Pseudo-Continuous MRI Acquisition for Long-Time-Constant Eddy Currents
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Solution Overview
Problem
Existing MRI systems face inefficiencies in measuring eddy currents with long time constants due to prolonged gradient durations, leading to inefficient data collection and vulnerability to magnetic drift, which affects image quality.
Innovation Solution
A method and system utilizing a train of gradient echo sequences to simultaneously generate and measure eddy currents during a calibration scan, enabling efficient and accurate estimation of eddy currents as a function of time, using bipolar eddy current excitation gradients to distinguish from B0 drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a prolonged excitation gradient pulse is used to measure eddy currents with long time constants, then the measurement can capture the full duration of the eddy currents, but data collection efficiency decreases and the system becomes vulnerable to magnet drift effects
Solution Approach 1:
The patent applies periodic action by using a train of gradient echo sequences with repeated excitation gradient pulses instead of a single prolonged pulse. The sequence is repeated multiple times (e.g., 8-16 repetitions) to collect sufficient data for measuring long time constant eddy currents while maintaining high data collection efficiency and minimizing vulnerability to magnet drift through the periodic nature of the acquisition
Solution Approach 2:
The patent implements continuity of useful action by ensuring that data acquisition continues throughout the entire duration of the eddy current decay using a continuous train of gradient echo sequences. This allows the system to continuously measure the eddy current signal as it decays over the long time constant period without idle intervals, maximizing productivity while maintaining measurement precision
2Measurement precision
If a prolonged excitation gradient pulse is used to measure eddy currents with long time constants, then the measurement can capture the full duration of the eddy currents, but the system becomes vulnerable to magnet drift effects such as metal movement or B0 drift
Solution Approach 1:
The patent applies periodic action by using a train of gradient echo sequences with repeated excitation gradient pulses instead of a single prolonged pulse. The sequence is repeated multiple times (e.g., 8-16 repetitions) to collect sufficient data for measuring long time constant eddy currents while maintaining high data collection efficiency and minimizing vulnerability to magnet drift through the periodic nature of the acquisition
Solution Approach 2:
The patent applies preliminary action by performing a preliminary calibration scan to measure the eddy current time constant before the actual imaging procedure. This preliminary measurement allows the system to characterize the eddy current behavior and adjust subsequent imaging parameters accordingly, ensuring accurate compensation for eddy current effects during the actual scan while minimizing the impact of magnet drift
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 efficient and less sensitive measurement of eddy currents with long time constants, improving the accuracy of calibration and enhancing image quality in MRI scans.
Implementation Method 1
In MRI, eddy currents are un-wanted electrical currents generated in metallic structures within the MRI system when the gradient field changes
Implementation Method 2
eddy currents are un-wanted electrical currents generated in metallic structures within the MRI system when the gradient field changes
Implementation Method 3
When utilizing these signals to produce images, magnetic field gradients (Gx, Gy, and Gz) are employed
Implementation Method 4
utilizing a train of gradient echo sequences to simultaneously generate and measure the eddy currents during the calibration scan, wherein both eddy current generation and measurement are completed within each gradient echo sequence
Data Source
AI summary
A system and a method for measuring eddy currents with long time constants includes initiating, via a processor, a calibration scan of a phantom utilizing a magnetic resonance imaging (MRI) scanner. The system and the method also include utilizing, via the processor, a train of gradient echo sequences to simultaneously generate and measure the eddy currents during the calibration scan. Both eddy current generation and measurement are completed within each gradient echo sequence of the train of gradient echo sequences. The system and the method further include acquiring, via the processor, k-space data from the train of gradient echo sequences. The system and the method still further include converting, via the processor, the k-space data to eddy current gradient fields. The system and the method even further include estimating, via the processor, the eddy currents as a function of time based on the eddy current gradient fields.