Reverse Centric Phase Encoding for TrueFISP MRI Saturation Artifacts
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Solution Overview
Problem
TrueFISP MRI acquisitions with intersecting planes suffer from saturation artifacts at the intersections of multiple planes, which are not effectively mitigated by previous methods such as interleaving or off-resonance banding artifact reduction techniques.
Innovation Solution
The use of paired reverse centric phase encoding, where the center of k-space is delayed in acquisition and phase encoding is performed using a reverse spiral pattern, grouping adjacent k-space lines to reduce saturation banding and eddy current artifacts, thereby improving image quality and contrast-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If intersecting plane acquisitions are used in TrueFISP MRI, then multiplanar guidance capability is improved, but saturation banding artifacts occur at plane intersections
Solution Approach 1:
The patent applies reverse centric phase encoding where the phase encoding order is inverted - starting from the center of k-space and moving outward to the edges, rather than the conventional approach of starting from the edges and moving to the center. This reversal changes the temporal sequence of magnetization saturation, allowing the center lines (which contain the most signal information) to be acquired before significant saturation occurs at the intersections of multiple planes, thereby reducing saturation banding artifacts while maintaining multiplanar imaging capability
2Speed
If conventional phase encoding is used, then acquisition speed is maintained, but eddy current artifacts and saturation banding persist
Solution Approach 1:
The patent implements paired reverse centric phase encoding where adjacent k-space lines are acquired in pairs with alternating phase encoding directions. This periodic alternation creates a pattern where eddy currents induced by gradient switching in one direction are compensated by the subsequent gradient switching in the opposite direction, thereby reducing eddy current artifacts while maintaining fast acquisition speed through the efficient reverse centric sampling pattern
Solution Approach 2:
The method delays the acquisition of the center of k-space until after the outer lines have been acquired, allowing the initial gradient switching to occur before the most signal-intensive portion of the acquisition. This preliminary action reduces the impact of eddy currents on the critical center lines that contain the majority of the image signal information
3Illumination intensity
If the center of k-space is acquired early, then signal intensity is maximized, but saturation artifacts increase at plane intersections
Solution Approach 1:
By inverting the phase encoding order to start from the center and move outward, the patent actually acquires the center lines first when saturation is minimal, maximizing signal intensity at the critical intersection regions. The reversal ensures that the most signal-intensive portion of the acquisition occurs before magnetization saturation has had time to develop at the plane intersections, thereby simultaneously achieving high signal intensity and reduced saturation artifacts
Data Source
AI summary
Systems methods, and other embodiments associated with acquiring intersecting TrueFISP images using grouped reverse centric phase encoding are described. One example method includes controlling an MRI apparatus to produce a TrueFISP sequence that delays acquisition of the center of k-space to reduce saturation banding artifacts. The example method also includes controlling the MRI apparatus to produce a TrueFISP sequence that reduces eddy current artifacts by grouping (e.g., pairing) lines in k-space. The method concludes by acquiring NMR signal in response to the TrueFISP sequence.