Method to obtain object boundary information in limited-angle computerized tomography

Claim 1

A method of obtaining object boundary information in limited-angle x-ray computerized tomography comprising: exposing said object to x-rays at multiple scanning angles within a limited angular range and generating x-ray projection data; processing, said projection data by doing curve fitting near the edges to more precisely determine end points between attenuated and unattenuated x-rays; backprojecting the projection data between said end points at every scanning angle to yield a backprojection strip which contains the support of said object, defined as the region where object density is non-zero; overlapping all of said backprojection strips to construct a region which is a polygon and the convex hull of said object, the smallest convex region containing said object; and using said constructed region as a priori information on the extent and location of said object and other a priori information, reconstruct and display said object by means of a limited-angle reconstruction technique.

Claim 2

A method of obtaining object boundary information in limited-angle x-ray computerized tomography comprising: exposing said object to x-rays at multiple scanning angles within a limited angular range and generating x-ray projection data; processing, said projection data by doing curve fitting near the edges to more precisely determine end points between attenuated and unattenuated x-rays; backprojecting the projection data between said end points at every scanning angle to yield a backprojection strip which contains the support of said object, defined as the region where object density is non-zero; overlapping all of said backprojection strips to construct a region which is a polygon and the convex hull of said object, the smallest convex region containing said object; and using said constructed region as a priori information on the extent and location of said object and other a priori information, reconstruct and display said object by means of a limited-angle reconstruction technique.

Claim 5

A method of reconstructing high quality images in a limited-angle x-ray computerized tomography (CT) system comprising: exposing an object to low energy x-rays and to usual CT energy x-rays at many scanning angles over a limited angular range and generating x-ray projection data at both exposures; processing said low energy projection data by fitting curves to the edges to more accurately determine the end points between attenuated and unattenuated x-rays; backprojecting the low energy projection data between said end points to form, at every scanning angle, a backprojection strip which contains the support of said object, the region where object density is non-zero; intersecting or superimposing all of said backprojection strips to construct a polygon-shaped region which is the convex hull of said object and the smallest convex region containing said object; and reconstructing and displaying said object by means of a limited-angle reconstruction procedure using (1) said constructed region as a priori information on the exterior boundary of said object, (2) the usual CT energy x-ray data and scanning angles, and (3) other a priori information.

Claim 6

A method of reconstructing high quality images in a limited-angle x-ray computerized tomography (CT) system comprising: exposing an object to low energy x-rays and to usual CT energy x-rays at many scanning angles over a limited angular range and generating x-ray projection data at both exposures; processing said low energy projection data by fitting curves to the edges to more accurately determine the end points between attenuated and unattenuated x-rays; backprojecting the low energy projection data between said end points to form, at every scanning angle, a backprojection strip which contains the support of said object, the region where object density is non-zero; intersecting or superimposing all of said backprojection strips to construct a polygon-shaped region which is the convex hull of said object and the smallest convex region containing said object; and reconstructing and displaying said object by means of a limited-angle reconstruction procedure using (1) said constructed region as a priori information on the exterior boundary of said object, (2) the usual CT energy x-ray data and scanning angles, and (3) other a priori information.