CT pulmonary angiogram

A CT pulmonary angiogram (CTPA) is a medical diagnostic test that employs computed tomography (CT) to obtain an image of the pulmonary arteries. It is primarily used to diagnose pulmonary embolism (PE), a condition where one or more arteries in the lungs become blocked by a blood clot.

CT pulmonary angiogram showing a saddle pulmonary embolism

Procedure

The procedure involves the injection of a contrast agent into a vein, usually in the arm, followed by a rapid series of CT scans. The contrast agent helps to highlight the pulmonary arteries, making it easier to detect any blockages or abnormalities. The patient is typically asked to hold their breath for a short period to reduce motion artifacts during the scan.

Indications

CTPA is indicated in patients with suspected pulmonary embolism, especially when there is a high clinical suspicion based on symptoms such as sudden onset of shortness of breath, chest pain, or unexplained hypoxemia. It is also used when other tests, such as a D-dimer test, suggest the presence of a clot.

Interpretation

The images obtained from a CTPA are interpreted by a radiologist. A normal CTPA will show clear pulmonary arteries without any filling defects. A positive CTPA for pulmonary embolism will show filling defects within the pulmonary arteries, indicating the presence of a clot.

CT pulmonary angiogram of pulmonary vessels

Advantages

CTPA is a highly sensitive and specific test for diagnosing pulmonary embolism. It provides a rapid and non-invasive method to visualize the pulmonary vasculature. Compared to other diagnostic methods, such as ventilation/perfusion scans, CTPA offers a more direct visualization of the clot.

Risks

The primary risks associated with CTPA include exposure to ionizing radiation and potential allergic reactions to the contrast agent. Patients with impaired kidney function may be at risk for contrast-induced nephropathy.

Alternatives

Alternatives to CTPA include ventilation/perfusion scans, ultrasound of the legs to detect deep vein thrombosis, and magnetic resonance imaging (MRI) in certain cases.

CT pulmonary angiogram with segmental and subsegmental pulmonary embolism

Related Pages

• Pulmonary embolism
• Computed tomography
• Contrast agent
• Radiology