CT PA HOW TO DO CT PULMONARY ANGIO, WHY DO CT PA, STEP BY STEP GUIDE CT PA.

CT Pulmonary Angiography (CTPA) is the standard imaging technique to evaluate pulmonary embolism (PE) and pulmonary vasculature. I’ll guide you step by step:

Patient Preparation

1. Indications: Suspected pulmonary embolism, pulmonary artery abnormalities, vascular malformations, pre-surgical evaluation.

2. Consent: Explain contrast use, possible side effects.

3. Check labs: Serum creatinine / GFR (to assess kidney function).

4. Check history: Allergy to iodine contrast, asthma, thyroid disease.

5. IV Access: Large bore IV cannula (18–20G) in antecubital vein.

6. Breath-hold training: Patient must hold breath during scan to avoid motion.

Scan Protocol

Scanner: Any multislice CT (64-slice or higher preferred).

• Patient position: Supine, head first.

• Scan range: From thoracic inlet to just below costophrenic angles.

• ECG gating: Not required (except for suspected RV strain/cardiac assessment).

Contrast Injection

• Contrast: Non-ionic iodinated contrast (e.g., 60–80 ml).

• Injection rate: 4–5 ml/sec (high flow).

• Use a power injector with saline chaser (30–40 ml).

Bolus Tracking (Smart Prep)

• ROI (Region of Interest): Main pulmonary artery / right ventricle outflow tract.

• Trigger threshold: ~100–150 HU.

• Start scan after 3–5 sec delay once threshold is reached.

Scan Parameters (Typical)

• kVp: 100–120 (depending on patient size).

• mAs: Automated (dose modulation ON).

• Slice thickness: 0.5–1.25 mm (thin slices for 3D).

• Pitch: 0.9–1.2.

• Rotation time: 0.5 sec.

• Reconstruction: Axial, coronal, sagittal, MIP (maximum intensity projection), VR (volume rendering).

Post-processing

• Review axial images first.

• Use MIP for vessel tracing.

• Evaluate pulmonary arteries from main PA → lobar → segmental → subsegmental levels.

• Check for: Filling defects, clot burden, right heart strain.

Tips for Best Quality

✅ Ensure tight bolus timing → scan during peak pulmonary artery opacification.
✅ Avoid respiratory motion → good breath-hold.
✅ Use saline flush → reduces streak artifacts from SVC/RA.
✅ In obese patients → increase kVp (120–140).