Image reconstruction methods

• US 5,644,612 A
• Filed: 04/10/1995
• Issued: 07/01/1997
• Est. Priority Date: 01/25/1993
• Status: Expired due to Term

• Current Assignee: Airdrie Partners I LP
• Original Assignee: Cardiac Mariners, Inc. (NovaRay Medical, Inc.)
• Inventors: Fiekowsky, Peter J., Solomon, Edward G., Moorman, Jack W., Melen, Robert E., Moorhouse, Abigail A., Wilent, deceased, John W.
• Primary Examiner(s): WONG, DON KITSUN
• Application Number:
  US08/419,730
• Time in Patent Office: 813 Days
• Field of Search: 378/98, 378/145, 378/146, 378/98.6, 378/4, 378/19, 378/98.2
• US Class Current: 378/98.2
• CPC Class Codes: A61B 6/06 Diaphragms
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies
• CPC Class Codes: A61B 6/4028 resulting in acquisition of views from substantially different positions, e.g. EBCT
• CPC Class Codes: A61B 6/4042 K-edge filters
• CPC Class Codes: A61B 6/4241 using energy resolving detectors, e.g. photon counting
• CPC Class Codes: A61B 6/4488 Means for cooling A61B6/045 takes precedence
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 90/39 Markers, e.g. radio-opaque or breast lesions markers
• CPC Class Codes: A61M 25/0108 using radio-opaque or ultrasound markers
• CPC Class Codes: G01T 1/20182 Modular detectors, e.g. tiled scintillators or tiled photodiodes stacked detectors G01T1/20181
• CPC Class Codes: G01T 1/20183 Arrangements for preventing or correcting crosstalk, e.g. optical or electrical arrangements for correcting crosstalk
• CPC Class Codes: G01T 1/20185 Coupling means between the photodiode and the scintillator, e.g. optical couplings using adhesives with wavelength-shifting fibres
• CPC Class Codes: G01T 1/202 the detector being a crystal
• CPC Class Codes: G01T 1/2971 using solid state detectors
• CPC Class Codes: G21K 1/025 using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation
• CPC Class Codes: H01J 35/147 Spot size control
• CPC Class Codes: H01J 35/153 Spot position control
• CPC Class Codes: H05G 1/10 Power supply arrangements for feeding the X-ray tube supply circuits with converters in general H02M; supply circuits for emitters and amplifiers H04B1/16 - H04B1/1623
• CPC Class Codes: H05G 1/64 Circuit arrangements for X-ray apparatus incorporating image intensifiers
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

An x-ray imaging system according to the present invention comprising a stepped scanning-beam x-ray source and a multi-detector array. The output of the multi-detector array is input to an image reconstruction engine which combines the outputs of the multiple detectors over selected steps of the x-ray beam to generate an x-ray image of the object. A collimating element, preferably in the form of a perforated grid containing an array of apertures, interposed between the x-ray source and an object to be x-rayed. A maneuverable positioner incorporating an x-ray sensitive marker allowing the determination of the precise position coordinates of the maneuverable positioner.

Claims

1. An imaging method comprising the steps of:

stepping an electron beam across an x-ray source in a pattern of steps AP_x by AP_y, to generate x-ray beams which pass through the object to be imaged before intersecting an array of DET_x by DET_y detectors;

measuring the x-ray intensity detected by each of the detectors comprising the detector array;

storing, in a memory, the equivalent of a data array (IMAGE) of size DET_x by DET_y containing the information indicative of the intensity measured by each detector for each step of the electron beam;

storing, in memory, the equivalent of a four dimensional array (PIXEL) of size DET_x by DET_y by AP_x by AP_y containing the IMAGE data for each step of the electron beam;

generating output values for forming the equivalent of a two dimensional array (OUTIMAGE) of size IP_x by IP_y, where OUTIMAGE(x,y) has the value;

##EQU9## where focus is a number between 0.1 and 10.0;

outputting the output values for analysis.

