Editor’s Choices

Magnetic Susceptibility from Quantitative Susceptibility Mapping Can Differentiate New Enhancing from Nonenhancing Multiple Sclerosis Lesions without Gadolinium Injection

Editor’s Choice

In 54 patients, new T2-weighted lesions were evaluated for enhancement on conventional T1-weighted imaging with gadolinium, and their susceptibility values were measured on quantitative susceptibility mapping. Eighty-six of 133 new lesions that were gadolinium-enhancing had relative susceptibility values significantly lower than those of nonenhancing lesions. Using susceptibility values to discriminate enhancing from nonenhancing lesions showed a sensitivity of 88.4% and specificity of 91.5%, with a cutoff value of 11.2 parts per billion for QSM.

Risk Factors for Ischemic Complications following Pipeline Embolization Device Treatment of Intracranial Aneurysms: Results from the IntrePED Study

Editor’s Choice

This is a retrospective subanalysis of the IntrePED study, which has beenpreviously published (AJNR Am J Neuroradiol 2015;36:108–15).Seven hundred ninety-three patients with 906 treated aneurysms were enrolled. Thirty-six (4.5%) patients had postoperative acute ischemic stroke, 21 of which occurred within 1 week of the procedure. There was no difference in the rate of acute stroke between the anterior and posterior circulations. Stroke rate was 3% in patients with 1 PED, and 7% in those with 2 PEDs. With multivariate analysis, the only variable independently associated with postoperative stroke was treatment of fusiform aneurysms. Among the patients with stroke, 10 (27.0%) died and 26 (73.0%) had major neurologic morbidity. The authors conclude that acute ischemic stroke following treatment of intracranial aneurysms with the PED is an uncommon but devastating complication, with 100% of patients having major morbidity or mortality.

Quantitative Susceptibility Mapping and R2* Measured Changes during White Matter Lesion Development in Multiple Sclerosis: Myelin Breakdown, Myelin Debris Degradation and Removal, and Iron Accumulation

Editor’s Choice

The authors characterized lesion changes on quantitative susceptibility mapping and R2* at various gadolinium enhancement stages (nodular, shell-like, nonenhancing) in 64 patients with 203 lesions. They found that: 1) active MS lesions with nodular enhancement show R2* decrease but no quantitative susceptibility mapping change; 2) late active lesions with peripheral enhancement show R2* decrease and quantitative susceptibility mapping increase in the lesion center; and 3) nonenhancing lesions show both quantitative susceptibility mapping and R2* increase, reflecting iron accumulation.

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