# US 8,542,230 B2 · Method for preparing CT image displays, and an arithmetic logic unit for carrying out this method

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- Number: US 8,542,230 B2
- Document ID: US8542230B2
- Status: Granted
- Kind: B2
- Application number: 12/725,946
- Filed: 2010-03-17
- Published: 2010-09-23
- Granted: 2013-09-24
- Earliest claimed: 2009-03-19
- Assignees: Siemens Aktiengesellschaft
- Applicants: Bernhard Krauss
- Inventors: Bernhard Krauss
- Web page: https://patentgrep.com/patent/US8542230B2

## CPC

- A61B 6/405: {Source units specially adapted to modify characteristics of the beam during the data acquisition process (A61B6/4021, A61B6/4035 take precedence)}
- A61B 6/032: {Transmission computed tomography [CT]}
- A61B 6/482: {involving multiple energy imaging}
- A61B 6/505: {for diagnosis of bone}
- G06T 12/30: Image post-processing, e.g. metal artefact correction
- G06T 2211/408: Dual energy
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

A method is disclosed for preparing CT image displays. In at least one embodiment, the method includes compiling N≧2 CT image data records of an area of a patient on the basis of N different X-ray energy spectra, each pixel or voxel being assigned an N-tuple CT numbers, each CT number of the N-tuple being assigned to the absorption value of one of the N X-ray energy spectra; carrying out material destruction over at least one predetermined subarea of the area of the patient represented in the CT image data records with reference to at least three materials including at least bone mineral, yellow bone marrow and red bone marrow; and outputting and/or displaying at least one CT image data record at least with reference to the predetermined subarea with absorption values relating to one of the N X-ray energy spectra or to a mathematically simulated spectrum from which the bone mineral content is extracted.

## Claims

### Claim 1

A method for preparing CT image displays, comprising:
compiling CT image data records of an area of a patient on the basis of N≧2 different X-ray energy spectra, each pixel or voxel of the CT image data records being assigned an N-tuple of CT numbers, each CT number of the N-tuple being assigned to an absorption value of one of the N different X-ray energy spectra;
carrying out material decomposition over at least one subarea of the area of the patient represented in the CT image data records with reference to at least three materials including at least bone mineral, yellow bone marrow and red bone marrow; and
at least one of outputting and displaying at least one CT image data record at least with reference to the subarea with absorption values relating to one of the N different X-ray energy spectra or to a mathematically simulated spectrum from which the bone mineral content is extracted.

### Claim 2 (depends on 1)

The method as claimed in claim 1, wherein the carrying out material decomposition determines an equal CT value change for yellow and red bone marrow if a first concentration of bone mineral exists, and
at least volume fractions of the yellow bone marrow and red bone marrow relative to a total volume of bone marrow, and the concentration of bone mineral are determined.

### Claim 3 (depends on 2)

The method as claimed in claim 2, wherein, in order to determine the volume fractions of the yellow bone marrow and red bone marrow and the concentration of the bone mineral, use is made of the following energy-dependent equation, and the solution of a system of equations is calculated per pixel or voxel:
x(E)=g×xgelb(E)+r×xrot(E)+c×ΔxKm(E) where r=(1−g) and:
x(E) corresponds to a measured absorption value with reference to the energy spectrum E,
g corresponds to a volume component of yellow bone marrow on the bone marrow,
xgelb(E) corresponds to an absorption value of yellow bone marrow with reference to the energy spectrum E,
r corresponds to a volume component of red bone marrow on the bone marrow,
xrot(E) corresponds to an absorption value of red bone marrow with reference to the energy spectrum E,
c corresponds to a concentration of the bone mineral, and
ΔxKm(E) corresponds to an increase in the absorption value of bone marrow per concentration of the bone mineral with reference to the energy spectrum E.

### Claim 4 (depends on 3)

The method as claimed in claim 3, wherein output pixel or voxel values are calculated in accordance with the following formula:
xA(E)=g×xgelb(E)+(1−g)×xrot(E)
where xA(E) is an output absorption value relating to the energy spectrum E.

