Blood flow determination apparatus

1. A blood flow determination method comprising:

controlling an intravascular ultrasound (IVUS) imaging probe to obtain a first ultrasound image of an inner lumen of a blood vessel at an imaging location, wherein the imaging location is behind an introduction location with respect to a flow direction of blood within the blood vessel, wherein the introduction location corresponds to a fluid that has been introduced into the blood vessel with a volumetric fluid flow rate that is known;

determining a speckle density in the first ultrasound image, wherein the speckle density is representative of a concentration of ultrasound scatterers in the inner lumen of the blood vessel at the imaging location;

determining a blood speckle density in a second ultrasound image showing only the blood;

determining a blood flow value indicative of a volumetric blood flow rate using a relation including the volumetric fluid flow rate and a ratio between the speckle density and the blood speckle density, wherein a value of the speckle density itself forms a portion of the relation such that:

the blood flow value is determined based on the concentration of the ultrasound scatterers; and

the speckle density is not used to determine a time for the fluid to travel a distance within the blood vessel; and

displaying the blood flow value.

2. The method of claim 1 , wherein the first ultrasound image shows a mixture of the blood and the fluid.

3. The method of claim 1 , wherein the relation comprises a non-linear relation between the blood flow value and the speckle density.

4. The method of claim 1 , wherein the relation comprises a non-linear function relating the value of the speckle density to the concentration of the ultrasound scatterers.

5. The method of claim 1 , wherein the speckle density is an average echogenicity signal.

6. The method of claim 1 ,

wherein the determining the speckle density is based on a speckle density curve,

wherein the value of the speckle density is based on a minima of the speckle density curve.

7. The method of claim 1 ,

wherein the fluid comprises saline, and

wherein the value of the speckle density is zero.

8. The method of claim 1 ,

further comprising:

generating a plurality of ultrasound images of the inner lumen of the blood vessel,

determining a plurality of speckle densities based on the plurality of ultrasound images; and

determining an average speckle density based on the plurality of speckle densities,

wherein the value of the speckle density is a value of the average speckle density.

9. The method of claim 1 ,

further comprising:

generating a plurality of ultrasound images at a plurality of introduction locations where the fluid has been introduced into the blood vessel;

determining a plurality of speckle densities based on the plurality of ultrasound images; and

determining a plurality of blood flow values indicative of a plurality of volumetric blood flow rates using the relation,

wherein the relation comprises the plurality of speckle densities.

10. The method of claim 1 ,

wherein determining the speckle density value is based on an entire region of the first ultrasound image, and

wherein the value of the speckle density comprises a spatial average value.

11. The method of claim 1 ,

further comprising segmenting a portion of the first ultrasound image that includes only the inner lumen of the blood vessel; and

wherein determining the speckle density value is based on the portion of the first ultrasound image.

12. The method of claim 1 , wherein the fluid comprises a contrast agent.

13. The method of claim 12 , further comprising:

generating an x-ray-based image of the blood vessel showing the contrast agent; and

displaying the x-ray-based image.

14. The method of claim 1 , further comprising controlling a fluid pump to introduce the fluid into the blood vessel.

15. The method of claim 14 , wherein the volumetric fluid flow rate is constant.