Dual Energy Radiography versus Quantitative Computer Tomography for the Diagnosis of Osteoporosis

In this study we compared dual energy radiography (DER), a new, highly precise x-ray densitometric technique recently devised for measurements of vertebral mineral density and quantitative computer tomography (QCT), a densitometric technique that selectively measures the trabecular compartment of the vertebra. DER and QCT measurements were obtained in 56 healthy (H) and 48 fractured osteoporotic (OP) women using a Hologic QDR 1000 bone densitometer and a GE 9800 scanner, respectively. DER was significantly correlated with QCT in both the H (r = 0.75; P less than 0.0001) and the OP subjects (r = 0.58; P less than 0.0001). DER decreased significantly with age in the H (P less than 0.05), but not in the OP women, whereas QCT was related to age in both the H (P less than 0.0001) and the OP subjects (P less than 0.01). The rate of bone loss with age was also higher with QCT than with DER in both normal and osteoporotic women. The difference in bone density between the H and the OP subjects was larger (P less than 0.05) with QCT than with DER. Receiver operating characteristic analysis revealed that QCT was a better predictor of vertebral fractures than DER. A larger percentage of OP subjects were 2 SD or more below the normal predicted value with QCT (41%) than with DER (29%). Furthermore, the slopes of the regressions of bone density with age for normal and osteoporotic women were significantly different (P less than 0.05) with QCT but not with DER. These findings are consistent with a disproportionate loss of trabecular bone with age in osteoporosis.(ABSTRACT TRUNCATED AT 250 WORDS)