Analysis of the photon beam treatment planning data for a scanning beam machine.
The characteristics of photon beams from the Scanditronix MM50 radiation therapy machine that are necessary for treatment planning are described. The MM50 uses a scanning beam instead of a conventional flattening filter to achieve flat dose distributions. At each beam energy, a scan pattern is chosen, depending on the field size; the small scan pattern (S) is used for field sizes up to 10 x 10 cm, the medium scan pattern (M) is used for field sizes up to 20 x 20 cm, and the large scan pattern (L) is used for the larger field sizes. The dose distributions of the beams associated with the 10 MV S, M, and L scan patterns, the 25 MV S, M, and L patterns, and the 50 MV S and M patterns are described. The data reported includes central axis data, beam profiles, and output factors. In addition to the measured data, our dose calculation model requires a pencil beam kernel for each beam. The kernel is constructed using the average photon energy spectrum, which is generated using a Monte Carlo simulation of the MM50. The simulation, based on EGS4, is also used to generate the radial variation of fluence and energy fluence, which is required by a new dose calculation model that does not require the measurement of beam profiles. The Monte Carlo generated data; the photon energy spectrum, the fluence, and the energy fluence are presented.
Lovelock
D M
DM
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Chui
C S
CS
Kutcher
G J
GJ
Mohan
R
R
D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D008961:Models, Structural; D009010:Monte Carlo Method; D017785:Photons; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods / Q000706:statistics & numerical data; D011882:Radiotherapy, High-Energy / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data