MRS Pulse Sequencing for Residual Signal Suppression in MRI
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Solution Overview
Problem
The existing MEGA-PRESS method in magnetic resonance spectroscopy (MRS) fails to effectively suppress the signal component of a targeted frequency, leading to interference in spectrum analysis due to residual signal components.
Innovation Solution
A magnetic resonance imaging apparatus employs a prepulse-added MEGA-PRESS technique using two frequency selective pulses with different frequency characteristics to suppress the signal component of a targeted frequency, optimizing the time between pulses and applying prepulses to enhance signal decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a frequency selective pulse (MEGA pulse) is applied to suppress a specific frequency component, then the targeted signal component should be suppressed, but residual signal components remain in the difference spectrum
Solution Approach 1:
The frequency selection process is segmented into multiple stages: a first frequency selective pulse applies initial frequency selection, followed by a second frequency selective pulse that applies additional frequency selection. This segmentation allows progressive suppression of unwanted frequency components, resolving the contradiction by achieving more reliable suppression through divided action stages.
Solution Approach 2:
A prepulse is applied before the excitation pulse to pre-suppress unwanted frequency components. This preliminary action ensures that when the main excitation pulse occurs, the residual signal components are already reduced, thereby improving the reliability of frequency selection without sacrificing precision.
2Reliability
If multiple frequency selective pulses are applied to improve frequency selection, then signal suppression improves, but the pulse sequence complexity increases
Solution Approach 1:
The frequency selective pulses are designed to serve multiple functions: they suppress unwanted frequency components, maintain desired signal components, and can be optimized for different echo times. This multi-functionality allows the pulse sequence to achieve reliable suppression without proportionally increasing complexity, as each pulse contributes to multiple objectives.
Solution Approach 2:
The pulse sequence parameters (frequency, duration, timing) are optimized to achieve effective suppression with minimal pulses. By carefully adjusting these parameters, the system achieves reliable signal suppression while keeping the pulse sequence complexity manageable, resolving the contradiction through parameter optimization.
3Measurement precision
If the time between frequency selective pulses is optimized, then signal decomposition improves, but acquisition time increases
Solution Approach 1:
The frequency selective pulses are applied periodically with optimized intervals that allow sufficient signal decomposition while minimizing total acquisition time. The periodic action is tuned to achieve the desired signal separation effect in the shortest possible time, resolving the contradiction between decomposition precision and acquisition time.
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 significantly reduces the residual signal component, improving the contrast and resolution of the difference spectrum, allowing for accurate analysis of J-coupling components and enhancing the accuracy of metabolite classification.
Implementation Method 1
Magnetic resonance imaging apparatus... magnetic resonance spectroscopy (MRS)... RF pulse applied in MRS excites all bandwidths
Data Source
AI summary
The sequence control circuitry repeatedly performs a first data acquisition for acquiring first data, using a first MRS pulse sequence including a first means based on a first pattern that includes frequency selective pulses, and a second data acquisition for acquiring second data, using a second MRS pulse sequence including a second means for selecting a second pattern that differs from the first pattern and includes frequency selective pulses. The frequency selective pulses make selection frequencies of frequency selective pulses before and after an excitation pulse differ and/or are optimized to make (tTE−tJ) differ from tJ wherein tJ is a time between the frequency selective pulses and tTE is an echo time.