A preliminary report on the use of gallium in clinical tracer studies.

Abstract

Dudley (1–5) and King (6, 7) have reported on the distribution of radiogallium in animals and on its excretion by both man and animals, while Mulry and Dudley (8), in 18 patients with radiographic evidence of malignant bone tumors, demonstrated increased deposition of gallium72 in the affected skeletal areas in 15. Conclusions based on these studies may be summarized as follows: 1. Gallium72 is a short-half-life isotope (14.3 hours) with energetic gamma emissions (the value for Iγ is 13.3 compared with 8.47 for radium) and moderately energetic beta particles, with an average energy of 0.45 mev. 2. Biological studies indicate that gallium72 has an early deposition in growing bone and that the more rapidly growing the bone the more rapid the uptake. It is excreted almost primarily by way of the kidneys, with a very small amount in the feces. It is apparent from the data presented that this isotope might be employed as a diagnostic tracer in studying the spread and extent of certain types of bone tumor. The purpose of this report is to present the preliminary results of a project utilizing gallium72 for clinical tracer studies. The objective was to evaluate this isotope as a possible diagnostic tool (a) in the determination of the spread of primary bone tumors to areas other than the primary site and (b) in the determination of the site and extent of early bone metastasis from malignant lesions in the soft tissues. The results presented here concern the preliminary part of this project, during which 72 tracer studies were performed on 63 patients. The advanced portion of the study is now under way with a simplified and improved technic and a more careful selection of patients. It is anticipated that the results will be more conclusive than those to be reported here. A continuous study was made of a group of patients with proved cancer of a type likely to metastasize to bone. Gallium72-tracer studies were repeated at three-to six-month intervals along with routine bone surveys at corresponding periods. The final evaluation cannot be made until sufficient time has elapsed for radiographic evidence of bone metastases to develop in a significant number of the patients. When this significant number is available, an attempt will be made to correlate the gallium studies with the radiographic findings. Procedure A tracer dose (0.5 millicurie) of gallium72 citrate, prepared as described by Dudley (4), was administered intravenously. Counts were made by means of an end-window Geiger tube (1∕2-inch diameter window with 3 1∕2-mg.∕cm. window thickness) shielded by 1 inch of lead. The distance between the window and end of the lead collimator, or the sleeve, was 1 inch. With the patient supine, skin surface counts were made at thirty-seven points over the skeleton, as indicated in Figure 1.