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  • 1.
    Almeida, Rosimary
    Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Tekniska högskolan.
    Severity of illness versus severity of disease: definitions and applications1996Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Outcome assessment should consist of two basic steps - "selection of a meaningful outcome" and "determination of what caused the outcome". The latter step requires comparisons, and therefore information about the initial status of the patients. Severity ratings attempt to group patients with similar initial status so that outcome comparisons are meaningful. They are consequently an essential ingredient in outcome assessment.

    This thesis aims at expanding the knowledge about outcome measurement focusing on the severity of a case with regard to definitions and applications of severity measures. Further, theoretical knowledge is integrated with practical needs for outcome assessment and methodology is developed for modelling the use of resources and interpreting the association between different severity measures.

    As with illness and disease, severity of illness and severity of disease are interchangeable terms in medical literature. Based on a holistic theory of health, these terms were differentiated. Severity of a case was described by two basic components - severity of disease and severity of illness. Essentially, severity of illness concerns suffering and disability, and severity of disease concerns risk of death, risk of suffering and risk of disability. These definitions were the core of a set of criteria for classifying severity measures or outcome measures.

    The role of a disease severity score in explaining resources use (e.g., intensity of technology utilization and length of hospital stay) in a neonatal intensive care unit was investigated. A disease severity score based on the death risk of the initial diagnosis was found to be an indicator of intensity of therapeutic technology together with gestational age and Apgar score. However, it does not show statistical significance to explain length of stay, which was explained by intensity of diagnostic technology and birthweight.

    The demand for patient classification systems (standard systems to describe a patient's condition) on a national and local level was investigated. There is little experience in the use of these systems, but at the same time there is a demand from the nurse managers for standard measures of a patient's need for care.

    There is still little knowledge about the association between severity of illness and severity of disease. This association was studied for patients with ulcerative colitis using data analysis techniques for dimension reduction such as cluster analysis, homogeneity analysis and non linear principal components analysis. A non linear relationship between illness and disease severity measures was found. The overall clinical judgement of disease activity was more related to illness patterns than symptoms or endoscopy and laboratory findings. In addition, the two measures of illness severity (Sickness Impact Profile and Rating Form for Inflammatory Bowel Disease Patient Concerns) were found to represent complementary information about a patient's illness experience. This illustrates the importance of conceptual knowledge in the selection process of an illness measure for outcome evaluations. These findings also reinforce the need for the development of systems to support interpretation of these kinds of complex associations, as traditional statistics have been shown to be of limited value under these circumstances.

  • 2.
    Hass, Ursula
    Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Tekniska högskolan.
    Assessment of assistive technology: outcomes, costs and quality1996Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Technology assessment aims at providing information about costs and effects, in order to support decision making and resource allocation. The purpose of this thesis is to, through empirical studies on assistive technologies, investigate the contribution of various kinds of outcome measures, and provide knowledge about outcomes, costs and quality of services.

    Welfare losses were found for disability groups compared to the general population. High health care utilization and needs for a better social life was also expressed by disabled people in the study.

    For stroke patients assistive devices amounted to about 1.3 per cent of the total costs for health care and services during the first year after stroke. Functional ability by admission to hospital was found to be an important predictor of the total cost. Those with assistive devices, although having achieved a high functional ability one year after the stroke, perceived and rated their life situation considerably more impaired than those without assistive devices. It was found that utilizers of assistive devices had low influence on the selection process.

    A new program, based on improved user participation, for the selection process of assistive devices was found to yield increased user participation, user satisfaction, increased number of devices, and consequently also higher costs for assistive technology. The outcome measures, indicating functional ability and health related quality of life, showed more vague improvements. Women below 64 years rated improved health related quality of life at a follow-up. No improvement in functional ability was found at this follow-up.

    An assessment of computer aided assistive technologies was performed. It was found that the average goal fulfilment was high regarding handling the equipment, functional ability, and activities and roles. No significant changes were found in health related quality of life and utility for the clients. However, clients with speech impairment rated impaired utility at the follow-up, and clients with other communication disabilities rated an improved utility. The average total cost per person (including selection process and device) amounted to SEK 14 800.

