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  • 101.
    Sandborg, Michael
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Tingberg, Anders
    Department of Radiation Physics, Malmö University Hospital, Malmö, Sweden.
    Ullman, Gustaf
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Trust and Institute of Cancer Research, London.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Comparison of clinical and physical measures of image quality in chest and pelvis computed radiography at different tube voltages2006Inngår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 33, nr 11, s. 4169-4175Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to study the dependence of image quality in digital chest and pelvis radiography on tube voltage, and to explore correlations between clinical and physical measures of image quality. The effect on image quality of tube voltage in these two examinations was assessed using two methods. The first method relies on radiologists' observations of images of an anthropomorphic phantom, and the second method was based on computer modeling of the imaging system using an anthropomorphic voxel phantom. The tube voltage was varied within a broad range (50–150  kV), including those values typically used with screen-film radiography. The tube charge was altered so that the same effective dose was achieved for each projection. Two x-ray units were employed using a computed radiography (CR) image detector with standard tube filtration and antiscatter device. Clinical image quality was assessed by a group of radiologists using a visual grading analysis (VGA) technique based on the revised CEC image criteria. Physical image quality was derived from a Monte Carlo computer model in terms of the signal-to-noise ratio, SNR, of anatomical structures corresponding to the image criteria. Both the VGAS (visual grading analysis score) and SNR decrease with increasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages are employed. Hence, a positive correlation between clinical and physical measures of image quality was found. The pros and cons of using lower tube voltages with CR digital radiography than typically used in analog screen-film radiography are discussed, as well as the relevance of using VGAS and quantum-noise SNR as measures of image quality in pelvis and chest radiography.

  • 102.
    Sandborg, Michael
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Önnerth, Magnus
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Comparison of human observer efficiency in pelvis radiographs in two different anatomical regions2004Rapport (Annet vitenskapelig)
    Abstract [en]

    The performance of an x-ray imaging system is often evaluated in terms of how well low-contrast details are visualised in the images. It is however difficult to obtain reliable results because a threshold for human visibility does not strictly exist. The degree of how well a low-contrast detail is ‘seen’ varies from ‘not seen’ to ‘clearly seen’ related to the certainty (or level of confidence) of detection. The visibility criterion is difficult to define, communicate and maintain which results in comparably large inter- and intraobserver variability.

    The detection probability depends not only on the imaging task, the technical performance of the imaging system and the observer´s skill and training but also on the projected anatomy in the region where the detail (i.e. lung nodule) is situated. This has been explored by Kundel et al (1985), Samei et al (1999), Håkansson et al (2004), and in Båth et al (2004) by ROC studies mainly in chest radiography.

    In this work, human observer detection efficiency was measured in a pelvis anthropomorphic phantom. Low-contrast lesions were constructed and positioned in two different regions, one region with a fairly homogeneous, the other region with a heterogeneous anatomical background. A group of human observers were asked to identify the lesion in a set of two-alternative forced choice (2-AFC) experiments.

  • 103.
    Sandborg, Mickael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Radiography and Flouroscopy: Physical principles and biohazards1995Rapport (Annet vitenskapelig)
    Abstract [en]

    Diagnostic radiology has come a long way since the discovery of ‘A New Kind of Rays’ in Würzburg by Professor Wilhelm Conrad Röntgen in November 1895. Professor Röntgen called the unknown rays ‘X rays’, but they are also, most appropriately and less mysteriously, referred to as Röntgen rays after their discoverer. In the last decades, imaging techniques using X rays has developed rapidly and play an important role in modern health care.

    The benefit of an X-ray examination for a patient could be assessed as how the patient’s risk situation is affected. The medical condition or illness leading to the examination may imply an increased risk of deteriorating health. Correct diagnosis and proper treatment, based on the information in the X-ray image, could lower the patient’s risk. For the individual the risks associated with the X-ray examination itself are small as is the radiation risk (patient absorbed dose) for well-designed imaging systems. Since the number of individuals undergoing X-ray examinations is very large, the collective absorbed dose to the whole population will be significant. Medical X-ray examinations are the manmade source giving the single largest radiation burden to the population, e.g., consisting 87% of the total radiation burden in the United Kingdom. Failure to diagnose is probably the largest single risk for the patient, but for some patients adverse effects of injected contrast media may be potentially hazardous.

