Showing papers on "Transducer published in 2001"

On the feasibility of remote palpation using acoustic radiation force.

Abstract: A method of acoustic remote palpation, capable of imaging local variations in the mechanical properties of tissue, is under investigation. In this method, focused ultrasound is used to apply localized (on the order of 2 mm3) radiation force within tissue. and the resulting tissue displacements are mapped using ultrasonic correlation based methods. The tissue displacements are inversely proportional to the stiffness of the tissue, and thus a stiffer region of tissue exhibits smaller displacements than a more compliant region. In this paper, the feasibility of remote palpation is demonstrated experimentally using breast tissue phantoms with spherical lesion inclusions, and in vitro liver samples. A single diagnostic transducer and modified ultrasonic imaging system are used to perform remote palpation. The displacement images are directly correlated to local variations in tissue stiffness with higher contrast than the corresponding B-mode images. Relationships between acoustic beam parameters, lesion characteristics and radiation force induced tissue displacement patterns are investigated and discussed. The results show promise for the clinical implementation of remote palpation.

Ultrasonics without a source: thermal fluctuation correlations at MHz frequencies.

Abstract: Noise generated in an ultrasonic receiver circuit consisting of transducer and amplifier is usually ignored, or treated as a nuisance. Here it is argued that acoustic thermal fluctuations, with displacement amplitudes of 3 fm, contain substantial ultrasonic information. It is shown that the noise autocorrelation function is the waveform that would be obtained in a direct pulse/echo measurement. That thesis is demonstrated in experiments in which direct measurements are compared to correlation functions. The thermal nature of the elastodynamic noise that generates these correlations is confirmed by an absolute measurement of their strength, essentially a measurement of the sample temperature.

Thermal treatment methods and apparatus with focused energy application

Abstract: A collapsible ultrasonic reflector incorporates a gasfilled reflector balloon (50), a liquid-filled structural balloon (28) and an ultrasonic transducer (20) disposed within the structural balloon. Acoustic energy emitted by the transducer is reflected by a highly reflective interface between the balloons. In a cardiac ablation procedure, the ultrasonic energy is focused into an annular focal regions (44) to ablate cardiac tissue extending in an annular path along the wall. Devices for stabilizing the balloon structure and for facilitating collapse and withdrawal of the balloon structure are also disclosed.

Design and fabrication of a new vibration-based electromechanical power generator

Abstract: A device is described for generating electrical power from mechanical energy in a vibrating environment. The design utilises an electromagnetic transducer and its operating principle is based on the relative movement of a magnet pole with respect to a coil. The approach is suitable for embedded remote microsystems structures with no physical links to the outside world. Simulation, modelling and test results following fabrication of a first prototype have demonstrated that generation of practical amounts of power within a reasonable space is possible. Power generation of more than 1 mW within a volume of 240 mm3 at a vibration frequency of 320 Hz has been obtained.

Electroactive polymer sensors

Abstract: The invention provides sensors that comprise a transducer that converts between mechanical energy and electrical energy. The transducer comprises an electroactive polymer in electrical communication with at least two electrodes. When a relatively small voltage difference is applied between the electrodes, deflection of the polymer results in a measurable change in electrical energy for the transducer. The change in electrical energy may correspond to a change in resistance, capacitance, or a combination thereof. Sensing electronics circuits in electrical communication with electrodes detect the electrical energy change.

Apparatus and method incorporating an ultrasound transducer onto a delivery member

Abstract: A medical device assembly and method provides an ultrasound transducer mounted onto a catheter shaft. The ultrasound transducer is mounted such that there is a radial separation between the transducer and the underlying catheter shaft. The transducer is mounted on support structures which do not bridge the gap between the transducer and delivery member. The location of the support structures provides for an “airbacked” transducer that is very efficient and prevents heat build-up in the materials in contact therewith.

