A very-low-cost dosimeter based on the off-the-shelf CD4007 MOSFET array for in vivo radiotherapy applications

Abstract Purpose This paper presents a low-cost MOSFET dosimeter suitable for in vivo radiotherapy applications. We analyze different methods to extract the threshold voltage and how this extraction is affected by the dose dependence of slope factor and carrier mobility. Also, we discuss fundamental aspects of the basic building blocks of a MOSFET dosimeter, namely, the radiation sensor, the reader circuit and temperature desensitization. Methods Experiments with ionizing radiation (6 MV X-ray beams) were carried out at the Centro de Pesquisas Oncologicas (CEPON) using linear accelerators to test the MOSFET dosimeter. Results The main performance parameters of the dosimeter prototype are radiation sensitivity about 100 mV/Gy (sensor's sensitivity is around 6.7 mV/Gy), thermal dependence of 0.5 cGy/°C, reproducibility is about 2.6%, and radiation beam attenuation of 0.14%. Conclusions The MOSFET dosimeter described in this article, which combines a simple and accurate readout procedure with a small size, low-cost, cable/battery-free sensor and very little attenuation of the radiation beam is a very appealing option for in vivo dosimetry.