  • 104.
    Siiskonen, T.
    et al.
    STUK Radiat and Nucl Safety Author, Finland.
    Ciraj-Bjelac, O.
    Univ Belgrade, Serbia.
    Dabin, J.
    Belgian Nucl Res Ctr SCK CEN, Belgium.
    Diklic, A.
    Univ Hosp Rijelca, Croatia.
    Domienik-Andrzejewska, J.
    NIOM, Poland.
    Farah, J.
    Paris Sud Univ Hosp, France.
    Fernandez, J. M.
    San Carlos Hosp and Complutense Univ, Spain.
    Gallagher, A.
    St James Hosp, Ireland.
    Hourdakis, C. J.
    EEAE Greek Atom Energy Commiss, Greece.
    Jurkovic, S.
    Univ Hosp Rijelca, Croatia; Univ Rijeka, Croatia.
    Jarvinen, H.
    STUK Radiat and Nucl Safety Author, Finland.
    Jarvinen, J.
    Turku Univ Hosp, Finland; Univ Turku, Finland.
    Knezevic, Z.
    RBI, Croatia.
    Koukorava, C.
    EEAE Greek Atom Energy Commiss, Greece.
    Maccia, C.
    CAATS, France.
    Majer, M.
    RBI, Croatia.
    Malchair, F.
    CAATS, France; ZEPHYRA, Belgium; Ctr Hosp Univ Liege CHULg, Belgium.
    Riccardi, L.
    Veneto Inst Oncol IOV IRCCS, Italy.
    Rizk, C.
    Natl Council Sci Res, Lebanon; St Joseph Univ, Lebanon.
    Sanchez, R.
    San Carlos Hosp and Complutense Univ, Spain.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Region Östergötland, Diagnostikcentrum, Medicinsk strålningsfysik.
    Merce, M. Sans
    Univ Hosp Geneva HUG, Switzerland; Univ Hosp Lausanne CHUV, Switzerland.
    Segota, D.
    Univ Hosp Rijelca, Croatia.
    Sierpowska, J.
    Cent Hosp Northern Karelia, Finland.
    Simantirakis, G.
    EEAE Greek Atom Energy Commiss, Greece.
    Sukupova, L.
    Inst Clin and Expt Med, Czech Republic.
    Thrapsanioti, Z.
    EEAE Greek Atom Energy Commiss, Greece.
    Vano, E.
    San Carlos Hosp and Complutense Univ, Spain.
    Establishing the European diagnostic reference levels for interventional cardiology2018Inngår i: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 54, s. 42-48Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Interventional cardiac procedures may be associated with high patient doses and therefore require special attention to protect the patients from radiation injuries such as skin erythema, cardiovascular tissue reactions or radiation-induced cancer. In this study, patient exposure data is collected from 13 countries (37 clinics and nearly 50 interventional rooms) and for 10 different procedures. Dose data was collected from a total of 14,922 interventional cardiology procedures. Based on these data European diagnostic reference levels (DRL) for air kerma-area product are suggested for coronary angiography (CA, DRL = 35 Gy cm(2)), percutaneous coronary intervention (PCI, 85 Gy cm(2)), transcatheter aortic valve implantation (TAVI, 130 Gy cm(2)), electrophysiological procedures (12 Gy cm(2)) and pacemaker implantations Pacemaker implantations were further divided into single-chamber (2.5 Gy cm(2)) and dual chamber (3.5 Gy cm(2)) procedures and implantations of cardiac resynchronization therapy pacemaker (18 Gy cm(2)). Results show that relatively new techniques such as TAVI and treatment of chronic total occlusion (CTO) often produce relatively high doses, and thus emphasises the need for use of an optimization tool such as DRL to assist in reducing patient exposure. The generic DRL presented here facilitate comparison of patient exposure in interventional cardiology.

  • 105.
    Simard, Trevor
    et al.
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Hibbert, Benjamin
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Natarjan, Machu
    Hamilton Health Sciences, Hamilton, Ontario, Canada.
    Mercuri, Mathew
    Department of Medicine, Columbia University, New York, NY.
    Hetherington, Simon
    Kettering, United Kingdom.
    Wright, Robert
    James Cook University Hospital, Middlesbrough, United Kingdom.
    Delewi, Ronak
    Academic Medical Center, University of Amsterdam, The Netherlands.
    Piek, Jan
    Academic Medical Center, University of Amsterdam, The Netherlands.
    Lehmann, Ralf
    Johann Wolfgang Goethe-University Frankfurt, Frankfurt, Germany.
    Ruzsa, Zoltan
    Cardiac and Vascular Center, Semmelweis University, Budapest, Hungary.
    Lange, Helmut
    Kardiologisch-Angiologische Praxis Herzzentrum Bremen, Bremen, Germany.
    Geijer, Håkan
    Department of Radiology, School of Medical Sciences, Örebro University, Örebro, Sweden.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Linköpings universitet, Medicinska fakulteten. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper.
    Kansal, Vinay
    Faculty of Undergraduate Medicine, University of Ottawa, Ontario, Canada.
    Bernick, Jordan
    Cardiovascular Research Methods Center, Ottawa, Ontario, Canada.
    Di Santo, Pietro
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Pourdjabbar, Ali
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Ramirez, Daniel
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Chow, Benjamin
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Chong, Aun
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Labinaz, Marino
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    Le May, Michel
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
    O’Brien, Edward
    Libin Cardiovascular Institute of Alberta, Calgary, Alberta, Canada.
    Wells, George
    Cardiovascular Research Methods Center, Ottawa, Ontario, Canada.
    So, Derek
    University of Ottawa Heart Institute, Ottawa, Ontario, Canada dso@ottawaheart.ca.
    Impact of Center Experience on Patient Radiation Exposure During Transradial Coronary Angiography and Percutaneous Intervention: A Patient-Level, International, Collaborative, Multi-Center Analysis2016Inngår i: Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease, ISSN 2047-9980, E-ISSN 2047-9980, Vol. 5, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background-—The adoption of the transradial (TR) approach over the traditional transfemoral (TF) approach has been hampered by concerns of increased radiation exposure—a subject of considerable debate within the field. We performed a patient-level, multi-center analysis to definitively address the impact of TR access on radiation exposure. Methods and Results-—Overall, 10 centers were included from 6 countries—Canada (2 centers), United Kingdom (2), Germany (2), Sweden (2), Hungary (1), and The Netherlands (1). We compared the radiation exposure of TR versus TF access using measured dose-area product (DAP). To account for local variations in equipment and exposure, standardized TR:TF DAP ratios were constructed per center with procedures separated by coronary angiography (CA) and percutaneous coronary intervention (PCI). Among 57 326 procedures, we demonstrated increased radiation exposure with the TR versus TF approach, particularly in the CA cohort across all centers (weighted-average ratios: CA, 1.15; PCI, 1.05). However, this was mitigated by increasing TR experience in the PCI cohort across all centers (r=0.8; P=0.005). Over time, as a center transitioned to increasing TR experience (r=0.9; P=0.001), a concomitant decrease in radiation exposure occurred (r=0.8; P=0.006). Ultimately, when a center’s balance of TR to TF procedures approaches 50%, the resultant radiation exposure was equivalent. Conclusions-—The TR approach is associated with a modest increase in patient radiation exposure. However, this increase is  eliminated when the TR and TF approaches are used with equal frequency—a guiding principle for centers adopting the TR approach.

