Diffusion-weighted Magnetic Resonance Imaging Studies Research Articles

Effects of Photon versus Carbon-Ion Irradiation in the Rat Cervical Spinal Cord - a Serial T2 and Diffusion-weighted Magnetic Resonance Imaging Study.

Carbon-ion irradiation is increasingly used at the skull base and spine near the radiation-sensitive spinal cord. To better characterize the invivo radiation response of the cervical spinal cord, radiogenic changes in the high-dose area were measured in rats using magnetic resonance imaging (MRI) diffusion measurements in comparison to conventional photon irradiations. In this longitudinal MRI study, we examined the gray matter (GM) of the cervical spinal cord in 16 female Sprague-Dawley rats after high-dose photon (n = 8) or carbon-ion (12C) irradiation (n = 8) and in 6 sham-exposed rats until myelopathy occurred. The differences in the diffusion pattern of the GM of the cervical spinal cord were examined until the endpoint of the study, occurrence of paresis grade II of both forelimbs was reached. In both radiation techniques, the same order of the occurrence of MR-morphological pathologies was observed - from edema formation to a blood spinal cord barrier (BSCB) disruption to paresis grade II of both forelimbs. However, carbon-ion irradiation showed a significant increase of the mean apparent diffusion coefficient (ADC; P = 0.031) with development of a BSCB disruption in the GM. Animals with paresis grade II as a late radiation response had a highly significant increase in mean ADC (P = 0.0001) after carbon-ion irradiation. At this time, a tendency was observed for higher mean ADC values in the GM after 12C irradiation as compared to photon irradiation (P = 0.059). These findings demonstrated that carbon-ion irradiation leads to greater structural damage to the GM of the rat cervical spinal cord than photon irradiation due to its higher linear energy transfer (LET) value.

Microstructural Changes in the Spinothalamic Tract of CPSS Patients: Preliminary Results from a Single-Center Diffusion-Weighted Magnetic Resonance Imaging Study.

Chronic pain after spinal surgery (CPSS), formerly known as failed back surgery syndrome, encompasses a variety of highly incapacitating chronic pain syndromes emerging after spinal surgery. The intractability of CPSS makes objective parameters that could aid classification and treatment essential. In this study, we investigated the use of cerebral diffusion-weighted magnetic resonance imaging. Cerebral 3T diffusion-weighted (DW-) MRI data from adult CPSS patients were assessed and compared with those of healthy controls matched by age and gender. Only imaging data without relevant artefacts or significant pathologies were included. Apparent diffusion coefficient (ADC) maps were calculated from the b0 and b1000 values using nonlinear regression. After skull stripping and affine registration of all imaging data, ADC values for fifteen anatomical regions were calculated and analyzed with independent samples T-tests. A total of 32 subjects were included (sixteen CPSS patients and sixteen controls). The mean ADC value of the spinothalamic tract was found to be significantly higher in CPSS patients compared with in healthy controls (p = 0.013). The other anatomical regions did not show statistically different ADC values between the two groups. Our results suggest that patients suffering from CPSS are subject to microstructural changes, predominantly within the cerebral spinothalamic tract. Additional research could possibly lead to imaging biomarkers derived from ADC values in CPSS patients.

677 Amide Proton Transfer-Weighted Imaging Versus Diffusion-Weighted Imaging for Monitoring Treatment Response in Glioma Patients: A Systematic Review and Meta-Analysis

