A CT brain perfusion scan is a rapid contrast-enhanced imaging test that measures cerebral blood flow, blood volume, and transit times by capturing sequential CT images. It helps detect areas of reduced perfusion in acute stroke, identify salvageable “penumbra” versus infarcted tissue, and assess tumor or other vascular abnormalities. The test uses intravenous contrast and exposes the patient to ionizing radiation.

Perfusion to the brain refers to the continuous delivery of blood — and therefore oxygen and nutrients — to brain tissue. It depends on cardiac output, arterial blood pressure, and cerebrovascular resistance with autoregulation adjusting flow. Adequate perfusion is essential for normal function; reduced perfusion causes ischemia, stroke, or cognitive dysfunction. Clinically it’s assessed by blood pressure, neurological exam and imaging (e.g., CT/MRI perfusion).

CT brain perfusion measures cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time‑to‑peak/Tmax. Traditional scanners cover a limited z‑axis slab (about 2–8 cm, commonly 4–8 cm) sampling key basal ganglia and cortical territories. Modern wide‑detector CT can provide whole‑brain coverage (up to about 16 cm), allowing assessment of both hemispheres and posterior fossa in acute stroke.

The CT perfusion imaging itself involves rapid repeated scans during contrast passage and usually takes about 4 to 10 minutes (the dynamic imaging phase is under a minute). Including preparation, positioning, contrast injection, and post-scan checks, most appointments last about 15 to 30 minutes. Emergency stroke protocols are streamlined, so total time may be shorter in acute settings.

A perfusion scan assesses blood flow through an organ (commonly lungs, heart, or brain) by tracking a small tracer or contrast. It detects areas with reduced or absent perfusion, helping diagnose conditions like pulmonary embolism, ischemia, or stroke, and evaluates tissue viability. Results guide treatment decisions, monitor disease progression, and assist surgical or interventional planning.

CT perfusion carries risks including ionizing radiation exposure, allergic reactions to iodinated contrast, and contrast‑induced kidney injury, especially in people with preexisting renal impairment. Other risks include injection‑site complications, inaccurate or misleading results from artifacts or timing, and variability in interpretation. In pregnancy, fetal radiation and contrast risks make CT perfusion generally avoided unless absolutely necessary.