Showing papers in "Ultrasound in Medicine and Biology in 1986"
TL;DR: In this article, Doppler frequencies in systole and diastole were recorded in 51 healthy subjects at 0.5 cm steps along the middle (MCA), anterior (ACA) and posterior cerebral artery (PCA) as well as the basilar artery (BA).
Abstract: The main application of ultrasound in neurology is the examination of extracranial arteries. Recently the Doppler sonographic measurement of flow velocity in the basal cerebral arteries through the intact skull was developed using a pulsed Doppler technique and 2 MHz emitting frequency. Doppler frequencies in systole and diastole were recorded in 51 healthy subjects at 0.5 cm steps along the middle (MCA), anterior (ACA) and posterior cerebral artery (PCA) as well as the basilar artery (BA). The averaged Doppler shift in the MCA was 2.3 +/- 0.4 kHz in systole and 1.15 +/- 0.25 kHz in diastole, in the ACA 1.8 +/- 0.35 kHz and 0.85 +/- 0.22 kHz, in the PCA 1.5 +/- 0.29 kHz and 0.74 +/- 0.18 kHz, in the BA 1.45 +/- 0.31 kHz and 0.72 +/- 0.22 kHz. Separation in four age groups showed a decrease of Doppler shift in the MCA of 20% from a mean age of 17 to 67 years. Static and dynamic compression tests were evaluated to assign transcranial Doppler signals to the MCA, ACA and PCA. No compression test was necessary for the identification of the BA insonated through the occipital foramen.
319 citations
TL;DR: Blood velocities have been measured transcranially, at small Doppler angles, in the middle cerebral artery of normal volunteers, and indicates that changes in middle cerebral blood velocity may be used to monitor changes in flow.
Abstract: Blood velocities have been measured transcranially, at small Doppler angles, in the middle cerebral artery of normal volunteers. Cerebral blood flow was changed by varying carbon dioxide tension. In four volunteers, the relationships between arterial pCO2 and percentage change in intensity weighted mean, median, and maximum Doppler-shifted frequencies in the internal carotid and middle cerebral arteries were linear with slopes of 2.5 and 2.8% per mm Hg change in pCO2. In 38 volunteers, the relationship between end-expiratory pCO2 and time-averaged maximum Doppler frequency was linear over the range of pCO2 20-60 mm Hg with slopes of 2.5 and 2.9 percentage change per mm Hg, for internal carotid and middle cerebral, respectively. These results are very similar to those reported using direct methods of measuring cerebral blood flow. As the transcranial Doppler method is reproducible, this indicates that changes in middle cerebral blood velocity may be used to monitor changes in flow.
268 citations
TL;DR: Both distensibility and cross-sectional compliance of the common carotid artery decreased linearly with age, starting in the third age decade, probably as a consequence of an increase in arterial diameter with age.
Abstract: Changes in distensibility and cross-sectional compliance of the common carotid artery with age were studied in 80 presumed healthy volunteers, varying in age between 20 and 69 y. The distensibility was assessed from the relative increase in arterial diameter during systole normalized with respect to the arterial pulse pressure. The cross-sectional compliance was obtained by multiplying the distensibility by the arterial diameter. The relative diameter changes of the common carotid artery during the cardiac cycle were recorded on-line with a high resolution multigate pulsed Doppler system. The arterial diameter was assessed from the width of the velocity profiles which can also be recorded on-line with this system. Arterial pulse pressure was determined from brachial artery cuff blood pressure measurements. Both distensibility and cross-sectional compliance of the common carotid artery decreased linearly with age, starting in the third age decade. The reduction in the latter parameter was less pronounced, probably as a consequence of an increase in arterial diameter with age.
247 citations
245 citations
TL;DR: Attenuation and backscatter of ultrasound in human breast tissues were measured over the frequency range relevant to breast imaging and showed that the attenuation coefficient of homogeneous regions of infiltrating duct carcinoma was higher than that of fat but somewhat less than thatof fibrous and parenchymal tissues.