Abstract Aim Monitoring treatment response in glioma (GM) patients remains a challenge, as tumour recurrence (TR) and treatment-related injury (TRI) both appear similarly on standard magnetic resonance imaging (MRI). Although diffusion-weighted MRI (DWI) is gold standard, equivocal patients still undergo invasive biopsies for diagnosis. Amide proton transfer-weighted MRI (APTw) may more accurately differentiate TR from TRI, reducing surgical intervention rates. Hence, this systematic review and meta-analysis aimed to determine how APTw compares to DWI in the identification of TR from TRI. Method A search strategy was used to select studies investigating the diagnostic ability of DWI or APTw in detecting TR from Ovid MEDLINE ®, Ovid Embase, Web of Science, Cochrane Central Register of Controlled Trials, and Thai Clinical Trials Registry. Selection criteria were applied to retrieve studies and methodologies critically appraised according to the QUADAS-2 tool. Conclusions from studies were synthesised, and the sensitivity and specificity for TR detection pooled. Results 18 studies were included in the analysis (11 DWI, 6 APTw, 1 both). For TR, APTw signal measured significantly higher, whereas apparent diffusion coefficients derived from DWI images were significantly lower. In DWI studies, combined sensitivity and specificity for TR was 84.4% (95% CI, 72.5%-91.7%) and 81.2% (95% CI, 67.9%-89.8%) accordingly. Meta-analysis was not performed for APTw due to limited study numbers. In general, studies had low methodological quality and were associated with a risk of bias. Conclusions Overall, though comparisons between DWI and APTw in monitoring GM treatment were inconclusive, this study supports the potential use of APTw in neurosurgery.

Volumetric tumor segmentation according to diffusion-weighted MRI data in predicting and evaluating the response to chemotherapy in bladder cancer

The purpose of the study was to develop and evaluate the technique for volumetric tumor segmentation based on diffusion-weighted magnetic resonance imaging (DW-MRI) in predicting and assessing the response to chemotherapy in patients with bladder cancer (BC). Material and Methods. We examined 26 patients with morphologically verified transitional cell carcinoma of the bladder. The group was characterized by the presence of one or several tumors with a size of 17 to 46 mm. Before planning chemotherapy according to the M-VAC scheme, a study and post-processing of DW-MRI with volumetric segmentation of lesions, assessment of the volume and apparent diffusion coefficient (ADC) in the entire tumor mass were performed. According to the ADC data, shape of the tumor and its relation to the bladder wall, the coefficient (C) for predicting the response to chemotherapy was calculated. Results. In the cases with a coefficient value below 0.51, a high risk of treatment failure was predicted, at C≥0.74, a positive effect of treatment was predicted. With a value of 0.51≤C<0.74, the prognosis was uncertain, stabilization was more likely. The sensitivity and specificity of the method were 92.3 % and 92.4 %, respectively. Conclusion. The method of volumetric segmentation makes it possible to predict and evaluate bladder cancer response to chemotherapy with a sufficiently high accuracy. The advantages of the method are the possibility of assessing the tumor regardless of the degree of filling of the bladder, with non-contrast MRI, and with large lesions.

Diffusion-Weighted Magnetic Resonance Imaging Demonstrates White Matter Alterations in Watershed Regions in Children With Moyamoya Without Stroke or Silent Infarct

BackgroundMoyamoya is a disease with progressive cerebral arterial stenosis leading to stroke and silent infarct. Diffusion-weighted magnetic resonance imaging (dMRI) studies show that adults with moyamoya have significantly lower fractional anisotropy (FA) and higher mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) compared with controls, which raises concern for unrecognized white matter injury. Children with moyamoya have significantly lower FA and higher MD in their white matter compared with controls. However, it is unknown which white matter tracts are affected in children with moyamoya. MethodsWe present a cohort of 15 children with moyamoya with 24 affected hemispheres without stroke or silent infarct compared with 25 controls. We analyzed dMRI data using unscented Kalman filter tractography and extracted major white matter pathways with a fiber clustering method. We compared the FA, MD, AD, and RD in each segmented white matter tract and combined white matter tracts found within the watershed region using analysis of variance. ResultsAge and sex were not significantly different between children with moyamoya and controls. Specific white matter tracts affected included inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, superior longitudinal fasciculus, thalamofrontal, uncinate fasciculus, and arcuate fasciculus. Combined watershed region white matter tracts in children with moyamoya had significantly lower FA (−7.7% ± 3.2%, P = 0.02) and higher MD (4.8% ± 1.9%, P = 0.01) and RD (8.7% ± 2.8%, P = 0.002). ConclusionsLower FA with higher MD and RD is concerning for unrecognized white matter injury. Affected tracts were located in watershed regions suggesting that the findings may be due to chronic hypoperfusion. These findings support the concern that children with moyamoya without overt stroke or silent infarction are sustaining ongoing injury to their white matter microstructure and provide practitioners with a noninvasive method of more accurately assessing disease burden in children with moyamoya.

