3D MRI k-Space Sampling with Golden Angle Interleaves
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques using non-Cartesian sampling trajectories, such as spiral and stack of spirals, require extensive planning and pre-planning to achieve clinically acceptable scan times without compromising image quality, which is complex and time-consuming.
Innovation Solution
A method and system that utilize a base waveform with a trajectory extending from the center to the periphery of k-space, repeated with rotational offsets by a predetermined angle, such as the golden angle, to create interleaved trajectories for efficient three-dimensional k-space sampling, simplifying the selection of sampling methodologies and tradeoffs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-Cartesian sampling trajectories (spiral, stack of spirals) are used to reduce scan time, then productivity is improved, but device complexity increases due to extensive planning and pre-planning requirements
Solution Approach 1:
The k-space sampling is divided into multiple segments or interleaves, where each interleaf samples a different angular range. This segmentation allows the complex 3D sampling to be broken down into manageable 2D spiral trajectories that can be executed sequentially, reducing the planning burden while maintaining fast sampling efficiency.
Solution Approach 2:
The patent transitions from conventional 2D spiral sampling to 3D spiral sampling by adding an angular dimension. Multiple interleaves are rotated relative to each other in the azimuthal direction, creating a three-dimensional sampling pattern that fills k-space more efficiently and reduces scan time while maintaining systematic control.
2Productivity
If undersampling is used to reduce acquisition time, then productivity is improved, but measurement precision deteriorates due to aliasing artifacts
Solution Approach 1:
The patent performs preliminary sampling of the central k-space region (low spatial frequencies) before acquiring peripheral regions (high spatial frequencies). This preliminary action ensures that the most critical image information is captured first, allowing for more robust undersampling strategies in the peripheral regions without severely compromising overall image quality.
Solution Approach 2:
Different sampling densities are applied to different regions of k-space. The central region is sampled more densely to capture low-frequency information critical for image contrast and overall structure, while peripheral regions are sampled more sparsely. This local differentiation of sampling quality allows undersampling to reduce acquisition time while preserving essential image quality.
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 simplifies the selection of k-space sampling methodologies and tradeoffs, reducing scan times while maintaining image quality, by using a consistent base waveform with rotational offsets to efficiently sample k-space in three dimensions.
Implementation Method 1
the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 2
If the substance, or tissue, is subjected to a magnetic field (excitation field B1) that is in the x-y plane and that is near the Larmor frequency, the net aligned moment, Mz, may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetic moment Mt
Implementation Method 3
This is accomplished by employing magnetic fields (Gx, Gy, and Gz) that have the same direction as the polarizing field B0, but which have a gradient along the respective x, y, and z axes. By controlling the strength of these gradients during each NMR cycle, the spatial distribution of spin excitation can be controlled and the location of the resulting NMR signals can be identified
Implementation Method 4
A NMR signal is emitted by the excited spins after the excitation signal B1 is terminated, this signal may be received and processed to form an image or produce a spectrum
Data Source
AI summary
A system and method for sampling k-space is provided that substantially simplifies the demands placed on the clinician to select and balance the tradeoffs of a particular selected sampling methodology. In particular, the present invention provides particularly advantageous sampling methodologies that simplify the selection of a particular k-space sampling methodology and, furthermore, the tradeoffs within a particular sampling methodology.