Regional measurement of bone calcium accretion rate and exchangeable pool with a whole-body counter: Method and studies in subjects without bone disease

Summary

A whole-body counter was used to measure the retention and distribution of radioactivity along the longitudinal axis of the body during 10 days after the intravenous injection of 50 µCi of⁴⁷Ca. These data and the simultaneous measurements of the serum specific activity allowed us to calculate, by the Bauer-Carlsson-Lindquist (BCL) formulas generalized by Marshall, the calcium accretion rate and exchangeable pool in 7 areas: skull, thorax, pelvis, thighs, knees, legs, and ankles and feet. For the whole body, the accretion rate was 336±115 mg/24 h, and the exchangeable pool 5668±1221 mg, in 26 subjects without bone disease. Both parameters were significantly correlated with body height; the exchangeable pool was significantly higher in men than in women.

The accretion rate and exchangeable pool expressed on a basis of bone content varied widely from one area to another, reflecting the ratio of spongy to compact bone: the thorax, pelvis, and arms, which contain 49% of the skeletal mass, accounted for 57% of the total accretion rate and 53% of the exchangeable pool; the skull, 18% of the skeletal mass, accounted for 14% of the accretion and 11% of the pool.