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 1 (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 cationexchanger 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 5 1,4,7,N9, N99,. 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 generatorderived metallic positron-emitter 68 Ga. Zn. 68 Ga is an excellent positron emitter, with 89% positron branching accompanied by low photon emission (1,077 keV, 3.22%) (1,2). 68 Ge/ 68 Ga radionuclide generators have been the object of development and investigation for almost 50 y. For a recent review on this and other PET radionuclide generator systems see Rösch et al. (3).Today, the most common commercially available 68 Ge/ 68 Ga radionuclide generator is based on a TiO 2 solid phase (Cyclotron Co. Ltd.) (4). The generators are produced with 68 Ge activities of up to 3.7 GBq. ''Ionic'' 68 Ga 31...

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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.

Five patients with hepatic metastases of midgut carcinoid underwent somatostatin receptor scintigraphy with indium-111 pentetreotide before and during treatment with octreotide. Octreotide treatment changed the biodistribution of 111In-pentetreotide significantly. Whereas the radioactivity in liver, spleen and kidney decreased, hepatic metastases showed increased contrast. In one patient, liver metastases could only be detected during octreotide treatment. These data suggest that the diagnostic reliability of somatostatin receptor scintigraphy in carcinoid liver metastases is not necessarily compromised by octreotide therapy. Because of different biodistributions, the detection of liver metastases may even be improved during octreotide therapy.

BACKGROUND In Hodgkin disease (HD), accurate assessment of the extent of disease is essential because it provides the basis for different treatment strategies. In addition to conventional imaging methods (CIM), positron emission tomography with fluorine‐18‐fluorodeoxyglucose (FDG‐PET) may permit reliable differentiation between lymphoma and nonmalignant tissue and thus improve determination of the stage of the disease. The aim of the current study was to assess the clinical value of FDG‐PET for primary staging, treatment monitoring, and assessment in a suspected case of recurrent HD. METHODS Eighty‐one patients with HD underwent 106 FDG‐PET studies using a dedicated whole body PET ring scanner. In 25 patients PET was part of the primary staging, 63 PET studies were undertaken for treatment monitoring after the completion of treatment, and in 18 patients PET was performed in cases of suspected recurrence of HD. PET scans were compared with CIM and verified histologically and/or by follow‐up evaluation (mean follow‐up duration, 20.4 months). RESULTS With regard to primary staging, in a patient to patient analysis, both PET scans and CIM were positive (i.e., showed pathologic foci indicative of HD) in 24 of 25 cases. In a staging‐relevant lesion to lesion analysis, accuracy in the determination of the stage of disease was 96% for PET versus 56% for CIM. PET led to a lower stage classification in 28% and a higher stage classification in 12% of cases, compared with the stage assumed with CIM. With regard to treatment monitoring, PET showed an accuracy of 91% compared with 62% for CIM. The negative predictive value of PET was 96%. With regard to suspected recurrence, PET findings were true‐positive in 10 of 12 PET scans and true‐negative in 5 of 6 PET scans, resulting in accuracy of 83%, which compares favorably with the accuracy rate of 56% for CIM. CONCLUSIONS It may be concluded that FDG‐PET is capable of determining the stage of HD with great accuracy and is capable of correctly detecting manifestations of HD in treatment monitoring and cases of suspected recurrence, in which CIM occasionally result in equivocal findings. The results of the current study suggest that FDG‐PET should become a routine tool in the staging/restaging of HD. Cancer 2001;91:302–10. © 2001 American Cancer Society.