MR Angiography Non-Cartesian Acquisition Spatial Resolution
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Solution Overview
Problem
Current MR angiography methods without contrast agents face limitations in achieving good spatial resolution along all three axes without significantly increasing measurement time, particularly in regions with weak pulsatile dynamics, such as the peripheral vasculature, where the difference between systolic and diastolic blood flow is minimal, and in larger volumes where vessels are not adequately filled with fresh blood.
Innovation Solution
The method employs RF saturation pulses to suppress spins in the examination region, followed by non-Cartesian k-space data acquisition using radial trajectories with spokes distributed irregularly to achieve high spatial resolution in the z-axis direction within an acceptable time frame, allowing for efficient depiction of vessels by under-sampling k-space and using alternating repetition periods to suppress fat signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If 3D methods with larger marked volumes are used to achieve good spatial resolution, then spatial resolution is improved, but vessels in peripheral regions are not adequately filled with fresh blood during the waiting period
Solution Approach 1:
The patent divides the examination volume into multiple thin 2D layers instead of using a single large 3D marked volume. Each layer is independently marked and acquired, allowing fresh blood to fill each thin layer during its respective waiting period. This segmentation resolves the contradiction by maintaining adequate vessel filling in each layer while achieving good spatial resolution through the stacking of multiple layers.
Solution Approach 2:
The patent transitions from conventional 3D volume marking to a 2.5D approach where multiple 2D layers are acquired sequentially. By adding the temporal dimension of sequential layer acquisition, the method allows each layer to be independently optimized for blood filling while maintaining overall volumetric coverage and spatial resolution.
2Manufacturing precision
If thin layers are used to improve spatial resolution in the z-axis, then spatial resolution is improved, but the obtainable signal-to-noise ratio becomes marginally low
Solution Approach 1:
The patent combines data from multiple acquisitions of the same thin layer, each benefiting from fresh blood inflow during the waiting period. By merging the signal information from these multiple acquisitions, the method maintains high spatial resolution of thin layers while improving the overall signal-to-noise ratio through signal accumulation.
Solution Approach 2:
The patent employs continuous inflow of fresh, unmarked blood during the waiting period tin, which continuously replenishes the signal in each thin layer. This continuous supply of fresh blood maintains adequate signal levels throughout the acquisition process, preventing signal depletion and maintaining high signal-to-noise ratio despite the thin layer thickness.
3Ease of manufacture
If conventional Cartesian k-space readout is used, then data acquisition is straightforward, but good spatial resolution along all three axes cannot be achieved without significantly increasing measurement time
Solution Approach 1:
The patent uses periodic radial spokes traversing through the k-space center in a star-like pattern, acquiring data from multiple thin layers during different cardiac cycles. This periodic radial sampling allows efficient undersampling of k-space while maintaining good spatial resolution along all three axes, resolving the contradiction between acquisition simplicity and resolution without significantly increasing measurement time.
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 good spatial resolution along all three axes without prolonging measurement time, effectively visualizing peripheral vasculature with improved signal-background suppression and coverage of larger volumes, such as the leg and abdominal regions, by optimizing the field of view and using efficient data acquisition and reconstruction techniques.
Implementation Method 1
the spins in the examination region are saturated by the radiation of at least one RF saturation pulse, which delivers a lower signal intensity as spins in a subsequent MR signal acquisition
Data Source
AI summary
In a method and apparatus for the creation of an MR image of a vascular structure of an examination region, the spins in the examination region are saturated by the irradiation of at least one RF saturation signal, which delivers a lower signal intensity as spins in a subsequent MR signal recording for the creation of the MR angiographic image, which flow through at least one blood vessel into the examination region, and are not saturated by the RF saturation pulse. Raw data space of the MR angiographic image is read out with a non-Cartesian trajectory in the MR signal acquisition for the creation of the MR angiographic image.