Systems and methods for ultrasound assisted lipolysis

Abstract: Cells are destroyed within a subcutaneous tissue region using a transducer disposed externally adjacent to a patient's skin. The transducer emits acoustic energy that is focused at a linear focal zone within the tissue region, the acoustic energy having sufficient intensity to rupture cells within the focal zone while minimizing heating. The transducer may include one or more transducer elements having a partial cylindrical shape, a single planar transducer element coupled to an acoustic lens, or a plurality of linear transducer elements disposed adjacent one another in an arcuate or planar configuration. The transducer may include detectors for sensing cavitation occurring with the focal zone, which is correlated to the extent of cell destruction. A frame may be provided for controlling movement of the transducer along the patient's skin, e.g., in response to the extent of cell destruction caused by the transducer.

Implantable pressure sensors and methods for making and using them

Abstract: An implant includes a pressure sensor, a controller for acquiring pressure data from the sensor, and an acoustic transducer for converting energy between electrical energy and acoustic energy. A capacitor is coupled to the acoustic transducer for storing electrical energy converted by the transducer and/or for providing electrical energy to operate the implant. The acoustic transducer may operate alternatively or simultaneously as an energy exchanger or an acoustic transmitter. During use, the implant is implanted within a patient's body, and an external transducer transmits a first acoustic signal into the patient's body, to energize the capacitor. The implant then obtains pressure data, and transmits a second acoustic signal to the external transducer, the second acoustic signal including the pressure data.

Mode and transducer selection for long range lamb wave inspection

Abstract: Lamb waves can propagate many metres along plate and shell structures, and so have great potential in ‘smart structure’ applications where it is important for a transducer to interrogate a signific...

Hifu application with feedback control using bubble detection

Abstract: High intensity focused ultrasound heating is provided by applying therapeutic ultrasonic waves using an array of transducers (64). Cavitation is detected by using some or all of the transducers in the array to detect ultrasonic waves emanating from or reflected from the patient's body or the interface. A feedback signal is generated based on such detection. If the feedback signal indicates the presence of cavitation, the therapeutic ultrasonic waves are terminated or altered. Obstacles to ultrasound transmission, such as bony structures (O) or bubbles (B) at the interface between the transducer array and the patient can be detected using the same transducers.

Systems and methods for reducing secondary hot spots in a phased array focused ultrasound system

Abstract: Systems and methods for performing a therapeutic procedure using focused ultrasound include providing a piezoelectric transducer including a plurality of transducer elements (22), such as a concave concentric ring array or a linear array of transducer elements. Drive circuitry (14) is coupled to the transducer for providing drive signals to the transducer elements at one of a plurality of discrete RF frequencies. A controller (16) is coupled to the drive circuitry for periodically changing a frequency of the drive signals to one of the plurality of discrete frequencies, while controlling a phase component of the drive signals to maintain the focus of the transducer at a primary focal zone during a single sonication.

Ultrasonic method and device for wound treatment

Abstract: The method and device of the present invention for wound treatment includes a transducer (7) to produce waves, preferably ultrasonic waves. The transducer has tip with the distal end (radiation surface). A liquid is directed to the radiation surface wherein an directed atomized particle spray (3) of the liquid is created upon contact of the liquid with the radiation surface. The spray (3) directed to the wound from at least 0.1 inches transmits wave trough particles and has an irrigation, mechanical cleansing, liquid energizing and bactericide effect.

Method for creating multiplanar ultrasonic images of a three dimensional object

Abstract: A method for creating multiple planar images of a volumetric region of an object without acquiring data from the entire volumetric region. The method includes sweeping a transducer across the volumetric region. At sampling positions during the sweep, ultrasonic beams from the transducer are transmitted into the volumetric region, which intersect one or more of a plurality of surfaces to be scanned. The number of transmitted beams during the sweep is fewer than the number of beams that would be transmitted to scan the entire volumetric region. Echoes from the volumetric region are received at the transducer in response to the transmitted beams. From the received echoes, planar images corresponding to the plurality of surfaces are formed. In a variation, the method includes receiving at the transducer fewer echoes from the volumetric region than the echoes that would be received from scanning the entire volumetric region. This enables the creation of planar images corresponding to buried surfaces within the volumetric region. Because only a finite plurality of surfaces of the region is being scanned rather than the entire volumetric region, planar images of high image quality and a broad field of view can be created and displayed in real-time. The method can also be performed by scanning the transducer. The method is carryied out by ultrasonic apparatus.

