Performance of virtual non-contrast images generated on clinical photon-counting detector CT for emphysema quantification: proof of concept
Lisa Jungblut, Thomas Sartoretti, Daniel Kronenberg, Victor Mergen, André Euler, Bernhard Schmidt, Hatem Alkadhi, Thomas Frauenfelder, Katharina Martini
Abstract
Objective: To evaluate the performance of virtual non-contrast images (VNC) compared to true non-contrast (TNC) images in photon-counting detector computed tomography (PCD-CT) for the evaluation of lung parenchyma and emphysema quantification. Methods: 65 (mean age 73 years; 48 male) consecutive patients who underwent a three-phase (non-contrast, arterial and venous) chest/abdomen CT on a first-generation dual-source PCD-CT were retrospectively included. Scans were performed in the multienergy (QuantumPlus) mode at 120 kV with 70 ml intravenous contrast agent at an injection rate of 4 ml s −1 . VNC were reconstructed from the arterial (VNC art ) and venous phase (VNC ven ). TNC and VNC images of the lung were assessed quantitatively by calculating the global noise index (GNI) and qualitatively by two independent, blinded readers (overall image quality and emphysema assessment). Emphysema quantification was performed using a commercially available software tool at a threshold of −950 HU for all data sets. TNC images served as reference standard for emphysema quantification. Low attenuation values (LAV) were compared in a Bland–Altman plot. Results: GNI was similar in VNC art (103.0 ± 30.1) and VNC ven (98.2 ± 22.2) as compared to TNC (100.9 ± 19.0, p = 0.546 and p = 0.272, respectively). Subjective image quality (emphysema assessment and overall image quality) was highest for TNC (p = 0.001), followed by VNC ven and VNC art . Both, VNC art and VNC ven showed no significant difference in emphysema quantification as compared to TNC (p = 0.409 vs. p = 0.093; respectively). Conclusion: Emphysema evaluation is feasible using virtual non-contrast images from PCD-CT. Advances in knowledge: Emphysema quantification is feasible and accurate using VNC images in PCD-CT. Based on these findings, additional TNC scans for emphysema quantification could be omitted in the future.