Non-contrast MRA Using RF Saturation and Cardiac Gating
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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 or multi-shot acquisition method is employed, synchronizing data acquisition with diastole and using RF saturation pulses to maximize arterial signal and suppress venous signal, allowing for short scan times and reduced motion artifacts, with the option of cardiac gating or multi-shot acquisition to minimize blood flow-related artifacts.
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 signal suppression are worsened
Solution Approach 1:
The patent applies preliminary RF saturation pulses to suppress venous signal before the main imaging sequence. By pre-saturating the venous blood signal in a region adjacent to the imaging slice, the method achieves venous suppression without requiring contrast agents, thereby maintaining patient safety while improving arterial conspicuity.
Solution Approach 2:
The patent utilizes flow-dependent signal characteristics by adjusting the timing parameters (delta time, inversion time) of the pulse sequence to exploit the different flow velocities between arterial and venous blood. This parameter optimization enhances arterial signal while suppressing venous signal in non-contrast conditions.
2Loss of time
If single shot acquisition is used to reduce scan time and motion artifacts, then scan time and motion sensitivity are improved, but blood flow-related artifacts are worsened
Solution Approach 1:
The patent applies preliminary RF saturation pulses before the single-shot acquisition to suppress venous signal. This pre-saturation step, combined with the single-shot sequence, allows for rapid imaging while reducing venous contamination and blood flow-related artifacts through the saturation of inflowing venous spins.
Solution Approach 2:
The patent employs periodic RF saturation pulses applied before each single-shot acquisition cycle. This periodic application of saturation pulses, synchronized with the cardiac cycle or repeated at fixed intervals, maintains venous suppression throughout the scan while enabling rapid single-shot imaging.
3Measurement precision
If multi-shot acquisition with echo train is used to improve image quality, then signal-to-noise ratio is improved, but blood flow-related artifacts are worsened
Solution Approach 1:
The patent applies preliminary RF saturation pulses before the multi-shot acquisition sequence to suppress venous signal. By pre-saturating the venous blood in the imaging slice and adjacent regions, the method reduces venous signal contribution during the echo train, thereby minimizing blood flow-related artifacts while maintaining the signal-to-noise ratio benefits of multi-shot acquisition.
4Measurement precision
If long TR acquisition sequences are used to improve signal-to-noise ratio, then signal-to-noise ratio is improved, but scan time is worsened
Solution Approach 1:
The patent applies preliminary RF saturation pulses to suppress venous signal before the imaging sequence. This allows for the use of longer TR sequences with improved signal-to-noise ratio, as the venous suppression is already established, reducing the need for excessively long scan times to achieve adequate contrast.
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 high arterial conspicuity and substantial venous signal suppression, reducing scan time and motion artifacts, allowing for accurate depiction of arterial anatomy across varying flow velocities within a single breath-hold, thus improving diagnostic capability.
Implementation Method 1
applying at least one radio frequency (RF) saturation pulse to a selected region and applying at least one RF saturation pulse to a prescribed imaging slice such that magnetic resonance signals in the selected region and in the prescribed imaging slice are suppressed
Implementation Method 2
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), 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
Implementation Method 3
When utilizing these 'MR' signals to produce images, magnetic field gradients (Gx, Gy, and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used
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. Alternatively, a two-dimensional multi-shot acquisition is employed to acquire k-space data using an echo train length that is sufficiently short so as to suppress flow-related artifacts, and such that cardiac gating is not required.