Brain FDG-PET Research Articles

A Comparison of Two Statistical Mapping Tools for Automated Brain FDG-PET Analysis in Predicting Conversion to Alzheimer’s Disease in Subjects with Mild Cognitive Impairment

Automated voxel-based analysis methods are used to detect cortical hypometabolism typical of Alzheimer's Disease (AD) on FDG-PET brain scans. We compared the accuracy of two clinically validated tools for their ability to identify those MCI subjects progressing to AD at followup, to evaluate the impact of the analysis method on FDG-PET diagnostic performance. SPMGrid and BRASS (Hermes Medical Solutions, Stockholm, Sweden) were tested on 131 MCI and elderly healthy controls from the EADC PET dataset. The concordance between the tools was tested by correlating the quantitative parameters (z- and t-values), calculated by the two software tools, and by measuring the topographical overlap of the abnormal regions (Dice score). Three independent expert readers blindly assigned a diagnosis based on the two map sets. We used conversion to AD dementia as the gold standard. The t-map and z-map calculated with SPMGrid and BRASS, respectively, showed a good correlation (R > .50) for the majority of individual cases (128/131) and for the majority of selected regions of interest (ROIs) (98/116). The overlap of the hypometabolic patterns from the two tools was, however, poor (Dice score .36). The diagnostic performance was comparable, with BRASS showing significantly higher sensitivity (.82 versus .59) and SPMGrid showing higher specificity (.87 versus .52). Despite similar diagnostic performance in predicting conversion to AD in MCI subjects, the two tools showed significant differences, and the maps provided by the tools showed limited overlap. These results underline the urgency for standardization across FDG-PET analysis methods for their use in clinical practice.

Early anterior cingulate involvement is seen in presymptomatic MAPT P301L mutation carriers

BackgroundPET imaging of glucose metabolism has revealed presymptomatic abnormalities in genetic FTD but has not been explored in MAPT P301L mutation carriers. This study aimed to explore the patterns of presymptomatic hypometabolism and atrophy in MAPT P301L mutation carriers.MethodsEighteen asymptomatic members from five families with a P301L MAPT mutation were recruited to the study, six mutation carriers, and twelve mutation-negative controls. All participants underwent standard behavioural and cognitive assessment as well as [18F]FDG-PET and 3D T1-weighted MRI brain scans. Regional standardised uptake value ratios (SUVR) for the PET scan and volumes calculated from an automated segmentation for the MRI were obtained and compared between the mutation carrier and control groups.ResultsThe mean (standard deviation) estimated years from symptom onset was 12.5 (3.6) in the mutation carrier group with a range of 7 to 18 years. No differences in cognition were seen between the groups, and all mutation carriers had a global CDR plus NACC FTLD of 0. Significant reduction in [18F] FDG uptake in the anterior cingulate was seen in mutation carriers (mean 1.25 [standard deviation 0.07]) compared to controls (1.36 [0.09]). A similar significant reduction was also seen in grey matter volume in the anterior cingulate in mutation carriers (0.60% [0.06%]) compared to controls (0.68% [0.08%]). No other group differences were seen in other regions.ConclusionsAnterior cingulate hypometabolism and atrophy are both apparent presymptomatically in a cohort of P301L MAPT mutation carriers. Such a specific marker may prove to be helpful in stratification of presymptomatic mutation carriers in future trials.

Validation of FDG-PET datasets of normal controls for the extraction of SPM-based brain metabolism maps.

An appropriate healthy control dataset is mandatory to achieve good performance in voxel-wise analyses. We aimed at evaluating [18F]FDG PET brain datasets of healthy controls (HC), based on publicly available data, for the extraction of voxel-based brain metabolism maps at the single-subject level. Selection of HC images was based on visual rating, after Cook's distance and jack-knife analyses, to exclude artefacts and/or outliers. The performance of these HC datasets (ADNI-HC and AIMN-HC) to extract hypometabolism patterns in single patients was tested in comparison with the standard reference HC dataset (HSR-HC) by means of Dice score analysis. We evaluated the performance and comparability of the different HC datasets in the assessment of single-subject SPM-based hypometabolism in three independent cohorts of patients, namely, ADD, bvFTD and DLB. Two-step Cook's distance analysis and the subsequent jack-knife analysis resulted in the selection of n= 125 subjects from the AIMN-HC dataset and n= 75 subjects from the ADNI-HC dataset. The average concordance between SPM hypometabolism t-maps in the three patient cohorts, as obtained with the new datasets and compared to the HSR-HC standard reference dataset, was 0.87 for the AIMN-HC dataset and 0.83 for the ADNI-HC dataset. Pattern expression analysis revealed high overall accuracy (> 80%) of the SPM t-map classification according to different statistical thresholds and sample sizes. The applied procedures ensure validity of these HC datasets for the single-subject estimation of brain metabolism using voxel-wise comparisons. These well-selected HC datasets are ready-to-use in research and clinical settings.

