Clinical evaluation of wavelet-compressed digitized screen-film mammography

The authors compared diagnostic accuracy and callback rates with conventional screen-film mammograms and wavelet-compressed digitized images. Sixty sets of mammograms (four views per case) were digitized at a spatial resolution of 100 μm. 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. 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. 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.