  • 106.
    Slatkin, Daniel
    et al.
    Brookhaven National Laboratory.
    Spanne, Per
    Brookhaven National Laboratory.
    Dilmanian, Avraham
    Brookhaven National Laboratory.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Microbeam Radiation Therapy1992Inngår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 19, s. 1395-1400Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is proposed to carry out radiotherapy and radiosurgery for brain lesions by crossfiring an array of parallel, closely spaced microbeams of synchrotron-generated x rays several times through an isocentric target, each microbeam in the array having an 25-µm-wide adjustable-height rectangular cross section. The following inferences from the known tissue sparing of 22-MeV deuteron microbeams in the mouse brain and the following exemplary Monte Carlo computations indicate that endothelial cells in the brain that are lethally irradiated by any microbeam in an array of adequately spaced microbeams outside an isocentric target will be replaced by endothelial cells regenerated from microscopically contiguous, minimally irradiated endothelium in intermicrobeam segments of brain vasculature. Endothelial regeneration will prevent necrosis of the nontargeted parenchymal tissue. However, neoplastic and/or nonneoplastic targeted tissues at the isocenter will be so severely depleted of potentially mitotic endothelial and parenchymal cells by multiple overlapping microbeams that necrosis will ensue. The Monte Carlo computations simulate microbeam irradiations of a 16-cm diameter, 16-cm-long cylindrical human head phantom using 50-, 100-, and 150-keV monochromatic x rays.

  • 107.
    Smedby, Örjan
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Fredrikson, Mats
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Yrkes- och miljömedicin. Linköpings universitet, Hälsouniversitetet.
    de Geer, Jakob
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Borgen, L
    Drammen Hospital, Norway .
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Quantifying the potential for dose reduction with visual grading regression2013Inngår i: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 86, nr 1021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives To propose a method to study the effect of exposure settings on image quality and to estimate the potential for dose reduction when introducing dose-reducing measures.

    Methods Using the framework of visual grading regression (VGR), a log(mAs) term is included in the ordinal logistic regression equation, so that the effect of reducing the dose can be quantitatively related to the effect of adding post-processing. In the ordinal logistic regression, patient and observer identity are treated as random effects using generalised linear latent and mixed models. The potential dose reduction is then estimated from the regression coefficients. The method was applied in a single-image study of coronary CT angiography (CTA) to evaluate two-dimensional (2D) adaptive filters, and in an image-pair study of abdominal CT to evaluate 2D and three-dimensional (3D) adaptive filters.

    Results For five image quality criteria in coronary CTA, dose reductions of 16–26% were predicted when adding 2D filtering. Using five image quality criteria for abdominal CT, it was estimated that 2D filtering permits doses were reduced by 32–41%, and 3D filtering by 42–51%.

    Conclusions VGR including a log(mAs) term can be used for predictions of potential dose reduction that may be useful for guiding researchers in designing subsequent studies evaluating diagnostic value. With appropriate statistical analysis, it is possible to obtain direct numerical estimates of the dose-reducing potential of novel acquisition, reconstruction or post-processing techniques.

  • 108.
    Smedby, Örjan
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Fredrikson, Mats
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Yrkes- och miljömedicin. Linköpings universitet, Hälsouniversitetet.
    de Geer, Jakob
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Quantifying effects of post-processing with visual grading regression2012Inngår i: Medical Imaging 2012: Image Perception, Observer Performance, and Technology Assessment / [ed] Craig K. Abbey; Claudia R. Mello-Thoms, SPIE - International Society for Optical Engineering, 2012, Vol. 8318, s. Art. no. 83181N-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For optimization and evaluation of image quality, one can use visual grading experiments, where observers rate some aspect of image quality on an ordinal scale. To take into account the ordinal character of the data, ordinal logistic regression is used in the statistical analysis, an approach known as visual grading regression (VGR). In the VGR model one may include factors such as imaging parameters and post-processing procedures, in addition to patient and observer identity. In a single-image study, 9 radiologists graded 24 cardiac CTA images acquired with ECG-modulated tube current using standard settings (310 mAs), reduced dose (62 mAs) and reduced dose after post-processing. Image quality was assessed using visual grading with five criteria, each with a five-level ordinal scale from 1 (best) to 5 (worst). The VGR model included one term estimating the dose effect (log of mAs setting) and one term estimating the effect of postprocessing. The model predicted that 115 mAs would be required to reach an 80% probability of a score of 1 or 2 for visually sharp reproduction of the heart without the post-processing filter. With the post-processing filter, the corresponding figure would be 86 mAs. Thus, applying the post-processing corresponded to a dose reduction of 25%. For other criteria, the dose-reduction was estimated to 16-26%. Using VGR, it is thus possible to quantify the potential for dose-reduction of post-processing filters.

  • 109.
    Smedby, Örjan
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Fredrikson, Mats
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Yrkes- och miljömedicin. Linköpings universitet, Hälsouniversitetet.
    de Geer, Jakob
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Visual grading regression with random effects2012Inngår i: MEDICAL IMAGING 2012: IMAGE PERCEPTION, OBSERVER PERFORMANCE, AND TECHNOLOGY ASSESSMENT, SPIE - International Society for Optical Engineering, 2012, Vol. 8318, s. Art. no. 831805-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    To analyze visual grading experiments, ordinal logistic regression (here called visual grading regression, VGR) may be used in the statistical analysis. In addition to types of imaging or post-processing, the VGR model may include factors such as patient and observer identity, which should be treated as random effects. Standard software does not allow random factors in ordinal logistic regression, but using Generalized Linear Latent And Mixed Models (GLLAMM) this is possible. In a single-image study, 9 radiologists graded 24 cardiac Computed Tomography Angiography (CTA) images with reduced dose without and after post-processing with a 2D adaptive filter, using five image quality criteria. First, standard ordinal logistic regression was carried out, treating filtering, patient and observer identity as fixed effects. The same analysis was then repeated with GLLAMM, treating filtering as a fixed effect and patient and observer identity as random effects. With both approaches, a significant effect (pless than0.01) of the filtering was found for all five criteria. No dramatic differences in parameter estimates or significance levels were found between the two approaches. It is concluded that random effects can be appropriately handled in VGR using GLLAMM, but no major differences in the results were found in a preliminary evaluation.

