Continuous Phase Error Correction in MR RF Excitation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic resonance (MR) measurement sequences with multidimensional, spatially-selective radio-frequency (RF) excitation pulses face challenges in correcting phase errors due to system inaccuracies and time-dependent errors, leading to artifacts and reduced measurement stability, especially in repeated imaging sequences where traditional calibration techniques are time-consuming and limited in validity.
Innovation Solution
A method for continuously correcting phase errors by radiating multidimensional, spatially-selective RF excitation pulses with calculated correction values based on acquired calibration gradient echoes, allowing for real-time adjustment of phase responses and phase differences during the MR measurement sequence, thereby improving precision and reducing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration techniques are used to correct phase errors, then measurement precision is improved, but measurement time is significantly increased and calibration validity is limited to short periods
Solution Approach 1:
The patent implements continuous correction of phase errors by repeatedly acquiring calibration gradient echoes and updating correction values throughout the measurement sequence. Instead of performing calibration once before imaging, the system continuously monitors and corrects phase errors caused by time-dependent factors such as eddy currents and subject movement, thereby maintaining calibration validity throughout the entire measurement process without significantly increasing total measurement time
Solution Approach 2:
The patent performs a preliminary calibration to obtain initial correction values before the main measurement sequence. These initial correction values are then used as a basis for subsequent continuous corrections. The preliminary calibration establishes the starting point for the continuous correction process, allowing the system to quickly adapt to time-dependent phase errors during the measurement sequence
2Productivity
If multidimensional spatially-selective RF excitation pulses are used, then productivity is improved by reducing measurement time, but phase errors increase due to system inaccuracies
Solution Approach 1:
The patent implements a feedback mechanism where calibration gradient echoes are acquired after each or multiple RF excitation pulses to monitor phase errors. The correction values derived from these echoes are then applied to subsequent RF excitation pulses. This closed-loop feedback system continuously compensates for phase errors introduced by multidimensional spatially-selective RF excitation, allowing the system to maintain high measurement speed while correcting for system inaccuracies and time-dependent phase variations
Solution Approach 2:
The patent makes the correction values dynamic by continuously updating them throughout the measurement sequence based on freshly acquired calibration gradient echoes. Instead of using static correction values from a single preliminary calibration, the system adapts the correction values in real-time to account for time-dependent phase errors such as those caused by eddy currents and subject movement, thereby maintaining phase accuracy throughout the fast measurement sequence
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 continuous correction of phase errors throughout the MR measurement sequence, enhancing the accuracy of MR imaging data by minimizing phase errors caused by system inaccuracies and time-dependent changes, such as eddy currents and subject movement, without significantly increasing measurement time or requiring extensive calibration.
Implementation Method 1
Magnetic resonance (MR) tomography is an imaging method that enables the acquisition of two-dimensional or three-dimensional image data sets
Implementation Method 2
A spatial coding of the acquired MR data is achieved by the application of different magnetic field gradients (for slice selection, phase coding or frequency coding)
Implementation Method 3
the calculation of a correction value for a phase response of the RF excitation pulse and a correction value for a phase difference of the RF excitation pulse from the plurality of calibration gradient echoes
Data Source
AI summary
In a method and magnetic resonance apparatus to continuously correct phase errors in a magnetic resonance measurement sequence in which multiple sequentially radiated, multidimensional, spatially-selective radio-frequency excitation pulses are used, multiple calibration gradient echoes are acquired in a calibration acquisition sequence and a correction value for a phase response and a correction value for a phase difference are calculated from the multiple calibration gradient echoes. Furthermore, an additional radio-frequency excitation pulse is radiated takes into account the correction values.