Effect of cholinergic treatment depends on cholinergic integrity in early Alzheimer's disease.

In early Alzheimer's disease, which initially presents with progressive loss of short-term memory, neurodegeneration especially affects cholinergic neurons of the basal forebrain. Pharmacotherapy of Alzheimer's disease therefore often targets the cholinergic system. In contrast, cholinergic pharmacotherapy of mild cognitive impairment is debated since its efficacy to date remains controversial. We here investigated the relationship between cholinergic treatment effects and the integrity of the cholinergic system in mild cognitive impairment due to Alzheimer's disease. Fourteen patients with high likelihood of mild cognitive impairment due to Alzheimer's disease and 16 age-matched cognitively normal adults performed an episodic memory task during functional magnetic resonance imaging under three conditions: (i) without pharmacotherapy; (ii) with placebo; and (iii) with a single dose of rivastigmine (3 mg). Cortical acetylcholinesterase activity was measured using PET with the tracer 11C-N-methyl-4-piperidyl acetate (MP4A). Cortical acetylcholinesterase activity was significantly decreased in patients relative to controls, especially in the lateral temporal lobes. Without pharmacotherapy, mild cognitive impairment was associated with less memory-related neural activation in the fusiform gyrus and impaired deactivation in the posterior cingulate cortex, relative to controls. These differences were attenuated under cholinergic stimulation with rivastigmine: patients showed increased neural activation in the right fusiform gyrus but enhanced deactivation of the posterior cingulate cortex under rivastigmine, compared to placebo. Conversely, controls showed reduced activation of the fusiform gyrus and reduced deactivation of the posterior cingulate under rivastigmine, compared to placebo. In both groups, the change in neural activation in response to rivastigmine was negatively associated with local acetylcholinesterase activity. At the behavioural level, an analysis of covariance revealed a significant group × treatment interaction in episodic memory performance when accounting for hippocampal grey matter atrophy and function. Our results indicate that rivastigmine differentially affects memory-related neural activity in patients with mild cognitive impairment and cognitively normal, age-matched adults, depending on acetylcholinesterase activity as a marker for the integrity of the cortical cholinergic system. Furthermore, hippocampal integrity showed an independent association with the response of memory performance to acetylcholinesterase inhibition.

FTO gene variant modulates the neural correlates of visual food perception.

Variations in the fat mass and obesity associated (FTO) gene are currently the strongest known genetic factor predisposing humans to non-monogenic obesity. Recent experiments have linked these variants to a broad spectrum of behavioural alterations, including food choice and substance abuse. Yet, the underlying neurobiological mechanisms by which these genetic variations influence body weight remain elusive. Here, we explore the brain structural substrate of the obesity-predisposing rs9939609 T/A variant of the FTO gene in non-obese subjects by means of multivariate classification and use fMRI to investigate genotype-specific differences in neural food-cue reactivity by analysing correlates of a visual food perception task. Our findings demonstrate that MRI-derived measures of morphology along middle and posterior fusiform gyrus (FFG) are highly predictive for FTO at-risk allele carriers, who also show enhanced neural responses elicited by food cues in the same posterior FFG area. In brief, these findings provide first-time evidence for FTO-specific differences in both brain structure and function already in non-obese individuals, thereby contributing to a mechanistic understanding of why FTO is a predisposing factor for obesity.

Dopaminergic correlates of metabolic network activity in Parkinson's disease.

