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Ultrasonic imaging is perhaps the most ubiquitous form of biomedical imaging currently employed in the clinical setting due its safety, affordability, and real-time imaging capabilities. However, the poor image quality of standard brightness mode (B-Mode) images has inspired research into alternative acoustic imaging modalities, such as sound speed imaging. Historically, sound speed tomography has been employed in transmission-mode because of the limited k-space coverage available in backscattered data. However, such imaging techniques require specialized hardware configurations, and are often only limited to tissue such as the breast where full angular coverage is available. A recent approach [Jaeger et al., UMB, 41: 235-250, 2015] has demonstrated the feasibility of sound speed imaging using only pulse-echo data, which only requires a single array probe, commonly available in a clinical setting. This approach allows for complementary k-space coverage by utilizing relative temporal shifts between success...

Big brown bats pursue flying insects in open areas, but they also hunt for prey near vegetation. The proximity of obstacles requires emission of sounds at short interpulse intervals (IPIs) to guide collision‐avoidance maneuvers, yet the bat has to locate obstacles distributed in depth for path planning, which requires longer IPIs. If IPIs are too short, the stream of echoes for one sound will still be arriving when the second sound is emitted, creating ambiguity about matching echoes to broadcasts. We investigated how bats cope with pulse‐echo ambiguity by recording sounds with a miniature radio microphone (Telemike) carried during flights through a dense array of obstacles (vertically hanging chains) that were distributed in depth. Array density forced bats to emit FM sounds at short intervals (strobe groups) with consequent pulse‐echo ambiguity. We found that when ambiguity occurred, bats shifted the FM sounds in strobe groups upward and downward in frequency by several kiloHertz to distinguish each bro...

Quantitative ultrasound (US) measurements have been suggested for screening of osteoporosis. However, soft tissues overlying bones affect reliability of the measurements. In this in vitro study, a novel dual frequency ultrasound (DFUS) technique is introduced for elimination of the errors induced by soft tissues on bone pulse‐echo US measurements. In DFUS, US reflection from soft tissue‐bone interface is measured with two different US frequencies. By knowing the frequency specific US attenuation and speed in adipose and lean tissues, the effect of soft tissue can be determined. DFUS, conducted at frequencies of 2.25 MHz and 5.0 MHz, was validated using human trabecular bone samples (n = 25) covered with heterogeneous soft tissues. DFUS, reduced (p < 0.01) the mean error induced by soft tissues from 58.6% to ‐4.9% and from 127.4% to 23.8% in broadband ultrasound backscattering and integrated reflection coefficients (at 5.0 MHz), respectively. Our results suggest that DFUS is a technique capable to minimize...

Ultrasound (US) thickness gauges typically analyse layered materials by utilizing ultrasound reflections between different layers and prior knowledge for the material order within the layered structure. In this study, a dual frequency ultrasound (DFUS) technique is applied to eliminate the effect of overlying layered structure on the measurements of the object of interest without prior knowledge of the order of materials within the multilayered structure. DFUS technique utilizes prior knowledge on US attenuation coefficient and speed at two frequencies in multilayered materials, consisting of two different material types. Then, US reflection from the front (first) and the back (last) surfaces of the multilayered structure is measured using two different US frequencies. No reflections from the internal interfaces are needed. The technique was validated using several elastomer samples and their combinations, measured at 2.25 MHz and 5.0 MHz. DFUS reduced the mean error, induced by the overlying elastomers, in reflection from the object of interest from 103.6 ‐ 289.4% to ‐15.9 ‐ 5.6% and from 37.5 ‐ 77.5% to ‐12.0 ‐ 4.9% with 5.0 MHz and 2.25 MHz, respectively. Based on these results, DFUS is a straightforward technique to analyse the multilayered structure without the need for echoes from internal interfaces.

With increasing seafood demand aquaculture is poised to become a major growth industry in the United States in the 21st century. In particular channel catfish represent an approximately $260 million industry in Mississippi with strong growth potential. A major portion of the costs associated with raising channel catfish are related to the cost of feed and aeration which are directly related to the total number of fish being raised in each pond. Crop insurance and bank loans are also contingent upon accurate population estimates. A high frequency, horizontally scanning, active pulse echo sonar system, the Aquascanner, has been developed to estimate pond populations. Commercial catfish ponds are typically 2 to 10 acres and, unlike many offshore fisheries, have fairly shallow depths of 1 to 2 m. The system components and its use will be presented along with results from field tests. [Work supported by US Dept. of Agriculture.]

