Boron-10 33 Phosphorus-32 35 Gold-198 37 Beads, Needles, and Applicators 38 Teletherapy 41 CONCLUSIONS 43 APPENDIX 44 SUGGESTED REFERENCES 47 United States Atomic Energy Commission Division of Technical Information Library of Congress Catalog Card Number: 66-62749 1966 [Illustration: THE COVER This multi-detector positron scanner is used to locate tumors. A radioisotope-labeled substance is injected into the body and subsequently concentrates in the tumor tissue. The radioisotope emits positrons that immediately decay and produce two gamma rays that travel in opposite directions. These rays are detected simultaneously on a pair of opposing detection crystals and a line is established along which the tumor is located. This method is one of many ways doctors use radioisotopes to combat disease. In this, as in many other procedures described in this booklet, the patient remains comfortable at all times.] [Illustration: THE AUTHOR Earl W. Phelan is Professor of Chemistry at Tusculum College, Greeneville, Tennessee. From 1952 to 1965, he served as Staff Assistant in the Laboratory Director’s Office at Argonne National Laboratory, where his duties included editing the Argonne Reviews and supplying information to students. For 22 years prior to moving to Argonne he served as Head of the Chemistry Department of the Valdosta State College In Georgia. He received his B.S. and Ph.D. degrees from Cornell University.] Radioisotopes in Medicine By EARL W. PHELAN INTRODUCTION History The history of the use of radioisotopes for medical purposes is filled with names of Nobel Prize winners. It is inspiring to read how great minds attacked puzzling phenomena, worked out the theoretical and practical implications of what they observed, and were rewarded by the highest honor in science.