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Dose corrections for low‐density tissue inhomogeneities and air channels for 10‐MV x rays
Author(s) -
Young M. E. J.,
Kornelsen R. O.
Publication year - 1983
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 - 10.1118/1.595392
Subject(s) - fluence , beam (structure) , dosimetry , photon , physics , optics , electron , computational physics , cathode ray , electron density , materials science , atomic physics , nuclear medicine , nuclear physics , medicine , laser
Methods of correcting for tissue inhomogeneities which consider only changes in the photon fluence are of limited usefulness for 10‐MV x rays. Although there is normally transient electronic equilibrium on the central axis beyond the depth of maximum buildup in soft tissue, when the beam enters a low‐density material the beam profile is degraded and there is a loss of lateral electron equilibrium which reduces the dose both within and beyond the inhomogeneity. This paper describes experimental measurements of the dose within and near large, low‐density inhomogeneities simulating lungs and also behind air channels (where similar effects occur). Methods of calculating correction factors are discussed.