Parkinson's disease (PD) is associated with distinct metabolic covariance patterns that relate to the motor and cognitive manifestations of the disorder. It is not known, however, how the expression of these patterns relates to measurements of nigrostriatal dopaminergic activity from the same individuals. To explore these associations, we studied 106 PD subjects who underwent cerebral PET with both (18) F-fluorodeoxyglucose (FDG) and (18) F-fluoro-L-dopa (FDOPA). Expression values for the PD motor- and cognition-related metabolic patterns (PDRP and PDCP, respectively) were computed for each subject; these measures were correlated with FDOPA uptake on a voxel-by-voxel basis. To explore the relationship between dopaminergic function and local metabolic activity, caudate and putamen FDOPA PET signal was correlated voxel-wise with FDG uptake over the entire brain. PDRP expression correlated with FDOPA uptake in caudate and putamen (P < 0.001), while PDCP expression correlated with uptake in the anterior striatum (P < 0.001). While statistically significant, the correlations were only of modest size, accounting for less than 20% of the overall variation in these measures. After controlling for PDCP expression, PDRP correlations were significant only in the posterior putamen. Of note, voxel-wise correlations between caudate/putamen FDOPA uptake and whole-brain FDG uptake were significant almost exclusively in PDRP regions. Overall, the data indicate that PDRP and PDCP expression correlates significantly with PET indices of presynaptic dopaminergic functioning obtained in the same individuals. Even so, the modest size of these correlations suggests that in PD patients, individual differences in network activity cannot be explained solely by nigrostriatal dopamine loss.

The integrity of the cholinergic system determines memory performance in healthy elderly.

The cholinergic system plays a central role in episodic memory-related processes in health and disease. Cerebral acetylcholinesterase (AChE) activity, a measure of the integrity of the cholinergic system, can be assessed in vivo using positron emission tomography (PET) and [(11)C]N-methyl-4-piperidyl acetate (MP4A). A close relationship between the kinetic constant k3 of MP4A and mnestic functions has been demonstrated for patients suffering from amnestic mild cognitive impairment and Alzheimer's disease. Under the hypothesis that AChE activity and memory are intimately linked in older age, we obtained MP4A-PET and structural magnetic resonance images as well as neuropsychological data from fourteen healthy older adults. Multiple regression analysis revealed that AChE activity in areas previously implicated in mnestic functions predicted episodic memory performance irrespective of cortical atrophy. Data suggest that in older adults the integrity of the cholinergic system underlies inter-individual variability in memory function.

Effects of noninvasive brain stimulation on language networks and recovery in early poststroke aphasia.

BACKGROUND AND PURPOSE: Modulation of activity in language networks using repetitive transcranial magnetic stimulation (rTMS) may possibly support recovery from poststroke aphasia. Case series and feasibility studies seem to indicate a therapeutic effect; however, randomized sham-controlled, proof-of-principle studies relating clinical effects to activation patterns are missing. METHODS: Twenty-four patients with subacute poststroke aphasia were randomized to a 10-day protocol of 20-minute inhibitory 1 Hz rTMS over the right triangular part of the posterior inferior frontal gyrus or sham stimulation, followed by 45 minutes of speech and language therapy. Activity in language networks was measured with O-15-water positron emission tomography during verb generation before and after treatment. Language performance was assessed using the Aachen Aphasia Test battery. RESULTS: The primary outcome measure, global Aachen Aphasia Test score change, was significantly higher in the rTMS group (t test, P=0.003). Increases were largest for subtest naming (P=0.002) and tended to be higher for comprehension, token test, and writing (P<0.1). Patients in the rTMS group activated proportionally more voxels in the left hemisphere after treatment than before (difference in activation volume index) compared with sham-treated patients (t test, P=0.002).There was a moderate but significant linear relationship between activation volume index change and global Aachen Aphasia Test score change (r2=0.25; P=0.015). CONCLUSIONS: Ten sessions of inhibitory rTMS over the right posterior inferior frontal gyrus, in combination with speech and language therapy, significantly improve language recovery in subacute ischemic stroke and favor recruitment of left-hemispheric language networks.

Noninvasive brain stimulation for treatment of right- and left-handed poststroke aphasics.