Dementia with Lewy bodies: Characteristics of the prodromal stage in a nationwide longitudinal cohort

AbstractBackgroundLittle is known about the prodromal phase of Dementia with Lewy bodies (DLB). In a large prospective cohort of patients attending memory clinics presenting either subjective cognitive impairment (SCI) and mild neurocognitive impairment (MCI) patients, we undertook an ancillary study aiming at detecting early DLB in a longitudinal framework.MethodWe conducted a french nationwide prospective cohort of patients with cognitive complaints and a minimum follow‐up of 4 years. Participants in the Memento cohort study were recruited for either isolated subjective cognitive impairment (SCI) or mild neurocognitive impairment (MCI). Among them, patients from 12 memory resource and research centers, representing eight hundred ninety‐two patients were included in the Lewy sub‐study. Probable Pro‐DLB diagnosis was done using a two‐criteria cut‐off score among the four core clinical features of Dementia with Lewy bodies. This Pro‐DLB group was compared to two other groups: one without any core symptoms (NS group), and the one with one core symptom (1S group). A comprehensive cognitive battery, brain 3D volumetric MRI, CSF, FDG PET and amyloid PET were done.ResultThe pro‐DLB group comprised 148 patients (16.6%). Compared to the other two groups, the neuropsychological profile of the pro‐DLB group showed, regarding cognition, more multidomain (59.8%) MCI with slower processing speed, semantic and neurovisual impairment, and regarding behavior, a higher proportion of patients with depression, anxiety, and apathy. Pro‐DLB patients also presented more autonomic symptoms, including lower libido, constipation, rhinorrhea, sicca syndrome, and photophobia. The Pro‐DLB group had isolated lower P‐Tau and no difference in terms of amyloid PET and FDG PET. Brain MRI analysis showed widening of sulci including fronto‐insular, occipital and olfactory sulci (FDR corrected). Evolution to dementia was not different between the three groups after 4 years of follow‐up.ConclusionPatients with pro‐DLB represented 16.6% of SCI and MCI patients, a finding consistent with the proportion observed at the stage of dementia. In addition to the core symptoms, pro‐DLB patients presented cognitive, behavioral and autonomic symptoms. Biomarkers confirmed the non‐Alzheimer profile. The occipital, fronto‐insular, and olfactory bulb involvement on brain MRI was consistent with the symptoms and known neuropathology.

Feasibility of Longitudinal Brain PET with Real-Time Arterial Input Function in Rats.

Preclinical dynamic brain PET studies remain hampered by the limitations related to the measurement of the arterial input function (AIF). In this regard, the use of an arterial-venous shunt is a promising method for the generation of real-time AIFs, but its application in longitudinal studies is still impeded by the cumbersome surgeries and high failure rates. We studied the feasibility and reproducibility of double arterial-venous shunt strategies for conducting longitudinal PET studies with real-time AIFs in rats. We studied the feasibility of double arterial-venous shunts in rats in the right/left inguinal region and evaluated inter-animal and intra-animal AIF reproducibilities. Image-derived input function (IDIF) was also obtained for comparison. Dynamic brain FDG PET studies were conducted to estimate kinetic constants and Cerebral Metabolic Rate of Glucose (CMRglc) obtained from standard 2-tissue compartment (2TCM) and Patlak analysis. We showed that longitudinal AIFs from double arterial-venous shunts can be obtained with very high success rate of the surgeries (88%). Our results provided highly reproducible AIF measurements with low inter-animal variabilities (11%) and intra-animal variabilities (5-10%) that were included into the kinetic models, such that longitudinal rate constants and CMRglc can be efficiently estimated without bias associated to the double shunt. Our results indicated that longitudinal IDIF can be also generated without bias along time but showing higher intra-animal uncertainties. We have demonstrated the feasibility and high reproducibility of conducting longitudinal AIF measurements and consequently accurate kinetic modeling using arterial shunt method.

Preliminary Results of a Response-Adapted Study of Ibrutinib and Isavuconazole with Temozolomide, Etoposide, Liposomal Doxorubicin, Dexamethasone, Rituximab (TEDDI-R) for Secondary CNS Lymphoma