    Measures on process and outcome can yield complementary results, and thus, they are important in order to understand the relations between quality of services and outcomes. Outcome measures are usually developed for the health care sector, and have the purpose to reflect the impact of health changes. This is a problem in assessments of assistive technology, since health, and disability or handicap, are not always closely related. The distinction between disability and handicap, as defined by the International Classification of Impairments, Disabilities, and Handicaps (ICIDH) by WHO 1980, is usually not reflected in outcome measures available.

  • 3.
    Maret, Eva
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Institutionen för medicin och hälsa. Linköpings universitet, Hälsouniversitetet.
    Tödt, Tim
    Linköpings universitet, Institutionen för medicin och hälsa, Kardiologi. Östergötlands Läns Landsting, Hjärtcentrum, Kardiologiska kliniken. Linköpings universitet, Hälsouniversitetet.
    Brudin, Lars
    Linköpings universitet, Institutionen för medicin och hälsa. Linköpings universitet, Hälsouniversitetet.
    Nylander, Eva
    Linköpings universitet, Institutionen för medicin och hälsa, Fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken. Linköpings universitet, Hälsouniversitetet.
    Swahn, Eva
    Östergötlands Läns Landsting, Hjärtcentrum, Kardiologiska kliniken. Linköpings universitet, Institutionen för medicin och hälsa, Kardiologi. Linköpings universitet, Hälsouniversitetet.
    Ohlsson, Jan
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Hälsouniversitetet.
    Engvall, Jan
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken. Linköpings universitet, Hälsouniversitetet.
    Functional measurements based on feature tracking of cine magnetic resonance images identify left ventricular segments with myocardial scar.2009Ingår i: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 7, nr 53, s. 1-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background

    The aim of the study was to perform a feature tracking analysis on cine magnetic resonance (MR) images to elucidate if functional measurements of the motion of the left ventricular wall may detect scar defined with gadolinium enhanced MR.

    Myocardial contraction can be measured in terms of the velocity, displacement and local deformation (strain) of a particular myocardial segment. Contraction of the myocardial wall will be reduced in the presence of scar and as a consequence of reduced myocardial blood flow.

    Methods

    Thirty patients (3 women and 27 men) were selected based on the presence or absence of extensive scar in the anteroseptal area of the left ventricle. The patients were investigated in stable clinical condition, 4-8 weeks post ST-elevation myocardial infarction treated with percutaneous coronary intervention. Seventeen had a scar area >75% in at least one anteroseptal segment (scar) and thirteen had scar area <1% (non-scar). Velocity, displacement and strain were calculated in the longitudinal direction, tangential to the endocardial outline, and in the radial direction, perpendicular to the tangent.

    Results

    In the scar patients, segments with scar showed lower functional measurements than remote segments. Radial measurements of velocity, displacement and strain performed better in terms of receiver-operator-characteristic curves (ROC) than the corresponding longitudinal measurements. The best area-under-curve was for radial strain, 0.89, where a cut-off value of 38.8% had 80% sensitivity and 86% specificity for the detection of a segment with scar area >50%. As a percentage of the mean, intraobserver variability was 16-14-26% for radial measurements of displacement-velocity-strain and corresponding interobserver variability was 13-12-18%.

    Conclusion

    Feature tracking analysis of cine-MR displays velocity, displacement and strain in the radial and longitudinal direction and may be used for the detection of transmural scar. The accuracy and repeatability of the radial functional measurements is satisfactory and global measures agree.

  • 4.
    Persson, Anders
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Brismar, Torkel
    Karolinska Institutet, CLINTEC, Röntgenavdelningen, Karolinska Universitetssjukhuset Huddinge.
    Lundström, Claes
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Dahlström, Nils
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Smedby, Örjan
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Othberg, Fredrik
    Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Hälsouniversitetet.
    Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta2006Ingår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 47, nr 2, s. 172-178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: To compare three methods for standardizing volume rendering technique (VRT) protocols by studying aortic diameter measurements in magnetic resonance angiography (MRA) datasets.

