Camilleri J, Mazurier J, Franck D, Dudouet P, Latorzeff I, Franceries X
INSERM, Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Service de radiothérapie, groupe Oncorad-Garonne, Clinique Pasteur, L'Atrium, 1, rue de la petite-vitesse, 31000 Toulouse, France.
Service de radiothérapie, groupe Oncorad-Garonne, Clinique Pasteur, L'Atrium, 1, rue de la petite-vitesse, 31000 Toulouse, France.
Phys Med. 2014 Sep;30(6):690-5. doi: 10.1016/j.ejmp.2014.02.003. Epub 2014 Mar 20.
The purpose of our work was to investigate the feasibility of using an EPID-based in-vivo dosimetry method initially designed for conformal fields on pelvic dynamic IMRT fields. The method enables a point dose delivered to the patient to be calculated from the transit signal acquired with an electronic portal imaging device (EPID). After defining a set of correction factors allowing EPID pixel values to be converted into absolute doses, several tests on homogeneous water-equivalent phantoms were performed to estimate the validity of the method in reference conditions. The effects of different treatment parameters, such as delivered dose, field size dependence and patient thickness were also studied. The model was first evaluated on a group of 53 patients treated by 3D conformal radiotherapy (3DCRT) and then on 92 patients treated by IMRT, both for pelvic cancers. For each measurement, the dose was reconstructed at the isocenter (DREC) and compared with the dose calculated by our treatment planning system (DTPS). Excellent agreement was found between DREC and DTPS for both techniques. For 3DCRT treatments, the mean deviation between DREC and DTPS for the 211 in-vivo dose verifications was equal to -1.0 ± 2.2% (1SD). Concerning IMRT treatments, the averaged deviation for the 418 fields verified was equal to -0.3 ± 2.6% (1SD) proving that the method is able to reconstruct a dose for dynamic IMRT pelvic fields. Based on these results, tolerance criteria and action levels were established before its implementation in clinical routine.
我们工作的目的是研究一种基于电子射野影像装置（EPID）的体内剂量测定方法用于盆腔动态调强放射治疗（IMRT）野的可行性，该方法最初是为适形野设计的。该方法能够根据用电子射野影像装置（EPID）采集的通过信号计算出输送给患者的点剂量。在定义了一组校正因子以使EPID像素值能够转换为绝对剂量之后，对均匀水等效体模进行了多项测试，以评估该方法在参考条件下的有效性。还研究了不同治疗参数的影响，如输送剂量、射野大小依赖性和患者厚度。该模型首先在一组53例接受三维适形放疗（3DCRT）的患者中进行评估，然后在92例接受IMRT的盆腔癌患者中进行评估。对于每次测量，在等中心处重建剂量（DREC）并与我们的治疗计划系统（DTPS）计算的剂量进行比较。两种技术在DREC和DTPS之间均发现了极好的一致性。对于3DCRT治疗，211次体内剂量验证中DREC与DTPS之间的平均偏差为-1.0±2.2%（1标准差）。对于IMRT治疗，418个验证射野的平均偏差为-0.3±2.6%（1标准差），证明该方法能够重建盆腔动态IMRT野的剂量。基于这些结果，在将其应用于临床常规之前建立了耐受标准和行动水平。