Individualised profiling of white matter organisation in moderate-to-severe traumatic brain injury patients

Background and purposeApproximately 65% of moderate-to-severe traumatic brain injury (m-sTBI) patients present with poor long-term behavioural outcomes, which can significantly impair activities of daily living. Numerous diffusion-weighted MRI studies have linked these poor outcomes to decreased white matter integrity of several commissural tracts, association fibres and projection fibres in the brain. However, most studies have focused on group-based analyses, which are unable to deal with the substantial between-patient heterogeneity in m-sTBI. As a result, there is increasing interest and need in conducting individualised neuroimaging analyses. Materials and methodsHere, we generated a detailed subject-specific characterisation of microstructural organisation of white matter tracts in 5 chronic patients with m-sTBI (29 – 49y, 2 females), presented as a proof-of-concept. We developed an imaging analysis framework using fixel-based analysis and TractLearn to determine whether the values of fibre density of white matter tracts at the individual patient level deviate from the healthy control group (n = 12, 8F, Mage = 35.7y, age range 25 – 64y). ResultsOur individualised analysis revealed unique white matter profiles, confirming the heterogenous nature of m-sTBI and the need of individualised profiles to properly characterise the extent of injury. Future studies incorporating clinical data, as well as utilising larger reference samples and examining the test–retest reliability of the fixel-wise metrics are warranted. ConclusionsIndividualised profiles may assist clinicians in tracking recovery and planning personalised training programs for chronic m-sTBI patients, which is necessary to achieve optimal behavioural outcomes and improved quality of life.

Quantification of New Intracerebral Lesions on Diffusion-weighted Magnetic Resonance Imaging After Transcarotid Artery Revascularization for Treatment of Carotid Stenosis

Quantification of New Intracerebral Lesions on Diffusion-weighted Magnetic Resonance Imaging After Transcarotid Artery Revascularization for Treatment of Carotid Stenosis

Track-weighted imaging analysis of white matter microstructures in healthy children: Sex and hemispheric differences.

Structural substrates of sex differences in human function and behavior have been elucidated in previous studies. Diffusion weighted magnetic resonance imaging (DW-MRI) is a widely used non-invasive imaging technique in studying human brain white matter structural organization. While many DW-MRI studies reporting sex differences in WM structure are based on diffusion tensor imaging (DTI) measures, tract specific microstructural differences require further investigation. In this study, we aim to investigate sex differences and sex-specific hemispheric differences in white matter microstructural development in healthy 8-year-old children based on novel track weighted imaging (TWI) analysis. Average pathlength map (APM) is a TWI contrast in which the average length of fibers passing through a voxel is utilized. In this study, we employed tract specific APM measures to evaluate sex differences in WM microstructural development. A total of 37 WM tracts were analyzed including 7 commissural tracts, 9 bilateral association tracts and 6 bilateral projection tracts. APM maps were generated for each tract. Tract-wise group tests were done using the mean values of APM maps. Sex differences were tested using general linear model based group comparisons. Age and total brain volume were included as covariates in the group analysis. Sex specific hemispheric differences were performed for the 15 bilateral tracts. One sample t-tests were done independently for left>right and right>left cases and the APM measures were controlled for age and total cerebral hemispheric volume. P-values<0.05 were considered significant after correcting for multiple comparisons accounting for the total number of tracts. Significant sex differences were revealed in APM measures between boys and girls in 11 WM tracts including rostral body of corpus callosum (CC), left inferior fronto-occipital fasciculus (IFOF), right cingulum, bilateral first and second segments of superior longitudinal fasciculus (SLF), right middle longitudinal fasciculus (MLF), bilateral fronto-pontine (FPT) and right parieto-occipital pontine tracts (POPT). The sex differences showed higher APM values for these 11 tracts in boys as compared to that of girls. In hemispheric differences analysis for both boys and girls, 2 tracts, arcuate fasciculus and optic radiation showed higher APM in left tracts as compared right; 5 tracts, IFOF, MLF, third segment of SLF, FPT and superior thalamic radiation showed higher APM in right tracts as compared to left. This indicates that boys and girls possess similar lateral asymmetries in these 7 tracts. Additionally, anterior thalamic radiation (ATR) showed higher APM in left tract and 4 tracts, first segment of SLF, POPT, inferior longitudinal fasciculus and cortico-spinal tract showed higher APM in right for boys. In girls, second segment of SLF and uncinate fasciculus showed higher APM in right hemisphere. These results indicate different lateral asymmetries between boys and girls for 7 tracts. Overall, boys showed higher average fiber length in most of the tracts, even after controlling for total brain volume.

