Analysis of blood clot echogenicity

The ability of B-mode ultrasound to follow effectively blood clot echogenicity changes over time under conditions of red cell preservation and lysis was evaluated. Blood clots were produced in cellulose dialysis tubing and then placed into appropriate baths of either saline or water. The echogenicity changes were then followed quantitatively using A-mode and qualitatively using B-mode imaging. Blood clots in saline showed an initial decrease followed by a leveling off in echogenicity. Blood clots in water showed a decline in echogenicity throughout the experiment. The A-mode imaging was effectively able to follow blood clot echogenicity changes under these controlled conditions.     

Red cell aggregation and the echogenicity of whole blood.

To study the relationship between red cell aggregation and whole blood echogenicity, red cell aggregation was quantitated by a photometric method, whole blood echogenicity was quantitated by videodensitometry and sedimentation rate was quantitated by a modified Westergren method. Changes in red cell aggregation were produced by alterations in the hematocrit. The results showed that red cell aggregation increased in a linear fashion with increases in hematocrit. The sedimentation rate decreased in a linear manner with increases in hematocrit. Whole blood echogenicity showed a biphasic response, with an initial increase in echogenicity, peaking at hematocrits varying from 14-24% and decreasing thereafter. Over the physiologic range of hematocrits, an increase in the formation of red cell aggregates is associated with a decrease in the echogenicity of whole blood. Thus, red cell aggregates were not visible using our ultrasound equipment at physiologic hematocrits, and the echo contrast in blood under our experimental conditions at these hematocrits must represent either plasma spaces, platelet aggregates or possibly white cell aggregates. The association between spontaneous contrast and a propensity for thromboembolism imply that platelet aggregates are the most likely origin of in vivo echo contrast in flowing blood.     

Ultrasound-induced thermal elevation in clotted blood and cranial bone

Ultrasound thermal effects have been hypothesized to contribute to ultrasound-assisted thrombolysis. To explore the thermal mechanism of ultrasound-enhanced thrombolysis with recombinant tissue plasminogen activator (rt-PA) for the treatment of ischemic stroke, a detailed investigation is needed of the heating produced in skull, brain and blood clots. A theoretical model is developed to provide an estimate for the worst-case scenario of the temperature increase in blood clots and on the surface of cranial bone exposed to 0.12- to 3.5-MHz ultrasound. Thermal elevation was also assessed experimentally in human temporal bone, human clots and porcine clots exposed to 0.12 to 3.5-MHz pulsed ultrasound in vitro with a peak-to-peak pressure of 0.25 MPa and 80% duty cycle. Blood clots exposed to 0.12-MHz pulsed ultrasound exhibited a small temperature increase (0.25 degrees C) and bone exposed to 1.0-MHz pulsed ultrasound exhibited the highest temperature increase (1.0 degrees C). These experimental results were compared with the predicted temperature elevations.     

Cyclic changes of blood echogenicity in high-frequency ultrasound.

Ultrasound images from human arteries obtained in vivo with an intravascular 30 MHz ultrasound imaging device show that blood echogenicity changes during the cardiac cycle. Quantitative measurements of blood echogenicity during the cardiac cycle suggest that these variations may be related to changes in the state of erythrocyte aggregation, which are induced by varying shear rate.     

Relation of in vivo blood flow to ultrasound echogenicity

The mechanism of echogenicity of flowing blood during real-time ultrasonography was investigated experimentally in vivo by scanning venous and arterial blood and venous blood subjected to varying degrees of obstruction. Luminal echoes were more intense in flowingblood of the vena cava than in aortic blood of dogs. Vena cava and portal echoes increased in intensity as flow was decreased progressively by obstruction. We believe that an important cause of echogenicity of flowing blood is red cell aggregation which is greatest at low shear rates (low flow velocity). Echogenicity decreases with increase in shear rate (higher flow velocity) which causes red cell disaggregation.     

The effect of extreme acid and alkali changes upon the echogenicity of blood

The degree of red cell aggregation is dependent upon multiple conditions. The purpose of these experiments was to ultrasonically determine the threshold and reversibility of human red cell aggregation to extreme pH changes at varying shear rates. Real-time B- and A-mode ultrasonography were used to measure echogenicity. Measurements were recorded at original, acidic, and alkaline pH and following return of both acidic and alkaline pH to neutral pH levels. The results showed that 1) neutral red cell suspensions did not become echogenic at any shear rate; 2) acidification produced a shear-related, partly reversible echogenicity; and 3) alkalinization caused a less intense but more shear-resistant and less reversible echogenicity. Alkalinization produced a microscopically discernible greater persistence of intense red cell aggregation. Cell membrane protein loss was detected by electrophoresis.     