Abstract: Attenuation and backscatter of ultrasound in human breast tissues were measured over the frequency range relevant to breast imaging (3-7 MHz). The first step in the measurement process consisted of generating an ultrasound attenuation image of a macroscopic slice of excised breast tissue. This image depicted the various tissue constituents in the samples so that a region of homogeneous tissue could be selected for further investigation. Ultrasound signals used in the computation of the frequency dependent attenuation and backscatter coefficients were then collected from several points within this region of interest. The measured attenuation and backscatter were averaged over all the points in the region of interest and plotted as functions of frequency which ranged from 3 to 7 MHz. The results showed that the attenuation coefficient of homogeneous regions of infiltrating duct carcinoma was higher than that of fat but somewhat less than that of fibrous and parenchymal tissues. On the other hand the backscattering coefficient of ductal carcinoma samples was similar to that of fat but much lower than the backscatter coefficient of parenchymal tissue. The discriminability of the different breast tissue types under these measures, as well as the relevance of the results to clinical imaging are discussed.
245 citations
TL;DR: Based on the acoustic and composition measurements, quantitative correlations of B/A and c with fat-water composition have been developed and inversion of these relationships provide a simple method to determine composition of a tissue sample from B/ a and c measurements.
Abstract: The acoustic nonlinearity parameter B A and sound speed c have been determined for excised normal and abnormal human livers at 20–37°C. These values are compared with analytic measurements of fat and water content of tissues. The results show that normal liver containing 71.0% water and 2.9% fat by weight has a B A value of 6.75 and sound speed of 1592 m/s at 37°C. Both these parameters increase at an average rate of 0.026°C and 1.5m/s/°C, respectively, as the temperature is raised from 20 to 37°C. Fatty liver (24% fat by weight) exhibits highest B A (9.12) and lowest c (1522 m/s) of all the livers studied. In contrast to normal livers sound speed in such a liver was found to decrease with temperature. Based on the acoustic and composition measurements, quantitative correlations of B A and c with fat-water composition have been developed. Inversion of these relationships provide a simple method to determine composition of a tissue sample from B A and c measurements.
138 citations
TL;DR: The data derived from the resting hyperaemia flow profile provides normal ranges for future comparison with patients suffering from peripheral vascular disease and a close correlation between volume flow and the reciprocal of pulsatility index (100/PI).
Abstract: A duplex ultrasound system was used to measure volumetric flow in the human common femoral artery. The accuracy of the technique was validated using a flow rig. The average resting common femoral artery flow rate in a population of subjects clinically unaffected by peripheral vascular disease was 350 +/- 141 mls min-1. Although mean common femoral artery diameter was greater in males (10 +/- 0.9 mm) than in females (7.8 +/- 0.7 mm) (p less than 0.01), there was no significant difference in resting blood flow. Repeated measurements in individual subjects showed a high variability, largely due to physiological fluctuations (75 percent of total variability). There was a close correlation between volume flow and the reciprocal of pulsatility index (100/PI). In normal subjects 100/PI represents a simpler method of determining individual changes in blood flow. The temporal variations in volume flow during periods of reactive hyperaemia had a characteristic profile, which was dependent on the duration of circulatory arrest. The data derived from the resting hyperaemia flow profile provides normal ranges for future comparison with patients suffering from peripheral vascular disease.
119 citations
TL;DR: In all of the individuals studied, sonography was able to depict changes in the thickness and texture of the endometrium which corresponded to the various phases of its development, including the secretory and proliferative phases.
Abstract: Pelvic sonograms were performed every 2-3 days in 10 volunteers in order to study changes in thickness and texture that occur in the normal endometrium. A total of 75 sonograms were performed. The accuracy of sonographic estimates of endometrial thickness was also evaluated in eight patients who underwent hysterectomy for reasons unrelated to the uterus. The majority of sonographic measurements of endometrial thickness in these patients were within 1 mm of the actual thickness as measured in the unfixed specimen. In all of the individuals studied, sonography was able to depict changes in the thickness and texture of the endometrium which corresponded to the various phases of its development. Specifically, the average thicknesses of the endometrium were greater in the secretory phase (3.6 +/- 1.4 mm) than in the proliferative phase (2.9 +/- 1.0 mm) (p less than or equal to 0.05). The texture of the endometrium varied throughout the cycle with the hypoechoic texture slightly more common than echoic in the proliferative phase, whereas the echogenic appearance was most common in the secretory phase. Those technical factors which optimized sonographic depiction of the endometrium are discussed, as well as the possible clinical applications of the sonographic depiction of normal and abnormal endometria.