Background: Secondary CNS B-cell lymphomas (SCNSL) are aggressive lymphomas with a very poor prognosis. Genetic subtypes of DLBCL with CNS tropism are enriched for chronic active B-cell receptor signaling and may respond to BTK inhibition (BTKi). CLL, MCL, and transformed lymphomas can also involve the CNS and are BTKi responsive. TEDDI-R achieves durable remissions in relapsed/refractory primary DLBCL of the CNS (PCNSL) but the profile of SCNSL tumors that are ibrutinib-responsive is unknown. We present preliminary results from a response-adapted trial of ibrutinib with TEDD-R in SCNSL. Methods: Pts with aggressive B-cell lymphomas with secondary CNS involvement are eligible if age ≥18 and adequate organ function. Pts must have relapsed after frontline therapy or can be untreated if brain parenchyma involved. Prior BTKi is allowed, but HIVinfection and EBV+ lymphomas are excluded. Baseline tests include brain MRI, FDG-PET brain and body, CSF with flow cytometry, Ommaya, and eye exam. Pts receive isavuconazole starting at 200mg BID x 3d prior to ibrutinib to prevent fungal infections associated with TEDDI-R and then 200mg daily unless ibrutinib stopped. Pts first receive ibrutinib 560mg daily x 14d in a window. If ≥20% reduction after ibrutinib, pts receive TEDDI-R for 4 cycles every 21d with IT cytarabine. Pts with <20% reduction after ibrutinib receive TEDD-R without ibrutinib for 4 cycles every 21d with IT cytarabine. No consolidation or maintenance is permitted. Surveillance for fungal infections includes chest CT after each cycle along with Beta-D glucan and aspergillus galactomannan in blood and CSF. Brain MRI and CT scans are performed after cycles 1, 2, and 4 to determine response. All remissions by MRI are confirmed with FDG-PET and CSF analysis. Surveillance brain MRI and CT scans are q3m for 1y, q4m x 1y, q6m x 1y, then annually. Results: 16 pts with a median age 67 (range 40-79) enrolled between June 2019 and July 2020. 15 (94%) pts had DLBCL comprising 9 (60%) non-GCB, 5 (33%) GCB, and 1 (7%) transformed from MZL. One pt had plasmablastic lymphoma. Eight (50%) pts had a MYC-rearrangement including 4 (25%) with both MYC and BCL2 or BCL6 rearrangements. Eight (50%) pts had isolated CNS disease and 8 (50%) had synchronous CNS and peripheral disease. All pts relapsed after a median of 2 (range 1-4) prior therapies and all (100%) pts received prior anthracycline. Seven pts (44%) had prior CNS prophylaxis and 8 pts (50%) had prior HD-MTX based salvage therapy. Toxicity was evaluated across 35 cycles. G3 and G4 neutropenia occurred in 49% and 29% of cycles, respectively, while febrile neutropenia occurred in 9% of cycles. The median (range) duration of neutropenia was 6 (1-13) days. Five (14%) cycles were complicated by ≥G3 infection, but no opportunistic infections (including Aspergillus) were observed. One pt developed a bacterial infection during cycle 1 and died. G3 and G4 thrombocytopenia occurred in 34% and 23% of cycles, respectively, and 1 pt developed G3 hematuria. G3 mucositis occurred in 9% of cycles and palmar-plantar-erythrodysesthesia led to dose reductions of liposomal doxorubicin in 5 (36%) pts. Of 15 pts who completed the 14d ibrutinib window and were evaluable, 8 (53%) were ibrutinib-responsive and 7 (47%) were ibrutinib-resistant (Figure 1). Clinical responses were concordant across anatomic compartments; of 8 pts with both CNS and peripheral disease, 5 (63%) responded to ibrutinib in both compartments while 3 (37%) did not respond in either compartment. All 8 ibrutinib responders had a non-GCB phenotype and six (75%) achieved CR. One died of treatment-related toxicity after a PR and 1 is still on therapy. Only two (29%) pts with ibrutinib-resistant tumors achieved PR and none have achieved CR. After a median follow-up of 5.1m, a landmark analysis starting after the ibrutinib window demonstrated the PFS for pts with ibrutinib-responsive compared to ibrutinib-resistant tumors was not reached vs. 0.9m (95% CI: 0.1-2m)(p=0.002)(Figure 2). Conclusions: Patients with SCNSL tumors that are ibrutinib-responsive achieve a high rate of complete response to TEDDI-R in both CNS and peripheral disease. Patients with tumors that are ibrutinib-resistant also respond poorly to TEDD-R. Toxicity is mainly hematologic, and no Aspergillus infections have occurred with the use of isavuconazole prophylaxis. Updated clinical results from this ongoing study (NCT03964090) and will be presented at the meeting. Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: ibrutinib for use in secondary cns lymphoma as part of a clinical trial

Phase 1 Study of Escalating Doses of Ibrutinib and Temozolomide, Etoposide, Liposomal Doxorubicin, Dexamethasone, Rituximab (TEDDI-R) with Isavuconazole for Relapsed and Refractory Primary CNS Lymphoma

