Rapid Acquisition Gradient Echo Images Research Articles

Loss of hippocampal dentation in hippocampal sclerosis and its relationship to memory dysfunction.

Hippocampal dentation (HD) is a "toothlike" morphological feature observed on the inferior aspect of the human hippocampus. It has been found that HD varies dramatically in healthy adults and is positively associated with verbal and visual memory. In this work, we evaluate the loss of HD and its association with memory dysfunction in patients with temporal lobe epilepsy (TLE) who have hippocampal sclerosis (HS). Fifty-eight unilateral HS patients with neuropsychological data were identified from a retrospective database. T1-weighted magnetization-prepared rapid acquisition gradient echo images (~1mm resolution) were upsampled to .25mm and were processed using ASHS software to obtain ultra-high-resolution segmentations and three-dimensional renderings. Dentes were counted on the epileptic and contralateral sides, and associations were tested between dentation on the epileptic versus contralateral sides and measures of verbal and visuospatial memory with respect to the dominant versus nondominant hemisphere. The median number of dentes in epileptic hippocampi was significantly lower than in contralateral hippocampi (p<.0001). Among cases with HS in the dominant hemisphere, verbal memory was significantly correlated with contralateral nondominant hemisphere dentation (r=.43, p=.04). Similarly, among cases of HS in the nondominant hemisphere, visual memory was significantly correlated with contralateral dominant hemisphere dentation (r=.48, p=.04). All other analyses were not significant. This is the first study characterizing dentation in TLE patients with HS and its memory correlates. There is marked loss of dentation in sclerotic hippocampi compared to the unaffected contralateral hippocampi. Material-specific measures of memory performance are paradoxically correlated with dentation contralateral to the side with HS, suggesting that contralateral functional capacity explains some of the variation in memory across TLE patients. HD is an important variable to consider in understanding memory loss in TLE.

Comparing the Precision and Reliability Between Three Radiographic Techniques for Measuring Sporadic Vestibular Schwannomas

Several methods exist for measuring vestibular schwannoma (VS) size radiographically. Our aim was to compare the precision and reproducibility of three different radiographic measurement techniques for assessing VS tumor size. Twenty patients with unilateral, sporadic VS previously untreated were identified. All patients had thin-slice T1 weighted, postcontrasted magnetization prepared rapid acquisition gradient echo images. Three measurement techniques were performed using within-subject and between-subject comparison. Experimental comparison of interobserver agreement between techniques was calculated. Interobserver intraclass correlation coefficients, repeatability coefficients, and relative smallest detectable difference were calculated and compared. Mean tumor measurements were: 10.3 mm (maximum linear dimension, [MLD]), 495.9 mm3 (orthogonal volumetric analysis, [OVA]), and 572.1 mm3 (segmented volumetric analysis, [SVA]). Interobserver correlation coefficient was excellent for all measurement techniques, but highest for segmented volumetric analysis. Repeatability coefficient was 1.44 mm for MLD, 298.9 mm3 for OVA, and 174.8 mm3 for SVA. The smallest detectable difference was 13.9% for MLD, 60.2% for OVA, and 30.6% for SVA. A subgroup analysis was performed for small tumors (<14 mm) and large tumors (>14 mm) and demonstrated increased precision of segmented volumetric analysis for larger tumors. Semi-automated segmented volumetric analysis appears more precise than either linear measurement or orthogonal volumetric analysis for reporting VS tumor size, and becomes increasingly precise for larger tumors. Tumor volume and tumor volume change over time using SVA may be more sensitive in surveilling VS than current measurement techniques.

Magnetic resonance imaging of carotid plaques: current status and clinical perspectives.

