Quantitative assessment of the Albira II PET/CT performance based on a range of radionuclides

Objectives: The performance characteristics of the Albira II pre-clinical PET system for the radionuclides ¹⁸F, ⁶⁸Ga, ⁶⁴Cu and ⁸⁹Zr was analyzed.

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 and axial field of view (FOV) are of 80 mm and 148 mm, respectively. 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 ¹⁸F, ⁶⁸Ga, ⁶⁴Cu and ⁸⁹Zr 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, spatial resolution, count rate linearity, convergence and recovery coefficients were analyzed.

Results: The sensitivities for the entire FOV (non-NEMA method) for ¹⁸F, ⁶⁸Ga, ⁶⁴Cu and ⁸⁹Zr were (3.78±0.05) %, (3.97±0.18) % and (3.79±0.37) % and (3.42±0.19) %, respectively. The sensitivity based on the NEMA protocol using the ²²Na point source yielded (5.53±0.06) %. The dead-time corrected true counts were linear for activities ≤ 7 MBq (¹⁸F and ⁶⁸Ga), ≤ 17 MBq (⁶⁴Cu) and ≤ 12 MBq (⁸⁹Zr) and the adjusted R² values were 蠅0.99. The spatial resolution calculated as per the NEMA protocol for a ²²Na point source at the center of the FOV yielded full widths at half maximum values of 1.52 mm, 1.47 mm and 1.48 mm in the x, y and z orientation, respectively. 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) and (0.96±0.09) for ¹⁸F, ⁶⁸Ga, ⁶⁴Cu and ⁸⁹Zr, respectively.

Conclusion: The Albira II pre-clinical PET system showed a good 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. Research Support: The authors gratefully acknowledge funding received for M²OLIE (Research Campus funded by the German Federal Ministry of Education and Research (BMBF) within the Framework “Forschungscampus: public-private partnership for Innovations”), MITIGATE from the European Community`s Seventh Framework Programme (FP7/2007-20013) under grant agreement no 602306 and Perspektivförderung ,,Translationale Radiochemie und Radiopharmazie“(Land Baden-Württemberg). Furthermore, the support by the “Bundesministerium für Bildung und Forschung” (Federal Ministry of Education and Research, BMBF 02NUK008F) and the “Bundesamt für Strahlenschutz” (Federal Office for Radiation Protection, BfS 3608S04001) for the establishment of the endowed professorship “Medizinische Strahlenphysik/Strahlenschutz” (Medical Radiation Physics/Radiation Protection) it is gratefully acknowledged. DH thanks the “Direktorat Jendral Pendidikan Tinggi” (Directorate General of Higher Education DIKTI of Ministry for Research, Technology and Higher Education, Republic Indonesia) for Grant Number: 2644/E4.4/K/2013.