Processing metal artifact in CT image

Patent metadata

Field	Value
Publication number	US-9953441-B2
Application number	US-201514959486-A
Country	US
Kind code	B2
Filing date	Dec 4, 2015
Priority date	Dec 4, 2014
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A method for processing metal artifacts in a CT image is provided. The method may comprise: performing a first metal artifact processing on the original image to obtain a first processed image COR1 and extracting the high frequency portion of the first processed image COR1 to obtain a first high-frequency image COR1HF; performing a second metal artifact processing on the original image to obtain a second processed image COR2 and extracting the high frequency portion of the processed image COR2 second to obtain a second high-frequency image COR2HF; perform a weighted combination the first processed image COR1, the first high-frequency image COR1HF and the second high-frequency image COR2HF by using a weighting function W to obtain a result image CORImp containing no metal artifact, but information of area near the metal artifact.

First claim

The invention claimed is:

1. A method for processing metal artifacts in a Computed Tomography (CT) image, the method comprising:
extracting a metal image from an original image;
performing a first metal artifact processing on the original image to obtain a first processed image COR1, wherein the original image is a reconstructed CT image based on scan data obtained by CT scanning a subject, and wherein the original image contains metal artifacts, and in the process of the first metal artifact processing, the scan data involving the metal artifacts is corrected based on a metal range in which a metal object is contained, wherein the metal range is determined by performing an orthographic projection on the metal image extracted from the original image;
extracting the high frequency portion of the first processed image COR1 to obtain a first high-frequency image COR1HF;
performing a second metal artifact processing on the original image to obtain a second processed image COR2, wherein in the second metal artifact processing, the metal artifacts are removed without affecting the tissue information of the subject;
extracting the high frequency portion of the second processed image COR2 to obtain a second high-frequency image COR2HF;
obtaining a weighting function W based on the metal image; and
performing a weighted combination for the first processed image COR1, the first high-frequency image COR1HF and the second high-frequency image COR2HF by using the weighting function W to obtain a result image CORImp;
wherein the weighted combination is performed according to the following equation: CORImp=COR1+(COR2HF−COR1HF)*W.

2. The method of claim 1 , wherein the metal artifacts include hardening artifacts and the second metal artifact processing comprises:
applying a hardening correction to the original image to reduce the hardening artifacts in the original image and to obtain the second processed image COR2.

3. The method of claim 2 , wherein the hardening correction comprises:
smoothing filtering the original image to obtain an Ori-Smo image;
smoothing filtering the first processed image COR1 to obtain a COR1-Smo image;
calculating the difference between the Ori-Smo image and the COR1-Smo image to obtain an image HardenArti containing hardening artifacts; and
calculating the difference between the original image and the image HardenArti to obtain the second processed image COR2.

4. The method of claim 1 , wherein the metal artifacts include strip artifacts and hardening artifacts and the second metal artifact processing comprises:
pre-processing scan data corresponding to the original image to reduce the strip artifacts in the original image and to obtain an Ori-Air image; and
applying a hardening correction to the Ori-Air image to reduce the hardening artifacts in the Ori-Air image and to obtain the second processed image COR2.

5. The method of claim 4 , wherein the hardening correction comprises:
smoothing filtering the Ori-Air image to obtain an Ori-Air-Smo image;
smoothing filtering the first processed image COR1 to obtain a COR1-Smo image;
calculating the difference between the Ori-Air-Smo image and the COR1-Smo image to obtain an image HardenArti containing only hardening artifacts; and
calculating the difference between the Ori-Air image and the image HardenArti to obtain the second processed image COR2.

6. The method of claim 1 , wherein obtaining a weighting function W based on the metal image comprises:
applying low-pass filtering to the metal image to obtain a low-frequency metal image; and
normalizing the low-frequency metal image to obtain the weighting function W.

7. A device for processing metal artifacts in a Computed Tomography (CT) image, the device comprising:
a processor which invokes machine readable instructions corresponding to a control logic for processing metal artifacts in a CT image stored on a storage medium and executes the machine readable instructions to:
extract a metal image from an original image;
perform a first metal artifact processing on the original image to obtain a first processed image COR1, wherein the original image is a reconstructed CT image based on scan data obtained by CT scanning a subject, and wherein the original image contains metal artifacts, and in the process of the first metal artifact processing, the scan data involving the metal artifacts is corrected based on a metal range in which a metal object is contained, wherein the metal range is determined by performing an orthographic projection on the metal image extracted from the original image;
extract the high frequency portion of the first processed image COR1 to obtain a first high-frequency image COR1HF;
perform a second metal artifact processing on the original image to obtain a second processed image COR2, wherein in the second metal artifact processing, the metal artifacts are removed without affecting the tissue information of the subject;
extract the high frequency portion of the second processed image COR2 to obtain a second high-frequency image COR2HF;
obtain a weighting function W based on the metal image; and
perform a weighted combination for the first processed image COR1, the first high-frequency image COR1HF and the second high-frequency image COR2HF by using the weighting function W to obtain a result image CORImp,
wherein the weighted combination is performed according to the following equation: CORImp=COR1+(COR2HF−COR1HF)*W.

8. The device according to claim 7 , wherein the metal artifacts include hardening artifacts and said machine readable instructions further cause the processor to:
apply a hardening correction to the original image to reduce the hardening artifacts in the original image and to obtain the second processed image COR2.

9. The device according to claim 8 , wherein said machine readable instructions further cause the processor to:
smoothing filter the original image to obtain an Ori-Smo image;
smoothing filter the first processed image COR1 to obtain a COR1-Smo image;
calculate the difference between the Ori-Smo image and the COR1-Smo image to obtain an image HardenArti containing hardening artifacts; and
calculate the difference between the original image and the image HardenArti to obtain the second processed image COR2.

10. The device according to claim 7 , wherein the metal artifacts include strip artifacts and hardening artifacts and said machine readable instructions further cause the processor to:
pre-process scan data corresponding to the original image to reduce the strip artifacts in the original image and to obtain an Ori-Air image; and
apply a hardening correction to the Ori-Air image to reduce the hardening artifacts in the Ori-Air image and to obtain the second processed image COR2.

11. The device according to claim 10 , wherein said machine readable instructions further cause the processor to:
smoothing filter the Ori-Air image to obtain an Ori-Air-Smo image;
smoothing filter the first processed image COR1 to obtain a COR1-Smo image;
calculate the difference between the Ori-Air-Smo image and the COR1-Smo image to obtain an image HardenArti containing hardening artifacts; and
calculate the difference between the Ori-Air image and the image HardenArti to obtain the second processed image COR2.

12. The device according to claim 7 , wherein said machine readable instructions further cause the processor to:
apply low-pass filtering to the metal image to obtain a low-frequency metal image; and
normalize the low-frequency metal image to obtain the weighting function W.

Assignees

• Shenyang Neusoft Medical Sys

Inventors

• Han Junlong
• Pang Ling
• Lou Shanshan

Classifications

• G06T12/30 Primary

  Image post-processing, e.g. metal artefact correction · CPC title

• G06T11/008 Primary

  Physics · mapped topic

• G06T5/70 Primary

  Denoising; Smoothing · CPC title

• G06T2207/20024

  Filtering details · CPC title

• G06T2207/10081

  Computed x-ray tomography [CT] · CPC title