# US 2008/0187091 A1 · Method of iterative reconstruction for energy discriminating computed tomography systems

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- Number: US 2008/0187091 A1
- Document ID: US20080187091A1
- Status: Published application
- Kind: A1
- Application number: 11/672,137
- Filed: 2007-02-07
- Published: 2008-08-07
- Earliest claimed: 2007-02-07
- Assignees: General Electric Company
- Inventors: Samit Kumar Basu; Bruno Kristiaan Bernard DeMan
- Web page: https://patentgrep.com/patent/US20080187091A1

## CPC

- G01N 23/046: using tomography, e.g. computed tomography [CT]
- G01N 2223/419: computed tomograph
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A new method extends iterated coordinate descent (“ICD”)—an optimization method employed in some statistical reconstruction algorithms—to handle material decomposition (“MD”) for energy discriminating computed tomography (“EDCT”) acquisitions.

## Claims

### Claim 1

A method for re-projecting images, comprising:
obtaining current path length estimates; and
linearizing one or more spectral models about the current path length estimates.

### Claim 2 (depends on 1)

The method of claim 1, wherein the step of obtaining current path length estimates further comprises:
re-projecting one or more component images.

### Claim 3 (depends on 1)

The method of claim 1, wherein the step of obtaining current path length estimates further comprises:
performing material decomposition of multi-spectral acquisition data in a projection domain.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
fixing all but one image pixel;
varying at least one component of the one image pixel;
arranging a system of linear equations; and
obtaining from the system of linear equations at least an optimal component value of the one image pixel.

### Claim 5 (depends on 4)

The method of claim 4, wherein the system of linear equations comprises a 2×2 matrix equation.

### Claim 6 (depends on 4)

The method of claim 4, further comprising:
updating the one image pixel based on its current component values and based on the calculated optimal values.

### Claim 7 (depends on 6)

The method of claim 6, further comprising:
adjusting the step of updating based on prior information about the image pixel and its component composition.

### Claim 8 (depends on 1)

The method of claim 1, further comprising:
iterating over all image pixels until convergence.

### Claim 9 (depends on 8)

The method of claim 8, further comprising:
displaying at least one final converged component image.

### Claim 10 (depends on 8)

The method of claim 8, further comprising:
analyzing at least one final converged component image.

### Claim 11

A computed tomography system, comprising:
a multi-spectral x-ray source;
a detector positioned to receive multi-spectral acquisition data from the multi-spectral x-ray source;
a computer processor configured to:
obtain current path length estimates; and
linearize one or more spectral models about the current path length estimates.

### Claim 12 (depends on 11)

The computed tomography system of claim 11, wherein the computer processor is further configured to:
fix all but one image pixel;
vary at least one component of the one image pixel;
arrange a system of linear equations; and
obtain from the system of linear equations at least an optimal component value of the one image pixel.

### Claim 13 (depends on 12)

The computed tomography system of claim 12, wherein the computer processor is further configured to:
update the one image pixel based on its current component values and based on the calculated optimal values.

### Claim 14 (depends on 13)

The computed tomography system of claim 13, wherein the computer processor is further configured to:
adjust the step of updating based on prior information about the image pixel and its component composition.

### Claim 15 (depends on 13)

The computed tomography system of claim 13, wherein the computer processor is further configured to:
iterate over all image pixels until convergence.

### Claim 16 (depends on 15)

The computed tomography system of claim 15, wherein the computer processor is further configured to:
display at least one final converged component image.

### Claim 17 (depends on 16)

The computed tomography system of claim 16, wherein the computer processor is further configured to:
analyze at least one final converged component image.

### Claim 18 (depends on 12)

The computed tomography system of claim 12, wherein the system of linear equations comprises a 2×2 matrix equation.

### Claim 19 (depends on 11)

The computed tomography system of claim 11, wherein the computer is further configured to re-project one or more component images to obtain the current path length estimates.

### Claim 20 (depends on 11)

The computed tomography system of claim 11, wherein the computer is further configured to perform material decomposition of multi-spectral acquisition data in a projection domain to obtain the current path length estimates.