Showing papers in "Ultrasound in Medicine and Biology in 1981"
TL;DR: It is observed that acoustic speed is superior to any attenuation or backscattering characteristics for distinguishing in vitro between specimens of tumours and normal human liver selected at random, when the data are corrected for variations between one subject and another.
Abstract: Ultrasonic speed, attenuation and backscattering were measured as functions of frequency and orientation in specimens of exercised human liver, with a view to establishing the usefulness of such measurements to characterize the pathology and structure of the tissue. It is observed that acoustic speed is superior to any attenuation or backscattering characteristics for distinguishing in vitro between specimens of tumours and normal human liver selected at random. However, when the data are corrected for variations between one subject and another, sound speed, attenuation and the mean back-scattering coefficient at a given frequency show a comparable degree of usefulness in this respect. Analysis of the periodicities present in the backscattering diffraction patterns did not contribute any improvement in the ability to distinguish between tissue states. On average, by comparison with normal liver, ultrasound travels about 1.5% (± 1%) slower, is attenuated by about 20% (± 30%) less at 3 MHz and is backscattered by about 80% (±115%) less at 3 MHz in the tumor specimens that were measured. Livers infiltrated by diffuse malignant disease appear to possess quite different ultrasonic propagation properties to normal liver although insufficient data are yet available for firm conclusions to be drawn.
210 citations
TL;DR: It is observed that the ultrasonic velocity decreases with both increasing water and fat contents, although the water content appears to have the overriding influence.
Abstract: Ultrasonic speed, attenuation and backscattering were measured as a function of frequency and compared with measurements of water content, fat content and collagen content in specimens of excised human liver. It is observed that the ultrasonic velocity decreases with both increasing water and fat contents, although the water content appears to have the overriding influence. An increase in the water content correlates well with decreasing attenuation and backscattering coefficients (and the slope of their frequency dependence), but positive dependences are found between these acoustic characteristics and the fat content. It is believed that the dependences on fat content are of secondary importance to those on water content and possibly arise as a result of an inverse relationship between the fat content and the water content. For the collagen content of liver specimens, positive correlations, barely significant, were found for attenuation and backscattering only after the data had first been corrected for variations in water content, while no significant velocity dependence was seen.
170 citations
TL;DR: It is concluded that transmission of echocardiographic contrast through a capillary bed is feasible though potentially dangerous.
Abstract: The pulmonary capillary bed normally removes echocardiographic contrast from the circulation, so contrast injected peripherally or on the right side of the heart is not seen on the left side of the heart in the absence of intracardiac or intrapulmonary shunts. Based on recent advances in the theoretic understanding of microbubble physiology, we propose several theoretic methods for causing the transmission of ultrasonic contrast through the lungs to enable opacification of the left side of the heart. Three of these methods are tested: (I) injection of ether, an organic compound which may pass the pulmonary capillaries in the liquid phase and cavitate in the pulmonary veins to yield left heart echo contrast, (2) injection of hydrogen peroxide, a substance which chemically decomposes on the left side of the heart to yield gaseous oxygen that can be imaged as echo contrast, and (3) injections of 5% dextrose in the pulmonary wedge position. The first two methods were tested in anesthetized pigs, and the third method in humans and anesthetized rabbits. All methods could cause transmission of echocardiographic contrast through the lungs. There were no adverse reactions in the human subjects. Pulmonary wedge injections in rabbits were associated with one large and three small myocardial infarctions out of 7 animals sacrificed 24 hr later. We conclude that transmission of echocardiographic contrast through a capillary bed is feasible though potentially dangerous.
121 citations
TL;DR: The observations suggest that there may be a threshold for these effects at approximately this intensity, and temporal average intensity appears to be a poor predictor for these biological effects.
Abstract: The larvae of Drosophila melanogaster were exposed to repetitive, microsecond length pulses of 2 MHz ultrasound. The observed effects included killing of larvae and delayed lethality in the pupal stage. The effects depended strongly upon the temporal peak intensity with killing observed at spatial. temporal peak intensities above 10 W/cm 2 . In fact, the observations suggest that there may be a threshold for these effects at approximately this intensity. Temporal average intensity appears to be a poor predictor for these biological effects. Marked decreases in survival rates were observed at spatial, temporal average intensities as low as 3 mW/cm 2 .
87 citations
TL;DR: Exposure of Na131I at varying pulsed regimes and intensities resulted in an increased efficiency of pulsed ultrasound to produce iodine release compared to continous wave exposures, and a model based on the concurrent operation of two mechanisms has been proposed.
