Clinical evaluation of wavelet-compressed digitized screen-film mammography

Rationale and Objectives. The authors compared diagnostic accuracy and call back 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 mu m. The images were wavelet comp ressed to a mean compression ratio of 8:1 and reviewed by three mammographe rs. Five regions were evaluated in each breast. Suspicion of malignancy was graded on a scale of 0% to 100%, and receiver operating characteristic (RO C) analysis was performed. Callback rates were calculated by using the Amer ican College of Radiology's Breast Imaging Reporting and Data System lexico n scale. Results. The mean diagnostic accuracy with compressed and conventional imag es was 0.832 and 0.860, respectively. The upper 95% confidence bound for th e difference in ROC areas was 0.061. The mean false-positive rate at a fixe d sensitivity of 0.90 was 0.041 for compressed images and 0.059 for convent ional images. The mean callback rates for normal, benign, and malignant reg ions 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 9 5% 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 r egions. Conclusion. Diagnostic accuracies were equivalent for both compressed and c onventional images. The mean false-positive rate at fixed sensitivity was m uch better with the compressed images. However, the callback rates for mali gnant lesions were lower when the compressed images were used.