蒙特卡罗法计算光子束中两个圆柱形电离室的射束质校正因子。

Monte Carlo calculated beam quality correction factors for two cylindrical ionization chambers in photon beams.

机构信息

Institute of Medical Physics and Radiation Protection, University of Applied Sciences Giessen (THM), Giessen, Germany.

Institute of Medical Physics and Radiation Protection, University of Applied Sciences Giessen (THM), Giessen, Germany; Department of Radiotherapy and Radiation Oncology, University Medical Center Giessen and Marburg, Marburg, Germany; Marburg Ionbeam Therapycenter (MIT), Marburg, Germany.

出版信息

Phys Med. 2022 Feb;94:17-23. doi: 10.1016/j.ejmp.2021.12.012. Epub 2021 Dec 28.

DOI:10.1016/j.ejmp.2021.12.012

PMID:34972070

Abstract

PURPOSE

Although several studies provide data for reference dosimetry, the SNC600c and SNC125c ionization chambers (Sun Nuclear Corporation, Melbourne, FL) are in clinical use worldwide for which no beam quality correction factors k are available. The goal of this study was to calculate beam quality correction factors k for these ionization chambers according to dosimetry protocols TG-51, TRS 398 and DIN 6800-2.

METHODS

Monte Carlo simulations using EGSnrc have been performed to calculate the absorbed dose to water and the dose to air within the active volume of ionization chamber models. Both spectra and simulations of beam transport through linear accelerator head models were used as radiation sources for the Monte Carlo calculations.

RESULTS

k values as a function of the respective beam quality specifier Q were fitted against recommended equations for photon beam dosimetry in the range of 4 MV to 25 MV. The fitting curves through the calculated values showed a root mean square deviation between 0.0010 and 0.0017.

CONCLUSIONS

The investigated ionization chamber models (SNC600c, SNC125c) are not included in above mentioned dosimetry protocols, but are in clinical use worldwide. This study covered this knowledge gap and compared the calculated results with published k values for similar ionization chambers. Agreements with published data were observed in the 95% confidence interval, confirming the use of data for similar ionization chambers, when there are no k values available for a given ionization chamber.

摘要

目的

尽管有几项研究提供了参考剂量学的数据，但 SNC600c 和 SNC125c 电离室（美国佛罗里达州墨尔本 Sun Nuclear 公司）已在全球临床使用，但尚无可用的束质修正因子 k。本研究的目的是根据 TG-51、TRS 398 和 DIN 6800-2 剂量学规程，计算这些电离室的束质修正因子 k。