Dose modeling of superficial brachytherapy applicator geometries using multiple radioisotopes

IF 3.2 2区医学 Q1 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Medical physics Pub Date : 2026-08-20 DOI:10.1002/mp.70641

Jin Jegal, HyeoungWoo Park, Seonghee Kang, Jung-in Kim, Chang Heon Choi, Siyong Kim

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引用次数: 0

Abstract

Background

Superficial brachytherapy enables localized dose delivery for superficial cutaneous lesions, but conventional applicators may be limited in treating extended, irregular, or curved surfaces. Geometric constraints, gaps or overlaps between adjacent applicators, and placement-related uncertainties can reduce dose uniformity, underscoring the need to optimize applicator geometry and deployment strategy.

Purpose

To enhance the efficacy of superficial brachytherapy for irregular or curved cutaneous surfaces, we conducted a dosimetric analysis of beta and photon sources utilizing modular circular and hexagonal applicator geometries. The study emphasizes dose uniformity, the impact of applicator dimensional variations, and the evaluation of alternative deployment strategies.

Methods

Monte Carlo simulations were performed for beta sources (P-32, Sr/Y-90, and Ho-166) and photon sources (I-125, Pd-103, and Yb-169). Applicator models incorporating a zirconia absorber with ceramic and tungsten shielding were constructed, and dose distributions were scored in a water-equivalent medium. Percent depth–dose (PDD) curves were generated for beta sources, and photon sources. Multi-applicator configurations were evaluated on planar and curved surfaces under both simultaneous and sequential delivery. Applicator-size effects were examined using two active radii (5.50 mm and 2.75 mm). Dose uniformity was quantified using the mean dose and the peak-to-valley ratio (PVR) at 1 mm depth.

Results

Beta sources were strongly affected by applicator size and geometry, producing larger variations in near-surface dose uniformity than photon sources. Sequential delivery reduced peak-to-valley modulation for all radioisotopes. Reducing the applicator radius increased the number of deliverable positions on curved surfaces by 60%–83%, increased mean dose by 28%–71%, and decreased PVR by 33%–86%, indicating improved uniformity. Photon sources showed more stable behavior, with lower sensitivity to applicator geometry and size.

Conclusion

Radioisotope type, applicator radius, and delivery mode significantly influence superficial dose distributions. Smaller applicators and sequential deployment improve dose uniformity, particularly for beta sources. These results provide practical guidance for radioisotope selection and modular applicator design in superficial brachytherapy.

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使用多种放射性同位素的浅表近距离照射器几何形状的剂量建模

背景：浅表近距离治疗能够对浅表皮肤病变进行局部剂量递送，但传统的涂药器在治疗扩大的、不规则的或弯曲的表面时可能受到限制。几何限制、相邻施药器之间的间隙或重叠以及与位置相关的不确定性会降低剂量均匀性，因此需要优化施药器的几何形状和部署策略。为了提高浅表近距离照射治疗不规则或弯曲皮肤表面的疗效，我们使用模块化圆形和六边形涂抹器对β和光子源进行了剂量学分析。该研究强调了剂量均匀性、施药器尺寸变化的影响以及对可选部署策略的评估。方法对β源（P-32、Sr/Y-90和Ho-166）和光子源（I-125、Pd-103和Yb-169）进行蒙特卡罗模拟。构建了带有陶瓷和钨屏蔽的氧化锆吸收器的涂抹器模型，并对水当量介质中的剂量分布进行了评分。生成了β源和光子源的百分比深度-剂量（PDD）曲线。在平面和曲面上评估了同时和顺序输送下的多施药器配置。使用两个有效半径（5.50 mm和2.75 mm）检查涂抹器尺寸效应。使用平均剂量和1 mm深度的峰谷比（PVR）来量化剂量均匀性。结果β源受涂药器尺寸和几何形状的影响较大，产生的近表面剂量均匀性变化比光子源大。顺序递送减少了所有放射性同位素的峰谷调制。减小涂药器半径可使曲面上的可交付位置数增加60%-83%，平均剂量增加28%-71%，PVR降低33%-86%，表明均匀性得到改善。光子源表现出更稳定的行为，对涂抹器几何形状和尺寸的敏感性较低。结论放射性同位素类型、施药器半径和给药方式对浅表剂量分布有显著影响。更小的涂抹器和顺序部署提高剂量均匀性，特别是对β源。这些结果为浅表近距离放射治疗中放射性同位素的选择和模块化涂药器的设计提供了实用的指导。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Medical physics 医学-核医学

CiteScore

6.80

自引率

15.80%

发文量

660

审稿时长

1.7 months

期刊介绍： Medical Physics publishes original, high impact physics, imaging science, and engineering research that advances patient diagnosis and therapy through contributions in 1) Basic science developments with high potential for clinical translation 2) Clinical applications of cutting edge engineering and physics innovations 3) Broadly applicable and innovative clinical physics developments Medical Physics is a journal of global scope and reach. By publishing in Medical Physics your research will reach an international, multidisciplinary audience including practicing medical physicists as well as physics- and engineering based translational scientists. We work closely with authors of promising articles to improve their quality.