Oiling of American white pelicans, common loons, and northern gannets in the winter following the Deepwater Horizon (MC252) oil spill.

The Natural Resource Damage Assessment and Restoration Trustees for the Deepwater Horizon oil spill assessed the external oiling of migratory bird species dependent on open water in the Gulf of Mexico following the aforementioned spill. The assessment was designed to evaluate birds that use open water during the winter within 40 km of the Gulf shoreline. We focused on the American white pelican (Pelecanus erythrorhynchos), common loon (Gavia immer), and northern gannet (Morus bassanus). Point counts (pelican, loon) or strip transects (gannet) were used and each target species was assessed for oiling (unoiled, trace, light, moderate, or heavy amounts) and photographed. Due to distance at sighting and/or poor visibility, not all visible birds were assessed. The percentage of birds oiled varied by species, with the common loon being the highest (23.6%), followed by American white pelican (16.9%), and northern gannet (6.9%). Most of the American white pelicans and common loons had trace (83% and 72%, respectively) or light levels (11% and 24%, respectively) of oiling. The northern gannet had just trace levels of oiling. Some pelicans (6%) and loons (4%) had moderate amounts of oiling. Based on expert derived-mortality estimates and our estimates of oil exposure, we used Monte Carlo simulations to predict expected decreases of 2.5%, 4%, and 11% in the observed population for the northern gannet, American white pelican, and common loon, respectively. While these values are underestimates of the true values given the long time lag (10-12 months) between the oil spill and the assessment, these data represent some of the few estimates of exposure for these species and describe minimum risk estimates to these species.

Changes in functional connectivity of the amygdala during cognitive reappraisal predict symptom reduction during trauma-focused cognitive-behavioral therapy among adolescent girls with post-traumatic stress disorder.

BACKGROUND: While trauma-focused cognitive-behavioral therapy (TF-CBT) is the 'gold standard' treatment for pediatric post-traumatic stress disorder (PTSD), little is known about the neural mechanisms by which TF-CBT produces clinical benefit. Here, we test the hypothesis that PTSD symptom reduction during TF-CBT among adolescent girls with PTSD is associated with changes in patterns of brain functional connectivity (FC) with the amygdala during cognitive reappraisal. METHOD: Adolescent girls with PTSD related to physical or sexual assault (n = 34) were enrolled in TF-CBT, delivered in an approximately 12-session format, in an open trial. Before and after treatment, they were engaged in a cognitive reappraisal task, probing neural mechanisms of explicit emotion regulation, during 3 T functional magnetic resonance imaging. RESULTS: Among adolescent girls completing TF-CBT with usable pre- and post-treatment scans (n = 20), improvements in self-reported emotion from pre- to post-treatment were positively related to improvements in PTSD symptoms. Adolescent girls with greater post-treatment symptom reduction were also able to suppress amygdala-insula FC while re-appraising, which was not evident in girls with less symptom reduction. Pre- to post-treatment changes in right amygdala to left insula FC that scaled with PTSD symptom reduction also scaled with improvements in emotion regulation. CONCLUSIONS: These preliminary results suggest the neurocircuitry mechanisms through which TF-CBT produces clinical outcomes, providing putative brain targets for augmenting TF-CBT response.

Laparoscopic ultrasonography versus operative cholangiography during laparoscopic cholecystectomy: review of the literature and a comparison with open intraoperative ultrasonography.

