Feasibility of simultaneous stress ^99mTc-sestamibi/rest ²⁰¹Tl dual-isotope myocardial perfusion SPECT in the detection of coronary artery disease

This study assesses feasibility and diagnostic accuracy of simultaneous stress ^99mTc-sestamibi/rest ²⁰¹Tl dual-isotope myocardial perfusion SPECT with Moore's correction method, in which contamination originating from lead x-rays produced in a collimator was subtracted in the ²⁰¹Tl windows. Methods: Eighty-one patients with suspected coronary artery disease received exercise ^99mTc-sestamibi injection, followed by rest ²⁰¹Tl injection 50 min later, and dual-isotope SPECT was performed (group 1). These results were compared with coronary angiographic findings. Furthermore, to estimate the accuracy of Moore's correction method, ²⁰¹Tl crosstalk into the ^99mTc acquisition window (group 2A, n=20) and ^99mTc crosstalk into the ²⁰¹Tl acquisition windows (group 2B, n = 20) were studied. For group 2A, stress ^99mTc-sestamibi SPECT (single ^99mTc-sestamibi SPECT) was performed, followed by ²⁰¹Tl injection at rest and dual-isotope SPECT acquisition 50 min later. For group 2B, rest ²⁰¹Tl SPECT (single ²⁰¹Tl SPECT) was performed, followed by ^99mTc-sestamibi injection at rest and dual-isotope SPECT acquisition 30 min later. Results: Sensitivity and specificity in group 1 were 83% and 99%, respectively, when ≥75% coronary artery narrowing was considered significant. In groups 2A and 2B, SPECT images were divided into 24 segments, and relative regional uptake in each segment was obtained. In group 2A, relative regional uptake of single ^99mTc-sestamibi SPECT correlated well with that of dual-isotope SPECT (r = 0.942). In group 2B, relative regional uptake of single ²⁰¹Tl SPECT correlated well with that of dual-isotope SPECT (r = 0.935). Furthermore, in low ²⁰¹Tl uptake segments with relative regional uptake in both single- and dual-isotope SPECT of ≤70%, the degree of concordance between single- and dual-rest ²⁰¹Tl was considered to be high with Bland-Altman analysis and the kappa statistic. Comparison of perfusion defect type demonstrated that, of 22 stress defects within infarct zones, 95% were irreversible and 5% were reversible. In contrast, of 28 stress defects within stenosed vessel zones in noninfarct zones, 89% were reversible and 11% were irreversible (P < 0.0001 versus infarct zones). Conclusion: Simultaneous dual-isotope imaging with Moore's correction method is feasible, with acceptable accuracy for detection of coronary artery disease and a small amount of crosstalk into each window.