We have recently investigated the use of two different nonlinear imaging methods for visualization of HIFU‐induced lesions. The hypothesis is that bubble activity at the location of the HIFU beam can be observed using diagnostic ultrasound with proper post‐beamforming signal processing of the rf data. In particular, pulse inversion (PI) and quadratic imaging techniques have been investigated for this purpose. Results from over 100 ex vivo tissue experiments clearly demonstrate the superiority of the nonlinear imaging techiques over conventional B‐scan imaging in terms of accurate mapping of lesion boundaries. We are currently examining imaging data to determine the use of nonlinear imaging methods for quantitative assessment of tissue damage. In this paper, we will describe a new experimental procedure for determining the existence of bubble activity associated with different levels of exposure to HIFU, from underexposure to overexposure conditions. Images from conventional B‐scan will be compared and con...

Instruments determine the time of flight through a prepared section of bone of uniform thickness. A multigated receiver can be set to capture successive pulse echoes. A clock turned on by the first pulse echo is turned off by the next. A faster driven transducer maps the bone section. Several tissue properties can be calculated from the time of flight, the amplitude, thickness of the bone section and its density. In particular, the variation of the elastic properties provides a detailed picture of stress distribution on the bone. Several examples will be shown.

This disclosure concerns the application of the pulse echo principle to the non-intrusive method of low liquid level sensing to determine the level of a liquid in a container. Generally, the sensor is attached to an outer wall of a liquid container by means of an epoxy adhesive. An ultrasonic pulse is transmitted through from the sensor into the container and is reflected back through the epoxy adhesive and the container wall. The acoustic reflection coefficient for the container wall varies depending on whether the wall is backed by a liquid, the level of which is being determined. Specific integral equations which are provided to manipulate the data and to render the sensor less sensitive to noise, wall thickness and reflections from thin liquid levels.

Ultrasonic velocity is widely used for nondestructive evaluation of material properties. In cases where the thickness of the test piece is not precisely known or varies spatially, it is desirable to be able to determine the ultrasonic velocity and the sample thickness simultaneously. In immersion tests, the velocity and the thickness may be determined simultaneously by measuring a number of times‐of‐flight [cf. Kuo et al., J. Acoust. Soc. Am. 88, 1679–1682 (1990)]. In this work the ‘‘simultaneous’’ method was tested in four different configurations of pulse echo and through transmission and was applied to the characterization of porosity in graphite polyimide and graphite–epoxy composites. In addition, the velocity‐thickness method was also implemented with water squirters. [Work supported by Center for NDE, Iowa State University.]

A second‐order time difference approach is suggested to solve problems with the pulse‐echo‐overlap method of measuring the phase sound velocity.

We have reported earlier the observation of backscattered leaky Raleigh waves from a liquid–solid interface [J. Acoust. Soc. Am. 72, 1018–1020 (1982)]. Now we have carried out experiments to observe backscattered leaky Lamb waves from a plate immersed in liquid, using a single transducer in pulse echo modes. Sharp peaks were observed at angles corresponding to backward propagating symmetrical and antisymmetrical Lamb modes. These backward propagating Lamb waves leak back at both sides of the plate.

The dependence of spectral variations within a reflected broad‐band ultrasonic pulse on the size and orientation of the reflector was determined experimentally. An analytical model is developed on the assumption that interference of the waves received from the edges of the reflecting surface is responsible for the variations of the received frequency spectra. It explains the experimental results very well. The feasibility of determining the size and orientation of hidden flaws in metals by this method is demonstrated.

Current methods for ultrasonic inspection of metals and other solid materials are limited by their inability to determine the geometry of concealed defects if these defects are comparable in size, or smaller than the width of the ultrasonic search beam. Whenever such relatively small flaws are involved, ultrasonic pulse echo testing, if conducted at a single frequency, will yield the flaw location only, but no information on the flaw geometry. It is therefore very difficult to interpret the test results. The difficulty can be overcome by introducing the novel ultrasonic test method described in this paper. In this procedure, ultrasonic signals are utilized which contain a broad band of frequencies, and in analogy to optics, can therefore be considered as “white” ultrasonic pulses. The form and spectral energy distribution, or “color,” of such ultrasonic pulses is influenced by the geometry of a defect from which they are reflected. Hence, an analysis of the defect echo yields information on the defect configuration. The successful application of the ultrasonic pulse analysis method for differentiating between flaws of various configurations is illustrated By a number of test examples.