118 citations
TL;DR: The transcranial pulsed Doppler ultrasound and spectral analysis was used for detection of blood velocities in the basal cerebral arteries to assess four patients who had occlusive extracranial carotid disease and indicated the major collateral source was from the vertebrobasilar system.
Abstract: Transcranial pulsed Doppler ultrasound and spectral analysis were used for detection of blood velocities in the basal cerebral arteries. The Doppler transducer was placed superior to the zygomatic arch and during insonation of the middle cerebral artery care was taken to obtain maximum Doppler-shift frequency signals since this allowed a small angle between the ultrasound beam and this artery. Doppler signals were obtained from the middle, anterior, and posterior cerebral arteries in 20 volunteers with the average depth of the Doppler gate at 4.9 (4.6-5.2 cm), 5.2 (4.9-5.4 cm), and 6.3 cm (6.0-6.9 cm), respectively. These measurements were in agreement with those obtained for 15 cadaver studies, in whom the distance from the proposed site of the Doppler transducer to each basal cerebral artery was measured as 4.7 +/- 0.6, 5.3 +/- 0.5, and 5.9 +/- 0.9 cm, respectively. The reproducibility of middle cerebral artery blood velocity values was tested in seven subjects and showed a variation of not more than 8% in any individual. The method was used in combination with common carotid compression to assess four patients who had occlusive extracranial carotid disease; in three the disease was more severe on one side and reversal of blood flow in the proximal ipsilateral anterior cerebral artery was demonstrated, consistent with cross flow from the contralateral side via the anterior communicating artery of the Circle of Willis. In the fourth patient augmentation of posterior cerebral artery blood velocities during common carotid compression indicated the major collateral source was from the vertebrobasilar system.
100 citations
TL;DR: An approach to ultrasonic tissue characterization, using textural features of the B-scan image, is described, and the potential of the techniques for conditions where a subtle but uniform change in parenchymal texture may be present is indicated.
Abstract: An approach to ultrasonic tissue characterization, using textural features of the B-scan image, is described. Portions of a B-scan image, 64 × 64 pixels spatially by 8 bits deep, are acquired from regions of interest and subjected to computer analysis. A systematic approach to defining a set of 93 textural features of a B-scan is described and methods and criteria for selecting optimum combinations of these are discussed. As a test of its power, the approach has been applied to the discrimination between the B-scan textures corresponding to livers and spleens of normal humans and various measures of “success” have been quantified both on a “training set only” and on a “training set plus test set” basis. The overall test probability of success of 82% on a single image and 94% on a subject yielding multiple images indicates the potential of the techniques for conditions where a subtle but uniform change in parenchymal texture may be present.
87 citations
TL;DR: The method yields quantifiable and repeatable secondary patterns of soft tissue movement in response to primary cardiac movement in a given subject, shows consistently different results as between normal livers and a variety of abdominal tumours, and is sensitive to either progress or therapeutically-induced regression of malignant disease.
Abstract: A method is described for quantifying tissue movement in vivo from the computation of correlation coefficient between pairs of A-scans with appropriate time separation. The method yields quantifiable and repeatable secondary patterns of soft tissue movement in response to primary cardiac movement in a given subject, shows consistently different results as between normal livers and a variety of abdominal tumours, and is sensitive to either progress or therapeutically-induced regression of malignant disease. While the results reported here have been obtained using somewhat simple and crude equipment, the method is well suited to implementation on a commercial real-time scanner.
TL;DR: Pulse-echo ultrasound imaging is modeled as imaging an organ of interest through an intervening planar tissue layer, such as liver through fat in the abdomen or brain through skull bone in the adult head to restore ultrasound image quality, and it is concluded that fat/organ planar interfaces do not degrade image quality significantly.
