Room: ePoster Forums
Purpose: The purpose of this project is to evaluate the feasibility of using a novel optical multi-point real-time array dosimeter, using fiber Bragg gratings (FBGs), for clinical radiation dosimetry measurements.
Methods: FBGs are written through the coating of a standard 125 micron diameter polyimide-coated silica fiber (OFS BF06160-02) with the phase-mask technique and a femtosecond laser (Coherent, Astrella). The resulting sensor is made of twenty 4mm-long FBGs, equally distributed over 20 cm. The change in wavelength of each FBGs is recorded at 1 kHz with a commercially available interrogator (si155, Micron Optics) and its sensing analysis software (ENLIGHT). Shifts in wavelength due to irradiation of the FBGs by a 6 MV beam is recorded for dose up to 20 Gy. All irradations were performed on a CLINACiX.
Results: The use of gamma radiation induce a linear shift (0.0605 pm/Gy) in the reflected wavelength of the FBGs, which is independent of the dose rate. A statistical error of 0.003 pm is obtained therefore limiting the detectable dose to 0.5 Gy for this early prototype. Preliminary results show that this shift is permanent, and therefore, exposure could be measured as many times as required post irradiation. A dose profile of 6 MV radiotherapy accelerator is also reproduced with a mean error of 6.3 0.7 % on the central region. Electrons beam response is not characterized yet, but is expected to produce a similar response.
Conclusion: The FBGs dosimeter is shown to allow for real-time dose measurement in 2D and the small size of its detector makes it a versatile tool. It is also important to mention that length of FBGs and spacing can be customized and hence, the spatial resolution and the amount of dose point can be increased significantly. Further optimization of materials will make the dosimeter more sensitive.