Abstract: A contained water ultrasonic densitometer employs pre-inflated bladders holding coupling fluid about ultrasonic transducers. The bladders in a relaxed state define a cavity smaller than the human heel so that when the heel is inserted, the bladders conform to the heel in a wiping action removing entrapped air.

Abstract: A scanning ultrasonic apparatus provides measurements of a bone at a number of spatially separated locations. These measurements may produce an image or may be used to automatically identify a measurement region of interest or to align a series of measurements with each other despite possible shifting in the bony member in between measurements.

Abstract: The invention relates to a measurement device for use in treatment of a patient's bone, containing a specific location, which is of the kind reflecting ultrasonic radiation and which is to be prevented from being contacted during the treatment. The measurement device comprises two ultrasound probes tat are to be located at opposite sides of the bone. Both probes are capable of receiving the reflected ultrasonic radiation, at least one of the probes being a transceiver. The two probes are operable to communicate with each other to generate measured data indicative of a relative position of said location in the bone with respect to the probes. The invention also relates to a measurement device for use in dental treatment of a patient's alveolar bone that contains a nerve canal. The measurement device comprises a plurality of transceivers arranged in two arrays supported with adjustable distance between them so as to be placed at opposite sides of the bone, respectively, inside the patient's mouth.

Abstract: A probe device is presented for use in an ultrasound-based measurement device for blood flow measurements in a patient's body. The probe comprises a housing containing a transducer arrangement. An outer surface of the housing, by which the probe is brought to a measurement location in the patient's body, is patterned so as to have at least one projecting portion. The design of the probe enables correct orientation of the transducers with respect to a blood vessel under measurements. The probe device is associated with an operation means for operating the probe, and an indication means for generating output data indicative of measurement results, which are incorporated in a common housing of a hand-held measurement device.

Abstract: An ultrasonic transmission unit for an imaging/quantitative ultrasound device provides for coaxial transducer crystals which may be operated independently with a first crystal operated alone for quantitative measurement and the first and second crystal operated together to provide a broad illumination for imaging of structure.

Abstract: Elastography can produce quality strain images in vitro and in vivo. Standard elastography uses a coherent cross-correlation technique to estimate tissue displacement and tissue strain using a subsequent gradient operator. While coherent estimation methods generally have the advantage of being highly accurate and precise, even relatively small undesired motions are likely to cause enough signal decorrelation to produce significant degradation of the elastogram. For elastography to become more universally practical in such applications as hand-held, intravascular and abdominal imaging, the limitations associated with coherent strain estimation methods that require tissue and system stability, must be overcome. In this paper, we propose the use of a spectral shift method that uses a centroid shift estimate to measure local strain directly. Furthermore, we also show theoretically that a spectral bandwidth method can also provide a direct strain estimation.

Abstract: An ultrasonic instrument employs a digital architecture to provide improved stability to sound speed measurements of human bone in vivo. A digitization of the received ultrasonic signal allows numerical analyses to be applied in determining precise arrival time of the waveform. The microprocessor may initiate the ultrasonic signal transmission and detect its arrival and may control the strength of the transmitted signal and the amplification of the received signal to optimize the signal path.

Abstract: An ultrasound system and method for calculation and display of tissue deformation parameters, such as tissue Doppler and strain rate imaging, are disclosed. An ultrasound acquisition technique that allows a high frame rate in tissue velocity imaging or strain rate imaging is employed. With this acquisition technique the same ultrasound pulses are used for the tissue image and the Doppler based image. The number of beams used in Doppler subframes are increased to allow tissue visualization based only on Doppler subframes. A sliding window technique is used for processing.

Abstract: In order to obtain an optimum PRF, the velocity distribution of an echo source is calculated based on the Doppler shift of an ultrasonic wave echo, the profile of the velocity distribution is calculated (172), the reflection of the profile is corrected (174), the maximum value of the velocity in the corrected profile is detected (176), and the PRF of the ultrasonic wave transmission is adjusted based thereon (178).

Abstract: Ultrasound measurement of bone quality using nonlinear analysis in combination with or alternatively using shear waves provide improved information about human bone conditions. Surface waves also provide a novel method to estimate shear wave velocity.