Correlation between the echogenicity of dysplastic nodules and their histopathologically determined fat content.

OBJECTIVE: To correlate the echogenicity of dysplastic nodules in cirrhotic liver with the difference in fat content between lesions and surrounding liver. METHODS: This retrospective study involved 65 histopathologically proved dysplastic nodules (39 high grade and 26 low grade). Their echogenicity compared with that of surrounding parenchyma was determined sonographically, and differences in the proportions of fat globules contained in the nodules and in surrounding liver tissue were evaluated histopathologically. The sonographic and histopathologic findings were correlated. RESULTS: Among the 65 dysplastic nodules, echogenicity was high in 30 (46%), equal in 5 (8%), and low in 30 (46%). In all cases, there was significant correlation between echogenicity on sonographic imaging and the difference in fat content between nodules and surrounding liver tissue (P < .01). There was, however, no significant correlation between the degree of dysplasia and sonographic echogenicity (P > .05). CONCLUSIONS: The echogenicity of dysplastic nodules correlated with their fat content. Echogenicity did not, however, predict whether the grade of a nodule was high or low.     

Survival and function of baboon RBCs released from clotted blood and washed before autologous transfusion

BACKGROUND: One alternative to an allogeneic transfusion is the salvaging of the patient's own shed blood. In this study, baboon blood was allowed to clot and the RBCs that were released from the clotted blood lysed with and without urokinase were washed before autologous transfusion. STUDY DESIGN AND METHODS: Forty-four studies were done in 13 baboons (Papio cynocephalus or Papio anubis) over a 3-year period. In 24 studies, a 50-mL volume of blood was collected without an anticoagulant and stored at 22 degrees C for as long as 72 hours before washing and autologous transfusion. In 20 other studies, a 50-mL volume of blood was collected without an anticoagulant and allowed to clot for 30 to 60 minutes. Urokinase, ranging from 2,500 to 10,000 units per mL, was added, and the blood was stored at 22 degrees C for 24 hours before washing and autologous transfusion. RESULTS: RBCs that were stored at 22 degrees C without urokinase for 24 hours exhibited an in vitro recovery value of 45 percent, a (51)Cr 24-hour posttransfusion survival of 86 percent, and an index of therapeutic effectiveness of 39 percent. The (51)Cr T(50) value was normal at 14 days, and RBC oxygen-transport function was slightly reduced. RBCs that were stored at 22 degrees C for 24 hours with 10,000 units per mL of urokinase exhibited an in vitro recovery value of 89 percent, a (51)Cr 24-hour posttransfusion survival value of 86 percent, and an index of therapeutic effectiveness of 76 percent. The (51)Cr T(50) value was normal at 14 days, and the RBC oxygen-transport function was only slightly reduced. CONCLUSION: Autologous baboon RBCs isolated from clotted blood treated or not treated with urokinase and washed before transfusion have excellent survival and normal or only slightly reduced oxygen-transport function.     

不同回声类型颈动脉斑块超声造影增强强度的分析

目的分析超声造影显示斑块内增强的程度与常规超声斑块回声强度之间的关系。方法颈动脉粥样硬化患者135例,其中双侧颈动脉病变的患者32例,共167个颈动脉斑块。所有患者超声造影检查时仪器参数设置保持一致。常规超声上将颈动脉斑块的回声分为低、中、混合及强回声4种类型。超声造影观察斑块内有无增强并将斑块增强的程度人为分为0～4级。定量分析计算动脉斑块内增强强度及斑块内增强强度与颈动脉管腔内增强强度的比值。结果不同回声类型颈动脉斑块超声造影增强分级的强度间差异有统计学意义(χMH=47.4,P<0.0001),斑块回声越低超声造影增强越明显。低回声斑块中有75.6%(31/41)达2级以上增强,而部分中等回声及混合斑块超声造影也可表现为明显增强,2级以上增强分别占56.8%(25/44)及62.3%(38/61)。强回声斑块则只有1个(1/21,4.8%)表现为2级增强。低、中、混合、强回声颈动脉斑块的超声造影增强强度分别为(4.33±3.34)dB、(3.71±3.40)dB、(3.16±2.56)dB、(0.96±0.37)dB,增强强度比值分别为0.24±0.17、0.21±0.17、0.19±0.13、0.06±0.02。不同回声类型颈动脉斑块的超声造影定量分析参数增强强度(t=7.75,P<0.0001)及增强强度比值(t=4.49,P<0.0001)的差异均有统计学意义,斑块回声越低,超声造影定量分析增强越显著,呈线性相关。结论超声造影可在常规超声评价斑块回声强弱的基础上提供更多关于斑块稳定性的信息,有助于对患者的筛选,进而采取合适的干预措施。     

