Picker Corporation

Washington University

University of Iowa Research Foundation

Research Foundation of State of N.y.

Donald L Snyder

Jerome R Cox, Jr

Rodney Arnold Mattson

Carl J Brunnett

Ge Wang

Michael W Vannier

Joseph A O'Sullivan

Ping-Chin Cheng

In the present invention, an iterative process is provided for cone-beam tomography (parallel-beam and fan-beam geometries are considered as its special cases), and applied to metal artifact reduction and local reconstruction from truncated data, as well as image noise reduction. In different embodiments, these iterative processes may be based upon the emission computerized tomography (CT) expectation maximization (EM) formula and/or the algebraic reconstruction technique (ART). In one embodiment, generation of a projection mask and computation of a 3D spatially varying relaxation factor are utilized to compensate for beam divergence, data inconsistence and incompleteness.

Iterative process for reconstructing cone-beam tomographic images

An improved method and apparatus for transaxial tomographic scanning of a patient. A scanning system is provided having a rotatably mounted X-ray radiation source/detector pair which orbits and radially scans the patient in the plane of orbit. The source provides a plurality of beams of radiation having axes in the orbital plane. The beams pass through the patient to an array of detectors each of which is aligned with one of the beams. Radiation intensity data is collected at predetermined orientations of each beam/detector pair as the assembly orbits about the patient. In a preferred embodiment the rotatably mounted source-detector pair is rotated as a unit through a preselected rotation angle .phi. about an axis effectively passing through the source. The axis and the source-detector pair connected to it are then orbited around the patient through an orbit angle .gamma. while maintaining the preselected rotation angle .phi.. The axis is orbited about an origin lying in the orbital plane. A set of measurements is taken during the orbit as the beams from the X-ray source sweep through substantially uniformly spaced, coplanar points [t(k), .phi.(n)] defined about the origin. After an orbit, the rotation angle .phi. is incremented, and the source detector pair re-orbits the patient for providing a new set of measurement data corresponding to the incremental rotation angle .phi.. Exact reconstruction is achieved after several orbit cycles when measurements are taken at the angles .phi., .gamma. characterized substantially as ##EQU1## WHERE D REPRESENTS THE DISTANCE BETWEEN THE ORIGIN AND THE CENTER OF ROTATION, AND K, N ARE INTEGERS.

Tomography system having nonconcurrent, compound axial scanning

A dual axial scanner in a transverse tomography system collects nonredundant data throughout one or more substantially 360.degree. orbital scan paths with uniform motion about a patient. A set of N X-ray beams scans the patient in a manner to allow collection of two sets of non-redundant data corresponding to a pair of 180.degree. scans in each 360.degree. scan. Overall time to conduct the study is decreased, and the number of required accelerations and decelerations of the assemblies is minimized. Adjacent beams of radiation are separated by an angle .alpha., which is one degree in the preferred embodiment to provide a radiation field of ##EQU1## degrees on either side of a center of the radiation field. The source and detector assemblies are positioned prior to the first orbit such that the field center is offset a distance D from a center of orbit lying in the orbital plane. The source and detector assemblies are mounted for rotation through a rotation angle .phi..sub.j about an orbital source axis which passes through the source assembly at a distance d from the center of orbit. While maintaining the offset distance D, the assemblies orbit the patient, and radiation intensity data is collected at predetermined angles .gamma..sub.j of orbit. In one embodiment for doubling the effective field size of the patient scanned, the source and detector assemblies are rotated about the source axis to provide the distance D. From an initial position on the center of orbit, the assemblies are rotated by an offset angle ##EQU2## degrees where R is the number of total orbits selected to constitute a complete study. In another embodiment for single field exposure the source and detector assemblies are rotated by the offset angle .phi. defined substantially by the equation ##EQU3## degrees, where 'b' is zero for an odd number N of detectors and is one for an even number N of detectors. For multiorbit studies, the assemblies are rotated between orbits by an amount ##EQU4## degrees depending on the study.

Transverse tomography system having multibeam orbital scanning with all

An improved method and apparatus for transaxial tomographic scanning a patient. A scanning system is provided having a rotatably mounted X-ray radiation source/detector assembly which orbits and scans the patient in a plane of orbit. The source provides a plurality of beams of radiation having axes in the orbital plane. The beams pass through the patient to an array of detectors each of which is and respectively aligned with a different one of the beams. Radiation intensity data is collected at predetermined orientation of each beam - detector pair as the assembly orbits about the patient. In one embodiment the source and detector are rotated as a unit through a rotation angle .phi. about center of rotation while the assembly orbits the patient through an orbit angle .gamma.. Measurements are taken as the beams from the X-ray source sweep, due to the source detector rotation relative to a patient, through substantially uniformly spaced, coplanar points [t, (k), .theta.(n)] defined from an origin lying in the plane of orbit. Exact reconstruction is achieved when measurements are taken at the angles .phi., .gamma. characterized substantially as

Tomography system having axial scanning

An improved method and apparatus for transaxial tomographic scanning of a patient. A scanning system is provided having a rotatably mounted X-ray radiation source/detector pair which orbits and radially scans the patient in the plane of orbit. The source provides a plurality of beams of radiation having axes in the orbital plane. The beams pass through the patient to an array of detectors each of which is aligned with one of the beams. Radiation intensity data is collected at predetermined orientations of each beam/detector pair as the assembly orbits about the patient. In a preferred embodiment the rotatably mounted source-detector pair is rotated as a unit through a preselected rotation angle .phi. about an axis effectively passing through the source. The axis and the source-detector pair connected to it are then orbited around the patient through an orbit angle .gamma. while maintaining the preselected rotation angle .phi.. The axis is orbited about an origin lying in the orbital plane. A set of measurements is taken during the orbit as the beams from the X-ray source sweep through substantially uniformly spaced, coplanar points [t(k), .theta.(n)] defined about the origin. After an orbit, the rotation angle .phi. is incremented, and the source detector pair re-orbits the patient for providing a new set of measurement data corresponding to the incremental rotation angle .phi.. Exact reconstruction is achieved after several orbit cycles when measurements are taken at the angles .phi., .gamma. characterized substantially as ##EQU1## OF ROTATION, AND K, N ARE INTEGERS.

Growing community of inventors

Clayton, MO, United States of America

Donald L Snyder