Novel Tc(III)-azide complexes [Tc(N)(CDO)(CDOH)B-R] (CDOH=cyclohexanedione dioxime) as potential radiotracers for heart imaging.

In this study, novel Tc(III)-azide complexes [Tc(N)(CDO)(CDOH)B-R] (Tc-ISboroxime-N: R=IS; Tc-MPboroxime-N: R=MP; Tc-PAboroxime-N: R=PA; Tc-PYboroxime-N: R=PY; and Tc-Uboroxime-N: R=5U) were evaluated as heart imaging agents.,Complexes [Tc(N)(CDO)(CDOH)B-R] (R=IS, MP, PA, PY and 5U) were prepared by ligand exchange between NaN and [TcCl(CDO)(CDOH)B-R]. Biodistribution and imaging studies were carried out in Sprague-Dawley rats. Image quantification was performed to compare their initial heart uptake and myocardial retention.,Tc-ISboroxime-N, Tc-PYboroxime-N and Tc-Uboroxime-N were prepared with high RCP (93-98%) while the RCP of Tc-MPboroxime-N and Tc-PAboroxime-N was 80-85%. The myocardial retention curves of Tc-ISboroxime-N, Tc-PYboroxime-N and Tc-Uboroxime-N were best fitted to the bi-exponential decay function. The half-time of the fast component was 1.6±0.4min for Tc-ISboroxime-N, 0.7±0.1min for Tc-PYboroxime-N and 0.9±0.4min for Tc-Uboroxime-N. The 2-min heart uptake from biodistribution studies followed the ranking order of Tc-ISboroxime-N (3.60±0.68%ID/g)>Tc-PYboroxime-N (2.35±0.37%ID/g)≫Tc-Uboroxime-N (1.29±0.06%ID/g). Tc-ISboroxime-N had the highest 2-min heart uptake among Tc radiotracers revaluated in SD rats. High quality SPECT images were obtained with the right and left ventricular walls being clearly delineated. The best image acquisition window was 0-5min for Tc-ISboroxime-N.,Both azide coligand and boronate caps had significant impact on the heart uptake and myocardial retention of complexes [Tc(N)(CDO)(CDOH)B-R]. Among the radiotracers evaluated in SD rats, Tc-ISboroxime-N has the highest initial heart uptake with the heart retention comparable to that of Tc-Teboroxime. Tc-ISboroxime-N is a promising alternative to Tc-Teboroxime for SPECT MPI.