Method and system for creating task-dependent three-dimensional images

• US 6,081,577 A
• Filed: 02/19/1999
• Issued: 06/27/2000
• Est. Priority Date: 07/24/1998
• Status: Expired due to Fees

• Current Assignee: Wake Forest University Health Sciences
• Original Assignee: Wake Forest University
• Inventors: Webber, Richard L.
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US09/252,632
• Time in Patent Office: 494 Days
• Field of Search: 378/4, 378/21, 378/22, 378/23, 378/62, 378/98.12, 378/207, 378/210, 378/901
• US Class Current: 378/23
• CPC Class Codes: A61B 6/5258 involving detection or reduction of artifacts or noise
• CPC Class Codes: A61B 6/548 Remote control of the apparatus or devices
• CPC Class Codes: G01N 2223/419 computed tomograph
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A system and method for producing three-dimensional representations of an object. A first series of projected images of the selected object is recorded in a first projection plane and a second series of projected images of the selected object is recorded in a second projection plane. The first and the second series of projected images are rendered at a common magnification. The first set of projected images is then integrated into a first three-dimensional volume and the second set of projected images is integrated into a second three-dimensional volume. The three-dimensional representation of the object is then produced by combining one projected image from the first set of projected images with one projected image from the second set of projected images. Alternatively, the three-dimensional representation is produced by merging the first three-dimensional volume with the second three-dimensional volume.

Claims

1. A system for synthesizing a three-dimensional representation of a selected object from a plurality of projected radiographic images of the selected object comprising:

a. at least one radiographic recorder for recording radiographic images of the selected object;

b. at least one source of radiation for irradiating the selected object to enable projected radiographic images of the selected object to be recorded on the radiographic recorder;

c. an image synthesizer for synthesizing a three-dimensional representation of the selected object from selected projections of the projected radiographic images recorded on the radiographic recorder; and

d. a display for displaying the three-dimensional representation, the display comprising;

i. stereoscopic spectacles to be worn by an observer;

ii. a target operatively connected to the stereoscopic spectacles;

iii. a detector operatively associated with the target for tracking movement of the target; and

iv. a monitor connected to the detector for receiving a signal from the detector indicative of movement of the target and for displaying an image pair of the three-dimensional representation in response to the signal.

2. A method for producing a three-dimensional representation of a selected object comprising the steps of:

a. recording projected radiographic images of the selected object;

b. synthesizing a three-dimensional representation of the selected object from selected projections of the projected radiographic images; and

c. displaying an image pair of the three-dimensional representation on a monitor, wherein the displayed image pair is responsive to changes in a viewing angle associated with an observer and produces a three-dimensional effect when viewed by the observer.

3. A system for synthesizing an image slice, consisting of an array of pixels with each pixel having an associated value, of a selected object at a selected slice position through the selected object from a plurality of projected radiographic images of the selected object comprising:

a. at least one radiographic recorder for recording radiographic images of the selected object, each radiographic image consisting of an array of pixels with each pixel having an associated value;

b. at least one source of radiation for irradiating the selected object to enable projected radiographic images of the selected object to be recorded on the radiographic recorder; and

c. an image synthesizer for synthesizing the image slice from selected projections of the projected radiographic images, wherein the image synthesizer comprises means for assigning a value to each pixel of the image slice equal to a non-linear combination of the attenuation values of a set of corresponding pixels in the projected images.

4. A method for synthesizing an image slice, consisting of an array of pixels with each pixel having an associated value, of a selected object at a selected slice position through the selected object from a plurality of projected radiographic images of the selected object comprising the steps of:

a. recording radiographic images of the selected object wherein each radiographic image consists of an array of pixels with each pixel having an associated value; and

b. synthesizing the image slice from selected projections of the projected radiographic images, wherein the synthesizing step comprises the step of assigning a value to each pixel of the image slice equal to a non-linear combination of the values of a set of corresponding pixels in the projected images.

5. The method of claim 4 wherein each set of corresponding pixels has a maximum value and the step of assigning a value to each pixel of the image slice comprises the step of assigning a value to each pixel of the image slice equal to the maximum value of the set of corresponding pixels.

6. The method of claim 4 wherein each set of corresponding pixels has a minimum value and the step of assigning a value to each pixel of the image slice comprises the step of assigning a value to each pixel of the image slice equal to the minimum value of the set of corresponding pixels.

7. A method for determining temporal changes of a selected object comprising the steps of:

a. generating a first set of slices of the selected object;

b. generating a second set of slices of the selected object;

c. correlating each slice of the first set of slices with a corresponding slice of the second set of slices;

d. aligning each slice of the first set of slices with the corresponding slice of the second set of slices to maximize the overlap of each slice of the first set of slices with the corresponding slice of the second set of slices; and

e. determining a difference between each slice of the first set of slices and the corresponding slice of the second set of slices.

8. A system for calibrating an uncollimated x-ray beam comprising:

a. at least one radiographic recorder for recording a gradient image;

b. at least one source of radiation to be calibrated; and

c. a source comparator positionable between the radiographic recorder and the source of radiation for producing the gradient image indicative of characteristics associated with the x-ray beam.

9. The system of claim 8 wherein the source comparator comprises two wedges, each wedge having a rectangular base defining two opposing edges and two right-triangular faces, wherein the right-triangular faces of each wedge lie in parallel planes at each of the opposing edges of the base such that the triangular faces are oriented as mirror images of each other to provide a tapered edge and wherein the wedges are arranged with the base of one wedge adjacent to the base of the other wedge with the tapered edges of the wedges forming a 90°

angle.

