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Analysis of the bremsstrahlung component in 6–18 MeV electron beams
Author(s) -
Rustgi Surendra N.,
Rodgers James E.
Publication year - 1987
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 - 10.1118/1.596018
Subject(s) - bremsstrahlung , collimated light , imaging phantom , physics , electron , ionization , atomic physics , electron scattering , scattering , perpendicular , photon , ionization chamber , nuclear physics , optics , laser , ion , geometry , mathematics , quantum mechanics
The magnitude of the bremsstrahlung component in the 6–18 MeV electron beams from a Varian Clinac 18 accelerator was measured directly using a 0.16 T magnetic field to deflect the electron beams. The central axis depth ionization curves were measured at 130‐ and 197‐cm source–surface distances in a Therados RFA‐3 water phantom with and without the magnet being placed between the 4×4 cm 2 electron cone and the water phantom. Results obtained clearly demonstrate that the bremsstrahlung component is primarily (>90%) generated in the electron scattering‐foil/collimation system and not in the water phantom. The x‐ray central axis depth ionization curves exhibit buildup and attenuation regions characteristic of megavoltage x‐ray beams. Ionization profiles of the x‐ray component, measured in a plane perpendicular to the central axis, were also examined. Analysis of bremsstrahlung production as a function of photon collimation jaw opening shows a strong dependence, especially for the smaller openings.