Multiple scattering distributions for therapeutic pion beams

Accurate treatment planning for therapeutic beams of negative pions requires knowledge of the multiple scattering of pions in biologically relevant materials. Complete spatial and angular scattering distributions have been measured for pions in scatterers of carbon, water and calcium. Measurements were made for targets varying in thickness from 0.5 to 21 g cm-2 and for pions with ranges of approximately 12 and 20 g cm-2. An array of scintillators, multiwire drift and multiwire proportional chambers was used to record the scattering of individual particles. These data are compared with the results of Molière scattering theory. The implications for pion treatment planning are discussed.