Abstract: A method of monitoring heat damage to a tissue during a heat ablation procedure is disclosed. The method comprising: providing images of the tissue, extracting at least one parameter being indicative of a biological response to heat, and using the parameter(s) for determining the heat damage to the tissue.

Abstract: An embodiment of a method of predicting maternal hypertension during pregnancy is disclosed. The method may include measuring a maternal blood velocity waveform and measuring a fetal blood velocity waveform. The method may further include the calculation of a coherence value using a magnitude-squared coherence function between the maternal and fetal blood velocity waveforms and comparing the coherence value to a predetermined threshold value.

Abstract: There is disclosed an ultrasound system for providing a color flow image. The system may include: a signal acquisition unit to obtain an ultrasound image signal of an object and a Doppler signal in a color box on said object, wherein said color box is set by a user; an input unit to receive color box setting information and region of interest (ROI) setting information; a processor to form a B-mode (Brightness-mode) image signal and a color flow image signal based on said ultrasound image signal and said Doppler signal, and form blood flow image information corresponding to said set ROI; and an output unit to display a B-mode image and a color flow image based on said B-mode image signal and said color flow image signal, and display said formed blood flow image information.

Abstract: A system including an implantable neurostimulator device capable of modulating cerebral blood flow to treat epilepsy and other neurological disorders. In one embodiment, the system is capable of modulating cerebral blood flow (also referred to as cerebral perfusion) in response to measurements and other observed conditions. Perfusion may be increased or decreased by systems and methods according to the invention as clinically required.

Abstract: The invention relates to a facility that can be used, in particular, to measure the flow conditions in a blood vessel. The facility comprises a catheter (16) having a bundle (15) of optical waveguides that connects control and measurement facilities (20) outside the body with an optical unit (10) at the catheter tip. The light (?K) generated by a cavitation light laser source (30) is beamed via the catheter (16) and the optical unit (10) into a focus region (2) in the vessel lumen, where it generates cavitation bubbles (3). The movement of the cavitation bubbles (3) with the blood flow is determined by the particle-measuring unit (20) that is based, for example, on phase-Doppler anemometry and/or the Doppler shift. As a result of suitable design of the optical unit (10), the focus region (2) can be displaced as desired radially and rotationally inside the vessel so that a vessel cross section can be scanned in a spatially resolved way.

Abstract: An ultrasound system is provided comprising an ultrasound probe having a 2D matrix of transducer elements transmitting a continuous wave (CW) Doppler transmit signal into an object of interest. The CW transmit signal includes a dither signal component and the probe receives ultrasound echo signals from the object in response to the CW transmit signal. The probe generates an analog CW receive signal based on the ultrasound echo signals. An analog to digital (A/D) converter converts the analog CW receive signal to a digital CW receive signal at a predetermined sampling frequency and a processor processes the digital CW receive signal in connection with CW Doppler imaging.

Abstract: The present invention is for an ultrasonic Doppler blood flow measurement device with which high-speed computation is possible, even when a memory having the characteristic of different read/write speeds in the row direction and the column direction is used for the buffer memory when computing blood flow information, without being affected by the slower read/write speed.

Abstract: An ultrasonic diagnostic imaging system produces a spectral Doppler display on which a parameter such as peak or mean velocity is automatically traced. If the user is dissatisfied with the automatically drawn trace (30), the user can manipulate a cursor (88) on the display screen to grab a point (82, 86) on the trace and drag the trace to a new location relative to the spectral display or manually redraw a portion of the trace. In an illustrated embodiment the spectral Doppler trace (80) includes defined key timing points in the heart cycle which can be adjusted by the user in both the velocity and time dimensions of the display. Graphically displayed values and calculations of the display are automatically updated in response to adjustment of the trace.

Abstract: A device for generation of a triggering signal (8) for synchronized acquisition of heart images in nuclear medicine, cardiology and radiology, comprising a detector connected to a circuit (6) of signal correction and an evaluation circuit (3). The detector includes a detector of physiological signals of arteries.

Abstract: An ultrasonic Doppler diagnostic apparatus sends ultrasonic waves to a specimen, receives a reflection signal of the ultrasonic waves from the specimen to detect a Doppler signal, obtains blood flow information indicating a peak flow velocity of coronary blood flow, and displays the flow velocity information before and after the administration of a drug to the specimen on a display unit. Then, at least velocity ranges of the flow velocity information before and after the administration of the drug to the specimen are adjusted, and during an ultrasonic scan of the specimen, data on a plurality of acquired images having different velocity ranges are adjusted to the same velocity range. A system control unit displays the data on the plurality of images adjusted to the same velocity range on the display unit.

