MRI Gradient Coil Load Estimation via Mutual Inductance
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Solution Overview
Problem
Current MRI technologies face challenges in accurately judging the practicability of imaging sequences based on electric load on gradient magnetic field generation systems, leading to suboptimal imaging conditions due to insufficient margin in electric current supply and discrepancies between gradient magnetic field current and actual field waveforms, especially in high-speed imaging methods like EPI.
Innovation Solution
The implementation of a magnetic resonance imaging apparatus with a condition setting unit and a judging unit that calculates the electric current and voltage supplied to the gradient magnetic field coil, using mutual inductance to determine the feasibility of imaging sequences and correct waveforms to ensure optimal conditions, including regridding processing to rearrange sampled data for accurate image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed imaging methods like EPI are used to reduce imaging time, then productivity is improved, but the gradient magnetic field coil experiences excessive thermal stress due to high-frequency pulse waveforms
Solution Approach 1:
The system performs preliminary calculation of the gradient magnetic field waveform using an equivalent circuit model before actual imaging. This allows prediction of the actual waveform deviations and thermal effects in advance, enabling pre-adjustment of imaging parameters or cooling protocols to prevent excessive temperature rise during high-speed EPI imaging
Solution Approach 2:
The system incorporates thermal management measures based on predicted waveform characteristics before imaging begins. By calculating the RMS value and thermal load in advance using the equivalent circuit model, the system can prepare appropriate cooling strategies or adjust pulse parameters to cushion against thermal stress during high-speed imaging
2Device complexity
If conventional methods are used to estimate electric power limits, then device complexity is reduced, but measurement precision of electric load is insufficient leading to suboptimal imaging conditions
Solution Approach 1:
The system replaces direct physical measurement of electric load with an electrical calculation approach. By using an equivalent circuit model to calculate voltage, current, and power parameters based on measured impedance and control signals, the system achieves high measurement precision without adding complex physical measurement hardware
Solution Approach 2:
The equivalent circuit model serves as an intermediary between the gradient magnetic field generation system and the control system. It translates easily measurable parameters (control signals, impedance) into accurate estimates of electric load and thermal stress, enabling precise monitoring without direct measurement of difficult-to-access parameters
3Device complexity
If the gradient magnetic field waveform is assumed to match the control signal waveform, then device complexity is reduced, but manufacturing precision of waveform control is insufficient due to actual deviations
Solution Approach 1:
The system uses the equivalent circuit model to create a virtual feedback loop. By calculating the actual waveform based on the circuit model and comparing it with the intended control signal, the system identifies deviations and can adjust control parameters to compensate, improving waveform accuracy without adding physical feedback sensors to the gradient coil system
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 allows for more precise estimation of electric power limits, enabling safer operation and optimization of imaging sequences by accurately judging the electric load, thereby improving image quality and reducing thermal stress on gradient magnetic field coils.
Implementation Method 1
This gradient magnetic field coil produces heat by being provided with pulse electric current during imaging
Implementation Method 2
This gradient magnetic field coil produces heat by being provided with pulse electric current during imaging
Implementation Method 3
MRI is an imaging method which magnetically excites nuclear spins of an object (a patient) set in a static magnetic field with an RF pulse having the Larmor frequency and reconstructs an image based on MR signals generated due to the excitation
Data Source
AI summary
A control device of a magnetic resonance (MRI) imaging apparatus includes a condition setting unit and a judging unit. The condition setting unit sets an imaging sequence to be performed by the magnetic resonance imaging apparatus based on set conditions of the set imaging sequence. The judging unit then (a) calculates a value of electric current supplied to a gradient magnetic field coil of the MRI apparatus to perform that set imaging sequence based on the set conditions of the set imaging sequence, (b) calculates a value of voltage that would need to be applied to the gradient magnetic field coil based on a mutual inductance of the gradient magnetic field to cause electric current flowing to the gradient magnetic field coil to become equal to the value of the calculated electric current, and (c) judges whether the set imaging sequence is practicable or not based on the calculated value of voltage.