Extrapolated skin dose assessment with optically stimulated luminescent dosimeters

Abstract

A novel method is described for the measurement and calculation of surface and skin dose during megavoltage x-ray therapy utilising an extrapolation technique with optically stimulated Dosimeters. The technique utilises three configurations of an Optically Stimulated Luminescence (OSL) detector which provide different effective depth of measurement points. This allows the user to assess percentage build up dose at effective depths of 0.35, 0.55 and 0.85 mm. Performing an extrapolation technique, percentage dose at other effective depths such as the surface (0 mm) or the Basal Cell layer (70 μm) depth can be estimated. Results have shown that extrapolated percentage dose of Dmax at a depth of 0.048 mm are 17.3% ± 2.3%, 28.2% ± 3.5% and 37.8% ± 3.8% for field sizes of 10 cm × 10 cm, 20 cm × 20 cm and 30 cm × 30 cm respectively. Comparative results measured with the Attix chamber which has an estimated effective depth of 0.048 mm were 16.5%, 28% and 36.8% respectively, thus showing close agreement (within 1%) with the extrapolation technique. The OSL extrapolation technique will allow users of OSL detectors to accurately assess surface and skin dose using this technique.

High-resolution entry and exit surface dosimetry in a 1.5 T MR-linac

“…However, it is deemed more appropriate to consider the OSLD data acquired experimentally at the shallowest depth of 0.16 mm due to the potential uncertainties associated with extrapolating from only two data points. Previous investigations that utilized OSLDs and TLDs for the determination of skin dose through extrapolation employed a minimum of three different TLD thicknesses [ 49 , 50 ] and OSLD configurations [ 51 ]. These studies also address the limitations of utilizing a linear fit in the build-up region for extrapolated predictions of skin dose [ 50 , 51 ].…”

“…Previous investigations that utilized OSLDs and TLDs for the determination of skin dose through extrapolation employed a minimum of three different TLD thicknesses [ 49 , 50 ] and OSLD configurations [ 51 ]. These studies also address the limitations of utilizing a linear fit in the build-up region for extrapolated predictions of skin dose [ 50 , 51 ]. At a near-equivalent WED, beam entry MO Skin ™ measurements were in good agreement, within 1.1% (percent difference) to pre-existing OSLD measurements performed at 5 × 5 cm 2 , 10 × 10 cm 2 , and 22 × 22 cm 2 field sizes.…”

The development of a cylindrical phantom for nanoDotTM calibration with multiple beam angles

“…The sensitivity correction factor for the nanoDot TM accounts for corrections needed due to non-uniformity in therapy applications. [1][2][3][4][5][6] It is employed for in vivo dosimetry to determine organ doses during irradiation, such as for the skin [7][8][9][10] and eye lens. 11 The nanoDot TM offers several advantages, including its small size and repeatable readout, making it a preferred choice for in vivo dosimetry.…”