# US 10,311,604 B2 · System and method for generating attenuation map

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- Number: US 10,311,604 B2
- Document ID: US10311604B2
- Status: Granted
- Kind: B2
- Application number: 15/317,376
- Filed: 2016-07-08
- Published: 2018-07-26
- Granted: 2019-06-04
- Earliest claimed: 2016-07-08
- Assignees: Shanghai United Imaging Healthcare Co., Ltd.
- Applicants: Shanghai United Imaging Healthcare Co., Ltd.
- Inventors: Wentao Zhu; Tao Feng; Hongdi Li; Miaofei Han
- Web page: https://patentgrep.com/patent/US10311604B2

## CPC

- G06T 12/20: Inverse problem, i.e. transformations from projection space into object space
- A61B 6/03: Computed tomography [CT]
- A61B 6/032: {Transmission computed tomography [CT]}
- A61B 6/037: {Emission tomography}
- A61B 6/5205: {involving processing of raw data to produce diagnostic data}
- A61B 6/5229: {combining image data of a patient, e.g. combining a functional image with an anatomical image}
- A61B 6/5235: {combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT}
- A61B 6/5247: {combining images from an ionising-radiation diagnostic technique and a non-ionising radiation diagnostic technique, e.g. X-ray and ultrasound}
- A61B 6/5294: {involving using additional data, e.g. patient information, image labeling, acquisition parameters}
- G06T 7/11: Region-based segmentation
- G06T 7/174: involving the use of two or more images
- G06T 7/337: {involving reference images or patches}
- G06T 2207/10081: Computed x-ray tomography [CT]
- G06T 2207/10088: Magnetic resonance imaging [MRI]
- G06T 2207/10104: Positron emission tomography [PET]
- G06T 2207/20076: Probabilistic image processing
- G06T 2207/20221: Image fusion; Image merging
- G06T 2207/30048: Heart; Cardiac
- G06T 2207/30061: Lung
- G06T 2207/30096: Tumor; Lesion
- G06T 2211/408: Dual energy
- G06T 2211/424: Iterative
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

A method for generating attenuation map is disclosed. The method includes acquiring an anatomic image and PET data indicative of a subject, wherein the anatomic image comprises a plurality of voxels. The method also includes fetching a reference image to register the anatomic image, the reference image includes voxel segmentation information. The method further includes segmenting the anatomic image into a plurality of regions based on the voxel segmentation information. The method further includes generating a first attenuation map corresponding to the anatomic image by assigning attenuation coefficients to the plurality of regions. The method further includes calculating a registration accuracy between the anatomic image and the reference image. The method further includes determining a probability distribution of attenuation coefficient. The method further includes updating the first attenuation map iteratively based on the probability distribution of attenuation coefficient and the PET data to obtain a final attenuation map.

## Claims

### Claim 1

A method of generating an attenuation map for positron emission tomography (PET) reconstruction, the method comprising:
acquiring PET data indicative of a subject;
acquiring an anatomic image indicative of the subject, wherein the anatomic image comprises a plurality of voxels;
fetching a reference image from a database, wherein the reference image comprises voxel segmentation information;
registering the reference image to the anatomic image;
segmenting the anatomic image into a plurality of regions based on the voxel segmentation information of the reference image;
generating a first attenuation map corresponding to the anatomic image by assigning attenuation coefficients to the plurality of regions of the anatomic image;
for a voxel of the plurality of voxels of the anatomic image,
determining a three-dimensional (3D) region in the anatomic image, wherein the voxel is the center of the 3D region;
calculating a registration accuracy of the 3D region between the anatomic image and the reference image;
determining a probability distribution of attenuation coefficient of the voxel based on the registration accuracy; and
iteratively updating the first attenuation map based on the probability distribution of attenuation coefficient of the voxel and the PET data to obtain a final attenuation map.

### Claim 2 (depends on 1)

The method of claim 1, the fetching the reference image is based on one or more types of characteristic information of the subject.

### Claim 3 (depends on 2)

The method of claim 2, wherein the one or more types of characteristic information comprise height, weight, gender of the subject, or an area of the subject to imaging.

### Claim 4 (depends on 1)

The method of claim 1, the registering the reference image to the anatomic image is based on at least one of optical flow, feature points, a contour, or grey scale information.

### Claim 5 (depends on 1)

The method of claim 1, the determining the probability distribution of attenuation coefficient of the voxel comprising:
calculating a statistical probability indicative of the voxel belonging to a certain region of the plurality of regions based on the registration accuracy; and
acquiring the probability distribution of attenuation coefficient of the voxel based on the statistical probability.

### Claim 6 (depends on 5)

The method of claim 5, wherein the at least one region of the plurality of regions is a spatial region.

