Parallel MR Fingerprinting with Self-Calibrating Transmit Encoding
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Solution Overview
Problem
Magnetic Resonance Imaging (MRI) at high field strengths faces challenges due to strong RF interference and non-uniform transmit-sensitivity profiles, leading to contrast artifacts, signal voids, and increased acquisition times, especially in whole-body imaging.
Innovation Solution
A system utilizing multiple independently driven coil elements to create diverse transmit-sensitivities, encoding spatial information into the spin evolution, allowing for robust parameter mapping without patient-specific calibrations, and enabling fast, high-fidelity parameter maps by exploiting non-uniformities in B1+(r) profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If parallel transmission is used to mitigate B1+ non-uniformity, then transmit sensitivity uniformity is improved, but device complexity and calibration requirements increase
Solution Approach 1:
The patent enables the MRF system to automatically adapt to B1+ non-uniformities without requiring external calibration procedures. The self-calibrating mechanism uses the acquired signal data itself to determine the actual B1+ distribution and adjust the excitation profiles accordingly, eliminating the need for separate calibration scans or manual adjustments.
Solution Approach 2:
The system dynamically adjusts the excitation parameters (amplitude and phase) of each transmit coil element based on the measured or estimated B1+ distribution. By changing these parameters adaptively, the system compensates for non-uniformities and achieves uniform transmit sensitivity across the field of view.
2Productivity
If conventional parallel imaging is used to accelerate acquisition, then productivity is improved, but image quality deteriorates due to aliasing artifacts
Solution Approach 1:
The patent employs dynamic adjustment of the readout trajectory orientation between different snapshots in the MRF time series. By varying the encoding direction adaptively, the system prevents coherent aliasing patterns from forming, allowing parallel imaging acceleration while maintaining image quality through incoherent artifact distribution.
3Illumination intensity
If high field strength is used to increase signal strength, then signal-to-noise ratio is improved, but RF interference effects worsen causing contrast artifacts and signal voids
Solution Approach 1:
The patent divides the transmit function into multiple independent coil elements, each contributing to the overall B1+ field. By segmenting the transmit system, the patent enables spatially selective excitation and better control over RF field distribution, mitigating the harmful interference effects that occur with single high-power transmit coils at ultra-high fields.
Solution Approach 2:
The system combines signals from multiple transmit coil elements with different spatial sensitivity profiles to create a composite B1+ field. This composite approach allows constructive interference in desired regions and destructive interference in problematic areas, reducing signal voids and contrast artifacts while maintaining overall signal strength.
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
Enables high-fidelity parameter mapping across large fields of view at ultra-high field strengths, reducing acquisition times and eliminating the need for cumbersome calibration scans, while maintaining diagnostic quality.
Implementation Method 1
A system utilizing multiple independently driven coil elements to create diverse transmit-sensitivities, encoding spatial information into the spin evolution
Implementation Method 2
Magnetic Resonance Fingerprinting (MRF), a technique recently introduced by Ma, et al., 2013, represents a paradigm shift for Magnetic Resonance Imaging (MRI)
Data Source
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AI summary
A general framework is for signal encoding in MRF that enables simultaneous transmit and receive encoding to accelerate the acquistion process, or improve the fidelity of the final image/parameter-map per unit scan time. The proposed method and systems capitalize on the distinct spatial variations in the sensitivity profile of each transmit-coil to reduce the acquistion time, and/or improve the fidelity of the final parameter-map per unit time.