Shirato H, Suzuki K, Nishioka T, Kamada T, Kagei K, Kitahara T, Morisawa H, Tsujii H
Department of Radiology, Faculty of Medicine, Hokkaido University, Sapporo, Japan.
Radiother Oncol. 1994 Aug;32(2):180-3. doi: 10.1016/0167-8140(94)90105-8.
RT-CT was developed as a simulator using CT scan for radiotherapy. Following three-dimensional treatment planning using CT images, the treatment center and treatment fields are projected to the patients' surface by laser beam on the C arm. The prototype had an accuracy of 3 mm which was equivalent to conventional X-ray simulators but was not adequate for use in stereotactic radiotherapy. A new RT-CT system was developed to have a precise localization capability for stereotactic radiotherapy. Using this stereotactic RT-CT (SRT-CT) after three-dimensional planning, the treatment center is projected to the stereotactic frame automatically. In this study, the values of the x, y and z coordinates of the target center determined by SRT-CT are compared with those determined by the traditional method using CT localizing plates. The discrepancies were within 1.0 mm in 90% and 1.5 mm in 100% of 30 measurements in 16 patients. The disadvantages of SRT-CT may be that the accuracy of localization depends on the quality of calibration of laser beams. The traditional CT localizing method has superiority over SRT-CT because of its solid coordinates but its accuracy is vulnerable to alignment of CT fiducial marker plates. Therefore, the SRT-CT and traditional CT localizing methods would be complementary to each other for precise localization.
RT-CT是作为一种利用CT扫描进行放射治疗的模拟设备而开发的。在使用CT图像进行三维治疗计划后，治疗中心和治疗野通过C臂上的激光束投射到患者体表。该原型机的精度为3毫米，与传统X射线模拟设备相当，但不足以用于立体定向放射治疗。开发了一种新的RT-CT系统，以具备用于立体定向放射治疗的精确定位能力。在三维计划后使用这种立体定向RT-CT（SRT-CT），治疗中心会自动投射到立体定向框架上。在本研究中，将SRT-CT确定的靶中心x、y和z坐标值与使用CT定位板的传统方法确定的值进行比较。在16例患者的30次测量中，90%的差异在1.0毫米以内，100%的差异在1.5毫米以内。SRT-CT的缺点可能是定位精度取决于激光束校准的质量。传统的CT定位方法因其坐标可靠而优于SRT-CT，但其精度容易受到CT基准标记板对齐的影响。因此，SRT-CT和传统CT定位方法在精确定位方面将相互补充。
