Showing papers on "Transducer published in 2000"

Smart remote monitoring system and method

Abstract: A remote monitoring system includes transducers, a transducer control module, a communications device, a monitoring system and end-user display terminals. The transducers are disposed on the property and/or equipment in a manner to measure specific characteristics or parameters and communicate with the transducer control module via a wireless communication protocol. The transducer control module receives and analyzes transducer measurements and detects alarm conditions. The transducer control module communicates with the monitoring system via a wide area network and the communications device. The monitoring system receives, stores and analyzes information received from the transducer control module and reports the information to the end-user terminals via a wide area network, such as the Internet, in response to user requests.

Magnetic non-contacting rotary transducer

Abstract: A magnetic rotary transducer for providing a signal indicative of a rotational position of a control shaft about a rotational axis over a defined range of rotation is disclosed. The magnetic rotary transducer comprises a pair of magnets and a rotor including a pair of loop pole pieces, and an elongated pole piece having a first end adjoined to one of the loop pole pieces and a second end adjoined to the other loop pole piece. Each loop pole piece includes an inner surface defining an air gap area. The control shaft is positioned within the air gap area of one of the loop pole pieces and adjoined thereto whereby the rotor synchronously rotates with the control shaft about the axis over the defined range of rotation. The pair of magnets are adjoined to the other loop pole piece whereby two separate and distinct magnetic fields are generated within the air gap are of the loop pole piece. The magnetic rotary transducer further comprises a magnetic flux sensitive transducer positioned within the air gap area. The magnetic flux sensitive transducer is operable to provide a signal indicative of the rotational position of the control shaft.

Ultrasound transducers for imaging and therapy

Abstract: Ultrasound applicators able to both image a treatment site and administer ultrasound therapy include an array of transducer elements that can be focused. In several embodiments, an electronically phased array is used for controlling the focal point of an ultrasound beam. The ultrasound beam produced thereby can also be electronically steered. To reduce the quality factor or Q of the array when the array is used for imaging, an electronic switch is selectively closed, placing a resistance in parallel with each of the array elements. A flexible array is employed in several embodiments and is selectively bent or flexed to vary its radius of curvature and thus control the focal point and/or a direction of focus of the array. In another embodiment, each of the transducer elements comprising the array are individually mechanically pivotable to steer the ultrasonic beam produced by the transducer elements.

Intrabody hifu applicator

Abstract: This invention is an apparatus, and method for applying sonic energy within the body of the living subject. A probe for applying son is energy within the body of a subject comprises a probe body (20) having a proximal (22), and a distal end (24) adapted for insertion into the body of a subject, a spatially distributed sonic transducer (30) disposed adjacent to the distal end (24) of the probe body (20), and a device (50, 52) for moving one portion of the spatially distributed transducer (44) relative to another portion of the transducer (42) while the distal end of the probe (24) is disposed within the body of the subject.

Visual imaging system for ultrasonic probe

Abstract: A non-invasive visual imaging system is provided, wherein the imaging system procures an image of a transducer position during diagnostic or therapeutic treatment. In addition, the system suitably provides for the transducer to capture patient information, such as acoustic, temperature, or ultrasonic images. For example, an ultrasonic image captured by the transducer can be correlated, fused or otherwise combined with the corresponding positional transducer image, such that the corresponding images represent not only the location of the transducer with respect to the patient, but also the ultrasonic image of the region of interest being scanned. Further, a system is provided wherein the information relating to the transducer position on a single patient may be used to capture similar imaging planes on the same patient, or with subsequent patients. Moreover, the imaging information can be effectively utilized as a training tool for medical practitioners.

IEEE 1451: A standard in support of smart transducer networking

Abstract: The IEEE 1451 smart transducer interface standards provide the common interface and enabling technology for the connectivity of transducers to microprocessors, control and field networks, and data acquisition and instrumentation systems. The standardized TEDS specified by IEEE 1451.2 allows the self-description of sensors and the interfaces provide a standardized mechanism to facilitate the "Plug and play " of sensors to networks. The network-independent smart transducer object model defined by IEEE 1451.1 allows sensor manufacturers to support multiple networks and protocols. Thus, transducer-to-network interoperability is on the horizon. The inclusion of P1451.3 and P1451.4 to the family of 1451 standards will meet the needs of the analog transducer users for high-speed applications. In the long run, transducer vendors and users, system integrators, and network providers can all benefit from the IEEE 1451 interface standards.