BACKGROUND: Accumulating evidence from single case studies, small case series and randomized controlled trials seems to suggest that inhibitory noninvasive brain stimulation (NIBS) over the contralesional inferior frontal gyrus (IFG) of right-handers in conjunction with speech and language therapy (SLT) improves recovery from poststroke aphasia. Application of inhibitory NIBS to improve recovery in left-handed patients has not yet been reported. METHODS: A total of 29 right-handed subacute poststroke aphasics were randomized to receive either 10 sessions of SLT following 20 min of inhibitory repetitive transcranial magnetic stimulation (rTMS) over the contralesional IFG or 10 sessions of SLT following sham stimulation; 2 left-handers were treated according to the same protocol with real rTMS. Language activation patterns were assessed with positron emission tomography prior to and after the treatment; 95% confidence intervals for changes in language performance scores and the activated brain volumes in both hemispheres were derived from TMS- and sham-treated right-handed patients and compared to the same parameters in left-handers. RESULTS: Right-handed patients treated with rTMS showed better recovery of language function in global aphasia test scores (t test, p < 0.002) as well as in picture-naming performance (ANOVA, p = 0.03) than sham-treated right-handers. In treated right-handers, a shift of activation to the ipsilesional hemisphere was observed, while sham-treated patients consolidated network activity in the contralesional hemisphere (repeated-measures ANOVA, p = 0.009). Both left-handed patients also improved, with 1 patient within the confidence limits of TMS-treated right-handers (23 points, 15.9-28.9) and the other patient within the limits of sham-treated subjects (8 points, 2.8-14.5). Both patients exhibited only a very small interhemispheric shift, much less than expected in TMS-treated right-handers, and more or less consolidated initially active networks in both hemispheres. CONCLUSION: Inhibitory rTMS over the nondominant IFG appears to be a safe and effective treatment for right-handed poststroke aphasics. In the 2 cases of left-handed aphasics no deterioration of language performance was observed with this protocol. However, therapeutic efficiency is less obvious and seems to be more related to the dominance pattern prior to the stroke than to the TMS intervention.

Cannabidiol enhances cerebral glucose utilization and ameliorates psychopathology and cognition: A case report in a clinically high-risk mental state.

Adolescent individuals often present with subtle, sub-threshold psychiatric syndromes that fluctuate or persist for years. These symptoms have been classified as Clinically High-Risk mental states (CHR), negatively affecting these individuals' psychosocial development and integration by reducing performance and affecting interpersonal relations. The pathophysiological underpinnings have not been studied in detail, contributing to the current lack of appropriate intervention strategies. This case report sheds new light on potential pathophysiological mechanisms of this condition, which may be addressed by novel treatment approaches such as cannabidiol. A 19-year-old student presented to our early intervention center with a marked cognitive decline within 6 months, anhedonia, ambivalence, social withdrawal, poverty of speech, and brief intermittent psychotic symptoms (delusions and hallucinations). He was diagnosed with CHR state, and we decided to treat him with the non-psychotomimetic phytocannabinoid cannabidiol. Cannabidiol is a promising compound carrying an orphan drug approval for rare certain childhood epilepsy types and is under investigation as an antipsychotic compound with a new mechanism of action compared to existing antipsychotics. We investigated the effect of oral cannabidiol (600 mg per day) over 4 weeks on psychopathology and cerebral glucose utilization. We observed no relevant side effects but a significant clinical improvement. In addition, positron emission tomography (PET) showed a considerable increase in cerebral [18F]fluoro-2-deoxyglucose (FDG) uptake in various brain regions. This finding suggests that cannabidiol may enhance cerebral glucose utilization, possibly via activation of peroxisome proliferator-activated receptor-gamma (PPAR-γ) by its endogenous ligand anandamide or related N-acylethanolamines. This mechanism may represent a new innovative treatment approach for CHR, especially given that many individuals with CHR and early psychosis do not substantially benefit from current psychopharmacological interventions.

11C-Methionine positron emission tomographic imaging of biologic activity of a recurrent glioblastoma treated with stereotaxy-guided laser-induced interstitial thermotherapy.

