基于实验和蒙特卡罗方法的新型 3mm 立体定向放射外科 3MV 射线束用微硅探测器的剂量学研究。

Experimental and Monte Carlo based dosimetric investigation of a novel 3 mm radiosurgery 3 MV beam using the microSilicon detector.

机构信息

University Clinic for Medical Radiation Physics, Medical Campus Pius Hospital, Carl von Ossietzky University, Oldenburg, Germany.

Bonifatius Hospital Lingen, Lingen, Germany.

出版信息

J Appl Clin Med Phys. 2024 Jun;25(6):e14388. doi: 10.1002/acm2.14388. Epub 2024 May 19.

DOI:10.1002/acm2.14388

PMID:38762906

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC11163500/

Abstract

BACKGROUND

The ZAP-X system is a novel gyroscopic radiosurgical system based on a 3 MV linear accelerator and collimator cones with a diameter between 4 and 25 mm. Advances in imaging modalities to detect small and early-stage pathologies allow for an early and less invasive treatment, where a smaller collimator matching the anatomical target could provide better sparing of surrounding healthy tissue.

PURPOSE

A novel 3 mm collimator cone for the ZAP-X was developed. This study aims to investigate the usability of a commercial diode detector (microSilicon) for the dosimetric characterization of this small collimator cone; and to investigate the underlying small field perturbation effects.

METHODS

Profile measurements in five depths as well as PDD and output ratio measurements were performed with a microSilicon detector and radiochromic EBT3 films. In addition, comprehensive Monte Carlo simulations were performed to validate the measurement observations and to quantify the perturbation effects of the microSilicon detector in these extremely small field conditions.

RESULTS

It is shown that the microSilicon detector enables an accurate dosimetric characterization of the 3 mm beam. The profile parameters, such as the FWHM and 20%-80% penumbra width, agree within 0.1 to 0.2 mm between film and detector measurements. The output ratios agree within the measurement uncertainty between microSilicon detector and films, whereas the comparisons of the PDD results show good agreement with the Monte Carlo simulations. The analysis of the perturbation factors of the microSilicon detector reveals a small field correction factor of approximately 3% for the 3 mm circular beam and a correction factor smaller than 1.5% for field diameters above 3 mm.

CONCLUSIONS

It could be shown that the microSilicon detector is well-suitable for the characterization of the new 3 mm circular beam of the ZAP-X system.

摘要

背景

ZAP-X 系统是一种基于 3MV 线性加速器和直径在 4 至 25 毫米之间的准直器圆锥体的新型陀螺式放射外科系统。成像方式的进步可以检测到早期的小病变，从而实现早期、微创治疗，较小的准直器与解剖靶区匹配可以更好地保护周围健康组织。

目的

开发了一种用于 ZAP-X 的新型 3 毫米准直器圆锥体。本研究旨在研究商用二极管探测器（microSilicon）用于该小准直器圆锥体剂量学特性的可用性；并研究潜在的小射野扰动效应。

方法

使用 microSilicon 探测器和放射性 EBT3 胶片进行了五个深度的轮廓测量以及 PDD 和输出比测量。此外，还进行了全面的蒙特卡罗模拟，以验证测量结果并量化微硅探测器在这些极小射野条件下的扰动效应。

结果

结果表明，microSilicon 探测器能够实现 3 毫米光束的精确剂量学特性。轮廓参数，如 FWHM 和 20%-80%半影宽度，在胶片和探测器测量之间的差异在 0.1 至 0.2 毫米之间。输出比在 microSilicon 探测器和胶片之间的测量不确定度内一致，而 PDD 结果的比较与蒙特卡罗模拟吻合良好。微硅探测器的扰动因子分析表明，对于 3 毫米圆形射束，小射野校正因子约为 3%，对于直径大于 3 毫米的射野，校正因子小于 1.5%。