Magnetization-prepared Rapid Acquisition Gradient-echo Sequence Research Articles

Optimal control in a magnetization-prepared rapid acquisition gradient-echo sequence.

This article proposes a numerical framework to determine the optimal magnetization preparation in a three-dimensional magnetization-prepared rapid gradient-echo (MP-RAGE) sequence to obtain the best achievable contrast between target tissues based on differences in their relaxation times. The benefit lies in the adaptation of the algorithm of optimal control, GRAdient Ascent Pulse Engineering (GRAPE), to the optimization of magnetization preparation in a cyclic sequence without full recovery between each cycle. This numerical approach optimizes magnetization preparation of an arbitrary number of radio frequency pulses to enhance contrast, taking into account the establishment of a steady state in the longitudinal component of the magnetization. The optimal control preparation offers an optimized mixed contrast in this traditional -weighted sequence. To show the versatility of the proposed method, numerical and in vitro results are described. Examples of contrasts acquired on brain regions of a healthy volunteer are presented for potential applications at 3 T.

Synthesized 7T MPRAGE From 3T MPRAGE Using Generative Adversarial Network and Validation in Clinical Brain Imaging: A Feasibility Study.

Ultra-high field 7T MRI can provide excellent tissue contrast and anatomical details, but is often cost prohibitive, and is not widely accessible in clinical practice. To generate synthetic 7T images from widely acquired 3T images with deep learning and to evaluate the feasibility of this approach for brain imaging. Prospective. 33 healthy volunteers and 89 patients with brain diseases, divided into training, and evaluation datasets in the ratio 4:1. T1-weighted nonenhanced or contrast-enhanced magnetization-prepared rapid acquisition gradient-echo sequence at both 3T and 7T. A generative adversarial network (SynGAN) was developed to produce synthetic 7T images from 3T images as input. SynGAN training and evaluation were performed separately for nonenhanced and contrast-enhanced paired acquisitions. Qualitative image quality of acquired 3T and 7T images and of synthesized 7T images was evaluated by three radiologists in terms of overall image quality, artifacts, sharpness, contrast, and visualization of vessel using 5-point Likert scales. Wilcoxon signed rank tests to compare synthetic 7T images with acquired 7T and 3T images and intraclass correlation coefficients to evaluate interobserver variability. P < 0.05 was considered significant. Of the 122 paired 3T and 7T MRI scans, 66 were acquired without contrast agent and 56 with contrast agent. The average time to generate synthetic images was ~11.4 msec per slice (2.95 sec per participant). The synthetic 7T images achieved significantly improved tissue contrast and sharpness in comparison to 3T images in both nonenhanced and contrast-enhanced subgroups. Meanwhile, there was no significant difference between acquired 7T and synthetic 7T images in terms of all the evaluation criteria for both nonenhanced and contrast-enhanced subgroups (P ≥ 0.180). The deep learning model has potential to generate synthetic 7T images with similar image quality to acquired 7T images. 2 TECHNICAL EFFICACY: Stage 1.

Cerebrospinal fluid neurofilament light and cerebral atrophy in younger-onset dementia and primary psychiatric disorders.

Neurodegeneration underpins the pathological processes of younger-onset dementia (YOD) and has been implicated in primary psychiatric disorders (PSYs). Cerebrospinal fluid (CSF) neurofilament light (NfL) has been used to investigate neurodegeneration severity through correlation with structural brain changes in various conditions, but has seldom been evaluated in YOD and PSYs. This retrospective study included patients with YOD or PSYs with magnetic resonance imaging (MRI) of the brain and CSF NfL analysis. Findings from brain MRI were analysed using automated volumetry (volBrain) to measure white matter (WM), grey matter (GM) and whole brain (WB) volumes expressed as percentages of total intracranial volume. Correlations between NfL and brain volume measurements were computed whilst adjusting for age. Seventy patients (47 with YOD and 23 with PSY) were identified. YOD types included Alzheimer disease and behavioural variant frontotemporal dementia. PSY included schizophrenia and major depressive disorder. MRI brain sequences were either fast spoiler gradient-echo (FSPGR) or magnetization-prepared rapid acquisition gradient-echo (MPRAGE). In the total cohort, higher NfL was associated with reduced WB in the FSPGR and MPRAGE sequences (r=-0.402 [95% confidence interval (CI), -0.593 to -0.147], P=0.008 and r=-0.625 [95% CI, -0.828 to -0.395], P < 0.001, respectively). Higher NfL was related to reduced GM in FSPGR (r=0.385 [95% CI, -0.649 to -0.014], P=0.017) and reduced WM in MPRAGE (r=-0.650 [95% CI, -0.777 to -0.307], P < 0.001). Similar relationships were seen in YOD, but not in PSY. Higher CSF NfL is related to brain atrophy in YOD, further supporting its use as a nonspecific marker of neurodegeneration severity.

