Neuroimaging Findings in Patients with COVID-19: A Systematic Review and Meta-Analysis.

OBJECTIVE: Central nervous system involvement in coronavirus disease 2019 (COVID-19) has been increasingly reported. We performed a systematic review and meta-analysis to evaluate the incidence of radiologically demonstrated neurologic complications and detailed neuroimaging findings associated with COVID-19. MATERIALS AND METHODS: A systematic literature search of MEDLINE/PubMed and EMBASE databases was performed up to September 17, 2020, and studies evaluating neuroimaging findings of COVID-19 using brain CT or MRI were included. Several cohort-based outcomes, including the proportion of patients with abnormal neuroimaging findings related to COVID-19 were evaluated. The proportion of patients showing specific neuroimaging findings was also assessed. Subgroup analyses were also conducted focusing on critically ill COVID-19 patients and results from studies that used MRI as the only imaging modality. RESULTS: A total of 1394 COVID-19 patients who underwent neuroimaging from 17 studies were included; among them, 3.4% of the patients demonstrated COVID-19-related neuroimaging findings. Olfactory bulb abnormalities were the most commonly observed (23.1%). The predominant cerebral neuroimaging finding was white matter abnormality (17.6%), followed by acute/subacute ischemic infarction (16.0%), and encephalopathy (13.0%). Significantly more critically ill patients had COVID-19-related neuroimaging findings than other patients (9.1% vs. 1.6%; p = 0.029). The type of imaging modality used did not significantly affect the proportion of COVID-19-related neuroimaging findings. CONCLUSION: Abnormal neuroimaging findings were occasionally observed in COVID-19 patients. Olfactory bulb abnormalities were the most commonly observed finding. Critically ill patients showed abnormal neuroimaging findings more frequently than the other patient groups. White matter abnormalities, ischemic infarctions, and encephalopathies were the common cerebral neuroimaging findings.

Pretreatment brain volumes can affect the effectiveness of deep brain stimulation in Parkinson's disease patients.

We aimed to assess whether brain volumes may affect the results of deep brain stimulation (DBS) in patients with Parkinson's disease (PD). Eighty-one consecutive patients with PD (male:female 40:41), treated with DBS between June 2012 and December 2017, were enrolled. Total and regional brain volumes were measured using automated brain volumetry (NeuroQuant). The Unified Parkinson Disease Rating Scale motor score quotient was used to assess changes in clinical outcome and compare the preoperative regional brain volume in patients categorized into the higher motor improvement and lower motor improvement groups based on changes in the postoperative scores. The study groups showed significant volume differences in multiple brain areas. In the higher motor improvement group, the anterior cingulate and right thalamus showed high volumes after false discovery rate (FDR) correction. In the lower motor improvement group, the left caudate, paracentral, right primary sensory and left primary motor cortex showed high volume, but no area showed high volumes after FDR correction. Our data suggest that the effectiveness of DBS in patients with PD may be affected by decreased brain volume in different areas, including the cingulate gyrus and thalamus. Preoperative volumetry could help predict outcomes in patients with PD undergoing DBS.

Optimized Image-Based Surrogate Endpoints in Targeted Therapies for Glioblastoma: A Systematic Review and Meta-Analysis of Phase III Randomized Controlled Trials.

OBJECTIVE: We aimed to determine the optimized image-based surrogate endpoints (IBSEs) in targeted therapies for glioblastoma through a systematic review and meta-analysis of phase III randomized controlled trials (RCTs). MATERIALS AND METHODS: A systematic search of OVID-MEDLINE and EMBASE for phase III RCTs on glioblastoma was performed in December 2017. Data on overall survival (OS) and IBSEs, including progression-free survival (PFS), 6-month PFS (6moPFS), 12-month PFS (12moPFS), median PFS, and objective response rate (ORR) were extracted. Weighted linear regression analysis for the hazard ratio for OS and the hazard ratios or odds ratios for IBSEs was performed. The associations between IBSEs and OS were evaluated. Subgroup analyses according to disease stage (newly diagnosed glioblastoma versus recurrent glioblastoma), types of test treatment, and types of response assessment criteria were performed. RESULTS: Twenty-three phase III RCTs published between 2000 and 2017, including 8387 patients, met the inclusion criteria. OS showed strong correlations with PFS (standardized ß coefficient [R] = 0.719), 6moPFS (R = 0.647), and 12moPFS (R = 0.638). OS showed no correlations with median PFS and ORR. In subgroup analysis according to types of therapies, PFS showed the highest correlations with OS in targeted therapies for cell cycle pathways (R = 0.913) and growth factor receptors and their downstream pathways (R = 0.962). 12moPFS showed the highest correlation with OS in antiangiogenic therapy (R = 0.821). The response assessment in neuro-oncology criteria provided higher correlation coefficients between OS and IBSEs than the Macdonald criteria. CONCLUSION: Overall, PFS is an optimized IBSE in targeted therapies for glioblastoma; however, 12moPFS is optimal in antiangiogenic therapy.

