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Abstract. Measurement of cerebral acetylcholine esterase (ACHE) activity is of clinical interest for the differential diagnosis of memory disorders and dementia. We developed and tested a non-invasive method for quantitation of regional cortical AChE activity with carbon-11-labelled N-methyl-4-piperidyl acetate ([sup 11]C-MP4A) that does not require arterial blood sampling. AChE activity was measured in terms of the rate constant for hydrolysis of [sup 11]C-MP4A (k[sub 3]). The physiological model is based on the very high AChE activity in the basal ganglia, which are used as a reference structure. Non-invasive k[sub 3] was compared with k[sub 3] determined with a standard technique by fitting kinetic tissue and metabolite-corrected plasma data in nine subjects with and without dementia. Across all regional values, a very high correlation of 0.92 was found, with a tendency towards moderate underestimation of k[sub 3] by 5%-14% with the non-invasive technique as compared to the invasive technique. In addition to its advantages with respect to practicability, the new non-invasive technique overcomes problems of the invasive technique that are related to interindividual variation of delay times between cerebral and peripheral tracer arrival and measurement of very small amounts of non-hydrolysed tracer in plasma samples. [ABSTRACT FROM AUTHOR]

Presents a study that developed ECAT high-resolution research tomograph, a three-dimensional brain tomograph employing the scintillator lutetium-oxy-orthosilicate and using depth of interaction information to achieve uniform isotropic resolution. System description; Performance measurements; Results and discussion.

In clinical gene-therapy trials for recurrent glioblastomas, transduction of the herpes simplex virus type-1 thymidine kinase (HSV-1-tk) gene with subsequent prodrug activation by ganciclovir was found to be safe, but clinical response was poor. We used positron-emission tomography (PET) with I-124-labelled 2'-fluoro-2'-deoxy-1b-D-arabino-furanosyl-5-iodo-uracil ([124I]-FIAU)-a specific marker substrate for gene expression of HSV-1-tk-to identify the location, magnitude, and extent of vector-mediated HSV-1-tk gene expression in a phase I/II clinical trial of gene therapy for recurrent glioblastoma in five patients. The extent of HSV-1-tk gene expression seemed to predict the therapeutic response. The expression of an exogenous gene introduced by gene therapy into patients with gliomas can be monitored non-invasively by PET. [ABSTRACT FROM AUTHOR]