The analysis of hypofractionation data led to very low α/β values (1-1.7 Gy) in all mentioned cases. Neglecting the correction for overall treatment time has little impact on the derivation of α/β values for prostate cancers.

    Conclusions: These results indicate that the high fractionation sensitivity is an intrinsic property of prostate carcinomas and they support the use of hypofractionation to increase the therapeutic gain for these tumours.

  • 87.
    Dasu, Alexandru
    et al.
    Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.
    Toma-Dasu, Iuliana
    Stockholm University.
    Will intrafraction repair have negative consequences on extreme hypofractionation in prostate radiation therapy?2015In: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 88, no 1056, p. Article ID 20150588-Article in journal (Refereed)
    Abstract [en]

    Objective: The aim of the present study was to investigate the impact of increasing fraction delivery time on the outcome of hypofractionated radiation therapy for prostate cancer.

    Methods: Monoexponential and biexponential repair models have been used for patients with prostate cancer to study the loss of biochemical control at 5 years for several clinically relevant irradiation times. The theoretical predictions were compared with newly reported clinical results from 4607 patients undergoing conventionally fractionated and hypofractionated prostate radiation therapy.

    Results: Time-demanding irradiation techniques appear to lead to biochemical control rates that sometimes are about 10–20 percentage points below predictions that neglect intrafraction repair. This difference appears to be of the same order of magnitude as that predicted by moderately slow to slow repair taking place during the irradiation time. The impact is largest for the patient risk groups receiving doses corresponding to the steepest part of the dose–response curve. By contrast, for treatment techniques requiring irradiation times shorter than about 20 min, the impact of intrafraction repair appears to be much smaller and probably difficult to be observed in the light of other sources of uncertainty in clinical data.

    Conclusion: Neglecting intrafraction repair might overestimate the effectiveness of some treatment schedules and could also influence any subsequent estimations of fractionation sensitivity for prostate tumours.

    Advances in knowledge: The effect of intrafraction repair for prostate cancer should be taken into account for long irradiation sessions as might be expected from scanned beams and/or from multiple intrafraction imaging sessions to check the positioning of the patient.

  • 88.
    Davidsson, Anette
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Georgiopoulos, Charalampos
    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.
    Dizdar (Dizdar Segrell), Nil
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuroscience. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Granerus, Göran
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Zachrisson, Helene
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Comparison between visual assessment of dopaminergic degeneration pattern and semi-quantitative ratio calculations in patients with Parkinsons disease and Atypical Parkinsonian syndromes using DaTSCAN (R) SPECT2014In: Annals of Nuclear Medicine, ISSN 0914-7187, E-ISSN 1864-6433, Vol. 28, no 9, p. 851-859Article in journal (Refereed)
    Abstract [en]

    Objective To verify if I-123-FP-CIT, DaTSCAN (R) can differentiate early stages of Parkinsons disease (PD) as well as patients with Atypical Parkinsonian syndromes (APS) from manifest Parkinsons disease. Methods 128 consecutive patients were investigated with I-123-FP-CIT SPECT during a 4-year period. All patients were diagnosed according to the established consensus criteria for diagnosis of PD (n = 53) and APS (n = 19). Remaining patients were grouped early PD (before onset of L-DOPA medication), (n = 20), vascular PD (n = 6), and non-PD syndromes (n = 30) and SWEDD (n = 1). SPECT images were analyzed visually according to a predefined ranking scale of dopaminergic nerve cell degeneration, distinguishing a posterior-anterior degeneration pattern (egg shape) from a more global and severe degeneration pattern (burst striatum). Striatum uptake ratios were quantitatively analyzed with the 3D software, EXINI. Results In the group of APS patients, the burst striatum pattern was most frequent and found in 61 % (11/18 patients). In PD patients, the egg shape pattern was dominating, especially in early PD where it was present in 95 % (19/20 patients). The positive predictive value for the egg shape pattern to diagnose PD was 92 % in this material (APS and all PD patients) and the specificity 90 % for the burst striatum pattern to exclude APS. The uptake ratios were reduced in both PD and APS patients and closely related to the image ranking. Conclusion In this study, we found that in more than half of the patients it was possible to differentiate between PD and APS by visual interpretation only. Similar results were obtained using semi-quantitative uptake ratios. Combining visual assessment with uptake ratios did not add to the discriminating power of DaTSCAN (R) SPECT in this material.

  • 89.
    Davidsson, Anette
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Georgiopoulos, Charalampos
    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.
    Dizdar Segrell, Nil
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuroscience. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Granerus, Göran
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Zachrisson, Helene
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Comparison between visual assessment of dopaminergic degeneration pattern and semi-quantitative ratio calculations in patients with Parkinson's disease and Atypical Parkinsonian snydromes using DaTSCAN SPECT2014Conference paper (Other academic)
    Abstract [en]

    Background: Parkinson's disease (PD) is a degenerative disorder characterized by the progressive degeneration of dopamine-containing cells in substantia nigra, and it is the second most common neurodegenerative disorder worldwide. It can be difficult to differentiate between idiopathic PD and Atypical Parkinsonian syndromes (APS). In a high percentage of APS patients, the right diagnosis is not established even during late stages of the disease. Currently there is no specific test to verify PD, especially in the early stages of the disease.

    The aim was to verify if 123I-FP-CIT, DaTSCAN ® can differentiate early stages of Parkinson's disease as well as patients with Atypical Parkinsonian syndromes from manifest Parkinson's disease.

