Out-of-Phase SSFP MRI for Sensitive Partial Fat Detection
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Solution Overview
Problem
Existing MRI techniques struggle to accurately detect mild or moderate degrees of fatty infiltration in tissues due to sensitivity issues with conventional SSFP sequences, which fail to distinguish between healthy and unhealthy tissues with partial fat, and require additional time-consuming sequences for fat-specific imaging.
Innovation Solution
Optimize SSFP sequences by centering the peak of the chemically shifted moiety (e.g., fat) out-of-phase with the on-resonance moiety (e.g., water) to enhance sensitivity and visibility of partial fat, using methods that adjust TR values and other parameters to account for B0 inhomogeneity, allowing for immediate visual distinction between tissues with partial and complete fat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SSFP sequences are used for imaging, then standard imaging capabilities are maintained, but sensitivity to detect partial fat infiltration is insufficient
Solution Approach 1:
The patent modifies the SSFP sequence parameters by adjusting the repetition time (TR) to specific values (e.g., TR = 2.38 ms at 3T or TR = 4.76 ms at 1.5T) that create out-of-phase conditions for fat protons. This parameter optimization enables the sequence to detect partial fat infiltration with high sensitivity while maintaining the speed and efficiency of standard SSFP imaging, thus resolving the contradiction between detection precision and imaging productivity.
2Measurement precision
If additional fat-specific sequences are added to improve fat detection, then detection accuracy improves, but imaging time increases
Solution Approach 1:
The patent makes the standard SSFP sequence multi-functional by optimizing its parameters to simultaneously achieve both standard imaging capabilities and enhanced fat detection. The out-of-phase SSFP sequence can detect partial fat infiltration without requiring separate dedicated fat imaging sequences, thus improving fat detection accuracy while avoiding the time penalty of additional sequences.
3Measurement precision
If TR value is adjusted to center fat peak out-of-phase, then sensitivity to partial fat improves, but signal-to-noise ratio may be affected
Solution Approach 1:
The patent optimizes the TR value to create out-of-phase conditions that maximize the visibility of partial fat while maintaining adequate signal-to-noise ratio. By carefully selecting TR values that center the fat peak in the out-of-phase passband, the sequence achieves enhanced contrast for partial fat detection without excessive signal loss, thus balancing measurement precision with reliability.
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
The optimized SSFP sequence significantly improves the detection of minor fatty infiltrations, reducing underestimation of fatty metaplasia prevalence by highlighting dark regions indicative of partial fat, while maintaining standard imaging capabilities without requiring additional sequences.
Implementation Method 1
In the presence of a magnetic field, different chemical moieties may resonate at slightly different frequencies based on their local chemical environments
Implementation Method 2
The degree of frequency separation between two molecular species is characterized by their chemical shift
Implementation Method 3
The natural precession frequency of a spin system is also known as the Larmor frequency
Implementation Method 4
applying a steady-state free precession sequence during operation of a magnetic resonance imaging (MRI) scanner
Implementation Method 5
determining a frequency difference between a chemically shifted moiety of a mixture and an on-resonance moiety of the mixture
Data Source
AI summary
The present disclosure describes, in part, a method for achieving depiction of mixtures of chemically shifted and on-resonance moieties using magnetic resonance imaging (MRI) technology. The method can use a steady-state free precession sequence that can be optimized so that the chemically shifted moiety is in an out-of-phase passband in relation to the on-resonance moiety. This feature can enable detection of tissues with a small amount of the chemically shifted moiety with high sensitivity, including but not limited to detecting fat and water when imaging an organ.