Wirelessly powered magnetic resonance imaging signal amplification system
Inventors
Qian, Chunqi • Murphy-Boesch, Joe • Koretsky, Alan • Dodd, Stephen John
Assignees
National Institutes of Health NIH • US Department of Health and Human Services
Publication Number
US-9864026-B2
Publication Date
2018-01-09
Expiration Date
2032-03-29
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Abstract
An implantable parametric circuit enables local signal amplification and wireless transmission of RF signals in connection with magnetic resonance imaging systems. The parametric circuit detects RF signal detected during magnetic resonance imaging procedure, amplifies the detected RF signal, and transmits the amplified RF signal in a wireless manner to an external pick-up coil. The parametric amplifier is also configured to use another RF signal generated by an external source as the primary power source. As a result, implanted or catheter coils could be used as a wireless signal transducer without the need for a battery or a power connection.
Core Innovation
The invention provides a wirelessly powered magnetic resonance imaging (MRI) signal amplification system comprising an implantable parametric circuit. This circuit locally amplifies and wirelessly transmits radio frequency (RF) signals detected during an MRI procedure to an external pick-up coil. The system uses another RF signal generated externally as the primary power source, enabling implanted or catheter coils to function as wireless signal transducers without requiring a battery or power connection.
The problem addressed is the heating risk caused by long conductive cables connected to interventional devices in MRI settings. Traditional setups use coaxial cables connecting RF coils in catheters or similar devices to MRI scanners, which can induce RF heating in surrounding tissue due to coupling of the RF field with the cables. Wireless transmission methods relying on passive inductive coupling have sensitivity limitations, and using low noise preamplifiers has been impractical due to the need for local DC power sources in implanted or catheter devices.
This invention overcomes these limitations by enabling wireless amplification of MRI RF signals using a parametric amplifier powered by an externally applied high-frequency RF pumping signal rather than local DC power. The pre-amplification circuit includes at least one resonator tuned to resonate at different frequencies corresponding to the MRI signal, the pumping source signal, and the amplified output signal. A varactor is used for frequency mixing to produce an amplified RF output signal which is wirelessly transmitted to an external coil for MRI image processing. This design minimizes tissue heating risks from conductive lines and eliminates the need for implanted power sources.
Claims Coverage
The claims disclose five main inventive features centered on a system for wireless MRI signal amplification comprising an ingestible device with a specific pre-amplification circuit and an external coil arrangement.
Pre-amplification circuit with three loop current (L-C) meshes
The system includes a pre-amplification circuit consisting of three loop current (L-C) meshes: the first resonating at the MRI signal frequency (first frequency) to generate an input current; the second resonating at the frequency of an externally generated pumping RF signal (second frequency) to generate a pumping current; and the third resonating at a third frequency to generate an amplified RF signal based on the mixing of input and pumping currents.
Use of a varactor within the third resonator for frequency mixing and amplification
The pre-amplification circuit includes a varactor integrated with the third L-C mesh, which performs frequency mixing of the input current (first frequency) and pumping current (second frequency) to produce an amplified current corresponding to the amplified RF output signal (third frequency).
External frequency generator providing a higher frequency pumping RF signal
An external frequency generator is employed to produce a second RF signal at the second frequency used to power the pre-amplification circuit wirelessly, eliminating the need for a local DC power source within the implantable or ingestible device.
External coil for wireless reception and transmission to MRI device
An external coil is configured to inductively receive the amplified third RF signal from the implantable device and transmit it to the MRI device for image processing, facilitating wireless signal transduction from inside the subject to the MRI system externally.
Ingestible device configured for in vivo reception, amplification, and wireless transmission
The system is embodied as an ingestible device containing the pre-amplification circuit that acquires the MRI RF signal from tissue surrounding the device, wirelessly amplifies it via the parametric amplifier, and wirelessly transmits the amplified signal to the external coil without wired connections or a battery.
In summary, the claims cover a wireless MRI signal amplification system utilizing a three-resonator parametric amplifier circuit powered by an external RF pumping signal, employing a varactor for frequency mixing, and including an external coil for wireless signal reception and transmission to an MRI device, all integrated in an ingestible or implantable device configuration.
Stated Advantages
Minimizes RF heating risks associated with long conductive cables in MRI interventional devices by eliminating physical DC power connections.
Enables wireless amplification and transmission of MRI RF signals from implanted or ingestible devices without the need for local batteries or wired power sources.
Improves detection sensitivity of weak MRI RF signals by local parametric amplification prior to wireless transmission to an external receiver.
Provides stable signal gain and low noise amplification enhancing overall MRI image quality for active interventional devices.
Documented Applications
Use with interventional devices such as catheters, guidewires, and ingestible capsules inserted into a subject undergoing MRI to enable real-time MRI guidance and device visualization.
Wireless signal transduction in implantable or in vivo MRI devices for improved acquisition and processing of MRI signals without requiring implanted power sources or wired connections.
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