Radiation exposure in nuclear cardiovascular studies.

Nuclear cardiovascular studies are being introduced in almost every Nuclear Medicine Department. The number of studies performed per week is increasing very rapidly. The physical characteristics including the specific gamma ray constant for radionuclides used in cardiovascular studies are listed. The radiation dose estimates to different organs of a patient administered with 201Tl and 99mTc radiopharmaceuticals are shown. The radiation levels measured around patients administered with 201Tl chloride, 99mTc HSA (human serum albumin), and 99mTc-MDP (methylene diphosphonate) are within the permissible limits. Radiation doses to different organs from nuclear cardiovascular studies are less than those associated with fluoroscopy, particularly cardiac catheterization. However, the gonadal doses received from cardiac catheterization and angiocardiography are considerably lower than nuclear cardiovascular studies.

Medical x-ray exposure of the human embryo and fetus.

In a period of 2 yr. 6 pregnant women who were not aware that they were pregnant at the time of radiological examination of their abdomen and pelvis, wanted to know the radiation dose received by their embryo or fetus. Radiation dose estimate to the embryo or fetus was made by performing dosimetry with a phantom and the equipment utilized for the actual procedure. The dose to the embryo or fetus varied between less than 50 mrads and 3.52 rads when fluoroscopy was also performed. As the radioimmunoassay test now enables immediate, (same day) detection of pregnancy after day 21 of the menstrual cycle, it is reasonable to recommend that (1) the test be performed in all patients whose pregnancy status is uncertain and (2) that a positive result will ensure minimization of any necessary diagnostic radiation dose. The risk to the embryo or fetus is discussed.

Two unusual causes of peripatellar nonmetastatic positive bone scans in patients with malignancies: case reports.

Bone scans performed with 99mTc-polyphosphate in two patients with epidermoid carcinoma of the lung each showed activity in one knee area. In the first case, radiographs of the area revealed Pellegrini-Stieda calcification over the internal femoral condyle. Uptake corresponded to this process, rather than to a lesion deep in the bone. In the second case, the activity accumulation in the right tibia was the only abnormality noted in the scan. An open biopsy revealed Paget's disease, and no radiographic evidence of Paget's disease was found in any other bone. These cases again illustrate that localized accumulation of a bone-scanning agent, in patients with known primary tumors, does not necessarily denote malignancy in bone.

Residual splenic function in the presence of thorotrast-associated hepatic tumor: case report.

A 50-year-old man had received intravenous colloidal thorium dioxide (thorotrast) 27 years previously. Scintiscans with both 99mTc-sulfur colloid and 131I-rose bengal revealed an extensive intrahepatic defect. At operation, the lesion proved to be an infiltrating hemangiosarcoma. The spleen was small but the chronic internal radiation of the spleen had not completely destroyed the function of radiocolloid uptake. Review of the literature disclosed other cases in which the spleen was still capable of accumulating radiocolloid some years after thorotrast administration. In at least one other instance, radiocolloid uptake was not accompanied by splenic ability to clear Howell-Jolly bodies: a disassociation of splenic functions. The effects of the internal radiation dose to the spleen from thorotrast are discussed and compared with the effects of external radiation. The discrepancy between the effects of the two doses may be related to the high relative biologic effectiveness of the alpha rays from thorotrast compared with gamma-radiation, to nonuniformity of distribution, and to the effects of reticuloendothelial blockade.