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Cardiovascular: Clinical ScienceNew' Applications and Findings for 'Old' Imaging Modalities |
1 Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
504
Objectives: Myocardial uptake of sestamibi and tetrofosmin increases with perfusion in a nonlinear relationship. Extraction fraction of both radiotracers decreases at higher flow rates and may result in underestimation of ischemia. We compared the extent of hypoperfusion following dipyridamole stress using SPECT imaging with 99mTc labeled tetrofosmin vs sestamibi in comparison with the gold standard of 82Rb PET imaging.
Methods: Patients (n=75, mean age=67) with known or suspected coronary artery disease underwent rest and dipyridamole stress imaging on three different days in random order using 99mTc tetrofosmin, 99mTc sestamibi or 82Rb imaging. Images were analyzed by two experts, using a 17 segment model and 5 grades to create summed stress scores (SSS), summed rest scores (SRS) and summed difference scores (SDS).
Results: SSS scores were similar for tetrofosmin, sestamibi and 82Rb imaging (6.7 + 10.5, 7.1+ 9.5, 7.9 + 7.5, not significant). SRS scores were also similar for tetrofosmin, sestamibi and 82Rb (5.3 + 9.2, 5.5 + 8.5, 3.8 + 5.6, not significant). However, SDS scores did differ with greater hypoperfusion with 82Rb imaging (4.4 + 5.2) compared with 99mTc tetrofosmin (1.4+/-2.8, p<0.0001) and 99mTc sestamibi (1.6 + 3.0, p<0.0001). The SDS scores for tetrofosmin versus sestamibi were not different.
Conclusions: For routine clinical detection of ischemia, stress tetrofosmin and sestamibi SPECT appear to be interchangeable. However, stress 82Rb PET did detect more ischemia and may be preferable in sites with this capability.
Research Support: Ontario Research Development Challenge Fund, GE Healthcare
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