Premium
Measurement of slice sensitivity profiles in spiral CT
Author(s) -
Polacin Arkadiusz,
Kalender Willi A.,
Brink James,
Vannier Michael A.
Publication year - 1994
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 - 10.1118/1.597251
Subject(s) - superposition principle , interpolation (computer graphics) , spiral (railway) , tomography , sensitivity (control systems) , impulse (physics) , optics , geometry , mathematics , materials science , physics , computer science , mathematical analysis , artificial intelligence , engineering , image (mathematics) , electronic engineering , quantum mechanics
In conventional computed tomography (CT), ramps, typically thin sheets of aluminum inclined at 45°, are established tools for measurements of slice sensitivity profiles (SSP). In spiral CT, however, they yield inconsistent results for different positions along the longitudinal axis. It is explained herein how ramp profiles result as a superposition of true SSPs and artifacts, the artifacts being caused by the slice interpolation process due to the difficult interpolation condition in this particular geometry. In direct consequence, ramp tests yield spatially variant results. As an alternative tool for measuring the slice sensitivity profile, the use of a thin high‐contrast sheet held between two disks which approximate the ideal test of a delta impulse in the longitudinal direction is suggested. Resulting SSPs are shown for both methods; the delta method, in agreement with theoretical predictions, provided smooth symmetrical SSPs independent of table position in agreement with theoretical predictions. It is concluded that ramps are inadequate test objects to determine SSPs in spiral CT.