Analysis of exposure technique of computed radiography

为了在计算机射线照相（CR）中正确地进行X射线数据采集和图像显示，需要知道探测器和显示器的动态范围，以及被射线照相的对象的动态范围。我们已经开发了一个计算机程序，使测量的动态范围的主题。在传统的射线照相技术中，我们通过改变曝光因子来将被摄体的动态范围保持在胶片的动态范围内。由于CR的动态范围宽，显示了图像处理，特别是空间滤波的有效性，因此应重新考虑曝光技术，以充分利用CR。我们开发了一个髋臼角的自动测量系统，它是先天性髋关节脱位（LCC）的诊断参数。由于CR的低对比度探测能力得到了改善，与传统系统相比，其角度测量可以在1/20的X射线剂量下进行。采用光纤环形结构将X射线CT与图像工作站和光盘存储单元连接起来。工作站有三个1024 x1024像素的非隔行CRT显示器。光盘系统可存储32个光盘盒（2.6G字节/盒）。该系统已在临床环境中运行了6个月，并对CRT进行了在线数据采集、长期存档以及CT和CR解释。

For proper x-ray data acquisition and image display in Computed Radiography(CR), it is necessary to know the dynamic ranges of the detector and display, and also of the subject being radiographed. We have developed a computer program which enables to measure the dynamic range of the subject. In the conventional radiographic techniques, we kept the dynamic range of the subject within the dynamic range of the film by changing the exposure factors. Exposure techniques should be reconsidered to take full advantage of CR, because the images with wide dynamic range show effectiveness of the picture processing, particularly spatial filtering.We have developed an automatic measurement system of acetabular angle which is a diagnostic parameter of congenital hip dislocation (LCC) using a computed radiography. Because of improved low-contrast detectability of the CR, the angle can be measured under one-twentieth X-ray dose comparing with conventional system.A network using fiber-optic ring architecture has been implemented to connect X-ray CT, with an image work-station and optical disk storage unit. The work-station has three, non-interlaced CRT monitors of 1024x1024 pixels. The optical disk system stores 32 optical disk cartridges (2.6Gbyte/cartridges). On-line date acquisition, long-term archiving, and CT and CR interpretation using CRT have been tested and the system has been working for 6 months in clinical environment.