A Review: Photonic Devices Used for Dosimetry in Medical Radiation

Abstract

Numerous instruments such as ionization chambers, hand-held and pocket dosimeters of various types, film badges, thermoluminescent dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) are used to measure and monitor radiation in medical applications. Of recent, photonic devices have also been adopted. This article evaluates recent research and advancements in the applications of photonic devices in medical radiation detection primarily focusing on four types; photodiodes – including light-emitting diodes (LEDs), phototransistors—including metal oxide semiconductor field effect transistors (MOSFETs), photovoltaic sensors/solar cells, and charge coupled devices/charge metal oxide semiconductors (CCD/CMOS) cameras. A comprehensive analysis of the operating principles and recent technologies of these devices is performed. Further, critical evaluation and comparison of their benefits and limitations as dosimeters is done based on the available studies. Common factors barring photonic devices from being used as radiation detectors are also discussed; with suggestions on possible solutions to overcome these barriers. Finally, the potentials of these devices and the challenges of realizing their applications as quintessential dosimeters are highlighted for future research and improvements.

Use of High-Field Electron Injection into Dielectrics to Enhance Functional Capabilities of Radiation MOS Sensors

“…We have monitored value of positive charge, accumulated in the gate dielectric after irradiation, by measuring an increment of voltage across the MOS sensor before and after influence of radiation (Figure 3, Sections 1 and 3 or 4 and 6, accordingly). Hence, by measuring ∆V I (+) or shift of threshold voltage of RADFET sensor, we can calculate integral absorbed dose of ionization radiation [1][2][3][4][5]9]. An advantage of the RADFET sensors in comparison with the MOS capacitors is the simpler technique to monitor the change of charge state of the dielectric when it is under radiation treatment.…”

“…An advantage of the RADFET sensors in comparison with the MOS capacitors is the simpler technique to monitor the change of charge state of the dielectric when it is under radiation treatment. This technique is based on measuring of threshold voltage shift of the FET [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. For the MOS capacitors based sensors, we monitor an accumulation of positive charge in the gate dielectric by using whether C-V measurements or voltage shift across the structure when it is under high-field injection of electrons under the mode of constant current flowing (Equation (4)).…”

“…As Figure 4 demonstrates, widening the distance between source and MOS sensor gate results in lowering of ionization current initiated in the dielectric film. We calculated a value of the ionization current by analyzing time dependence of voltage across the structure using Equations (1)(2)(3)(4)(5). In Figure 4 (Section 3), all the current flowing through the MOS structure is capacitive and rising rate of voltage, in accordance with Equation (5), is totally defined by the value of constant current flowing through the sample.…”

“…Nowadays in the field of medicine, space devices, nuclear power, etc., metal-oxide-semiconductor (MOS) sensors of a radiation are widely utilized [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Most frequently, these sensors are based on p-channel MOSFET (radiation sensitive field effect transistors (RADFET) sensors).…”

“…Most frequently, these sensors are based on p-channel MOSFET (radiation sensitive field effect transistors (RADFET) sensors). In a gate dielectric of the sensors, when these are under an ionization radiation, a positive charge is accumulated and rising of density of surface states takes place [1][2][3][4][5]9]. As a result, one observes a change of threshold voltage of RADFET sensors.…”