Spinal bone density measured with a 5 s scan

Abstract

Absorptiometry provides a convenient, non-invasive method of measuring bone mass in the skeleton with high precision and low radiation dose to the patient (Tothill, 1989). Dual photon absorptiometry (DPA) based on the radionuclide source 153Gd was developed for measuring bone mineral density (BMD) at the clinically important sites of the spine and the hip (Wilson & Madsen, 1977). Recently, dual X-ray absorptiometry (DXA) has superseded DPA (Cullum et al, 1989). Compared with DPA, DXA has advantages of improved precision (coefficient of variation of 1% for spinal DXA compared with 2–3% for DPA) and shorter scanning times (6–8 min for DXA compared with 20–30 min for DPA) (Sorenson et al, 1989). Use of an X-ray tube instead of a radionuclide eliminates the problems associated with radioactive decay of the source (Lindsay et al, 1987). In the most recent development in DXA technology at least two manufacturers have introduced scanners based on a fan beam configuration coupled to a multidetector scanning head (Pommet et al, 1991; Steiger et al, 1991). Compared with the conventional configuration of a pencil X-ray beam linked to a single detector, scanning times are considerably shortened. In the instrument used for the study described in this report, the Hologic QDR-2000, fan beam scans of the lumbar spine (L1–L4) can be performed in either 1 min (sampling 5 lines cm−1 or 2 min (sampling 10 lines cm−1) depending on the precision required.