Strid K G, Kälebo P
Institute for Applied Biotechnology, Gothenburg, Sweden.
Acta Radiol. 1988 Jul-Aug;29(4):465-72.
The mass of hard-tissue specimens is assessed by optimised microradiography followed by computer-assisted videodensitometry. Radiographs are produced with 27 kV roentgen radiation, filtered through 0.5 to 1 mm of aluminium, on high-resolution glass plates. Aluminium step wedges are used for density calibration, the result being expressed as 'aluminium equivalent mass'. The plates are subjected to digital image analysis by an operator in interaction with a computer-based image processor, a television camera being used for image input. The program stored in the computer provides calibration of geometry and--via the step wedge images--of densitometry, background adjustment, etc. Measurement takes place by integration over the specimen-image area. No assumptions being needed concerning a specific attenuation model, the errors stemming from the common presumption of exponential attenuation are eliminated. Density profiles or maps of mass distribution are readily obtained from the computer. From measurements of aluminium phantom samples, the total random error (coefficient of variation) was determined at 1.8 per cent, the microradiographic and videodensitometric procedures contributing 1.6 per cent and 0.9 per cent, respectively, whereas the systematic error was negligible. Since specimens need not be sectioned, this method does not interfere with subsequent histologic preparation.
通过优化的显微放射照相术，随后进行计算机辅助视频密度测定法来评估硬组织标本的质量。使用27 kV的伦琴射线，通过0.5至1毫米厚的铝进行过滤，在高分辨率玻璃板上产生射线照片。铝阶梯楔形块用于密度校准，结果以“铝当量质量”表示。操作人员与基于计算机的图像处理器交互，对玻璃板进行数字图像分析，使用电视摄像机进行图像输入。计算机中存储的程序提供几何校准以及通过阶梯楔形块图像进行的密度测定校准、背景调整等。通过对标本图像区域进行积分来进行测量。由于无需对特定衰减模型进行假设，消除了因指数衰减这一常见假设而产生的误差。很容易从计算机中获得密度分布图或质量分布图谱。通过对铝体模样品的测量，确定总随机误差（变异系数）为1.8%，显微放射照相术和视频密度测定法分别贡献1.6%和0.9%，而系统误差可忽略不计。由于标本无需切片，该方法不会干扰后续的组织学制备。