Abstract: Disclosed are a vascular disease examination system capable of examining and diagnosing vascular diseases such as arterial obliteration by determining the feature quantities of blood flow velocity waveforms or blood pressure waveforms or blood flow rates, and a bypass vascular diagnosing system. A blood flow velocity or blood pressure at a target location of the body is measured A waveform analysis unit 4 determines the feature quantity of a blood flow waveform (or blood pressure waveform), for displaying on an output unit 5. The feature quantity includes a time constant, Fourier transform value, differentiated value, integrated value, rise/fall time, and sharpness or gradient of rise. Feature quantity of a blood flow velocity waveform (or blood pressure waveform) indicated in numeric value enables a correct examination/diagnosis.

Abstract: An ultrasonic diagnostic apparatus has a scanning executing unit, a Doppler signal obtaining unit, a storage unit, a removing unit, a blood flow information obtaining unit, and a B-mode image generating unit. The scanning executing unit executes a first scanning that is iteratively performed by a predetermined period so as to obtain a B-mode image of an object and executes a second scanning that is iteratively performed a predetermined number of times by a first period between the first scanning so as to obtain a two-dimensional distribution of a blood flow information and that is iteratively performed by a second period while inserting the first scanning. The Doppler signal obtaining unit sequentially obtains a Doppler signal from a reflection signal obtained by the second scanning. The storage unit stores, for each raster direction, a Doppler signal string at unequal time intervals collected for the first period and the second period by the Doppler signal obtaining unit.

Abstract: Blood-flow image display equipment for displaying a CFM image that is not affected by a motion of a tissue in an object area during capturing of images or is affected in a reduced manner.

Abstract: A new method is introduced to evaluate the flow through a constriction based on Doppler data and the principle of mass conservation. This principle, properly inserted within a combination of data rearrangements allows the extraction of the complete velocity field and the optimal evaluation of the flow through the constriction. The digital implementation of the method into electronic equipments, like an echographic machine, gives an additional capability of quantifying specific valvular flows and improves diagnostic potential.

Abstract: Ultrasonic acoustic imaging finds many uses, particularly in the field of non-invasive medical testing. Detection of Doppler shifted acoustic frequencies permits observation of flow of a particle-containing liquid, for example, blood flow. In order to see slower moving blood by Doppler ultrasound investigation, as the blood moves from major blood vessels into arterioles and capillaries, it is necessary to lower the pulse repetition frequency. The herein disclosed invention is an interleaving technique that lowers the effective pulse repetition frequency at each probe position without exacting these system penalties.

Abstract: A medical ultrasound viewing system for processing a sequence of three-dimensional (3-D) ultrasound images far performing a quantitative estimation of a flow through a body organ comprising means for performing steps of acquiring a sequence of 3D color flow images, of said flow; assessing the flow velocity values in the 3D images, constructing isovelocity surfaces (6) by segmentation of the flow velocity values; computing the volume (Vol) delimited by the isovelocity surfaces; and using the flow velocity value (V) and the volume (Vol) computed from a segmented surface for computing the surface of an orifice (3) of the organ through which the flow propagates.

Abstract: A method and a device are provided for examining the properties of the global, in particular the primary, hemostasis functions in whole blood or platelet-rich plasma. A volumetric blood flow is preferably adjusted, depending on the measured pressure of the volumetric flow, so that the shear rate or the shear force, whose action in the reaction opening causes blood components, in particular thrombocytes, to deposit, follows a predetermined characteristic curve and in particular is held constant.

Abstract: The present invention is directed to an ultrasound imaging system and method for Doppler processing of data. The ultrasonic imaging system efficiently addresses the data computational and processing needs of Doppler processing. Software executable sequences in accordance with a preferred embodiment of the present invention determines the phase shift and the auto-correlation phase of filtered image data. In a preferred embodiment, the system of ultrasonic imaging also includes a sequence of instructions for Doppler processing that provides the functions for demodulation, Gauss Match filtering, auto-correlation calculation, phase shift calculation, frame averaging, and scan conversion implemented with Single Instruction Multiple Data (SIMD) or Multiple Instruction Multiple Data (MIMD) instructions.

