MR Scanner B0 Compensation via Spectrally Selective Pulses
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Solution Overview
Problem
Magnetic resonance tomography scanners face challenges in producing high-quality images due to inhomogeneities in the static magnetic field B0, which are difficult to correct with existing shim coils and gradient pulse designs, leading to suboptimal image quality and increased electromagnetic load on patients.
Innovation Solution
A method and system for a magnetic resonance tomography scanner that determines and compensates for spatial variations in the B0 field using a B0 field map, generating spectrally selective excitation pulses that account for different Larmor frequencies and gradient fields, thereby improving image homogeneity and reducing the need for active or passive shimming and electromagnetic load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If shim coils are used to improve B0 field homogeneity, then magnetic field homogeneity is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/shim-coil-based field correction system with a computational approach. The controller calculates corrected excitation pulses that account for B0 inhomogeneities and gradient pulse effects through numerical optimization, eliminating the need for complex shim coil adjustments and achieving field homogeneity improvement through software rather than additional hardware
Solution Approach 2:
The patent changes the parameters of the excitation pulses (amplitude, phase, frequency, temporal shape) based on calculated B0 field maps and gradient pulse characteristics. By dynamically adjusting these pulse parameters through optimization algorithms, the system compensates for field inhomogeneities without requiring physical shim coil modifications
2Stability of the object's composition
If gradient pulses are designed to account for eddy currents, then dynamic field stability is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary calculation of the B0 field map and determines corrected excitation pulse parameters before actual image acquisition. By pre-calculating the compensation needed for eddy currents and B0 inhomogeneities based on the planned gradient pulse sequence, the system eliminates dynamic field instabilities without requiring complex real-time gradient pulse modifications during scanning
Solution Approach 2:
The patent uses measured or calculated B0 field maps as feedback to iteratively optimize the excitation pulse parameters. The system incorporates information about actual field conditions and gradient pulse effects into the pulse design, creating a closed-loop approach that improves dynamic field stability through computational feedback rather than hardware complexity
3Ease of operation
If conventional excitation pulses are used, then device operation is simple, but image quality deteriorates due to B0 inhomogeneity and gradient effects
Solution Approach 1:
The patent enables the MR scanner to self-correct for B0 inhomogeneities and gradient pulse effects through automated calculation of corrected excitation pulses. The controller independently determines the optimal pulse parameters based on the B0 field map and sequence parameters without requiring manual intervention or complex operator adjustments, maintaining ease of operation while significantly improving image quality
Solution Approach 2:
The patent creates a composite approach by combining conventional excitation pulse design with computationally derived correction factors. The corrected excitation pulses integrate both the standard pulse sequence structure and additional compensation components that account for B0 inhomogeneity and gradient effects, achieving high image quality while maintaining operational simplicity through automated synthesis
4Stability of the object's composition
If active or passive shimming is performed to improve field homogeneity, then magnetic field homogeneity is improved, but electromagnetic load on patients increases
Solution Approach 1:
The patent replaces hardware-based shimming methods (active or passive) with a computational correction approach. By calculating and applying corrected excitation pulses that compensate for B0 inhomogeneities, the system achieves field homogeneity improvement without requiring additional electromagnetic fields from shim coils, thereby reducing the electromagnetic load on patients
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 enhances image quality by precisely controlling nuclear spin excitation, reducing deviations in the B0 field and gradient pulses, and optimizing image acquisition based on patient-specific parameters, leading to improved fat saturation and reduced SAR load.
Implementation Method 1
a field magnet for generating a static homogeneous magnetic field B0
Implementation Method 2
gradient coils for generating magnetic field gradients, which span a space
Implementation Method 3
a transmitter and an antenna for generating a magnetic alternating field B1 for exciting nuclear spins
Implementation Method 4
The precession or return of the spins from this excited state into a state with less energy in turn generates, as a response, a magnetic alternating field which is received by way of antennas
Data Source
AI summary
The disclosure relates to a magnetic resonance tomography scanner and to a method for operating the magnetic resonance tomography scanner. The method includes determining a B0 field map. The method further includes determining an excitation of the nuclear spins to be achieved and a spectrally selective excitation pulse for transmission by a transmitter by way of an antenna as a function of the B0 field map. In the method, the excitation pulse is configured here to generate the excitation of the nuclear spins to be achieved in the patient. The excitation pulse is then output by way of the antenna.