    Material and Methods: Datasets from 20 patients previously examined with gadolinium-enhanced MRA and with digital subtraction angiography (DSA) for abdominal aortic aneurysm were retrospectively evaluated by three independent readers. The MRA datasets were viewed using VRT with three different standardized transfer functions: the percentile method (Pc-VRT), the maximum-likelihood method (ML-VRT), and the partial range histogram method (PRH-VRT). The aortic diameters obtained with these three methods were compared with freely chosen VRT parameters (F-VRT) and with maximum intensity projection (MIP) concerning inter-reader variability and agreement with the reference method DSA.

    Results: F-VRT parameters and PRH-VRT gave significantly higher diameter values than DSA, whereas Pc-VRT gave significantly lower values than DSA. The highest interobserver variability was found for F-VRT parameters and MIP, and the lowest for Pc-VRT and PRH-VRT. All standardized VRT methods were significantly superior to both MIP and F-VRT in this respect. The agreement with DSA was best for PRH-VRT, which was the only method with a mean error below 1 mm and which also had the narrowest limits of agreement (95% of cases between 2.1 mm below and 3.1 mm above DSA).

    Conclusion: All the standardized VRT methods compare favorably with MIP and VRT with freely selected parameters as regards interobserver variability. The partial range histogram method, although systematically overestimating vessel diameters, gives results closest to those of DSA.

  • 5.
    Ragnehed, Mattias
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan. Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Hälsouniversitetet.
    Application of fMRI in clinical situations2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Since its discovery in the early 1990's functional MRI (fMRI) has become the most widely used technique for mapping of brain functions. Its non-invasiveness and the large number of MR-scanners have contributed to the popularity of fMRI. In recent years the interest in using fMRI as a clinical instrument has increased, primarily for pre-operative planning. The purpose of this work is to improve the applicability of fMRI to clinical situations.

    In order to attain the objectives the capacity of analysis methods for fMRI was evaluated, design of paradigms to suit patients was looked into and the effects of an anxiolytic was investigated.

    Especially when fMRI is used in the clinic it is crucial that the analysis method employed is sensitive and reliable. It was confirmed that the method developed by Friman et al. is a worthy competitor to other analysis methods. In general the abilities of patients are reduced compared with healthy volunteer subjects. Therefore one has to design the tasks and task instructions to be readily comprehensible. In addition it is not uncommon that patients are anxious before the examinations and the unfamiliar environment in the MR department. Some need a small dose of an anxiolytic to be able to undergo the examination. The effect of an anxiolytic on healthy volunteers was evaluated. No effects on the fMRI results was identified but the results were confounded by a large session effect.

    Delarbeten
    1. Performance of canonical correlation analysis in language tests by functional MRI
    Öppna denna publikation i ny flik eller fönster >>Performance of canonical correlation analysis in language tests by functional MRI
    Visa övriga...
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper a new method based on constraitwd canonical correlation analysis (CCA) for the analysis of fMRI data is evaluated. In particular the method benefits from a powerful way of choosing temporal basis functions in additiou to an adaptive spatial filtering scheme. A modified receiver operating characteristic (ROC) method was used to quantify the results and to compare it with traditionally used statistics in an objective way. The evaluation was performed using real fMRI data form a language test. It was shown that the CCA based method offers a significant gain in detection power.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-97715 (URN)
    Tillgänglig från: 2013-09-20 Skapad: 2013-09-20 Senast uppdaterad: 2014-10-02
    2. Paradigm design of sensory–motor and language tests in clinical fMRI
    Öppna denna publikation i ny flik eller fönster >>Paradigm design of sensory–motor and language tests in clinical fMRI
    2004 (Engelska)Ingår i: Neurophysiologie clinique, ISSN 0987-7053, E-ISSN 1769-7131, Vol. 34, nr 6, s. 267-277Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Functional magnetic resonance imaging (fMRI) paradigms on sensory–motor and language functions are reviewed from a clinical user’s perspective. The objective was to identify special requirements regarding the design of fMRI paradigms for clinical applications. A wide range of methods for setting up fMRI examinations were found in the literature. It was concluded that there is a need for standardised procedures adapted for clinical settings. Sensory–motor activation patterns do not vary much at different hand motion tasks. Nevertheless it is one of the most important clinical tests. In contrast, the language system is much more complex. In several studies it has been observed that word production tasks are preferable in determination of language lateralisation. Broca’s area is activated by most tasks, whereas sentence processing and semantic decision also involve activation in temporoparietal and frontal areas. However, combined task analysis (CTA) of several different tasks has been found to be more robust and reliable for clinical fMRI compared to separate task analysis.