Abstract: The invention relates to a method of forming a very accurate vascular map or road map to be associated with the current X-ray image during an invasive vascular intervention. The vascular map is derived from a four-dimensional model of the vascular tree, that is, from a spatially three-dimensional, time-dependent model, the time dependency relating to natural motions of the body such as notably the heartbeat and/or the respiration. In particular the rhythm of the heartbeat or the respiration can be determined by means of a sensor so as to be used for synchronized selection and display of the corresponding three-dimensional vascular model.

Abstract: A repairing procedure for treating Superficial and/or Perforant Venous Insufficiency of the lower limbs, by means of the application of Clips, Stoppers and/or Artificial Valves. The procedure consists of the strategic and specific closure of different reflux levels in the internal and/or external saphenous veins and perforants veins, in an extravascular way by means of the use of titanium clips, or in endovascular way by means of the use of stoppers or artificial valves. In the case of using Artificial Valves the vascular function is reestablished.

Abstract: An implantable blood flow monitoring system for providing synchronized blood vessel flow and myocardial wall contractility data to an external monitor independent of transcutaneous leads. Synchronized electrocardiogram data allows and provides comprehensive monitoring. A means is provided for transmitting synchronized cardiac function data and blood flow data to a distant remote location to facilitate continual physician monitoring.

Abstract: Methods, apparatuses, media and signals for evaluating a vessel. One method includes receiving at least one measurement of a physical dimension of the vessel, and producing an indication of abnormality in the vessel, in response to the at least one received measurement and at least one population-based parameter for the vessel. Producing may include producing an indication of stenosis of the vessel, in response to the physical dimension measurement and a population-based reference dimension for the vessel. This may include producing a population-based percent stenosis value in response to a ratio of the physical dimension measurement to the population-based reference dimension. Producing may further include identifying a shape characteristic of the vessel, which may include producing a tapering comparison value in response to the tapering of the vessel and a population-based average tapering value. The vessel may include a coronary artery segment, for example.

Abstract: A blood rheology measuring apparatus has a measuring portion for measuring blood circulation information inside of a living body from outside of the living body. The blood circulation information is a maximum blood flow velocity for one pulse. An information processing portion processes the measured information from the measuring portion to obtain information concerning a blood rheology of the living body.

Abstract: Disclosed is a velocity estimator using a level crossing rate. The velocity estimator comprises a power calculator for calculating power values of a signal received from a mobile terminal; a mean power calculator for calculating mean power values for M power values according to a predetermined down-sampling factor M; an interpolator for interpolating the mean power values according to a predetermined interpolation ratio L; a root mean square calculator for calculating a root mean square value using an output of the interpolator; a level crossing counter for counting a level crossing frequency representing how many times the output of the interpolator crosses a level crossing threshold determined according to the root mean square value, for a predetermined time period; and a velocity calculator for calculating a velocity estimation value of the mobile terminal using the level crossing frequency.

Abstract: The invention relates to systems and methods for assessing blood flow in single or multiple vessels and segments, for assessing vascular health, for conducting clinical trials, for screening therapeutic interventions for effect, for assessing risk factors, for evaluating intracranial pressure and for analyzing the results in a defined manner. The invention enables direct monitoring of therapies, substances and devices on blood vessels, especially those of the cerebral vasculature. Relevant blood flow parameters include mean flow velocity, systolic acceleration, and pulsatility index. Measurement and analysis of these parameters, and others, provides details regarding the vascular health of individual and multiple vessels and a global analysis of an individual's overall vascular health.

Abstract: A method and associated apparatus are disclosed for determining the location of an effective center of fluid flow in a vessel using an ultrasound apparatus. Ultrasound energy is propagated along an axis of propagation and projects upon the vessel. A Doppler-shifted signal reflected from the fluid in the vessel is received and a set of quantities expressed as a density is derived from the Doppler shifted signal for each of a set of coordinates, the density being a function of the Doppler shift in frequency associated with each of the coordinates. One of a mean, mode or median is calculated for each of the dimensions of the set of coordinates in conjunction with the density associated therewith. This calculation is repeated throughout the field of view of the vessel to define a centerline.

