Abstract: A Class-E amplifier has bee adapted for use in the radio frequency section of a magnetic resonance imaging (MRI) system. A drive signal is produces by modulating the envelope of a radio frequency carrier signal and then applied to a switch in the Class-E amplifier. The switch is connected in series with a choke between a supply voltage terminal and circuit ground with an output node formed between the choke and the switch. The output node is coupled to circuit ground by a shunt capacitor. In a preferred embodiment, a pair of such amplifiers, that are ? radians out of phase, are connected to each rung of a transverse electromagnetic transmit array type radio frequency coil of the MRI system.

Abstract: Methods and systems are provided for redundancy management of a fly-by-wire avionics system. A control module for producing a control signal is provided comprising a common processing partition for receiving a flight input signal and at least one first mode input signal, a first processing partition coupled to the common processing partition and configured to receive the first mode input signals and flight input signal from the common processing partition, and a second processing partition coupled to the common processing partition. The first processing partition produces a first mode output signal in response to one of the first mode input signals and flight input signal. The second processing partition generates a second mode signal in response to the flight input signal when the first processing partition fails. The common processing partition produces the control signal in response to one of the first mode output signal and second mode signal.

Abstract: A medical device, such as a cardiac pacing device for an animal, includes an intravascular antenna that has a first coil for engaging a wall of a first blood vessel to receive a radio frequency signal. The first coil includes a first winding wound helically in a rotational direction along a longitudinal axis from a first end of the coil to a second end. A second winding that is connected to the a first winding at the second end, is wound helically in the same rotational direction along the longitudinal axis from the second end to the first end. An electronic circuit is implanted in the animal and is connected to the antenna to receive an electrical signal therefrom.

Abstract: A medical device adapted for implantation into a patient receives electrical power from an extracorporeal power supply. The medical device has a first receiver for a first wireless signal, a power circuit that extracts energy from the first wireless signal to power the medical device, and a feedback signal generator that transmits a second wireless signal indicating a magnitude of energy extracted from the first wireless signal. The extracorporeal power supply includes a source of electrical power and a power transmitter that emits the first wireless signal. A second receiver enables the extracorporeal power supply to receive the second wireless signal. A feedback controller manipulates the first wireless signal in response to the second wireless signal to ensure that sufficient electrical energy is provided to the medical device without wasting electrical power from the source.

Abstract: A system for stimulating tissue of the patient includes an implantable medical device and an external power source. The medical device receives and extracts electrical energy from a first wireless signal and has a detector circuit that senses a physiological characteristic of the patient. The sensing can occur simultaneously while electrical stimulation pulses are applied to the tissue. A feedback transmitter that sends information related to the physiological characteristic via a second wireless signal. The external power source transmits the first wireless signal and extracts the information from a second wireless signal. When the information indicates existence of a predefined condition, a communication module, that preferably includes a cellular telephone sends a message for reception by the remote monitor to alert medical personnel.

Abstract: An implantable electronic medical device is compatible with a magnetic resonance imaging (MRI) scanner. The device has a housing with exterior walls, each formed by a dielectric substrate with electrically conductive layers on interior and exterior surfaces. A series of slots divide each layer into segments. Segmenting the layers provides high impedance to eddy currents produced by fields of the MRI scanner, while capacitive coupling of the segments provides radio frequency shielding for components inside the housing. Electrical leads extending from the housing have a pair of coaxially arranged conductors and traps that attenuate currents induced in the conductors by the fields of the MRI scanner.

Abstract: An intravascular mesh type electrode carrier eliminates material and mechanical transitions between an electrical lead and an electrode by interweaving the conductor of the lead into the carrier mesh. The mesh material of the electrode carrier can be electrically conductive so that the entire carrier functions as the electrode. Alternatively, the mesh material may either be non-conductive or have an outer non-conductive coating, in which cases only the exposed section of the first conductor acts as an electrode. With a non-conductive mesh material, a second electrode lead can be woven through the mesh of the electrode carrier to provide a second electrode.

