Bouzid Dounia, Bert Julien, Dupre Pierre-Francois, Benhalouche Saadia, Pradier Olivier, Boussion Nicolas, Visvikis Dimitris
a Inserm UMR1101 , LaTIM, Brest , France.
b Department of Radiotherapy , CHRU Brest , France.
Acta Oncol. 2015 Nov;54(10):1788-95. doi: 10.3109/0284186X.2015.1016623. Epub 2015 Mar 24.
Intraoperative radiotherapy (IORT) is continuously gaining ground in cancer treatment. However, there is currently no planning system associated with these devices, which precludes patient-specific dose delivery optimization. The objective of this study was the development and validation of a Monte Carlo simulation (MCS)-based dosimetry platform using the Intrabeam™ system.
After surgical resection of the tumor this system delivers a single dose fraction at the surface of an applicator irradiating the tumor bed through a 50 kV x-ray beam. The GATE MCS platform was used in this study combining the phase space obtained by modeling the x-ray source and the detailed modeling of the additional parts of the Intrabeam™ system. The model was validated by comparing simulated versus experimental measurements of depth dose curves (DDC) and isotropy. A clinical validation study was also carried out using patient computed tomography images.
The mean deviation between measured and simulated DDC was 2.9% ± 4.4% and 5.9% ± 5.7% for the bare needle and the use of applicators, respectively. A good agreement with experimental measurements was also found in terms of dose isotropy with a maximum difference of 2.04% for the 40 mm diameter applicator. A patient study revealed a mean absolute deviation of 0.06 Gy between simulated and thermoluminescent dosimeters (TLD) measured skin doses.
This study shows the potential of using the GATE MCS platform to model three-dimensional dose distributions of the Intrabeam™ system for use in IORT.
术中放疗（IORT）在癌症治疗中越来越受到重视。然而，目前尚无与这些设备相关的计划系统，这使得无法实现针对患者的剂量输送优化。本研究的目的是开发并验证一种基于蒙特卡罗模拟（MCS）的剂量测定平台，该平台使用Intrabeam™系统。
在肿瘤手术切除后，该系统通过50 kV的X射线束在施源器表面单次给予剂量，照射肿瘤床。本研究使用GATE MCS平台，将通过对X射线源建模获得的相空间与Intrabeam™系统其他部分的详细建模相结合。通过比较深度剂量曲线（DDC）和各向同性的模拟测量值与实验测量值来验证模型。还使用患者计算机断层扫描图像进行了临床验证研究。
裸针和使用施源器时，测量的和模拟的DDC之间的平均偏差分别为2.9%±4.4%和5.9%±5.7%。在剂量各向同性方面也发现与实验测量结果有良好的一致性，40毫米直径施源器的最大差异为2.04%。一项患者研究显示，模拟皮肤剂量与热释光剂量计（TLD）测量的皮肤剂量之间的平均绝对偏差为0.06 Gy。
本研究表明使用GATE MCS平台对Intrabeam™系统的三维剂量分布进行建模以用于术中放疗的潜力。