Abstract: An ultrasonic diagnosis apparatus comprises an ultrasound probe, a transmitter (including a transmitting pulse generator and a transmitting beamformer), a receiver (including a preamplifier and a receiving beamformer), a CFM processor (including a moving-element signal extractor and a velocity corrector), a tomographic image processor, and a display unit. The apparatus scans a desired section of a subject by transmitting and receiving an ultrasound pulse to and from the subject, and displays images obtained by the scanning. The velocity corrector comprises a pulsation-characterizing-velocity (velocities of a moving element) calculator, a representative velocity (reference velocity) calculator, and a corrector to correct the velocities of the moving element based on the standard velocity. The corrected velocity data is visualized on display unit. The ultrasonic diagnosis apparatus makes it possible to display the pulsatility of blood vessels in an easier and useful way.

Abstract: A medical diagnostic method, system and related equipment particularly adapted to diagnose disorders of the blood circulation serving the head and neck, and especially the brain. A preferred use of the system is early, rapid, accurate, diagnosis of stroke, especially whether the stroke is due to blockage of a blood vessel or leakage from the blood vessel.

Abstract: The present invention relates generally to systems and methods for assessing blood flow in blood vessels, for assessing vascular health, for conducting clinical trials, for screening therapeutic interventions for adverse effects, and for assessing the effects of risk factors, therapies and substances, including therapeutic substances, on blood vessels, especially cerebral blood vessels, all achieved by measuring various parameters of blood flow in one or more vessels and analyzing the results in a defined matter. The relevant parameters of blood flow include mean flow velocity, systolic acceleration, and pulsatility index. By measuring and analyzing these parameters, one can ascertain the vascular health of a particular vessel, multiple vessels and an individual. Such measurements can also determine whether a substance has an effect, either deleterious or advantageous, on vascular health. In one of many embodiments, the present invention further provides an expert system for achieving the above.

Abstract: A tracking system for stone treatment by extracorporeal shock wave lithotripsy includes a data processing unit, a motion controller, a servo-moving platform, a stone image-processing module, a stone localization module, and a moving-mechanism control module. With the use of the stone-tracking system, the performance of an extracorporeal shock wave lithotriptor can be greatly improved, resulting in less side effect such as tissue damage.

Abstract: Methodology for determining the bounds of a patient's acoustic window is described. Medical application acoustic array designs with apertures accommodated by patient acoustic windows and merged acoustic windows are exemplified.

Abstract: A volume dataset describes at least one tubular vessel and its environment. For processing the volume dataset, an operating point is first defined. A computer then determines slice planes containing the operating point and a sectional area enclosed by the vessel and contained in the respective slice plane for each of the slice planes. Finally, the computer determines the slice plane with the minimum sectional area and determines a working slice plane on the basis of this slice plane.

Abstract: The present invention relates to a method and associated apparatus for improving the accuracy with which the speed of a fluid, such as a liquid, in particular blood flowing in a duct, such as a blood vessel, in particular the aorta, is measured by means of a signal emitted by a Doppler transducer (4). In characteristic manner, according to the method, the Doppler transducer is associated with a programmable memory (50) which contains at least one correction data item for correcting the Doppler signal transmitted by the transducer (4) to a transducer control and computer unit (8). Said computer unit (8) incorporates said signal correction data item in its computation (at 16) of each speed measurement on the basis of each signal emitted by the Doppler transducer, and it computes the speed value while taking account of said correction data item so as to provide a corrected measurement of the speed of said fluid, thereby improving its accuracy.

Abstract: A stent graft includes a tubular prosthetic graft, a support structure expandable between contracted and enlarged conditions, and a biosensor attached thereto. The biosensor may be directly attached to an outer surface of the graft, to struts defining the support structure, or by one or more filaments configured to dispose the biosensor beyond an outer surface of the stent graft. When the biosensor is attached by one or more filaments, the stent graft is mounted in a contracted profile on a delivery apparatus with the biosensor disposed adjacent to the stent graft thereon. The stent graft is introduced into a blood vessel in the contracted profile, and advanced endolumenally until it is positioned across an aneurysm.

Abstract: The present invention is directed toward an ultrasonography apparatus for measuring and/or monitoring hemodynamic activity, such as blood flow. The present invention comprises a doppler ultrasound unit, one or more transducers, and a portable body.