Rupture of a vulnerable carotid plaque is one of the leading causes of stroke. Carotid magnetic resonance imaging (MRI) is able to visualize all the main hallmarks of plaque vulnerability. Various MRI sequences have been developed in the last two decades to quantify carotid plaque burden and composition. Often, a combination of multiple sequences is used. These MRI techniques have been extensively validated with histological analysis of carotid endarterectomy specimens. High agreement between the MRI and histological measures of plaque burden, intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), fibrous cap (FC) status, inflammation and neovascularization has been demonstrated. Novel MRI sequences allow to generate three-dimensional isotropic images with a large longitudinal coverage. Other new sequences can acquire multiple contrasts using a single sequence leading to a tremendous reduction in scan time. IPH can be easily identified as a hyperintense signal in the bulk of the plaque on strongly T1-weighted images, such as magnetization-prepared rapid acquisition gradient echo images, acquired within a few minutes with a standard neurovascular coil. Carotid MRI can also be used to evaluate treatment effects. Several meta-analyses have demonstrated a strong predictive value of IPH, LRNC, thinning or rupture of the FC for ischemic cerebrovascular events. Recently, in a large meta-analysis based on individual patient data of asymptomatic and symptomatic individuals with carotid artery stenosis, it was shown that IPH on MRI is an independent risk predictor for stroke, stronger than any known clinical risk parameter. Expert recommendations on carotid plaque MRI protocols have recently been described in a white paper. The present review provides an overview of the current status and applications of carotid plaque MR imaging and its future potential in daily clinical practice.

Identification of carotid non-hemorrhagic lipid-rich necrotic core by magnetization-prepared rapid acquisition gradient-echo imaging: Validation by contrast-enhanced T1 weighted imaging

Identification of carotid non-hemorrhagic lipid-rich necrotic core by magnetization-prepared rapid acquisition gradient-echo imaging: Validation by contrast-enhanced T1 weighted imaging

CAIDE Dementia Risk Score Indicates Cortical Thinning in Low‐Risk, Middle‐Aged Adults

Increased risk for the future development of Alzheimer's disease begins as early as midlife and can be predicted using modifiable cardiovascular and lifestyle‐related risk factors. The Cardiovascular Risk Factors, Aging and Incidence of Dementia (CAIDE) dementia risk score has been used to predict late life risk of dementia based on midlife vascular risk factors. Additionally, in older adults with mild or subjective cognitive impairment, higher CAIDE scores were associated with greater atrophy in the middle temporal and frontal regions of the brain.PurposeWe aimed to determine if CAIDE score is associated with cortical thickness in middle‐aged cognitively intact adults at risk for cardiovascular disease. We hypothesized individuals with higher CAIDE scores would have reduced cortical thickness in a priori regions associated with memory and attention‐executive function.MethodsA total of 155 middle‐age adults (49±6 years, 52.4% female) classified as cognitively normal were studied. CAIDE score was calculated using the original model that excludes ApoE e4 genotype. This includes age, sex, education level, systolic blood pressure, body mass index, total cholesterol, and physical inactivity. Each factor is given a specific weight and the total score ranges from 0 to 14. Cortical thickness was obtained from high resolution magnetization‐prepared rapid acquisition gradient‐echo images. Thickness values for 24 a priori regions of interest associated with memory and executive function were extracted and analyzed.ResultsA majority of the participants (95.5%) in this sample were categorized as low‐risk, having a CAIDE score of 8 or lower. After using a corrected p‐value (p=0.006) for multiple correlations, there were several significant negative associations between CAIDE score and cortical thickness. These include the right parahippocampal (r=−0.251, p=0.002), left pars opercularis (r=−0.244, p=0.002), right superior frontal (r=−0.229, p=0.004) and left superior frontal (r=−0.247, p=0.002) regions.ConclusionsHigher CAIDE scores in midlife are associated with lower cortical thickness in middle‐age adults at risk for cardiovascular disease. This finding supports the notion that cardiovascular risks may contribute to early alteration of brain structure. We propose that the CAIDE dementia risk score may be useful in predicting future risk of dementia even in low‐risk populations who have no indication of clinically significant cognitive impairment.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Identification of carotid lipid-rich necrotic core and calcification by 3D magnetization-prepared rapid acquisition gradient-echo imaging