Fully automated detection of focal cortical dysplasia: Comparison of MPRAGE and MP2RAGE sequences.

The detection of focal cortical dysplasia (FCD) in magnetic resonance imaging is challenging. Voxel-based morphometric analysis and automated FCD detection using an artificial neural network (ANN) integrated into the Morphometric Analysis Program (MAP18) have been shown to facilitate FCD detection. This study aimed to evaluate whether the detection of FCD can be further improved by feeding this approach with magnetization prepared two rapid acquisition gradient echoes (MP2RAGE) instead of magnetization-prepared rapid acquisition gradient echo (MPRAGE) datasets. MPRAGE and MP2RAGE datasets were acquired in a consecutive sample of 32 patients with FCD and postprocessed using MAP18. Visual analysis and, if available, histopathology served as the gold standard for assessing the sensitivity and specificity of FCD detection. Out-of-sample specificity was evaluated in a cohort of 32healthy controls. The sensitivity and specificity of FCD detection were 82.4% and 62.5% for the MPRAGE and 97.1% and 34.4% for the MP2RAGE sequences, respectively. Median volumes of true-positive voxel clusters were .16ml for the MPRAGE and .52ml for the MP2RAGE sequences compared to .08- and .04-ml volumes of false-positive clusters. With regard to cluster volumes, FCD detection was substantially improved for the MP2RAGE data when the estimated optimal threshold of .23ml was applied (sensitivity = 72.9%, specificity = 83.0%). In contrast, the estimated optimal threshold of .37ml for the MPRAGE data did not improve FCD lesion detection (sensitivity = 42.9%, specificity = 79.5%). In this study, the sensitivity of FCD detection by morphometric analysis and an ANN integrated into MAP18 was higher for MP2RAGE than for MPRAGE sequences. Additional usage of cluster volume information helped to discriminate between true- and false-positive MP2RAGE results.

Comparison of ultrafast wave-controlled aliasing in parallel imaging (CAIPI) magnetization-prepared rapid acquisition gradient echo (MP-RAGE) and standard MP-RAGE in non-sedated children: initial clinical experience.

Fast magnetic resonance imaging (MRI) sequences are advantageous in pediatric imaging as they can lessen child discomfort, decrease motion artifact and improve scanner availability. To evaluate the feasibility of an ultrafast wave-CAIPI (controlled aliasing in parallel imaging) MP-RAGE (magnetization-prepared rapid gradient echo) sequence for brain imaging of awake pediatric patients. Each MRI included a standard MP-RAGE sequence and an ultrafast wave-MP-RAGE sequence. Two neuroradiologists evaluated both sequences in terms of artifacts, noise, anatomical contrast and pathological contrast. A predefined 5-point scale was used by two independent pediatric neuroradiologists. A Wilcoxon signed-rank test was used to evaluate the difference between sequences for each variable. Twenty-four patients (14 males; mean age: 11.5±4.5years, range: 1month to 17.8years) were included. Wave-CAIPI MP-RAGE provided a 77% reduction in scan time using a 32-channel coil and a 70% reduction using a 20-channel coil. Visualization of the pathology, artifacts and pathological enhancement (including parenchymal, leptomeningeal and dural enhancement) was not significantly different between standard MP-RAGE and wave-CAIPI MP-RAGE (all P>0.05). For central (P<0.001) and peripheral (P<0.001) noise, and the evaluation of the anatomical structures (P<0.001), the observers favored standard MP-RAGE over wave-CAIPI MP-RAGE. Ultrafast brain imaging with wave-CAIPI MP-RAGE is feasible in awake pediatric patients, providing a substantial reduction in scan time at a cost of subjectively increased image noise.

Predicting Neuroimaging Biomarkers for Antidepressant Selection in Early Treatment of Depression.

