The contraindications to cardiac PET are similar to SPECT (Chap. 8), which include the standard contraindications to pharmacological stress testing when PET perfusion imaging is being done. Inability to lie flat or lie still for the period of acquisition, claustrophobia and extreme weight (>350–400 lbs.) are usually preferred not to undergo PET imaging. Finally, women who are pregnant or breast-feeding are contraindication.

The equipment required for a standard cardiac PET examination includes the radionuclides and the PET camera, mostly as a hybrid (with CT) unit. The radionuclides used for PET imaging have a considerably shorter half-life as compared to SPECT tracers. PET radionuclides are produced either from a cyclotron such as fluoro-2-deoxyglucose F-18 FDG and N-13 ammonia or a generator such as rubidium Rb-82. As the name implies, PET imaging involves a positron that collides with an electron to produce two 511 keV gamma rays/photons emitted collinear to each other at 180° angle. The PET detectors are configured to only register the photon pairs if they strike opposite detectors at approximately the same time that has been termed the coincidence detection. The summations of multiple coincidence events are used to reconstruct the PET image to be used for analysis.

The CT scanner provides addition information such as coronary artery calcium scoring and/or noninvasive coronary angiography, but more importantly for PET imaging is in registration and attenuation correction.

The PET camera, similar to SPECT, is made of multiple small detector crystals arranged in a 360° ring and photomultiplier tubes to convert the scintillation events to electrical signal and digitalization to provide the counts that are used in quantification and image processing. Three types of detector crystals are available: (1) Bismuth germanate (BGO) (2) Lutetium oxyorthosilicate (LSO) (3) Gagolinium oxyorthosilicate (GSO).

The clinically available PET tracers for myocardial perfusion studies are Rb-82, and N-13 ammonia. Figure 9.1 shows the radiotracers myocardial uptake in relation to coronary blood flow with O-15 being the ideal tracer and the roll-off phenomenon seen with other tracers at higher coronary blood flows. N-13 ammonia, due to the short half-life (10 min), requires an on-site (nearby) cyclotron. It has excellent myocardial uptake/retention with established flow quantification and applications in exercise and pharmacological stress testing. Rubidium-82 is produced on-site from a Strontium-82 generator (replaced every 4 weeks) with a half-life of 76 s. Due to the short half-life, it can only be used in pharmacological stress testing. It has with high extraction at high flows (enhances the detection of moderate-severe CAD). Rb-82 is extracted by myocardial cells via the Na/K ATPase pump. The radiation dosimetry from Rb-82 varies from 1.75 to 7.5 mSv total effective dose. Depending on the left ventricular ejection fraction, typically imaging can commence 70–90 s after the injection if LVEF >50 % and delayed slightly longer (~110 s) if LVEF <50 %.

For metabolism imaging, the F-18 FDG tracer (the only FDA approved agent), an analog to glucose, is used. F-18 is produced in a cyclotron and decays with a half-life of 110 min, which allows sufficient time to be produced and distributed in a radius of several hours from the production site. FDG is transported into the cells similar to glucose and is then phosphorylated by hexokinase to FDG-6-phosphate, which is then trapped in the myocardium for PET imaging. The whole body dosimetry from 10 mCi dose is 7 mSv (Tables 9.2 and 9.3).