Barbier Paolo, Alimento Marina, Berna Giovanni, Celeste Fabrizio, Gentile Francesco, Mantero Antonio, Montericcio Vincenzo, Muratori Manuela
Centro Cardiologico Monzino, IRCCS, Milano, Italy.
J Am Soc Echocardiogr. 2007 May;20(5):527-36. doi: 10.1016/j.echo.2006.10.006.
Large files produced by standard compression algorithms slow down spread of digital and tele-echocardiography. We validated echocardiographic video high-grade compression with the new Motion Pictures Expert Groups (MPEG)-4 algorithms with a multicenter study.
Seven expert cardiologists blindly scored (5-point scale) 165 uncompressed and compressed 2-dimensional and color Doppler video clips, based on combined diagnostic content and image quality (uncompressed files as references). One digital video and 3 MPEG-4 algorithms (WM9, MV2, and DivX) were used, the latter at 3 compression levels (0%, 35%, and 60%).
Compressed file sizes decreased from 12 to 83 MB to 0.03 to 2.3 MB (1:1051-1:26 reduction ratios). Mean SD of differences was 0.81 for intraobserver variability (uncompressed and digital video files). Compared with uncompressed files, only the DivX mean score at 35% (P = .04) and 60% (P = .001) compression was significantly reduced. At subcategory analysis, these differences were still significant for gray-scale and fundamental imaging but not for color or second harmonic tissue imaging. Original image quality, session sequence, compression grade, and bitrate were all independent determinants of mean score.
Our study supports use of MPEG-4 algorithms to greatly reduce echocardiographic file sizes, thus facilitating archiving and transmission. Quality evaluation studies should account for the many independent variables that affect image quality grading.
标准压缩算法生成的大文件减缓了数字和远程超声心动图的传播速度。我们通过一项多中心研究验证了采用新型运动图像专家组（MPEG）-4算法对超声心动图视频进行高级压缩的效果。
7名心脏病专家基于诊断内容和图像质量（以未压缩文件作为参考），对165个未压缩和压缩后的二维及彩色多普勒视频片段进行盲法评分（5分制）。使用了1个数字视频和3种MPEG-4算法（WM9、MV2和DivX），后3种算法采用3种压缩级别（0%、35%和60%）。
压缩后的文件大小从12至83MB降至0.03至2.3MB（压缩比为1:1051至1:26）。观察者内变异性（未压缩和数字视频文件）的平均标准差为0.81。与未压缩文件相比，仅DivX在35%（P = .04）和60%（P = .001）压缩级别时的平均评分显著降低。在亚类分析中，这些差异在灰度和基本成像方面仍然显著，但在彩色或二次谐波组织成像方面不显著。原始图像质量、检查顺序、压缩级别和比特率均为平均评分的独立决定因素。
我们的研究支持使用MPEG-4算法大幅减小超声心动图文件大小，从而便于存档和传输。质量评估研究应考虑影响图像质量分级的众多独立变量。