Due to the biological heterogeneity, 60%-70% of patients with major depressive disorder (MDD) do not respond to or achieve remission from first-line antidepressants. Predicting neuroimaging biomarkers for early antidepressant treatment could guide initial antidepressant therapy. To assess for neuroimaging biomarkers for antidepressant selection in early antidepressant treatment. Prospective. A total of 85 MDD patients from the major site and 33 MDD patients from an out-of-sample test site. A 3.0 T, T1-weighted imaging using a magnetization-prepared rapid acquisition gradient-echo sequence and diffusion tensor imaging (DTI) using an echo-planar sequence. Baseline DTI data of patients who achieved early improvement after 2-weeks of antidepressant treatment (selective serotonin reuptake inhibitors [SSRI] or serotonin-norepinephrine reuptake inhibitors [SNRI]) were analyzed. An ensemble model was constructed using data from the major site and then applied to assess the early response of patients at the out-of-sample test site. Support vector machine combined with leave-one-out cross-validation were applied to construct the whole model from individual base models from different brain regions. Discriminative biomarkers were evaluated by calculating the changes in sensitivity and specificity obtained when removing a single base model from the whole model, the base model being removed changing in each run. Training performance over MDD patients at the major site achieved 75% accuracy while performance with accuracy of 70% was achieved in the out-of-sample test site. Assessing sensitivity and specificity changes following the removal of single base models from the prominent model highlighted the functions of two neural circuitries: SSRI-related emotion regulation circuitry, centered on the hippocampus (sensitivity changes: 10%) and amygdala (sensitivity changes: 11%); and SNRI-related emotion and reward circuitry, centered on the putamen (specificity changes: 8%) and orbital part of superior frontal gyrus (specificity changes: 12%). These findings support future research on clinical antidepressant selection for MDD. 1 TECHNICAL EFFICACY: Stage 2.

Histological validation of simultaneous non-contrast angiography and intraplaque hemorrhage imaging (SNAP) for characterizing carotid intraplaque hemorrhage.

This study sought to validate the performance of simultaneous non-contrast angiography and intraplaque hemorrhage (SNAP) imaging in characterizing carotid IPH by histology. Thirty-five patients with carotid atherosclerotic disease (symptomatic 50-70% stenosis or > 70% stenosis) scheduled for carotid endarterectomy underwent 3.0-T carotid MR imaging by acquiring SNAP and magnetization-prepared rapid acquisition gradient-echo (MP-RAGE) sequences. Presence and area of IPH were separately evaluated on SNAP and MP-RAGE images. Presence and area of IPH were also assessed on histology. Agreement between SNAP/MP-RAGE and histology was determined in identify and quantify IPH using Cohen kappa, Spearman correlation, and Bland-Altman analyses. Of all 35 patients (mean age: 63.1 ± 8.8 years; 27 males), 128 slices with successful registration were eligible for analysis. The accuracy, sensitivity, specificity, and positive and negative predictive values were 86.7%, 85%, 89.6%, 93.2%, and 78.2% for SNAP, and76.6%, 75%, 79.2%, 85.7%, and 65.5% for MP-RAGE in identification of IPH, respectively. In identification of IPH, the kappa value between SNAP and histology and between MP-RAGE and histology was 0.725 and 0.520, respectively. The correlation between SNAP and histology (r = 0.805, p < 0.001) was stronger than that between MP-RAGE and histology (r = 0.637, p < 0.001) in measuring IPH area. Bland-Altman analysis showed that, in measuring IPH area, the bias of SNAP (1.4 mm2, 95% CI: - 0.016 to 2.883) was smaller than that of MP-RAGE (1.7 mm2, 95% CI: - 0.039 to 3.430) compared with histology. This validation study by histology demonstrates that SNAP sequence better identifies and quantifies carotid intraplaque hemorrhage compared with traditional MP-RAGE sequence. • SNAP imaging showed better agreement with histology compared with MP-RAGE imaging, especially for the IPHs with small size. • SNAP sequence is a more effective tool to identify and quantify carotid IPH than traditional sequence of MP-RAGE that can help clinicians to optimizing the treatment strategy. • The plaque components of rich lipid pools or loose matrix and chronic/old IPH (cholesterol crystals) can lead to false positive and false negative results in SNAP and MP-RAGE imaging for identifying IPH.

Longitudinal Imaging of Tumor Volume, Diffusivity, and Perfusion After Preoperative Endovascular Embolization in Supratentorial Hemispheric Meningiomas

To describe longitudinal image changes in supratentorial hemispheric meningiomas based on magnetic resonance imaging after preoperative embolization using calibrated microspheres. A total of 14 patients with symptomatic supratentorial meningiomas were included in a prospective, mono-centric, mono-arm study. Magnetic resonance imaging changes on diffusion-weighted imaging, dynamic contrast susceptibility-perfusion-weighted imaging, susceptibility-weighted imaging, and magnetization-prepared rapid acquisition gradient-echo sequence T1-weighted postcontrast sequences 6 and 48 hours after embolization were evaluated and correlated with angiographic and clinical data. The mean age of the patients was 63 ± 12.7 years with an equal female/male ratio. Twelve meningiomas were World Health Organization grade I and II tumors. After embolization, baseline apparent diffusion coefficient (901 ± 166 mm2/s) decreased significantly within 6 hours (696 ± 115 mm2/s, P= 0.0008) as well within 48 hours (752 ± 134 mm2/s; P= 0.0147). Baseline mean ratio of relative cerebral blood volume (rCBV)tumor/rCBVwhite matter (3.67 ± 1.83) and relative cerebral blood flow (rCBF)tumor/rCBFwhite matter (2.89 ± 1.57) significantly decreased after embolization within 6 hours (rCBVtumor/rCBVwhite matter of 1.45 ± 0.9; P= 0.0007, rCBF of 1.16 ± 0.68; P= 0.0029) and 48 hours (rCBV of 1.50 ± 1.07; P=0.0009, rCBFtumor/rCBFwhite matter of 1.19 ± 0.8; P=0.003). The viable enhanced baseline mean tumor volume (54.3 ± 34.9 mm3) was sustainably and significantly diminished within 6 hours (26.6 ± 20.8 mm3; P= 0.02) and 48 hours (29.7 ± 22.5 mm3; P= 0.035) after embolization. There was a good correlation between angiographic devascularization rate and the embolized tumor volume at 6 hours (r= 0.7; P= 0.03) and 48 hours (r= 0.78; P= 0.041). Preoperative meningioma embolization with calibrated microspheres is safe and effectively induces a significant and sustainable tissue transformation over 48 hours.