In patients with recurrent glioblastoma multiforme (GBM), local minimally invasive treatment modalities have gained increasing interest recently because they are associated with fewer side effects than open surgery. For example, local tumor coagulation by laser-induced interstitial thermotherapy (LITT) is such a minimally invasive technique. We monitored the metabolic effects of stereotaxy-guided LITT in a patient with a recurrent GBM using amino acid positron emission tomography (PET). Serial 11C-methyl-L-methionine positron emission tomography (MET-PET) and contrast-enhanced computed tomography (CT) were performed using a hybrid PET/CT system in a patient with recurrent GBM before and after LITT. To monitor the biologic activity of the effects of stereotaxy-guided LITT, a threshold-based volume of interest analysis of the metabolically active tumor volume (MET uptake index of ≥ 1.3) was performed. A continuous decline in metabolically active tumor volume after LITT could be observed. MET-PET seems to be useful for monitoring the short-term therapeutic effects of LITT, especially when patients have been pretreated with a multistep therapeutic regimen. MET-PET seems to be an appropriate tool to monitor and guide experimental LITT regimens and should be studied in a larger patient group to confirm its clinical value.

Volumetry of [¹¹C]-methionine positron emission tomographic uptake as a prognostic marker before treatment of patients with malignant glioma.

The purpose of this positron emission tomography (PET) study was to compare the prognostic value of pretreatment volume of ¹¹C]-methionine (MET) uptake and semiquantitative MET uptake ratio in patients with malignant glioma. The study population comprised 40 patients with malignant glioma. Pretreatment magnetic resonance imaging (MRI) and MET-PET imaging were performed before the initiation of glioma treatment in all patients. The pretreatment MET uptake ratios and volumes were assessed. To create prognostically homogeneous subgroups, patients' pretreatment prognostic factors were stratified according to the six classes of Radiation Therapy Oncology Group recursive partitioning analysis (RTOG RPA). Univariate and multivariate analyses were performed to determine significant prognostic factors. Survival analyses identified the pretreatment volume of MET uptake and a higher RTOG RPA class as significant predictors. In contrast, pretreatment maximum areas of contrast enhancement on MRI and semiquantitative MET uptake ratios could not be identified as significant prognostic factors. The patients' outcomes and Karnofsky Performance Scale scores were significantly correlated with pretreatment volume of MET uptake but not with semiquantitative MET uptake ratio. The data suggest that pretreatment volumetry of MET uptake but not the semiquantitative MET uptake ratio is a useful biologic prognostic marker in patients with malignant glioma.

The severity of ischemia determines and predicts malignant brain edema in patients with large middle cerebral artery infarction.

BACKGROUND: In order to determine the impact of the severity of ischemia on malignant edema formation, we investigated various degrees of perfusional deficit by (11)C-flumazenil PET in patients with large middle cerebral artery (MCA) infarction. METHODS: 17 patients with large MCA stroke were included. Cerebral blood flow (CBF) was measured 15.9 ± 6.4 h after the ictus. Patients were divided into a malignant (n = 9) and a benign group (n = 8) as a function of their clinical courses and edema. Edema was measured as maximal midline shift on follow-up CTs. Total hypoperfusion volume was divided into different subvolumes according to the degree of CBF reduction. RESULTS: Subvolumes of severe ischemia relative to total ischemic area were significantly larger in the malignant group than in the benign group and were significantly correlated with edema formation. The highest correlation and best predictive values for edema formation with a sensitivity, specificity, and a positive and negative predictive value of 100% were found for subvolumes with severe ischemia. Correlation coefficients and prediction decreased for subvolumes with less severe perfusional deficit, pointing to the risk of misclassifying patients when relying on the volume of total perfusional deficit alone. CONCLUSIONS: Malignant MCA infarction seems to be determined more by the volume of severe perfusional deficit than that of total perfusional deficit. Assessment of severely ischemic areas allows prediction of malignant edema formation and might help to select candidates for hemicraniectomy.

Effects of repetitive transcranial magnetic stimulation in aphasic stroke: a randomized controlled pilot study.