  • 110.
    Stenström, Mats
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Olander, Birger
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Söderberg, Jonas
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Absorbed dose aspects on in vivo microtomography on small experimental animals2001Inngår i: Journal of Bone and Mineral Research, ISSN 0884-0431, E-ISSN 1523-4681Artikkel i tidsskrift (Fagfellevurdert)
  • 111.
    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 tomosynthesis2011Inngår 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-10Konferansepaper (Annet vitenskapelig)
    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 %.

  • 112. Tapiovaara, M
    et al.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    How should low-contrast detail detectability be measured in fluoroscopy?2004Inngår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 31, nr 9, s. 2564-2576Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship and precision of four methods for measuring the low-contrast detail detectability in fluoroscopic imaging were studied. These included the physical measurement of the accumulation rate of the square of the signal-to-noise ratio (SNRrate2), two-alternative forced-choice (2-AFC) experiments, sixteen-alternative forced-choice (16-AFC) experiments and subjective determination of the threshold contrast. The precision and sensitivity of the threshold contrast measurement were seen to be modest in the constancy testing of fluoroscopic equipment: only large changes in system performance could be reliably detected by that method. The measurement of the SNRrate2 is suggested instead. The relationship between the results of the various methods were studied, and it was found that human performance can be related to SNRrate2 by introducing the concept of the effective image information integration time (teff). When measured for an unlimited observation time, it depicts the saturation of human performance in detecting a static low-contrast detail in dynamic image noise. Here, teff was found to be about 0.6 s in 2-AFC tests and 0.3 s in 16-AFC tests. © 2004 American Association of Physicists in Medicine.

  • 113. Tapiovaara, M
    et al.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Dance, DR
    a search for improved technique factors in paediatric fluroscopy.1999Inngår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 44, s. 537-559Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 114.
    Tapiovaara, Markku
    et al.
    Finnish Centre for Radiat. & Nucl. Safety.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Evaluation of image quality in fluoroscopy by measurements and Monte Carlo calculations1995Inngår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 40, nr 4, s. 589-607Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The authors have studied image quality in fluoroscopy, as related to the detectability of low-contrast iodine or acrylic (PMMA) details added to a homogeneous 20 cm thick PMMA phantom, by experimental measurements of the signal-to-noise ratio (SNR) and by Monte Carlo calculation. The agreement between the measured and calculated SNR at equal absorbed dose in the phantom showed that the imaging performance of X-ray image intensifier (XRII) based fluoroscopic systems is well understood and can be mainly accounted for by X-ray attenuation in the phantom and the detail, and by the interaction statistics of primary and secondary (scattered) X-ray quanta in the input phosphor of the XRII. The electronic noise sources in the video chain bad only a small effect on the detectability of the details studied here. The optimal X-ray tube potential was 50-60 kV for detecting the low-contrast iodine detail in the phantom, and 70-100 kV for detecting the thin PMMA detail. For the task of detecting the iodine detail the use of a fibre-interspaced antiscatter grid improved the dose-to-information conversion efficiency of the imaging system by a factor of 2.2 as compared to imaging without the grid, and additional filtering of the X-ray beam by 0.25 mm Cu increased the efficiency by a factor of 1.6. Monte Carlo results were further used to estimate the potential of increasing the dose-to-information conversion efficiency by imaging system design changes. For the detection task of a static, low-contrast, low-spatial-frequency iodine contrast material detail embedded in a 20 cm thick soft-tissue phantom, the greatest contributions for further improvement could be achieved by improved antiscatter devices, X-ray spectrum modification, and by decreasing the absorption in the material layers in front of the CsI phosphor of the XRII. Contrary to this, no significant efficiency increase could be obtained by increasing the CsI phosphor coating thickness from the present value of 180 mg cm-2, or by changes in the video chain characteristics. The maximum potential of efficiency improvement is a factor of 6.3 when compared to the reference fluoroscopy system operated at 60 kV with 2.7 mm Al primary beam filtration, and a factor of 3.9 when compared to the reference system at 50 kV with the primary beam filtration added by 0.25 mm Cu.

  • 115.
    Tapiovaara, Markku
    et al.
    n/a.
    Servomaa, Antti
    n/a.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Hälsouniversitetet.
    Dance, David
    n/a.
    Optimizing the imaging conditions in paediatric fluoroscopy2000Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 90, nr 1-2, s. 211-216Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Patient dose and image quality were studied in paediatric fluoroscopy. The study consisted of two parts: theoretical calculation of optimal imaging conditions by the Monte Carlo method and clinical measurements of dose rate and SNR2rate at six hospitals. For many imaging tasks the most efficient imaging technique in fluoroscopy is obtained by using high filtration, relatively low X ray tube potential and a fibre-interspaced and -covered grid for all but the smallest patients and X ray field sizes. The clinical measurements supported our theoretical results and revealed a notable variation in image quality and dose rate among the hospitals studied. Notable patient dose rate reduction seems possible in paediatric fluoroscopy by adjusting the equipment to work with more efficient imaging factors and a low image receptor input dose rate.

  • 116.
    Tesselaar, Erik
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Dahlström, Nils
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    CLINICAL AUDIT OF IMAGE QUALITY IN RADIOLOGY USING VISUAL GRADING CHARACTERISTICS ANALYSIS2016Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, nr 1-4, s. 340-346Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to assess whether an audit of clinical image quality could be efficiently implemented within a limited time frame using visual grading characteristics (VGC) analysis. Lumbar spine radiography, bedside chest radiography and abdominal CT were selected. For each examination, images were acquired or reconstructed in two ways. Twenty images per examination were assessed by 40 radiology residents using visual grading of image criteria. The results were analysed using VGC. Inter-observer reliability was assessed. The results of the visual grading analysis were consistent with expected outcomes. The inter-observer reliability was moderate to good and correlated with perceived image quality (r2 5 0.47). The median observation time per image or image series was within 2 min. These results suggest that the use of visual grading of image criteria to assess the quality of radiographs provides a rapid method for performing an image quality audit in a clinical environment.

