A PHANTOM FOR EVALUATING BONE-MINERAL DENSITY OF THE HAND BY DUAL-ENERGY X-RAY ABSORPTIOMETRY

Dual-energy x-ray absorptiometry (DXA) is a precise, widely used metho d for measuring bone mineral density (BMD), usually of the lumbar spin e and femoral neck. Recent developments, such as a lower x-ray tube cu rrent and pixel by pixel analysis, enable smaller bones and thinner ti ssue volumes, as in the hand, to be measured. Measurements of hand bon e mineral content (BMC) and BMD could be useful in assessing disease s everity in early rheumatoid arthritis and in monitoring disease progre ssion and response to therapeutic intervention. A phantom is required for evaluating the software, measuring long-term precision and compari ng with other DXA methods. This note describes the design and evaluati on of a band phantom for use on a Lunar DPX-L dual-energy x-ray absorp tiometer. The phantom consists of three sections representing the meta carpals, and proximal and distal phalanges, using aluminium and Perspe x as the bone and lean tissue equivalents respectively. The BMD of the three sections is approximately 1.0, 0.6 and 0.3 g cm(-2). The phanto m demonstrates limitations in the potential accuracy of BMD determinat ion at low densities using the Small Animal Software on the Lunar DPX- L. Improved recognition of low-density regions was obtained with the L unar EXPERT with precision values of 0.9, 1.1 and 2.0% for the three s ections of the phantom respectively.