2. The method of claim 1 wherein the x-ray beams are passed through x-ray transmissive areas of a collimator before they are passed through the object to be imaged.

3. The method of claim 2 wherein the x-ray transmissive areas are cylindrically shaped and each of whose axis intersects the detector array substantially at the center of the array.

4. The method of claim 1 where FOCUS corresponds to a factor of the proportionate distance of the plane of the object to be imaged and the x-ray source, and of the ratio of the spacing between the centers of adjacent detectors and the spacing between the steps of the electron beam.

5. An imaging method comprising the steps of:

stepping an electron beam across an x-ray source in a pattern of steps AP_x by AP_y, to generate x-ray beams pass through the object to be imaged before intersecting an array of DET_x by DET_y detectors;

measuring the x-ray intensity detected by each of the detectors comprising the detector array;

digitizing the x-ray intensity values from each of the DET_x by DET_y detectors;

storing, in memory, the equivalent of a two dimensional matrix (SENSOR) of size DET_x by DET_y containing the digitized information indicative of the intensity measured by each detector for each step of the electron beam;

summing SENSOR(j,i) for j=1 to DET_y and i=1 to DET_x into a destination image pixel array DEST(y-j*FOCUS, x-i*FOCUS) to obtain an output value, where FOCUS is a number between 0.1 and 10.0;

outputting the output values for analysis.

6. The method of claim 5 wherein the output values are normalized by dividing each value by DET_x *DET_y.

7. The method of claim 5 wherein the x-ray beams are passed through x-ray transmissive areas of a collimator before they are passed through the object to be imaged.

8. The method of claim 7 wherein the x-ray transmissive areas are cylindrically shaped and each of whose axis intersects the detector array substantially at the center of the array.

9. The method of claim 5 where FOCUS corresponds to a factor of the proportionate distance of the plane of the object to be imaged and the x-ray source, and of the ratio of the spacing between the centers of adjacent detectors and the spacing between the steps of the electron beam.

10. A method for generating a three dimensional image comprising

stepping an electron beam across an x-ray source in a pattern of steps AP_x by AP_y, to generate x-ray beams which pass through a plane of the object to be imaged before intersecting an array of DET_x by DET_y detectors;

measuring the x-ray intensity detected by each of the detectors comprising the detector array;

storing, in a memory, the equivalent of a data array (IMAGE) of size DET_x by DET_y containing the information indicative of the intensity measured by each detector for each step of the electron beam;

storing, in memory, the equivalent of a four dimensional array (PIXEL) of size DET_x by DET_y by AP_x by AP_y containing the IMAGE data for each step of the electron beam;

generating first output values for forming the equivalent of a two dimensional array (OUTIMAGE1) of size IP_x by IP_y, where OUTIMAGE1(x,y) has the value;

##EQU10## where FOCUS1 is a number between 0.1 and 10.0 and corresponds to the location of a first plane in the object to be imaged;

generating second output values for forming the equivalent of a two dimensional array (OUTIMAGE2) of size IP_x by IP_y, where OUTIMAGE2(x,y) has the value;

##EQU11## where FOCUS2 is a number between 0.1 and 10.0 and corresponds to the location of a second plane in the object to be imaged;

outputting the first and second output values for analysis.

11. The method of claim 10 wherein the ratio of the distance of a plane of the object to be imaged from the x-ray source, and the distance between the detector array and the x-ray source (ZRATIO) is a known real number corresponding to planes between the detector array and the x-ray source;

the ratio of the spacing between the steps of the electron beam and the centers of the detectors (PIXELRATIO) is known; and

, FOCUS1 is equal to ZRATIO1*PIXELRATIO and FOCUS2 is equal to ZRATIO2*PIXELRATIO.

12. The method of claim 10 wherein the x-ray beams are passed through x-ray transmissive areas of a collimator before they are passed through the object to be imaged.

13. The method of claim 12 wherein the x-ray transmissive areas are cylindrically shaped and each of whose axis intersects the detector array substantially at the center of the array.