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Showing papers on "Electromagnetic coil published in 1995"


Journal ArticleDOI
TL;DR: This study demonstrates for the first time that a predictable performance enhancement is achieved using microcoils as small as 50 microns in diameter in NMR microspectroscopy experiments.

286 citations


Journal ArticleDOI
TL;DR: In this paper, a set of formulas for the self and mutual impedances of planar coils on ferromagnetic substrates were derived directly from Maxwell's equations and therefore serve as a useful yardstick for simpler approximations.
Abstract: The high frequency operation of magnetic components, in applications such as filters, makes them ideal candidates for thick film technology along with resistors and capacitors. This in turn leads to distinct advantages over labor intensive wire wound components: improved reliability, repeatability, accuracy and consequential cost reductions. This paper establishes a new set of formulas for the self and mutual impedances of planar coils on ferromagnetic substrates. A planar coil in air is a special case of the generalized formulas. The formulas are derived directly from Maxwell's equations and therefore serve as a useful yardstick for simpler approximations. The formulas take full account of the current density distribution in the coil cross-section and the eddy current losses in the substrate. Experimental and calculated impedances up to 100 MHz are presented for a four layer device with three turns per layer which is 150 /spl mu/m thick and 40 mm/sup 2/ in area. >

258 citations


Patent
15 Sep 1995
TL;DR: In this paper, a thrombus is generated in an aneurysm, arteriovenous malformation or fistula by means of a catheter having an insulated heating coil coupled to an insulated delivery wire.
Abstract: A thrombus is generated in an aneurysm, arteriovenous malformation or fistula by means of a catheter having an insulated heating coil coupled to an insulated delivery wire. In one embodiment, two delivery wires are coupled to heating coils to provide a closed circuit. The heating coils may be in the form of a double helix or a single helix in combination with a straight heating coil. The heating coils are permanently connected to the delivery wires. Alternatively, a single insulated heating coil may be attached to a single insulated delivery wire with a uninsulated coil attached to the tip of the insulated heating coil. The electrical circuit is then made through the heating coil and non-insulated electrode coil into the vascular system and to a body electrode. A catheter may also be used for heating blood within the vascular system which is directly flowed into a tumoral mass for the purposes of thermal treatment of cancer.

219 citations


Journal ArticleDOI
24 Apr 1995
TL;DR: The machinable Rogowski coil as mentioned in this paper is a special type of mutual inductors often used to measure high AC and transient currents, and its performance is compared to that of other designs.
Abstract: Rogowski coils are special types of mutual inductors often used to measure high AC and transient currents. Traditional designs are reviewed. The significant sources of error associated with typical coil designs are examined. A "machinable Rogowski coil" is introduced and discussed. The reasoning behind critical design choices is discussed. The improved performance of the machinable coil is compared to that of other designs. Test and calibration methods are discussed.

212 citations


Patent
16 Oct 1995
TL;DR: In this article, an apparatus is provided for electrocoagulating blood and tissue at an occlusion site by means of application of an alternating signal or current through a detachable coil on the end of a microcatheter.
Abstract: An apparatus is provided for electrocoagulating blood and tissue at an occlusion site by means of application of an alternating signal or current through a detachable coil on the end of a microcatheter. A Guglielmi Detachable Coil (GDC) is preferably used in the combination with radio frequency energy to cause local heating at the coil. Once carbonization of blood at the detachment zone of the GDC coil occurs, the impedance of the entire system increases. The impedance increase is detected to automatically turn off the alternating current and then to apply a direct current to electrolytically detach the GDC coil from the microcatheter.

200 citations


Patent
Kurt J. Tekulve1
16 Mar 1995
TL;DR: A conically helically shaped embolization coil as mentioned in this paper is used for occluding a blood vessel, aneurysm, and the like, and is wound into a longitudinally extending coil with a plurality of tightly spaced turns.
Abstract: A conically helically shaped embolization coil (10) for occluding a blood vessel, aneurysm, and the like. The embolization coil includes a continuous platinum-tungsten alloy wire strand (11) wound into a longitudinally extending coil (12) having a plurality of tightly spaced turns (13). The longitudinally extending coil is wound into a conically helically shaped coil (15) with a plurality of radially expanding turns (16) that has spacing that increases proximally from the distal end (29) of the coil. Distal turn (17) of the radially expanding turns has a minor diameter (18) less than a minimum diameter (34) of a vessel (32) of which the embolization is to be positioned therein. Uncompressed proximal turn (19) of the radially expanding turns has a major diameter (20) greater than a maximum diameter (33) of the vessel in which the coil to be positioned. The conically helically shaped coil and particular diameter ensure that the coil is precisely positioned in a vessel lumen without longitudinal displacement of the delivery catheter. The coil is stress relieved and, in particular, heat treated by heating the coil to a stress relief temperature of the continuous wire strand and cooled to relieve residual stresses formed during the winding of the coil and to minimize the formation of new residual stresses formed during the cool down period of the heat treatment. Thrombogenic fibers (26) are positioned in the tightly spaced turns of the coil to attract thrombus and build up a mass that occludes the vessel lumen.

