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Materials and Methods: An anthropomorphic chest phantom containing various configurations of simulated lesions (5, 8, 10 and 12mm; +100, -630 and -800 Hounsfield Units, HU) was imaged on a modern CT system over a tube current range (20, 40, 60 and 80mA). Images were reconstructed with (IR) and filtered back projection (FBP). An ATOM 701D (CIRS, Norfolk, VA) dosimetry phantom was used to measure organ dose. Effective dose was calculated. Eleven observers (15.11±8.75 years of experience) completed a free response study, localizing lesions in 544 single CT image slices. A modified jackknife alternative free-response receiver operating characteristic (JAFROC) analysis was completed to look for a significant effect of two factors: reconstruction method and tube current. Alpha was set at 0.05 to control the Type I error in this study.
Results: For modified JAFROC analysis of reconstruction method there was no statistically significant difference in lesion detection performance between FBP and IR when figures-of-merit were averaged over tube current (F(1,10)=0.08, p = 0.789). For tube current analysis, significant differences were revealed between multiple pairs of tube current settings (F(3,10) = 16.96, p<0.001) when averaged over image reconstruction method.
Conclusion: The free-response study suggests that lesion detection can be optimized at 40mA in this phantom model, a measured effective dose of 0.97mSv. In high-contrast regions the diagnostic value of IR, compared to FBP, is less clear.
This will count as one of your downloads.
You will have access to both the presentation and article (if available).
This full-day course will provide attendees with the statistical tools needed for current bioengineering and medical imaging research. It will describe observer performance data acquisition strategies and their analyses. Observer performance methods are a set of highly evolved tools that are loosely referred to as "ROC analyses", but which now encompass two-alternative forced choice (2AFC), receiver operating characteristic (ROC), location ROC (LROC), region of interest (ROI) and free-response ROC (FROC) methods. They are used to assess radiologist performance, to perform technology comparison studies, for image quality assessment, and to assess CAD algorithms developed for mammography and lung cancer screening.
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