A prototype of a 3D-printed zoomorphic mouse model for small animal PET scanner calibration

Positron emission tomography (PET) scanner for small animals is of great importance for developing new radiopharmaceuticals for molecular diagnosis and therapy and, thus, for potential clinical applications. The calibration procedure of these systems is essential for quantitative studies and image quality evaluation. It requires several steps, materials, and a suitable phantom. This study aimed to develop a 3D-printed mouse phantom based on the DM_BRA voxel mouse phantom and demonstrate its applicability for small animal PET studies. The physical mouse phantom consists of the 3D printing of a minimum of 2 mm thick with an empty internal cavity corresponding to the real dimensions of the DM_BRA voxel phantom. The model was impermeabilized with epoxy resin to prevent leakage. Counting efficiency and count rates performance evaluations were conducted using the PET scanner (LabPET4 Solo, GE Healthcare Technologies) at the Molecular Image Laboratory (LIM/CDTN/CNEN) in Brazil. Tests revealed that the counting efficiency of the system is about 6.4kCPS·MBq^-1. In general, the absolute values from DM_BRA zoomorphic phantom count rates curves are lower than those from the recommended NEMA NU 4-2008 cylindrical phantom. However, the shape of the count rates curves from both phantoms are very similar: (i) prompt curves increase up to their maximum value at 100MBq and after decrease slowly to around 90 % of the maximum value at 180MBq; (ii) true curves reached their maximum value around 100MBq, corresponding to 50 % of prompt counts; (iii) random curves reach similar plateau value around 50 % of prompt counts; (iv) NEC curves in both studies reach their maximum value at 90MBq. The study revealed that despite the lower counts rates performance, the zoomorphic model offers an anatomically representative design. Its adaptability for different radionuclides and straightforward preparation enhances its usability in routine laboratory protocols.