High spatial resolution dosimetry with uncertainty analysis using Raman micro-spectroscopy readout of radiochromic films

Abstract

Purpose: The purpose of this work is to develop a new approach for high spatial resolution dosimetry based on Raman micro-spectroscopy scanning of radiochromic film (RCF). We generate dose calibration curves over an extended dose range from 0-50 Gy and with improved sensitivity to low (<2 Gy) doses, in addition to evaluating uncertainties. Methods: Samples of RCF (EBT3) were irradiated at a broad dose-range of 0.03 Gy-50 Gy. Raman spectra were acquired with a custom-built Raman micro-spectroscopy setup involving a 500 mW, multimode 785 nm laser. The depth of focus of 34 um enabled the concurrent collection of Raman spectra from the RCF active layer and the polyester laminate. The pre-processed Raman spectra were normalized to the intensity of the 1614 cm-1 Raman peak from the polyester laminate that was unaltered by radiation. The experimental, fitting and total dose uncertainty was determined across the entire dose range for the dosimetry system of Raman micro-spectroscopy and RCF. Results: High resolution in the dose response of the RCF, even down to 0.03 Gy, was obtained in this study. The dynamic range of the calibration curves based on all three Raman peaks in the RCF extended up to 50 Gy with no saturation. At a spatial resolution of 30X30 um^2, the total uncertainty in estimating dose in the 0.5 Gy to 50 Gy dose range was [6 - 9]% for all three Raman calibration curves. This consisted of the experimental uncertainty of [5 - 8]%, and the fitting uncertainty of [2.5 - 4.5]%. Conclusions: The high spatial resolution experimental dosimetry technique based on Raman micro-spectroscopy and RCF presented here, could become useful for applications in, as well as for applications based on small field dosimetry.