Characteristics of perivascular space dilatation in normal aging.

The increased incidence of dilated perivascular spaces (dPVSs) visible on MRI has been observed with advancing age, but the relevance of PVS dilatation to normal aging across the lifespan has yet to be fully clarified. In the current study, we sought to find out the age dependence of dPVSs by exploring changes in different characteristics of PVS dilatation across a wide range of age. For 1220 healthy subjects aged between 18 and 100 years, PVSs were automatically segmented and characteristics of PVS dilatation were assessed in terms of the burden, location, and morphology of PVSs in the white matter (WM) and basal ganglia (BG). A machine learning model using the random forests method was constructed to estimate the subjects' age by employing the PVS features. The constructed machine learning model was able to estimate the age of the subjects with an error of 9.53 years on average (correlation = 0.875). The importance of the PVS features indicated the primary contribution of the burden of PVSs in the BG and the additional contribution of locational and morphological changes of PVSs, specifically peripheral extension and reduced linearity, in the WM to age estimation. Indeed, adding the PVS location or morphology features to the PVS burden features provided an improvement to the performance of age estimation. The age dependence of dPVSs in terms of such various characteristics of PVS dilatation in healthy subjects could provide a more comprehensive reference for detecting brain disease-related PVS dilatation.

MR-self Noise2Noise: self-supervised deep learning-based image quality improvement of submillimeter resolution 3D MR images.

OBJECTIVES: The study aimed to develop a deep neural network (DNN)-based noise reduction and image quality improvement by only using routine clinical scans and evaluate its performance in 3D high-resolution MRI. METHODS: This retrospective study included T1-weighted magnetization-prepared rapid gradient-echo (MP-RAGE) images from 185 clinical scans: 135 for DNN training, 11 for DNN validation, 20 for qualitative evaluation, and 19 for quantitative evaluation. Additionally, 18 vessel wall imaging (VWI) data were included to evaluate generalization. In each scan of the DNN training set, two noise-independent images were generated from the k-space data, resulting in an input-label pair. 2.5D U-net architecture was utilized for the DNN model. Qualitative evaluation between conventional MP-RAGE and DNN-based MP-RAGE was performed by two radiologists in image quality, fine structure delineation, and lesion conspicuity. Quantitative evaluation was performed with full sampled data as a reference by measuring quantitative error metrics and volumetry at 7 different simulated noise levels. DNN application on VWI was evaluated by two radiologists in image quality. RESULTS: Our DNN-based MP-RAGE outperformed conventional MP-RAGE in all image quality parameters (average scores = 3.7 vs. 4.9, p < 0.001). In the quantitative evaluation, DNN showed better error metrics (p < 0.001) and comparable (p > 0.09) or better (p < 0.02) volumetry results than conventional MP-RAGE. DNN application to VWI also revealed improved image quality (3.5 vs. 4.6, p < 0.001). CONCLUSION: The proposed DNN model successfully denoises 3D MR image and improves its image quality by using routine clinical scans only. KEY POINTS: • Our deep learning framework successfully improved conventional 3D high-resolution MRI in all image quality parameters, fine structure delineation, and lesion conspicuity. • Compared to conventional MRI, the proposed deep neural network-based MRI revealed better quantitative error metrics and comparable or better volumetry results. • Deep neural network application to 3D MRI whose pulse sequences and parameters were different from the training data showed improvement in image quality, revealing the potential to generalize on various clinical MRI.

Identification of the intraparotid facial nerve on MRI: a systematic review and meta-analysis.

OBJECTIVES: Accurate preoperative localization of the intraparotid facial nerve (IFN) on MRI could reduce intraoperative injury. This study aimed to assess the detection rate of the IFN and its branches on MRI. METHODS: PubMed-MEDLINE and Embase databases were searched for articles published up to October 2019. The inclusion criteria were (a) adults, (b) MRI-based identification of IFN by radiologists, (c) original articles, and (d) detailed results to assess the proportion of visible IFN. Two radiologists reviewed the original articles. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was used to determine the quality of the selected studies. The DerSimonian-Laird random effects model was utilized to calculate the pooled estimates. Between-studies heterogeneity was evaluated using the chi-squared statistic test and Higgins' inconsistency index (I2). A subgroup meta-regression was performed to explore the factors causing study heterogeneity. RESULTS: Nine original articles with 209 subjects were included. MRI reported a high pooled detection rate of 99.8% (95% CI, 98.4-100%) for the main trunk of the IFN. The pooled rates for the temporofacial and cervicofacial branches were 90.4% (95% CI, 84.1-96.7%) and 96.3% (95% CI, 96.1-99.5%), respectively. Heterogeneity was detected only in the temporofacial branch (I2 = 83%) as a result of both slice thickness and the use of steady-state sequences with diffusion-weighted imaging (DWI) implementation. CONCLUSIONS: MRI showed an overall high detection rate of the IFN and its branches. Furthermore, an increased identification was observed in studies that used a slice thickness of < 1 mm and steady-state sequences with DWI implementation. KEY POINTS: • MRI showed an overall high detection rate of the intraparotid facial nerve and its branches. • Higher detection rate was observed in studies that used a slice thickness of < 1 mm and steady-state sequences with diffusion-weighted imaging.