S180. MICROSTRUCTURE COMPLEXITY OF THE THALAMUS IN SCHIZOPHRENIA: A NODDI STUDY

BackgroundSchizophrenia is a neurodevelopmental disease arising from complex interactions between genetic and environmental factors that cause disconnectivity within core brain networks including the thalamus. The thalamus has a central role in the pathophysiology of schizophrenia, however to what extent and how it is affected at the microstructural level is still a matter of debate. In the current study, we apply the Neurite Orientation Dispersion and Density Imaging (NODDI) [1], a recently developed MRI technique, which allows the estimation of the microstructural complexity of dendrites and axons in vivo.MethodsTwenty-three patients with schizophrenia (SCHZ) were recruited from the Service of General Psychiatry (Lausanne University Hospital, Switzerland) (40.18 ± 9.2yo; 18/5 males/females) and 27 healthy controls (HC) (37.7 ± 7.95yo; 18/9 males/females). Magnetization-Prepared Rapid Acquisition Gradient Echo (MPRAGE) and a diffusion spectrum imaging (DSI) was performed on a 3-Tesla scanner (MAGNETOM Trio a Tim system, Siemens, Germany). Thalamus segmentation was performed on the MPRAGE sequence with an in house-pipeline using Freesurfer v5.0.0 for segmentation which was then refined to remove voxels within the ventricles and/or overlapping the internal capsule [2]. Orientation Dispersion Index (ODI), Intracellular Volume Fraction (ICVF) and, Isotropic Volume Fraction (ISOVF) were estimated based on the DSI sequence with NODDI [1]. General Linear Models (GLM) were estimated with outcome measures (ICVF, ISOVF, ODI) as dependent variables, group membership as a fixed factor (HC vs. SCHZ) and age and gender as potential covariates.References1Battistella G, Najdenovska E, Maeder P, et al. Robust thalamic nuclei segmentation method based on local diffusion magnetic resonance properties. Brain Struct Funct 2016. DOI:10.1007/s00429-016-1336-4.2Zhang H, Schneider T, Wheeler-kingshott CA, Alexander DC. NeuroImage NODDI : Practical in vivo neurite orientation dispersion and density imaging of the human brain. Neuroimage 2012; 61: 1000–16.ResultsMean ODI was significantly increased in schizophrenia patients compared to controls in the right thalamus (F(1,48)=5.032, p= .030, np2 = .095) and in the left thalamus (F(1,48)=4.500, p= .039, np2 = .086). When controlled for age and gender, the difference remained significant for the right thalamus (F(1, 46) = 4.197, p = .046, np2 = .084) but reduced to trend level for the left thalamus (F(1, 46) = 4.029, p = .051, np2 = .081). There were no significant differences on the other measures (ICVF, ISOVF).DiscussionOur results show that the thalamus is affected in patients with SCHZ at the microstructural level. The observed increase in ODI, which estimates the dispersion of neurite orientations, suggests disrupted neurite organization in patients as compared to HC.

Three-Dimensional Radial VIBE Sequence for Contrast-Enhanced Brain Imaging: An Alternative for Reducing Motion Artifacts in Restless Children.

