A diagnostic formulation is provided comprising a tropane having aradioactive concentration of at least 1.6 mCi/mL at least about 51 hours postcreation.The diagnostic formulation optionally comprises a radiolabeled dopaminetransporter(DAT) ligand useful in the diagnosis of Parkinsons disease (PD). One exampleof aradiolabeled dopamine transporter (DAT) ligand is [123-lodine]-213-earbomethoxy-3-.beta.-(4-fluorophenyl)-N-(3-iodo-E-allyl) nortropane.