Introduction: Tc-99m-Teboroxime ([(TcCl)-Tc-99m(CDO)(CDOH)(2)BMe]) is a member of the BATO (boronic acid adducts of technetium dioximes) class of Tc-99m(III) complexes. This study sought to explore the impact of co-ligands on solution stability, heart uptake and myocardial retention of [Tc-99m(L)(CDO)(CDOH)(2)BMe] (Tc-99m-Teboroxime: L = Cl; Tc-99m-Teboroxime(F): L = F; Tc-99m-Teboroxime(SCN): L = SCN; and Tc-99m-Teboroxime(N-3): L = N-3). Methods: Radiotracers Tc-99m-Teboroxime(L) (L = F, SCN and N-3) were prepared by reacting Tc-99m-Teboroxime with NaF, NaSCN and NaN3, respectively. Biodistribution and imaging studies were carried out in Sprague-Dawley rats. Image quantification was performed to compare their heart retention and liver clearance kinetics. Results: Complexes Tc-99m-Teboroxime(L) (L = F, SCN and N-3) were prepared in high yield with high radiochemical purity. All new radiotracers were stable for >6 h in the kit matrix. In its HPLC chromatogram, Tc-99m-Teboroxime showed one peak at similar to 15.5 min, which was shorter than that of Tc-99m-Teboroxime(F) (similar to 16.4 min). There were two peaks for Tc-99m-Teboroxime(SCN) at 16.5 and 18.3 min. Tc-99m-Teboroxime(N-3) appeared as a single peak at 18.4 min. Their heart retention and liver clearance curves were best fitted to the hi-exponential decay function. The half-times of fast/slow components were 1.6 +/- 0.4/60.7 +/- 8.9 min for Tc-99m-Teboroxime, 0.8 +/- 0.2/101.7 +/- 20.7 min for Tc-99m-Teboroxime(F), 1.2 +/- 0.3/84.8 +/- 16.6 min for Tc-99m-Teboroxime(SCN), and 2.9 +/- 0.9/51.6 +/- 5.0 min for Tc-99m-Teboroxime(N-3). The 2-min heart uptake followed the order of Tc-99m-Teboroxime (3.00 +/- 0.37%ID/g) > Tc-99m-Teboroxime(N-3) (2.66 +/- 0.01 %ID/g) approximate to Tc-99m-Sestamibi (2.55 +/- 0.46 %ID/g) > (TcN)-Tc-99m-MPO (2.38 +/- 0.15 %ID/g). Tc-99m-Teboroxime remains the best in first-pass extraction. The best image acquisition window is 0-5 min for Tc-99m-Teboroximine and 0-15 min for Tc-99m-Teboroximine (N-3). Conclusion: Co-ligands had significant impact on the heart uptake and myocardial retention of complexes [Tc-99m(L)(CDO)(CDOH)(2)BMe] (L = Cl, F, SCN and N-3). Future studies should be directed towards minimizing the liver uptake and radioactivity accumulation in the blood vessels while maintaining their high heart uptake. (c) 2014 Elsevier Inc. All rights reserved.