Background and purposeThis study sought to investigate the feasibility of three-dimensional MPRAGE in identifying the lipid-rich necrotic core (LRNC) and calcification (CA) of carotid atherosclerotic plaques. Materials and methodsTwelve patients (mean age 68.4 ± 11.8 years; 7 males) with carotid atherosclerotic plaques on ultrasound were included and underwent multicontrast magnetic resonance (MR) vessel wall imaging. The contrast enhanced T1W (CE-T1W) images were considered as reference for identifying LRNC. The signal intensity of LRNC, CA, sterno-cleidomastoid muscle and fibrous tissue (FT) was measured on CE-T1W, T1W, T2W, and MPRAGE images, respectively. The relative signal intensity (rSI) of LRNC and CA against muscle or FT was compared among four sequences. Area under the curve (AUC) of rSIs of LRNC, CA and FT against muscle on MPRAGE, T1W and T2W images in discriminating the LRNC or CA from FT and the other plaque component was calculated. ResultsOf 352 slices, 88 (25.0%) had LRNC, 31 (8.8%) had CA, 14 (4.0%) had both LRNC and CA, and 247 (70.2%) had no components. Among four imaging sequences, MPRAGE images showed the lowest rSI of LRNC (0.34 ± 0.18) and CA (0.20 ± 0.16) against muscle, followed by T1W (0.48 ± 0.18 and 0.33 ± 0.21), CE-T1W (0.58 ± 0.23 and 0.40 ± 0.21) and T2W (0.71 ± 0.47 and 0.43 ± 0.40) images. In addition, the MPRAGE images showed the lowest rSI of LRNC (0.57 ± 0.26) and CA (0.33 ± 0.23) against FT. MPRAGE showed greater AUC than T2W and T1W in discriminating the LRNC (0.827 vs. 0.703 vs. 0.635) and CA (0.917 vs. 0.838 vs. 0.825). ConclusionMPRAGE sequence might be a potential non-contrast enhanced imaging tool for identification of carotid LRNC and CA.

Spinal cord volume loss: A marker of disease progression in multiple sclerosis.

Cross-sectional studies have shown that spinal cord volume (SCV) loss is related to disease severity in multiple sclerosis (MS). However, long-term data are lacking. Our aim was to evaluate SCV loss as a biomarker of disease progression in comparison to other MRI measurements in a large cohort of patients with relapse-onset MS with 6-year follow-up. The upper cervical SCV, the total brain volume, and the brain T2 lesion volume were measured annually in 231 patients with MS (180 relapsing-remitting [RRMS] and 51 secondary progressive [SPMS]) over 6 years on 3-dimensional, T1-weighted, magnetization-prepared rapid-acquisition gradient echo images. Expanded Disability Status Scale (EDSS) score and relapses were recorded at every follow-up. Patients with SPMS had lower baseline SCV (p < 0.01) but no accelerated SCV loss compared to those with RRMS. Clinical relapses were found to predict SCV loss over time (p < 0.05) in RRMS. Furthermore, SCV loss, but not total brain volume and T2 lesion volume, was a strong predictor of EDSS score worsening over time (p < 0.05). The mean annual rate of SCV loss was the strongest MRI predictor for the mean annual EDSS score change of both RRMS and SPMS separately, while correlating stronger in SPMS. Every 1% increase of the annual SCV loss rate was associated with an extra 28% risk increase of disease progression in the following year in both groups. SCV loss over time relates to the number of clinical relapses in RRMS, but overall does not differ between RRMS and SPMS. SCV proved to be a strong predictor of physical disability and disease progression, indicating that SCV may be a suitable marker for monitoring disease activity and severity.

Early regional cuprizone-induced demyelination in a rat model revealed with MRI.

The cuprizone model of demyelination is well established in the mouse as a tool for the study of the mechanisms of both demyelination and remyelination. It is often desirable, however, to have a larger model, such as the rat, especially for imaging-based studies, yet initial work has failed to show demyelination in cuprizone-fed rats. Several recent studies have demonstrated demyelination in the rat, but only in the corpus callosum. In this study, we acquired high-resolution, three-dimensional images of the whole brain every 2weeks, using a T1 -weighted magnetization-prepared rapid acquisition gradient echo imaging sequence, optimized for myelin contrast, in order to assess myelination across the entire rat brain over a period of 8weeks on a 1% cuprizone diet. We observed a consistent pattern of demyelination, beginning in the cerebellum by 4weeks and involving more rostral regions of the brain by 8weeks on the cuprizone diet, with validation using Luxol fast blue histology. This imaging technique permits the effects of cuprizone-induced demyelination to be followed longitudinally in a single animal, over the entire brain. In turn, this may facilitate the establishment of the cuprizone model of demyelination in the rat.

