THORACIC CT IMAGES - EFFECT OF LOSSY IMAGE COMPRESSION ON DIAGNOSTIC-ACCURACY

PURPOSE: To evaluate the effects of lossy image (noninvertible) compre ssion on diagnostic accuracy of thoracic computed tomographic images. MATERIALS AND METHODS: Sixty images from patients with mediastinal ade nopathy and pulmonary nodules were compressed to six different levels with tree-structured vector quantization. Three radiologists then used the original and compressed images for diagnosis. Unlike many previou s receiver operating characteristic-based studies that used confidence rankings and binary detection tasks, this study examined the sensitiv ity and predictive value positive scores from nonbinary detection task s. RESULTS: At the 5% significance level, there was no statistically s ignificant difference in diagnostic accuracy of image assessment at co mpression rates of up to 9:1. CONCLUSION The techniques presented for evaluation of image quality do not depend on the specific compression algorithm and provide a useful approach to evaluation of the benefits of any lossy image processing technique.