Measurement of total body calcium in bone disease

The irregular shape of the human body and the non-uniformity of distribution of elements within the body make absolute quantitation using in-vivo neutron activation relatively difficult. However, if the mass of an element can be assessed with reasonable accuracy, then a single measurement of a patient could reveal how far body content varied from normal. The accuracy with which body calcium can be measured using cyclotron-produced neutrons and different sizes of phantom discussed. The neutron beam was produced by 16.7 MeV deuterons accelerated in the Medical Research Council Cyclotron, on Be target. The average neutron energy was 7.5 MeV reaching a maximum of about 18 MeV. According to the results randomuncertainties amount to +-8% at the 95% confidence level and the systematic error is about the same. Consequently, only relatively large deviations in total body Ca from normal would be detectable. However, bone mass in, for instance, osteoporotic patients may frequently deviate by more than 20% from normal. In such conditions, the method would be able to provide clinically useful information. (T.G.)