Radiomics may increase the prognostic value for survival in glioblastoma patients when combined with conventional clinical and genetic prognostic models.

OBJECTIVES: To evaluate the additional prognostic value of multiparametric MR-based radiomics in patients with glioblastoma when combined with conventional clinical and genetic prognostic factors. METHODS: In this single-center study, patients diagnosed with glioblastoma between October 2007 and December 2019 were retrospectively screened and grouped into training and test sets with a 7:3 distribution. Segmentations of glioblastoma using multiparametric MRI were performed automatically via a convolutional-neural network. Prognostic factors in the clinical model included age, sex, type of surgery/post-operative treatment, and tumor location; those in the genetic model included statuses of isocitrate dehydrogenase-1 mutation and O-6-methylguanine-DNA-methyltransferase promoter methylation. Univariate and multivariate Cox proportional hazards analyses were performed for overall survival (OS) and progression-free survival (PFS). Integrated time-dependent area under the curve (iAUC) for survival was calculated and compared between prognostic models via the bootstrapping method (performances were validated with prediction error curves). RESULTS: Overall, 120 patients were included (training set, 85; test set, 35). The mean OS and PFS were 25.5 and 18.6 months, respectively. The prognostic performances of multivariate models improved when radiomics was added to the clinical model (iAUC: OS, 0.62 to 0.73; PFS, 0.58 to 0.66), genetic model (iAUC: OS, 0.59 to 0.67; PFS, 0.59 to 0.65), and combined model (iAUC: OS, 0.65 to 0.73; PFS, 0.62 to 0.67). In the test set, the combined model (clinical, genetic, and radiomics) demonstrated robust validation for risk prediction of OS and PFS. CONCLUSIONS: Radiomics increased the prognostic value when combined with conventional clinical and genetic prognostic models for OS and PFS in glioblastoma patients. KEY POINTS: • CNN-based automatic segmentation of glioblastoma on multiparametric MRI was useful in extracting radiomic features. • Patients with glioblastoma with high-risk radiomics scores had poor overall survival (hazards ratio 8.33, p < 0.001) and progression-free survival (hazards ratio 3.76, p < 0.001). • MR-based radiomics improved the survival prediction when combined with clinical and genetic factors (overall and progression-free survival iAUC from 0.65 to 0.73 and 0.62 to 0.67, respectively; both p < 0.001).

Multiphasic Computed Tomography Angiography Findings for Identifying Pseudo-Occlusion of the Internal Carotid Artery.

BACKGROUND AND PURPOSE: Differentiation between pseudo-occlusion and true occlusion of internal carotid artery (ICA) is important in treatment planning for acute ischemic stroke patients. We compared the findings of multiphasic computed tomography angiography between cervical ICA pseudo-occlusion and true occlusion at the cervical ICA in patients with anterior circulation acute ischemic stroke to determine their diagnostic value. METHODS: Thirty patients with nonvisualization of the proximal ICA were included. Diagnosis of pseudo- or true occlusion of the ICA was made based on digital subtraction angiography. Diagnostic performances of multiphasic computed tomography angiography findings-(1) a flame-shaped stump and (2) delayed contrast filling at the cervical ICA- were evaluated and compared. The Fisher exact test, χ2 test, or Wilcoxon rank-sum test and McNemar test were used in the data analysis. RESULTS: Twelve patients had true proximal ICA occlusion and 18 had pseudo-occlusion. Delayed contrast filling at the cervical ICA on multiphasic computed tomography angiography was found in all patients with pseudo-occlusion of the ICA, while 1 case of true occlusion showed delayed contrast filling (P<0.001). The presence of a flame-shaped stump was not significantly different between the pseudo- and true occlusion groups. The sensitivity of delayed contrast filling (0.94 [95% CI, 0.73-1]) was significantly higher than that of flame-shaped stump (0.75 [95% CI, 0.36-0.83]). CONCLUSIONS: We demonstrated that the delayed filling sign on multiphasic computed tomography angiography could be a useful and readily available finding for differentiating proximal ICA pseudo-occlusion from true occlusion.