Abstract: A radio frequency antenna is provided for use with a medical device for implantation into an animal. The antenna comprises a coil formed by a wire that includes a core formed of a shape-memory material with an electrically conductive first layer applied to an outer surface of the core. A second layer, of an electrically insulating and biologically compatible material, extends around the first layer. If necessary to reduce friction a lubricant is place between the first and second layers. If second layer is formed of porous material or a non-biological compatible material, a biological compatible outer layer surrounds the second layer thereby providing a barrier that is impermeable to body fluids of the animal.

Abstract: A medical device, such as a cardiac pacing device for an animal, includes an intravascular antenna that has a first coil for engaging a wall of a first blood vessel to receive a radio frequency signal. The first coil includes a first winding wound helically in a rotational direction along a longitudinal axis from a first end of the coil to a second end. A second winding that is connected to the a first winding at the second end, is wound helically in the same rotational direction along the longitudinal axis from the second end to the first end. An electronic circuit is implanted in the animal and is connected to the antenna to receive an electrical signal therefrom.

Abstract: A catheter system and method are employed to implant components of a medical device inside an animal. The catheter system includes a plurality of coaxial catheters and sheaths between which electrically interconnected components of the medical device are releasably held. A guide wire is inserted to a desired location inside the animal and the plurality of catheters and sheaths is slid as an assembly along the guide wire to that location. One of the sheaths is moved with respect to the other catheters and sheaths to release one of the components. The guide wire and the remaining catheters and sheaths are repositioned to a second location inside the animal and manipulated to release another component. Additional components can be implanted by further repositioning and manipulating steps. The catheter system is removed from the animal leaving the components in place.

Abstract: An radio frequency antenna assembly is provided for a medical device such as one capable of being implanted into a patient. The antenna assembly includes a plurality of antennas, each oriented to receive a radio frequency signal propagating along a different axis. This facilitates reception of the radio frequency signal regardless of the orientation of its propagation axis to the medical device. In other cases, the radio frequency signal has a plurality of components, each propagating along a different axis, and each antenna of the assembly receives a different one of those components. The individual electrical signals produced in each antenna are additively combined into a single signal having greater strength than each of the individual electrical signals.

Abstract: An apparatus for stimulating tissue of a medical patient includes a power transmitter which periodically transmits a pulse of a radio frequency signal to a intravascular stimulator that is implanted in a vein or artery. The intravascular stimulator employs energy from the radio frequency signal to charge a storage device which serves as an electrical power supply. The intravascular stimulator also detects an electrical signal produced within the patient and responds thereto by applying a pulse of voltage from the storage device to a pair of electrodes implanted in the vascular system of the animal.

Abstract: An abnormally rapid ventricular cardiac rate that results from atrial fibrillation can be reduced by stimulating a vagal nerve of the heart. An apparatus for such stimulation includes a power transmitter that emits a radio frequency signal. A stimulator, implanted in a blood vessel adjacent the vagal nerve, has a pair of electrodes and an electrical circuit thereon. The electrical circuit receives the radio frequency signal and derives an electrical voltage from the energy of that signal. The electrical voltage is applied in the form of pulses to the pair of electrodes, thereby stimulating the vagal nerve. The pattern of that stimulating pulses can be varied in response to characteristics of the atrial fibrillation or the ventricular contractions.

Abstract: A cardiac pacemaker includes a power transmitter which periodically transmits a pulse of a radio frequency signal to a vascular electrode-stent that is implanted in a vein or artery of an animal. The vascular electrode-stent employs energy from the radio frequency signal to charge a storage device which serves as an electrical power supply. The vascular electrode-stent also detects a cardiac signal emitted from the sinus node of the heart and responds thereto by applying a pulse of voltage from the storage device to a pair of electrodes implanted in the vascular system of the animal. Application of the voltage pulse to the electrodes stimulates contraction of the heart.

Abstract: Medical devices implanted in a patient can be activated and powered by an RF signal. Unless the medical device is properly oriented with respect to the transmitting antennas enough signal energy may not be received to power that device. However, optimum orientation can not be assured due to constraints on the implantation position. The present transmitting antenna is flat and omnidirectional thereby eliminating the need to properly orient the implanted medical device.