Structural Parameters Obtained by Pixel-by-Pixel Processing of DXA Images: Poster Presentation at the 2016 Annual Meeting of the American Society of Biomechanics

While bone mineral density (BMD) from DXA has traditionally been used to quantify fracture risk, recent studies have shown it is possible to improve bone strength prediction by including additional engineering metrics, such as section modulus and cross sectional moment of inertia. These engineering metrics are almost exclusively calculated by peripheral QCT (pQCT) scanners. However, unlike DXA scanners, pQCT scanners are rarely found in clinical settings. In a 2017 study, Baker et al. (1) developed and validated a pixel-by-pixel method to calculate engineering properties at the distal femur using a Hologic QDR-1000 W DXA scanner and compared them against similar parameters measured using a Stratec XCT-3000 pQCT scanner. Baker et al. found excellent agreement between standard DXA and pixel-by-pixel measured BMD (r2 = 0.996). Cross-sectional moment of inertia about the anteroposterior axis measured using DXA and pQCT also correlated very strongly (r2 = 0.99). Finally, cross-sectional moment of inertia (CSMI) about the anteroposterior axis measured using DXA also correlated strongly with pQCT measured bone strength index (r2 = 0.99). These correlations indicate that DXA scans are able to measure equivalent pQCT parameters. In the experimental study described in this poster, we performed mechanical testing of cadaver femora in three-point bending to failure and showed significant and strong correlations between CSMI (derived from pixel-by-pixel DXA measurements) and failure moment, and strong correlations between Section Modulus and failure moment. This indicates that DXA has the potential to be used clinically to provide an estimate of fracture-risk at the knee in fracture-prone populations such as those with spinal cord injuries. To check out our software for processing DXA scans from a Hologic QDR1000/W pencil-beam scanner visit: https://simtk.org/projects/va-dxamoi Baker AM, Wagner DW, Kiratli BJ, Beaupre GS. Pixel-Based DXA-Derived Structural Properties Strongly Correlate with pQCT Measures at the One-Third Distal Femur Site. Ann Biomed Eng. 2017 May;45(5):1247-1254. doi:10.1007/s10439-017-1796-6. Epub 2017 Jan 19. PubMed PMID: 28105580