METHOD FOR CODED-SOURCE PHASE CONTRAST X-RAY IMAGING

• US 20150146848A1
• Filed: 03/14/2013
• Published: 05/28/2015
• Est. Priority Date: 05/14/2012
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology, The General Hospital Corporation (Mass General Brigham, Inc.)
• Original Assignee: The General Hospital Corporation (Mass General Brigham, Inc.)
• Inventors: Gupta, Rajiv, Velasquez-Garcia, Luis Fernando, Lanza, Richard, Horn, Berthold KP, Akinwande, Tayo
• Granted Patent: US 10,045,752 B2
• Time in Patent Office: Days
• US Class Current: 378/57
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/40 Arrangements for generating radiation specially adapted for radiation diagnosis
• CPC Class Codes: A61B 6/4007 characterised by using a plurality of source units
• 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 6/4405 the apparatus being movable or portable, e.g. handheld or mounted on a trolley
• CPC Class Codes: A61B 6/484 involving phase contrast X-ray imaging
• CPC Class Codes: G01N 23/041 Phase-contrast imaging, e.g. using grating interferometers
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
• CPC Class Codes: G01V 5/224 Multiple energy techniques using one type of radiation, e.g. X-rays of different energies
• CPC Class Codes: G21K 2207/005 Methods and devices obtaining contrast from non-absorbing interaction of the radiation with matter, e.g. phase contrast
• CPC Class Codes: H01J 2201/30449 Metals and metal alloys
• CPC Class Codes: H01J 2235/062 Cold cathodes
• CPC Class Codes: H01J 2235/068 Multi-cathode assembly
• CPC Class Codes: H01J 35/025 X-ray tubes with structurally associated circuit elements
• CPC Class Codes: H01J 35/04 Electrodes ; Mutual position thereof; Constructional adaptations therefor
• CPC Class Codes: H01J 35/045 Electrodes for controlling the current of the cathode ray, e.g. control grids
• CPC Class Codes: H01J 35/065 Field emission, photo emission or secondary emission cathodes
• CPC Class Codes: H01J 35/116 Transmissive anodes acting as a window H01J35/186
• CPC Class Codes: H01J 35/186 used as targets or X-ray converters

Abstract

Described here is a method for performing phase contrast imaging using an array of independently controllable x-ray sources. The array of x-ray sources can be controlled to produce a distinct spatial pattern of x-ray radiation and thus can be used to encode phase contrast signals without the need for a coded aperture. The lack of coded aperture increases the flexibility of the imaging method. For instance, because a fixed, coded aperture is not required, the angular resolution of the imaging technique can be increased as compared to coded-aperture imaging. Moreover, the lack of a radioopaque coded aperture increases the photon flux that reaches the subject, thereby increasing the attainable signal-to-noise ratio.

Claims

1. A method for phase contrast imaging using an array of independently controllable x-ray sources, the steps of the method comprising:

a) directing an array of independently controllable x-ray sources to produce x-ray radiation in a distinct spatial pattern by selectively energizing x-ray sources in the array;

b) detecting phase-contrast signals of the x-ray radiation after the x-ray radiation passes through a subject using an x-ray detector; and

c) reconstructing an image of the subject by performing a compressed sensing reconstruction technique on the detected phase-contrast signals, wherein the reconstructed image depicts an image contrast indicative of phase shifts in the x-ray radiation.

2. The method as recited in claim 1 in which the x-ray sources have a focal spot sized less than about twenty micrometers.

3. The method as recited in claim 1 in which the x-ray detector is separated from the subject by at least about one meter.

4. The method as recited in claim 1 in which the x-ray detector has an effective detector pitch of less than about ten micrometers.

5. The method as recited in claim 1 in which the distinct spatial pattern is selected as at least one of a uniformly redundant array (URA) and a modified uniformly redundant array (MURA).

6. The method as recited in claim 1 in which step c) includes determining a target image, X, that minimizes an objective function defined as, ∥

Ψ

X∥

₁;

wherein Ψ

is a sparsifying transform that transforms the target image, X, into a sparse domain.

7. The method as recited in claim 5 in which the sparsifying transform is a discrete gradient transform.

8. The method as recited in claim 1 in which the subject is at least one of a human and an animal

9. The method as recited in claim 1 in which the subject is at least one of a piece of luggage and a cargo container.

10. The method as recited in claim 9 in which the at least one of a piece of luggage and a cargo container includes an explosive, and the method further comprises identifying the explosive by analyzing the image reconstructed in step c).