Real-Time Gradient Correction in MRI Systems
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) systems face temperature-related deviations in gradient responses, leading to inaccuracies in image reconstruction due to unaccounted temperature changes during imaging, which traditional single-static gradient correction methods fail to address effectively.
Innovation Solution
A method involving the application of a nominal test gradient within the MRI pulse sequence, repeated acquisition of gradient responses, and determination of a gradient characterization function to correct for temperature-induced deviations, allowing for real-time compensation of artifacts in the gradient fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional single-static gradient correction methods are used, then device complexity is reduced, but temperature-related deviations in gradient response lead to manufacturing precision deterioration
Solution Approach 1:
The patent transitions from static gradient correction to dynamic correction by continuously monitoring temperature changes during the MRI examination and adjusting gradient correction parameters in real-time. Temperature sensors monitor gradient coil temperature, and correction factors are updated dynamically to compensate for thermal effects on gradient response, thereby maintaining precision without requiring overly complex static correction systems.
Solution Approach 2:
The patent implements a feedback mechanism where temperature sensors continuously monitor the temperature of gradient coils during operation. This temperature data is fed back to the control system, which then adjusts gradient correction parameters accordingly. The system measures actual gradient response, compares it to expected values, and applies corrective adjustments based on the measured deviations, creating a closed-loop control system that maintains accuracy.
2Manufacturing precision
If repeated gradient response acquisition is performed during imaging, then temperature-related deviations are corrected improving manufacturing precision, but measurement time increases
Solution Approach 1:
The patent combines gradient correction measurements with the actual imaging process by using the same gradient pulses that are applied during image acquisition to also measure gradient response. The system simultaneously performs imaging and gradient characterization, eliminating the need for separate correction measurement sequences. This merging of functions allows continuous correction without significant time penalty.
Solution Approach 2:
The patent maintains continuous gradient monitoring and correction throughout the entire imaging process rather than performing discrete corrections. Temperature is monitored continuously, and gradient correction parameters are updated throughout the examination, ensuring that correction is always current without requiring interruption of the imaging sequence for measurement.
3Measurement precision
If gradient characterization function is determined based on repeated measurements, then gradient field correction precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces temperature as an intermediary parameter that mediates between gradient coil physical state and gradient response characteristics. Instead of directly measuring complex gradient response deviations, the system measures temperature (a simple physical quantity) and uses pre-determined temperature-correction relationships to adjust gradient parameters. This intermediary approach simplifies the correction system while maintaining high precision.
Solution Approach 2:
The patent changes the correction approach from adjusting multiple gradient parameters simultaneously to primarily adjusting based on temperature parameter changes. By focusing correction on temperature-dependent variations in gradient response, the system reduces the dimensionality of the correction problem while maintaining accuracy for the dominant source of deviation.
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 precise correction of gradient fields in real-time, reducing temperature-related artifacts and improving image quality by incorporating temperature variations into the image recording and reconstruction processes.
Implementation Method 1
with the aid of a gradient system, a magnetic field gradient, by which the magnetic resonance frequency (Larmor frequency) at the location in question is determined, is applied
Implementation Method 2
the body to be examined is usually exposed to a relatively high main magnetic field of, for example, 1.5 tesla, 3 tesla or 7 tesla. After the main field has been applied, nuclei are aligned in the examination object along the field with a nuclear magnetic dipole moment
Implementation Method 3
Using a radiofrequency transmission system, radiofrequency excitation signals (RF-pulses) are then emitted using appropriate antenna facilities, which is intended to lead to the nuclear spins of certain nuclei that have been resonantly excited by this radio frequency field
Implementation Method 4
During the relaxation of the nuclear spins that have been excited, radiofrequency signals (e.g., magnetic resonance signals) are resonantly emitted. These signals are received by appropriate receive antennas
Data Source
AI summary
A correction method for reducing temperature-related deviations in a gradient response of an MR pulse sequence in MR imaging is provided. An MR pulse sequence that includes at least one nominal test gradient is run. A gradient response to the at least one nominal test gradient is repeatedly acquired by a magnetic field measurement in an examination region. A gradient system transfer function is determined based on the gradient response. A corrected MR pulse sequence is determined based on the gradient system transfer function and of the at least one nominal test gradient.