Body composition analysis using CT and MRI: intra-individual intermodal comparison of muscle mass and myosteatosis

Computed tomography (CT) and magnetic resonance imaging (MRI) can quantify muscle mass and quality. However, it is still unclear if CT and MRI derived measurements can be used interchangeable. In this prospective study, fifty consecutive participants of a cancer screening program underwent same day low-dose chest CT and MRI. Cross-sectional areas (CSA) of the paraspinal skeletal muscles were obtained. CT and MRI muscle fat infiltration (MFI) were assessed by mean radiodensity in Hounsfield units (HU) and proton density fat fraction (MRI(PDFF)), respectively. CSA and MFI were highly correlated between CT and MRI (CSA: r = 0.93, P < 0.001; MFI: r = − 0.90, P < 0.001). Mean CSA was higher in CT compared to MRI (46.6cm(2) versus 43.0cm(2); P = 0.05) without significance. Based on MRI(PDFF), a linear regression model was established to directly estimate skeletal muscle fat content from CT. Bland–Altman plots showed a difference between measurements of − 0.5 cm(2) to 7.6 cm(2) and − 4.2% to 2.4% regarding measurements of CSA and MFI, respectively. In conclusion, the provided results indicate interchangeability of CT and MRI derived imaging biomarkers of skeletal muscle quantity and quality. Comparable to MRI(PDFF), skeletal muscle fat content can be quantified from CT, which might have an impact of analyses in larger cohort studies, particularly in sarcopenia patients.