  • 117.
    Tesselaar, Erik
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    ASSESSING THE USEFULNESS OF THE QUASI-IDEAL OBSERVER FORQUALITY CONTROL IN FLUOROSCOPY2016Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, nr 1-4, s. 360-364Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to evaluate the reliability of the square of the signal-to-noise ratio rate, SNR2rate, as a precise measurement for quality control test in a digital fluoroscopy system. The quasi-ideal model observer was used to measure SNR2rate. The dose rate, pulse rate and field of view were varied, and their effect on dose efficiency, defined as SNR2rate=PKA;rate, was evaluated (where PKA;rate is the air kerma-area product rate). Measurements were repeated to assess reproducibility. The relative standard deviation in SNR2rate=PKA;rate over seven consecutive measurements was 5 %. No significant variation in SNR2rate=PKA;rate was observed across different pulse rates (10–30 pulses s-1). The low-dose-rate setting had a superior dose efficiency compared with the medium- and high-dose-rate settings. A smaller field of view resulted in higher dose efficiency. The results show that SNR2rate=PKA;rate measurements offer the high precision required in quality control constancy tests.

  • 118. Tingberg, A
    et al.
    Båth, M
    Håkansson, M
    Medin, J
    Besjakov, J
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Mattsson, S
    Månsson, LG
    Evaluation of image quality of lumbar spine images: A comparison between FFE and VGA2005Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 53-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: The aim of the present study is to compare two different methods for evaluation of the quality of clinical X-ray images. Methods: Based on fifteen lumbar spine radiographs, two new sets of images were created. A hybrid image set was created by adding two distributions of artificial lesions to each original image. The image quality parameters spatial resolution and noise were manipulated and a total of 210 hybrid images were created. A set of 105 disease-free images was created by applying the same combinations of spatial resolution and noise to the original images. The hybrid images were evaluated with the free-response forced error experiment (FFE) and the normal images with visual grading analysis (VGA) by nine experienced radiologists. Results: In the VGA study, images with low noise were preferred over images with higher noise levels. The alteration of the MTF had a limited influence on the VGA score. For the FFE study, the visibility of the lesions was independent of the sharpness and the noise level. No correlation was found between the two image quality measures. Conclusions: FFE is a precise method for evaluation of image quality, but the results are only valid for the type of lesion used in the study, whereas VGA is a more general method for clinical image quality assessment. The results of the FFE study indicate that there might be a potential to lower the dose levels in lumbar spine radiography without losing important diagnostic information. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 119. Tingberg, A
    et al.
    Båth, M
    Håkansson, M
    Medin, J
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Mattsson, S
    Gunnar Månsson, L
    Comparison of two methods for evaluation of image quality of lumbar spine radiographs2004Inngår i: SPIE Proc Jfr 2001 Preceedings of SPIE ISSN 1605-7422, ISSN 1017-2653, Vol. 5372Artikkel i tidsskrift (Fagfellevurdert)
  • 120. Tingberg, A
    et al.
    Eriksson, F
    Medin, J
    Besjakov, J
    Båth, M
    Håkansson, M
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Almen, A
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Mattsson, S
    Månsson, LG
    Inter-observer variation in masked and unmasked images for quality evaluation of clinical radiographs2005Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 62-68Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: To investigate the influence of masking on the inter-observer variation in image quality evaluation of clinical radiographs of chest and lumbar spine. Background: Inter-observer variation is a big problem in image quality evaluation since this variation is often much bigger than the variation in image quality between, for example, two radiographic systems. In this study, we have evaluated the effect of masking on the inter-observer variation. The idea of the masking was to force every observer to view exactly the same part of the image and to avoid the effect of the overall 'first impression' of the image. A discussion with a group of European expert radiologists before the study indicated that masking might be a good way to reduce the inter-observer variation. Methods: Five chest and five lumbar spine radiographs were collected together with detailed information regarding exposure conditions. The radiographs were digitised with a high-performance scanner and five different manipulations were performed, simulating five different exposure conditions. The contrast, noise and spatial resolution were manipulated by this method. The images were printed onto the film and the individual masks were produced for each film, showing only the parts of the images that were necessary for the image quality evaluation. The quality of the images was evaluated on ordinary viewing boxes by a large group of experienced radiologists. The images were examined with and without the masks with a set of image criteria (if fulfilled, 1 point, and not fulfilled, 0 point), and the mean score was calculated for each simulated exposure condition. Results: The results of this study indicate that - contrary to what was supposed - the inter-observer variation increased when the images were masked. In some cases, especially for chest, this increase was statistically significant. Conclusions: Based on the results of this study, image masking in studies of fulfilment of image criteria cannot be recommended. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 121. Tingberg, A
    et al.
    Herrmann, C
    Lanhede, B
    Almen, A
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    McVey, G
    Mattsson, S
    Panzer, W
    Besjakov, J
    Månsson, LG
    Kheddache, S
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, DR
    Tylen, U
    Zankl, M
    Influence of the characteristic curve on the clinical image quality of lumbar spine and chest radiographs2004Inngår i: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 77, nr 915, s. 204-215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The "European Guidelines on Quality Criteria for Diagnostic Radiographic Images" do not address the choice of the film characteristic (H&D) curve, which is an important parameter for the description of a radiographic screen-film system. The image contrast of clinical lumbar spine and chest radiographs was altered by digital image processing techniques, simulating images with different H&D curves, both steeper and flatter than the original. The manipulated images were printed on film for evaluation. Seven experienced radiologists evaluated the clinical image quality by analysing the fulfilment of the European Image Criteria (ICS) and by visual grading analysis (VGA) of in total 224 lumbar spine and 360 chest images. A parallel study of the effect of the H&D curve has also been made using a theoretical model. The contrast (ΔOD) of relevant anatomical details was calculated, using a Monte Carlo simulation-model of the complete imaging system including a 3D voxel phantom of a patient. Correlations between the calculated contrast and the radiologists' assessment by VGA were sought. The results of the radiologists' assessment show that the quality in selected regions of lumbar spine and chest images can be significantly improved by the use of films with a steeper H&D curve compared with the standard latitude film. Significant (p<0.05) correlations were found between the VGA results and the calculations of the contrast of transverse processes and trabecular details in the lumbar spine vertebrae, and with the contrast of blood vessels in the retrocardiac area of the chest.

