Disrupted Functional Connectivity Within and Between Resting-State Networks in the Subacute Stage of Post-stroke Aphasia.

Background: Post-stroke aphasia (PSA) results from brain network disorders caused by focal stroke lesions. However, it still remains largely unclear whether the impairment is present in intra- and internetwork functional connectivity (FC) within each resting-state network (RSN) and between RSNs in the subacute stage of PSA. Objectives: This study aimed to investigate the resting-state FC within and between RSNs in patients with PSA and observe the relationships between FC alterations and Western Aphasia Battery (WAB) measures. Methods: A total of 20 individuals with subacute PSA and 20 healthy controls (HCs) were recruited for functional MRI (fMRI) scanning, and only patients with PSA underwent WAB assessment. Independent component analysis was carried out to identify RSNs. Two-sample t-tests were used to calculate intra- and internetwork FC differences between patients with PSA and HCs. The results were corrected for multiple comparisons using the false discovery rate (FDR correction, p < 0.05). Partial correlation analysis was performed to observe the relationship between FC and WAB scores with age, gender, mean framewise displacement, and lesion volume as covariates (p < 0.05). Results: Compared to HCs, patients with PSA showed a significant increase in intranetwork FC in the salience network (SN). For internetwork FC analysis, patients showed a significantly increased coupling between left frontoparietal network (lFPN) and SN and decreased coupling between lFPN and right frontoparietal network (rFPN) as well as between lFPN and posterior default mode network (pDMN) (FDR correction, p < 0.05). Finally, a significant positive correlation was found between the intergroup difference of FC (lFPN-rFPN) and auditory-verbal comprehension (p < 0.05). Conclusion: Altered FC was revealed within and between multiple RSNs in patients with PSA at the subacute stage. Reduced FC between lFPN and rFPN was the key element participating in language destruction. These findings proved that PSA is a brain network disorder caused by focal lesions; besides, it may improve our understanding of the pathophysiological mechanisms of patients with PSA at the subacute stage.

The feasibility of non-contrast-enhanced zero echo time magnetic resonance angiography for characterization of intracranial atherosclerotic disease.

BACKGROUND: Accurate and non-invasive assessment of intracranial atherosclerotic disease (ICAD) is important because of its effect on treatment planning. The aim of this study is to investigate if zero echo time (zTE) magnetic resonance angiography (zTE-MRA) is feasible in the characterization of ICAD. METHODS: A total of 175 patients with ICAD were recruited. ZTE-MRA and time-of-flight (TOF)-MRA sequences were conducted for all participants using a 3T clinical MR system. Forty-one patients also underwent digital subtraction angiography (DSA), and were confirmed to have intracranial arterial stenosis (ICAS). Weighted kappa (κ) statistics were used to assess the inter-observer agreement and diagnostic consistency of both zTE- and TOF-MRA, using DSA as a reference. The Wilcoxon signed-rank test was used to evaluate differences in image quality between zTE- and TOF-MRA images. The nonparametric test of multiple paired samples was used to compare the results of vascular stenosis diagnosis between zTE-, TOF-MRA and DSA. RESULTS: Supported by high inter-observer agreement (weighted κ=0.78), zTE-MRA generated significantly higher scores than TOF-MRA for susceptibility artifact signal (mean: 3.03±0.98 vs. 2.72±1.09; P=0.017) and flow signal in parent artery (mean: 3.63±0.49 vs. 3.07±0.82; P<0.001). Additionally, zTE-MRA showed more robust diagnostic performance than TOF-MRA for patients with ICAD and degree of vascular stenosis (P<0.05), and was highly consistent with reference DSA images (weighted κ=0.80). CONCLUSIONS: ZTE-MRA has potential for use as a routine clinical method for patients with ICAD.

Disrupted Resting-state Functional Connectivity of the Nucleus Basalis of Meynert in Parkinson's Disease with Mild Cognitive Impairment.

