Direct Regional Comparison of Whole-Body DXA and Whole-Body CT Measurements of Fat Mass and Fat-Free Mass in Limbs and Abdomen.

Objectives: To measure fat mass (FM) and fat-free mass (FFM) in the limbs and abdomen using whole-body DXA and compare them with whole-body CT, emphasizing precise regional comparisons to demonstrate the correlation between the methods.

Methods: Fifty-eight healthy adults (aged 20-69) who underwent both whole-body DXA and whole-body CT were included in this study. The CT scans included the entire body except the head, and image segmentation was employed for body composition analysis. Total limb FM, FFM, segmental abdominal FM, and visceral adipose tissue (VAT) were measured from both DXA and CT.

Results: The DXA-derived total limb FM and segmental abdominal FM were significantly lower than the CT-derived FM, whereas the DXA-derived total limb FFM was higher than the CT-derived FFM (p < 0.001). Despite these differences, very strong positive correlations were observed between DXA and CT for total limb FM (r = 0.951), total limb FFM (r = 0.992), and segmental abdominal FM (r = 0.984) (p < 0.001). The correlation for VAT was also strong (r = 0.861) (p < 0.001).

Conclusions: Our study demonstrated very strong correlation in direct regional comparisons between whole-body DXA and CT, supporting the reliability of DXA for analysing FM and FFM in the limbs and abdomen.

Advances in knowledge: We compared FM and FFM in the limbs and abdomen between whole-body DXA and CT through a region-by-region comparison, demonstrating a more direct correlation between the two methods.