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Träfflista för sökning "WFRF:(Mattsson Anders) ;pers:(Båth M.)"

Sökning: WFRF:(Mattsson Anders) > Båth M.

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1.
  • Grahn, Anna, et al. (författare)
  • Clinical evaluation of a new set of image quality criteria for mammography.
  • 2005
  • Ingår i: Radiation protection dosimetry. - 0144-8420. ; 114:1-3, s. 389-94
  • Tidskriftsartikel (refereegranskat)abstract
    • The European Commission (EC) quality criteria for screen-film mammography are used as a tool to assess image quality. A new set of criteria was developed and initially tested in a previous study. In the present study, these criteria are further evaluated using screen-film mammograms that have been digitised, manipulated to simulate different image quality levels and reprinted on film. Expert radiologists have evaluated these manipulated images using both the original (EC) and the new criteria. A comparison of three different simulated dose levels reveals that the new criteria yield a larger separation of image criteria scores than the old ones. These results indicate that the new set of image quality criteria has a higher discriminative power than the old set and thus seems to be more suitable for evaluation of image quality in mammography.
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2.
  • Timberg, Pontus, et al. (författare)
  • Visibility of microcalcification clusters and masses in breast tomosynthesis image volumes and digital mammography: A 4AFC human observer study.
  • 2012
  • Ingår i: Medical physics. - 0094-2405. ; 39:5, s. 2431-2437
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To investigate the visibility of simulated lesions in digital breast tomosynthesis (BT) image volumes compared with 2D digital mammography (DM). Methods: Simulated lesions (masses and microcalcifications) were added to images of the same women acquired on a DM system (Mammomat Novation, Siemens) and a BT prototype. The same beam quality was used for the DM and BT acquisitions. The total absorbed dose resulting from a 25-projection BT acquisition and reconstruction (BT(25)) was approximately twice that of a single DM view. By excluding every other projection image from the reconstruction (BT(13)), approximately the same dose as in DM was effected. Simulated microcalcifications were digitally added with varying contrast to the DM and BT images. Simulated masses with 8 mm diameter were also added to BT images. A series of 4-alternative forced choice (4AFC) human observer experiments were conducted. Four medical physicists participated in all experiments, each consisting of 60 trials per experimental condition. The observers interpreted the BT image volumes in cine-mode at a fixed image sequence speed. The required threshold contrast (S(t)) to achieve a detectability index (d') of 2.5 (i.e., 92.5% correct decisions) was determined. Results: The S(t) for mass detection in DM was approximately a factor of 2 higher than required in BT indicating that the detection of masses was improved under BT conditions compared to DM. S(t) for microcalcification detection was higher for BT than for DM at both BT dose levels (BT(25) and BT(13)), with a statistically significant difference in S(t) between DM and BT(13). These results indicate a dose-dependent decrease in detection performance in BT for detection of microcalcifications. Conclusions: In agreement with previous investigations, masses of size 8 mm can be detected with less contrast in BT than in DM indicating improved detection performance for BT. However, for the investigated microcalcifications, the results of this study indicate potentially worse performance for BT than for DM at the same dose level.
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3.
  • Tingberg, Anders, et al. (författare)
  • Comparison of two methods for evaluation of image quality of lumbar spine radiographs
  • 2004
  • Ingår i: Proceedings of SPIE. - SPIE. - 277-786X. - 0819452858 ; 5372, s. 251-262
  • Konferensbidrag (refereegranskat)abstract
    • Purpose To evaluate the image quality of clinical radiographs with two different methods, and to find correlations between the two methods. 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 The VGA study showed that images with low noise are 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 spatial resolution and the noise level. Discussion In this study we found no correlation between the two methods, probably because the detectability of the artificial lesions was not influenced by the manipulations of noise level and resolution. Hence, the detection of lesions in lumbar spine radiography may not be a quantum-noise limited task. The results show the strength of the VGA technique in terms of detecting small changes in the two image quality parameters. The method is more robust and has a higher statistical power than the ROC related method and could therefore, in some cases, be more suitable for use in optimization studies.
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4.
  • Tingberg, Anders, et al. (författare)
  • Detectability of pathological lesions in lumbar spine radiography
  • 2005
  • Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - SPIE - International Society for Optical Engineering. - 9780819457196 ; 5749, s. 518-526
  • Konferensbidrag (refereegranskat)abstract
    • Thirty images with added simulated pathological lesions at two different dose levels (100% and 10% dose) were evaluated with the free-response forced error experiment by nine experienced radiologists. The simulated pathological lesions present in the images were classified according to four different parameters: the position within the lumbar spine, possibility to perform a symmetrical (left-right) comparison, the lesion contrast, and the complexity of the surrounding background where the lesion was situated. The detectability of each lesion was calculated as the fraction of radiologists who successfully detected the lesion before a false positive error was made. The influence of each of the four parameters on lesion detectability was investigated. The results of the study show that the influence of lesion contrast is the most important factor for detectability. Since the dose level had a limited effect on detectability, large dose savings can be made without reducing the detectability of pathological lesions in lumbar spine radiography.
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