What is the role of helical (spiral) CT scanning in the workup of venous thromboembolism (VTE)?

Updated: Nov 05, 2020
  • Author: Vera A De Palo, MD, MBA, FCCP; Chief Editor: Vinod K Panchbhavi, MD, FACS, FAOA, FABOS, FAAOS  more...
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Helical (spiral) computed tomography (CT) allows for the imaging of pulmonary vessels by way of intravenous (IV) contrast material as the patient moves through a gantry at a constant rate and the radiography source rotates. PE is diagnosed by identifying filling defects, which are either central or adherent to the wall (see the image below).

Helical CT scan of the pulmonary arteries. A filli Helical CT scan of the pulmonary arteries. A filling defect in the right pulmonary artery is present, consistent with a pulmonary embolism.

The advantage of helical CT is that it is minimally invasive and allows concurrent visualization of the parenchyma, pleura, and mediastinum. When looking at the main, lobar, and segmental veins, helical CT has a sensitivity of about 93%. Its positive predictive value is approximately 95%.

The limitations of helical CT include the need for contrast and the requirement for a higher dose of radiation than is used with some other diagnostic modalities. Obliquely or horizontally oriented vessels (eg, those of the segmental branches of the right middle lobe and lingula) are poorly visualized. The scan is technically inadequate or inconclusive in approximately 1-10% of cases.

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