Open AccessA 3D star shot to determine the gantry, collimator, and couch axes positions
Author(s) -
Corns Robert,
Yang Kaida,
Ross Mason,
Bhandari Shiva,
Aryal Makunda,
Ciaccio Peter
Publication year - 2022
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.13623
Subject(s) - isocenter , collimator , imaging phantom , linear particle accelerator , optics , physics , cylinder , shot (pellet) , scanner , coincidence , computer science , mathematics , beam (structure) , geometry , materials science , medicine , alternative medicine , pathology , metallurgy
Abstract A linear accelerator has three independent axes that are nominally intersecting at the isocenter. Modern treatment techniques require the coincidence of these axes to lie within a 1‐mm diameter sphere. A solution to verify this requirement is to wrap a film on a cylindrical surface, align the cylinder to the linac's isocenter and gantry axis, and take multiple exposures of slits, rotating either the gantry, collimator, or couch between exposures. The resulting exposure pattern is the 3D equivalent of the 2D star shot and encodes sufficient information to determine each axis’ position in 3D. Moreover, this method uses a single sheet 8“x10” film, a standard film scanner, and a phantom that can be readily built in‐house, making a practical solution to this 3D‐measurement problem.