High-Field MRI Amyloid Plaque Imaging via Respiratory Gating
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Solution Overview
Problem
Current MRI methods are inefficient in visualizing amyloid plaques in vivo without contrast agents, particularly in Alzheimer's disease, due to low spatial resolution and long scan times, which are not suitable for in vivo imaging.
Innovation Solution
A high-resolution MRI method using respiratory and cardiac triggering, combined with a double spin-echo pulse sequence and zoom imaging, to acquire images of amyloid plaques in the brain without contrast agents, employing a high-field strength magnetic resonance imaging system and physiological monitoring for precise respiratory gating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI methods are used to image amyloid plaques without contrast agents, then the imaging can be performed non-invasively, but the spatial resolution is insufficient to visualize individual plaques
Solution Approach 1:
The patent employs a high-field strength MRI system (9.4 Tesla) to achieve the spatial resolution necessary for visualizing individual amyloid plaques. The high magnetic field strength increases signal-to-noise ratio and enables resolution of structures as small as 35 μm, directly resolving the spatial resolution limitation of conventional MRI methods
2Measurement precision
If high-resolution imaging parameters are used to visualize individual amyloid plaques, then spatial resolution is improved, but scan time becomes excessively long for in vivo imaging
Solution Approach 1:
The patent implements respiratory gating where image acquisition is synchronized to specific phases of the respiratory cycle. This periodic action allows scanning to proceed in repeated cycles, capturing data at optimal moments while maintaining high resolution, thereby reducing the effective scan time compared to continuous high-resolution scanning
Solution Approach 2:
The patent applies preparatory pulse sequences before each imaging pulse sequence to create uniform view-to-view longitudinal magnetization. This preliminary action ensures consistent signal intensity across respiratory cycles, eliminating the need for repeated scans to achieve uniformity and reducing total scan time
3Measurement precision
If respiratory gating is applied to reduce motion artifacts, then image quality is improved, but scan time increases due to triggering delays
Solution Approach 1:
The patent applies a preparatory pulse sequence before each imaging pulse sequence to pre-establish uniform longitudinal magnetization. This preliminary action compensates for variations introduced by respiratory triggering, ensuring consistent signal intensity without requiring extended scan times for correction
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
Enables the visualization of individual amyloid plaques as small as 35 μm in vivo without contrast agents, allowing for non-invasive longitudinal studies of plaque biology and potential therapeutic interventions, with reduced scan times and improved signal-to-noise ratio.
Implementation Method 1
the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 2
If the substance, or tissue, is subjected to a magnetic field (excitation field B1) which is in the x-y plane and which is near the Larmor frequency, the net aligned longitudinal magnetization Mz may be rotated, or 'tipped', into the x-y plane to produce a net transverse magnetization Mt. A signal is emitted by the excited spins after the excitation signal B1 is terminated
Implementation Method 3
When utilizing these signals to produce images, magnetic field gradients (Gx, Gy and Gz) are employed. Typically, the region to be imaged is scanned by a sequence of measurement cycles in which these gradients vary according to the particular localization method being used
Implementation Method 4
The spin-warp technique... employs a variable amplitude phase encoding magnetic field gradient pulse prior to the acquisition of NMR spin-echo signals to phase encode spatial information in the direction of this gradient
Implementation Method 5
The readout gradient present during the spin-echo acquisition encodes spatial information in the orthogonal direction
Implementation Method 6
Each pulse sequence in the image acquisition is triggered by a signal from a physiological monitor which detects a specific point in the respiratory cycle
Implementation Method 7
a preparatory pulse sequence precedes each imaging pulse sequence to create uniform view-to-view longitudinal magnetization in the presence of non-uniform view-to-view respiratory trigger times
Data Source
AI summary
Amyloid plaque in the brain of a subject is imaged in an MRI system with or without the use of a contrast agent. Contrast is achieved using a spin-echo pulse sequence that is both respiratory gated and cardiac gated to reduce motion artifacts at the very high image resolution required to see plaque. A preparatory pulse sequence is used to insure longitudinal magnetization remains constant for all the acquired views even if the effective TR changes during the scan due to irregular breathing.