190 citations


Patent
20 Jun 1995
TL;DR: In this paper, a non-contacting charging device is described, in which electric power of a charger is supplied without direct contact to a storage battery, and which includes in the charger 1 a primary coil 103 and circuits 104, 105 for supplying AC power to the primary coil, and also in the radio communication device having a stored battery 210, a secondary coil 212 that couples electromagnetically with the primary coils 103 and a circuit 211 for supplying the induced current power generated in the secondary coil to the storage battery as charging power.
Abstract: A non-contacting charging device is disclosed which performs charging in which electric power of a charger 1 is supplied without direct contact to a storage battery 210, and which includes in the charger 1 a primary coil 103 and circuits 104, 105 for supplying AC power to the primary coil, and also includes in the radio communication device having a storage battery 210, a secondary coil 212 that couples electromagnetically with the primary coil 103 and a circuit 211 for supplying the induced current power generated in the secondary coil to the storage battery as charging power. This device is provided with halt signal generating circuits 203, 209, and 214 for generating a halt signal that commands a halt of supply of AC power to the primary coil, and a halting circuit for halting supply of AC power to the primary coil in response to a halt signal, the halt signal generating circuit being provided in the radio communication device. If it is necessary to make or receive a call during charging of the radio communication device, a halt signal is generated on the radio communication device side to halt charging, thereby eliminating the attractive force caused by the electromagnetic induction in effect between the radio communication device and the charger, and allowing removal of the radio communication device from the charger with a minimum of effort.

180 citations


Patent
28 Sep 1995
TL;DR: In this paper, a novel RF coil attached to an invasive device, such as a catheter, is used to detect magnetic resonance (MR) signals for monitoring the position of the device within a subject and for the acquisition of high-resolution magnetic resonance images of the tissue surrounding the device.
Abstract: A novel RF coil attached to an invasive device, such as a catheter, is used to detect magnetic resonance (MR) signals for monitoring the position of the device within a subject and for the acquisition of high-resolution magnetic resonance images of the tissue surrounding the device. The novel coil is sensitive to a small volume of MR active tissue during tracking procedures, but is sensitive to a larger volume during imaging procedures. During tracking, the MR signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to applied magnetic gradients to determine the position of the coil in several dimensions. The position of the novel coil, and hence the device, as determined by the tracking system is superimposed upon independently acquired medical diagnostic images. Magnetic Resonance images of the tissue surrounding the novel coil can be obtained by detecting the MR response signals from the novel coil using gradient-recalled, spin-echo or other MR imaging sequences.

179 citations


Patent
06 Apr 1995
TL;DR: In this article, a single eddy current coil is used to measure multiple parameters of conductive targets simultaneously using a single fixed frequency, such as the thickness of a target and the distance of the target from the coil.
Abstract: This invention uses a single eddy current coil to measure multiple parameters of conductive target simultaneously using a single fixed frequency. For example, the system consisting of the sensor coil, connecting cable, and signal conditioning electronics, can measure the thickness of a target and the distance of the target from the coil. Alternatively, it could simultaneously measure the distance of the target to the coil, i.e. lift-off, and one of the electrical properties of the target, such as the resistivity. The present system is useful in material characterization of targets where the lift-off information can be used to correct for any lift-off induced error in the apparent resistivity. In general, it can determine any pair of two characteristics of the target/sensor relationship simultaneously. This invention provides significant improvement in accuracy and flexibility of eddy current sensors and can be manufactured at a low cost due to the use of a single coil and a single fixed frequency in the signal conditioning electronics. An alternative sensor configuration utilizing two sensors differentially to produce a cladding insensitive--displacement measurement is also contemplated by the present invention.

