Vertebral Bone Mineral Density Measured with Dual Photon Absorptiometry Using a Gamma Camera: Clinical Application to Metabolic Bone Diseases
Dual photon absorptiometry (DPA) with a gamma camera, instead of a rectilinear scanner, has been developed for vertebral bone mineral density (BMD) measurement. The system consists of 50 mCi (1,850 MBq) 153-Gd as the emitting source, and an Anger-type gamma camera with a rectangular Nal (Tl) crystal and 22 photomultiplier tubes. The effective field of a view was enough to cover more than 3 vertebrae. With the patient sitting, data acquisition was performed. The spatial resolution and uniformity of the gamma camera were good. With the introduction of a correction equation, the error in calculated BMD due to body thickness was reduced. A data acquisition of 7.5 to 15 min led to a satisfactory C.V. value (less than 2.0%). The precision (1.63% of C.V. in vitro and 3.53% in vivo) and accuracy (r=0.999) of the BMD measurements were also good. Vertebral BMD values in 300 normal Japanese females decreased with aging. Although in involutional osteoporosis and secondary hyperparathyroidism both vertebral and radial % BMDs decreased, in steroid-induced osteoporosis and primary hyperparathyroidism, disproportionate bone loss (relatively lower in vertebral bone) was demonstrated. Thus, it was shown that a newly developed DPA system using a gamma camera provided sufficient precision and accuracy to quantificaticn of vertebral BMD, and its application should provide reliable information for clarification of the pathophysiology of metabolic bone diseases.