Non-contrast MRA Using ECG-Gated Single-Shot Acquisition
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Solution Overview
Problem
Current non-contrast enhanced magnetic resonance angiography (MRA) methods are limited by sensitivity to patient motion, inadequate arterial conspicuity, and long scan times, and struggle to accurately depict arterial anatomy across a wide range of flow velocities while effectively suppressing venous signals.
Innovation Solution
A two-dimensional single shot acquisition method that synchronizes a quiescent interval with systolic arterial flow and data acquisition during diastole, combined with the use of saturation pulses in contiguous slabs to enhance venous suppression, allowing for rapid imaging with high arterial conspicuity and minimal venous signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If non-contrast enhanced MRA methods are used to avoid gadolinium administration, then patient safety is improved, but arterial conspicuity and venous suppression are worsened
Solution Approach 1:
A saturation pulse is applied in a first slab before the imaging slice to pre-saturate venous spins that will flow into the imaging slice. This preliminary action ensures that when blood flows from the first slab into the imaging slice during the quiescent interval, the venous signal is already suppressed, improving arterial conspicuity without requiring contrast agents.
Solution Approach 2:
The imaging volume is divided into multiple slabs, with the first slab positioned upstream relative to the imaging slice. This segmentation allows selective saturation of venous blood in the first slab while leaving arterial blood unsaturated, enabling differential signal suppression based on flow direction and origin.
2Productivity
If single shot acquisition is used to reduce scan time, then productivity is improved, but motion sensitivity is worsened
Solution Approach 1:
The pulse sequence is synchronized to the cardiac cycle using ECG gating, with the saturation pulse applied during systole and the quiescent interval timed to coincide with diastole. This periodic synchronization ensures that data acquisition occurs during a motion-minimized phase of the cardiac cycle, reducing motion artifacts while maintaining the speed benefits of single-shot acquisition.
3Manufacturing precision
If quiescent interval is extended to improve venous suppression, then arterial conspicuity is improved, but scan time is worsened
Solution Approach 1:
The saturation pulse is applied in advance in the first slab to pre-saturate venous spins before they enter the imaging slice. This preliminary saturation allows the quiescent interval to be kept short while still achieving effective venous suppression, because the saturation effect is established before the blood enters the imaging region rather than requiring prolonged suppression during the interval itself.
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
This approach enables fast and motion-resistant imaging of peripheral arteries with significant venous signal suppression, achieving high arterial conspicuity and reducing scan time to within a single breath-hold, while maintaining accuracy across varying flow velocities.
Implementation Method 1
A saturation pulse is applied in a first slab to saturate the magnetization of blood in the first slab
Implementation Method 2
When utilizing these 'MR' signals to produce images, magnetic field gradients (Gx, Gy, and Gz) are employed
Implementation Method 3
the individual magnetic moments of the nuclei in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Data Source
AI summary
A method for non-contrast enhanced magnetic resonance angiography (“MRA”) that has a short scan time and is insensitive to patient motion is provided. More particularly, the method provides significant arterial conspicuity and substantial venous signal suppression. A two-dimensional single shot acquisition is employed and timed to occur a specific time period after the occurrence of an R-wave in a contemporaneously recorded electrocardiogram. In this manner, k-space data is acquired that is substantially insensitive to variations in arterial flow velocity, or heart rate, and that further substantially suppresses unwanted venous signal in a prescribed imaging slice.