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Characterizing output for dynamic wedges
Author(s) -
Liu Chihray,
Zhu Timothy C.,
Palta Jatinder R.
Publication year - 1996
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 - 10.1118/1.597677
Subject(s) - wedge (geometry) , normalization (sociology) , weighting , optics , mathematics , physics , acoustics , sociology , anthropology
The output factor for the dynamic wedge, unlike that for the physical wedge, is a complex function of the field dimension along the moving jaw and wedge angle. The large change in output (varying as much as 40% for 45° and 60° wedge angles) can be attributed clearly to the segmented treatment tables (STTs), which specify cumulative monitor unit weighting as a function of jaw position, y . We found that the output factor (in air or water) on the central axis for the dynamic wedge can be characterized by multiplying the output factor (in air or water) for an open field by a normalization factor, which is determined from the STTs, thus indicating that collimator scatter is similar for both the dynamic wedge field and the open field. The introduction of the normalization factor decreases the commissioning time for dynamic wedges significantly and is useful for quality assurance.