Some dosimetry problems in negative pion radiotherapy

Momentum beams of negative pions are considered for radiotherapy. It is shown that the measurement of dose in this respect presents problems which are different from those encountered when using the more usual type of radiation. This difference arises principally from the nuclear interaction processes produced when the negative pion comes to rest. These processes, which are superimposed on the Bragg peak of the beam, produce a complex mixture of charged particles together with a beam contamination of muons and electrons. Some experimental studies of depth dose distributions, dose estimates, and other parameters to be considered for radiotherapy of cancer with beams of negative pions are discussed.