BACKGROUND: Laparoscopic ultrasonography (LUS) has been used increasingly over the last several years as a new imaging modality. To define the role of LUS during laparoscopic cholecystectomy, we evaluated LUS by prospectively comparing it with operative cholangiography (OC), by reviewing the literature on LUS, and by retrospectively comparing it with intraoperative ultrasonography performed during open cholecystectomy. STUDY DESIGN: LUS and OC were compared prospectively in 100 consecutive patients during laparoscopic cholecystectomy. The success rate of examination, the time required, the accuracy in diagnosing bile duct calculi, and the delineation of biliary anatomy were evaluated. RESULTS: The success rate of examination was 95% for LUS and 92% for OC. The main reason for unsatisfactory LUS was incomplete visualization of the distal common bile duct. The time required was 8.2 minutes for LUS and 15.9 minutes for OC (p<0.0001). Nine patients had bile duct calculi. LUS had one false-negative result and OC had two false-positives and one false-negative. The accuracies of LUS and OC were comparable except for a slightly better positive predictive value of LUS (100% versus 77.8%; p>0.1). In a literature review, 12 recent prospective studies comparing LUS and OC and three studies on open intraoperative ultrasonography were reviewed. Twelve studies of LUS with a total of 2,059 patients demonstrated results similar to the present study. The success rate was 88% to 100% for both tests. The time for LUS was approximately 7 minutes, about half of the time needed for OC. Overall, LUS was associated with fewer false-positive results than OC; the positive predictive value and specificity of LUS were better, while the sensitivity and negative predictive value of LUS and OC were comparable. OC detected ductal variations or anomalies more distinctly than LUS. Compared with open intraoperative ultrasonography, LUS had a slightly lower success rate and required a slightly longer time because it was technically more demanding, but the two procedures had a similar accuracy for diagnosing bile duct calculi. CONCLUSIONS: Because of their different advantages and disadvantages, LUS and OC can be used in a complementary manner. There is a learning curve for LUS because of its technical difficulty. Once learned, however, LUS can be used as the primary screening procedure for bile duct calculi because of its safety, speed, and cost-effectiveness. OC can be used selectively, particularly when ductal anatomic variations or anomalies or bile duct injuries are suspected.

A brief history of Doppler ultrasound in the diagnosis of peripheral vascular disease.

The history of Doppler ultrasound in peripheral vascular diagnosis is considered in terms of basic developments, clinical applications and impact on medical practice. Many early developments occurred at Osaka University in Japan and the University of Washington in the United States. Through progressive steps, Doppler ultrasound technology has provided clinical applications in blood-flow sensing, waveform analysis, localizing blood flow and two-dimensional (2-D) mapping of blood flow. An important advance was the development of duplex and color Doppler scanning. Real time velocity measurements and flow mapping have led to many clinical applications. Two important applications have been detection and grading of atherosclerotic plaques in the internal carotid artery and the diagnosis of deep venous thrombosis. Doppler ultrasound is the preferred noninvasive imaging method for each of these clinical problems. The recent reaffirmation of carotid endarterectomy as the appropriate management for certain categories of carotid atherosclerotic occlusive disease has led to guidelines for selecting patients for carotid endarterectomy. New Doppler ultrasound criteria are being developed to identify categories of stenosis that relate to these guidelines. The establishment of Doppler ultrasound has led to training programs for technologists and physicians, certification of technologists and establishment of standards and quality control measures for vascular laboratories.

Determination of carotid plaque risk by ultrasonic tissue characterization.

This in vitro study investigated the ability of ultrasonic tissue characterization (UTC) to discriminate between plaques from asymptomatic and symptomatic patients and to compare UTC findings with quantitative measurements of plaque morphology. A total of 34 plaque specimens removed at carotid endarterectomy were scanned transversely at intervals of 1 mm, and compared to tissue cross-sections examined by optical microscopy employing computer-assisted planimetry. UTC was performed by spectral analysis of backscattered radiofrequency signals. The slope, intercept and total power parameters of the spectrum were evaluated. Discriminant analysis was used to compare the ability of the UTC spectral parameters and morphological constituents to correctly classify plaques according to their symptom group membership. UTC correctly classified 88.2% of the plaques. Thrombus was present in 93.9% of the plaques, and there was little difference in the morphological constituents of plaques from asymptomatic and symptomatic patients. Morphological constituents correctly classified 60.7% of the plaques. We conclude, in this preliminary study, that UTC can discriminate between carotid plaques from asymptomatic and symptomatic patients with moderate accuracy, despite a similarity in their morphological composition. UTC discrimination is not related to differences in the type or amount of morphological constituents in the plaques.

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.

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.

Operative ultrasound in general surgery.

BACKGROUND: Since the introduction of real-time B-mode ultrasound during surgery almost 20 years ago, the use of operative ultrasound (OUS) has gradually expanded to a variety of surgical fields. METHODS: A review of the history, technology, and specific applications of OUS in general surgery is presented with our clinical results of over 2300 operations. RESULTS: The benefits provided by OUS are the acquisition of new information not otherwise available, complement to or replacement for operative radiography, confirmation of satisfactory completion of an operation, and guidance of surgical procedures. OUS possesses many advantages as an intraoperative tool, including safety, speed, unique imaging information, wide applicability, high accuracy and procedure guidance capability. CONCLUSION: OUS is gaining wider acceptance in hepatobiliary, pancreatic, endocrine, and vascular surgery. Newer OUS modalities-color Doppler imaging and laparoscopic ultrasound-potentially may widen the applications of OUS in general surgery.

