Perfusionsrate

Perfusionsrate, or perfusion rate, is a measure of the volume of blood delivered to a given mass of tissue per unit time. It is commonly expressed in milliliters per minute (mL/min) and, when normalized to tissue mass, in units such as mL/min per 100 g. The perfusion rate indicates how quickly tissue is supplied with oxygen and nutrients and how efficiently waste products are cleared; it varies by tissue type and physiological state.

Physiologically, the perfusion rate is governed by cardiac output, arterial pressure, and regional vascular resistance, as well as capillary density and local autoregulatory mechanisms that adjust flow to match metabolic demand. Within a region, perfusion can be heterogeneous, with zones of higher or lower flow reflecting both normal variation and pathological changes.

Measurement and estimation: Perfusion rate is estimated with imaging and tracer techniques. Dynamic contrast-enhanced MRI or CT perfusion provides regional flow maps. PET with perfusion tracers can quantify blood flow, and arterial spin labeling MRI measures flow without contrast. Doppler ultrasound estimates flow in major vessels, while microsphere methods are used in animal studies. In superficial tissues, laser Doppler or laser speckle imaging can assess microvascular perfusion.

Applications: Perfusion rate is used to assess tissue viability and treatment response in stroke and myocardial ischemia, to characterize tumor perfusion, and to monitor organ perfusion during transplantation or ex vivo perfusion systems.

Variability: The perfusion rate changes with time and physiological conditions; temperature, anesthesia, medications, and disease can markedly alter it.