三维治疗计划系统模拟全身照射的应用研究

目的:采用三维治疗计划系统(3D-TPS)模拟计算全身照射(TBI)的剂量分布.材料和方法:对于全身照射,设置源皮距(SSD)为380 cm,射野大小为40 cm×40 cm,光栏角度为45°,采用自制大水箱测量了直线加速器8 MV光子线水中的百分深度剂量(PDD)和离轴比(OAR).上述相同照射条件下,在3D-TPS中进行水体模的PDD和OAR的模拟计算并与之测量结果进行对比,确认3D-TPS是否能够模拟计算TBI的剂量分布.采用3D-TPS计算人形体模的TBI剂量分布,采用剂量胶片和热释光测量对计算结果进行了比较和确认.结果:对于水体模中的百分深度量和离轴比,3D-TPS的模拟计算结果与大水箱的测量结果最大误差分别为3%和6%左右.对于人形体模的模拟计算,3D-TPS的模拟计算结果与胶片和热释光的测量结果基本符合.结论:3D-TPS可以较准确地模拟计算全身照射的剂量分布.通过3D-TPS对每个特定病人制作相应补偿块,为更均匀剂量的全身照射治疗提供了可能.

The Application Study of the TBI Simulation of Three Dimension Treatment Planning System

Purpose: Simulating calculation the dose distribution of the total body irradiation (TBI) with three dimension treatment planning system(3D-TPS ). Materials and Methods: For TBI, the source skin distance(SSD) is 380 cm, field size is 40 cm × 40cm, and collimator angle is 45°. The percent dose depth (PDD) and onset axis ratio (OAR) of the linac accelerator is measured with the big water phantom self-made. In the same radiation condition, the PDD and OAR of water which is simulated calculation with the 3D-TPS is compared with the measurement results to confirm whether the 3D-TPS can calculate the TBI dose distribution. The dose distribution of the human phantom is calculated with 3D-TPS, which is compared and confirmed with the film and TLD measurements. Results: The maximum error of PDD and OAR in the water phantom between the measurements and calculations of 3D-TPS are 3% and 6%. The calculation results of the 3D-TPS is according with the measurement results of the film and TLD approximately. Conclusions: 3D-TPS could simulate calculation the dose distribution for TBI accurately. It is possible to improve more uniform dose for TBI with corresponding compensator for specific patient.