    Materials and methods: 121 consecutive patients were investigated with 123I-FP-CIT SPECT, during a four year period. All patients were diagnosed according to the established consensus criteria for diagnosis of Parkinson's disease (PD), (n=53), Atypical Parkinsonian syndromes (APS) (n=18). Remaining patients were grouped early PD (before onset the of L-dopa medication), (n=20), and non-PD syndromes (n=30). SPECT images were analysed visually according to a predefined ranking scale of dopaminergic degeneration, distinguishing a posterior-anterior degeneration pattern (egg shape) to a more global and severe degeneration pattern (burst striatum). Striatum ratios were quantitatively analysed with the 3D software, EXINI.

    Results: In the group of APS patients the burst striatum pattern was most frequent and found in 61% (11/18 patients). In PD patients the egg shape pattern was dominating, especially in early PD where it was present in 95% (19/20 patients). The sensitivity of burst striatum degeneration pattern was 61% (95%-CI 36-83%), specificity 90% (95%-CI 81-96%). The sensitivity of egg shape pattern was 74% (95%-CI 62-84%), specificity 90% (95%-CI 47-90%). The uptake ratios were reduced in both PD and APS patients and closely related to the image pattern. The lowest putamen/caudate ratio was found in early PD.

    Conclusion: In this study we found that in more than half of the patients it was possible to differentiate between PD and APS by visual interpretation only. Similar results were obtained using semi-quantitative uptake ratios, but combining visual assessment with uptake ratios did not add to the discriminating power of DATSCAN ® SPECT in this material

    References: Kahraman D, Eggers C, Schicha H, Timmermann L, Schmidt M. Visual assessment of dopaminergic degeneration pattern in 123I-FP-CIT SPECT differentiates patients with atypical parkinsonian syndromes and idiopathic Parkinson's disease. J Neurol. 2012;259:251-60

  • 90. Order onlineBuy this publication >>
    De Geer, Jakob
    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).
    On the use of computed tomography in cardiac imaging2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background

    Cardiac Computed Tomography Angiography (CCTA) is becoming increasingly useful in the work‐up of coronary artery disease (CAD). Several potential methods for increasing the diagnostic yield of cardiac CT are available.

    Purpose

    Study I: To investigate whether the use of a 2‐D, non‐linear adaptive noise reduction filter can improve CCTA image quality.

    Study II: To evaluate the variation in adenosine stress dynamic CT perfusion (CTP) blood flow as compared to stress 99mTc SPECT. Secondly, to compare the perfusion results from manual and automatic myocardial CTP segmentation.

    Study III: To evaluate the accuracy of non‐invasive, CCTA‐derived Fractional Flow Reserve (cFFR).

    Study IV: To evaluate the prognostic value of CCTA in terms of major adverse cardiac events (MACE).

    Materials and methods

    Study I: Single images from 36 consecutive CCTA exams performed with two different dose levels were used. Image quality in full dose, low‐dose and noise‐reduced low‐dose images was graded using visual grading analysis. Image noise was measured.

    Study II: CTP and SPECT were performed in 17 patients, and the variation in per AHA‐segment blood flow was evaluated and compared. CTP results from manual and automated image segmentation were compared.

    Study III: CCTA datasets from 21 patients were processed using cFFR software and the results compared to the corresponding invasively measured FFR (invFFR).

    Study IV: 1205 consecutive patients with chest pain of unknown origin underwent CCTA. Baseline data and data on subsequent MACE were retrieved from relevant registries. Survival, hazard ratios and the three‐year incidence of cardiac events and readmissions were calculated.

    Results

    Study I: There was significant improvement in perceived image quality for all criteria when the filter was applied, and a significant decrease in image noise.

    Study II: The correlation coefficients for CTP vs. SPECT were 0.38 and 0.41 (p<0.001, for manual and automated segmentation respectively. Mean per patient CTP blood flow in normal segments varied between 94‐183 ml/100 ml tissue/min for manual segmentation, and 104‐196 ml/100 ml tissue/min for automated segmentation. The Spearman rank correlation coefficient for manual vs. automated segmentation CTP was ρ = 0.88 (p<0.001) and the Intraclass Correlation Coefficient (ICC) was 0.93 (p<0.001).

    Study III: The Spearman rank correlation coefficient for cFFR vs. invFFR was ρ = 0.77 (p<0.001) and the ICC was 0.73 (p<0.001). Sensitivity, specificity, positive predictive value and negative predictive value for significant stenosis (FFR<0.80, per vessel) were 0.83, 0.76, 0.56 and 0.93 respectively.

    Study IV: The hazard ratio for non‐obstructive CAD vs. normal coronary arteries was 5.13 (95% C.I 1.03‐25.43, p<0.05), and 151.40 (95% C.I 37.03‐619.08, p<0.001) for obstructive CAD vs. normal coronary arteries. The three‐year incidence of MACE was 1.1% for patients with normal vessels on CCTA, 2.5% for patients with non‐obstructive CAD and 42.7% for patients with obstructive CAD (p<0.001).

    Conclusions:

    Study I: Image quality and noise levels of low dose images were significantly improved with the filter, even though the improvement was small compared to the image quality of the corresponding diastolic full‐dose images.

    Study II: Correlation between dynamic CTP and SPECT was positive but weak. There were large variations in CTP blood flow in normal segments on SPECT, rendering the definition of an absolute cut‐off value for normal vs. ischemic myocardium difficult. Manual and automatic segmentation were equally useful.

