The use of molecular sieves to simulate hot lesions in 18F-fluorodeoxyglucose -: positron emission tomography imaging

We investigated the use of a kind of zeolite, the Bowie chabazite, to produce radioactive sources of different shapes, dimensions and activity concentrations that can be used for lesion simulation in positron emission tomography ( PET) imaging. The F-18-fluorodeoxyglucose (F-18-FDG) uptake of a group of 12 zeolites was studied as a function of their weight (120-1520 mg) and of the activity concentration of the F-18-FDG solution (1-37 MBq ml(-1)), using a multiple linear regression model. The reproducibility, homogeneity and stability over time of the F-18-FDG uptake were assessed. The fit of the regression model is good (r(2) = 0.83). This relation allows the production of zeolites of a desired F-18-FDG activity using knowledge of the concentration of the soaking solution and the weight of the zeolite. The reproducibility of the F-18-FDG uptake after heating the zeolites is elevated (CV% = 3.68). The almost complete regeneration of the zeolites allows us to reuse them in successive experiments. The stability of the F-18-FDG uptake on zeolites is far from ideal. When placed in a saline solution the 'activated' zeolites release the F-18-FDG with an effective half-time of 53 min. The sealing of the zeolites in plastic film bags has been demonstrated to be effective in preventing any release of F-18-FDG. These features, together with their variable dimensions and shapes, make them ideal F-18-FDG sources with a fixed target-to-background ratio that can be placed anywhere in a phantom to study lesion detectability in PET imaging.