Impact of 18F-FET PET/MRI on Clinical Management of Brain Tumor Patients.

Multiparametric PET/MRI with the amino-acid analog O-(2-18F-fluoroethyl)-l-tyrosine (18F-FET) enables the simultaneous assessment of molecular, morphologic, and functional brain tumor characteristics. Although it is considered the most accurate noninvasive approach in brain tumors, its relevance for patient management is still under debate. Here, we report the diagnostic performance of 18F-FET PET/MRI and its impact on clinical management in a retrospective patient cohort. Methods: We retrospectively analyzed brain tumor patients who underwent 18F-FET PET/MRI between 2017 and 2018. 18F-FET PET/MRI examinations were indicated clinically because of equivocal standard imaging results or the clinical course. Histologic confirmation or clinical and standard imaging follow-up served as the reference standard. We evaluated 18F-FET PET/MRI accuracy in identifying malignancy in untreated suspected lesions (category, new diagnosis) and true progression during adjuvant treatment (category, detection of progression) in a clinical setting. Using multiple regression, we also estimated the contribution of single modalities to produce an optimal PET/MRI outcome. We assessed the recommended and applied therapies before and after 18F-FET PET/MRI and noted whether the treatment changed on the basis of the 18F-FET PET/MRI outcome. Results: We included 189 patients in the study. 18F-FET PET/MRI allowed the identification of malignancy at new diagnosis with an accuracy of 85% and identified true progression with an accuracy of 93%. Contrast enhancement, 18F-FET PET uptake, and tracer kinetics were the major contributors to an optimal PET/MRI outcome. In the previously equivocal patients, 18F-FET PET/MRI changed the clinical management in 33% of the untreated lesions and 53% of the cases of tumor progression. Conclusion: Our results suggest that 18F-FET PET/MRI helps clarify equivocal conditions and profoundly supports the clinical management of brain tumor patients. The optimal modality setting for 18F-FET PET/MRI and the clinical value of a simultaneous examination need further exploration. At a new diagnosis, multiparametric 18F-FET PET/MRI might help prevent unnecessary invasive procedures by ruling out malignancy; however, adding static 18F-FET PET to an already existing MRI examination seems to be of equal value. At detection of progression, multiparametric 18F-FET PET/MRI may increase therapy effectiveness by distinguishing between tumor progression and therapy-related imaging alterations.

Incidental findings of typical iNPH imaging signs in asymptomatic subjects with subclinical cognitive decline.

BACKGROUND: The etiology of idiopathic normal pressure hydrocephalus (iNPH) remains unclear. Little is known about the pre-symptomatic stage. This study aimed to investigate the association of neuropsychological data with iNPH-characteristic imaging changes compared to normal imaging and unspecific atrophy in a healthy population. METHODS: We extracted data from the community-dwelling Austrian Stroke Prevention Family Study (ASPS-Fam) database (2006-2010). All subjects underwent a baseline and identical follow-up examination after 3-5 years with MR imaging and an extensive neuropsychological test battery (Trail Making Test B, short physical performance balance, walking speed, memory, visuo-practical skills, composite scores of executive function and g-factor). We categorized the subjects into "iNPH"-associated, non-specific "atrophy," and "normal" based on the rating of different radiological cerebrospinal fluid (CSF) space parameters. We noted how the categories developed over time. We assessed the association of the image categories with the neuropsychological data, different demographic, and lifestyle parameters (age, sex, education, alcohol intake, arterial hypertension, hypercholesterolemia), and the extent of white matter hyperintensities. We investigated whether neuropsychological data associated with the image categories were independent from other parameters as confounders. RESULTS: One hundred and thirteen subjects, aged 50-70 years, were examined. The imaging category "iNPH" was only present at follow-up. A third of subjects with "atrophy" at baseline changed to the category "iNPH" at follow-up. More white matter hyperintensities (WMH) were present in later "iNPH" subjects. Subjects with "iNPH" performed worse than "normal" subjects on executive function (p = 0.0118), memory (p = 0.0109), and Trail Making Test B (TMT-B. p < 0.0001). Education, alcohol intake, diabetes, arterial hypertension, and hypercholesterolemia had no effect. Age, number of females, and the extent of white matter hyperintensities were higher in "iNPH" than in "normal" subjects but did not significantly confound the neuropsychological results. CONCLUSIONS: Apparent asymptomatic subjects with "iNPH" imaging characteristics presented with subclinical cognitive decline and showed worse executive function, memory, and TMT-B results than "normal" subjects. WMH seem to play a role in the etiology before ventriculomegaly. Clinical screening of individuals with incidental iNPH-characteristic imaging and conspicuous results sof these neurocognitive tests needs further validation.