    Study III: The correlation between cFFR and invFFR was good, indicating that noninvasively estimated cFFR performs on a similar level as invasively measure FFR.

    Study IV: The long‐term risk for MACE was very low in patients without obstructive CAD on CCTA, though there seemed to be a substantial increase in the risk for MACE even in patients with non‐obstructive CAD as compared to normal coronary arteries. In addition, even patients with normal coronary arteries or non‐obstructive CAD continued to have a substantial number of readmissions for chest pain or angina pectoris.

    List of papers
    1. The efficacy of 2D, non-linear noise reduction filtering in cardiac imaging: a pilot study
    Open this publication in new window or tab >>The efficacy of 2D, non-linear noise reduction filtering in cardiac imaging: a pilot study
    2011 (English)In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 52, no 7, p. 716-722Article in journal (Refereed) Published
    Abstract [en]

    Background: Computed tomography (CT) is becoming increasingly popular as a non-invasive method for visualizing the coronary arteries but patient radiation doses are still an issue. Postprocessing filters such as 2D adaptive non-linear filters might help to reduce the dose without loss of image quality. less thanbrgreater than less thanbrgreater thanPurpose: To investigate whether the use of a 2D, non-linear adaptive noise reduction filter can improve image quality in cardiac computed tomography angiography (CCTA). less thanbrgreater than less thanbrgreater thanMaterial and Methods: CCTA examinations were performed in 36 clinical patients on a dual source CT using two patient dose levels: maximum dose during diastole and reduced dose (20% of maximum dose) during systole. One full-dose and one reduced-dose image were selected from each of the examinations. The reduced-dose image was duplicated and one copy postprocessed using a 2D non-linear adaptive noise reduction filter, resulting in three images per patient. Image quality was assessed using visual grading with three criteria from the European guidelines for assessment of image quality and two additional criteria regarding the left main artery and the overall image quality. Also, the HU value and its standard deviation were measured in the ascending and descending aorta. Data were analyzed using Visual Grading Regression and paired t-test. less thanbrgreater than less thanbrgreater thanResult: For all five criteria, there was a significant (P andlt; 0.01 or better) improvement in perceived image quality when comparing postprocessed low-dose images with low-dose images without noise reduction. Comparing full dose images with postprocessed low-dose images resulted in a considerably larger, significant (P andlt; 0.001) difference. Also, there was a significant reduction of the standard deviation of the HU values in the ascending and descending aorta when comparing postprocessed low-dose images with low-dose images without postprocessing. less thanbrgreater than less thanbrgreater thanConclusion: Even with an 80% dose reduction, there was a significant improvement in the perceived image quality when using a 2D noise-reduction filter, though not approaching the quality of full-dose images. This indicates that cardiac CT examinations could benefit from noise-reducing postprocessing with 2D non-linear adaptive filters.

    Place, publisher, year, edition, pages
    Informa Healthcare / Wiley-Blackwell / Royal Society of Medicine Press, 2011
    Keywords
    Cardiac, CT angiography, heart, adults, image manipulation
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-71803 (URN)10.1258/ar.2011.100511 (DOI)000295759600007 ()
    Available from: 2011-11-04 Created: 2011-11-04 Last updated: 2017-12-08
    2. Large variation in blood flow between left ventricular segments, as detected by adenosine stress dynamic CT perfusion.
    Open this publication in new window or tab >>Large variation in blood flow between left ventricular segments, as detected by adenosine stress dynamic CT perfusion.
    Show others...
    2015 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 35, no 4, p. 291-300Article in journal (Refereed) Published
    Abstract [en]

    BACKGROUND: Dynamic cardiac CT perfusion (CTP) is based on repeated imaging during the first-pass contrast agent inflow. It is a relatively new method that still needs validation.

    PURPOSE: To evaluate the variation in adenosine stress dynamic CTP blood flow as compared to (99m) Tc SPECT. Secondarily, to compare manual and automatic segmentation.

    METHODS: Seventeen patients with manifest coronary artery disease were included. Nine were excluded from evaluation for various reasons. All patients were examined with dynamic stress CTP and stress/rest SPECT. CTP blood flow was compared with SPECT on a per segment basis. Results for manual and automated AHA segmentation were compared.

    RESULTS: CTP showed a positive correlation with SPECT, with correlation coefficients of 0·38 and 0·41 for manual and automatic segmentation, respectively (P<0·0001). There was no significant difference between the correlation coefficients of the manual and automated segmentation procedures (P = 0·75). The average per individual global CTP blood flow value for normal segments varied by a factor of 1·9 (manual and automatic segmentation). For the whole patient group, the CTP blood flow value in normal segments varied by a factor of 2·9/2·7 (manual/automatic segmentation). Within each patient, the average per segment blood flow in normal segments varied by a factor of 1·3-2·0/1·2-2·1 (manual/automatic segmentation).

    CONCLUSION: A positive but rather weak correlation was found between CTP and (99m) Tc SPECT. Large variations in CTP blood flow suggest that a cut-off value for stress myocardial blood flow is inadequate to detect ischaemic segments. Dynamic CTP is hampered by a limited coverage.

