SU-GG-T-93: Investigation of Various Phantom Materials for Very High Energy Electron (VHEE) Beams 150-250 MeV: A Monte Carlo Study

Abstract

Purpose: Very high energy electrons (150–250 MeV) is a new possible modality for radiation therapy. It is important to establish accurate dosimetry for this range of energies. In this study we evaluated the properties of dose deposition in various phantom materials for very high energy electron (VHEE) beams. Methods and Materials: A general purpose Monte Carlo code PENELOPE (2003) was used to generate phantom geometries modeling solid water, liquid water, polystyrene, and soft tissue (ICRP). A 10×10 cm2 electron beam was modeled for 50×50×50 cm3 phantoms for energies of 150, 180, and 200 MeV. A 10×10 cm2 electron beam was modeled for 50×50×12 cm3 for current clinical energy of 18 MeV. For all simulations 2E7 incident primary particles were used. Results: For the 200MeV beam, the max dose is as follows: Solid Water 4.15E-12Gy; Liquid Water 4.31E-12Gy; Polystyrene 4.04E-12Gy; Soft Tissue (ICRP) 4.26E-12Gy. Standard calibration procedures compare measurements taken in a medium and compare to measurements made in water, for the same geometries. The dose at dmax is consistently less in the phantom and other materials than for water: Solid Water 96.3%; Polystyrene 93.7%; Soft Tissue (ICRP) 98.8%. Similar and consistent results are seen at the lower energies. Conclusions: Given the consistency of dmax and dose at dmax for the energies and materials studied, it would seem appropriate to use water equivalent phantoms to quantify output of a VHEE beam when scaled appropriately. Measurements made in solid water are most close to the measurements in water.