Klein David, Briere Tina Marie, Kudchadker Rajat, Archambault Louis, Beaulieu Luc, Lee Andrew, Beddar Sam
Department of Radiation Physics, Unit 94, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030.
Radiat Meas. 2012 Oct 1;47(10):921-929. doi: 10.1016/j.radmeas.2012.08.005. Epub 2012 Aug 24.
The goal of this work was to demonstrate the feasibility of using a plastic scintillation detector (PSD) incorporated into a prostate immobilization device to verify doses in vivo delivered during intensity-modulated radiation therapy (IMRT) and volumetric modulated-arc therapy (VMAT) for prostate cancer. The treatment plans for both modalities had been developed for a patient undergoing prostate radiation therapy. First, a study was performed to test the dependence, if any, of PSD accuracy on the number and type of calibration conditions. This study included PSD measurements of each treatment plan being delivered under quality assurance (QA) conditions using a rigid QA phantom. PSD results obtained under these conditions were compared to ionization chamber measurements. After an optimal set of calibration factors had been found, the PSD was combined with a commercial endorectal balloon used for rectal distension and prostate immobilization during external beam radiotherapy. This PSD-enhanced endorectal balloon was placed inside of a deformable anthropomorphic phantom designed to simulate male pelvic anatomy. PSD results obtained under these so-called "simulated treatment conditions" were compared to doses calculated by the treatment planning system (TPS). With the PSD still inserted in the pelvic phantom, each plan was delivered once again after applying a shift of 1 cm anterior to the original isocenter to simulate a treatment setup error.The mean total accumulated dose measured using the PSD differed the TPS-calculated doses by less than 1% for both treatment modalities simulated treatment conditions using the pelvic phantom. When the isocenter was shifted, the PSD results differed from the TPS calculations of mean dose by 1.2% (for IMRT) and 10.1% (for VMAT); in both cases, the doses were within the dose range calculated over the detector volume for these regions of steep dose gradient. Our results suggest that the system could benefit prostate cancer patient treatment by providing accurate in vivo dose reports during treatment and verify in real-time whether treatments are being delivered according to the prescribed plan.
这项工作的目标是证明将塑料闪烁探测器（PSD）集成到前列腺固定装置中，以验证在前列腺癌的调强放射治疗（IMRT）和容积调强弧形治疗（VMAT）期间体内输送剂量的可行性。这两种治疗方式的治疗计划都是为一名接受前列腺放射治疗的患者制定的。首先，进行了一项研究，以测试PSD准确性对校准条件的数量和类型是否存在依赖性（若有）。该研究包括在质量保证（QA）条件下，使用刚性QA体模对每个正在实施的治疗计划进行PSD测量。将在这些条件下获得的PSD结果与电离室测量结果进行比较。找到一组最佳校准因子后，将PSD与用于外照射放疗期间直肠扩张和前列腺固定的商用直肠内气囊相结合。将这种PSD增强型直肠内气囊放置在一个可变形的拟人化体模内，该体模旨在模拟男性盆腔解剖结构。将在这些所谓的“模拟治疗条件”下获得的PSD结果与治疗计划系统（TPS）计算的剂量进行比较。在盆腔体模中仍插入PSD的情况下，在将等中心向前移1 cm模拟治疗设置误差后，每个计划再次实施。对于使用盆腔体模进行模拟治疗条件的两种治疗方式，使用PSD测量的平均总累积剂量与TPS计算的剂量相差不到1%。当等中心移位时，PSD结果与TPS计算的平均剂量相差1.2%（IMRT）和10.1%（VMAT）；在这两种情况下，剂量都在这些陡峭剂量梯度区域探测器体积计算出的剂量范围内。我们的结果表明，该系统可为前列腺癌患者的治疗带来益处，通过在治疗期间提供准确的体内剂量报告，并实时验证治疗是否按照规定计划进行。
