Synthesis, characterization and pre-clinical evaluation of (99m) Tc-tricarbonyl complexes as potential myocardial perfusion imaging agents.

Myocardial perfusion imaging is an established Nuclear Medicine investigation. Current myocardial perfusion imaging agents sestamibi and tetrofosmin have number of drawbacks; low heart uptake coupled with uptake into the surrounding tissues leads to a poorer image quality. There is a need for continued research into designing and evaluating potentially superior myocardial imaging agents. Tri-carbonyl-technetium and rhenium complexes were prepared by combination with mono-dentate and bi-dentate ligands. Complexes were characterized by HPLC, MAS, nuclear magnetic resonance, infrared, single-crystal X-ray diffraction and partition coefficient determinations. (99m) Tc(CO)3 complexes were administered intravenously to Sprague Dawley rats, and tissue distribution studies were carried out at 15 min and 1 h p.i. Radiochemical purity was assessed as >90%. 1-10-phenanthroline, 2,2'-bipyridine and imidazole complexes gave the highest heart uptake. The percentage injected dose per gram (n = 3) at 1 h for 1-10-phenanthroline/imidazole was blood 0.21 ± 0.01, heart 1.12 ± 0.11, kidney 3.61 ± 1.13, liver 0.62 ± 0.06, lung 0.28 ± 0.12, spleen 0.24 ± 0.05, small intestine contents 1.87 ± 0.92; and for 2,2'-bipyridine /imidazole was blood 0.23 ± 0.02, heart 1.07 ± 0.18, kidney 3.31 ± 1.28, liver 0.56 ± 0.09, lung 0.14 ± 0.02, spleen 0.2 ± 0.1, small intestine content 1.05 ± 0.48. Further investigation to evaluate more complexes based on 1,10-phenanthroline, 2,2'-bipyridine and imidazole derivatives could potentially lead to agents with an increased heart uptake and faster clearance from the liver and gastrointestinal tract.

Evaluation of 99mTc(CO)5I as a potential lung perfusion agent.

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.

Etiology of child acute stiff neck.

STUDY DESIGN: The results of MRI study of 10 children with acute stiff-neck who were treated in the Department of Spine Surgery in Saint-Petersburg State Pediatric Medical Academy. OBJECTIVES: To demonstrate the MRI findings in children with acute stiff neck and suggest other explanations to this findings. SUMMARY OF BACKGROUND DATA: The etiology of child's acute stiff-neck has been debated in the published data. Most authors supported the basic role of atlantoaxial fixation in this condition. But modern investigations using MRI and CT show another explanations. METHODS: A total of 10 patients aged 5 to 14 years with typical stiff neck with acute onset were studied by MRI in first 12 hours. RESULTS: In all 10 investigations typical changes that disappeared in a few days were found. There were triangle or oblong high intensity zone near the external edges of backbone discs C2-C3 or C3-C4. The zones were always on the side where the patients felt pain. CONCLUSION: In our opinion, the main reason of the child's acute stiff-neck is a rapid or gradual strangulation of the vascularized tissue in uncovertebral zones in C2-C3, C3-C4 caused by a head movement or a neck's prolonged incurvationed position during a profound sleep. It causes a "wedge" of hydropic tissues that irritate the back longitudinal ligaments. As the result, a head has antalgic position and, in the most severe cases, is blocked.