Investigating fiberglass casting materials and cross-system modality measurements in DXA and X-ray forearm imaging

Abstract

Falls on an outstretched hand (FOOSH) injuries often lead to distal radius fractures (DRFs). X-ray imaging is used to visualize fracture morphology and provide qualitative information; however, quantitative information is not readily available without more advanced imaging modalities. This study investigated the impact of fibreglass cast thickness on the accuracy of areal bone mineral density (aBMD) and bone mineral content (BMC) measurements obtained through Dual-Energy X-ray Absorptiometry (DXA). It evaluated the potential of a novel dual-energy spectral X-ray detector (Reveal 35C) as a point-of-care alternative. Eight cadaveric forearm specimens were scanned under baseline, two-roll, and four-roll cast conditions using both imaging modalities. Simulated DRFs were induced via quasi-static loading, followed by post-fracture imaging to assess structural integrity and imaging fidelity. Results showed that DXA-derived aBMD and BMC significantly decrease with increasing cast thickness. The mid-distal subregion of interest (MD-sROI) shows the most consistent attenuation trend. In contrast, the ultra distal (UD-sROI) and one-third distal (OTD-sROI) subregions of interest showed greater variability, particularly in specimens with lower density. The Reveal 35C detector showed a strong correlation with the DXA system under uncasted conditions (R2 = 0.82-0.89), but correlations are markedly lower in casted scans (R2 = 0.29-0.63). This discrepancy highlights cast-induced imaging distortions. Through fracture testing, it is shown that specimens with higher aBMD and BMC generally sustained greater loads prior to fracture. Findings from this study indicate that DXA-derived aBMD and BMC are susceptible to errors caused by fiberglass medical casts and variations in positioning during imaging. Meanwhile, the Reveal 35C system shows promise as a viable alternative for bedside fracture monitoring through calibration, but limited in enabling virtual cast removal and longitudinal assessment.