BACKGROUND AND PURPOSE: Although functional imaging studies suggest that recruitment of contralesional areas hinders optimal functional reorganization in patients with aphasic stroke, only limited evidence is available on the efficacy of noninvasive brain stimulation such as repetitive transcranial magnetic stimulation aimed at suppression of contralateral overactivation. METHODS: In this randomized, controlled, blinded pilot study, the effect of 1-Hz repetitive transcranial magnetic stimulation over right-hemispheric Broca homolog in subjects with poststroke aphasia in the subacute stage was examined. According to their group allocation, patients received, in addition to conventional speech and language therapy, multiple sessions of repetitive transcranial magnetic stimulation either over the right-hemispheric inferior frontal gyrus (intervention group) or over the vertex (control group). The primary outcome parameter was the change in laterality indices as quantified by activation positron emission tomography before and after the 2-week intervention period. The clinical efficacy was evaluated with the Aachen Aphasia Test. RESULTS: At baseline, no group differences were discovered for age, laterality indices, or mean Aachen Aphasia Test scores. Four patients were lost to follow-up, but none due to side effects of the transcranial magnetic stimulation. Positron emission tomography revealed an activation shift toward the right hemisphere in the control group (P=0.0165), which was absent in the intervention group. Furthermore, the latter improved significantly clinically by a mean of 19.8 points in the Aachen Aphasia Test total score (P=0.002), whereas the control group did not. There was however no clear linear relationship between the extent of laterality shift and clinical improvement (r=0.193, P=nonsignificant). CONCLUSIONS: Repetitive transcranial magnetic stimulation might be an effective, safe, and feasible complementary therapy for poststroke aphasia.

Imaging of non- or very subtle contrast-enhancing malignant gliomas with [¹¹C]-methionine positron emission tomography.

In patients with World Health Organization (WHO) grade III glioma with a lack of or minimal (< 1 cm3) magnetic resonance imaging (MRI) contrast enhancement, the volume of the metabolically active part of the tumor was assessed by [¹¹C]-methionine positron emission tomography (MET-PET). Eleven patients with WHO grade III gliomas underwent MET-PET and MRI (contrast-enhanced T1- and T2-weighted images). To calculate the volumes in cubic centimeters, threshold-based volume of interest analyses of the metabolically active tumor (MET uptake index ≥ 1.3), contrast enhancement, and the T2 lesion were performed after coregistration of all images. In all patients, the metabolically active tumor volume was larger than the volume of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) enhancement (20.8 ± 18.8 vs 0.29 ± 0.25 cm3; p < .001). With the exception of one patient, the volumes of contrast enhancement were located within the metabolically active tumor volume. In contrast, in the majority of patients, MET uptake overlapped with the T2 lesion and reached beyond it (in 10 of 12 MRIs/MET-PET scans). The present data suggest that in patients with WHO grade III glioma with minimal or a lack of contrast enhancement, MET-PET delineates metabolically active tumor tissue. These findings support the use of combined PET-MRI with radiolabeled amino acids (eg, MET) for the delineating of the true extent of active tumor in the diagnosis and treatment planning of patients with gliomas.

Spreading depolarizations cycle around and enlarge focal ischaemic brain lesions.

How does infarction in victims of stroke and other types of acute brain injury expand to its definitive size in subsequent days? Spontaneous depolarizations that repeatedly spread across the cerebral cortex, sometimes at remarkably regular intervals, occur in patients with all types of injury. Here, we show experimentally with in vivo real-time imaging that similar, spontaneous depolarizations cycle repeatedly around ischaemic lesions in the cerebral cortex, and enlarge the lesion in step with each cycle. This behaviour results in regular periodicity of depolarization when monitored at a single point in the lesion periphery. We present evidence from clinical monitoring to suggest that depolarizations may cycle in the ischaemic human brain, perhaps explaining progressive growth of infarction. Despite their apparent detrimental role in infarct growth, we argue that cycling of depolarizations around lesions might also initiate upregulation of the neurobiological responses involved in repair and remodelling.

Patient-tailored, imaging-guided, long-term temozolomide chemotherapy in patients with glioblastoma.

