MRI B1 Field Homogeneity via RF Polarization Averaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic resonance imaging (MRI) data quality is compromised by B1 field inhomogeneities, leading to fluctuations in image brightness and contrast, especially at high magnetic field strengths, due to variations in the electrical and dielectric properties of the examination subject, making it difficult to achieve uniform excitation and resulting in signal attenuation or dropout.
Innovation Solution
A method involving multiple scanning operations with different polarizations of radio-frequency signals is used to acquire raw data, where the magnetic resonance image data set is determined by averaging the results, ensuring that at least one polarization exceeds the homogeneity threshold in all areas, thereby reducing signal attenuation and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple transmission channels with different polarizations are used, then B1 field homogeneity is improved, but measurement time increases
Solution Approach 1:
The measurement process is segmented into multiple independent scanning operations, each using a different polarization. Instead of performing one comprehensive measurement, the total measurement is divided into several partial measurements that can be acquired separately and then combined, allowing parallel processing and reduced total measurement time.
Solution Approach 2:
Multiple raw data sets acquired with different polarizations are merged through averaging to produce a single composite data set. This combining process integrates the advantages of different polarizations, achieving superior B1 field homogeneity that exceeds what any single polarization could provide alone.
2Reliability
If multiple scanning operations with different polarizations are performed and averaged, then signal attenuation is reduced, but acquisition time increases
Solution Approach 1:
The acquisition process uses periodic scanning operations with different polarizations alternating in sequence. Each polarization is applied in periodic intervals, allowing the system to cycle through different excitation patterns and combine their effects, thereby reducing signal attenuation through temporal diversification of the measurement approach.
Solution Approach 2:
The polarization parameters (phase and amplitude relationships between transmission channels) are changed between scanning operations. By varying these parameters across multiple scans and averaging the results, the method compensates for signal attenuation that would occur with any single parameter setting, improving overall signal quality.
3Manufacturing precision
If patient-adaptive shimming is implemented, then image homogeneity is improved, but device complexity increases
Solution Approach 1:
Instead of implementing complex patient-adaptive shimming hardware and control systems, the method creates simplified copies or models of the problem by acquiring multiple data sets with different polarizations. These copies are then processed through straightforward averaging, achieving homogeneity improvement without the need for complex real-time shimming adjustments.
Solution Approach 2:
The method uses multiple disposable polarization configurations rather than investing in complex, expensive, and difficult-to-maintain adaptive shimming systems. Each polarization scan is a simple, independent measurement that can be quickly executed and discarded, with the final result derived from averaging multiple such simple measurements rather than from complex real-time optimization.
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 enhances the homogeneity of the B1 field and reduces signal attenuation across the scan area, resulting in higher-quality MRI data sets with improved signal-to-noise ratio and image homogeneity, even in areas prone to signal loss, without the need for complex patient-adaptive shimming or additional measurement time.
Implementation Method 1
a radio-frequency transmitter coil apparatus emits radio-frequency excitation pulses that are often referred to as radio-frequency pulses. The cumulative effect of the radio-frequency pulses ('excitation') generates a radio-frequency field that is usually referred to as the B1 field and flips (deflects) the spins of resonant excited nuclei
Implementation Method 2
The excited spins of the nuclei then radiate radio-frequency signals that can be received using suitable receiving antennas, in particular including the transmitter coil apparatus itself, which then also acts as a receiver coil apparatus, and processed in such a way that magnetic resonance image data can be reconstructed
Data Source
AI summary
In a method and apparatus for acquiring a magnetic resonance image data set of a scan area of an examination subject, the image data are acquired with a magnetic resonance apparatus having a transmitter coil that emits a radio-frequency signal having at least two transmission channels so that different polarizations of the radio-frequency signal are produced, and a magnetic resonance sequence is used to acquire raw data for the magnetic resonance image data set, wherein raw data are acquired during at least two scanning operations with the magnetic resonance sequence, with different polarizations of the radio-frequency signals being used for at least two of the at least two scanning operations, following which the magnetic resonance image data set is determined by averaging the raw data.