MRI and Quantitative Magnetic Susceptibility Maps of the Brain after Serial Administration of Gadobutrol: A Longitudinal Follow-up Study.

Background The relationship between administration of macrocyclic gadolinium-based contrast agents and T1-weighted signal intensity (SI) change of the globus pallidus (GP) and dentate nucleus (DN) is, to the knowledge of the authors, not known. Purpose To determine if quantitative susceptibility mapping (QSM) can detect changes in magnetic susceptibility of the GP and DN after serial administration of macrocyclic gadobutrol in patients with primary brain tumors. Materials and Methods Patients diagnosed with primary brain tumors from August 2014 to February 2019 were eligible for this single-center retrospective study. Among 501 consecutive adult patients who were given at least one administration of gadobutrol, those who were previously administered an unknown or linear gadolinium-based contrast agent were excluded. Brain MRI scans with three-dimensional gradient-recalled-echo image phase data for QSM processing were reviewed. Regions of interest were drawn on the GP and DN on the basis of semiautomatic thresholding. Univariable generalized estimation equations were used to determine the associations between MRI measures (SI on T1-weighted images and magnetic susceptibility on QSM) and number of gadobutrol doses. Potential confounding factors were adjusted for in multivariable generalized estimating equation. Results Ninety patients (mean age, 51 years ± 17 [standard deviation]; 51 men) with 199 MRI scans were analyzed. In models adjusted for repeated observations between injections, the number of injections of gadobutrol was associated with the magnetic susceptibility of the GP (1.4 × 10-3 ppm/number of gadobutrol injections; P = .01) and DN (8.1 × 10-4 ppm/number of gadobutrol injections; P = .03). After adjustment for confounders, the number of gadobutrol injections remained an independent predictor of increased magnetic susceptibility in the GP (1.3 × 10-3 ppm/number of gadobutrol injections; 95% confidence interval: 0.39 × 10-3, -2.4 × 10-3; P = .006). There were no associations between number of gadobutrol injections and SI or magnetic susceptibility in the DN. Conclusion The magnetic susceptibility of the globus pallidus increased after serial administration of gadobutrol. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Wang and Prince in this issue.

Dual-energy CT for differentiating acute intracranial hemorrhage from contrast staining or calcification: a meta-analysis.

PURPOSE: This study aimed to comprehensively evaluate the diagnostic performance of dual-energy CT (DECT) for differentiating acute intracranial hemorrhage (ICH) from contrast staining or small calcifications via a systematic review and meta-analysis. METHODS: The PubMed-MEDLINE, EMBASE, and Cochrane Library databases were searched up to November 10, 2019. Original studies (prospective or retrospective cohort studies) with the primary aim of detecting ICH using DECT were selected. The diagnostic performance of DECT was assessed using bivariate and hierarchical summary receiver operating characteristic models. Quality assessment was performed according to the Quality Assessment of Diagnostic Accuracy Studies-2, while between-study heterogeneity was assessed using Higgins' inconsistency index (I2). To explore heterogeneity, subgroup meta-regression analyses were performed. Deeks' funnel plot asymmetry test was used for assessing publication bias. RESULTS: Nine studies comprising 402 patients with 453 lesions were included for data synthesis. The overall pooled sensitivity and specificity of DECT for ICH detection were 96% (95% CI, 77-99%) and 98% (95 CI, 93%-100%), respectively. Substantial and moderate between-study heterogeneities were observed for sensitivity (I2 = 90.3%) and specificity (I2 = 57.9%), respectively. In meta-regression analysis, type of cohort affected heterogeneity-studies including only stroke patients showed lower sensitivity (43.5% vs. 94.2%) but higher specificity (98.7% vs. 92.6%) than those with mixed etiologies (P < 0.001). Deeks' funnel plot asymmetry test revealed publication bias (P = 0.020). CONCLUSION: DECT demonstrated excellent diagnostic performance in terms of differentiating acute ICH from contrast staining and small calcifications. However, publication bias suggests the possibility of overestimated diagnostic performance, warranting large-scale, prospective cohort studies.

