Jean-Christophe Ferré

Abnormal functional lateralization and activity of language brain areas in typical specific language impairment (developmental dysphasia)

Atypical functional lateralization and specialization for language have been proposed to account for developmental language disorders, yet results from functional neuroimaging studies are sparse and inconsistent. This functional magnetic resonance imaging study compared children with a specific subtype of specific language impairment affecting structural language (n = 21), to a matched group of typically developing children using a panel of four language tasks neither requiring reading nor metalinguistic skills, including two auditory lexico-semantic tasks (category fluency and responsive naming) and two visual phonological tasks based on picture naming. Data processing involved normalizing the data with respect to a matched pairs paediatric template, groups and between-groups analysis, and laterality indices assessment within regions of interest using single and combined task analysis. Children with specific language impairment exhibited a significant lack of left lateralization in all core language regions (inferior frontal gyrus-opercularis, inferior frontal gyrus-triangularis, supramarginal gyrus and superior temporal gyrus), across single or combined task analysis, but no difference of lateralization for the rest of the brain. Between-group comparisons revealed a left hypoactivation of Wernickes area at the posterior superior temporal/supramarginal junction during the responsive naming task, and a right hyperactivation encompassing the anterior insula with adjacent inferior frontal gyrus and the head of the caudate nucleus during the first phonological task. This study thus provides evidence that this subtype of specific language impairment is associated with atypical lateralization and functioning of core language areas.

Time-of-flight MR angiography at 3 T versus digital subtraction angiography in the imaging follow-up of 51 intracranial aneurysms treated with coils

OBJECTIVE To compare 3D time-of-flight MR angiography (TOF-MRA) at 3 Tesla (3T) with digital subtraction angiography (DSA) for the evaluation of intracranial aneurysm occlusion after endovascular coiling. METHODS In a prospective study, 51 consecutive patients (25 females, 26 males; median age, 51 years) with 51 saccular aneurysms treated with endovascular coiling underwent simultaneous DSA and 3T TOF-MRA at follow-up. DSA and TOF-MRA images were analyzed independently by two senior neuroradiologists. Findings were assigned to 1 of 3 categories in the Raymond classification: complete obliteration, residual neck or residual aneurysm. Agreement between observers and techniques was evaluated using kappa statistics. RESULTS DSA images were not interpretable for one patient. Interobserver agreement was determined as excellent for DSA (kappa=0.86) and TOF-MRA (kappa=0.80). After reaching a consensus, DSA follow-up showed 26 (51%) complete obliterations, 20 (39%) residual necks and 4 (8%) residual aneurysms. TOF-MRA showed 23 (45%) complete obliterations, 22 (43%) residual necks and 6 (12%) residual aneurysms. Comparison between TOF-MRA and DSA showed excellent agreement between the techniques (kappa=0.86). In the four cases that were misclassified, TOF-MRA findings were assigned to a higher class than for DSA. CONCLUSION TOF-MRA at 3T is at least as efficient as DSA for the evaluation of intracranial aneurysm occlusion after endovascular treatment with detachable coils. We suggest that TOF-MRA at 3T might be used as the primary method for imaging follow-up of coiled intracranial aneurysms.

Chronic and treatment-resistant depression: a study using arterial spin labeling perfusion MRI at 3Tesla.

The aim of the present study was to compare patients displaying chronic and treatment-resistant depression with healthy controls, using the resting-state perfusion with arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) technique at 3T. The study focused on the subgenual anterior cingulate cortex (sACC), which is a key component in the pathophysiology of depression. Six patients with chronic and treatment-resistant depression and six healthy control subjects were included. ASL is an innovative imaging technique which sidesteps the limitations of other functional neuroimaging techniques (functional MRI, positron emission tomography). A statistical analysis of perfusion maps was performed using SPM2 software. Statistically significant hyperperfusion regions were found in the depressed patient group compared with the healthy control group in the following: the bilateral sACC, left prefrontal dorsomedian cortex, left ACC and left subcortical areas (putamen, pallidum and amygdala). This study confirmed the involvement of the sACC in depression, particularly chronic and treatment-resistant depression, using ASL at 3T, a safe perfusion technique that seems to be appropriate for investigating functional abnormalities in psychiatric disorders.