The purpose of this study was to evaluate the usefulness of radially sampled 3D fat-suppressed T1-weighted gradient-echo sequences (radial volumetric interpolated breath-hold examination [radial VIBE]) for contrast-enhanced brain MRI of children through comparison with a magnetization-prepared rapid-acquisition gradient-echo (MP-RAGE) sequence. Sixty-five consecutive contrast-enhanced brain MRI examinations performed with axial MP-RAGE and radial VIBE sequences were included. For quantitative analysis, coefficients of variation of gray matter and white matter and CSF and relative contrast between tissue types (gray matter and white matter, gray matter and CSF, and white matter and CSF) for each sequence were calculated. For qualitative assessment, motion, pulsation artifacts, overall image quality, and lesion conspicuity were retrospectively scored on a 5-point scale. Quantitative and qualitative subgroup analyses were performed for patients with serious motion artifacts. Images obtained with the radial VIBE sequence had fewer motion and pulsation artifacts than those obtained with the MP-RAGE sequence (MP-RAGE vs radial VIBE motion score, 3.57 ± 1.00 vs 4.52 ± 0.51; pulsation score, 3.57 ± 0.60 vs 4.91 ± 0.21; all p < 0.001). Among 25 images with serious motion artifacts, radial VIBE images had significantly higher scores for all qualitative parameters, including overall image quality, than did MP-RAGE images (overall image quality for MP-RAGE vs radial VIBE, 2.63 ± 0.82 vs 3.42 ± 0.55, p < 0.001). The study showed that a radial fat-suppressed T1-weighted gradient-echo sequence is a viable alternative to conventional cartesian acquisition for contrast-enhanced brain imaging of restless children.

47. Effect of Antipsychotic Medication on Hippocampal Function and Neurochemistry: A Longitudinal Study in Patients With Schizophrenia

Background: Our prior studies with PET and 15O have shown associations between hippocampal function and treatment response to antipsychotic drugs (APDs). In addition, we found elevated hippocampal glutamate in unmedicated patients with schizophrenia (SZ) but not in medicated. Here, we use a longitudinal design to evaluate the relationship between glutamate and function of the hippocampus in SZ in relation to treatment response to APDs. Methods: 34 SZ were scanned while unmedicated and after 6 weeks of APD. 23 matched healthy controls were also scanned twice six weeks apart. Imaging was done on a 3T head-only scanner equipped with a circularly polarized transmit/receive head coil. A high-resolution structural scan was acquired using the 3D T1-weighted magnetization-prepared rapid acquisition gradient-echo sequence ([TR/TE/ TI] = 2300/3.93/1100ms; flip angle = 12°; 256 × 256 matrix; and 1mm isotropic voxels). Eyes open resting-state fMRI (rsfMRI) was acquired using the gradient recalled echo-planar-imaging sequence (TR/TE = 2000/30ms, flip angle = 70°, field of view = 192mm3, 6mm slice thickness, 1mm gap, 30 axial slices, 225 acquisitions). rsfMRI data were preprocessed and analyzed using CONN toolbox and SPM12. Resting-state magnetic resonance spectroscopy was collected with a voxel prescribed in the left hippocampus (2.7 × 1.5 × 1cm) using the PRESS sequence optimized for glutamate (TR/TE = 2000/80ms, spectral bandwidth = 1024 points, 640 averages) and analyzed in jMRUI. A median split was used to separate SZ into treatment responders and non-responders (calculated as percent change in BPRS positive symptoms). Results: Before treatment, those who subsequently responded to treatment were characterized by significantly elevated glutamate levels compared to both healthy controls and nonresponders. Treatment responders but not non-responders or healthy controls glutamate levels significantly decreased over the 6-week course of treatment. Additionally, treatment responders demonstrated reduced hippocampal blood oxygen-level-dependent (BOLD) fMRI signal compared to healthy controls and nonresponders. Conclusion: Before treatment, both hippocampal glutamate levels and hippocampal BOLD signal appear to differentiate good treatment responders from poor treatment responders.

Motion-insensitive carotid intraplaque hemorrhage imaging using 3D inversion recovery preparation stack of stars (IR-prep SOS) technique.

Carotid artery imaging is important in the clinical management of patients at risk for stroke. Carotid intraplaque hemorrhage (IPH) presents an important diagnostic challenge. 3D magnetization prepared rapid acquisition gradient echo (MPRAGE) has been shown to accurately image carotid IPH; however, this sequence can be limited due to motion- and flow-related artifact. The purpose of this work was to develop and evaluate an improved 3D carotid MPRAGE sequence for IPH detection. We hypothesized that a radial-based k-space trajectory sequence such as "Stack of Stars" (SOS) incorporated with inversion recovery preparation would offer reduced motion sensitivity and more robust flow suppression by oversampling of central k-space. A total of 31 patients with carotid disease (62 carotid arteries) were imaged at 3T magnetic resonance imaging (MRI) with 3D IR-prep Cartesian and SOS sequences. Image quality was determined between SOS and Cartesian MPRAGE in 62 carotid arteries using t-tests and multivariable linear regression. Kappa analysis was used to determine interrater reliability. In all, 25 among 62 carotid plaques had carotid IPH by consensus from the reviewers on SOS compared to 24 on Cartesian sequence. Image quality was significantly higher with SOS compared to Cartesian (mean 3.74 vs. 3.11, P < 0.001). SOS acquisition yielded sharper image features with less motion (19.4% vs. 45.2%, P < 0.002) and flow artifact (27.4% vs. 41.9%, P < 0.089). There was also excellent interrater reliability with SOS (kappa = 0.89), higher than that of Cartesian (kappa = 0.84). By minimizing flow and motion artifacts and retaining high interrater reliability, the SOS MPRAGE has important advantages over Cartesian MPRAGE in carotid IPH detection. 1 J. Magn. Reson. Imaging 2017;45:410-417.