Method for calculating transducer capacitance to determine transducer temperature

Abstract: A method for calculating the capacitance of a transducer (C0) without knowing the exact resonance frequency of a transducer/blade combination is achieved by sweeping across a broad frequency range which contains resonant and non-resonant frequencies where C0 can be measured. A pre-defined frequency range is set independently of the resonance frequency of a specific transducer/blade combination. C0 of the transducer/blade is measured at several different frequencies within the pre-defined frequency range to ensure that invalid C0 measurements are disregarded, and the temperature of the transducer is calculated based on valid C0 measurements. The determined transducer temperature, based on C0 measurements, can be used to optimize performance and/or provide a safety shutdown mechanism for the generator.

Miniature broadband acoustic transducer

Abstract: An acoustic transducer is disclosed including: a fixed perforated member; a freely movable diaphragm spaced from the perforated member; a support ring in the perforated member maintaining the proper spacing between the diaphragm and the perforated member near the perimeter; means of suspension allowing the diaphragm to rest freely on the support ring and yet mechanically decouples the diaphragm from the perforated member; means of applying an electrical field in the space between the perforated member and the diaphragm; means of detecting the change of electrical capacitance between the perforated member and the diaphragm when the diaphragm moves in response to an incident acoustic sound pressure wave.

Acoustic biosensor for monitoring physiological conditions in a body implantation site

Abstract: An acoustic biosensor is provided for deployment at an implantation site within a body, such as an abdominal aortic aneurysm. The biosensor includes a sensor element for measuring a physiological condition at the implantation site, and for generating an information signal representative of the physiological condition. The biosensor further includes a piezoelectric transducer element for converting an externally originated acoustic interrogation signal into energy for operating the sensor, and for modulating the interrogation signal, e.g., by employing a switching element to alternate the mechanical impedance of the transducer element, to transmit the information signal outside of the body.

Diagnostic medical ultrasound systems and transducers utilizing micro-mechanical components

Abstract: The use of any micro-mechanical component in an ultrasound system is disclosed. In particular, the use of micro-relays, micro-switches and inductors in the transducer probe head, in the transducer connector, coupled with the system transducer connector(s) or anywhere else in the system. In an ultrasound system, micro-mechanical components such as micro-fabricated switches, relays and inductors permit impressive size reduction, cost reduction, signal-integrity enhancement and improved operational flexibility.

Ka/Ku dual band feedhorn and orthomode transducer (OMT)

Abstract: A dual band, higher and lower frequency range transducer with a circular coaxial waveguide feed is described having a first junction for connection of a lower frequency range outer waveguide of the coaxial waveguide feed to at least two rectangular or ridge waveguides offset from the longitudinal axis of the transducer and a second junction for connection of the at least two rectangular or ridge waveguides to a further waveguide. A third junction is provided for connecting an inner waveguide of the coaxial waveguide feed to a higher frequency range waveguide. The transducer comprises at least first and second parts joined across a first plane substantially perpendicular to the longitudinal axis and including at least a portion of the higher frequency range waveguide extending within the first plane of the join. A seal such as an “O” ring seal may be placed easily in the plane of the join thus preventing moisture ingress. Similarly, a feed horn and input and output ports may be sealingly attached to the first and second parts of the transducer. The first and second junctions are preferably impedance matched turnstile junctions.

Acoustic switch and apparatus and methods for using acoustic switches within a body

Abstract: An implant for insertion or implantation within a body includes an electrical circuit for performing one or more commands when the implant is activated, an energy storage device, and a switch coupled to the electrical circuit and the energy storage device. An acoustic transducer is coupled to the switch, the acoustic transducer being activatable upon acoustic excitation by an external acoustic energy source for closing the switch to allow current flow from the energy storage device to the electrical circuit. The one or more commands includes measuring a physiological parameter with a biosensor coupled to the electrical circuit, or controlling a therapeutic device coupled to the electrical circuit. The therapeutic device or biosensor may be activated for a predetermined time or until the switch is opened in response to another acoustic excitation of the acoustic transducer.