Liver echogenicity: relation to systemic blood pressure and other components of the metabolic syndrome

We studied the impact of liver echogenicity among other potential predictors of systemic blood pressure (BP) and the metabolic syndrome. 38 persons (32 males, six females, aged 29 to 66) had their liver echogenicities scored, BPs measured and standard serum laboratory tests studied. There was a significant correlation between both systolic (r=0.438, p=0.006) and diastolic (r=0.498, p=0.001) BP and liver echogenicity. Liver echogenicity was the strongest predictor for systolic BP and the second strongest (after body mass index, BMI) for diastolic BP. Body height may modify the relation between liver echogenicity and systolic BP. Liver echogenicity also correlated significantly with BMI (r=0.527, p=0.001), serum triglycerides (r=0.472, p=0.003) and, to a lesser degree, with serum total cholesterol (r=0.305, p=0.066). Incidentally found increased liver echogenicity should alert the US performer and the clinician reading the report on the possibility of elevated BP or other features of the metabolic syndrome.     

Cyclic changes in blood echogenicity under pulsatile flow are frequency dependent

Previous in vivo and in vitro studies have demonstrated that blood echogenicity varies under pulsatile flow, but such changes could not always be measured at physiological stroke rates. The apparent contradiction between these studies could be a result of the use of different ultrasound frequencies. Backscattered signals from porcine blood were measured in a pulsatile Couette flow apparatus. Cyclic changes in shear rate for stroke rates of 20 to 70 beats per minute (BPM) were applied to the Couette system, and different blood samples were analyzed (normal blood and blood with hyperaggregating erythrocytes promoted with dextran). To confirm that cyclic echogenicity variations were observable, spectral analysis was performed to verify if changes in echo-amplitude corresponded to the stroke rate applied to the flow. Echogenicity was measured with two single-element transducers at 10 and 35 MHz. At 35 MHz, cyclic variations in backscatter were observed from 20 to 70 BPM. However at 10 MHz, they were detected only at 20 BPM. For all cases except for hyperaggregating red blood cells (RBCs) at 20 BPM, the magnitude of the cyclic variations were higher at 35 MHz. We conclude that cyclic variations in RBC aggregation exist at physiological stroke rates, unlike what has been demonstrated in previous in-vitro studies at frequencies of 10 MHz. The increased sensitivity at 35 MHz to small changes in aggregate size might be the explanation for the better characterization of RBC aggregation at high stroke rates. Our results corroborate in-vivo observations of cyclic blood echogenicity variations in patients using a 30-MHz intravascular ultrasound catheter.     

The effects of temperature on blood flow ultrasonic echogenicity in vitro.

An explanation of the mechanism of ultrasonic echogenicity in flowing blood is proposed based upon an in vitro study that indicates a causal relation between red cell aggregation and these echoes. Echogenicity was measured in vitro at 37 degrees, 24 degrees, and 0 degree C as blood flow shear rates were varied. Echogenicity increased at higher temperatures and lower shear rates. The directions of changes in blood echogenicity exactly paralleled previously known changes in red cell aggregation resulting from changes in temperature. The authors consider this to be further evidence that red cell aggregation is an important cause of low-intensity echoes observed in clinical ultrasonography of the heart and circulation.     

The in vitro echogenicity of flowing blood in patients with vascular disease and the effect of naftidrofuryl

Blood echogenicity was measured in four patient groups with circulatory disturbances (myocardial infarction, stroke, claudication, and deep venous thrombosis) at hospital admission and one week later. The recording was done by an A-mode ultrasonic method at three shear rates down to 4.1 s-1. The rheological effects of adding an anti-aggregatory drug, naftidrofuryl, was tested in vitro at concentrations ranging from 10(-8)-10(-6) M. Echogenicity was lowest in blood from healthy volunteers and significantly greater in blood from patients with claudication. The in vitro addition of naftidrofuryl significantly lowered the echogenicity of blood samples taken from patients with venous thrombosis in the lower extremities. The authors suggest that increased blood echogenicity, which can be pharmacologically manipulated, may be a nonspecific indicator of disease.     

