4D Flow MRI Slab Acquisition for Saturation Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current MRI systems for 4D imaging of fluid flow within a volume, such as blood in vessels, face challenges with low signal-to-noise ratio and motion artifacts due to whole-volume acquisition, often requiring contrast agents, which can be problematic for certain procedures and patients, especially those with renal insufficiencies.
Innovation Solution
The method involves acquiring multiple slabs of images with each slab aligned to maintain magnetically unsaturated portions of the fluid during acquisition, allowing for continuous supply of unsaturated fluid, thereby reducing saturation and enhancing signal quality without the need for contrast agents. The MRI system uses a magnet assembly and controller to direct the acquisition and merging of these slabs to form a 4D image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If whole-volume acquisition is used for 4D imaging, then complete volumetric coverage is achieved, but signal-to-noise ratio deteriorates due to nuclear saturation
Solution Approach 1:
The patent divides the volume into multiple slabs that are acquired sequentially rather than imaging the entire volume at once. Each slab is imaged separately with its own set of RF pulses, preventing nuclear saturation across the whole volume while maintaining complete volumetric coverage through combination of individual slab images.
2Ease of operation
If free-breathing acquisition is used, then patient comfort is improved, but motion artifacts increase
Solution Approach 1:
By segmenting the volume into multiple slabs and acquiring them sequentially during free breathing, the patent reduces the temporal duration each slab is imaged, minimizing motion artifacts within each slab while maintaining patient comfort through breath-free acquisition protocol.
Solution Approach 2:
The patent employs navigator echoes to detect diaphragm position and adjusts the acquisition timing and slab positioning based on respiratory phase, allowing free-breathing acquisition while compensating for motion to maintain image quality.
3Measurement precision
If contrast agents are used to enhance signal, then signal-to-noise ratio improves, but patient safety deteriorates due to renal insufficiency risks
Solution Approach 1:
The patent uses the patient's own unsaturated nuclear magnetization as the signal source by implementing a slab-cycling acquisition sequence that continuously refreshes the magnetization in each slab. This self-service approach eliminates the need for external contrast agents while maintaining adequate signal-to-noise ratio through optimized pulse sequences and timing.
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 improves the signal-to-noise ratio and reduces motion artifacts, enabling accurate 4D flow imaging without the use of contrast agents, making it suitable for patients with renal issues and other procedures where contrast agents are undesirable.
Implementation Method 1
Magnetic resonance imaging ('MRI') is a widely accepted and commercially available technique for obtaining digitized visual images representing the internal structure of objects having substantial populations of atomic nuclei that are susceptible to nuclear magnetic resonance ('NMR')
Implementation Method 2
Many MRI systems use superconductive magnets to impose a strong main magnetic field on the nuclei in the object to be imaged. The nuclei are excited by a radio frequency ('RF') signal at characteristics NMR (Larmor) frequencies
Implementation Method 3
By spatially disturbing localized magnetic fields surrounding the object and analyzing the resulting RF responses from the nuclei as the excited protons relax back to their lower energy normal state, a map or image of these nuclei responses as a function of their spatial location is generated
Data Source
AI summary
A method for phase-contrast imaging a fluid within a volume of an imaged subject is provided. The method includes acquiring a plurality of slabs, each slab imaging the fluid flowing within a portion of the volume; and volume merging the plurality of slabs to form an image of the volume. Each slab of the plurality is aligned with respect to the volume such that each slab of the plurality is continuously supplied with a plurality of magnetically unsaturated portions of the fluid during acquisition.