Radiopharmacokinetics and radiation dose from 99mTc-HM-PAO (Preliminary report)

Whole body retention measurements were performed in volunteers after i.v. injection of ^99mTc-HM-PAO (Ceretec^®). The organ accumulation was measured in mice and data were transferred to standard man according to ICRP. Absorbed dose calculations were made with these data by using the concept of absorbed fractions (MIRD method). In man, the whole body retention and the retention in the brain could be calculated by direct measurement, absorbed doses to the other organs could only be derived from animal data. The absorbed dose to the brain derived from human data (10.3 Gy/MBq) is greater by a factor of 2 than that derived from animal data. The highest absorbed dose was received by the thyroid (24.4 Gy/MBq), the absorbed dose to the ovaries, testes and whole body ranged from 2.8 to 4.2 Gy/MBq.Dedicated to Professor Dr. Guenter Liess on the occasion of his 65th anniversary     

A kinetic model for99mTc-DMSA in the rat

A pharmacokinetic model was developed for the renal imaging agent^9mTc-DMSA in anesthetized rats, which incorporated data from serial measurements of blood and urine simultaneously with dynamic images obtained over an 8-h period. Animals which received a 10 mg/kg dose of unlabeled DMSA immediately before^99mTc-DMSA injection had a significantly reduced kidney accumulation and greater urinary elimination of^99mTc than animals which received the radiopharmaceutical alone. The kidney clearance was also significantly lower in rats receiving unlabeled DMSA, but no significant difference was determined between the urine clearance estimates of the two animal groups. Because the increase in the amount eliminated in the urine was not coupled with a significant change in urine clearance, it would appear that unlabeled DMSA saturated the kidney uptake mechanism(s) of^99mTc-DMSA without modifying the urinary clearance process. This interpretation is consistent with the hypothesis that renal handling of^99m'Tc-DMSA is governed by both glomerular filtration and peritubular capillary uptake. The simultaneous acquisition of blood, urine and non invasive image data allows for a comprehensive and informative model of the physiological disposition of^99mTc-DMSA.