Structured Reporting of Acute Ischemic Stroke - Consensus-Based Reporting Templates for Non-Contrast Cranial Computed Tomography, CT Angiography, and CT Perfusion. / Strukturierte Befundung beim ischämischen Schlaganfall: Konsensbasierte Befundvorlagen für die native Computertomografie, CT-Angiografie und CT-Perfusion des Neurokraniums.

PURPOSE: Structured reporting is an essential step in establishing standardized quality standards in diagnostic radiology. The German Society of Radiology and the German Society of Neuroradiology aim to provide templates for the structured reporting of different radiological examinations. METHOD: The Information Technology working group of the German Society of Radiology developed structured templates for the radiological reporting of different indications in consensus with specialist support by experts. RESULTS: We present a template for the structured reporting of examinations of patients with acute ischemic stroke by non-contrast computed tomography, CT angiography, and CT perfusion. This template is provided on the website www.befundung.drg.de for free use. CONCLUSION: Implementation of the structured template may increase quality and provide a minimum standard for radiological reports in patients with acute ischemic stroke. KEY POINTS: · The German Society of Radiology and the German Society of Neuroradiology are providing support for the development of structured templates in German.. · We present a template for the structured reporting of examinations of patients with acute ischemic stroke by non-contrast computed tomography, CT angiography, and CT perfusion. This template is provided on the website www.befundung.drg.de for free use.. · Implementation of the structured template may increase quality and provide a minimum standard for radiological reports in patients with acute ischemic stroke.. CITATION FORMAT: · Brendle C, Bender B, Selo N et al. Structured Reporting of Acute Ischemic Stroke - Consensus-Based Reporting Templates for Non-Contrast Cranial Computed Tomography, CT Angiography, and CT Perfusion. Fortschr Röntgenstr 2021; 193: 1315 - 1317.

Glioma-Specific Diffusion Signature in Diffusion Kurtosis Imaging.

PURPOSE: This study aimed to assess the relationship between mean kurtosis (MK) and mean diffusivity (MD) values from whole-brain diffusion kurtosis imaging (DKI) parametric maps in preoperative magnetic resonance (MR) images from 2016 World Health Organization Classification of Tumors of the Central Nervous System integrated glioma groups. METHODS: Seventy-seven patients with histopathologically confirmed treatment-naïve glioma were retrospectively assessed between 1 August 2013 and 30 October 2017. The area on scatter plots with a specific combination of MK and MD values, not occurring in the healthy brain, was labeled, and the corresponding voxels were visualized on the fluid-attenuated inversion recovery (FLAIR) images. Reversely, the labeled voxels were compared to those of the manually segmented tumor volume, and the Dice similarity coefficient was used to investigate their spatial overlap. RESULTS: A specific combination of MK and MD values in whole-brain DKI maps, visualized on a two-dimensional scatter plot, exclusively occurs in glioma tissue including the perifocal infiltrative zone and is absent in tissue of the normal brain or from other intracranial compartments. CONCLUSIONS: A unique diffusion signature with a specific combination of MK and MD values from whole-brain DKI can identify diffuse glioma without any previous segmentation. This feature might influence artificial intelligence algorithms for automatic tumor segmentation and provide new aspects of tumor heterogeneity.

Longitudinal Reproducibility of CO2-Triggered BOLD MRI for the Hemodynamic Evaluation of Adult Patients with Moyamoya Angiopathy.

