What is a CTA Chest?
CTA chest (Computed Tomography Angiography of the chest) is a specialized CT scan that uses intravenous contrast material timed to coincide with peak arterial or venous enhancement, producing thin-section volumetric images that are interpreted using multiplanar reformations and 3-D renderings to evaluate the thoracic vasculature, airways, and surrounding structures. 1
Technical Definition and Key Components
CTA chest requires three essential elements that distinguish it from standard contrast-enhanced CT 1:
- Precise timing of image acquisition to capture peak vascular enhancement (typically 15-20 seconds after contrast injection or using bolus tracking over the ascending aorta) 1
- Thin-section volumetric acquisition that allows for detailed visualization of vascular structures 1
- Multiplanar reformations and 3-D renderings as required components for interpretation, not just optional post-processing 1
Primary Clinical Applications
CTA chest is most commonly used to evaluate 1:
- Pulmonary vasculature: Detection of pulmonary embolism, pulmonary artery stenosis, and assessment of pulmonary blood flow 1
- Aortic pathology: Evaluation of aortic aneurysms, dissection, and other thoracic aortic diseases 1
- Airway compromise: Assessment of airway obstruction related to vascular structures, particularly useful with dynamic protocols 1
- Cardiac complications: Detection of pericardial abnormalities, cardiac chamber rupture, and extracardiac cardiac injuries in trauma settings 1
- Infectious complications: Identification of septic pulmonary infarcts, abscesses, and paravalvular complications in endocarditis 1
Important Distinction from Cardiac CT
CTA chest is NOT the same as coronary CTA or gated cardiac CT 2:
- CTA chest is performed without ECG synchronization, resulting in cardiac motion artifacts that prevent detailed coronary artery evaluation 2
- For coronary artery assessment, you need a dedicated ECG-gated coronary CTA, which uses cardiac synchronization to minimize motion artifacts and provide superior visualization of coronary arteries 3, 2
- Standard CTA chest is adequate for evaluating non-cardiac thoracic structures but cannot reliably assess coronary stenosis or plaque 2
Contrast Administration Protocol
The technical execution requires 1, 4:
- Contralateral arm injection (opposite to the side being evaluated when assessing thoracic outlet) to minimize streak artifact 1
- High-flow injection using a power injector (≥4 mL/s) with non-ionic iodinated contrast (≥350 mg/mL) 5
- Venous phase imaging (CTV) obtained 120-180 seconds after injection when venous assessment is needed 1
Common Pitfalls to Avoid
Be aware of these limitations 1, 2, 5:
- Cannot evaluate coronary arteries reliably - motion artifacts from lack of ECG gating prevent accurate coronary assessment 2
- Heavy calcification can create blooming artifacts that limit interpretation of vessel stenosis 5
- Timing errors can result in inadequate arterial opacification or venous contamination 5
- Radiation exposure is a consideration, though modern techniques have reduced doses significantly 3
When to Order CTA Chest vs Other Studies
Choose CTA chest when evaluating 1:
- Suspected pulmonary embolism - this is a primary indication 2
- Aortic pathology including dissection or aneurysm 2
- Post-surgical complications after cardiac surgery, including assessment of branch pulmonary arteries with stents 1
- Right-sided endocarditis complications to identify septic emboli and abscesses 1
- Thoracic outlet syndrome with vascular symptoms, using neutral and stressed positioning 1
Do NOT order CTA chest if you need coronary artery evaluation - order dedicated coronary CTA with ECG gating instead 3, 2.