CT-based quantitative evaluation of the efficacy after radiofrequency ablation in patients with benign thyroid nodules.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of CT for quantitative assessment of the neck structures after RFA in patients with benign thyroid nodules. MATERIALS AND METHODS: This single-center, retrospective cohort study included 38 patients with benign thyroid nodules who had received RFA and had available pre- and post-treatment CT images. Changes in the tracheal anteroposterior (AP)/transverse diameter ratio, cross-sectional tracheal area, midline deviation of the trachea, and anterior neck angle after RFA were quantitatively measured using CT. Volume reduction rates (VRRs) for the thyroid gland and nodules were measured using CT and US, respectively, and the intraclass correlation coefficient (ICC) was calculated. The paired Wilcoxon signed-rank test was used to compare pre- and post-treatment CT-based measurements, and univariate linear regression analysis was performed to determine the association of VRR with the mean delivered radiofrequency energy, number of RFA sessions, and initial thyroid volume. RESULTS: After RFA, the tracheal AP/transverse diameter ratio and midline deviation were significantly decreased while the tracheal area and anterior neck angle were significantly increased (all, p < 0.001). The thyroid volume reduction was also significant (VRR, 42.1% ± 21.1%, p < 0.001), with moderate consistency between the CT-based thyroid VRR and US-based nodule VRR (ICC = 0.68, 95% confidence interval = 0.38-0.83, p < 0.001). The mean delivered radiofrequency energy (p = 0.565), number of RFA sessions (p = 0.209), and initial thyroid volume (p = 0.363) showed no significant association with VRR. CONCLUSION: CT-based quantitative assessments may be useful for evaluating improvements in the neck structures after RFA for benign thyroid nodules.

Comparison of efficacy and complications between radiofrequency ablation and repeat surgery in the treatment of locally recurrent thyroid cancers: a single-center propensity score matching study.

PURPOSE: To compare the efficacy and complication rates of radiofrequency ablation (RFA) and repeat surgery in the treatment of locally recurrent thyroid cancers. MATERIALS AND METHODS: A total of 221 patients with locally recurrent thyroid cancers who underwent either RFA (n = 96) or repeat surgery (n = 125) between March 2008 and March 2017 were retrospectively enrolled (range of follow-up, 1-10 years). Each cohort consisted of 70 patients after propensity score adjustment. Patients with more than three recurrent lesions were excluded. The primary and secondary end points were recurrence-free survival and complication rates, respectively. Recurrence-free survival curves were compared via the log-rank test. The complications-voice changes, hypocalcemia, and immediate procedural complications-were compared between the groups. In addition, pretreatment serum thyroglobulin (Tg) levels and those at the last follow-up were also compared between the two groups to examine therapeutic efficacy. RESULTS: After propensity score matching, both groups showed no significant differences in baseline characteristics. The recurrence-free survival rates were comparable between the RFA and surgery groups (p = .2). There were no significant differences in mean serum Tg levels and their mean decrease after treatment between the groups (p = .891 and p = .963, respectively). Immediate procedural complications and voice changes also showed no significant between-group differences (p = .316, p = .084, respectively). Hypocalcemia occurred only in the repeat surgery group (n = 18). Overall complications were significantly more frequent in the repeat surgery group (RFA, n = 7; surgery, n = 27; p < .001). CONCLUSION: RFA may be an effective and safe alternative to repeat surgery in the treatment of a small number of locally recurrent thyroid cancers.

Deep gray matter iron measurement in patients with liver cirrhosis using quantitative susceptibility mapping: Relationship with pallidal T1 hyperintensity.

