Positioner and Clothing Artifact Can Affect One-third Radius BMD Measurement

摘要

This report identifies a radius DXA confounder and technical approach to avoid this inaccuracy. Initially, a precision study revealed substantial differences (p < 0.001) in radius BMD least significant change (LSC) ranging from 0.038 to 0.073 g/cm² between three technologists that each performed assessments in 30 men and 30 women. Subsequently, visual examination of all 360 forearm DXA images, including bone, soft tissue, neutral and air point typing was performed. Errors in automated “soft tissue” identification were observed; compared to the manufacturer’s ideal depiction, suboptimal soft tissue point-typing was present in 30/360 scans (8.3%) involving 27 individuals. These point-typing deviations appeared to result from inclusion of forearm positioner slots at the scan field edges or clothing covering the forearm. Twenty-four individuals had a paired scan appropriately point-typed, thus allowing evaluation of the effect on BMD measurement. In those with incorrect point-typing associated with positioner slots, the mean one-third radius BMD was ~7% higher. In conclusion, positioner slots at the edges of the distal scan field can lead to automated soft tissue identification inaccuracies, and consequent erroneous one-third radius BMD measurement. DXA technologists should avoid slot inclusion in forearm scans and evaluate point-typing as part of routine analysis.