Feasibility of positron range correction in 82-Rubidium cardiac PET/CT

Abstract

Background: Myocardial perfusion imaging (MPI) using positron emission tomography (PET) tracers is an essential tool in investigating diseases and treatment responses in cardiology. 82Rubidium (82Rb)-PET imaging is advantageous for MPI due to its short half-life, but cannot be used for small animal research due to the long positron range. We aimed to correct for this, enabling MPI with 82Rb-PET in rats.Methods: The effect of positron range correction (PRC) on 82Rb-PET was examined using two phantoms, and in-vivo on rats. A NEMA NU-4-inspired phantom was used for image quality evaluation (%standard deviation (%SD), spill-over ratio (SOR), and recovery coefficient (RC)). A cardiac phantom was used for assessing spatial resolution. Two rats underwent rest 82Rb-PET to optimize number of iterations, type of PRC, and respiratory gating.Results: NEMA NU-4 metrics (no PRC vs PRC): %SD 0.087 vs 0.103; SOR (air) 0.022 vs 0.002, SOR (water) 0.059 vs 0.019; RC (3 mm) 0.219 vs 0.584, RC (4 mm) 0.300 vs 0.874, RC (5 mm) 0.357 vs 1.197. Cardiac phantom full-width at half maximum (FWHM) and full-width at tenth maximum (FWTM) (no PRC vs PRC): FWTM 6.73 mm vs 3.26 mm (true: 3 mm), FWTM 9.27 mm vs 7.01 mm. The in-vivo scans with respiratory gating had a homogeneous myocardium clearly distinguishable from the blood pool.Conclusion: PRC improved the spatial resolution for the phantoms and in-vivo at the expense of slightly more noise. Combined with respiratory gating, the spatial resolution achieved using PRC should allow for quantitative MPI in small animals.