Objectives: In recent years several [F-18]-labelled amyloid PET tracers have been developed and have obtained clinical approval. There is accumulating evidence that early (post injection) acquisitionswith these tracers are equally informative as conventional blood flow andmetabolismstudies for diagnosis of Alzheimer's disease, but there have been few side-by-side studies. Therefore, we investigated the performance of early acquisitions of [F-18]florbetaben (FBB) PET compared to [F-18]-fluorodeoxyglucose (FDG) PET in a clinical setting.Methods: All subjects were recruited with clinical suspicion of dementia due to neurodegenerative disease. FDG PET was undertaken by conventional methods, and amyloid PET was performed with FBB, with early recordings for the initial 10 min (early-phase FBB), and late recordings at 90-110 min p.i. (late-phase FBB). Regional SUVR with cerebellar and globalmean normalization were calculated for early-phase FBB and FDG PET. Pearson correlation coefficients between FDG and early-phase FBB were calculated for predefined cortical brain regions. Furthermore, a visual interpretation of disease pattern using 3-dimensional stereotactic surface projections (3DSSP) was performed, with assessment of intra-reader agreement.Results: Among a total of 33 patients (mean age 67.5 +/- 11.0 years) included in the study, 18 were visually rated amyloid-positive, and 15 amyloid-negative based on late-phase FBB scans. Correlation coefficients for earlyphase FBB vs. FDG scans displayed excellent agreement in all target brain regions for global mean normalization. Cerebellar normalization gave strong, but significantly lower correlations. 3D representations of early-phase FBB visually resembled the corresponding FDG PET images, irrespective of the amyloid-status of the late FBB scans.Conclusions: Early-phase FBB acquisitions correlate on a relative quantitative and visual level with FDG PET scans, irrespective of the amyloid plaque density assessed in late FBB imaging. Thus, early-phase FBB uptake depicts a metabolism-like image, suggesting it as a valid surrogatemarker for synaptic dysfunction, which could ultimately circumvent the need for additional FDG PET investigation in diagnosis of dementia. (C) 2016 The Author(s). Published by Elsevier Inc.

Introduction: Magnet resonance image (MRI)-based segmentations are widely used for clinical brain research, especially in conjunction with positron-emission-tomography (PET). Although artifacts due to segmentation errors arise commonly, the impact of these artifacts on PET quantitation has not yet been investigated systematically. Therefore, the aim of this study was to assess the effect of segmentation errors on [F-18]-AV45 and [F-18]-FDG PET quantitation, with and without correction for partial volume effects (PVE). Material and Methods: 119 subjects with both [F-18]-AV45, and [F-18]-FDG PET as well as T1-weighted MRI at baseline and at two-year follow-up were selected from the ADNI cohort, and their MRI brain images were segmented using PMOD 3.5. MRIs with segmentation artifacts were masked with the corresponding [F-18]-FDG PET standard-uptake-value (SUV) images to elucidate and quantify the impact of artifacts on PET analyses for six defined volumes-of-interest (VOI). Artifact volumes were calculated for each VOI, together with error-[%] and root-mean-square-errors (RMSE) in uncorrected and PVE corrected SUV results for the two PET tracers. We also assessed the bias in longitudinal PET data. Results: Artifacts occurred most frequently in the parietal cortex VOI. For [F-18]-AV45 and [F-18]-FDG PET, the percentage-errors were dependent on artifact volumes. PVEC SUVs were consequently more distorted than were their uncorrected counterparts. In static and longitudinal assessment, a small subgroup of subjects with large artifacts (>= 1500 voxels; 5.06 cm(3)) accounted for much of the PET quantitation bias. Conclusion: Large segmentation artifacts need to be detected and resolved as they considerably bias PET quantitation, especially when PVEC is applied to PET data.

Late life depression (LLD) even in subsyndromal stages shows high conversion rates from cognitively normal (CN) to mild cognitive impairment (MCI). Results of [(18)F]-fluorodesoxyglucose positron-emission-tomography (FDG-PET) were inconsistent in LLD patients, whereas atrophy was repeatedly described. Therefore, we set out to investigate FDG metabolism and the effect of atrophy correction (PVEC) in geriatric CN patients with depressive symptoms. 21 CN subjects with positive item for the depression category (DEP) in the Neuropsychiatric-Inventory-Questionnaire and 29 CN subjects with an absent depression item (NON-DEP) were selected from the ADNI cohort. FDG-PETs were analyzed in individual PET space using volumes-of-interest (VOI) and statistical-parametric-mapping (SPM) approaches. VOI- and MRI-based PVEC were applied to PET data. DEP subjects showed significant hypometabolism in fronto-temporal cortices and the posterior cingulate cortex (PCC) when contrasted against NON-DEP in uncorrected data. Both in VOI- and SPM-based approaches PVEC eliminated significance in PCC, while fronto-temporal regions remained significant or even attained significance such as in case of the left amygdala. Subsyndromally depressed CN subjects had decreased FDG metabolism in mood-related brain regions, which may be relevant to their elevated risk for conversion from CN to MCI. Methodological advances in PET analyses should be considered in future studies as PVEC relevantly changed results of FDG-PET for detecting apparent metabolic differences between DEP and NON-DEP subjects. Furthermore, VOI-based analyses in individual PET space will allow a more accurate consideration of variability in anatomy, especially in subcortical regions.

1843 Objectives Previous studies have reported an association between stroke and dementia with a prevalence of post-stroke dementia (PSD) of about 20 % within a few months after the event but the pathophysiology is currently incompletely understood. The aim of this study is to assess whether post-acute amyloid-PET can serve as a prediction marker for subsequent PSD. Methods This is a prospective study in patients with acute stroke and lack of prior dementia. Patients undergo cognitive testing at repeated time points and are based on that classified as cognitively normal (CN), mild cognitively impaired (MCI) or as demented. Amyloid-PET using [18F]flutemetamol is performed 6 months after the stroke aside from structural imaging with MRI, as well as FDG-PET. The amyloid-PETs were visually assessed as well as evaluated by VOI-based approaches, using cerebellar cortex as the reference region, leading to standardized-uptake-value ratios (SUVR). Results 37 patients (11f; 71 ± 9y) underwent an amyloid-PET. 12/37 patients were classified as CN, 24/37 as MCI and 1/37 as demented. 1/12 CN and 1/24 MCI patients were visually rated as amyloid(+). In a group analysis of the SUVR there was no difference in neocortical [18F]flutemetamol uptake in MCI patients compared to CN patients. A manually applied VOI covering the peri-infarct region showed a significant lower amyloid deposition compared to a mirrored VOI in the contralateral hemisphere (1.80 vs 1.88; p Conclusions Until now it seems that amyloid-pathology is less frequent in PSD and that amyloid deposition both in the peri-infarct region as well as in the ipsilateral hemisphere is rather decreased compared to the contralateral side in the chronic phase. Further patients need to be recruited and followed-up in order to see if this trend proves true. Research Support Flutemetamol was provided by GE.