Alpha Stent for Coiling of Unruptured, Wide-Necked, Distal Internal Carotid Artery Aneurysms: Safety and Effectiveness at 6 Months.

OBJECTIVE: The Alpha stent (CGBio), a new intracranial stent featuring a re-sheathable mesh design with improved wall apposition at the curved segment, was clinically evaluated. We report the 6-month follow-up results from a prospective, single-center study in which the stent was used for coiling of wide-necked distal internal carotid artery (ICA) aneurysms. MATERIALS AND METHODS: Between April 2016 and 2018, 50 patients (mean age, 56.5 years, 45 females [90%]) with 54 unruptured distal ICA aneurysms (average diameter: 5.6 ± 1.7 mm) were enrolled. The primary endpoint for effectiveness was successful coil embolization with the Alpha stent, and subsequent complete or near-complete occlusion at the 6-month magnetic resonance angiography assessment. The primary safety endpoint was the absence of serious adverse events (SAEs) up to 6 months from the procedure. RESULTS: The primary effectiveness endpoint was observed in 94.4% (51/54) aneurysms. In one patient with technical failure, the stent could not be deployed because of parent artery tortuosity; therefore, a different type of stent was used. Of the 53 aneurysms treated with the Alpha stent, complete occlusion was achieved in 64.1% (34/53) cases, and near-complete occlusion was achieved in 32.0% (17/53) cases by the 6-month follow-up. Two cases (3.7%) required retreatment because of major recurrence. In 4% (2/50) patients, SAEs, i.e., retinal artery thromboembolism and corona radiata lacunar infarction, were reported after the procedure. CONCLUSION: For endovascular treatment of unruptured, wide-necked, distal ICA aneurysms, coil embolization using the newly developed Alpha stent showed excellent procedural and mid-term clinical follow-up results in terms of effectiveness and safety.

Comparative Value of 2-Hydroxyglutarate-to-Lipid and Lactate Ratio versus 2-Hydroxyglutarate Concentration on MR Spectroscopic Images for Predicting Isocitrate Dehydrogenase Mutation Status in Gliomas.

Purpose: To compare the ability of 2-hydroxyglutarate (2HG)-to-lipid and lactate (2HG/[lipid + lactate]) ratio with the ability of 2HG concentration alone to predict the isocitrate dehydrogenase (IDH) mutation status in patients with glioma. Materials and Methods: In this retrospective study, consecutive patients with histopathologically proven glioma were enrolled between July 2016 and February 2019. A total of 79 patients were enrolled (mean age, 44 years; 49 men). The 2HG concentration and other MR spectroscopic parameters were measured by single-voxel point-resolved spectroscopy before surgery. The diagnostic performance of the 2HG concentration and 2HG/(lipid + lactate) ratio were calculated. Internal validation was assessed by the bootstrap approach with 1000 bootstrap resamples. Differences in the predictive accuracy of 2HG/(lipid + lactate) ratio and 2HG concentration were determined by calculating the integrated discrimination improvement. The diagnostic accuracy (sensitivity, specificity, and area under the receiver operating characteristic curve [AUC]) of these measures was also compared separately in patients with glioblastomas and patients with lower-grade gliomas. Results: Of the 79 enrolled patients, 28 had IDH mutations and 51 had wild-type IDH. The sensitivity, specificity, and AUC of 2HG concentration for predicting IDH-mutant gliomas were 89% (25 of 28), 67% (34 of 51), and 0.80 (95% confidence interval [CI]: 0.70, 0.88; C statistic, 0.80), respectively. The sensitivity, specificity, and AUC of the 2HG/(lipid + lactate) ratio for predicting IDH-mutant gliomas were 79% (22 of 28), 92% (47 of 51), and 0.90 (95% CI: 0.81, 0.96; C statistics, 0.90), respectively. The optimal cutoff value for the 2HG/(lipid + lactate) ratio was 0.63. The 2HG/(lipid + lactate) ratio was significantly better for predicting IDH mutation status than the 2HG concentration alone (P < .01). In glioblastoma, the 2HG/(lipid + lactate) ratio was also better for predicting IDH mutations than the 2HG concentration alone, with borderline significance (P = .052). In lower-grade glioma, the 2HG/(lipid + lactate) ratio and the 2HG concentration showed comparable diagnostic performance (P = .72). Conclusion: The 2HG/(lipid + lactate) ratio is more accurate for predicting IDH mutation status in patients with glioma than the 2HG concentration alone.Keywords: Brain/Brain Stem, CNS, MR-Imaging, MR-Spectroscopy, Neoplasms-Primary, Neuro-Oncology© RSNA, 2020.

Repeatability of amide proton transfer-weighted signals in the brain according to clinical condition and anatomical location.

