Low cerebral glucose extraction rates in the human medial temporal cortex and cerebellum

Oxygen extraction fraction is not uniform in human brain: a positron emission tomography study

The regional differences in cerebral oxygen extraction fraction (OEF) in brain were investigated using positron emission tomography (PET) in detail with consideration of systemic errors in PET measurement estimated by simulation studies. The cerebral blood flow (CBF), cerebral blood volume (CBV), OEF, and cerebral metabolic rate of oxygen (CMRO2) were measured on healthy men by PET with 15O-labeled gases. The OEF values in the pons and the parahippocampal gyrus were significantly smaller than in the other brain regions. The OEF value in the lateral side of the occipital cortex was largest among the cerebral cortical regions. Simulation studies have revealed that errors in OEF caused by regional differences in the distribution volume of 15O-labeled water, as well as errors in OEF caused by a mixture of gray and white matter, must be negligible. The regional differences in OEF in brain must exist which might be related to physiological meanings.Article title: Kindly check and confirm the edit made in the article title.I have checked the article title and it is OK as is. Trial registration: The UMIN clinical trial number: UMIN000033382, https://www.umin.ac.jp/ctr/index.htm.

Regional and interindividual relationships between cerebral perfusion and oxygen metabolism

Quantitative measurements of resting cerebral blood flow (CBF) and metabolic rate of oxygen (CMRO₂) show large between-subject and regional variability, but the relationships between CBF and CMRO₂ measurements regionally and globally are not fully established. Here, we investigated the between-subject and regional associations between CBF and CMRO₂ measures with independent and quantitative PET techniques. We included resting CBF and CMRO₂ measurements from 50 healthy volunteers (aged 22-81 yr), and calculated the regional and global values of oxygen delivery (Do₂) and oxygen extraction fraction (OEF). Linear mixed-model analysis showed that CBF and CMRO₂ measurements were closely associated regionally, but no significant between-subject association could be demonstrated, even when adjusting for arterial Pco₂ and hemoglobin concentration. The analysis also showed regional differences of OEF, reflecting variable relationship between Do₂ and CMRO₂, resulting in lower estimates of OEF in thalami, brainstem, and mesial temporal cortices and higher estimates of OEF in occipital cortex. In the present study, we demonstrated no between-subject association of quantitative measurements of CBF and CMRO₂ in healthy subjects. Thus, quantitative measurements of CBF did not reflect the underlying between-subject variability of oxygen metabolism measures, mainly because of large interindividual OEF variability not accounted for by Pco₂ and hemoglobin concentration.NEW & NOTEWORTHY Using quantitative PET-measurements in healthy human subjects, we confirmed a regional association of CBF and CMRO₂, but did not find an association of these values across subjects. This suggests that subjects have an individual coupling between perfusion and metabolism and shows that absolute perfusion measurements does not serve as a surrogate measure of individual measures of oxygen metabolism. The analysis further showed smaller, but significant regional differences of oxygen extraction fraction at rest.

Interindividual and regional relationship between cerebral blood flow and glucose metabolism in the resting brain

Studies of the resting brain measurements of cerebral blood flow (CBF) show large interindividual and regional variability, but the metabolic basis of this variability is not fully established. The aim of the present study was to reassess regional and interindividual relationships between cerebral perfusion and glucose metabolism in the resting brain. Regional quantitative measurements of CBF and cerebral metabolic rate of glucose (CMR_glc) were obtained in 24 healthy young men using dynamic [¹⁵O]H₂O and [¹⁸F]fluorodeoxyglucose positron emission tomography (PET). Magnetic resonance imaging measurements of global oxygen extraction fraction (gOEF) and metabolic rate of oxygen ([Formula: see text]) were obtained by combined susceptometry-based sagittal sinus oximetry and phase contrast mapping. No significant interindividual associations between global CBF, global CMR_glc, and [Formula: see text] were observed. Linear mixed-model analysis showed a highly significant association of CBF with CMR_glc regionally. Compared with neocortex significantly higher CBF values than explained by CMR_glc were demonstrated in infratentorial structures, thalami, and mesial temporal cortex, and lower values were found in the striatum and cerebral white matter. The present study shows that absolute quantitative global CBF measurements appear not to be a valid surrogate measure of global cerebral glucose or oxygen consumption, and further demonstrates regionally variable relationship between perfusion and glucose metabolism in the resting brain that could suggest regional differences in energy substrate metabolism. NEW & NOTEWORTHY Using method-independent techniques the study cannot confirm direct interindividual correlations of absolute global values of perfusion with oxygen or glucose metabolism in the resting brain, and absolute global perfusion measurements appear not to be valid surrogate measures of cerebral metabolism. The ratio of both perfusion and oxygen delivery to glucose metabolism varies regionally, also when accounting for known methodological regional bias in quantification of glucose metabolism.

