Reduction of Poor Contrast Enhancement of the Pulmonary Artery in Computed Tomography Angiography Using an Alternative Respiratory Maneuver

Abstract

The aim of the study was to compare the effects of different respiratory maneuvers in computed tomography pulmonary angiography for the diagnosis of pulmonary embolism (PE) on the contrast enhancement of pulmonary circulation and on the quality of lung window images. A retrospective analysis of 520 examinations, half obtained after deep inspiration followed by breath-holding and half solely during breath-holding. Subjective quality analyses and objective measurements of pulmonary arterial enhancement and lung parenchyma attenuation were performed. Elimination of deep inspiration reduced suboptimal opacification of the pulmonary artery (PA), from 7.3% to 2.7%, with 2.7% of the deep inspiration scans having attenuation values <150 Hounsfield units (HU). The prevalence of PE was similar between the groups (19% vs. 23%, respectively), with excellent interobserver diagnostic agreement (κ=0.89 to 0.91). Lung windows were compromised in 6.9% of the studies with respiratory pause, and these examinations had a higher attenuation of the lung parenchyma (median: -709.8 HU) compared with deep inspiration (-794.8 HU). A positive correlation between attenuation of the PA and the ascending aorta was observed (r=0.40 to 0.56). Eliminating deep inspiration before image acquisition had opposite effects with the same magnitude: it caused a reduction in inadequate PA enhancement at the cost of an increased number of nondiagnostic lung images and did not compromise diagnostic consistency for PE.