Optimising CT-chest protocols and the added value of venous-phase contrast timing; Observational case-control

To optimize CT chest protocol by comparing venous contrast timing with arterial timing for contrast opacification in vessels, qualitative image quality and radiologists' satisfaction and diagnostic confidence in assessing for potential nodal, pleural and pulmonary disease in general oncology outpatients.

Matched case-control study performed following CT protocol update. 92 patients with a range of primary malignancies with 2 CT chests in a 2-year period, one with an arterial phase protocol and the second in the 60 second venous phase, were included. Contrast attenuation in aorta, pulmonary artery and liver were measured. Subjective measurements assessed perivenous artefact, confidence in nodal pleural and pulmonary assessment and presence of pulmonary emboli. Statistical analysis was performed using paired and unpaired t-tests.

Venous-phase CT demonstrated more consistent enhancement of the vessels, with higher attenuation of the nodes, pulmonary and pleural lesions. There was a significant reduction in perivenous beam hardening artefact on venous-phase CT (P < 0.001). Diagnostic confidence was significantly higher for nodal assessment and pleural abnormality visibility (P < 0.001) and pleural assessment (P < 0.05). There was no significant difference in pulmonary mass visibility. There was adequate enhancement to diagnose significant pulmonary emboli (PE) with 4 incidental PEs detected on the venous phase, extending to segmental vessels.

Venous-phase CT chest performs better than arterial-phase on all fronts, without compromising assessment of incidental pulmonary emboli. When intravenous contrast is indicated in a routine chest CT (excluding a CT-angiogram), the default timing should be a venous or 60s phase.