Arterial spin labeling (ASL) perfusion: Techniques and clinical use

Arterial spin labeling (ASL) perfusion is a MRI technique to quantify tissue blood flow. ASL is a non-invasive technique that labels the protons in the arterial blood by radiofrequency pulses, without the exogenous injection of contrast media. This article has three goals: 1) present the principles of ASL perfusion, the types of labeling and the ways to obtain the mapping; 2) specify and the quality criteria for the mapping obtained, while emphasizing the artifacts; and 3) describe the main encephalic and renal applications.

Arterial spin labeling for motor activation mapping at 3T with a 32-channel coil: reproducibility and spatial accuracy in comparison with BOLD fMRI.

Functional arterial spin labeling (fASL) is an innovative biomarker of neuronal activation that allows direct and absolute quantification of activation-related CBF and is less sensitive to venous contamination than BOLD fMRI. This study evaluated fASL for motor activation mapping in comparison with BOLD fMRI in terms of involved anatomical area localization, intra-individual reproducibility of location, quantification of neuronal activation, and spatial accuracy. Imaging was performed at 3T with a 32-channel coil and dedicated post-processing tools were used. Twelve healthy right-handed subjects underwent fASL and BOLD fMRI while performing a right hand motor activation task. Three sessions were performed 7days apart in similar physiological conditions. Our results showed an activation in the left primary hand motor area for all 36 sessions in both fASL and BOLD fMRI. The individual functional maps for fASL demonstrated activation in ipsilateral secondary motor areas more often than the BOLD fMRI maps. This finding was corroborated by the group maps. In terms of activation location, fASL reproducibility was comparable to BOLD fMRI, with a distance between activated volumes of 2.1mm and an overlap ratio for activated volumes of 0.76, over the 3 sessions. In terms of activation quantification, fASL reproducibility was higher, although not significantly, with a CVintra of 11.6% and an ICC value of 0.75. Functional ASL detected smaller activation volumes than BOLD fMRI but the areas had a high degree of co-localization. In terms of spatial accuracy in detecting activation in the hand motor area, fASL had a higher specificity (43.5%) and a higher positive predictive value (69.8%) than BOLD fMRI while maintaining high sensitivity (90.7%). The high intra-individual reproducibility and spatial accuracy of fASL revealed in the present study will subsequently be applied to pathological subjects.

Construction and assessment of a 3-T MRI brain template

New MR imaging protocols enable visualization of brain structures. However, for dedicated clinical applications such as targeting deep brain stimulation (DBS), a more accurate localization requires the use of atlases. We developed a three-dimensional digitized mono-subject anatomical template of the human brain based on 3-T magnetic resonance images (MRI). By averaging 15 registered T1 image acquisitions, we have shown that the final image corresponds to an optimal image, limited by the performance of the 3-T MR machine. We compared different preprocessing workflows for template construction. With the optimal strategy, along with validated existing processing methods, one T1 template and one T1-T2 mixing template were created in order to improve visualization of spatially complex deep structures. Reduction of voxel size to 0.25 mm(3) was also advantageous to observe fine structures and white matter/gray matter intensity crossings. Results demonstrated that such a template also improved inter-patient registration for population comparison in DBS. These MR templates are made freely available to our community (http://www.vmip.org/mritemplate) to serve as a reference for neuroimage processing methods.

Prognostic factors for outcomes after mechanical thrombectomy with solitaire stent

BACKGROUND AND PURPOSE Endovascular mechanical thrombectomy is emerging as a promising therapeutic approach for acute ischemic stroke. This study was aimed at identifying factors influencing outcomes after thrombectomy with a Solitaire stent device. MATERIALS AND METHODS Forty-five consecutive patients treated with thrombectomy using Solitaire FR were retrospectively included. Clinical, imaging and logistic variables were analyzed. A multivariate logistic regression analysis was used to identify variables influencing clinical outcome, based on discharge NIHSS score change and mRS at 3 months. RESULTS Patient mean age and initial NIHSS score was 58 years (range 24-88) and 17 (range 6-32), respectively. An MRI was performed for 80% of patients, showing severe DWI lesion for 28% of patients and associated FLAIR hyperintensity for 58% of patients. Mean time from symptom onset to recanalization was 299min for the 32 ACO and 473min for the 13 PCO. Angiographic efficacy (TICI 2b-3) was achieved for 93% of patients and good clinical outcomes at discharge and at 3 months (mRS≤2) were achieved for 49% and 58% of patients, respectively. Independent prognostic factors for predicting good clinical outcomes at discharge were a short time to recanalization and FLAIR negativity. At 3 months, they were a short time to recanalization and patient age. DWI lesion severity was an associated prognostic factor. CONCLUSION Two main prognostic factors for predicting a good clinical outcome after thrombectomy at 3 months were short time from symptom onset to recanalization and patient age.