Abstract: A bone mineral density meter comprises first input device which enters a sound of speed in a bone; second input device which enters a weight of the person to be measured; third input device which enters fat free mass of the person to be measured; arithmetic device which computes the bone mineral density based on data from said first input device and data from said second input device and said third input device; and display which displays a bone mineral density value computed by said arithmetic device. The present invention allows a bone mineral density to be safely estimated, at a low cost, and with proper accuracy and without having to worry about exposure to X-rays.

Abstract: A method of assessment of bone conditions comprises acquiring of unilateral sequential ultrasonic measurements along the trajectory over the surface of an examined bone. The method utilizes measurements of a set of ultrasonic parameters from a plurality of ultrasonic transfucers moved along the tested bone surface. Measured parameters are displayed as profile graphs characterizing bone conditions. The set of measured and displayed ultrasonic parameters can include: velocity of a longitudinal wave; velocity of a flexural wave; attenuation of the longitudinal wave; attenuation of the flexural wave; frequency slope of attenuation of the longitudinal wave; frequency slope of attenuation of the flexural wave; changes of spectral characteristics of propagating the longitudinal wave; and changes of spectral characteristics of propagating the flexural wave.

Abstract: The end diastole and end systole images from an acquired cardiac loop are shown side by side on an image display for automatic border tracing. The border tracings can be used to calculate ejection fraction in real time. The cardiac loops may be first acquired then processed for automatic border definition, or the acquired images can be processed in real time to indicate their suitability for automatic border detection as they are acquired.

Abstract: An ultrasonic measuring device and method for determining bone density and structure includes an electronic control unit, a positioning unit housing at least a transducer pair and carrying a receiving unit, the unit being adapted to be coupled to a bone segment of the human body and carrying a locating device for ascertaining the position of the bone segment with respect to the unit, and an electronic unit for determining a first waveform representing an ultrasonic signal transmitted through the metaphysis portion of the bony segment and a second waveform representing an ultrasonic signal transmitted through the diaphysis portion, and an electronic processor and display for displaying the first and second waveforms as a measured output.

Abstract: An ultrasonic densitometer has opposed ultrasonic transducers with inflatable bladders containing a coupling fluid. The bladders are affixed to a housing with a simple mounting. The densitometer sizes the bladder diameter so as to be moved into contact to the patient with inflation only. The densitometer further controls the geometry of the inflated bladders so as to provide improved immobilization of the patient. The coupling fluid allows the bladder also to couple the ultrasonic energy to the patient member.

Abstract: Systems and methods for assessment of tissue properties, noninvasively, by acquiring data relating to at least one aspect of intrinsic and/or induced tissue displacement, or associated biological responses, are provided. Data relating to tissue displacement and associated biological changes may be acquired by detecting acoustic properties of tissue using ultrasound interrogation pulses, preferably in a scatter or Doppler detection mode. Based on this data, tissue properties are assessed, characterized and monitored. Specific applications for systems and methods of the present invention include non-invasive assessment and monitoring of intracranial pressure (ICP), arterial blood pressure (ABP), CNS autoregulation status, vasospasm, stroke, local edema, infection and vasculitus, as well as diagnosis and monitoring of diseases and conditions that are characterized by physical changes in tissue properties.

Abstract: An ultrasonic probe (10) for measuring the depth of detachment between a tooth (30) and the tooth's supporting tissue includes a probe head (12) having an ultrasonic transducer (35). An incident acoustic wave pulse (50) is transmitted through a coupling medium at a critical angle of incidence for refraction at the interface between the coupling medium and the tooth surface (29, 31) to effect modal conversion to a surface acoustic wave pulse along the surface of the tooth (30). The critical angle of incidence is established by means of an angular setting of the ultrasonic transducer (35) in the probe head (12), a combination of the aforementioned angular setting with the ability to rock the probe head (12) to find the critical angle of incidence, and/or a phased array implementation. The disclosure also includes an algorithm for determining the depth of detachment based on the time lapse between transmission and detection of the reflection of the acoustic wave pulses.

Abstract: The end diastole and end systole images from an acquired cardiac loop are shown side by side on an image display for automatic border tracing. The border tracings can be used to calculate ejection fraction in real time. The cardiac loops may be first acquired then processed for automatic border definition, or the acquired images can be processed in real time to indicate their suitability for automatic border detection as they are acquired.

