HF Pulse Optimization for Magnetic Resonance Sequences
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Solution Overview
Problem
Current magnetic resonance systems face challenges in efficiently calculating multi-channel pulses with a large number of variables, leading to increased computing time and potential inaccuracies, especially with higher gradient field strengths and longer time steps, which complicates the optimization of magnetization distribution.
Innovation Solution
Incorporating the transmission bandwidth into the HF pulse optimization method using a correction factor in the Jacobi matrix elements, allowing for reduced time steps and variables while maintaining optimization accuracy, even with longer sampling times and higher gradient field strengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of time steps in HF pulse optimization is increased to improve accuracy, then the precision of magnetization distribution optimization is improved, but the computing time and number of variables increase significantly
Solution Approach 1:
The patent changes the parameter of time step length in the HF pulse optimization. By using longer time steps (e.g., 10-20 μs instead of 1-10 μs) while incorporating transmission bandwidth considerations into the optimization model, the method reduces the total number of time steps required, thereby decreasing computing time and the number of variables while maintaining optimization accuracy.
2Productivity
If higher gradient field strengths are used to accelerate the measurement process, then the measurement speed is improved, but the calculation accuracy of multi-channel pulses deteriorates
Solution Approach 1:
The patent modifies the optimization approach to account for transmission bandwidth effects that become significant at higher gradient field strengths. By incorporating correction factors related to transmission bandwidth into the Jacobi matrix elements of the optimization model, the method maintains calculation accuracy even when using higher gradient fields to accelerate the measurement process.
3Loss of time
If longer time steps are used to reduce the number of variables, then the computing time is reduced, but the accuracy of magnetization distribution optimization deteriorates
Solution Approach 1:
The patent introduces transmission bandwidth considerations as a correcting parameter in the optimization model. This allows the use of longer time steps (reducing computing time) while compensating for the loss of accuracy through the bandwidth correction factors incorporated into the optimization calculations.
Solution Approach 2:
The patent introduces transmission bandwidth correction factors as an intermediary element in the optimization process. These correction factors mediate between the simplified model (longer time steps, fewer variables) and the accurate physical reality, allowing accurate optimization results without requiring excessively fine time discretization.
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 reduces the number of variables and computing time required for optimizing magnetic resonance system control sequences, achieving accurate magnetization distribution and accelerating measurement processes without significant deterioration in results, even under higher gradient field conditions.
Implementation Method 1
high-frequency excitation signals (HF signals) are transmitted via a high-frequency transmission system. The high-frequency transmission system is intended to cause the nuclear spins of specific atoms resonantly excited by the high-frequency field to be tilted
Implementation Method 2
During the relaxation of the nuclear spins, high-frequency signals (so-called magnetic resonance signals), are emitted. The high-frequency signals are received by suitable receiver antennas
Data Source
AI summary
A method and a control sequence determination device for determining a magnetic resonance system control sequence is disclosed. The magnetic resonance system control sequence includes a multi-channel pulse with a plurality of individual high-frequency (HF) pulses to be transmitted in parallel by the magnetic resonance system via different independent high-frequency transmission channels. In one embodiment, the method includes calculating a multi-channel pulse based on an MR excitation quality parameter in an HF pulse optimization method. An HF pulse includes a plurality of successive HF partial pulses in discrete time steps. The method further includes considering, in the course of the HF pulse optimization method, a transmission bandwidth of an HF partial pulse to be transmitted during a discrete time step. A method for operating a magnetic resonance system and a magnetic resonance system that includes the control sequence determination device are disclosed.