Method and means of correcting for a shift in the center of rotation of a rotating fan beam CT system

Patent · Tue Mar 14 00:00:00 EST 1989

OSTI ID:5911530

Gulberg, G T; Crawford, C R

In a fan beam computed tomographic system having a detector system for taking a plurality of projections at a plurality of angles, each projection defining a plurality of projection bins, the computed tomographic system having a given center of rotation which is shifted from the midline of the fan by a shift distance which varies as a function of projection angle, a method compensating for the shift in performing the computed tomographic reconstruction comprising the steps of, producing a weighting function for each projection bin in each projection set which is dependent on the detector geometry and the magnitude of the shift for the respective projections, weighting the information in each projection bin with its associated weighting function to produce corrected projection sets, convolving the corrected projection sets with a filter function to produce convolved corrected projection sets, setting up a coordinate system in pixelized space taking into account the shift and its variance as a function of projection angle, and back projecting the convolved corrected projection sets in to the pixelized space using the coordinate system to produce a CT image corrected for the variable shift. The patent also describes an improved apparatus for compensating for the shift in performing the computed tomographic reconstruction. Finally, the patent describes a set of geometric parameters including a distance between the apex of the fan and the detector, a distance between the apex of the fan and the center of rotation of the detector, a position of a point on the detector defined by the midline of the fan, and a center of rotation shifted with respect to the projection as a function of projection angle.

• Assignee: General Electric Co., Waukesha, WI
• Patent Number(s): US 4812983
• OSTI ID: 5911530
• Resource Relation: Patent File Date: Filed date 31 Jul 1986
• Country of Publication: United States
• Language: English

Related Subjects

47 OTHER INSTRUMENTATION
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
COMPUTERIZED TOMOGRAPHY
CORRECTIONS
BEAM DYNAMICS
IMAGE PROCESSING
IMAGE SCANNERS
PHASE SHIFT
RADIATION DETECTORS
ROTATION
DIAGNOSTIC TECHNIQUES
MEASURING INSTRUMENTS
MOTION
PROCESSING
TOMOGRAPHY
440300* - Miscellaneous Instruments- (-1989)
990220 - Computers
Computerized Models
& Computer Programs- (1987-1989)