Method and apparatus for acquiring and processing only a necessary volume of radon data consistent with the overall shape of the object for efficient three dimensional image reconstruction

• US 5,333,164 A
• Filed: 12/11/1991
• Issued: 07/26/1994
• Est. Priority Date: 12/11/1991
• 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:
  US07/805,163
• Time in Patent Office: 958 Days
• Field of Search: 378/4, 378/14, 378/8, 378/901, 364/413.15, 364/413.16, 364/413.17, 364/413.26
• US Class Current: 378/8
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• 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 2211/416 Exact reconstruction
• CPC Class Codes: G06T 2211/421 Filtered back projection [FBP]
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

An improved method and apparatus is disclosed for retaining only necessary cone beam projection data acquired along a three dimensional scanning trajectory in order to ensure more computationally efficient processing of Radon data for computerized tomographic image reconstruction consistent with the overall shape of an object irradiated by a cone beam source. If the scanning trajectory is such that an otherwise complete see of Radon data is acquired the image so reconstructed will also be exact. The invention is directed to restricting image reconstruction processing to only that region of support in Radon space actually occupied by the object itself; therefore, computational approximations consistent with the overall shape of the object can be applied to improve image reconstruction efficiency.

Claims

1. A method for reconstructing an image of a three dimensional object using an inverse Radon transform comprising the steps of:

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

providing an object therebetween;

irradiating said object within a field of view of said irradiating beam source;

scanning said irradiated object along a preselected scanning trajectory to acquire a plurality of beam attenuation data at said array detector for a plurality of select source positions;

organizing said beam attenuation data in the form of line integrals through said object for each of said plurality of source positions;

determining from said beam attenuation data values representing planar integrals;

organizing said planar integrals onto discrete polar grids on a predetermined plurality of planes coaxial with respect to a reference axis in Radon space;

retaining on each said plane only evaluated planar integral values residing within a corresponding overall projected region of support of said object in Radon space in order to truncate each said polar grid to represent source beams actually penetrating said object;

reconstructing a two dimensional projected image of said object onto each said plane from said retained integral values using parallel processing;

organizing said plurality of two dimensional projection image data from said plurality of coaxial planes onto a plurality of planes slicing normally through said reference axis; and

reconstructing two dimensional images on each planar slice using parallel processing to collectively provide a three dimensional reconstructed image of said object.

2. Method according to claim 1 wherein said detector comprises a planar detector.

3. Method according to claim 1 wherein said preselected scanning trajectory is selected to ensure the acquisition of a uniform distribution of Radon data.

4. Method according to claim 1 wherein said scanning trajectory provides a complete set of Radon data for exact image reconstruction from normal projection data.

5. Method according to claim 1, wherein the step of retaining only evaluated planar integral values residing within the overall shape of the projected region of support of the object further comprises making applicable computational approximations in redistributing retained Radon data consistent with the overall shape of the object.

6. Method according to claim 5 wherein the overall shape of the object being substantially flat extends much less in one dimension than in any other orthogonal dimension.

7. An apparatus for acquiring and processing only necessary Radon data for image reconstruction of a three dimensional object irradiated by a mutually spaced scanning source having improved computational efficiency, said apparatus comprising:

a radiation beam source;

array radiation detector means fixed with respect to said mutually spaced source;

means for scanning said irradiated object along a preselected scanning trajectory by rotating said object relative to said mutually spaced source;

detector means providing a plurality of source beam attenuation data corresponding to a plurality of source positions;

means for acquiring said plurality of source beam attenuation data;

means for selective computational processing reconstructing a three dimensional image of said object by a Radon inversion technique;

said processing means selectively retaining a truncated Radon data set representing a subset ot source beam attenuation data wherein said beams actually penetrate the object;

said processing means including means for suitably organizing and redistributing computational processing said truncated data set to provide faster parallel processing;

a plurality of parallel processors for converting said plurality of source beam attenuation data into a corresponding plurality of planar integrals in Radon space subset therof being retained as said truncated Radon data see for computationally reconstructing only Radon data necessary for image reconstruction of said object alone;

means for storing and retrieving computations; and

means for displaying computations.

8. Apparatus according to claim 7 further comprising cone beam radiation source.

9. Apparatus according to claim 7 further comprising planar detection means.

10. Apparatus according to claim 7 wherein said scanning trajectory acquires a complete set of Radon data exact image reconstruction.

11. Apparatus according to claim 7 wherein said means for data acquisition comprises means for discretely sampling select projection data to provide a uniform distribution of Radon data.