141 citations


Patent
05 Jun 1995
TL;DR: In this paper, a method and apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame is proposed, where the driver applies signals to the source to generate a plurality of electromagnetic fields which are distinguishable from one another and a remote sensor senses each of the generated electromagnetic fields.
Abstract: A method and apparatus for determining the position and orientation of a remote object relative to a reference coordinate frame includes providing a source having a plurality of field-generating elements, wherein the field-generating elements generate electromagnetic fields and have spatially independent components defining a source reference coordinate frame. A driver applies signals to the source to generate a plurality of electromagnetic fields which are distinguishable from one another and a remote sensor has a plurality of field-sensing elements which sense each of the generated electromagnetic fields. A processor processes the output of the sensor in a remote object position and orientation relative to the source reference coordinate frame. At least one of the field-generating elements of the source has at least one electrically conductive sheet and a planar coil including a plurality of coplanar concentric rings above the conductive sheet. The planar coil is configured in a manner that a signal applied to that coil will cause a current density at each ring that is inversely proportional to the square of the radius of that ring. The planar coil may be made from a conductor formed as a simple or foliated spiral. The planar coil and the electrically conductive sheet may be formed from printed circuit board stock. A dihedral source may be made from a pair of orthogonal electrically conductive sheets each having a planar coil above the sheet. A trihedral source may be made from three electrically conducting sheets each having a planar coil above the sheet.

133 citations


Patent
06 Dec 1995
TL;DR: A floating mass transducer for assisting hearing in a person is provided in this article, where the magnet assembly and coil are configured such that conducting alternating electrical current through the coil results in vibration of the magnet and coil relative to one another.
Abstract: A floating mass transducer for assisting hearing in a person is provided Inertial vibration in the floating mass transducer (100) produces vibrations in the inner ear In an exemplary embodiment, the floating mass transducer comprises a magnet assembly (12) and a coil (14) secured inside a housing (10) which is attached to bone within the middle ear The coil is more rigidly secured to the housing than the magnet The magnet assembly and coil are configured such that conducting alternating electrical current through the coil results in vibration of the magnet assembly and coil relative to one another The vibration is caused by the interaction of the magnetic fields of the magnet assembly and coil Because the coil is more rigidly secured to the housing than the magnet assembly, the vibrations of the coil cause the housing to vibrate The floating mass transducer may generate vibrations in the inner ear by being attached to the skull or through a mouthpiece

Patent
King James D1, Donoho Harold F1
29 Mar 1995
TL;DR: In this paper, an H-field electromagnetic heating system for fusion bonding, particularly useful in the sealing of telecommunications cables and closures, comprises a composite bonding material having a bonding matrix and susceptors, the susceptors being magnetically reactive at a frequency above 50 MHz.
Abstract: An H-field electromagnetic heating system for fusion bonding, particularly useful in the sealing of telecommunications cables and closures, comprises a composite bonding material having a bonding matrix and susceptors, the susceptors being magnetically reactive at a frequency above 50 MHz, and an applicator for applying radiant electromagnetic energy to the composite bonding material, at a frequency above 50 MHz (preferably 75-500 MHz). The applicator may take the form of a quarter-wave resonator having an inner conductor and an outer conductor which at least partially surrounds the inner conductor, the two conductors being shorted at a common end. The material to be heated is placed between the conductors. The inner conductor may include a resonator tube which is capacitively coupled to the power supply by a capacitive probe connected to the center conductor of a coaxial connector. Different applicators (having different geometries) may be used with the same power supply, or a variety of heater adapters may be provided which can be removably attached to the applicator base. An alternative applicator employs many wires, electrically insulated from one another, each forming a coil with a common axis, and all of the wires being electrically connected in parallel. Several of these wires are stacked to form multiple layers of coils, such that the effective resistance of said applicator is reduced and the current-carrying capacity is increased. Individual capacitors may be connected in series with a respective one of the wire coils, to make the current in the coils more uniform for coil circumferences which are greater than 0.1 of the wavelength of the radiant electromagnetic energy.