BACKGROUND: The liver is a central organ for the metabolism of iron and manganese and the places where those metals are commonly deposited overlap in the brain. PURPOSE/HYPOTHESIS: To elucidate the relationship between pallidal T1 hyperintensity and iron deposition in the deep gray matter of liver cirrhosis patients using quantitative susceptibility mapping (QSM). STUDY TYPE: Retrospective case-control study SUBJECTS: In all, 38 consecutive liver cirrhosis patients who received brain magnetic resonance imaging (MRI) as pretransplant evaluation. FIELD STRENGTH/SEQUENCE: QSM was reconstructed from 3D multi- or single-echo phase images at 3T. T1 -weighted images were used for the assessment of pallidal hyperintensity and pallidal index (PI). ASSESSMENT: Patients were divided into two groups according to the presence of pallidal hyperintensity by consensus of two radiologists. Susceptibility values were acquired for five deep gray matter structures. STATISTICAL TEST: QSM measures were compared between two groups using the t-test. We also calculated Pearson correlations between QSM measures and PI. RESULTS: In all, 26 patients showed pallidal hyperintensity (T1 h group) and 12 did not (T1 n group). The susceptibility of the globus pallidus (GP) in the T1 h group (120.6 ± 38.1 ppb) was significantly lower than that in the T1 n group (150.0 ± 35.2, P = 0.030). The susceptibility of the dentate nucleus (DN) in the T1 h group (88.1 ± 31.0) was significantly lower than that in the T1 n group (125.6 ± 30.6, P = 0.001). Negative correlation between the susceptibility of GP (r = -0.37, P = 0.022) and the PI, and between DN (r = -0.43, P < 0.001) and the PI was found. DATA CONCLUSION: Liver cirrhosis patients with pallidal T1 hyperintensity had lower susceptibility values in the GP and DN than those without it. This suggests a possible interaction between iron and manganese in the brains of liver cirrhosis patients. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1342-1349.

Correlation-based perfusion mapping using time-resolved MR angiography: A feasibility study for patients with suspicions of steno-occlusive craniocervical arteries.

PURPOSE: To explore the feasibility of using correlation-based time-delay (CTD) maps produced from time-resolved MR angiography (TRMRA) to diagnose perfusion abnormalities in patients suspected to have steno-occlusive lesions in the craniocervical arteries. MATERIALS AND METHODS: Twenty-seven patients who were suspected to have steno-occlusive lesions in the craniocervical arteries underwent both TRMRA and brain single-photon emission computed tomography (SPECT). TRMRA was performed on the supra-aortic area after intravenous injection of a 0.03 mmol/kg gadolinium-based contrast agent. Time-to-peak (TTP) maps and CTD maps of the brain were automatically generated from TRMRA data, and their quality was assessed. Detection of perfusion abnormalities was compared between CTD maps and the time-series maximal intensity projection (MIP) images from TRMRA and TTP maps. Correlation coefficients between quantitative changes in SPECT and parametric maps for the abnormal perfusion areas were calculated. RESULTS: The CTD maps were of significantly superior quality than TTP maps (p < 0.01). For perfusion abnormality detection, CTD maps (kappa 0.84, 95% confidence interval [CI] 0.67-1.00) showed better agreement with SPECT than TTP maps (0.66, 0.46-0.85). For perfusion deficit detection, CTD maps showed higher accuracy (85.2%, 95% CI 66.3-95.8) than MIP images (66.7%, 46-83.5), with marginal significance (p = 0.07). In abnormal perfusion areas, correlation coefficients between SPECT and CTD (r = 0.74, 95% CI 0.34-0.91) were higher than those between SPECT and TTP (r = 0.66, 0.20-0.88). CONCLUSION: CTD maps generated from TRMRA were of high quality and offered good diagnostic performance for detecting perfusion abnormalities associated with steno-occlusive arterial lesions in the craniocervical area. KEY POINTS: • Generation of perfusion parametric maps from time-resolved MR angiography is clinically useful. • Correlation-based delay maps can be used to detect perfusion abnormalities associated with steno-occlusive craniocervical arteries. • Estimation of correlation-based delay is robust for low signal-to-noise 4D MR data.

Linear sign in cystic brain lesions ≥5 mm: A suggestive feature of perivascular space.

OBJECTIVE: To determine the prevalence of a linear sign within enlarged perivascular space (EPVS) and chronic lacunar infarction (CLI) ≥ 5 mm on T2-weighted imaging (T2WI) and time-of-flight (TOF) magnetic resonance angiography (MRA), and to evaluate the diagnostic value of the linear signs for EPVS over CLI. METHODS: This study included 101 patients with cystic lesions ≥ 5 mm on brain MRI including TOF MRA. After classification of cystic lesions into EPVS or CLI, two readers assessed linear signs on T2WI and TOF MRA. We compared the prevalence and the diagnostic performance of linear signs. RESULTS: Among 46 EPVS and 51 CLI, 84 lesions (86.6%) were in basal ganglia. The prevalence of T2 and TOF linear signs was significantly higher in the EPVS than in the CLI (P < .001). For the diagnosis of EPVS, T2 and TOF linear signs showed high sensitivity (> 80%). TOF linear sign showed significantly higher specificity (100%) and accuracy (92.8% and 90.7%) than T2 linear sign (P < .001). CONCLUSIONS: T2 and TOF linear signs were more frequently observed in EPVS than CLI. They showed high sensitivity in differentiation of them, especially for basal ganglia. TOF sign showed higher specificity and accuracy than T2 sign. KEY POINTS: • Linear sign is a suggestive feature of EPVS. • Time-of-flight magnetic resonance angiography can reveal the lenticulostriate artery within perivascular spaces. • Linear sign helps differentiation of EPVS and CLI, especially in basal ganglia.

