MYOCARDIAL PERFUSION AND FUNCTION IMAGING AT REST WITH SIMULTANEOUS TL-201 AND TC-99M BLOOD-POOL DUAL-ISOTOPE GATED SPECT

We present a simultaneous gated SPECT (G-SPECT) dual-isotope technique using Tl-201 for perfusion and Tc-99m blood-pool labeling for functio n imaging. Methods: Seventeen patients (13 with previous myocardial in farction, MI) and a control group of three normal volunteers were inve stigated. They received, 15 min after a Tl-201 stress/redistribution p rotocol with reinjection, 900-950 MBq Tc-99m-HSA for blood-pool labeli ng. Eight frames per R-R interval were recorded in the G-SPECT mode wi th three windows: window A with 20% centered at 71 keV for Tl-201, win dow B with 10% centered at 105 keV for Te scatter contamination and wi ndow C centered at 140 keV with 20% for Tc-99m. Nongated, crosstalk-co rrected Tl-201 SPECT perfusion images were reconstructed according to normalized projection-by-projection subtraction from data from windows A and B. G-SPECT data from window C were reconstructed with the same reconstruction limits to allow topographic correlations of left ventri cular perfusion and wall motion abnormalities. Polar maps of perfusion and function were used to divide the myocardium into 20 segments. Per fusion was expressed as the percentage of thallium uptake and function corresponding to diastolic to systolic shortening normalized by end d iastolic volume, Results: Segmental comparison of uncontaminated-to-co ntaminated and corrected Tl-201 patient images demonstrated an overall agreement score of 93%, with a kappa statistic of 0.76 +/- 0.06 when normal perfused segments were excluded. Segmental matching of perfusio n against function at rest showed no correlation far the 10 patients w ith preserved ejection fraction of 59% +/- 8% nor for the control grou p, For the remaining seven patients with an ejection fraction of 34% /- 10%, there was linear correlation between perfusion and function (r (2) = 0.61). Conclusions: The feasibility of dual Tl-Tc G-SPECT was ex amined at rest and suggests low perfusion hypokinesis that matches lin ear dependence for CAD patients with low ejection fraction.