Citation: Paino, J.; Cameron, M.; Large, M.; Barnes, M.; Engels, E.; Vogel, S.; Tehei, M.; Corde, S.; Guatelli, S.; Rosenfeld, A.; et al. DoseMRT: A Software Package for Individualised Monte Carlo Dose Calculations of Synchrotron- Generated Microbeam Radiation Therapy. Radiation 2023, 3, 123–137. https://doi.org/10.3390/ radiation3020011 Academic Editor: Alexandros Georgakilas Received: 11 April 2023 Revised: 16 June 2023 Accepted: 16 June 2023 Published: 20 June 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Article DoseMRT : A Software Package for Individualised Monte Carlo Dose Calculations of Synchrotron-Generated Microbeam Radiation Therapy Jason Paino 1,2 , Matthew Cameron 1,2,3 , Matthew Large 1,2 , Micah Barnes 1,2 , Elette Engels 1,2,3 , Sarah Vogel 1,2 , Moeava Tehei 1,2,4 , Stéphanie Corde 1,2,5 , Susanna Guatelli 1,2 , Anatoly Rosenfeld 1,2 and Michael Lerch 1,2,4, * 1 Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522, Australia; jpaino@uow.edu.au (J.P.) 2 Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia 3 Imaging and Medical Beamline, Australian Nuclear Science and Technology Organisation-Australian Synchrotron, Kulin Nation, Clayton, VIC 3168, Australia 4 Molecular Horizons, School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia 5 Department of Radiation Oncology, Prince of Wales Hospital, Randwick, NSW 2031, Australia * Correspondence: mlerch@uow.edu.au Simple Summary: A new software package, DoseMRT has been developed and validated for use in synchrotron-generated broad beam and microbeam radiation treatment fields. This package uses Geant4 Monte Carlo dose calculations at the core of a novel integrated workflow intended for use in a pre-clinical workflow. DoseMRT allows for rudimentary treatment planning and dose calculations in geometry defined by individual patient computed tomography scans. This software is validated in anatomically complex phantoms and demonstrated as used in an in vivo animal trail at the Australian Synchrotron. Abstract: This work describes the creation and experimental validation of DoseMRT, a new software package, and its associated workflow for dose calculations in synchrotron-generated broad beam and microbeam radiation treatment fields. The DoseMRT software package allows users to import CT DICOM datasets into Geant4 for Monte Carlo dose calculations. It also provides basic treatment planning capabilities, simplifying the complexity of performing Geant4 simulations and making our Monte Carlo dose calculation algorithm accessible to a broader range of users. To demonstrate the new package, dose calculations are validated against experimental measurements performed in homogeneous water tank phantoms and the anatomically complex Alderson Radiotherapy Phantom for both broad-beam and microbeam configurations. Additionally, DoseMRT is successfully utilised as the primary method for patient-specific treatment prescription in an in vivo experiment involving tumour-bearing rats at the Imaging and Medical Beamline of the Australian Synchrotron. Keywords: Geant4; dose calculation; in vivo treatment simulation; DICOM; synchrotron; MRT 1. Introduction Synchrotron microbeam radiation therapy (MRT) is a next-generation radiation treat- ment modality currently under preclinical development. The use of spatially fractionated radiation at extremely high dose rates has been proven to increase the dose tolerance of healthy tissue over that of cancerous tissue [1], greatly extending the scope of treatment options, particularly near radiosensitive tissues. As synchrotron facilities continue to see increased use for in vitro and in vivo experiments [2], it is essential to perform dose calculations in models with a geometry that matches the anatomical complexity of the Radiation 2023, 3, 123–137. https://doi.org/10.3390/radiation3020011 https://www.mdpi.com/journal/radiation