MRI Eddy Field Correction via Triggered Time-Point Data
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Solution Overview
Problem
Existing MRI technologies face challenges in accurately suppressing the deterioration in image quality caused by eddy magnetic fields, especially when imaging is performed in synchronization with external trigger signals like ECG signals.
Innovation Solution
The MRI apparatus employs processing circuitry to continuously generate time-point data, estimate eddy magnetic fields at a second time point using series of gradient magnetic fields and time differences, and correct the frequency or phase of RF transmitting and receiving signals to mitigate the effects of eddy magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a variation in magnetic resonance frequency is calculated by accumulating eddy magnetic fields resulting from a series of gradient magnetic fields, then the suppression of eddy magnetic field effects is improved, but the accuracy of cumulative value determination deteriorates when imaging is performed in synchronization with external trigger signals
Solution Approach 1:
The system pre-calculates and stores eddy magnetic field values at multiple time points before actual imaging. When an external trigger signal is received, the system can quickly retrieve and apply the appropriate pre-calculated eddy magnetic field values without needing to accumulate them in real-time, thus maintaining both accuracy and synchronization capability
Solution Approach 2:
The system dynamically adjusts the selection of eddy magnetic field values based on the timing of external trigger signals. Instead of using a fixed accumulation method, the system flexibly selects from pre-calculated values at different time points, allowing accurate compensation even when imaging timing varies due to external triggers
2Productivity
If gradient magnetic fields are applied to generate MR signals, then image acquisition is enabled, but eddy currents flow through metal components causing deterioration in image quality
Solution Approach 1:
The system converts the harmful eddy magnetic field effects into useful information by calculating and storing eddy magnetic field values at multiple time points. These calculated values are then used to correct the MR signals, transforming the previously harmful eddy current effects into a beneficial correction mechanism that improves image quality
Solution Approach 2:
The system implements a feedback mechanism where eddy magnetic field values are calculated based on applied gradient magnetic fields, stored for later use, and then applied to correct subsequent MR signals. This closed-loop approach continuously compensates for eddy current effects, allowing gradient fields to be applied for image acquisition while maintaining 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
This approach allows for accurate estimation and suppression of eddy magnetic field effects, even in synchronization with external triggers, thereby improving image quality and reliability in MRI scans.
Implementation Method 1
a gradient coil configured to generate a series of gradient magnetic fields
Implementation Method 2
an eddy current flows through metal, such as a heat shield plate of a static magnetic field coil, in the vicinity of the gradient coil. An eddy current magnetic field (hereinafter abbreviated as an 'eddy magnetic field') is generated by each eddy current.
Implementation Method 3
estimate a value of the eddy magnetic field at a second time point... by using the series of gradient magnetic fields and respective time differences
Data Source
AI summary
In one embodiment, an MRI apparatus includes processing circuitry configured to continuously generate time-point data in increments of a predetermined time length; generate a series of gradient magnetic fields based on a predetermined pulse sequence; acquire an external trigger in association with trigger-time-point data corresponding to an acquisition time point of the external trigger; estimate a value of an eddy magnetic field at a second time point by using the gradient magnetic fields and respective time differences between the first time-point data and the second time-point data, wherein the respective time differences change depending on when the external trigger is acquired; calculate a frequency or phase variation of an MR signal at the second time point; and correct a frequency or phase of an RF transmitting signal or the MR signal, by using the calculated frequency variation or the phase variation.