MRI Imaging Sequence Control for Magnet Pressure and Quench Prevention
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Solution Overview
Problem
The challenge of predicting and preventing Gradient Coil Induced Heating (GCIH) in MRI apparatuses, which can lead to quenching of superconductive magnets due to vibrations and heat generation, is difficult to manage accurately, necessitating non-optimal imaging sequence adjustments to avoid magnet pressure rises.
Innovation Solution
A magnetic resonance imaging apparatus that includes a processing circuit to predict magnet internal pressure and temperature based on the relationship between the gradient field coil's driving frequency and the magnet's conditions, using an equivalent circuit model to adjust the imaging sequence to avoid quenching by estimating energy consumption and adjusting the sequence before execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gradient field coil is driven at high specifications to improve imaging quality and speed, then productivity and image quality improve, but the gradient field coil vibrates due to Lorentz force, generating heat in the superconductive magnet and causing internal pressure rise that may lead to quenching
Solution Approach 1:
The system performs preliminary prediction of magnet internal pressure and temperature based on the imaging sequence before actual imaging. By calculating the cumulative vibration energy and comparing it against safety thresholds, the system identifies potential GCIH risks in advance and adjusts the imaging sequence proactively to prevent quenching while maintaining high-speed imaging capability
2Reliability
If the imaging sequence is adjusted to avoid vibration resonance points to prevent GCIH, then magnet safety improves, but the imaging sequence is no longer optimized, reducing productivity and image quality
Solution Approach 1:
The system dynamically adjusts imaging sequence parameters such as repetition time (TR), echo time (TE), and gradient waveform timing to change the driving frequency away from resonance points. By optimizing these parameters within safety constraints, the system maintains high imaging efficiency while preventing GCIH through frequency modulation rather than simply reducing imaging speed
3Reliability
If the gradient field generation system is driven at lower specifications to prevent quenching, then magnet safety improves, but the imaging quality and diagnostic capability deteriorate
Solution Approach 1:
The system implements dynamic adjustment of gradient field strength and timing parameters during the imaging sequence based on real-time prediction of vibration energy accumulation. This allows the gradient field generation system to operate at high specifications when safe and reduce power only when necessary to avoid resonance, maintaining high image quality while preventing quenching through adaptive power control
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 apparatus effectively prevents quenching by optimizing the imaging sequence to control heat input and internal pressure, ensuring safe operation of the superconductive magnet.
Implementation Method 1
a gradient field coil that adds special positional information to an MR signal by applying a gradient field to an imaging space where an object is placed
Implementation Method 2
The gradient field coil is vibrated by a Lorentz force when a pulse current is repetitively supplied during imaging
Implementation Method 3
the gradient field coil generates a leakage flux outside. If the vibration of the gradient field coil propagates into the magnet, or a vibration occurs in the magnet due to an eddy current generated by the leakage flux, heat is generated in the magnet
Implementation Method 4
heat is generated in the magnet, and liquid helium evaporates. Since this raises the internal pressure in a superconductive magnet
Data Source
AI summary
According to one embodiment, a magnetic resonance imaging apparatus includes a processing circuit. The processing circuit is configured to predict, based on an imaging sequence of magnetic resonance imaging and a relationship between a driving frequency of a gradient field coil and one of a magnet internal pressure and a magnet temperature of a static field magnet, the one of the magnet internal pressure and the magnet temperature at the time of execution of the imaging sequence, adjusts the imaging sequence based on a prediction result, and execute the adjusted imaging sequence.