    National Category
    Clinical Medicine
    Identifiers
    urn:nbn:se:liu:diva-113400 (URN)10.1111/cpf.12163 (DOI)000356312800007 ()24842265 (PubMedID)
    Available from: 2015-01-17 Created: 2015-01-17 Last updated: 2017-12-05
    3. Software-based on-site estimation of fractional flow reserve using standard coronary CT angiography data.
    Open this publication in new window or tab >>Software-based on-site estimation of fractional flow reserve using standard coronary CT angiography data.
    Show others...
    2016 (English)In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, no 10, p. 1186-1192Article in journal (Refereed) Published
    Abstract [en]

    BACKGROUND: The significance of a coronary stenosis can be determined by measuring the fractional flow reserve (FFR) during invasive coronary angiography. Recently, methods have been developed which claim to be able to estimate FFR using image data from standard coronary computed tomography angiography (CCTA) exams.

    PURPOSE: To evaluate the accuracy of non-invasively computed fractional flow reserve (cFFR) from CCTA.

    MATERIAL AND METHODS: A total of 23 vessels in 21 patients who had undergone both CCTA and invasive angiography with FFR measurement were evaluated using a cFFR software prototype. The cFFR results were compared to the invasively obtained FFR values. Correlation was calculated using Spearman's rank correlation, and agreement using intraclass correlation coefficient (ICC). Sensitivity, specificity, accuracy, negative predictive value, and positive predictive value for significant stenosis (defined as both FFR ≤0.80 and FFR ≤0.75) were calculated.

    RESULTS: The mean cFFR value for the whole group was 0.81 and the corresponding mean invFFR value was 0.84. The cFFR sensitivity for significant stenosis (FFR ≤0.80/0.75) on a per-lesion basis was 0.83/0.80, specificity was 0.76/0.89, and accuracy 0.78/0.87. The positive predictive value was 0.56/0.67 and the negative predictive value was 0.93/0.94. The Spearman rank correlation coefficient was ρ = 0.77 (P < 0.001) and ICC = 0.73 (P < 0.001).

    CONCLUSION: This particular CCTA-based cFFR software prototype allows for a rapid, non-invasive on-site evaluation of cFFR. The results are encouraging and cFFR may in the future be of help in the triage to invasive coronary angiography.

    Place, publisher, year, edition, pages
    Sage Publications, 2016
    Keywords
    Cardiac; computed tomography angiography (CTA); heart; arteries; adults; computer applications – detection/diagnosis
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:liu:diva-123579 (URN)10.1177/0284185115622075 (DOI)000382967500007 ()26691914 (PubMedID)
    Note

    Funding agencies: Department of Radiology, Region Ostergotland; Swedish Heart-Lung-foundation [20120449]

    Available from: 2015-12-29 Created: 2015-12-29 Last updated: 2017-12-01Bibliographically approved
    Download full text (pdf)
    fulltext
    Download (pdf)
    omslag
    Download (jpg)
    presentationsbild
  • 91.
    de Geer, Jakob
    et al.
    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).
    Coenen, Adriaan
    Erasmus MC, Netherlands.
    Kim, Young-Hak
    Univ Ulsan, South Korea.
    Kruk, Mariusz
    Inst Cardiol, Poland; Inst Cardiol, Poland.
    Tesche, Christian
    Med Univ South Carolina, SC 29425 USA.
    Schoepf, U. Joseph
    Med Univ South Carolina, SC 29425 USA.
    Kepka, Cezary
    Inst Cardiol, Poland; Inst Cardiol, Poland.
    Yang, Dong Hyun
    Univ Ulsan, South Korea.
    Nieman, Koen
    Erasmus MC, Netherlands; Stanford Univ, CA 94305 USA; Stanford Univ, CA 94305 USA.
    Persson, 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 Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Effect of Tube Voltage on Diagnostic Performance of Fractional Flow Reserve Derived From Coronary CT Angiography With Machine Learning: Results From the MACHINE Registry2019In: American Journal of Roentgenology, ISSN 0361-803X, E-ISSN 1546-3141, Vol. 213, no 2, p. 325-331Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE. Coronary CT angiography (CCTA)-based methods allow noninvasive estimation of fractional flow reserve (cFFR), recently through use of a machine learning (ML) algorithm (cFFR(ML)). However, attenuation values vary according to the tube voltage used, and it has not been shown whether this significantly affects the diagnostic performance of cFFR and cFFR(ML). Therefore, the purpose of this study is to retrospectively evaluate the effect of tube voltage on the diagnostic performance of cFFR(ML). MATERIALS AND METHODS. A total of 525 coronary vessels in 351 patients identified in the MACHINE consortium registry were evaluated in terms of invasively measured FFR and cFFR(ML). CCTA examinations were performed with a tube voltage of 80, 100, or 120 kVp. For each tube voltage value, correlation (assessed by Spearman rank correlation coefficient), agreement (evaluated by intraclass correlation coefficient and Bland-Altman plot analysis), and diagnostic performance (based on ROC AUC value, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy) of the cFFR(ML) in terms of detection of significant stenosis were calculated. RESULTS. For tube voltages of 80, 100, and 120 kVp, the Spearman correlation coefficient for cFFR(ML) in relation to the invasively measured FFR value was rho = 0.684, rho = 0.622, and rho = 0.669, respectively (p amp;lt; 0.001 for all). The corresponding intraclass correlation coefficient was 0.78, 0.76, and 0.77, respectively (p amp;lt; 0.001 for all). Sensitivity was 100.0%, 73.5%, and 85.0%, and specificity was 76.2%, 79.0%, and 72.8% for tube voltages of 80, 100, and 120 kVp, respectively. The ROC AUC value was 0.90, 0.82, and 0.80 for 80, 100, and 120 kVp, respectively (p amp;lt; 0.001 for all). CONCLUSION. CCTA-derived cFFR(ML) is a robust method, and its performance does not vary significantly between examinations performed using tube voltages of 100 kVp and 120 kVp. However, because of rapid advancements in CT and postprocessing technology, further research is needed.

