Dual-Module VSASL for Background Tissue Signal Suppression
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Solution Overview
Problem
Current velocity selective arterial spin labeling (VSASL) methods suffer from sub-optimal signal-to-noise ratio (SNR) and temporal SNR due to noise and artefacts from motion, eddy currents, and diffusion attenuation, necessitating additional background suppression (BS) pulses that reduce ASL signal and deposit RF energy, limiting their use at ultra-high fields.
Innovation Solution
A dual-module (dm-VSASL) approach that inverts stationary spins using VS pulses, switches label/control conditions, and adjusts timing to suppress background tissue signals without additional RF pulses, balancing gradient configurations to improve SNR and reduce artefacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional background suppression pulses are used to reduce noise and artifacts, then temporal SNR is improved, but RF energy exposure increases and ASL signal is reduced
Solution Approach 1:
The patent combines the background suppression function with the arterial spin labeling function into a single integrated pulse sequence. The VSASL labeling pulses are designed to simultaneously suppress background tissue signals while labeling arterial blood, eliminating the need for separate BS pulses. This merging approach maintains temporal SNR improvement while reducing total RF energy exposure.
Solution Approach 2:
The labeling pulses in the VSASL sequence are designed to perform multiple functions: they label arterial blood for perfusion imaging while simultaneously suppressing background tissue signals. This multi-functionality allows a single pulse to achieve both ASL signal generation and background suppression, reducing the need for additional dedicated BS pulses.
2Measurement precision
If additional background suppression pulses are used to reduce noise and artifacts, then temporal SNR is improved, but ASL signal is reduced
Solution Approach 1:
The patent merges the background suppression capability into the VSASL labeling pulses themselves. By designing the labeling sequence to inherently suppress background signals through velocity-selective mechanisms, the system achieves temporal SNR improvement without requiring additional BS pulses that would further reduce the already limited ASL signal.
3Area of stationary object
If conventional MRI techniques are used to image body parts, then spatial selection is achieved, but background tissue signals interfere with perfusion imaging
Solution Approach 1:
The patent applies velocity-selective labeling to create local differentiation between moving arterial blood and stationary background tissues. By making the labeling effect dependent on tissue velocity rather than just spatial location, the system achieves selective labeling of perfusing blood while suppressing stationary tissue signals, improving perfusion imaging specificity.
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
Enhances SNR and reduces RF energy exposure, improving image quality and patient safety by effectively suppressing background tissues, particularly at ultra-high fields, while maintaining stable arterial spin labeling.
Implementation Method 1
a radio frequency (RF) magnetic field to manipulate the spins
Implementation Method 2
a static magnetic field along a Z-direction to polarize the magnetic spins
Implementation Method 3
gradient fields along mutually orthogonal x, y, or Z directions to spatially select a body part for imaging
Data Source
AI summary
A method of operating a magnetic resonance imaging (MRI) system includes configuring the system to receive an input indicative of time intervals to be used for imaging a target object; controlling the one or more RF coils to apply a first order of modules including at least a first control module at a first time point and a first labeling module at a second time point to a target object, controlling the one or more RF coils to operate a second order of modules including at least a second labeling module at a third time point and a second control module at a fourth time point to the target object, wherein all the four modules invert the magnetization of the target object to suppress the MRI signal.