Optimization of a simultaneous dual-isotope ²⁰¹Tl/¹²³I-MIBG myocardial SPECT imaging protocol with a CZT camera for trigger zone assessment after myocardial infarction for routine clinical settings: Are delayed acquisition and scatter correction necessary?

Background: Dual-isotope ²⁰¹Tl/¹²³I-MIBG SPECT can assess trigger zones (dysfunctions in the autonomic nervous system located in areas of viable myocardium) that are substrate for ventricular arrhythmias after STEMI. This study evaluated the necessity of delayed acquisition and scatter correction for dual-isotope ²⁰¹Tl/¹²³I-MIBG SPECT studies with a CZT camera to identify trigger zones after revascularization in patients with STEMI in routine clinical settings.

Methods: Sixty-nine patients were prospectively enrolled after revascularization to undergo ²⁰¹Tl/¹²³I-MIBG SPECT using a CZT camera (Discovery NM 530c, GE). The first acquisition was a single thallium study (before MIBG administration); the second and the third were early and late dual-isotope studies. We compared the scatter-uncorrected and scatter-corrected (TEW method) thallium studies with the results of magnetic resonance imaging or transthoracic echography (reference standard) to diagnose myocardial necrosis.

Results: Summed rest scores (SRS) were significantly higher in the delayed MIBG studies than the early MIBG studies. SRS and necrosis surface were significantly higher in the delayed thallium studies with scatter correction than without scatter correction, leading to less trigger zone diagnosis for the scatter-corrected studies. Compared with the scatter-uncorrected studies, the late thallium scatter-corrected studies provided the best diagnostic values for myocardial necrosis assessment.

Conclusions: Delayed acquisitions and scatter-corrected dual-isotope ²⁰¹Tl/¹²³I-MIBG SPECT acquisitions provide an improved evaluation of trigger zones in routine clinical settings after revascularization for STEMI.