Selective-Inversion MRI Fat Suppression for Residual Olefinic Signals
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Solution Overview
Problem
Existing MR imaging techniques, such as SPIR and SPAIR, fail to completely suppress the fat signal from olefinic protons, which can obscure critical diagnostic details due to their chemical shift proximity to water protons, leading to incomplete fat suppression.
Innovation Solution
A method that employs a spectrally selective inversion RF pulse with a flip angle and delay time adjustment to ensure that the MR signals from different spectral species of fat protons cancel each other out, using a preparation sequence followed by an imaging sequence to generate MR images with full fat suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SPIR or SPAIR techniques are used to suppress fat signals, then the main spectral components of fat signal are eliminated, but the olefinic proton fat signal remains and obscures critical diagnostic details
Solution Approach 1:
The patent segments the fat signal into two distinct spectral species: (1) bulk methylene protons and other aliphatic fat protons, and (2) olefinic protons. By applying separate spectrally selective inversion RF pulses targeted at each species' specific chemical shift, the method achieves comprehensive suppression of all fat signal components, preventing the residual olefinic proton signal from obscuring diagnostic details while maintaining the effectiveness against bulk fat protons.
2Reliability
If a spectrally selective inversion RF pulse is applied to suppress fat protons, then the MR signal from targeted fat protons is reduced, but the suppression is incomplete for olefinic protons due to their chemical shift proximity to water protons
Solution Approach 1:
The patent applies the local quality principle by designing spectrally selective inversion RF pulses with different frequency offsets tailored to each fat proton spectral species. The first pulse is centered at the chemical shift of bulk methylene protons, while the second pulse is centered at the chemical shift of olefinic protons. This localized spectral targeting ensures that each pulse suppresses only its intended fat proton population without significantly affecting water protons or other tissue signals, achieving both comprehensive fat suppression and high spectral selectivity.
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
Achieves nearly complete suppression of fat signals, enhancing diagnostic clarity by ensuring that contributions from both spectral species of fat protons are minimized in the MR image, thereby improving diagnostic accuracy.
Implementation Method 1
spectrally selective inversion RF pulse that is specifically tuned to the resonance frequency of fat protons
Implementation Method 2
utilize the interaction between magnetic fields and nuclear spins in order to form two-dimensional or three-dimensional images
Implementation Method 3
a delay time passes allowing the nuclear magnetization of fat protons to recover towards its equilibrium state
Data Source
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AI summary
The invention relates to a system and associated method of magnetic resonance imaging. The method comprises: subjecting at least one portion of the object (10) to a preparation sequence (PRE) comprising a spectrally selective inversion radiofrequency, RF, pulse (21) having a flip angle (α) to selectively invert nuclear magnetization associated with fat protons within the at least one portion of the object (10); after a delay time (TD), subjecting the at least one portion of the object (10) to an imaging sequence (1M) comprising at least one excitation RF pulse (28) and switched magnetic field gradients (29) to generate magnetic resonance, MR, signals (27), wherein the delay time (TD) and/or the flip angle (α) are determined such that contributions from a first spectral species of fat protons affected by the inversion RF pulse (21) and a second spectral species of fat protons not affected by the inversion RF pulse (21) to the MR signals substantially cancel each other out; acquiring the MR signals (27) from the at least one portion of the object (10); and reconstructing an MR image from the acquired MR signals (27), wherein contributions from both the first and second spectral species of fat protons are suppressed in the MR image due to the selective inversion by the preparation sequence (PRE) in combination with the determined delay time (TD) and/or flip angle (α).