Diagnostic Performance in PACS Workstation.

我们研究了临床安全的X线照片压缩比。对54张2048方数字化X线片采用非均匀块编码方法进行压缩，并在1000线CRT或激光打印机胶片上显示。将92对压缩图像和原始图像裁剪成1024个方形ROI，由3名放射科医生在每对图像的最佳显示窗口上观察。结果表明：（1）以12的比例，CRT上60%的解剖结构和病理结构与X线片上79%的解剖结构和病理结构有差异; (2)当比值为8时，在解剖结构上有差异的分别为7%和10%。(3)当比值为5时，在解剖结构上没有发现差异。我们得出结论，在临床诊断中，数据压缩比5是绝对安全的，比率8是相对安全的。

We investigated a clinically safe compression ratio of radiographs. Fifty-four 2048 square digitized radiographs were compressed with non-uniform block coding method and displayed in a 1000-line CRT or in a laser printer films. Ninety two pairs of compressed and original images trimmed into 1024 square ROIs were observed by 3 radiologists on the displaying windows optimum for each pair of images. The differnces between compressed and original images were evaluated with the following results : (1) Using the ratio of 12, some differences were recognized on both anatomic and pathologic structures in 60% on CRTs and 79% on films. (2) With the ratio of 8, some differences were recognized on anatomic structures in 7% and 10% respectively. (3) With the ratio of 5, no differences were found on anatomical structures. We concluded that the data compression ratio 5 is the absolutely safe and the ratio 8 is a relatively safe in clinical diagnosis.