MRI Coil Array with Varying Element Sizes for Asymmetrical Imaging
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Solution Overview
Problem
Current MRI systems face challenges in reducing scan time for objects with significantly different fields of view along two phase encoding directions, leading to suboptimal performance and noise amplification in parallel acceleration techniques.
Innovation Solution
A modular coil array with varying coil element sizes is used to accommodate asymmetrical field-of-view subjects, where one set of coil elements is optimized for sensitivity along one phase encoding axis and another set for the other, allowing for improved signal-to-noise ratio and noise reduction in two-dimensional parallel imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional coil arrays with uniform element sizes are used, then the system is simple to manufacture and operate, but the signal-to-noise ratio deteriorates when imaging subjects with asymmetrical field-of-view
Solution Approach 1:
The patent applies local quality by varying the dimensions of individual coil elements within the array based on their specific spatial positions and the local field-of-view requirements. Each coil element is sized optimally for its location, creating non-uniform dimensions across the array that match the asymmetrical anatomy being imaged, thereby improving signal-to-noise ratio without sacrificing manufacturability
Solution Approach 2:
The patent implements asymmetry by designing coil elements with different dimensions rather than uniform sizes. The coil array is configured with elements that have varying lengths and widths tailored to the asymmetrical field-of-view of the subject (e.g., lower extremities), allowing optimal signal reception from different anatomical regions while maintaining practical manufacturing through modular construction
2Productivity
If parallel acceleration techniques are applied to reduce scan time, then productivity increases, but noise amplification occurs in asymmetrical imaging applications
Solution Approach 1:
The patent reduces noise amplification during parallel acceleration by optimizing the sensitivity distribution of individual coil elements to match the local signal characteristics. Each coil element's dimensions are tuned to maximize signal reception from its specific region, creating a sensitivity profile that works synergistically with parallel imaging reconstruction algorithms to minimize noise amplification while maintaining accelerated scan speeds
Solution Approach 2:
The patent changes the physical parameters of the coil elements (dimensions, orientations, and positions) to optimize the overall array sensitivity distribution. By adjusting these parameters based on the asymmetrical field-of-view requirements, the system achieves better conditioning of the sensitivity matrix used in parallel imaging reconstruction, thereby reducing noise amplification factors while maintaining high acceleration capabilities
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 enhances image quality and reduces noise amplification, particularly in applications like lower extremities imaging, by optimizing coil element sizes based on the depth of the field-of-view, resulting in improved signal-to-noise ratio and faster scan times.
Implementation Method 1
The MR signals acquired with an MRI system are signal samples of the subject of the examination in Fourier space
Implementation Method 2
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), 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
If the substance, or tissue, is subjected to a magnetic field (excitation field B1) that is in the x-y plane and that is near the Larmor frequency, the net aligned moment, Mz, may be rotated, or 'tipped ', into the x-y plane to produce a net transverse magnetic moment Mt
Data Source
AI summary
The present invention is a coil array for an MRI system that is designed to improve 2D accelerated imaging of an object having significantly different fields of view in two phase-encoding directions. This is achieved by having a first set of coil elements whose sizes are tuned to optimize acceleration along a first phase-encoding direction and a second set of coil elements whose sizes are tuned to optimize acceleration along a second-phase encoding direction. Images acquired in accordance with the present invention exhibit improved signal to noise ratio at a given acceleration factor when compared to images acquired using a traditional MR coil array.