Methods and apparatus for obtaining low-dose imaging

• US 7,570,732 B2
• Filed: 11/22/2006
• Issued: 08/04/2009
• Est. Priority Date: 11/09/2005
• Status: Expired due to Fees

• Current Assignee: Dexela Limited (Varex Imaging Corporation)
• Original Assignee: Dexela Limited (Varex Imaging Corporation)
• Inventors: Bullard, Edward, Stewart, Alexander, Stanton, Martin
• Primary Examiner(s): SONG, HOON K
• Application Number:
  US11/603,876
• Publication Number:
  US 20070242794A1
• Time in Patent Office: 986 Days
• Field of Search: 378 4- 20, 378/901, 378/108, 378/207
• US Class Current: 378/7
• CPC Class Codes: A61B 6/02 Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
• CPC Class Codes: A61B 6/405 Source units specially adapted to modify characteristics of the beam during the data acquisition process A61B6/4021, A61B6/4035 take precedence
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/4291 the detector being combined with a grid or grating
• CPC Class Codes: A61B 6/466 adapted to display 3D data
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/502 for diagnosis of breast, i.e. mammography
• CPC Class Codes: A61B 6/5258 involving detection or reduction of artifacts or noise
• CPC Class Codes: A61B 6/542 involving control of exposure
• CPC Class Codes: G01N 2223/423 multispectral imaging-multiple energy imaging
• CPC Class Codes: G01N 23/04 and forming images of the material

Abstract

In one aspect, A method of imaging an object of interest positioned in an exposure area is provided. The method comprises obtaining projection data of the object by providing radiation to the exposure area and detecting at least some of the radiation exiting the object to form the projection data, performing a first reconstruction of the projection data to form at least one bootstrap image, obtaining first data based on information provided by the at least one bootstrap image, and performing a second reconstruction of the projection data based, at least in part, on the first data to form at least one second image.

Claims

1. A method of imaging an object of interest positioned in an exposure area, the method comprising:

obtaining projection data of the object by providing radiation from a radiation source to the exposure area and detecting, by at least one detector, at least some of the radiation exiting the object to form the projection data;

performing a first reconstruction of the projection data to form at least one bootstrap image;

obtaining first data based on information provided by the at least one bootstrap image including estimating an exit spectrum indicative of the energy spectrum of radiation exiting the object based, at least in part, on density information provided by the at least one bootstrap image; and

performing a second reconstruction of the projection data based, at least in part, on the first data to form at least one second image.

2. The method of claim 1, wherein estimating the exit spectrum includes estimating an emission spectrum indicative of the energy spectrum of radiation emitted by the radiation source.

3. The method of claim 2, wherein estimating the exit spectrum includes modifying the emission spectrum based on the density information in the at least one bootstrap image to estimate the exit spectrum.

4. The method of claim 1, wherein performing the second reconstruction includes performing the second reconstruction using the exit spectrum to account for at least some beam hardening effects.

5. The method of claim 1, wherein the first reconstruction is performed assuming that the detected radiation is substantially of a single energy, and the second reconstruction is performed assuming that the detected radiation includes energies distributed according to the exit spectrum.

6. The method of claim 5, wherein further comprising differentiating portions of the detected radiation contributive by respective energies in the exit spectrum.

7. The method of claim 6, further comprising, computing, from the detected radiation and based on the exit spectrum, a radiation intensity of radiation at a plurality of energies present in the exit spectrum.

8. The method of claim 7, wherein the second reconstruction is performed by reconstructing the radiation intensity for each of the plurality of energies according to a respective attenuation function characteristic of the respective energy.

9. The method of claim 1, wherein obtaining the first data includes obtaining information about locations of material within the object to facilitate estimating an amount of scattered radiation.

10. The method of claim 1, wherein obtaining first data includes obtaining boundary information indicative of a boundary of the object in the at least one bootstrap image.

11. The method of claim 10, wherein performing the second reconstruction includes using the boundary information to constrain the second reconstruction.

12. A method of imaging an object of interest positioned in an exposure area, the method comprising:

obtaining projection data of the object by providing radiation from a radiation source to the exposure area and detecting, by at least one detector, at least some of the radiation exiting the object to form the projection data;

performing a first reconstruction of the projection data to form at least one bootstrap image;

obtaining first data based on information provided by the at least one bootstrap image including obtaining information about locations of material within the object to facilitate estimating an amount of scattered radiation;

performing a second reconstruction of the projection data based, at least in part, on the first data to form at least one second image;

dividing an image of the object in the at least one bootstrap image into a plurality of regions;

determining a depth of each of the plurality of regions with respect to a reference point related to a radiation source that provides the radiation to the exposure area;

estimating an amount of scattered radiation resulting from each of the plurality of regions based on the possibility that radiation passing through the respective region would scatter at the associated depth;

summing the estimates of scattered radiation to provide an estimate of the total scattered radiation; and

modifying the projection data based, at least in part, on the estimate of the total scattered radiation.

13. A method of imaging an object of interest positioned in an exposure area, the method comprising:

obtaining projection data of the object by providing radiation from a radiation source to the exposure area and detecting, by at least one detectors, at least some of the radiation exiting the object to form the protection data;

performing a first reconstruction of the projection data to form at least one bootstrap image;

obtaining first data based on information provided by the at least one bootstrap image including obtaining boundary information indicative of a boundary of the object in the at least one bootstrap image, wherein obtaining the boundary information includes determining which pixels in the bootstrap image are outside of the boundary of the object, and wherein constraining the second reconstruction includes assigning zero-density values to pixels identified as being outside the boundary of the object; and

performing a second reconstruction of the projection data based, at least in part, on the first data to form at least one second image including using the boundary information to constrain the second reconstruction.

14. A method of imaging an object of interest positioned in an exposure area, the method comprising:

obtaining projection data of the object by providing radiation from a radiation source to the exposure area and detecting, by at least one detector, at least some of the radiation exiting the object to form the projection data;

arranging at least one density fiducial in the exposure area, prior to obtaining the projection data, such that at least some of the radiation encounters the at least one density fiducial;

performing a first reconstruction of the projection data to form at least one bootstrap image;

obtaining first data based on information provided by the at least one bootstrap image; and

performing a second reconstruction of the projection data based, at least in part, on the first data to form at least one second image.

15. The method of claim 14, wherein arranging the at least one density fiducial includes arranging at least one density fiducial in contact with the object to demarcate at least a portion of a boundary of the object.

16. The method of claim 15, wherein obtaining the first data includes obtaining boundary information indicative of a boundary of the object based at least in part on the image of the at least one density fiducial in the bootstrap image.

17. The method of claim 16, wherein reconstruction includes constraining the second reconstruction based on the boundary information.

18. The method of claim 17, wherein constraining the second reconstruction includes assigning zero-density values to regions indicated, by the boundary information, as being outside the boundary of the object.