Use of a Collimated Source of Fast Neutrons to Measure Malignant Tumor Electrolyte Exchange Kinetics

A facility has been designed and installed which makes it possible to measure the rate of exchange of sodium and chlorine from any selected body site. The subject is positioned so that fast neutrons can be directed on the tissue of interest. An eight second irradiation is carried out during which approximately 1 rad of radiation dose is delivered to the tissue. The subject is rapidly transferred (1-2 min.) to another facility where the irradiated volume can be placed between two NaI(T1) crystals for counting. A series of gamma-ray spectra are collected over a period of approximately 1 hour. Sodium and chlorine intensities are obtained from each spectrum by use of a least-square computer fitting program. The intensities are corrected for radioactive decay and then used to compute the tissue electrolyte exchange rates by means of a leastsquare multiple exponential component fitting program. The methodology employed has allowed an early component with 1-10 minute half-time to be obtained in sodium and chlorine tissue exchange for the first time.