  • 122.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Båth, Magnus
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    Tapiovaara, Markku
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Development of a Monte Carlo based model for optimization using the Laguerre‐Gauss Hotelling observer2008Inngår i: Medical physics, ISSN 0094-2405Artikkel i tidsskrift (Fagfellevurdert)
  • 123.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    Royal Surrey County Hospital, Guildford.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Svalkvist, Angelica
    University of Gothenburg.
    Båth, Magnus
    University of Gothenburg.
    A Monte Carlo-based model for simulation of digital chest tomosynthesis2010Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 139, nr 1-3, s. 159-163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to calculate synthetic digital chest tomosynthesis projections using a computer simulation model based on the Monte Carlo method. An anthropomorphic chest phantom was scanned in a computed tomography scanner, segmented and included in the computer model to allow for simulation of realistic high-resolution X-ray images. The input parameters to the model were adapted to correspond to the VolumeRAD chest tomosynthesis system from GE Healthcare. Sixty tomosynthesis projections were calculated with projection angles ranging from +15 to −15°. The images from primary photons were calculated using an analytical model of the anti-scatter grid and a pre-calculated detector response function. The contributions from scattered photons were calculated using an in-house Monte Carlo-based model employing a number of variance reduction techniques such as the collision density estimator. Tomographic section images were reconstructed by transferring the simulated projections into the VolumeRAD system. The reconstruction was performed for three types of images using: (i) noise-free primary projections, (ii) primary projections including contributions from scattered photons and (iii) projections as in (ii) with added correlated noise. The simulated section images were compared with corresponding section images from projections taken with the real, anthropomorphic phantom from which the digital voxel phantom was originally created. The present article describes a work in progress aiming towards developing a model intended for optimisation of chest tomosynthesis, allowing for simulation of both existing and future chest tomosynthesis systems.

  • 124.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Malusek, Alexandr
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    The Royal Marsden NHS Trust, United Kingdom.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Calculation of images from an anthropomorphic chest phantom using Monte Carlo methods2006Inngår i: Proceedings of SPIE, 2006, Vol. 6142Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Monte Carlo (MC) computer simulation of chest x-ray imaging systems has hitherto been performed using anthropomorphic phantoms with too large (3 mm) voxel sizes. The aim for this work was to develop and use a Monte Carlo computer program to compute projection x-ray images of a high-resolution anthropomorphic voxel phantom for visual clinical image quality evaluation and dose-optimization. An Alderson anthropomorphic chest phantom was imaged in a CT-scanner and reconstructed with isotropic voxels of 0.7 mm. The phantom was segmented and included in a Monte Carlo computer program using the collision density estimator to derive the energies imparted to the detector per unit area of each pixel by scattered photons. The image due to primary photons was calculated analytically including a pre-calculated detector response function. Attenuation and scatter of x-rays in the phantom, grid and image detector was considered. Imaging conditions (tube voltage, anti-scatter device) were varied and the images compared to a real computed radiography (Fuji FCR 9501) image. Four imaging systems were simulated (two tube voltages 81 kV and 141 kV using either a grid with ratio 10 or a 30 cm air gap). The effect of scattered radiation on the visibility of thoracic vertebrae against the heart and lungs is demonstrated. The simplicity in changing the imaging conditions will allow us not only to produce images of existing imaging systems, but also of hypothetical, future imaging systems. We conclude that the calculated images of the high-resolution voxel phantom are suitable for human detection experiments of low-contrast lesions.

  • 125.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, D
    Hunt, R
    Alm-Carlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    The influence of patient thickness and imaging system on patient dose and physical image quality in digital chest imaging2005Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 114, nr 1-3, s. 294-297Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to study the influence of patient thickness, tube voltage and image detector on patient dose, contrast and ideal observer signal-to-noise ratio (SNRI), for pathological details positioned at different regions in the image in posterior-anterior (PA) chest radiology. A Monte Carlo computational model was used to compute measures of physical image quality (contrast, SNRI) and patient effective dose, E. Two metastasis-like details positioned in the central right lung and right lung near the spine, respectively, were studied. The tube voltage was varied between 100 and 150 kV and the patient thickness between 20 and 28 cm. Both, a computed radiography (CR) system and a direct radiography (DR) system, were investigated. The DR system provides both lower doses and better image quality compared with the CR system. The SNRI2/E is ∼2.9 times higher for the DR system compared with the CR system. © The Author 2005. Published by Oxford University Press. All rights reserved.

  • 126.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Foundation Trust and Institute of Cancer Research, London, UK.
    Hunt, Roger A.
    Joint Department of Physics, The Royal Marsden NHS Foundation Trust and Institute of Cancer Research, London, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Towards optimization in digital chest radiography using Monte Carlo modelling2006Inngår i: Physics in medicine and biology, ISSN 0031-9155, Vol. 51, nr 11, s. 2729-2743Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Monte Carlo based computer model of the x-ray imaging system was used to investigate how various image quality parameters of interest in chest PA radiography and the effective dose E vary with tube voltage (90–150 kV), additional copper filtration (0–0.5 mm), anti-scatter method (grid ratios 8–16 and air gap lengths 20–40 cm) and patient thickness (20–28 cm) in a computed radiography (CR) system. Calculated quantities were normalized to a fixed value of air kerma (5.0 µGy) at the automatic exposure control chambers. Soft-tissue nodules were positioned at different locations in the anatomy and calcifications in the apical region. The signal-to-noise ratio, SNR, of the nodules and the nodule contrast relative to the contrast of bone (C/CB) as well as relative to the dynamic range in the image (Crel) were used as image quality measures. In all anatomical regions, except in the densest regions in the thickest patients, the air gap technique provides higher SNR and contrast ratios than the grid technique and at a lower effective dose E. Choice of tube voltage depends on whether quantum noise (SNR) or the contrast ratios are most relevant for the diagnostic task. SNR increases with decreasing tube voltage while C/CB increases with increasing tube voltage.