BACKGROUND AND PURPOSE: Hemodynamic evaluation of moyamoya patients is crucial to decide the treatment strategy. Recently, CO2-triggered BOLD MRI has been shown to be a promising tool for the hemodynamic evaluation of moyamoya patients. However, the longitudinal reliability of this technique in follow-up examinations is unknown. This study aims to analyze longitudinal follow-up data of CO2-triggered BOLD MRI to prove the reliability of this technique for long-term control examinations in moyamoya patients. METHODS: Longitudinal CO2 BOLD MRI follow-up examinations of moyamoya patients with and without surgical revascularization have been analyzed for all 6 vascular territories retrospectively. If revascularization was performed, any directly (by the disease or the bypass) or indirectly (due to change of collateral flow after revascularization) affected territory was excluded based on angiography findings (group 1). In patients without surgical revascularization between the MRI examinations, all territories were analyzed (group 2). RESULTS: Eighteen moyamoya patients with 39 CO2 BOLD MRI examinations fulfilled the inclusion criteria. The median follow-up between the 2 examinations was 12 months (range 4-29 months). For 106 vascular territories analyzed in group 1, the intraclass correlation coefficient was 0.784, p < 0.001, and for group 2 (84 territories), it was 0.899, p < 0.001. Within the total follow-up duration of 140 patient months, none of the patients experienced a new stroke. CONCLUSIONS: CO2 BOLD MRI is a promising tool for mid- and long-term follow-up examinations of cerebral hemodynamics in moyamoya patients. Systematic prospective evaluation is required prior to making it a routine examination.

Dynamic Susceptibility Perfusion Imaging for Differentiating Progressive Disease from Pseudoprogression in Diffuse Glioma Molecular Subtypes.

RATIONALE AND OBJECTIVES: Advanced adjuvant therapy of diffuse gliomas can result in equivocal findings in follow-up imaging. We aimed to assess the additional value of dynamic susceptibility perfusion imaging in the differentiation of progressive disease (PD) from pseudoprogression (PsP) in different molecular glioma subtypes. MATERIALS AND METHODS: 89 patients with treated diffuse glioma with different molecular subtypes (IDH wild type (Astro-IDHwt), IDH mutant astrocytomas (Astro-IDHmut) and oligodendrogliomas), and tumor-suspect lesions on post-treatment follow-up imaging were classified into two outcome groups (PD or PsP) retrospectively by histopathology or clinical follow-up. The relative cerebral blood volume (rCBV) was assessed in the tumor-suspect FLAIR and contrast-enhancing (CE) lesions. We analyzed how a multilevel classification using a molecular subtype, the presence of a CE lesion, and two rCBV histogram parameters performed for PD prediction compared with a decision tree model (DTM) using additional rCBV parameters. RESULTS: The PD rate was 69% in the whole cohort, 86% in Astro-IDHwt, 52% in Astro-IDHmut, and 55% in oligodendrogliomas. In the presence of a CE lesion, the PD rate was higher with 82%, 94%, 59%, and 88%, respectively; if there was no CE lesion, however, the PD rate was only 44%, 60%, 40%, and 33%, respectively. The additional use of the rCBV parameters in the DTM yielded a prediction accuracy for PD of 99%, 100%, 93%, and 95%, respectively. CONCLUSION: Utilizing combined information about the molecular tumor type, the presence or absence of CE lesions and rCBV parameters increases PD prediction accuracy in diffuse glioma.

Determinants of activity of brown adipose tissue in lymphoma patients.

The determinants of brown adipose tissue (BAT) activity are not yet known in detail but might serve as future therapeutic targets against obesity and the metabolic syndrome. We analyzed 235 datasets of lymphoma patients with two PET/CT examinations at different time points retrospectively. We assessed the anthropometric characteristics, features related to the metabolic syndrome, thyroid dysfunction, season of the PET/CT examination, weight change, prior cancer history, lymphoma subgroups, disease activity, and specific lymphoma-related therapies, and evaluated their association with BAT activity. We found BAT activity in 12% of all examinations, and the incidence of BAT activity after initially negative examinations was 10%. In multivariate regression analysis, the prevalence of BAT activity was associated with age, body mass index, sex, the season of the examination, diabetes mellitus, arterial hypertension, and medication on the beta-receptors. New BAT activity arose more often in patients without preceding lymphoma-related therapy. No specific medication was associated with BAT activity. In conclusion, this study confirms the potential connection of BAT with the metabolic syndrome. Preceding lymphoma-related therapy might have an inhibitory effect on the recruitment of BAT.

