Ohgiya Yoshimitsu, Gokan Takehiko, Nobusawa Hiroshi, Hirose Masanori, Seino Noritaka, Fujisawa Hidefumi, Baba Maiko, Nagai Kyoko, Tanno Keisuke, Takeyama Nobuyuki, Munechika Hirotsugu
Department of Radiology, Showa University School of Medicine, Tokyo, Japan.
Radiology. 2003 Apr;227(1):124-7. doi: 10.1148/radiol.2271020067. Epub 2003 Feb 19.
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).
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.
At ROC analysis, no statistically significant difference was detected for all cases considered together (Az [area under the ROC curve] = 0.887 +/- 0.038 [mean +/- SD] on noncompressed images, Az = 0.897 +/- 0.038 on 10:1 compressed images, and Az = 0.842 +/- 0.073 on 20:1 compressed images; P >.05).
JPEG compression at ratios of 10:1 and 20:1 was tolerated in the detection of acute cerebral infarction at CT.
评估10:1和20:1的联合图像专家组（JPEG）压缩率对计算机断层扫描（CT）检测急性脑梗死的影响。
对25例急性脑梗死患者和25例无病变患者的CT图像采用JPEG算法分别以10:1和20:1的比例进行压缩。使用彩色软拷贝计算机单色阴极射线管显示器查看原始图像和压缩图像上的正常及异常切片。5名观察者采用50分制（0分表示肯定无病变；25分表示可疑；50分表示肯定有病变）对病变的有无进行评分。采用受试者操作特征（ROC）曲线分析评估诊断准确性。采用双尾配对学生t检验对测试区域进行分析，P值小于0.05定义为有显著差异。
在ROC分析中，综合考虑所有病例时未检测到统计学上的显著差异（未压缩图像的ROC曲线下面积[Az] = 0.887±0.038[平均值±标准差]，10:1压缩图像的Az = 0.897±0.038，20:1压缩图像的Az = 0.842±0.073；P>.05）。
在CT检测急性脑梗死时，10:1和20:1比例的JPEG压缩是可接受的。
