Axial and Total-Body Bone Densitometry Using a Narrow-Angle Fan-Beam

Abstract

We assessed a new dual-energy bone densitometer, the PRODIGY, that uses a narrow-angle fanbeam (4.58) oriented parallel to the longitudinal axis of the body (i.e., perpendicular to the usual orientation). High-resolution scans across the body can be stepped at 17 mm intervals. The energy-sensitive array detector uses cadmium zinc telluride, which allowed rapid photon counting. Spine and femur scans required 30 s, and totalbody scans required 4-5 min; the dose was only 3.7 mrem and 0.04 mrem respectively, or about 5 to 10 times lower than conventional fan-beam densitometry. We found only a small influence of soft-tissue thickness on bone mineral density (BMD) results. There was also a small ( + 1%) influence of height above the tabletop on BMD results. A software correction for object height allowed a first-order correction for the large magnification effects of position on bone mineral content (BMC) and area. Consequently, the results for BMC and area, as well as BMD, with PRODIGY corresponded closely to those obtained using the predecessor DPX densitometer, both in vitro and in vivo; there was a generally high correlation (r = 0.98-0.99) for BMD values. Spine and femur values for BMC, area and BMD averaged within 0.5% in vivo (n = 122), as did total-body BMC and BMD (n = 46). PRODIGY values for total-body lean tissue and fat also corresponded within 1% to DPX values. Regional and total-body BMD were measured with 0.5% precision in vitro and 1% precision in vivo. The new PRODIGY densitometer appears to combine the low dose and high accuracy of pencil-beam densitometry with the speed of fan-beam densitometers.

DXA Estimates of Vertebral Volumetric Bone Mineral Density in Children: Potential Advantages of Paired Posteroanterior and Lateral Scans

“…Two studies demonstrate that this technique is subject to negligible magnification effects (31,32); this latest advance may be particularly important for pediatric applications that rely on PA scans.…”

Bone mineral content, corrected for height or bone area, measured by DXA is not reduced in children with chronic renal disease or in hypoparathyroidism

“…However, as recent data from Leonard et al have shown that total body BMC, as assessed by DXA, correlates with pQCT-assessed measurements of bone strength when the data are adjusted for height [21], we also examined a subset of our cohort who were prepubertal, and adjusted their data for height and found that our observations persisted at the level of the lumbar spine. Concerns that the manufacturer's reference population may not accurately represent the normal range for our population are minimised by the recent publication of similar reference data using the same family of DXA scanners and the close concordance between the Lunar DPX and the Lunar Prodigy scanners [17,22].…”

Validation of DXA Body Composition Estimates in Obese Men and Women

“…The departure of our findings from those of Sopher et al (7) could be related to the use of DPX/DPX-L systems by the latter and a Prodigy system in the current study. Although Prodigy devices are calibrated to allow results to be obtained over a wide tissue thickness range (23), errors remain apparent at larger tissue thicknesses.…”