Abstract: The ultrasonic scatterer of the invention comprises gas-containing particles having an average particle size of 0.01 &mgr;m to 10 &mgr;m, the ultrasonic imaging method of the invention comprises transmitting an ultrasonic wave continuing for ten cycles or more; transmitting an ultrasonic wave continuing for four cycles or more and less than ten cycles after a predetermined period passes, and the ultrasonic imaging apparatus of the invention comprises transmitting means for sending a driving signal to the ultrasonic probe so as to transmit, to a subject, an ultrasonic wave continuing for four cycles or more and less than ten cycles after a predetermined period passes subsequently to transmitting, to the subject, of an ultrasonic wave continuing for ten cycles or more.

Abstract: The contrast-to-tissue ratio is improved while imaging contrast infused tissue. A subject is infused with contrast medium having microbubbles at a fundamental frequency. First and second transmit pulses are transmitted into the subject. The first and second transmit pulses each comprise first, or basic, and second, or seed, signals. The basic signal has a frequency based on the fundamental frequency and the seed signal has a subharmonic frequency based on the frequency of the basic signal. The first and second transmit pulses are phase inverted with respect to each other. Received echoes from first and second transmit pulses are filtered at a subharmonic or ultraharmonic frequency to remove tissue response and pass microbubble response.

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: The object of the invention is to provide an ultrasonograph wherein the decrease of the density of a stabilized microbubble contrast agent in a desired living area can be inhibited, radiating ultrasonic energy required to acquire satisfactory image signal-to-noise ratio and an enough frame rate. The invention is based upon an ultrasonograph for obtaining an image of the inside of a living body by transmitting/receiving an ultrasonic wave to the living body into which a contrast agent is introduced using an ultrasonic probe and is characterized in that the ultrasonic probe transmits an ultrasonic pulse acquired by superimposing higher harmonics including at least a second harmonic of a fundamental wave on the fundamental wave.

Abstract: An ultrasound detectable instrument (10) includes bubble generating means comprising two elements (32a, 32b) which, upon contact with each other in the presence of a fluid, react with each other to produce gas bubbles which may be detected by sonic imaging equipment. The two elements comprise first and second radially displaced layers of said elements within a fluid permeable carrier material.

Abstract: A contrast echo image of the myocardium and a cardiac chamber obtained by use of ultrasound diagnostic equipment is analyzed so as to determine the volume of blood within the myocardium. The contrast echo image is divided into a plurality of calculation regions, each being considered to have a uniform acoustic field intensity and covering a portion of a myocardium image region and a corresponding portion of a cardiac chamber image region. For each calculation region, a difference in intensity between the myocardium image region and the cardiac chamber image region is obtained, and the myocardium image region is colored in accordance with the difference.

Abstract: An ultrasonic diagnostic apparatus by which an image having superior space resolution is obtained. The apparatus includes: first means for transmitting an ultrasonic wave, which is continued for at least two cycles, to an object to be inspected, and for detecting an echo signal which is produced by reflection of the transmitted ultrasonic wave from tissue of the object to be inspected to thereby obtain a detection signal; second means for delaying the detection signal by such a time duration corresponding to one cycle of the transmitted ultrasonic wave to thereby obtain a delayed detection signal; and third means for obtaining image information related to the tissue of the object to be inspected based upon a difference between the detection signal and the delayed detection signal.

Abstract: An apparatus and method for providing an ultrasonic image of an object by use of subharmonic acoustic signals. In specific embodiments the invention provides an acoustic transducer design and a method for obtaining an image by focusing a receiving portion of the transducer on a plurality of focal points and constructing the image from the received signals. Comparison with images generated from a fundamental frequency image can be used to enhance the final image.

Abstract: A medical or surgical device or tool that is designed to be implanted or inserted inside the human or mammalian body, having at least part of its surface coated whereby the ultrasound visibility of said device or tool in vivo is enhanced, wherein the coating comprises one or more of the following: (i) a matrix material containing a plurality of contrast enhancing elements; (ii) magnesium; (iii) a liquid or polymer which alters its ultrasound imaging properties upon elevating the temperature from ambient to physiological temperature; (iv) a liquid or polymer which alters its ultrasound imaging properties as a result of a change in pH; (v) an essentially non-polymeric bio-compatible compound which forms a discontinuous coating. Preferably the device or tool is a radioactive source for use in brachytherapy, and in particular a radioactive seed.

