T2-weighted Fluid-attenuated Inversion Recovery Sequences Research Articles

Auditory Effects of Acoustic Noise From 3-T Brain MRI in Neonates With Hearing Protection.

Neonates with immature auditory function (eg, weak/absent middle ear muscle reflex) could conceivably be vulnerable to noise-induced hearing loss; however, it is unclear if neonates show evidence of hearing loss following MRI acoustic noise exposure. To explore the auditory effects of MRI acoustic noise in neonates. Prospective. Two independent cohorts of neonates (N = 19 and N = 18; mean gestational-age, 38.75 ± 2.18 and 39.01 ± 1.83 weeks). T1-weighted three-dimensional gradient-echo sequence, T2-weighted fast spin-echo sequence, single-shot echo-planar imaging-based diffusion-tensor imaging, single-shot echo-planar imaging-based diffusion-kurtosis imaging and T2-weighted fluid-attenuated inversion recovery sequence at 3.0 T. All neonates wore ear protection during scan protocols lasted ~40 minutes. Equivalent sound pressure levels (SPLs) were measured for both cohorts. In cohort1, left- and right-ear auditory brainstem response (ABR) was measured before (baseline) and after (follow-up) MRI, included assessment of ABR threshold, wave I, III and V latencies and interpeak interval to determine the functional status of auditory nerve and brainstem. In cohort2, baseline and follow-up left- and right-ear distortion product otoacoustic emission (DPOAE) amplitudes were assessed at 1.2 to 7.0 kHz to determine cochlear function. Wilcoxon signed-rank or paired t-tests with Bonferroni's correction were used to compare the differences between baseline and follow-up ABR and DPOAE measures. Equivalent SPLs ranged from 103.5 to 113.6 dBA. No significant differences between baseline and follow-up were detected in left- or right-ear ABR measures (P > 0.999, Bonferroni corrected) in cohort1, or in DPOAE levels at 1.2 to 7.0 kHz in cohort2 (all P > 0.999 Bonferroni corrected except for left-ear levels at 3.5 and 7.0 kHz with corrected P = 0.138 and P = 0.533). A single 40-minute 3-T MRI with equivalent SPLs of 103.5-113.6 dBA did not result in significant transient disruption of auditory function, as measured by ABR and DPOAE, in neonates with adequate hearing protection. 2. Stage 5.

Autoimmune Encephalitis–Related Seizures and Epilepsy: Diagnostic and Therapeutic Approaches

Autoimmune Encephalitis–Related Seizures and Epilepsy: Diagnostic and Therapeutic Approaches

Myelin Imaging in Human Brain Using a Short Repetition Time Adiabatic Inversion Recovery Prepared Ultrashort Echo Time (STAIR-UTE) MRI Sequence in Multiple Sclerosis.

Background Water signal contamination is a major challenge for direct ultrashort echo time (UTE) imaging of myelin in vivo because water contributes most of the signals detected in white matter. Purpose To validate a new short repetition time (TR) adiabatic inversion recovery (STAIR) prepared UTE (STAIR-UTE) sequence designed to suppress water signals and to allow imaging of ultrashort T2 protons of myelin in white matter using a clinical 3-T scanner. Materials and Methods In this prospective study, an optimization framework was used to obtain the optimal inversion time for nulling water signals using STAIR-UTE imaging at different TRs. Numeric simulation and phantom studies were performed. Healthy volunteers and participants with multiple sclerosis (MS) underwent MRI between November 2018 and October 2019 to compare STAIR-UTE and a clinical T2-weighted fluid-attenuated inversion recovery sequence for assessment of MS lesions. UTE measures of myelin were also performed to allow comparison of signals in lesions and with those in normal-appearing white matter (NAWM) in patients with MS and in normal white matter (NWM) in healthy volunteers. Results Simulation and phantom studies both suggest that the proposed STAIR-UTE technique can effectively suppress long T2 tissues with a broad range of T1s. Ten healthy volunteers (mean age, 33 years ± 8 [standard deviation]; six women) and 10 patients with MS (mean age, 51 years ± 16; seven women) were evaluated. The three-dimensional STAIR-UTE sequence effectively suppressed water components in white matter and selectively imaged myelin, which had a measured T2* value of 0.21 msec ± 0.04 in the volunteer study. A much lower mean UTE measure of myelin proton density was found in MS lesions (3.8 mol/L ± 1.5), and a slightly lower mean UTE measure was found in NAWM (7.2 mol/L ± 0.8) compared with that in NWM (8.0 mol/L ± 0.8) in the healthy volunteers (P < .001 for both comparisons). Conclusion The short repetition time adiabatic inversion recovery-prepared ultrashort echo time sequence provided efficient water signal suppression for volumetric imaging of myelin in the brain and showed excellent myelin signal contrast as well as marked ultrashort echo time signal reduction in multiple sclerosis lesions and a smaller reduction in normal-appearing white matter compared with normal white matter in volunteers. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Messina and Port in this issue.

