MRI B1 Field Correction via Frequency-Dependent Transfer Function
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Solution Overview
Problem
Magnetic Resonance Imaging (MRI) systems face inadequate image quality when RF pulses are excited at frequencies other than the center frequency, leading to suboptimal flip angle distribution and image homogeneity.
Innovation Solution
A method to determine and apply a frequency-dependent transfer function to correct the B1 field, allowing for accurate flip angle excitation even when RF pulses are not at the center frequency, by measuring and correcting the transmission signal using the transfer function, which reflects the relationship between the RF transmitting voltage and the generated B1 field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If RF pulses are transmitted at frequencies other than the center frequency, then the bandwidth utilization is improved, but the image quality and flip angle distribution deteriorate
Solution Approach 1:
The patent applies parameter changes by determining a frequency-dependent transfer function that characterizes the transmitting system's response at different frequencies. This transfer function is then used to adjust the transmission signal parameters (amplitude, phase) to compensate for frequency-dependent deviations in the B1 field, thereby maintaining accurate flip angle distribution across the frequency spectrum
Solution Approach 2:
The patent implements feedback by measuring the actual B1 field distribution at different frequencies and using this information to calculate and apply correction factors to the transmission signal. The transfer function is determined based on measured data and fed back into the transmission system to optimize performance across the frequency range
2Adaptability or versatility
If the transmitting system operates at different frequencies, then the imaging flexibility is improved, but the image homogeneity deteriorates
Solution Approach 1:
The patent changes parameters by determining a frequency-dependent transfer function that captures the system's behavior across different frequencies. This transfer function enables dynamic adjustment of transmission parameters to maintain uniform B1 field distribution and image homogeneity regardless of the operating frequency
Solution Approach 2:
The patent applies preliminary action by pre-determining the transfer function across the frequency range before actual imaging. This pre-characterization allows the system to apply appropriate corrections in advance for any frequency within the range, ensuring consistent image quality without requiring real-time adjustments during scanning
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 significantly improves image quality and homogeneity by ensuring correct flip angle excitation across various frequencies, enhancing the overall performance of the MRI system.
Implementation Method 1
The RF transmitting antenna is operated, for example, by at least one RF amplifier. The at least one RF amplifier transmits a transmission signal by a RF transmitting voltage to the RF transmitting antenna. The transmission signal has, for example, a sinusoidal shape having a particular transmit frequency... From the RF irradiation, a magnetic alternating field results having a transmit frequency, which is also called the B1 field.
Implementation Method 2
Magnetic Resonance Imaging (MRI) is a known examination technique for generating images of the inside of a body of a patient, and is based on the physical phenomenon of magnetic resonance (MR).
Implementation Method 3
The transmitting system includes at least one RF antenna, which may also be called a RF transmitting antenna... The irradiated excitation pulses are capable of deflecting nuclear spins in order to obtain a desired flip angle distribution for the respective examination.
Data Source
AI summary
The disclosure relates to a method for determining a transfer function of a transmitting system of a magnetic resonance device, to a method for the correction of a transmission signal of a magnetic resonance device, to a corresponding magnetic resonance device, and to a computer program product for carrying out the method. The method includes determining a transfer function using a transmission characteristic of a transmitting system of the magnetic resonance device, wherein the transfer function is frequency-dependent. A transmission signal may be corrected using the transfer function. An excitation pulse may be emitted by the transmitting system using the corrected transmission signal.