Acute cerebral infarction: Effect of JPEG compression on detection at CT

PURPOSE: To evaluate the effect of Joint Photographic Experts Group (JPEG) compression ratios of 10:1 and 20:1 on detection of acute cerebral infarction at computed tomography (CT). MATERIALS AND METHODS: CT images obtained in 25 patients with acute cerebral infarction and 25 patients with no lesions were compressed by means of a JPEG algorithm at ratios of 10:1 and 20:1. Normal and abnormal sections (on original and compressed images) were reviewed by using a color soft-copy computed monochrome cathode ray tube monitor. Five observers rated the presence or i absence of a lesion with a 50-point scale (0, definitely absent; 25, equivocal; and 50, definitely present). Diagnostic accuracy was evaluated with receiver operating characteristic (ROC) curve analysis. Significant difference was defined as a P value less than .05 for the area tested with a two-tailed paired Student t test. RESULTS: At ROC analysis, no statistically significant difference was detected for all cases considered together (A(z) [area under the ROC curve] = 0.887 +/- 0.038 [mean +/- SD] on noncompressed images, A(z) = 0.897 +/- 0.038 on 10:1 compressed images, and A(z) = 0.842 +/- 0.073 on 20:1 compressed images; P > .05). CONCLUSION: JPEG compression at ratios of 10:1 and 20:1 was tolerated in the detection of acute cerebral infarction at CT. (C) RSNA, 2003.