Feasibility of simultaneous dual isotope acquisition for myocardial perfusion imaging with a cadmium zinc telluride camera

Background We studied the impact of technetium-99m (Tc-99m) in the thallium-201 (Tl-201) energy window (70 keV) to determine if CZT cardiac cameras allow us to perform simultaneous dual-isotope acquisition for myocardial perfusion imaging. Methods We included 117 consecutive patients. We injected 0.7 MBq/kg of(201)Tl at stress, performed the first scan (image T1), then injected at rest 2 MBq/kg of(99m)Tc-tetrofosmin and immediately acquired a second scan with reconstruction in the energy window of thallium (image T2). A corrected thallium image was created by the subtraction of(99m)Tc downscattered photons (image TS). We compared spectra, image quality, and semiquantitative scores on T1, T2, and TS images. Results Though T2 images were of worse quality, TS images were of equal quality compared to T1 images in most cases. Scores show an underestimation of abnormalities in 20% of patients on T2 images and in 10% on TS images. Conclusions Despite the improved energy resolution of CZT cameras, downscatter of technetium in the(201)Tl window leads to an underestimation of the pathological territory in 10% to 20% of cases. It does not allow us to use simultaneous dual-isotope acquisition in clinical practice without additional tools for scatter correction.