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.