Analysis of exposure technique of computed radiography

为了在计算机射线照相(CR)中获得正确的X射线数据和图像显示，有必要知道探测器和显示器的动态范围，以及被照相对象的动态范围。我们已经开发了一个计算机程序，它能够测量对象的动态范围。在传统的射线照相技术中，我们通过改变曝光系数来保持被摄体的动态范围在胶片的动态范围内。为了充分发挥CR的优势，曝光技术应重新考虑，因为大动态范围的图像显示了图像处理的有效性，特别是空间滤波。我们开发了一种使用计算机X线摄影的髋臼角度自动测量系统，它是先天性髋关节脱位的诊断参数。由于提高了CR的低对比度探测能力，与传统系统相比，可以在二十分之一的X射线剂量下进行角度测量，采用光纤环形结构实现了X射线CT与图像工作站和光盘存储单元的网络连接。该工作站有三个1024x1024像素的非隔行扫描CRT显示器。光盘系统存储32个光盘盒(2.6G字节/盒)。使用CRT进行了在线数据采集、长期存档以及CT和CR判读的测试，该系统已在临床环境中运行了6个月。

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.