EXTERNAL COUNTING OF Ca47 AND Sr85 IN STUDIES OF LOCALISED SKELETAL LESIONS IN MAN*

In isotope experiments in animals it is sometimes useful to make serial sampling of critical organs in addition to blood and excreta. In man it is often impossible or undesirable to make such a sampling. Here the external counting technique has proved useful-for example, for measurements over the thyroid of the j131 radiation after administration of this isotope. Improved equipment and new y-emitting isotopes and isotope compounds have expanded the applicability of external counting techniques to a wide variety of problems, including those of haematology, cardiology, liver and kidney metabolism. The use of external counting techniques for study of problems in bone metabolism has formerly been hampered by the lack of suitable isotopes. This situation has now improved, and in a previous communication (Bauer and Ray 1958) it was shown how external counting of Sr85 in man might furnish useful data for an interpretation of the kinetics of strontium metabolism in particular, and also of bone metabolism in general. These results and earlier experiments on fracture healing in rats (Bauer 1954) suggested that external counting techniques might be of special interest in the study of localised skeletal lesions in man. On this basis a pilot study of a variety of skeletal lesions was made, the results of which will be presented in this communication. THE PATIENTS This paper is based on studies in seventy-five patients, all ofwhom received an intravenous or intramuscular injection of Sr85 or Ca47, or ofboth. When the injection was given intravenously continuous recording over various body sites was made during the first hour or two hours after injection. From then on counting was made at irregular intervals during two to three weeks. When the isotope was given intramuscularly, counting was usually started twelve to twenty-four hours after injection. In a few patients more than one study was made (sometimes before and after treatment of a lesion). Pertinent data of the case histories are recorded in the legends of Figures and Tables. Most of the patients were in hospital during the studies; and, in most of these, determinations on serum samples and excreta were made, the results ofwhich will be discussed in a forthcoming publication