  • 92.
    De Geer, Jakob
    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). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Gjerde, Marcus
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Cardiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Brudin, Lars
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Department of Clinical Physiology in Kalmar, Linköping University, County Council of Kalmar, Kalmar, Sweden.
    Olsson, Eva
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    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 Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Engvall, Jan
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Large variation in blood flow between left ventricular segments, as detected by adenosine stress dynamic CT perfusion.2015In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 35, no 4, p. 291-300Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Dynamic cardiac CT perfusion (CTP) is based on repeated imaging during the first-pass contrast agent inflow. It is a relatively new method that still needs validation.

    PURPOSE: To evaluate the variation in adenosine stress dynamic CTP blood flow as compared to (99m) Tc SPECT. Secondarily, to compare manual and automatic segmentation.

    METHODS: Seventeen patients with manifest coronary artery disease were included. Nine were excluded from evaluation for various reasons. All patients were examined with dynamic stress CTP and stress/rest SPECT. CTP blood flow was compared with SPECT on a per segment basis. Results for manual and automated AHA segmentation were compared.

    RESULTS: CTP showed a positive correlation with SPECT, with correlation coefficients of 0·38 and 0·41 for manual and automatic segmentation, respectively (P<0·0001). There was no significant difference between the correlation coefficients of the manual and automated segmentation procedures (P = 0·75). The average per individual global CTP blood flow value for normal segments varied by a factor of 1·9 (manual and automatic segmentation). For the whole patient group, the CTP blood flow value in normal segments varied by a factor of 2·9/2·7 (manual/automatic segmentation). Within each patient, the average per segment blood flow in normal segments varied by a factor of 1·3-2·0/1·2-2·1 (manual/automatic segmentation).

    CONCLUSION: A positive but rather weak correlation was found between CTP and (99m) Tc SPECT. Large variations in CTP blood flow suggest that a cut-off value for stress myocardial blood flow is inadequate to detect ischaemic segments. Dynamic CTP is hampered by a limited coverage.

  • 93.
    De Geer, Jakob
    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).
    Sandstedt, Mårten
    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).
    Björkholm, Anders
    Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Alfredsson, Joakim
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Cardiology in Linköping.
    Janzon, Magnus
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Cardiology in Linköping.
    Engvall, Jan
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    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.
    Software-based on-site estimation of fractional flow reserve using standard coronary CT angiography data.2016In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, no 10, p. 1186-1192Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The significance of a coronary stenosis can be determined by measuring the fractional flow reserve (FFR) during invasive coronary angiography. Recently, methods have been developed which claim to be able to estimate FFR using image data from standard coronary computed tomography angiography (CCTA) exams.

    PURPOSE: To evaluate the accuracy of non-invasively computed fractional flow reserve (cFFR) from CCTA.

    MATERIAL AND METHODS: A total of 23 vessels in 21 patients who had undergone both CCTA and invasive angiography with FFR measurement were evaluated using a cFFR software prototype. The cFFR results were compared to the invasively obtained FFR values. Correlation was calculated using Spearman's rank correlation, and agreement using intraclass correlation coefficient (ICC). Sensitivity, specificity, accuracy, negative predictive value, and positive predictive value for significant stenosis (defined as both FFR ≤0.80 and FFR ≤0.75) were calculated.

    RESULTS: The mean cFFR value for the whole group was 0.81 and the corresponding mean invFFR value was 0.84. The cFFR sensitivity for significant stenosis (FFR ≤0.80/0.75) on a per-lesion basis was 0.83/0.80, specificity was 0.76/0.89, and accuracy 0.78/0.87. The positive predictive value was 0.56/0.67 and the negative predictive value was 0.93/0.94. The Spearman rank correlation coefficient was ρ = 0.77 (P < 0.001) and ICC = 0.73 (P < 0.001).

    CONCLUSION: This particular CCTA-based cFFR software prototype allows for a rapid, non-invasive on-site evaluation of cFFR. The results are encouraging and cFFR may in the future be of help in the triage to invasive coronary angiography.

  • 94.
    de las Heras Gala, Hugo
    et al.
    Helmholtz Zentrum München, Munich, Germany.
    Torresin, Alberto
    ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy.
    Dasu, Alexandru
    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. The Skandion Clinic, Uppsala, Sweden.
    Rampado, Osvaldo
    A.O.U. Città della Salute e della Scienza, Torino, Italy.
    Delis, Harry
    International Atomic Energy Agency, Vienna, Austria.
    Hernández Girón, Irene
    Leiden University Medical Center, Leiden, The Netherlands.
    Theodorakou, Chrysoula
    The Christie NHS Foundation Trust, Manchester, UK.
    Andersson, Jonas
    University of Umeå, Umeå, Sweden.
    Holroyd, John
    Dental X-ray Protection Services, PHE, UK.
    Nilsson, Mats
    Skane University Hospital, Malmö, Sweden.
    Edyvean, Sue
    Public Health England (PHE), Chilton, Didcot, Oxfordshire, UK.
    Gershan, Vesna
    Faculty of Natural Sciences and Mathematics, Skopje, Macedonia.
    Hadid-Beurrier, Lama
    Hôpital Jean-Verdier, Paris, France.
    Hoog, Christopher
    Centre Antoine Lacassagne, Nice, France.
    Delpon, Gregory
    Centre René Gauducheau, Nantes, France.
    Sancho Kolster, Ismael
    Institut Català d’Oncologia, L’Hospitalet de Llobregat, Spain.
    Peterlin, Primož
    Institute of Oncology Ljubljana, Slovenia.
    Garayoa Roca, Julia
    Fundación Jiménez Díaz, Madrid, Spain.
    Caprile, Paola
    Pontificia Universidad Católica de Chile, Santiago, Chile.
    Zervides, Costas
    University of Nicosia, Medical School, Nicosia, Cyprus.
    Quality control in cone-beam computed tomography (CBCT): EFOMP-ESTRO-IAEA protocol2017Report (Refereed)
    Abstract [en]

