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Radiation exposure from 131I-containing radionuclides
788
May 1974 The Journal o f P E D I A T R I C S
Radiation exposure from 1311-contain&gradionuclides
IN THE ARTICLE by Hansen, Wasnich, De Vries, and Sunshine1 a patient with bile ascites is described in whom the diagnosis was confirmed by the use of intravenously administered 131I-rose bengal. The authors point out that had they "suspected the diagnosis of bile a s c i t e s , or h a d t h e y p l a n n e d to e v a l u a t e h e r postoperatively, they would have injected 0.5 to 1.0/zCi of radionuclide, counted a sample of ascitic fluid, and not performed a liver scan." A liver scan necessitates the injection of 50/xCi of radionuclide but can provide information about liver and biliary disease that is of value in managing a patient with hepatobiliary disease, but the authors indicate that, had they suspected the diagnosis, they could have confirmed the diagnosis with a much smaller dose of 131I-rose bengal. One might ask why we should be concerned about the administration of seemingly small amounts of radioactive rose bengal. In the average infant 50 /zCi of 131I-rose bengal will result in a whole-body exposure of several hundred mrads, which is an exposure that should not be ignored in an infant with a normal life expectancy. But we should realize that the major source of irradiation is from the beta decay of 131I and that target organs such as the thyroid may absorb substantially higher doses of radiation than the whole body. As an example, if 50 tzCi of Na13q were administered to an infant and 20 per cent were absorbed by the thyroid (weight, 2 grams), the average dose to the thyroid would be approximately 500 rads. If rose bengal is administered intravenously to an infant with a patent biliary tree and the thyroid is not blocked with Lugol's solution, the thyroid will accumulate a significant amount of 1311.2 Infants with obstructed bile ducts will accumulate even larger amounts of iodine
Vol. 84, No. 5, pp. 788
because the 131I-rose bengal that is trapped in the liver or that accumulates in the peritoneal cavity will gradually release the 131I into the circulation)Therefore, it is important to block the thyroid even when radionuclides with attached 131I are utilized. Hansen and associates reported that no 13!I was present in the thyroid, owing to the use of Lugol's solution. In order to effectively block the thyroid accumulation o f 131I, Lugol's solution should See related article, p. 719.
be administered before and for five days after the administration of the radionuclide. Regardless of the dose of 1311 and the form in which it is administered, the thyroid should be blocked, providing one is not concerned with the diagnosis of thyroid disease. The potential absorbed dose of irradiation is 100 rads per microcurie of 131I per gram of thyroid tissue. The use of Lugol's solution and the lowest possible dose of radionuclide are precautions that can reduce the radiation exposure of the thyroid to minimal levels. Robert L. Brent Departments of Radiology and Pediatrics Stein Research Center 920 Chancellor St. Philadelphia, Pa. 19107
REFERENCES 1. Hansen, R. C., Wasnich, R. D., De Vries, P. A., and Sunshine, P.: Bile Ascites in infancy: Diagnosis with 1311rose bengal, J. PEOIATR.83: 719, 1974. 2. Jacobson, A. G., and Brent, R. L.: The fate of 1311-tagged rose bengal in the rat, Am. J. Roentgenot. 79: 1004, 1958. 3. Brent, R. L., and Geppert, L. G.: The use of radioactive rose bengal in the evaluation of infantile jaundice, J. Dis. Child. 98: 720, 1959.
May 1974 The Journal o f P E D I A T R I C S
Radiation exposure from 1311-contain&gradionuclides
IN THE ARTICLE by Hansen, Wasnich, De Vries, and Sunshine1 a patient with bile ascites is described in whom the diagnosis was confirmed by the use of intravenously administered 131I-rose bengal. The authors point out that had they "suspected the diagnosis of bile a s c i t e s , or h a d t h e y p l a n n e d to e v a l u a t e h e r postoperatively, they would have injected 0.5 to 1.0/zCi of radionuclide, counted a sample of ascitic fluid, and not performed a liver scan." A liver scan necessitates the injection of 50/xCi of radionuclide but can provide information about liver and biliary disease that is of value in managing a patient with hepatobiliary disease, but the authors indicate that, had they suspected the diagnosis, they could have confirmed the diagnosis with a much smaller dose of 131I-rose bengal. One might ask why we should be concerned about the administration of seemingly small amounts of radioactive rose bengal. In the average infant 50 /zCi of 131I-rose bengal will result in a whole-body exposure of several hundred mrads, which is an exposure that should not be ignored in an infant with a normal life expectancy. But we should realize that the major source of irradiation is from the beta decay of 131I and that target organs such as the thyroid may absorb substantially higher doses of radiation than the whole body. As an example, if 50 tzCi of Na13q were administered to an infant and 20 per cent were absorbed by the thyroid (weight, 2 grams), the average dose to the thyroid would be approximately 500 rads. If rose bengal is administered intravenously to an infant with a patent biliary tree and the thyroid is not blocked with Lugol's solution, the thyroid will accumulate a significant amount of 1311.2 Infants with obstructed bile ducts will accumulate even larger amounts of iodine
Vol. 84, No. 5, pp. 788
because the 131I-rose bengal that is trapped in the liver or that accumulates in the peritoneal cavity will gradually release the 131I into the circulation)Therefore, it is important to block the thyroid even when radionuclides with attached 131I are utilized. Hansen and associates reported that no 13!I was present in the thyroid, owing to the use of Lugol's solution. In order to effectively block the thyroid accumulation o f 131I, Lugol's solution should See related article, p. 719.
be administered before and for five days after the administration of the radionuclide. Regardless of the dose of 1311 and the form in which it is administered, the thyroid should be blocked, providing one is not concerned with the diagnosis of thyroid disease. The potential absorbed dose of irradiation is 100 rads per microcurie of 131I per gram of thyroid tissue. The use of Lugol's solution and the lowest possible dose of radionuclide are precautions that can reduce the radiation exposure of the thyroid to minimal levels. Robert L. Brent Departments of Radiology and Pediatrics Stein Research Center 920 Chancellor St. Philadelphia, Pa. 19107
REFERENCES 1. Hansen, R. C., Wasnich, R. D., De Vries, P. A., and Sunshine, P.: Bile Ascites in infancy: Diagnosis with 1311rose bengal, J. PEOIATR.83: 719, 1974. 2. Jacobson, A. G., and Brent, R. L.: The fate of 1311-tagged rose bengal in the rat, Am. J. Roentgenot. 79: 1004, 1958. 3. Brent, R. L., and Geppert, L. G.: The use of radioactive rose bengal in the evaluation of infantile jaundice, J. Dis. Child. 98: 720, 1959.