Breathing Technique Recommendations for Pulmonary CT Angiography

Preferred Shallow Breath‑Hold

Patients should be coached to maintain a shallow breath‑hold (rather than deep inspiration) during CTPA acquisition to optimize pulmonary artery opacification. The technique prevents a transient interruption of contrast caused by increased intrathoracic negative pressure that draws unopacified blood from the inferior vena cava into the right heart and pulmonary circulation, which would otherwise degrade arterial enhancement. 1, 2
Deep inspiratory breath‑hold can provoke a right‑to‑left shunt of contrast through a patent foramen ovale, resulting in markedly reduced pulmonary artery enhancement while the aorta remains densely opacified. This pattern indicates inadequate pulmonary arterial opacification despite preserved systemic contrast. 1, 2

For patients who are dyspneic or otherwise unable to hold their breath, a shallow free‑breathing acquisition is an acceptable alternative for evaluating the central pulmonary arteries. This approach, combined with high‑threshold bolus triggering, yields high‑quality images of the main and segmental arteries. 1, 2

Avoid pairing deep inspiration with a Valsalva maneuver, as this can exacerbate right‑to‑left shunting through a patent foramen ovale and further compromise pulmonary artery enhancement. 1, 2

Technologists should explicitly instruct patients on the shallow breath‑hold technique before scanning to ensure optimal contrast distribution. 1, 2
If the initial images show a transient interruption of contrast (dense contrast in the superior vena cava with unopacified pulmonary arteries), the examination should be repeated after reinforcing shallow breath‑hold coaching. 1, 2
Application of modern iterative reconstruction and deep‑learning reconstruction algorithms can reduce image noise without increasing radiation dose, thereby improving image quality in challenging cases (e.g., patients with limited breath‑hold capacity). 1, 2