Abstract: Methods, systems and devices are provided for monitoring and quantifying the movement of fluid in a target region. Generally, an imaging agent is introduced into a target region through fluid flow. The imaging agent in the target region is then disrupted using appropriate methods such as the application of ultrasonic energy. As fluid flow brings undisrupted imaging agent into the target region, the rate of accumulation is monitored and quantified thereby providing the exchange rate and flow rate of the fluid in the target region. The disclosed invention is particularly useful for medical applications such as determining the flow rate of blood in an organ or tissue.

Abstract: A method and apparatus for displaying reference background and flow ultrasound images. The method comprises: transmitting at least first and second broadband pulses to a common transmit focal position; receiving at least first and second ultrasound reflections associated with the at least first and second broadband pulses; forming a flow/contrast agent signal component based on the at least first and second ultrasound reflections; forming a B-mode background signal component based on independent processing of at least one of the at least first and second ultrasound reflections; and displaying an ultrasound image including a flow image component in a first image portion of a display and a B-mode reference image component based on at least one of the at least first and second ultrasound reflections, said B-mode reference image component displayed in a second image portion of said display.

Abstract: Systems and methods are described for the manufacture and use of a dual-purpose array for ultrasound imaging. In one configuration, the array is useful as an array for normal imaging. This array can be designed as a 1.x-D (1.0, 1.25, 1.5, 1.75, etc.) array. In another configuration, the array is useful as a square annular array. While the principle architecture envisioned is a square ring, a rectangular ring or other approximation to a circular ring can be used when more rows and more complicated interconnects are used. In particular, when two annular arrays of different geometry are enabled, the attenuation compensated volume flow meter (ACVF) uniform method for measuring volume flow rate can be applied at desired time in a cardiac cycle. The systems and methods provide advantages because the array may be used for normal imaging in other applications, and still enable volume flow rate measurements.

Abstract: A guiding catheter includes a Doppler sensor disposed at a distal end of a flexible shaft. The Doppler sensor can sense a blood flow turbulence level within a chamber of the heart or a blood vessel of the heart. Detecting changes in a blood flow turbulence level is used to assist guiding of the distal end of the flexible shaft. The Doppler sensor may include a piezoelectric sensor or an optical sensor. The sensor readings may be processed to show turbulence through a time domain or frequency domain presentation of velocity. The sensor readings can be used to modulate an audible waveform to indicate turbulence. The guiding catheter may further include steering apparatus enabling deflection of the distal tip.

Abstract: Ultrasound Doppler probe 2 is placed above the vein downstream of the infusion site. Processor 4 converts the output from the probe 2 into a form that may be displayed as an image on display unit 5. It also determines whether the velocity corresponds to a flow of contrast medium along the vein. If the cannula 13 is properly sited and the contrast medium flows as desired along the vein, this will lead to an increased flow velocity in the vein. This is detected by ultrasound probe 2 and, as described above, the processor unit 4 will therefore determine that no extravasation has occurred. However, where extravasation of contrast medium occurs this results in a low or zero velocity output from the probe 2 from which the processor unit 4 determines that extravasation has occurred. It therefore immediately sends a “stop” signal to pump controller 11 which stops pump 10.

Abstract: An ultrasound imaging method and system includes a two-dimensional array transducer scanhead coupled to a beamformer. The beamformer and scanhead obtain signals corresponding to ultrasound echoes reflected from a measurement volume extending across a blood vessel. The signals are processed by a Doppler processor to generate data corresponding to a three-dimensional Doppler image of blood flow velocity in the sample volume. The signals are also processed by a B-mode processor to generate data corresponding to a cross section through the vessel. An image processor transforms the data corresponding to the three-dimensional Doppler image to data corresponding to a projection of the three-dimensional Doppler image onto a plane. The image processor also combines the transformed Doppler data with the B-mode data to create a composite image. Volume flow rate can also be determined by integrating the flow velocity in the projection of the three-dimensional Doppler image.

Abstract: An apparatus for measuring parameters preparatory to a stent replacement of an aneurytic blood vessel in a patient (26) includes a computed tomography (CT) scanner (10) that acquires image data (28) corresponding to multiple two-dimensional image slices. A reconstruction processor (32) reconstructs a three-dimensional image representation (34) from the image data (28). A tracking processor (40) produces a tracked vessel (92) including at least a centerline (80) and selected vessel boundaries (86). A user interface (44) displays a rendering (242) of the image representation to an associated user (42), measures selected vascular parameters corresponding to the stent parameters (276), and graphically superimposes the measured parameters on the rendering of the image representation (270, 272).

