Determination of Nitrogen in Living Patients

THE technique of in vivo activation analysis has been used in the sequential study of whole-body calcium¹. Neutrons are produced by bombarding a lithium target with 10 MeV protons from the 1.5 m Nuffield cyclotron. The patients, after being irradiated to a dose of about 1.5 rem, are transferred to a whole-body counter in which the activities induced in calcium, sodium and chlorine are monitored. We briefly describe here a new technique for making in vivo measurements on line by counting during the period of irradiation. In particular we have examined the feasibility of measuring the whole-body nitrogen content and of detecting trace amounts of the toxic element cadmium. Liquid phantoms simulating the conditions in the human body are used for these studies.