Patent
09 May 1995
TL;DR: In this article, two small snare coils are joined at their distal ends (68, 70) to form a loop, and the proximal ends of the coils are attached to one or more elongated actuator members (20, 22).
Abstract: A device for retrieving foreign bodies, such as a vaso-occlusive coil or other articles from within vessels such as those of the cardiovascular system. Two small snare coils (60, 62) are joined at their distal ends (68, 70) to form a loop. The proximal ends of the coils are attached to one or more elongated actuator members (20, 22). The loop size is adjusted by manipulation of one or more of the proximal ends (26, 44) of the elongated actuator members. This retrieval device may be used to ensnare and either reposition or remove foreign bodies within a vessel lumen.

Journal ArticleDOI
TL;DR: In this paper, a tutorial paper on modeling and design of transformers and coupled inductors is presented, with a brief review of electromagnetic laws and magnetic circuit models, including both magnetizing and leakage effects.
Abstract: A tutorial paper is presented on modeling and design of transformers and coupled inductors. Beginning with a brief review of electromagnetic laws and magnetic circuit models, the magnetic and electric models of transformers and coupled inductors are developed, including both magnetizing and leakage effects. It is shown that while the voltage waveforms on the windings are primarily related by the turns ratio for both devices, the winding currents of transformers and coupled inductors are determined by very different mechanisms. An integrated structure with both transformer and coupled inductor on the same core is also discussed, as well as the special case of the coupled inductor used on a multiple-output transformer-isolated converter. >

PatentDOI
TL;DR: In this article, an improved partially implantable hearing device has been presented, which has a high coercivity permanent target magnet mounted to the ossicular chain by METABOND adhesive and being driven by an air core driving coil optimally implanted in a contactless manner at a spacing of approximately 1 mm.
Abstract: An improved partially implantable hearing device has a high coercivity permanent target magnet mounted to the ossicular chain by METABOND adhesive and being driven by an air core driving coil optimally implanted in a contactless manner at a spacing of approximately 1 mm. therefrom. The drive coil responds to auditory vibrations sensed by an externally concealed unit which converts these signals to an electrical signal transmitted to an externally located antenna which transmits same to an internally mounted antenna electronically connected to the air core electromagnetic driving coil.

Patent
John J. Grevious1
03 Feb 1995
TL;DR: In this paper, a feedback coil coupled to an output coil is designed to produce an output voltage just above a regulated power supply level for the output stage of the transmitting antenna until a desired output level is achieved.
Abstract: An efficient low cost means for regulating the output level of a magnetic field transmitter. A feedback coil tightly coupled to an output coil is designed to produce an output voltage just above the supply level for the output stage of the transmitter when the desired output level is achieved. The feedback sense coil tightly coupled to an output coil is designed to produce an output voltage just above a regulated power supply level for the output stage of the transmitting antenna until a desired output level is achieved. The feedback coil is diode coupled to the regulated power supply lines of the transmitter. When the output level increases above the regulation level the diodes begin to conduct returning energy to the supply and preventing further increase of the transmitting antenna signal.

Patent
25 Apr 1995
TL;DR: In this paper, the authors proposed a reader for radio frequency identification tags (24) having at least one magnetic field transmitting and receiving coil (26) which is oriented in a given plane and which is responsive to a received magnetic exciter field of a first frequency to produce and radiate an identifying magnetic field comprised of a carrier at a second different frequency modulated by an identifying code.
Abstract: A reader (32) for radio frequency identification tags (24) having at least one magnetic field transmitting and receiving coil (26) which is oriented in a given plane and which is responsive to a received magnetic exciter field of a first frequency to produce and radiate an identifying magnetic field comprised of a carrier at a second different frequency modulated by an identifying code. The reader comprises a first circuit (37) for producing a radio frequency signal of the first frequency; a first magnetic field coupling arrangement (34, 36, 38) connected to the output of said first circuit (37) for producing a corresponding exciter field at the first frequency to be magnetically coupled to the receiving coil (26) of the tag (24), with the first magnetic field coupling arrangement including a solenoidal exciter coil (34) having at least one wound exciter winding and a longitudinal axis disposed substantially perpendicular to the plane of the tag coil (26); a second magnetic field coupling arrangement (42, 44) for receiving a magnetic field of the second frequency produced by the tag (24) and providing a corresponding electrical signal, with the second magnetic field coupling arrangement including at least one receiver coil (42, 44) disposed adjacent one end of the solenoidal coil (34); and circuitry (46) connected to the receiver coil (42, 44) for decoding the received electrical signal. Preferably the tag (24) is disposed on the lid (22) of a trash or waste bin (14) with the tag coil (26) being substantially horizontal, and the axis of the exciter coil (34), which is disposed substantially vertically. According to the preferred embodiment, the reader (32) is disposed on the end of a robot arm (12) mounted on a trash truck (10) and a switch (58) is additionally provided on the arm to enable counting of the number of bins (14) which has been lifted by the robot arm (12).

