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.
Measurements using an Optical Fiber OFS including an inorganic scintillator placed on the surface of a phantom show that the particle energy distribution inside the phantom remains unchanged. The backscattered intensity measured using an Optical Fiber Sensor (OFS) exhibits a linear relationship with the total radiation dose delivered to the phantom, and this relationship shows that the OFS can be used for indirect dose measurement when located on the surface of the phantom i.e. that arising from the energetic backscattered electrons and photons. Such a device can therefore be used as a clinical in-vivo dosimeter, being located on the patient’s body surface. In addition, the measurement results for the same OFS located inside and outside the radiation field of a compound water based phantom are analyzed. The differences in measurement of the fluorescence signal in response to various tissue materials representing bone or tumor tissue in the irradiation field are strongly related to the material's ability to block the scattered rays from the water phantom, as well as the scattered X-rays generated by the material located within the phantom.
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