Contrast-enhancement influences skeletal muscle density, but not skeletal muscle mass, measurements on computed tomography

Low skeletal muscle mass and density have recently been discovered as prognostic and predictive parameters to guide interventions in various populations, including cancer patients. The gold standard for body composition analysis in cancer patients is computed tomography (CT). To date, the effect of contrast-enhancement on muscle composition measurements has not been established. The aim of this study was to determine the effect of contrast-enhancement on skeletal muscle mass and density measurements on four-phase CT studies. In this observational study, two observers measured cross-sectional skeletal muscle area corrected for patients' height (skeletal muscle index [SMI]) and density (SMD) at the level of the third lumbar vertebra on 50 randomly selected CT examinations with unenhanced, arterial, and portal-venous phases. The levels of agreement between enhancement phases for SMI and SMD were calculated using intra-class correlation coefficients (ICCs). Mean SMI was 42.5 (±9.9) cm2/m2 on the unenhanced phase, compared with 42.8 (±9.9) and 43.6 (±9.9) cm2/m2 for the arterial and portal-venous phase, respectively (both p