3D Coronary Flow MRI for Non-Invasive Stenosis Quantification
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Solution Overview
Problem
Current methods for assessing the hemodynamic relevance of coronary artery stenosis are unreliable and invasive, or non-invasive methods are inaccurate due to scan time limitations and reliance on unmeasured assumptions.
Innovation Solution
A 3D flow MRI method that combines morphological imaging with flow quantification using segmented imaging sequences and additional flow encoding gradients to generate spatially resolved flow parameters directly from MR signals, allowing for simultaneous generation of morphological and flow images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If invasive pressure measurements are taken under X-RAY (Angiography), then hemodynamic relevance can be assessed with FFR, but the procedure is invasive and requires ionizing radiation
Solution Approach 1:
The patent replaces the mechanical/invasive catheter-based pressure measurement system with a non-invasive MRI-based flow measurement system. Phase contrast MRI velocity measurements are combined with computational fluid dynamics to derive hemodynamic parameters without requiring physical insertion of catheters or exposure to ionizing radiation.
Solution Approach 2:
The patent introduces computational fluid dynamics simulations as an intermediary between non-invasive MRI flow measurements and hemodynamic parameter assessment. The CFD simulations process the MRI velocity data to calculate pressure drops and FFR values, serving as a mediator that translates flow measurements into hemodynamic relevance information without requiring direct pressure measurements.
2Ease of operation
If non-invasive cardiovascular magnetic resonance imaging with cardiac perfusion acquisition is performed, then hemodynamic relevance can be assessed, but the measurement is indirect and only performed in 2D due to scan time limitations
Solution Approach 1:
The patent transitions from 2D perfusion imaging to 3D phase contrast MRI flow measurement. By acquiring velocity-encoded MRI data in three dimensions, the system directly measures blood flow through the coronary arteries, providing spatially resolved flow information that captures the full complexity of coronary hemodynamics without the limitations of 2D projections.
Solution Approach 2:
The patent replaces the indirect perfusion-based assessment with direct flow measurement using phase contrast MRI. Instead of measuring the effect of stenosis on myocardial perfusion, the system directly quantifies blood flow velocity and volume in the coronary arteries, providing a more accurate and direct assessment of hemodynamic relevance.
3Ease of operation
If virtual FFR is calculated based on CT angiography and computational fluid dynamic simulations, then non-invasive hemodynamic assessment is possible, but the calculation is based on many unmeasured assumptions and boundary conditions
Solution Approach 1:
The patent makes the system self-sufficient by acquiring all necessary boundary conditions and input parameters directly through MRI measurements. The phase contrast MRI provides both the flow rates and pressure information needed for CFD simulations, eliminating the need for external assumptions about inlet flow conditions, wall shear stress, or pressure gradients that plague CT-based virtual FFR methods.
Solution Approach 2:
The patent implements a feedback loop where MRI flow measurements are used to validate and refine the CFD simulations. The measured flow rates serve as ground truth to verify the accuracy of simulated flow patterns, allowing iterative optimization of the hemodynamic model to match actual patient physiology, thereby reducing reliance on unmeasured assumptions.
4Measurement precision
If 3D flow MRI with segmented imaging sequences and flow encoding gradients is used, then direct non-invasive flow measurement is achieved, but the scan time and sequence complexity increase
Solution Approach 1:
The patent divides the 3D k-space acquisition into multiple segmented trajectories, where each segment covers a portion of k-space. This allows parallel acquisition of flow-encoded and non-flow-encoded data within the same cardiac cycle, reducing the total number of heartbeats required and minimizing motion artifacts while maintaining high flow measurement accuracy.
Solution Approach 2:
The patent employs periodic flow encoding gradients applied in a repeating pattern throughout the 3D imaging sequence. By synchronizing the gradient application with the cardiac cycle and using periodic refocusing pulses, the system efficiently encodes flow information at multiple time points without proportionally increasing scan time, leveraging the periodic nature of cardiac motion to reduce acquisition duration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables direct, non-invasive measurement of blood flow in coronary arteries with improved signal-to-noise ratio and reduced acquisition time, providing accurate hemodynamic parameters without the need for invasive procedures or computational fluid dynamics.
Implementation Method 1
MR signals of the heart are detected taking into account the heartbeat using a 3D imaging sequence
Implementation Method 2
a quantitative flow parameter of blood flowing in the coronary artery is determined taking into account the flow encoding segments and the additional segments
Data Source
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AI summary
The invention discloses a method for determining a quantitative flow parameter in a coronary artery of a heart, wherein the method comprises at a magnetic resonance imaging system the steps of determining a heartbeat of the heart, detecting MR signals from the heart, taking into account the heartbeat, using a 3D imaging sequence of a region of interest comprising the heart, wherein the 3D imaging sequence is a segmented imaging sequence comprising flow encoding segments in which additional flow encoding gradients are switched in different gradient directions, and additional segments without additional flow encoding gradients, generating a plurality of 3D k-space sets from the detected MR signals detected in the additional segments and the flow encoding segments, generating at least one morphological MR image of the heart showing at least one coronary artery of the heart based on the detected MR signals, and determining the quantitative flow parameter of blood flowing in the coronary artery taking into account the flow encoding segments and the additional segments.