Abstract: Systems and methods for visualizing ablation lesions are provided. A contrast agent is injected into an artery that feeds blood to tissue surrounding an ablation lesion. During or after contrast agent injection, the ablation lesion and surrounding tissue is imaged using an imager that is responsive to the injected contrast agent. In one non-limiting embodiment, the contrast agent comprises echogenic particles, e.g., echogenic microbubbles, and the imager is an ultrasound imager.

Abstract: Apparatus for precision location of a tool such as a surgical tool within an obscured region such as an internal space of the human or animal body, the apparatus comprising: a planar scanning unit for scanning planes within said obscured region using an imaging scan, and a locator, associated with said tool and with said scanning unit, for determining a location of said tool, and for selecting a plane including said tool location. The apparatus allows the planar scan to follow the tool automatically and saves skill and effort on the part of the surgeon.

Abstract: A system and method for ultrasound imaging of breast tissue by injecting an ultrasound contrast agent into a duct lumen of a patient's breast to enhance the imaging of one or more ducts within a specified lobe of the breast to improve characterization of a lesion or lesions within the duct system of the specified lobe are disclosed. The ultrasound contrast agent used to improve breast imaging may be injected into the duct lumen through an orifice on the nipple and/or a duct wall into the duct lumen. The ultrasound contrast agent may be injected prior to and/or during ultrasound imaging. The ultrasound contrast agent may be an acoustically detectable gas such as a halogenated hydrocarbon, halogenated alkane gases, nitrogen, helium, argon and/or xenon. The halogenated alkane gas may be a perfluorinated hydrocarbon such as saturated perfluorocarbon, unsaturated perfluorocarbon, and/or cyclic perfluorocarbon. The acoustically detectable gas may alternatively be mixed in a liquid solution.

Abstract: In the quantification of bodies, especially bubbles, in ultrasonic diagnosis, the problem exists that the concentration of bodies, especially bubbles, is often so high that the image data that is obtained relative to the visualization becomes saturated, such that a quantification is impossible. To solve this problem, it is proposed that the bodies that are contained in the sectional layers of an object under examination first be excited by means of ultrasound to produce characteristic signals and to pick up these signals, to form data sets from the signals, to convert the data sets into an image of the body arrangement in the object under examination and to determine the number of bodies therefrom, whereby at least two ultrasonic signal sets from overlapping sectional layers in the object under examination are picked up.

Abstract: The present disclosure relates to contrast imaging. More particularly, the present disclosure relates to apparatus and methods for contrast imaging in which the elevation beamwidth is controlled to reduce image artifacts, which result from contrast agent being carried into the image region by motion or respiration and not by reperfusion.

Abstract: The contrast-to-tissue ratio is improved while imaging contrast infused tissue. A subject is infused with contrast medium having microbubbles at a fundamental frequency. First and second transmit pulses are transmitted into the subject. The first and second transmit pulses each comprise first, or basic, and second, or seed, signals. The basic signal has a frequency based on the fundamental frequency and the seed signal has a subharmonic frequency based on the frequency of the basic signal. The first and second transmit pulses are phase inverted with respect to each other. Received echoes from first and second transmit pulses are filtered at a subharmonic or ultraharmonic frequency to remove tissue response and pass microbubble response.

Abstract: Ultrasonic imaging to receive a signal from contrast agent microbubbles in arterioles of a myocardium, without being masked by a signal from microbubbles in capillaries of the myocardium. For example, high power ultrasonic energy is emitted to destroy microbubbles in the arterioles and capillaries. A time delay passes from the destruction. The time delay is sufficiently long to allow the arterioles to refill with microbubbles and sufficiently short so that the capillaries do not completely refill with microbubbles. Ultrasonic imaging is then performed to receive a signal between harmonics from the microbubbles refilled in the arterioles. Various other destructive and non-destructive imaging techniques are disclosed.

