Duch M A, Ginjaume M, Chakkor H, Ortega X, Jornet N, Ribas M
Institut de Tècniques Energètiques (INTE), Universitat Politècnica de Catalunya, Barcelona, Spain.
Radiother Oncol. 1998 Jun;47(3):319-24. doi: 10.1016/s0167-8140(98)00013-9.
In total body irradiation (TBI) treatments in vivo dosimetry is recommended because it makes it possible to ensure the accuracy and quality control of dose delivery. The aim of this work is to set up an in vivo thermoluminescence dosimetry (TLD) system to measure the dose distribution during the TBI technique used prior to bone marrow transplant. Some technical problems due to the presence of lung shielding blocks are discussed.
Irradiations were performed in the Hospital de la Santa Creu i Sant Pau by means of a Varian Clinac-1800 linear accelerator with 18 MV X-ray beams. Different TLD calibration experiments were set up to optimize in vivo dose assessment and to analyze the influence on dose measurement of shielding blocks. An algorithm to estimate midplane doses from entrance and exit doses is proposed and the estimated dose in critical organs is compared to internal dose measurements performed in an Alderson anthropomorphic phantom.
The predictions of the dose algorithm, even in heterogeneous zones of the body such as the lungs, are in good agreement with the experimental results obtained with and without shielding blocks. The differences between measured and predicted values are in all cases lower than 2%.
The TLD system described in this work has been proven to be appropriate for in vivo dosimetry in TBI irradiations. The described calibration experiments point out the difficulty of calibrating an in vivo dosimetry system when lung shielding blocks are used.
在全身照射（TBI）治疗中，推荐进行体内剂量测定，因为这有助于确保剂量传递的准确性和质量控制。本研究的目的是建立一个体内热释光剂量测定（TLD）系统，以测量骨髓移植前使用的TBI技术过程中的剂量分布。讨论了由于肺部屏蔽块的存在而产生的一些技术问题。
在圣十字圣保罗医院，使用配备18MV X射线束的瓦里安Clinac - 1800直线加速器进行照射。开展了不同的TLD校准实验，以优化体内剂量评估，并分析屏蔽块对剂量测量的影响。提出了一种根据入射剂量和出射剂量估算中平面剂量的算法，并将关键器官中的估算剂量与在阿尔德森人体模型中进行的内部剂量测量结果进行比较。
即使在身体的异质区域（如肺部），剂量算法的预测结果与有无屏蔽块时获得的实验结果也高度吻合。测量值与预测值之间的差异在所有情况下均低于2%。
本研究中描述的TLD系统已被证明适用于TBI照射的体内剂量测定。所描述的校准实验指出了使用肺部屏蔽块时校准体内剂量测定系统的困难。