The basal nucleus of Meynert (BNM) shows structural abnormalities in Parkinson's disease with mild cognitive impairment (PD-MCI). However, it is yet unknown whether functional connectivity (FC) in the BNM (BNM-FC) is altered in patients with PD-MCI. Therefore, in this study, we compared the BNM-FC of patients with PD-MCI and PD patients with normal cognition (PD-NC), to evaluate the relationship between the observed differences of BNM-FC and neuropsychological test scores. Three patient groups, namely PD-MCI, PD-NC, and healthy controls (HCs) (n = 22 each) including were recruited for functional magnetic resonance imaging (fMRI) scanning and neuropsychological assessment. Analysis of covariance was used to assess the inter-group differences. The relationships between BNM-FC and results of cognitive tests were evaluated by partial correlation analysis. Multivariate pattern analysis was used to test whether PD-MCI can be distinguished from PD-NC based on the BNM-FC. Classifier performance was assessed through permutation testing. Compared to PD-NC and HCs, PD-MCI showed reduced BNM-FC in the right superior parietal lobe (SPL) and the right postcentral gyrus. Furthermore, a positive correlation was observed between BNM-FC and the clock copying test (CLOX)/auditory verbal learning test (AVLT) immediate recall scores. We found that 86.36% subjects were correctly classified based on the BNM-FC using the leave-one-out cross-validation (LOOCV) method, with a sensitivity of 90.91% and specificity of 81.82%. Our study provides new insights into the neural basis of cognitive dysfunction in PD patients. We also found that BNM-FC can be an effective feature to distinguish PD-MCI from PD-NC.

Dynamic Alterations of Spontaneous Neural Activity in Parkinson's Disease: A Resting-State fMRI Study.

Objective: To investigate the dynamic amplitude of low-frequency fluctuations (dALFFs) in patients with Parkinson's disease (PD) and healthy controls (HCs) and further explore whether dALFF can be used to test the feasibility of differentiating PD from HCs. Methods: Twenty-eight patients with PD and 28 demographically matched HCs underwent resting-state functional magnetic resonance imaging (rs-fMRI) scans and neuropsychological tests. A dynamic method was used to calculate the dALFFs of rs-fMRI data obtained from all subjects. The dALFF alterations were compared between the PD and HC groups, and the correlations between dALFF variability and disease duration/neuropsychological tests were further calculated. Then, the statistical differences in dALFF between both groups were selected as classification features to help distinguish patients with PD from HCs through a linear support vector machine (SVM) classifier. The classifier performance was assessed using a permutation test (repeated 5,000 times). Results: Significantly increased dALFF was detected in the left precuneus in patients with PD compared to HCs, and dALFF variability in this region was positively correlated with disease duration. Our results show that 80.36% (p < 0.001) subjects were correctly classified based on the SVM classifier by using the leave-one-out cross-validation method. Conclusion: Patients with PD exhibited abnormal dynamic brain activity in the left precuneus, and the dALFF variability could distinguish PD from HCs with high accuracy. Our results showed novel insights into the pathophysiological mechanisms of PD.

Segmental Liver Stiffness Evaluated with Magnetic Resonance Elastography Is Responsive to Endovascular Intervention in Patients with Budd-Chiari Syndrome.

OBJECTIVE: To assess segmental liver stiffness (LS) with MRI before and after endovascular intervention in patients with Budd-Chiari syndrome (BCS). MATERIALS AND METHODS: Twenty-three patients (13 males and 10 females; mean age, 42.6 ± 12.6 years; age range, 31-56 years) with BCS as a primary liver disease were recruited for this study. Two consecutive magnetic resonance elastography (MRE) examinations were performed before the endovascular treatment. Fifteen patients who underwent endovascular intervention treatment also had follow-up MRE scans within three days after the procedure. LS was measured in three liver segments: the right posterior, right anterior, and left medial segments. Inter-reader and inter-exam repeatability were analyzed with intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Segmental LS and clinical characteristics before and after the intervention were also compared. RESULTS: Within three days of the endovascular intervention, all three segmental LS values decreased: LS of the right posterior segment = 7.23 ± 0.88 kPa (before) vs. 4.94 ± 0.84 kPa (after), LS of the right anterior segment = 7.30 ± 1.06 kPa (before) vs. 4.77 ± 0.85 kPa (after), and LS of the left medial segment = 7.22 ± 0.87 kPa (before) vs. 4.87 ± 0.72 kPa (after) (all p = 0.001). There was a significant correlation between LS changes and venous pressure gradient changes before and after treatments (r = 0.651, p = 0.009). The clinical manifestations of all 15 patients significantly improved after therapy. The MRE repeatability was excellent, with insignificant variations (inter-reader, ICC = 0.839-0.943: inter-examination, ICC = 0.765-0.869). Bland-Altman analysis confirmed excellent agreement (limits of agreement, 13.4-19.4%). CONCLUSION: Segmental LS measured by MRE is a promising repeatable quantitative biomarker for monitoring the treatment response to minimally invasive endovascular intervention in patients with BCS.

