Effectiveness of an Interactive CAD System for Mammographic Mass Detection

N. Karssemeijer, M. Samulski, M. Kallenberg, A. Hupse, C. Boetes and G. den Heeten

94th Radiological Society of North America Scientific Assembly and Annual Meeting 2008.


PURPOSE To study effectiveness of an interactive CAD system for reading mammograms, in which readers may probe regions for CAD information to improve decision making. METHOD AND MATERIALS Interactive use of CAD was studied using a dedicated mammographic workstation. Readers could probe image locations for presence of CAD information using a mouse. If a computer detection was available the CAD region was displayed with a color-coded boundary, ranging from red for regions with a high malignancy rating to green for regions with low ratings. The number of CAD regions that could be activated was set to two false positives per image on average. CAD results were obtained from the ImageChecker V8.0 (Hologic). In an observer study we investigated the effect of this system on detection performance. Seven readers participated in the study, of which two were certified mammographers and five were non-radiologists with mammogram reading experience. The radiologists each read 60 cases including 20 with cancer, the non-radiologists read 120 cases of which 40 had cancer. All cancers selected were missed at screening and were retrospectively identified as visible. Cases with only microcalcifications were excluded. Mammograms were read with and without CAD in two different sessions. Readers reported localized findings with malignancy ratings per finding scored on a continuous scale. Sensitivity, defined as correct cancer localization fraction, was computed per reader as a function of the fraction of normal cases that would be recalled, based on the malignancy ratings. Reading time per case was recorded. RESULTS Mean sensitivity in an interval of negative recalls less than 10% was 27.1% in the sessions without CAD and 36.9% in the CAD assisted sessions. Performance increase was significant (p<0.01). Mean sensitivity of the two radiologists was 27.4% and 32.7% resp. without and with CAD, which was comparable to that of the non-radiologists on the same subset of cases. On average, readers probed 13.6 locations per case for CAD information. Average reading time was 105 s/case in the sessions without CAD and was not higher when CAD was used (104 s/case). CONCLUSION Results suggest that detection performance increases with interactive use of CAD without affecting reading time. CLINICAL RELEVANCE/APPLICATION Interactive use of CAD in screening mammography is a fundamental change from current practice and may increase effectiveness of the technology for masses.