Computer simulation analysis of image and patient dosage in Rotational Panoramic Radiography

旋转全景放射成像的图像质量和患者剂量受各种机械因素的影响。如x射线光束的垂直角度，光束宽度，以及光束的运动模式。为了分别评估各因素对图像和剂量的影响，我们引入了计算机模拟方法。首先，构建了用数值表示组织器官的头部仿真模型；客观组织器官为空气、软组织、海绵骨、皮质骨、牙齿组织、唾液腺、甲状腺、晶状体。其次，开发了在计算机中再现实际图像形成过程的仿真程序。利用该程序可以同时模拟多种力学因素下的图像和剂量分布。目前的仿真程序存在以下问题。1. 头部幻像的结构与人的结构不够接近。2. 需要更准确地确定头部虚影中各元素的x射线衰减系数。3. 散射辐射根本不考虑。这些问题将在不久的将来得到解决。

The image quality and the patient dosage in rotational panoramic radiography are affected by various mechanical factors. such as the vertical angle of x-ray beam, beam width, and beam movement pattern. In order to evaluate separately the effect of each factor on the image and the dosage, we introduced a computer simulation method.At first, the head phantom for simulation, which represented tissues and organs by numerical values, was constructed. Objective tissues and organs were air, soft tissue, spongy bone, cortical bone, tooth tissue, salivary grand, thyroid grand and eye lens. Next, the simulation program for reproducing the actual image formation process in the computer was developed. With this program, the image and the dosage distribution could be simultaneously simulated under several mechanical factors.The present simulation program has the problems as follows. 1. The structure of the head phantom is not sufficiently faithful to that of the human. 2. X-ray attenuation coefficients of each element in the head phantom should be decided more accurately. 3. The scatter radiation is not considered at all.These problems will be resolved in near future.