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Biomedical subjects

J Justin

Publications and source records attributed to J Justin.

At least 19 recordsLinked to original sources
PubMed1997

Carotid plaque typing by multiple-parameter ultrasonic tissue characterization.

We evaluated the ability of ultrasonic tissue characterization (UTC), based on backscattered echo signals, to distinguish among the components of advanced carotid plaques. We performed spectral analysis of echo signals acquired from human carotid endarterectomy specimens in vitro to calculate three parameters of the calibrated power spectrum: slope, intercept and total power for fibrous, lipid pool and thrombus constituents of plaque. Plaque constituents were identified histologically. We evaluated classification efficacy by discriminant function analysis. Slope and intercept parameters alone provided correct classification in 92.5%, 57.6% and 72.4% of fibrous, lipid pool and thrombus plaque components, respectively. Slope, intercept and total power used in combination improved classification of the three tissue types to 93.0%, 69.7% and 81.0%. The overall proportion of correctly classified tissue regions increased from 84.5% to 88.0% by the combined use of the three parameters. The improvement in classification that occurred when we included total power as a third parameter suggests that ultrasound plaque components may not consist solely of small, randomly distributed isotropic scatterers. Our ability to identify plaque thrombi provides motivation for future studies of parameter-based imaging methods for identifying such plaque that presents an increased risk of embolic neurologic ischemic events.

Arteriosclerosis↗
PubMed1997

In vivo detection of carotid plaque thrombus by ultrasonic tissue characterization.

The purpose of the study was to determine whether ultrasonic tissue characterization could detect carotid plaque thrombus in vivo. Patients undergoing carotid endarterectomy were examined preoperatively and the ultrasonic tissue characterization findings were compared to those of optical microscopy of the removed plaque specimens. Ten of 15 patients studied had plaque thrombus. Ultra-ultrasonic tissue characterization entailed an analysis of parameters obtained from the power spectrum of backscattered ultrasound signals. Data were obtained with a nominal 10 MHz sector scanning transducer with an effective bandwidth of 3 to 13 MHz. The parameters were the slope and intercept derived from the linear regression of the normalized spectrum and total power (log of the integrated power of the normalized spectrum over the effective bandwidth). The combined effect of the three parameters was determined by discriminant function analysis and showed a significant difference (P < 0.05) between nonthrombus and plaque thrombus in a small sample of patients with advance carotid atherosclerosis. These parameters applied singly could not provide such a distinction. Correct classification of carotid plaque thrombus using the multiple-parameter analysis revealed a sensitivity of 90%, specificity of 80%, and accuracy of 86.7%. This study demonstrates that analysis utilizing a combination of multiple spectral parameters was able to detect carotid plaque thrombus in vivo.

Aged↗
PubMed1995

Roles of hematocrit and fibrinogen in red cell aggregation determined by ultrasonic scattering properties.

Parameters of the power spectrum of backscattered echoes were applied to quantitatively evaluate red cell aggregation in vitro. Human red cell suspensions were circulated in a closed loop of tubing, and ultrasonic, radiofrequency, echo-signal data were obtained using a 10-MHz transducer. Data acquisition was performed at 30-s to 1-min intervals for 5 min after flow stoppage. Two parameters of the normalized power spectrum of the echo signals, spectral slope and Y-intercept, were computed, and estimates of two scattering properties, the scatterer size and acoustic concentration were calculated from these parameters using equations based on scattering theory. Size and acoustic concentration were observed as they changed over time after the stoppage of flow. The key findings were that hematocrit affected the rate of cell aggregation while fibrinogen controlled aggregate size and acoustic concentration.

Adult↗
PubMed1995

Determining the acuteness and stability of deep venous thrombosis by ultrasonic tissue characterization.

PURPOSE: The intent of the study was to determine whether ultrasonic tissue characterization (UTC) could indicate acuteness and stability of deep venous thrombosis (DVT) of the lower extremities. METHODS: Thrombi presenting as filling defects on color Doppler imaging in the common or superficial femoral or popliteal veins in 50 extremities in 45 patients with DVT were studied. Acute DVT was less than 4 days duration, and chronic DVT was greater than 21 days duration. UTC analysis of parameters from the normalized power spectrum of backscattered ultrasound signals from venous filling defects was performed. This spectrum approaches a straight line, and its basic parameters, slope, and Y-intercept are related to scatterer size, concentration, and the square of the scatterer-to-medium acoustic impedances. Ten of the DVT extremities were reexamined at 1 week to assess UTC changes that would indicate thrombus instability. RESULTS: Acute DVT (19 of the 50 extremities) could be distinguished from chronic DVT, mainly on the basis of significantly higher intercept values for the acute group, which were 11.6 relative decibels (dBr) higher than those of the chronic DVT group. Discriminant linear analysis of the two parameters indicated a sensitivity of 94.7% and specificity of 90.3% in correctly diagnosing acute DVT. In a small sample of 10 extremities reexamined at 1 week, acute DVT extremities showed a mean 9.4 dBr decrease in intercept values with no significant change in slope. CONCLUSIONS: UTC distinguished clinically defined acute from chronic DVT. In a small series of extremities, UTC revealed significant instability of acute thrombi in a selected patient population.

