Method and apparatus for calibrating an imaging system

• US 6,632,020 B2
• Filed: 10/12/2001
• Issued: 10/14/2003
• Est. Priority Date: 10/12/2001
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Thomas, Jerry A., Eberhard, Jeffrey Wayne, Tkaczyk, John Eric, Kaufhold, John Patrick, Gonzalez Trotter, Dinko E.
• Primary Examiner(s): Dunn, Drew A.
• Assistant Examiner(s): THOMAS, COURTNEY D
• Application Number:
  US09/975,892
• Publication Number:
  US 20030072417A1
• Time in Patent Office: 732 Days
• Field of Search: 378/207, 378/62, 378/98.8, 378/51, 378/53, 378/56, 250/252.1
• US Class Current: 378/207
• CPC Class Codes: A61B 6/4035 the source being combined with a filter or grating
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/583 using calibration phantoms

Abstract

A method for calibration of an imaging system includes providing a calibration phantom system including a first phantom element material block having a first surface at a first height, wherein the first phantom element material block at least partially includes a first material having a first attenuation coefficient. Providing a calibration phantom system also includes providing a second phantom element material block having a second surface at a second height different than the first height, the second phantom element material block at least partially including a second material having a second attenuation coefficient different than the first attenuation coefficient, wherein the first phantom element material block and said second phantom element material block are co-positioned on a detector. The method also includes imaging the calibration phantom system to obtain phantom images, processing the phantom images, and extracting a plurality of calibration values from the processed phantom images.

Claims

1. A calibration phantom system for use with an imaging system, said calibration phantom comprising:

a first phantom element material block having a first surface at a first height, said first phantom element material block at least partially comprising a first material having a first attenuation coefficient;

a second phantom element material block having a second surface at a second height different than said first height, said second phantom element material block at least partially comprising a second material having a second attenuation coefficient different than said first attenuation coefficient, said first phantom element material block and said second phantom element material block co-positioned on a detector;

a first radiation shielding plate positioned on top of said first phantom element material block, said first radiation shield plate having at least one opening extending therethrough; and

a second radiation shielding plate positioned on top of said second phantom element material block, said second radiation shield plate having at least one opening extending therethrough.

2. A calibration phantom element material block in accordance with claim 1 wherein said first phantom element material block is substantially rectangular.

3. A calibration phantom system in accordance with claim 1 wherein said first radiation shielding plate is substantially rectangular.

4. A calibration phantom system in accordance with claim 1 wherein said element material block comprise a breast-equivalent material.

5. A calibration phantom system in accordance with claim 1 wherein said first phantom element and said second phantom elements are co-positioned in decreasing order of attenuation coefficients.

6. A calibration phantom system in accordance with claim 1 wherein said radiation shielding plate extends over a surface of said element material block.

7. A calibration phantom system in accordance with claim 1 wherein said radiation shielding plate comprises a metallic material.

8. A calibration phantom system in accordance with claim 7 wherein said radiation shielding plate at least partially comprises at least one of lead, tungsten, and aluminum.

9. A method for calibration of an imaging system, the imaging system including a radiation source and a digital detector, said method comprising:

providing a calibration phantom system including a first phantom element material block having a first surface at a first height, said first phantom element material block at least partially comprising a first material having a first attenuation coefficient, and a second phantom element material block having a second surface at a second height different than said first height, said second phantom element material block at least partially comprising a second material having a second attenuation coefficient different than said first attenuation coefficient, said first phantom element material block and said second phantom element material block co-positioned on a detector;

imaging the calibration phantom system to obtain phantom images using the digital detector and radiation source;

processing the phantom images;

extracting a plurality of calibration values from the processed phantom images; and

using the calibration values to adjust a plurality of pixel intensities in the acquired images.

10. A method in accordance with claim 9 wherein imaging the calibration phantom system comprises:

positioning the calibration phantom system on the digital detector;

setting image acquisition parameters for at least one image; and

acquiring at least one digital image and at least one film-screen image.

11. A method in accordance with claim 9 wherein processing the phantom images comprises:

pre-processing at least one phantom image;

estimating a scatter kernel of at least one pre-processed image;

estimating the primary x-ray events on the detector using the scatter kernel estimates; and

estimating a radiation pixel noise using the primary x-ray events.

12. A method in accordance with claim 11 wherein estimating a scatter kernel comprises estimating a scatter kernel using a radiation shielding plate having at least one opening extending therethrough.

