Cerebral blood flow (CBF) is a measure of the blood supply to the brain's in a given unit of time. Cerebral blood flow depends on mean arterial blood pressure (MAP), intracranial pressure (ICP), and cerebrovascular resistance (CVR), and can be calculated as follows:
CBF = (<b>MAP</b> – <b>ICP</b>) \/ CVR
Normal value
A healthy brain has a resting CBF of 45-60 ml per 100g of tissue per minute[^1].
Correlating CBF values
CBF (ml per 100g of tissue per minute) | Condition[^1] | |
> 60 | Hyperemia (CBF > tissue demand) | |
45-60 | Normal brain at rest | |
75-80 | ||
20-30 | ||
< 20 | Ischemia | |
16-18 | EEG becomes isoelectric (flat line) | |
15 | Physiological paralysis | |
12 | BAER changes | |
10 | Alterations in cell membrane transport (cell death; stroke) |
Measurement
CBF can be measured locally, for example, using a QFlow 500™ perfusion probe (Hemedex), or with the aid of MR perfusion[^2] or [CT perfusion](\/lexikon\/ct-perfusion)[^3].
rCBF
The term rCBF is used in MR perfusion and CT perfusion and stands for relative CBF, as CBF is reported as a ratio between white and gray matter.
qCBF
The term qCBF is also used in MR perfusion and CT perfusion and stands for quantitative CBF, providing a calculated CBF value in ml per 100g of tissue per minute.