Comparative study of bone mineral density estimated by various methods of single- and dual-energy quantitative computed tomography: the capability of the four-equation four-unknown method.

A dual-energy (DE) quantitative computed tomography (QCT) method, the four-equation four-unknown method (DEQCT 4E-4U), was assessed and compared to single-energy (SE) QCT and standard DEQCT (two-line method). The results of this study indicate that bone mineral density (BMD) was more accurately estimated by the present method than by the SEQCT or standard DEQCT techniques on the basis of a phantom study when a large fat content was present. The results of both the phantom study and a human study also showed that the present method corrected for fat in estimating BMD in the presence of high-fat content. These findings suggest that use of this method for estimating BMD can provide useful information in studies assessing the metabolic state of bone. We propose that CT numbers estimated from excised vertebral bone marrow can serve as a soft-tissue correction for the present method.