Plaque morphology effect on periprocedural asymptomatic cerebral embolism in carotid artery stenting using first-generation carotid stents: A diffusion-weighted magnetic resonance imaging study.

Silent cerebral embolism with carotid artery stenting (CAS) may contribute to dementia and cognitive decline. Moreover, clinically silent embolism is an important index of peri-procedural stroke risk. The purpose of this study was to compare the periprocedural asymptomatic cerebral embolism rates of CAS procedures performed for noncalcified and calcified carotid artery plaques using diffusion-weighted magnetic resonance imaging (DW-MRI). Five hundred and seventy clinically uncomplicated patients who underwent CAS at our center from December 2010 to June 2020 (mean [standard deviation, SD] age 69.3 [8.2 years]) were analyzed retrospectively. The patients were divided into 2 groups with noncalcified (268 patients) and calcified (302 patients) plague. Cerebral DW-MRI was performed for the patients before and after CAS and compared. The presence of periprocedural new ipsilateral diffusion limitations detected on cerebral DW-MRI was noted as a significant finding. Ipsilateral diffusion limitations of the non-calcified and calcified plaque groups detected on cerebral DW-MRI were compared. The presence of periprocedural asymptomatic ipsilateral DW-MRI lesions was higher in patients in the noncalcified plaque group (45 [16.8%]) than in patients in the calcified plaque group (31 [10.3%]; P = 0.02). This study demonstrated that the rate of ipsilateral asymptomatic cerebral embolism detected on cerebral DW-MRI was higher in the CAS procedures performed for noncalcified carotid artery plaques than in those performed for calcified plaques.

Should we change our carotid stenting technique? Does balloon postdilatation increase periprocedural cranial embolism? A diffusion-weighted magnetic resonance imaging study.

IntroductionSilent cranial embolism has been demonstrated to cause dementia, cognitive decline and even ischemic stroke.AimTo compare the periprocedural asymptomatic cranial embolism rates of classical carotid artery stenting (CAS) and non-classical CAS methods using cranial diffusion-weighted magnetic resonance imaging (DW-MRI).Material and methods367 clinically uncomplicated patients who underwent CAS at our center between December 2010 and June 2020 (mean age: 69.3 ±11.9) were analyzed retrospectively. The patients were divided into 2 groups, classical CAS (130 patients) and non-classical CAS (237 patients). Classical CAS patients were defined as those who received a stent after suboptimal balloon dilatation (with a 3.0–4.0 mm balloon at 8–10 atmosphere (atm)) and underwent balloon postdilatation after stent deployment (with a 5.0–5.5 mm balloon at 8–10 atm). Non-classical CAS patients were defined as those in whom a stent was deployed after optimal balloon dilatation (with a 4.0–5.0 mm balloon at 10–14 atm) and did not undergo balloon postdilatation.ResultsPeriprocedural asymptomatic ipsilateral microembolism on cranial DW-MRI was detected in 25 (10.5%) patients in the non-classical CAS group and 24 (18.5%) in the classical CAS group. This difference between the two groups was found to be statistically significant (p = 0.033).ConclusionsThe rate of ipsilateral asymptomatic cranial embolism detected on cranial DW-MRI was lower in the CAS procedures in which optimal predilatation was performed but postdilatation after stent deployment was not performed compared to the CAS procedures in which suboptimal predilatation and postdilatation after stent deployment were performed.