The phase value of putamen measured by susceptibility weighted images in Parkinson's disease and in other forms of Parkinsonism: a correlation study with F18 FP-CIT PET.

BACKGROUND: Iron deposition of basal ganglia in Parkinson's disease (PD) can be measured using susceptibility weighted images (SWI) on magnetic resonance imaging (MRI). Fluoropropyl carbomethoxy-3b-4-iodophenyltropane (F18 FP-CIT) positron emission tomography (PET) has been used to differentiate Parkinsonism. PURPOSE: To compare SWI phase values in Parkinsonian syndrome and age-matched control and to correlate them with F18 FP-CIT PET. MATERIAL AND METHODS: Retrospectively, patients with Parkinsonian movement disorder (n = 62) and age-matched control (n = 16) were enrolled. Mean phase values on SWI were measured by region of interest (ROI) in putamens and caudate heads. Mean standardized uptake value (SUV) on F18 FP-CIT were measured in the same ROIs of PD (n = 40) and other forms of Parkinsonism (n = 22). A statistical analysis was performed to compare the phase values and SUVs and to correlate them between groups. RESULTS: The putaminal mean phase values were higher in Parkinsonism than in the control (P ≤ 0.001). There was no difference of phase value in caudate head among the groups. Also, the mean phase value of putamen between PD and other forms of Parkinsonism was not different. Mean SUV of F18 FP-CIT in the putamen was lower in PD than other forms of Parkinsonism (P ≤ 0.014). However, there was no significant correlation between phase values and mean SUV (P > 0.05). CONCLUSION: The putaminal phase value was higher than in Parkinsonian syndrome than in the age-matched controls. F18 FP-CIT PET/CT showed different tracer activity between PD and other forms of Parkinsonism. However, no correlation between phase and SUV values was discovered.

Non-stenotic intracranial arteries have atherosclerotic changes in acute ischemic stroke patients: a 3T MRI study.

INTRODUCTION: The aim of this study is to evaluate the degree of atherosclerotic changes in intracranial arteries by assessing arterial wall thickness using T1-weighted 3D-turbo spin echo (3D-TSE) and time-of-flight MR angiography (TOF-MRA) in patients with acute ischemic stroke as compared with unaffected controls. METHODS: Thirty-three patients with acute ischemic stroke and 36 control patients were analyzed. Acute ischemic stroke patients were divided according to TOAST classification. At both distal internal carotid arteries and basilar artery without stenosis, TOF-MRA was used to select non-stenotic portion of assessed arteries. 3D-TSE was used to measure the area including the lumen and wall (AreaOuter) and luminal area (AreaInner). The area of the vessel wall (AreaVW) of assessed intracranial arteries and the ratio index (RI) of each patient were determined. RESULTS: AreaInner, AreaOuter, AreaVW, and RI showed good inter-observer reliability and excellent intra-observer reliability. AreaInner did not significantly differ between stroke patients and controls (P = 0.619). However, AreaOuter, AreaVW, and RI were significantly larger in stroke patients (P < 0.001). The correlation coefficient between AreaInner and AreaOuter was higher in the controls (r = 0.918) than in large vessel disease patients (r = 0.778). RI of large vessel disease patients was significantly higher than that of normal control, small vessel disease, and cardioembolic groups. CONCLUSION: In patients with acute ischemic stroke, wall thickening and positive remodeling are evident in non-stenotic intracranial arteries. This change is more definite in stroke subtype that is related to atherosclerosis than that in other subtypes which are not.

Supra-aortic low-dose contrast-enhanced time-resolved magnetic resonance (MR) angiography at 3 T: comparison with time-of-flight MR angiography and high-resolution contrast-enhanced MR angiography.