  • 127.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Trust, London, UK .
    Hunt, Roger
    Joint Department of Physics, The Royal Marsden NHS Trust, London, UK .
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Distributions of scatter to primary ratios and signal to noise ratios per pixel in digital chest imaging2005Inngår i: Radiation protection dosimetry, ISSN 0144-8420, Vol. 114, nr 1-3, s. 355-358Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to calculate distributions of scatter-to-primary ratios (s/p) and signal-to-noise ratios per pixel (SNRp) in chest images. Such distributions may provide useful information on how physical image quality (contrast, SNR) is distributed over the posterior/anterior (PA) chest image. A Monte Carlo computer program was used for the calculations, including a model of both the patient (voxel phantom) and the imaging system (X-ray tube, anti-scatter grid and image detector). The calculations were performed for three PA thicknesses 20, 24 and 28 cm. For a 24 cm patient, the s/p varies between 0.5 in the lung to 2.5 behind the spine and heart. The corresponding variation of the SNRp is a factor of 3, with the highest values in the lung. Increasing the patient thickness from 20 to 28 cm increases the s/p by a factor of 2.2 behind the spine and heart.

  • 128.
    Ullman, Gustaf
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Dance, David R.
    Joint Department of Physics, The Royal Marsden NHS Trust, London, UK.
    Yaffe, Martin
    Department of Medical Biophysics, University of Toronto, Sunnybrook and Women's College Health Sciences Centre, Ontario, Canada.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    A search for optimal x‐ray spectra in iodine contrast media mammography2005Inngår i: Physics in medicine and biology, ISSN 0031-9155, Vol. 50, nr 13, s. 3143-3152Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this work was to search for the optimal x-ray tube voltage and anode–filter combination in digital iodine contrast media mammography. In the optimization, two entities were of interest: the average glandular dose, AGD, and the signal-to-noise ratio, SNR, for detection of diluted iodine contrast medium. The optimum is defined as the technique maximizing the figure of merit, SNR2/AGD. A Monte Carlo computer program was used which simulates the transport of photons from the x-ray tube through the compression plate, breast, breast support plate, anti-scatter grid and image detector. It computes the AGD and the SNR of an iodine detail inside the compressed breast. The breast thickness was varied between 2 and 8 cm with 10–90% glandularity. The tube voltage was varied between 20 and 55 kV for each anode material (Rh, Mo and W) in combination with either 25 µm Rh or 0.05–0.5 mm Cu added filtration. The x-ray spectra were calculated with MCNP4C (Monte Carlo N-Particle Transport Code System, version 4C). A CsI scintillator was used as the image detector. The results for Rh/0.3mmCu, Mo/0.3mmCu and W/0.3mmCu were similar. For all breast thicknesses, a maximum in the figure of merit was found at approximately 45 kV for the Rh/Cu, Mo/Cu and W/Cu combinations. The corresponding results for the Rh/Rh combination gave a figure of merit that was typically lower and more slowly varying with tube voltage. For a 4 cm breast at 45 kV, the SNR2/AGD was 3.5 times higher for the Rh/0.3mmCu combination compared with the Rh/Rh combination. The difference is even larger for thicker breasts. The SNR2/AGD increases slowly with increasing Cu-filter thickness. We conclude that tube voltages between 41 and 55 kV and added Cu-filtration will result in significant dose advantage in digital iodine contrast media mammography compared to using the Rh/Rh anode/filter combination at 25–32 kV.

  • 129.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Validation of Voxman Monte Carlo code and calibration for digital systems2003Rapport (Annet vitenskapelig)
    Abstract [en]

    The objective of this work was to test the Monte Carlo model ‘Voxman’ against measurements on x-ray systems in the clinic. X-ray transmission experiments are performed to test of the accuracy of the Monte Carlo photon transport. Experiments were also performed with an image plate (CR) system in the clinic to compare the measured pixel values with calculated pixel values. Measurements were also performed with the automatic exposure control (AEC) chambers used in Linköping and Motala. The purpose for those measurements was to choose a normalisation of the entrance surface dose.

  • 130.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Båth, M.
    Department of Radiation Physics, Göteborg, Sweden.
    Håkansson, M.
    Department of Radiation Physics, Göteborg, Sweden.
    Börjesson, S.
    Department of Radiation Physics, Göteborg, Sweden.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    On the extent of quantum noise limitation in digital chest radiography2004Rapport (Annet vitenskapelig)
    Abstract [en]

    The aim for this work was to study to what extent the detection of nodules is quantum noise limited, based on the combined results from a nodule-detection clinical trial and a Monte Carlo computational model of a digital chest imaging system. The Monte Carlo computer program computes measures of physical image quality such as image contrast, C and signalto-noise ratio, SNR for nodules of any size. A computed radiography (CR) imaging system used simulated. The patient anterior-posterior thickness was 25 cm and nodules with diameters between 1-40 mm were included. The image contrast and SNR was calculated for 1600 (40x40) positions in the chest image and averaged over five anatomical regions of interest (lateral pulmonary, retrocardial, hilar, lower- and upper mediastinal regions). Threshold contrasts for each region, Cth, corresponding to Az=0.80 for detecting a 10 mm nodule, were deduced from the clinical trial. A threshold is also used for the quantum noise signal-to-noise ratio, SNRth. The model computes the diameter of a disk-shaped object that is required to comply with the two criteria: SNR≥SNRth and C≥Cth. A system is said to be quantum noise limited when the nodule size required to fulfil both criteria is not limited by the contrast but by the SNR. The required nodule diameter is largest in the hilar region (25 mm) and smallest in the lateral pulmonary region (11 mm). When the threshold SNRth=25 is used, the lower mediastinal region is quantum noise limited already at low speed classes (S>100). The hilar region is never quantum noise limited at realistic speed classes (S<1000). The accuracy of this model will be tested in the future by more sophisticated modelling of anatomical background and noise in the SNR-expression.

