Investigation of YAG:Ce-based optical fibre sensor for use in ultra-fast external beam radiotherapy dosimetry

Radiation dosimetry plays a crucial role in the quality assurance in radiotherapy. To date, this is limited to monitoring the overall dose over the complete beam time, and so, there is limited information on the actual beam quality. An optical fibre sensor is developed based on cerium-doped yttrium aluminum garnet (YAG:Ce) scintillator. The temporal resolution and the stability of this scintillator-based optical fibre sensor have been experimentally evaluated and directly compared with similarly fabricated sensors based on terbium activated gadolinium oxysulfide and commercial plastic scintillating fibre, BCF-12. The photon yield and repeatability of the YAG-based sensor are compared in the clinical setting with the BCF-12 sensor and both show a high stability. The coefficient of variation of the YAG sensor is 0.7%, which is lower than the BCF sensor with a coefficient of variation of 1.4%.