BACKGROUND: Low-dose, time-resolved, contrast-enhanced, magnetic resonance angiography (TR-CEMRA) has been described previously; however, a comparative study between low dose TR-CEMRA and time-of-flight MRA (TOF-MRA) in the diagnosis of supra-aortic arterial stenosis has not yet been published. PURPOSE: To demonstrate the feasibility and effectiveness of low-dose TR-CEMRA compared with TOF-MRA, using high-resolution contrast-enhanced MRA (HR-CEMRA) as the reference standard. MATERIAL AND METHODS: This prospective study consisted of 30 consecutive patients. All patients underwent TOF-MRA of the neck and circle of Willis and supra-aortic HR-CEMRA, followed by supra-aortic low-dose TR-CEMRA. Gadoterate meglumine (Gd-DOTA, Dotarem(®), Guerbet, Roissy CdG Cedex, France) was injected at a dose of 0.1 mmol/kg for HR-CEMRA, followed by a 0.03 mmol/kg bolus for low-dose TR-CEMRA. Three readers evaluated the assessibility and image quality, and then two readers classified each stenosis into the following categories: normal (0-30%), mild stenosis (31-50%), moderate (51-70%), severe (71-99%), and occlusion. RESULTS: TR-CEMRA and HR-CEMRA showed a greater number of assessable arterial segments than TOF-MRA (P < 0.01). For TR-CEMRA, 29 cases showed within or better than the diagnostic range, whereas all 30 cases were in the diagnostic range for TOF-MRA and HR-CEMRA. For evaluation of stenosis in a total of 743 arterial segments, both TR-CEMRA and TOF-MRA results agreed with those of HR-CEMRA in 729 segments (98.1%), with excellent inter-observer agreement of TR-CEMRA; stenosis was overestimated in nine segments (1.2%) and underestimated in five segments (0.7%). For diagnosis of stenosis using 30% as the cut-off value on HR-CEMRA, the sensitivity and specificity were 88.2% and 99.3%, respectively, for the TR-CEMRA procedure, versus 94.1% and 99.6%, respectively, for TOF-MRA. CONCLUSION: Low-dose TR-CEMRA is feasible and effective in the diagnosis of supra-aortic arterial stenosis, and could be more useful option than TOF-MRA.

Dosimetric Effects of Magnetic Resonance Imaging-assisted Radiotherapy Planning: Dose Optimization for Target Volumes at High Risk and Analytic Radiobiological Dose Evaluation.

Based on the assumption that apparent diffusion coefficients (ADCs) define high-risk clinical target volume (aCTVHR) in high-grade glioma in a cellularity-dependent manner, the dosimetric effects of aCTVHR-targeted dose optimization were evaluated in two intensity-modulated radiation therapy (IMRT) plans. Diffusion-weighted magnetic resonance (MR) images and ADC maps were analyzed qualitatively and quantitatively to determine aCTVHR in a high-grade glioma with high cellularity. After confirming tumor malignancy using the average and minimum ADCs and ADC ratios, the aCTVHR with double- or triple-restricted water diffusion was defined on computed tomography images through image registration. Doses to the aCTVHR and CTV defined on T1-weighted MR images were optimized using a simultaneous integrated boost technique. The dosimetric benefits for CTVs and organs at risk (OARs) were compared using dose volume histograms and various biophysical indices in an ADC map-based IMRT (IMRTADC) plan and a conventional IMRT (IMRTconv) plan. The IMRTADC plan improved dose conformity up to 15 times, compared to the IMRTconv plan. It reduced the equivalent uniform doses in the visual system and brain stem by more than 10% and 16%, respectively. The ADC-based target differentiation and dose optimization may facilitate conformal dose distribution to the aCTVHR and OAR sparing in an IMRT plan.

Non-contrast-enhanced 4D MR angiography with STAR spin labeling and variable flip angle sampling: a feasibility study for the assessment of Dural Arteriovenous Fistula.

INTRODUCTION: This study aimed to evaluate the feasibility of non-contrast-enhanced 4D magnetic resonance angiography (NCE 4D MRA) with signal targeting with alternative radiofrequency (STAR) spin labeling and variable flip angle (VFA) sampling in the assessment of dural arteriovenous fistula (DAVF) in the transverse sinus. METHODS: Nine patients underwent NCE 4D MRA for the evaluation of DAVF in the transverse sinus at 3 T. One patient was examined twice, once before and once after the interventional treatment. All patients also underwent digital subtraction angiography (DSA) and/or contrast-enhanced magnetic resonance angiography (CEMRA). For the acquisition of NCE 4D MRA, a STAR spin tagging method was used, and a VFA sampling was applied in the data readout module instead of a constant flip angle. Two readers evaluated the NCE 4D MRA data for the diagnosis of DAVF and its type with consensus. The results were compared with those from DSA and/or CEMRA. RESULTS: All patients underwent NCE 4D MRA without any difficulty. Among seven patients with patent DAVFs, all cases showed an early visualization of the transverse sinus on NCE 4D MRA. Except for one case, the type of DAVF of NCE 4D MRA was agreed with that of reference standard study. Cortical venous reflux (CVR) was demonstrated in two cases out of three patients with CVR. CONCLUSION: NCE 4D MRA with STAR tagging and VFA sampling is technically and clinically feasible and represents a promising technique for assessment of DAVF in the transverse sinus. Further technical developments should aim at improvements of spatial and temporal coverage.

