Enhancement of electron beam dose distributions by longitudinal magnetic fields: Monte Carlo simulations and magnet system optimization

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Abstract
A Monte Carlo electron–photon transport code was developed in order to determine the effects of static, longitudinal, magnetic fields on dose distributions produced by high‐energy electron beams, and to optimize the design of a superconducting magnet system. As a result of these simulations, a 20‐cm‐i.d., 30‐cm‐o.d., 15‐cm‐tall, single‐coil, magnet system was designed that could be incorporated into a mobile treatment table for use with a standard radiation therapy accelerator. Operating at a current density of 18 kA/cm2, the magnet would produce field strengths of 1–4 T in the phantom and 0.01 T at the accelerator exit window. Magnetically enhanced dose distributions, calculated for 20‐ and 30‐MeV electron beams, show a pronounced Bragg peak, steeper gradients to the sides and rear, and a roughly fourfold increase in the peak dose to entrance dose ratios relative to those similarly calculated without a magnetic field. These magnetically enhanced dose distributions have the potential for sparing intervening tissue when high‐energy electrons are used for the treatment of deep‐seated tumors.
Funding Information
  • Presbyterian Historical Society (CA‐27704, CA‐06519)