Click on image to view larger version.
FIGURE 3. 82Rb time–activity curves at rest (A) and after adenosine stress (B). Solid circles represent the activity concentration in left atrium and open circles represent the activity concentration in myocardial tissue. Although the first few minutes after infusion of 82Rb are not usually included in clinical acquisition protocols, it is precisely this period that is of interest if myocardial perfusion is to be quantified. Dynamic imaging of the heart during this time allows analysis of the 82Rb concentration in both arterial blood and myocardial tissue as a function of time. Disparity between myocardial perfusion SPECT and 82Rb PET studies is shown (C). Clinically indicated adenosine dual-isotope gated SPECT images (left panel) without attenuation correction show regional 99mTc-sestamibi perfusion defect in anterior and inferior regions (arrow). On the rest 201Tl images, the anterior defect became reversible while the inferior defect persisted. Corresponding 82Rb PET myocardial perfusion tomograms performed in the same patient are shown on the right panel. PET images were acquired after an infusion of adenosine and 1,110 MBq of 82Rb (top) and at rest after another 1,110-MBq infusion of 82Rb (bottom). 82Rb PET images show normal distribution of radiotracer in all myocardial regions, without evidence for reversible or fixed defects to suggest myocardial ischemia or infarction. Although high-energy positrons of 82Rb degrade spatial resolution and the short half-life increases statistical noise, high-quality images free from attenuation artifacts can be produced with 82Rb PET with only 1,110-MBq injected dose. (Adapted from (28).)
