Ricke J, Maass P, Lopez Hänninen E, Liebig T, Amthauer H, Stroszczynski C, Schauer W, Boskamp T, Wolf M
Department of Radiology, Charité, Humboldt-University Medical School, Berlin, Germany.
Invest Radiol. 1998 Aug;33(8):456-63. doi: 10.1097/00004424-199808000-00006.
The aim of this study was to evaluate different lossy image compression algorithms in direct comparison.
Computed radiographs were reviewed after compression with Wavelet, Fractal, and Joint Photographic Expert Group (JPEG) algorithms. For receiver operating characteristic (ROC) analysis, 54 thoracic computed radiographs (31 showing pulmonary nodules) were compressed with a ratio of 1:60. Five images of a test-phantom were coded at 1:13. All images were reviewed on a PC. Uncompressed images were reviewed at a PC and at a radiologic workstation (with image processing).
For thorax images, decrease of diagnostic accuracy was significant with Wavelets. Fractal performed worse than Wavelets. No ROC curve was observed for JPEG due to poor image quality. No diagnostic loss was noted comparing PC and Workstation review. For low-contrast details of the phantom, results of Wavelet compression were equal to uncompressed images. Fewer true positives and increased true negatives were noted with Wavelets though. Wavelets were superior to JPEG, and JPEG images were superior to Fractal. Workstation review was superior to PC review.
Only Wavelets provided accurate review of low-contrast details at a compression of 1:13. Frequency filtering of Wavelets affects contrast even at a low compression ratio. JPEG performed better than Fractal at low and worse at high compression ratio.
本研究旨在直接比较不同的有损图像压缩算法。
对经小波、分形和联合图像专家组（JPEG）算法压缩后的计算机X线摄影图像进行评估。为进行受试者操作特征（ROC）分析，将54张胸部计算机X线摄影图像（31张显示肺结节）以1:60的比例进行压缩。对测试体模的5张图像以1:13的比例进行编码。所有图像均在个人电脑上进行评估。未压缩的图像在个人电脑和放射学工作站（进行图像处理）上进行评估。
对于胸部图像，小波算法导致诊断准确性显著下降。分形算法的表现比小波算法更差。由于图像质量差，未观察到JPEG算法的ROC曲线。在个人电脑和工作站评估之间未发现诊断损失。对于体模的低对比度细节，小波压缩的结果与未压缩图像相当。不过，小波算法检测到的真阳性较少，真阴性增加。小波算法优于JPEG算法，JPEG图像优于分形算法。工作站评估优于个人电脑评估。
只有小波算法在1:13的压缩比例下能提供对低对比度细节的准确评估。即使在低压缩比例下，小波算法的频率滤波也会影响对比度。JPEG算法在低压缩比例下表现优于分形算法，在高压缩比例下表现更差。
