Angular dependence of the nanoDot OSL dosimeter

Abstract

Purpose: Optically stimulated luminescent detectors (OSLDs) are quickly gaining popularity as passive dosimeters, with applications in medicine for linac output calibration verification, brachytherapy source verification, treatment plan quality assurance, and clinical dose measurements. With such wide applications, these dosimeters must be characterized for numerous factors affecting their response. The most abundant commercial OSLD is the InLight/OSL system from Landauer, Inc. The purpose of this study was to examine the angular dependence of the nanoDot dosimeter, which is part of the InLight system. Methods: Relative dosimeter response data were taken at several angles in 6 and 18 MV photon beams, as well as a clinical proton beam. These measurements were done within a phantom at a depth beyond the build-up region. To verify the observed angular dependence, additional measurements were conducted as well as Monte Carlo simulations in MCNPX. Results: When irradiated with the incident photon beams parallel to the plane of the dosimeter, the nanoDot response was 4% lower at 6 MV and 3% lower at 18 MV than the response when irradiated with the incident beam normal to the plane of the dosimeter. Monte Carlo simulations at 6 MV showed similar results to the experimental values. Examination of the results in Monte Carlo suggests the cause as partial volume irradiation. In a clinical proton beam, no angular dependence was found. Conclusions: A nontrivial angular response of this OSLD was observed in photon beams. This factor may need to be accounted for when evaluating doses from photon beams incident from a variety of directions.

AAPM TG 191: Clinical use of luminescent dosimeters: TLDs and OSLDs

“…A different linearity correction or calibration curve is therefore needed for proton applications. No angular dependence was noted for OSLD (within 0.5%) in the SOBP of a 200 MeV clinical proton beam …”

“…Current commercial OSLDs are in a disk‐type form, which can introduce angular dependence for geometrical reasons when comparing an edge‐on irradiation to an en‐face irradiation, as electrons may preferentially scatter out of the thin but relatively high‐density disk with an edge‐on irradiation. At megavoltage energies, mixed results have been found between edge‐on and en‐face signal per dose, ranging from 0% to 1%, 2% , and 4%). Detailed Monte Carlo simulations supported that there is a 2% effect at 6 MV .…”

Study of thermoluminescence response of purple to violet amethyst quartz from Balikesir, Turkey

“…While the first readout was performed immediately after the exposure the other readouts were carried out respectively after 1, 6 h and 1, 2, 7 and 26 days. 1990s by Akselrod's group and were later characterized for radiotherapy applications by the same and other investigators [32,21,22]. Al2O3:C OSLDs commercially known as nanoDots (Landauers, Inc., Glenwood, IL) are designed for use in single point radiation assessments and measure minimum occupational radiation dose of 0.1 mGy (www.landauer.com/Industry/Products/ Dosimeters/nanoDot_OSLD.aspx).…”

In Vivo Dosimetry In External Radiotherapy

“…The optical photon fluence is proportional to the dose. [15] The biggest films: radiographic and radiochromic. Radiographic films comprise a transparent substrate and an emulsion layer coated on either side of the substrate.…”