摘要
目的3DCRT/IMRT治疗前行CBCT扫描,测定分次治疗间摆位误差,为头颈部肿瘤制定放疗计划CTV外放PTV提供参考依据。方法采用Varian-21EX直线加速器机载影像系统(OBI),在三维适形或调强放疗前行锥形束CT(CBCT)扫描,系统自动重建成断层图像,获得患者腹背、头脚、左右方向的摆位数据,并直接与治疗计划CT扫描图像相匹配得出两者间误差。结果统计268组CBCT扫描摆位误差数据显示,在左右、头脚、腹背方向平均误差分别为(1.2±1.7)mm、(1.8±3.2)mm、(0.5±2.0)mm,绝对最大值分别为7mm、12mm、7mm,以头脚方向的移动幅度稍大。小于3mm和5mm的误差在三个方向上分别为58%、43%、76%和85%、81%、94%。结论通过对本组CBCT扫描测得的误差数据分析,头颈部肿瘤在设计三维适形或调强放疗计划外放PTV时,考虑由摆位而引起的误差边界(SM)一般要3～5mm。
Objective To analyze the set-up error for head and neck cancer patients with three-dimensional conformal and intensity modulated radiotherapy to calculate CTV referential safety margins of PTV based on pre-treatment CBCT scans.Methods Varian-21EX linear accelerator on-board imaging system （OBI） was used to acquire CBCT scans in three-dimensianal conformal radiotherapy or intensity modulated radiation therapy before delivery.The anterior-posterior, superior-interferior and rightleft set-up datas of patients can be obtained from the tomography images automatically restructured by the system. The set-up error can be obtained by matching CBCT and plan CT images. Results According to 268 CBCT scans ,the set-up error in head and neck cancer radiotherapy in three directions （RL,SI,AP）was （1.2 ± 1.7） mm, （1.8 ± 3.2） mm, （0.5 ± 2.0） mm respectively and the absolute maximum was 7mm, 12mm, 7mm respectively. The movement range in superior-interferior direction was slightly larger than the other two directions. Within 3ram and 5mm of which accounted for 58 % ,43 % ,76 % and 85 %,81%,94 % respectively. Conclusion This study has laid a theoretic foundation for our CTV margins by analyzing the set-up error in head and neck cancer three-dimensional conformal radiotherapy or intensity modulated radiation therapy based on CBCT scans . Taking into account the set-up error, the SM（set-up margin）caused by set-up error should be carefully considered and 3 - 5mm was appropriate.
出处
《中国医疗设备》
2009年第6期18-20,共3页
China Medical Devices
关键词
锥形束CT
临床靶区
计划靶区
摆位误差
cone-beam CT
clinieal target volume
planning target volume
set-up errors
