Radiocolloid scans in evaluating splenic response to external radiation.

By use of 99mTc-sulfur colloid, splenic size as well as liver/spleen ratio of ratioactivity was determined after external radiation of the abdomen. In six patients receiving about 2,000 R whole-abdominal radiation, there was no atrophy of the spleen or abnormal distribution in the liver/spleen ratio of radioactivity (that is, the spleen was still functional). Serial studies in a 7-year-old boy with acute lymphoblastic leukemia in remission showed that 1,450 R splenic radiation did not result in any appreciable change in the length of the organ. In a woman with lymphosarcoma, a change in spleen size did not occur until a dose of 1,800 R was delivered. Another patient had apparently normal uptake of radiocolloid 5 years after 3,600 R. Hence the normal spleen and the spleen affected by other diseases may be far more resistant to external radiation than the spleen diseased with chronic myelocytic leukemia. Spleen scans can be useful in documenting the response of the organ to radiation.