Adaptive Multi-Band MR Imaging for Artifact Reduction
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Solution Overview
Problem
Multi-band magnetic resonance imaging introduces signal artifacts and limited protocol flexibility due to fixed parameters and imperfect anti-aliasing reconstruction, leading to increased thermal noise, magnetization transfer effects, and leakage contamination, which degrade image quality and reduce the effectiveness of quantitative imaging applications.
Innovation Solution
An adaptive multi-band imaging system and method that uses adaptive RF pulses and reconstruction parameters, allowing for the excitation and reconstruction of only necessary slices, varying slice spacing, and applying different CAIPI parameters to reduce noise amplification and aliasing artifacts, while calculating a total leakage factor to quantify and minimize signal contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-band imaging with fixed parameters is used to accelerate imaging acquisition, then imaging speed is improved, but image quality deteriorates due to signal artifacts, thermal noise, and leakage contamination
Solution Approach 1:
The patent applies dynamics by making the MB factor adaptive rather than fixed. The system dynamically adjusts the MB factor based on slice characteristics, spacing, and protocol requirements. This allows the imaging system to optimize between speed and quality on a per-protocol basis, resolving the contradiction by making the acceleration factor flexible rather than static.
Solution Approach 2:
The patent changes key parameters including the MB factor, slice spacing, and CAIPI phase shifts to optimize both speed and quality. By adjusting these parameters adaptively based on the specific imaging protocol and anatomical region, the system can achieve high acceleration when appropriate while maintaining image quality when needed.
2Productivity
If higher MB factor is used to reduce imaging time, then productivity is improved, but device complexity increases due to imperfect anti-aliasing reconstruction and need for multiple parameters optimization
Solution Approach 1:
The patent optimizes multiple parameters including MB factor, slice spacing, and CAIPI phase shifts to simplify the reconstruction process while maintaining high acceleration. By carefully selecting these parameters, the system reduces the complexity of anti-aliasing reconstruction even at higher MB factors.
3Ease of operation
If fixed parameter multi-band imaging is used, then ease of operation is improved, but adaptability deteriorates due to inability to adjust to different protocols and regions
Solution Approach 1:
The patent implements adaptive determination of the MB factor based on the specific imaging protocol and anatomical region. This dynamic approach maintains ease of operation by automatically selecting appropriate parameters while improving adaptability to different clinical requirements and imaging scenarios.
4Loss of time
If simultaneous excitation of multiple slices is performed, then loss of time is reduced, but harmful factors increase due to increased thermal noise and magnetization transfer effects
Solution Approach 1:
The patent optimizes slice spacing and MB factor to minimize thermal noise and magnetization transfer effects while maintaining fast acquisition. By adjusting these parameters, the system reduces harmful effects even when simultaneously exciting multiple slices.
Solution Approach 2:
The patent applies different parameters locally based on the imaging protocol and anatomical region. This allows optimization of slice spacing and MB factor for specific regions, reducing thermal noise and magnetization transfer effects in sensitive areas while maintaining overall acquisition speed.
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 enhances image quality by reducing signal leakage and thermal noise, improving protocol flexibility, and optimizing image reconstruction, resulting in higher signal-to-noise ratio and more accurate images by tailoring imaging parameters to specific regions and protocols.
Implementation Method 1
Radio-frequency (RF) excitation pulses are directed into the examination subject to excite nuclear magnetic resonances, and subsequent relaxation of the excited nuclear magnetic resonances can generate RF signals
Implementation Method 2
Rapidly switched magnetic gradient fields can be superimposed on the base magnetic field, in various orientations, to provide spatial coding of the RF signal data
Data Source
AI summary
A magnetic resonance method and system are provided for providing improved multi-band (MB) magnetic resonance imaging. The adaptive MB imaging can be achieved by providing one or more modified multi-band excitation pulse sequences that include at least either one nullified “dummy” slice within a slab that is not excited simultaneously with the other slices during a single multislice acquisition sequence, or one excitation slice group that utilizes a non-uniform slice spacing between simultaneously excited slices. Adaptive GRAPPA or slice-GRAPPA kernel sizes can also be used during image reconstruction to improve speed without excessive point spread blurring or MB reconstruction failure. A total leakage factor (TLF) can also be determined based on test images using modified MB excitation sequences, and used to improve the adaptive MB procedure.