A compact and low cost dosimetry system based on MOSFET for in vivo radiotherapy

A compact and low-cost dosimetry system based on MOSFET for in vivo radiotherapy has been developed and characterized. This electronic system consists of a wireless sensor module containing a general-purpose MOSFET and a microcontrolled reader unit. Various methods, developed in previous works, to extend the linear range and reduce noise and thermal drift have been implemented and tested in the present system. A complete dose response characterization of the system has been carried out, including thermal drift, fading effect, linear range, sensitivity, and angular dependence for a 60Co source and for 6 MV and 18 MV photon beams provided by a linear accelerator. As a result, a procedure to use the system has been built, including the recalibration conditions to enhance the dosimeter life. The system provides suitable values for monitoring in vivo radiotherapy treatments in a reliable way. Although the present system has specifications that are comparable to those of some available commercial dosimetry systems, also based on MOSFET, the sensors here considered have a larger range of use.