Editor’s Choices

Association of Automatically Quantified Total Blood Volume after Aneurysmal Subarachnoid Hemorrhage with Delayed Cerebral Ischemia

Editor’s Choice

The authors retrospectively studied clinical and radiologic data of 333 consecutive patients with aneurysmal SAH between January 2009 and December 2011. Adjusted odds ratios werecalculated for the association between automatically quantified total blood volume on NCCT and delayed cerebral ischemia (clinical, radiologic, and both). The adjusted OR of total blood volume for delayed cerebral ischemia was 1.02 per milliliter of blood. They conclude that a higher total blood volume measured with the automated quantification method is significantly associated with delayed cerebral ischemia.

Electrophysiologic Validation of Diffusion Tensor Imaging Tractography during Deep Brain Stimulation Surgery

Editor’s Choice

Eleven patients underwent subthalamic nucleus deep brain stimulation. DTI and high-resolution T1- and T2-weighted MRI were performed at 3T. The electrode positions and current amplitudes that elicited corticospinal tract effects during the operation were studied to determine relative corticospinal tract distance. The mean intraoperative electrophysiologic corticospinal tract distance was 3.0 mm +/- 0.6 mm; the mean image-derived corticospinal tract distance (DTI fiber tractography) was 3.0 mm +/- 1.3 mm. DTI fiber tractography depicted the medial corticospinal border in concordance with electrophysiology under 2 different conditions and modeling approaches. Under both conditions, the electrophysiologic measurements were clearly related to the DTI fiber tractography.

Cortical Perfusion Alteration in Normal-Appearing Gray Matter Is Most Sensitive to Disease Progression in Relapsing-Remitting Multiple Sclerosis

Editor’s Choice

Bookend perfusion was used to quantify parameters in normal-appearing and lesional tissue at different relapsing-remitting MS stages in 39 patients and 19 age-matched healthy controls. Perfusion parameters such as CBF, CBV, and MTT were compared along with cognitive performance. White matter lesion but not cortical lesion perfusion was significantly reduced in cognitively impaired patients with relapsing-remitting MS versus unimpaired patients with relapsing-remitting MS. Perfusion reduction with disease progression was greater in normal-appearing gray matter and normal-appearing white matter compared with cortical lesions and white matter lesions. The authors conclude that the greatest changes are present within NAGM and NAWM, necessitating absolute rather than relative lesion perfusion measurement.

Improved Leakage Correction for Single-Echo Dynamic Susceptibility Contrast Perfusion MRI Estimates of Relative Cerebral Blood Volume in High-Grade Gliomas by Accounting for Bidirectional Contrast Agent Exchange

Editor’s Choice

The authors’ hypothesis is that incorporating bidirectional contrast agent transport into the DSC MR imaging signal model will improve rCBV estimates in brain tumors. A unidirectional contrast agent extravasation model (Boxerman-Weisskoff) was compared with a bidirectional contrast agent exchange model. For both models, they compared the goodness of fit with the parent leakage-contaminated relaxation rate curves and the difference between modeled interstitial relaxation rate curves and dynamic contrast-enhanced MR imaging in 21 patients with glioblastoma. The authors conclude that the bidirectional model more accurately corrects for the T1 or T2* enhancement arising from contrast agent extravasation due to blood-brain barrier disruption in high-grade gliomas by incorporating interstitial washout rates into the DSC MR imaging relaxation rate model.

Endovascular Management of Tandem Occlusion Stroke Related to Internal Carotid Artery Dissection Using a Distal to Proximal Approach: Insight from the RECOST Study

Editor’s Choice

The authors analyzed all carotid artery dissection tandem occlusion strokes and isolated anterior circulation occlusions from their ongoing prospective stroke data base. For carotid artery dissection, the revascularization procedure consisted of initial distal recanalization by a stent retriever in the intracranial vessel. Following assessment of the circle of Willis, ICA stent placement was only performed in case of insufficiency. Two hundred fifty-eight patients with an anterior circulation stroke were analyzed, including 20 with carotid artery dissection–related occlusion. Only 5 carotid artery dissections (25%) necessitated cervical stent placement. No early ipsilateral stroke recurrence was recorded, despite the absence of stent placement in 15 patients (75%) with carotid artery dissection. Mechanical endovascular treatment of carotid artery dissection tandem occlusions is safe and effective compared with isolated anterior circulation occlusion stroke therapy. The authors favor a complete evaluation of the circle of Willis in these patients, which requires a contralateral femoral puncture, allowing selective contralateral common carotid and vertebrobasilar catheterizations.

