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Photon dose perturbations due to small inhomogeneities
Author(s) -
Yu Cedric X.,
Wong John W.,
Purdy James A.
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 - 10.1118/1.596106
Subject(s) - photon , physics , dosimetry , medical imaging , optics , medical physics , nuclear medicine , medicine , radiology
An apparatus capable of measuring small fractional changes in ionization current has been used to study the effect of small inhomogeneities on photon dose in water. Small ring‐shaped inhomogeneities were introduced into a water phantom and measurements have been made for 4‐, 6‐, and 18‐MV x‐rays. The results show (1) beyond the range of secondary electrons, the dose perturbation is basically a photon transport phenomenon which becomes less important as the beam energy increases; (2) within the range of secondary electrons, dose perturbation also involves electron transport, which has a strong dependence on atomic number and could result in a substantially large effect on dose deposition.