OBJECTIVES: To investigate whether clinical condition, imaging session, and locations affect repeatability of amide proton transfer-weighted (APTw) magnetic resonance imaging (MRI) in the brain. MATERIALS AND METHODS: Three APTw MRI data sets were acquired, involving two intrasession scans and one intersession scan for 19 healthy, 15 glioma, and 12 acute stroke adult participants (mean age 53.8, 54.6, and 68.5, respectively) on a 3T MR scanner. The mean APTw signals from five locations in healthy brain (supratentorial and infratentorial locations) and from entire tumor and stroke lesions (supratentorial location) were calculated. The within-subject coefficient of variation (wCV) and intraclass correlation coefficient (ICC) were calculated for each clinical conditions, image sessions, and anatomic locations. Differences in APTw signals between sessions were analyzed using repeated-measures analysis of variance. RESULTS: The ICC and wCV were 0.96 (95% confidence interval [CI], 0.91-0.99) and 16.1 (12.6-21.3) in glioma, 0.93 (0.82-0.98) and 15.0 (11.4-20.6) in stroke, and 0.84 (0.72-0.91) and 34.0 (28.7-41.0) in healthy brain. There were no significant differences in APTw signal between three sessions, irrespective of disease condition and location. The ICC and wCV were 0.85 (0.68-0.94) and 27.4 (21.8-35.6) in supratentorial, and 0.44 (- 0.18 to 0.76) and 32.7 (25.9 to 42.9) in infratentorial locations. There were significant differences in APTw signal between supra- (mean, 0.49%; 95% CI, 0.38-0.61) and infratentorial locations (1.09%, 0.98-1.20; p < 0.001). CONCLUSION: The repeatability of APTw signal was excellent in supratentorial locations, while it was poor in infratentorial locations due to severe B0 inhomogeneity and susceptibility which affects MTR asymmetry. KEY POINTS: • In supratentorial locations, APTw MRI showed excellent intrasession and intersession repeatability in brains of healthy controls and patients with glioma, as well as in stroke-affected regions. • APTw MRI showed excellent repeatability in supratentorial locations, but poor repeatability in infratentorial locations. • Considering poor repeatability in the infratentorial locations, the use of APTw MRI in longitudinal assessment in infratentorial locations is not indicated.

The "Central Vein Sign" on T2*-weighted Images as a Diagnostic Tool in Multiple Sclerosis: A Systematic Review and Meta-analysis using Individual Patient Data.

We aimed to evaluate the pooled incidence of central vein sign on T2*-weighted images from patients with multiple sclerosis (MS), and to determine the diagnostic performance of this central vein sign for differentiating MS from other white matter lesions and provide an optimal cut-off value. A computerized systematic search of the literature in PUBMED and EMBASE was conducted up to December 14, 2018. Original articles investigating central vein sign on T2*-weighted images of patients with MS were selected. The pooled incidence was obtained using random-effects model. The pooled sensitivity and specificity were obtained using a bivariate random-effects model. An optimal cut-off value for the proportion of lesions with a central vein sign was calculated from those studies providing individual patient data. Twenty-one eligible articles covering 501 patients with MS were included. The pooled incidence of central vein sign at the level of individual lesion in patients with MS was 74% (95% CI, 65-82%). The pooled sensitivity and pooled specificity for the diagnostic performance of the central vein sign were 98% (95% CI, 92-100%) and 97% (95% CI, 91-99%), respectively. The area under the HSROC curve was 1.00 (95% CI, 0.99-1.00). The optimal cut-off value for the proportion of lesions with a central vein sign was found to be 45%. Although various T2*-weighted images have been used across studies, the current evidence supports the use of the central vein sign on T2*-weighted images to differentiate MS from other white matter lesions.

Primary Central Nervous System Lymphoma: Diagnostic Yield of Whole-Body CT and FDG PET/CT for Initial Systemic Imaging.

Background Updated guidelines for suspected primary central nervous system lymphoma (PCNSL) are lacking. Purpose To investigate the diagnostic yield of initial systemic imaging in patients suspected of having PCNSL by using contrast material-enhanced chest and abdominopelvic CT and/or whole-body fluorine 18 fluorodeoxyglucose (FDG) PET/CT. Materials and Methods This retrospective study included 304 patients examined at a single tertiary hospital between January 1998 and October 2018. Consecutive adults (age >18 years) who were confirmed to have newly diagnosed PCNSL on the basis of findings at stereotactic brain biopsy were recruited. All patients were examined with contrast-enhanced chest and abdominopelvic CT and/or whole-body FDG PET/CT before initiation of PCNSL treatment. The diagnostic yield of CT and PET/CT was determined before therapy and at the time of recurrence in the brain. A χ2 test was performed to compare the diagnostic yield according to study date in order to assess for possible changes in technology during the study period. Results A total of 304 patients (180 men with a mean age [±standard deviation] of 58 years ± 13 and 124 women with a mean age of 59 years ± 13) were included. The diagnostic yield of CT and PET/CT for initial staging was 2% (six of 304 patients; 95% confidence interval [CI]: 0.7%, 4.3%), and these tests yielded false-positive findings in 13 of the 304 patients (4%; 95% CI: 2.3%, 7.2%). Diagnostic yield did not differ between patients evaluated before 2009 and those evaluated in 2009 and later (P = .82). The diagnostic yield of systemic imaging at recurrence was 1.5% (one of 68 patients; 95% CI: 0.0%, 7.9%), and these tests yielded false-positive findings in four of those 68 patients (6%; 95% CI: 1.6%, 14.4%). Conclusion Contrast-enhanced chest and abdominopelvic CT and/or whole-body fluorine 18 fluorodeoxyglucose PET/CT for initial staging, as well as for recurrence of suspected primary central nervous system lymphoma, had a low diagnostic yield. © RSNA, 2019 See also the editorial by Jara in this issue.

