Contrast media volume is significantly related to patient lung volume during CT pulmonary angiography when employing a patient-specific contrast protocol

Aim: The purpose of this study is to investigate the relationship between contrast media volume and patient lung volume when employing a patient-specific contrast media formula during pulmonary computed tomography angiography (CTA). Materials and methods: IRB approved this retrospective study. CTA of the pulmonary arteries was performed on 200 patients with suspected pulmonary embolism (PE). The contrast media volume (CMV) was calculted by employing a patient-specific contrast formula. Lung volume was quantified employing semi-automated lung software that calculated lung volumes (intellispace -Philips). The mean cross-sectional opacification profile of central and peripheral pulmonary arteries and veins were measured for each patient and arteriovenous contrast ratio (AVCR) calculated for each lung segment.  Mean body mass index (BMI) and lung volume were quantified. Receiver operating (ROC) and visual grading characteristics (VGC) measured reader confidence in emboli detection and image quality respectively. Inter and intra-observer variations were investigated employing Cohen’s kappa methodology. Results: Results showed that the mean pulmonary arterial opacification of the main pulmonary circulation (343.88±73HU), right lung; upper (316.51±23HU), middle (312.5±39HU) and lower (315.23±65HU) lobes and left; upper (318.76±83HU), and lower (321.91±12HU) lobes. The mean venous opacification of all pulmonary veins was below 182±72HU. AVCR was observed at all anatomic locations (p<0.0002) where this ratio was calculated. Moreover, larger volumes of contrast significantly correlated with larger lung volumes (r=0.89, p<0.03) and radiation dose (p<0.03). VGC and ROC analysis demonstrated increased area under the curve: 0.831 and 0.99 respectively (p<0.02). Inter-observer variation was observed as excellent (κ = 0.71). Conclusion: We conclude that increased CMV is significantly correlated to increased patient lung volume and radiation dose when employing a patient-specific contrast formula. The effects patient habitus is highlighted.