Continuous optoacoustic monitoring of hemoglobin concentration and hematocrit

Abstract: An optoacoustic apparatus is disclosed which includes a radiation source of pulsed radiation and a probe having a front face to be placed in contact with a tissue site of an animal body. The probe further includes an optical fiber terminating at the surface of the front face of the probe and connected at their other end to a pulsed laser. The front face of the probe also has mounted therein or thereon a piezoelectric transducer for detecting an acoustic response to the radiation pulses connected to a processing unit which converts the transducer signal into a measure of hemoglobin concentration and/or hematocrit of blood.

Miniature silicon condenser microphone and method for producing same

Abstract: A silicon condenser microphone package is disclosed. The silicon condenser microphone package comprises a transducer unit, a substrate, and a cover. The substrate includes an upper surface having a recess formed therein. The transducer unit is attached to the upper surface of the substrate and overlaps at least a portion of the recess wherein a back volume of the transducer unit is formed between the transducer unit and the substrate. The cover is placed over the transducer unit and includes an aperture.

Structural insights into the early steps of receptor—transducer signal transfer in archaeal phototaxis

Abstract: Electron paramagnetic resonance-based inter-residue distance measurements between site-directed spin-labelled sites of sensory rhodopsin II (NpSRII) and its transducer NpHtrII from Natronobacterium pharaonis revealed a 2:2 complex with 2-fold symmetry. The core of the complex is formed by the four transmembrane helices of a transducer dimer. Upon light excitation, the previously reported flap-like movement of helix F of NpSRII induces a conformational change in the transmembrane domain of the transducer. The inter-residue distance changes determined provide strong evidence for a rotary motion of the second transmembrane helix of the transducer. This helix rotation becomes uncoupled from changes in the receptor during the last step of the photocycle.

Understanding the role of the gas in the voids during corona charging of cellular electret films - a way to enhance their piezoelectricity

Abstract: The influence of the corona-charging process on the piezoelectric transducer coefficient d33 of a cellular electret film has been investigated. An increased corona voltage can be considered as a way to enhance the charge density and thus also the resulting piezoelectric effect. Higher corona-charging voltages are possible with increased ambient pressure or in suitable dielectric gases. The effect of the gas inside the voids has also been studied. Enhanced transducer coefficients were obtained by corona charging in N2 or N2O gas atmospheres at 100-450 or 100-140 kPa pressures, respectively. The highest transducer coefficients of about 790 pCN-1 were obtained when N2 gas was filled into the voids of a cellular polymer film by means of consecutive vacuum and high-pressure treatments at 295 or 313 K.

A freehand elastographic imaging approach for clinical breast imaging: system development and performance evaluation

Abstract: A prototype freehand elastographic imaging system has been developed for clinical breast imaging. The system consists of a fast data acquisition system, which is able to capture sequences of intermediate frequency echo frames at full frame rate from a commercial ultrasound scanner whilst the breast is deformed using hand-induced transducer motion. Two-dimensional echo tracking was used in combination with global distortion compensation and multi-compression averaging to minimise decorrelation noise incurred when stress is applied using hand-induced transducer motion. Experiments were conducted on gelatine phantoms to evaluate the quality of elastograms produced using the prototype system relative to those produced using mechanically induced transducer motion. The strain sensitivity and contrast-to-noise ratio of freehand elastograms compared favourably with elastograms produced using mechanically induced transducer motion. However, better dynamic range and signal-to-noise ratio was achieved when elastograms were created using mechanically induced transducer motion. Despite the loss in performance incurred when stress is applied using hand-induced transducer motion, it was concluded that the prototype system performed sufficiently well to warrant clinical evaluation.

Implementing guided wave mode control by use of a phased transducer array

Abstract: A multichannel time-delay system has been built and applied to a transducer array for implementing guided wave mode control. The time-delay system has a capability of sending high energy controllable tone-burst signals from eight independent channels with arbitrary time delays from 0 to 30 /spl mu/s with resolution of 0.025 /spl mu/s. Software time delays are also provided for summing up received signals of each channel. Theoretical discussions indicate the impact of the time delay capability on the bandwidth and sensitivity improvement of a transducer array for guided wave generation. Determination of both physical and software time delay values is based on a knowledge of dispersion curves and element spacing. Based on reference signals, a non-knowledge-based automatic time-delay searching algorithm was introduced for guided wave mode selection. Experiments were conducted with a phased comb transducer array mounted on a carbon steel pipe. The experimental results show that signal to noise ratio has been greatly improved by use of the time-delay system. Some other benefits of the phased array, including unidirection generation and mode control flexibility, are discussed.