Additional Value of Early-Phase 18F-FP-CIT PET Image for Differential Diagnosis of Atypical Parkinsonism

PURPOSE

Regional cerebral perfusion is coupled to metabolism in general. Early perfusion dominant imaging using F-FP-CIT PET (pCIT) may provide complementary information to delayed dopamine transporter dominant images. We investigated the ability of pCIT to differentiate atypical Parkinson disorder from Parkinson disease (PD) compared to FDG and the image quality for optimizing the acquisition time.

METHODS

Sixty-seven subjects [PD, 23 subjects; multiple system atrophy-cerebellar type (MSA-C), 27 subjects; MSA-Parkinson type (MSA-P), 12 subjects; and progressive supranuclear palsy (PSP), 5 subjects] underwent F-FP-CIT and FDG PET. Using dynamic PET data acquired during the first 10 minutes after F-FP-CIT administration, we generated potential perfusion images of 0 to 5 (pCIT-5m), 0 to 7 (pCIT-7m), and 0 to 10 (pCIT-10m) minutes. We compared regional uptake between groups in pCIT and FDG images and image quality among pCIT images using visual, quantitative, or statistical parametric mapping analyses.

RESULTS

Regional cerebral uptake of pCITs correlated well to that of the FDG images (R > 0.5, all). Multiple system atrophy-cerebellar type and MSA-P groups show different regional uptake patterns compared with PD group on pCITs in quantitative and statistical parametric mapping analyses, analogous to FDG images, but not in the PSP group. In visual analysis, concordance rates between each pCIT and FDG image were high (92.3%-96.0%, regional; 86.2%-93.1%, diagnostic), and there was no significant difference among pCITs. However, pCIT-10m discriminated PSP better than others and showed higher signal-to-noise ratio (P = 0.001).

CONCLUSION

F-FP-CIT PETs with the first 10 minutes could be useful for the differential diagnosis of atypical Parkinson disorder by providing complementary FDG-like information to the dopamine transporter binding on late-phase FP-CIT images.

Cerebral Glucose Metabolism Assessment in Rat Models of Alzheimer's Disease: An 18F-FDG-PET Study

OBJECTIVE

This study was designed to detect the brain glucose metabolism in rat models of Alzheimer's disease (AD) by the application of (18)F-2-fluoro-deoxy-d-glucose positron emission tomography ((18)F-FDG-PET) and to provide new insights for the early detection of AD.

METHODS

Forty Wistar rats were randomly divided into 2 groups. Fifteen sham-operated rats were used as a control group. The remaining rats as a premodel group were intracerebroventricularly injected with ibotenic acid and were intraperitoneally injected with d-galactose, of which 15 rats were included as the experimental group. The above-mentioned 2 groups were assigned to Y-maze test and underwent (18)F-FDG-PET scanning. Positron emission tomography images were processed with SPM 2.0.

RESULTS

The learning and memory skills were weakened in AD rats. Besides, the glucose metabolic activity of AD rats decreased in hippolampus, hypothalamus, insular cortex, piriform cortex, striatum, cingulate gyrus, stria terminalis, and parietal lobe and increased in olfactory bulb, cerebellum, midbrain, pontine, and retrosplenial cortex compared with the control group. Dorsal thalamus had shown both enhanced and reduced glucose metabolic activity.

