MRI Array Coil Phase Control for Magnetic Coupling
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Solution Overview
Problem
In multi-channel array coils for MRI apparatuses, magnetic coupling between sub-coils leads to signal cancellation and reduced sensitivity, deteriorating image quality.
Innovation Solution
Each sub-coil is connected to a signal processing circuit to maintain a phase difference of less than 90 degrees between its generated rotating magnetic field and the field influenced by adjacent sub-coils, using transmission-reception magnetic coupling prevention circuits to prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If sub-coils are arranged close to each other in a multi-channel array coil, then the sensitivity region becomes wider, but magnetic coupling occurs causing signal cancellation and sensitivity reduction
Solution Approach 1:
A magnetic coupling prevention circuit is introduced as an intermediary component between adjacent sub-coils. This circuit includes a prevention coil wound around a magnetic core positioned between the sub-coils, which actively counteracts the magnetic coupling by generating an opposing magnetic field that cancels the interfering flux from adjacent coils, thereby preventing signal cancellation while maintaining close spacing for wide sensitivity region
Solution Approach 2:
The magnetic coupling prevention circuit is configured to preemptively counteract magnetic coupling effects before they cause signal cancellation. By positioning the prevention coil and magnetic core between adjacent sub-coils and adjusting its parameters (number of turns, core material, positioning), the system creates a preliminary opposing magnetic field that neutralizes the harmful magnetic flux from neighboring coils before it can interfere with the detection signal
2Productivity
If the number of channels in a multi-channel array coil is increased for high-speed imaging, then imaging speed increases, but magnetic coupling between more sub-coils causes greater signal cancellation
Solution Approach 1:
The solution segments the magnetic coupling prevention function into individual prevention circuits for each sub-coil or between adjacent sub-coil groups. Each prevention circuit independently handles the magnetic coupling with its neighboring coils, allowing the system to scale to higher channel counts (32 channels, 128 channels) without cumulative magnetic interference, thereby maintaining both high imaging speed and signal quality
Solution Approach 2:
Magnetic coupling prevention circuits are introduced as intermediary components between adjacent sub-coils in the expanded array. These prevention circuits with magnetic cores and coils actively counteract the magnetic flux from neighboring coils, enabling high channel count configurations to achieve high-speed imaging while preventing signal cancellation through active magnetic field management
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 suppresses signal cancellation and maintains desired sensitivity, even with magnetic coupling, thereby enhancing image quality and sensitivity across the multi-channel array coil.
Implementation Method 1
Irradiation of a radio frequency magnetic field on a subject and detection of a nuclear magnetic resonance signal generated from the subject are performed by an RF coil having a loop part (coil loop) that performs an irradiation and detection
Implementation Method 2
When RF coils having the same resonance characteristics are arranged close to each other, they interfere with each other by a magnetic coupling
Implementation Method 3
each of the sub-coils is connected to a signal processing circuit so that a phase difference between a rotating magnetic field generated by the sub-coil and a rotating magnetic field generated by the influence of a current flowing through a sub-coil of a coupling counterpart is less than 90 degrees in a region of interest
Data Source
AI summary
In a multi-channel array coil used as an RF coil of an MRI apparatus, even when magnetic coupling occurs between the respective sub-coils, it is possible to suppress the influence of a current flowing through the sub-coil of a coupling counterpart to maintain the desired sensitivity and suppress deterioration of image quality. Therefor, even when magnetic coupling occurs between sub-coils constituting the multi-channel array coil used as the RF coil of the MRI apparatus, the sub-coils are connected to a signal processing circuit so that a phase difference between a rotating magnetic field generated by the influence of a current flowing through the sub-coil of the coupling counterpart and a rotating magnetic field generated by the sub-coil is less than 90 degrees.