Three-dimensional derivation of a proximal isokinetic shell of a proximal flow convergence zone and three-dimensional PISA flow measurement

A device for measuring flow rate of blood in human body using adaptive three-dimensional derivation of a proximal isokinetic shell of a proximal flow convergence zone that forms in an observation area in the blood, wherein magnitude of velocity of the blood at each point of the proximal isokinetic shell is the same, and wherein device comprises:

• a color Doppler ultrasound device configured to obtain locally distributed velocity measurements in an area surrounding the observation area, said velocity measurements representing at least one directional component of the local velocity of the blood in a respective measurement direction;
• a control and evaluation system configured to execute a series of steps comprising
• a) selecting one of the velocity measurement values obtained by the color Doppler ultrasound device as a velocity reference value,
• b) preparing an approximation surface as an initial proximal isokinetic shell in such a way that the entire flow, at least substantially, in the flow convergence zone penetrates the approximation surface,
• c) establishing a plurality of approximation points on the approximation surface,
• d) determining a velocity measurement vkj at each approximation point,
• e) calculating a corrected velocity vkkj at each approximation point as a function of the velocity measurement at the respective approximation point, the respective measurement direction;
• and a surface normal at the respective approximation point,
• f) determining a correction direction by comparing the corrected velocity with the velocity reference value,
• g) shifting the approximation points in the respective correction direction to new positions, if necessary,
• h) acquiring a new approximation surface such that the new approximation surface at least approaches the new positions of the approximation points, and
• i) repeating steps (c) through (h) until the change of the new approximation surface is sufficiently minimal compared to the old approximation surface,
• j) determining surface area of the new approximation surface acquired in step (i),
• k) calculating the flow rate of blood by multiplying the surface area of the new approximation surface by the velocity reference value;
• and
• a non-transitory storage means configured to store the velocity measurements obtained by the color Doppler ultrasound device, the velocity reference value, at least one approximation surface of the proximal isokinetic shell, and the plurality of approximation points.

A non-transitory computer readable medium comprising a set of instructions that when executed by a computer processor, result in a series of steps being performed which carry out a method of measuring flow rate of blood in human body, using adaptive three-dimensional derivation of a proximal isokinetic shell of a proximal flow convergence zone that forms in an observation area in the blood, wherein magnitude of velocity of the blood at each point of the proximal isokinetic shell is the same, the method comprises the steps of:

• a) storing locally distributed velocity measurements in an area surrounding the observation area obtained using a color Doppler ultrasound device, said velocity measurements representing at least one directional component of the local velocity of the blood in a respective measurement direction,
• b) selecting one of the velocity values obtained in step (a) as a velocity reference value,
• c) preparing an approximation surface as an initial proximal isokinetic shell in such a way that the entire flow, at least substantially, in the flow convergence zone penetrates the approximation surface,
• d) establishing a plurality of approximation points on the approximation surface,
• e) determining a velocity measurement vkj at each approximation point,
• f) calculating a corrected velocity vkk, at each approximation point as a function of the velocity measurement at the respective approximation point, the respective measurement direction;
• and a surface normal at the respective approximation point,
• g) determining a correction direction by comparing the corrected velocity with the velocity reference value,
• h) shifting the approximation points in the respective correction direction to new positions, if necessary,
• i) acquiring a new approximation surface such that the new approximation surface at least approaches the new positions of the approximation points, and
• j) repeating steps d) through i) until the change of the new approximation surface is sufficiently minimal compared to the old approximation surface,
• k) determining surface area of the new approximation surface acquired in step (j),
• l) calculating the flow rate of blood by multiplying the surface area of the new approximation surface by the velocity reference value.