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The arterial resistivity index (also called as Resistance index, abbreviated as RI), developed by Léandre Pourcelot , is a measure of pulsatile blood flow that reflects the resistance to blood flow caused by microvascular bed distal to the site of measurement.
After Shigeo Satomura who detected for the first time the blood flow with a Doppler Ultrasound machine, [1] Gene Strandness measured the blood pressure at the ankle (1967), Léandre Pourcelot proposed the Arterial resistivity index (1974), and Gosling the Pulsatility index (1974).
Cerebroplacental ratio is a tool used in obstetric ultrasound to predict adverse pregnancy outcome. [1] It is measured by dividing the pulsatility index of the middle cerebral artery of the foetus by the pulsatility index of the umbilical artery of the foetus.
One parameter to quantify this difference is the pulsatility index (PI), which is equal to the difference between the peak systolic velocity and the minimum diastolic velocity divided by the mean velocity during the cardiac cycle. This value decreases with distance from the heart.
Artist's depiction of a foetus at 38 weeks' gestation. Foetal cerebral redistribution or 'brain-sparing' is a diagnosis in foetal medicine.It is characterised by preferential flow of blood towards the brain at the expense of the other vital organs, and it occurs as a haemodynamic adaptation in foetuses which have placental insufficiency.
In fluid dynamics, a flow with periodic variations is known as pulsatile flow, or as Womersley flow.The flow profiles was first derived by John R. Womersley (1907–1958) in his work with blood flow in arteries. [1]
This page was last edited on 8 December 2023, at 14:57 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.
In particular, laser Doppler holography of the eye fundus, the choroid constitutes the predominant contribution to the high frequency laser Doppler signal. It is however possible to circumvent its influence by subtracting the spatially averaged baseline signal, and achieve high temporal resolution and full-field imaging capability of pulsatile ...