Ernesto Mainegra-Hing

arXiv2021

Introducing the Voxel Interactive Contour Tool for Online Radiation Intensity Analytics (VICTORIA)

In this paper, the Voxel Interactive Contour Tool for Online Radiation Intensity Analytics (VICTORIA) web viewer is presented as a solution to the issue of inaccessible, expensive, and insecure Digital Imaging and Communications in Medicine (DICOM) and Monte Carlo (MC) dose viewers. VICTORIA is a tool for the visualization and comparison of dose distributions with underlying anatomy that is accessible, free, designed with security in mind, and available on the web. The code is open-source and under the GNU General Public License, and it can be found at the EGSnrc Github repo in the DICOM-viewer branch. The viewer should be useful for researchers using EGSnrc file types .egsphant and .3ddose from the EGSnrc toolkit, patients who want a simple tool to view files, or researchers using DICOM Computed Tomography (CT) and DICOM Radiotherapy (RT) Dose files in low- or middle-income countries without access to treatment planning systems.

physics.med-ph↗

arXiv2021

A study of Type B uncertainties associated with the photoelectric effect in low-energy Monte Carlo simulations

The goal of this manuscript is to estimate Type B uncertainties in absorbed-dose calculations arising from the different implementations in current state-of-the-art Monte Carlo codes of low-energy photon cross-sections (<200 keV). Monte Carlo simulations are carried out using three codes widely used in the low-energy domain: PENELOPE-2018, EGSnrc, and MCNP. Mass energy-absorption coefficients for water, air, graphite, and their respective ratios; absorbed dose; and photon-fluence spectra are considered. Benchmark simulations using similar cross-sections have been performed. The differences observed between these quantities when different cross-sections are considered are taken to be a good estimator for the corresponding Type B uncertainties. A conservative Type B uncertainty for the absorbed dose (k=2) of 1.2%-1.7% (<50 keV), 0.6%-1.2% (50-100 keV), and 0.3% (100-200 keV) is estimated. The photon-fluence spectrum does not present clinically relevant differences that merit considering additional Type B uncertainties except for energies below 25 keV, where a Type B uncertainty of 0.5% is obtained. Below 30 keV, mass energy-absorption coefficients show Type B uncertainties (k=2) of about 1.5% (water and air), and 2% (graphite), reaching values about 1% (40-50 keV) and 0.5% (50-75 keV). Type B uncertainties for the water-to-graphite ratios are observed for energies below 30 keV, about 0.7% (k=2). In contrast with the intermediate (about 500 keV) or high (about 1 MeV) energy domains, Type B uncertainties due to the different cross-sections implementation cannot be considered subdominant with respect to Type A uncertainties or even to other sources of Type B uncertainties. Therefore, the values reported here should be accommodated within the uncertainty budget in low-energy photon dosimetry studies.

physics.med-ph↗