CONCLUSION

Our data indicate that the changed glucose metabolism in cerebral regions in (18)F-FDG-PET imaging could be an important predictor for early AD.

The effect of Ginkgo biloba extract (EGb 761) on parameters of oxidative stress in different regions of aging rat brains after acute hypoxia

BACKGROUND AND AIMS

Neurodegenerative processes of aging seem to be associated with oxidative stress by reactive oxygen species (ROS). This study investigates the influence of age and of acute respiratoric hypoxia on parameters of oxidative stress in different brain regions of Wistar rats and the protective effects of Ginkgo extract (EGb 761) as a radical scavenger.

METHODS

Biopsies of frontal and temporal cortices, the cerebellum, and the brainstem of young and old rats (each group n=6-8: normoxic - hypoxic; unprotected - EGb-protected) were analyzed for malondialdehyde (MDA) levels, superoxide dismutase (SOD) activity, glutathione (GSH) content, and creatine kinase (CK) activity. Experimental hypoxia: downregulation of oxygen partial pressure to 5 vol. % for 20 minutes. EGb administration: daily 100 mg/kg of body weight in drinking water for 3 months.

RESULTS

Effects of age: While most oxidative stress parameters in the temporal cortex, the cerebellum, and the brainstem are increased, this is not the case in the frontal cortex; after additional hypoxia SOD and GSH are diminished in the temporal cortex and the brainstem of old rats. EGb treatment causes contradictory alterations in young, old, and hypoxic brain regions. Minor effects are seen in old hypoxic brains, while there are some protective effects in old normoxic brainstems and cerebellums.

CONCLUSIONS

The old brain appears to adapt appropriately to chronic oxidative stress and to the specific conditions of shortterm hypoxia. EGb's protective effect is especially notable in the brainstem and the cerebellum.

Functional genomics of brain aging and Alzheimer's disease: focus on selective neuronal vulnerability

Pivotal brain functions, such as neurotransmission, cognition, and memory, decline with advancing age and, especially, in neurodegenerative conditions associated with aging, such as Alzheimer’s disease (AD). Yet, deterioration in structure and function of the nervous system during aging or in AD is not uniform throughout the brain. Selective neuronal vulnerability (SNV) is a general but sometimes overlooked characteristic of brain aging and AD. There is little known at the molecular level to account for the phenomenon of SNV. Functional genomic analyses, through unbiased whole genome expression studies, could lead to new insights into a complex process such as SNV. Genomic data generated using both human brain tissue and brains from animal models of aging and AD were analyzed in this review. Convergent trends that have emerged from these data sets were considered in identifying possible molecular and cellular pathways involved in SNV. It appears that during normal brain aging and in AD, neurons vulnerable to injury or cell death are characterized by significant decreases in the expression of genes related to mitochondrial metabolism and energy production. In AD, vulnerable neurons also exhibit down-regulation of genes related to synaptic neurotransmission and vesicular transport, cytoskeletal structure and function, and neurotrophic factor activity. A prominent category of genes that are up-regulated in AD are those related to inflammatory response and some components of calcium signaling. These genomic differences between sensitive and resistant neurons can now be used to explore the molecular underpinnings of previously suggested mechanisms of cell injury in aging and AD.

Comparison of SPM and NEUROSTAT in voxelwise statistical analysis of brain SPECT and MRI at the early stage of Alzheimer's disease

OBJECTIVE

Neuroimaging plays a major role in the early diagnosis of Alzheimer's disease (AD). Recent advances in voxelwise statistical analysis after anatomic standardization of images have made this early diagnosis easier and more objective than visual inspection. We present comparative observations of NEUROSTAT, statistical parametric mapping (SPM) 99, and SPM2 in the early diagnosis of AD using brain perfusion single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI).