Background: Primary DLBCL of the CNS (PCNSL) relies on chronic active B-cell receptor (BCR) signaling. Ibrutinib targets BCR signaling through BTK inhibition (BTKi), which may also impair innate immunity. We showed that ibrutinib and temozolomide, etoposide, liposomal doxorubicin, dexamethasone, rituximab (TEDDI-R) induces durable remissions in relapsed/refractory PCNSL but 7 (39%) pts developed Aspergillus infections without fungal prophylaxis. Newer triazoles are effective against Aspergillus but inhibit ibrutinib clearance through CYP3A4. Isavuconazole has less effect on CYP3A4 and less hepatotoxicity than voriconazole. We hypothesized that ibrutinib and isavuconazole could be safely co-administered in TEDDI-R and ameliorate the risk of Aspergillus while maintaining efficacy. We studied escalating doses of ibrutinib in TEDDI-R with isavuconazole to determine the safety profile, ibrutinib PK, and clinical activity in relapsed/refractory PCNSL. Methods: Pts with relapsed/refractory PCNSL, age ≥18, ECOG PS ≤2, and adequate organ function were enrolled. Previous BTKi, HIV, EBV+, and pregnancy were excluded. Pts had baseline MRI brain, FDG-PET brain and body, Ommaya placed, CSF with flow cytometry, and eye exam. Isavuconazole 200mg BID x 3d started prior to ibrutinib then 200mg daily. Three dose levels of ibrutinib (280mg, 420mg, 560mg) were given continuously through each cycle. Pts received up to 6 cycles of TEDDI-R with IT cytarabine. No one received maintenance or consolidation. If a DLT occurred in the first 3 pts at a given ibrutinib dose level, 3 more pts were treated before escalating. Full safety and PK data was reviewed after two dose levels prior to escalating. An expansion of 10 pts was planned at the highest ibrutinib dose level to confirm safety and clinical activity. Surveillance for fungal infections included chest CT mid-cycle 1 and after each cycle along with Beta-D glucan and aspergillus galactomannan in blood and CSF. Brain MRI was performed after cycles 1, 2, 4, and 6 to determine response and screen for CNS Aspergillus. All remissions by MRI were confirmed with FDG-PET and CSF analysis. Surveillance brain MRI were q3m for 1y, q4m x 1y, q6m x 1y, then annually. Primary objective was to identify the highest dose of ibrutinib safely co-administered with isavuconazole in TEDDI-R that achieves adequate PK concentrations. Results: 13 relapsed/refractory PCNSL pts enrolled between 11/2018 and 06/2020. 10 (77%) pts were male and the median age was 65 (range 46-77), including 3 pts ≥age 70. 13 (100%) pts had prior high-dose MTX, and 2 (15%) pts had prior autologous stem cell transplant (ASCT). Three evaluable pts received ibrutinib 280mg, 3 pts received ibrutinib 420mg, and 6 pts received ibrutinib 560mg. One pt in the 280mg cohort was not evaluable. Toxicity was evaluated in 13 pts across 49 cycles and the toxicity was mainly hematologic. G3 and G4 neutropenia occurred in 45% and 37% of cycles, respectively, while febrile neutropenia occurred in 8% of cycles. The median (range) duration of neutropenia was 4.5 (1-12) days. One pt with prior ASCT stopped after 4 cycles due to myelosuppression. Four (8%) cycles were complicated by ≥G3 infection, but no opportunistic infections (including Aspergillus) were observed. G3 and G4 thrombocytopenia occurred in 22% and 8% of cycles, respectively, and 1 pt developed melena with no overt GI bleeding. ≥G3 mucositis occurred in 6% of cycles and 1 patient stopped therapy after 5 cycles due to recurrent mucositis. Palmar-plantar-erythrodysesthesia led to dose reductions of liposomal doxorubicin in 9 (69%) pts, but only 1 G3 event occurred. Twelve pts were evaluable for response, and 11 (92%) pts have responded and all after receiving only 1 cycle (Figure 1). All 8 (100%) pts who have completed at least 4 cycles have achieved CR and the other 4 remain on therapy. Six (75%) pts who achieved CR remain in remission while 2 (25%) pts relapsed within 3 months of stopping therapy. After a median potential f/u of 5.2 months, the 1-year PFS is estimated at 60.0% (95% CI, 12.6-88.2) and the OS is 100%. Conclusions: Ibrutinib 560mg was safely co-administered with isavuconazole in TEDDI-R for relapsed/refractory PCNSL. No DLTs were observed, no cases of Aspergillus occurred, and no new safety signals. The first 8 (100%) patients who have completed therapy achieved complete response. Updated clinical results from this ongoing study (NCT02203526) will be presented at the meeting. Disclosures Lai: Abbvie: Consultancy; Agios: Consultancy; Jazz: Speakers Bureau; Macrogenics: Consultancy; Astellas: Speakers Bureau.

Associating Type 2 Diabetes Risk Factor Genes and FDG-PET Brain Metabolism in Normal Aging and Alzheimer's Disease.

Background: Several studies have linked type 2 diabetes (T2D) to an increased risk of developing Alzheimer’s disease (AD). This has led to an interest in using antidiabetic treatments for the prevention of AD. However, the underlying mechanisms explaining the relationship between T2D and AD have not been completely elucidated.Objective: Our objective was to examine cerebral 18F-fluorodeoxyglucose (FDG) uptake during normal aging and in AD patients in regions associated with diabetes genetic risk factor expression to highlight which genes may serve as potential targets for pharmaceutical intervention.Methods: We calculated regional glucose metabolism differences in units of standardized uptake values (SUVR) for 386 cognitively healthy adults and 335 clinically probable AD patients. We then proceeded to extract gene-expression data from the publicly available Allen Human Brain Atlas (HBA) database. We used the nearest genes to 46 AD- and T2D-associated SNPs previously identified in the literature, and mapped their expression to the same 34 cortical regions in which we calculated SUVRs. SNPs with a donor consistency of 0.40 or greater were selected for further analysis. We evaluated the associations between SUVR and gene-expression across the brain.Results: Of the 46 risk-factor genes, 15 were found to be significantly correlated with FDG-PET brain metabolism in healthy adults and probable AD patients after correction for multiple comparisons. Using multiple regression, we found that five genes explained a total of 72.5% of the SUVR variance across the healthy adult group regions, while four genes explained a total of 79.3% of the SUVR variance across the probable AD group regions. There were significant differences in whole-brain SUVR as a function of allele frequencies for two genes.Conclusions: These results highlight the association between risk factor genes for T2D and regional glucose metabolism during both normal aging and in probable AD. Highlighted genes were associated with mitochondrial stability, vascular maintenance, and glucose intolerance. Pharmacological intervention of these pathways has the potential to improve glucose metabolism during normal again as well as in AD patients.