7.0 T MRI detection of cerebral microinfarcts in patients with a symptomatic high-grade carotid artery stenosis.

In the current study, the presence of cerebral cortical microinfarcts (CMIs) was evaluated in a series of 21 patients with a symptomatic high-grade >50% stenosis of the carotid artery. A T2-weighted fluid-attenuated inversion recovery sequence and a T1-weighted turbo field echo sequence of the brain were obtained at 7.0 Tesla magnetic resonance imaging. Primary study endpoint was the number of CMIs and macroinfarcts. In total, 53 cerebral infarcts (35 macroinfarcts; 18 CMIs) were found ipsilateral to the symptomatic carotid artery, in 14 patients (67%). In four of these patients, both CMIs and macroinfarcts were visible. In the contralateral hemisphere, seven infarcts (five macroinfarcts and two CMIs) were found in five patients (24%). In the ipsilateral hemispheres, the number of CMIs and macroinfarcts were significantly correlated (P=0.02). Unpaired comparison of medians showed that the number of CMIs in the ipsilateral hemisphere was significantly higher than the number of CMIs in the contralateral hemisphere (P=0.04). No significant correlation was found between stenosis grade and the number of any infarct. The current study shows that in symptomatic patients with significant extracranial carotid artery stenosis, CMIs are part of the total cerebrovascular burden and these CMIs prevail with a similar pattern as observed macroinfarcts.

Topographic diagnosis of internuclear ophthalmoparesis: evidence from a lesion-behavior mapping study

The syndrome of internuclear ophthalmoparesis (INO) is very common and almost always associated with a homolateral lesion localized to the medial longitudinal fasciculus (MLF) making INO among the most eloquent syndromes in neurologic practice [1–5]. However, to the best of our knowledge, there is no statistical anatomical approach comparing patients with INO vs. without INO identifying the brainstem structures involved. Thus, the present voxel based lesion-mapping (VLBM) approach allows for the first time precise statistical lesion localization and the direct comparison of the voxels affected in patients showing INO vs. the voxels affected in patients without INO [6]. Forty-four patients with magnetic resonance imaging (MRI) documented brainstem lesions (mean age 64 years; standard deviation (SD) 16.9 years; right-sided lesions 52 %; left-sided lesions 48 %) and a control group of 30 healthy age-matched controls (mean age 58 years; SD 10.4 years (independent t test p = 0.117)) participated in the study. Fifteen patients presented with an INO (four patients each with left-sided and bilateral INO and seven patients with right-sided INO) and 29 patients without. The INO was detected clinically by an experienced neuroophthalmologist and confirmed by electro-oculography [1]. To verify the INO, the versional disconjugacy index (VDI), defined as the ratio of the abducting and the adducting eye velocity and its corresponding z-scores which represents a standardized number in relation to the present control group, was applied [7, 8]. With respect to the z-score and the VDI, a difference was seen between the patient group without INO, the INO group and the controls (one-way ANOVA, p = 0) (see Table 1). Thirty-seven patients (84 %) had a lesion due to ischemic stroke, one patient (2 %) due to a bleeding, and one patient (14 %) due to multiple sclerosis (MS) demonstrated by MRI (1.5T scanner Vision, Siemens, Erlangen, Germany). The MRI T2-weighted fluid-attenuated inversionrecovery sequences, diffusion-weighted sequences, T2 and Gadolinium T1-sequences were applied. The MRI dataset was first prepared using the isolation algorithm of the SUIT toolbox [9, 10]. Afterwards the automated normalization algorithm provided by SPM8 and the SUIT toolbox implemented in SPM8 were applied [9, 10]. The lesions were then delineated directly on the normalized lesions of the individual normalized MRI scans with MRIcroN software [6] (http://www.mccauslandcenter.sc.edu/mricro/ mricron/install.html). To evaluate the relationship between lesion location and INO, i.e., to analyze whether patients with INO differ with respect to their lesion location from patients without INO, a subtraction analysis was conducted. Subtraction analysis reflects the relative frequency of damage. Statistical VLBM analysis was performed by using the dichotomic Liebermeister test implemented in the B. Baier (&) F. Thomke Department of Neurology, University of Mainz, Langenbeckstr. 1, 55131 Mainz, Germany e-mail: baierb@uni-mainz.de

On the debated role of temporo-parietal dysfunction in patients with basal ganglia neglect

