What type of Computed Tomography (CT) scan is ordered to assess for a pulmonary embolism (PE)?

From the Guidelines

A CT pulmonary angiogram (CTPA) is the preferred imaging test to assess for pulmonary embolism. This specialized CT scan uses intravenous contrast material to visualize the pulmonary arteries and detect filling defects caused by blood clots. The procedure typically takes about 15 minutes to complete, with the actual scanning time being only seconds. Patients should inform their provider about any contrast allergies, kidney problems, or pregnancy before undergoing the test. CTPA is preferred over standard CT scans because it specifically highlights the pulmonary vasculature, allowing for direct visualization of emboli. It offers advantages over ventilation-perfusion (V/Q) scans including faster acquisition time, higher sensitivity and specificity, and the ability to identify alternative diagnoses if pulmonary embolism is not present. The test requires the patient to hold their breath briefly during the scan to minimize motion artifacts and optimize image quality.

Key Points

• CTPA is the primary imaging modality for evaluating patients suspected of having acute pulmonary embolism 1
• CTPA has played an increasingly significant role in the diagnosis of PE since the first major clinical study in 1992 by Remy-Jardin et al 1
• Technological advancements in CT have led to improved resolution of the pulmonary arteries, large and small 1
• The American College of Radiology Appropriateness Criteria recommend CTPA as the major diagnostic modality currently used for the diagnosis of PE 1
• CTPA is preferred over standard CT scans because it specifically highlights the pulmonary vasculature, allowing for direct visualization of emboli 1

Considerations

• Patients with a low pretest probability of PE and who meet all Pulmonary Embolism Rule-Out Criteria do not require d-dimer measurements or imaging studies 1
• Patients with a high pretest probability of PE should undergo imaging with CTPA 1
• Ventilation-perfusion scans should be reserved for patients who have a contraindication to CTPA or if CTPA is not available 1

From the Research

CT Scan Type for Pulmonary Embolism Assessment

• The type of CT scan ordered to assess for a pulmonary embolism is Computed Tomography Pulmonary Angiography (CTPA) 2, 3, 4, 5, 6.

Characteristics of CTPA

• CTPA has been shown to have a high sensitivity and specificity for the diagnosis of pulmonary embolism 2.
• It is the imaging test of first choice for diagnosing pulmonary embolism 2, 3.
• CTPA can determine the presence or absence of pulmonary embolism with sufficient certainty without the need for additional imaging tests after a negative result 2.

Alternative Imaging Modalities

• Compression ultrasonography and ventilation-perfusion scintigraphy are reserved for patients with concomitant symptomatic deep vein thrombosis or a stringent contraindication for CTPA, respectively 2.
• Magnetic resonance pulmonary angiography is not a suitable alternative for CTPA 2, but magnetic resonance angiography can aid in the detection and pre-procedural planning of endovascular therapy in patients who are not candidates for CTPA 5.

Advances in CTPA

• Current pulmonary CTA techniques involve ever lower doses of contrast medium and radiation along with advanced postprocessing applications to enhance image quality, diagnostic accuracy, and provide added value in patient management 3.
• Dual-energy CT can detect and quantify lung perfusion abnormalities 4.
• Personalized injection of contrast agent in CTPA has good diagnostic value for pulmonary embolism, with good imaging effect and safe profile, and has a lower radiation dose requirement 6.