MRI Gradient Coil Frequency Correction via Temperature Feedback
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in maintaining image quality due to heat-generated shifts in the center frequency of hydrogen atoms' magnetic resonance caused by the gradient magnetic field coil, particularly during long-duration imaging, leading to degraded image quality.
Innovation Solution
An MRI apparatus and method that includes a gradient magnetic field coil unit, a temperature measuring unit, a data storing unit, and a pulse setting unit, which measures temperature changes, calculates the shift in the center frequency of hydrogen atoms, and corrects the RF pulse frequency accordingly to maintain image quality despite temperature-induced frequency shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gradient magnetic field coil is operated for long-duration imaging, then imaging productivity is improved, but temperature of the coil rises causing center frequency shift and image quality degradation
Solution Approach 1:
The system continuously monitors temperature changes in the gradient magnetic field coil and uses this feedback to dynamically adjust the center frequency of RF pulses. This closed-loop control ensures that image quality is maintained despite temperature-induced frequency shifts during long-duration imaging.
Solution Approach 2:
The system changes the operational parameters of the RF pulse by adjusting its center frequency based on real-time temperature measurements. This parameter adaptation allows the system to compensate for thermal effects without interrupting the imaging sequence.
2Reliability
If cooling system is added to maintain coil temperature, then center frequency stability is improved, but device complexity and operational cost increase
Solution Approach 1:
The system replaces mechanical cooling systems with a software-based frequency compensation approach. By using temperature sensing and computational adjustment of RF pulse frequencies, the system achieves frequency stability without the complexity of active cooling infrastructure.
Solution Approach 2:
The system uses the temperature information naturally generated during normal operation to self-correct the frequency drift. The gradient coil's own thermal signature is measured and used to adjust the RF parameters, turning a potential problem into a self-regulating mechanism.
3Manufacturing precision
If RF pulse center frequency is set based on prescan, then initial image quality is good, but frequency shift during imaging degrades later image quality
Solution Approach 1:
The system transitions from a static frequency setting (based on prescan) to a dynamic frequency adjustment mechanism. The center frequency of RF pulses is continuously adapted during imaging based on real-time temperature measurements, allowing the system to maintain accuracy throughout the entire imaging duration.
Solution Approach 2:
The system performs preliminary temperature monitoring and frequency adjustment calculations during the imaging sequence itself, allowing proactive compensation for thermal drift before it significantly impacts image quality.
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
The solution ensures high-quality images are obtained regardless of temperature-induced frequency shifts, minimizing the impact of heat generation on MRI image quality and reducing the need for extensive cooling, thus reducing operational costs and enhancing imaging efficiency.
Implementation Method 1
a gradient magnetic field coil that generates a gradient magnetic field in an imaging region according to electric current supplied to the gradient magnetic field coil
Implementation Method 2
a temperature measuring unit that measures temperature of the gradient magnetic field coil
Implementation Method 3
The center frequency of an RF pulse, such as a fat suppression prepulse and a 90° excitation pulse, is set based on the Larmor frequency of hydrogen atoms that depends on the intensity of the static magnetic field
Data Source
AI summary
In one embodiment, an MRI apparatus (20) includes “a temperature measuring unit (70A to 70D) performing temperature measurement of a gradient magnetic field coil unit (26)”, a data storing unit (100), a pulse setting unit (102), and an imaging unit. The data storing unit stores the first and second data indicating a shift of a center frequency of magnetic resonance of hydrogen atoms. The first data corresponds to a case of temperature rise of the gradient magnetic field coil unit, and the second data corresponds to a case of temperature fall of that. The pulse setting unit corrects a center frequency of an RF pulse by calculating an estimated shift of the center frequency based on data corresponding to result of the temperature measurement out of the first and second data. The imaging unit performs magnetic resonance imaging based on the corrected RF pulse.