Multi-band RF Pulse Side-band Suppression in MRI
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Solution Overview
Problem
Multi-band excitations in magnetic resonance imaging (MRI) scans suffer from side-band artefacts due to RF hardware limitations, particularly when high frequency modulation or high power scans are used, leading to overlapping or folding of side-band signals into the main lobe, which degrade image quality.
Innovation Solution
A method is introduced to generate improved multi-band RF pulses by deriving a pre-compensating term from the initial pulse and additional side-band signals, allowing for the creation of a second pulse that suppresses side-bands, thereby preventing unintentional excitation of slices and enhancing image quality by correcting side-bands before data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-band excitation is used to accelerate MRI scans by exciting multiple slices simultaneously, then scanning efficiency is improved, but side-band artefacts appear in the resulting images due to RF hardware limitations
Solution Approach 1:
The patent applies preliminary action by deriving a pre-compensating term from the first multiband RF pulse and additional signal before the actual excitation occurs. This pre-compensating term is added to the original RF pulse to create a second multiband RF pulse that already accounts for and suppresses the side-band artefacts that would otherwise appear during multi-band excitation, thereby maintaining both scanning efficiency and image quality
2Productivity
If high frequency modulation multi-band excitations are used to improve scanning speed, then productivity increases, but side-band artefacts worsen due to spectra overlap and folding into main lobe
Solution Approach 1:
The patent performs preliminary compensation by deriving a pre-compensating term from the first multiband RF pulse and additional signal before excitation. This pre-compensating term is added to the original RF pulse to create a second multiband RF pulse that pre-suppresses the side-band artefacts that would otherwise overlap or fold into the main lobe during high frequency modulation multi-band excitation
Solution Approach 2:
The patent applies preliminary anti-action by deriving a pre-compensating term that generates a signal opposite to the side-band artefacts. This pre-compensating term is added to the original RF pulse to create a second multiband RF pulse that produces anti-phase side-band signals, causing destructive interference that suppresses the harmful side-band artefacts before they can degrade image quality
3Measurement precision
If high power scans are used to improve signal strength, then measurement precision may improve, but side-band artefacts increase due to RF hardware non-linearities
Solution Approach 1:
The patent applies preliminary action by deriving a pre-compensating term from the first multiband RF pulse and additional signal before the high power scan occurs. This pre-compensating term is added to the original RF pulse to create a second multiband RF pulse that already accounts for and suppresses the side-band artefacts that would otherwise be generated by RF hardware non-linearities during high power excitation
Solution Approach 2:
The patent employs feedback by using the additional signal (which represents the side-band artefacts) to derive the pre-compensating term. This creates a feedback loop where the system measures the actual side-band signals produced by the RF hardware and uses that information to generate a compensating term that suppresses those same artefacts in subsequent scans
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 method effectively suppresses side-band artefacts, improving the quality of MR data and reducing the need for post-processing corrections, thereby enhancing the accuracy and efficiency of MRI scans.
Implementation Method 1
multi-band excitation accelerates multi slice magnetic resonance imaging (MRI) scans by exciting and acquiring more than one slice at the same time
Implementation Method 2
at least part of the subject is within the imaging zone
Data Source
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AI summary
The present invention relates to a method for side-band suppression in a Magnetic Resonance imaging, MRI, system (100), the method comprising providing a first multiband RF pulse for simultaneously exciting at least two slices in a subject (118) at a first and a second frequency band (301,303) and to acquire using the MRI system (100) signals (307, 308) from the excited two slices and at least one additional signal (309) at a third frequency band (305), the additional signal (309) resulting from a sideband excitation of a slice different from the two slices; using the first multiband RF pulse for determining the additional signal (309); deriving a pre-compensating term from the first multiband RF pulse and the additional signal (309), adding the pre-compensating term to the first multiband RF pulse to obtain a second multiband RF pulse, thereby replacing the first multiband RF pulse by the second multiband RF pulse for suppressing at least part of the additional signal (309).