Effects of bilateral tDCS over DLPFC on response inhibition, craving, and brain functional connectivity in Internet gaming disorder: A randomized, double-blind, sham-controlled trial with fMRI.

Background and aims: Impaired inhibitory control accompanied by enhanced craving is hallmark of addiction. This study investigated the effects of transcranial direct current stimulation (tDCS) on response inhibition and craving in Internet gaming disorder (IGD). We examined the brain changes after tDCS and their correlation with clinical variables. Methods: Twenty-four males with IGD were allocated randomly to an active or sham tDCS group, and data from 22 participants were included for analysis. Participants self-administered bilateral tDCS over the dorsolateral prefrontal cortex (DLPFC) for 10 sessions. Stop-signal tasks were conducted to measure response inhibition and participants were asked about their cravings for Internet gaming at baseline and post-tDCS. Functional magnetic resonance imaging data were collected at pre- and post-tDCS, and group differences in resting-state functional connectivity (rsFC) changes from the bilateral DLPFC and nucleus accumbens were examined. We explored the relationship between changes in the rsFC and behavioral variables in the active tDCS group. Results: A significant group-by-time interaction was observed in response inhibition. After tDCS, only the active group showed a decrease in the stop-signal reaction time (SSRT). Although craving decreased, there were no significant group-by-time interactions or group main effects. The anterior cingulate cortex (ACC) showed group differences in post- versus pre-tDCS rsFC from the right DLPFC. The rsFC between the ACC and left middle frontal gyrus was negatively correlated with the SSRT. Discussion and conclusion: Our study provides preliminary evidence that bilateral tDCS over the DLPFC improves inhibitory control and could serve as a therapeutic approach for IGD.

Intramural hematoma detection by susceptibility-weighted imaging in intracranial vertebral artery dissection.

BACKGROUND: The radiologic diagnosis of vertebral artery dissection (VAD) depends on characteristic intraluminal findings on angiography and intramural hematoma or a double-lumen sign on high-resolution vessel wall imaging. We aimed to evaluate the accuracy of intramural hematoma sign on susceptibility-weighted imaging (SWI) in VAD. METHODS: We retrospectively analyzed SWI, phase map images and brain computed tomography (CT) of the consecutive patients who suffered an ischemic stroke in the vertebral artery territory from August 2010 to July 2012. We divided the patients into 2 groups: the VAD group and the nondissection group. VAD was diagnosed by conventional catheter angiographic findings (aneurysmal dilatation, pearl-and-string or tapered steno-occlusion) and pathognomonic findings such as intramural hematoma or a double-lumen sign on the source images of TOF-MRA, high-resolution T1-weighted MRI or high-resolution T2-weighted MRI. Intramural hematoma sign was considered positive if the patient had an eccentric or concentric hypointense signal lesion in the vertebral artery on SWI, a corresponding hyperintense signal on phase map and no evidence of calcification on the brain CT, suggesting blood products other than calcification. Two experienced neuroradiologists blinded to clinical information and angiographic findings were asked to judge for the presence of intramural hematoma sign on SWI. The accuracy of intramural hematoma sign on SWI was evaluated. Phase value, demographic and clinical data were compared between the VAD and the nondissection groups. RESULTS: Thirty-nine patients were included: 10 in the VAD group and 29 in the non-dissection group. Among the VAD group cases, intramural hematoma sign on SWI was positive in 9 of the 10 VAD cases and in 1 out of the 29 cases in the nondissection group. The intramural hematoma sign on SWI was significantly associated with VAD (p < 0.001), and showed sensitivity of 90% and specificity of 96.6%. Mean phase values of intramural hematomas (n = 9) were all positive and those of calcified lesions (n = 13) were all negative (0.45 radian vs. -0.42 radian, p < 0.001). CONCLUSIONS: The intramural hematoma sign on SWI was significantly associated with VAD and the phase map values were higher in intramural hematomas when compared with atherosclerotic calcifications.