Background PET/CT imaging is widely used in oncology and provides both metabolic and anatomic information. Because of the relatively poor spatial resolution of PET/CT imaging technique the detection of small lesions is limited. The low spatial resolution introduces the partial-volume effect (PVE) which negatively affects images both visually and quantitatively. The aim of our research was to investigate the effect of 4 mm and 2 mm voxel size on image quality and on detection of small spheres. MethodsWe used the NEMA body phantom with six fillable spheres. The spheres and background were filled with a solution of 18F-FDG, in ratio spheres vs background 2:1, 3:1, 4:1 and 8:1 In all images reconstructed with 2 mm and 4 mm voxel size the contrast recovery coefficient (CRC), contrast to noise ratio (CNR) in standardized uptake value (SUV) were evaluated.ResultsFor phantom spheres ≤ 13 mm, we found significant higher CRC, SUV and CNR using small-voxel reconstructions. CRC and SUV did not differ for large spheres (≥ 17 mm) using 2 mm and 4 mm voxel size. On the other hand, CNR for large spheres (≥ 17 mm) was significantly decreased in 2 mm voxel size images compared to the 4 mm.ConclusionAccording to our results, the reconstruction with 2 mm voxel size can improve precise lesion localization, image contrast, and image quality.