Diffusion measurement of intraplaque hemorrhage and intramural hematoma using diffusion weighted MRI at 3T in cervical artery.

To assess the difference between carotid haemorrhagic plaque and non-haemorrhagic plaque by using diffusion-weighted imaging (DWI) and to evaluate carotid intraplaque haemorrhage (IPH) and intramural hematoma (IMH) of cervical artery dissection with apparent diffusion coefficient (ADC) measurement. Fifty-one symptomatic patients underwent 3.0-T carotid MR imaging, including conventional sequences, three-dimensional (3D) magnetization-prepared rapid acquisition gradient-echo (MPRAGE) sequence, and DWI. Thirty-nine patients with carotid plaque and eight patients with IMH of cervical artery dissection were finally included. The groups of hemorrhagic plaque, non-hemorrhagic plaque and IMH were divided according to 3D MPRAGE sequence. ADC values of different groups were measured, and t tests were performed. The mean ADC values of hemorrhagic plaques, non-hemorrhagic plaque and IMH were (1.284 ± 0.327) × 10(-3)mm(2)/s, (1.766 ± 0.477) × 10(-3)mm(2)/s, and (0.563 ± 0.119) × 10(-3)mm(2)/s, respectively. The mean ADC values of hemorrhagic and non-hemorrhagic regions in the hemorrhagic plaque group were (0.985 ± 0.376) × 10(-3)mm(2)/s and (1.480 ± 0.465) × 10(-3)mm(2)/s, respectively. The differences between the hemorrhagic plaque and non-hemorrhagic plaque, hemorrhagic region and non-hemorrhagic region in hemorrhagic plaque, and the hemorrhagic region in the hemorrhagic plaque and IMH of artery dissection were significant (P < 0.05). DWI may be a useful complement to conventional MR imaging for identifying haemorrhage of carotid plaques and differentiate IMHs from IPH. • ADC values of IPH are lower than the plaque without IPH. • DWI might be a useful complement to identify IPH. • IMH may be differentiated from IPH by using DWI.

Frontolimbic Morphometric Abnormalities in Intermittent Explosive Disorder and Aggression

BackgroundConverging evidence from neuroimaging studies suggests that impulsive aggression, the core behavior in the DSM-5 diagnosis intermittent explosive disorder (IED), is regulated by frontolimbic brain structures, particularly orbitofrontal cortex, ventral medial prefrontal cortex, anterior cingulate cortex, amygdala, insula, and uncus. Despite this evidence, no brain volumetric studies of IED have been reported as yet. This study was conducted to test the hypothesis that gray matter volume in frontolimbic brain structures of subjects with IED is lower than in healthy subjects and subjects with other psychiatric conditions. MethodsHigh-resolution magnetic resonance imaging scans using a three-dimensional magnetization-prepared rapid acquisition gradient-echo sequence were performed in 168 subjects (n = 53 healthy control subjects, n = 58 psychiatric controls, n = 57 subjects with IED). Imaging data were analyzed by voxel-based morphometry methods employing Statistical Parametric Mapping (SPM8) software. ResultsGray matter volume was found to be significantly lower in subjects with IED compared with healthy control subjects and psychiatric controls in orbitofrontal cortex, ventral medial prefrontal cortex, anterior cingulate cortex, amygdala, insula, and uncus. These differences were not due to various confounding factors or to comorbidity with other disorders previously reported to have reduced gray matter volume. Gray matter volume in these areas was significantly and inversely correlated with measures of aggression. ConclusionsReductions in the gray matter volume of frontolimbic structures may be a neuronal characteristic of impulsively aggressive individuals with DSM-5 IED. These data suggest an anatomic correlate accounting for functional deficits in social-emotional information processing in these individuals.