Abstract: An ultrasound image is obtained by subjecting an object containing an ultrasound contrast enhancement agent to a first imaging pulse burst and then to a second release pulse and then to a second imaging pulse to obtain two images and then comparing the two images to obtain an enhanced image.

Abstract: Ultrasound diagnosis apparatus includes a transceiver unit, an adding processor, a filter, and an image processor. The transceiver unit insonifies an object injected with a contrast agent via an ultrasound transmission signal transmitted at a fundamental frequency f0 with at least two transmission rates. The adding processor adds a first component of the ultrasound echo signal and second component of the ultrasound echo signal. The first component is transmitted at a first rate of the at least two transmission rates and the second component is transmitted at a second rate of the at least two transmission rates. The filter suppresses at least a first frequency band of an addition result that is centered about a frequency 2·f0. The image processor then generates image data based on a suppressing result.

Abstract: An ultrasonically visible solid device for inserting into a non-gas target medium comprises an echogenic surface having structures entrapping gas when the device is in the target medium, the entrapped gas causing the device to be ultrasonically visible, wherein the gas-entrapping structures are covered with a flexible overcoat that does not significantly reduce the compressibility of the gas trapped in the structures.

Abstract: The invention is directed biopsy site markers and methods of marking a biopsy site, so that the location of the biopsy cavity is readily visible by conventional imaging methods, particularly by ultrasonic imaging. The biopsy site markers of the invention have high ultrasound reflectivity, presenting a substantial acoustic signature from a small marker, so as to avoid obscuring diagnostic tissue features in subsequent imaging studies, and can be readily distinguished from biological features. The several disclosed embodiments of the biopsy site marker of the invention have a high contrast of acoustic impedance as placed in a tissue site, so as to efficiently reflect and scatter ultrasonic energy, and preferably include gas-filled internal pores. The markers may have a non-uniform surface contour to enhance the acoustic signature. The markers have a characteristic form which is recognizably artificial during medical imaging.

Abstract: A contrast effect measuring unit 104 measures the contrast effect of an ultrasound contrast agent in a patient 110. The control unit 106 determines a desired contrast agent infusion rate, based on the contrast effect measured by the contrast effect measuring unit 104 and programmed contrast effect parameters. The control unit 106 controls an infusion unit 102 to infuse the patient 110 with the determined infusion rate. An ultrasound imaging unit 108 performs an ultrasound imaging test on the patient 110. This process is continued through the course of the ultrasound imaging test, to maintain a steady contrast effect and a steady signal enhancement level for the patient 110.

Abstract: A method and apparatus in an ultrasound imaging system is disclosed that enhances the contrast-to-tissue ratio and signal-to-noise ratio of contrast imaging using stepped-chirp waveforms. The first waveform component is employed with a first frequency optimized to initiate the bubble dynamics and the second waveform component is employed with a second frequency optimized to produce an enhanced bubble nonlinear response. The first waveform component and the at least a second waveform component are transmitted as a single stepped-chirp transmit pulse. At least one of a center frequency, an amplitude, a starting phase, and a bandwidth of the waveform components are adjusted to generate the single stepped-chirp transmit pulse. A relative phase, a switch time, and a time delay between the waveform components are also adjusted for maximal enhancement of bubble nonlinear response.

Abstract: A method for providing a virtual contrast agent for blood vessels in a body portion for angioscopy comprising deriving data from a 3D model using, for example, magnetic resonance imaging, computerized tomography (CT), and 3D angio. The data is segmented to provide a segmented 3D model of the blood vessels. A first procedure image is made with a contrast agent present. The 3D model is then registered with the first procedural image and “virtual camera parameters” are obtained. The 3D model is rendered and overlaid onto a second procedure image without contrast, whereby a virtual contrast is achieved.

Abstract: Systems and/or methods provide for ultrasound imaging through the use of a dynamic nonlinear post-beamforming filter (e.g., based on a pth-order Volterra model) capable of separating the linear and nonlinear components of image data. A coefficient identification algorithm for deriving coefficients for filter is also provided.