METHODS

We performed voxel-by-voxel statistical group analysis for brain perfusion SPECT and gray matter images segmented from MRI between 61 patients with very early AD and 82 age-matched healthy volunteers. Anatomic standardization was performed using NEUROSTAT, SPM99, and SPM2 using both original and common templates.

RESULTS

The location of significant reduction of regional cerebral blood flow (rCBF) for SPECT and gray matter concentration for MRI were identical among these three methods irrespective of the templates used. When using the original template, the significance of peak rCBF reduction in the posterior cingulate gyri was higher in SPM99 and SPM2 than that in NEUROSTAT. On the other hand, when using the common template, the significance of peak rCBF reduction in the posterior cingulate gyri was higher in NEUROSTAT and SPM2 than that in SPM99. NEUROSTAT showed almost the equal significance of peak rCBF reduction between the used templates. Almost the equal significance of reduction in gray matter concentration was observed in the parahippocampal gyri among the three methods.

CONCLUSIONS

NEUROSTAT, SPM99, and SPM2 showed identical location of significant reductions in rCBF and gray matter concentration in very early AD patients. Used templates for anatomic standardization are relevant to the results of voxelwise statistical analysis in SPM, less prominently in SPM2 than in SPM99, whereas irrelevant in NEUROSTAT.

Joint penalized-likelihood reconstruction of time-activity curves and regions-of-interest from projection data in brain PET

This paper presents a novel statistical approach for joint estimation of regions-of-interest (ROIs) and the corresponding time-activity curves (TACs) from dynamic positron emission tomography (PET) brain projection data. It is based on optimizing the joint objective function that consists of a data log-likelihood term and two penalty terms reflecting the available a priori information about the human brain anatomy. The developed local optimization strategy iteratively updates both the ROI and TAC parameters and is guaranteed to monotonically increase the objective function. The quantitative evaluation of the algorithm is performed with numerically and Monte Carlo-simulated dynamic PET brain data of the 11C-Raclopride and 18F-FDG tracers. The results demonstrate that the method outperforms the existing sequential ROI quantification approaches in terms of accuracy, and can noticeably reduce the errors in TACs arising due to the finite spatial resolution and ROI delineation.

Direct comparison study between FDG-PET and IMP-SPECT for diagnosing Alzheimer's disease using 3D-SSP analysis in the same patients

PURPOSE

The purpose of this study was to evaluate and compare the diagnostic ability of 2-[(18)F]-fluoro-2-deoxy-D: -glucose (FDG) positron emission tomography (PET) and N-isopropyl-p-(123)I iodoamphetamine single photon emission computed tomography (IMP-SPECT) using three-dimensional stereotactic surface projections (3D-SSP) in patients with moderate Alzheimer's disease (AD).

MATERIALS AND METHODS

FDG-PET and IMP-SPECT were performed within 3 months in 14 patients with probable moderate AD. Z-score maps of FDG-PET and IMP-SPECT images of a patient were obtained by comparison with data obtained from control subjects. Four expert physicians evaluated and graded the glucose hypometabolism and regional cerebral blood flow (rCBF), focusing in particular on the posterior cingulate gyri/precunei and parietotemporal regions, and determined the reliability for AD. Receiver operating characteristic (ROC) curves were applied to the results for clarification. To evaluate the correlation between two modalities, the regions of interest (ROIs) were set in the posterior cingulate gyri/precunei and parietotemporal region on 3D-SSP images, and mean Z-values were calculated.

CONCLUSION

No significant difference was observed in the area under the ROC curve (AUC) between FDG-PET and IMP-SPECT images (FDG-PET 0.95, IMP-SPECT 0.94). However, a significant difference (P < 0.05) was observed in the AUC for the posterior cingulate gyri/precuneus (FDG-PET 0.94, IMP-SPECT 0.81). The sensitivity and specificity of each modality were 86%, and 97% for FDG-PET and 70% and 100% for IMP-SPECT. We could find no significant difference between FDG-PET and IMP-SPECT in terms of diagnosing moderate AD using 3D-SSP. There was a high correlation between the two modalities in the parietotemporal region (Spearman's r = 0.82, P < 0.001). The correlation in the posterior cingulate gyri/precunei region was lower than that in the parietotemporal region (Spearman's r = 0.63, P < 0.016).

