title: High-helical-pitch, cone-beam computed tomography.
abstract: The object of a helical, cone-beam computed tomography, HCBCT, system is faster scan times for the volume of interest for a patient. The maximum helical-pitch that still produces good quality images limits the reduction in scan time. Although this is a three-dimensional problem, an extension of the completeness condition for a two-dimensional fan-beam reconstruction method serves as a guide to estimate the maximum helical-pitch. In HCBCT, each pixel in an arbitrary image slice is irradiated over a different range of gantry rotation angles. This leads to the idea of a different, or inconsistent, range of backprojection angles for each pixel in order to increase the helical-pitch while satisfying the completeness condition. Using inconsistent backprojection, the normalized helical-pitch ratio increases from 0.90 to 1.40 (for a source radius of 600 mm and field of view of 500 mm), where the normalized helical-pitch ratio is the linear advance of the patient couch per gantry revolution to the full axial height of the area detector (as projected at the isocentre).
authors.affiliation: Bio-Imaging Research, Inc., Lincolnshire, IL 60069, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Silver
mesh_terms: D000465:Algorithms; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D014055:Tomography, Emission-Computed / Q000295:instrumentation* / Q000379:methods*