Caudal Image Contrast Inversion in MPRAGE at 7 Tesla: Problem and Solution

The magnetization-prepared rapid-acquisition gradient-echo (MPRAGE) sequence regularly shows caudal image contrast inversion at 7 T and therefore reduced clinical applicability. The investigators report the technical source of this problem and present a practical solution. A total of 71 subjects were scanned using a 7-T whole-body magnetic resonance imaging system using a 32-channel transmit/receive head coil. In 39 subjects, 45 high-resolution T1 contrast image data sets were acquired with the standard MPRAGE sequence. A modified sequence with an adiabatic wideband uniform rate smooth truncation pulse for magnetization preparation was used for 45 further scans in 39 subjects. In total, seven subjects underwent scans with both sequences. The homogeneity of T1 contrast and the occurrence of caudal image contrast inversion were evaluated in consensus reading by two neuroradiologists. Caudal image contrast inversion was depicted in 19 acquisitions (42.2%) using the standard MPRAGE sequence. Using the adiabatic wideband uniform rate smooth truncation pulse for magnetization preparation, caudal image contrast inversion was depicted in only three acquisitions (6.7%). A χ(2) test showed a significant difference between the two preparation pulses (P < .001). Magnetization preparation with an adiabatic wideband uniform rate smooth truncation pulse in the MPRAGE sequence at 7 T can significantly reduce the occurrence of caudal image contrast inversion and improves signal homogeneity.

Focal multiple sclerosis lesions abound in ‘normal appearing white matter’

Background: The ‘normal appearing white matter’ (NAWM) in multiple sclerosis (MS) is known to be abnormal using quantitative magnetic resonance (MR) techniques. The aetiology of the changes in NAWM remains debatable. Objective: To investigate whether high-field and ultra high-field T1-weighted magnetization prepared rapid acquisition gradient echo (MPRAGE) MRI enables detection of MS white matter lesions in areas defined as NAWM using high-field T2-weighted fluid attenuation inversion recovery (FLAIR) MRI; that is, to ascertain whether undetected lesions are likely contributors to the burden of abnormality in similarly defined NAWM. Methods: Fourteen MS patients underwent MRI scans using 3T FLAIR and MPRAGE and 7 Tesla (7T) MPRAGE sequences. Independent observers identified lesions on 3T FLAIR and (7T and 3T) MPRAGE images. The detection of every individual lesion was then compared for each image type. Results: We identified a total of 812 white matter lesions on 3T FLAIR. Using 3T MPRAGE, 186 additional lesions were detected that were not detected using 3T FLAIR. Using 7T MPRAGE, 231 additional lesions were detected that were not detected using 3T FLAIR. Conclusions: MRI with 3T and 7T MPRAGE enables detection of MS lesions in areas defined as NAWM using 3T FLAIR. Focal MS lesions contribute to the abnormalities known to exist in the NAWM.

P1-316: Decreased white matter volumes in asymptomatic individuals at increased risk for familial Alzheimer's disease

Background: While much of structural imaging has focused on gray matter, the quantification of white matter integrity is of interest not only because of the noted white matter pathology seen in Alzheimer’s disease (AD), but also because of the apparent breakdown of myelin in AD. To date there has been no longitudinal study of white matter integrity within asymptomatic samples at elevated risk for late-onset AD, the purpose of this study. Methods: Cognitively normal participants age 50 years and above were chosen from an ongoing longitudinal study, comparing those with increased genetic risk for AD to matched controls. 95 of the high-risk and 91 of the controls had structural scans at baseline (Time 1) and 87 high-risk and 74 controls at three-year follow-up (Time 2). Participants were imaged at each time point on the same 1.5 Tesla Philips Intera-NT system equipped with Galaxy gradients (66mT/m at 110 mT/m/s). High resolution anatomical images of the brain for structural measurements were acquired using a T1weighted, 3D MP-RAGE (Magnetization Prepared Rapid Acquisition Gradient Echo) sequence with the following parameters: TR 8.6 ms, TE 3.9 ms, FOV 240 mm, 8, matrix size 256x256, slice thickness 1.5 mm, 124 slices). Pre-processing was performed using a semiautomated method, followed by the manual removal of remaining skull and dura. All measurements were conducted by one rater blind to group status. Scans were then segmented into separate tissue classes using an adaptive fuzzy C-means algorithm. Volumes of gray matter and white matter tissue as well as total brain volume were calculated. Results: At both Time 1 and Time 2, the high-risk sample showed significantly smaller white matter volumes (Time 1 p 0.05, Time 2 p 0.04). Change across the time points, however, did not significantly differ between groups (control -50ccm, high-risk -53.28ccm). Conclusions: While the similar rate of white matter loss across groups may reflect aging, this would not provide an explanation for the initial significantly smaller white matter volume seen in the high-risk group. Further study is needed to more fully understand the significance of reduced white matter volume as it relates to AD. P1-317 DIFFUSION TENSOR IMAGING IN FRONTOTEMPORAL LOBAR DEGENERATION

IC-P2-076: White matter volume in individuals at increased risk for Alzheimer's disease