Iron and Non-Iron-Related Characteristics of Multiple Sclerosis and Neuromyelitis Optica Lesions at 7T MR

Editor’s Choice

Twenty-one patients with MS and 21 patients with neuromyelitis optica underwent 7T high-resolution 2D-gradient-echo-T2* and 3D-susceptibility-weighted imaging. An in-house-developed algorithm was used to reconstruct quantitative susceptibility mapping from SWI. Of the patients with MS, 19 (90.5%) demonstrated at least 1 quantitative susceptibility mapping–hyperintense lesion, and 11/21 (52.4%) had iron-laden lesions. No quantitative susceptibility mapping–hyperintense or iron-laden lesions were observed in any patients with neuromyelitis optica. The authors conclude that ultra-high-field MR imaging may be useful in distinguishing MS from neuromyelitis optica.

Mapping the Orientation of White Matter Fiber Bundles: A Comparative Study of Diffusion Tensor Imaging, Diffusional Kurtosis Imaging, and Diffusion Spectrum Imaging

Editor’s Choice

The authors evaluated fiber bundle orientations from DTI and diffusional kurtosis compared with diffusion spectrum imaging as a criterion standard to assess the performance of each technique. DTI, diffusional kurtosis imaging, and diffusion spectrum imaging datasets were acquired during 2 independent sessions in 3 volunteers. While orientation estimates from all 3 techniques had comparable angular reproducibility, diffusional kurtosis imaging decreased angular error throughout the white matter compared with DTI. Diffusion spectrum imaging and diffusional kurtosis imaging enabled the detection of crossing-fiber bundles. They conclude that fiber bundle orientation estimates from diffusional kurtosis imaging have less systematic error than those from DTI.

Abstract

BACKGROUND AND PURPOSE

White matter fiber tractography relies on fiber bundle orientation estimates from diffusion MR imaging. However, clinically feasible techniques such as DTI and diffusional kurtosis imaging use assumptions, which may introduce error into in vivo orientation estimates. In this study, fiber bundle orientations from DTI and diffusional kurtosis imaging are compared with diffusion spectrum imaging as a criterion standard to assess the performance of each technique.

MATERIALS AND METHODS

For each subject, full DTI, diffusional kurtosis imaging, and diffusion spectrum imaging datasets were acquired during 2 independent sessions, and fiber bundle orientations were estimated by using the specific theoretic assumptions of each technique. Angular variability and angular error measures were assessed by comparing the orientation estimates. Tractography generated with each of the 3 reconstructions was also examined and contrasted.

RESULTS

Orientation estimates from all 3 techniques had comparable angular reproducibility, but diffusional kurtosis imaging decreased angular error throughout the white matter compared with DTI. Diffusion spectrum imaging and diffusional kurtosis imaging enabled the detection of crossing-fiber bundles, which had pronounced effects on tractography relative to DTI. Diffusion spectrum imaging had the highest sensitivity for detecting crossing fibers; however, the diffusion spectrum imaging and diffusional

Differentiation of Speech Delay and Global Developmental Delay in Children Using DTI Tractography-Based Connectome

Editor’s Choice

This study investigated whether diffusion tensor imaging tractography-based connectome can differentiate global developmental delay from speech delay in young children. Twelve children with pure speech delay, 14 children with global developmental delay, and 10 children with typical development underwent 3T DTI. Whole-brain connectome analysis was performed by using 116 cortical ROIs. Network metrics were measured at individual regions: strength, efficiency, cluster coefficient, and betweeness. Compared with typical development, global and local efficiency were significantly reduced in both global developmental delay and speech delay. Nodal strength of the cognitive network was reduced in global developmental delay, whereas the nodal strength of the language network was reduced in speech delay. This finding resulted in a high accuracy of >83% to discriminate global developmental delay from speech delay.

Abstract

ROIs showing significantly altered network metrics in the group comparison of TD > GD. In the 2D connectogram, the color of anatomic label scales the P value of group difference in the AAL template. Similarly, the color of each circle represents the P value of individual metrics. The 3D connectogram shows individual pair-wise pathways having significant group differences in nodal strength (ie, the greater radius of the sphere, the greater the group difference). In both 2D and 3D connectograms, block arrows indicate the hippocampal network whose nodal properties are significantly reduced in GD compared with TD.
ROIs showing significantly altered network metrics in the group comparison of TD > GD. In the 2D connectogram, the color of anatomic label scales the P value of group difference in the AAL template. Similarly, the color of each circle represents the P value of individual metrics. The 3D connectogram shows individual pair-wise pathways having significant group differences in nodal strength (ie, the greater radius of the sphere, the greater the group difference). In both 2D and 3D connectograms, block arrows indicate the hippocampal network whose nodal properties are significantly reduced in GD compared with TD.

BACKGROUND AND PURPOSE

Pure speech delay is a common developmental disorder which, according to some estimates, affects 5%–8% of the population. Speech delay may not only be an isolated condition but also can be part of a broader condition such as global developmental delay. The present study investigated whether diffusion tensor imaging tractography-based connectome can differentiate global developmental delay from speech delay in young children.

