Processing of generator-produced 68Ga for medical application.

UNLABELLED: The (68)Ge/(68)Ga generator provides an excellent source of positron-emitting (68)Ga. However, newly available "ionic" (68)Ge/(68)Ga radionuclide generators are not necessarily optimized for the synthesis of (68)Ga-labeled radiopharmaceuticals. The eluates have rather large volumes, a high concentration of H(+) (pH of 1), a breakthrough of (68)Ge, increasing with time or frequency of use, and impurities such as stable Zn(II) generated by the decay of (68)Ga, Ti(IV) as a constituent of the column material, and Fe(III) as a general impurity. METHODS: We have developed an efficient route for the processing of generator-derived (68)Ga eluates, including the labeling and purification of biomolecules. Preconcentration and purification of the initial generator eluate are performed using a miniaturized column with organic cation-exchanger resin and hydrochloric acid/acetone eluent. The purified fraction was used for the labeling of nanomolar amounts of octreotide derivatives either in pure aqueous solution or in buffers. RESULTS: Using the generator post-eluate processing system, >97% of the initially eluated (68)Ga activity was obtained within 4 min as a 0.4-mL volume of a hydrochloric acid/acetone fraction. The initial amount of (68)Ge(IV) was decreased by a factor of 10(4), whereas initial amounts of Zn(II), Ti(IV), and Fe(III) were reduced by factors of 10(5), 10(2), and 10, respectively. The processed (68)Ga fraction was directly transferred to solutions containing labeling precursors-for example, DOTA-dPhe(1)-Tyr(3)-octreotide (DOTATOC) (DOTA = 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid). Labeling yields of >95% were achieved within 10 min. Overall yields reached 70% at 20 min after generator elution relative to the eluted (68)Ga activity, not corrected for decay. Specific activities of (68)Ga-DOTATOC were 50 MBq/nmol using a standard protocol, reaching 450 MBq/nmol under optimized conditions. CONCLUSION: Processing on a cation-exchanger in hydrochloric acid/acetone media represents an efficient strategy for the concentration and purification of generator-derived (68)Ga(III) eluates. The developed scheme guarantees high yields and safe preparation of injectable (68)Ga-labeled radiopharmaceuticals for routine application and is easy to automate. Thus, it is being successfully used in clinical environments and might contribute to a new direction for clinical PET, which could benefit significantly from the easy and safe availability of the radionuclide generator-derived metallic positron-emitter (68)Ga.

Positron emission tomography with [(18)F]FDG in the diagnosis of Creutzfeldt-Jakob disease (CJD).

The aim of this study was to explore the sites of metabolic changes with [(18)F]2-fluoro-2-desoxy-D-glucose (FDG) and positron emission tomography (PET) in patients with Creutzfeldt-Jakob disease and to correlate the findings with clinical symptoms. Static [(18)F]FDG-PET studies of eight patients with the diagnosis of confirmed or probable CJD were retrospectively analysed by two physicians from departments of nuclear medicine independently with a strong interrater agreement (kappa=0,98). The clinical data of the patients, based on a standardized evaluation by physicians from the German Creutzfeldt-Jakob disease surveillance study, was correlated with the PET findings. [(18)F]FDG-PET shows widespread hypometabolism in CJD. All patients had a reduction of cerebral glucose metabolism in at least one temporal or parietal region. Additionally in 7 of our own 8 cases and 3 of 4 cases from the literature the occipital lobe, the cerebellum or the basal ganglia were involved. These findings differ from typical patterns of hypometabolism in Alzheimer's disease and other neurodegenerative disorders. In two thirds of the cases the distribution was markedly asymmetric. Myoclonus was present in five out of our eight own cases. Our data suggest that myoclonus might correlate with metabolic impairment of contralateral parietal and temporal lobes. In three of four patients with visual symptoms FDG uptake was reduced in the visual cortex bilaterally. Typical hyperintensities on MRI were only found in two of the eight cases at the time of PET-studies. Our results demonstrate that [(18)F]FDG-PET appears to be a sensitive investigation in CJD and could be useful to differentiate CJD from other neurodegenerative disorders.