Silent Multi-Gradient Echo MRI Pulse Sequence
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Solution Overview
Problem
Conventional MRI systems generate significant acoustic noise due to large changes in magnetic field gradients, which can interfere with medical imaging procedures and patient comfort, especially during fMRI scans where brain activity and cognitive functions are being evaluated.
Innovation Solution
The implementation of a silent, multi-gradient echo pulse sequence that uses a closed k-space trajectory with iterative updates of magnetic field gradients and RF excitation pulses, allowing for self-refocusing of signals and reducing the need for large current changes in the MRI coils, thereby minimizing acoustic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large changes in magnetic field gradients are used for conventional MRI imaging, then imaging speed and coverage are improved, but acoustic noise increases significantly
Solution Approach 1:
The k-space is divided into multiple radial spokes that are acquired sequentially. Each spoke represents a segment of the total k-space data, allowing the imaging process to be broken down into smaller, quieter acquisition steps while maintaining overall imaging efficiency.
Solution Approach 2:
The patent employs periodic RF excitation pulses combined with periodic gradient updates to acquire data along multiple radial spokes. This periodic action allows for systematic coverage of k-space while maintaining gradient stability between updates, reducing noise-generating gradient switches.
2Measurement precision
If multiple gradient echoes are acquired for T2* mapping, then measurement precision is improved, but scan time increases
Solution Approach 1:
The patent acquires multiple gradient echoes continuously following each RF excitation pulse without requiring separate excitations for each echo. This continuous acquisition of multiple echoes within a single TR period improves T2* mapping precision while minimizing the increase in scan time.
Solution Approach 2:
The gradient echoes are prepared and acquired in advance within a single TR period, allowing T2* data to be collected efficiently before the next RF excitation. This preliminary acquisition of multiple echoes prevents time loss that would occur with sequential single-echo acquisitions.
3Measurement precision
If gradient updates are performed between RF excitations, then spatial encoding is improved, but acoustic noise increases
Solution Approach 1:
The patent dynamically adjusts the gradient amplitude and direction for each radial spoke based on the current acquisition phase. This dynamic gradient control maintains accurate spatial encoding for each spoke while minimizing the magnitude of gradient changes, thereby reducing acoustic noise from gradient coil switching.
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 significantly reduces acoustic noise during MRI operations, enhancing patient comfort and potentially improving the accuracy of diagnostic procedures by minimizing external noise interference.
Implementation Method 1
Due to a relationship between the angular speed of the precession of a gyromagnetic material and the strength of the magnetic field, a magnetic field gradient may generate a spatial distribution of precession speeds.
Implementation Method 2
With the removal of the RF magnetic field pulse, the gyromagnetic nuclei may return to the basal state in a relaxation trajectory. During the relaxation, the gyromagnetic nuclei may emit RF signals that can be measured by an acquisition coil.
Data Source
AI summary
Methods and systems for production of silent, multi-gradient-echo, magnetic resonance images are provided. The methods employ iterative application of small updates to the magnetic field gradient followed by a short, non-selective radiofrequency pulse excitation and for free induction decay data acquisition. The magnetic field gradient updates allow for silent, self-refocusing pulse sequence. Subsequent applications of the magnetic field gradients allow for multiple echo data acquisitions, which may allow fast, silent production of T2*-weighted images.