Implementation of the Wobbling Technique with Spatial Resolution Enhancement Approach in the Xtrim-PET Preclinical Scanner: Monte Carlo Simulation and Performance Evaluation

Purpose: This study aims to develop and implement a wobbling data acquisition mode in the Xtrim-PET scanner to enhance spatial resolution in preclinical Positron Emission Tomography (PET) imaging. Materials and Methods: To evaluate the performance of the Xtrim-PET scanner with the wobbling motion, simulations were conducted using the Gate Monte Carlo toolkit. The positions of all detected Lines Of Responses (LORs) were adjusted based on the magnitude of the wobbling movement to minimize image blurring. Different stop point configurations ranging from 4 to 256 were investigated to optimize the number of wobbling points. The performance of the wobbling data acquisition mode was assessed using IQ NEMA-NU4 and Hot-Rod phantoms, as well as phantoms resembling mice and rats. Two reconstruction methods were employed to assess image quality: Filtered Back-Projection (FBP) with various filters and the iterative method, OSEM, with 5 and 10 iterations. Results: The results from NEMA tests using Monte Carlo simulations closely matched experimental measurements, demonstrating the accuracy of the simulations. Based on sinograms obtained from the uniform cylinder phantom scan and considering the constraints associated with the mechanical movement system, it was decided to use 4 stopping points for the wobbling movement. The implementation of the wobbling technique resulted in a spatial resolution of 0.91 mm at the center of the scanner, while without the technique, the resolution was 1.93 mm. The wobbling motion did not significantly affect sensitivity, NECR, or SF values. However, it notably improved spatial resolution, especially with the OSEM method, enhancing image quality by up to 52.8%. Conclusion: The wobbling technique offers a substantial enhancement in spatial resolution for preclinical PET scanners. Although achieving sub-micrometer spatial resolutions theoretically seems feasible by increasing the number of stopping points, practical limitations present challenges. Nonetheless, the wobbling