Abstract: An improved method and apparatus for non-invasively assessing one or more hemodynamic parameters associated with the circulatory system of a living organism. In one aspect, the invention comprises a method of measuring a hemodynamic parameter by measuring a non-calibrated value of the parameter non-invasively, and inducing a stress of the circulatory system while measuring a second parameter. The response of the circulatory system to the stress is determined directly from the subject, and a calibration function is derived from the response and applied to the non-calibrated measured value to produce a calibrated measure of the actual value of the hemodynamic parameter. Methods of using backscattered acoustic energy for determination of hemodynamic markers are also disclosed.

Abstract: A mechanical diagnostic probe is used to determine the thickness of articular cartilage, so that any degeneration in the articular cartilage can be detected at an early stage. The probe advantageously allows for calibrating the speed of the ultrasound in situ thereby allowing for more accurate measurements of the tissue thickness. The probe also can be used to monitor the condition of the cartilage after surgery and/or after or during physical rehabilitation of the cartilage. The probe is comprised of a probe handle and a probe, which is comprised of an ultrasonic transducer, strain-gauges, and a linear displacement actuator. A predetermined displacement then is applied to the indenter tip and a computer program is then used to analyze the results.

Abstract: A remote palpation technique in breast imaging or the like ican involve the use of multiple applications of radiation force in rapid succession throughout a two-dimensional plane in the target tissue, and the combination of the small, two-dimensional displacement maps from each force location into a single, larger remote palpation image. Apparatus for carrying out the foregoing method is also disclosed.

Abstract: An improved apparatus and method for providing a measurement of the characteristic behavior of an acoustic wave in a bone of a subject. A preferred embodiment has first and second transducers and a mounting arrangement for mounting the transducers in spaced relationship with respect to the bone. The first transducer may transmit acoustic energy over a broad solid angle, thereby behaving as a point source of acoustic energy. Additionally or alternatively, the second transducer may collect acoustic energy over a broad solid angle, thereby behaving as a point receiver. A signal processor in communication with the second transducer provides a measurement that is a function of at least one of transient spectral or transient temporal components of the signal received by the second transducer.

Abstract: An ultrasonic instrument employs a digital architecture to provide improved stability to sound speed measurements of human bone in vivo. A digitization of the received ultrasonic signal allows numerical analyses to be applied in determining precise arrival time of the waveform. The microprocessor may initiate the ultrasonic signal transmission and detect its arrival and may control the strength of the transmitted signal and the amplification of the received signal to optimize the signal path.

Abstract: A device adapted to measure the volume of a body cavity including a base, a sensor adapted to detect when a body cavity of the wearer reaches a predetermined volume and a signal mechanism. The sensor is moveably mounted on the base so as to facilitate aiming of the sensor toward the body cavity. The signal mechanism is adapted to provide a signal once the predetermined body cavity volume is reached. Alternatively, the device may comprise a first sensor and a second sensor which are oriented differently toward the body cavity and which each measure a distance between the front wall and the back wall of the body cavity. The device also includes a signal mechanism which provides a once a predetermined volume of the body cavity is reached, wherein the volume is calculated based on the greater of the distances measured between the front wall and the back wall of the body cavity.

Abstract: An ultrasound system and method for calculation and display of tissue deformation parameters are disclosed. An ultrasound acquisition technique that allows a high frame rate in tissue velocity imaging or stain rate imaging is employed. The tissue deformation parameter strain is determined by an accumulation of stain rate estimates for consecutive frames over an interval. The interval may be a triggered interval generated by, for example, an R-wave in an ECG trace. The strain calculation may be improved by moving the sample volume from which the stain rate is accumulated from frame-to-frame according to the relative displacement of the tissue within the original sample volume. The relative displacement of the tissue is defined by the instantaneous tissue velocity of the sample volume. An estimation of strain rate based upon a spatial derivative of tissue velocity is improved by adaptively varying the spatial offset, dr. The spatial offset, dr, can be maximized to cover the entire tissue segment (e.g.

Abstract: A method of calibrating an ultrasound bone analysis apparatus having a pair of transducer assemblies. Each transducer assembly has a transducer and a coupling pad, and is movable relative to the other so that a face of each pad can be moved to a position in which they mutually contact at a first compression and to a position where the faces contact body parts at a second compression different than the first compression. The method according to the present application includes transmitting an ultrasound signal from one transducer and receiving a signal corresponding to the transmitted ultrasound signal through the other transducer when the transducer assemblies are in the first position and the second position. A time for the ultrasound signal to pass through the body part is determined, and a width of the body part based on positions of the transducers is determined.

