FFR Index Calculation with Adaptive Boundary Conditions
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for determining the fractional flow reserve (FFR) index, such as invasive pressure wire measurements and non-invasive computational fluid dynamics (CFD) simulations, face challenges in accurately estimating FFR due to unclear boundary conditions, particularly the constant resistance assumption at coronary outlets, leading to estimation errors.
Innovation Solution
An iterative approach is employed to estimate and correct boundary conditions based on the severity of a vessel stenosis, using initial assumptions of healthy vessels and iteratively refining resistance estimates through CFD simulations until a stopping criterion is met, resulting in a more accurate FFR index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a lumped model with constant resistor is used at coronary outlets to estimate boundary conditions, then the computational process is simplified, but the estimation accuracy of FFR deteriorates due to the unrealistic assumption that resistance is constant
Solution Approach 1:
The patent transforms the static constant resistance model into a dynamic model where resistance varies with flow rate. The resistance at coronary outlets is modeled as a function of flow rate using the relationship R = R0 * (Q/Q0)^(-1), where R0 and Q0 are reference values. This dynamic adjustment of resistance based on actual flow conditions significantly improves FFR estimation accuracy while maintaining computational feasibility.
Solution Approach 2:
The patent changes the resistance parameter from a fixed constant value to a variable that depends on flow rate. By implementing the resistance-flow relationship R(Q) = R0 * (Q/Q0)^(-1), the model adapts resistance values according to actual physiological conditions, resolving the contradiction between model simplicity and accuracy.
2Measurement precision
If iterative correction of boundary conditions is implemented based on stenosis severity, then the FFR estimation accuracy is improved, but the computational complexity and processing time increase
Solution Approach 1:
The patent implements a feedback mechanism where the initially estimated FFR value is used to correct the boundary conditions (resistance values) at coronary outlets. The corrected resistance values are then used in a subsequent CFD simulation to obtain a more accurate FFR. This iterative feedback process continues until convergence, significantly improving accuracy while managing computational complexity through efficient convergence criteria.
Solution Approach 2:
The patent performs a preliminary CFD simulation with initial boundary conditions to obtain a first FFR estimate before refining the boundary conditions. This preliminary action provides the basis for subsequent corrections, allowing the iterative process to start from a reasonable approximation and converge more efficiently, thus managing computational complexity.
3Ease of operation
If the resistance at coronary outlets is assumed to be constant, then the boundary conditions are easier to define, but the physiological accuracy deteriorates because actual resistance varies with flow conditions
Solution Approach 1:
The patent transforms the resistance parameter from a fixed constant to a variable that changes with flow rate according to the relationship R(Q) = R0 * (Q/Q0)^(-1). This parameter change maintains ease of operation by using a simple mathematical relationship while dramatically improving physiological accuracy by capturing the flow-dependent nature of vascular resistance.
Solution Approach 2:
The patent introduces dynamics into the boundary condition model by making resistance dependent on flow rate. The dynamic resistance model R(Q) reflects actual physiological behavior where vascular resistance changes with blood flow conditions, resolving the contradiction between ease of definition and physiological accuracy.
Data Source
AI summary
A method includes obtaining a boundary condition estimate. The boundary condition estimate includes at least an estimated outlet resistance of a vessel with a stenosis. The method further includes correcting the boundary condition estimate based on a severity of the stenosis, thereby creating a corrected boundary condition. The method further includes determining an FFR index based on the corrected boundary condition. The method further includes displaying the FFR index. A computing system includes a computer readable storage medium with instructions that iteratively determine at least an FFR index based on a severity of a stenosis of a vessel. The computing system further includes a computer processor that processes the instructions and generates the FFR index based on the severity of the stenosis of the vessel.