MRI RF Coil Noise Correlation Reduction via Opposite Current Flow
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Solution Overview
Problem
Multichannel array coils in MRI systems face challenges in achieving high sensitivity and wide sensitivity regions while minimizing noise, as noise correlation between subcoils can degrade the signal-to-noise ratio (SNR) and signal strength due to magnetic coupling and thermal noise.
Innovation Solution
The RF coil is designed with multiple subcoils where electromagnetic coupling is adjusted to reduce noise correlation by allowing current to flow in opposite directions between subcoils, using circuit components like capacitors and inductors to create a figure-of-eight current path, thereby intensifying electric fields between subcoils and reducing noise correlation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple subcoils are arranged in a multichannel array coil to expand the sensitivity region, then the sensitivity region is expanded, but noise correlation increases due to magnetic coupling between adjacent subcoils
Solution Approach 1:
The patent converts the harmful magnetic coupling between adjacent subcoils into a beneficial effect by intentionally designing the coupling to create opposite-direction current flow. This figure-of-eight current pattern reduces noise correlation while maintaining the expanded sensitivity region provided by multiple subcoils.
Solution Approach 2:
The patent adjusts electromagnetic coupling parameters between subcoils to optimize performance. By controlling the degree and nature of magnetic coupling, the system achieves reduced noise correlation while preserving the expanded sensitivity region benefits of multichannel configuration.
2Power
If the number of channels in a multichannel coil is increased to improve signal strength, then signal strength is improved, but noise increases simultaneously due to thermal noise and noise correlation
Solution Approach 1:
The patent transforms the typically harmful thermal noise and noise correlation into a beneficial configuration. By inducing opposite-direction current flow through controlled magnetic coupling, the system reduces noise correlation effects, allowing multiple channels to contribute constructively to signal strength without proportional noise increase.
Solution Approach 2:
The patent introduces asymmetry in the current flow pattern between adjacent subcoils, creating a figure-of-eight pattern where currents flow in opposite directions. This asymmetric configuration reduces noise correlation and allows signal strength to scale with the number of channels while noise increases more slowly.
3Object-affected harmful factors
If adjacent subcoils are placed with overlapping coil loops to minimize magnetic coupling, then magnetic coupling is reduced, but device complexity and adjustment difficulty increase
Solution Approach 1:
Instead of trying to eliminate magnetic coupling through complex overlapping arrangements, the patent inverts the approach by intentionally utilizing magnetic coupling to create the desired opposite-direction current flow. This simplifies the coil arrangement while achieving the goal of reduced noise correlation.
Solution Approach 2:
The patent converts the harmful effect of magnetic coupling into a beneficial mechanism for reducing noise correlation. By allowing and controlling magnetic coupling between adjacent subcoils, the system achieves simplified geometry with reduced noise correlation, avoiding the need for complex overlapping arrangements.
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 configuration effectively reduces noise correlation, enhances SNR, and maintains high sensitivity across a wide region, resulting in improved image quality without complex configurations.
Implementation Method 1
adjacent subcoils are electromagnetically coupled, allowing for current to flow in the other subcoil in the form of sub-current
Implementation Method 2
an electric field generated in a subject by current passing through the subcoils may operate to reduce mutual noise between the subcoils
Data Source
AI summary
A multichannel array coil of an MRI apparatus achieves both a wide sensitivity and low noise. An RF coil (array coil) is provided with a plurality of subcoils. Each of those subcoils is adjusted to be receivable of nuclear magnetic resonance signals, and also adjusted so that a part of current (first current) passing through one subcoil upon receipt of the signals flows into the other subcoil in the form of sub-current. A flowing direction of the first current is opposite to the flowing direction of the sub-current, and an electric field generated by the first current within a subject and an electric field generated by the first sub-current within the subject intensify each other in the space between a first loop coil unit and a second loop coil unit. Accordingly, noise correlation that is determined by an inner product of the electric fields is reduced, thereby achieving low noise.