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A Study of the Effect of Thorium Dioxide Sol Injected in Rabbits

1938; Radiological Society of North America; Volume: 30; Issue: 3 Linguagem: Inglês

10.1148/30.3.370

1527-1315

Clifford R. Orr, George D. Popoff, Raymond S. Rosedale, B. R. Stephenson,

Radiation Therapy and Dosimetry

THE large number of recent contributions to the literature suggesting the use of radio-active substances as a diagnostic method—such as hepatolienography, arteriography—and as a therapeutic measure, has prompted the present investigation. Following the unpublished work of C. R. Orr and B. R. Stephenson, of our laboratories, who, in 1932, were successful in producing shadowgrams with a section of liver from a patient injected with thorium dioxide sol, we set about determining the latent effects of this radio-active material. Two methods of approach were used: (1) experimental animals were injected with the sol and detailed microscopic examinations made of the reticulo-endothelial structure after periods of from 24 hours to 385 days; and (2) roentgen films were exposed to prepared ampules of the sol, to dried specimens of the liver and spleen, and to histological sections in an effort to demonstrate radio-activity. We wish to add our findings to those of the increasing group of workers who believe that the use of radio-active salts, particularly the thorium preparations, is fraught with grave danger. Radio-Activity Thorium is a well-known radio-active element which disintegrates slowly (22), taking several years to reach equilibrium with its disintegration products (Fig. 1). When Then thorium preparations are first made they are free of these products, with the exception of radiothorium. It will be observed in Figure 1 that the original radiothorium has practically disappeared at the end of 12 years and that the total radio-activity is at a minimum at the end of five years. From this point on the activity again increases, attaining a value of 54 per cent of the maximum in ten years and of nearly 90 per cent at the end of 25 years. Applying the above known facts concerning thorium to the thorium dioxide sol, Schlund (22) found by measurement that one ampule of the freshly prepared sol radiates as many alpha particles per second as one microgram of radium; thus the alpha-ray activity of three ampules (the average human dose) is equivalent to three micrograms of radium. He stated, however, that if the sol is prepared from thorium nitrate which has aged five years, when the activity is at a minimum, it will contain only half this amount, or the equivalent of 1.5 micrograms of radium. Taft (72, 73) reported a method of determining the radio-activity of a dose of thorium dioxide sol in the patient's body and found it to give off gamma rays equivalent to 1.37 microgram of radium. “Small as this may seem,” he states, “it is the amount found in the bodies of the girls who died of radium poisoning contracted when they painted radium on watch dials, and those who use it are on dangerous ground.” The Radium Institute of the Academy of Freiburg, according to Kadrnka (46), investigated the activity of 100 c.c. of thorium dioxide sol and found it to have a radio-activity equivalent to 1.24 microgram of radium.