Neuroimaging Studies of Brain Structure in Older Adults with Bipolar Disorder: A Review.

Bipolar disorder (BD) is a common mood disorder that can have severe consequences during later life, including suffering and impairment due to mood and cognitive symptoms, elevated risk for dementia and an especially high risk for suicide. Greater understanding of the brain circuitry differences involved in older adults with BD (OABD) in later life and their relationship to aging processes is required to improve outcomes of OABD. The current literature on gray and white matter findings, from high resolution structural and diffusion-weighted magnetic resonance imaging (MRI) studies, has shown that BD in younger age groups is associated with gray matter reductions within cortical and subcortical brain regions that subserve emotion processing and regulation, as well as reduced structural integrity of white matter tracts connecting these brain regions. While fewer neuroimaging studies have focused on OABD, it does appear that many of the structural brain differences found in younger samples are present in OABD. There is also initial suggestion that there are additional brain differences, for at least a subset of OABD, that may result from more pronounced gray and white matter declines with age that may contribute to adverse outcomes. Preclinical and clinical data supporting neuro-plastic and -protective effects of mood-stabilizing medications, suggest that treatments may reverse and/or prevent the progression of brain changes thereby reducing symptoms. Future neuroimaging research implementing longitudinal designs, and large-scale, multi-site initiatives with detailed clinical and treatment data, holds promise for reducing suffering, cognitive dysfunction and suicide in OABD.

Opposing white matter microstructure abnormalities in 22q11.2 deletion and duplication carriers

Deletions and duplications at the 22q11.2 locus are associated with significant neurodevelopmental and psychiatric morbidity. Previous diffusion-weighted magnetic resonance imaging (MRI) studies in 22q11.2 deletion carriers (22q-del) found nonspecific white matter (WM) abnormalities, characterized by higher fractional anisotropy. Here, utilizing novel imaging and processing methods that allow separation of signal contribution from different tissue properties, we investigate whether higher anisotropy is driven by (1) extracellular changes, (2) selective degeneration of secondary fibers, or (3) volumetric differences. We further, for the first time, investigate WM microstructure in 22q11.2 duplication carriers (22q-dup). Multi-shell diffusion-weighted images were acquired from 26 22q-del, 19 22q-dup, and 18 healthy individuals (HC). Images were fitted with the free-water model to estimate anisotropy following extracellular free-water elimination and with the novel BedpostX model to estimate fractional volumes of primary and secondary fiber populations. Outcome measures were compared between groups, with and without correction for WM and cerebrospinal fluid (CSF) volumes. In 22q-del, anisotropy following free-water elimination remained significantly higher compared with controls. BedpostX did not identify selective secondary fiber degeneration. Higher anisotropy diminished when correcting for the higher CSF and lower WM volumes. In contrast, 22q-dup had lower anisotropy and greater extracellular space than HC, not influenced by macrostructural volumes. Our findings demonstrate opposing effects of reciprocal 22q11.2 copy-number variation on WM, which may arise from distinct pathologies. In 22q-del, microstructural abnormalities may be secondary to enlarged CSF space and more densely packed WM. In 22q-dup, we see evidence for demyelination similar to what is commonly observed in neuropsychiatric disorders.

