Pencil beam scanning dosimetry for large animal irradiation

• Type of Material: Article
• Authors: Liyong Lin, Emory University; Timothy D. Solberg, University of Pennsylvania; Alexandro Carabe, University of Pennsylvania; James E. McDonough, University of Pennsylvania; Eric Diffenderfer, University of Pennsylvania; Jenine K. Sanzari, University of Pennsylvania; Ann R. Kennedy, University of Pennsylvania; Keith Cengel, University of Pennsylvania
• Language: English
• Date: 2014-09-01
• Publisher: Oxford University Press (OUP): Policy C - Option B
• Publication Version: Final Published Version
• Copyright Statement: © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1093/jrr/rru029
• Title of Journal or Parent Work: Journal of Radiation Research
• ISSN: 0449-3060
• Volume: 55
• Issue: 5
• Start Page: 855
• End Page: 861
• Grant/Funding Information: This work was supported by the Center of Acute Radiation Research (CARR) grant from the National Space Biomedical Research Institute (NSBRI) through NASA NCC 9–58, NIH Training Grant 2T32CA00967 and NIH CA-140116.
• Keywords: total body irradiation; Life Sciences & Biomedicine - Other Topics; DOSE DISTRIBUTION; solar particle event; SOLAR PARTICLE EVENT; large animal; pencil beam scanning; PROTON RADIATION; proton therapy; SPOT PROFILES; Biology; VERIFICATION; Life Sciences & Biomedicine; PORCINE MODEL; Oncology; PHOTONS; Science & Technology; Radiology, Nuclear Medicine & Medical Imaging
• Research Categories: Health Sciences, Oncology; Health Sciences, Radiology

Abstract

The space radiation environment imposes increased dangers of exposure to ionizing radiation, particularly during a solar particle event. These events consist primarily of low-energy protons that produce a highly inhomogeneous depth-dose distribution. Here we describe a novel technique that uses pencil beam scanning at extended source-to-surface distances and range shifter (RS) to provide robust but easily modifiable delivery of simulated solar particle event radiation to large animals. Thorough characterization of spot profiles as a function of energy, distance and RS position is critical to accurate treatment planning. At 105 MeV, the spot sigma is 234 mm at 4800 mm from the isocentre when the RS is installed at the nozzle. With the energy increased to 220 MeV, the spot sigma is 66 mm. At a distance of 1200 mm from the isocentre, the Gaussian sigma is 68 mm and 23 mm at 105 MeV and 220 MeV, respectively, when the RS is located on the nozzle. At lower energies, the spot sigma exhibits large differences as a function of distance and RS position. Scan areas of 1400 mm (superior-inferior) by 940 mm (anterior-posterior) and 580 mm by 320 mm are achieved at the extended distances of 4800 mm and 1200 mm, respectively, with dose inhomogeneity <2%. To treat large animals with a more sophisticated dose distribution, spot size can be reduced by placing the RS closer than 70 mm to the surface of the animals, producing spot sigmas below 6 mm.