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目的建立针对调强放射治疗患者的剂量学验证方法。方法对100例患者进行的剂量验证共有3个测量项目一是采用小灵敏体积的电离室在仿人形模体中测量靶区剂量参考点(一般是射野等中心点)的绝对剂量,二是采用胶片测量一个治疗计划的所有射野在仿人形模体内形成的复合剂量分布,三是采用胶片或半导体探测器阵列在干水模体中测量单个射野的强度分布。由于完成全3个测量项目占用机器的时间过长,实际操作时采用自适应的方式,即首先测量靶区剂量参考点的绝对剂量,如果剂量误差在允许范围内,则不再进行其他的测量;如果剂量误差超出允许范围,则增加两个电离室测量点,并采用胶片测量横断面的剂量分布和(或)射野强度分布。结果93%患者的计划可以顺利实施,其他患者的计划需要调整铅门位置或完全重新设计。87%患者计划的剂量误差在临床可以接受的范围内,其他患者的计划需要对射野机器跳数进行修正;修正系统误差后,有96%患者计划的剂量误差在临床可以接受的范围内。结论利用已有的设备条件建立了患者调强放射治疗计划的剂量学验证方法,这种方法随着设备条件的改善和经验的积累还会进一步完善。针对患者的计划进行剂量学验证是很有必要的。
Objective To establish a dosimetric verification method for patients with IMRT. Methods There are 3 measurement items in 100 patients: one is to measure the reference dose (usually the center of the field) in the humanoid phantom with a small sensitive chamber, and the other is The film was used to measure the composite dose distribution of all the radiation fields in a simulated humanoid phantom and the third was to measure the intensity distribution of a single field in a dry water phantom using a film or semiconductor detector array. Since all three measurement items take up the machine for an extended period of time, the actual operation adopts an adaptive method that firstly measures the absolute dose of the target dose reference point, and if the dose error is within the allowable range, no other measurement is performed If the dose error is outside the allowable range, add two ionization chamber measurement points and measure the cross-sectional dose distribution and / or field intensity distribution using film. Results Ninety-three percent of patients planned well and others planned to adjust the lead-door position or completely redesign. Eighty-seven percent of patients planned dose errors were within clinically acceptable limits. Other patients’ plans required corrections to field machine hops; 96% of patients planned dose errors were within clinically acceptable limits after systematic errors were corrected. Conclusion The dosimetric verification method of IMRT plan was established by using the existing equipment conditions. This method will be further improved with the improvement of equipment conditions and the accumulation of experience. Dose-based verification of patient plans is necessary.