Abstract: Conventional ultrasound imaging devices are designed based on the assumption of a homogeneous tissue medium of constant acoustic velocity = 1540 m/sec. However, the body consists of tissue layers of varying thicknesses and velocities which range from 1470 m/sec in fat to 3200 m/sec in skull bone. Refraction effects from these layers degrade ultrasound image quality. In this paper, pulse-echo ultrasound imaging is modeled as imaging an organ of interest through an intervening planar tissue layer, such as liver through fat in the abdomen or brain through skull bone in the adult head. Refraction effects from planar tissue layer interfaces are analyzed using Snell's law and measured using phantoms. We also introduce an on-line phased array correction technique based on planar tissue layers to restore ultrasound image quality. We conclude that fat/organ planar interfaces do not degrade image quality significantly. However, refraction effects at a skull/brain planar interface degrades resolution and target acquisition and introduces geometric distortion. Our plane layer phased array correction technique significantly improves image quality in phantoms through lucite aberrators and improves adult cephalic ultrasound image quality when used through the top of the adult skull. The correction technique is robust even in the presence of inaccurate estimates of skull thickness.
TL;DR: The test-object described comprises a thin-walled plastic tube embedded in tissue-mimicking material that is suitable for use with a wide range of Doppler units which employ pulsed and continuous ultrasound in the frequency range 1 to 10 MHz.
Abstract: Versatility in test-objects for ultrasonic Doppler units is desirable. The test-object described comprises a thin-walled plastic tube embedded in tissue-mimicking material. Blood is simulated using a mixture of water and glycerol with sephadex particles to act as scatterers. The test-object is suitable for use with a wide range of Doppler units which employ pulsed and continuous ultrasound in the frequency range 1 to 10 MHz. Calibration of several types of Doppler and imaging duplex systems has been performed for flow velocities up to 100 cm/s through a 10 mm tube. Above this velocity, for this tube dimension, turbulence occurs and prevents the accurate measurement of flow velocity. The versatility of the test-object is further enhanced by the feasibility of manufacturing vessels of different shape and size. Slow flow through the tissue equivalent material may also be detected.
TL;DR: The indices suggested for cardiac contractility were not as closely related to each other, and moreover the differences between them showed no clear pattern, and none of the indices varied independently of the others.
Abstract: Various Doppler waveform indices have been used for assessment of the fetal circulation. Comparisons were made to show what relations exist between the indices, and to identify any differences or difficulties which might arise from using one as opposed to another in clinical practice. Both normal pregnancy and cases of fetal growth failure were studied. Indices were obtained from the maximum velocity envelope of the umbilical artery waveform using a curve fitting technique. The values were very reproducible for all indices. The FHR, which varied over the entire normal range, did not significantly affect the values of any index. The downstream impedance indices calculated included the AB ratio, pulsatility index (PI) and Pourcelot ratio. These all gave very closely correlated results for normals but discrepancies occurred in the at risk group, where values were elevated. This could be attributed to differences in the underlying distributions. The indices suggested for cardiac contractility were not as closely related to each other, and moreover the differences between them showed no clear pattern. None of the indices varied independently of the others. The rising slope, which is by definition related to the PI, was more highly correlated with the downstream indices than the relative flow rate index.
TL;DR: Biochemical composition and structure of normal and atherosclerotic aorta therefore, specifically affect the employed acoustical parameter.
Abstract: For five groups of aortic specimens (normals and with different degrees of atherosclerosis) the ultrasonic backscatter coefficient was measured as a function of frequency in the range 4–15 MHz. The results of the study are related to two classes of structure, connective and fatty tissue (whose relative amount in the arterial wall is related to the different stages of atherosclerosis), as the main determinants of the scattering from aorta. The structure of connective tissue in the aorta produces a power law frequency dependence of the backscatter coefficient typical of small scale structures (Ka ⪡ 1). Fatty tissue introduces a frequency dependence of the backscatter coefficient typical of structures of intermediate scale (Ka ⋍ 1). Biochemical composition and structure of normal and atherosclerotic aorta therefore, specifically affect the employed acoustical parameter.
TL;DR: Echo-Doppler velocimetry is considered to be useful in the diagnosis of renovascular disease and also in the evaluation of abnormalities of renal vascular resistance in hypertensive patients.
