Electron-beam arc therapy using a high energy betatron.

Dose distributions in electron-beam arc therapy were investigated using the electron beam from a Brown Boveri 45 MeV betatron. This variable isocenter machine is equipped with an angular speed control device that synchronizes the radiation dose rate with the rotation speed about the isocenter. An Alderson Rando phantom was used with Kodak RP/V film to measure isodensity distributions that were then converted to isodose curves. The effects of varying field size, isocenter depth, and air gap between collimator and phantom were examined, along with changes in the dose distributions produced by wax bolus in part of the arc.