Phased Array MR Coil for TMS-fMRI Signal-to-Noise Ratio
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Solution Overview
Problem
Current combined transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) systems face limitations due to a low signal-to-noise ratio (SNR) and the need for large MR coils, which compromise the accuracy and speed of data acquisition, especially for fast dynamic processes.
Innovation Solution
The system spatially arranges the TMS coil and MR coil to allow TMS stimulation through the MR coil, with a thinner MR coil design and phased array configuration, and electronic components strategically placed to minimize thickness and prevent motion, enabling improved SNR and faster signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If large sized MR coils are used to accommodate both the head and TMS coil, then the coils can accommodate both components, but the signal-to-noise ratio is reduced due to large distance from the head
Solution Approach 1:
The MR coil is divided into multiple independent coil elements arranged in a phased array configuration. Each element can be independently controlled and optimized, allowing the system to achieve high SNR by selectively activating only the necessary coil elements rather than using a single large coil that must maintain distance from the head.
Solution Approach 2:
The patent transitions from a single large 2D coil plane to a 3D phased array configuration with multiple coil elements positioned at different spatial locations. This dimensional change allows simultaneous proximity to multiple regions of the head, achieving high SNR without requiring a single large coil that would be positioned far from the head.
2Measurement precision
If accumulation and statistical processing of the weak MR signal are performed, then the signal can be enhanced, but the measurement time is extended which causes patient discomfort and prevents visualization of fast dynamic processes
Solution Approach 1:
The phased array coil configuration enables rapid data acquisition by simultaneously collecting signals from multiple coil elements. This parallel signal collection approach eliminates the need for lengthy signal accumulation and statistical processing, allowing fast dynamic processes to be captured without prolonged measurement times that would cause patient discomfort.
3Length of moving object
If the MR coil is made thinner to allow TMS coil placement, then the TMS coil can be positioned for effective stimulation, but the coil structure becomes more complex requiring strategic placement of electronic components
Solution Approach 1:
The MR coil is segmented into multiple thin coil elements, each with its own electronic components. This segmentation allows the overall coil structure to remain thin while distributing electronic components across multiple elements, reducing the complexity burden on any single location and enabling effective TMS coil placement.
Solution Approach 2:
The patent moves electronic components from a centralized 2D plane to a distributed 3D arrangement across multiple coil elements. This dimensional redistribution allows the main coil structure to remain thin for effective TMS placement while managing electronic component complexity through spatial distribution rather than dense packing.
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 enhances the signal-to-noise ratio and accelerates data acquisition in TMS/fMRI studies, reducing patient discomfort and enabling visualization of dynamic processes that were previously challenging.
Implementation Method 1
A pulsed magnetic field from the TMS coil 1 induces an electric current in the part of the brain cortex, locally depolarizing its neurons
Implementation Method 2
the head of the patient is subjected to a strong static magnetic field, which causes polarization of the nuclear spins in the body
Implementation Method 3
Electromagnetic radiation with a frequency equal to the Larmor frequency of the nucleus of interest, usually hydrogen nuclei (i.e. protons), further referred to as a MR transmit pulse, excites the selected spin system to a higher energy level, and causes the protons to precess around the direction of the static magnetic field
Data Source
AI summary
A method for transcranial magnetic stimulation (TMS) of a stimulation area of medical interest, combined with functional magnetic resonance imaging (fMRI) for visualization of the response of, for example neurons, is disclosed. An ultra-thin magnetic resonance coil, MR coil, positioned in the immediate vicinity over an area where the response of, for example neurons, is to be detected, and preferably sandwiched between the TMS coil and the area, provides an excellent signal-to-noise ratio. The TMS can be performed directly through the MR coil. A great deal of flexibility in the number of the TMS and MR coils in use and their spatial arrangement is provided. A corresponding system for the TMS/fMRI studies is also provided.