Coded-aperture X-ray imaging

Patent metadata

Field	Value
Publication number	US-9952163-B2
Application number	US-201414898281-A
Country	US
Kind code	B2
Filing date	May 29, 2014
Priority date	Jun 21, 2013
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A method of X-ray imaging includes passing an X-ray beam through a pre-sample mask 8 with a plurality of apertures 32 , through a sample 10 , and then through a detector mask 6 with aligned apertures 34 . The beams are detected. The detector mask 6 and pre-sample mask 8 are moved with respect to one another to identify the position of maximum intensity and then moved to two further positions on equal and opposite spacings on either side of the maximum. Images are acquired and a transmission image, refraction image and scattering image calculated.

First claim

The invention claimed is:

1. A method of X-ray imaging, comprising:
passing an X-ray beam through an absorbing pre-sample mask with one or more apertures spaced apart in the x direction;
passing the X-ray beam through a sample;
detecting the X-rays using a spatially resolving detector representing a detector mask having one or more apertures spaced apart in the x-direction at a corresponding spacing to the apertures in the pre-sample mask, to provide one or more images I i , wherein i is the number of images with the relative position of the pre-sample mask and detector mask at respective position or positions x i , wherein i is the number of positions and
obtaining a dark field image of the sample by calculating the dark field image from the captured image or images I i at respective positions x i

using a formulation representing the image intensity as a function of scattering, transmission and refraction, wherein obtaining a dark field image comprises solving the equation

I
⁡

(
x
)

I
0

=

t
⁡

(

O
*
L

)

⁢

(

x
-

Δ
⁢

⁢

x
R

)

from the captured image or images Ii at respective positions x i to obtain the dark field image of the sample;
where * denotes convolution, I 0 is the beam intensity passing through the sample aperture, the illumination function L(x) describes how the detected beam intensity changes as a function of the relative displacement x between the pre-sample and the detector mask, in the absence of the sample, t represents the transmission of the sample, Δx R represents the refraction induced by the sample and O(x) describes the scattering of the sample, represented in the dark field image.

2. The method according to claim 1 , wherein the step of detecting the X-rays provides at least two images I 1 , and I 2 with the relative position of the pre-sample mask and detector mask at least two respective positions x 1 , and x 2 ;
further comprising calculating a transmission image of the sample, and/or a the refraction image of the sample from the captured images in addition to the dark field image.

3. The method according to claim 2 further comprising measuring L pixel by pixel and using the measured value of L for each pixel when solving the equation from the captured image to calculate at least two of the transmission image, the refraction image and the dark field images.

4. The method according to claim 2 , wherein the step of calculating the images includes solving:

I
⁡

(
x
)

I
0

=

t
⁢

∑

m
=
1

M

⁢

∑

n
=
1

N

⁢

A
mn

⁢

exp
⁡

[

-

(

x
-

μ

mn
⁢

)

2

2
⁢

σ
mn
2

]

wherein the scattering O is represented by a sum of M Gaussian functions and the illumination function L is represented by the sum of N Gaussian functions, σ mn 2 =σ m 2 +σ n 2 , σ m 2 is the variance of the m-th Gaussian function describing the scattering U caused by the sample, σ n 2 is the variance of the n-th Gaussian function describing the illumination function L, A mn =A m A n (1/√{square root over (2πσ mn 2 )}), with A m and A n the scalars representing the amplitudes of the Gaussian distributions.

5. The method according to claim 4 , wherein x 3 =x 1 , M=N=1 and the step of calculating at least two of a transmission image t of the sample, a refraction image Δx R of the sample and a scattering image σ M 2 of the sample solve:

I
1

=

t
⁢

A
MN

2
⁢

πσ
MN
2

Assignees

• Ucl Business Plc

Inventors

• Endrizzi Marco
• Olivo Alessandro
• Diemoz Paul
• Millard Thomas
• Vittoria Fabio

Classifications

• A61B6/4035

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

• G01N2223/401

  image processing · CPC title

• A61B6/5205

  involving processing of raw data to produce diagnostic data · CPC title

• A61B6/4291

  the detector being combined with a grid or grating · CPC title

• G01N23/041

  Phase-contrast imaging, e.g. using grating interferometers · CPC title