False-Positive Measurement at 2-Hydroxyglutarate MR Spectroscopy in Isocitrate Dehydrogenase Wild-Type Glioblastoma: A Multifactorial Analysis.

Background Isocitrate dehydrogenase (IDH) mutation has become one of the most important prognostic biomarkers in glioma management. Measurement of 2-hydroxyglutarate (2HG) with MR spectroscopy has shown high pooled sensitivity, although false-positive results with MR spectroscopy have been reported. Purpose To investigate factors associated with false-positive 2HG measurements at MR spectroscopy in patients with IDH wild-type glioblastoma. Materials and Methods This retrospective study was approved by the institutional review board, and informed consent was waived. Consecutive patients with histopathologically confirmed pre- and posttreatment glioblastoma were evaluated between December 2017 and August 2018. Spectroscopy parameters, including 2HG measurements, were obtained with single-voxel point-resolved spectroscopy, and apparent diffusion coefficient (ADC) values were calculated. Necrosis was graded according to the proportion of necrosis within a volume of interest. Poisson regression analyses were performed to determine factors related to false-positive 2HG measurements. Results A total of 82 patients were included (mean age, 55 years ± 12 [standard deviation]; 40 men). The 2HG measurement showed a false-positive rate of 21% (17 of 82; 95% CI: 13%, 31%) in patients with IDH wild-type glioblastoma. Multivariable analysis revealed that necrosis (prevalence ratio [PR], 3.9; 95% CI: 1.6, 9.4; P = .01) and ADC value (PR, 0.1 × 10-3 mm2/sec; 95% CI: [0.0, 0.7] × 10-3 mm2/sec; P = .02) were associated with a greater false-positive rate for the 2HG measurement. Necrosis of more than 20% was associated with a higher rate of false-positive 2HG measurements (50%) than was necrosis of 20% or less (15%, P = .01). The 2HG false-positive rate was higher in patients with pretreatment glioblastoma (46%) than in those with posttreatment glioblastoma (14%, P < .01). Among 17 patients with false-positive findings, 15 (88%; 95% CI: 64%, 99%) had a lactate concentration of 2.0 mmol/L or higher, and 14 (82%, 95% CI: 57%, 96%) had a lactate concentration of 3.0 mmol/L or higher. Conclusion Necrosis and apparent diffusion coefficient were associated with false-positive measurements of 2-hydroxyglutarate at MR spectroscopy in patients with isocitrate dehydrogenase wild-type glioblastoma. © RSNA, 2019 Online supplemental material is available for this article.

MRI as a diagnostic biomarker for differentiating primary central nervous system lymphoma from glioblastoma: A systematic review and meta-analysis.

BACKGROUND: Accurate preoperative differentiation of primary central nervous system lymphoma (PCNSL) and glioblastoma is clinically crucial because the treatment strategies differ substantially. PURPOSE: To evaluate the diagnostic performance of MRI for differentiating PCNSL from glioblastoma. STUDY TYPE: Systematic review and meta-analysis. SUBJECTS: Ovid-MEDLINE and EMBASE databases were searched to find relevant original articles up to November 25, 2018. The search term combined synonyms for "lymphoma," "glioblastoma," and "MRI." FIELD STRENGTH/SEQUENCE: Patients underwent at least one MRI sequence including diffusion-weighted imaging (DWI), dynamic susceptibility-weighted contrast-enhanced imaging (DSC), dynamic contrast-enhanced imaging (DCE), arterial spin labeling (ASL), susceptibility-weighted imaging (SWI), intravoxel incoherent motion (IVIM), and magnetic resonance spectroscopy (MRS) using 1.5 or 3 T. ASSESSMENT: Quality assessment was performed according to the Quality Assessment of Diagnostic Accuracy Studies-2 tool. STATISTICAL TESTS: Hierarchical logistic regression modeling was used to obtain pooled sensitivity and specificity. Meta-regression was performed. RESULTS: Twenty-two studies with 1182 patients were included. MRI sequences demonstrated high overall diagnostic performance with pooled sensitivity of 91% (95% confidence interval [CI], 87-93%) and specificity of 89% (95% CI, 85-93%). The area under the hierarchical summary receiver operating characteristic curve was 0.92 (95% CI, 0.90-0.94). Studies using DSC or ASL showed high diagnostic performance (sensitivity of 93% [95% CI, 89-97%] and specificity of 91% [95% CI, 86-96%]). Heterogeneity was only detected in specificity (I2 = 66.84%) and magnetic field strength was revealed to be a significant factor affecting study heterogeneity. DATA CONCLUSION: MRI showed overall high diagnostic performance for differentiating PCNSL from glioblastoma, with studies using DSC or ASL showing high diagnostic performance. Therefore, MRI sequences including DSC or ASL is a potential diagnostic tool for differentiating PCNSL from glioblastoma. LEVEL OF EVIDENCE: 3 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;50:560-572.