Acute Disease↗
PubMed1994

Accuracy of viscera slide detection of abdominal wall adhesions by ultrasound.

Viscera slide is the normal, longitudinal movement of the intraabdominal viscera caused by respiratory excursions of the diaphragm. By detecting areas of restricted viscera slide, ultrasonic imaging was used to identify anterior abdominal wall adhesions prior to laparotomy or laparoscopy. Transcutaneous ultrasound examination was performed on 110 patients. A prediction of adhesions was made for each patient and then compared to the findings during subsequent laparotomy or laparoscopy. Only patients with previous abdominal surgery or history of peritonitis demonstrated adhesions. Sensitivity and specificity of viscera slide ultrasound in predicting adhesions were 90% and 92%. Nine out of 10 false results involved misinterpretation of ultrasound images of the lower one-third of the abdomen. Ultrasonic imaging of viscera slide is highly accurate in detecting abdominal wall adhesions. This technique is most useful in guiding the insertion of trocar in laparoscopic surgery, and as a noninvasive method in studying the formation of adhesions.

Abdominal Muscles↗
PubMed1993

Effect of perfusion and blood content on ultrasonic backscattering of liver tissue.

The purpose of this study was to determine the effect of blood flow perfusion and red cell content on ultrasonic scattering by liver tissue. Data acquisition for ultrasonic tissue characterization (UTC) employing analysis of the backscattered echoes from the power spectrum was obtained from the same region of pig liver tissue under four conditions: 1) normal perfusion in situ, 2) ischemia in situ in the living pig, 3) ischemia in situ immediately postmortem, and 4) immediately after excision of the liver. Discriminant function analysis was used to evaluate differences in the two basic parameters from the normalized power spectrum: slope and intercept. Normal perfused liver had significantly higher intercept values and lower slope values than liver under the other three conditions. Excised liver showed the lowest intercept and highest slope values (p < 0.01). These experiments indicate that differences in perfusion produce significant differences in ultrasonic scattering by liver tissue (ischemia caused a 3 dB drop in intercept amplitude). Normal or ischemic in vivo and in vitro liver tissue is associated with different patterns of ultrasonic scattering, and scattering data under these various circumstances are not equivalent.

Animals↗
PubMed1993

Ultrasonic tissue characterization of experimental venous intimal hyperplasia.

Ultrasonic tissue characterization (UTC) employing slope and Y-intercept parameters from the normalized power spectrum of backscattered echoes was employed in vivo to study compositional changes in the walls of pig jugular veins in which thrombi were experimentally induced. Light microscopy revealed these changes to be intimal hyperplasia with an early predominance of smooth muscle cells and a later mixture of smooth muscle cells and collagen deposits. UTC distinguished intimal hyperplasia from previously reported data from luminal thrombosis UTC. Furthermore, UTC was able to discriminate between early (predominantly smooth muscle cells) and older (smooth muscle cells plus collagen deposits) intimal hyperplasia. The study suggests that intimal hyperplasia in the experimental model used may be organized thrombus and that UTC may be able to follow both the development of wall changes as well as luminal changes occurring in venous thrombosis.

Animals↗
PubMed1993

Age determination of experimental venous thrombi by ultrasonic tissue characterization.

PURPOSE: The ability of ultrasonic tissue characterization based on radiofrequency signal processing to detect compositional differences in thrombi of varying ages was evaluated in vivo. METHODS: Thrombi were produced in 49 jugular veins of 26 anesthetized 18 to 20 kg pigs by partial ligation and application of direct electric current. Thrombi were imaged 30 minutes after formation and 1, 7, and 14 days later with a color Doppler ultrasound scanner that identified the thrombi, and acquired radio frequency data for ultrasonic tissue characterization analysis. Ultrasonic tissue characterization used two parameters from the normalized power spectrum, slope, and intercept, which are related to scatterer size, scatterer concentration, and acoustic-impedance differences between scatterers and surrounding medium. Previous in vitro studies demonstrated that lower slope and higher intercept values correlated with greater cellularity and more-dense fibrin mesh. Histologic examination was performed for each time period. The values of slope and intercept for each timed observation were compared by a multilinear discriminant analysis. RESULTS: There were no statistical differences between day 0 and day 1. Statistically-significant differences in ultrasonic tissue characterization parameters were seen between all other time intervals with p values < 0.01. Older thrombi tended to demonstrate higher slope and lower intercept values. These ultrasonic tissue characterization changes correlated with a red cell and fibrin-mesh density reduction, which was confirmed by histologic findings and was indicative of partial spontaneous thrombolysis. The degree of spontaneous thrombolysis provides an estimate of the age of thrombi. CONCLUSION: Ultrasonic tissue characterization is capable of distinguishing age differences in thrombi in an animal model and has the potential for noninvasive application in clinical diagnosis.

Animals↗
PubMed1993

Differentiation of breast tumors by ultrasonic tissue characterization.

