DUAL-ENERGY BONE DENSITOMETRY USING A SINGLE 100-NS X-RAY PULSE

A pulsed, portable hard x-ray source has been developed for medical im aging and flash x-ray absorptiometry. The source is powered by a Marx generator that drives a field emission x-ray tube which produces a 30- 300 keV x-ray pulse of 100 ns duration. The x-ray fluence has dual-ene rgy properties. The x-ray energy is relatively high early in the pulse and lower later in the pulse. The feasibility of using a single x-ray pulse for precision bone densitometry was analyzed. A computer simula tion model was developed for the x-ray source, the filtration that enh ances the dual-energy distribution, the absorption of the energy distr ibution by bone mineral and soft tissue, and the dual-energy detection system. It is feasible to determine the bone mineral density (BMD) of axial sites such as the lumbar spine and proximal femur with 2% preci sion over an area that is 15-20 mm in size, depending on the bone mine ral and soft tissue thicknesses. An algorithm for determining the abso lute BMD, to an accuracy of 2%, using a Plexiglas(TM)/TiO2 calibration phantom is discussed. At a distance of 50 cm from the source, the pat ient exposure is 3.7 mR. The average absorbed bone and tissue doses ar e 0.6 and 4.3 mrem, respectively. Factors that facilitate diagnostic m easurements in clinical settings are the short patient observation tim e and the portability of the x-ray source. (C) 1998 American Associati on of Physicists in Medicine. [S0094-2405(98)00810-4].