Technical considerations of dual-energy X-ray absorptiometry-based bone mineral measurements for pediatric studies.

Dual X-ray absorptiometry (DXA) measurements have been shown to provide useful information on bone mineral status in young pediatric subjects. The purpose of this study was to challenge this system under various conditions to determine the clinical and experimental parameters that may be encountered which could interfere with DXA-based bone mineral content (BMC) and bone mineral density (BMD) measurements. Variations in data acquisition, including the covering of step phantom (external calibration standard) with a cotton blanket or partial exclusion of step phantom in the scan field, tissue freezing, or the presence of small nonmetallic objects, did not significantly alter DXA BMC or BMD measurements. By contrast, the presence of movement artifact, radiographic contrast media, and nonmetallic orthopedic casts significantly interfered with DXA BMC and BMC measurements. Variability in operator-dependent analysis of DXA scans occurred with regional analysis of whole body scans for DXA BMC and BMD measurements (average coefficient of variation was 2.9% and 1%, respectively, depending on the region analyzed) but did not affect the total (whole body) result. A minor adjustment in the manual delineation of the step phantom during data analysis may result in almost a 30% difference in DXA BMC and BMD. We conclude that movement artifact, radiographic contrast media, nonmetallic or orthopedic cast, and variations in operator-dependent data analysis may interfere with DXA BMC and BMD measurement in young pediatric subjects. Therefore, appropriate care should be taken to reduce or eliminate such interference.