DETECTION OF DISCRETE WHITE-MATTER LESIONS AFTER IRREVERSIBLE COMPRESSION OF MR-IMAGES

PURPOSE: To validate the use of techniques of irreversible compression of images, which can be performed using a block-based discrete cosine transform technique as defined by the Joint Photographic Experts Grou p, before they can be used in clinical applications, by evaluating the effect of compression on the ability of observers to detect discrete white matter lesions on MR images of the brain, METHODS: Sixty T2- and intermediate-weighted spin-echo images were compressed with varying d egrees of coefficient quantization with compression ratios from 1:1 to more than 40:1, randomized, and evaluated by three observers blinded to the degree of compression. RESULTS: No significant difference in th e number of lesions detected was apparent until compression ratios rea ched 40:1, despite a significant subjective loss in perceived image qu ality at 20:1, Only small (less than or equal to 5-mm) lesions were mi ssed at the highest degree of compression. No significant differences were observed in the detection of confluent periventricular white matt er disease at any degree of compression tested. CONCLUSIONS: The use o f high degrees of irreversible compression of MR images may be accepta ble for diagnostic tasks.