WASAB1 Signal Post-Processing for Rapid B0 and B1 Mapping
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Solution Overview
Problem
Existing magnetic resonance imaging (MRI) techniques, particularly Chemical Exchange Saturation Transfer (CEST) imaging, face challenges in accurately and efficiently correcting for inhomogeneities in static magnetic field B0 and excitation field B1, leading to long calculation times and loss of signal polarity, which are prohibitive for clinical applications.
Innovation Solution
A post-processing method for WASAB1 acquisition sequences that estimates the parameters B0 and B1 using a simplified model with two parameters, based on detecting and preserving the polarity of the experimental signal, allowing for rapid and robust corrections by constructing a polarized set of samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a simplified two-parameter model is used for post-processing WASAB1 sequences, then calculation time is reduced and productivity is improved, but measurement precision of B0 and B1 parameters may deteriorate
Solution Approach 1:
The patent transforms the complex four-parameter estimation problem into a simplified two-parameter problem by changing the parameter space. Instead of estimating amplitude, frequency, phase, and damping simultaneously, the method estimates only the static magnetic field B0 and excitation field B1 parameters, which are the clinically relevant quantities. This parameter reduction dramatically decreases calculation time while maintaining sufficient accuracy for clinical applications.
Solution Approach 2:
The patent extracts and preserves only the essential polarity information from the experimental signal while discarding less critical components. By focusing on the sign of the signal rather than its full magnitude and phase characteristics, the method simplifies the data processing requirements and reduces computational burden while retaining the key information needed for accurate B0 and B1 mapping.
2Measurement precision
If polarity detection is implemented in the post-processing method, then measurement precision of B0 and B1 is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or computational signal processing mechanisms with a simpler polarity detection approach. Instead of using sophisticated phase analysis or full signal reconstruction algorithms, the method simply detects the sign of the signal at specific time points, which can be implemented with minimal computational resources while still achieving high measurement precision for B0 and B1 parameters.
3Measurement precision
If existing four-parameter adjustment methods are used, then measurement precision is maintained, but loss of time occurs due to long calculation times
Solution Approach 1:
The patent performs preliminary action by detecting the polarity of the experimental signal before the main parameter estimation process. This preliminary polarity information is then used to guide the simplified two-parameter fitting procedure, ensuring that the reduced computational method still achieves accurate results. By preparing this key information in advance, the method avoids the need for time-consuming full signal analysis while maintaining precision.
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
The method significantly reduces calculation times and enhances the accuracy of B0 and B1 estimations, producing high-quality parametric maps suitable for clinical applications, enabling precise characterization of lesions and biomarkers.
Implementation Method 1
Magnetic resonance imaging is based on an analysis of the response of the proton of a water molecule when it is excited in a magnetic field
Implementation Method 2
a nuclear magnetic resonance imaging device 1, as illustrated by way of non-limitative example by FIGS. 1 and 2
Implementation Method 3
Chemical Exchange Saturation Transfer (CEST) imaging, face challenges in accurately and efficiently correcting for inhomogeneities
Implementation Method 4
applying a radiofrequency pulse according to different determined resonant frequencies w, such that chemical species of interest reach a state of saturation
Implementation Method 5
The WASAB1 sequence was invented... Simultaneous mapping of water shift and B1 (WASAB1)—application to field-inhomogeneity correction of CEST MRI data
Implementation Method 6
makes it possible to simultaneously map the static magnetic field B0 and the excitation magnetic field B1
Data Source
AI summary
The invention relates to a method for carrying out post-processing on a first set of samples measuring the magnitude of a WASAB1 signal delivered by a magnetic-resonance medical-imaging apparatus. Such a method comprises a step of detecting the samples of a first set Z, for which samples the respective polarities of the values of the measured signal are known, and of constructing a second set Y of “polarised” samples. Such a method further comprises a step of fitting a determined model to said second set Y, the two parameters of the determined model describing the static magnetic field B0 and excitation magnetic field B1 of the magnetic-resonance medical-imaging apparatus, respectively, and of producing an estimation of the parameters B0 and B1 of the model. Such a method relates to any magnetic-resonance-imaging application in which a correction for inhomogeneities in the fields B0 and B1 is required.