MRI Extended Field-of-View Imaging via Continuous Table Motion
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Solution Overview
Problem
Current MRI systems face challenges in efficiently acquiring images over extended fields-of-view, particularly in magnetic resonance angiography, due to limitations in spatial and temporal resolution, and the need for accelerated imaging techniques that are hindered by coil sensitivity and gradient mapping issues.
Innovation Solution
The method interlaces multi-station and continuously moving table techniques, allowing for accurate bolus tracking and efficient application of accelerated imaging by determining sensitivity profiles at predetermined stations and alternating between stationary and intermediate scans with specific phase encoding during table movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multi-station imaging technique is used to image extended FOV, then coverage area is improved, but acquisition time increases and temporal resolution deteriorates
Solution Approach 1:
The patent implements continuously moving table imaging where the patient table moves continuously through the imaging zone during data acquisition, eliminating idle table movement time between stations. This continuous operation maintains useful imaging action throughout the extended FOV coverage, resolving the contradiction between coverage area and acquisition time by ensuring no time is wasted on table repositioning.
Solution Approach 2:
The system transitions from static multi-station imaging to dynamic continuously moving table imaging. The table velocity is controlled and synchronized with the imaging pulse sequence, allowing the imaging zone to dynamically track the moving patient. This dynamic approach enables extended FOV coverage without the time penalties of stationary multi-station techniques.
2Loss of time
If accelerated imaging techniques are applied during table movement, then acquisition time is reduced, but image quality deteriorates due to motion artifacts and gradient mapping issues
Solution Approach 1:
The system performs preliminary calibration scans to determine coil sensitivity profiles and gradient mapping characteristics at different table positions before actual imaging. This preliminary characterization data is stored and used to correct images acquired during continuous table movement, enabling accelerated imaging techniques to be applied without sacrificing image quality. The gradient non-linearity and coil sensitivity variations are pre-measured and compensated.
Solution Approach 2:
The system implements feedback correction where images acquired during continuous table movement are corrected using the pre-determined sensitivity profiles and gradient mapping data. The reconstruction process incorporates feedback from the calibrated system characteristics to compensate for motion-related artifacts and gradient non-linearities, maintaining image quality while enabling accelerated acquisition.
3Manufacturing precision
If stationary scan with accelerated imaging is used at predetermined stations, then spatial resolution is improved, but productivity decreases due to repeated table stopping
Solution Approach 1:
The system eliminates the stop-start pattern of traditional multi-station imaging by implementing continuous table movement throughout the examination. The useful imaging action continues uninterrupted as the table moves through multiple imaging zones, maintaining spatial resolution through proper gradient encoding while dramatically improving patient throughput by eliminating repeated table stopping and repositioning.
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 significantly reduces acquisition time, improves spatial resolution, and maintains accurate tracking of contrast agent bolus, enhancing image quality and patient throughput by optimizing data acquisition across extended fields-of-view.
Implementation Method 1
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 2
the individual magnetic moments of the excited nuclei in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 3
spatial information is encoded in one direction by applying a phase encoding gradient (Gy) along that direction
Implementation Method 4
a spin-echo signal is acquired in the presence of a readout magnetic field gradient (Gx) in a direction orthogonal to the phase encoding direction. The readout gradient present during the spin-echo acquisition encodes spatial information in the orthogonal direction.
Data Source
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AI summary
The present invention provides an MRI system for imaging of a subject over extended field-of-view (FOV) that employs both accelerated data acquisition, which is employed while the subject is stationary, and traditional data acquisition, which is employed while the subject is moved through the MRI system. This approach provides improved spatial resolution and time efficiency compared to traditional extended FOV imaging techniques.