### Claim 5 (depends on 1)

The method as claimed in claim 1, wherein, in the case of the material composition, volume fractions are determined for each of the three materials of bone mineral, yellow bone marrow and red bone marrow.

### Claim 6 (depends on 5)

The method as claimed in claim 5, wherein, in order to determine the volume fractions of the bone mineral, yellow bone marrow and red bone marrow, use is made of the following energy-dependent equation, and the solution of a system of equations is calculated per pixel or voxel:
x(E)=g×xgelb+r×xrot+k×xKm, where r=1−g−k and:
x(E) corresponds to a measured absorption value with reference to the energy spectrum E,
g corresponds to a volume component of the yellow bone marrow,
xgelb corresponds to an absorption value of yellow bone marrow with reference to the energy spectrum E,
r corresponds to a volume component of red bone marrow,
xrot corresponds to an absorption value of red bone marrow with reference to the energy spectrum E,
k corresponds to a volume component of bone minerals and
xKm corresponds to an absorption value of bone mineral with reference to the energy spectrum E.

### Claim 7 (depends on 5)

The method as claimed in claim 5, wherein, in the case of output pixel or voxel values, the output value is calculated on the assumption that the pixel or voxel consists exclusively of the materials of yellow and red bone marrow, the relationship of the determined volume fractions being maintained.

### Claim 8 (depends on 6)

The method as claimed in claim 6, wherein output pixel or voxel values are calculated and normalized in accordance with the following formula:
x
A
⁡
(
E
)
=
g
1
-
k
×
x
gelb
⁡
(
E
)
+
1
-
k
-
g
1
-
k
×
x
rot
⁡
(
E
)
,
where xA(E) is an output absorption value in relation to the energy spectrum (E).

### Claim 9 (depends on 1)

The method as claimed in claim 1, wherein, with reference to their absorption values, output pixel or voxel values are represented in gray-scale values.

### Claim 10 (depends on 9)

The method as claimed in claim 9, wherein the output pixel or voxel values are rescaled linearly or nonlinearly.

### Claim 11 (depends on 10)

The method as claimed in claim 10, wherein the rescaled pixel or voxel values is displayed by different coloration of the pixel or voxel.

### Claim 12 (depends on 1)

The method as claimed in claim 1, wherein the subarea is comprised exclusively of bone.

### Claim 13 (depends on 12)

The method as claimed in claim 12, wherein the subarea comprising bone is determined on the basis of a segmentation.

### Claim 14 (depends on 1)

The method as claimed in claim 1, wherein the method is carried out on the basis of at least two CT displays that were respectively calculated by simulating a monochromatic radiation from originally measured raw data.

### Claim 15 (depends on 1)

The method as claimed in claim 1, wherein at least one extremity is selected as the scanned area of the patient.

### Claim 16 (depends on 1)

The method as claimed in claim 1, wherein a 2-dimensional CT image data record is output.

### Claim 17 (depends on 1)

The method as claimed in claim 1, wherein a 3-dimensional CT image data record is output.

### Claim 18 (depends on 1)

An arithmetic logic unit, comprising:
a memory with program code, the program code executing the method steps as claimed in claim 1 when executed and being stored in the memory.

### Claim 19 (depends on 6)

The method as claimed in claim 6, wherein, in the case of output pixel or voxel values, the output value is calculated on the assumption that the pixel or voxel consists exclusively of the materials of yellow and red bone marrow, the relationship of the determined volume fractions being maintained.

### Claim 20 (depends on 7)

The method as claimed in claim 7, wherein output pixel or voxel values are calculated and normalized in accordance with the following formula:
x
A
⁡
(
E
)
=
g
1
-
k
×
x
gelb
⁡
(
E
)
+
1
-
k
-
g
1
-
k
×
x
rot
⁡
(
E
)
,
where xA(E) is an output absorption value in relation to the energy spectrum (E).

### Claim 21 (depends on 18)

A CT system comprising the arithmetic logic unit of claim 18.

### Claim 22 (depends on 1)

A non-transitory computer readable medium including program segments for, when executed on a computer device, causing the computer device to implement the method of claim 1.