Amide proton transfer-weighted MRI in distinguishing high- and low-grade gliomas: a systematic review and meta-analysis.

PURPOSE: Grading of brain gliomas is of clinical importance, and noninvasive molecular imaging may help differentiate low- and high-grade gliomas. We aimed to evaluate the diagnostic performance of amide proton transfer-weighted (APTw) MRI for differentiating low- and high-grade gliomas on 3-T scanners. METHODS: A systematic literature search of Ovid-MEDLINE and EMBASE was performed up to March 28, 2018. Original articles evaluating the diagnostic performance of APTw MRI for differentiating low- and high-grade gliomas were selected. The pooled sensitivity and specificity were calculated using a bivariate random-effects model. A coupled forest plot and a hierarchical summary receiver operating characteristic curve were obtained. Heterogeneity was investigated using Higgins inconsistency index (I2) test. Meta-regression was performed. RESULTS: Ten original articles with a total of 353 patients were included. High-grade gliomas showed significantly higher APT signal intensity than low-grade gliomas. The pooled sensitivity and specificity for the diagnostic performance of APTw MRI for differentiating low-grade and high-grade gliomas were 88% (95% CI, 77-94%) and 91% (95% CI, 82-96%), respectively. Higgins I2 statistic demonstrated heterogeneity in the sensitivity (I2 = 68.17%), whereas no heterogeneity was noted in the specificity (I2 = 44.84%). In meta-regression, RF saturation power was associated with study heterogeneity. Correlation coefficients between APT signal intensity and Ki-67 cellular proliferation index ranged from 0.430 to 0.597, indicating moderate correlation. All studies showed excellent interobserver agreement. CONCLUSIONS: Although heterogeneous protocols were used, APTw MRI demonstrated excellent diagnostic performance for differentiating low- and high-grade gliomas. APTw MRI could be a reliable technique for glioma grading in clinical practice.

Imaging prediction of isocitrate dehydrogenase (IDH) mutation in patients with glioma: a systemic review and meta-analysis.

OBJECTIVES: To evaluate the imaging features of isocitrate dehydrogenase (IDH) mutant glioma and to assess the diagnostic performance of magnetic resonance imaging (MRI) for prediction of IDH mutation in patients with glioma. METHODS: A systematic search of Ovid-MEDLINE and EMBASE up to 10 October 2017 was conducted to find relevant studies. The search terms combined synonyms for 'glioma', 'IDH mutation' and 'MRI'. Studies evaluating the imaging features of IDH mutant glioma and the diagnostic performance of MRI for prediction of IDH mutation in patients with glioma were selected. The pooled summary estimates of sensitivity and specificity and their 95% confidence intervals (CIs) were calculated using a bivariate random-effects model. The results of multiple subgroup analyses are reported. RESULTS: Twenty-eight original articles in a total of 2,146 patients with glioma were included. IDH mutant glioma showed frontal lobe predominance, less contrast enhancement, well-defined border, high apparent diffusion coefficient (ADC) value and low relative cerebral blood volume (rCBV) value. For the meta-analysis that included 18 original articles, the summary sensitivity was 86% (95% CI, 79%-91%) and the summary specificity was 87% (95% CI, 78-92%). In a subgroup analysis, the summary sensitivity of 2-hydroxyglutarate magnetic resonance spectroscopy (MRS) [96% (95% CI, 91-100%)] was higher than the summary sensitivities of other imaging modalities. CONCLUSIONS: IDH mutant glioma consistently demonstrated less aggressive imaging features than IDH wild-type glioma. Despite the variety of different MRI techniques used, MRI showed the potential to non-invasively predict IDH mutation in patients with glioma. 2-Hydroxyglutarate MRS shows higher pooled sensitivity than other imaging modalities. KEY POINTS: • IDH mutant glioma showed frontal lobe predominance, less contrast enhancement, well-defined border, high ADC value, and low rCBV value. • The diagnostic performance of MRI for prediction of IDH mutation in patients with glioma is within a clinically acceptable range, the summary sensitivity was 86% (95% CI, 79-91%) and the summary specificity was 87% (95% CI, 78-92%). • In a subgroup analysis, the summary sensitivity of 2-hydroxyglutarate MRS [96% (95% CI, 91-100%)] was higher than the summary sensitivities of other imaging modalities.

