Random Blip Gradient Encoding for Simultaneous Multislice MRI
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Solution Overview
Problem
Current simultaneous multislice MRI techniques are inefficient, requiring prolonged imaging times and struggling to reliably separate aliased pixels, which limits their clinical applicability, especially in methods that sample multiple lines of k-space following each RF excitation.
Innovation Solution
A random blip gradient encoding scheme is employed in MRI systems to impart random phase shifts to echo signals from multiple slice locations, generating incoherent aliasing artifacts that facilitate the use of compressed sensing reconstruction techniques for faster data acquisition and improved image separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If simultaneous multislice imaging is implemented using multichannel RF receiver arrays, then imaging time is reduced, but the separation of aliased pixels becomes unreliable
Solution Approach 1:
The patent applies parameter changes by introducing controlled phase shifts through slice-encoding gradient blips with randomly assigned magnitudes. This modifies the phase parameters of the MR signals from different slices, creating incoherent aliasing patterns that enable reliable separation using compressed sensing algorithms while maintaining reduced imaging time
2Reliability
If structured blip gradient encoding is used to improve slice separation, then aliasing separation capability is enhanced, but imaging efficiency is reduced
Solution Approach 1:
The patent inverts the conventional structured blip gradient approach by using random instead of structured phase encoding. This inversion leverages compressed sensing theory which benefits from incoherent (random) sampling patterns rather than coherent structured patterns, thereby achieving both improved separation reliability and maintained imaging efficiency
3Productivity
If multiple slices are excited and acquired at once, then productivity is improved, but the complexity of data reconstruction increases
Solution Approach 1:
The patent introduces slice-encoding gradient blips as an intermediary mechanism that embeds slice-specific phase information into the k-space data during acquisition. This intermediary encoding simplifies the reconstruction process by providing explicit phase relationships that compressed sensing algorithms can exploit, thereby reducing reconstruction complexity while maintaining high productivity
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 imaging time and enhances the separation of aliased pixels, enabling more efficient and reliable simultaneous multislice imaging by leveraging incoherent aliasing and compressed sensing frameworks.
Implementation Method 1
The RF excitation field excites spins in the plurality of slice locations
Implementation Method 2
establishing at least one readout magnetic field gradient along a frequency-encoding direction following the application of the RF excitation field, in order to form echo signals
Implementation Method 3
sequentially producing a plurality of slice-encoding magnetic field gradient blips along a slice-encoding direction while the at least one readout magnetic field gradient is established such that the slice-encoding magnetic field gradient blips are played out between readout lines. Each sequential slice-encoding magnetic field gradient blip has a randomly assigned magnitude such that a random phase shift related to the randomly assigned magnitude is imparted to the formed echo signals
Data Source
AI summary
Systems and methods for simultaneous multislice (“SMS”} magnetic resonance imaging (“MRI”}, in which a random blip gradient encoding scheme is utilized to impart a different phase to each of a plurality of different slice locations. Because of the random blip gradient encoding, the amount of the imparted phase is randomized for each phase encoding step in a Cartesian k-space trajectory. This data acquisition strategy leads to incoherent aliasing artifacts across the simultaneously excited slices. Images of the individual slices can be reconstructed using a compressed sensing framework.