Quantitative gamma-ray computed tomography of the radius in normal subjects and osteoporotic patients.

A new design of gamma-ray computed tomography (CT) scanner was used to measure bone density in 516 normal adults and in 116 female patients with osteoporotic fractures. Trabecular bone density (TBD) was measured for a core of the ultradistal radius; cortical bone mass per unit length (MLS) and mass per unit volume (MVS) were computed for the radius shaft. TBD, MLS and MVS peaked at the age of about 40 in females and fell by 32%, 15% and 24%, respectively, by the age of 65. In males, TBD decreased from the third decade and MLS and MVS peaked in the fourth decade. The corresponding falls by 65 years were 20%, 6% and 7%. In patients with Colles' fracture TBD and MLS were reduced by 13% and 10%, respectively, relative to age matched normal female subjects. For patients with vertebral crush fracture the reductions relative to age matched normal females were 36%, 17% and 16% for TBD, MLS and MVS. In fracture patients the deficit in TBD was significantly greater than that for cortical bone but TBD was no better at discriminating normal and osteoporotic individuals because of its larger normal range. We conclude that gamma-ray CT may best be used for monitoring changes in bone rather than as a diagnostic screening tool.

Comparison of broadband ultrasonic attenuation of the os calcis and quantitative computed tomography of the distal radius.

The measurement of broadband ultrasonic attenuation (BUA) in the os calcis, which consists of predominantly trabecular bone, has been compared by others with single photon absorptiometry of forearm cortical bone. We have compared BUA in 24 female subjects with the separate measurement of trabecular and cortical bone in the distal radius using quantitative computed tomography (QCT). BUA was highly significantly correlated with each of the measurements in the radius (P less than 0.001). Paradoxically, BUA was found to be best correlated with the bone mass per unit length in the radial shaft (r = 0.85) rather than with radial trabecular bone (r = 0.66). The degree of correlation was not sufficient to predict radial bone mass accurately in individuals. Broadband ultrasonic attenuation, however, appears to be a useful measurement of bone in the appendicular skeleton.