Positioner and Clothing Artifact Can Affect One-Third Radius Bone Mineral Density Measurement

Abstract

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.

Common Mistakes in the Dual-Energy X-ray Absorptiometry (DXA) in Turkey. A Retrospective Descriptive Multicenter Study

“…In a typical DXA evaluation, there is usually a gradual increase in vertebral area progressing from L2 to L4. If this is not evident in the results, it is necessary to check the selection of ROI levels (7,16,19). In our study, ROI definition errors were the most common problem in lumbar spine measurements (Figure 4a-d).…”

“…The selection of the ROI can be a major source of error even for experienced operators, especially in roto-scoliosis of the lumbar spine (7,16,19). In a typical DXA evaluation, there is usually a gradual increase in vertebral area progressing from L2 to L4.…”

Artifacts and Incidental Findings Encountered on Dual-Energy X-Ray Absorptiometry: Atlas and Analysis

“…Variation in positioning will lead to alteration (often increase) in measured hip BMD [121][122][123][124][125] and may also affect radius measurements. 126 Patients with scoliosis cannot lie with their spines straight on the table, which can make it difficult to properly delineate vertebral levels. DEXA images are typically used to assess proper positioning.…”

Fracture Risk Assessment

“…One must also consider inherent errors within DXA technology and human error involved in scan acquisition and interpretation [46][47][48][49] . Accuracy errors (3% to 7%) and precision errors (1% to 2%) have been reported in DXA software [50][51][52] .…”