Abstract: The renal blood flow velocity characteristics in 8 normal controls, 19 essential hypertensive patients and 8 hypertensive patients with renovascular disease were evaluated using echo-Doppler velocimetry. Two different approaches for ultrasonic detection of the renal artery, the translumbar and the transabdominal approach, were used. Renal Doppler sonograms were analyzed by measuring the acceleration index and the peak-systolic frequency/end-diastolic frequency (S/D) ratio. Renovascular patients who required surgery were examined before and after angioplasty. Doppler signals could be detected in all 35 subjects by using the translumbar approach. The acceleration index of the affected renal arteries significantly correlated to the percent stenosis of the renal artery determined by angiography. The acceleration index in the affected renal artery was improved by surgical treatment. The S/D ratio in essential hypertensives was significantly higher than that in the normal controls. There was a significant inverse correlation between the S/D ratio and creatinine clearance. Echo-Doppler velocimetry is considered to be useful in the diagnosis of renovascular disease and also in the evaluation of abnormalities of renal vascular resistance in hypertensive patients.
TL;DR: The most significantly separating acoustic parameters in the comparison of normal livers from focal tumours were found to be the speed, the attenuation slope, the reflectivity, and the signal to noise ratio.
Abstract: Freshly excised human liver specimens (77) were investigated echographically and histologically. The echography was concerned with the acoustic parameters: speed of sound, impedance, several attenuation parameters, and the texture parameters: reflectivity and the signal to noise ratio. It was found that the speed and impedance, the attenuation parameters, and the texture parameters did not correlate with each other. The major correlation between histologic parameters was found for the focal collagen content to the parenchymal content (r = −0.72). The most important correlations of the acoustic parameters to the histologic ones were: attenuation slope to the focal collagen content (r = +0.63) and the reflectivity to the water content (r = −0.55). The most significantly separating acoustic parameters in the comparison of normal livers from focal tumours were found to be the speed, the attenuation slope, the reflectivity, and the signal to noise ratio. A Fisher discriminant analysis revealed a specificity of 91% and a sensitivity of 83% of the separation of tumours from normals when the speed of sound and two parameters of the frequency dependence of the attenuation were considered.
TL;DR: A model is presented that enables the detailed effects of spectral broadening to be calculated for a continuous wave (CW) Doppler system by using geometric boundary arguments.
Abstract: A model is presented that enables the detailed effects of spectral broadening to be calculated for a continuous wave (CW) Doppler system by using geometric boundary arguments. The model assumes a uniform distribution of isotropic scatterers and treats the transmitter and receiver crystals as incremental sources and receivers. Detailed results for rectangular and circular geometries are presented in order to provide a physical understanding of the manner in which spectral broadening arises. Results are given for the circular geometry, to illustrate the manner in which the received spectrum is affected by the transducer size and distance from the vessel.
TL;DR: Duplex scanning promises to become the definitive, noninvasive method of assessing both the anatomy and flow characteristics of all major arteries outside the thorax and skull that are common sites for the development of atherosclerosis.
Abstract: Ultrasound has come to play an increasingly important role in investigating atherosclerosis. The simple, continuous wave directional devices may be used to measure limb blood pressure and assess velocity patterns from accessible arteries. The recent combined B-mode and pulsed Doppler systems are being used regularly to study the carotid bifurcation in the neck. With improvements in image resolution, Doppler technology and signal processing methods, it is now feasible to evaluate the morphology of the plaque and accurately predict the degree of stenosis by the recorded velocity changes in the residual lumen. By the development of transducers of low transmitting frequency (less than 5 mHz), it is now possible to evaluate arteries at greater depth such as the renal and mesenteric vessels. Duplex scanning promises to become the definitive, noninvasive method of assessing both the anatomy and flow characteristics of all major arteries outside the thorax and skull that are common sites for the development of atherosclerosis.
TL;DR: There was no difference in the PI between sexes nor correlation between the PI and age, and following the ingestion of a meal in a group of 15 subjects the PI decreased by 46% (p less than 0.001).
