Melon P G, Beanlands R S, DeGrado T R, Nguyen N, Petry N A, Schwaiger M
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0028.
J Am Coll Cardiol. 1992 Nov 1;20(5):1277-83. doi: 10.1016/0735-1097(92)90388-4.
The aim of this study was to compare the myocardial retention of technetium-99m (Tc-99m) sestamibi and thallium-201 over a wide range of blood flow at different time points after tracer injection.
Technetium-99m sestamibi has been proposed as a new perfusion tracer with better physical characteristics than those of thallium-201 for scintigraphic imaging. However, no studies have simultaneously compared the ability of both tracers to assess myocardial blood flow during pharmacologic vasodilation.
The myocardial retention of Tc-99m sestamibi and thallium-201 were compared over a wide range of blood flow induced by regional coronary occlusion and dipyridamole infusion in an open chest dog model. Myocardial retention of both tracers was determined by in vitro tissue counting at 2, 5, and 20 min after tracer injection and was correlated with microsphere-determined blood flow.
Thallium-201 demonstrated greater absolute tissue retention than did Tc-99m sestamibi. At 2 min after tracer injection, there was an almost linear relation between the retention of both tracers and myocardial blood flow over a wide flow range. However, this relation was not maintained over time. At 20 min after injection, the retention of both tracers underestimated myocardial blood flow at higher flow rates. At 2, 5 and 20 min after injection, increments of relative tracer retention between the different levels of flow were always greater for thallium-201 than for Tc-99m sestamibi.
Thallium-201 displays more suitable physiologic characteristics as a flow tracer and may allow better differentiation of myocardial regions with different levels of coronary flow reserve. For both tracers, early cardiac imaging may minimize underestimation of blood flow at higher flow rates.
本研究旨在比较注射示踪剂后不同时间点，锝-99m（Tc-99m）甲氧基异丁基异腈和铊-201在广泛血流范围内的心肌摄取情况。
锝-99m甲氧基异丁基异腈已被提议作为一种新的灌注示踪剂，用于闪烁成像时，其物理特性优于铊-201。然而，尚无研究同时比较这两种示踪剂在药物性血管扩张期间评估心肌血流的能力。
在开胸犬模型中，通过局部冠状动脉闭塞和双嘧达莫输注诱导广泛的血流，比较Tc-99m甲氧基异丁基异腈和铊-201的心肌摄取情况。在注射示踪剂后2、5和20分钟，通过体外组织计数确定两种示踪剂的心肌摄取情况，并与微球测定的血流相关联。
铊-201的绝对组织摄取量比Tc-99m甲氧基异丁基异腈更高。在注射示踪剂后2分钟，在广泛的血流范围内，两种示踪剂的摄取与心肌血流之间几乎呈线性关系。然而，这种关系并未随时间保持。在注射后20分钟，在较高流速下，两种示踪剂的摄取均低估了心肌血流。在注射后2、5和20分钟，不同血流水平之间铊-201的相对示踪剂摄取增量总是大于Tc-99m甲氧基异丁基异腈。
铊-201作为一种血流示踪剂显示出更合适的生理特性，并且可能更好地区分具有不同冠状动脉血流储备水平的心肌区域。对于这两种示踪剂，早期心脏成像可能会最大限度地减少在较高流速下对血流的低估。
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