Verification of the Varskin Beta Skin Dose Calculation Computer Code

Abstract

The computer code VARSKIN is used extensively to calculate dose to the skin resulting from contaminants on the skin or on protective clothing covering the skin. The code uses six pre-programmed source geometries, four of which are volume sources, and a wide range of user-selectable radionuclides. Some verification of this code had been carried out before the current version of the code, version 3.0, was released, but this was limited in extent and did not include all the source geometries that the code is capable of modeling. This work extends this verification to include all the source geometries that are programmed in the code over a wide range of beta radiation energies and skin depths. Verification was carried out by comparing the doses calculated using VARSKIN with the doses for similar geometries calculated using the Monte Carlo radiation transport code MCNP5. Beta end-point energies used in the calculations ranged from 0.3 MeV up to 2.3 MeV. The results showed excellent agreement between the MCNP and VARSKIN calculations, with the agreement being within a few percent for point and disc sources and within 20% for other sources with the exception of a few cases, mainly at the low end of the beta end-point energies. The accuracy of the VARSKIN results, based on the work in this paper, indicates that it is sufficiently accurate for calculation of skin doses resulting from skin contaminations, and that the uncertainties arising from the use of VARSKIN are likely to be small compared with other uncertainties that typically arise in this type of dose assessment, such as those resulting from a lack of exact information on the size, shape, and density of the contaminant, the depth of the sensitive layer of the skin at the location of the contamination, the duration of the exposure, and the possibility of the source moving over various areas of the skin during the exposure period if the contaminant is on protective clothing.

Personalized irradiation therapy for NMSC by rhenium-188 skin cancer therapy: a long-term retrospective study

“…The application area, also called irradiation area, included both the lesion area and the 5 mm security margin around it. For each patient, the applied radioactivity was measured using a dose calibrator, and the treatment time was calculated using a multi-point source, real-time integration software program (VARSKIN 3.0; US Nuclear Regulatory Commission), which had already been validated as a proper method by comparison with the results with an independent Monte Carlo calculation (8).…”

A novel tool for predicting the dose distribution of non‐sealed 188Re (Rhenium) resin in non‐melanoma skin cancers (NMSC) patients

“…2,4 VARSKIN allows the calculation of the dose at a specified depth, assuming a homogenous activity distribution in several reference geometries. We run VARSKIN version 5.2 18 for each combination of target area and depth to obtain a LUT with the same sampling as the MCbased one, in order to obtain a point-by-point dosimetric comparison.…”

“…Other authors observed and reported that the dose calculated on the skin surface using VARSKIN is within 10% of other deterministic and probabilistic methods for point-like and planar sources. 18,22 Discrepancies with other methods appear when VARSKIN is used to model the presence of air-gaps or cover material (e.g., protective clothing). Compared to the EGS4 results, 23 VARSKIN underestimates the absorbed dose by nearly a factor of two in scenarios using high energy beta sources.…”

Hanford External Dosimetry Technical Basis Manual PNL-MA-842

“…Development of the VARSKIN 3 computer code was commissioned by the NRC. VARSKIN 3 has undergone V&V testing by its author (Durham 2006b) as well as by the NRC (Sherbini et al 2008) and has been generally accepted for use by the NRC. The NRC testing expanded upon previous testing performed by the code's author and third parties to include all the source geometries that are programmed in the code over a wide range of beta energies and skin depths.…”