Universal RF Pulse Sequences for Parallel MRI
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Solution Overview
Problem
Current parallel transmission MRI techniques are laborious and time-consuming, limiting their clinical application due to the need for individual B1 and ΔB0 map acquisition and online numerical calculations for each patient, which is impractical for clinical settings, especially when patient comfort and time constraints are considered.
Innovation Solution
Designing 'universal' sequences of RF pulses and gradient waveforms optimized for a cohort rather than individual subjects, allowing offline computation and reducing the burden on clinicians, making parallel transmission more accessible and efficient by using pre-designed pulse sequences that are robust across various subjects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual B1 and ΔB0 map acquisition and online numerical calculations are performed for each patient, then nuclear spin excitation homogeneity is improved, but procedure time and operational complexity increase significantly
Solution Approach 1:
The patent pre-calculates and stores optimal RF pulse parameters in a lookup table during an offline calibration phase using representative phantom objects. During actual patient imaging, the system simply retrieves pre-computed parameters based on measured B1 and ΔB0 maps, avoiding time-consuming online optimization calculations while maintaining excitation homogeneity
Solution Approach 2:
The patent creates a simplified model or lookup table that copies the essential characteristics of complex optimization results. Instead of performing full numerical optimization for each patient, the system uses pre-computed parameter sets that replicate the optimal solution structure, significantly reducing computational burden during clinical procedures
2Manufacturing precision
If individual B1 andΔB0 map acquisition and online numerical calculations are performed for each patient, then nuclear spin excitation homogeneity is improved, but device complexity and operational burden increase
Solution Approach 1:
The complex numerical optimization is performed once during offline calibration and the results are stored in a lookup table. During patient imaging, the system only needs to measure B1 and ΔB0 maps and retrieve pre-computed parameters, dramatically simplifying the operational workflow and reducing the computational expertise required
Solution Approach 2:
The system automatically measures B1 and ΔB0 maps and retrieves appropriate pre-computed parameters without requiring manual intervention or complex optimization operations by the operator. The lookup table structure enables automatic parameter selection based on measured field characteristics
3Manufacturing precision
If adiabatic pulses are used to reduce B1 inhomogeneity, then field homogeneity is improved, but specific absorption rate (SAR) and pulse duration increase
Solution Approach 1:
The patent modifies RF pulse parameters (amplitude, phase, duration) based on pre-computed optimization results that account for specific B1 andΔB0 conditions. This allows achieving field homogeneity with lower SAR by using tailored non-adiabatic pulses instead of universally applying long-duration adiabatic pulses
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 universal sequences provide effective nuclear spin excitation homogeneity, performing better than standard approaches without the need for individual calibration, and are applicable across different subjects, reducing the time and complexity of MRI procedures while maintaining clinical relevance.
Implementation Method 1
A pulse sequence comprises one or more radio-frequency (RF) pulses and at least one magnetic field gradient waveform, allowing manipulating the nuclear spins of a sample immersed in a static magnetic field
Implementation Method 2
This leads to enhanced non-uniformities in the radio-frequency (B1) field, and therefore to the appearance of low-SNR zone across the images
Implementation Method 3
Static magnetic field inhomogeneity (ΔB0) induces similar problems
Data Source
AI summary
A method of designing a pulse sequence for parallel-transmission magnetic resonance imaging comprises: a) acquiring, for each member of a cohort, inhomogeneity maps of radio-frequency fields generated within the member; b) computing, for each member of the cohort, a spatial distribution of flip angles of nuclear spins obtained using the pulse sequences, and c) computing a single cost or merit function representative of a difference between the spatial distributions of flip angles and a target distribution, and iteratively adjusting design parameters of the pulse sequences to optimize the cost or merit function; the steps b) and c) being carried out iteratively using a computer. A method of performing parallel-transmission magnetic resonance imaging on a subject using a pulse sequence designed by such a method is provided.