Patent
04 Dec 1995
TL;DR: A thrombogenic occlusion coil as discussed by the authors is a helical metallic coil with axially spaced windings and a plurality of strands of a throm bogenic polymer extending axially through the central core of the coil, the ends of the strands being bound together.
Abstract: A thrombogenic occlusion coil 10,20 for occluding a blood vessel comprising a helical metallic coil 11,21 having a plurality of axially spaced windings (13) and a plurality of strands (12,22) of a thrombogenic polymer extending axially through the central core of the coil, the ends of the strands being bound together.

Journal ArticleDOI
04 Jun 1995
TL;DR: In this article, the Underwriters Laboratories Inc. (UL) K-factor rated dry type transformer and the recommended practices given in ANSI/IEEE C57.110 are reviewed.
Abstract: The use of adjustable-speed drives requires transformers capable of withstanding high levels of harmonic currents under normal operating conditions. Experience has been that overheating problems are much more common with dry-type transformers than with liquid-filled transformers. Transformer insulation life is determined by the hot spot temperature but confirmation of hot spot temperature rise is one performance characteristic which is ignored in industry standards. This is especially important for transformers rated for nonsinusoidal load currents. The design of transformers for nonsinusoidal load currents should include an analysis of the eddy loss distribution in the windings and calculation of the hot spot temperature rise. Calculations and thermal tests giving only average winding temperature rises are not sufficient. Thermal tests with nonsinusoidal currents and measurements of hot spot temperature rises are extremely difficult on large transformers. The combination of testing and analysis may be the only economically practical approach. Analysis indicates that the dry type transformer hot spot temperature is very sensitive to the eddy loss magnitude and distribution. The Underwriters Laboratories Inc. (UL) K-factor rated dry type transformer and the recommended practices given in ANSI/IEEE C57.110 are reviewed. When purchasing transformers subject to nonsinusoidal load currents, considerations should be given to the manufacturer's development program and capability to calculate the eddy loss distribution and hot spot temperatures.

Journal ArticleDOI
TL;DR: In this article, an inductive superconducting fault current limiter has been built and tested, which mainly consists of a copper coil, a super-conducting tube, and an iron core which are concentrically arranged.
Abstract: An inductive superconducting fault current limiter has been built and tested. It mainly consists of a copper coil, a superconducting tube, and an iron core which are concentrically arranged. The device is essentially a transformer with the secondary winding being the tube. The tube has diameter of 20 cm, a height of 35 cm, and is made of Bi2212 ceramic, fabricated by partial melting. The ceramic has the voltage current characteristic V-I/sup /spl alpha// with /spl alpha//spl ap/5. The critical current density defined by the 1 /spl mu/V/em criterion is about 1400 A/cm/sup 2/. Depending on the number of turns of the coil, the nominal current of the device was between 130 A and 250 A. In short circuit tests in a 480 V circuit, the prospective fault current of 8 kA was limited to about 5 times the nominal current. The test results are in good agreement with detailed simulations of both the normal operation (e.g. impedance, AC-losses) and the behaviour under fault conditions (i.e. evolution of the current). >

Journal ArticleDOI
TL;DR: In this article, the authors proposed a new method to calculate the signal-to-noise ratio (SNR) of MR signals obtained from single receiver coils and arrays of receiver coils.
Abstract: Describes a new method to calculate the signal-to-noise ratio (SNR) of MR signals obtained from single receiver coils and arrays of receiver coils. The coils are assumed to be placed on the surface of a conducting half-space and the SNR is sample-noise dominated. While in conventional methods line integrals over the electric currents in the coils are chosen to calculate the electric and magnetic fields, this new method uses surface integrals over magnetic dipoles covering the area enclosed by the antenna to derive these fields. Using this method, the SNR for simple circular and square coils was analytically calculated. The calculations show that the theoretical difference in SNR between circular and square antennas is very low. Furthermore, based on the new method, a derivation of the ultimate gain in SNR for arrays of surface coils is presented. The SNR of such an array approaches a limit even if the total number of coils is increased to infinity. This ultimate SNR of a coil array is 35.8% above that of a single circular-shaped, size-optimized and linear polarized coil. >

