Medical image processing apparatus, medical image processing method, and X-ray diagnostic apparatus

1. A medical image processing apparatus comprising processing circuitry configured to

generate, from a time series of images of a blood vessel, a reference image from a contrast image of the blood vessel acquired in time series, wherein the reference image is acquired in a presence of a contrast agent,

conduct a transformation process on blood vessel images other than the reference image such that blood vessel shapes of the blood vessel in the blood vessel images other than the reference image match a blood vessel shape of the blood vessel in the reference image by warping the blood vessel shapes on a pixel by pixel basis with respect to the blood vessel shape in the reference image,

for each pixel of a plurality of pixels,

calculate a pixel value that is assigned to the pixel based on the transformed blood vessel images after the transformation process,

determine a parameter based on a temporal change of the calculated pixel value of the pixel based on the transformed blood vessel images after the transformation process, and

determine a color that corresponds to the parameter,

generate a color image by assigning colors to pixels of the color image such that the assigned colors to the pixels of the color image correspond to the determined colors for the determined parameters of the plurality of pixels based on the transformed blood vessel images after the transformation process, and

display the color image on a display, wherein the processing circuitry is configured to generate subtraction images by conducting subtraction on the contrast image and mask images, and

perform image processing to determine an optimum subtraction image for the contrast image among the generated subtraction images, wherein optimum subtraction images are determined for each of a set of contrast images corresponding to the blood vessel images other than the reference image.

2. The medical image processing apparatus according to claim 1 , wherein, for each pixel of the plurality of pixels, the processing circuitry is configured to determine, as the parameter, a flow time of a contrast agent injected into an object in accordance with the temporal change of the calculated pixel value of the pixel based on the transformed blood vessel images and determine a color that corresponds to the flow time at the pixel.

3. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to generate the reference image in accordance with a result of a correlation calculation between the contrast image of the blood vessel and the time series of images of the blood vessel other than the reference image.

4. The medical image processing apparatus according to claim 1 ,

wherein the processing circuitry is configured to generate the reference image from the contrast image of the blood vessel in accordance with a biological signal based on contrast images of a periodically moving object, the biological signal being acquired from the periodically moving object by a biosignal acquisition device, which is connected to the medical image processing apparatus.

5. The medical image processing apparatus according to claim 4 ,

wherein the processing circuitry is configured to generate the reference image using as the contrast image of the blood vessel a blood vessel image in a phase near maximum expiration based on a respiration phase, the respiration phase being acquired by the biosignal acquisition device as the biological signal.

6. The medical image processing apparatus according to claim 4 ,

wherein the processing circuitry is configured to generate the reference image using as the contrast image of the blood vessel a blood vessel image in a phase near mid-diastole based on a heart phase, the heart phase being acquired by the biosignal acquisition device as the biological signal.

7. The medical image processing apparatus according to claim 4 , wherein the processing circuitry is configured to generate the reference image by subtracting (1) the contrast image of the blood vessel and (2) a non-contrast image of the blood vessel in the time series that has an identical phase to the biological signal of the contrast image of the blood vessel.

8. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to generate the reference image by subtracting (1) the contrast image of the blood vessel and (2) a non-contrast image of the blood vessel in the time series that has a fewest number of pixels having an opposite phase with respect to a pixel value at each position of the contrast image of the blood vessel.

9. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to generate the reference image by subtracting (1) the contrast image of the blood vessel and (2) an image obtained by performing low-frequency processing on the contrast image of the blood vessel.

10. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to display the color image as a still image.

11. The medical image processing apparatus according to claim 1 , wherein the processing circuitry is configured to display the color image as an animation.