Image reconstruction for photoacoustic scanning of tissue structures.

Abstract: Photoacoustic signal generation can be used for a new medical tomographic technique. This makes it possible to image optically different structures, such as the (micro)vascular system in tissues, by use of a transducer array for the detection of laser-generated wide-bandwidth ultrasound. A time-domain delay-and-sum focused beam-forming technique is used to locate the photoacoustic sources in the sample. To characterize the transducer response, simulations have been performed for a wide variety of parameter values and have been verified experimentally. With these data the weight factors for the spectrally and temporally filtered sensor signals are determined in order to optimize the signal-to-noise ratio of the beam former. The imaging algorithm is investigated by simulations and experiments. With this algorithm, for what is to our knowledge the first time, the three-dimensional photoacoustic imaging of complex optically absorbing structures located in a highly diffuse medium is demonstrated. When 200-mum-diameter hydrophone elements are used, the depth resolution is better than 20 mum, and the lateral resolution is better than 200 mum, independent of the depth for our range of imaging (to ~6 mm). Reduction of the transducer diameters and adaptation of the weight factors, at the cost of some increase of the noise level, will further improve the lateral resolution. The synthetic aperture algorithm used has been shown to be suitable for the new technique of photoacoustic tissue scanning.

Sonic element and catheter incorporating same

Abstract: A catheter carrying a radially-expansible ultrasonic transducer is threaded into the circulatory system and then the transducer is actuated to provide ultrasonic energy in a ring-like zone surrounding a blood vessel. Desirably, the transducer is arranged to focus the ultrasonic energy into a narrow, ring-like focal zone having an extent, in the axial direction along the catheter, less than the axial extent of the transducer. The transducer desirably is expanded after threading so that during application of the ultrasonic energy, the transducer bears on the interior wall of a blood vessel through a balloon covering the transducer. The transducer may include one or more resilient spiral elements carrying a flexible piezoelectric material.

Miniaturized ultrasound apparatus and method

Abstract: Ultrasound apparatus for examining tissue in a region of interest in a body comprising a housing having a viewing aperture An ultrasonic transducer is provided comprised of an array of ultrasonic elements disposed in the viewing aperture Electrical pulses are supplied to the transducer for transducer excitation to introduce ultrasonic signals into the body for reflection from the tissue in the region of interest The transducer is capable of converting ultrasonic signals reflected from the tissue within the body to the transducer to provide electrical signals The electrical signals are gain corrected in accordance with time In-phase and out-of-phase components of the electrical signals are provided and then digitized The digitized electrical signals are collected to form one image for a single frame of the tissue in the region of interest in the body from transducer excitations less than thirty-three in number which is then displayed

Low-cost accelerometer

Abstract: An apparatus is mounted to an object, and a signal from the apparatus is used to monitor the acceleration of the object. The apparatus includes a circuit board (802) which has beam-like section (710) with a distal end (812) which flexes in response to acceleration of the object. The apparatus also includes a multi-layer, piezoelectric capacitor as a transducer (404), which is supported by the beam (710), whereby the transducer (404) generates a signal responsive to the flexible of the beam (710). Also, a neutral axis passes through the beam (710) even if the transducer were removed.

Optoacoustic monitoring of blood oxygenation

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 close proximity to or in contact with a tissue site of an animal body. The probe further includes a plurality of optical fibers 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 transducer for detecting an acoustic response from blood in the tissue site to the radiation pulses connected to a processing unit which converts the transducer signal into a measure of venous blood oxygenation.