### Claim 7 (depends on 5)

The method of claim 5 further comprising
designating, if the statistical probability is 1, the voxel as belonging to the certain region of the plurality of regions.

### Claim 8 (depends on 7)

The method of claim 7, wherein the certain region of the plurality of regions comprises a plurality of voxels with a same probability distribution of attenuation coefficient, and the plurality of voxels of the certain region are assigned with a same attenuation coefficient.

### Claim 9 (depends on 5)

The method of claim 5 further comprising
designating, if the statistical probability is less than 1, the voxel as belonging to at least two regions of the plurality of regions.

### Claim 10 (depends on 9)

The method of claim 9, the voxel is designated as belonging to one region of the at least two regions as the final attenuation map is obtained.

### Claim 11 (depends on 1)

The method of claim 1, wherein the anatomic image is a magnetic resonance (MR) image or a computed tomography (CT) image.

### Claim 12

A method of image reconstruction for positron emission tomography (PET) comprising:
acquiring PET data indicative of a subject;
acquiring a PET image by reconstructing the PET data, wherein the PET data is attenuation corrected by an attenuation map, wherein the attenuation map is generated by following steps:
acquiring an MR image indicative of the subject, wherein the MR image comprises a plurality of voxels;
fetching a reference image from a database, wherein the reference image comprises voxel segmentation information;
registering the reference image to the MR image;
segmenting the MR image into a plurality of regions based on the voxel segmentation information of the reference image;
generating a first attenuation map corresponding to the MR image by assigning attenuation coefficients stored in the database to the plurality of regions of the MR image;
for a voxel of the plurality of voxels of the MR image,
determining a three-dimensional (3D) region in the MR image, wherein the voxel is the center of the 3D region;
calculating a registration accuracy of the 3D region between the MR image and the reference image;
determining a probability distribution of attenuation coefficient of the voxel based on the registration accuracy;
updating the PET data based on the first attenuation map and generating a first PET image; and
updating the first attenuation map based on the probability distribution of attenuation coefficient and the PET data of the first PET image to obtain a second attenuation map.

### Claim 13 (depends on 12)

The method of claim 12, the updating the first attenuation map based on the probability distribution of attenuation coefficient and the PET data of the first PET image to obtain the second attenuation map comprising:
acquiring the probability distribution of attenuation coefficient of the voxel in one or more regions based on the registration accuracy; and
acquiring the second attenuation map based on a function relating to the probability distribution and the PET data of the first PET image.

### Claim 14 (depends on 13)

The method of claim 13, wherein the function is a penalized likelihood function.

### Claim 15 (depends on 12)

The method of claim 12, further comprising:
updating the PET data of the first PET image to generate a second PET image while keeping the second attenuation map fixed; and
updating the second attenuation map to generate a third attenuation map while keeping the PET data of the second PET image fixed.

### Claim 16 (depends on 12)

The method of claim 12, the segmenting the MR image into a plurality of regions based on the voxel segmentation information of the reference image comprising:
assigning the voxels belonging to one region of the plurality of regions with an attenuation coefficient.

### Claim 17

An imaging system comprising:
a storage configured to store PET data of a subject and a set of instructions;
at least one processor in communication with the storage, wherein when executing the instructions, the at least one processor is configured to cause the imaging system to:
receive an anatomic image indicative of the subject, wherein the anatomic image comprises a plurality of voxels;
fetch a reference image from a database, wherein the reference image comprises voxel segmentation information;
register the reference image to the anatomic image;
segment the anatomic image into a plurality of regions based on the voxel segmentation information;
generate a first attenuation map corresponding to the anatomic image by assigning attenuation coefficients to the plurality of regions of the anatomic image;
for a voxel of the plurality of voxels of the anatomic image,
determining a three-dimensional (3D) region in the anatomic image, wherein the voxel is the center of the 3D region;
calculate a registration accuracy of the 3D region between the anatomic image and the reference image;
determining a probability distribution of attenuation coefficient of the voxel based on the registration accuracy;
update the PET data based on the first attenuation map and generating a first PET image;
update the first attenuation map based on the probability distribution of attenuation coefficient and the PET data of the first PET image to obtain a second attenuation map.

### Claim 18 (depends on 17)

The imaging system of claim 17, wherein the anatomic image is a magnetic resonance (MR) image or a computed tomography (CT) image.

### Claim 19 (depends on 17)

The imaging system of claim 17, wherein the at least one processor is configured to cause the imaging system further to:
receive characteristic information of the subject.

### Claim 20 (depends on 19)

The imaging system of claim 19, wherein the fetching the reference image is based on the characteristic information of the subject.