The Concentration of P32 in Some Superficial Tissues of Living Patients1

The turnover of a radio-element in an organ can be followed either by assays on tissues taken from a large group of animals sacrificed or biopsied at different times, or by successive in vivo determinations of the concentration on a single group of animals which need be neither sacrificed nor biopsied. The latter alternative, so desirable in medical studies on man, is feasible because many radio-elements can be detected and measured at a distance, without disturbing the biochemical processes in which they are taking part. In its most general terms, the problem consists in measuring at points external to the human body the radiation emitted by a radioactive substance taken up by a definite region of the body. The success of measuring such radiation will depend on the penetrating properties of the radiation and on the degree to which the radioactive isotope is localized in the tissue in question. Gamma ray-emitting isotopes of elements which are localized to a high degree are obviously the most desirable. T...