Method and system for image processing to determine patient-specific blood flow characteristics

1. A method of image processing to determine a blood flow characteristic, comprising:

receiving patient-specific image data that includes a representation of at least a vessel and a stenosis in the vessel of a patient;

estimating an outlet flow rate of the stenosis based on a cross-sectional metric at an outlet of the stenosis, a cross-sectional metric at an inlet of the stenosis, and an estimated blood flow rate or pressure at the inlet of the stenosis;

estimating a fractional flow reserve (“FFR”) or resistance to flow of blood through the stenosis based on the estimated blood flow rate or pressure at the inlet of the stenosis, the estimated outlet flow rate, and a computational fluid dynamics simulation;

assigning, to the estimated FFR or resistance of the vessel, one of a plurality of different pre-defined visual indicators based on an empirical model and one of the estimated outlet flow rate or the estimated FFR or resistance; and

generating a display indicative of the visual indicators assigned to the estimated FFR or resistance.

2. The method of claim 1 , wherein the assignment includes generating a numerical value for the FFR and, further comprising:

assigning the visual indicator based on the numerical value.

3. The method of claim 1 , wherein the features include one or more of a degree of stenosis, a stenosis length, a stenosis position, a ventricular chamber size, a myocardial mass, a geometry of a coronary artery, and a center line of a coronary artery.

4. The method of claim 3 , wherein the features include one or more of a subset of at least one patient-specific image corresponding to one or more intensities along the vessel, heart rate, subject age, or a result of a computational fluid dynamic simulation.

5. The method of claim 1 , further comprising:

performing a subsequent computational fluid dynamics simulation based on the estimated outlet flow rate of the stenosis and the estimated resistance.

6. The method of claim 5 , further comprising:

determining the FFR for the stenosis based on a result of the subsequent computational fluid dynamics simulation.

7. The method of claim 1 , further comprising:

estimating a point estimation of FFR for the stenosis and generating an indication of the estimated point estimation of FFR.

8. The method of claim 1 , further comprising:

determining the flow rate at the inlet of the stenosis using a library trained with patient data, including at least one of image or non-image data, and flow rate measurements of other patients determined via cardiac catheterization.

9. The method claim 8 , further comprising:

determining a velocity based on the outlet flow rate.

10. The method of claim 1 , further comprising:

iteratively estimating the resistance by:

calculating an initial resistance as a function of the aortic blood pressure at the inlet of the stenosis and the outlet flow rate;

performing the computational fluid dynamic simulation;

generating a subsequent resistance based on the initial resistance and a result of the computational fluid dynamic simulation, wherein the subsequent resistance is the estimated resistance; and

repeating the acts of performing and generating using a current resistance until stopping iteration criteria is satisfied.

11. A system for image processing to determine a blood flow characteristic, comprising:

a data storage device storing instructions for assigning a visual indicator to a fractional flow reserve (“FFR”) for a stenosis; and

a processor configured to execute the instructions to perform a method comprising:

receiving patient-specific image data that includes a representation of at least a vessel and a stenosis in the vessel of a patient;

estimating at least one condition of a stenosis of a vessel, including at least one of an FFR, an estimated outlet flow rate of the stenosis, or an estimated resistance to flow of blood through the stenosis, wherein:

based on the received patient-specific image data, an outlet flow rate of the stenosis is estimated as a function of a cross-sectional metric at an outlet of the stenosis, a cross-sectional metric at an inlet of the stenosis, and a flow rate at the inlet of the stenosis, and

a resistance is estimated based on an aortic blood pressure at the inlet of the stenosis, the outlet flow rate, and a computational fluid dynamics simulation;

assigning, to the estimated FFR, estimated outlet flow rate, or estimated resistance, one of a plurality of different pre-defined visual indicators based on an empirical model, and at least one of the estimated FFR, the estimated outlet flow rate, or the estimated resistance; and

generating a display indicative of the visual indicators assigned to the estimated FFR, estimated outlet flow rate, or estimated resistance.

12. The system of claim 11 , further configured for:

determining the flow rate at the inlet of the stenosis using a library trained with patient data, including at least one of image or non-image data, and flow rate measurements of other patients determined via cardiac catheterization.

13. The system of claim 11 , further configured for:

estimating a velocity for the stenosis based on a flow rate.

14. The system of claim 11 , further configured for:

performing a computational fluid dynamics (“CFD”) simulation based on the at least one condition; and

determining an FFR for the stenosis based on a result of the CFD simulation.