Using ion chambers with wedge-shaped absorbers for electron energy measurements.

A parallel-plate ionization chamber placed behind a wedge-shaped absorber and exposed to a radiotherapeutic electron beam exhibits an energy-dependent response. Such a device designed to produce a linear energy dependence has been built and tested. The device yields results during exposure, and the difficulties of film handling, associated with similar procedures, have been eliminated. The precision of the device makes it suitable for use as a routine means of monitoring energy for quality assurance purposes.