Central nervous system effects of subdissociative doses of (S)-ketamine are related to plasma and brain concentrations measured with positron emission tomography in healthy volunteers.

Plasma concentrations, maximum regional brain concentrations, and specific regional binding in the brain after administration of 0, 0.1, and 0.2 mg/kg doses of (S)-ketamine were measured in a randomized, double-blind, crossover study in five volunteers and were related to induced effects such as analgesia, amnesia, and mood changes.

A method for coregistration of PET and MR brain images.

Unlabelled: Combining MRI morphological data with functional PET data offers significant advantages in research as well as in many clinical situations. Automatic methods are needed, however, to coregister the data from the two modalities.

Methods: Simulated PET images were created by simple and automatic segmentation of MR images followed by the assignment of different uptake values to various tissue types.

Liquid chromatographic analysis of brain homogenates and microdialysates for the quantification of L-[beta-11C]DOPA and its metabolites for the validation of positron emission tomography studies.

The clinical use of positron emission tomography, PET, with selected radiolabelled tracer molecules visualizing and quantitating physiological processes in the tissue relies in many situations on compartmental models for the interpretation of the radiosignal. Validation of such models must, therefore, include chromatographic analysis of the radioactivity composition of the signal. Rapid and sensitive liquid chromatographic methods amenable for automation for the analysis of [11C] labelled L-DOPA and its metabolites were therefore developed and validated for the quantitation of radioactivity composition in rat brain microdialysates as well as homogenates.

An automated liquid chromatographic plasma analysis of amino acids used in combination with positron emission tomography (PET) for determination of in vivo plasma kinetics.

Quantification of physiological processes measured with positron emission tomography (PET) requires an "input" function which can be the concentration of administered radio-tracer in plasma. Radioactive nuclides used in PET have short half lives (2-20 min) and a limited time is available for the PET investigation including analysis of the composition of the radioactive signal in plasma. Therefore, an automated method for the analysis and separation of beta-[11C]-L-5-hydroxy-tryptophan ([11C]-L-5-HTP), beta-[11C]-L-3,4-dihydroxy-phenylalanine ([11C]-L-DOPA) and L-[methyl-11C]-methionine and their respective metabolites in plasma was developed.

Accurate attenuation correction despite movement during PET imaging.

Unlabelled: Recent methods to realign PET images are useful to correct minor changes in position due to subject movement. When using measured attenuation correction in the presence of larger subject movements, the attenuation data will not correctly represent the conditions of the emission scan and hence lead to erroneous attenuation correction.

Methods: In the presence of subject movement between two emission scans (EM1 and EM2), the first scan was assumed to be correctly aligned with the transmission scan.

A rapid and accurate method to realign PET scans utilizing image edge information.

Unlabelled: Movement during or between PET examinations is a common and serious problem. Consequently, there is a great need for rapid, accurate and robust methods to realign image sets.

Methods: Derivative information from the image sets was used to extract areas containing edge information.

Labelling of polysaccharides using [11C]cyanogen bromide. In vivo and in vitro evaluation of 11C-hyaluronan uptake kinetics.

A method for the 11C-labelling of polysaccharides in high specific radioactivity is described. Dextran and hyaluronan were treated with [11C]cyanogen bromide in aqueous solution at pH 11.5 to give 30-47% radiochemical yields with higher than 98% radiochemical purity in synthesis times of 24-26 min counted from the end of bombardment.

Pyridoxine effect on synthesis rate of serotonin in the monkey brain measured with positron emission tomography.

The influence of the co-factor pyridoxine, vitamin B6, on the activity of aromatic amino acid decarboxylase enzyme was studied by positron emission tomography, PET in the brain of the Rhesus monkey using the precursor for serotonin synthesis 5-hydroxy-L-tryptophan (5-HTP) radiolabelled with 11C in the beta-position. The rate constant for the formation of serotonin in the corpus striatum was calculated using a two tissue compartment model with reference area in the brain. In baseline investigations, the mean rate constants (+/-S.

Brain kinetics of (R)- and (S)-[N-methyl-11C]ketamine in the rhesus monkey studied by positron emission tomography (PET).

The regional brain kinetics of the two enantiomers of the NMDA channel blocker ketamine radiolabelled with 11C was studied in the Rhesus monkey by means of positron emission tomography (PET). The uptake in brain areas which showed high radioactivities was blocked in a dose-dependent manner for both 11C-labelled enantiomers with simultaneous doses of the respective unlabelled (S)- or (R)-ketamine, indicating specific binding. The binding in the striatum and cortical areas of (S)-[N-methyl-11C]ketamine was selective and displaceable by the (R)-enantiomer and by MK-801.

Labelling of proteins with 11C in high specific radioactivity: [11C]albumin and [11C]transferrin.

A method for the 11C-labelling of proteins for use in positron emission tomography is presented. Human iron-free transferrin and human serum albumin were treated with [11C]cyanogen bromide of high specific radioactivity under physiological conditions to give the labelled proteins in high radiochemical yields using a simple and rapid procedure. In a typical experiment, 2.

Differentiation of pituitary adenoma and meningioma: visualization with positron emission tomography and [11C]-L-deprenyl.

Seven patients with clinically nonsecreting pituitary adenoma and 5 patients with meningioma were examined with positron emission tomography using [11C]-LL-deprenyl and [11C]-LL-methionine. The dynamics of the uptake of [11C]-L-deprenyl in the pituitary adenomas demonstrated a rapid and high uptake immediately after the injection, and, later, an almost constant level was observed that was equal to or higher than that observed in normal brain tissue. In the meningiomas, however, the initially high uptake was followed by a marked decrease with time, reaching a level that was approximately half that observed in brain tissue.