10. A method for matching an output of a first radiation source with an output of a second radiation source comprising the steps of:

a. positioning a source comparator between the first radiation source and a detector;

b. exposing the source comparator to the output from the first radiation source to record a first gradient image on the detector;

c. positioning the source comparator between the second radiation source and a detector; and

d. adjusting the output from the second radiation source so that a second gradient image, recorded by exposing the source comparator to the output from the second radiation source, resembles the first gradient image.

11. The method of claim 10 wherein the step of adjusting the output from the second radiation source comprises the steps of:

a. adjusting a beam energy of the second radiation source so that a measured gradient value associated with the second gradient image approaches a measured gradient value associated with the first gradient image;

b. adjusting a filtration of the second radiation source so that an angle of maximum gradient relative to an edge of the source comparator associated with the second gradient image approaches an angle of maximum gradient relative to an edge of the source comparator associated with the first gradient image; and

c. adjusting the second radiation source so that a beam exposure associated with the second gradient image approaches a beam exposure associated with the first gradient image.

12. The method of claim 10 wherein the positioning steps comprise the step of positioning a source comparator comprising two wedges, each wedge having a rectangular base defining two opposing edges and two right-triangular faces, wherein the right-triangular faces of each wedge lie in parallel planes at each of the opposing edges of the base such that the triangular faces are oriented as mirror images of each other to provide a tapered edge and wherein the wedges are arranged with the base of one wedge adjacent to the base of the other wedge with the tapered edges of the wedges forming a 90°

angle.

13. A method for synthesizing an image of a selected object at a selected slice position through the selected object from a plurality of projected radiographic images of the selected object comprising the steps of:

a. providing at least one radiographic recorder for recording radiographic images of the selected object;

b. identifying at least one fiducial reference in fixed position relative to the selected object, the fiducial reference defining a first and a second object point;

c. providing at least one source of radiation for irradiating the selected object to enable projected radiographic images of the selected object and the fiducial reference to be recorded on the radiographic recorder;

d. recording projected radiographic images of the selected object and the fiducial reference at different relative positions between (1) the source of radiation, (2) the selected object and the fiducial reference, and (3) the radiographic recorder, each projected radiographic image comprising a first reference image associated with the first object point and a second reference image associated with the second object point;

e. transforming the projected radiographic image to render each of the projected radiographic images at a common magnification;

f. shifting each of the projected radiographic images by an amount sufficient to align the first reference images of each projected radiographic image;

g. determining a projected reference image distance for each projected radiographic image, the projected reference image distance corresponding to a measured distance between the first and the second reference images; and

h. determining the position of the radiation source within a plane parallel to an image plane from an estimate of an actual distance between the first and the second object points obtained using a sinusoidal curve fitting procedure.

14. A method for synthesizing a three-dimensional representation of a selected object from a plurality of projected radiographic images of the selected object comprising the steps of:

a. providing at least one radiographic recorder for recording radiographic images of the selected object;

b. providing at least one fiducial reference in fixed position relative the selected object;

c. providing at least one source of radiation for irradiating the selected object and the fiducial reference to enable projected radiographic images of the selected object and the fiducial reference to be recorded on the radiographic recorder;

d. recording a first projected radiographic image of the selected object in a first projection plane;

e. recording a second projected radiographic image of the object in a second projection plane, the second projection plane intersecting the first projection plane at a known angle;

f. transforming each of the first and the second projected radiographic images to render each of the projected radiographic images at a common magnification;

g. using the known angle between the first and the second projection planes to transform the first and the second projected radiographic images such that the first and the second projected radiographic images occupy the same volume; and

h. combining the first and second projected radiographic images into a three-dimensional representation of the selected object.

15. The method of claim 14 comprising the step of limiting the three-dimensional representation to the logical intersection of the first and second projected radiographic images.

16. The method of claim 14 comprising the steps of:

a. recording a third projected radiographic image in a third projection plane, the third projection plane intersecting the first projection plane at a second known angle;

b. transforming the third projected radiographic image to render the third projected radiographic image at the common magnification;

c. using the second known angle between the first and the third projection planes to transform the third projected radiographic image such that the first, the second, and the third projected radiographic images occupy the same volume; and

d. combining the third projected radiographic image with the three-dimensional representation of the selected object.

17. A method for synthesizing a three-dimensional representation of a selected object from a plurality of projected radiographic images of the selected object comprising the steps of:

a. providing at least one radiographic recorder for recording radiographic images of the selected object;

b. providing at least one fiducial reference in fixed position relative the selected object;

c. providing at least one source of radiation for irradiating the selected object and the fiducial reference to enable projected radiographic images of the selected object and the fiducial reference to be recorded on the radiographic recorder;

d. recording a first set of projected radiographic images of the selected object;

e. recording a second set of projected radiographic images of the object;

f. integrating the first set of projected radiographic images into a first three-dimensional volume and integrating the second set of projected radiographic images into a second three-dimensional volume;

g. transforming each of the first and the second three-dimensional volumes to render each of the first and the second three-dimensional volumes at a common magnification;

h. rotating the second three-dimensional volume by an angle corresponding to the angular disparity between the first and the second three-dimensional volumes; and

i. merging the first and the second three-dimensional volumes to form a three-dimensional representation of the selected object.