A statistical investigation of normal regional intra-subject heterogeneity of brain metabolism and perfusion by F-18 FDG and O-15 H2O PET imaging

BACKGROUND

The definite evaluation of the regional cerebral heterogeneity using perfusion and metabolism by a single modality of PET imaging has not been well addressed. Thus a statistical analysis of voxel variables from identical brain regions on metabolic and perfusion PET images was carried out to determine characteristics of the regional heterogeneity of F-18 FDG and O-15 H2O cerebral uptake in normal subjects.

METHODS

Fourteen normal subjects with normal CT and/or MRI and physical examination including MMSE were scanned by both F-18 FDG and O-15 H2O PET within same day with head-holder and facemask. The images were co-registered and each individual voxel counts (Q) were normalized by the global maximal voxel counts (M) as R = Q/M. The voxel counts were also converted to z-score map by z = (Q - mean)/SD. Twelve pairs of ROIs (24 total) were systematically placed on the z-score map at cortical locations 15-degree apart and identically for metabolism and perfusion. Inter- and intra-subject correlation coefficients (r) were computed, both globally and hemispherically, from metabolism and perfusion: between regions for the same tracer and between tracers for the same region. Moments of means and histograms were computed globally along with asymmetric indices as their hemispherical differences.

RESULTS

Statistical investigations verified with data showed that, for a given scan, correlation analyses are expectedly alike regardless of variables (Q, R, z) used. The varieties of correlation (r's) of normal subjects, showing symmetry, were mostly around 0.8 and with coefficient of variations near 10%. Analyses of histograms showed non-Gaussian behavior (skew = -0.3 and kurtosis = 0.4) of metabolism on average, in contrast to near Gaussian perfusion.

CONCLUSION

The co-registered cerebral metabolism and perfusion z maps demonstrated regional heterogeneity but with attractively low coefficient of variations in the correlation markers.

Aging and gene expression in the primate brain

It is well established that gene expression levels in many organisms change during the aging process, and the advent of DNA microarrays has allowed genome-wide patterns of transcriptional changes associated with aging to be studied in both model organisms and various human tissues. Understanding the effects of aging on gene expression in the human brain is of particular interest, because of its relation to both normal and pathological neurodegeneration. Here we show that human cerebral cortex, human cerebellum, and chimpanzee cortex each undergo different patterns of age-related gene expression alterations. In humans, many more genes undergo consistent expression changes in the cortex than in the cerebellum; in chimpanzees, many genes change expression with age in cortex, but the pattern of changes in expression bears almost no resemblance to that of human cortex. These results demonstrate the diversity of aging patterns present within the human brain, as well as how rapidly genome-wide patterns of aging can evolve between species; they may also have implications for the oxidative free radical theory of aging, and help to improve our understanding of human neurodegenerative diseases.

Transcriptional profiles in human and chimpanzee reveal a diversity of aging patterns present within the human brain, as well as how rapidly genome-wide patterns of aging can evolve between species.

Increased temporal lobe gyrification in preterm children

Preterm birth often results in significant learning disability, and previous magnetic resonance imaging (MRI) studies of preterm children have demonstrated reduction in overall cortical tissue with particular vulnerability in the temporal lobe. We measured cortical gyrification in 73 preterm and 33 term control children at 8 years of age and correlated these findings with tests of language ability to determine the associations among preterm birth, neurodevelopment and functional outcome. Preterm children demonstrated significantly increased bilateral temporal lobe gyrification index compared to term controls. Left temporal gyrification index was significantly negatively correlated with left temporal lobe gray matter volume as well as reading recognition scores in the preterm group. Cortical development in the temporal lobe appears to be differentially vulnerable to preterm birth.