Abstract: Elastography can produce quality strain images in vitro and in vivo. Standard elastography uses a coherent cross-correlation technique to estimate tissue displacement and tissue strain using a subsequent gradient operator. While coherent estimation methods generally have the advantage of being highly accurate and precise, even relatively small undesired motions are likely to cause enough signal decorrelation to produce significant degradation of the elastogram. For elastography to become more universally practical in such applications as hand-held, intravascular and abdominal imaging, the limitations associated with coherent strain estimation methods that require tissue and system stability, must be overcome. In this paper, we propose the use of a spectral shift method that uses a centroid shift estimate to measure local strain directly. Furthermore, we also show theoretically that a spectral bandwidth method can also provide a direct strain estimation.

Abstract: The invention relates to an ultrasonic diagnostic imaging method for determining propagation parameters of transient shear wave front, comprising steps of forming transient shear waves in a tissue (5), acquiring ultrasonic image data (S,S*) of the tissue, along image lines (i), during a time delay (TSW) a transient shear wave front to propagate over a depth (z) in said tissue, estimating the tissue velocity (V) for each line, constructing a tissue velocity image sequence [I(V)] from the ultrasonic data (S,S*) and the tissue velocities (V) on the lines, and deriving the velocities (CSW) of the shear wave front at instants of the sequence. Tissue parameters such as elasticity are then calculated from said front velocity. The invention also relates to an ultrasonic diagnostic imaging system having processing means (100, PROCESSING1, PROCESSING2) for carrying out this method. The processing means may be a computer program product having instruction to this end.

Abstract: A method of determining the viability of a hibernating or stunned myocardial segment comprises the administration of ribose, a vasodilator and an inotropic agent. The preferred agent is dobutamine, which has both a vasodilation and an inotropic effect. The segments may be identified by myocardial imaging by any known means, such as echocardiography, Thallium-201 tracing or positron emission tomography. Ribose is preferably given one minute to three hours prior to administration of the vasodilator and inotropic agents.

Abstract: A method and system for ultrasonic imaging of bone tissue. A wide band scanning crystal transmits an ultrasonic signal of high frequency and multiple full waves into the bone tissue, and a second wide band scanning crystal receives the transmitted signal. The transmission frequency is progressively decreased until the number of full waves in the received signal equals that of the transmitted signal. At that frequency, the upper frequency limit, the number of full waves in the transmitted signal is gradually increased until the received signal contains at least two consecutive full waves of equal amplitude. The resultant transmission signal is then used to measure signal attenuation and velocity in bone tissue, in terms of standard bone imaging techniques. A lower frequency limit, below which the received signal undergoes distortion, is defined, and ultrasonic velocity depicted as a function of transmission frequency.

Abstract: An ultrasonic diagnostic imaging system is provided with synthesized transmit focus. Several beams are transmitted, each with a different transmit focus. Echoes received from the differently focused beams are combined to form a scanline with an extended focus. The echoes are preferably weighted and/or phase adjusted prior to being combined. Combining is performed in the r.f. domain before nonlinear processing of the signals such as amplitude detection. The resultant extended focus scanline exhibits the property of dynamic transmit focusing.

Abstract: A contained water ultrasonic densitometer employs pre-inflated bladders holding coupling fluid about ultrasonic transducers. The bladders in a relaxed state define a cavity smaller than the human heel so that when the heel is inserted, the bladders conform to the heel in a wiping action removing entrapped air.

Abstract: A contained water ultrasonic densitometer employs pre-inflated bladders holding coupling fluid about ultrasonic transducers. The bladders in a relaxed state define a cavity smaller than the human heel so that when the heel is inserted, the bladders conform to the heel in a wiping action removing entrapped air.

Abstract: A method and a system for storing and managing dimensional measurement values and the underlying ultrasound images utilize a report generator that operates to generate an examination report of an ultrasound examination having saved measurement values. The examination report allows for an expedient access to the corresponding ultrasound images that were used to derive the measurement values. In addition, the report generator operates to automatically save the ultrasound image when a measurement value that was computed from that ultrasound image is saved. This feature ensures that for each saved measurement value, the corresponding ultrasound image is also saved. The system utilizes ultrasound waves to image various anatomical features of a patient or a fetus. Examples of anatomical features that may be imaged by the system include the femur, the humerus and the head of a fetus. These ultrasound images are used to compute measurements of the anatomical features.