Patent
05 Sep 1995
TL;DR: An electromagnetic shield for an NMR radio frequency coil designed to resonate at a selected Larmor frequency was proposed in this paper, which includes an electrically conductive layer surrounding the coil.
Abstract: An electromagnetic shield for an NMR radio frequency coil designed to resonate at a selected Larmor frequency. The shield includes an electrically conductive layer surrounding the coil. This electrically conductive layer has a thickness substantially the same as one skin depth at the selected Larmor frequency. As such, the conductive layer efficiently conducts radio frequency currents at the selected Larmor frequency thereby conducting and containing the radio frequency coils at the selected Larmor frequency within the coil. Simultaneously, an electrically conductive layer, due to its thinness, very inefficiently conducts eddy currents of the type induced by the lower frequency DC gradient current switching transients the gradients are utilized to magnetically localize an image slice or volume. Consequently, the conductive layer simultaneously attenuates low frequency eddy current propagation of the type induced by the switching field gradient currents in the NMR application, and therefore does not substantially shield or effect the gradient fields across the coil.

Journal ArticleDOI
TL;DR: Spiral scanning gradient waveforms can be optimized with respect to blurring from off‐resonance effects by minimizing the readout time by maximizing the gradient amplitude during the scan.
Abstract: Spiral scanning gradient waveforms can be optimized with respect to blurring from off-resonance effects by minimizing the readout time. This is achieved by maximizing the gradient amplitude during the scan so that the edge of k-space is reached as quickly as possible. Gradient hardware constraints are incorporated by considering a circuit model for the gradient coil and amplifier. The optimized gradient waveforms are determined by a set of coupled differential equations. The resulting solutions have shorter readout time than solutions that do not consider the circuit model.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method for stress grading on high voltage motor and generator stator windings, which can be characterized in terms of two parameters, a threshold stress and a gradient index, based on simple current and voltage measurements.
Abstract: Stress grading on high voltage motor and generator stator windings is becoming more important as the electrical stress in the ground insulation is increased. While there are a variety of possible ways to relieve surface stress, non-linear resistive tapes have been almost universally adopted because of their simplicity and efficiency. However, selection and quality control on these materials has been problematic, as the means to characterize these materials has not been clearly set out. Most types of material can be characterized in terms of two parameters, a threshold stress and a gradient index, which can be determined from simple current and voltage measurements. It is hoped, therefore, that manufactures of grading products will adopt such measurements and publish these values as a matter of course. This will enable coil manufacturers to improve the specification and quality control of stress grading coatings. >

Journal ArticleDOI
TL;DR: An analytic correction method was developed and applied to correct the signal intensity nonuniformity caused by the inhomogeneous reception profile of surface coils used for magnetic resonance imaging of the brain at 1.5 T.
Abstract: An analytic correction method was developed and applied to correct the signal intensity nonuniformity caused by the inhomogeneous reception profile of surface coils used--because of their higher sensitivity--for magnetic resonance imaging of the brain at 1.5 T. The reception profile was analytically modeled by using the Biot-Savart law. The correction considerably improved visual interpretation of the images by modeling and removing the dependence of signal intensity on distance from the coil. The method can be used for single or multiple coils of any planar geometry and in any orientation. Application of this technique allows imaging of the brain with surface coils, yielding increased resolution and signal-to-noise ratio, without the penalty of image nonuniformity.

Journal ArticleDOI
TL;DR: High spatial resolution two‐ or three‐dimensional chemical shift images of normal brain were obtained in 17‐minute acquisitions and coverage and SNR increases demonstrated are similar to those obtained in magnetic resonance phased array imaging.
Abstract: Two and four-coil phased array detectors have been developed to increase the sensitivity of proton spectroscopic imaging of the human brain. These include a quadrature figure-8 coil for the study of the vertex, several arrays of 2-4 small overlapping (6-8 cm diameter) circular coils and a combination figure-8 coil plus circular coil. These were constructed in our laboratory and tested to assess their utility for brain spectroscopy. Methods for optimally combining the data from the independent receivers based on the analytical coil maps or measured signal to noise ratios (SNRs) of the data were investigated. High spatial resolution (0.2-0.4 cm3 voxel size) two- or three-dimensional chemical shift images of normal brain were obtained in 17-minute acquisitions. These spatial resolutions are comparable to those previously obtained with conventional small surface coils, but the specialized detectors allow this sensitivity to be achieved for a larger region or for previously inaccessible areas such as the top of the head. The coverage and SNR increases demonstrated are similar to those obtained in magnetic resonance phased array imaging.