Design considerations for piezoelectric polymer ultrasound transducers

Abstract: Much work has been published on the design of ultrasound transducers using piezoelectric ceramics, but a great deal of this work does not apply when using the piezoelectric polymers because of their unique electrical and mechanical properties. The purpose of this paper is to review and present new insight into seven important considerations for the design of active piezoelectric polymer ultrasound transducers: piezoelectric polymer materials selection, transducer construction and packaging requirements, materials characterization and modeling, film thickness and active area design, electroding selection, backing material design, and front protection/matching layer design. Besides reviewing these design considerations, this paper also presents new insight into the design of active piezoelectric polymer ultrasonic transducers. The design and fabrication of an immersible ultrasonic transducer, which has no adhesive layer between the active element and backing layer, is included. The transducer features direct deposition of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer onto an insulated aluminum backing substrate. Pulse-echo tests indicated a minimum insertion loss of 37 dB and -6 dB bandwidth of 9.8 to 22 MHz (71%). The use of polymer wear-protection/quarter-wave matching layers is also discussed. Test results on a P(VDF-TrFE) transducer showed that a Mylar/sup TM/ front layer provided a slight increase in pulse-echo amplitude of 15% (or 1.2 dB) and an increase in -6 dB pulse-echo fractional bandwidth from 86 to 95%. Theoretical derivations are reported for optimizing the active area of the piezoelectric polymer element for maximum power transfer at resonance. These derivations are extended to the special case for a low profile (i.e., thin) shielded transducer. A method for modeling the non-linear loading effects of a commercial pulser-receiver is also included.

Implantable cochlear stimulator system incorporating combination electrode/transducer

Abstract: A hearing aid system provides acoustic modulation of the fluid within the cochlea of the inner ear corresponding to a first frequency range of sensed acoustic signals, e.g., lower-to-middle frequencies of the audible range, and electrical stimulation of the cochlea corresponding to a second frequency range, e.g., high frequencies of the audible range. In a preferred implementation, a short electrode/transducer array is provided for use with the hearing system. Such array is adapted to be inserted into the basal region of the scala tympani of the cochlea. The electrode/transducer array includes a plurality of spaced-apart electrode contacts through which electrical stimulation is provided to stimulate ganglion cells located in the basal region of the cochlea, which cells are responsible for perceiving the higher frequencies of the acoustic energy. The electrode/transducer further includes an acoustic modulator as an integral part thereof, in fluid communication with an acoustic transducer, through which acoustic modulation may be coupled to the fluid within the cochlea, thereby allowing normal hearing processes to occur in the cochlea. In the preferred implementation, the lower frequencies of sensed acoustic energy are processed to provide modulation of the acoustic modulator. An implantable cochlear stimulator (ICS), including the acoustic transducer and coil, and implantable speech processor (ISP), including an implantable microphone, are used with the system. In an alternative embodiment, the acoustic modulator within the electrode/transducer array is used as a sensor, to sense fluid modulation within the cochlea resulting from a functioning middle ear, and the acoustic transducer converts such sensed fluid modulation to electrical signals, thereby providing the function of an microphone implanted in the cochlea.

System and method for assessing body-tissue properties using a medical ultrasound transducer probe with a body-tissue parameter measurement mechanism

Abstract: A system and method for diagnostic ultrasound imaging with a probe combining one or more ultrasound imaging transducer elements and a body-tissue parameter measurement mechanism to detect body-tissue properties. At least one ultrasound transducer element provides an ultrasound image field of view of at least a portion of the body-tissue being measured by the parameter measurement mechanism. The parameter measurement mechanism is typically a mechanically or electrically operated mechanism attached to the probe near at least one ultrasound transducer element in order to combine information from the body-tissue parameter measurement mechanism and ultrasound transducer element for easier identification of abnormal body-tissue properties (e.g., tumors, dead, or diseased body-tissue).

Backward mode detection of laser-induced wide-band ultrasonic transients with optoacoustic transducer

Abstract: Time-resolved piezoelectric detection of wide-band ultrasonic transients induced by laser pulses in absorbing medium was studied. An optoacoustic transducer was developed for measuring the profiles of ultrasonic transients propagating in backward direction out of the laser-irradiated medium. For this purpose, an optical fiber for delivery of laser pulses to the surface of absorbing medium and a wide-band lithium niobate acoustic transducer were incorporated in one compact system, optoacoustic front surface transducer (OAFST). The transducer possesses temporal resolution (rise time) of 3.5 ns, low effective thermal noise pressure (10 Pa), and high sensitivity of piezoelectric detection (10 μV/Pa) over the ultrasonic frequency range from 1 to 100 MHz. Nd:YAG laser pulses at 355 nm were employed to generate distribution of acoustic sources in water solutions of potassium chromate with various concentrations. A temporal course of ultrasonic transients launched into an optically and acoustically transparent me...