The ability of ultrasonic tissue characterization to differentiate and classify benign and malignant breast tissues in vivo in patients with palpable breast masses and in vitro in excised breast tissue was evaluated. One-hundred and twenty-four in vivo and 89 in vitro studies were performed using a technique of UTC based on parameters from the power spectrum of backscattered echoes. Sensitivities and specificities for diagnosing carcinoma were 86 and 84% for in vivo studies and 94 and 92% for in vitro studies. These UTC parameters provided threshold values for color-coding breast lesion images. The results of this preliminary investigation suggest that UTC provides a basis for assessing more accurately lesions suspected of being malignant prior to biopsy and possibly for evaluating breast lesions noninvasively.

Breast Neoplasms↗
PubMed1992

Cellularity and fibrin mesh properties as a basis for ultrasonic tissue characterization of blood clots and thrombi.

This in vitro study was designed to evaluate the ability of ultrasonic tissue characterization (UTC) based on power spectrum analysis of backscattered radio-frequency echo signals to distinguish two prominent variables of thrombi: cellularity (primarily red cell content) and fibrin-mesh density. Six types of clots simulating thrombus components were prepared by varying red-cell and platelet concentrations and shear forces during clotting. Data were acquired with a linear-array transducer, digitized, and analyzed in terms of slope and intercept parameters obtained from normalized power spectra of radio-frequency echo signals. Increased cellularity and fibrin-mesh density both produced lower slope and higher intercept values, which permitted statistically significant discrimination of cellularity and mesh density in the six types of clots analyzed. Shearing forces and (to a lesser degree) platelet concentrations increased fibrin-mesh density. This study suggests that UTC based upon the power spectrum of echo signals may be used to detect and follow compositional differences that have clinical relevance in the diagnosis and follow-up of thrombi.

Blood Coagulation↗
PubMed1991

Technique of ultrasonic detection and mapping of abdominal wall adhesions.

A technique for noninvasive ultrasound examination to detect and map abdominal wall adhesions is described. The examination is based on the demonstration of movement of abdominal viscera during real-time imaging. This movement is called viscera slide and either occurs spontaneously as a result of respiratory movement or may be induced by manual compression. Abdominal wall adhesions produce a restriction of viscera slide. Ultrasonic demonstration of restricted viscera slide has been used for the precise localization and mapping of abdominal wall adhesions prior to abdominal surgery. The technique may be particularly useful in providing safe initial access in patients undergoing laparoscopy who are at increased risk for trocar injury of viscera due to abdominal wall adhesions resulting from previous surgery or peritonitis.

Abdominal Muscles↗
PubMed1990

Ultrasonic tissue characterization of blood clots.

Ultrasonic tissue characterization based on an analysis of the power spectrum of backscattered signals obtained with ultrasound was used to distinguish morphologic components of blood clots. The three morphologic features for which discrimination was attempted were loose fibrin, red-cell, and dense fibrin clots. The UTC was able to distinguish the morphologic blood components tested. This in vitro work was based on the analysis of parameters related to ultrasound-tissue interaction and on inferences related to the physical properties of scatterer properties (scatterer size, scatterer concentration, and ratio of scatterer to medium acoustic impedances). The ability to distinguish these blood-clot components suggests that UTC may be able to distinguish red from white thrombi and to assess the structures and changes within thrombi associated with the age of the thrombus, their mechanical properties, and treatment monitoring.

Blood Coagulation↗
PubMed1989

Ultrasonic evaluation of erythrocyte aggregation dynamics.

The dynamics of aggregation and disaggregation of blood of varying hematocrit in oscillatory flow in a distensible horizontal tube was determined by measuring the developing echo intensity of the blood samples with a 10 MHz B-mode ultrasonic scanner. Early aggregation could be detected within 10 sec. of stoppage of flow. The rate of echo intensity buildup and thus, presumably the rate of aggregation when flow was stopped was inversely related to hematocrit, as was the rate of echo intensity reduction when flow was resumed. Polycythemic blood of 60% hematocrit showed no echo intensity increase over 5 min. Increasing the shear stress when flow was resumed resulted in rapid decreases in aggregation. In all cases, disaggregation following flow resumption was faster than aggregation following flow stoppage.

Adult↗
PubMed1987

Calcium-dependent protein kinase reactions associated with parotid gland secretory granule membranes.

Rat parotid secretory granule membranes were examined for the presence of calcium-dependent protein kinase activities and kinase substrates. Protein kinase C (C-kinase), which is stimulated by certain phospholipids, was present in the membranes, as indicated by its ability to catalyze the phosphorylation of histone. Two substrates for protein kinase C were seen in the granule membranes. The cytosolic fraction from the cell contained kinase activity, which was stimulated by phosphatidylserine and which caused the phosphorylation of two granule membrane polypeptides. In addition, when both granule membranes and cytosol were incubated together, phosphorylation of the cytosolic substrates was inhibited, indicating that the granule membrane substrates were phosphorylated preferentially. The results indicate that the granule membranes may react with cytosolic protein kinase C activity in a way which would direct an intracellular calcium and diacylglycerol signal toward the granule membrane. Since these signals occur during stimulation by various agonists, the mechanism may contribute to secretion.

Animals↗