3D Analysis of Cortical and Trabecular Bone From Hip DXA: Precision and Trend Assessment Interval in PostmenopausalWomen

Abstract The 3D distribution of the cortical and trabecular bone mass is a critical component in determining the resistance of a bone to fracture that is not assessed in standard dual-energy X-ray absorptiometry (DXA) exams. In this work, we assessed in vivo short-term precision of measurements provided by 3D modeling techniques from DXA scans and trend assessment intervals (TAIs) in postmenopausal women. Subjects included to study precision errors were scanned twice, with repositioning for duplicate hip scans, using either a Lunar iDXA scanner (GE Healthcare, Madison, WI) or a Discovery W scanner (Hologic, Inc., Waltham, MA). Postmenopausal women having baseline and 18-mo follow-up visit were scanned using a Lunar iDXA device to assess TAIs. TAIs indicate what time intervals are required to allow accurate assessment of response to treatment or progression of disease. The 3D-SHAPER software (Galgo Medical, Barcelona, Spain) was used to derive 3D measurements from hip DXA scans. Least significant changes were 10.39 and 8.72 mg/cm 3 for integral volumetric bone mineral density (BMD), 9.64 and 9.59 mg/cm 3 for trabecular volumetric BMD, and 6.25 and 5.99 mg/cm 2 for cortical surface BMD, using the Lunar iDXA and Discovery W scanners, respectively. TAIs in postmenopausal women were 2.9 yr (integral volumetric BMD), 2.6 yr (trabecular volumetric BMD), and 3.5 yr (cortical surface BMD), using the Lunar iDXA scanner. As a comparison, TAIs for areal BMD were 2.8 yr at neck and 2.7 yr at total femur. Least significant changes of measurements provided by 3D modeling techniques from DXA were assessed. TAIs in postmenopausal women were similar to those measured for areal BMD measurements. DXA-derived 3D measurements could potentially provide additional indicators to improve patient monitoring in clinical practices.