The acute effects of smoking on the cyclic variations in blood echogenicity of carotid artery

The objective of this research is to study the cyclic variations in echogenicity (CVE) as an acute response to smoking. CVEs, caused by the aggregation of red blood cells (RBC) were measured from the cross-sectional images of the common carotid artery using coded harmonic imaging of a commercial ultrasound system. The amplitude of the CVE (A_cve) was analyzed among 28 smokers before and after smoking. A_cve was increased in 22 smokers and decreased in six smokers after 1-2 cigarettes were smoked. Heart rate (HR) was also estimated from the ultrasonic images before and after smoking. The smokers were optimally divided into two clusters with respect to the change in A_cve and the intrinsic characteristics of smokers (i.e., daily consumed cigarettes and smoking years) through a two-step cluster analysis (TSCA). The increase in A_cve after smoking was significantly higher in the heavy smoker cluster compared with the light smoker cluster. The results suggest that the acute changes in A_cve in response to smoking are different between heavy smokers and light smokers. This preliminary study demonstrates the potential application of coded harmonic ultrasound imaging to detect or characterize RBC aggregation. In addition, the results may be useful for understanding the acute physiologic changes caused by smoking. (E-mail: paeng@jejunu.ac.kr)     

A simple method for DNA isolation from clotted blood extricated rapidly from serum separator tubes

BACKGROUND: After clinical laboratory tests have been performed, it can be difficult to obtain DNA without further patient involvement. Although the blood clot remaining within the serum-separation tube after serum collection is a source of DNA, recovery of the clot from the tube is a significant challenge. METHOD: We devised a method to efficiently remove clotted blood from the serum-separation gel and extract DNA from clotted whole blood samples, obtaining maximum yield of the DNA without DNA contamination by the separation gel. The method involved centrifugation of the sample in the inverted original 10-mL collection tube to displace the separation gel for easy isolation of the blood clot and shearing of the blood clot by centrifugation through a 20-gauge wire mesh cone at 2000 g in a swinging-bucket rotor. After erythrocyte lysis and proteinase-K digestion of the fragmented clot, DNA was precipitated with isopropanol in the presence of glycogen. RESULTS: The mean amount of DNA obtained from a 4-mL clotted blood sample prepared by this method was 37.1 microg for clots processed soon after collection, with a reduction to 0.439 microg for clots stored for 1 month before extraction. The quality of the DNA was comparable to that extracted directly from whole blood, and it was found to be suitable for PCR-mediated analysis. CONCLUSION: We have formulated a method that overcomes the difficulties of safely extricating a blood clot from serum-separation tubes, allowing rapid DNA extraction for the purposes of genetic investigation.     

Lower limb vein enlargement and spontaneous blood flow echogenicity are normal sonographic findings during pregnancy

PURPOSE: We studied pregnancy-induced changes in lower limb venous function. METHODS: We used plethysmography and sonography to assess the changes in venous wall distensibility, saphenous vein diameters, and spontaneous blood flow echogenicity in the common femoral veins in 190 consecutive women during and after uncomplicated pregnancies (total of 409 examinations). RESULTS: The percentage of women with clinical symptoms and signs of venous insufficiency increased significantly during pregnancy. The mean diameters of the great and small saphenous veins also increased significantly, while occlusive venous plethysmography showed a decrease in parameters indicating vein distensibility. Spontaneous blood flow echogenicity in the common femoral veins was clearly visible or marked in 6% of cases during the first trimester of pregnancy, 63% during the second trimester, and 96% during the third trimester, versus 6% after delivery (p < 0.0001). The mean hematocrit decreased and the mean fibrinogen concentration increased during pregnancy. CONCLUSIONS: The increase in lower limb venous pressure seen during pregnancy leads to venous overdistention and worsens blood stasis. Decreased venous flow velocity and rheological alterations result in increased red cell aggregation, giving rise to spontaneous blood flow echogenicity. Spontaneous blood flow echogenicity is therefore a normal finding during pregnancy and should not be mistaken for venous thrombosis.