A Preliminary Evaluation of the Lunar Expert-XL for Bone Densitometry and Vertebral Morphometry

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Abstract
We have evaluated the Lunar Expert‐XL for standard bone mineral densitometry (BMD) and for morphometric imaging of the spine in the lateral projection. The short‐term precision in vitro of the Expert‐XL for BMD measurements was 0.7% for the Hologic and European spine phantoms, and the long‐term stability (15‐month) measurements had a 1.1% coefficient of variation. The precision in vivo for three operators examining a group of 10 premenopausal women was 0.9–1.5% for lumbar spine (L2–L4), 1.7–2.2% for the femoral neck, and 0.9% for the total hip region of interest. For a group of nine postmenopausal women, the lumbar spine, femoral neck, and total femur precision ranges were 2.0–2.4, 1.2–2.9, and 1.6–1.7% respectively. For L2–L4, BMD comparison between the Expert‐XL and DPX‐L yielded a correlation coefficient of r = 0.98, a slope of 0.86, and an intercept of 0.139 g/cm2. The femoral neck results were r = 0.92, slope = 1.00, and intercept = 0.03 g/cm2. In an evaluation of the Expert‐XL for lateral morphometry, we employed a group of 16 postmenopausal women. Comparison of vertebral dimensions between the Expert‐XL and radiographic morphometry showed strong agreement (r = 0.97), but the interobserver variability for vertebral height was higher for the Expert‐XL than for radiographs (3–5% vs. 1–2%). In a subset of four women who had repeat scans, the interscan precision for measuring vertebral dimensions was 1.9, 4.1, and 4.3% for the L1–L4, T12–T8, and T7–T5 levels respectively. In the Expert‐XL images, it was possible to identify clearly L4–T4 in 10 of 16 patients and L4–T6 in 15 of 16, indicating potential utility for vertebral fracture prescreening.