Method and apparatus for calibrating an imaging system

• US 20030072417A1
• Filed: 10/12/2001
• Published: 04/17/2003
• Est. Priority Date: 10/12/2001
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Thomas, Jerry A., Gonzalez Trotter, Dinko E., Eberhard, Jeffrey Wayne, Tkaczyk, John Eric, Kaufhold, John Patrick
• Granted Patent: US 6,632,020 B2
• Time in Patent Office: Days
• 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, the imaging system including a radiation source and a digital detector. The method 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

11. 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;

a radiation shielding plate positioned on top of said first phantom element material block; 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.

13. 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;

processing the phantom images; and

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

14. A method in accordance with claim 13 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.

15. A method in accordance with claim 13 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

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

16. A method in accordance with claim 13 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.

17. A method in accordance with claim 15 wherein estimating a scatter kernel comprises estimating a scatter kernel using a radiation shielding plate.

18. A method in accordance with claim 17 wherein using a radiation shielding plate comprises using an radiation shielding plate which extends over a surface of an element material block.

19. 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.

20. 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;

process the phantom images;

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

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; 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.

2. A calibration phantom system in accordance with claim 1 further comprising a first radiation shielding plate positioned on top of said first phantom element material block and a second radiation shielding plate positioned on top of said second phantom element material block

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

4. A calibration phantom system in accordance with claim 2 wherein said first radiation shielding plate is substantially rectangular.

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

6. 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.

7. A calibration phantom system in accordance with claim 2 wherein said radiation shielding plate extends over a surface of said element material block.

8. A calibration phantom system in accordance with claim 2 wherein said radiation shielding plate comprises an opening.

9. A calibration phantom system in accordance with claim 2 wherein said radiation shielding plate comprises a metallic material.

10. A calibration phantom system in accordance with claim 9 wherein said radiation shielding plate at least partially comprises at least one of lead, tungsten, and aluminum.

21. A computer readable medium in accordance with claim 20 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.

22. A computer readable medium in accordance with claim 20 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.

23. A computer readable medium in accordance with claim 20 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.

24. A computer readable medium in accordance with claim 22 wherein to estimate a scatter kernel, said program further configured to estimate a scatter kernel using a radiation shielding plate.

24-1. A computer readable medium in accordance with claim 22 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.

25. 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-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

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