Papillary tumor of the pineal region: a single-center experience.

Papillary tumor of the pineal region (PTPR) is a rare entity. Its clinical presentation is diverse, and establishing an accurate and timely diagnosis may be challenging. Treatment recommendations are based on the evidence level of case series. Recently, several key advances have been made for immunohistochemical characterization, molecular diagnostics, and neurosurgical treatment of PTPR. Here, we describe our single-center experience.

Association of dynamic susceptibility magnetic resonance imaging at initial tumor diagnosis with the prognosis of different molecular glioma subtypes.

PURPOSE: The updated 2016 CNS World Health Organization classification differentiates three main groups of diffuse glioma according to their molecular characteristics: astrocytic tumors with and without isocitrate dehydrogenase (IDH) mutation and 1p/19q co-deleted oligodendrogliomas. The present study aimed to determine whether dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) is an independent prognostic marker within the molecular subgroups of diffuse glioma. METHODS: Fifty-six patients with treatment-naive gliomas and advanced preoperative MRI examination were assessed retrospectively. The mean and maximal normalized cerebral blood volume values from DSC-MRI within the tumors were measured. Optimal cutoff values for the 1-year progression-free survival (PFS) were defined, and Kaplan-Meier analyses were performed separately for the three glioma subgroups. RESULTS: IDH wild-type astrocytic tumors had a higher mean and maximal perfusion than IDH-mutant astrocytic tumors and oligodendrogliomas. Patients with IDH wild-type astrocytic tumors and a low mean or maximal perfusion had a significantly shorter PFS than patients of the same group with high perfusion (p = 0.0159/0.0112). Furthermore, they had a significantly higher risk for early progression (hazard ratio = 5.6/5.1). This finding was independent of the methylation status of O6-methylguanin-DNA-methyltransferase and variations of the therapy. Within the groups of IDH-mutant astrocytic tumors and oligodendrogliomas, the PFS of low and highly perfused tumors did not differ. CONCLUSION: High perfusion upon initial diagnosis is not compellingly associated with worse short-term prognosis within the different molecular subgroups of diffuse glioma. Particularly, the overall highly perfused group of IDH wild-type astrocytic tumors contains tumors with low perfusion but unfavorable prognosis.

Impact of diverse chemotherapeutic agents and external factors on activation of brown adipose tissue in a large patient collective.

Increased activity of brown adipose tissue (BAT) activity in adults is thought to prevent obesity. Therefore, regulators of BAT activity might serve as anti-obesity therapy in future, but are not investigated thoroughly up to now. In our study, we assessed retrospectively the association of BAT activity with several external factors and diverse chemotherapeutic and immunosuppressive agents in a collective of 702 patients. The patients underwent at least two clinically indicated PET/CT examinations in the course of different oncological and inflammatory diseases. BAT activity was identified according to predefined PET/CT criteria in all examinations. In multivariate analysis, the type of disease, the disease activity and the therapeutic regimen did not influence BAT activity. In contrast, sex and age were confirmed as independent factors for BAT activity. For the association of therapeutic agents with BAT activity, we examined 53 different disease-related agents, which were applied to patients without initial BAT activity between their PET/CT examinations. Out of these, cytarabine therapy was significantly associated with increased new onset of BAT activity. Cytarabine is a therapeutic agent for lymphoma patients. Further targeted studies might investigate the usefulness of Cytarabine serving as possible therapeutic approach against obesity via BAT regulation.

Diffusion kurtosis imaging histogram parameter metrics predicting survival in integrated molecular subtypes of diffuse glioma: An observational cohort study.