  • 131.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Distributions of scatter-to-primary ratios in chest PA radiography using grid or air gap for scatter-rejection2004Rapport (Annet vitenskapelig)
    Abstract [en]

    The aim for this work was to calculate distributions of scatter-to-primary ratios (εs/εp) and signal-to-noise ratios per pixel (SNRp) for a large set of imaging systems with either grid or air gap for scatter rejection. Grids with ratio 8-16 and air gap length 20 and 40 cm were used. The tube voltage was varied between 90-150 kV and three patient thickness between 20-28 cm were tested in order to compare scatter-rejections techniques for different conditions. Distributions of this sort may provide useful information on how physical image quality (contrast, SNR) is distributed over the chest PA image. A Monte Carlo computer program was used for the calculations, including a model of both the patient (voxel phantom) and the imaging system. The mean value of the εs/εp is 0.39 in the hilar region and 1.72 in the lower mediastinal region. For a 28 cm patient, the corresponding values are 0.42 in the hilar region and 2.58 in the lower mediastinal region. The grid with ratio 16 is the most efficient scatter rejection technique in all regions except the hilar region. In the hilar region, the most efficient technique is the 40 cm air gap.

  • 132.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Optimisation of chest radiology by computer modelling of image quality measures and patient effective dose2004Rapport (Annet vitenskapelig)
    Abstract [en]

    A set of modelled computed radiography (CR) systems are compared with a reference system. Calculations are performed, which compares the effective dose and a set of figures of merit corresponding to the image quality of both the modelled systems and the reference system. For a nodule with soft tissue corresponding, the signal-to-noise ratio, SNR, is found to decrease with increasing tube voltage. On the other hand, the ratio of the contrast of the nodule compared to the contrast of a rib (nodule-to-rib contrast-ratio) is found to increase with increasing tube voltage.

  • 133.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Implementation of pathologies in the Monte Carlo model in chest and breast imaging2003Rapport (Annet vitenskapelig)
    Abstract [en]

    The Monte Carlo simulation model of the chest and breast imaging systems including a voxelised model of the patient are used to compute measures of image quality and patient absorbed dose. It is important that the model computes measures of image quality of pathological details that are similar in size, composition and position as real pathological details in typical chest and breast images. Moreover, the other partners of the co-coordinated research project will produce hybrid images with pathological details and have these images assessed by a group of radiologist. The model will then be used to study to what extent variations in clinical image quality can be explained by variations in physical image quality, for example signal-to-noise ratio. This report summarizes the selection of pathological details to include in the model of chest and breast imaging systems.

  • 134.
    Ullman, Gustav
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet.
    Sandborg, Michael
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Tingberg, Anders
    Department of Radiation Physics, Malmö University Hospital, Sweden.
    Dance, David R
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Hunt, Roger
    Department of Physics, The Royal Marsden NHS Trust, UK.
    Alm Carlsson, Gudrun
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Comparison of clinical and physical measures of image quality in chest PA and pelvis AP views at varying tube voltages2004Rapport (Annet vitenskapelig)
    Abstract [en]

    Image quality in digital chest PA and pelvis AP was assessed using two different methods; one based on observations of images of an anthropomorphic phantom, one based on computer modelling using an anthropomorphic voxel phantom. The tube voltage was varied within a broad range (50-150 kV), including those values typically used with screen-film radiography. The tube charge was altered so that approximately the same effective dose was achieved in the modelled patient (anthropomorphic phantom). Two x-ray units were employed using a digital image detector (computed radiography, CR, system) with standard tube filtration and anti-scatter device. Clinical image quality was assessed by a group of radiologists using a visual grading analysis (VGA) technique based on the revised CEC image criteria. Physical image quality was derived from the computer model in terms of the signal-to-noise ratio, SNR for fixed effective dose in the voxel phantom. The computer model uses Monte Carlo simulations of the patient and complete imaging system. Both the VGAS (visual grading analysis score) and SNR increase with decreasing tube voltage in both chest PA and pelvis AP examinations, indicating superior performance if lower tube voltages than used today are employed in digital radiology. A positive correlation between clinical and physical measures of image quality was found. The pros and cons of using lower tube voltages with CR digital radiography than typically used in analogue screen-film radiography are discussed as well as the relevance of using VGAS and quantum noise SNR as measures of image quality.

  • 135. Wise, K N
    et al.
    Sandborg, Michael
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik.
    Persliden, J
    Alm Garlsson, Gudrun
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen.
    Sensitivity of coefficients for converting entrance surface dose and kerma-area product to effective dose and energy imparted to the patient.1999Inngår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 44, s. 1937-1954Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 136.
    Örtenberg, Alexander
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Medicinska fakulteten.
    Magnusson, Maria
    Linköpings universitet, Institutionen för systemteknik, Datorseende. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Medicinska fakulteten.
    Sandborg, Michael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Alm Carlsson, Gudrun
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Malusek, Alexandr
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten.
    PARALLELISATION OF THE MODEL-BASED ITERATIVE RECONSTRUCTION ALGORITHM DIRA2016Inngår i: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, nr 1-4, s. 405-409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New paradigms for parallel programming have been devised to simplify software development on multi-core processors and many-core graphical processing units (GPU). Despite their obvious benefits, the parallelisation of existing computer programs is not an easy task. In this work, the use of the Open Multiprocessing (OpenMP) and Open Computing Language (OpenCL) frameworks is considered for the parallelisation of the model-based iterative reconstruction algorithm DIRA with the aim to significantly shorten the code’s execution time. Selected routines were parallelised using OpenMP and OpenCL libraries; some routines were converted from MATLAB to C and optimised. Parallelisation of the code with the OpenMP was easy and resulted in an overall speedup of 15 on a 16-core computer. Parallelisation with OpenCL was more difficult owing to differences between the central processing unit and GPU architectures. The resulting speedup was substantially lower than the theoretical peak performance of the GPU; the cause was explained.

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