VERSE RF Pulse Amplitude Reduction in MRI
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Solution Overview
Problem
Traditional variable-rate selective excitation (VERSE) techniques in magnetic resonance imaging (MRI) reduce RF transmit power but often compromise signal noise ratio (SNR) and image contrast due to off-resonance effects.
Innovation Solution
The method involves generating slice-selection gradient waveforms with time-varying amplitudes and modifying RF pulses using excitation and refocusing VERSE factors to maintain the offset between slice profiles before and after VERSE modification, ensuring consistent SNR and contrast while reducing RF transmit power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional VERSE techniques are applied to reduce RF transmit power, then RF transmit power and SAR are reduced, but SNR and image contrast deteriorate due to off-resonance effects
Solution Approach 1:
The patent changes the amplitude parameters of slice-selection gradient waveforms using time-varying VERSE factors (excitation and refocusing) to reduce RF transmit power while maintaining slice profile alignment. By dynamically adjusting gradient amplitudes during the pulse sequence, the method reduces SAR and RF power without compromising SNR or contrast, directly resolving the technical contradiction between energy efficiency and measurement precision.
2Use of energy by moving object
If traditional VERSE techniques are applied to reduce RF transmit power, then RF transmit power and SAR are reduced, but image contrast deteriorates due to off-resonance effects
Solution Approach 1:
The patent applies parameter changes by introducing time-varying VERSE factors that modulate slice-selection gradient amplitudes. This dynamic adjustment maintains proper slice profile alignment between excitation and refocusing pulses, preserving image contrast while reducing RF transmit power and SAR, thus resolving the contradiction between energy efficiency and manufacturing precision.
3Object-affected harmful factors
If slice-selection gradient waveform amplitudes are reduced to lower RF transmit power, then SAR is reduced, but off-resonance effects increase causing SNR and contrast degradation
Solution Approach 1:
The patent employs dynamics by using time-varying VERSE factors that continuously adjust slice-selection gradient amplitudes during the RF pulse sequence. This dynamic modulation allows the system to reduce peak gradient amplitudes (lowering SAR) while maintaining appropriate gradient areas for proper slice profile alignment, thereby reducing SAR without degrading SNR through off-resonance effects.
Data Source
AI summary
A system and method for modifying RF pulse generated by an MRI system are provided. The method may include: obtaining an excitation variable-rate selective excitation (VERSE) factor and a refocusing VERSE factor; determining a first slice-selection gradient waveform based on an excitation factor and a reference excitation slice-selection gradient waveform; determining a second slice-selection gradient waveform based on a refocusing factor and a reference refocusing slice-selection gradient waveformslice-selection gradient waveformslice-selection gradient waveform; determining an excitation pulse based on the first slice-selection gradient waveform; determining a refocusing pulse based on the second slice-selection gradient waveform, wherein a ratio of the decimal part of the excitation factor to the decimal part of the refocusing factor is equal to a ratio of the amplitude of the first reference waveform to the amplitude of the reference refocusing slice-selection gradient waveform.