PURPOSE: The aim of the study was to assess the predictive value of preoperatively assessed diffusion kurtosis imaging (DKI) metrics as prognostic factors in the 2016 World Health Organization Classification of Tumors of the Central Nervous System integrated glioma groups. MATERIAL AND METHODS: Seventy-seven patients with histopathologically confirmed treatment-naïve glioma were retrospectively assessed between 08/2013 and 10/2017 using mean kurtosis (MK) and mean diffusivity (MD) histogram parameters from DKI, overall and progression-free survival, and relevant prognostic molecular data (isocitrate dehydrogenase, [IDH]; alpha-thalassemia/mental retardation syndrome X-linked, [ATRX]; chromosome 1p/19q loss of heterozygosity). Receiver operating characteristic (ROC) analysis was performed on metric variables to determine the optimal cutoff-values. The Kaplan-Meier method was used to assess univariate survival data. A multivariate Cox proportional hazards model was performed on significant results from the univariate analysis. RESULTS: There were significant differences in overall and progression-free survival between patient age (p = 0.001), resection statuses (p = 0.002), WHO glioma grades (p < 0.0001), and integrated molecular profiles (p < 0.0001). Survival was significantly better in patients with lower MK and higher MD values globally (p = 0.009), in gliomas without chromosome 1p/19q LOH (p < 0.0001), and those with retained ATRX expression (p = 0.008). CONCLUSIONS: Patient age and MK from DKI from DKI are relevant factors for preoperatively predicting overall and progression-free survival. Regarding the molecular subgroups, they seem to be predictive in gliomas with ATRX retention, representing a feature of IDH wild-type gliomas.

In Vivo Molecular Profiling of Human Glioma : Cross-Sectional Observational Study Using Dynamic Susceptibility Contrast Magnetic Resonance Perfusion Imaging.

PURPOSE: To assess the diagnostic performance of dynamic susceptibility contrast perfusion magnetic resonance perfusion imaging (DSC-MRI) for in vivo human glioma molecular profiling. METHODS: In this study 100 patients with histopathologically confirmed glioma who provided written informed consent were retrospectively assessed between January 2016 and February 2017 in two prospective trials that were approved by the local institutional review board. Cerebral blood volume (CBV) measurements from DSC-MRI were assessed, and histogram parameters of relative CBV (rCBV) results were compared among World Health Organization (WHO) 2016 based histological findings and molecular characteristics. A classification and regression tree (CART) algorithm with 10-fold cross-validation was used to calculate the diagnostic accuracy. RESULTS: The 90th percentile (C90) of rCBV was significantly lower in patients with the isocitrate dehydrogenase 1/2 (IDH1/2) mutation (2.86 ± 1.21; p < 0.001) and loss of alpha-thalassemia mental retardation syndrome X­linked (ATRX) expression (2.23 ± 0.91; p < 0.001) than in those with the IDH1/2 wild type (4.78 ± 2.34) and maintained ATRX expression (4.30 ± 2.02). The standard deviation (SD) of rCBV was significantly higher in glioblastoma (GBM) with methylated O6-methylguanine DNA methyltransferase (MGMT; 1.99 ± 0.73; p = 0.001) than in those with unmethylated MGMT (1.20 ± 0.45). In CART analysis, rCBV predicted the molecular subgroup in 76.3% of astroglial tumors; however, the diagnostic performance was reduced to 48.1% by including oligodendrogliomas with chromosome 1p/19q co-deletion in the analysis due to substantial overlap of rCBV values between OD1p/19q-LOH and IDHwt GBM. CONCLUSION: The DSC-MRI procedure may provide insight into the IDH1/2 mutation and ATRX expression status and MGMT methylation profile of diffuse glioma; however, taking integrated oligodendroglioma into account limits the diagnostic performance of rCBV in non-invasively predicting the molecular subtype.

Contrast enhancement predicting survival in integrated molecular subtypes of diffuse glioma: an observational cohort study.

