Application of dynamic virtual reality visualization technology for real-time tumor-tracking radiation therapy

为了提高体内运动肿瘤放射治疗的准确性，研究如何利用虚拟现实技术。为了实现真实空间和虚拟空间的配准，研制了一个2.0mm的金标记物，并将其中的三个标记物插入人体肿瘤附近。治疗室安装了两台荧光透视X射线摄像机。两台摄像机可以计算标记物的三维位置，精度为0.5 mm。肿瘤的平移、旋转和变形都可以在放疗开始时计算，并且可以在放疗前相应地调整肿瘤的位置。自动模式识别技术，实时比较虚拟“计划标记”的三维坐标与“实际标记”的三维坐标每隔0.03秒照射一次使得只有当肺和肝肿瘤位于计划位置时才能照射到它们，精确度为2 mm。或直肠前列腺癌，该系统是有用的，以改善剂量分布。该系统使用比常规放疗更高的辐射剂量，对肺和肝肿瘤进行了良好的控制。虚拟现实技术与模式识别技术相结合，是实现四维（时间和空间）治疗计划和实时肿瘤跟踪放射治疗的重要工具。

To improve the accuracy of radiotherapy for tumors moving in the body, how to use virtual reality technology was investigated. For the registration of real-space and virtual-space, a 2.0 mm gold marker was developed and three of them were inserted near the tumor in human body. Tow fluoroscopic x-ray cameras were installed in the treatment room. The three dimensional position of the markers can be calculated by the two cameras with an accuracy of 0.5 mm. Translation, rotation, and distortion of the tumor can be all calculated at the start of radiotherapy and the position of the tumor can be adjusted before the radiotherapy accordingly. Automatic patter recognition technology with real-time comparison of the three-dimensional co-ordinates of virtual "planned marker" with the three-dimensional co-ordinates of "actual marker" every 0.03 seconds made it possible to irradiate lung and liver tumors only when they are located at the planned position within an accuracy of 2 mm. Tumors very close to the critical normal structure such as spinal cord for spinal schwannoma or rectum for prostate carcinoma, the system was useful to improve dose distribution. Lung and liver tumors were well controlled by the system using higher radiation dose than conventional radiotherapy. Virtual reality technology with the aid of pattern recogtion technology was revealed to be an important tool for the four-dimensional (time and space) treatment planning and real-time tumor tracking radiotherapy.