MRI Tx Rx Coil Array Using Mutual Inductance and PIN Diodes
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Solution Overview
Problem
Conventional MRI systems face inefficiencies in RF energy transmission, leading to higher specific absorption rates (SAR) and energy loss, as they often use whole body coils that apply RF energy to the entire body, including areas not being scanned, and existing local Tx coil techniques require dedicated wiring or are less efficient.
Innovation Solution
A single-layer coil array that functions as both a transmit (Tx) and receive (Rx) coil, utilizing PIN diodes and mutual inductance to resonate at different frequencies in Tx and Rx modes, allowing for efficient energy transfer and reduced energy loss without the need for additional wiring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If whole body coils are used to transmit RF energy, then RF energy can be transmitted to the entire body, but specific absorption rate (SAR) increases and energy is wasted on areas not being scanned
Solution Approach 1:
The patent divides the coil array into multiple independently controllable coil elements that can be selectively activated. Instead of transmitting RF energy through a whole body coil, only the specific coil elements corresponding to the region of interest are activated, segmenting the energy transmission to avoid unnecessary exposure and energy waste in other body areas.
Solution Approach 2:
The patent implements local quality by enabling different regions of the coil array to have different operational states. Specific coil elements are tuned and activated only in the regions where imaging is required, while other regions remain inactive or are tuned to different frequencies, thereby concentrating RF energy locally where needed and reducing overall SAR and energy loss.
2Loss of energy
If dedicated wiring is used for local Tx coils, then efficient energy transmission can be achieved, but device complexity increases
Solution Approach 1:
The patent makes the coil array universally functional by enabling each coil element to serve both as a transmit element and a receive element. The same coil elements that transmit RF energy can also detect the MR signals, eliminating the need for separate dedicated wiring for transmit coils and simplifying the overall system architecture while maintaining efficiency.
Solution Approach 2:
The patent merges the transmit and receive functions into a single integrated coil array system. By combining what would traditionally be separate transmit coil wiring and receive coil wiring into a shared coil element structure, the patent reduces device complexity while achieving efficient energy transmission and signal reception.
3Device complexity
If the same coil array is used for both transmit and receive functions, then device complexity is reduced, but frequency tuning between Tx and Rx modes becomes challenging
Solution Approach 1:
The patent implements dynamic frequency tuning capability where the resonant frequency of each coil element can be adjusted in real-time. By using variable capacitors or tunable matching circuits, each coil element can be dynamically retuned between the transmit frequency and the receive frequency, allowing the same physical coil array to adapt to different operational modes without requiring separate fixed-frequency coils.
Solution Approach 2:
The patent changes the electrical parameters (specifically capacitance or impedance) of the coil elements to achieve frequency transformation. By modifying the capacitive loading or matching network parameters of each coil element, the resonant frequency is shifted between the Tx and Rx operating frequencies, enabling the same hardware to support both functions with different frequency settings.
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 enables more targeted RF energy application, reducing SAR and energy loss, while maintaining efficient energy transfer and imaging capabilities, and is simpler to implement compared to existing techniques.
Implementation Method 1
A first coil element of the at least four RF coil elements is inductively coupled to a second coil element of the at least four RF coil elements
Implementation Method 2
A first switch circuit of the at least four RF coil elements is configured to transform an impedance of the at least four RF coil elements
Data Source
AI summary
An example magnetic resonance imaging (MRI) radio frequency (RF) coil array comprises: at least one row of RF coil elements arranged radially around a cylindrical axis, wherein each row comprises: at least four RF coil elements circumferentially enclosing the cylindrical axis, wherein each RF coil element of that row is configured to operate in a Tx mode and in a Rx mode, wherein, in the Rx mode, each RF coil element of that row is tuned to a working frequency of the MRI RF coil array, and wherein, in the Tx mode, each RF coil element of that row is tuned to an additional frequency that is different than the working frequency, wherein the additional frequency is such that, a mode frequency of a selected mode resulting from coupling among the RF coil elements of that row is at the working frequency.