The rapid monitoring of structures using interdigital Lamb wave transducers

Abstract: The use of interdigital PVDF transducers for the quick inspection of large, plate-like structures is discussed. The transducers are designed to excite a particular Lamb mode in the structure, the region of the structure that is insonified being controlled by the transducer design. An example is given of the monitoring of an aluminium plate by a single, circular transducer operating in pulse-echo mode, the a0 Lamb mode at a frequency of about 1 MHz being transmitted and received. The transducer is split into segments so that the angular location of a reflector can be defined, the radial location of the reflector being determined from the time of arrival of the echo.

Investigation of a large-area phased array for focused ultrasound surgery through the skull.

Abstract: Non-invasive treatment of brain disorders using ultrasound would require a transducer array that can propagate ultrasound through the skull and still produce sufficient acoustic pressure at a specific location within the brain. Additionally, the array must not cause excessive heating near the skull or in other regions of the brain. A hemisphere-shaped transducer is proposed which disperses the ultrasound over a large region of the skull. The large surface area covered allows maximum ultrasound gain while minimizing undesired heating. To test the feasibility of the transducer two virtual arrays are simulated by superposition of multiple measurements from an 11-element and a 40-element spherically concave test array. Each array is focused through an ex vivo human skull at four separate locations around the skull surface. The resultant ultrasound field is calculated by combining measurements taken with a polyvinylidene difluoride needle hydrophone providing the fields from a 44-element and a 160-element virtual array covering 88% and 33% of a hemisphere respectively. Measurements are repeated after the phase of each array element is adjusted to maximize the constructive interference at the transducer's geometric focus. An investigation of mechanical and electronic beam steering through the skull is also performed with the 160-element virtual array, phasing it such that the focus of the transducer is located 14 mm from the geometric centre. Results indicate the feasibility of focusing and beam steering through the skull using an array spread over a large surface area. Further, it is demonstrated that beam steering through the skull is plausible.

Submicron track-width pole-tips for electromagnetic transducers

Abstract: A trailing pole-tip for an electromagnetic transducer is formed as a layer oriented substantially perpendicular to other layers of the transducer, allowing the pole-tip to be made much thinner than conventional pole-tips. The novel pole-tip is formed on an edge or sidewall of a base layer instead of being formed on top of an existing layer. Potential errors in pole-tip thickness are much less than standard error tolerances for conventional pole-tip thickness. Having a greatly reduced pole-tip width significantly reduces the track width so that many more tracks can fit on a media surface, providing a large increase in areal density.

Method and apparatus for analyzing cells in a whole blood sample

Abstract: A blood analyzing instrument comprises a single transducer for simultaneously measuring the DC volume, RF conductivity, light scattering and fluorescence characteristics of blood cells passing through a cell-interrogation zone. Preferably, the transducer comprises an electro-optical flow cell which defines a cell-interrogation zone having a square transverse cross-section measuring approximately 50 x 50 microns, and having a length, measured in the direction of cell flow, of approximately 65 microns.

Ultrasound diagnostic device

Abstract: An ultrasound diagnostic device is provided which is portable, small, light weight and easy to use. Preferably, the ultrasound diagnostic device is very small and light weight. The weight of the ultrasound diagnostic device normally will be approximately 6 or 7 pounds, including electrical control circuitry, a battery pack, a carrying strap and a transducer assembly. The ultrasound diagnostic device is similar in design to a laptop computer, except that it is smaller than typical laptop computers. The ultrasound diagnostic device comprises a console portion and a display portion. To open the device, the user simply flips open the display portion by lifting up on the display portion at a location near the front end of the device. The display portion is in a hinging relationship with the console portion so that when the user lifts up on display portion, the display portion is rotated upwards and away from the console portion. A transducer assembly is attached to the ultrasound diagnostic device and comprises a transducer cable, a transducer handle, a transducer and a transducer connector. The transducer connector comprises a latch which engages a mating mechanism comprised in a receptacle formed in the console portion. The connector enables different types of transducer assemblies to be implemented with the ultrasound diagnostic device, depending on the bodily feature being imaged. The ultrasound diagnostic device may be adapted to be harnessed with a carrying apparatus, e.g., a strap assembly, which enables the user to carry the device in a manner similar to the manner in which a person carries a camera around his or her neck. The user may operate the device when it is strapped to the user's body. The ultrasound device may include a handle to facilitate hand carriability.