While much of structural imaging has focused on gray matter, the quantification of white matter integrity is of interest not only because of the noted white matter pathology seen in Alzheimer's disease (AD), but also because of the apparent breakdown of myelin in AD. To date there has been no longitudinal study of white matter integrity within asymptomatic samples at elevated risk for late-onset AD, the purpose of this study. Cognitively normal participants age 50 years and above were chosen from an ongoing longitudinal study, comparing those with increased genetic risk for AD to matched controls. 95 of the high-risk and 91 of the controls had structural scans at baseline (Time 1) and 87 high-risk and 74 controls at three-year follow-up (Time 2). Participants were imaged at each time point on the same 1.5 Tesla Philips Intera-NT system equipped with Galaxy gradients (66mT/m at 110 mT/m/s). High resolution anatomical images of the brain for structural measurements were acquired using a T1-weighted, 3D MP-RAGE (Magnetization Prepared Rapid Acquisition Gradient Echo) sequence with the following parameters: TR=8.6 ms, TE=3.9 ms, FOV=240 mm, θ=8°, matrix size =256x256, slice thickness=1.5 mm, 124 slices). Pre-processing was performed using a semi-automated method, followed by the manual removal of remaining skull and dura. All measurements were conducted by one rater blind to group status. Scans were then segmented into separate tissue classes using an adaptive fuzzy C-means algorithm. Volumes of gray matter and white matter tissue as well as total brain volume were calculated. At both Time 1 and Time 2, the high-risk sample showed significantly smaller white matter volumes (Time 1 p = 0.05, Time 2 p = 0.04). Change across the time points, however, did not significantly differ between groups (control = -50ccm, high-risk = -53.28ccm). While the similar rate of white matter loss across groups may reflect aging, this would not provide an explanation for the initial significantly smaller white matter volume seen in the high-risk group. Further study will be needed to more fully understand the significance of reduced white matter volume as it relates to AD.

“TARGET BYPASS”

To introduce a method for preoperative targeting of a proper recipient artery in superficial temporal artery-to-middle cerebral artery anastomosis. Six operations for superficial temporal artery-to-middle cerebral artery anastomosis in four patients with moyamoya disease or moyamoya-like disease and two operations in two patients with atherosclerotic cerebrovascular occlusive disease accompanied by coronary artery stenosis were performed using our method. Before surgery, a 3-Tesla magnetic resonance imaging study was performed with axial T1-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo sequences and three-dimensional time-of-flight magnetic resonance angiography. Data on quantitative regional cerebral blood flow were obtained by iodine-123-labeled N-isopropyl-iodoamphetamine single-photon emission computed tomography or positron emission computed tomography. The magnetic resonance angiography and regional cerebral blood flow data sets were registered with the magnetization-prepared rapid acquisition gradient-echo data set by means of the coregistration function of the SPM2 software. We examined the arteries located on or near the cortex where the regional cerebral blood flow had significantly decreased and used the coregistered data set and MRIcro software to select the cortical artery with the largest diameter as the target recipient artery. At the surgery, the data sets were applied to the neuronavigation system and the actual site of the target was confirmed in the operation before scalp incision. The superficial temporal artery was anastomosed with the target through a small craniotomy. Successful bypass surgery to the target was confirmed in all cases. The "target bypass" method might be effective for cases with moyamoya disease or for cases requiring surgery through a small craniotomy.

“Target Bypass”: A Method for Preoperative Targeting of A Recipient Artery in Superficial Temporal Artery-to-Middle Cerebral Artery Anastomoses

To introduce a method for preoperative targeting of a proper recipient artery in superficial temporal artery-to-middle cerebral artery anastomosis. Six operations for superficial temporal artery-to-middle cerebral artery anastomosis in four patients with moyamoya disease or moyamoya-like disease and two operations in two patients with atherosclerotic cerebrovascular occlusive disease accompanied by coronary artery stenosis were performed using our method. Before surgery, a 3-Tesla magnetic resonance imaging study was performed with axial T1-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo sequences and three-dimensional time-of-flight magnetic resonance angiography. Data on quantitative regional cerebral blood flow were obtained by iodine-123-labeled N-isopropyl-iodoamphetamine single-photon emission computed tomography or positron emission computed tomography. The magnetic resonance angiography and regional cerebral blood flow data sets were registered with the magnetization-prepared rapid acquisition gradient-echo data set by means of the coregistration function of the SPM2 software. We examined the arteries located on or near the cortex where the regional cerebral blood flow had significantly decreased and used the coregistered data set and MRIcro software to select the cortical artery with the largest diameter as the target recipient artery. At the surgery, the data sets were applied to the neuronavigation system and the actual site of the target was confirmed in the operation before scalp incision. The superficial temporal artery was anastomosed with the target through a small craniotomy. Successful bypass surgery to the target was confirmed in all cases. The "target bypass" method might be effective for cases with moyamoya disease or for cases requiring surgery through a small craniotomy.