Volumetric analysis of regional cerebral development in preterm children

Preterm birth is frequently associated with both neuropathologic and cognitive sequelae. This study examined cortical lobe, subcortical, and lateral ventricle development in association with perinatal variables and cognitive outcome. High-resolution volumetric magnetic resonance imaging scans were acquired and quantified using advanced image processing techniques. Seventy-three preterm and 33 term control children ages 7.3-11.4 years were included in the study. Results indicated disproportionately enlarged parietal and frontal gray matter, occipital horn, and ventricular body, as well as reduced temporal and subcortical gray volumes in preterm children compared with control subjects. Birth weight was negatively correlated with parietal and frontal gray, as well as occipital horn volumes. Intraventricular hemorrhage was associated with reduced subcortical gray matter. Ventricular cerebrospinal fluid was negatively correlated with subcortical gray matter volumes but not with white matter volumes. Maternal education was the strongest predictor of cognitive function in the preterm group. Preterm birth appears to be associated with disorganized cortical development, possibly involving disrupted synaptic pruning and neural migration. Lower birth weight and the presence of intraventricular hemorrhage may increase the risk for neuroanatomic abnormality.

Persistent vegetative state: evaluation of brain metabolism and brain perfusion with PET and SPECT

Patients in persistent vegetative state (PVS) after severe head trauma were investigated with 99mTc-ECD SPECT and 18F-FDG PET to further characterize the degree of brain damage and to obtain insight into changes of brain perfusion and glucose metabolism. 18F-FDG PET and 99mTc-ECD SPECT were performed in 16 patients in PVS. Quantitative PET data were compared with that obtained from seven normal controls. After spatial normalization into Talairach space, global grey matter values and regional data using predefined ROI sets were derived. For comparison of PET and SPECT, regional data were normalized to their individual mean grey matter values. Patients in PVS showed significantly lower values of cerebral glucose metabolism than did the controls. The mean reduction of grey matter values in cortical and subcortical structures was 58%, except in the vermis cerebelli, where only a reduction of 16% was found compared to the controls. Comparing the glucose metabolism and perfusion within the patient group, the pattern of both modalities was similar in the neocortex and internal ganglia. In the cerebellar hemispheres a relatively higher perfusion than glucose metabolism was found. The overall reduction of 58% of glucose metabolism in grey matter structures is in accordance with other PET studies investigating PVS patients with different disease histories. The relative preserved activity of vermis cerebelli seems to be an uncommon finding not described by other authors up to now.

Sexual dimorphism in rat cerebrum and cerebellum: different patterns of catalytically active creatine kinase isoenzymes during postnatal development and aging

During postnatal development, maturation and aging the Wistar rat cerebrum and cerebellum synthesize, in a different sex-dependent manner, catalytically active dimeric cytosolic (c) muscle-type (MM) and heart-type (MB) creatine kinase (CK), besides the supposedly sole type brain-specific (BB) CK. In both sexes, typical and atypical neuromuscular cCK isoenzymes were present during the study for 26 months. As in rat heart, females showed more cerebral cCK variants (41%) in comparison to males. Female rats exhibited about 93% more cerebellar variants of cCK isoenzymes as compared to males. The male cerebellum showed predominantly BB- and MB-CK during the whole study in comparison to the female one that contained all neuromuscular cCK variants. Only female rats showed decreases and increases of cerebral CK specific activity. In contrast to males, coinciding with the weaning period, cerebral female CK activity decreased 45% from 14 to 21 days and increased about 3-fold in female rats and only 1.3-fold in males from 21 to 45 days of age. Contrary to the remarkable 4-fold increase of chicken brain CK specific activity exhibited at old age, the rat did not show another cerebral CK activity increase during senescence in either sex. However, sex differences of CK specific activity appeared in the cerebellum at all ages. From the sex-specific plateau phase at 45-60 days until 2.2 years of age, about a 41% independent increase of cerebellar CK specific activity was observed in both sexes. After puberty, the differential cerebellum-cerebrum values of CK specific activity were higher for female rats than males during youth, adulthood and senescence. The present work shows that in rat cerebrum and cerebellum, production of ATP through anaerobic transphosphorylation by the CK/PC system is sex-and age-specific, especially in the cerebellum, when glycolysis and the Krebs cycle lose capacity. As in rat heart, under physiological conditions at all ages the several cCK isoenzymes do participate in a gender-specific manner, in favor of females, in diverse functions of the different cell compartments of glial and neuronal cells with regard to their high and fluctuating energy demands not completely covered by anaerobic and aerobic glycolysis.

