Search results for "Flow velocity"
showing 10 items of 227 documents
Blood flow velocity waveforms of the fetal middle cerebral artery in a normal population: reference values from 18 weeks to 42 weeks of gestation
2002
The aim of this prospective cross-sectional study was to establish new Doppler reference curves for peak blood flow velocities (Vmax, Vmean, Vmin) and impedance indices (PI, RI) of the middle cerebral artery at 18-42 weeks of gestation by an automatic wave form analysis integrated into the ultrasound device. In 962 low-risk pregnancies, blood flow velocities were derived from the middle cerebral artery with pulsed color Doppler ultrasonography. Reference curves were constructed for the individual parameters based on a growth function from a four-parameter class of monotonic continuous functions according to the smallest square principle for maximum blood flow velocities, as well as on a pol…
Sympathetic Vasomotor Response of the Radial Artery in Patients With Diabetic Foot Syndrome
2003
OBJECTIVE—Neurophysiological assessment of the peripheral autonomic system is characterized by various limitations. An alternative approach to laser Doppler and venous plethymography is the assessment of the sympathetic vasomotor response of the radial artery obtained by continuous wave Doppler sonography. Nomogram data have been established and demonstrate the temporary disappearance of diastolic flow after coughing or deep inspiration. RESEARCH DESIGN AND METHODS—We assessed the sympathetic vasomotor response in 25 patients (mean age 64 years, range 43–76) with diabetic foot syndrome. The Doppler data were correlated with nerve conduction studies of the median and peroneal nerve, the exte…
Endovascular Embolization of a Large High-Flow Splenic Arteriovenous Fistula and Aneurysm Using the Amplatzer Vascular Plug II.
2015
We describe the use of an Amplatzer Vascular Plug (AVP) II for embolizing a large high-flow splenic arteriovenous fistula and an aneurysm in a young patient. This patient presented to our center with persistent mild abdominal discomfort, 5 years after open splenectomy. Contrast-enhanced computed tomography angiography showed the presence of a fistula between the splenic arterial and splenic venous remnants and a resultant fusiform aneurysmal dilatation of the residual splenic vein. We decide to embolize the splenic artery with a 12-mm diameter AVP II with an oversizing by 70% of the vessel diameter. Celiac angiography performed 5 min postembolization revealed complete obliteration of the sp…
In Silico Shear and Intramural Stresses are Linked to Aortic Valve Morphology in Dilated Ascending Aorta
2017
Objective/Background: The development of ascending aortic dilatation in patients with bicuspid aortic valve (BAV) is highly variable, and this makes surgical decision strategies particularly challenging. The purpose of this study was to identify new predictors, other than the well established aortic size, that may help to stratify the risk of aortic dilatation in BAV patients.Methods: Using fluid-structure interaction analysis, both haemodynamic and structural parameters exerted on the ascending aortic wall of patients with either BAV ( n = 21) or tricuspid aortic valve (TAV; n = 13) with comparable age and aortic diameter (42.7 +/- 5.3 mm for BAV and 45.4 +/- 10.0 mm for TAV) were compared…
RadioAstron reveals a spine-sheath jet structure in 3C 273
2021
We present Space-VLBI RadioAstron observations at 1.6 GHz and 4.8 GHz of the flat spectrum radio quasar 3C 273, with detections on baselines up to 4.5 and 3.3 Earth Diameters, respectively. Achieving the best angular resolution at 1.6 GHz to date, we have imaged limb-brightening in the jet, not previously detected in this source. In contrast, at 4.8 GHz, we detected emission from a central stream of plasma, with a spatial distribution complementary to the limb-brightened emission, indicating an origin in the spine of the jet. While a stratification across the jet width in the flow density, internal energy, magnetic field, or bulk flow velocity are usually invoked to explain the limb-brighte…
Platelet-endothelial interaction in tumor angiogenesis and microcirculation
2003
Activated platelets release angiogenic growth factors and have therefore been proposed to contribute to tumor angiogenesis within a potentially prothrombotic tumor microcirculation. The aim of the study was to investigate interactions of platelets with the angiogenic microvascular endothelium of highly vascularized solid tumors during growth and in response to endothelial stimulation in comparison with normal subcutaneous tissue. Experiments were performed in the dorsal skinfold chamber preparation of C57BL/6J mice bearing the Lewis lung carcinoma (LLC-1) or methylcholanthrene-induced fibrosarcoma (BFS-1). Fluorescently labeled rolling and adherent platelets, red blood cell velocity, and ve…
The automated assesment of artery hemodynamic parameters from ultrasound video
2012
The custom designed video processing software for analysis of B-mode and Doppler-mode ultrasound video has been proposed in this work. The software allows adjusting user-defined thresholds and tolerance levels to enhance contour detection in noisy and artifacted ultrasound images. The developed software is able to evaluate 16 hemodynamic parameters (artery diameter, pulse rate and flow velocity related parameters) in each cardiac cycle. The measurements were performed intermittently recording artery diameter (B-mode) and flow velocity (Doppler-mode). Software has validated in femoral artery measurements. The hemodynamic parameters computed by software were consistent with those obtained by …
Cardiac output following fetoscopic coagulation of major placental vessels in fetal sheep.
2008
Objectives To measure changes in cardiac output (CO) after partial cord occlusion in fetal sheep in order to investigate pathophysiological fetal adaptation mechanisms in a simulated acute placental insufficiency model under standardized conditions, with the aim of finding relevant methods for monitoring human fetuses during stress situations. Methods We used minimally invasive, percutaneous endoscopic techniques to close umbilical vessels in mid-gestational fetal sheep. Placental blood flow was reduced by preferentially closing first arterial and then the concomitant venous umbilical vessels within a short time interval. The investigations were carried out on 11 pregnant ewes at a median g…
[Diagnosis of coronary microvascualar dysfunction in diabetic patients with cardiac syndrome X: comparison by current methods].
2013
The study population included 208 patients with chest pain and uninjured coronary arteries that we split into two populations: diabetics (72 patients) and non-diabetics (136 patients). We split patients with chest pain and uninjured coronary arteries that had a myocardial scintigraphy into two populations: patients with positive scintigraphy and negative. We calculated, on angiographic images of each patient, stored on suitable digital supports, Timi Frame Count (TFC), Myocardial Blush Grade (MBG) and Total Myocardial Blush Score (TMBS) using the protocol described by Gibson and Yusuf. On the basis of Yusuf's experience we imagined a new index: the Total Timi Frame Count as the sum of the t…
Color Doppler ultrasonography of the eye and orbit
1993
Color Doppler imaging is the recent development in ultrasonography that allows simultaneous two-dimensional structural imaging in Doppler evaluation of blood flow. With this technique, it is possible for the first time to indirectly display the fine orbital vessels such as the ophthalmic artery and its branches, the central retinal artery, the posterior ciliary artery, and the lacrimal artery. Also, the display of venous structures such as the superior ophthalmic vein, the vortex vein, and the central retinal vein is possible. In addition to the qualitative display of those vessels, the hemodynamics in those vessels can be quantitatively assessed by looking at the Doppler spectrum and deter…