Abstract: The present invention is directed toward a new method that combines interpolation between neighboring A-lines with cross-correlation for high precision estimation of the transverse displacement. Due to this high precision lateral estimation, the method of the present invention can produce quality lateral-elastograms that display the lateral component of the strain tensor. These higher precision lateral displacement estimates also allow a finer correction for the lateral decorrelation that corrupts the axial estimation. The method of the present invention may be employed to divide the lateral-elastogram by the axial-elastogram on a pixel-by-pixel basis, in order to produce a new image that displays the distribution of Poisson's ratios in the tissue.

Abstract: The present invention relates generally to a medical device, and more particularly to ultrasound apparatus and methods for the identification and characterization of tissues, tissue transitions and tissue constituent structures.

Abstract: A bone sonometer or densitometer or small C-arm having a card reader that requires a charge to a card in order to carry out a patient examination but not procedures that may be similar or even identical to a patient examination from the machine's point of view, such as calibration procedures involving the use of phantoms. The card can be rejuvenated locally or from a remote location, via a communication link. Instead of a card, remote per-use authorization can be provided upon making a charge. In the case of a small C-arm, the card can keep track of radiation dosage to a user associated therewith.

Abstract: The concentration and/or radii of a contrast agent in a fluid can be estimated by acquiring ultrasound spectral data, performing spectral analysis to generate a linear estimation of the power spectrum, and correlating at least one spectral parameter to a predetermined distribution function for the contrast agent. If the mean radius squared of particles is known, then the concentration of contrast agent particles can be calculated. If the concentration is constant, then relative variations in mean radius squared can be determined.

Abstract: A method for determining, through an interposing medium, the mechanical properties of a solid having a surface, including transmitting a first ultrasonic wave along a transmission path from a first location through the interposing medium, along the surface and from the surface through the interposing medium to a second location; measuring the travel time of the first wave along the transmission path; measuring the thickness of the interposing medium; measuring the acoustic velocity of the interposing medium; and calculating the acoustic velocity in the solid based on the distance between the locations, the thickness of the interposing medium and the acoustic velocity in the interposing medium.

Abstract: A system for estimating the volume of fluid in the bladder sequentially scans the bladder with ultrasonic beams that section the bladder into a number of transverse planes. The system determines, from the scan lines associated with a given plane, a plurality of points on each of the front and back walls of the bladder. It then fits a curve to the set of front wall points and another curve to the set of back wall points, to determine an outline of the bladder in the plane. The system next calculates the cross sectional area of the bladder in the plane based on the two curves. After determining the area in each of the planes, the system determines the volume of the bladder by summing weighted version of the planar areas. The system includes a transducer that consists of a plurality of piezo-electric elements held in a relatively thin elastomeric pad and/or substrate that is acoustically impedance matched to skin.

Abstract: A method and system for determining the location of a region of interest throughout a sequence of images is provided. The system, in response to user input or automatically, identifies a region of interest associated with anatomy represented in an image. The data associated with the region of interest is compared with data for other or subsequent images. A maximum degree of correlation between the data associated with the region of interest and data for the subsequent image is determined. A translation and/or rotation associated with the maximum correlation determines the position of a region of interest designator in the subsequent image. The process may be repeated for a plurality of images. The same process may be used to determine the position of the designator in previous images.

Abstract: An ultrasonic system for grading meat transmits an ultrasonic signal into the meat and detects the resulting back-scattered signal. The envelope of the back-scattered signal is determined. A decaying exponential curve having the form y=exp(−Dt) is fitted to the envelope, where D is the attenuation factor for the curve and t is time. A grade of the meat is then determined as a function of the attenuation factor. It may be possible to improve the accuracy of this approach by measuring the total back-scattered energy from the back-signal and generating a grade for the meat based on a polynomial function of both the attenuation factor and the total back-scattered energy. Optionally, accuracy may be further enhanced by removing any anomalies in the back-scattered signal resulting from fat deposits in the meat before calculating the attenuation factor.

Abstract: A method for distracting a coxofemoral joint of a patient having two hind legs includes the steps of placing the patient in ventral recumbency, positioning a distractor between the upper thighs so that the distractor acts as a fulcrum for lateral displacement of the coxofemoral joint, and applying inward pressure to the stifle regions to distract the coxofemoral joint. Related methods are also disclosed for imaging a distracted coxofemoral joint and for evaluating the likelihood of developing laxity of a coxofemoral joint in a patient. The imaging can be non-radiographic. A distractor apparatus, suitable for use in the methods, is also described.