On the debated role of temporo-parietal dysfunction in patients with basal ganglia neglect

FLAIR*: A Combined MR Contrast Technique for Visualizing White Matter Lesions and Parenchymal Veins

To evaluate a magnetic resonance (MR) imaging contrast technique, called FLAIR*, that combines the advantages of T2-weighted fluid-attenuated inversion recovery (FLAIR) contrast and T2*-weighted contrast on a single image for assessment of white matter (WM) diseases such as multiple sclerosis (MS). This prospective pilot study was HIPAA compliant and institutional review board approved. Ten patients with clinically definite MS (eight men, two women; mean age, 41 years) provided informed consent and underwent 3.0-T MR imaging. Images from a T2-weighted FLAIR sequence were combined with images from a T2*-weighted segmented echo-planar imaging sequence performed during contrast material injection, yielding high-isotropic-resolution (0.55 × 0.55 × 0.55 mm(3)) FLAIR* images. Qualitative assessment was performed for image quality, lesion conspicuity, and vein conspicuity. Contrast-to-noise ratio (CNR) was calculated to compare normal-appearing WM (NAWM) with cerebrospinal fluid, lesions, and veins. To evaluate the differences in CNR among imaging modalities, a bootstrap procedure clustered on subjects was used, together with paired t tests. High-quality FLAIR* images of the brain were produced at 3.0 T, yielding conspicuous lesions and veins. Lesion-to-NAWM and NAWM-to-vein CNR values were significantly higher for FLAIR* images than for T2-weighted FLAIR images (P < .0001). Findings on FLAIR* images included intralesional veins for lesions located throughout the brain and a hypointense rim around some WM lesions. High-isotropic-resolution FLAIR* images obtained at 3.0 T yield high contrast for WM lesions and parenchymal veins, making it well suited to investigate the relationship between WM abnormalities and veins in a clinical setting.

Delayed posthypoxic leukoencephalopathy following a morphine overdose

We describe one patient and review the literature to define delayed posthypoxic leukoencephalopathy, its etiology, pathophysiology and prognosis. We present a 54-year-old man with confusion and diffuse rigidity following a morphine overdose that had required intubation three weeks previously. A brain CT scan showed bilateral globi pallidi hypodensities and diffusion-weighted brain MRI (DWI) was consistent with acute cerebral anoxia. On day 20 after the initial presentation, the patient insidiously progressed to a state of “akinetic mutism”. The brain MRI showed diffuse hyperintensity of the white matter on T2-weighted fluid-attenuated inversion recovery sequences. These areas were bright on DWI and were hypointense on the apparent diffusion coefficient map. An extensive autoimmune, metabolic, toxicological, and infectious work-up included arylsulfatase A enzyme levels, which were unremarkable. Therapy with levodopa was initiated with subsequent improvement of the diffuse rigidity. At discharge, the patient continued to be lethargic with moderate rigidity but began to display signs of recovery. He eventually fully recovered with residual mild confusion. Thus, delayed hypoxic leukoencephalopathy is a rare complication of hypoxic–ischemic encephalopathy, occurring in 2.75% of victims of carbon monoxide poisoning. It typically manifests two to 40days after apparent recovery from an obtunded state. Prognosis is variable, but recovery can be complete. This report brings to light an important syndrome that can easily be misdiagnosed. Patients who present with these clinical and radiographic features should be treated fully and given time to recover without abrupt withdrawal of care.

MRI diffusion-weighted imaging of the brain: Contributions to image contrast from CSF signal reduction, use of a long echo time and diffusion effects

The contributions of CSF signal reduction, use of a long echo time and diffusion weighting to the appearance of pulsed gradient spin echo (PGSE) images are analysed by reference to T2-weighted spin echo and T2-weighted fluid attenuated inversion recovery (FLAIR) pulse sequences. Both PGSE and T2-weighted FLAIR sequences reduce CSF signal and produce very heavy T2 weighting allowing the specific additional contribution produced by the diffusion weighting of PGSE sequences to be recognized. Considerable advantage accrues from CSF suppression with both PGSE and FLAIR sequences through reduction in partial volume effects and artefacts. The very heavy T2 weighting with both these pulse sequences highlights certain white matter tracts and provides high sensitivity to disease. The additional diffusion weighting with PGSE sequences can enhance or reduce white matter tract signals and may enhance or reduce lesion conspicuity relative to the FLAIR sequences. Many of the benefits attributed to the diffusion-weighted PGSE sequence may result from the reduction of the CSF signal and the heavy T2 weighting of the sequence without a contribution from diffusion effects. However, additional anatomical detail, sensitivity to myelination and increased lesion conspicuity may result from the diffusion weighting.