MRI RF Pulse Merging for Contrast and Power Reduction
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques face challenges in achieving optimized contrast preparation using multi-spectral, spatially non-selective RF-pulses due to long execution times and high RF peak power demands, particularly in applications like emergency room imaging where speed is critical.
Innovation Solution
The method involves selecting multiple spatially non-selective initial RF-pulses with predefined shapes and frequencies, overlapping them to create a combined RF-pulse that maximizes temporal overlap while keeping the peak amplitude within the MRI system's capacity, thereby reducing preparation duration and RF peak power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple spatially non-selective RF-pulses are applied to generate magnetization transfer effects, then contrast quality is improved, but preparation time increases and RF peak power demand increases
Solution Approach 1:
The patent combines multiple spatially non-selective RF-pulses with different frequencies into a single composite RF-pulse. By merging these pulses temporally and spectrally, the method achieves the magnetization transfer effects of multiple pulses while reducing the total preparation time and avoiding the sequential application delay
Solution Approach 2:
The patent transitions from temporal separation of RF-pulses to spectral multiplexing. Instead of applying pulses one after another in time, the invention uses frequency differentiation to apply multiple pulses simultaneously, adding a spectral dimension to the RF-pulse design
2Measurement precision
If multiple spatially non-selective RF-pulses are applied to generate magnetization transfer effects, then contrast quality is improved, but RF peak power demand increases
Solution Approach 1:
The patent combines multiple spatially non-selective RF-pulses with different frequencies into a single composite RF-pulse. By merging these pulses temporally and spectrally, the method achieves the magnetization transfer effects of multiple pulses while reducing the total preparation time and avoiding the sequential application delay
Solution Approach 2:
The patent modifies the frequency parameter of RF-pulses to create a multi-spectral composite pulse. By varying the frequency across different frequency offsets, the method achieves spectral selectivity without increasing peak power, as the total power is distributed across multiple frequency components
3Measurement precision
If RF-pulses with high amplitude are applied to achieve saturation of bound water protons, then magnetization transfer effect is improved, but specific absorption rate (SAR) limits are exceeded
Solution Approach 1:
The patent modifies the frequency parameter of RF-pulses to create a multi-spectral composite pulse. By varying the frequency across different frequency offsets, the method achieves spectral selectivity without increasing peak power, as the total power is distributed across multiple frequency components
Solution Approach 2:
The patent segments the total RF power across multiple frequency offsets. Instead of concentrating all power at a single frequency, the composite pulse distributes power across multiple spectral components, reducing the peak amplitude at any single frequency while maintaining the overall magnetization transfer effect
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 allows for efficient generation of desired magnetization transfer effects in a shorter duration and with lower RF peak amplitudes, enhancing contrast in MRI images while adhering to hardware limitations, such as specific absorption rate (SAR) limits.
Implementation Method 1
Magnetization Transfer (MT) effects on standard MR imaging procedures... each spatially selective RF-pulse which gets applied 'on-resonance' from the perspective of spins in a desired slice location will (partially) saturate bound water protons
Implementation Method 2
Chemically selective saturation or Chemical exchange saturation transfer
Implementation Method 3
overlapping them to create a combined RF-pulse that maximizes temporal overlap while keeping the peak amplitude within the MRI system's capacity
Implementation Method 4
Selective pulses are usually done by applying a magnetic field gradient throughout the volume. This gradient causes the protons to spin at different frequencies, depending on where they are along that gradient
Data Source
AI summary
A method for controlling a magnetic resonance imaging system, including: selecting a plurality of spatially non-selective initial RF-pulses each having a predefined pulse shape and a predefined frequency; determining a combined RF-pulse from the initial RF-pulses by choosing a time-offset comprising a relative application time-shift between the initial RF-pulses, wherein this time-offset is chosen such that the initial RF-pulses overlap; and including the combined RF pulse in a pulse sequence applied in a magnetic resonance imaging system.