Tilted-grating approach for scanning-mode x-ray grating interferometry

Patent metadata

Field	Value
Publication number	US-2017082559-A1
Application number	US-201515309222-A
Country	US
Kind code	A1
Filing date	Feb 25, 2015
Priority date	May 7, 2014
Publication date	Mar 23, 2017
Grant date	—

Abstract

Among the existent X-ray phase-contrast modalities, grating interferometry appears as a promising technique for commercial applications, since it is compatible with conventional X-ray tubes. However, since applications such as medical imaging and homeland security demand covering a considerable field of view, the fabrication of challenging and expensive large-area gratings would be needed. A scanning setup is a good solution, because it uses cheaper line detectors instead of large-area 2D detectors and would require smaller gratings. In this setup, the phase-retrieval using the conventional phase-stepping approach would be slow, so having a faster method to record the signals becomes fundamental. To tackle this problem, a scanning-mode grating interferometer configuration is used, in which a grating is tilted to form Moire fringes perpendicular to the grating lines. The sample is then translated along the fringes, so each line detector records a different phase step for each slice of the sample.

First claim

1 - 10 . (canceled)

11 . A method to retrieve absorption, differential phase contrast (DPC) and dark field signals from a Moire fringe pattern obtained by detuning a grating interferometer system having an X-ray source, a phase grating, an analyzer grating and a line sensitive detector, which comprises the steps of:
tilting one of the phase grating and the analyzer grating; and scanning either a sample or the grating interferometer system along the Moire fringe pattern.

12 . The method according to claim 11 , which further comprises producing the Moire fringe pattern of a desired period by tilting one of the phase grating and the analyzer grating by a predetermined angle.

13 . The method according to claim 12 , which further comprises calculating a tilting angle using:
a period P 2 of the analyzer grating; a number n of detector lines; a number m of the periods P 2 that are to be covered; a separation D between the detector lines of the line sensitive detector; and employing formulas:

δ
x

=

m


p
2

n

θ
=

arc




tan


(

δ
x

D

)

where θ is the tilting angle.

14 . The method according to claim 11 , which further comprises using reference and sample data acquired with the grating interferometer system to retrieve the absorption, the DPC and the dark-field signals either by Fourier Component.

15 . The method according to claim 11 , wherein:
the grating interferometer system having the phase grating and the analyzer grating one of the phase grating and the analyzer grating is tilted; or the grating interferometer system having a source grating, the phase grating and the analyzer grating either only the phase grating or only the analyzer grating or a pair of the source grating and the phase grating or a pair of the phase grating and the analyzer grating is tilted.

16 . The method according to claim 11 , wherein compatible with radiography, tomosynthesis and computed tomography either the sample or the grating interferometer system is rotated to acquire multiples views.

17 . A grating interferometer system for obtaining absorption, differential phase contrast (DPC) and dark-field data from quantitative X-ray images from a sample, the grating interferometer system comprising:
an X-ray source; gratings including one of a phase grating and an analyzer grating or a source grating, said phase grating and said analyzer grating; a position-sensitive detector; means for recording images of said position-sensitive detector; means for evaluating intensities for each pixel in a series of the quantitative X-ray images, in order to identify characteristics of an object for each individual pixel as an absorption-dominated pixel and/or a DPC-dominated pixel and/or an X-ray dark-field dominated pixel; means to tilt either said phase grating or said analyzer grating by a predetermined angle; and means to move the sample or said x-ray source, said gratings and said position-sensitive detector to perform a scanning of a probe.

18 . The system according to claim 17 , wherein said phase grating is a line grating, an absorption grating or a phase grating that is a low-absorption grating but generating a considerable X-ray phase shift and of fl or odd multiples thereof.

19 . The system according to claim 17 , wherein said analyzer grating is a line grating having a high X-ray absorption contrast with its period being a same as that of a self-image of said phase grating, wherein said analyzer grating is placed closely in front of said position-sensitive detector with its lines parallel to those of said phase grating, before tilting said phase grating or said analyzer grating.

20 . The system according to claim 17 , wherein for near-field-regime operation, a distance between said gratings is chosen freely within the near-field-regime, and a Talbot-regime is chosen according to:

D

n
,
sph

=

L
·

D
n

L
-

D
n

=

L
·
n
·

p
1
2

/
2





η
2


λ

L
-

n
·

p
1
2

/
2





η
2


λ

where


n
=
1

,
3
,

5



…



,
and



Assignees

• Scherrer Inst Paul

Inventors

• Arboleda Carolina
• Stampanoni Marco
• Wang Zhentian

Classifications

• A61B6/4208

  characterised by using a particular type of detector · CPC title

• A61B6/484

  involving phase contrast X-ray imaging · CPC title

• G21K2207/005

  Methods and devices obtaining contrast from non-absorbing interaction of the radiation with matter, e.g. phase contrast · CPC title

• A61B6/4035

  the source being combined with a filter or grating · CPC title

• G21K1/025

  using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation · CPC title