Investigation of the imaging characteristics of the ALBIRA II small animal PET system for 18F, 68Ga and 64Cu

Abstract Aim In this study the performance characteristics of the Albira II PET sub-system and the response of the system for the following radionuclides 18 F, 68 Ga and 64 Cu was analyzed. Materials and methods The Albira II tri-modal system (Bruker BioSpin MRI GmbH, Ettlingen, Germany) is a pre-clinical device for PET, SPECT and CT. The PET sub-system uses single continuous crystal detectors of lutetium yttrium orthosilicate (LYSO). The detector assembly consists of three rings of 8 detector modules. The transaxial field of view (FOV) has a diameter of 80 mm and the axial FOV is 148 mm. A NEMA NU-4 image quality phantom (Data Spectrum Corporation, Durham, USA) having five rods with diameters of 1, 2, 3, 4 and 5 mm and a uniform central region was used. Measurements with 18 F, 68 Ga and 64 Cu were performed in list mode acquisition over 10 h. Data were reconstructed using a maximum-likelihood expectation-maximization (MLEM) algorithm with iteration numbers between 5 and 50. System sensitivity, count rate linearity, convergence and recovery coefficients were analyzed. Results The sensitivities for the entire FOV (non-NEMA method) for 18 F, 68 Ga and 64 Cu were (3.78 ± 0.05)%, (3.97 ± 0.18)% and (3.79 ± 0.37)%, respectively. The sensitivity based on the NEMA protocol using the 22 Na point source yielded (5.53 ± 0.06)%. Dead-time corrected true counts were linear for activities ≤7 MBq ( 18 F and 68 Ga) and ≤17 MBq ( 64 Cu) in the phantom. The radial, tangential and axial full widths at half maximum (FWHMs) were 1.52, 1.47 and 1.48 mm. Recovery coefficients for the uniform region with a total activity of 8 MBq in the phantom were (0.97 ± 0.05), (0.98 ± 0.06), (0.98 ± 0.06) for 18 F, 68 Ga and 64 Cu, respectively. Conclusion The Albira II pre-clinical PET system has an adequate sensitivity range and the system linearity is suitable for the range of activities used for pre-clinical imaging. Overall, the system showed a favorable image quality for pre-clinical applications.