    Abstract [fr]

    Les paradigmes utilisés en Imagerie par Résonance Magnétique fonctionnelle (IRMf) pour l’étude des fonctions sensori-motrice et du langage sont passés en revue du point de vue d’un clinicien. L’objectif était de souligner les exigences spéciales nécessaires à la mise en place d’un paradigme d’IRMf dans le cadre d’études cliniques. Un très grand nombre de procédures pour la réalisation d’examens en IRMf existent dans la littérature. Il a été mis en évidence que la mise en place de procédures standardisées, adaptées aux études cliniques était nécessaire. Les patterns d’activation sensori-motrice ne varient pas plus que les tâches de mouvements de la main. Néanmoins c’est l’un des tests les plus importants en pratique clinique. Au contraire, le système du langage est beaucoup plus complexe. Un grand nombre d’études ont montré que l’utilisation de tâches de production de mots était préférable pour étudier la latéralisation du langage. L’aire de Broca est activée par beaucoup de tâches, alors que le traitement des phrases et la décision sémantique entraînent une activation des aires frontales et temporopariétales. Cependant, dans un contexte d’IRMf clinique, l’analyse des tâches combinées de plusieurs tâches différentes est plus robuste et plus fiable que l’analyse des tâches séparées.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-24683 (URN)10.1016/j.neucli.2004.09.006 (DOI)000228731600002 ()6919 (Lokalt ID)6919 (Arkivnummer)6919 (OAI)
    Tillgänglig från: 2009-10-07 Skapad: 2009-10-07 Senast uppdaterad: 2017-12-13
    3. Influence of diazepam on clinically designed FMRI
    Öppna denna publikation i ny flik eller fönster >>Influence of diazepam on clinically designed FMRI
    Visa övriga...
    2007 (Engelska)Ingår i: The Journal of Neuropsychiatry and Clinical Neurosciences, ISSN 0895-0172, E-ISSN 1545-7222, Vol. 19, nr 2, s. 164-172Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The authors investigated the effect of diazepam on clinically relevant measures from functional magnetic resonance imaging (fMRI) examinations. Twenty volunteers were scanned twice. Using a double-blind randomized study design, the volunteers received placebo on one occasion, and on the other, 5 mg of diazepam. Three functional tests were used: motor, word generation, and working memory. Images were analyzed individually for each subject and the number of activated voxels and the laterality index were calculated. No significant effects related to the drug were detected. In contrast, the motor and working memory tasks showed a significant decrease in the number of activated voxels between Sessions 1 and 2, independently of diazepam administration. These results indicate that diazepam may be administered for premedication prior to fMRI investigations.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-17989 (URN)10.1176/appi.neuropsych.19.2.164 (DOI)000245666300009 ()17431063 (PubMedID)
    Tillgänglig från: 2009-04-30 Skapad: 2009-04-30 Senast uppdaterad: 2017-12-13Bibliografiskt granskad
  • 6.
    Ragnehed, Mattias
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Håkansson, Irene
    Linköpings universitet, Institutionen för nervsystem och rörelseorgan. Linköpings universitet, Hälsouniversitetet.
    Nilsson, Maritha
    National Board of Forensic Sciences, Linköping.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Söderfeldt, Birgitta
    Department of Clinical Science and Education, Sodersjukhuset, Karolinska Institutet, Stockholm, Sweden.
    Engström, Maria
    Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Influence of diazepam on clinically designed FMRI2007Ingår i: The Journal of Neuropsychiatry and Clinical Neurosciences, ISSN 0895-0172, E-ISSN 1545-7222, Vol. 19, nr 2, s. 164-172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The authors investigated the effect of diazepam on clinically relevant measures from functional magnetic resonance imaging (fMRI) examinations. Twenty volunteers were scanned twice. Using a double-blind randomized study design, the volunteers received placebo on one occasion, and on the other, 5 mg of diazepam. Three functional tests were used: motor, word generation, and working memory. Images were analyzed individually for each subject and the number of activated voxels and the laterality index were calculated. No significant effects related to the drug were detected. In contrast, the motor and working memory tasks showed a significant decrease in the number of activated voxels between Sessions 1 and 2, independently of diazepam administration. These results indicate that diazepam may be administered for premedication prior to fMRI investigations.

