A Multi-Contrast, Multi-Resolution Phantom for Radionuclide Imaging Using a Single Activity Concentration Fill

The goal of the work is to design and prototype radionuclide phantom inserts constructed using a machinable porous material of water-like attenuation. The porous material enables multiple activity concentration `contrasts´ while using a single concentration phantom fill. Further, features of multiple sizes are present within each of the contrasts. Available resolution phantoms for radionuclide imaging only allow for a single high-contrast measurement (1:0) and do not mimic typical patient imaging conditions that include a background activity. A hot rod phantom pattern was made using two porous materials and imaged alongside a non-porous equivalent inside a uniform cylinder. The phantom with inserts was imaged using [18F]-FDG on a PET/CT system. Using geometrically-defined image masks, mean values for the hot rod features and between-rod spaces were derived and the contrast recovery ratios compared for the non-porous and porous inserts. One of the prototype materials (EXP-1826) demonstrated reduced feature contrast ( ~ 40%) between the rods and the background. This material, with hydrophilic treatment, became fully saturated during phantom filling-simplifying the imaging process. Measurements of the rod contrast recovery in the various phantom sections demonstrated the phantom´s utility for comparing and potentially optimizing image reconstruction parameter settings under varying imaging conditions at reduced contrast.