Dosimetric Characteristics of a PIN Diode for Radiotherapy Application

Abstract

The PIN diode developed by Bhabha Atomic Research Centre (BARC) was modified for its use as a dosimeter in radiation therapy. For this purpose the diode was mounted on a printed circuit board (PCB) and provided with necessary connections so that its response against irradiation can be recorded by a standard radiotherapy electrometer. The dosimetric characteristics of the diode were studied in Co-60 gamma rays as well as high energy X-rays. The measured sensitivity of this PIN diode is 4 nC/cGy which is about ten times higher than some commercial diode dosimeters. The leakage current from the diode is 0.04 nA. The response of the PIN diode is linear in the range of 20-1000 cGy which covers the full range of radiation dose encountered in radiotherapy treatments. The non-linearity of the diode response is 3.5% at 20 cGy and it is less than 1.5% at higher dose values. Its repeatability is within 0.5%.The angular response variation is about 5.6% within 6608 with respect to normal beam incidence. The response of the PIN diode at 6 and 18 MV X-rays varies within 2% with respect to its response at Co-60 gamma rays. The source to surface distance (SSD) dependence of the PIN diode was studied for Co-60 beam. It was found that the response of the diode decreases almost linearly relative to given dose for beams with constant collimator setting but increasing SSD (decreasing dose-rate). Within this study the diode response varied by about 2.5% between the maximum and minimum SSD. The dose-rate dependence of the PIN diode for 6 and 15 MV-rays was studied. The variation in response of diode for both energies in the studied dose range is less than 1%. The field size dependence of the PIN diode response is within 1% with respect to the response of ionisation chamber. These studies indicate that the characteristics of the PIN diode are suitable for use in radiotherapy dosimetry.

Evaluation of dosimetric characteristics of a ternary nanocomposite based on High Density Polyethylene/Bismuth Oxide/Graphene Oxide for gamma-rays

“…9 b, which is evaluated in Table 3 , accordingly. It can be found that the sensitivity of the B 60 sample is more than eight times greater than the PIN diode dosimeter at the therapy level which was studied by Kumar et al 51 . Also, the sensitivity of the B 60 nanocomposite dosimeter in this research is significantly higher than the conventional dosimeters in radiotherapy, whose sensitive volume is often filled with free-air.…”

Evaluation of monoxide film-based dosimeters for surface dose detection in electron therapy

“…To evaluate the dose-rate dependence, doses of 50, 100, 200, and 400 MU were irradiated for the dose-rate settings of 100, 200, and 400 MU/min. The measured signal was normalized based on a dose rate of 200 MU, and the RSD (n = 3) for the value measured at 100 MU was calculated following the method reported in the diode study, and evaluated based on the reported diode error of 1.1% [ 18 , 19 ]. At this time, the results of the diode were as in [ 18 ], which was conducted under similar evaluation conditions to this study.…”

Wearable Dosimeters for Medical and Defence Applications: A State of the Art Review

“…A number of diode dosimeters are commercially available from vendors such as Veridose (Cardinal Health Management Services, USA), Isorad (Sun Nuclear, USA), T60010 (PTW, Germany), and EDP (Scanditronix Wellhofer, Sweden. [ 80 ] Another device called as DIGIDOSE – digital pocket radiation dosimeter has been developed by BARC [ 81 ] for detection of X & Gamma radiation doses. It is based on a commercially available Silicon (Si) rectifier diode operating at a low reverse bias of about 4 V. [ 81 ] A TLD based ring type dosimeter by ISRN Dosimetry Lab [ 82 ] is also available as a commercial product which can be worn on the finger; in this case the film (lithium fluoride) produces luminescence based on its exposure to ionising radiation.…”

“…A number of diode dosimeters are commercially available from vendors such as Veridose (Cardinal Health Management Services, USA), Isorad (Sun Nuclear, USA), T60010 (PTW, Germany), and EDP (Scanditronix Wellhofer, Sweden. [80] Another device called as DIGIDOSE -digital pocket radiation dosimeter The case houses both the MND and communications dongle and allows access to the USB Type-C port on communications dongle, b) WDD sensitivity in cps/nv as a function of source distance. The flux at the location of the detectors was determined by MCNP6 simulations by calculating the average flux in the phantom volume at each source location.…”