Reliability of fast magnetic resonance imaging for acute ischemic stroke patients using a 1.5-T scanner.

OBJECTIVES: To determine whether fast scanned MRI using a 1.5-T scanner is a reliable method for the detection and characterization of acute ischemic stroke in comparison with conventional MRI. METHODS: From May 2015 to June 2016, 862 patients (FLAIR, n = 482; GRE, n = 380; MRA, n = 190) were prospectively enrolled in the study, with informed consent and under institutional review board approval. The patients underwent both fast (EPI-FLAIR, ETL-FLAIR, TR-FLAIR, EPI-GRE, parallel-GRE, fast CE-MRA) and conventional MRI (FLAIR, GRE, time-of-flight MRA, fast CE-MRA). Two neuroradiologists independently assessed agreements in acute and chronic ischemic hyperintensity, hyperintense vessels (FLAIR), microbleeds, susceptibility vessel signs, hemorrhagic transformation (GRE), stenosis (MRA), and image quality (all MRI), between fast and conventional MRI. Agreements between fast and conventional MRI were evaluated by generalized estimating equations. Z-scores were used for comparisons of the percentage agreement among fast FLAIR sequences and fast GRE sequences and between conventional and fast MRA. RESULTS: Agreements of more than 80% were achieved between fast and conventional MRI (ETL-FLAIR, 96%; TR-FLAIR, 97%; EPI-GRE, 96%; parallel-GRE, 98%; fast CE-MRA, 86%). ETL- and TR-FLAIR were significantly superior to EPI-FLAIR in the detection of acute ischemic hyperintensity and hyperintense vessels, while parallel-GRE was significantly superior to EPI-GRE in the detection of susceptibility vessel sign (p value < 0.05 for all). There were no significant differences in the other scores and image qualities (p value > 0.05). CONCLUSIONS: Fast MRI at 1.5 T is a reliable method for the detection and characterization of acute ischemic stroke in comparison with conventional MRI. KEY POINTS: • Fast MRI at 1.5 T may achieve a high intermethod reliability in the detection and characterization of acute ischemic stroke with a reduction in scan time in comparison with conventional MRI.

In Vivo Mapping and Quantification of Creatine Using Chemical Exchange Saturation Transfer Imaging in Rat Models of Epileptic Seizure.

PURPOSE: To evaluate signal changes in the hippocampus of epileptic seizure rat models, based on quantified creatine chemical exchange saturation transfer (CrCEST) signals. PROCEDURES: CEST data and 1H magnetic resonance spectroscopy (1H MRS) data were obtained for the two imaging groups: control (CTRL) and epileptic seizure-induced (ES; via kainic acid [KA] injection) groups. CrCEST signals in the hippocampal regions were quantitatively evaluated; correlations between CrCEST signals and phosphocreatine (PCr) and total creatine (tCr; PCr + Cr) concentrations, derived from the analysis of 1H MRS data, were investigated as a function of time changes (before KA injection, 3 and 5 h after KA injection). RESULTS: Measured CrCEST signals were exhibited significant differences between before and after KA injection in the ES group. At each time point, CrCEST signals showed significant correlations with PCr concentration (all |r| > 0.59; all P < 0.05); no significant correlations were found between CrCEST signals and tCr concentrations (all |r| < 0.22; all P > 0.05). CONCLUSIONS: CrCEST can adequately detect changes in the concentration of Cr as a result of energy metabolism, and may serve as a potentially useful tool for diagnosis and assessment of prognosis in epilepsy.

Comparison of MRI and PET as Potential Surrogate Endpoints for Treatment Response After Stereotactic Radiosurgery in Patients With Brain Metastasis.

OBJECTIVE: The purpose of this study is to compare the diagnostic performance of MRI and PET for differentiating tumor recurrence from radiation necrosis in patients with brain metastasis treated with stereotactic radiosurgery. MATERIALS AND METHODS: The Ovid-Medline and Embase databases were searched up to November 11, 2017, to find relevant studies. Pooled sensitivity and specificity from entire included studies were obtained using hierarchic logistic regression modeling. Metaregression was performed. RESULTS: Twenty studies including 728 patients with 872 brain metastases were selected. MRI showed a pooled sensitivity of 84% (95% CI, 72-91%) and specificity of 88% (95% CI, 71-96%). PET showed a pooled sensitivity of 84% (95% CI, 78-88%) and specificity of 86% (95% CI, 81-90%). There were no statistically significant differences in the diagnostic performance of MRI and PET using indirect (p = 0.80) or direct (p = 0.48) comparisons. The diagnostic performance of advanced MRI was significantly higher than that of conventional MRI (p = 0.01). Advanced MRI (sensitivity, 86% [95% CI, 74-93%]; specificity, 95% [95% CI, 82-98%]) showed a significantly higher diagnostic performance than did PET (p < 0.01). All the included studies used perfusion MRI as an advanced MRI technique. CONCLUSION: MRI and PET showed high diagnostic performance for the detection of tumor recurrence after stereotactic radiosurgery in patients with brain metastasis. There was no significant difference in the diagnostic performance between MRI and PET. Because of heterogeneity and paucity in studies, caution may be needed in applying the results.

