Optimization of window settings for virtual monoenergetic imaging in dual-energy CT of the liver: a multi-reader evaluation of standard monoenergetic and advanced imaged-based monoenergetic datasets

OBJECTIVES: To evaluate optimal window settings for display of virtual monoenergetic reconstructions in third-generation dual-source, dual-energy computed tomography (DECT) of the liver. METHODS: Twenty-nine subjects were prospectively evaluated with DECT in arterial (AP) and portal venous (PVP) phases. Three reconstructed datasets were calculated: standard linearly-blended (LB120), 70-keV standard virtual monoenergetic (M70), and 50-keV advanced image-based virtual monoenergetic (M50+). Two readers assessed optimal window settings (width and level, W/L), establishing a mean for each reconstruction which was used for a blinded assessment of liver lesions. RESULTS: The optimal W/L for M50+ were significantly higher for both AP (W=429.3±44.6HU, L=129.4±9.7HU) and PVP (W=376.1±14.2HU, L=146.6±7.0HU) than for LB120 (AP, W=215.9±16.9HU, L=82.3±9.4HU) (PVP, W=173.4±8.9HU, L=69.3±6.0HU) and M70 (AP, W=247.1±22.2HU, L=72.9±6.8HU) (PVP, W=232.0±27.9HU, L=91.6±14.4HU). Use of the optimal window setting for M50+ vs. LB120 resulted in higher sensitivity (AP, 100% vs. 86%; PVP, 96% vs. 63%). CONCLUSIONS: Application of dedicated window settings results in improved liver lesion detection rates in advanced image-based virtual monoenergetic DECT when customized for arterial and portal venous phases