Myocardial perfusion imaging (MPI) has been in clinical use for over 30 years, providing an effective, reliable, and relatively simple tool for diagnosis, risk stratification, and follow-up of patients with suspected or know coronary artery disease (CAD). The unique strength of nuclear imaging is its ability to provide tools for imaging biochemical and metabolic processes, and receptor and transporter functions at molecular and cellular levels in intact organisms under various physiologic conditions. Metabolic imaging using radiolabeled glucose analogues ((18)F-fluorodeoxyglucose [(18)FDG]) provides a unique ability to image myocardial ischemia directly ("hot spot" imaging) in patients with known or suspected CAD. Exercise (18)FDG imaging can potentially overcome some of the limitations of currently used stress-rest MPI. In this article, we describe recent studies using exercise (18)FDG for imaging myocardial ischemia and its potential use in routine clinical practice.

See related article, pp. 763-768Myocardial perfusion imaging is the most commonly used procedure in nuclear medicine. 1 Availability of thallium-201 made it possible to study myocardial perfusion non-invasively at rest and with exercise in mid70s. 2 Development of Tc-99m based perfusion tracers ( 99m Tc-sestamibi and 99m Tc-ttrofosminin) in early 90s overcame many of the limitations of Tl-201 and is largely responsible for MPI becoming the centerpiece of non-invasive techniques for the evaluation of coronary artery disease. 3 Despite the widespread use of 99m Tc labeled myocardial perfusion tracers, artifacts due to attenuation and extra-cardiac activity continue to be important limitations of these agents. Furthermore, these agents do not provide quantitative information about myocardial blood flow. Therefore, the search for an ideal perfusion tracer is still on. Positron emission tomography (PET) offers several advantages over single photon emission computed tomography (SPECT): better imaging characteristics due to higher photon flux, more robust attenuation correction, shorter image acquisition time and possibility of obtaining quantitative information about myocardial perfusion. It is thought PET imaging may be able to overcome the limitations of currently used SPECT perfusion tracers. Whereas a number of PET tracers are currently available for myocardial perfusion imaging, they all suffer from significant limitations:13 N-ammonia and 15 O-water require on-site cyclotron for their production, 82 Rb is generator produced, but given an extremely short half-life this can only be used with pharmacological stress. Therefore, attention is turning toward developing ligands, which can be labeled with generator produced PET radionuclides, or with cyclotron-produced radionuclides with relatively longer halflife, which do not necessarily require on-site cyclotrons. In this respect, gallium-68 and copper-64 are potentially attractive PET tracers, which can be eluted from generators with long shelf life. However, so far no suitable ligands have been developed to exploit the use of 68 Ga and 64 Cu as myocardial perfusion tracers. Interestingly, Yu and colleagues have presented preliminary experimental data in this issue of the journal on BMS-747158-02, a pyridazinone analog, which can be labeled with F-18 and used as a myocardial perfusion tracer. 4 Any new potential myocardial perfusion imaging agent has to undergo a series of elaborate studies to characterize its biokinetics and behavior in in vitro and in vivo studies to detect any possible interaction with a multitude of physiological and pharmacological variables. Myocardial uptake of an ideal myocardial perfusion tracer should correlate directly and linearly with myocardial blood flow over a wide range and should not be affected by other metabolic and physiological variables.Yu and colleagues studied myocardial and other organ uptake of 18 F-BMS747158-02 under fasting and non-fasting conditions and with the use of two different anesthetic agents (pentobarbital and k...

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Myocardial perfusion imaging has been in extensive clinical use for well over 30 years. This technique is used for diagnosing, risk stratification, and long-term follow-up of patients with suspected or known coronary artery disease (CAD). A unique strength of nuclear imaging is its ability to provide a repertoire of tools for imaging metabolic and biochemical processes and receptor and transporter functions at molecular and cellular levels in intact organisms, under a wide variety of physiological conditions. Despite their high resolution and technical sophistication, other imaging modalities do not have this capability. Metabolic imaging techniques using radiolabeled free fatty acid and glucose analogues provide a unique ability to image myocardial ischemia directly in patients with known or suspected CAD. These techniques can overcome many of the limitations of currently used stress-rest perfusion imaging. In this article, we describe recent studies using 18 FDG for imaging myocardial ischemia.