COMPARATIVE FEASIBILITY OF SEPARATE OR SIMULTANEOUS REST TL-201 STRESS TECHNETIUM-99M-SESTAMIBI DUAL-ISOTOPE MYOCARDIAL PERFUSION SPECT

Separate or simultaneous rest (TI)-T-201/stress Tc-99m-sestamibi dual- isotope SPECT are potentially efficient myocardial perfusion imaging p rotocols which combine the use of a high-resolution Tc-99m tracer for stress perfusion assessment and (TI)-T-201, th, current single-photon agent of choice, for viability assessment. Methods: To investigate the feasibility of dual-isotope myocardial perfusion SPECT protocols usin g rest (TI)-T-201 and stress sestamibi, (TI)-T-201 crosstalk into the (TC)-T-99m acquisition window (Group 1, n = 26 patients) and Tc-99m cr osstalk into (TI)-T-201 windows (Group 2, n = 25) were studied. For Gr oup I,treadmill exercise with sestamibi injection and poststress SPECT (''virgin'' sestamibi images) were performed, followed by rest (TI)-T -201 injection and SPECT acquisition using dual-isotope windows (conta minated or ''dual'' images). For Group 2, the order was reversed: rest (TI)-T-201 SPECT (virgin (TI)-T-201 images) was performed first, foll owed by exercise sestamibi injection and dual-isotope SPECT. Results: The contribution of (TI)-T-201 scatter to the dual sestamibi images (G roup 1) was measured to be 2.9% +/- 2.1%, while Tc-99m crosstalk contr ibuted 26.7% +/- 13.0% to the dual (TI)-T-201 images (Group 2). Image quality was considered good to excellent in 92% of the sestamibi (virg in and dual) images and 88% of the virgin (TI)-T-201 SPECT, but only i n 23% of the dual (TI)-T-201 studies. Conclusions: Technetium-99m cros stalk into (TI)-T-201 windows is substantial; therefore, simultaneous dual-isotope protocols, which involve assessment of (TI)-T-201 images contaminated by Tc-99m, are not recommended. On the other hand, becaus e of the small amount of (TI)-T-201 crosstalk into the (TC)-T-99m wind ow, a separate acquisition dual-isotope approach employing the rest (T I)-T-201 (virgin)/stress sestamibi sequence is acceptable.