Radiation dosimetry for the adult female and fetus from iodine-131 administration in hyperthyroidism.

Through a study of the iodine kinetics of 127 patients, we have developed radiation dose estimates to major organs and the fetus for patients with varying degrees of hyperthyroidism. We observed a negative correlation between maximum thyroid uptake and biologic half-time of iodine in the thyroid and used this correlation to predict the biologic half-time at fixed values of maximum thyroid uptake. Dose estimates to the bladder, gonads, marrow, thyroid, uterus, and whole body were estimated for maximum thyroid uptakes from 20% to 100%. Bladder dose varied from 0.6 to 1.0 mGy/MBq and dose to the uterus varied from 0.036 to 0.063 mGy/MBq under different model assumptions. Dose estimates to the fetus and fetal thyroid were approximated at all stages of pregnancy. Average fetal dose was a maximum between 0 and 2 mo of pregnancy, with the maximum ranging from 0.048 mGy/MBq to 0.083 mGy/MBq, depending on model assumptions. Some radiation risks for irradiation of the fetus and the fetal thyroid are discussed.

Phagocytic labeling of leukocytes with 99mTc-albumin colloid for nuclear imaging.

A procedure is described for the phagocytic labeling of white blood cells (WBC) with high specific activity 99mTc--albumin colloid (TAC). The preparation contains approximately equal activities of granulocytes and monocytes. Heparinized whole blood (40 cm3) yields a preparation containing a total of 148-222 MBq (4-6 mCi) TAC-WBC including about 20% free TAC. The complete preparation time is 75 min. Imaging is completed 30 min to 4 h post administration of the TAC-WBC. Quality control methods and imaging protocols are described.

Radiolabeled red cell viability. I. Comparison of 51Cr, 99mTc, and 111In for measuring the viability of autologous stored red cells.

The simultaneous determination of autologous 99mTc red cell (RBC) and 51Cr RBC viability at 24 hours was measured in 19 normal volunteers whose RBCs had been stored in additive media (Nutracel) for 42 or 49 days. The ratio of the 51Cr:99mTc value was 1.23. In this experiment we also calculated 51Cr RBC viability by both the single-isotope method (extrapolation) and the double-isotope method (using 125I human serum albumin for an independent plasma volume) in the same volunteers. The corresponding viability values were not significantly different. The simultaneous determination of autologous 111In-oxine RBC and 51Cr RBC viability at 24 hours was measured in 19 other normal volunteers whose RBCs had been stored in citrate-phosphate-dextrose-adenine (CPDA-1) for 1 or 15 days. The ratio of the 51Cr:111In value was 1.1. Use of these 24-hour viability ratios as conversion factors permits direct comparison of 99mTc or 111In RBC viability with a 51Cr standard, and therefore expands the application of these newer RBC radiolabels.

Radiolabeled red cell viability. II. 99mTc and 111In for measuring the viability of heterologous red cells in vivo.

The authors developed a double in vivo crossmatch method using 2 to 3 ml of potential donor blood labeled with either 400 microCi of 99mTc or 30 microCi of 111In-oxine. Data are presented for 19 crossmatches on nine patients, using one blood specimen labeled with 99mTc or two specimens, one labeled with 99mTc and the other with 111In. Normal values are given for standardization purposes. This method appears to have advantages over earlier in vivo crossmatch techniques using 51Cr-labeled RBCs. These advantages include the rapidity with which the in vivo crossmatch may be repeated, the ready availability of 99mTc and 111In-oxine, and the lower radiation absorbed doses with the shorter-lived radionuclides.