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Loss of field flatness in AECL teletherapy units from misadjustment of the collimator
Author(s) -
Heintz Philip H.
Publication year - 1975
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 - 10.1118/1.594170
Subject(s) - flatness (cosmology) , collimator , hinge , optics , radiation , physics , cosmology , classical mechanics , quantum mechanics
Atomic Energy of Canada Limited 60 Co teletherapy units have adjustable collimator hinges to adapt to source diameters from 0.75 to 2.50 cm. Adjustment of the collimator hinge to the manufacturer's settings can cause a loss of radiation field flatness as high as 20% for large fields. The recommended settings appear to clip the top corners of tall source capsules. Opening the hinge adjustment restores field flatness, without changing penumbra or the inverse square law behavior of the teletherapy unit.