Blood flow determination apparatus

A blood flow determination method comprising:

• determining a speckle density value indicative of a level of a speckle density in 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 is introduced into the blood vessel with a volumetric fluid flow rate that is known;
• determining a blood speckle density value indicative of the level of the speckle density in a second ultrasound image only showing blood;
• determining a fluid speckle density value indicative of the level of the speckle density in a third ultrasound image only showing the fluid;
• determining a blood flow value indicative of a volumetric blood flow rate based on a relation including two or more values of a plurality of values, wherein the plurality of values comprises the speckle density value, the volumetric fluid flow rate, the blood speckle density value, and the fluid speckle density value, wherein a first value of the two or more values is the speckle density value, and wherein a second value of the two or more values is the blood speckle density value or the fluid speckle density value;
• and
• displaying the blood flow value.