2-Hydroxyglutarate MR spectroscopy for prediction of isocitrate dehydrogenase mutant glioma: a systemic review and meta-analysis using individual patient data.

Background: Noninvasive and accurate modality to predict isocitrate dehydrogenase (IDH) mutant glioma may have great potential in routine clinical practice. We aimed to investigate the diagnostic performance of 2-hydroxyglutarate (2HG) magnetic resonance spectroscopy (MRS) for prediction of IDH mutant glioma and provide an optimal cutoff value for 2HG. Methods: A systematic literature search of Ovid-MEDLINE and EMBASE was performed to identify original articles investigating the diagnostic performance of 2HG MRS up to March 20, 2018. Pooled sensitivity and specificity were calculated using a bivariate random-effects model. Subgroup analysis and meta-regression were performed to explain heterogeneity effects. An optimal cutoff value for 2HG was calculated from studies providing individual patient data. Results: Fourteen original articles with 460 patients were included. The pooled sensitivity and specificity for the diagnostic performance of 2HG MRS for prediction of IDH mutant glioma were 95% (95% CI, 85-98%) and 91% (95% CI, 83-96%), respectively. The Higgins I2 statistic demonstrated that heterogeneity was present in the sensitivity (I2 = 50.69%), but not in the specificity (I2 = 30.37%). In the meta-regression, echo time (TE) was associated with study heterogeneity. Among the studies using point-resolved spectroscopy (PRESS), a long TE (97 ms) resulted in higher sensitivity (92%) and specificity (97%) than a short TE (30-35 ms; sensitivity of 90%, specificity of 88%; P < 0.01). The optimal 2HG cutoff value of 2HG using individual patient data was 1.76 mM. Conclusion: 2HG MRS demonstrated excellent specificity for prediction of IDH mutant glioma, with TE being associated with heterogeneity in the sensitivity. Key Points: 1. HG MRS has excellent diagnostic performance in the prediction of IDH mutant glioma. 2. The pooled sensitivity was 95% and the pooled specificity was 91%. 3. Echo time was associated with study heterogeneity in the meta-regression.

Perfusion MRI as a diagnostic biomarker for differentiating glioma from brain metastasis: a systematic review and meta-analysis.

OBJECTIVES: Differentiation of glioma from brain metastasis is clinically crucial because it affects the clinical outcome of patients and alters patient management. Here, we present a systematic review and meta-analysis of the currently available data on perfusion magnetic resonance imaging (MRI) for differentiating glioma from brain metastasis, assessing MRI protocols and parameters. METHODS: A computerised search of Ovid-MEDLINE and EMBASE databases was performed up to 3 October 2017, to find studies on the diagnostic performance of perfusion MRI for differentiating glioma from brain metastasis. Pooled summary estimates of sensitivity and specificity were obtained using hierarchical logistic regression modelling. We conducted meta-regression and subgroup analyses to explain the effects of the study heterogeneity. RESULTS: Eighteen studies with 900 patients were included. The pooled sensitivity and specificity were 90% (95% CI, 84-94%) and 91% (95% CI, 84-95%), respectively. The area under the hierarchical summary receiver operating characteristic curve was 0.96 (95% CI, 0.94-0.98). The meta-regression showed that the percentage of glioma in the study population and the study design were significant factors affecting study heterogeneity. In a subgroup analysis including patients with glioblastoma only, the pooled sensitivity was 92% (95% CI, 84-97%) and the pooled specificity was 94% (95% CI, 85-98%). CONCLUSIONS: Although various perfusion MRI techniques were used, the current evidence supports the use of perfusion MRI to differentiate glioma from brain metastasis. In particular, perfusion MRI showed excellent diagnostic performance for differentiating glioblastoma from brain metastasis. KEY POINTS: • Perfusion MRI shows high diagnostic performance for differentiating glioma from brain metastasis. • The pooled sensitivity was 90% and pooled specificity was 91%. • Peritumoral rCBV derived from DSC is a relatively well-validated.

Effect of cerebral embolus size on the timing of cardiac surgery for infective endocarditis in patients with neurological complications.