12. A medical image processing method comprising:

generating, from a time series of images of a blood vessel, a reference image from a contrast image of the blood vessel acquired in the time series, wherein the reference image is acquired in a presence of a contrast agent;

conducting a transformation process on blood vessel images other than the reference image such that blood vessel shapes of the blood vessel in the blood vessel images other than the reference image match a blood vessel shape in the reference image by warping the blood vessel shapes on a pixel by pixel basis with respect to the blood vessel shape in the reference image,

for each pixel of a plurality of pixels,

calculating a pixel value that is assigned to the pixel based on the transformed blood vessel images after the transformation process,

determining a parameter based on a temporal change of the calculated pixel value of the pixel based on the transformed blood vessel images after the transformation process, and

determining a color that corresponds to the parameter,

generating a color image by assigning colors to pixels of the color image such that the assigned colors to the pixels of the color image correspond to the determined colors for the determined parameters of the plurality of pixels based on the transformed blood vessel images after the transformation process, and

displaying the color image on a display, wherein the medical image processing method further comprises: generating subtraction images by conducting subtraction on the contrast image and mask images; and

performing image processing to determine an optimum subtraction image for the contrast image among the generated subtraction images, wherein optimum subtraction images are determined for each of a set of contrast images corresponding to the blood vessel images other than the reference image.

13. The medical image processing method according to claim 12 , further comprising, for each pixel of the plurality of pixels, determining, as the parameter, a flow time of a contrast agent injected into an object in accordance with the temporal change of the calculated pixel value of the pixel based on the transformed blood vessel images and determining a color that corresponds to the flow time at the pixel.

14. The medical image processing method according to claim 12 , further comprising generating the reference image in accordance with a result of a correlation calculation between the contrast image of the blood vessel and the blood vessel images other than the reference image.

15. The medical image processing method according to claim 12 , further comprising generating the reference image from the contrast image of the blood vessel in accordance with a biological signal that is acquired from a periodically moving object by a biosignal acquisition device.

16. The medical image processing method according to claim 15 , further comprising generating the reference image by subtracting (1) the contrast image of the blood vessel and (2) a non-contrast image of the blood vessel in the time series that has an identical phase to the biological signal of the contrast image of the blood vessel.

17. The medical image processing method according to claim 12 , further comprising generating the reference image by subtracting (1) the contrast image of the blood vessel and (2) a non-contrast image of the blood vessel in the time series that has a fewest number of pixels having an opposite phase with respect to a pixel value at each position of the contrast image of the blood vessel.

18. The medical image processing method according to claim 12 , further comprising generating the reference image by subtracting (1) the contrast image of the blood vessel and (2) an image obtained by performing low-frequency processing on the contrast image of the blood vessel.

19. The medical image processing method according to claim 12 , further comprising displaying the color image as a still image or an animation.

20. An X-ray diagnostic apparatus comprising processing circuitry configured to

generate, from a time series of images of a blood vessel, a reference image from a contrast image of the blood vessel acquired in the time series, wherein the reference image is acquired in a presence of a contrast agent,

conduct a transformation process on blood vessel images other than the reference image such that blood vessel shapes of the blood vessel in the blood vessel images other than the reference image match a blood vessel shape of the blood vessel in the reference image by warping the blood vessel shapes on a pixel by pixel basis with respect to the blood vessel shape in the reference image,

for each pixel of a plurality of pixels,

calculate a pixel value that is assigned to the pixel based on the transformed blood vessel images after the transformation process,

determine a parameter based on a temporal change of the calculated pixel value of the pixel based on the transformed blood vessel images after the transformation process, and

determine a color that corresponds to the parameter,

generate a color image by assigning colors to pixels of the color image such that the assigned colors to the pixels of the color image correspond to the determined colors for the determined parameters of the plurality of pixels based on the transformed blood vessel images after the transformation process, and

display the color image on a display, wherein the processing circuitry is configured to generate subtraction images by conducting subtraction on the contrast image and mask images, and

perform image processing to determine an optimum subtraction image for the contrast image among the generated subtraction images, wherein optimum subtraction images are determined for each of a set of contrast images corresponding to the blood vessel images other than the reference image.