Abstract: An ultrasonic diagnostic apparatus includes an ultrasonic probe, a transmitter for transmitting an ultrasonic wave pulse having peaks at fundamental frequencys, and a receiver for receiving an echo signal corresponding to the ultrasonic wave pulse. The echo signal contains a difference frequency component as well as a fundamental frequency component centered on a fundamental frequency. A difference frequency component is extracted by attenuating the fundamental frequency component of the echo signal. Ultrasonic image data is generated on the basis of the extracted difference frequency component.

Abstract: A method and system for displaying a parametric image showing tissue perfusion includes an ultrasonic imaging system coupled to an ECG device. The ECG device triggers the imaging system to obtain contrast image data showing tissue perfusion at a respective predetermined time during each of a plurality of heartbeats. Parametric image data for discrete locations in the area of interest such as the myocardium is determined from the temporal contrast data acquired during reperfusion of the tissue in the area of interest. The parameters are mapped to a display value such as color to produce a parametric perfusion ultrasound image. Sequences of images may be produced which depict both perfusion characteristics and dynamic wall motion of the myocardium in a common image sequence.

Abstract: The present invention relates to a] A device for producing an image of a body part into which a contrasting agent has been introduced, the device including an image detecting device modifying the contrasting agent to provide a modified image, and a processor acquiring and processing the modified image so as to create an image which represents a rate of flow of blood or other fluid in the body part. The device may be an ultrasound imaging device or may be a magnetic resonance imaging device.

Abstract: Systems and methods for enhanced color-flow imaging of contrast-agent perfused blood vessels and other tissues within a patient's body are disclosed. The method generally comprises, introducing one or more contrast agents into the body, power-modulating transmit pulses into the body, receiving echoes from the body, processing the received echoes to reduce tissue-generated echoes and echoes from stationary contrast agent, using a color-flow processor to generate a color-encoded display responsive to contrast-agent motion. The method may be implemented by a system with a an excitation-signal source, a transducer, an ultrasound-processing system having multiple image processors including a color-flow processor, as well as, a clutter filter, and an arbiter, and a display-processing system.

Abstract: A method for imaging diseased tissue is provided. The method provides delivering to the diseased tissue a liposomal imaging agent comprising liposomes containing an imaging agent. The liposomal imaging agent is bound to an antibody by an antigenic linker so that the antibody binds the liposomal imaging agent to the diseased tissue. The liposomes are broken to release the imaging agent using a catheter, and the imaging agent is viewed using an imaging technique. The tissue can also be treated by delivering a therapeutic agent to the tissue using the catheter, for example, within the liposomes of the liposomal imaging agent.

Abstract: An injection catheter is provided with a piezoelectric ultrasound emitting device atits distal end, capable of emitting ultrasound of different energy levels. It can be used to image the location of penetration of an internal organ of a patient by the catheter needle, by supply of echocontrast material through the needle and analysis of the ultrasound reflections therefrom. It can also be used to cause tissue perturbation or disruption at the imaged location, e.g. to initiate tissue angiogenesis, by choice of suitable ultrasound energy level of emission, and for delivery of therapeutic substances such as DNA to the disrupted tissue, for better uptake in gene therapy.

Abstract: Prostate abnormalities such as cancer may be detected by ultrasonic determination of the in-flow kinetics of contrast agent-containing blood in the prostate and/or by observation of disease-related asymmetries in the the spoke-like vascular pattern of the prostate.

Abstract: Polymeric contrast agents are used to test for blood vessel permeability, such as, for example, to diagnose sepsis. The agent is injected and images are obtained at various time intervals after injection. For increased accuracy, the blood circulation levels of the agents may optionally be monitored.

Abstract: Polymeric contrast agents are used to monitor myocardial neovascularization. The agent is injected and images of the myocardium are obtained at various time intervals after injection. Localized image enhancement indicates an area of increased angiogenesis.

Abstract: A medical diagnostic ultrasonic imaging system acquires receive beams from spatially distinct transmit beams. The receive beams alternate in type between at least first and second types across the region being imaged. The first and second types of receive beams differ in at least one scan parameter other than transmit and receive line geometry, and can for example differ in transmit phase, transmit or receive aperture, system frequency, transmit focus, complex phase angle, transmit code or transmit gain. Receive beams associated with spatially distinct ones of the transmit beams (including at least one beam of the first type and at least one beam of the second type) are then combined. In this way, many two-pulse techniques, including, for example, phase inversion techniques, synthetic aperture techniques, synthetic frequency techniques, and synthetic focus techniques, can be used while substantially reducing the frame rate penalty normally associated with such techniques.

