Method and apparatus for pre-processing cone beam projection data for exact three dimensional computer tomographic image reconstruction of a portion of an object

• US 5,390,226 A
• Filed: 07/02/1992
• Issued: 02/14/1995
• Est. Priority Date: 07/02/1992
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Tam, Kwok C.
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US07/908,114
• Time in Patent Office: 957 Days
• Field of Search: 378/4, 378/8, 378/14, 378/19, 378/901, 364/413.14, 364/413.15, 364/413.16, 364/413.19
• US Class Current: 378/19
• CPC Class Codes: G06T 11/005 Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating
• CPC Class Codes: G06T 2211/421 Filtered back projection [FBP]
• CPC Class Codes: G06T 2211/432 Truncation
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

An improved method and apparatus for preprocessing cone beam attenuation data to reconstruct a three dimensional image of a particular region of interest of an object by a process of inverse Radon transformation is described. The number of required operations is substantially reduced by selectively retaining for further processing only that cone beam attenuation data acquired within a select closed region of the surface of the array detector wherein this region provides data corresponding to beams actually attenuated in passing through the region of interest of the object. In this manner, unnecessary beam attenuation data is discarded at the earliest possible opportunity to expedite image processing.

Claims

1. A method of pre-processing beam attenuation data for reconstructing a three dimensional (3D) image of a user selectable portion of an object using an inverse Radon transformation comprising the steps of:

providing a mutually spaced irradiating beam source and a surface array radiation detector in fixed relationship to one another;

providing said object therebetween;

irradiating at least said portion of said object within a field of view of said source;

rotationally scanning said portion with respect to said fixed source and detector along a trajectory enclosing upper and lower extents of said portion by respective upper and lower scan paths joined therebetween by a connecting scan path;

identifying a select region on said array detector surface as a beam projection of said object bounded between similar said upper and lower scan path projections;

acquiring beam attenuation data at said array detector surface for a plurality of source positions along said scan trajectory;

retaining only beam attenuation data acquired within said select region; and

processing only said retained data to reconstruct a 3D image of said object by said inverse Radon transformation.

2. Method according to claim 1 wherein said source is a cone beam source.

3. Method according to claim 1 wherein said detector surface is a planar surface.

4. Method according to claim 1 wherein a complete set of Radon data is acquired for reconstruction of an exact 3D image of said portion.

5. Apparatus for pre-processing cone beam attenuation data for exact three dimensional (3D) image reconstruction of a is user selectable portion of an object comprising:

a radiation beam source;

a surface array radiation detector means mutually spaced a fixed distance apart from said source;

means for relatively rotating said object with respect to said fixed source and detector along a scanning trajectory to irradiate at least said portion of said object within a field of view of said source;

means for identifying a select region of said detector surface corresponding to cone beam data passing through said portion;

means for acquiring beam attenuation data at said detector surface for a plurality of source positions along said scanning trajectory;

means for retaining only beam attenuation data acquired within said select region of said detector surface; and

means for processing said retained data into a 3D image of said portion by a Radon inversion transformation.

6. Apparatus according to claim 5 wherein said beam source is a cone beam source.

7. Apparatus according to claim 5 wherein said surface array radiation detector is a planar array radiation detector.

8. Apparatus according to claim 5 wherein said means for rotating along said scanning trajectory further includes means for scanning along upper and lower scan paths respectively enclosing upper and lower extents of said portion of said object and a connecting scan path therebetween thereby allowing a complete set of Radon data to be acquired for reconstruction of an exact 3D image of said portion.