    Quality control of cone-beam computed tomography (CBCT) systems is an essential part of quality assurance to periodically check that quality requirements are met, reduce uncertainties and errors and reduce the likelihood of accidents and incidents. Radiation exposure levels must be measured to ensure that patient doses associated with CBCT examinations are kept as low as reasonably achievable consistent with the required diagnostic information. The main purpose of this document is to present procedures for quality control of CBCT systems used for dental, radiotherapy, interventional radiology and guided surgery applications.

    The ‘Quality control in cone-beam computed tomography’ is the second of the series on quality control protocols. The European Federation of Organizations for Medical Physics (EFOMP) published the first document on ‘Quality Controls in digital mammography’ in 2015. These books are freely available online at efomp.org and can be used as both, in-depth working guides to everyday practice and an up-to-date reference sources for medical physicists engaged in quality control of medical imaging systems.

    This book is the result of the experience and knowledge of an international group of leading medical physics experts and an excellent illustration of the synergy that can be achieved when every team member works at their best and collaboratively follows the whole process through its completion.

  • 95.
    de las Heras Gala, Hugo
    et al.
    Helmholtz Zentrum München, Munich, Germany.
    Torresin, Alberto
    ASST Grande Ospedale Metropolitano Niguarda, Milano, Italy.
    Dasu, Alexandru
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. The Skandion Clinic, Uppsala, Sweden.
    Rampado, Osvaldo
    A.O.U. Città della Salute e della Scienza, Torino, Italy.
    Delis, Harry
    International Atomic Energy Agency, Vienna, Austria.
    Hernández Girón, Irene
    Leiden University Medical Center, Leiden, The Netherlands.
    Theodorakou, Chrysoula
    The Christie NHS Foundation Trust, Manchester, UK.
    Andersson, Jonas
    University of Umeå, Umeå, Sweden.
    Holroyd, John
    Dental X-ray Protection Services, PHE, UK.
    Nilsson, Mats
    Skane University Hospital, Malmö, Sweden.
    Edyvean, Sue
    Public Health England (PHE), Chilton, Didcot, Oxfordshire, UK.
    Gershan, Vesna
    Faculty of Natural Sciences and Mathematics, Skopje, Macedonia.
    Hadid-Beurrier, Lama
    Hôpital Jean-Verdier, Paris, France.
    Hoog, Christopher
    Centre Antoine Lacassagne, Nice, France.
    Delpon, Gregory
    Centre René Gauducheau, Nantes, France.
    Sancho Kolster, Ismael
    Institut Català d’Oncologia, L’Hospitalet de Llobregat, Spain.
    Peterlin, Primož
    Institute of Oncology Ljubljana, Slovenia.
    Garayoa Roca, Julia
    Fundación Jiménez Díaz, Madrid, Spain.
    Caprile, Paola
    Pontificia Universidad Católica de Chile, Santiago, Chile.
    Zervides, Costas
    University of Nicosia, Medical School, Nicosia, Cyprus.
    Quality control in cone-beam computed tomography (CBCT) EFOMP-ESTRO-IAEA protocol (summary report)2017In: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 39, p. 67-72Article in journal (Refereed)
    Abstract [en]

    The aim of the guideline presented in this article is to unify the test parameters for image quality evaluation and radiation output in all types of cone-beam computed tomography (CBCT) systems. The applications of CBCT spread over dental and interventional radiology, guided surgery and radiotherapy. The chosen tests provide the means to objectively evaluate the performance and monitor the constancy of the imaging chain. Experience from all involved associations has been collected to achieve a consensus that is rigorous and helpful for the practice.

    The guideline recommends to assess image quality in terms of uniformity, geometrical precision, voxel density values (or Hounsfield units where available), noise, low contrast resolution and spatial resolution measurements. These tests usually require the use of a phantom and evaluation software. Radiation output can be determined with a kerma-area product meter attached to the tube case. Alternatively, a solid state dosimeter attached to the flat panel and a simple geometric relationship can be used to calculate the dose to the isocentre. Summary tables including action levels and recommended frequencies for each test, as well as relevant references, are provided.

    If the radiation output or image quality deviates from expected values, or exceeds documented action levels for a given system, a more in depth system analysis (using conventional tests) and corrective maintenance work may be required.