Impaired metabolic brain networks associated with neurotransmission systems in the α-synuclein spectrum

IntroductionWhile the involvement of multiple neurotransmitter systems in α-synucleinopathies is reported, a comprehensive study on their metabolic connectivity reconfiguration in the preclinical and clinical disease-spectrum is lacking. We aimed to investigate shared and disease-specific neural vulnerabilities of the nigro-striato-cortical dopaminergic, noradrenergic and cholinergic networks within the α-synuclein-spectrum, by means of metabolic connectivity approach. MethodsWe collected 34 polysomnography-confirmed isolated REM sleep behaviour disorder (iRBD) subjects, 29 idiopathic Parkinson's disease (PD) patients without dementia, 30 patients with probable dementia with Lewy bodies (DLB), and 50 healthy controls for comparisons. Neurotransmission networks' analyses were performed through multivariate partial correlations based on FDG-PET brain metabolic data. ResultsWe found: a) the nigro-striato-cortical dopaminergic network with a limited reconfiguration in individuals with iRBD, but moderate-to-severe alterations in patients with DLB and PD; b) an extended connectivity alteration of the noradrenergic network in all groups; c) changes within the cholinergic networks connectivity in the whole disease-spectrum, with some differences: PD with only moderate connectivity reconfiguration and DLB with the most severe alterations, some of these shared with iRBD. ConclusionsSynucleinopathies can be considered multisystem disorders, with common and disease-specific neurotransmission networks reconfigurations. The present findings indicate dopaminergic connectivity alterations only when associated with parkinsonism, a very early involvement of noradrenergic networks, occurring in both the iRBD and in symptomatic PD/DLB patients and cholinergic alterations with disease-specific vulnerabilities shared by iRBD and DLB. The latter finding may represent an early biomarker of disease progression to dementia.

Metabolic scoring in autoimmune epilepsy-Should APE scores be modified?

We evaluate the potential utility of F-18 FDG-PET in addition to MRI in the diagnostic work-up of patients with autoimmune epilepsy (AE) and propose the inclusion of functional imaging in the antibody prevalence in epilepsy (APE) scoring system. This was a retrospective analysis in 60 patients, diagnosed and treated for AE, of whom 40 were antibody negative (presumed AE) and 20 were antibody positive (definitive AE). All patients had undergone a dedicated brain and whole body FDG-PET in the department of Nuclear Medicine. In the antibody negative group, MRI supported a diagnosis of AE in 23 patients. Both MRI and PET were indicative in 12 cases, and standalone PET was positive in 8. While MRI alone was diagnostic in 57% (23/40), the combined yield of both modalities was 77% (31/40). When PET scores were added to assign the APE score in MRI negative cases, average APE score was 5.4. In the antibody positive group, MRI supported the diagnosis of AE in 7 patients. Both MRI and PET were positive in 4 patients and standalone PET was positive in 5 patients. While MRI alone was diagnostic in 35% (7/20), the combined yield of both modalities was 60% (12/20). When PET scores were added to assign the APE score in MRI negative cases, average APE score was 6.1. The inclusion of metabolic information from PET distinctly improved (the sensitivity of) APE scores to predict autoimmune origin even in antibody negative cases. A larger prospective study of similar type could justify adoption of FDG-PET into the standard diagnostic procedure.

Diagnostic Impact of Cerebrospinal Fluid Biomarkers in Atypical Dementias in Canada.

In Canada, standard dementia workup consists of clinical, neurological, and cognitive evaluation, as well as structural brain imaging. For atypical dementia presentations, additional FDG-PET brain imaging is recommended. Cerebrospinal fluid (CSF) biomarkers have recently been proposed as the gold standard for in vivo detection of Alzheimer's disease (AD) pathophysiology (NIA-AA research framework, 2018). As clinical implementation of CSF assessment is still limited in Canada, the present study assessed its impact on diagnostic accuracy in atypical neurodegenerative disorders in the clinical practice. This retrospective clinical chart review included patients with cognitive complaints who underwent lumbar puncture (LP) in addition to the standard diagnostic workup. CSF analysis determined the presence of biological AD based on reduced amyloid-β42-to-total-tau index (ATI) and increased phosphorylated-tau (p-tau) levels. CSF-based diagnoses were compared to standard workup and FDG-PET-based diagnoses. A total of 28 patients with atypical dementia presentations were included in the present study after evaluation for cognitive complaints at a specialized dementia clinic between November 2017 and July 2019. CSF analysis changed or better specified the initial clinical diagnosis in 43.0% of cases (alternative diagnosis revealed in 25% and excluded in 18%). In patients with additional FDG-PET imaging (n = 23), FDG-PET and CSF-based diagnosis did not correspond in 35% of patients, even though FDG-PET appeared to increase diagnostic accuracy compared to the initial clinical diagnosis. CSF biomarkers improved diagnostic accuracy in atypical cognitively-impaired patients beyond standard workup and FDG-PET imaging. These results support CSF analysis implementation for atypical dementias in Canada, in addition to the standard diagnostic workup.

