Different types of radiotracers available for stress testing

What are the different types of radiotracers available for stress testing?

There are three basic categories: thallium-201 ( 201 Tl) and technetium-99m ( 99m Tc)-labeled compounds for SPECT, and positron emitting compounds for PET. 

The below table compares 201 Tl and 99m Tc-labeled compounds. The most commonly used 99m Tc-labeled compounds are tetrofosmin and sestamibi, which have similar imaging and chemical characteristics. 99m Tc-labeled compounds generally provide more flexibility in terms of imaging times.

Because of the photon energy and the number of photons emitted, 99m Tc-labeled compounds are generally easier to use for image acquisition and analysis. PET radiotracers, such as rubidium-82 ( 82 Rb), nitrogen-13 ( 13 N) ammonia, and fluorine-18 ( 18 F) fluorodeoxyglucose (FDG), can be used to evaluate myocardial perfusion and glucose metabolism, respectively. 13 N ammonia has a short (20 minute) half-life, so there are some logistical limitations in using this for PET cardiac imaging.

Comparison of 99m Tc-Labeled Compounds and 201 Tl for Cardiac SPECT SMPI

Energy140 keV (ideal for gamma camera)69-83 keV (suboptimal for gamma camera)
First-pass studies of ventricular functionFeasibleNot feasible
Gated imagingReadily accomplishedCount rate marginal for gated imaging
Stress/rest imagingTwo injections required since there is no radiotracer redistribution over timeCan be accomplished with one injection since there is radiotracer redistribution over time

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