Assessment of pulmonary vasculature volume with automated threshold-based 3D quantitative CT volumetry: In vitro and in vivo validation

Objectives: To validate the ability of threshold-based 3D CT volumetry to enable measurement of volume of visible pulmonary vessels on CT. Materials and methods: In vivo, 3D CT volumetry was validated in seven phantoms that consisted of silicone tubes embedded in a foam block. With the true volume value as reference standard, the accuracy of CT measurement at various lower thresholds of −600 HU, −500 HU, −300 HU and −200 HU were compared. The volume measurements obtained when filled with varied concentration of iodinated contrast media (1:100, 1:200 and 1:500) were also compared. In vivo validation was performed in sixteen patients (9 men, 7 women; mean age, 52.1 years). Inter-scan and inter-observer agreement and reproducibility for pulmonary vasculature volume measurement were evaluated with Bland–Altman analysis. Results: In vitro, the mean value measured under lower threshold of −300 HU (relative error = 1.5%) were the closest to the true values and have no significant difference (P = 0.375). There were no significant differences among the phantom measurement values with different filled concentration (1:100, 1:200 and 1:500). In vivo, the inter-scan reproducibility of volume measurements was good, with a correlation coefficient of 0.82 and ICC (intraclass correlation coefficient) of 0.86. Inter-observer agreement was excellent with a correlation coefficient of 0.91 and ICC of 0.95. Conclusions: The threshold-based 3D quantitative CT volumetry enables accurate and reproducible measurement of pulmonary vessels volume.