Abstract: A transcutaneous Doppler ultrasound technique was used to investigate superior mesenteric artery blood velocity waveforms in normal subjects. The shape of the waveforms was quantified by means of the pulsatility index (PI). The mean value ± standard error of the mean of the PI measured in 82 normal subjects in the resting and fasting state was 3.57 ± 0.11. There was no difference in the PI between sexes nor correlation between the PI and age. Following the ingestion of a meal in a group of 15 subjects the PI decreased by 46% (p
TL;DR: Results suggest that both dissolved N2O and CO2 gases in solution suppressed not only the chemical effect but also the biological effect.
Abstract: The influence of dissolved gases (O2, Ar, N2O, and CO2) on the chemical and biological effects of 1.2 MHz continuous wave ultrasound was investigated. Spin-trapping of OH and H radicals with 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) and observation of iodine liberation from a potassium iodide-starch solution were employed for monitoring the chemical effects, while lysing of mouse L5178Y cells was employed for monitoring the biological effects. The effectiveness of the dissolved gases in producing OH-DMPO adducts and H-DMPO adducts was O2 greater than Ar greater than N2O = CO2 approximately equal to O and Ar greater than O2 = N2O = CO2 approximately equal to O, respectively. A result similar to the yield of OH-DMPO was obtained from the liberation of iodine induced by ultrasound. In addition, the effectiveness of the dissolved gases in lysing mouse L5178Y cells by ultrasound was O2 = Ar greater than N2O = CO2 approximately equal to O. These results suggest that both dissolved N2O and CO2 gases in solution suppressed not only the chemical effect but also the biological effect.
TL;DR: It is concluded that the 1st and the 5th hyperechoic layers are partially generated by ultrasound reflection at the interface liquid/wall.
Abstract: In order to evaluate the real number and anatomical correspondence of the ultrasonographically recognizable layers within the gastric wall, we used a high frequency (7.5 MHz) rotating transducer to examine five surgical specimens of the stomach suspended in a water bath. Five layers were always clearly distinguishable within the gastric wall, whose thickness was 3-6 mm. Fine needles and lancets were localized at the level of the 3rd hyperechoic layer when inserted in the submucosa and in the 4th hypoechoic layer when inserted in the muscolaris propria. Thin echogenic bands were always displayed on both sides of other homogeneous tissues (spleen, myometrium) suspended in water. On the basis of these findings and also taking in account the physical laws of ultrasound interactions with tissues, we conclude that the 1st and the 5th hyperechoic layers are partially generated by ultrasound reflection at the interface liquid/wall. The 2nd hypoechoic layer corresponds to the deepest part of the mucosa; the 3rd hyperechoic to the submucosa and the submucosa/muscularis propria interface and the 4th hypoechoic layer to the muscularis propria.
TL;DR: Fetal echocardiography should be part of the prenatal evaluation of fetuses with extracardiac anomalies and of those with nonimmune hydrops, and any fetus suspected to have an abnormality of cardiac structure from the four-chamber view of the heart usually visualized while obtaining the abdominal circumference should also be evaluated.
Abstract: Fetal echocardiograms were performed in 266 gravidae over a one-year period for a variety of previously identified indications. The largest group consisted of 112 patients referred because of other family members with congenital heart disease (CHD). Of these, only one fetus had CHD. The groups with the highest incidence of CHD were those suspected on general obstetrical scan to have structural cardiac disease (50% abnormal) and those scanned after extracardiac anomalies were found (26% abnormals). Forty rhythm abnormalities were encountered, 85% isolated premature atrial extra-systoles. We conclude that fetal echocardiography should be part of the prenatal evaluation of fetuses with extracardiac anomalies and of those with nonimmune hydrops. Any fetus suspected to have an abnormality of cardiac structure from the four-chamber view of the heart usually visualized while obtaining the abdominal circumference should also be evaluated.
TL;DR: An esophageal probe with a precision micromanipulator and a transversely oriented 32 element ultrasonic array which operates at 3.5 MHz is developed to acquire images for left ventricular volume estimation with a three-dimensional reconstruction method.