Abstract: An ultrasonic bone testing apparatus has a foot well assembly and a shin guide assembly which are mechanically coupled to secure a foot and lower leg of patient during the measurement process. The shin guide assembly includes a molded form which has a shin restraint section, an instep guide section and a foot restraint section. An instep support guide having sliding blocks is mounted on the molded form. The sliding blocks are inserted into respective channels of respective bridge brackets of the foot well assembly to attach the shin guide assembly to the foot well assembly. The apparatus further includes a transducer drive mechanism for positioning a pair of transducer assemblies. A controller automatically modifies the positioning of the transducer assemblies until ultrasonic coupling is achieved and a receiving transducer receives a signal of a predetermined quality.

Abstract: The present disclosure teaches a system for analyzing ultrasonic image that provides an output of a measurement of muscle width from an ultrasonic image input of an outline of a muscle from an animal or carcass. The muscle that is used in the preferred embodiment is the longissimus dorsi muscle when an ultrasonic scan is taken in a transverse direction relative to the backbone. The analysis is done with a computer that receives the electronic input of rows and columns of gray level pixel data from an ultrasonic scan image of the outline of the muscle of the animal or carcass. The software is set to select a region of the ultrasonic image input to analyze to determine a first edge of the muscle. The selected region is divided into subregions Sj,.sub.k. J designates a row and ranges between 1 and n. K designates a column and ranges between 1 and o such that o is greater than 1. The subregions are aligned in rows and columns throughout the ultrasonic image input.

Abstract: A bone assessment apparatus for diagnosing bone by transmitting and receiving measuring waves (in particular ultrasonic waves) is provided. A body part (e.g. a foot) is gripped by a pair of transducer assemblies, and ultrasonic waves are transmitted and received in this state. Each transducer assembly comprises an ultrasonic transducer and a coupler. The transverse cross-sectional area of the ultrasonic wave beam is adjusted by adjusting the contact area of the coupler on the body part, by changing the vibrating area of the ultrasonic transducer, or by fitting an attachment which narrows the ultrasonic wave beam to the transducer assembly. The transverse cross-sectional area of the ultrasonic wave beam may be changed depending on the size of the body part to be measured.

Abstract: A method of evaluating the status of bone tissue useful in the diagnosis of osteoporosis measuring a characteristic of ultrasound transmission through the calcaneus at a number of locations at an image forming degree of spatial resolution, deriving from said measurements information regarding the location of an approximately circular (as seen by measurements from the side) area of reduces attenuation in the calcaneus, optionally making further ultrasound measurements which reflect said bone tissue status, and evaluating said bone tissue status based on such said measurements and/or said further measurements at said location.

Abstract: The invention provides for ultrasonic methods and devices that provide for reproducible positioning of an ultrasonic transducer(s) in the heel using anatomic landmarks for broadband ultrasonic attenuation or speed of sound measurements. The invention provides for improved interrogation devices that reproducibly position transducer(s) over an interrogation site in the heel.

Abstract: Methods and apparatus are provided for measurement and analysis of patient anatomy with an ultrasound imaging system which generates an ultrasound image of a region of a patient and provides coordinates of walls of vessels in the image. In response to placement of a cursor within the vessel in the ultrasound image, one or more parameters of the vessel in the vicinity of the cursor are determined automatically from the wall coordinates. The determined parameter values are recorded. The vessel parameters may include vessel diameter, vessel center coordinates and/or vessel wall directions. The vessel may be automatically mapped by moving the cursor to multiple positions along the vessel and determining the parameters of interest at each cursor position. The smallest vessel diameter may be determined and highlighted in the ultrasound image.

Abstract: An imaging system incorporating the invention includes a transducer for scanning an imaging beam through a region of interest (ROI) which includes a structure or function to be imaged on a display, such as an anatomical structure or a hemodynamic function. A processor is responsive to a changes in the image that are caused by changes in imaging beam position, to calculate at least a first measure of a feature of the structure or function and to cause the display to manifest the first measure by a first indication. The processor may also be responsive to a further change in the image brought about by movement of the imaging beam, to calculate at least a second measure of the feature and to cause the display to manifest the second measure by a second indication. The user is thereby able to determine by display of the first and second indications, of the relative difference in positions of the transducer.