MRI Frequency-Dependent Antenna Calibration for Non-Cartesian Trajectories
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques face challenges in speeding up data acquisition without compromising resolution, contrast, and susceptibility to artifacts, particularly when using non-Cartesian trajectories, as they fail to account for the frequency-dependent sensitivity of receiving antennas, leading to scanning errors.
Innovation Solution
A method and control device for MRI that determine frequency-dependent calibration values for the sensitivity of receiving antennas, allowing for accurate image reconstruction by considering the frequency-dependent sensitivity, especially in non-Cartesian trajectories, and utilizing these values to reduce scanning errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-Cartesian trajectories are used to speed up data acquisition, then productivity is improved, but measurement precision deteriorates due to scanning errors from ignoring frequency-dependent sensitivity
Solution Approach 1:
The patent applies parameter changes by determining calibration values at multiple frequency points (e.g., 5 different frequencies) and using these frequency-dependent calibration values to correct the sensitivity profiles of receiving antennas. This allows the system to account for frequency variations in non-Cartesian trajectories, thereby maintaining measurement precision while enabling faster acquisition speeds through non-Cartesian sampling patterns.
2Measurement precision
If frequency-dependent calibration values are determined for multiple frequency encoding patterns, then measurement precision is improved, but loss of time increases due to additional calibration measurements
Solution Approach 1:
The patent implements partial action by determining calibration values at a limited number of discrete frequency points (e.g., 5 frequencies) rather than continuously across the entire frequency range. This partial sampling approach provides sufficient accuracy for image reconstruction while avoiding the excessive time cost of comprehensive frequency-dependent calibration at every possible frequency point.
Solution Approach 2:
The patent achieves universality by using a single set of frequency-dependent calibration values to correct sensitivity profiles across multiple frequency encoding patterns and different non-Cartesian trajectories. These calibration values serve multiple functions: they correct for frequency-dependent sensitivity variations, enable accurate image reconstruction for different trajectory types, and reduce scanning errors across various imaging scenarios without requiring separate calibration for each pattern.
3Ease of operation
If conventional calibration methods are used that ignore frequency dependency, then ease of operation is maintained, but manufacturing precision deteriorates due to scanning errors in non-Cartesian trajectories
Solution Approach 1:
The patent replaces the conventional mechanical/simplistic calibration approach with a frequency-dependent calibration system that automatically determines calibration values at multiple frequency points. This substitution introduces computational complexity but eliminates the need for manual adjustment and provides accurate correction for frequency-dependent sensitivity variations, thereby improving trajectory scanning accuracy while maintaining operational ease through automated processing.
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 enables reduced scanning errors and improved image quality by accounting for the frequency-dependent sensitivity of receiving antennas, particularly in non-Cartesian trajectories, without significantly increasing measurement time.
Implementation Method 1
When the excited nuclear spins are relaxed, radio-frequency signals, known as magnetic resonance signals, are resonantly emitted and are received by suitable receiving antennas
Implementation Method 2
Following creation of the basic field, nuclei in the examination object align themselves with a non-vanishing nuclear magnetic dipole moment, frequently also called spin, along the field. This collective behavior of the spin system is described as macroscopic 'magnetization'.
Implementation Method 3
Using a radio-frequency transmission system, radio-frequency excitation signals (RF pulses) are transmitted by suitable antenna devices, which results in the macroscopic 'magnetization' being tilted by a defined flip angle with respect to the magnetic field lines of the basic magnetic field.
Implementation Method 4
In addition to the basic field, a magnetic field gradient is generated by a gradient system, by means of which the magnetic resonance frequency (Larmor frequency) is determined at the respective location.
Data Source
AI summary
In a method and control device for magnetic resonance imaging, raw magnetic resonance data are acquired from one region of an examination object by a number of magnetic resonance receiving antennas of a magnetic resonance system. Calibration values are determined that represent the sensitivity of at least one of the magnetic resonance receiving antennas. An image reconstruction is performed on the basis of the raw magnetic resonance data, taking into consideration the determined calibration values. The determination of the calibration values is frequency-dependent.