Movement artifact and dual X-ray absorptiometry

Dual-energy X-ray absorptiometry (DXA) scanning is used with increasing fre quency to measure bone mass and body composition in adults as well as child ren. Without sedation, children may move during the study. The effect of mo vement decreases the precision of DXA scanning (1). However, the amount and types of movements that alter scan results are not known. Eleven adults we re scanned five times using a Hologic QDR-2000. Prescribed movements were d esigned to simulate movements that may occur in the clinical setting. These movements included: slow horizontal movements, fast horizontal movements, isolated movements of the extremities and head, and slow vertical movements . In addition, 90 sequential DXA scans were reviewed for movement. Movement was noted in 23% of 90 sequential DXA scans ordered for clinical purposes at a children's hospital. Equal percents of subjects over 15 and 15 or youn ger moved during DXA scans. Movement during DXA scanning results in unpredi ctable alterations in the assessment of bone mineral content (BMC), lean ma ss, and fat mass. Movement artifact, especially vertical movements, may be difficult to detect on DXA printouts.