Comparison of correction techniques for simultaneous Tl-201/(TC)-T-99m myocardial perfusion SPECT imaging: a dog study

We compared two correction methods for simultaneous Tl-201/Tc-99m dual-isot ope single-photon emission computed tomography (SPECT). Both approaches use the information from the third energy window placed between the photopeak windows of the Tl-201 and Tc-99m. The first approach, described by Moore et al, corrects only for the contribution of the Tc-99m to the Tl-201 primary 70 keV window. We developed the three-window transformation dual-isotope c orrection method, which is a simultaneous cross-talk correction. The two co rrection methods were compared in a simultaneous Tl-201/Tc-99m sestamibi ca rdiac dog study. Three separate acquisitions were performed in this dog stu dy: two single-isotope and one dual-isotope acquisition. The Tl-201 single- isotope images were used as references. The total number of counts, and the contrast between the left ventricular cavity (LVC) and the myocardium, wer e used in 70 keV short-axis slices as parameters for evaluating the results of the dual-isotope correction methods. Three consecutive short-axis slice s were used to calculate averaged contrast and the averaged total number of counts. The total number of the counts was 667 000 +/- 500 and 414 500 +/- 400 counts for the dual-isotope (Tl-201 + Tc-99m) and single-isotope (Tl-2 01-only) 70 keV images, respectively. The corrected dual-isotope images had 514 700 +/- 700 and 368 000 +/- 600 counts for Moore's correction and our approach, respectively. Moore's method improved contrast in the dual-isotop e 70 keV image to 0.14 +/- 0.03 from 0.11 +/- 0.02, which was the value in the 70 keV non-corrected dual-isotope image. Our method improved the same c ontrast to 0.22 +/- 0.03. The contrast in the Tl-201 single-isotope 70 keV image was 0.28 +/- 0.02. Both methods improved the 70 keV dual-isotope imag es. However, our approach provided slightly better images than Moore's corr ection when compared with Tl-201-only 70 keV images.