4D Flow MRI Hepatic Vasculature Imaging with 2D Excitation
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Solution Overview
Problem
Current 4D Flow MRI techniques for hepatic vasculatures have limitations such as extended scan time due to a large field of view with low resolution, and the use of traditional 90-180 cross section navigators can interfere with the imaging signal, making them ineffective for portal venous flow measurements in the liver.
Innovation Solution
The implementation of two-dimensional MRI excitation with parallel transmit technology and a 'zoom' function to reduce the field of view, allowing selective excitation of the portal venous system, thereby minimizing measurement data and improving resolution and scan efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional 4D Flow MRI uses a large field of view to cover the entire hepatic region, then the coverage area is improved, but the image resolution deteriorates and scan time is extended
Solution Approach 1:
The patent divides the imaging task into two segments: first acquiring a low-resolution overview image of the entire hepatic region to identify the portal venous system location, then acquiring a high-resolution 4D Flow image only of the identified portal venous system region. This segmentation allows the system to maintain both broad coverage and high resolution by processing different regions with different resolution requirements.
Solution Approach 2:
The patent introduces a temporal dimension by performing two sequential imaging acquisitions: an initial anatomical localization scan followed by a targeted 4D Flow velocity measurement scan. This time-based dimensionality change allows the system to first identify where to image, then image only that specific region with high resolution, resolving the contradiction between coverage area and image resolution.
2Area of stationary object
If traditional 4D Flow MRI uses a large field of view, then the coverage area is improved, but the scan time is extended
Solution Approach 1:
The patent segments the imaging process into two phases: a quick anatomical localization phase that rapidly identifies the portal venous system, followed by a focused 4D Flow acquisition phase that measures velocity only in the identified region. This segmentation reduces total scan time by avoiding unnecessary high-resolution velocity measurements in extraneous anatomical regions while still providing comprehensive coverage through the initial localization scan.
3Measurement precision
If traditional 90-180 cross section navigator is used for motion correction, then the navigation accuracy is improved, but the imaging signal is interfered with
Solution Approach 1:
The patent extracts the motion correction function from the main imaging sequence by using a separate, dedicated navigator echo acquisition. The navigator echo is acquired independently before the main 4D Flow imaging sequence, allowing motion information to be collected without the RF pulses and gradients of the main sequence interfering with or contaminating the velocity measurement signal.
Solution Approach 2:
The patent introduces a navigator echo as an intermediary mechanism that mediates between the need for motion correction and the need to preserve imaging signal integrity. The navigator echo serves as a separate communication channel for motion information, allowing the main imaging sequence to proceed without being disrupted by navigator-related RF pulses or gradient 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 results in higher image resolution and shorter acquisition times, while avoiding interference from extraneous anatomy and navigator pulses, enhancing the effectiveness of 4D Flow MRI for hepatic vasculature imaging.
Implementation Method 1
Time-resolved three-directional three-dimensional (3D) phase-contrast MRI, often referred to as '4D Flow MRI' or simply '4D Flow,' is a powerful tool for the noninvasive measurement of blood flow in the cardiovascular system
Data Source
AI summary
A computer-implemented method of visualizing blood flow through a patient using magnetic resonance imaging (MRI) includes receiving an image of the portal venous system of the patient's liver at a full field of view. A reduced field of view is defined which encompasses the portal venous system of the patient's liver and excludes extraneous anatomy in the full field of view. A navigator area is defined in the full field of view and outside of the reduced field of view. Transmit channels are used to selectively excite the reduced field of view and the navigator area throughout a cardiac cycle of the patient. Measurement data is acquired in response to the selective excitation. The acquired data is used to generate time-resolved 3D datasets. Additionally, a 3D visualization of blood flow though the portal venous system is generated based on the time-resolved 3D datasets.