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Acute Cerebral Infarction: Effect of JPEG Compression on Detection at CT¹

¹ From the Department of Radiology, Showa University School of Medicine, Tokyo, Japan (Y.O., T.G., H.N., M.H., N.S., M.B., K.N., K.T., N.T., H.M.); and Department of Radiology, Showa University Northern Yokohama Hospital, Japan (H.F.). From the 2001 RSNA scientific assembly. Received February 8, 2002; revision requested April 18; final revision received July 16; accepted August 29. Address correspondence to Y.O., Department of Radiology, Showa University School of Medicine, 1-5-8 Hatanodai Shinagawa-ku, Tokyo 142-0064, Japan (e-mail: yogiya@gd5.so-net.ne.jp).

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 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.

© RSNA, 2003

Index terms: Brain, CT, 10.12111 • Computed tomography (CT), image processing • Data compression • Images, interpretation

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