A compact dosimetric system for MOSFETs based on passive NFC tag and smartphone

- Dosimetric system based on a batteryless NFC tag (passive tag) without connection between the smartphone and the readout circuit.
- The whole system is designed using commercial circuits and devices.
- MOSFET dosimeter in unbiased mode.
- The bipolar buffer is used to reduce the thermal dependence of the source voltage measured at constant current.
- Sensitivity of (4.75 ± 0.15) mV/Gy in agreement with our previous dosimetric system.

In this work we describe and evaluate a dosimetric system based on an NFC (Near Field Communication) tag and a smartphone that uses commercial MOSFETs as radiation sensors. The tag is designed with commercial integrated circuits and the smartphone is the power source of the tag configured as a readout unit, user interface and storage unit. The NFC tag is supplied wirelessly by the smartphone via NFC, using a home-made structure to align the tag coil and smartphone coil in order to achieve a good inductive coupling. In this case, the commercial DMOS transistor ZVP3306 is used as dosimeter in unbiased mode, connected to the tag before and after each irradiation session to perform the sensor reading. An evaluation of the dosimetric system has been carried out irradiating three transistors with photon beam of 6 MV up to 20 Gy. The average sensitivity found is (4.75 ± 0.15) mV/Gy, which is in good agreement with the results found with our previously developed dosimetric system. Therefore, this miniaturised dosimetric system can be considered as a promising and low cost electronic architecture to be used for dosimetry control in radio-therapy treatments.