Janhom A, van der Stelt P F, van Ginkel F C
Department of Oral Radiology, Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands.
Dentomaxillofac Radiol. 2000 Jan;29(1):20-7. doi: 10.1038/sj/dmfr/4600488.
To determine the interaction between image noise and file compression, with special emphasis on the accuracy of caries diagnosis.
Fifty-nine bitewing radiographs of patients were taken simultaneously with Ektaspeed Plus (Eastman-Kodak, Rochester, NY, USA) film without lead foil and the Digora storage phosphor system (Soredex, Helsinki, Finland). Three different levels of Gaussian noise were added to the original digital images which were then compressed with JPEG 53. Seven observers evaluated the presence and depth of caries lesions on selected approximal surfaces on a 5-point scale. The results of JPEG 27 compression from a previous study were also included. ROC analysis was used together with multivariate analysis of variance (MANOVA).
JPEG 27 and 53 reduced the file size down to 7% and 4.6% of the original respectively. ROC curve analysis showed no significant difference between image conditions (original, JPEG 27, and JPEG 53) at the same noise level. JPEG 27 and 53 had larger Az scores than their original counterparts at the same noise level. However, MANOVA showed that for depth estimation of enamel lesions JPEG 53 resulted in a higher observer error.
Both JPEG 53 and 27 could reduce some of the adverse effect of noise from the image by removing high spatial frequencies. JPEG 53, resulting in a compression ratio of 1:21, does not compromise the diagnostic performance in general. JPEG 53 compression may however affect the ability to detect enamel lesions.
确定图像噪声与文件压缩之间的相互作用，特别关注龋齿诊断的准确性。
使用无铅箔的Ektaspeed Plus（美国纽约罗切斯特伊士曼柯达公司）胶片和Digora存储磷光体系统（芬兰赫尔辛基Soredex公司）同时拍摄59例患者的咬合翼片。对原始数字图像添加三种不同水平的高斯噪声，然后用JPEG 53进行压缩。七名观察者以5分制评估选定邻面龋损的存在情况和深度。还纳入了先前一项研究中JPEG 27压缩的结果。采用ROC分析和多变量方差分析（MANOVA）。
JPEG 27和53分别将文件大小缩小至原始大小的7%和4.6%。ROC曲线分析表明，在相同噪声水平下，图像条件（原始、JPEG 27和JPEG 53）之间无显著差异。在相同噪声水平下，JPEG 27和53的Az值高于其原始图像。然而，MANOVA显示，对于釉质病变深度估计，JPEG 53导致观察者误差更高。
JPEG 53和27均可通过去除高空间频率来减少图像噪声的一些不利影响。压缩率为1:21的JPEG 53总体上不会损害诊断性能。然而，JPEG 53压缩可能会影响检测釉质病变的能力。