Technique of laparoscopic ultrasound examination of the liver and pancreas.

Since the introduction of a recent laparoscopic ultrasound (LU), the value of this modality in examining the liver and pancreas has been reported. However, a precise scanning technique of LU has not previously been described. Based on our experience with intraoperative ultrasound during laparotomy, we have developed a technique for complete examination of the entire organs using a rigid LU probe. A 7.5-MHz rigid probe, 10 mm in diameter, was employed. The scanning was performed through three trocar ports: right subcostal, subxiphoid, and umbilical. For the liver, the subcostal scanning provided fundamental transverse views. The subxiphoid and umbilical scanning delineated the areas unable to be imaged by the subcostal scanning. For the pancreas, the subcostal and umbilical scanning demonstrated longitudinal and transverse views, respectively. The subxiphoid scanning enhanced examination of the pancreatic head. Three basic probe maneuvers (advancement-withdrawal, lateral movement, and rotation) and various scanning techniques (contact, probe-standoff, and compression scanning) should be utilized appropriately. With a rigid probe, complete LU examination of the liver and pancreas is possible using these techniques. We believe the present scanning method will help more surgeons learn LU.

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.

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.

Oversaturation of color may obscure small intraluminal partial occlusions in color Doppler imaging.

Color Doppler imaging has been reported to have a low degree of accuracy in diagnosing nonocclusive deep venous thrombosis. In this modality the color saturation while diagnosing deep vein thrombosis depends on the blood flow velocity and the sensitivity setting of the color image. To determine the effect of color saturation on the detection of thrombi, an in vitro experiment was performed using a closed-loop tube circulation system with a simulated small intraluminal partial occlusion. Heparinized blood was circulated at three different velocities (2, 5.5, and 9 cm/sec) and the vessels were scanned longitudinally and transversely with color Doppler imaging at three color sensitivity settings (low, medium, and high sensitivity). In appropriate color sensitivity settings (i.e., the low, medium, and high sensitivity for the velocity of 9,5.5 and 2 cm/sec, respectively), the color was saturated adequately in the tube lumen so that the partial occlusion was delineated as a color filling defect in the color field. In undersaturated color conditions, the partial occlusion was depicted owing to its echogenicity, but not as a color filling defect. In over-saturated color conditions, such as the high color sensitivity at the high velocity, the partial occlusion was obscured by the excessive amount of color. The over saturation of color may be one of the reasons color Doppler imaging fails to detect deep vein thrombosis, particularly small intraluminal thrombi.

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.

Intimal hyperplasia producing thrombus organization in an experimental venous thrombosis model.

PURPOSE: A venous thrombosis animal model demonstrated similarities between intimal hyperplasia and thrombus organization. This has prompted the evaluation of a hypothesis that intimal hyperplasia may be the mechanism for thrombus organization in veins with normal pressure. METHODS: Thrombi were produced in surgically exposed jugular veins of anesthetized, 18 to 20 kg pigs. Thrombosis was induced by a combination of devascularization, electric injury produced by a low amperage, direct current, and permanent partial ligation (50% diameter reduction). Vein segments were harvested at 0, 1, 2, 7, 14, and 60 days and histologically examined for fibrin, red blood cells, platelets, smooth muscle cells, endothelial cells, elastic fibers, and collagen deposits. RESULTS: Forty vein segments in 20 pigs were evaluated. Luminal thrombi with thickened walls developed in all specimens. All luminal thrombi demonstrated partial spontaneous thrombolysis over the period of observation. Intimal thickening consisting primarily of smooth muscle cells by day 2 was apparent and progressed until about 2 weeks, when collagen deposits became prominent within the neointima. The neointima frequently comprised half the cross-sectional area of the veins. Endothelial cells were present in the intima as single cells or as lining for clefts formed within the thickened intima. CONCLUSIONS: Smooth muscle cell proliferation with collagen deposition characteristic of intimal hyperplasia seemed to be the mechanism of thrombus organization in the experimental thrombosis model used in this study in which extensive stimulation was used to produce thrombosis.

Experimental assessment of spectrum analysis of ultrasonic echoes as a method for estimating scatterer properties.

