Plaque region extracting method and apparatus therefor

1. A plaque region extracting method comprising:

extracting first image data including a blood vessel wall from image data acquired by imaging a subject including blood vessels;

filtering an intermediate region in the first image data to generate intermediate second image data;

processing the difference between the first image data and the second image data to generate third image data; and

extracting a plaque in the blood vessel on the basis of the third image data.

2. The plaque region extracting method according to claim 1 , wherein

the second image data is generated by filtering the first image data along the traveling direction of the blood vessel to find the value of the intermediate region.

3. The plaque region extracting method according to claim 1 , wherein

the third image data is generated from the difference between the first image data and the second image data by enhancing image regions lower in pixel value than peripheral portions in the first image data.

4. The plaque region extracting method according to claim 1 , wherein

the plaque is extracted from the blood vessel in accordance with levels of thresholds based on a standard deviation which is found from the pixel value of the first image data.

5. A plaque region extracting apparatus comprising:

a blood vessel wall data extracting unit which extracts first image data including a blood vessel wall from image data acquired by imaging a subject including blood vessels;

an intermediate image data generating unit which filters an intermediate region in the first image data to generate intermediate second image data;

an enhancement processing unit which processes the difference between the first image data and the second image data to generate third image data; and

a plaque extracting unit which extracts a plaque in the blood vessel on the basis of the third image data.

6. The plaque region extracting apparatus according to claim 5 , wherein

the intermediate image data generating unit generates the second image data by filtering the first image data along the traveling direction of the blood vessel to find the value of the intermediate region.

7. The plaque region extracting apparatus according to claim 5 , wherein

the enhancement processing unit generates the third image data from the difference between the first image data and the second image data by enhancing image regions lower in pixel value than peripheral portions in the first image data.

8. The plaque region extracting apparatus according to claim 5 , wherein

the plaque extracting unit extracts the plaque from the blood vessel in accordance with levels of thresholds based on a standard deviation which is found from the pixel value of the first image data.

9. The plaque region extracting apparatus according to claim 5 , wherein

the image data is CT image data, and

the plaque extracting unit finds a standard deviation of CT values from a required part of the blood vessel, multiplies the standard deviation by different numerical values to calculate thresholds, separates the difference of the CT values in accordance with regions that are sorted by the thresholds, and thereby determines the certainty factor of the plaque region.

10. The plaque region extracting apparatus according to claim 5 , wherein

the plaque extracting unit finds thresholds on the basis of a statistical analytic value of a pixel value in a required part of the blood vessel, and uses the thresholds to find plaque regions different in reliability.

11. The plaque region extracting apparatus according to claim 5 , wherein

the image data is CT image data, and

the intermediate image data generating unit generates the second image data by filtering the intermediate region along the center line direction of the blood vessel included in the first image data,

the enhancement processing unit generates, from the difference of CT values between the first image data and the second image data, differential image data as the third image data in which image regions lower in the pixel value than peripheral portions are enhanced, and the enhancement processing unit generates, from the differential image data, a differential value distribution that indicates the number of pixels versus the difference of the CT values, and

the plaque extracting unit finds a standard deviation of the CT values from a required part of the blood vessel, integrally multiplies the standard deviation by different numerical values to calculate thresholds, separates the difference of the CT values in accordance with regions that are sorted by the thresholds, and thereby determines the certainty factor of the plaque region.

12. The plaque region extracting apparatus according to claim 11 , wherein

the plaque extracting unit sets, as the thresholds, the standard deviation, double the standard deviation, and triple the standard deviation, and the plaque extracting unit unconditionally determines the difference of the CT values equal to or more than triple the standard deviation as the plaque region, determines the difference of the CT values between triple the standard deviation and double the standard deviation as the plaque region with a first condition, and determines the difference of the CT values between double the standard deviation and the standard deviation as the plaque region with a second condition.

13. The plaque region extracting apparatus according to claim 11 , wherein

the first condition is to be adjacent to the unconditionally determined plaque region or to have a given volume or more, and

the second condition is to be adjacent to the determined plaque region.