INTRODUCTION: To assess the predictive value of magnetic resonance imaging (MRI) gadolinium enhancement as a prognostic factor in the 2016 World Health Organization Classification of Tumors of the Central Nervous System integrated glioma groups. METHODS: Four-hundred fifty patients with histopathologically confirmed glioma were retrospectively assessed between 07/1997 and 06/2014 using gadolinium enhancement, survival, and relevant prognostic molecular data [isocitrate dehydrogenase (IDH); alpha-thalassemia/mental retardation syndrome X-linked (ATRX); chromosome 1p/19q loss of heterozygosity; and O6-methylguanine DNA methyltransferase (MGMT)]. The Kaplan-Meier method was used to assess univariate survival data. A multivariate Cox proportional hazards model was performed on significant results from the univariate analysis. RESULTS: There were significant differences in survival between patient age (p < 0.0001), WHO glioma grades (p < 0.0001), and integrated molecular profiles (p < 0.0001). Patients with IDH1/2 mutation, loss of ATRX expression, and methylated MGMT promoter showed significantly better survival than those with the IDHwild-type (p < 0.0001), retained ATRX expression (p < 0.0001), and unmethylated MGMT promoter (p = 0.019). Survival was significantly better in patients without gadolinium enhancement (p = 0.009) who were in the IDHwild-type glioma and glioma with retained ATRX expression groups (p = 0.018 and 0.030, respectively). CONCLUSIONS: In univariate analysis, the presence of gadolinium enhancement on preoperative MRI scans is an unfavorable factor for survival. Regarding the molecular subgroups, gadolinium enhancement is an unfavorable prognostic factor in gliomas with IDHwild-type and those with ATRX retention. However, in multivariate analysis only patient age, IDH1/2 mutation status, MGMT promoter methylation status, and WHO grade IV are relevant for predicting survival.

Glioma grading by dynamic susceptibility contrast perfusion and 11C-methionine positron emission tomography using different regions of interest.

PURPOSE: The use of dynamic susceptibility contrast (DSC) perfusion and 11C-methionine positron emission tomography (MET-PET) for glioma grading is currently not standardized. The purpose of this study was to identify regions of interest (ROIs) that enable the best performance and clinical applicability in both methods, as well as to evaluate the complementarity of DSC perfusion and MET-PET in spatial hotspot definition. METHODS: In 41 patient PET/MRI datasets, different ROIs were drawn: in T2-hyperintense tumour, in T2-hyperintense tumour and adjacent oedema and in tumour areas with contrast enhancement, altered perfusion or pathological radiotracer uptake. The performance of DSC perfusion and MET-PET using the different ROIs to distinguish high- and low-grade gliomas was assessed. The spatial overlap of hotspots identified by DSC perfusion and MET-PET was assessed visually. RESULTS: ROIs in T2 fluid attenuated inversion recovery (FLAIR) sequence-hyperintense tumour revealed the most significant differences between high- and low-grade gliomas and reached the highest diagnostic performance in both DSC perfusion (p = 0.046; area under the curve = 0.74) and MET-PET (p = 0.007; area under the curve = 0.80). The combination of methods yielded an area under the curve of 0.80. Hotspots were completely overlapped in one half of the patients, partially overlapped in one third of the patients and present in only one method in approximately 20% of the patients. CONCLUSIONS: For multi-parametric examinations with DSC perfusion and MET-PET, we recommend an ROI definition based on T2-hyperintense tumour. DSC perfusion and MET-PET contain complementary information concerning the spatial hotspot definition.

Glioma Grading and Determination of IDH Mutation Status and ATRX loss by DCE and ASL Perfusion.

PURPOSE: To evaluate arterial spin labeling (ASL) perfusion and dynamic contrast-enhanced (DCE) perfusion in glioma grading according to the previous WHO classification of 2007, as well as concerning isocitrate dehydrogenase (IDH) mutation status and ATRX expression as required by the new WHO 2016 brain tumor classification. METHODS: The mean values of Ktrans, Kep, Ve, and Vp by DCE perfusion, and cerebral blood flow (CBF) by ASL perfusion were assessed retrospectively in 40 patients with initial glioma diagnosis. Perfusion parameters were correlated and compared concerning glioma grading, IDH mutation status and ATRX expression. RESULTS: The DCE and ASL perfusion parameters showed merely moderate correlation. The Ktrans, Ve, and CBF by DCE perfusion were different in low-grade and high-grade gliomas (p = 0.0018, p < 0.0001, and p = 0.0038, respectively). Ve was useful in distinguishing high-grade from low-grade gliomas (p = 0.024, sensitivity = 1.00, specificity = 0.80). CBF by ASL perfusion enabled discrimination of astrocytomas with and without IDH mutation (p = 0.014, sensitivity = 0.75, specificity = 0.88) and showed a trend for the discrimination of astrocytomas with IDH mutation from oligodendrogliomas (p = 0.074). CONCLUSION: In conclusion, DCE and ASL perfusion are complementary in the differentiation of gliomas. The discrimination of low- and high-grade gliomas is possible by the DCE perfusion parameter Ve, while ASL perfusion shows potential for the differentiation of the IDH and ATRX mutation status of gliomas following the new WHO classification 2016. Both perfusion techniques might represent different aspects of brain tumor perfusion.