Development of brain white matter and math computation ability in children born very preterm and full-term

Children born very preterm (VPT; <32 weeks’ gestation) have alterations in brain white matter and poorer math ability than full-term (FT) peers. Diffusion-weighted magnetic resonance imaging studies suggest a link between white matter microstructure and math in VPT and FT children, although longitudinal studies using advanced modelling are lacking. In a prospective longitudinal cohort of VPT and FT children we used Fixel-Based Analysis to investigate associations between maturation of white matter fibre density (FD), fibre-bundle cross‐section (FC), and combined fibre density and cross‐section (FDC) and math computation ability at 7 (n = 136 VPT; n = 32 FT) and 13 (n = 130 VPT; n = 44 FT) years, as well as between change in white matter and math computation ability from 7 to 13 years (n = 103 VPT; n = 21 FT). In both VPT and FT children, higher FD, FC and FDC in visual, sensorimotor and cortico-thalamic/thalamo-cortical white matter tracts were associated with better math computation ability at 7 and 13 years. Longitudinally, accelerated maturation of the posterior body of the corpus callosum (FDC) was associated with greater math computation development. White matter-math associations were similar for VPT and FT children. In conclusion, white matter maturation is associated with math computation ability across late childhood, irrespective of birth group.

A Longitudinal Study of White Matter Development in Relation to Changes in Autism Severity Across Early Childhood

BackgroundCross-sectional diffusion-weighted magnetic resonance imaging studies suggest that young autistic children have alterations in white matter structure that differ from older autistic individuals. However, it is unclear whether these differences result from atypical neurodevelopment or sampling differences between young and older cohorts. Furthermore, the relationship between altered white matter development and longitudinal changes in autism symptoms is unknown. MethodsUsing longitudinal diffusion-weighted magnetic resonance imaging acquired over 2 to 3 time points between the ages of approximately 2.5 to 7.0 years in 125 autistic children and 69 typically developing control participants, we directly tested the hypothesis that autistic individuals have atypical white matter development across childhood. Additionally, we sought to determine whether changes in white matter diffusion parameters were associated with longitudinal changes in autism severity. ResultsAutistic children were found to have slower development of fractional anisotropy in the cingulum bundle, superior longitudinal fasciculus, internal capsule, and splenium of the corpus callosum. Furthermore, in the sagittal stratum, autistic individuals who increased in autism severity over time had a slower developmental trajectory of fractional anisotropy compared with individuals whose autism decreased in severity. In the uncinate fasciculus, autistic individuals who decreased in autism symptom severity also had greater increases in fractional anisotropy with age. ConclusionsThese longitudinal findings indicate that previously reported differences in diffusion-weighted magnetic resonance imaging measures between younger and older autism cohorts are attributable to an atypical developmental trajectory of white matter. Differences in white matter development between individuals whose autism severity increased, remained stable, or decreased suggest that these functional differences are associated with fiber development in the autistic brain.

Characterization of pediatric head and neck masses with quantitative analysis of diffusion-weighted imaging and measurement of apparent diffusion coefficients

Purpose:Our objective was to investigate the accuracy of quantitative diffusion-weighted imaging (DWI) to determine the histopathologic diagnosis of pediatric head and neck lesions.Materials and Methods:This retrospective study included 100 pediatric patients recently diagnosed with head and neck tumors. All patients underwent preoperative conventional magnetic resonance imaging (MRI) and DWI. Each lesion was evaluated according to signal characteristics, enhancement pattern, and diffusivity. The average apparent diffusion coefficient (ADC) obtained from each tumor was compared to the histological diagnosis of benign, locally malignant, or malignant categories.Results:Our retrospective study showed a significant negative correlation between average ADC and tumor histopathologic diagnosis (P < 0.001, r = -0.54). The mean ADC values of benign, locally malignant lesions, and malignant tumors were 1.65 ± 0.58 × 10–3, 1.43 ± 0.17 × 10–3, and 0.83 ± 0.23 × 10–3 mm2 s-1, respectively. The ADC values of benign and locally malignant lesions were overlapped. We found a cut-off value of ≥1.19 × 10–3 mm2s-1 to differentiate benign from malignant pediatric head and neck masses with a sensitivity of 97.3%, specificity of 80.0%, positive predictive value of 94.7%, and negative predictive value of 88.9%.Conclusion:Diffusion-weighted MRI study is an accurate, fast, noninvasive, and nonenhanced technique that can be used to characterize head and neck lesions. DWI helps to differentiate malignant from benign lesions based on calculated ADC values. Additionally, DWI is helpful to guide biopsy target sites and decrease the rate of unnecessary invasive procedures.