Characterization of one-dimensional capacitive micromachined ultrasonic immersion transducer arrays

Abstract: We report on the characterization of 1D arrays of capacitive micromachined ultrasonic transducers (cMUT). A 275/spl times/5600 /spl mu/m 1D CMUT array element is experimentally characterized, and the results are found to be in agreement with theoretical predictions. As a receiver, the transducer has a 0.28-fm//spl radic/Hz displacement sensitivity, and, as a transmitter, it produces 5 kPa/V of output pressure at the transducer surface at 3 MHz with a DC bias of 35 V. The transducer has more than 100% fractional bandwidth around 3 MHz, which makes it suitable for ultrasound imaging. The radiation pattern of isolated single elements, as well as those of array elements are measured, and two major sources of acoustical crosstalk are identified. A weakly dispersive non-leaky interface wave (Stoneley wave) is observed to be propagating at the silicon substrate-fluid interface at a speed close to the speed of sound in the fluid. This wave causes internal reflections, spurious resonance, and radiation from the edges of the silicon substrate. The large lateral component of the particle velocity generated by the membranes at the edge of the cMUT array elements is found to be the source of this interface wave. Lowest order Lamb waves in the silicon substrate are also found to contribute to the crosstalk between elements. These waves are excited at the edges of individual vibrating membranes, where they are anchored to the substrate, and result in a narrowing of the beam profile of the array elements. Several methods, such as trench isolation and wafer thinning, are proposed and implemented to modify the acoustical cross coupling between array elements.

Self-writing of servo patterns in disk drives

Abstract: A method and system for self-servo writing a disk drive by transferring a servo reference pattern by magnetic printing onto at least one storage surface of a reference disk, wherein a resulting printed reference pattern includes embedded servo information providing servo timing and transducer head position information; assembling the disk drive including the steps of installing at least said disk into the disk drive and enclosing said disk and the data transducers within a housing sealed against particulate contamination from an eternal ambient environment; reading the printed reference pattern from said disk via at least one transducer head to generate a readback signal; sampling the readback signal at a sampling rate to generate a sampled signal; processing the sampled signal waveform specturm to generate a recovered signal including the embedded servo information and a fundamental frequency of the sampled signal; using the servo information from the recovered signal to precisely position and maintain the data transducers at concentric track locations of disk storage surfaces; and self-writing disk drive servo patterns onto the storage surfaces at the concentric track locations with the data transducers in accordance with disk drive servo pattern features.

Pressure Measurement Device

Abstract: A device measures pressures in animals and humans and includes a pressure transmission catheter (PTC) filled with a pressure transmitting medium and implantable in an area in having a physiological pressure. A transducer communicates with the pressure transmitting medium to provide a pressure signal representing variations in the physiologic pressure on electrical wires. A connecting catheter carries the electrical wires to signal processing and telemetry circuitry, which transmits a telemetry signal representing the pressure signal to a receiver external to the animal or human. A housing holds the signal processing and telemetry circuitry, but the transducer is remote from the housing. The device is particularly useful in measuring venous pressure, pulmonary pressure, bladder pressure, or intracranial pressure without significant head pressure artifact and with a sufficient dynamic response. One embodiment of the PTC includes a multi-durometer stem.

A High Power Ultrasonic Linear Motor Using a Longitudinal and Bending Hybrid Bolt-Clamped Langevin Type Transducer

Abstract: A hybrid transducer type ultrasonic linear motor using the 1st longitudinal and the 2nd bending vibration modes of a bolt-clamped Langevin type transducer has been proposed and studied for accomplishing high mechanical output The longitudinal vibration generates the mechanical driving force and the bending vibration controls the frictional force To obtain large vibration amplitude and large mechanical output, a method of tuning the longitudinal resonance frequency to the bending one was investigated using finite element simulations, and demonstrated experimentally To avoid magnetic interaction, we employed phosphor bronze for the bolt of the transducer The prototype motor achieved the no-load velocity of 047 m/s and the maximum output mechanical force of 92 N