Association between the Onset of Idiopathic Normal Pressure Hydrocephalus Symptoms and Reduced Default Mode Network Connectivity

Objective: The aim was to examine the association between connectivity changes in the default mode network (DMN) and the progression of idiopathic normal pressure hydrocephalus (iNPH). Methods: We retrospectively recruited cases of preclinical and clinical iNPH from 2,196 patients who had received whole-body ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) scanning. We included 31 cases with asymptomatic ventriculomegaly with features of iNPH on MRI (AVIM; reported as preclinical iNPH) and 12 with iNPH. We performed a voxel-based analysis of the brain FDG-PET images of the AVIM and iNPH groups as well as for each background-matched normal control (NC) group, using Statistical Parametric Mapping 12. Volume of interest (VOI)-based analysis was also performed. We set the VOI as the region from the precuneus to the posterior cingulate cortices (PCC), and compared the mean regional standardized uptake value ratio (SUVR) between the AVIM and iNPH group FDG-PET/CT images and each corresponding NC group. Results: The voxel-based analysis showed a greater decreased FDG uptake in the PCC in the iNPH group than in the AVIM group. The VOI-based analysis revealed no significant difference in the mean SUVR of the AVIM group and the corresponding NC group, but that of the iNPH group was significantly lower than that of its corresponding NC group. Conclusions: DMN connectivity was reduced in the clinical iNPH group but not in the preclinical group. These data suggest that alterations in the functional connectivity of the DMN are related to the onset of iNPH symptoms.

Intensity normalization methods in brain FDG-PET quantification

BackgroundThe lack of standardization of intensity normalization methods and its unknown effect on the quantification output is recognized as a major drawback for the harmonization of brain FDG-PET quantification protocols. The aim of this work is the ground truth-based evaluation of different intensity normalization methods on brain FDG-PET quantification output. MethodsRealistic FDG-PET images were generated using Monte Carlo simulation from activity and attenuation maps directly derived from 25 healthy subjects (adding theoretical relative hypometabolisms on 6 regions of interest and for 5 hypometabolism levels). Single-subject statistical parametric mapping (SPM) was applied to compare each simulated FDG-PET image with a healthy database after intensity normalization based on reference regions methods such as the brain stem (RRBS), cerebellum (RRC) and the temporal lobe contralateral to the lesion (RRTL), and data-driven methods, such as proportional scaling (PS), histogram-based method (HN) and iterative versions of both methods (iPS and iHN). The performance of these methods was evaluated in terms of the recovery of the introduced theoretical hypometabolic pattern and the appearance of unspecific hypometabolic and hypermetabolic findings. ResultsDetected hypometabolic patterns had significantly lower volumes than the introduced hypometabolisms for all intensity normalization methods particularly for slighter reductions in metabolism . Among the intensity normalization methods, RRC and HN provided the largest recovered hypometabolic volumes, while the RRBS showed the smallest recovery. In general, data-driven methods overcame reference regions and among them, the iterative methods overcame the non-iterative ones. Unspecific hypermetabolic volumes were similar for all methods, with the exception of PS, where it became a major limitation (up to 250 cm3) for extended and intense hypometabolism. On the other hand, unspecific hypometabolism was similar far all methods, and usually solved with appropriate clustering. ConclusionsOur findings showed that the inappropriate use of intensity normalization methods can provide remarkable bias in the detected hypometabolism and it represents a serious concern in terms of false positives. Based on our findings, we recommend the use of histogram-based intensity normalization methods. Reference region methods performance was equivalent to data-driven methods only when the selected reference region is large and stable.

Clinical, MRI and 18F-FDG-PET/CT analysis of progressive supranuclear palsy

BackgroundProgressive supranuclear palsy (PSP) is a kind of neurodegenerative disease. In the present study, the clinical and magnetic resonance imaging (MRI) features of PSP were analyzed, and fluorodeoxyglucose positron emission tomography (FDG PET) brain imaging was performed to preliminarily explore the characteristics of cerebral glucose metabolism, so as to make a more accurate and differential diagnosis. MethodsIn accordance with the diagnostic criteria, the clinical symptoms, the unified Parkinson’s disease rating scale (UPDRS), the mini-mental state examination (MMSE), the activities of daily living (ADL), and the magnetic resonance image (MRI) of 19 patients with PSP were examined and FDG-PET brain imaging was performed. Visual analysis and statistical parameter diagram were used to analyze the characteristics. ResultsConcerning the clinical characteristics, 84.21% of the patients with PSP had early recurrent falls, 63.15% had vertical supranuclear ophthalmoplegia, and 47.37% had symptoms of dementia. The MRI scans showed that 57.89% of the patients had a “hummingbird” sign in the middle sagittal position. The FDG-PET imaging indicated that glucose metabolism in the midbrain and frontal lobe was decreased in patients with PSP. ConclusionsStudying the clinical and MRI features of patients with PSP can be helpful in the diagnosis, especially as some signs could be found in the early stage by FDG PET, enhancing early diagnosis and differentiation.

Utility of FDG-PET in diagnosis of Alzheimer-related TDP-43 proteinopathy.

