Fatha Mohammad Abdul, Raj Sathiya, Pawar Y S, Saminathan Sathiyan
RadiationPhysics, Kidwai Memorial Institute of Oncology, Bangalore, India.
RadiationOncology, Kidwai Memorial Institute of Oncology, Bangalore, India.
Radiol Phys Technol. 2025 Sep;18(3):726-733. doi: 10.1007/s12194-025-00925-y. Epub 2025 Jun 12.
The International Atomic Energy Agency (IAEA) released a protocol named Technical Report Series (TRS-398) to measure the absorbed dose in water for external radiotherapy beams. It provides a unified approach for using calibrated ionization chambers that are traceable to standard laboratories in determining the absorbed dose to water. The objective of the study was to compare the reference dosimetry [dose at 10 cm depth ( )] between TRS-398 and its revised version. Reference dosimetry was performed for flattened photon beam with nominal energies of 6, 10, and 15 MV as well as flattening filter free (FFF) beam of energies 6 FFF and 10 FFF based on the guidelines of both TRS-398 and its revised version using two different ionization chambers of varying sensitive volumes such as 0.65 cm (FC65-G) & 0.13 cm (CC13) IBA ionization chambers with calibration coefficient traceable to absorbed dose to water (D) standards. The comparison of absorbed dose at 10 cm ( ) depth using both protocols with FC65-G chamber shows a difference ranging from 0.40 to 0.63% in FF beams and 0.03 to 0.05% in FFF beams. For CC13 chamber, the difference ranged from -0.60 to -0.77% in FF beams and -0.40 to -0.50% in FFF beams. The differences in absorbed dose between TRS-398 old and revised protocols were evaluated and a variation of up to 0.63% in was observed for FC65-G and -0.77% in was observed for CC13 chamber. The use of old value affects the reference dose measurements, which overestimates the results by an average of 0.5%. The use of cross-calibrated chamber following the old protocol in determining the underestimates the results by maximum of -0.77% in FF beams and -0.5% in FFF beams.
国际原子能机构（IAEA）发布了一份名为《技术报告系列》（TRS - 398）的规程，用于测量外照射放疗束在水中的吸收剂量。它为使用可溯源至标准实验室的校准电离室来确定水的吸收剂量提供了统一方法。本研究的目的是比较TRS - 398及其修订版之间的参考剂量测定法（10厘米深度处的剂量）。根据TRS - 398及其修订版的指南，使用两个不同灵敏体积的电离室，如0.65立方厘米（FC65 - G）和0.13立方厘米（CC13）的IBA电离室，其校准系数可溯源至水的吸收剂量（D）标准，对标称能量为6、10和15兆电子伏特的扁平光子束以及能量为6 FFF和10 FFF的无均整滤过（FFF）束进行参考剂量测定。使用FC65 - G电离室，两种规程在10厘米深度处吸收剂量的比较显示，在FF束中差异范围为0.40%至0.63%，在FFF束中差异范围为0.03%至0.05%。对于CC13电离室，在FF束中差异范围为 - 0.60%至 - 0.77%，在FFF束中差异范围为 - 0.40%至 - 0.50%。评估了TRS - 398旧版和修订版规程之间吸收剂量的差异，对于FC65 - G电离室，在10厘米深度处观察到高达0.63%的变化，对于CC13电离室观察到 - 0.77%的变化。使用旧的10厘米深度处剂量值会影响参考剂量测量，平均高估结果0.5%。按照旧规程使用交叉校准电离室在确定10厘米深度处剂量时，在FF束中最多低估结果 - 0.77%，在FFF束中最多低估 - 0.5%。
