Search results for "doppler"
showing 10 items of 637 documents
Arterial and Venous Cerebral Blood Flow Velocities and Their Correlation in Healthy Volunteers and Traumatic Brain Injury Patients.
2020
Few studies have explored the cerebral venous compartment or the correlation between venous and arterial cerebral blood flows. We aimed to correlate cerebral blood flow velocities in the arterial (middle cerebral artery) and venous (straight sinus) compartments in healthy volunteers and traumatic brain injury (TBI) patients. In addition, we determined the normative range of these parameters.A total of 122 healthy volunteers and 95 severe TBI patients of both sexes were included and stratified into 3 age groups as follows: group 1 (aged, 18 to 44 y); group 2 (aged, 45 to 64 y); group 3 (older than 65 y). Transcranial Doppler systolic cerebral blood flow velocity, diastolic cerebral blood flo…
Transcranial Doppler sonography in dementia of Alzheimer type.
1994
The intention of this study was to examine the relation of clinical variables and cognitive dysfunction to cerebrovascular blood flow in a sample of patients with Alzheimer''s disease without any sign or symptom of cardiovascular or cerebrovascular disease. The patients met DSM-III-R criteria for dementia of Alzheimer type. Blood flow velocities in the anterior, middle (MCA) and posterior cerebral arteries were recorded using transcranial Doppler sonography. Several psychometric tests including the Mini-Mental State Examination (MMSE) were performed. The patients’ age correlated significantly with the systolic flow velocity in the left MCA (r = –0.57) explaining 24% of the total variance; t…
Photoreactive flow changes in the posterior cerebral artery in control subjects and patients with occipital lobe infarction.
1995
Background and Purpose Photoreactive flow changes of the posterior cerebral artery (PCA) in control subjects and patients with unilateral occipital lobe infarction were investigated to study the hypothesis that occipital lobe infarction of varying extent leads to a reduced visually activated flow increase in the ipsilateral PCA. Methods Maximum mean flow velocity (MFV) of the PCA was investigated by transcranial Doppler sonography after photic stimulation of the retina. Results In 25 control subjects MFV was increased by 30.6±9.7%. In 13 patients with unilateral occipital lobe infarction the ipsilateral MFV increase was significantly lower than in control subjects. Nine patients with homon…
Blood-brain barrier disruption by low-frequency ultrasound.
2006
Background and Purpose— A recent study showed a dramatic increase in cerebral hemorrhage comprising atypical locations with low-frequency ultrasound–mediated recombinant tissue plasminogen activator–thrombolysis in humans. Here, we provide a possible explanation for this phenomenon by a side effect observed in a study using the similar ultrasound device. Methods— The study was originally undertaken to investigate by transcranial Doppler sonography, positron emission tomography and perfusion MRI whether transcranial application of wide-field low-frequency ultrasound (300 kHz) improves cerebral hemodynamics in patients with cerebral small vessel disease. Results— Showing no clear positive ef…
Comparison of right ventricular longitudinal strain imaging, tricuspid annular plane systolic excursion, and cardiac biomarkers for early diagnosis o…
2012
Aims To determine the role of assessing right ventricular (RV) function, using standard echocardiography and Doppler myocardial imaging (DMI), in the early diagnosis of cardiac amyloidosis and in the prediction of mortality. Methods and results Patients with primary systemic (AL) amyloidosis seen at our institution from 1 February 2004 through 31 October 2005 (N = 249) were categorized by left ventricular thickness and E′ velocity and compared with 38 age- and sex-matched controls. Standard echocardiographic and DMI examination were used to measure echocardiographic parameters of RV function: systolic tissue velocity, strain rate, and strain were determined for basal and middle RV free wall…
Embolic stroke, sinus rhythm and left atrial mechanical function
2004
A 64-year-old man manifested a stroke two years after restoration of sinus rhythm through a radiofrequency catheter ablation. Transesophageal echo- cardiography demonstrated the presence of a thrombus in the left atrial appendage. Left atrial volumes and different parameters of atrial emptying showed that, de- spite the persistence of the sinus rhythm, atrial mechanical function was severely impaired. After atrial ablation procedures echocardiography can be useful to stratify pa- tients according to their risk of developing embolic events and hence be of help in deciding whether or not discontinuation of anticoagulant therapy is the appropri- ate choice.
Positronics of radiation-induced effects in chalcogenide glassy semiconductors
2015
Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.
Positron annihilation probing of crystallization effects in TAS-235 glass affected by Ga additions
2014
Abstract Crystallization effects in Te20As30Se50 glass known also as TAS-235 affected by Ga additions to Ga2Te20As28Se50 and Ga5Te20As25Se50 compositions are probed with positron annihilation spectroscopy in the measuring modes exploring positron lifetimes and Doppler broadening of annihilation line. Occurring of cubic-phase Ga2Se3 droplets with character nanoscale sizes in partially-crystallized Ga2Te20As28Se50 alloy is shown to be associated with agglomeration of intrinsic free-volume voids, this process being enhanced over microcrystalline scale in Ga5Te20As25Se50 alloy. Crystallization changes in the void structure of TAS-235 glass are considered in terms of free-volume evolution under …
High-Resolution Spectroscopy in Fast Atomic Beams
1977
Narrow optical resonances have been observed in fast beams of Na and Cs atoms, obtained from ion beams by charge-transfer collisions with Na, K, or Cs. Corresponding to the narrowing of the velocity distribution, occurring by acceleration, the Doppler width along the beam direction is considerably reduced [1, 2].
Positron Annihilation with Electrons of Admixture Atoms in Some Binary Nickel Alloys
2005
Weighted difference curves have been shortly presented as a proper tool allowing to analyze in another way two-detector Doppler spectra regarding positron annihilation with admixture electrons in some nickel alloys. The analysis of low and middle momentum parts of Doppler spectra for investigated alloys reflects the annihilation of positrons with admixture electrons. There is no distinct signal of annihilations with admixture electrons from the positron lifetime data for well-annealed samples.