Elter A, Rippke C, Johnen W, Mann P, Hellwich E, Schwahofer A, Dorsch S, Buchele C, Klüter S, Karger C P
Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany.
Phys Med Biol. 2021 Dec 16;66(24). doi: 10.1088/1361-6560/ac3e0c.
In MR-guided radiotherapy (MRgRT) for prostate cancer treatments inter-fractional anatomy changes such as bladder and rectum fillings may be corrected by an online adaption of the treatment plan. To clinically implement such complex treatment procedures, however, specific end-to-end tests are required that are able to validate the overall accuracy of all treatment steps from pre-treatment imaging to dose delivery.In this study, an end-to-end test of a fractionated and online adapted MRgRT prostate irradiation was performed using the so-called ADAM-PETer phantom. The phantom was adapted to perform 3D polymer gel (PG) dosimetry in the prostate and rectum. Furthermore, thermoluminescence detectors (TLDs) were placed at the center and on the surface of the prostate for additional dose measurements as well as for an external dose renormalization of the PG. For the end-to-end test, a total of five online adapted irradiations were applied in sequence with different bladder and rectum fillings, respectively.A good agreement of measured and planned dose was found represented by highγ-index passing rates (3%/3mmcriterion) of the PG evaluation of98.9%in the prostate and93.7%in the rectum. TLDs used for PG renormalization at the center of the prostate showed a deviation of-2.3%.The presented end-to-end test, which allows for 3D dose verification in the prostate and rectum, demonstrates the feasibility and accuracy of fractionated and online-adapted prostate irradiations in presence of inter-fractional anatomy changes. Such tests are of high clinical importance for the commissioning of new image-guided treatment procedures such as online adaptive MRgRT.
在用于前列腺癌治疗的磁共振引导放疗（MRgRT）中，分次治疗期间的解剖结构变化，如膀胱和直肠充盈情况，可通过在线调整治疗计划来校正。然而，要在临床上实施如此复杂的治疗程序，需要进行特定的端到端测试，以验证从治疗前成像到剂量输送的所有治疗步骤的整体准确性。在本研究中，使用所谓的ADAM-PETer体模对分次及在线调整的MRgRT前列腺照射进行了端到端测试。该体模经过改装，可在前列腺和直肠中进行三维聚合物凝胶（PG）剂量测定。此外，热释光探测器（TLD）放置在前列腺的中心和表面，用于额外的剂量测量以及PG的外部剂量归一化。对于端到端测试，分别针对不同的膀胱和直肠充盈情况，依次进行了总共五次在线调整照射。PG评估的高γ指数通过率（3%/3mm标准）表明测量剂量与计划剂量吻合良好，前列腺中的通过率为98.9%，直肠中的通过率为93.7%。用于前列腺中心PG归一化的TLD显示偏差为-2.3%。所展示的端到端测试能够在前列腺和直肠中进行三维剂量验证，证明了在存在分次间解剖结构变化的情况下，分次及在线调整的前列腺照射的可行性和准确性。此类测试对于新的图像引导治疗程序（如在线自适应MRgRT）的调试具有高度的临床重要性。
