New SPECT and PET Radiopharmaceuticals for Imaging Cardiovascular Disease
Table 4
Commercial PET Radiotracers for Myocardial Perfusion Imaging [51, 52].
82Rb+ = 1.2 min, = 511 keV} 82Rb+ [(Average = 1.48 MeV; Average range in H2O (FWHM) = 1.7 mm)] 82Sr-82Rb Generator (CardioGen-82, Bracco)
Rubidium-82 Chloride (82RbCl) (i) K+ mimic (monovalent cation), active myocardial transmembrane transport via Na+/K+-ATPase (ii) myocardial uptake 50%–60% at rest and 25–30% at high flow rates (iii) myocardial retention of 30%–55% at rest and high flow rate, respectively
13N = 10 min, = 511 keV} 13N [(Average = 0.49 MeV, Average range in H2O (FWHM) = 1.4 mm)] 13N [Cyclotron production {16O(p,n)13N}]
13N-Ammonia (13NH3) (i) clears rapidly from blood pool, localizes in myocardium via passive diffusion if in neutral form as NH3 or via Na+/K+-ATPase as (depending on serum pH) (ii) intracellular metabolic conversion to 13N-glutamine (glutamine synthetase), trapping and incorporation into cellular pool (iii) myocardial uptake of 94% at rest and 95% at high flow rates (iv) myocardial retention of 60%–90% at rest and high flow rate, respectively
15O = 2.04 min, = 511 keV} 15O [(Average = 0.74 MeV, Average range in H2O (FWHM) = 1.5 mm)] 15O [Cyclotron production {14N(d,n)15O}]
15O-Water (15O-H2O) (i) myocardial uptake >95% at rest and >100% at high flow rates (ii) diffuses freely between blood pool and myocardium (no retention) (iii) short half-life, poor contrast between myocardium and blood pool due to free diffusion (iv) relative perfusion images are technically demanding and require blood pool subtraction (v) ideal tracer for quantitative analysis of myocardial blood flow
