Background and purpose: Phase analysis of gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has been validated as a reliable tool to assess left-ventricular (LV) mechanical dyssynchrony. The initial results were all confirmed from studies using technetium-99m (Tc-99m) sestamibi or tetrofosmin as the radiotracers. The purpose of this study was to evaluate the feasibility of phase analysis in thallium-201 (Tl-201) gated SPECT MPI.
Materials and methods: Seventeen patients referred from a cardiology clinic for evaluation of coronary artery disease were studied. All patients underwent both Tl-201 and Tc-99m sestamibi gated SPECT MPI within 1 week. An additional 34 patients with Tl-201 gated SPECT and 22 patients with Tc-99m sestamibi gated SPECT, who had a low likelihood of coronary artery disease, normal LV function, and normal perfusion on MPI, were used as normal controls. LV dyssynchrony parameters, including phase standard deviation (PSD) and phase histogram bandwidth (PHB), were measured using a standard phase analysis tool and compared between Tl-201 and Tc-99m sestamibi images.
Results: The LV dyssynchrony parameters correlated well (r=0.93 for PSD and r=0.84 for PHB) between Tl-201 and Tc-99m sestamibi images. The dyssynchrony parameters of Tl-201 were significantly larger than those of Tc-99m sestamibi (PSD: 24.5±12.0 vs. 17.4±9.7, P<0.001; PHB: 74.7±35.5 vs. 50.6±25.0, P<0.001). In comparison with normal controls, Tl-201 and Tc-99m sestamibi images showed concordant results.
Conclusion: LV dyssynchrony parameters correlated well between Tl-201 and Tc-99m sestamibi images, even though the values were significantly larger for Tl-201 than for Tc-99m sestamibi. Tl-201 images showed results similar to those of Tc-99m sestamibi in the diagnosis of LV dyssynchrony.