Medical Physics Department, National Physical Laboratory, Teddington, United Kingdom; NIHR University College London Hospitals Biomedical Research Centre, UCL Cancer Institute, University College London, London, United Kingdom.
Medical Physics Department, National Physical Laboratory, Teddington, United Kingdom.
Int J Radiat Oncol Biol Phys. 2020 Jul 1;107(3):587-596. doi: 10.1016/j.ijrobp.2020.03.001. Epub 2020 Mar 10.
Lack of standardization and inaccurate dosimetry assessment in preclinical research is hampering translational opportunities for new radiation therapy interventions. The aim of this work was to develop and implement an end-to-end dosimetry test for small animal radiation research platforms to monitor and help improve accuracy of dose delivery and standardization across institutions.
The test is based on a bespoke zoomorphic heterogeneous mouse and WT1 Petri dish phantoms with alanine as a reference detector. Alanine measurements within the mouse phantom were validated with Monte Carlo simulations at 0.5 mm Cu x-ray reference beam. Energy dependence of alanine in medium x-ray beam qualities was taken into consideration. For the end-to-end test, treatment plans considering tissue heterogeneities were created in Muriplan treatment planning systems (TPS) and delivered to the phantoms at 5 institutions using Xstrahl's small animal irradiation platforms. Mean calculated dose to the pellets were compared with alanine measured dose.
Monte Carlo simulations and in phantom alanine measurements in NPL's reference beam were in excellent agreement, validating the experimental approach. At 1 institute, initial measurements showed a larger than 12% difference between calculated and measured dose caused by incorrect input data. The physics data used by the calculation engine were corrected, and the TPS was recommissioned. Subsequent end-to-end test measurements showed differences <5%. With an anterior field, 4 of the participating institutes delivered dose within 5% to both phantoms.
An end-to-end dosimetry test was developed and implemented for dose evaluation in preclinical irradiation with small animal irradiation research platforms. The test was capable of detecting treatment planning commissioning errors and highlighted critical elements in dose calculation. Absolute dosimetry with alanine in relevant preclinical irradiation conditions showed reasonable levels of accuracy compared with TPS calculations. This work provides an independent and traceable dosimetric validation in preclinical research involving small animal irradiation.
临床前研究中缺乏标准化和剂量评估不准确，阻碍了新的放射治疗干预措施的转化机会。本研究旨在开发和实施一种用于小动物放射研究平台的端到端剂量测试，以监测和帮助提高跨机构的剂量传递准确性和标准化。
该测试基于定制的类动物异质小鼠和 WT1 培养皿体模，以丙氨酸作为参考探测器。在 0.5mmCu X 射线参考射束下，通过蒙特卡罗模拟验证了小鼠体模内丙氨酸的测量值。考虑了中质 X 射线束质的丙氨酸能量依赖性。对于端到端测试，在 Muriplan 治疗计划系统（TPS）中创建了考虑组织不均匀性的治疗计划，并使用 Xstrahl 的小动物照射平台在 5 个机构将其输送到体模。比较了计算得到的到小球的平均剂量与丙氨酸测量的剂量。
蒙特卡罗模拟和 NPL 参考射束中的体模内丙氨酸测量值非常吻合，验证了实验方法。在一个机构中，初始测量值显示计算剂量与测量剂量之间存在超过 12%的差异，原因是输入数据不正确。校正了计算引擎使用的物理数据，并重新调整了 TPS。随后的端到端测试测量值差异<5%。对于前野，4 个参与机构的两个体模的剂量均在 5%以内。
为了评估小动物照射研究平台在临床前照射中的剂量，开发并实施了一种端到端剂量测试。该测试能够检测治疗计划的调试错误，并突出剂量计算中的关键要素。在相关临床前照射条件下，使用丙氨酸进行绝对剂量测量与 TPS 计算相比具有合理的准确性。这项工作为涉及小动物照射的临床前研究提供了独立且可追踪的剂量验证。
