PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 11935669

[Transcranial color-coded Doppler sonography: getting started].

J Krejza·W Rudziński·Z Mariak
View original source ↗Export metadata ↓

Abstract

Transcranial color Doppler sonography, in contrary to conventional transcranial Doppler ultrasound, allows outlining of the parenchymal structures and visualization of the vessel examined. Angle-corrected blood velocities can be obtained which are closer to in-situ values. In this educational assay, we demonstrate cerebral vascular anatomy using 3-D MR angiographic images of the major cerebral arteries to show their relationship to neighboring structures, the acoustic window, and the ultrasound beam. We describe principles of the examination, and discuss the different types of physiological flow velocity spectra. We show how to identify with color Doppler ultrasonography the main intracranial arterial trunks, and how to avoid pitfalls caused by anatomic variability of their course and location. We draw attention on significant age and sex dependency of blood flow parameters which makes standardization of obtained transcranial Doppler results indispensable for clinical valuable concluding.

Explore related subjects

Blood Flow VelocityCerebrovascular CirculationCerebrovascular DisordersHumansImage Processing, Computer-AssistedImaging, Three-DimensionalUltrasonography, Doppler, ColorUltrasonography, Doppler, TranscranialJournal ArticleReview

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J Krejza, W Rudziński, Z Mariak. 2001. [Transcranial color-coded Doppler sonography: getting started].. https://pubmed.ncbi.nlm.nih.gov/11935669/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2003

Pharmacological rationale for the use of somatostatin and analogues in portal hypertension.

Somatostatin and its analogue octreotide have been used for two decades to treat oesophageal variceal haemorrhage. The drug was introduced because of its capacity to decrease portal venous pressure without major side effects. In clinical trials assessing the efficacy of somatostatin and long-acting analogues in arresting variceal haemorrhage, conflicting results have been obtained. Furthermore, in haemodynamic studies evaluating the effects of somatostatin and analogues in patients with cirrhosis, divergent effects were observed. The main reason for these differences is probably related to different affinities of the drugs for different somatostatin receptor subtypes. The effects of somatostatin and analogues are mediated via five different G-protein coupled receptors (somatostatin receptor subtypes 1-5), which regulate the activity of ion channels (Ca2+, K+, Na+ and Cl-) and enzymes (adenyl cyclase, phospholipase C, phospholipase A2, phosphoinositide 3-kinase and guanylate cyclase) responsible for the synthesis or degradation of intracellular second messengers including cyclic AMP, inositol 1,4,5-trisphosphate, diacylglycerol and cyclic GMP. Despite universal use of somatostatin, the cellular and biochemical mechanisms of its effects in portal hypertension are relatively poorly studied and remain incompletely understood. In this review, we summarize relevant signal transduction of somatostatin and analogues, the haemodynamic effects of the drugs and the possible mechanisms by which these effects are mediated.

Blood Flow Velocity↗
PubMed2003

Estimation of capillary density in human skeletal muscle based on maximal oxygen consumption rates.

A previously developed Krogh-type theoretical model was used to estimate capillary density in human skeletal muscle based on published measurements of oxygen consumption, arterial partial pressure of oxygen, and blood flow during maximal exercise. The model assumes that oxygen consumption in maximal exercise is limited by the ability of capillaries to deliver oxygen to tissue and is therefore strongly dependent on capillary density, defined as the number of capillaries per unit cross-sectional area of muscle. Based on an analysis of oxygen transport processes occurring at the microvascular level, the model allows estimation of the minimum number of straight, evenly spaced capillaries required to achieve a given oxygen consumption rate. Estimated capillary density values were determined from measurements of maximal oxygen consumption during knee extensor exercise and during whole body cycling, and they range from 459 to 1,468 capillaries/mm2. Measured capillary densities, obtained with either histochemical staining techniques or electron microscopy on quadriceps muscle biopsies from healthy subjects, are generally lower, ranging from 123 to 515 capillaries/mm2. This discrepancy is partly accounted for by the fact that capillary density decreases with muscle contraction and muscle biopsy samples typically are strongly contracted. The results imply that estimates of maximal oxygen transport rates based on capillary density values obtained from biopsy samples do not fully reflect the oxygen transport capacity of the capillaries in skeletal muscle.

Blood Flow Velocity↗