In vivo neutron activation analysis; a new technique in nutritional research

Abstract

In vivo neutron activation analysis (IVNAA) has ushered in a new era of clinical diagnosis, therapy evaluation, and modeling of body composition.~ 3 Direct determination of several key elements of the body has been made possible by delayed and prompt gamma IVNAA. Measurement of total body nitrogen (protein) by prompt gamma neutron activation (PGNAA) is of particular importance in nutrition studies. Measurement of total body calcium (TBCa) by delayed neutron activation (DGNAA) yields accurate information on the bone mineral mass, because 99% of the body calcium resides in skeletal tissue. Along with calcium, total body sodium, chlorine (TBCI), and phosphorus are activated and thus can be measured. Naturally occurring 4°K total body potassium (TBK) is automatically measured by whole body counting. Elemental composition studies made with the use of IVNAA have shown the relationship between body elements and compartments. Body composition models have been considerably refined with the data obtained by in vivo nuclear techniques.l-° Determination of body composition has been used by a number of investigators to achieve nutritional assessment of individuals with a variety of disorders and dysfunctions. 4-9 The analyses rest both on a database derived from measurements made of normal subjects, reflecting the parameters of age and sex, and on serial measurements that reflect ongoing processes and the effects of therapeutic programs, such as nutritional regimens.