一种用于预测非黑色素瘤皮肤癌（NMSC）患者非密封 Re（铼）树脂剂量分布的新工具。

A novel tool for predicting the dose distribution of non-sealed Re (Rhenium) resin in non-melanoma skin cancers (NMSC) patients.

机构信息

Department of Medical Physics, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy.

Medical Physics Specialization School, Alma Mater Studiorum, University of Bologna, Bologna, Italy.

出版信息

Med Phys. 2023 Jul;50(7):4600-4612. doi: 10.1002/mp.16346. Epub 2023 Mar 30.

DOI:10.1002/mp.16346

PMID:36919341

Abstract

BACKGROUND

High-dose rate brachytherapy using a non-sealed Rhenium resin ( Re) is a recently approved treatment option for non-melanoma skin cancer (NMSC). The treatment goal is to deliver a personalized absorbed dose to the deepest point of neoplastic infiltration corresponding to the minimal target dose. The treatment consists of the application of a Re-based resin over a plastic foil placed on the target skin surface. However, there is no treatment planning tool to assess the Re activity needed for a personalized treatment.

PURPOSE

The paper aims to present a novel Monte Carlo (MC)-based tool for Re-based resin activity and dose calculation, experimentally validated using Gafchromic EBT3 films.

METHODS

MC simulations were carried out using FLUKA modeling density and composition of Re resin. The MC-based look up table (LUT) was incorporated in an ad hoc developed tool. The proposed tool allows the personalized calculation of treatment parameters (i.e., activity to be dispensed, the treatment duration, and dose volume histograms), according to the target dimension. The proposed tool was compared using Bland-Altman analysis to the previous calculation approaches conducted using VARSKIN in a retrospective cohort of 76 patients. The tool was validated in ad hoc experimental set ups using a stack of calibrated Gafchromic EBT3 films covered by a plastic film and exposed using a homogenous activity distribution of Re eluate and a heterogeneous activity distribution of Re resin mimic the patient treatment.

RESULTS

The agreement between the proposed tool and VARSKIN was evaluated on the investigated cohort with median range of target area, target depth, and treatment time equal to 4.8 [1.0-60.1] cm , 1.1 [0.2-3.0] mm, and 70 [21-285] min, with a median range of target dose (Gy) of 23.5 [10-54.9]. The calculated minimal target doses, ranged from 1% to 10% for intermediate target depths (1.2 ± 0.7 mm), while showing significant differences in the estimation of superficial (maximal) target doses. The agreement between MC calculation and measurements at different plans in a stack of Gafchromic EBT3 films was within 10% for both the homogenous and heterogeneous activity distribution of Re. Worst agreements were observed for absorbed doses lower than 0.3 Gy.

CONCLUSIONS

Our results support the implementation of our MC-based tool in the practical routine for calculating the Re resin activity and treatment parameters necessary for obtaining the prescribed minimal target dose.

摘要

背景

高剂量率近距离放射治疗使用非密封的铼（Re）树脂是一种最近批准的非黑色素瘤皮肤癌（NMSC）治疗选择。治疗目标是将个性化的吸收剂量递送到肿瘤浸润的最深处，对应于最小靶剂量。治疗包括将基于 Re 的树脂应用于放置在目标皮肤表面上的塑料箔上。然而，目前还没有治疗计划工具来评估个性化治疗所需的 Re 活性。

目的

本文旨在介绍一种新的基于蒙特卡罗（MC）的 Re 基树脂活性和剂量计算工具，该工具已通过 Gafchromic EBT3 薄膜进行了实验验证。

方法

使用 FLUKA 对 Re 树脂的建模密度和组成进行 MC 模拟。基于 MC 的查找表（LUT）被合并到一个专门开发的工具中。根据目标尺寸，该工具允许个性化计算治疗参数（即要分配的活性、治疗持续时间和剂量体积直方图）。使用 Bland-Altman 分析将该工具与使用 VARSKIN 在 76 名患者的回顾性队列中进行的先前计算方法进行了比较。该工具在专用实验设置中使用校准的 Gafchromic EBT3 薄膜堆叠进行了验证，这些薄膜被塑料薄膜覆盖，并使用 Re 洗脱液的均匀活性分布和 Re 树脂模拟物的不均匀活性分布进行了暴露，以模拟患者的治疗。

结果

在调查队列中评估了新工具与 VARSKIN 的一致性，该队列的靶区面积、靶区深度和治疗时间的中位数范围分别为 4.8 [1.0-60.1] cm、1.1 [0.2-3.0] mm 和 70 [21-285] min，靶区剂量（Gy）中位数范围为 23.5 [10-54.9]。计算的最小靶剂量在中间靶深度（1.2 ± 0.7 mm）时为 1%至 10%，而在估计浅表（最大）靶剂量时存在显著差异。在 Gafchromic EBT3 薄膜叠层的不同计划中，MC 计算与测量结果的一致性在 Re 的均匀和不均匀活性分布下均在 10%以内。对于低于 0.3 Gy 的吸收剂量，观察到最差的一致性。