  • 96.
    deSouza, Nandita M.
    et al.
    Cancer Res UK Imaging Ctr, England; Royal Marsden Hosp, England.
    Achten, Eric
    Ghent Univ Hosp, Belgium.
    Alberich-Bayarri, Angel
    QUIBIM SL Fe Hlth Res Inst, Spain.
    Bamberg, Fabian
    Univ Freiburg, Germany.
    Boellaard, Ronald
    Vrije Univ Amsterdam, Netherlands.
    Clement, Olivier
    Hop Europeen Georges Pompidou, France.
    Fournier, Laure
    Hop Europeen Georges Pompidou, France.
    Gallagher, Ferdia
    Univ Cambridge, England.
    Golay, Xavier
    UCL Inst Neurol, England.
    Heussel, Claus Peter
    Heidelberg Univ, Germany.
    Jackson, Edward F.
    Univ Wisconsin, WI USA.
    Manniesing, Rashindra
    Radboud Univ Nijmegen, Netherlands.
    Mayerhofer, Marius E.
    Med Univ Vienna, Austria.
    Neri, Emanuele
    Univ Pisa, Italy.
    OConnor, James
    Univ Manchester, England.
    Oguz, Kader Karli
    Hacettepe Univ Hosp, Turkey.
    Persson, 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 Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Smits, Marion
    Erasmus MC, Netherlands.
    van Beek, Edwin J. R.
    Queens Med Res Inst, Scotland.
    Zech, Christoph J.
    Univ Basel, Switzerland.
    Validated imaging biomarkers as decision-making tools in clinical trials and routine practice: current status and recommendations from the EIBALL* subcommittee of the European Society of Radiology (ESR)2019In: Insight into Imaging, ISSN 1869-4101, E-ISSN 1869-4101, Vol. 10, no 1, article id UNSP 87Article in journal (Refereed)
    Abstract [en]

    Observer-driven pattern recognition is the standard for interpretation of medical images. To achieve global parity in interpretation, semi-quantitative scoring systems have been developed based on observer assessments; these are widely used in scoring coronary artery disease, the arthritides and neurological conditions and for indicating the likelihood of malignancy. However, in an era of machine learning and artificial intelligence, it is increasingly desirable that we extract quantitative biomarkers from medical images that inform on disease detection, characterisation, monitoring and assessment of response to treatment. Quantitation has the potential to provide objective decision-support tools in the management pathway of patients. Despite this, the quantitative potential of imaging remains under-exploited because of variability of the measurement, lack of harmonised systems for data acquisition and analysis, and crucially, a paucity of evidence on how such quantitation potentially affects clinical decision-making and patient outcome. This article reviews the current evidence for the use of semi-quantitative and quantitative biomarkers in clinical settings at various stages of the disease pathway including diagnosis, staging and prognosis, as well as predicting and detecting treatment response. It critically appraises current practice and sets out recommendations for using imaging objectively to drive patient management decisions.

    Download full text (pdf)
    fulltext
  • 97. Order onlineBuy this publication >>
    Drissi, Natasha Morales
    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).
    Brain Networks and Dynamics in Narcolepsy2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Narcolepsy is a chronic sleep disorder, characterised by excessive daytime sleepiness with frequent uncontrollable sleep attacks. In addition to sleeprelated problems, changes in cognition have also been observed in patients with narcolepsy and has been linked to the loss of Orexin-A in a number of studies. Results from previous functional and structural neuroimaging studies would suggest that the loss of Orexin-A has numerous downstream effects in terms of both resting state glucose metabolism and perfusion and reduction in cortical grey matter.

    Specifically, studies investigating narcolepsy with positron emission tomography (PET) and single photon emission computed tomography (SPECT) have observed aberrant perfusion and glucose metabolism in the hypothalamus and thalamus, as well as in prefrontal cortex. A very recent PET study in a large cohort of adolescents with type 1 narcolepsy further observed that the hypoand hypermetabolism in many of these cortico-frontal and subcortical brain regions also exhibited significant correlations with performance on a number of neurocognitive tests. These findings parallel those found in structural neuroimaging studies, where a reduction of cortical grey matter in frontotemporal areas has been observed.

    The Aim of this thesis was to investigate mechanisms and aetiology behind the symptoms in narcolepsy through the application of different neuroimaging techniques. I present in this thesis evidence supporting that the complaints about subjective memory deficits in narcolepsy are related to a misallocation of resources.

    I further describe how this has its seat in defective default mode network activation, possibly involving alterations to GABA and Glutamate signaling. In addition to this, I present our findings of a structural deviation in an area of the brainstem previously not described in the aetiology of narcolepsy.

    This finding may have implications for further understanding the aetiology of the disease and the specific neuronal populations involved.

    In addition to this, I show evidence from adipose tissue measurements in specific compartments, confirming that weight gain in narcolepsy is characterized by centrally located weight gain and may be specifically related to OX changes, but maybe not brown adipose tissue volume.

    The findings presented in this thesis provides new insights to the pathophysiology of narcolepsy beyond the well-known depletion of OX producing neurons in the hypothalamus.

