A group of four patients with RA were examined to test the hypothesis that there is a change in the endogenous opioid system in the brain during inflammatory pain. Regional cerebral opioid receptor binding was quantified using the opioid receptor antagonist [11C] diprenorphine and positron emission tomography (PET). In the four patients studied in and out of pain, significant increases in [11C]diprenorphine binding were seen in association with a reduction in pain. Increases were seen in most of the areas of the brain that were sampled apart from the occipital cortex. Significant region-specific increases over and above the more generalized changes were also seen in the frontal, cingulate and temporal cortices in addition to the straight gyrus. These findings are consistent with the hypothesis that there are substantial increases in occupancy by endogenous opioid peptides during inflammatory pain.
The aim of this work is to calculate, directly from projection data, concise images characterizing the spatial and temporal distribution of labelled compounds from dynamic PET data. Conventionally, image reconstruction and the calculation of parametric images are performed sequentially. By combining the two processes, low-noise parametric images are obtained, using a computationally feasible parametric iterative reconstruction (PIR) algorithm. PIR is performed by restricting the pixel time-activity curves to a positive linear sum of predefined time characteristics. The weights in this sum are then calculated directly from the PET projection data, using an iterative algorithm based on a maximum-likelihood iterative algorithm commonly used for tomographic reconstruction. The ability of the algorithm to extract known kinetic components from the raw data is assessed, using data from both a phantom experiment and clinical studies. The calculated parametric images indicate differential kinetic behaviour and have been used to aid in the identification of tissues which exhibit differences in the handling of labelled compounds. These parametric images should be helpful in defining regions of interest with similar functional behaviour, and with FDG Patlak analysis.
focal decreases in the thalamus and increases in the cerebellar nuclei with no changes in cerebral cortex. We previously reported lower ["CIFMZ binding in cerebral cortex of IGE patients treated with valproate (VPA) than in cerebral cortex of controls. We now report high-resolution three-dimensional ["CIFMZ PET studies in a larger number of subjects using an improved method to detect differences in cBZR between IGE patients and controls and a more powerful longitudinal design to determine the functional effect of VPA.Methods: We compared parametric images of [ "CIFMZ volume of distribution (FMZVD) in 10 IGE patients before and after addition of VPA and in 20 normal subjects.Results: Mean FMZVD was significantly higher in the cerebral cortex (1 1%, p = 0.009), thalamus (14%, p = 0.018), and cerebellum (15%, p = 0.027) of the 10 IGE patients as compared with that of 20 normal controls. Using statistical parametric mapping, no significant areas of focal abnormality of FMZVD were detected. Addition of VPA was not associated with a significant change in mean FMZVD in any brain area.Conclusions: Our finding of increased FMZVD in IGE could reflect microdysgenesis or a state of cortical hyperexcitability. Our data suggest that short-term VPA therapy does not affect the number of available cBZR in patients with IGE.
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