Conrath J, Erginay A, Giorgi R, Lecleire-Collet A, Vicaut E, Klein J-C, Gaudric A, Massin P
Department of Ophthalmology, Hôpital Lariboisière, Assistance Publique--Hôpitaux de Paris, Université Paris 7, Paris, France.
Eye (Lond). 2007 Apr;21(4):487-93. doi: 10.1038/sj.eye.6702238. Epub 2006 Feb 3.
To compare the effect of classic Joint Photographic Experts Group (JPEG) and JPEG2000 compression algorithms on detection of diabetic retinopathy (DR) lesions.
In total, 45 colour fundus photographs obtained with a digital nonmydriatic fundus camera were saved in uncompressed Tagged Interchanged Files Format (TIFF) format (1.26 MB). They were graded jointly by two retinal specialists at a 1 month interval for soft exudates, hard exudates, macular oedema, newvessels, intraretinal microvascular abnormalities (IRMA), and retinal haemorrhages and/or microaneurysms. They were compressed to 118, 58, 41, and 27 KB by both algorithms and 24 KB by classic JPEG, placed in random order and graded again jointly by the two retina specialists. Subjective image quality was graded, and sensitivity, specificity, positive and negative predictive values, and kappa statistic were calculated for all lesions at all compression ratios.
Compression to 118 KB showed no effect on image quality and kappa values were high (0.94-1). Image degradation became important at 27 KB for both algorithms. At high compression levels, IRMA and HMA detection were most affected with JPEG2000 performing slightly better than classic JPEG.
Performance of classic JPEG and JPEG2000 algorithms is equivalent when compressing digital images of DR lesions from 1.26 MB to 118 KB and 58 KB. Higher compression ratios show slightly better results with JPEG2000 compression, but may be insufficient for screening purposes.
比较经典的联合图像专家组（JPEG）和JPEG2000压缩算法对糖尿病视网膜病变（DR）病变检测的影响。
总共45张使用数码免散瞳眼底相机拍摄的彩色眼底照片以未压缩的标记交换文件格式（TIFF）保存（1.26MB）。由两位视网膜专家每隔1个月联合对软渗出、硬渗出、黄斑水肿、新生血管、视网膜内微血管异常（IRMA）以及视网膜出血和/或微动脉瘤进行分级。照片通过两种算法分别压缩至118、58、41和27KB，通过经典JPEG压缩至24KB，然后随机排序，再由两位视网膜专家联合进行分级。对主观图像质量进行评分，并计算所有压缩率下所有病变的敏感性、特异性、阳性和阴性预测值以及kappa统计量。
压缩至118KB对图像质量无影响，kappa值较高（0.94 - 1）。对于两种算法，在27KB时图像退化变得明显。在高压缩水平下，IRMA和HMA检测受影响最大，JPEG2000的表现略优于经典JPEG。
当将DR病变的数字图像从1.26MB压缩至118KB和58KB时，经典JPEG和JPEG2000算法的性能相当。更高的压缩率下，JPEG2000压缩的结果略好，但可能不足以用于筛查目的。
