Phase Rotation Scheme for MR Spectroscopy Echo Suppression
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Solution Overview
Problem
Existing magnetic resonance spectroscopy techniques face challenges in suppressing unwanted coherences and echoes, particularly at high field strengths, due to minor inaccuracies in radio-frequency pulses and refocusing pulses, which can generate unwanted signals that interfere with the desired echo.
Innovation Solution
A universally valid phase rotation scheme for pulse sequences with five radio-frequency pulses is introduced, where the third and fourth pulses maintain the same phase, allowing for arbitrary phase rotation of the first, second, and fifth pulses, effectively combining PRESS and semi-LASER sequence phases to suppress unwanted coherences and echoes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If adiabatic refocusing pulses are used at high field strengths, then bandwidth coverage is improved, but unwanted coherences and echoes are generated due to phase variations
Solution Approach 1:
The patent applies phase rotation to the adiabatic refocusing pulses, changing the phase parameter systematically across multiple acquisitions. This allows the unwanted coherences and echoes to be suppressed through phase cycling while maintaining the bandwidth advantages of adiabatic pulses at high field strengths
Solution Approach 2:
The patent implements a periodic phase rotation scheme where the phase of the adiabatic refocusing pulses is incremented systematically across repeated acquisitions. This periodic phase modulation enables the separation and suppression of unwanted signals while preserving the desired echo signal
2Reliability
If phase rotation is applied to suppress unwanted echoes, then signal quality is improved, but the complexity of the pulse sequence increases
Solution Approach 1:
The patent segments the phase rotation application by assigning different phase rotation schemes to different pulse groups (excitation pulse, first refocusing pulse, second refocusing pulse). This segmentation allows for systematic suppression of unwanted signals while maintaining manageable sequence complexity through structured phase management
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 enables effective suppression of unwanted echoes and coherences, enhancing signal quality by allowing for customizable phase rotation schemes, particularly beneficial at high field strengths, and improving the visibility of metabolites in magnetic resonance spectroscopy.
Implementation Method 1
method for acquiring a magnetic resonance signal from an examination subject
Implementation Method 2
90° excitation pulse followed by acquisition of the FID (Free Induction Decay)
Implementation Method 3
voxel-selective spectroscopy sequence
Implementation Method 4
the sequence is repeated a number of times with respectively different phases of the radio-frequency pulses and the signals acquired in the process are added together
Data Source
AI summary
In a method and magnetic resonance (MR) apparatus for acquiring an MR signal from an examination subject according to a pulse sequence, a first radio-frequency pulse is applied with a first phase and a gradient field is simultaneously applied in a first direction. Second and third radio-frequency pulses, with second and third phases, respectively, are applied simultaneously with a gradient field in a second direction. A fourth and a fifth radio-frequency pulse, with a fourth and a fifth phase, respectively, are applied and simultaneously with a gradient field in a third direction. A signal with a receiver phase is acquired =. The pulse sequence is repeated a number of times under phase rotation, wherein the third and fourth radio-frequency pulses in each repetition have the same phase, and the signals acquired in the repetition are added.