Optical Fiber Dosimeters for Brachytherapy

Fiber-optic scintillation-based dosimeters are compact and radiation-resistant devices that are used for real-time monitoring of the dose rate at specific locations in the vicinity of tumorous tissue during brachytherapy radiation treatment of prostate or cervical cancer. These dosimeters are based on scintillators, which are materials that emit light when exposed to ionizing radiation. The scintillation light is collected by an optical fiber, which transmits the optical signal to a photodetector and dedicated electronic circuitry for further signal processing. 

The Brussels Photonics Team B-PHOT of the VUB has developed such dosimeters, consisting of scintillating sensor tips attached to 0.5mm diameter polymer optical fiber. The sensor tips consist of inorganic scintillators, i.e. Gd2O2S:Tb for low dose rate brachytherapy, and Y2O3:Eu+4YVO4:Eu for high dose rate brachytherapy, dispersed in a polymer host. The shape and size of the tips are optimized using non-sequential ray tracing simulations towards maximizing the collection and coupling of the scintillation signal into the POF. They are then manufactured by means of a custom moulding process implemented on a commercial hot embossing machine, paving the way towards mass production.

• Very small and minimally intrusive, allowing for localized monitoring of the dose rate at specific locations in the vicinity of tumorous tissue. 
• This allows to accurately determine the radiation dose delivered to critical organs near the treatment zone, such as the bladder, the urethra and the rectal wall during radiation treatment.
• Custom fabrication methods allow mass manufacturing of the sensor tips in a repeatable fashion. 
• The sensor tips are compatible with automated assembly on a plastic optical fiber.
• Dosimetry experiments in water phantoms have shown that the sensors feature good consistency in the magnitude of the average photon count rate. 
• Whilst individual calibration remains necessary, the dosimeters therefore show great potential for in-vivo dosimetry brachytherapy.