Abstract: We have developed an esophageal probe with a precision micromanipulator and a transversely oriented 32 element ultrasonic array which operates at 3.5 MHz. The probe allows us to obtain multiple two-dimensional images of the heart with known angular relationships between them over a series of cardiac cycles. Our ultimate purpose is to acquire images for left ventricular volume estimation with a three-dimensional reconstruction method. Technical details of the probe design are given. In vitro tests have shown that the imaging plane can be angulated within 1.5° root mean square error. In vivo results with dogs have demonstrated its ability to obtain multiplanar short axis images of the heart.
TL;DR: In this article, ultrasonic duplex scanning was used for flow velocity measurement in the extracranial carotid vessels in 92 presumably healthy volunteers aged 20-82 and in 14 patients aged 23-72 with normal carotids on angiography.
Abstract: Ultrasonic duplex scanning was used for flow velocity measurement in the extracranial carotid vessels in 92 presumably healthy volunteers aged 20–82 and in 14 patients aged 23–72 with normal carotid vessels on angiography. Velocities were examined as a function of age, diameter, blood pressure, side, or position in the vessel. The peak systolic velocities and late diastolic velocities in the CCA showed an age-dependent decrease (p < 0.001), and the same was true of the peak systolic velocity in the proximal ICA on the right side (p < 0.05) and the late diastolic velocity in the right (p < 0.01) and left (p < 0.001) proximal ICA. The change in velocity was inversely correlated to diameter and blood pressure. The systolic and late diastolic velocities were significantly (p < 0.05 and 0.001 respectively) faster in the left CCA at low position than in the right, and, conversely, in the right ICA (p < 0.05) than in the left. At CCA high position faster diastolic velocities were noted than at CCA low, on both sides. All age-dependent quotients comprised a peak systolic velocity in the CCA, whereas the quotient between the late distolic velocities in proximal ICA and CCA high did not show age dependency. Reproducibility of peak systolic and late diastolic velocities in the CCA, ICA, and ECA, expressed as the mean percentage difference, varied between 6.4 ± 4.6% and 12.7 ± 6.4%.
TL;DR: Results are significant in terms of clinical application of ultrasonically induced hyperthermia for treatment of intraocular tumors and the noninvasive monitoring of tumors by use of diagnostic ultrasound.
Abstract: Cells derived from human skin malignant melanoma were implanted subcutaneously in athymic nude mice. Tumors which developed at the implant site were treated with ultrasonically induced hyperthermia at 49°C for 30 min. Tumors were scanned with a computerized diagnostic ultrasound system before and after treatment. Light (LM) and electron (EM) micrographs of tumors were obtained after scanning. Changes in ultrasonic tissue characterization parameters following treatment were well correlated with histopathologic changes observed in tumors. The results are significant in terms of clinical application of ultrasonically induced hyperthermia for treatment of intraocular tumors and the noninvasive monitoring of tumors by use of diagnostic ultrasound.
TL;DR: In vitro experiments with the new probe show that a tip acceleration of about 100 g is enough to remove ox-liver tissue and then the rate of removal is comparable to that obtained with the CUSA operating at maximum vibration amplitude, and the results of this investigation show that beyond a certain tip acceleration amplitude the removal rate does not increase significantly.
Abstract: The Cavitron Ultrasonic Surgical Aspirator (CUSA) has been applied in neurosurgery for several years, but its mode of action is not yet clear and its efficiency at removing soft tissue has not been quantified. We describe here how we have measured the rate of removing soft tissue per unit time, taking ox-liver tissue as the test material. A motor-driven vibrator/aspirator has been developed in our laboratory. It has permitted us to examine the effect of varying independently frequency, amplitude of the vibration, and suction pressure on the removal rate. The results of this investigation show that beyond a certain tip acceleration amplitude (about 100 g) the removal rate does not increase significantly. Also the removal rate is more or less independent of vibration amplitude within the range between 300 μm and 1 mm. Our in vitro experiments with the new probe show that a tip acceleration of about 100 g is enough to remove ox-liver tissue and then the rate of removal is comparable to that obtained with the CUSA operating at maximum vibration amplitude. Analysis of the particle size of the debris collected from CUSA and from our motor-driven device shows that the particle size distribution is similar over the range of 0.5 μm d