    List of papers
    1. Altered Brain Microstate Dynamics in Adolescents with Narcolepsy
    Open this publication in new window or tab >>Altered Brain Microstate Dynamics in Adolescents with Narcolepsy
    Show others...
    2016 (English)In: Frontiers in Human Neuroscience, ISSN 1662-5161, E-ISSN 1662-5161, Vol. 10, no 369Article in journal (Refereed) Published
    Abstract [en]

    Narcolepsy is a chronic sleep disorder caused by a loss of hypocretin-1 producing neurons in the hypothalamus. Previous neuroimaging studies have investigated brain function in narcolepsy during rest using positron emission tomography (PET) and single photon emission computed tomography (SPECT). In addition to hypothalamic and thalamic dysfunction they showed aberrant prefrontal perfusion and glucose metabolism in narcolepsy. Given these findings in brain structure and metabolism in narcolepsy, we anticipated that changes in functional magnetic resonance imaging (fMRI) resting state network (RSN) dynamics might also be apparent in patients with narcolepsy. The objective of this study was to investigate and describe brain microstate activity in adolescents with narcolepsy and correlate these to RSNs using simultaneous fMRI and electroencephalography (EEG). Sixteen adolescents (ages 13-20) with a confirmed diagnosis of narcolepsy were recruited and compared to age-matched healthy controls. Simultaneous EEG and fMRI data were collected during 10 min of wakeful rest. EEG data were analyzed for microstates, which are discrete epochs of stable global brain states obtained from topographical EEG analysis. Functional fMRI data were analyzed for RSNs. Data showed that narcolepsy patients were less likely than controls to spend time in a microstate which we found to be related to the default mode network and may suggest a disruption of this network that is disease specific. We concluded that adolescents with narcolepsy have altered resting state brain dynamics.

    Place, publisher, year, edition, pages
    FRONTIERS MEDIA SA, 2016
    Keywords
    narcolepsy; default mode network; functional magnetic resonance imaging (fMRI); electroencephalography (EEG); microstates; resting state networks; orexin; sleep
    National Category
    Neurology
    Identifiers
    urn:nbn:se:liu:diva-131167 (URN)10.3389/fnhum.2016.00369 (DOI)000380989900001 ()27536225 (PubMedID)
    Note

    Funding Agencies|Research Council of South East Sweden (FORSS); Knut and Alice Wallenberg foundation (KAW); strategic research area of systems neurobiology at Linkoping University; Country council of Ostergotland Sweden

    Available from: 2016-09-20 Created: 2016-09-12 Last updated: 2019-01-04
    2. Evidence for cognitive resource imbalance in adolescents with narcolepsy
    Open this publication in new window or tab >>Evidence for cognitive resource imbalance in adolescents with narcolepsy
    Show others...
    2018 (English)In: Brain Imaging and Behavior, ISSN 1931-7557, E-ISSN 1931-7565, Vol. 12, no 2, p. 411-424Article in journal (Refereed) Published
    Abstract [en]

    The study investigated brain activity changes during performance of a verbal working memory task in a population of adolescents with narcolepsy. Seventeen narcolepsy patients and twenty healthy controls performed a verbal working memory task during simultaneous fMRI and EEG acquisition. All subjects also underwent MRS to measure GABA and Glutamate concentrations in the medial prefrontal cortex. Activation levels in the default mode network and left middle frontal gyrus were examined to investigate whether narcolepsy is characterized by an imbalance in cognitive resources. Significantly increased deactivation within the default mode network during task performance was observed for the narcolepsy patients for both the encoding and recognition phases of the task. No evidence for task performance deficits or reduced activation within the left middle frontal gyrus was noted for the narcolepsy patients. Correlation analyses between the spectroscopy and fMRI data indicated that deactivation of the anterior aspect of the default mode in narcolepsy patients correlated more with increased concentrations of Glutamate and decreased concentrations of GABA. In contrast, deactivation in the default mode was correlated with increased concentrations of GABA and decreased concentrations of Glutamate in controls. The results suggested that narcolepsy is not characterized by a deficit in working memory but rather an imbalance of cognitive resources in favor of monitoring and maintaining attention over actual task performance. This points towards dysregulation within the sustained attention system being the origin behind self-reported cognitive difficulties in narcolepsy.

    Place, publisher, year, edition, pages
    Springer-Verlag New York, 2018
    Keywords
    EEG, GABA, MRS, Narcolepsy, Working memory, fMRI
    National Category
    Radiology, Nuclear Medicine and Medical Imaging
    Identifiers
    urn:nbn:se:liu:diva-145535 (URN)10.1007/s11682-017-9706-y (DOI)000429029000011 ()28321606 (PubMedID)2-s2.0-85015625386 (Scopus ID)
    Available from: 2018-03-05 Created: 2018-03-05 Last updated: 2019-05-01Bibliographically approved
    3. Unexpected Fat Distribution in Adolescents With Narcolepsy
    Open this publication in new window or tab >>Unexpected Fat Distribution in Adolescents With Narcolepsy
    Show others...
    2018 (English)In: Frontiers in Endocrinology, ISSN 1664-2392, E-ISSN 1664-2392, Vol. 9, article id 728Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    FRONTIERS MEDIA SA, 2018
    Keywords
    orexin; hypocretin; brown adipose tissue; visceral adipose tissue; subcutaneous adipose tissue; BMI; magnetic resonance imaging (MRI); obesity
    National Category
    Endocrinology and Diabetes
    Identifiers
    urn:nbn:se:liu:diva-153502 (URN)10.3389/fendo.2018.00728 (DOI)000452268600001 ()
    Note

    Funding Agencies|Research Council of South East Sweden [FORSS-480551]; Knut and Alice Wallenberg foundation [KAW 2013.0076]

    Available from: 2019-01-02 Created: 2019-01-02 Last updated: 2019-06-14
    Download full text (pdf)
    Brain Networks and Dynamics in Narcolepsy
    Download (png)
    presentationsbild
  • 9