We present two patients with glioblastoma with an unusually stable clinical course and long-term survival who were treated after surgery and radiotherapy with adjuvant temozolomide (TMZ) chemotherapy for 17 and 20 cycles, respectively. Afterward, adjuvant TMZ chemotherapy was discontinued in one patient and the dosage of TMZ was reduced in the other. In addition to clinical status and magnetic resonance imaging, the biologic activity of the tumors was monitored by repeated methyl-11C-l-methionine (MET) and 3'-deoxy-3'-18F-fluorothymidine (FLT) positron emission tomography (PET) studies in these patients. In these patients, repeated MET- and FLT-PET imaging documented complete response to the initial treatment regimen, including resection, radiation, and TMZ, and during the course of the disease, recurrent, uncontrollable tumor activity. Continuation or dose escalation of TMZ in both patients was shown to be ineffective to overcome the metabolic activity of the tumor. Our data suggest that repeated MET- and FLT-PET imaging provide information on the biologic activity of a tumor that is highly useful to monitor and detect changes in activity.

Volumetry of [(11)C]-methionine PET uptake and MRI contrast enhancement in patients with recurrent glioblastoma multiforme.

PURPOSE: We investigated the relationship between three-dimensional volumetric data of the metabolically active tumour volume assessed using [(11)C]-methionine positron emission tomography (MET-PET) and the area of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) enhancement assessed using magnetic resonance imaging (MRI) in patients with recurrent glioblastoma (GBM). MATERIAL AND METHODS: MET-PET and contrast-enhanced MRI with Gd-DTPA were performed in 12 uniformly pretreated patients with recurrent GBM. To calculate the volumes in cubic centimetres, a threshold-based volume-of-interest (VOI) analysis of the metabolically active tumour volume (MET uptake indexes of > or = 1.3 and > or = 1.5) and of the area of Gd-DTPA enhancement was performed after coregistration of all images. RESULTS: In all patients, the metabolically active tumour volume as shown using a MET uptake index of > or = 1.3 was larger than the volume of Gd-DTPA enhancement (30.2 + or - 22.4 vs. 13.7 + or - 10.6 cm(3); p = 0.04). Metabolically active tumour volumes as shown using MET uptake indexes of > or =1.3 and > or = 1.5 and the volumes of Gd-DTPA enhancement showed a positive correlation (r = 0.76, p = 0.003, for an index of > or =1.3, and r = 0.74, p = 0.005, for an index of > or =1.5). CONCLUSION: The present data suggest that in patients with recurrent GBM the metabolically active tumour volume may be substantially underestimated by Gd-DTPA enhancement. The findings support the notion that complementary information derived from MET uptake and Gd-DTPA enhancement may be helpful in developing individualized, patient-tailored therapy strategies in patients with recurrent GBM.

[11C]-L-methionine positron emission tomography in the management of children and young adults with brain tumors.

Only a few Methyl-[11C]-L-methionine (MET) positron emission tomography (PET) studies have focused on children and young adults with brain neoplasm. Due to radiation exposure, long scan acquisition time, and the need for sedation in young children MET-PET studies should be restricted to this group of patients when a decision for further therapy is not possible from routine diagnostic procedures alone, e.g., structural imaging. We investigated the diagnostic accuracy of MET-PET for the differentiation between tumorous and non-tumorous lesions in this group of patients. Forty eight MET-PET scans from 39 patients aged from 2 to 21 years (mean 15 +/- 5.0 years) were analyzed. The MET tumor-uptake relative to a corresponding control region was calculated. A receiver operating characteristic (ROC) was performed to determine the MET-uptake value that best distinguishes tumorous from non-tumorous brain lesions. A differentiation between tumorous (n = 39) and non-tumorous brain lesions (n = 9) was possible at a threshold of 1.48 of relative MET-uptake with a sensitivity of 83% and a specificity of 92%, respectively. A differentiation between high grade malignant lesions (mean MET-uptake = 2.00 +/- 0.46) and low grade tumors (mean MET-uptake = 1.84 +/- 0.31) was not possible. There was a significant difference in MET-uptake between the histologically homogeneous subgroups of astrocytoma WHO grade II and anaplastic astrocytoma WHO grade III (P = 0.02). MET-PET might be a useful tool to differentiate tumorous from non-tumorous lesions in children and young adults when a decision for further therapy is difficult or impossible from routine structural imaging procedures alone.

