SUMMARY Using the '8f-fluoro-2-deoxy-d-glucose technique and positron emission tomography (PET), the local cerebral glucose utilisation (lCMRGlc) was measured in four non-demented patients with early-onset, bilateral Parkinson's disease characterised by the predominance of akinesia. The study was done twice, first in the untreated condition, and then after levodopa had been resumed. Despite a marked clinical improvement, we found no alteration in lCMRGlc between the first and second studies in any of the brain structure analysed. Compared to control values, lCMRGlc in the basal ganglia was moderately increased in both studies. These essentially negative findings agree with most previous human or animal studies, and indicate that the functional alterations in the central dopaminergic systems of patients with Parkinson's disease have metabolic correlates that are too small to be demonstrated by current PET devices.The typical symptomatic triad of Parkinson's disease, that is akinesia, rigidity, and tremor, implies that functional alterations take place in certain cerebral structures. Since energy metabolism in the brain has been shown to be coupled to function,' changes in regional energy mnetabolism specific to the functional abnormalitves of Parkinson's disease might be expected to occur. Such changes should be found in the structures deprived of their normal dopaminergic afferences, principally the striatum2 and the cortico-limbic areas3 and, as a secondary effect, in the structures receiving projections from these structures.In the attempt to use local energy metabolism as a marker of disordered dopaminergic transmission systems, several studies of the local cerebral glucose utilisation (lCMRGlc) using '4C-2-deoxy-D-glucose ('4CDG) autoradiography in rats with unilateral destruction of the dopaminergic systems have failed to show any consistent pattern of changes,4-9 although some reported striking alterations.4 5 Human studies of Parkinson' s disease patients have been, for methodological reasons, restricted to 2-dimensional '33xenon regional cerebral blood flow (rCBF)'0-'2 or Address for reprint requests: JC Baron, MD, Service Hospitalier Fr6d&ric Joliot,
We evaluated the precision and accuracy of in vivo measurements of spine bone mineral density (BMD) and bone mineral content (BMC) in five ewes using dual-energy X-ray absorptiometry (DXA, Lunar DPX-L). The short-term in vivo reproducibility expressed as the coefficient of variation (CV) varied from 0.9 to 1.6% for spine BMD and from 1 to 3.1% for spine BMC. The ex vivo measurements, performed in 20 cm of water to simulate soft tissue thickness, correlated closely with the in vivo measurements, yielding an r value of 0.98 and 0.97 for spine BMD and BMC, respectively. The accuracy was determined by comparing the total BMC of each vertebra measured in vivo with the corresponding ash weight. The correlation coefficient between the two measurements was r = 0.98, with an accuracy error of 5.6%. We concluded that the DXA allows a precise and accurate measurement of spine bone mineral in live ewes using the methodology designed for humans.
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