COMPARISON OF THE DETERMINATION OF BODY CALCIUM BY IN-VIVO NEUTRON-ACTIVATION ANALYSIS (IVNAA) AND DUAL-ENERGY X-RAY ABSORPTIOMETRY (DEXA)

The measurement of total body calcium is an important tool in the diag nosis and treatment of many diseases associated with bone. This measur ement is done by IVNAA or DEXA. A knowledge of normal bone mineral mas s for a given person is necessary to determine whether or not a measur ed quantity is normal or low. The factors that determine bone mineral mass in a person are not clearly known. IVNAA indicates that bone mine ral mass is a function of height but not the age whereas the reverse i s indicated by DEXA. In this work, we have measured the bone mineral m ass of over 200 normal volunteers by IVNAA and DEXA and have developed a methametical model for DEXA (for lumbar spine and femoral neck) as a function of height, age, weight and years after menopause. In determ ining the bone mineral mass, height is the predominant factor under 20 years of age and age appears to be the dominant factor for over 20 ye ars. The equation derived is useful in calculating the normal bone min eral mass in a patient against which the measured value can be compare d.