Abstract: Iodine-131 labeled sodium iodide was used to demonstrate an iodine release reaction indicative of cavitation activity. Exposure of Na131I at varying pulsed regimes (1:1 duty cycle, 60 sec-60 μsec pulse duration) and intensities (10–30W/cm2) resulted in an increased efficiency of pulsed ultrasound to produce iodine release compared to continous wave exposures. A model based on the concurrent operation of two mechanisms has been proposed to explain this phenomenon.
66 citations
TL;DR: Arterial occlusive disease in peripheral blood vessels can be evaluated with an ultrasound scanning system designed to generate real-time cross sectional tissue images and to assess the character of blood flow at any point using multi-gate Doppler methods.
Abstract: Arterial occlusive disease in peripheral blood vessels can be evaluated with an ultrasound scanning system designed to generate real-time cross sectional tissue images and to assess the character of blood flow at any point using multi-gate Doppler methods. A new-generation echo/Doppler system. Duplex scanner IV, incorporates digital display technology to store both echo target location and flow velocity parameters for color composite imaging. Many display formats are possible. In B -mode format echographic tissue images are supplemented with flow information acquired at a specific point in time over 20–30 cardiac cycles by a slow spatial sweep of the Doppler beam in the region of interest. Image storage also makes possible a novel M/Q-mode presentation wherein anatomical interfaces and flow velocities are detected along a single line of sight and displayed as a function of time.
58 citations
TL;DR: It is shown in this paper that relatively simple ultrasound techniques, in combination with specific scanning protocols, can provide a more accurate diagnosis for pathologies in the breast of young subjects than does X-ray mammography.
Abstract: It is shown in this paper that relatively simple ultrasound techniques, in combination with specific scanning protocols, can provide a more accurate diagnosis for pathologies in the breast of young subjects than does X-ray mammography. Static, B -mode ultrasound instrumentation with close-interval scanning and transducers designed for the specific examination regime, was used to examine 116 symptomatic breast patients under 30 yr of age. Approximately 50% of the patients were diagnosed by ultrasound as fibroadenoma cases; biopsy of 22% of these cases indicated 100% diagnostic accuracy for the ultrasound technique. Thirty-one percent of the cases diagnosed as fibroadenoma by ultrasound were also examined by X-ray mammography; in 80% of these cases, X-ray mammography did not adequately image the mass.
52 citations
TL;DR: Focused ultrasound at a center frequency of 9.8 MHz was used to create lesions of the retina and choroid in the proptosed eye of the anesthetized albino rabbit and results were compared to those obtained under continuous-wave exposures.
Abstract: Focused ultrasound at a center frequency of 9.8 MHz was used to create lesions of the retina and choroid in the proptosed eye of the anesthetized albino rabbit. Pulsed ultrasound was employed and results were compared to those obtained under continuous-wave (CW) exposures. Short pulses (e.g. 100 μsec) delivered at high repetition frequencies (e.g. 3 KHz) produced the same average intensity threshold values as those found for CW conditions. Longer pulses (e.g. 0.1 sec) delivered at low repetition frequencies (e.g. 2 Hz) produced lesions at lower temporally averaged intensities. The lowered thresholds are related to cyclical blanching occurring in insonified choroidal blood vessels. All lesion-producing intensities (approximately 100 W/cm2) were orders of magnitude larger than diagnostic levels.
48 citations
TL;DR: Computer simulations of the interdependence of different pairs of the parameters of spherically focusing ultrasonic transducers were performed, taking the ultrasonic attenuation in biological tissue into consideration, and the effect of thermal conduction on the temperature distribution was discussed.
Abstract: Computer simulations of the interdependence of different pairs of the parameters of spherically focusing ultrasonic transducers were performed, taking the ultrasonic attenuation in biological tissue into consideration. The maximum distance and gain of the last intensity maximum were calculated with different frequencies between 0.3 and 5 MHz and frequencies around 1 MHz were found to be most useful for hyperthermia. The relationships between the distance of the last axial maximum and the radius of curvature, as well as between the intensity gain and radius of curvature with different diameters of ultrasonic transducers operating with a frequency of 1 MHz were calculated. Also the effect of thermal conduction on the temperature distribution was discussed.
44 citations
TL;DR: A new type of pulse-Doppler that employs only a single processing channel consisting of double delay line canceller and delay line phase-detector has promise in making true Doppler imaging available with B -mode imaging systems as well as for investigating velocity profiles and diameter of peripheral arteries.
