MRI Spin-Lock Pulse Sequences for Neuroelectric Oscillation Imaging
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Solution Overview
Problem
Current neuroimaging techniques, such as fMRI, EEG, and MEG, fail to accurately localize neuronal activity with high spatial and temporal resolution due to limitations in spatial and temporal resolution, and the inability to simultaneously achieve both.
Innovation Solution
Development of MRI protocols and pulse sequences that allow for the non-invasive imaging of neuroelectric activity by transmitting a specific pulse sequence to a subject, including a radiofrequency excitation pulse followed by a spin-lock pulse and a second RF excitation pulse, to obtain MR image signals that accurately localize neuronal activity with high spatial and temporal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fMRI based on BOLD contrast is used, then spatial resolution is improved, but temporal resolution deteriorates
Solution Approach 1:
The patent uses spin-lock pulses as an intermediary mechanism to detect neuronal magnetic field oscillations. The spin-lock pulse locks the magnetization vector along a specific axis, making the MRI signal sensitive to oscillating magnetic fields generated by neuronal activity. This intermediary approach allows direct detection of neural oscillations while maintaining the spatial resolution advantages of MRI.
2Loss of time
If EEG or MEG is used, then temporal resolution is improved, but spatial resolution deteriorates
Solution Approach 1:
The patent merges the temporal sensitivity of oscillation detection with the spatial localization capability of MRI. By combining the spin-lock pulse technique (which detects oscillations) with MRI's spatial encoding gradients, the method achieves both high temporal and spatial resolution simultaneously, overcoming the limitations of separate EEG/MEG and fMRI approaches.
3Reliability
If spin-lock pulse is applied continuously, then sensitivity to neuroelectric oscillations is improved, but signal-to-noise ratio deteriorates due to Mx and My components
Solution Approach 1:
The patent extracts only the Mz signal component by applying spoiler gradients before the second RF pulse. The spoiler gradients dephase and eliminate the Mx and My signal components, leaving only the Mz component that contains information about neuroelectric oscillations. This extraction improves the signal-to-noise ratio by removing unwanted signal components.
4Loss of information
If multiple signal components (Mx, My, Mz) are obtained, then comprehensive neuronal activity information is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent converts the potentially harmful effect of Mx and My signal components (which reduce signal-to-noise ratio) into a benefit by using spoiler gradients to selectively eliminate them. The harmful noise from Mx and My components is transformed into useful information by their complete removal, leaving only the beneficial Mz component that carries neuronal oscillation information.
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 proposed solution enables the generation of neuroactivation maps with high temporal and spatial accuracy, directly imaging neuroelectric activity and overcoming the limitations of existing techniques by isolating the Mz signal component and eliminating Mx and My components, thereby enhancing signal-to-noise ratio and sensitivity.
Implementation Method 1
followed by a spin-lock pulse applied along a second axis and having a frequency
Implementation Method 2
electronically transmitting a pulse sequence to a subject, wherein the pulse sequence comprises a first radiofrequency (RF) excitation pulse
Implementation Method 3
then spoiler gradients are applied to dephase and eliminate Mx and My signal components before the second RF excitation pulse is transmitted
Data Source
AI summary
In vivo methods of non-invasively imaging neuro-electro-magnetic oscillations (NEMO) are carried out by electronically transmitting a pulse sequence to a subject. The pulse sequence has a first excitation pulse, typically applied along an x-axis, followed by a spin-lock pulse applied along a different axis, typically a y-axis, and having a defined frequency, followed by a second RF excitation pulse. Then MR image signal of neuroelectric activity associated with evoked and/or spontaneous neuroelectric oscillations is obtained after the second RF excitation pulse and a neuroactivity (i.e., brain activation) map based on the obtained MR image signal is generated, the neuroactivity map having high temporal and spatial accuracy of the neuroelectric activity.