Over response correction of optical fiber sensor in radiation measurement

In radiation measurement, optical fiber sensors (OFS) have many advantages compared to commercial dosimeters, including high spatial resolution. Due to the OFS measurement principle (fluorescence), the recorded measurement results differ from the standard dose value, such as that obtained using an ionization chamber. In this study, a physical correction function is established to considerably reduce the difference. This function quantifies the over-response of OFS to low-energy scattered photons and low-energy electrons. The specific expression of the function is derived from experimental measurement results obtained using the OFS and a commercial standard dosimeter when subject to two different radiation field sizes irradiated using a clinical linac. Following the application of the correction of the function, the measurement difference between the OFS and the standard dosimeter is greatly reduced for a range of radiation fields, in which case the maximum difference decreased from 42.2% to 1.5%. The dose correction method is based on existing quality assurance (QA) protocols used in radiotherapy and is simple and convenient to apply. This research has further promoted the application of OFSs in radiation dose measurement, including radiotherapy QA and in-patient use.