Radiotherapy Department, Hospital Metropolitano, Av. Mariana de Jesús, Quito, Ecuador.
Department of Physics, Faculty of Philosophy, Sciences and Letters at Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, Monte Alegre, Ribeirão Preto, 14040-900, São Paulo, Brazil.
Med Phys. 2021 Jun;48(6):3208-3215. doi: 10.1002/mp.14859. Epub 2021 May 6.
Intensity-modulated radiotherapy with simultaneous integrated boost (SIB) presents several attractive advantages to be employed in clinical practice. Its secure application demands a rigorous quality assurance (QA) procedure, ideal for three-dimensional (3D) dose distribution measurements. Thus, a gel dosimetry methodology to evaluate the dose delivery of SIB treatments is presented and compared to conventional gamma evaluation.
MAGIC-f gel dosimeter with magnetic resonance images for dose reading were used following its standard procedures. Four SIB QA plans created in gel dosimeter phantoms were used. The gel measured and treatment planning system (TPS) calculated doses were compared using 3D gamma analyses (3%/3mm/15% threshold). Two structures were artificially on the TPS dose distribution expected on the phantom by converting the 1.7 and 2.0 Gy isodose levels into structures to represent the treatment. The gel and TPS dose-volume histogram (DVH) were compared based on five dose points: D95%, D90%, D50%, D10%, and D5%.
Approvals of 93%, 96%, 98%, and 92% were achieved in the 3D gamma analyses for the plans QA 1, 2, 3, and 4. In the DVH analyses, QA plan 1 measured and expected curves showed a good agreement. QA plan 2 showed deviations in the highest doses for both structures with a maximum deviation (Δ ) of 8.0%. QA plans 3 and 4 showed the highest dose variation between the gel and TPS in the smaller doses of the DVH (Δ of 7.2% and -8.9%, respectively). For QA plan 4, the curves of the 1.7 Gy structure presented a good agreement, but deviations in the smaller dose region of the DVH occurred for the 2 Gy structure (Δ of 7.7%).
A methodology for 3D dose evaluation of complex SIB treatments was proposed. It provided an important overview of the dose distributions. Their results significantly complemented the usual gamma analysis results.
调强放疗同步整合推量（SIB）具有许多吸引人的优势，适合在临床实践中应用。为了安全应用，需要进行严格的质量保证（QA）程序，非常适合用于三维（3D）剂量分布测量。因此，本文提出了一种用于评估 SIB 治疗剂量分布的凝胶剂量学方法，并将其与传统的伽马评估进行了比较。
使用 MAGIC-f 凝胶剂量计及其磁共振成像进行剂量读取，遵循其标准程序。在凝胶体模中创建了四个 SIB QA 计划。通过三维伽马分析（3%/3mm/15%阈值）比较凝胶测量值和治疗计划系统（TPS）计算值。通过将 1.7 和 2.0 Gy 等剂量线转换为结构来模拟在体模上预期的 TPS 剂量分布，在 TPS 剂量分布上人为地创建了两个结构。根据五个剂量点（D95%、D90%、D50%、D10%和 D5%）比较了凝胶和 TPS 的剂量-体积直方图（DVH）。
QA 计划 1、2、3 和 4 的 3D 伽马分析通过率分别达到了 93%、96%、98%和 92%。在 DVH 分析中，QA 计划 1 的测量曲线和预期曲线吻合良好。QA 计划 2 显示两个结构的最高剂量都存在偏差，最大偏差（Δ）为 8.0%。QA 计划 3 和 4 在 DVH 的较小剂量下显示出凝胶和 TPS 之间的最高剂量变化（分别为 7.2%和-8.9%的Δ）。对于 QA 计划 4，1.7 Gy 结构的曲线吻合良好，但在 DVH 的较小剂量区域出现了 2 Gy 结构的偏差（Δ为 7.7%）。
本文提出了一种用于复杂 SIB 治疗 3D 剂量评估的方法。它提供了剂量分布的重要概述。其结果显著补充了常规伽马分析结果。
