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Physical performance characteristics of spiral CT scanning
Author(s) -
Kalender Willi A.,
Polacin Arkadiusz
Publication year - 1991
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 - 10.1118/1.596607
Subject(s) - imaging phantom , image quality , interpolation (computer graphics) , image resolution , optics , pixel , sensitivity (control systems) , spiral (railway) , noise (video) , linear interpolation , iterative reconstruction , raster scan , image noise , physics , mathematics , geometry , artificial intelligence , image (mathematics) , computer science , motion (physics) , mathematical analysis , classical mechanics , electronic engineering , polynomial , engineering
CT scanning in spiral geometry is achieved by continuously transporting the patient through the gantry in synchrony with continuous data acquisition over a multitude of 360‐deg scans. Data for reconstruction of images in planar geometry are estimated from the spiral data by interpolation. The influence of spiral scanning on image quality is investigated. Most of the standard physical performance parameters, e.g., spatial resolution, image uniformity, and contrast, are not affected; results differ for pixel noise and slice sensitivity profiles. For linear interpolation, pixel noise is expected to be reduced by a factor of 0.82; reduction factors of 0.81 to 0.83 were measured. Slice sensitivity profiles are changed as a function of table feed d , measured in millimeters per 360‐deg scan; they are smoothed as the original profile is convolved with the object motion function. The motion function is derived for linear interpolation that constitutes a triangle with a base line width of 2 d and a maximal height equal to 1/ d . Calculations of both the full width at half‐maximum and the shape of the profiles were in good agreement with experimental results. The effect of the widened profiles, in particular of their extended tail ends, on image quality is demonstrated in phantom measurements.