Abstract: The gain for multiple mode imaging and/or contrast agent imaging is automatically adjusted. The gain algorithm separately determines gain parameters for two different types of imaging, such as tissue and contrast agent imaging. The gain based on the contrast agent image may be optimized to provide maximum sensitivity, such as by mapping noise values measured prior to injection of contrast agent to low values within the dynamic range or somewhat below the display dynamic range. The automatic gain based on the contrast agent image may be free of variance calculations. One of the two gain parameters is selected as the system gain, or the two gain parameters are combined to form the system gain. The presence of contrast agents within the image may be determined, and different gain parameters used based on the presence or absence of contrast agents. Various ones or combinations of the gain adjustments summarized above may be used.

Abstract: A method and apparatus are described for ultrasonically imaging tiny blood vessels with the aid of a contrast agent. The locations of microbubbles of the contrast agent are detected in a series of images as the microbubbles move through the blood vessels. These images are temporally processed to identify the moving microbubbles, and persistence processed to depict images which show the tracks followed by the microbubbles through the blood vessels. A maximum intensity persistence can be used to show the steady buildup of microbubble tracks through the vasculature, or a slow decay employed so that the tracks will fade to black over time.

Abstract: A method and apparatus are described for ultrasonically imaging tiny blood vessels with the aid of a contrast agent. The locations of microbubbles of the contrast agent are detected in a series of images as the microbubbles move through the blood vessels. These images are temporally processed to identify the moving microbubbles, and persistence processed to depict images which show the tracks followed by the microbubbles through the blood vessels. A maximum intensity persistence can be used to show the steady buildup of microbubble tracks through the vasculature, or a slow decay employed so that the tracks will fade to black over time.

Abstract: An ultrasonic imaging apparatus and method are described for imaging nonlinear response objects such as contrast agents at greater depths. Transmit pulses include two fundamental frequency components, one of which is to produce harmonic components at the fundamental frequency of the other component. In the presence of a contrast agent these harmonic components are used for imaging the contrast agent. When the contrast agent is not present imaging is performed using the fundamental echoes of the other echo frequency. Preferably the harmonic frequency of the first fundamental component is aligned with the second fundamental frequency. The technique is especially useful when imaging contrast agents at low MI and at significant depths in the 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: The present invention provides an implantable biomarker for finding a location inside a patient while performing minimally invasive or open surgical procedures. The implantable biomarker includes a dielectric base that includes two opposing sides from which extend a plurality of wave-guide rods. The implantable biomarker is preferably mounted upon a surgical instrument or surgical implant and used in conjunction with an image-guided system to enable a surgeon to quickly and easily find the location without requiring extensive x-rays or the use of expensive and cumbersome equipment.

Abstract: A system and method for fundamental real-time imaging of the non-linear response of tissue perfused with a contrast agent are disclosed. An image with increased sensitivity to non-linear responses can be achieved by detecting the ultrasound response at the fundamental frequency from tissue perfused with a contrast agent and excited by multiple excitation levels. The responses detected from the multiple excitation levels may be gain corrected in an amount corresponding to the difference in magnitude of the excitation levels, then mathematically combined. The mathematical manipulation serves to remove linear responses to the fundamental excitation from the detected image. An ultrasonic contrast agent and tissue imaging system can be implemented with a transducer, first and second transmitters, a receiver, a control system, a processing system and a display.

Abstract: Systems and/or methods provide for ultrasound imaging through the use of a dynamic nonlinear post-beamforming filter (e.g., based on a pth-order Volterra model) capable of separating the linear and nonlinear components of image data. A coefficient identification algorithm for deriving coefficients for filter is also provided.

