Medical image processing apparatus and X-ray CT apparatus

1. A medical image processing apparatus comprising:

processing circuitry configured to

set a first region of interest in a region corresponding to cardiac muscle on a cross-section of a heart included in image data;

set a second region of interest that is larger than the first region of interest in a region including the region;

determine a threshold for removing noise included in the second region of interest based on a frequency distribution of a signal value in the first region of interest; and

carry out blood flow dynamic analysis on the second region of interest using signal values included in a range based on the threshold.

2. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to set the first region of interest by setting a boundary of the cardiac muscle on the cross-section of the heart in a manner excluding a signal other than signal derived from a contrast material flowing into the cardiac muscle.

3. The medical image processing apparatus according to claim 2 , wherein the processing circuitry is configured to set the first region of interest by extracting the cardiac muscle on the cross-section of the heart, performing dilation processing on an inner contour corresponding to an inner wall of the extracted cardiac muscle, and performing reduction processing on an outer contour corresponding to an outer wall of the cardiac muscle.

4. The medical image processing apparatus according to claim 3 , wherein the processing circuitry is configured to receive an input operation from an operator and perform the dilation processing and the reduction processing in response to the received input operation.

5. The medical image processing apparatus according to claim 2 , wherein the processing circuitry is configured to extract the cardiac muscle on the cross-section of the heart, deform a region surrounded by a contour of the extracted cardiac muscle such that a frequency distribution of a signal value in the region surrounded by the contour is approximate to a normal distribution, and set the deformed region as the first region of interest.

6. The medical image processing apparatus according to claim 2 , wherein the processing circuitry is configured to set an inner boundary corresponding to an inner wall of the cardiac muscle in a manner excluding a signal derived from a lumen surrounded by the cardiac muscle from a region surrounded by the boundary of the cardiac muscle.

7. The medical image processing apparatus according to claim 2 , wherein the processing circuitry is configured to set an outer boundary corresponding to an outer wall of the cardiac muscle in a manner excluding a signal derived from a lumen adjacent to a lumen surrounded by the cardiac muscle from a region surrounded by the boundary of the cardiac muscle.

8. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to divide the region into a plurality of partial regions, set the first region of interest in each of the partial regions, and set the second region of interest in each of the partial regions.

9. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to determine a threshold for a frequency distribution of a signal value in the first region of interest using a mean value, a standard deviation, or variance and carries out blood flow dynamic analysis on the second region of interest using a signal value lower than the threshold.

10. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to cause a display to display a display image including the first region of interest and the second region of interest displayed on the cross-section of the heart.

11. An X-ray Computed Tomography (CT) apparatus comprising:

processing circuitry configured to

collect image data including a heart;

set a first region of interest in a region corresponding to cardiac muscle on a cross-section of the heart included in the image data;

set a second region of interest that is larger than the first region of interest in a region including the region;

determine a threshold for removing noise included in the second region of interest based on a frequency distribution of a signal value in the first region of interest; and

carry out blood flow dynamic analysis on the second region of interest using signal values included in a range based on the threshold.

12. The X-ray CT apparatus according to claim 11 , wherein the processing circuitry is configured to set the first region of interest by setting a boundary of the cardiac muscle on the cross-section of the heart in a manner excluding a signal other than signal derived from a contrast material flowing into the cardiac muscle.

13. The X-ray CT apparatus according to claim 12 , wherein the processing circuitry is configured to set the first region of interest by extracting the cardiac muscle on the cross-section of the heart, performing dilation processing on an inner contour corresponding to an inner wall of the extracted cardiac muscle, and performing reduction processing on an outer contour corresponding to an outer wall of the cardiac muscle.

14. The X-ray CT apparatus according to claim 13 , wherein the processing circuitry is configured to receive an input operation from an operator and perform the dilation processing and the reduction processing in response to the received input operation.

15. The X-ray CT apparatus according to claim 12 , wherein the processing circuitry is configured to extract the cardiac muscle on the cross-section of the heart, deform a region surrounded by a contour of the extracted cardiac muscle such that a frequency distribution of a signal value in the region surrounded by the contour is approximate to a normal distribution, and set the deformed region as the first region of interest.

16. The X-ray CT apparatus according to claim 12 , wherein the processing circuitry is configured to set an inner boundary corresponding to an inner wall of the cardiac muscle in a manner excluding a signal derived from a lumen surrounded by the cardiac muscle from a region surrounded by the boundary of the cardiac muscle.

17. The X-ray CT apparatus according to claim 12 , wherein the processing circuitry is configured to set an outer boundary corresponding to an outer wall of the cardiac muscle in a manner excluding a signal derived from a lumen adjacent to a lumen surrounded by the cardiac muscle from a region surrounded by the boundary of the cardiac muscle.

18. The X-ray CT apparatus according to claim 11 , wherein the processing circuitry is configured to divide the region into a plurality of partial regions, set the first region of interest in each of the partial regions, and set the second region of interest in each of the partial regions.

19. The X-ray CT apparatus according to claim 11 , wherein the processing circuitry is configured to determine a threshold for a frequency distribution of a signal value in the first region of interest using a mean value, a standard deviation, or variance and carries out blood flow dynamic analysis on the second region of interest using a signal value lower than the threshold.

20. The X-ray CT apparatus according to claim 11 , wherein the processing circuitry is configured to cause a display to display a display image including the first region of interest and the second region of interest displayed on the cross-section of the heart.