Differences in cerebral metabolic impairment between early and late onset types of Alzheimer's disease

The purpose of this study was to delineate the specific patterns of cerebral glucose metabolism with regard to the time of onset of Alzheimer's disease (AD).

METHODS

Two groups of 20 AD patients with different ages of onset were examined. The early onset (EO) and late onset (LO) groups had mean ages of onset of 53.9 and 72.7 years. Groups of age-matched normal subjects were used as controls. A regional relative cerebral glucose metabolic image of each subject was obtained by 2-[18F] fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET). NEUROSTAT program was used for spatial normalization and voxel-based statistical parametric mapping (SPM) 99 was used for statistical analyses.

RESULTS

Both AD groups had significant hypometabolic regions in the bilateral parieto-temporal regions compared with the age-matched groups. The EO group had more severe hypometabolism in the bilateral parietal and posterior cingulate cortices and precuneus region than the LO group. However, LO group showed no significant hypometabolic regions compared to the EO group.

CONCLUSION

The effects of time of AD onset were delineated as a double dissociation, that is, EO AD patients have a more severe reduction of glucose metabolism. Our finding suggests the existence of biological subtypes of AD.

Cerebral metabolic changes associated with Lyme disease

There are no positron emission tomography (PET) studies reported in the literature with regards to brain metabolism and function in patients with Lyme disease. These patients frequently present with various neurological symptoms, including memory problems. We used [(18)F]fluorodeoxyglucose (FDG) PET to determine the metabolic landscape in 23 patients with Lyme disease. Images were evaluated for cortical and subcortical abnormalities by two experienced reviewers blinded to the clinical information. The most striking finding was hypometabolism in the temporal lobes in 17/23 (74%) patients. Of these, 12 had bilateral temporal lobe hypometabolism, two had left temporal lobe, and three had right temporal lobe hypometabolism. Seven of the patients with temporal lobe hypometabolism had diffuse cortical hypometabolism that included the frontal and parietal lobes. Lyme disease appears to have two primary patterns of brain involvement on FDG PET scans, specific temporal lobe hypometabolism or a diffuse cortical hypometabolism. The involvement of the temporal lobes in both patterns is likely associated with the memory disturbances described in many of these patients. Although there was no clear diagnostic pattern, and many of the defects were mild, FDG PET imaging may provide important information regarding the areas of the brain affected in patients with neurological symptoms associated with Lyme disease.

Variation in FDG uptakes in different regions in normal human brain as a function of the time (30 and 60 minutes) after injection of FDG

OBJECTIVE

The authors' goal was to determine whether FDG uptakes in various regions of the brain are different for early and late scanning time in positron emission tomography (PET).

METHOD

F-18 fluorodeoxyglucose (FDG) PET was performed on 15 healthy normal subjects to obtain early and late acquisition glucose metabolic images (30 and 60 min after FDG injection), respectively. The two sets of images were compared in a voxel-by-voxel analysis.

RESULTS

In the bilateral posterior cingulate gyrus, parietal and frontal association cortices, and subcallosal cortices, the FDG uptakes were larger on the late scan image than on the early scan image, and the FDG uptakes were larger in the cerebellar hemisphere, vermis and frontal basis on the early scan image than on the late scan image.

CONCLUSIONS

These results suggest that there are different regional FDG uptakes depending on the scanning time after FDG injection and we must be careful in replacing conventional FDG PET scanning with early scanning in FDG PET study.