Clinical evaluation of wavelet-compressed digitized screen-film mammography.

RATIONALE AND OBJECTIVES: The authors compared diagnostic accuracy and callback rates with conventional screen-film mammograms and wavelet-compressed digitized images. MATERIALS AND METHODS: Sixty sets of mammograms (four views per case) were digitized at a spatial resolution of 100 microm. The images were wavelet compressed to a mean compression ratio of 8:1 and reviewed by three mammographers. Five regions were evaluated in each breast. Suspicion of malignancy was graded on a scale of 0% to 100%, and receiver operating characteristic (ROC) analysis was performed. Callback rates were calculated by using the American College of Radiology's Breast Imaging Reporting and Data System lexicon scale. RESULTS: The mean diagnostic accuracy with compressed and conventional images was 0.832 and 0.860, respectively. The upper 95% confidence bound for the difference in ROC areas was 0.061. The mean false-positive rate at a fixed sensitivity of 0.90 was 0.041 for compressed images and 0.059 for conventional images. The mean callback rates for normal, benign, and malignant regions were 0.023, 0.305, and 0.677, respectively, for compressed images and 0.036, 0.447, and 0.750, respectively, for conventional images. The upper 95% confidence bound for the (absolute) differences in callback rates was 0.012 for normal regions, 0.163 for benign regions, and 0.138 for malignant regions. CONCLUSION: Diagnostic accuracies were equivalent for both compressed and conventional images. The mean false-positive rate at fixed sensitivity was much better with the compressed images. However, the callback rates for malignant lesions were lower when the compressed images were used.

Film-screen versus digitized mammography: assessment of clinical equivalence.

OBJECTIVE: The purpose of this study was to determine whether diagnostic accuracy and callback rates using digitized film images are equivalent to those using film-screen mammograms. MATERIALS AND METHODS: Sixty sets of mammograms (four views per case) were digitized at a spatial resolution of 100 microm. The images were reviewed by seven mammographers. Five regions were evaluated in each breast. Each region was scored on a scale of 0 100% for suspicion of malignancy, and a receiver operating characteristic analysis was performed. Callback rates were calculated using a published lexicon scale. RESULTS: The observers' mean diagnostic accuracies using films and digitized images were 0.872 and 0.848, respectively. The upper 95% confidence boundary on the difference in accuracy was 0.066. The mean callback rate for normal, benign, and malignant areas using films versus digitized images was 0.048 versus 0.055, 0.498 versus 0.441, and 0.786 versus 0.737, respectively. The upper 95% confidence boundary for the absolute difference in callback rates was 0.037, 0.026, and 0.130 for normal, benign, and malignant areas, respectively. CONCLUSION: The diagnostic accuracies of the digitized images and films were similar; however, an increase in callback rates of 0.037 (i.e., upper 95% confidence boundary) for normal results and a reduction in the callback rates of 0.130 for malignant lesions is important. The use of digitized film images, at a spatial resolution of 100 microm, may compromise patient treatment in clinical practice.