WHAT IS PERFUSION, WHAT IS CT PERFUSION, WHY DO CT PERFUSION (WHY DR CT PERFUSION), HOW TO DO CT PERFUSION?

 

🔹 WHAT IS PERFUSION?

Perfusion refers to the flow of blood through the blood vessels of an organ or tissue. In radiology, we're particularly interested in measuring how well blood is flowing through tissues, like the brain, lungs, liver, or kidneys.

---

🔹 WHAT IS CT PERFUSION (CTP)?

CT Perfusion is a specialized CT scan technique that helps evaluate blood flow (perfusion) in organs, usually the brain.

It answers:

• How much blood is reaching the tissue?

• How fast is it flowing?

• Is there any blockage or reduced perfusion?

---

🔸 WHY DO CT PERFUSION (WHY DR CT PERFUSION)?

Usually done in:

🧠 Brain:

• Stroke diagnosis (Ischemic vs hemorrhagic).

• Penumbra detection (tissue at risk but not yet dead).

• Tumor evaluation (tumors have abnormal perfusion).

🫁 Lungs:

• Pulmonary embolism workup (less common with CTPA available).

🩺 Other uses:

• Evaluate response to cancer treatment.

• Assess renal or hepatic perfusion.

---

🔹 HOW TO DO CT PERFUSION

✅ Protocol (typically brain perfusion):

1. Patient Prep:

   • Secure IV access (18G or 20G).

   • Explain procedure—patient must stay still.

2. Scanner Setup:

   • Select Perfusion CT Protocol (usually on 64-slice or higher CT).

   • Set appropriate coverage area (e.g., basal ganglia to high parietal for stroke).

   • Thin slices: 5 mm or less.

   • Duration: ~45-60 seconds dynamic scan.

3. Contrast Injection:

   • Inject iodinated contrast (~40–50 mL @ 4–6 mL/sec).

   • Followed by saline flush.

4. Dynamic Acquisition:

   • Scanner continuously takes images over time (cine acquisition).

   • Tracks the passage of contrast through brain vessels and tissues.

5. Post-processing:

   • Software generates perfusion maps:

     • CBF (Cerebral Blood Flow)

     • CBV (Cerebral Blood Volume)

     • MTT (Mean Transit Time)

     • TTP (Time to Peak)

6. Interpretation:

   • Radiologist reads the perfusion maps to detect infarct core, penumbra, etc.

---

🔸 Key Terms in Brain Perfusion:

Parameter	Meaning	Clinical Use
CBF	Blood flow per minute	Reduced in stroke
CBV	Volume of blood in tissue	Helps identify infarct core
MTT	Average time blood spends in tissue	Prolonged in ischemia
TTP	Time for contrast to reach peak	Delayed in blockage