Anatomy of nerve fiber bundles at micrometer-resolution in the vervet monkey visual system.

Although the primate visual system has been extensively studied, detailed spatial organization of white matter fiber tracts carrying visual information between areas has not been fully established. This is mainly due to the large gap between tracer studies and diffusion-weighted MRI studies, which focus on specific axonal connections and macroscale organization of fiber tracts, respectively. Here we used 3D polarization light imaging (3D-PLI), which enables direct visualization of fiber tracts at micrometer resolution, to identify and visualize fiber tracts of the visual system, such as stratum sagittale, inferior longitudinal fascicle, vertical occipital fascicle, tapetum and dorsal occipital bundle in vervet monkey brains. Moreover, 3D-PLI data provide detailed information on cortical projections of these tracts, distinction between neighboring tracts, and novel short-range pathways. This work provides essential information for interpretation of functional and diffusion-weighted MRI data, as well as revision of wiring diagrams based upon observations in the vervet visual system.

The Incidence of Central Neurological Disorders Among Patients With Isolated Dizziness and the Diagnostic Yield of Neuroimaging Studies.

Dizziness is a common symptom among emergency department (ED) patients and is often associated with benign processes. The aim of this study was to investigate the incidence of severe central neurological pathologies in isolated dizziness cases and the diagnostic efficiency of neuroimaging studies. All applications for isolated dizziness to an academic ED between January 1, 2011, and December 31, 2017 were retrospectively reviewed. The frequency of these admissions, the demographic data of the patients, the results of cranial computed tomography (CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) studies, and the central neurological causes of isolated dizziness were recorded. The percentage of patients with isolated dizziness among all ED admissions was 2.5% (29,510/1,190,857). The median age of these patients was 52 years (interquartile range: 38 to 66) and 58% were female. During the study period, the rate of neuroimaging studies for isolated dizziness increased year by year, and a total of 6406 (21.7%) cranial CTs and 2896 (9.8%) DW-MRIs were performed. The diagnostic yield of neuroimaging studies was 0.6% for cranial CT and 3.9% for DW-MRI. Central neurological disorders were detected in 143 (0.48%) patients with isolated dizziness. The most common causes were posterior circulation ischemic strokes (47.5%), other ischemic strokes (18.9%), vertebrobasilar insufficiency (10.5%), and transient ischemic attack (8.4%). Isolated dizziness is rarely associated with central neurological pathologies. Neuroimaging studies, especially cranial CT, have low diagnostic yield in isolated dizziness and should therefore not be routine in the evaluation process.

Comparison of Embolic Protection with Proximal and Distal Protection Devices: Periprocedural Complications, Clinical Outcomes, and Cerebral Embolic Lesions on Diffusion-Weighted Magnetic Resonance Imaging

Two main types of embolic protection devices have been used during carotid artery stenting (CAS): distal protection devices (DPDs) and proximal protection devices (PPDs). We compared the complications, clinical outcomes, and new ischemic lesions on diffusion-weighted magnetic resonance imaging (DWI) studies between patients who had undergone CAS using a DPD or PPD. We performed a retrospective review of the data from patients who had undergone CAS from March 2010 to January 2016. The periprocedural and 30-day adverse events and new ischemic lesions on DWI studies after CAS were evaluated. CAS was performed in 103 patients (DPD, n=60; PPD, n= 43). The number of patients with new ischemic lesions was greater in the DPD than in the PPD group (78% vs. 56%; P= 0.014). Most lesions (>90%) were tiny (≤3 mm), and the average number of new tiny lesions per patient was significantly greater in the DPD than in the PPD group (mean, 9.6 vs. 4.0; P= 0.008). No significant differences in the periprocedural or 30-day adverse rates were noted between the 2 groups. Intolerance during the procedure occurred in 5 patients (12%) in the PPD group, 4of whom had poor collateral circulation. The number of new ischemic lesions per patient and the incidence of ischemic lesions found on DWI were significantly greater in the DPD than in the PPD group. The lack of differences in the periprocedural and 30-day adverse rates between the 2 groups suggests that cerebral microemboli might not be associated with the clinical outcomes. For patients with poor collateral status, DPDs should be used preferentially to avoid the neurologic compromise associated with PPDs.

