Method for tracing organ motion and removing artifacts for computed tomography imaging systems

• US 6,236,705 B1
• Filed: 06/17/1999
• Issued: 05/22/2001
• Est. Priority Date: 06/17/1998
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Stergiopoulos, Stergios, Dhanantwari, Amar C.
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US09/334,640
• Time in Patent Office: 705 Days
• Field of Search: 378/4, 378/8, 378/15, 378/901
• US Class Current: 378/8
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A method of tracking organ motion and removing motion artifacts in X-ray computer tomography scans is disclosed. An object is irradiated by two sources such that the object is irradiated from a same location at two different time instances. Projection measurement data are detected by a receiving sensor array. The projection measurement data of the object irradiated from the same location at the two different time instances are correlated using a spatial overlap correlator method in order to obtain data indicative of organ motion. The projection measurement data and the data indicative of organ motion are then processed using an adaptive processing method to remove artifacts due to organ motion.

Claims

1. A method of tracking motion present during computer tomography scan data acquisition of an object, the method comprising the steps of:

capturing a plurality of image pairs, each image within an image pair captured from substantially a same perspective view of the object;

comparing each image within an image pair of the image pairs to another image of the same image pair to extract differences; and

,

determining motion using the extracted differences.

2. A method of tracking motion present during computer tomography scan data acquisition of an object as defined in claim 1, wherein the step of capturing a plurality of image pairs comprises the steps of:

a) disposing a source at a first position;

b) emitting energy and capturing an image;

c) altering a parameter of the system such that the emitted energy appears to originate from a second other position;

d) emitting energy and capturing an image;

e) moving the source to the second other position; and

,

iterating steps (b) through (e) wherein the second other position is a different position from the second other position of a previous iteration.

3. A method of tracking motion present during computer tomography scan data acquisition of an object as defined in claim 1, wherein the motion is determined as an amplitude difference between data indicative of the compared images.

4. A method of removing motion artifacts in image data of computer tomography scans of an object comprising the steps of:

providing to a processor image data of the object, the image data containing motion artifacts due to motion of the object;

providing to the processor data indicative of the motion of the object; and

,

using the processor, removing the motion artifacts from the image data using adaptive interference canceling.

5. A method of removing motion artifacts in reconstructed images of computer tomography scans of an object as defined in claim 4, wherein the image data and the data indicative of the motion of the object are provided to the processor as sensor time series.

6. A method of tracking motion of components of an object present during computer tomography scan data acquisition of the object, the method comprising the steps of:

rotating intermittently a scanner comprising a source and a receiving sensor array in angular step increments around the object such that the object is irradiated from successive locations at successive time instances;

acquiring projection measurement data at each time instance using the receiving sensor array; and

,

providing to a processor the projection measurement data for processing;

processing the projection measurement data, the processing comprising the steps of;

determining successive sensor time series segments, each segment being associated with a full rotation of the scanner and a time difference Δ

t to a previous segment;

determining an amplitude difference between successive time series segments; and

,

determining data indicative of organ movement by processing the amplitude differences using a filter back-projection algorithm.

7. A method of tracking motion of components of an object present during computer tomography scan data acquisition of the object as defined in claim 6, wherein the scanner is rotated a plurality of full rotations.

8. A method of tracking motion of components of an object present during computer tomography scan data acquisition of the object as defined in claim 7, comprising the step of:

using the processor for generating an animated image tracking organ movement.

9. A computer tomography system for acquiring projection image data of an object and for tracking motion of the object during the data acquisition comprising:

a source disposed at a first position for emitting energy in order to irradiate the object;

a receiving sensor array for capturing image pairs, wherein each image within an image pair is captured from substantially a same perspective view of the object;

means for irradiating the object such that the emitted energy appears to originate from a second other position;

a mechanism for moving the source to the second other position; and

,

a processor for comparing the image pairs to extract differences and for determining motion using the extracted differences.

10. A computer tomography system for acquiring projection image data of an object and for tracking motion of the object during the data acquisition as defined in claim 9, wherein the means for irradiating the object such that the emitted energy appears to originate from a second other position comprises a second other source.

11. A computer tomography system for acquiring projection image data of an object and for tracking motion of the object during the data acquisition as defined in claim 9, wherein the means for irradiating the object such that the emitted energy appears to originate from a second other position comprises a flying focal point.

12. A method of tracking phases of a motion cycle of an object present during computer tomography scan data acquisition of the object, the method comprising the steps of:

a) providing to a processor sensor time series, the sensor time series being indicative of projection image data of the object;

b) using the processor, processing the sensor time series to determine spatial overlap correlator time series indicative of amplitude and direction of the object motion;

c) determining a phase of interest of the motion cycle; and

,

d) autocorrelating the spatial overlap correlator time series with respect to the phase of interest.

13. A method of tracking phases of a motion cycle of an object present during computer tomography scan data acquisition of the object as defined in claim 12, comprising the step of smoothing the spatial overlap correlator time series.

14. A method of tracking phases of a motion cycle of an object present during computer tomography scan data acquisition of the object as defined in claim 12, wherein the steps c) and d) are repeated for different phases of interest.

15. A method of tracking phases of a motion cycle of an object present during computer tomography scan data acquisition of the object as defined in claim 12, comprising the steps of:

e) selecting segments of the spatial overlap correlator time series, the segments being indicative of projection image data of the object, the object being at the phase of interest of the motion cycle;

f) creating a sinogram of the object at the phase of interest from the selected segments; and

,

g) reconstructing an image of the object at the phase of interest using the sinogram.

16. A method of tracking phases of a motion cycle of an object present during computer tomography scan data acquisition of the object as defined in claim 15, wherein the segments are selected based on a level of correlation of the autocorrelated sensor time series.

17. A method of tracking phases of a motion cycle of an object present during computer tomography scan data acquisition of the object as defined in claim 15, wherein missing segments of the sinogram are obtained by interpolation.

18. A method of tracking phases of a motion cycle of an object present during computer tomography scan data acquisition of the object as defined in claim 15, wherein the steps are e), f) and g) are repeated for different phases of interest to create a motion picture.