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Miroslavov AE, Gorshkov NI, Lumpov AL, Yalfimov AN, Suglobov DN, Ellis BL, Braddock R, Smith AM, Prescott MC, Lawson RS, Sharma HL: Evaluation of 99mTc (CO) 5I as a potential lung perfusion agent. Nucl Med Biol. 2009 Jan;36(1):73-9.
INTRODUCTION: The use of (99m) Tc-macroggregated albumin for lung perfusion imaging is well established in nuclear medicine. However, there have been safety concerns over the use of blood-derived products because of potential contamination by infective agents, for example, Variant Creutzfeldt Jakob Disease. Preliminary work has indicated that Tc (CO)(5) I is primarily taken up in the lungs following intravenous administration. The aim of this study was to evaluate the biodistribution and pharmacokinetics of (99m) Tc (CO)(5) I and its potential as a lung perfusion agent. METHODS: (99m) Tc (CO)(5) I was synthesized by carbonylation of (99m) TcO (4-) at 160 atm of CO at 170 degrees C in the presence of HI for 40 min. Radiochemical purity was determined by HPLC using (99) Tc (CO)(5) I as a reference. (99m) Tc (CO)(5) I was administered by ear-vein injection to three chinchilla rabbits, and dynamic images were acquired using a gamma camera (Siemens E-cam) over 20 min. Imaging studies were also performed with (99m) Tc-labeled macroaggregated albumin ((99m) Tc-MAA) and (99m) TcO (4-) for comparison. (99m) Tc (CO)(5) I was administered intravenously to Sprague-Dawley rats, and tissue distribution studies were obtained at 15 min and 1 h postinjection. Comparative studies were performed using (99m) Tc-MAA. RESULTS: Radiochemical purity, assessed by HPLC, was 98%. The retention time was similar to that of (99) Tc (CO)(5) I. The dynamic images showed that 70% of (99m) Tc (CO)(5) I appeared promptly in the lungs and remained constant for at least 20 min. In contrast, (99m) TcO (4-) rapidly washed out of the lungs after administration. As expected (99m) Tc-MAA showed 90% lung accumulation. The percentage of injected dose per gram of organ +/-S.D. at 1 h for (99m) Tc (CO)(5) I was as follows: blood, 0.22+/-0.02; lung, 12.8+/-2.87; liver, 0.8+/-0.15; heart, 0.15+/-0.01; kidney, 0.47+/-0.08. The percentage of injected dose per organ +/-S.D. at 1 h was as follows: lung, 22.47+/-2.31; liver, 10.53+/-1.8; heart, 0.18+/-0.01; kidney, 1.2+/-0.17. Tissue distribution studies with (99m) Tc-MAA showed 100% lung uptake. CONCLUSION: (99m) Tc (CO)(5) I was synthesized with a high radiochemical purity and showed a high accumulation in the lungs. Further work on the mechanism and optimization of lung uptake of (99m) Tc-pentacarbonyl complexes is warranted. |
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