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Previous studies have suggested that mechanical revascularization in acute ischemic stroke (AIS) patients could be affected by clot histology. In this 7-T micro-MRI study, we used R2* relaxometry of clot analogs to evaluate the relationship between texture parameters of R2* maps and clot constituents.Twelve AIS clot analogs were experimentally generated to obtain a wide range of red blood cell concentrations. All clots underwent a MR acquisition using a 7-T micro-MR system. A 3D multi-echo gradient-echo sequence was performed and R2* maps were generated. First order and second order statistics of R2* histograms within the clots were calculated. Iron concentration in clots was measured using absorption spectrometry and red blood cell count (RBC) was obtained by histopathological analysis.RBC count was strongly correlated with iron concentration within clots (r=0.87, P.001). Higher RBC count and iron concentration were significantly correlated with first order parameters including: (a) global positive shift of the R2* histogram with higher '10th percentile', 'median', 'mean' and '90th percentile'; (b) increase of the global magnitude of voxel values with higher 'total energy' and 'root mean squared'; (c) greater uniformity of the voxel values with higher 'uniformity' and lower 'entropy'. Second order statistical parameters confirmed that higher RBC count and iron concentration correlated with (a) greater concentration of high gray-level values in the image; (b) more "coarse" texture of R2* maps.Texture analysis of MRI-R2* maps can accurately estimate the red blood cell count and iron content of AIS clot analogs.

Introduction Cerebral white matter hyperintensity (WMH) on FLuid Attenuated Inversion Recovery (FLAIR) is linked to less favourable outcome in patients with acute ischemic stroke (AIS) but data on their relevance in patients with large vessel occlusion (LVO) treated with mechanical thrombectomy (MT) are sparse. In this post-hoc analysis of the MT arm of the THRACE trial and multicenter retrospective cohorts, we aimed to determine the influence of WMH burden on clinical outcome, rate of symptomatic intracranial hemorrhage (ICH) and procedural success in AIS patients treated by MT with current stentriever/aspiration devices. Patients and methods Patients from the MT arm of THRACE trial, and prospective cohorts from two academic comprehensive stroke centers were pooled and retrospectively analyzed. WMH volumes were obtained by semi-automated planimetric segmentation and tested in association with the rate of favourable outcome (mRS 0-2 at at 90 days), successful recanalization after MT (mTICI ≥ 2B), and symptomatic ICH. Results A total of 535 subjects met inclusion criteria between 2015 and 2018 (49 % female, mean age 68,0 years ± 15,0 Overall, 458 (85,6 %) patients presented with detectable WMH (median volume 5,7cc IQR [2,8–12,7]). Patients demonstrated increasingly worse outcomes with increasing WMH volumes), with 57 % of patients in the 1st quartile of WMH volume demonstrating favourable outcome vs. 27 % in the 4th (p Conclusion Our study provides evidence that patients with AIS due to LVO and severe WMH as assessed by pre-treatment MRI, are at higher risk for less favourable outcome following MT, despite similar rates of sICH and procedural success. Since 27 % of patients with severe WMH in our sample experienced favourable outcome at 3 months, severe WMH burden may not preclude MT.

Introduction La signification du rehaussement de la paroi des anevrismes intra-crâniens non rompus en IRM 3-Tesla demeure aujourd’hui incertaine. L’objectif de cette etude etait d’evaluer la prevalence du rehaussement de la paroi anevrismale dans une cohorte de patients presentant un anevrisme non rompu avant decision therapeutique. Methodes Nous avons inclus retrospectivement les patients consecutifs avec anevrisme intracrânien non rompu adresses dans notre service pour imagerie cerebrale complementaire avant decision therapeutique entre novembre 2015 et avril 2017. Les donnees cliniques et d’imagerie incluant des sequences d’IRM 3D-T1 Turbo Spin Echo apres injection de gadolinium ont ete collectees. Resultats Parmi les 68 patients (81 anevrismes) inclus, un rehaussement de la paroi anevrismale etait objective pour 31 (45,6 %) patients et 34 (42,0 %) anevrismes. La taille de l’anevrisme etait fortement associee au rehaussement de la paroi (Odds Ratio 2,60 ; IC 95 % : 1,61–4,19, p = 0,001). Une valeur seuil de 4,1 mm etait predictive d’un rehaussement de la paroi de l’anevrisme avec une sensibilite de 82,4 % et une specificite de 85,1 %. Il n’etait pas retrouve d’association entre les caracteristiques cliniques et le rehaussement anevrismal. Conclusion Notre etude suggere que la taille de l’anevrisme est un determinant majeur du rehaussement de la paroi pour les anevrismes intra-crâniens non rompus.

Objectif L’imagerie des caillots responsables d’AVC ischemiques est un potentiel biomarqueur pour la decision therapeutique, le diagnostic etiologique et le pronostic. L’IRM permet d’estimer la concentration en fer des tissus, a l’aide du QSM (quantitative susceptibility mapping) ou de la relaxivite R2*. Notre but etait de predire la concentration en globules rouges et en fer d’analogues experimentaux de caillots en IRM. Materiel et methode Vingt-deux analogues de caillots de concentrations croissantes en globules rouges (0 %, 20 %, 40 %, 60 %, 80 %, 99 %) ont ete analyses en IRM 7 teslas ex vivo avec une sequence 3D echo de gradient T2 multi-echo (voxel : 0,125 × 0,125 × 0,125 mm, nombre d’echos : 4, TR : 50ms, TE : 7 – 28ms) au cours de 4 sessions. Les cartes parametriques de susceptibilite magnetique et de R2* etaient calculees a l’aide de la toolbox MEDI (Cornell University). Au decours des acquisitions, la quantite de fer au sein de chaque caillot etait mesuree en photometrie d’absorption atomique electrothermique et la quantite de globules rouges par analyse histologique apres coloration MSB. Resultats Les valeurs de R2* etait correlees significativement a la concentration en fer (R2 = 0,2729 p = 0,022). Les valeurs de susceptibilite magnetique en QSM n’etaient pas correlees significativement avec la concentration en fer ou en globules rouges malgre une tendance observable. Cette absence de correlation est expliquee par un defaut de reproductibilite inter-sessions. Conclusion Les valeurs de R2* d’analogues de caillots sont correlees a leur concentration en fer. Une validation de ces resultats sur des caillots retires en thrombectomie mecanique est necessaire.