Chung Hyun-Tai, Park Woo-Yoon, Kim Tae Hoon, Kim Yong Kyun, Chun Kook Jin
Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea.
Department of Radiation Oncology, Chungbuk National University College of Medicine, Cheongju, Korea.
J Appl Clin Med Phys. 2018 Jul;19(4):148-154. doi: 10.1002/acm2.12365. Epub 2018 Jun 3.
The aim of this study was to assess the accuracy and stability of frameless gamma knife radiosurgery (GKRS). The accuracies of the radiation isocenter and patient couch movement were evaluated by film dosimetry with a half-year cycle. Radiation isocenter assessment with a diode detector and cone-beam computed tomography (CBCT) image accuracy tests were performed daily with a vendor-provided tool for one and a half years after installation. CBCT image quality was examined twice a month with a phantom. The accuracy of image coregistration using CBCT images was studied using magnetic resonance (MR) and computed tomography (CT) images of another phantom. The overall positional accuracy was measured in whole procedure tests using film dosimetry with an anthropomorphic phantom. The positional errors of the radiation isocenter at the center and at an extreme position were both less than 0.1 mm. The three-dimensional deviation of the CBCT coordinate system was stable for one and a half years (mean 0.04 ± 0.02 mm). Image coregistration revealed a difference of 0.2 ± 0.1 mm between CT and CBCT images and a deviation of 0.4 ± 0.2 mm between MR and CBCT images. The whole procedure test of the positional accuracy of the mask-based irradiation revealed an accuracy of 0.5 ± 0.6 mm. The radiation isocenter accuracy, patient couch movement accuracy, and Gamma Knife Icon CBCT accuracy were all approximately 0.1 mm and were stable for one and a half years. The coordinate system assigned to MR images through coregistration was more accurate than the system defined by fiducial markers. Possible patient motion during irradiation should be considered when evaluating the overall accuracy of frameless GKRS.
本研究的目的是评估无框架伽玛刀放射外科手术（GKRS）的准确性和稳定性。通过半年周期的胶片剂量测定法评估辐射等中心和患者治疗床移动的准确性。安装后一年半的时间里，每天使用供应商提供的工具进行二极管探测器的辐射等中心评估和锥束计算机断层扫描（CBCT）图像准确性测试。每月使用模体检查两次CBCT图像质量。使用另一个模体的磁共振（MR）和计算机断层扫描（CT）图像研究使用CBCT图像进行图像配准的准确性。在使用人体模体的胶片剂量测定法的整个过程测试中测量总体位置准确性。中心和极端位置的辐射等中心位置误差均小于0.1毫米。CBCT坐标系的三维偏差在一年半的时间内保持稳定（平均0.04±0.02毫米）。图像配准显示CT和CBCT图像之间的差异为0.2±0.1毫米，MR和CBCT图像之间的偏差为0.4±0.2毫米。基于面罩照射的位置准确性的整个过程测试显示准确性为0.5±0.6毫米。辐射等中心准确性、患者治疗床移动准确性和伽玛刀Icon CBCT准确性均约为0.1毫米，并在一年半的时间内保持稳定。通过配准分配给MR图像的坐标系比由基准标记定义的系统更准确。评估无框架GKRS的总体准确性时应考虑照射期间患者可能的运动。
