SYSTEMS AND METHODS FOR GENERATING X-RAY PHASE CONTRAST IMAGES USING A CONVENTIONAL X-RAY IMAGING SYSTEM

• US 20150103970A1
• Filed: 10/12/2013
• Published: 04/16/2015
• Est. Priority Date: 10/12/2013
• Status: Active Grant

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Chen, Guang-Hong
• Granted Patent: US 9,155,510 B2
• Time in Patent Office: Days
• US Class Current: 378/5
• CPC Class Codes: A61B 6/03 Computed tomography [CT] echo-tomography A61B8/14
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4405 the apparatus being movable or portable, e.g. handheld or mounted on a trolley
• CPC Class Codes: A61B 6/4441 the rigid structure being a C-arm or U-arm
• CPC Class Codes: A61B 6/482 involving multiple energy imaging
• CPC Class Codes: A61B 6/484 involving phase contrast X-ray imaging
• CPC Class Codes: A61B 6/5205 involving processing of raw data to produce diagnostic data
• CPC Class Codes: A61B 6/582 Calibration
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G01J 9/00 Measuring optical phase difference devices or arrangements for controlling the phase of light beams G02F1/01; Determining degree of coherence; Measuring optical wavelength spectrometry G01J3/00
• CPC Class Codes: G01N 23/046 using tomography, e.g. computed tomography [CT]
• CPC Class Codes: G01N 23/087 using polyenergetic X-rays
• CPC Class Codes: G01N 23/20083 by using a combination of at least two measurements at least one being a transmission measurement and one a scatter measurement
• CPC Class Codes: G06T 11/005 Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating

Abstract

Described here are systems and methods for generating x-ray phase contrast images from conventional x-ray attenuation data. X-ray attenuation coefficients generated over a range of x-ray energies are used to compute the x-ray phase signal up to a calibration constant. This calibration constant is computed from provided calibration data, which may be obtained using a dedicated x-ray differential phase contrast imaging system to measure the decrement of the refractive index of a calibration phantom.

Claims

1. A method for producing an x-ray phase contrast image of an object from attenuation data acquired with an x-ray imaging system, the steps of the method comprising:

a) providing calibration data that includes a first calibration factor defining an energy dependence for a first component of x-ray attenuation and a second calibration factor defining an energy dependence for a second component of x-ray attenuation;

b) acquiring attenuation data from the object using an x-ray imaging system, the attenuation data containing attenuation information associated with x-rays having at least two different energies;

c) producing from the attenuation data, a first spatial map indicative of the first component of x-ray attenuation and a second spatial map indicative of the second component of x-ray attenuation; and

d) producing an x-ray phase contrast image using the calibration data and the first and second spatial maps.

2. The method as recited in claim 1, wherein step d) includes weighting the first spatial map with the first calibration factor, weighting the second spatial map with the second calibration factor, and combining the weighted first and second spatial maps.

3. The method as recited in claim 1, wherein step c) includes reconstructing a first image at a first energy level and a second image at a second energy level and processing the first and second images to produce the first and second spatial maps.

4. The method as recited in claim 1, wherein step a) includes acquiring phase contrast data from a calibration phantom using an x-ray phase contrast imaging system, acquiring dual energy attenuation data from the calibration phantom using an x-ray imaging system, and fitting the phase contrast data and the dual energy attenuation data to a physical model to derive the first and second calibration factors.

5. The method as recited in claim 4, wherein the physical model in step a) models a complex refractive index of x-rays.

6. The method as recited in claim 1, wherein step b) includes acquiring attenuation data associated with two different x-ray energies.

7. The method as recited in claim 6, wherein step b) includes acquiring the attenuation data using an x-ray imaging system configured to switch between a high tube potential and a low tube potential when acquiring data along adjacent view angles.

8. The method as recited in claim 6, wherein step b) includes acquiring the attenuation data using a dual-source x-ray imaging system.

9. The method as recited in claim 6, wherein step b) includes performing a first scan to acquire attenuation data at the first x-ray energy and performing a second scan to acquire attenuation data at the second x-ray energy.

10. The method as recited in claim 6, wherein step b) includes acquiring the attenuation data using an x-ray imaging system that includes a sandwich detector that discriminates attenuation data at a first energy detected in a first portion of the detector from attenuation data at a second energy in a second portion of the detector.

11. The method as recited in claim 6, wherein step b) includes acquiring the attenuation data using an x-ray imaging system that includes a photon-counting detector capable of reading out data at different energy bins.

12. The method as recited in claim 6, wherein the x-ray imaging system is at least one of a C-arm imaging system and a computed tomography imaging system.

13. The method as recited in claim 1, further comprising producing another x-ray phase contrast image indicative of an x-ray phase contrast at a different energy level than the x-ray phase contrast image produced in step d) by scaling the x-ray phase contrast image produced in step d) by a scaling factor.

14. The method as recited in claim 1, wherein the first component of x-ray attenuation quantifies x-ray attenuation associated with photoelectric effects and the second component of x-ray attenuation quantifies x-ray attenuation associated with Compton scattering.

15. The method as recited in claim 1, wherein the first component of x-ray attenuation quantifies x-ray attenuation associated with a first material and the second component of x-ray attenuation quantifies x-ray attenuation associated with a second material.

16. The method as recited in claim 15, wherein the first material is water and the second material is bone.

17. The method as recited in claim 15, wherein step a) includes:

acquiring phase contrast data from a calibration phantom using an x-ray phase contrast imaging system, wherein the calibration phantom contains materials with similar attenuation properties as the first and second materials;

acquiring dual energy attenuation data from the calibration phantom using an x-ray imaging system;

and fitting the phase contrast data and the dual energy attenuation data to a physical model to derive the first and second calibration factors.

18. The method as recited in claim 17, wherein the first material is water and the second material is bone.