177Lutetium SPECT/CT: Evaluation of collimator, photopeak and scatter correction

Purpose The goal of this study was to find the optimal combination of collimator, photopeak and scatter correction for(177)Lutetium (Lu-177) SPECT/CT imaging. Methods Three experiments [sphere-to-background ratios (SBR) 50:1, 10:1, and 2:1] were performed with the NEMA Image Quality phantom filled with(177)Lu-trichloride. SPECT/CT acquisitions were performed with the medium-energy low-penetration (MELP) collimator and(99m)Tc/Krypton collimator. For each acquisition six reconstructions, all with attenuation correction (AC), were made: the 113-keV photopeak only, the 208-keV photopeak only and both photopeaks combined, each with or without scatter correction (SC). Image quality was assessed using contrast-to-noise ratios (CNR), quantification accuracy by means of recovery coefficients (RCs) and the spatial resolution using line profiles. Results With SBR 50:1 and 10:1, both collimators met theRose criterion(CNR > 5), whereas the MELP collimator showed a higher CNR for the 2:1 ratio. The RC(mean)was higher with the MELP collimator, most explicit after the 208-keV AC/SC reconstruction for all acquisitions. The line profiles showed a better spatial resolution for the MELP collimator and the 208-keV AC/SC reconstructions. Conclusion Lu-177 SPECT/CT image quality and quantification was most optimal when acquired with the MELP collimator and reconstructed using the 208-keV photopeak, with AC and SC.