RadteraCTA Chest — Pulmonary Embolism (CTPA)
CTA+ ContrastVascular
Indications
- Suspected acute pulmonary embolism (elevated D-dimer / Wells score, pleuritic pain, dyspnea, hypoxia)
- Suspected chronic thromboembolic disease
- Right heart strain assessment in known PE
- Follow-up of treated PE when clinically indicated
Patient prep
- Screen eGFR/contrast allergy; premedicate if indicated
- Large-bore IV (18-20 G, antecubital preferred) for high flow rate
- Coach a SHORT end-inspiratory or quiet breath-hold (deep inspiration can draw unopacified IVC blood causing transient interruption artifact)
- Supine, arms up
Contrast
Agentiodinated, high concentration (e.g. iohexol 350 or iopamidol 370)
RouteIV
Dose≈60-100 mL at 4-5 mL/s followed by saline flush
TimingBolus tracking with ROI in main pulmonary artery, trigger ~100-150 HU; or test bolus / SmartPrep ~ pulmonary arterial peak (~6-10 s post threshold)
Technique
- Supine, arms up; helical volume from lung apices through diaphragm/costophrenic angles (caudo-cranial often used to reduce respiratory motion at bases)
- 100-120 kV (lower kV, e.g. 80-100 kV, improves iodine conspicuity and lowers dose/contrast volume); mAs per scanner with AEC
- Thin reconstruction (0.625-1 mm) for subsegmental arteries; soft-tissue and lung kernels
- Coronal/sagittal reformats; optional thin MIP along vessels
- Iterative reconstruction; bolus tracking in main PA
Series / Sequences
| # | Series / Sequence | Plane | Thickness | Notes |
|---|---|---|---|---|
| 1 | Axial PA-phase (soft tissue) | axial | 0.625-1.25 mm | Standard kernel; evaluate to subsegmental level for filling defects |
| 2 | Axial lung | axial | 1-1.5 mm | Lung kernel; infarct, alternative diagnosis |
| 3 | Coronal/sagittal reformat | coronal | 2-3 mm | Vessel course, clot burden |
| 4 | Thin MIP (optional) | axial | 5-10 mm | Vessel tracking |
Key points
- Optimal timing targets PEAK pulmonary arterial enhancement (not systemic) — bolus tracking ROI in the main PA is key; mistimed studies are the main cause of nondiagnostic exams
- Lower kV (80-100) boosts iodine signal, enabling reduced contrast volume
- Assess RV strain: RV/LV diameter ratio >1.0, septal bowing, contrast reflux into IVC/hepatic veins
- Suboptimal breath-hold causes transient interruption of contrast bolus at the lung bases — caudocranial scanning and short breath-hold help
References
• ACR–NASCI–SPR Practice Parameter for the Performance and Interpretation of Cardiac CT / Thoracic CTA
• ACR Appropriateness Criteria: Suspected Pulmonary Embolism
• Radiopaedia: CT pulmonary angiogram (protocol) link
• RadioGraphics: CT Pulmonary Angiography — Technique and Pitfalls
• ACR Appropriateness Criteria: Suspected Pulmonary Embolism
• Radiopaedia: CT pulmonary angiogram (protocol) link
• RadioGraphics: CT Pulmonary Angiography — Technique and Pitfalls
Source: Researched — verify against your institution
Reference template — verify and adapt to your scanner, vendor and institution before clinical use. Not a substitute for clinical judgment.