Abstract: A new type of pulse-Doppler is described and results illustrating in vivo operation presented. The system uses a phase detection principle to produce an output proportional to the velocity of moving structures continously as a function of depth into the tissue, similar to an A -mode display. It employs only a single processing channel consisting of double delay line canceller and delay line phase-detector. Operation is equivalent to a parallel processing multiple-gate Doppler having a very large number of gates. This relatively simple system has promise in making true Doppler imaging available with B -mode imaging systems as well as for investigating velocity profiles and diameter of peripheral arteries.
39 citations
TL;DR: The method uses various combinations of voltage steps which are applied to the transducer as excitation pulses, which results in an appreciable shortening of the received signal.
Abstract: A method for the generation of short ultrasound pulses by a piezoelectric transducer is presented. The method uses various combinations of voltage steps which are applied to the transducer as excitation pulses. Compared with conventional excitation used in echo systems this results in an appreciable shortening of the received signal. A qualitative explanation of the results obtained is given.
TL;DR: The demonstration that peritoneal macrophages exposed in vivo to ultrasound also had depressed phagocytic abilities indicated that the reduced clearance of carbon from the blood of mice was not entirely due to damage to the liver.
Abstract: Swiss mice insonated with a 2 megaHertz (MHz) wave at an energy level of 8.9-milliwatts/square centimeter (mW/cm2) applied over the liver had an impaired ability to clear injected colloidal carbon from their blood compared to untreated mice. Mice evaluated immediately after treatment had a depressed phagocytic index (K) and clearance half-time ( T 1 2 ) but their phagocytic index corrected for liver and spleen weight (α) was normal. All three parameters deviated from normal if the clearance assay was conducted 48 or 72 hr after insonation, indicating a latency of the effect of ultrasound on the phagocytic system. The demonstration that peritoneal macrophages exposed in vivo to ultrasound also had depressed phagocytic abilities indicated that the reduced clearance of carbon from the blood of mice was not entirely due to damage to the liver.
TL;DR: It is shown that the TIH displays well the center frequency as well as the width of a spectrum but does not give any more detailed information about the shape of the spectrum.
Abstract: The relation between the time interval histogram (TIH) and the spectrum of an ultrasound Doppler signal is investigated theoretically. It is shown that the TIH displays well the center frequency as well as the width of a spectrum but does not give any more detailed information about the shape of the spectrum.
TL;DR: Ulasonic observation of the ovary at 8–12 hr intervals reveals typical appearances when ovulation has take place and possibly signifies luteinisation of the unruptured follicle when no collapse of the follicle is observed before.
Abstract: Ultrasonic observation of the ovary at 8–12 hr intervals reveals typical appearances when ovulation has take place. Shortly after ovulation there is an increase in solid echoes as the cystic follicle decreases in size until a small, less intense echogenic area (“cystic or structural loosening”) stays visible within the ovary. This either stays unchanged during the luteal phase or increases up to a cystic corpus luteum. Premensturally, the ovary regains its more homogenous solid structure. When cystic alteration has taken place, solid echoes invade the cystic corpus luteum which continuously decreases in size once menstruation has started. A cystic structure, similar to a cystic corpus luteum, in the second part of the menstrual cycle possibly signifies luteinisation of the unruptured follicle when no collapse of the follicle is observed before. After multifollicular development, the collapse of the predominant follicle may be difficult to outline when, simultaneous to ovulation, other follicles enlarge as in patients treated with gonadotrophins.
TL;DR: The ability to identify both low and high grade stenoses with this system provides a basis for routine screening of patients with suspected carotid disease.
Abstract: Ultrasonic imaging of the carotid artery bifurcation using a 30 channel pulsed Doppler system has been studied in a prospective trial. The results were compared to X-ray contrast angiography. Ninety per cent of the lesions of less than 50% were detected, as were all total occlusions of the internal carotid artery. The overall sensitivity was 93% and specificity 100%. Lateral ultrasonic scans were important in detecting lesions of less than 50% stenosis providing the diagnostic information in 48% of these vessels. The ability to identify both low and high grade stenoses with this system provides a basis for routine screening of patients with suspected carotid disease.
TL;DR: There is a considerable variation in the fields produced by transducers of the same type, and the correspondence between the theoretical and experimental results can be improved in most cases by using a model in which each crystal vibrates like a flexible plate rather than like a rigid piston.