The problem of defect‐size determination by means of ultrasonic pulse‐echo testing and the benefits accrued from the utilization of a system that permits simultaneous testing at two different frequencies are discussed. The design of a dual‐frequency pulse‐echo test system employing only a single ultrasonic transducer is described, and its usefulness is examined for discriminating between disklike discontinuities (flat‐bottom holes) of various diameters. In addition, experiments are described that indicate that the frequency dependence of ultrasonic‐energy losses and the longitudinal‐wave velocities in materials can be determined faster and with a higher degree of reliability by dual‐frequency testing than by conventional methods. Also reported is an experimental investigation of the frequency dependence of transducer coupling in contact testing involving interposed layers of liquid couplant.

Various ultrasonic properties of whitefish (Coregonus dupeaformis) tissues have been determined. The sound velocity, impedance, and absorption were measured at 22°C with pulse echo techniques for the frequencies of 1, 2, 3, 7, and 11 MHz. The average impedance and absorption of fresh whitefish myomere with a fat content of approximately 8% were 1.634 × 105 cgs units and 0.7 dB/cm/MHz, respectively. No significant velocity or absorption anisotropy was observed for the muscle tissues. The effects of freezing on velocity and absorption were investigated. The mean velocity in thawed flesh was only 0.8% higher than in fresh flesh, but increases up to 100% or more were noted in the absorption. This increase depended on the rate at which freezing proceeded; a longer freezing period generally resulted in greater absorption.

A new type of ultrasonic pulse‐echo method that makes use of interaural localization is described in this Letter. The basic idea of this method is to receive pulse echoes reflected from an object with two receiving transducers and to hear the echo signals stereophonically after they are converted to audible frequencies. The principles of the system and some results of preliminary experiments that make use of an ultrasonic pulse of 500 kHz are presented.

The standard pulse‐echo ultrasonic technique has been used successfully with longitudinal waves to over 400°C in single‐crystal and polycrystalline Armco iron at 7 Mc sec. The method was used to measure both the high temperature damping and the elastic properties of the iron. The details of using the pulse echo method at elevated temperatures are described in considerable detail. Oscilloscope traces of high temperature echo‐decay patterns are presented.

Transducer completely immersed in ultrasonic propagating liquid can be oscillated back and forth at a high rate, without producing significant turbulence in liquid, if oscillation velocity varies as a predetermined smooth continuous function of time.

The temperature dependences of ultrasonic attenuation and velocity in a high Tc superconductor BiSrCaCuO were measured by the ultrasonic pulse echo method, in the temperature range 77–300 K. Ultrasonic attenuation anomalies were found at 95, 135, and 250 K; the slope of ultrasonic velocity was changed at these temperatures respondingly. There are two superconductive phases in BiSrCaCuO samples at 87 and 120 K found from x‐ray examining. The ultrasonic anomalies at 95 and 135 K are related to the superconductive transition at 87 and 120 K resulting from microstructure instability. The same phenomenon has also been found by internal friction experiments [H. Shen et al., Proc. of 2nd Internal Friction and Ultrasonic Attenuation Conference of China, C63 (1988)]. An ultrasonic anomaly at 250 K is a relaxation process, similar to the mechanism in YBCuO [M‐F. Xu et al., Phy. Rev. B 37, 3675 (1988)].

A system for improving the pulse-echo type of testing to determine certain parameters of tubes, such as internal diameter, external diameter, wall thickness, etc. A pair of pulses are directed transversely to the tube wall so that the transit times of the respective pulses and their reflections from a tube surface, are substantially different. From the value of the transit times associated with each pulse pair the respective parameter is derived. Inaccuracies due to undesired oscillations of the driving shaft for rotating the pulse transducer within the tube to be tested are eliminated. By means of auxiliary reflective surfaces each pair of pulses emitted from the transducer are directed transversely relative to the respective tube wall in substantially one and the same plane.

