A MONTE CARLO COMPUTER PROGRAM FOR CALCULATIONS WITH NEGATIVE PION BEAMS* H. A. Wright, R. N. Hamm, and J. E. Turner
Health and Safety Research Division, Oak Ridge National Laboratory Oak Ridge, Tennessee 37830 A Monte Carlo computer code, PION-1, has been written for calculations of dose distributions in phantoms irradiated by negative pion beams. Emphasis in the development of PION- has been on applications to cancer radiotherapy, and all physical processes thought to be significant for such applications have been treated. The code allows for muon and electron contamination of the pion beams, elastic and inelastic scattering of pions in flight by atomic nuclei, capture of stopped negative pions, transport of secondary particles (including neutrons) produced during nuclear interactions, multiple Coulomb scattering, and range straggling. Calculations can be made with inhomogeneities, such as regions of bone, lung, or air, in tissue phantoms. PIONis a full three-dimensional transport code and, consequently, there are no restrictions on the incident radiation which can be treated. The phantom is divided into subvolumes and a calculation provides the total dose within each subvolume as well as a breakdown of that dose into contributions from different particle types (pion, muon, electron, proton, neutron, or heavy charged particle) and also into contributions from different LET intervals. PIONuses experimental data for interaction cross sections or particle production spectra where available and is not dependent on theoretical models. A calculation of the transport of lo4 incident particles plus all secondary particles they produce typically requires 3 to 4 minutes on an IBM 360 Model 91 computer< A number of examples are given of the kind of information that can be obtained with PION-1. The relative effects of various physical processes on dose distribution patterns are also assessed. *Research sponsored by the Biomedical and Environmental Research Division, U.S. Department of Energy under contract W-7405-eng-26 with the Union Carbide Corporation.
PION TREATMENT PLANNING WITH THE STANFORD MEDICAL PION GENERATOR
Cindy H.C. Yuen, Ph.D., Peter Fessenden, Ph.D., Gloria C. Li, Ph.D. David A. Pistenma, Ph.D., M.D., Malcolm A. Bagshaw, M.D. Department of Radiology, Stanford University, Stanford, CA 94305 The Stanford Medical Pion Generator (SMPG) provides 60 simultaneous pion beams converging nearly radially toward the axis of a cylindrical phantom. The dose calculations utilize a ray tracing program whose input parameters These include are related to SMPG design and operating characteristics. target size and position, mean pion momentum, intensity of each pion beam, electron and muon contamination, and star neutrons. The calculational program takes into consideration the effects of attenuation in flight, range