A diffusion-weighted imaging tract-based spatial statistics study of autism spectrum disorder in preschool-aged children

BackgroundThe core symptoms of autism spectrum disorder (ASD) are widely theorized to result from altered brain connectivity. Diffusion-weighted magnetic resonance imaging (DWI) has been a versatile method for investigating underlying microstructural properties of white matter (WM) in ASD. Despite phenotypic and etiological heterogeneity, DWI studies in majority male samples of older children, adolescents, and adults with ASD have largely reported findings of decreased fractional anisotropy (FA) across several commissural, projection, and association fiber tracts. However, studies in preschool-aged children (i.e., < 30–40 months) suggest individuals with ASD have increased measures of WM FA earlier in development.MethodsWe analyzed 127 individuals with ASD (85♂, 42♀) and 54 typically developing (TD) controls (42♂, 26♀), aged 25.1–49.6 months. Voxel-wise effects of ASD diagnosis, sex, age, and their interaction on DWI measures of FA, mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) were investigated using tract-based spatial statistics (TBSS) while controlling mean absolute and relative motion.ResultsCompared to TD controls, males and females with ASD had significantly increased measures of FA in eight clusters (threshold-free cluster enhancement p < 0.05) that incorporated several WM tracts including regions of the genu, body, and splenium of the corpus callosum, inferior frontal-occipital fasciculi, inferior and superior longitudinal fasciculi, middle and superior cerebellar peduncles, and corticospinal tract. A diagnosis by sex interaction was observed in measures of AD across six significant clusters incorporating areas of the body, genu, and splenium of the corpus collosum. In these tracts, females with ASD showed increased AD compared to TD females, while males with ASD showed decreased AD compared to TD males.ConclusionsThe current findings support growing evidence that preschool-aged children with ASD have atypical measures of WM microstructure that appear to differ in directionality from alterations observed in older individuals with the condition. To our knowledge, this study represents the largest sample of preschool-aged females with ASD to be evaluated using DWI. Microstructural differences associated with ASD largely overlapped between sexes. However, differential relationships of AD measures indicate that sex likely modulates ASD neuroanatomical phenotypes. Further longitudinal study is needed to confirm and quantify the developmental relationship of WM structure in ASD.

Diffusion-weighted Renal MRI at 9.4\u2009Tesla Using RARE to Improve Anatomical Integrity

Diffusion-weighted magnetic resonance imaging (DWI) is a non-invasive imaging technique sensitive to tissue water movement. By enabling a discrimination between tissue properties without the need of contrast agent administration, DWI is invaluable for probing tissue microstructure in kidney diseases. DWI studies commonly make use of single-shot Echo-Planar Imaging (ss-EPI) techniques that are prone to suffering from geometric distortion. The goal of the present study was to develop a robust DWI technique tailored for preclinical magnetic resonance imaging (MRI) studies that is free of distortion and sensitive to detect microstructural changes. Since fast spin-echo imaging techniques are less susceptible to B0 inhomogeneity related image distortions, we introduced a diffusion sensitization to a split-echo Rapid Acquisition with Relaxation Enhancement (RARE) technique for high field preclinical DWI at 9.4 T. Validation studies in standard liquids provided diffusion coefficients consistent with reported values from the literature. Split-echo RARE outperformed conventional ss-EPI, with ss-EPI showing a 3.5-times larger border displacement (2.60 vs. 0.75) and a 60% higher intra-subject variability (cortex = 74%, outer medulla = 62% and inner medulla = 44%). The anatomical integrity provided by the split-echo RARE DWI technique is an essential component of parametric imaging on the way towards robust renal tissue characterization, especially during kidney disease.