In vitro experiments using weak scatterers ranging in size from mean longest diameter of 26.9 to 83.0 microns were performed to test the validity of theoretical predictions for scatterer size and concentration derived from normalized power spectrum parameters of ultrasonic backscatterer echoes. Scatterers consisting of cell clusters were suspended in collagen gel and scanned by a 10 MHz transducer system. Optical measurements validated theoretical predictions that (1) slope value is a function solely of scatterer size; (2) intercept value is a function of scatterer size and concentration; and (3) midband fit value increases as scatterer concentration increases, and, to a lesser extent, as size increases. These results were obtained under relatively ideal conditions of minimal attenuation and scatterer spacing (not closer than two scatterer diameters) and were consistent with the assumptions underlying the scattering theory.

Technique of ultrasound examination during laparoscopic cholecystectomy.

Intracorporeal ultrasonography was used as a new method to examine the bile ducts during laparoscopic cholecystectomy. A prototype rigid 7.5-MHz ultrasound probe, 10 mm in diameter and 50 cm in length, was introduced during 25 laparoscopic cholecystectomies. A dual scanning technique was developed for complete examination of the bile duct. This entailed transverse scanning via the subxyphoid trocar and longitudinal scanning via the umbilical trocar. The intrahepatic ducts were also visualized by placing the probe on the liver surface. Color Doppler imaging was useful to quickly distinguish the duct from vascular structures. Laparoscopic ultrasonography clearly delineated the bile ducts in all operations except one. The time required for imaging was significantly shorter for ultrasonography than for cholangiography. Our preliminary experience demonstrates that a complete examination of the bile ducts can be performed with intracorporeal ultrasonography in a relatively short period of time.

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.

Operative ultrasonography during hepatobiliary and pancreatic surgery.

On the basis of our experience with operative ultrasonography during hepatobiliary and pancreatic surgery, its indications, benefits, and disadvantages are summarized. High-resolution operative ultrasound scanning of the liver, biliary tract, and pancreas was performed during 357, 735, and 242 operations, respectively. The benefits of operative ultrasonography were categorized as acquisition of diagnostic information otherwise not available, replacement for or complement to operative radiography, and guidance of surgical procedures. Operative ultrasonography provided beneficial information during 73 of 82 hepatic operations (89.0%), 57 of 69 noncalculous biliary operations (82.6%), and 177 of 242 pancreatic operations (73.1%). Operative ultrasonography was significantly superior (sensitivity 93.3%) to other screening tests for diagnosing liver metastasis from colorectal carcinoma evaluated in 189 patients, and it detected previously unrecognized metastatic tumors in 18 patients (9.5%). For screening common bile duct calculi during 666 operations, operative ultrasonography and operative cholangiography were comparable in all indices of accuracy except for a higher predictability of a positive test of operative ultrasonography (94.8% versus 71.7%). For diagnosing portal vein invasion of pancreatic carcinoma, operative ultrasonography provided better overall accuracy than preoperative studies (89.7% versus 64.1%). On the basis of operative ultrasound findings, previously planned surgical procedures were altered in 32 of 82 hepatic operations (39.0%) and 24 of 145 pancreatic operations for chronic pancreatitis (16.6%). Operative ultrasound guidance of various surgical procedures was performed during 88 hepatic and 84 pancreatic operations, including 40 ultrasound-guided hepatectomies and 42 pancreatotomies. Operative ultrasonography has a number of advantages, such as safety and speed in performance, wide application, high diagnostic accuracy, and ability of guiding procedures. Its disadvantages are the limitation of the fields of view in certain applications, the need for special equipment, and a slow learning curve.

Operative color Doppler imaging for general surgery.

Operative CDI was performed during 125 general surgical operations (53 hepatic, 25 biliary, 24 pancreatic, 7 esophagogastric, 10 pulmonary, 3 kidney transplant, and 3 soft tissue operations). Operative CDI provided beneficial information in 108 of 125 operations (86.4%). On the basis of operative CDI findings, surgical management was altered in 34 of 125 operations (27.2%), most frequently hepatic and pancreatic operations. Operative CDI demonstrated advantages over B-mode imaging in (1) detection and localization of small blood vessels that are impossible or difficult to identify by B-mode imaging, (2) rapid and definitive distinction of blood vessels from other hypoechoic areas, such as tissue spaces and ducts, (3) determination of the relation of tumors to vascular structures such as vascular invasion of carcinoma, (4) confirmation of blood flow to organs after surgical procedures, and (5) clearer needle localization for guidance of needle placement by color motion marking.

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.