Extravascular hemodynamic acoustic sensor

Abstract: An implantable medical device such as a pacemaker or implantable cardioverter defibrillator or stand-alone hemodynamic monitor that uses an acoustic transducer responsive to heart sounds to detect the hemodynamic status of a patient. A hermetic housing encloses the device electronics and the device housing includes at least one substantially planar face configured to act as a diaphragm in response to acoustic waves. A transducer positioned inside the device housing provides an output signal to the device electronics responsive to vibration of the diaphragm. Embodiments of the transducer include a piezoelectric element and laser interferometer. The hemodynamic information may be used in various ways including arrhythmia discrimination and pacing and sensing optimization.

A cylindrical shaped micro ultrasonic motor utilizing PZT thin film (1.4 mm in diameter and 5.0 mm long stator transducer)

Abstract: A cylindrical micro ultrasonic motor utilizing PZT thin film was fabricated and successfully operated on. The dimensions of a stator transducer were 1.4 mm in outer diameter, 1.2 mm in inner diameter, and 5.0 mm in length. This volume is 17% compared to our previous motor (2.4 mm in diameter and 10 mm long stator transducer). To deposit a PZT thin film, a hydrothermal method was adopted. In this study, we developed an “improved nucleation process”, and succeeded in improving the performance of the deposited PZT thin film. The thickness of a PZT thin film was 12 μm, and the d31 factor was −25 pC/N. The resonance frequency of the stator transducer was 227 kHz and the vibration amplitude was 58 nmp–p at 4.0 Vp–p driving voltage. The rotor was driven by frictional force and the revolving direction was reversible. The maximum revolution speed was 680 rpm and the maximum torque was 0.67 μN m. The experimental conditions were 20 Vp–p and 5.3 mN pre-load. These results were investigated using an equivalent circuit from the point of a scale law. The performances of smaller ultrasonic motors were discussed. The output torque of the motor with 0.1 mm diameter was estimated at 27 nN m.

Two mechanisms for transducer adaptation in vertebrate hair cells

Abstract: Deflection of the hair bundle atop a sensory hair cell modulates the open probability of mechanosensitive ion channels. In response to sustained deflections, hair cells adapt. Two fundamentally distinct models have been proposed to explain transducer adaptation. Both models support the notion that channel open probability is modulated by calcium that enters via the transduction channels. Both also suggest that the primary effect of adaptation is to shift the deflection-response [I(X)] relationship in the direction of the applied stimulus, thus maintaining hair bundle sensitivity. The models differ in several respects. They operate on different time scales: the faster on the order of a few milliseconds or less and the slower on the order of 10 ms or more. The model proposed to explain fast adaptation suggests that calcium enters and binds at or near the transduction channels to stabilize a closed conformation. The model proposed to explain the slower adaptation suggests that adaptation is mediated by an active, force-generating process that regulates the effective stimulus applied to the transduction channels. Here we discuss the evidence in support of each model and consider the possibility that both may function to varying degrees in hair cells of different species and sensory organs.

Application-specific sensor systems based on CMOS chemical microsensors

Abstract: We report on results achieved with three different types of polymer-coated chemical microsensors fabricated in industrial CMOS technology followed by post-CMOS anisotropic etching and film deposition. The first and most extensively studied transducer is a microcapacitor sensitive to changes in dielectric properties of the polymer layer upon analyte absorption. An on-chip integrated ΣΔ-converter allows for detecting the minute capacitance changes. The second transducer is a resonant cantilever sensitive to predominantly mass changes. The cantilever is electrothermally excited; its vibrations are detected using a piezoresistive Wheatstone bridge. In analogy to acoustic wave devices, analyte absorption in the polymer causes resonance frequency shifts as a consequence of changes in the oscillating mass. The last transducer is a microcalorimeter consisting of a polymer-coated sensing thermopile and an uncoated reference thermopile each on micromachined membranes. The measurand is the absorption or desorption heat of organic volatiles in the polymer layer. The difference between the resulting thermovoltages is processed with an on-chip low-noise differential amplifier. Gas test measurements with all three transducer principles will be presented. The goal is to combine the three different transducer principles and vary the polymers in an array type structure to build a new generation of application-specific microsensor systems.