To evaluate FDG-PET as an antemortem diagnostic tool for Alzheimer-related TAR DNA-binding protein of 43 kDa (TDP-43) proteinopathy. We conducted a cross-sectional neuroimaging-histologic analysis of patients with antemortem FDG-PET and postmortem brain tissue from the Mayo Clinic Alzheimer's Disease Research Center and Study of Aging with Alzheimer spectrum pathology. TDP-43-positive status was assigned when TDP-43-immunoreactive inclusions were identified in the amygdala. Statistical parametric mapping (SPM) analyses compared TDP-43-positive (TDP-43[+]) with TDP-43-negative cases (TDP-43[-]), correcting for field strength, sex, Braak neurofibrillary tangle, and neuritic plaque stages. Cross-validated logistic regression analyses were used to determine whether regional FDG-PET values predict TDP-43 status. We also assessed the ratio of inferior temporal to medial temporal (IMT) metabolism as this was proposed as a biomarker of hippocampal sclerosis. Of 73 cases, 27 (37%) were TDP-43(+), of which 6 (8%) had hippocampal sclerosis. SPM analysis showed TDP-43(+) cases having greater hypometabolism of medial temporal, frontal superior medial, and frontal supraorbital (FSO) regions (p unc < 0.001). Logistic regression analysis showed only FSO and IMT to be associated with TDP-43(+) status, identifying up to 81% of TDP-43(+) cases (p < 0.001). An IMT/FSO ratio was superior to the IMT in discriminating TDP-43(+) cases: 78% vs 48%, respectively. Alzheimer-related TDP-43 proteinopathy is associated with hypometabolism in the medial temporal and frontal regions. Combining FDG-PET measures from these regions may be useful for antemortem prediction of Alzheimer-related TDP-43 proteinopathy. This study provides Class II evidence that hypometabolism in the medial temporal and frontal regions on FDG-PET is associated with Alzheimer-related TDP-43 proteinopathy.

CSF p-tau/Aβ42 ratio and brain FDG-PET may reliably detect MCI "imminent" converters to AD.

To know whether mild cognitive impairment (MCI) patients will develop Alzheimer's disease (AD) dementia in very short time or remain stable is of crucial importance, also considering new experimental drugs usually tested within very short time frames. Here we combined cerebrospinal fluid (CSF) AD biomarkers and a neurodegeneration marker such as brain FDG-PET to define an objective algorithm, suitable not only to reliably detect MCI converters to AD dementia but also to predict timing of conversion. We included 77 consecutive MCI patients with neurological/neuropsychological assessment, brain 18F-FDG-PET and CSF analysis available at diagnosis and a neuropsychological/neurological evaluation every 6months for a medium- to a long-term follow-up (at least 2 and up to 8years). Binomial logistic regression models and Kaplan-Meier survival analyses were performed to determine the best biomarker (or combination of biomarkers) in detecting MCI converters to AD dementia and then, among the converters, those who converted in short time frames. Thirty-five out of 77 MCI patients (45%) converted to AD dementia, with an average conversion time since MCI diagnosis of 26.07months. CSF p-tau/Aβ42 was the most accurate predictor of conversion from MCI to AD dementia (82.9% sensitivity; 90% specificity). CSF p-tau/Aβ42 and FDG-PET-positive MCIs converted to AD dementia significantly earlier than the CSF-positive-only MCIs (median conversion time, 17.1 vs 31.3months). CSF p-tau/Aβ42 ratio and brain FDG-PET may predict both occurrence and timing of MCI conversion to full-blown AD dementia. MCI patients with both biomarkers suggestive for AD will likely develop an AD dementia shortly, thus representing the ideal target for any new experimental drug requiring short periods to be tested for.

Combined brain and spinal FDG PET allows differentiation between ALS and ALS mimics.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder with on average a 1-year delay between symptom onset and diagnosis. Studies have demonstrated the value of [18F]-FDG PET as a sensitive diagnostic biomarker, but the discriminatory potential to differentiate ALS from patients with symptoms mimicking ALS has not been investigated. We investigated the combination of brain and spine [18F]-FDG PET-CT for differential diagnosis between ALS and ALS mimics in a real-life clinical diagnostic setting. Patients with a suspected diagnosis of ALS (n = 98; 64.8 ± 11years; 61M) underwent brain and spine [18F]-FDG PET-CT scans. In 62 patients, ALS diagnosis was confirmed (67.8 ± 10years; 35M) after longitudinal follow-up (average 18.1 ± 8.4months). In 23 patients, another disease was diagnosed (ALS mimics, 60.9 ± 12.9years; 17M) and 13 had a variant motor neuron disease, primary lateral sclerosis (PLS; n = 4; 53.6 ± 2.5years; 2M) and progressive muscular atrophy (PMA; n = 9; 58.4 ± 7.3years; 7M). Spine metabolism was determined after manual and automated segmentation. VOI- and voxel-based comparisons were performed. Moreover, a support vector machine (SVM) approach was applied to investigate the discriminative power of regional brain metabolism, spine metabolism and the combination of both. Brain metabolism was very similar between ALS mimics and ALS, whereas cervical and thoracic spine metabolism was significantly different (in standardised uptake values; cervical: ALS 2.1 ± 0.5, ALS mimics 1.9 ± 0.4; thoracic: ALS 1.8 ± 0.3, ALS mimics 1.5 ± 0.3). As both brain and spine metabolisms were very similar between ALS mimics and PLS/PMA, groups were pooled for accuracy analyses. Mean discrimination accuracy was 65.4%, 80.0% and 81.5%, using only brain metabolism, using spine metabolism and using both, respectively. The combination of brain and spine FDG PET-CT with SVM classification is useful as discriminative biomarker between ALS and ALS mimics in a real-life clinical setting.