Patent
19 Oct 1995
TL;DR: In this article, an RF coil construction for MRI apparatus is described, consisting of three butterfly coils extending in a longitudinal direction and overlapping with three single loop coils, each of which has flexible wings which can be wrapped over the body of a patient.
Abstract: An RF coil construction for MRI apparatus and comprising, preferably, three butterfly coils extending in a longitudinal direction and overlapping with three single loop coils. Each of the three butterfly coils have flexible wings which can be wrapped over the body of a patient. The signals from two of the butterfly coils and two of the single loop coils are simultaneously processed in a phased array manner. The resultant RF coil construction provides in-depth imaging over a large FOV with a high SNR and good homogeniety, and is well suited for imaging the lower extremities of a patient without moving the patient or the coils. Further, the butterfly coils receive signals in the horizontal direction, and the single loop coils receive signals in the vertical direction. The combining of such signals realizes quadrature operation and improves the SNR. Also described is a mesh coil that can be operated to function as the equivalent of one butterfly coil and one single loop coil.

Patent
12 Jun 1995
TL;DR: In this paper, an infusion pump for delivering a selected medication to a patient is provided with an inductance flow sensor for monitoring and verifying delivery of medication in response to pump operation.
Abstract: An infusion pump for delivering a selected medication to a patient is provided with an inductance flow sensor for monitoring and verifying delivery of medication in response to pump operation The flow sensor comprises a compact inductor coil wrapped about a pump discharge conduit, in combination with a magnetically attractable core pin disposed within the discharge conduit for movement to a position within the inductor coil in response to pump outflow A control circuit operates with minimal power requirements to monitor coil inductance changes as a result of core pin displacement to confirm medication delivery to the patient in response to pump operation A magnet mounted at one end of the inductor coil draws and retains the core pin at a position retracted from the coil in the absence of pump outflow

Patent
23 Feb 1995
TL;DR: In this article, an electrical coil wound around a mandrel is engaged to the fixed magnetic core such that flux is induced in the core when current is supplied to the coil, driving the plunger against the force of the spring.
Abstract: Micromechanical structures capable of actuation for purposes such as fluid flow control are formed on substrates in sizes in the range of one or two millimeters or less using micromechanical processing techniques. A magnetic core having a gap therein is fixed on the substrate, and a plunger is mounted by a spring for movement parallel to the substrate in response to the flux provided to the gap of the fixed core. An electrical coil wound around a mandrel is engaged to the fixed magnetic core such that flux is induced in the core when current is supplied to the coil, driving the plunger against the force of the spring. A micromechanical fluid control unit includes a metal frame structure formed by electrodeposition on a substrate with the inner wall of the frame having slots formed therein to admit a separator wall which divides the interior of the frame into separate chambers, with a cover secured over the top of the frame and the separator wall to seal the chambers. A plunger actuator can be mounted within the frame with fixed core sections extending through the walls of the frame, and with the mandrel and coil engaged to the fixed core sections outside of the frame to provide magnetic flux to a gap to actuate the plunger within the sealed enclosure.

Patent
31 May 1995
TL;DR: In this paper, a power supply comprising a coil a switching transistor for establishing a conduction path between the input terminal and the coil during an on-time and for interrupting the conduction paths between the inputs and the coils during an off-time is presented.
Abstract: A power supply comprising a coil a switching transistor for establishing a conduction path between the input terminal and the coil during an on-time and for interrupting the conduction path between the input terminal and the coil during an off-time. A diode is provided for sustaining a conduction path for the current through the coil (20) upon interruption of the conduction path between the input terminal (20) and the coil and an apparatus is provided for varying the ratio between the on-time and the off-time of the switching transistor in response to a difference between an output voltage across the load and a first reference voltage (VI). The power supply exhibits an improved efficiency by maintaining the ratio constant if the output voltage lies between two reference values. Within this voltage window defined by the two reference values the power supply is self-regulating, as a result of which the control may be disabled so that the efficiency is improved.