Abstract: A knowledge of the shape of the fields generated by Doppler ultrasonic probes is of particular importance in vessel imaging and in blood flow research. In this study the combined effects of the transmitting and receiving crystals of four types of commonly used Doppler probe have been calculated numerically using two different theoretical models, and the results compared with experimental measurements. The results show that there is a considerable variation in the fields produced by transducers of the same type, and that the correspondence between the theoretical and experimental results can be improved in most cases by using a model in which each crystal vibrates like a flexible plate rather than like a rigid piston. Theoretical iso-echo contours at various distances from the transducer face are presented for each of the four types of transducers studied.
TL;DR: Mitotically synchronized Chinese hamster V-79 cells were exposed to continous wave 1 MHz ultrasound at a spatial peak intensity of 3 W/cm 2 at 37°C and many of these intact but nonviable cells appeared to be morphologically damaged.
Abstract: Mitotically synchronized Chinese hamster V-79 cells were exposed to continous wave 1 MHz ultrasound at a spatial peak intensity of 3 W/cm 2 at 37°C. A fraction of the cells was lysed immediately, and a second fraction was rendered nonviable. Many of these intact but nonviable cells appeared to be morphologically damaged. The remaining viable cells formed smaller colonies than did unexposed controls, apparently because of the death of one daughter cell at or shortly after the first division. There were no apparent effects on cells surviving beyond that period, and progression through the cell cycle was unperturbed.
TL;DR: Using either the center frequency or a computed mean frequency to represent a broadband pulse, both the −20 dB pulse-echo response beam width and the divergence of the beam as it propagates through tissue-like material can be well approximated.
Abstract: A means of estimating the pulse-echo response beam width and the position of the peak: in the pulse-echo axial response for clinical ultrasonic transducers is presented. Using a simple model based on continuous wave propagation, equations describing the width of a transmitted beam and the axial pressure amplitude as a function of distance from the transducer have been adapted to describe broadband transducers. The efficacy of these adaptations is verified by comparison to actual measurements performed on both focused and non-focused transducers for attenuating paths as well as “lossless” water paths. By using either the center frequency or a computed mean frequency to represent a broadband pulse, both the −20 dB pulse-echo response beam width and the divergence of the beam as it propagates through tissue-like material can be well approximated. Also, for nonattenuating paths, the position of the peak in the axial pressure profile, and, hence, the focal plane position, can be estimated from the phys ical dimensions of the focused transducer and the center or mean frequency.
TL;DR: The ultrasonic velocity at 100 MHz and room temperature was measured in fresh, excised mammalian liver, kidney, spleen, and pancreas and mouse kidney and the results show excellent agreement with measurements at low MHz frequencies.
Abstract: The ultrasonic velocity at 100 MHz and room temperature (23–26°C) was measured in fresh, excised mammalian liver, kidney, spleen, and pancreas and mouse kidney. The results show excellent agreement with measurements at low MHz frequencies. A significant velocity difference is reported between kidney cortex and medulla, but no difference was observed between the exocrine and islets of Langerhans in the first measurements of velocity in the pancreas.
TL;DR: Liver tissue of anaesthetised mice, exposed by dissection, has been treated while bathed in saline with therapeutic intensity levels of ultrasound for periods up to 2 min, initiated by cavitation events occurring in the saline surrounding the liver.
Abstract: Liver tissue of anaesthetised mice, exposed by dissection, has been treated while bathed in saline with therapeutic intensity levels of ultrasound for periods up to 2 min. Samples of tissue were taken on completion of the irradiations and prepared for light and electron microscope examination. Specimens irradiated with 0.8 MHz ultrasound contained patches of damaged tissue several hundred microns across at depths of up to 2 mm below the incident surface. In specimens treated with 1.5 MHz ultrasound, the surface few hundred microns of tissue was modified, and after 3 MHz irradiation no changes were found. When the abdominal wall covered the liver surface, no effects were observed at any frequency. The lowest intensity at which damage occurred was the same as that at which acoustic emission associated with cavitation could just be detected. The effects may be initiated by cavitation events occurring in the saline surrounding the liver.
TL;DR: Three parameters α, DR and D n ( A ), i.e. the efficiency, the dynamic range and the normalized axial resolution are used to evaluate the performance of ultrasound transducers for diagnostic imaging equipment and determine optimum conditions for use in the design of high frequency array transducers.
Abstract: Three parameters α, DR and D n ( A ), i.e. the efficiency, the dynamic range and the normalized axial resolution are used to evaluate the performance of ultrasound transducers for diagnostic imaging equipment. These parameters determine optimum conditions for use in the design of high frequency array transducers. A newly-developed piezoelectric ceramic material composed of (Pb,Sr)(Ti,Zr)O 3 or Pb[(Mg 13 , Nb 23 ), Ti,Zr]O 3 which satisfies the above-mentioned conditions was used to fabricate a co-phase array ultrasound transducer. The transducer showed good electrical and acoustic performance in accordance with theoretical considerations.
