Comparison Between 201 Tl and 99m Tc Sestamibi Uptake During Adenosine-Induced Vasodilation as a Function of Coronary Stenosis Severity

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Abstract
Background Myocardial uptake of either 201Tl or 99mTc-sestamibi (sestamibi) is known to plateau at high coronary flow rates. However, few direct comparisons have been made between these tracers to determine what effect differences in the uptake plateau for the two tracers may have on the detection of coronary stenoses of various severities. Methods and Results Twenty-two dogs were instrumented with flow transducers on the left anterior descending (LAD) and circumflex (LCx) arteries. In 6 nonstenotic dogs, adenosine was infused directly into the LAD, whereas 16 dogs with either critical (n=7) or mild (n=9) LAD stenoses received an intravenous infusion. At peak flow, 201Tl (0.5 mCi), sestamibi (5 to 8 mCi), and radiolabeled microspheres were injected simultaneously. Five minutes later, dogs were killed, and ex vivo imaging of heart slices and gamma-well counting of multiple myocardial samples was performed. Neither 201Tl nor sestamibi uptake increased in direct proportion to flow. In the 6 nonstenotic dogs,...

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