Angular Elliptic Centric View Ordering for 3D MR Acquisitions
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Solution Overview
Problem
Existing MR imaging techniques face challenges in minimizing the total traveled distance in k-space while preserving spectral elliptic centric ordering, leading to large gradient waveforms and eddy current-induced artifacts, especially in high-frequency regions.
Innovation Solution
An angular elliptic centric view ordering scheme is implemented, where a cost function is calculated for each encoding point in k-space, sorting points based on a monotonically increasing cost to reduce gradient polarity switches and total path length, thereby minimizing eddy current effects and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If elliptic centric view ordering is used to acquire central k-space quickly, then contrast enhancement is improved, but large jumps in high-frequency regions cause gradient polarity switches and eddy current artifacts
Solution Approach 1:
The patent applies different ordering strategies to different regions of k-space: elliptic centric ordering for the central region to capture contrast quickly, and a modified sequential ordering for the outer high-frequency regions to minimize gradient polarity switches. This local differentiation resolves the contradiction by optimizing each region's acquisition pattern according to its specific requirements.
Solution Approach 2:
The k-space acquisition is segmented into multiple segments with different ordering patterns. The central region uses one ordering pattern optimized for contrast, while the outer regions use another pattern optimized for minimizing artifacts. This segmentation allows simultaneous optimization of both contrast enhancement and artifact reduction.
2Ease of manufacture
If purely index-based Cartesian spiral centric view ordering is used, then implementation is simple, but it is only suitable when field of view in phase encode directions are similar
Solution Approach 1:
The patent modifies the ordering parameters based on the specific field of view configuration. By calculating appropriate ellipticity and ordering parameters based on the phase encode direction dimensions, the system adapts to different field of view configurations while maintaining the computational efficiency of algorithmic ordering.
3Object-affected harmful factors
If random acquisition is used in central region and radial/spiral/sequential ordering in outer regions, then artifacts are reduced, but complexity increases and uncertainty is introduced in the most important region
Solution Approach 1:
Instead of using random ordering in the central region as suggested by prior art, the patent inverts the approach by using deterministic elliptic centric ordering in the central region to eliminate uncertainty, while applying modified ordering in the outer regions to reduce artifacts. This inversion resolves both the artifact and complexity issues.
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 reduces the number of gradient polarity switches and total k-space path length, resulting in improved image quality with reduced eddy current artifacts, particularly in contrast-enhanced studies and dynamic applications like TRICKS and MR angiography.
Implementation Method 1
magnetic field gradients (Gx, Gy, and Gz) are employed
Implementation Method 2
A signal is emitted by the excited spins after the excitation signal B1 is terminated and this signal may be received and processed to form an image
Implementation Method 3
such jumps cause large amplitude gradient waveforms with opposite polarities to be played out in alternating fashion, giving rise to eddy current induced artifacts
Data Source
AI summary
A magnetic resonance imaging (MRI) apparatus includes an MRI system having a plurality of gradient coils positioned about a bore of a magnet. An RF transceiver system and an RF switch are controlled by a pulse module to transmit and receive RF signals to and from an RF coil assembly to acquire MR images. The MRI apparatus also includes a computer programmed to calculate a cost for each point to be acquired in k-space, acquire MR data based on the calculated cost for each point, and generate an MR image using the acquired MR data.