  • 7.
    Sigfridsson, Andreas
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Andersson, Mats
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Wigström, Lars
    Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Kvitting, John-Peder Escobar
    Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Thorax-kärlkliniken.
    Knutsson, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Improving Temporal Fidelity in k-t BLAST MRI Reconstruction2007Ingår i: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2007: 10th International Conference, Brisbane, Australia, October 29 - November 2, 2007, Proceedings, Part II / [ed] Ayache, N; Ourdelin, S; Maeder, A, Springer Berlin/Heidelberg, 2007, s. 385-392Konferensbidrag (Refereegranskat)
    Abstract [en]

    Studies of myocardial motion using magnetic resonance imaging usually require multiple breath holds and several methods have been proposed in order to reduce the scan time. Rapid imaging using k-t BLAST has gained much attention with its high reduction factors and image quality. Temporal smoothing, however, may reduce the accuracy when assessing cardiac function. In the present work, a modified reconstruction filter is proposed, that preserves more of the high temporal frequencies. Artificial decimation of a fully sampled data set was used to evaluate the reconstruction filter. Compared to the conventional k-t BLAST reconstruction, the modified filter produced images with sharper temporal delineation of the myocardial walls.  Quantitative analysis by means of regional velocity estimation showed that the modified reconstruction filter produced more accurate velocity estimations.

  • 8.
    Svalkvist, Angelica
    et al.
    Dept. of Radiation Physics, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
    Ullman, Gustaf
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
    Håkansson, Markus
    Dept. of Radiation Physics, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden and Dept. of Diagnostic Radiology, Södra Älvsborgs Sjukhus, Sahlgrenska University Hospital, Gothenburg, Sweden.
    Dance, David R.
    NCCPM, Royal Surrey County Hospital, Guildford , UK.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicinsk teknik, Centrum för medicinsk bildvetenskap och visualisering. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Båth, Magnus
    Dept. of Radiation Physics, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden and fDept. of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden.
    Investigation of the effect of varying scatter-to-primary ratios on nodule contrast in chest tomosynthesis2011Ingår i: Medical Imaging 2011: Physics of Medical Imaging / [ed] Norbert J. Pelc; Ehsan Samei; Robert M. Nishikawa, SPIE - International Society for Optical Engineering, 2011, s. 79615Y-1-79615Y-10Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The primary aim of the present work was to analyze the effects of varying scatter-to-primary ratios on the appearance of simulated nodules in chest tomosynthesis section images. Monte Carlo simulations of the chest tomosynthesis system GE Definium 8000 VolumeRAD (GE Healthcare, Chalfont St. Giles, UK) were used to investigate the variation of scatter-to-primary ratios between different angular projections. The simulations were based on a voxel phantom created from CT images of an anthropomorphic chest phantom. An artificial nodule was inserted at 80 different positions in the simulated phantom images, using five different approaches for the scatter-to-primary ratios in the insertion process. One approach included individual determination of the scatter-to primary-ratio for each projection image and nodule location, while the other four approaches were using mean value, median value and zero degree projection value of the scatter-to-primary ratios at each nodule position as well as using a constant scatter-to-primary ratio of 0.5 for all nodule positions. The results indicate that the scatter-to-primary ratios vary up to a factor of 10 between the different angular tomosynthesis projections (±15°). However, the error in the resulting nodule contrast introduced by not taking all variations into account is in general smaller than 10 %.

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