Comparative assessment of dual-photon absorptiometry and dual-energy radiography.

The advent of DER represents a significant advance for the field of bone densitometry and reduces scanning time for both spine and hip measurements, and correlation of DPA versus quantitative computed tomography (CT) and DER versus quantitative CT was good.

Abstract

Dual-energy bone densitometry can be performed with two types of scanners. The traditional dual-photon absorptiometry (DPA) machines use an isotope source, whereas the newly introduced dual-energy radiography (DER) devices use an incorporated x-ray tube. The authors evaluated the performance of DPA and DER devices at their institution. The short-term precision error in vivo was 1.2% for femoral neck measurements with DER. Long-term precision error in vitro was reduced from 1.30% (DPA) to 0.44% (DER). The scanning time for both spine and hip measurements was reduced from 20-40 minutes to 6-7 minutes. Intraosseous fat sensitivity remained the same, at a level of 12 mg/cm2 apparent decrease of bone mineral density (BMD) per 10% fat by volume change, and for both devices there was no shift in BMD when phantom thickness was increased by 1.5 inches. The correlation of DPA and DER was high: r = .98 for the spine and r = .95 for the femoral neck. Correlation of DPA versus quantitative computed tomography (CT) (r = .83) and DER versus quantitative CT (r = .85) was good. The advent of DER represents a significant advance for the field of bone densitometry.