Transient Global Amnesia as a Presenting Manifestation of Cerebral Venous Thrombosis

Transient Global Amnesia as a Presenting Manifestation of Cerebral Venous Thrombosis

Central Adiposity and Cortical Thickness in Midlife.

Excessive visceral fat is associated with greater metabolic fluctuation and increased risk for dementia in older adults. The aim of the current study is to directly determine the impact of central adiposity on brain structure at midlife by examining the thickness of the cerebral cortex. High-resolution magnetization-prepared rapid acquisition gradient-echo images were obtained from 103 participants aged 40 to 60 years (mean [standard deviation] = 49.63 [6.47] years) on a 3-T Siemens Skyra scanner. Visceral fat was measured using dual-energy x-ray absorptiometry. Individuals with higher visceral fat mass and volume had significantly thicker cortex in the right posterior cingulate gyrus (β = 0.29 [p = .019] and β = 0.31 [p = .011], respectively), controlling for age, systolic blood pressure, total cholesterol level, and blood glucose level. Visceral fat was significantly associated with thicker cortex in the posterior cingulate gyrus. Although future studies are necessary, these results indicate that central adiposity is associated with significant metabolic changes that impinge upon the central nervous system in middle age.

Simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) imaging for carotid atherosclerotic disease evaluation.

A simultaneous noncontrast angiography and intraplaque hemorrhage (SNAP) MR imaging technique is proposed to detect both luminal stenosis and hemorrhage in atherosclerosis patients in a single scan. Thirteen patients with diagnosed carotid atherosclerotic plaque were admitted after informed consent. All scans were performed on a 3T MR imaging system with SNAP, 2D time-of-flight and magnetization-prepared 3D rapid acquisition gradient echo sequences. The SNAP sequence utilized a phase sensitive acquisition, and was designed to provide positive signals corresponding to intraplaque hemorrhage and negative signals corresponding to lumen. SNAP images were compared to time-of-flight images to evaluate lumen size measurements using linear mixed models and the intraclass correlation coefficient. Intraplaque hemorrhage identification accuracy was evaluated by comparing to magnetization-prepared 3D rapid acquisition gradient echo images using Cohen's Kappa. Diagnostic quality SNAP images were generated from all subjects. Quantitatively, the lumen size measurements by SNAP were strongly correlated (intraclass correlation coefficient = 0.96, P < 0.001) with those measured by time-of-flight. For intraplaque hemorrhage detection, strong agreement (κ = 0.82, P < 0.001) was also identified between SNAP and magnetization-prepared 3D rapid acquisition gradient echo images. In conclusion, a SNAP imaging technique was proposed and shows great promise for imaging both lumen size and carotid intraplaque hemorrhage with a single scan.

In vivo evaluation of cortical thickness with magnetic resonance imaging in patients with bipolar disorder.

Changes in cortical thickness can be related to neuropsychiatric disorders and neurodegenerative processes. Previous studies have been conducted to characterize the pattern of changes in cortical thickness in several psychiatric diseases. The aim of the present study was to evaluate changes in cortical thickness with magnetic resonance imaging (MRI) in patients with bipolar disorder. Twenty-seven patients with bipolar disorder (14 male, 36.0 ± 16.2 years old; 13 female, 41.6 ± 10.7 years old) and 40 healthy controls (16 male, 36.0 ± 10.5 years old; 24 female, 37.0 ± 4.7 years old) underwent 3T MRI. Sagittal T1-weighted magnetization prepared rapid acquisition gradient echo images were acquired (voxel size, 1.33 mm3; 128 slices; in-plane matrix resolution, 256 × 256; flip angle, 7o; repetition time, 2530 ms; echo time, 3.39 ms; inversion time, 1100 ms). Cortical segmentation was performed using FreeSurfer 4.0.5. The results indicated both thinning and thickening of the cerebral cortex in patients with bipolar disorder compared with controls, depending on gender. Significant (p < .01) thickening was observed in the right hemisphere superior-parietal cortex in female patients with bipolar disorder, and significant (p < .05) thinning was observed in the left hemisphere caudal-anterior cingulate in male patients with bipolar disorder. The other regions did not show significant differences. The results suggest that an analysis of cortical thickness with MRI in patients with bipolar disorder may allow identification of areas that may be morphologically changed compared with controls. Demonstration of these alterations will elucidate the pathophysiology of bipolar disorder and may contribute to better therapies for this disorder.

