Department of Radiology, Kanazawa University Hospital, Kanazawa, Ishikawa, Japan.
Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan.
J Appl Clin Med Phys. 2021 Feb;22(2):58-68. doi: 10.1002/acm2.13152. Epub 2020 Dec 27.
The Catalyst HD (C-RAD Positioning AB, Uppsala, Sweden) optical surface imaging (OSI) system is able to manage interfractional patient positioning, intrafractional motion monitoring, and non-contact respiratory gating without x-ray exposure for radiation therapy. In recent years, a novel high-precision surface registration algorithm for stereotactic radiosurgery (SRS algorithm) has been released. This study aimed to evaluate the technical performance of the OSI system using rigid phantoms, by comparing the conventional and SRS algorithms. To determine the system's technical performance, isocenter displacements were calculated by surface image registration via the OSI system using head, thorax, and pelvis rigid phantoms. The reproducibility of positioning was evaluated by the mean value calculated by repeating the registration 10 times, without moving each phantom. The accuracy of positioning was evaluated by the mean value of the residual error, where the 10 offset values given to each phantom were subtracted from the isocenter displacement values. The stability of motion monitoring was evaluated by measuring isocenter drift during 20 min and averaging it over 10 measurements. For the head phantom, all tests were compared with the mask types and algorithms. As a result, for all sites and both algorithms, the reproducibility, accuracy, and stability for translation and rotation were <0.1 mm and <0.1°, <1.0 mm and <1.0°, and <0.1 mm and <0.1°, respectively. In particular, the SRS algorithm had a small absolute error and standard deviation of calculated isocenter displacement, and a significantly higher reproducibility and accuracy than the conventional algorithm (P < 0.01). There was no difference in the stability between the algorithms (P = 0.0280). The SRS algorithm was found to be suitable for the treatment of rigid body sites with less deformation and small area, such as the head and face.
Catalyst HD（C-RAD 定位 AB，乌普萨拉，瑞典）光学表面成像（OSI）系统能够在不进行 X 射线辐射的情况下管理分次间患者定位、分次内运动监测和非接触式呼吸门控，用于放射治疗。近年来，一种用于立体定向放射外科（SRS 算法）的新型高精度表面配准算法已经发布。本研究旨在通过比较传统算法和 SRS 算法，使用刚性体模评估 OSI 系统的技术性能。为了确定系统的技术性能，通过使用 OSI 系统对头、胸和骨盆刚性体模进行表面图像配准，计算等中心位移。通过重复注册 10 次，不移动每个体模，计算平均值来评估定位的重复性。通过从等中心位移值中减去 10 个偏移值的平均值来评估定位的准确性。通过测量 20 分钟内的等中心漂移并将其平均 10 次测量值来评估运动监测的稳定性。对于头部体模，所有测试均与面罩类型和算法进行了比较。结果表明，对于所有部位和两种算法，平移和旋转的重复性、准确性和稳定性均<0.1mm 和<0.1°、<1.0mm 和<1.0°、<0.1mm 和<0.1°。特别是，SRS 算法的计算等中心位移的绝对误差和标准偏差较小，且重复性和准确性明显高于传统算法（P<0.01）。两种算法的稳定性无差异（P=0.0280）。SRS 算法适用于变形较小且面积较小的刚性体部位的治疗，如头部和面部。