Correlation of Brown Adipose Tissue with Other Body Fat Compartments and Patient Characteristics: A Retrospective Analysis in a Large Patient Cohort Using PET/CT.

RATIONALE AND OBJECTIVES: The objective of this study was to assess the relationship of brown adipose tissue (BAT) activity with different fat compartments of the body, body mass index (BMI), outdoor temperature, thyroid-stimulating hormone (TSH) levels, blood glucose, age, and sex in a large patient population using F-18-fluordesoxyglucose positron emission tomography-computer tomography (FDG-PET/CT) scans obtained under thermoneutral conditions. MATERIALS AND METHODS: FDG-PET/CT scans of 4852 patients were retrospectively analyzed for BAT activity. The volumes of the different fat compartments visceral adipose tissue (VAT), subcutaneous adipose tissue (SCAT), and liver fat, were assessed by computed tomography. Age, sex, TSH levels, blood glucose levels, BMI, primary disease, and the outdoor temperature were determined. Multiple linear regression analyses were performed to identify independent relationships between the parameters. RESULTS: The VAT, SCAT, and liver fat content were lower in BAT-positive patients than in BAT-negative patients (each P < 0.0001). BAT-positive patients had a lower BMI (P < 0.0001) and were more often female (P < 0.0001), younger (P < 0.0001), and had higher TSH levels (P = 0.0002), whereas the outdoor temperature and the blood glucose level were not different compared to BAT-negative patients. Age, sex, VAT, and SCAT were independent factors related to BAT. CONCLUSIONS: Age, sex, and VAT are the most important determinants of BAT activity under thermoneutral conditions. VAT reflects the association between BAT activity and body fat mass more clearly than BMI. The strength of the association between VAT and BAT decreases during aging in men, but increases in women. This may indicate a different importance of BAT activity for obesity in men and in women.

Effect of Perfusion on Diffusion Kurtosis Imaging Estimates for In Vivo Assessment of Integrated 2016 WHO Glioma Grades : A Cross-Sectional Observational Study.

PURPOSE: To assess the role of perfusion-related signal decay on diffusion kurtosis imaging (DKI) estimates for in vivo stratification of glioma according to the integrated approach of the 2016 World Health Organization classification of tumors of the central nervous system (2016 CNS WHO). METHODS: In this study 77 patients with histopathologically confirmed glioma were retrospectively assessed between January 2013 and February 2017 in a prospective trial. Mean kurtosis (MK) and mean diffusivity (MD) metrics from DKI were assessed by two physicians blinded to the study from a volume of interest around the entire solid tumor. Wilcoxon's signed-rank test compared perfusion-biased and perfusion-corrected MK (MKpb and MKpc) and MD (MDpb, MDpc) values. One-way ANOVA was used to compare MKpb&pc and MDpb&pc values between 2016 WHO glioma grades. Spearman's correlation coefficient was used to correlate them with 2016 WHO glioma grades. Receiver operating characteristic (ROC) analysis was performed on MKpb&pc and MDpb&pc for the significant results. RESULTS: The MKpc values were significantly higher than MKpb values (p < 0.001), whereas MDpc values were significantly lower than MDpb values (p < 0.001). For stratifying gliomas, MKpb values (ROC AUC range, 0.818-0.979) showed a higher diagnostic performance than MKpc values (ROC AUC range, 0.773-0.975), whereas MDpb values (ROC AUC range, 0.744-0.928) showed less diagnostic performance than MDpc values (ROC AUC range, 0.753-0.934). The diagnostic accuracy of MKpb was 80.0%. CONCLUSION: The MK and MD estimates of DKI are influenced by microcapillary blood perfusion; however, taking the effect of perfusion on DKI metrics into account does not substantially impact their overall diagnostic performance in classifying glioma according to the 2016 CNS WHO.