MATERIALS AND METHODS

Twelve children with pure speech delay (39.1 ±

Interrogating the Functional Correlates of Collateralization in Patients with Intracranial Stenosis Using Multimodal Hemodynamic Imaging

Editor’s Choice

The authors assessed correlations among baseline perfusion and arterial transit time artifacts, cerebrovascular reactivity, and the presence of collateral vessels on digital subtraction angiography. Arterial spin-labeling MRI and DSA were compared with BOLD MR imaging measures of hypercapnic cerebrovascular reactivity in 18 patients with symptomatic intracranial stenosis. In regions with normal-to-high signal on ASL, collateral vessel presence on DSA strongly correlated with declines in cerebrovascular reactivity (as measured on BOLD MRI). These data support the use of ASL MR imaging rather than invasive DSA to assess the presence of collateralization, even for patients with internal carotid stenosis from nonatherosclerotic etiologies. Also, collaterals identified on ASL with arterial transit artifacts correlated with decreased CVR compared with regions not perfused via collaterals.

Abstract

A, Arterial transit artifacts (arrow) at the ganglionic level on ASL MR imaging in the M3 region (ASPECTS designation criteria) representing leptomeningeal collateralization. B, A similar distribution is shown in an early venous phase anteroposterior right ICA angiogram showing leptomeningeal collaterals (arrows) arriving at the periphery of the ischemic site.
A, Arterial transit artifacts (arrow) at the ganglionic level on ASL MR imaging in the M3 region (ASPECTS designation criteria) representing leptomeningeal collateralization. B, A similar distribution is shown in an early venous phase anteroposterior right ICA angiogram showing leptomeningeal collaterals (arrows) arriving at the periphery of the ischemic site.

BACKGROUND AND PURPOSE

The importance of collateralization for maintaining adequate cerebral perfusion is increasingly recognized. However, measuring collateral flow noninvasively has proved elusive. The aim of this study was to assess correlations among baseline perfusion and arterial transit time artifacts, cerebrovascular reactivity, and the presence of collateral vessels on digital subtraction angiography.

MATERIALS AND METHODS

The relationship between the presence of collateral vessels on arterial spin-labeling MR imaging and DSA was compared with blood oxygen level–dependent MR imaging measures of hypercapnic cerebrovascular reactivity in patients with symptomatic intracranial stenosis (n = 18). DSA maps were reviewed by a neuroradiologist and assigned the following scores: 1, collaterals to the periphery of the ischemic site; 2, complete irrigation of the ischemic bed via collateral flow; and 3, normal

Clinical Feasibility of Synthetic MRI in Multiple Sclerosis: A Diagnostic and Volumetric Validation Study

Editor’s Choice

SyMRI is a quantitative synthetic MR imaging method where a single saturation recovery TSE sequence is used to estimate the proton density, longitudinal relaxation rate, and transverse relaxation rate and allows for a free range of synthetic weightings. Twenty patients with MS and 20 healthy controls were enrolled and synthetic MR imaging was implemented on a Siemens 3T scanner. Diagnostic accuracy, lesion detection, and artifacts were assessed by blinded neuroradiologic evaluation, and CNR by manual tracing. Synthetic PD-, T1-, and T2-weighted images were of sufficient or good quality and were acquired in 7% less time than with conventional MRI. Synthetic FLAIR images suffered from artifacts. Also, synthetic MRI provided segmentations with the shortest processing time (16 seconds) and the lowest repeatability error for brain volume. Synthetic MRI can be an alternative to conventional MRI for generating diagnostic PD-, T1-, and T2-weighted images in patients with MS with fast and robust volumetric measurements.

Abstract

Conventional (top row) and synthetic (middle row) axial noncontrast MR imaging in a 49-year-old male patient with MS, from left to right: T1-, PD-, and T2-weighted, and FLAIR images. The bottom row shows brain tissue segmentations of the WM (cyan), GM (green), CSF (magenta), and other remaining brain tissues (yellow) from SyMRI.
Conventional (top row) and synthetic (middle row) axial noncontrast MR imaging in a 49-year-old male patient with MS, from left to right: T1-, PD-, and T2-weighted, and FLAIR images. The bottom row shows brain tissue segmentations of the WM (cyan), GM (green), CSF (magenta), and other remaining brain tissues (yellow) from SyMRI.

BACKGROUND AND PURPOSE

Quantitative MR imaging techniques are gaining interest as methods of reducing acquisition times while additionally providing robust measurements. This study aimed to implement a synthetic MR imaging method on a new scanner type and to compare its diagnostic accuracy and volumetry with conventional MR imaging in patients with MS and controls.

MATERIALS AND METHODS

Twenty patients with MS and 20 healthy controls were enrolled after ethics approval and written informed consent. Synthetic MR imaging was implemented on a Siemens 3T scanner. Comparable conventional and synthetic proton-density–, T1-, and T2-weighted, and