With increased life expectancy, deterioration of bone health has emerged as a serious threat to quality of life due to fragility fractures. We explored the clinical feasibility of the use of a 41Ca tracer for long-term bone health monitoring in comparison with a clinical predictor e.g. bone mineral density (BMD). A healthy woman was injected with 125 ng of 41Ca intravenously in 1990, just before she become perimenopausal. 41Ca/Canat ratios were measured in urine samples collected for over 10 years until 2 years beyond menopause (2000). 6 years of data are shown. Bone mineral density (BMD) was determined using dual X-ray absorptiometry (DEXA) at the spine (L1-L4) from 1988 to 2001. The calcium ratio followed a standard WINSAAM model prediction for the calcium metabolism study using a compartmental model. The spine BMD measured by DEXA remained in a steady state of around 1.451 g/cm2 for five years (1992-1996). No bone loss was apparent from preliminary BMD data. Both AMS measurements and BMD measurements show no bone loss during the overlapping period of the measurements. This comparison is essential to explore clinical applications of AMS. With AMS it is possible to monitor 41Ca levels frequently, a major advantage for studying dynamic variations in bone health. This feature may help in the study of bone dynamics during the transition between premenopause and menopause, and in the early prediction of fracture risk for prevention or treatment. The study of long term dynamic bone health monitoring, a manifold increase in detection sensitivity, and a negligible amount of radiation dose associated with lifelong tracer studies are the key features that make 41Ca a very attractive option for clinical usage.
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