Radiotherapy dosimetry based on perflourinated polymer opitcal fibres

The complexity of treating cancerous cells in patients using radiotherapy, requires precision in terms of the total dose received by the patient. The use of scintillating materials at the tip of the fibre for real time dosimetry dominate the current development of optical fibre dosimeters, however, they are limited to single point sensing. The changes in the structural and chemical properties in optical fibres on exposure to radiation gives rise to attenuation of the optical signal i.e. Radiation Induced Attenuation (RIA). This has proven to be a useful feature in monitoring radiation from gamma sources (Cobalt60 sources) using PMMA (polymethyl methacrylate) fibres and perfluorinated graded-index polymer optical fibre (Cytop). The aim of this study is to investigate the performance of Cytop fibre in monitoring low doses of X-ray radiation (up to 10 Gy), produced by clinical linear accelerators (linac) for real time monitoring. The radiation induced attenuation (RIA) were measured across a 1 m length of Cytop fibre when the fibre was exposed to different radiation energy (6 MV, 10 MV) from the linac. The result of this study shows that the sensor has a good sensitivity of 0.0693 ± 0.004 dB/m/Gy and 0.0711 ± 0.004 dB/m/Gy at the wavelength of 695 nm and 817 nm respectively, for a radiation energy of 6 MV. Preliminary results demonstrate the potential of the Cytop fibre as a dosimeter for radiation treatment. The Cytop fibre sensor also exhibits a higher sensitivity, in the order of 3, when compared to PMMA optical fibres.