Non invasive scintigraphic method for biodistribution study of radiopharmaceuticals

Biodistribution studies can be done by invasive or noninvasive methods. The aim of this study was to evaluate the percentage of retained dose (RD) in the organs of interest in noninvasive and invasive study of biodistribution of 99mTc-DMSA (dimercaptosuccinic acid), 99mTc-MAA (macro aggregated human serum albumin) and 99mTc-MDP (methylene diphosphonate) and to compare with the invasive method described in the United States Pharmacopoeia (USP). Lyophilized reagents (DMSA, MAA and MDP) and sodium pertechnetate was obtained from IPEN-CNEN/SP. The radioactive concentration was 123 MBq mL-1 (99mTc-DMSA and 99mTc-MAA) and 617 MBq mL-1 (99mTc-MDP). 99mTc-DMSA and 99mTc-MDP were injected via the tail vein and 99mTc-MAA in the penile vein of rats. The scintigraphic images were obtained in a Nucline TH/22 Mediso gamma camera. The animals were sacrificed after the acquisition of images. The organs were removed and the activity of each organ of interest was measured in an ionization chamber. The renal uptake of 99mTc-DMSA by noninvasive method was (47,02 ± b 2,87)% up to (49,37 ± b 3,41)%. By the invasive method it was observed RD (49.27 ± b 1.88)%. The %RD of 99mTc-MAA in the lungs by non-invasive method varied from (94,22 ± b 0,17)% to (94,67 ± b 0,25)%. Bone scintigraphy with 99mTc-MDP showed significant uptake in the skeleton. The method proposed for noninvasive scintigraphic study biodistribution of radiopharmaceuticals was feasible, with results comparable to those obtained by invasive method described in USP. (author)