Dosimetry for total-body electron-beam therapy in the treatment of mycosis fungoides

A 6 MeV linear accelerator was adapted for superficial total-body electron-beam therapy. The energy of the electron beam was reduced to 2.5 MeV by a 1 cm × 1 m × 2 m polystyrene screen placed 4.5 m from the accelerator. The patients were treated behind the screen, which acted as a scatterer and also contained three parallel-plate ionization chambers for dosimetry and beam monitoring. The bremsstrahlung dose was reduced to 0.7% of the electron dose by lining the collimators of the accelerator with aluminum. Instrumentation and techniques developed in determining the depth dose, dose distributions, and bremsstrahlung dose are discussed.