Improving quality of arterial spin labeling MR imaging at 3 Tesla with a 32-channel coil and parallel imaging.

To compare 12‐channel and 32‐channel phased‐array coils and to determine the optimal parallel imaging (PI) technique and factor for brain perfusion imaging using Pulsed Arterial Spin labeling (PASL) at 3 Tesla (T).

Hemodynamic Quantification in Brain Arteriovenous Malformations With Time-Resolved Spin-Labeled Magnetic Resonance Angiography

Background and Purpose— Unenhanced time-resolved spin-labeled magnetic resonance angiography enables hemodynamic quantification in arteriovenous malformations (AVMs). Our purpose was to identify quantitative parameters that discriminate among different AVM components and to relate hemodynamic patterns with rupture risk. Methods— Sixteen patients presenting with AVMs (7 women, 9 men; mean age 37.1±15.9 years) were assigned to the high rupture risk or low rupture risk group according to anatomic AVM characteristics and rupture history. High temporal resolution (<70 ms) unenhanced time-resolved spin-labeled magnetic resonance angiography was performed on a 3-T MR system. After dedicated image processing, hemodynamic quantitative parameters were computed. T tests were used to compare quantitative parameters among AVM components, between the high rupture risk and low rupture risk groups, and between the hemorrhagic and nonhemorrhagic groups. Results— Among the quantitative parameters, time-to-peak (P<0.001) and maximum outflow gradient (P=0.01) allowed discriminating various intranidal flow patterns with significantly different values between feeding arteries and draining veins. With 9 AVMs classified into the high rupture risk group (whose 6 were hemorrhagic) and 7 into the low rupture risk group, the observed venous-to-arterial time-to-peak ratio was significantly lower in the high rupture risk (P=0.003) and hemorrhagic (P=0.001) groups. Conclusions— Unenhanced time-resolved spin-labeled magnetic resonance angiography allows AVM-specific combined anatomic and quantitative analysis of AVM hemodynamics.

Mechanical thrombectomy with the ERIC retrieval device: initial experience

Objective To report our experience with the Embolus Retriever with Interlinked Cage (ERIC) stentriever for use in mechanical endovascular thrombectomy (MET). Methods Thirty-four consecutive patients with acute stroke (21 men and 13 women; median age 66 years) determined appropriate for MET were treated with ERIC and prospectively included over a 6-month period at three different centers. The ERIC device differs from typical stentrievers in that it is designed with a series of interlinked adjustable nitinol cages that allow for fast thrombus capture, integration, and withdrawal. The evaluated endpoints were successful revascularization (Thrombolysis in Cerebral Infarction (TICI) 2b–3) and good clinical outcomes at 3 months (modified Rankin Scale (mRS) 0–2). Results Locations of the occlusions included the middle cerebral artery (13 patients), terminal carotid artery (11 patients), basilar artery (1 patient), and tandem occlusions (9 patients). IV thrombolysis was performed in 20/34 (58.8%) patients. Median times from symptom onset to recanalization and from puncture to recanalization were 325.5 min (180–557) and 78.5 min (14–183), respectively. Used as the first-line device, ERIC achieved a successful recanalization in 20/24 (83.3%) patients. Successful recanalization was associated with lower National Institutes of Health Stroke Scale scores at 24 h (8±6.5 vs 21.5±2.1; p=0.008) and lower mRS at 3 months (2.7±2.1 vs 5.3±1.1; p=0.04). Three procedural complications and four asymptomatic hemorrhages were recorded. Good clinical outcomes at 3 months were seen in 15/31 (48.4%) patients. Conclusions The ERIC device is an innovative stentriever allowing fast, effective, and safe MET.