Hjärnperfusion

Hjärnperfusion, or brain perfusion, refers to the passage of blood through the brain’s vasculature to deliver oxygen and nutrients and to remove waste. It is typically described by cerebral blood flow (CBF), the amount of blood reaching a given amount of brain tissue per unit time (commonly ml/100 g/min). Perfusion depends on cerebral perfusion pressure, vascular resistance, and the integrity of the microcirculation. Cerebral autoregulation helps keep CBF relatively constant over a range of blood pressures, while metabolic demand, carbon dioxide levels, and neural activity can modulate perfusion.

Physiology and regulation are governed by neurovascular coupling, whereby increases in neuronal activity trigger local vasodilation and increased blood flow to meet metabolic needs. The brain also has specialized parameters such as cerebral blood volume (CBV) and mean transit time (MTT), which together with CBF and other metrics help describe tissue perfusion status. Disruptions to perfusion can lead to ischemia, edema, or tissue death, and compensatory mechanisms may vary across brain regions and pathophysiologic conditions.

Measurement and imaging techniques for hjärnperfusion include invasive and noninvasive methods. Noninvasive imaging commonly used in clinical practice involves CT perfusion (CTP) and MR perfusion (PWI), which provide maps of CBF, CBV, and parameters like mean transit time or Tmax to identify hypoperfused tissue. Additional methods include PET and SPECT perfusion studies, and transcranial Doppler ultrasound assesses blood flow velocity in major vessels. Perfusion imaging is particularly important in acute stroke to distinguish irreversibly damaged tissue from potentially salvageable penumbra and to guide treatment decisions, while also informing oncologic and traumatic brain injury assessments.