Search results
Results from the WOW.Com Content Network
Arterial input function (AIF), also known as a plasma input function, refers to the concentration of tracer in blood-plasma in an artery measured over time. The oldest record on PubMed shows that AIF was used by Harvey et al. [1] in 1962 to measure the exchange of materials between red blood cells and blood plasma, and by other researchers in 1983 for positron emission tomography (PET) studies.
Flow-mediated dilation (FMD) refers to dilation (widening) of an artery when blood flow increases in that artery. [1] [2] The primary cause of FMD is release of nitric oxide by endothelial cells. [1] To determine FMD, brachial artery dilation following a transient period of forearm ischemia is measured using ultrasound. [3]
The Fick principle states that blood flow to an organ can be calculated using a marker substance if the following information is known: Amount of marker substance taken up by the organ per unit time; Concentration of marker substance in arterial blood supplying the organ; Concentration of marker substance in venous blood leaving the organ
Alternatively, in order to find the efficiency of the lungs in replenishing blood oxygen levels, the a-vO 2 diff may instead be taken by comparing blood from the pulmonary artery and the pulmonary vein; in this case a negative value for a-vO 2 diff would be obtained as the oxygen content of the blood would have increased. [citation needed]
Acid–base and blood gases are among the few blood constituents that exhibit substantial difference between arterial and venous values. [6] Still, pH, bicarbonate and base excess show a high level of inter-method reliability between arterial and venous tests, so arterial and venous values are roughly equivalent for these. [44]
For this reason, the blood flow velocity is the fastest in the middle of the vessel and slowest at the vessel wall. In most cases, the mean velocity is used. [18] There are many ways to measure blood flow velocity, like videocapillary microscoping with frame-to-frame analysis, or laser Doppler anemometry. [19]
Blood flow is one the most important factors affecting the delivery of oxygen and other nutrients to tissues. Abnormal blood flow is associated with many diseases such as stroke and cancer. Tumors from cancer can generate abnormal tumor blood flow compared to the surrounding tissue. Current treatments attempt to decrease blood flow to cancer cells.
Coronary flow reserve is used in diagnostics and treatment of patients with conditions such as coronary artery disease and syndrome X. [7] In the treatment of these conditions, vasodilators are used to allow sufficient blood to flow past a stenosis, for example, and the measurement of CFR enables the efficacy of such interventions to be measured.