Apparatus and methods for cleaning and/or processing delicate parts

Abstract: The invention utilizes harmonics of certain clamped ultrasound transducers to generate ultrasound within the liquid of an ultrasonic tank and in a frequency range of between about 100 khz to 350 khz (i.e., “microsonic” frequencies). The application of microsonic frequencies to liquid preferably occurs simultaneously with a sweeping of the microsonic frequency within the transducer's harmonic bandwidth to reduce or eliminate (a) standing waves within the liquid, (b) other resonances, (c) high energy cavitation implosion, and (d) non-uniform sound fields, each of which is undesirable for cleaning and/or processing of semiconductor wafers and other delicate parts. The invention can also drive ultrasonic transducers such that the frequency of applied energy has a sweep rate within the ultrasonic bandwidth of the transducers; and that sweep rate is also varied so that the sweep rate is substantially non-constant during operation. This reduces or eliminates resonances which are created by transducers operating with a single sweep rate. An ultrasound generator of the invention sometimes utilizes amplitude modulation (AM), and the AM frequency is swept over time so as to reduce resonances. AM control is preferably provided by selecting a portion of the rectified power line frequency. In applications which utilize multiple generators, multiple transducers, and one or more tanks, simultaneously, the invention synchronizes the operation of the generators to a common FM signal to reduce beat frequencies between generators. Each such generator can also be adjusted, through AM, to control the process characteristics within the associated tank. Two or more transducers are sometimes used by the invention, in combination, to broaden the overall bandwidth of acoustical energy applied to the liquid around the primary frequency or one of the harmonics. The bandwidths of the transducers are made to overlap such that an attached generator can drive the transducers, in combination, to deliver ultrasound to the liquid in a broader bandwidth. In a single chamber ultrasound system, two or more generators, each operating or optimized to generate a different range of frequencies, are connected to a multiplexer; and the desired frequency range is selected, and hence the right generator, according to the cavitation implosion energy that is desired within the tank chemistry.

System and methods for controlling distribution of acoustic energy around a focal point using a focused ultrasound system

Abstract: A focused ultrasound system includes a plurality of transducer elements disposed about and having an angular position with a central axis. Drive signals drive respective transducer elements that include phase shift values based upon the angular position of each respective transducer element. The phase shift values are based upon an oscillation function that oscillates about the central axis between minimal and maximal phase shift values such that a first on-axis focal zone and a second off-axis focal zone are created. An amplitude and frequency of the oscillation function are controlled to adjust relative acoustic energy levels of the first and second focal zones, and to adjust a radius of the second focal zone, respectively. In addition, the drive signals include an additional predetermined phase shift based upon a radial position of each respective transducer element to adjust a focal distance of the focal zones.

Implantable acoustic bio-sensing system and method

Abstract: An implantable biosensor system for monitoring and optionally alleviating a physiological condition in a patient is provided and includes (a) at least one sensor for sensing at least one parameter of a physiological condition and for generating electrical sensor signals representative of the physiological condition; and (b) a first acoustic activatable transducer being directly or indirectly coupled with the at least one sensor, the first acoustic activatable transducer being for converting a received acoustic interrogation signal from outside the patient's body into an electrical power for energizing the processor, the first acoustic activatable transducer further being for converting the electrical sensor signals of the at least one sensor into acoustic signals receivable out of the patient's body, such that information pertaining to the at least one parameter of the physiological condition can be relayed outside the patient's body upon generation of an acoustic interrogation signal.

Method and apparatus for the noninvasive determination of arterial blood pressure

Abstract: A method and apparatus for determining the mean arterial blood pressure (MAP) of a subject during tonometric conditions. In one embodiment, the apparatus comprises one or more pressure and ultrasound transducers placed over the radial artery of a human subject's wrist, the latter transmitting and receiving acoustic energy so as to permit the measurement of blood velocity during periods of variable compression of the artery. During compression, the ultrasound velocity waveforms are recorded and processed using time-frequency analysis. The time at which the mean time-frequency distribution is maximal corresponds to the time at which the transmural pressure equals zero, and the mean pressure read by the transducer equals the mean pressure within the artery. In another aspect of the invention, the ultrasound transducer is used to position the transducer over the artery such that the accuracy of the measurement is maximized. In yet another aspect of the invention, a wrist brace useful for measuring blood pressure using the aforementioned apparatus is disclosed.