Noninvasive quantification of 18F-FLT human brain PET for the assessment of tumour proliferation in patients with high-grade glioma.

PURPOSE: Compartmental modelling of 3'-deoxy-3'-[18F]-fluorothymidine (18F-FLT) PET-derived kinetics provides a method for noninvasive assessment of the proliferation rate of gliomas. Such analyses, however, require an input function generally derived by serial blood sampling and counting. In the current study, 18F-FLT kinetic parameters obtained from image-derived input functions were compared with those from input functions derived from arterialized blood samples. METHODS: Based on the analysis of 11 patients with glioma (WHO grade II-IV) a procedure for the automated extraction of an input function from 18F-FLT brain PET data was derived. The time-activity curve of the volume of interest with the maximum difference in 18F-FLT uptake during the first 5 min after injection and the period from 60 to 90 min was corrected for partial-volume effects and in vivo metabolism of 18F-FLT. For each patient a two-compartment kinetic model was applied to the tumour tissue using the image-derived input function. The resulting kinetic rate constants K1 (transport across the blood-brain barrier) and Ki (metabolic rate constant or net influx constant) were compared with those obtained from the same data using the input function derived from blood samples. Additionally, the metabolic rate constant was correlated with the frequency of tumour cells stained with Ki-67, a widely used immunohistochemical marker of cell proliferation. RESULTS: The rate constants from kinetic modelling were comparable when the blood sample-derived input functions were replaced by the image-derived functions (K1,img and K1,sample, r = 0.95, p < 10(-5); Ki,img and Ki,sample, r = 0.86, p < 0.001). A paired t-test showed no significant differences in the parameters derived with the two methods (K1,img and K1,sample, p = 0.20; Ki,img and Ki,sample, p = 0.92). Furthermore, a significant correlation between Ki,img and the percentage of Ki-67-positive cells was observed (r = 0.73, p = 0.01). CONCLUSION: Kinetic modelling of 18F-FLT brain PET data using image-derived input functions extracted from human brain PET data with the practical procedure described here provides information about the proliferative activity of brain tumours which might have clinical relevance especially for monitoring of therapy response in future clinical trials.

Glioma proliferation as assessed by 3'-fluoro-3'-deoxy-L-thymidine positron emission tomography in patients with newly diagnosed high-grade glioma.

PURPOSE: The aim of this study was to investigate the relationship between the in vivo derived kinetic parameters of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) and the proliferation rate measured in vitro by Ki-67 staining in patients with newly diagnosed high-grade gliomas. EXPERIMENTAL DESIGN: Thirteen patients with newly diagnosed high-grade gliomas were investigated with (18)F-FLT and methyl-(11)C- l-methionine ((11)C-MET) positron emission tomography (PET) and T1-, Gd-T1-, and T2-weighted magnetic resonance imaging on consecutive days. Tracer kinetic parameters of (18)F-FLT as well as the standardized uptake value and the tumor-to-background (T/B) ratio of (18)F-FLT and (11)C-MET were determined. Data of kinetic modeling, standardized uptake value, and T/B values derived from (18)F-FLT-PET were compared with T/B values derived from (11)C-MET-PET and to the in vitro proliferation marker Ki-67. RESULTS: A significant correlation was observed between the metabolic rate constant Ki and the proliferation index as measured by Ki-67 immunostaining [Ki, r=0.79 (P=0.004)]. Also, the phosphorylation rate constant k3 correlated with Ki-67 [k3, r=0.76 (P=0.006)], whereas the rate constant for transport through the blood brain barrier K1 showed a weaker correlation with Ki-67 [K1, r=0.62 (P=0.044)]. No significant correlation between (11)C-MET and (18)F-FLT uptake ratios and Ki-67 was observed. CONCLUSIONS: This study shows that kinetic analysis of (18)F-FLT tracer uptake is essential for the in vivo assessment of tumor proliferation in high-grade gliomas, whereas uptake ratios of (11)C-MET and (18)F-FLT failed to correlate with the in vitro determined proliferation marker. Thus, kinetic analysis of (18)F-FLT might provide an accurate method for the assessment of early response to glioma treatment in the future.