PSEN1 variants in Korean patients with clinically suspicious early-onset familial Alzheimer\u2019s disease

Pathogenic variants in the PSEN1 gene are known to be the most common cause of early-onset Alzheimer’s disease but there are few data on the frequency and spectrum of PSEN1 variants in Korea. In this study, we investigated PSEN1 variants in a consecutive series of clinically suspicious early-onset familial AD (EOFAD) Korean patients and their clinical characteristics and imaging findings. From January 2007 to December 2013, EOFAD patients with very early onset AD (<50 yr), early onset AD (<60 yr) with two or more relatives with AD, and early onset AD (<60 yr) with one or more first-degree relatives with very early onset AD (<50 yr) were enrolled in this study. Sequence analysis of the PSEN1 gene was performed by Sanger sequencing. Neuroimaging data and conventional brain MRIs and FDG-PET and/or [11C] PiB-PET scans were analyzed in patients with PSEN1 variants. Among the 28 patients with EOFAD, six (21.4%, 6/28) patients had pathogenic or likely pathogenic variants in the PSEN1 gene. Two pathogenic variants were p.Glu120Lys and p.Ser170Phe and four likely pathogenic variants were p.Thr119Ile, p.Tyr159Cys, p.Leu282Pro, and p.Ala285Ser. Two patients had variants of unknown significance, p.Tyr389His and p.Tyr389Ser. EOFAD patients with PSEN1 variants showed early AD onset, frequent visuospatial dysfunction, movement disorders, and rapid disease progression. Brain MRIs revealed diffuse cortical atrophy, including parietal lobe atrophy, and/or hippocampal atrophy. FDG-PET scans also revealed significant hypometabolism in the bilateral temporo-parietal regions. Our findings provide insight to better understand the genetic background of Korean EOFAD patients.

Impairment of Everyday Spatial Navigation Abilities in Mild Cognitive Impairment Is Weakly Associated with Reduced Grey Matter Volume in the Medial Part of the Entorhinal Cortex.

Research in rodents identified specific neuron populations encoding information for spatial navigation with particularly high density in the medial part of the entorhinal cortex (ERC), which may be homologous with Brodmann area 34 (BA34) in the human brain. The aim of this study was to test whether impaired spatial navigation frequently occurring in mild cognitive impairment (MCI) is specifically associated with neurodegeneration in BA34. The study included baseline data of MCI patients enrolled in the Alzheimer's Disease Neuroimaging Initiative with high-resolution structural MRI, brain FDG PET, and complete visuospatial ability scores of the Everyday Cognition test (VS-ECog) within 30 days of PET. A standard mask of BA34 predefined in MNI space was mapped to individual native space to determine grey matter volume and metabolic activity in BA34 on MRI and on (partial volume corrected) FDG PET, respectively. The association of the VS-ECog sum score with grey matter volume and metabolic activity in BA34, APOE4 carrier status, age, education, and global cognition (ADAS-cog-13 score) was tested by linear regression. BA28, which constitutes the lateral part of the ERC, was used as control region. The eligibility criteria led to inclusion of 379 MCI subjects. The VS-ECog sum score was negatively correlated with grey matter volume in BA34 (β= -0.229, p = 0.022) and age (β= -0.124, p = 0.036), and was positively correlated with ADAS-cog-13 (β= 0.175, p = 0.003). None of the other predictor variables contributed significantly. Impairment of spatial navigation in MCI is weakly associated with BA34 atrophy.

Image reconstruction methods affect software-aided assessment of pathologies of [18F]flutemetamol and [18F]FDG brain-PET examinations in patients with neurodegenerative diseases

PurposeTo assess how some of the new developments in brain positron emission tomography (PET) image reconstruction affect quantitative measures and software-aided assessment of pathology in patients with neurodegenerative diseases. MethodsPET data were grouped into four cohorts: prodromal Alzheimer’s disease patients and controls receiving [18F]flutemetamol, and neurodegenerative disease patients and controls receiving [18F]FDG PET scans. Reconstructed images were obtained by ordered-subsets expectation maximization (OSEM; 3 iterations (i), 16/34 subsets (s), 3/5-mm filter, ±time-of-flight (TOF), ±point-spread function (PSF)) and block-sequential regularized expectation maximization (BSREM; TOF, PSF, β-value 75–300). Standardized uptake value ratios (SUVR) and z-scores were calculated (CortexID Suite, GE Healthcare) using cerebellar gray matter, pons, whole cerebellum and whole brain as reference regions. ResultsIn controls, comparable results to the normal database were obtained with OSEM 3i/16 s 5-mm reconstruction. TOF, PSF and BSREM either increased or decreased the relative uptake difference to the normal subjects’ database within the software, depending on the tracer and chosen reference area, i.e. resulting in increased absolute z-scores. Normalizing to pons and whole brain for [18F]flutemetamol and [18F]FDG, respectively, increased absolute differences between reconstructions methods compared to normalizing to cerebellar gray matter and whole cerebellum when applying TOF, PSF and BSREM. ConclusionsSoftware-aided assessment of patient pathologies should be used with caution when employing other image reconstruction methods than those used for acquisition of the normal database.