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Extraction of the photon spectra from measured beam parameters
Author(s) -
Bloch Peter,
McDonough James
Publication year - 1998
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598257
Subject(s) - monte carlo method , photon , fluence , attenuation , beam (structure) , physics , dosimetry , computational physics , spectral line , photon energy , radiation , optics , nuclear medicine , mathematics , statistics , laser , medicine , astronomy
Knowledge of the photon spectrum of a radiotherapy beam is often needed for three‐dimensional (3‐D) dose calculations using Monte Carlo methods and/or algorithms employing energy deposition kernels. Direct measurement of the x‐ray energy fluence spectrum is not feasible for the high‐energy photon beams used clinically. In this paper, the spectrum is extracted from basic beam data that are readily obtained for a clinical beam. We describe the photon spectrum using just two parameters. One parameter, which determines the high‐energy part of the spectrum, is obtained using the measured dose in the buildup region for a small field, where electron contamination of the beam can be neglected. The other parameter is extracted from the photon beam attenuation in water. The results compare favorably to spectra generated from Monte Carlo simulations.