Reduced Gray Matter Volume in the Frontotemporal Cortex of Patients with Early Subacute Sclerosing Panencephalitis

Subacute sclerosing panencephalitis (SSPE) is a persistent infection of the central nervous system by the measles virus. Patients in the initial stages of SSPE show behavioral symptoms and usually normal cranial MR imaging findings. We aimed to investigate the gray matter volume changes in patients with early SSPE. Seventeen patients with SSPE with normal cranial MR imaging findings and 30 sex- and age-matched control subjects were included in the study. Clinical parameters of the patients were quantified by using a neurologic disability index (NDI) as defined previously. We obtained T1-weighted magnetization-prepared rapid acquisition gradient echo images from the patients and control subjects, and we applied an optimized method of voxel-based morphometry. We performed a cross-sectional analysis to search the gray matter volume differences between the patients and control subjects. The correlation between the gray matter distribution and the duration of symptoms, immunoglobulin G index, and NDI scores was tested. We found that the cortical gray matter volume of patients was reduced in the frontotemporal regions including the bilateral cingulate cortex and amygdala. There was no correlation between the gray matter distribution of patients and the duration of symptoms or the NDI scores. The current study demonstrated gray matter volume reduction in the frontotemporal cortex of patients with SSPE without any apparent lesions on conventional MR imaging. Because the cingulate cortex and amygdala are involved in emotion processing, gray matter loss in these regions may contribute to the development of early behavioral symptoms of SSPE.

Inflammation and atrophy in multiple sclerosis: MRI associations with disease course

Brain atrophy may be a useful surrogate marker of axonal loss and disease progression in multiple sclerosis (MS). Several studies have suggested that inflammatory disease activity is a risk factor for atrophy in the early stages of the disease, but may become less important later in the disease course. We aimed to investigate the relationships between atrophy and active inflammation at different stages of the disease course using brain volume measurements from magnetic resonance imaging (MRI) in patients with both relapsing–remitting (RR) ( n=95) and secondary progressive (SP) ( n=76) MS. Conventional dual echo and three-dimensional magnetization-prepared rapid-acquisition gradient echo imaging were performed in all patients and in 31 healthy controls. Supratentorial and infratentorial brain, and lateral ventricular volumes were determined using modern design stereology. Patients with SP MS had smaller supratentorial ( p=0.003) and infratentorial brain volumes ( p=0.0003), and larger lateral ventricles ( p=0.02) than patients with RR MS. RR MS patients with T 1-enhancing lesions had smaller supratentorial ( p=0.02) and infratentorial ( p=0.002) brain volumes and larger ventricles ( p=0.002) than those without enhancing lesions. SP MS patients with enhancing lesions also had significantly larger lateral ventricles ( p=0.03). Categorical analysis showed that more RR MS patients with enhancing lesions had smaller supratentorial brain ( p=0.005), or larger lateral ventricular ( p=0.028) volumes, and more SP MS patients with enhancing lesions had increased lateral ventricle volumes ( p=0.013), than patients without enhancements. The number of enhancing lesions was significantly correlated with lateral ventricular volumes in both RR MS ( r=0.39, p=0.0001) and SP MS ( r=0.46, p<0.0001). Our data shows that the presence of active inflammation on a single MRI in the course of RR and SP MS, is associated with a higher risk and higher level of brain atrophy. These findings emphasise the important long-term relationship between inflammation and atrophy in MS and provide additional support for the strategy of early anti-inflammatory treatment to protect tissue integrity.