Estimation of the delivered patient dose in lung IMRT treatment based on deformable registration of 4D-CT data and Monte Carlo simulations
Estimation of the delivered patient dose in lung IMRT treatment based on deformable registration of 4D-CT data and Monte Carlo simulations
复制标题
DOI：
10.1088/0031-9155/51/11/006
复制
发表时间：
2006-06-07
影响因子：
3.5
通讯作者：
Choi, Noah C.
中科院分区：
文献类型：
--
作者：
Flampouri, Stella;Jiang, Steve B.;Choi, Noah C.
本研究的目的是准确估计肺IMRT治疗中由于呼吸运动和自由呼吸螺旋CT伪影导致的计划剂量和输送剂量之间的差异，并估计这种差异对临床结果的影响。本回顾性研究选择了6例具有代表性肿瘤运动、大小和位置的患者。对于每一个病人，我们都获得了自由呼吸螺旋CT和10期4D-CT扫描。使用商业治疗计划系统为每位患者创建四个IMRT计划。前两个计划基于自由呼吸螺旋CT上的GTV轮廓，GTV到PTV的扩展分别为1.5 cm和2.0 cm。第三个计划是基于ITV的，ITV是由自由呼吸螺旋CT、吸气末（EOI）和呼气末（EOE）4D-CT上勾画的CTV体积的联合形成的复合体积。第四个计划基于EOE 4D-CT上勾画的GTV。所有4个计划的处方剂量均为60戈伊。蒙特卡罗剂量计算引擎MCSIM使用IMRT计划的注量图和射束设置参数对自由呼吸CT和4D-CT数据进行绝对剂量计算。在呼吸阶段之间进行CT变形配准，以估计肿瘤和健康组织的运动轨迹。然后，计算整个呼吸周期的复合剂量分布，作为输送剂量的最终估计值。根据所有四个计划的复合剂量计算EUD值。对于具有最大运动效应的患者，对于第一、第二、第三和第四计划，计划剂量和递送剂量之间CTV的EUD差异分别为33、11、1和0戈伊。还研究了准确剂量预测所需的呼吸阶段数。随着4D-CT、可变形配准和蒙特卡罗模拟的出现，可以精确计算输送剂量，并将我们的输送剂量与使用现有技术估计的剂量进行比较。
The purpose of this study is to accurately estimate the difference between the planned and the delivered dose due to respiratory motion and free breathing helical CT artefacts for lung IMRT treatments, and to estimate the impact of this difference on clinical outcome. Six patients with representative tumour motion, size and position were selected for this retrospective study. For each patient, we had acquired both a free breathing helical CT and a ten-phase 4D-CT scan. A commercial treatment planning system was used to create four IMRT plans for each patient. The first two plans were based on the GTV as contoured on the free breathing helical CT set, with a GTV to PTV expansion of 1.5 cm and 2.0 cm, respectively. The third plan was based on the ITV, a composite volume formed by the union of the CTV volumes contoured on free breathing helical CT, end-of-inhale (EOI) and end-of-exhale (EOE) 4D-CT. The fourth plan was based on GTV contoured on the EOE 4D-CT. The prescribed dose was 60 Gy for all four plans. Fluence maps and beam setup parameters of the IMRT plans were used by the Monte Carlo dose calculation engine MCSIM for absolute dose calculation on both the free breathing CT and 4D-CT data. CT deformable registration between the breathing phases was performed to estimate the motion trajectory for both the tumour and healthy tissue. Then, a composite dose distribution over the whole breathing cycle was calculated as a final estimate of the delivered dose. EUD values were computed on the basis of the composite dose for all four plans. For the patient with the largest motion effect, the difference in the EUD of CTV between the planed and the delivered doses was 33, 11, 1 and 0 Gy for the first, second, third and fourth plan, respectively. The number of breathing phases required for accurate dose prediction was also investigated. With the advent of 4D-CT, deformable registration and Monte Carlo simulations, it is feasible to perform an accurate calculation of the delivered dose, and compare our delivered dose with doses estimated using prior techniques.