Dual energy radiography (DER): a preliminary comparative study.

Dual energy radiography (DER) has been recently proposed as a new technique for the non invasive measurement of vertebral mineral density. This preliminary study was undertaken to assess the short-term precision of DER and to compare DER to dual photon absorptiometry (DPA) measurements. Three DER measurements were obtained in 19 healthy volunteers (mean age 34.7 +/- 9.3 years) over a 3 week period. In addition, both DER and DPA measurements were obtained in 52 women (mean age 54.3 +/- 12.5 years). The coefficient of variation for the DER measurements was 1.00%. A highly significant correlation (r = 0.94; p less than 0.0001) was found between DPA and DER. Using this curve a conversion factor of -6.8% was calculated to convert DER to DPA values. Both DER and DPA were significantly and similarly correlated with age (r = -0.43, p less than 0.005; r = -0.38, p less than 0.05, respectively). The rates of bone loss, 0.66% per year for DER and 0.57% per year for DPA, were also similar with the two techniques. From these data, it is concluded that DER is a precise new method for vertebral bone mass measurements.