MRI Vessel Encoding Using Unipolar Gradient Lobes
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Solution Overview
Problem
Current MRI techniques face challenges in non-invasively mapping perfusion territories and estimating source vessel locations, especially in cases of vascular disease where collateral routes of circulation are difficult to identify, and are sensitive to resonance offsets, leading to incomplete and spatially inhomogeneous separation of feeding arteries.
Innovation Solution
The use of unipolar vessel encoding gradient lobes and pseudo-continuous radio frequency tagging pulses to modulate blood vessel magnetization, combined with an encoding scheme using transverse gradient pulses, allows for efficient separation and identification of vascular perfusion territories and source vessel locations without prior knowledge of their locations, providing high signal-to-noise ratio and improved vessel selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual detection based on additional imaging or angiography is used to locate source vessels, then the locations of source vessels can be identified, but the process becomes more complex and time-consuming
Solution Approach 1:
The MRI system automatically detects and encodes source vessel locations using the imaging data itself, without requiring external angiography or manual intervention. The pseudo-continuous tagging pulses with unipolar gradient lobes enable the system to self-identify vessel positions and encode perfusion territories directly from the perfusion imaging data.
Solution Approach 2:
The method extracts source vessel location information directly from the perfusion imaging data by using unipolar gradient lobes that encode spatial information into the signal. This extraction eliminates the need for separate angiography procedures while maintaining accurate vessel location identification.
2Reliability
If pulsed tagging methods with 3D slab or volume selective tag are used, then arterial blood can be tagged, but the separation of feeding arteries is incomplete and spatially inhomogeneous
Solution Approach 1:
The method segments the tagging process by using unipolar gradient lobes applied during pseudo-continuous tagging to encode different spatial locations with distinct phase information. This segmentation enables complete and homogeneous separation of multiple feeding arteries within a single tagging plane, overcoming the limitations of volume-selective tagging.
Solution Approach 2:
The invention adds a phase encoding dimension to the tagging process by applying unipolar gradient lobes that impart location-dependent phase shifts. This dimensional addition allows differentiation of vessels within the tagging plane based on their spatial positions, achieving complete separation that was not possible with conventional pulsed methods.
3Measurement precision
If bipolar vessel encoding gradient lobes are used, then vessel encoding can be achieved, but the method is sensitive to resonance offsets at the tagging plane
Solution Approach 1:
The method inverts the gradient lobe polarity from bipolar to unipolar configuration. This inversion eliminates the sensitivity to resonance offsets that plagues bipolar encoding, while still achieving complete vessel encoding through the cumulative phase effects of the unipolar gradients applied during the pseudo-continuous tagging sequence.
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 accurate and efficient mapping of vascular perfusion territories and source vessel locations, reducing sensitivity to resonance offsets and improving the separation of feeding arteries, facilitating better patient management in clinical applications such as stroke diagnosis and tumor evaluation.
Implementation Method 1
applying a train of pseudo-continuous radio frequency tagging pulses to modulate a first magnetization of one or more blood vessels
Implementation Method 2
applying an encoding scheme using unipolar transverse gradient pulses to modulate a second magnetization of blood vessels
Data Source
AI summary
Techniques, systems computer program products are disclosed for mapping of vascular perfusion territories by applying a train of pseudo-continuous radio frequency tagging pulses to modulate a first magnetization of one or more blood vessels that supply blood to one or more vascular perfusion territories, applying an encoding scheme using unipolar transverse gradient pulses to modulate a second magnetization of blood vessels of the vascular perfusion territories, obtaining efficiency for each blood vessel based on the applied encoding scheme and separating the vascular perfusion territories by using the obtained tagging efficiency in a decoding process.