We assessed the dosimetric safety of a potential diapeutic Gadolinium-based contrast agent for diagnostic MR imaging and MR-guided radiotherapy by calculating depth-dependent reactions rates in a spread-out Bragg peak (SOBP) in water. Energy-dependent cross-sections for inelastic proton reactions on Gadolinium were folded with proton energy spectra at depth. Particle transport, dose, and phase space scoring was performed using Geant4-based TOPAS Monte Carlo software. The isotopic Terbium yield at depth was calculated to be between 103 to 105 atoms/mmolnatGd per Gray SOBP dose in a 2.4 cm3 volume. At currently achievable Gadolinium concentrations of 0.2 µmol/cm3 this yields approximately 26 atoms/(cm3 GySOBP), corresponding to less than 1 Bq activity. Additional dose from evaporation neutrons and subsequent capture gammas is on the order of 1 µSv/GySOBP. Thus, use of this long-lived contrast agent is dosimetrically safe at current concentrations and induced radioactivity is negligible.
|Original language||English (US)|
|Journal||Journal of Physics: Conference Series|
|State||Published - Oct 16 2020|
|Event||20th Biannual Micro-Mini and Nano Dosimetry and Innovative Technologies in Radiation Oncology, MMND ITRO 2020 - Wollongong, Australia|
Duration: Feb 10 2020 → Feb 16 2020
ASJC Scopus subject areas
- Physics and Astronomy(all)