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Half‐value layer and intensity variations as a function of position in the radiation field for film‐screen mammography
Author(s) -
Terry James A.,
Waggener Robert G.,
Miller Blough Melissa A.
Publication year - 1999
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 - 10.1118/1.598513
Subject(s) - intensity (physics) , inverse square law , optics , radiant intensity , half value layer , radiation , position (finance) , materials science , photon , field intensity , physics , nuclear magnetic resonance , finance , classical mechanics , gravitation , economics , radiation shielding
Differences in half‐value layer (HVL) and radiation intensity are investigated as a function of position in the mammographic radiation field. Sources of systematic variation include the heel effect, the inverse square law, and differential photon path lengths through thicknesses of inherent and added filtration. The combination of these effects can increase the HVL by as much as 9% and reduce intensity by as much as 40% along the cathode‐anode axis. To the left and right of the x‐ray field central axis, reductions in radiation intensity of up to 9% and minor increases in HVL are noted as well. Optical density variations as a function of position in the field correlate well with the measured radiation intensity changes.