Quantification of segment soft and rigid tissue masses in living people is important
for a variety of clinical and biomechanical research applications including wobbling
mass modeling. Although Dual-energy X-ray Absorptiometry (DXA) is widely accepted
as a valid method for this purpose, the reliability of manual segmentation from DXA
scans using custom regions of interest (ROIs) has not been evaluated to date. Upper
and lower extremity images of 100 healthy adults who underwent a full body DXA scan
in the supine position were manually segmented by 3 measurers independently using
custom ROIs. Actual tissue masses (fat mass, lean mass, bone mineral content) of the
arm, arm with shoulder, forearm, forearm and hand, thigh, leg, and leg and foot segments
were quantified bilaterally from the ROIs. There were significant differences between-measurers,
however, percentage errors were relatively small overall (<1-5.98%). Intraclass correlation
coefficients (ICCs) were very high between and within-measurers, ranging from 0.990
to 0.999 and 0.990 to 1.00 for the upper and lower extremities, respectively, suggesting
excellent reliability. Between and within-measurer errors were comparable in general,
and differences between the tissue types were small on average (maximum of 42 and
53g for upper and lower extremities, respectively). These results suggest that manual
segmentation of DXA images using ROIs is a reliable method of estimating soft and
rigid tissues in living people.