Study of the response of plastic scintillation detectors in small‐field 6 MV photon beams by Monte Carlo simulations

Abstract

Purpose:To investigate the response of plastic scintillation detectors ͑PSDs͒ in a 6 MV photon beam of various field sizes using Monte Carlo simulations. Methods: Three PSDs were simulated: A BC-400 and a BCF-12, each attached to a plastic-core optical fiber, and a BC-400 attached to an air-core optical fiber. PSD response was calculated as the detector dose per unit water dose for field sizes ranging from 10ϫ 10 down to 0.5ϫ 0.5 cm 2 for both perpendicular and parallel orientations of the detectors to an incident beam. Similar calculations were performed for a CC01 compact chamber. The off-axis dose profiles were calculated in the 0.5ϫ 0.5 cm 2 photon beam and were compared to the dose profile calculated for the CC01 chamber and that calculated in water without any detector. The angular dependence of the PSDs' responses in a small photon beam was studied. Results: In the perpendicular orientation, the response of the BCF-12 PSD varied by only 0.5% as the field size decreased from 10ϫ 10 to 0.5ϫ 0.5 cm 2 , while the response of BC-400 PSD attached to a plastic-core fiber varied by more than 3% at the smallest field size because of its longer sensitive region. In the parallel orientation, the response of both PSDs attached to a plastic-core fiber varied by less than 0.4% for the same range of field sizes. For the PSD attached to an air-core fiber, the response varied, at most, by 2% for both orientations. Conclusions:The responses of all the PSDs investigated in this work can have a variation of only 1%-2% irrespective of field size and orientation of the detector if the length of the sensitive region is not more than 2 mm long and the optical fiber stems are prevented from pointing directly to the incident source.

Dosimetric performance and array assessment of plastic scintillation detectors for stereotactic radiosurgery quality assurance

“…If only large fields are considered, the PSD can be compared to the SD, the IC and Gafchromics, all four detectors are within a 1.3% margin for the 35 mm cone. Finally, the response of PSD has been evaluated with Monte Carlo by Wang and Beddar 24 and has shown variations within 0.4% for field sizes ranging from 0.5 Â 0.5 cm 2 to 10 Â 10 cm 2 .…”

Refinement of MLC modeling improves commercial QA dosimetry system for SRS and SBRT patient‐specific QA

“…In contrast to diode detectors, PSD are energy independent and hence no daisy chain method was necessary. However, PSD are susceptible to over responding when exposed to radiation due to Cherenkov light generated in the optic fiber . To overcome this issue, a SuperMAX electrometer (Standard Imaging) was used for online Cherenkov radiation correction.…”

Technical Note: Evaluation of plastic scintillator detector for small field stereotactic patient‐specific quality assurance

“…There are many publications on the dosimetric characteristics of the PSD . Among which, several studies demonstrated that the PSD achieved similar dose response to other widely accepted benchmarks, such as Monte Carlo, Gafchromic films and diamond detectors .…”