Sound velocity along a straight segment is estimated by measuring ultrasound pulse travel time as ultrasound pulses are directed along the straight segment from successively different transmitting or receiving positions. A sequence of data pairs comprising travel times and distances traveled is measured and plotted on a graph. Estimated sound velocity is derived from the slope of affine equation fitted to the plotted points.

Method and apparatus for measurement of ice thickness employing ultra-sonic pulse echo technique, wherein an ultra-sonic pulse is emitted from a transducer at the ice-accreting surface of a structure, the pulse is reflected at the periphery of the accreted ice and the reflection is detected. The time delay is calibrated and related to ice thickness and accretion rate.

Apparatus and method for the examination of specimens, particularly human tissue in vivo, by pulse-echo ultrasonic methods. To compensate for the variable and unpredictable attenuation of examining signals when reflected from different targets within the specimen, the echoes are processed -- for instance by frequency analysis -- to produce at least two sets of echo-amplitude information. These sets of information are in turn processed to produce a quantity indicative of the attenuation actually undergone by signals in examining each particular target. This quantity may then be applied to the "A" - scan, "B" - scan or other displays of the echoes of the examining signals to compensate them for the effects of varying attenuation. The apparatus may also include similar uncompensated displays and displays directly representing the attenuation co-efficients of the regions of tissue under scan; comparison of these with the compensated displays may reveal further useful information.

An apparatus and method for making wall thickness measurements. It is particularly applicable to pipeline use. It uses a pulse-echo acoustic arrangement with a single piezoelectric transducer sending and receiving acoustic signals from both faces. It has a pair of reflectors, one for each face of the transducer so that acoustic energy is directed both normal to the wall and at an angle in order to simultaneously measure the wall thickness and find any anomaly such as pitting or the like. For pipeline use there may be a plurality of instruments situated around the periphery of a unit to scan the walls as it travels through the pipeline.

Electronic means, including an analog-to-digital converter responsive to samples of the output from an analog angle sensor directly coupled to an immersed oscillated transducer, is used to trigger the energization of the transducer at each of a predetermined number of equal increments in angle position during each cycle of oscillation of the transducer, with the triggered angle positions during a certain half-cycle of oscillation being interlaced with the triggered angle position during the other half-cycle of oscillation.

A pulse-echo ultrasonic transducer probe includes a substantially centrally disposed axial bore running therethrough and a radial slot extending from the bore to the periphery of its housing. A slotted cap dimensioned to rotatably fit over the top of the housing is provided with a hollow semi-circular stem extending into the bore, the slot of the cap being aligned with the longitudinal opening of the stem. The slot of the cap and that of the transducer, when passing a surgical instrument through the bore into an opaque body, are rotatably adjusted so that they are out of registry with one another for supporting the surgical instrument and for maintaining the instrument in the center of an ultrasonic search beam. Subsequently, after the instrument has reached the desired position in the body the slots are brought into registry for providing removal of the transducer probe from around the instrument.

Measurements of the velocity of sound in suspensions of human erythrocytes were made using a Panametrics 5054 ultrasonic time intervalometer. Data was taken using the pulse echo overlap method for sound velocity at a frequency of 2.25 MHz. The erythrocyte suspensions had a hematocrit of 45% and were made using either 0.75, 0.9, or 1.1% saline solutions. The erythrocyte samples were placed in a chamber maintained at a specified temperature for 10 min to allow thermal equilibrium to be reached and stirred throughout the measurement procedure. The velocity measurements were made by having the pulse of sound pass through a buffer region and observing the echoes received from the front and rear interfaces of the sample chamber as well as a target rod placed in the chamber. For all suspensions studied the velocity of sound increases in a nonlinear manner by about 40 m/s in the temperature range from 25° to 60°C. Details of this variation depend upon the suspending medium and age of the cells. [This work was supported in part by the National Science Foundation.]

Longitudinal elastic wave attenuation measurements have been made in a vanadium single crystal in the frequency range of 45 to 435 Mc in both the normal and superconducting states, using pulse echo techniques. Novel experimental features include the use of a superconducting niobium electromagnet (supplied by Stanley H. Autler, Lincoln Laboratory, Massachusetts Institute of Technology). Throughout the frequency range the product ql >1. (Supported by Office of Naval Research.)