Intravenous Contrast Media-Related Variations in CT-Derived Body Composition Metrics: Associations With Sex and Adipose Tissue.

OBJECTIVES: To investigate the changes in CT-derived body composition metrics across CT phases and identify factors associated with muscle enhancement in healthy individuals. METHODS: This single-center retrospective study included individuals who underwent three-phase abdominal CT. We calculated skeletal muscle, visceral fat, subcutaneous fat, and intermuscular adipose tissue (IMAT) area and attenuation metrics and examined their differences across CT phases. We employed multiple regression to identify factors influencing muscle enhancement. RESULTS: A total of 129 individuals (94 men; median age, 59.00 years) were included. Skeletal muscle index, visceral fat index, and IMAT area significantly varied across CT phases, whereas subcutaneous fat index remained stable. All attenuation metrics significantly changed across all phases, with women exhibiting greater muscle enhancement changes than men (p < .05). The prevalence of sarcopenia and myosteatosis decreased from the precontrast to the portal phase (p < .05). In the sex-specific regression analysis, in women, lower precontrast subcutaneous fat attenuation (SFA) was associated with greater muscle enhancement (b = 0.96-0.97, p < .05) both in the absolute difference and percent change analyses, while in men, higher IMAT (b = 1.13, p = .044) was positively associated with muscle enhancement in the percent change analysis. CONCLUSION: Lower precontrast SFA in women and higher IMAT proportion in men were associated with greater muscle enhancement. ADVANCES IN KNOWLEDGE: These findings suggest potentially significant sex-specific differences in muscle quality assessments between pre- and postcontrast CT, particularly among individuals with varying subcutaneous and intermuscular adipose tissue.