Abstract: A composition for ultrasonic imaging is described having a microbubble population of controlled fragility. The microbubbles comprise an outer shell and a hollow core. The ratio of shell thickness to microbubble diameter is substantially similar across the population of microbubbles. A method of using such composition for imaging a fluid filled cavity, vessel or tissue is described.

Abstract: A noninvasive method to determine cerebral blood flow velocity response to face recognition tasks of a human subject, including steps of obtaining a subject's cerebral blood flow velocity in cerebral arteries on both sides of the brain using a microcomputer integrated with a transcranial Doppler ultrasound instrument with two probes placed on the temples and sample volumes focused on cerebral vessels on both sides and calculating laterality index for both arteries. Simultaneously, testing the subject with face or object processing tasks presented on the screen of a digital computer while monitoring the mean blood flow velocity during each stage of the task in real-time. Processing the acquired data to determine the spectrum analysis using a microcomputer that is operatively connected to a computer workstation for image retrieval and cross matching.

Abstract: A non-invasive method and system to determine face and object processing in a human subject, said method with high temporal resolution, user-friendly and portable, including steps of obtaining a subjects baseline cerebral blood flow velocity in cerebral arteries using a transcranial Doppler ultrasound instrument with sample volumes focused on cerebral vessels on both sides using two probes place on the temples and calculating laterality index for both arteries. Simultaneously, testing the subject with face and object processing tasks presented on the screen of a digital computer and using a computer input peripheral device while simultaneously monitoring the mean blood flow velocity during each stage of the task in real-time. Processing the acquired data using a microprocessor operatively connected to a computer work station for image retrieval.

Abstract: The present invention relates generally to systems and methods for assessing blood flow in blood vessels, for assessing vascular health, for conducting clinical trials, for screening therapeutic interventions for adverse effects, and for assessing the effects of risk factors, therapies and substances, including therapeutic substances, on blood vessels, especially cerebral blood vessels, all achieved by measuring various parameters of blood flow in one or more vessels and analyzing the results in a defined matter. The relevant parameters of blood flow include mean flow velocity, systolic acceleration, and pulsatility index. By measuring and analyzing these parameters, one can ascertain the vascular health of a particular vessel, multiple vessels and an individual. Such measurements can also determine whether a substance has an effect, either deleterious or advantageous, on vascular health. In one of many embodiments, the present invention further provides an expert system for achieving the above.

Abstract: One embodiment of the present system and method is directed to the identification of tissues within a vascular object by analyzing ultrasound data collected from the vascular object by non-invasive scans. By identifying and characterizing types of tissue from ultrasound data, an assessment can be made about the health condition of a patient without an invasive procedure. Other applications of the present system will also be appreciated including identifying other types of tissues.

Abstract: The present invention provides an ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus comprises an ultrasonic probe (1) for transmitting ultrasonic pulses into a living body and receiving ultrasonic reflected waves from the living body, a phase-detecting section (5) for detecting each phase of the ultrasonic reflected waves, and a phase-difference detecting section (6) for determining a phase difference in the repetition period of the ultrasonic transmitting/receiving operation according to the detected phase signals.

Abstract: An adaptive clutter filtering for ultrasound color flow imaging is provided including an iterative algorithm that is used to select the best clutter filter for each packet of color flow data. If significant clutter motion is present, a high pass filter cutoff frequency is automatically set to suppress the clutter and associated flash artifacts. The cutoff frequency is chosen according to the frequency of the clutter—the lower the clutter frequency, the lower the cutoff frequency can be. If clutter frequencies are low, lower filter cutoffs allow for maximum low flow detection. In this manner, the filter cutoff frequency can be optimized based on the data for each pixel in the color flow image.

Abstract: An apparatus and method for detecting the highest velocity of fluid flow with in a volume having multiple sources of fluid flow with different velocities. There are multiple pairs of receiving transducers arranged about a region wherein each transducer in a pair is positioned on the same axis with respect to the region. A transmitting transducer is positioned at the region to provide an output frequency signal, which frequency signal is transmitted to the fluid flow area volume. This causes Doppler shifted frequency signals to be reflected, with the Doppler shift being a function of the fluid flow velocity. Each of the receiving transducers receive the Doppler shifted signals. Signal processing means are responsive to the Doppler shifted signals and the original transmitted output frequency signal to process those signals to provide a velocity signal for each pair of transducers. One then selects the maximum velocity signal obtained from the pair.