The optimal timing of cardiac surgery remains unclear for patients with neurological complications of infective endocarditis (IE). However, neuroimaging findings may allow more refined clinical decision-making. We analyzed clinical and advanced neuroimaging data for 135 patients with IE who had preoperatively diagnosed ischemic cerebral complications (86 patients) or hemorrhagic complications (49 patients), between January 1997 and May 2013. The effect of early surgery (within 3 and 7 days of ischemic and hemorrhagic complications respectively) on in-hospital mortality and 1-year adverse outcomes (mortality, relapse, or new embolic events) was estimated. Small cerebral emboli (≤2 cm) led to early surgery (cases with ischemic complications: 57% vs 26%, p = 0.04; cases with hemorrhagic complications: 56% vs 13%, p = 0.02). Early surgery was not significantly associated with increased rates of in-hospital mortality and 1-year adverse outcomes among patients with ischemic complications (14% vs 9%, odds ratio [OR] 1.67, 95% confidence interval [CI] 0.44-6.38, p = 0.52; 17% vs 14%, OR 1.27, 95% CI 0.39-4.14, p = 0.7 respectively). Only 1 patient (4%) with hemorrhagic complications experienced in-hospital mortality in the early surgery group, and early surgery was not significantly associated with 1-year adverse outcomes (21% vs 12%, OR 1.93, 95% CI 0.41-9.16, p = 0.46). The risks of in-hospital mortality and 1-year adverse outcome were not increased, even if cardiac surgery had been carried out earlier than previously described. Our findings suggest that early surgery, when indicated, may be performed for patients with IE and neurological complications, especially if the cerebral embolus has a diameter of ≤2 cm.

Multiparametric MRI as a potential surrogate endpoint for decision-making in early treatment response following concurrent chemoradiotherapy in patients with newly diagnosed glioblastoma: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the value of multiparametric MRI for determination of early treatment response following concurrent chemoradiotherapy in patients with newly diagnosed glioblastoma. METHODS: A computerized search of Ovid-MEDLINE and EMBASE up to 1 October 2017 was performed to find studies on the diagnostic performance of multiparametric MRI for differentiating true progression from pseudoprogression. The beginning search date was not specified. Pooled estimates of sensitivity and specificity were obtained using hierarchical logistic regression modeling. We performed meta-regression and sensitivity analyses to explain the effects of the study heterogeneity. RESULTS: Nine studies including 456 patients were included. Pooled sensitivity and specificity were 84 % (95 % CI 74-91) and 95 % (95 % CI 83-99), respectively. Area under the hierarchical summary receiver operating characteristic curve was 0.95 (95 % CI 0.92-0.96). Meta-regression showed true progression in the study population, the mean age and the reference standard were significant factors affecting heterogeneity. CONCLUSION: Multiparametric MRI may be used as a potential surrogate endpoint for assessment of early treatment response, especially in the differentiation of true progression from pseudoprogression. However, based on the current evidence, monoparametric and multiparametric MRI perform equally in the clinical context. Further evaluation will be needed. KEY POINTS: • Multiparametric MRI shows high diagnostic performance for early treatment response in glioblastoma. • Multiparametric MRI could differentiate true progression from pseudoprogression in newly diagnosed glioblastoma. • The normalized rCBV derived from DSC was the most commonly used parameter.

Spontaneous and Unruptured Chronic Intracranial Artery Dissection : High-resolution Magnetic Resonance Imaging Findings.

PURPOSE: The aim of this article is to present high-resolution magnetic resonance imaging (HR-MRI) findings of chronic stage spontaneous and unruptured intracranial artery dissection (ICAD). MATERIAL AND METHODS: From March 2012 to April 2016 a total of 29 patients (15 male and14 female, age range 37-68 years) with chronic stage spontaneous and unruptured ICAD (vertebral artery 27, posterior inferior cerebellar artery 1 and middle cerebral artery 1) were retrospectively enrolled. Patients underwent HR-MRI more than 2 months (median interval 564 days, range 69-391 days) after symptom onset and were diagnosed at symptom onset or at the first imaging acquisition, which included luminal angiography and/or HR-MRI with clinical information. The HR-MRI findings were evaluated against those of luminal angiography on the basis of the lumen wall morphology, including thickening, contrast enhancement and residual dissection. RESULTS: The HR-MRI findings were classified into complete normalization (normal lumen and wall with or without mild enhancement, n = 6), complete normalization with minimal wall changes (focal wall thickening with enhancement but normal luminal angiography, n = 8), incomplete normalization (focal wall thickening with enhancement with dilatation and stenosis on luminal angiography, n = 4), dissecting aneurysm (fusiform aneurysm with residual dissection findings, n = 8) and occlusion (small outer arterial diameter with diffuse contrast enhancement, n = 3). CONCLUSION: The use of HR-MRI can demonstrate the distinguishing morphological features of chronic stage of spontaneous and unruptured ICAD as complete normalization, complete normalization with minimal wall changes, incomplete normalization, dissecting aneurysm and occlusion.