13. A method in accordance with claim 12 wherein using a radiation shielding plate comprises using a radiation shielding plate which extends over a surface of an element material block.

14. A method in accordance with claim 9 wherein extracting a plurality of calibration values from the processed phantom images comprises extracting calibration values from the processed image to calculate a calibration curve.

15. A method for calibration of an imaging system, the imaging system including a radiation source and a digital detector, said method comprising:

providing a calibration phantom system including a first phantom element material block having a first surface at a first height, said first phantom element material block at least partially comprising a first material having a first attenuation coefficient, and a second phantom element material block having a second surface at a second height different than said first height, said second phantom element material block at least partially comprising a second material having a second attenuation coefficient different than said first attenuation coefficient, said first phantom element material block and said second phantom element material block co-positioned on a detector;

imaging the calibration phantom system to obtain phantom images, wherein said imaging comprises positioning the calibration phantom system on the digital detector;

setting image acquisition parameters for at least one image, and acquiring at least one digital image and at least one film-screen image;

processing the phantom images, wherein said processing comprises pre-processing at least one phantom image, estimating a scatter kernel of at least one pre-processed image, estimating the primary x-ray events on the detector using the scatter kernel estimates, and estimating a radiation pixel noise using the primary x-ray events; and

extracting a plurality of calibration values from the processed phantom images.

16. A computer readable medium encoded with a program executable by a computer for calibration of an imaging system, the imaging system including a radiation source and a digital detector, said program configured to instruct the computer to:

image the calibration phantom system to obtain phantom images, wherein the calibration phantom system includes a first phantom element material block having a first surface at a first height, said first phantom element material block at least partially comprising a first material having a first attenuation coefficient, and a second phantom element material block having a second surface at a second height different than said first height, said second phantom element material block at least partially comprising a second material having a second attenuation coefficient different than said first attenuation coefficient, said first phantom element material block and said second phantom element material block co-positioned on a detector, a first radiation shielding plate positioned on top of said first phantom element material block, said first radiation shield plate having at least one opening extending therethrough; and

a second radiation shielding plate positioned on top of said second phantom element material block, said second radiation shield plate having at least one opening extending therethrough;

process the phantom images;

extract a plurality of calibration values from the processed phantom images.

17. A computer readable medium in accordance with claim 16 wherein to image the calibration phantom system, said program further configured to:

position the calibration phantom system on the digital detector;

set image acquisition parameters for at least one image; and

acquire at least one digital image and at least one film-screen image.

18. A computer readable medium in accordance with claim 16 wherein to process the phantom images, said program further configured to:

pre-process at least one phantom image;

estimate a scatter kernel of at least one pre-processed image;

estimate the primary x-ray events on the detector using the scatter kernel estimates; and

estimate a radiation pixel noise using the primary x-ray events.

19. A computer readable medium in accordance with claim 18 wherein to estimate a scatter kernel, said program further configured to estimate a scatter kernel using a radiation shielding plate.

20. A computer readable medium in accordance with claim 16 wherein to extract a plurality of calibration values from the processed phantom images, said program further configured to extract calibration values from the processed image to calculate a calibration curve.

21. A computer readable medium in accordance with claim 18 wherein to estimate a scatter kernel, said program further configured to estimate a scatter kernel using a radiation shielding plate extending over a surface of an element material block.

23. A computer readable medium in accordance with claim 20 wherein to estimate a scatter kernel, said program further configured to estimate a scatter kernel using a radiation shielding plate extending over a surface of an element material block.

22. A computer readable medium encoded with a program executable by a computer for calibration of an imaging system, the imaging system including a radiation source and a digital detector, said program configured to instruct the computer to:

provide a calibration phantom system including a first phantom element material block having a first surface at a first height, said first phantom element material block at least partially comprising a first material having a first attenuation coefficient, and a second phantom element material block having a second surface at a second height different than said first height, said second phantom element material block at least partially comprising a second material having a second attenuation coefficient different than said first attenuation coefficient, said first phantom element material block and said second phantom element material block co-positioned on a detector;

image the calibration phantom system to obtain phantom images, wherein said imaging comprises positioning the calibration phantom system on the digital detector;

setting image acquisition parameters for at least one image, and acquiring at least one digital image and at least one film-screen image;

process the phantom images, wherein said processing comprises pre-processing at least one phantom image, estimating a scatter kernel of at least one pre-processsed image, estimating the primary x-ray events on the detector using the scatter kernel estimates, and estimating a radiation pixel noise using the primary x-ray events; and

extract a plurality of calibration values from processed phantom images.