Dual photon absorptiometry in lumbar vertebrae. II. Precision and reproducibility.

Bone mineral content in lumbar vertebrae is determined by the attenuation of 59.6 keV (241Am) and 662 keV (137Cs) photons using the intermittent scanning technique. The precision, mainly influenced by decay variations, is analyzed mathematically. The reproducibility in patient measurements is also affected by variations in positioning, movements during measurement and base line errors. In four normal subjects the reproducibility ranged from 3.4 to 5.7%. The long-term stability was better than 1% during a five-month period as tested by phantom measurements.