ECG-gated SPECT myocardial perfusion imaging using adenosine pharmacologic stress: Does choice of radionuclide matter?

Abstract Introduction: Opinions vary as to whether Tc-99m radionuclides are superior for myocardial perfusion (P) imaging based on their imaging characteristics, or Tl-201 is better because of its uptake kinetics and less problem with inferior wall scatter from splanchnic organs. We designed this study to compare these 2 agents in patients imaged after pharmacologic stress using adenosine (Adenoscan®). Methods: 3 expert reviewers blinded to all clinical data interpreted in random sequence and by consensus the non-gated and gated rest and post-stress SPECT scans of 233 pts (52% male): 116 Tl-201/Tl-201 and 117 Tc-99m-Sestamibi (MIBI)/MIBI. 183 pts had coronary angiography ≤ 90 days (26%=0 CAD; 33%=1 VD; 41%=MVD) and 50 had low CAD likelihood. Average age was 68 yrs; mean body mass index (BMI) was 29±5. Images were interpreted for quality (stress and rest P and stress and rest gated scans separately) using a 4-point scale; interpretive certainty using a 5-point scale; sensitivity, specificity, and accuracy for > 50% CAD; and for normalcy. Patients were matched prospectively for gender, BMI, and presence/extent of CAD; logistic regression was utilized to control for these variables. Results: While image quality for stress P and gated scans was high independent of tracer (p=ns), rest P quality was superior with Tl-201 (84% excellent/good vs 68%) (p = 0.05) as was rest function quality (90% vs 82%) (p = 0.017). More MIBI scans had significant hepatic (38% vs 13%) (p Conclusions: Using current imaging protocols, SPECT image quality with adenosine stress is high and unaffected by radionuclide; for both Tl-201 and MIBI ECG-gating improves interpretive certainty. Thallium-201 appears to enhance sensitivity for CAD detection after adenosine stress with no loss in specificity and equal normalcy.