NCTeam, Strahlenklinik, Universitätsklinikum Essen, Essen, Germany.
Servei de Física i Protecció Radiològica, Hospital Universitari Vall d'Hebron, Institut de Recerca (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.
Med Phys. 2018 Apr;45(4):1699-1707. doi: 10.1002/mp.12777. Epub 2018 Feb 23.
Brachytherapy with Ru/ Rh plaques offers good outcomes for small-to-medium choroidal melanomas and retinoblastomas. The dose measurement of the plaques is challenging, due to the small range of the emitted beta particles and steep dose gradients involved. The scarce publications on film dosimetry of Ru/ Rh plaques used solid phantoms. This work aims to develop a practical method for measuring the absorbed dose distribution in water produced by Ru/ Rh plaques using EBT3 radiochromic film.
Experimental setups were developed to determine the dose distribution at a plane perpendicular to the symmetry axis of the plaque and at a plane containing the symmetry axis. One CCA and two CCX plaques were studied. The dose maps were obtained with the FilmQA Pro 2015 software, using the triple-channel dosimetry method. The measured dose distributions were compared to published Monte Carlo simulation and experimental data.
A good agreement was found between measurements and simulations, improving upon published data. Measured reference dose rates agreed within the experimental uncertainty with data obtained by the manufacturer using a scintillation detector, with typical differences below 5%. The attained experimental uncertainty was 4.1% (k = 1) for the perpendicular setup, and 7.9% (k = 1) for the parallel setup. These values are similar or smaller than those obtained by the manufacturer and other authors, without the need of solid phantoms that are not available to most users.
The proposed method may be useful to the users to perform quality assurance preclinical tests of Ru/ Rh plaques.
Ru/Rh 贴敷器近距离治疗中小尺寸脉络膜黑色素瘤和视网膜母细胞瘤的效果良好。由于发射β粒子的能量范围小，涉及陡峭的剂量梯度，因此贴敷器的剂量测量具有挑战性。关于 Ru/Rh 贴敷器的胶片剂量测量的文献很少，这些文献都使用了固体体模。本研究旨在开发一种实用的方法，使用 EBT3 光致变色胶片测量 Ru/Rh 贴敷器在水中产生的吸收剂量分布。
开发了实验装置，以确定垂直于贴敷器对称轴的平面和包含对称轴的平面上的剂量分布。研究了一个 CCA 和两个 CCX 贴敷器。使用 FilmQA Pro 2015 软件，通过三通道剂量测定法获得剂量图。将测量的剂量分布与发表的蒙特卡罗模拟和实验数据进行比较。
测量结果与模拟结果吻合良好，优于已发表的数据。在实验不确定度范围内，使用闪烁探测器由制造商获得的参考剂量率与使用三通道剂量测定法测量的参考剂量率一致，典型差异低于 5%。垂直设置的实验不确定度为 4.1%（k=1），平行设置的实验不确定度为 7.9%（k=1）。这些值与制造商和其他作者获得的值相似或更小，而无需使用大多数用户无法获得的固体体模。
所提出的方法可用于 Ru/Rh 贴敷器的临床前质量保证测试。