TL;DR: It has been discovered that three theoretically derived plots of acoustic scattering for rigid immovable spheres appearing in two standard reference works are only qualitatively correct and therefore could be misleading.
Abstract: It has been discovered that three theoretically derived plots of acoustic scattering for rigid immovable spheres appearing in two standard reference works are only qualitatively correct and therefore could be misleading. The reason for the inaccuracy is shown to be premature truncation of the infinite series resulting from the theory. Quantitative plots resulting from exact computations and those corresponding to premature truncations are displayed. The main purpose of this note is to alert others, who may wish to check their programming of theoretical expressions for scattering of ultrasonic waves from spheres, to the error of using the plots in the standard reference works and to suggest that they use the exact results presented here.
TL;DR: The variable intersecting zone Doppler unit has been linked with a real-time ultrasonic scanner to study blood flow in the pregnant uterus and overcomes the problem of lack of localisation normally associated with continuous wave doppler devices while retaining the low noise and high velocity measurement features of these instruments.
Abstract: A continuous wave Doppler system has been constructed with which a localised region may be studied by arranging for the transmission zone and the reception zone of the beam to intersect at the selected region. This intersecting zone technique overcomes the problem of lack of localisation normally associated with continuous wave Doppler devices while retaining the low noise and high velocity measurement features of these instruments. The variable intersecting zone Doppler unit has been linked with a real-time ultrasonic scanner to study blood flow in the pregnant uterus. Sites studied include the placenta, the cord, the foetal aorta and umbilical vein.
TL;DR: The ultrasonic method allows a reliable determination of the fourth ventricular size both in normal cases, in cases of hydrocephalus and in cerebellar atrophies with otherwise normal ventricular systems.
Abstract: 123 neuropediatric children were examined ultrasonically by A - and B -scan in the sagittal plane to visualize echoes from the subtentorial space. The ultrasonic beam was directed from the anterior part of the vertex to just above the sella into the subtentorial region. An echo from an interface corresponding very well with the location of the caudal part of the roof of the fourth ventricle was found in 97.6% of the cases. The origin of the echo was validated by 26 PEG examinations, both in normal and in pathological cases, and additionally in cases returning to normal after a successful shunt operation. In 20 cases with a normal sized fourth ventricle the ultrasonic finding was confirmed by a normal CT scan. The method allows a reliable determination of the fourth ventricular size both in normal cases, in cases of hydrocephalus and in cerebellar atrophies with otherwise normal ventricular systems. When the size of the fourth ventricle is compared with the other ventricles, measured ultrasonically, conclusions about the patency of the aqueduct can be drawn. It is not possible with this technique to diagnose a dilation of the cisterna magna.
TL;DR: Comparisons showed that changes found with 200, but not 50, sec of irradiation indicate that there is a threshold between these times for the appearance of the changes evoked under the conditions used.
Abstract: Batteries of 23 chemical and 7 hematological blood constituents and factors were determined to indicate possible damage to female albino Swiss-Webster mice of ultrasonic irradiation in vivo (2MHz continuous wave, 1 W/cm 2 , 34°C). Untreated, sham-treated, and treated mice were used. Effects observed 2 and 24 hr after ultrasonic exposure for 200 sec, and those seen 24 hr after 50 and 200 sec exposure, were compared. These comparisons showed: (1) Sham treatment alone induced significant changes in levels of certain of the blood constituents. (2) Some significant differences between the treatment and the shamtreatment groups were separately apparent 2 and 24 hr after irradiation, indicating recovery at 24 hr from certain of the 2 hr effects. Other changes, probably more significant, were still present 24 hr after treatment. (3) Changes found with 200, but not 50, sec of irradiation indicate that there is a threshold between these times for the appearance of the changes evoked under the conditions used.
TL;DR: The Minivisor is a potentially useful portable device for screening of an obstetric population and a good correlation between both measurements was obtained.
Abstract: A comparative study between a linear-array real-time hand-held scanner (Minivisor) and a conventional scanner (Diasonograph) in the assessment of the fetal biparietal diameter (B.P.D.) is presented. A total of 160 patients between 15 and 41 weeks of gestation was included in the study. A good correlation between both measurements was obtained. The reproducibility of the B.P.D. measurement was better and the scanning time considerably shorter when using the Minivisor. It seems therefore that the Minivisor is a potentially useful portable device for screening of an obstetric population.