Spatial distributions of cholinergic impairment and neuronal hypometabolism differ in MCI due to AD.

Elucidating the relationship between neuronal metabolism and the integrity of the cholinergic system is prerequisite for a profound understanding of cholinergic dysfunction in Alzheimer's disease. The cholinergic system can be investigated specifically using positron emission tomography (PET) with [11C]N-methyl-4-piperidyl-acetate (MP4A), while neuronal metabolism is often assessed with 2-deoxy-2-[18F]fluoro-d-glucose-(FDG) PET. We hypothesised a close correlation between MP4A-perfusion and FDG-uptake, permitting inferences about metabolism from MP4A-perfusion, and investigated the patterns of neuronal hypometabolism and cholinergic impairment in non-demented AD patients. MP4A-PET was performed in 18 cognitively normal adults and 19 patients with mild cognitive impairment (MCI) and positive AD biomarkers. In nine patients with additional FDG-PET, the sum images of every combination of consecutive early MP4A-frames were correlated with FDG-scans to determine the optimal time window for assessing MP4A-perfusion. Acetylcholinesterase (AChE) activity was estimated using a 3-compartmental model. Group comparisons of MP4A-perfusion and AChE-activity were performed using the entire sample. The highest correlation between MP4A-perfusion and FDG-uptake across the cerebral cortex was observed 60-450 s after injection (r = 0.867). The patterns of hypometabolism (FDG-PET) and hypoperfusion (MP4A-PET) in MCI covered areas known to be hypometabolic early in AD, while AChE activity was mainly reduced in the lateral temporal cortex and the occipital lobe, sparing posterior midline structures. Data indicate that patterns of cholinergic impairment and neuronal hypometabolism differ significantly at the stage of MCI in AD, implying distinct underlying pathologies, and suggesting potential predictors of the response to cholinergic pharmacotherapy.

Altered cerebral glucose metabolism in a family with clinical features resembling mitochondrial neurogastrointestinal encephalomyopathy syndrome in association with multiple mitochondrial DNA deletions.

OBJECTIVE: To determine the involvement of cerebral metabolism in 2 siblings with mitochondrial neurogastrointestinal encephalomyopathy syndrome (MNGIE)-like disease with multiple mitochondrial DNA (mtDNA) deletions. DESIGN: Case report. SETTING: Department of Neurology at a university medical center. PATIENTS: Two siblings with MNGIE-like disease with multiple mtDNA deletions. MAIN OUTCOME MEASURES: Clinical, biochemical, genetic, and imaging findings, including cerebral magnetic resonance imaging, proton magnetic resonance spectroscopy, and positron emission tomography with fluorine 18-labeled deoxyglucose (FDG-PET). RESULTS: Genetic analysis of muscle DNA revealed multiple mtDNA deletions, while no mutations were detected in ECGF1, POLG1, ANT1, or Twinkle. Cerebral magnetic resonance imaging and proton magnetic resonance spectroscopy findings were unremarkable. Reduced regional glucose metabolism was found in a patchy and asymmetrical pattern predominantly in the frontotemporal region in both siblings by means of FDG-PET. CONCLUSIONS: The discrepancy between absence of clinical signs of cerebral involvement and the substantial impairment of glucose metabolism reflects a chronic subclinical encephalopathy. To our knowledge, the predominantly frontotemporal distribution has not been described previously in mitochondrial disorders.