Abstract: A method and system for contrast agent imaging with a catheter transducer is provided. The catheter transducer may comprise an intra-vascular, intra-cardiac or other transducer for insertion into or through a small space. The catheter transducer is inserted within the heart or other portion of a patient. Contrast agents, such as micro-spheres, are injected into the patient. Using the catheter transducer, ultrasonic acoustic energy is transmitted, and reflected energy is received. The reflected energy is responsive to the contrast agents. An image processor generates an image of the tissue and contrast agents as a function of the reflected energy. The image provides an indication of perfusion. Alternatively, the ultrasound system calculates perfusion. By generating intra-vascular images or data, interference from other tissues is avoided. Therefore, the perfusion information obtained may have higher resolution. Images with better resolution better assist doctors in medical diagnosis.

Abstract: In a method for examining a living subject with an imaging method making use of the concentration of a contrast agent having a physical property that is identifiable with the imaging method in a region of interest (ROI) of the subject presented in time-successive images acquired with the imaging method representing quantitative values of the physical property, a histogram of the quantitative values of the physical property in the ROI is produced for each of the individual images, and the contrast agent concentration in the ROI is determined on the basis of the frequency of occurrence of the quantitative values of the physical property in the ROI.

Abstract: A fluid injection arrangement, particularly involving a systematic fluid injection programming capability, in the context of patient imaging systems, in which phases of contrast medium infection and flushing medium injection can be freely and selectably ordered so as to make available to the operator and patient a vast array of possible protocols than has hitherto been essentially unattainable. Also contemplated is the use of a “hold” phase, involving an indefinite pause between phases of a protocol, in connection with such imaging systems. Further contemplated is the use of a “pause” phase in which a pause of fixed duration is pre-programmed into the protocols of MRI Injector systems.

Abstract: In an ultrasonic diagnostic apparatus, a set of transmitting conditions ML1 optimal for existential diagnosis and two transmitting conditions ML2 and ML3 optimal for qualitative diagnosis are defined for the contrast echo method and selected appropriately according to a sequence of diagnosis for the purpose of gathering and processing ultrasonic images. The transmitting conditions can be switched automatically, from one to the other, or in accordance with a command issued by the operator due to the program registered in advance. A flash transmission is conducted on the transmitting conditions MLh between an existential diagnosis and a qualitative diagnosis. This enables the user to observe the new in-flow of contrast medium into the region being observed.

Abstract: Systems and methods for enhanced color-flow imaging of contrast-agent perfused blood vessels and other tissues within a patient's body are disclosed. The method generally comprises, introducing one or more contrast agents into the body, power-modulating transmit pulses into the body, receiving echoes from the body, processing the received echoes to reduce tissue-generated echoes and echoes from stationary contrast agent, using a color-flow processor to generate a color-encoded display responsive to contrast-agent motion. The method may be implemented by a system with a an excitation-signal source, a transducer, an ultrasound-processing system having multiple image processors including a color-flow processor, as well as, a clutter filter, and an arbiter, and a display-processing system.

Abstract: An apparatus and method of imaging contrast agents within a patient's body. The apparatus includes an imaging system transmitting at multiple frequencies to elicit a response from the contrast agent at corresponding multiple frequencies, forms images corresponding to each frequency, and the combines the formed images.

Abstract: A method and system for controlling a dynamic range of a medical diagnostic image provided by a medical diagnostic system. A target dynamic range is identified independent of a dynamic range of an original medical image. A presentation map is generated defining a relation between the dynamic range of the original medical image representative of a patient and the target dynamic range. A gray level-optical density model may define the relation between gray levels of the original medical image and target optical densities of the presentation map, the gray level-optical density model being calculated based on film characteristics, selected optical densities for anatomical structure or on a measured dynamic range. A presentation image is created having the target dynamic range based on a the presentation map and original medical image.

Abstract: Methods and systems for detecting contrast agents is provided. Differences between different sized vessels throughout a period of contrast agent enhancement are identified without significantly depleting the available contrast agent. Dual detection paths are used for imaging, such as one path for detecting nonlinear response and another path for detecting differences between the responses to two or more pulses. Where echoes from two or more pulses of acoustic energy are combined to detect the nonlinear response, the nonlinear response may also include signals originating from a loss-of-correlation (LOC) or motion between received pulses. These signals generated from LOC or motion can be produced from agent disruption where a second received echo is different from a first received echo due to a change in a bubble's shape (i.e., destruction), or from simple spatial translation between acoustic pulses as seen from the same spatial location, respectively.