Sen Amarjit, West Matthew K
Department of Radiation Oncology, Cancer Treatment Centers of America, Tulsa, OK 74133, USA.
J Med Phys. 2009 Oct;34(4):194-9. doi: 10.4103/0971-6203.56078.
A helical tomotherapy machine combines a straight 6 MV linear accelerator mounted on a ring gantry with CT technology for image-guided intensity-modulated radiation therapy (IMRT) treatment. A fan beam created by the collimator and jaws produces a maximum of 40 x 5 cm(2) field size at the isocenter. The gantry and hence the fan beam rotates at a constant speed while the couch moves linearly into the gantry bore, thus producing a helical delivery. The beam is modulated by a 64-leaf binary multileaf collimator (MLC), which enables IMRT treatment. The linac can be operated at a lower voltage (3.5 MV) and dose rate to produce megavoltage CT images, which are used for image-guided patient setup. We have installed two such units since 2004 and treated more than 2000 patients. The machine comes "precommissioned" from the manufacturer, and the beam characteristics and IMRT plans on phantom are measured and compared with manufacturer's data after acceptance tests are performed on site. Our experience with commissioning the machines and periodic quality assurance with tolerance limits for optimal performance are described.
螺旋断层放射治疗机将安装在环形机架上的直线型6兆伏直线加速器与用于图像引导调强放射治疗（IMRT）的CT技术相结合。由准直器和钳夹产生的扇形束在等中心处产生最大40×5平方厘米的射野尺寸。机架以及扇形束以恒定速度旋转，同时治疗床直线移入机架孔，从而产生螺旋式射束传输。射束由64叶二元多叶准直器（MLC）调制，可实现IMRT治疗。直线加速器可以在较低电压（3.5兆伏）和剂量率下运行，以产生兆伏级CT图像，用于图像引导的患者摆位。自2004年以来，我们已安装了两台这样的设备，并治疗了2000多名患者。该机器由制造商进行“预调试”，在现场进行验收测试后，测量射束特性和体模上的IMRT计划，并与制造商的数据进行比较。本文描述了我们调试这些机器的经验以及具有最佳性能公差限度的定期质量保证情况。