Diagnostic accuracy of magnetic resonance angiography for Budd-Chiari syndrome: A meta-analysis.

In recent years, the role of magnetic resonance angiography (MRA) in the diagnosis of Budd-Chiari Syndrome (BCS) has been the focus of various clinical studies. The purpose of the present study was to perform a meta-analysis of the diagnostic performance of MRA in patients with BCS by using digital subtraction angiography as a reference method. The search strategy for relevant research articles was based on the Cochrane Handbook for Systematic Reviews, and literature databases (including PubMed, Medline and China National Knowledge Infrastructure) and reference lists of retrieved studies published from 2000 to 2016 were searched. The Quality Assessment of Diagnostic Accuracy Studies tool was used to assess the methodological quality of these research studies by two reviewers independently. Summary estimates of the sensitivity, specificity, positive/negative likelihood ratio (LR+/-), diagnostic odds ratio (DOR) and the summary receiver operating characteristic (SROC) curve of MRA in identifying BCS were obtained. The pooled MRA estimates had a sensitivity of 97.6% [95% confidence interval (CI), 95.1-99.0%], a specificity of 70.7% (95% CI, 54.5-83.9%), an LR+ of 3.163 (95% CI, 2.03-4.94) and an LR- of 0.045 (95% CI, 0.02-0.09). The overall DOR was 94.053 (95% CI, 32.71-270.41). The area under the SROC curve was 0.972. In conclusion, MRA is an accurate modality for evaluating BCS.

Texture analysis of diffusion weighted imaging for the evaluation of glioma heterogeneity based on different regions of interest.

The present study aimed to explore the role of texture analysis with apparent diffusion coefficient (ADC) maps based on different regions of interest (ROI) in determining glioma grade. Thirty patients with glioma underwent diffusion-weighted imaging (DWI). ADC values were determined from the following three ROIs: i) whole tumor; ii) solid portion; and iii) peritumoral edema. Texture features were compared between high-grade gliomas (HGGs) and low-grade gliomas (LGGs) using the non-parametric Wilcoxon rank-sum test or the unpaired Student's t-test. Receiver operating characteristic (ROC) curves were constructed to determine the optimum threshold for inhomogeneity values in discrimination of HGGs from LGGs. With a spearman rank correlation model, the aforementioned ADC inhomogeneity values were correlated with the Ki-67 labeling index. With whole tumor ROI, inhomogeneity values proved to be significantly different between HGGs and LGGs (P<0.001). With solid portion ROI, inhomogeneity and median values showed significant difference between HGGs and LGGs (P=0.001 and P=0.043, respectively). With peritumoral edema ROI, entropy and edema volume demonstrated positive results (P=0.016, P<0.001). The whole tumor inhomogeneity parameter performed with better diagnostic accuracy (P=0.048) than selecting the solid portion ROI. The association between inhomogeneity and Ki-67 labeling index was significantly positive in whole tumor and solid portion ROI (R=0.628, P<0.001 and R=0.470, P=0.009). Texture analysis of DWI based on different ROI can provide various significant parameters to evaluate tumor heterogeneity, which were correlated with tumor grade. Particularly, the inhomogeneity value derived from whole tumor ROI provided high diagnostic value and predicting the status of tumor proliferation.

Non-contrast-enhanced MR angiography in the diagnosis of Budd-Chiari syndrome (BCS) compared with digital subtraction angiography (DSA): Preliminary results.

Non-CE MRA techniques (true steady-state free-precession, SSFP) have been used effectively for the selective visualization of the portal venous system and inferior vena cava. Budd-Chiari Syndrome (BCS) encompasses a number of conditions that cause the obstruction of the hepatic outflow tract from the small hepatic veins to the junction of the inferior vena cava (IVC) and right atrium. The purpose of this study was to diagnose BCS with IVC obstruction using respiratory triggered three-dimensional (3D) true SSFP with T-SLIP and compare to digital subtraction angiography (DSA). The image acquisition of 3D true SSFP scans was successfully performed in 108 patients (≧2 score). The mean and SDs of the relative SNR and CNR were 55.96±2.32 and 30.72±1.56, respectively. Intergroup agreement for the detection of the 4 types (membranous obstruction, segmental occlusion, and membranous obstruction with a hole and segmental stenosis) of BCS with IVC obstruction was excellent between the Time-SLIP and the DSA. In conclusion, Time-SLIP for the detection of IVC obstruction BCS does not require the use of contrast. This procedure can achieve a high success rate, high accuracy rate and fine image quality for the diagnosis of IVC obstruction BCS.