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Rebecca Recker¹, Arash Adami¹, Beatriz Tone¹, Rich Hartman¹, Jerome Badaut², Hui Tian¹, Stephen Ashwal¹, Andre Obenaus¹

¹Loma Linda University School of Medicine, Loma Linda, California , USA; ²Centre Hospitalier Universitaire Vadois, Lausanne, Switzerland

Neonatal hypoxic-ischemic encephalopathy clinically presents with global diffuse injury.  However, the most popular rat pup models of neonatal HIE induce a focal unilateral injury.  The bilateral carotid artery occlusion (BCAO) model has been shown to induce bilateral injury in 10d old rat pups, an age that developmentally correlates with the term neonate. T2 and DWI assessment of gradation of injury was obtained that allows for candidate selection for future therapeutic treatment. Injury stratification was performed using a novel rat pup scoring system (RPSS) system which correlated with lesion volume.

Quan Jiang¹, ², Lakshman Gollapalli², Mark E. Haack², ³, Guang Liang Ding¹, Zheng Gang Zhang¹, Li Zhang¹, Lian Li¹, Ying Wang¹, James R. Ewing¹, Jia Ni Hu², Hassan Bagher-Ebadian¹, Michael Chopp¹

¹Henry Ford Health System, Detroit, Michigan, USA; ²Wayne State University, Detroit, Michigan, USA; ³MRI Institute for Biomedical Research, Detroit, Michigan, USA

We investigated the evolution of angiogenesis using high-resolution susceptibility-weighted imaging incorporating phase information (SWI) after sildenafil treatment of embolic stroke. We demonstrate that SWI can detect and identify cerebral angiogenesis after ischemic stroke. By combining information from blood-to-brain transfer constant of Gd-DTPA (Ki) measurement, SWI can stage the progress of angiogenesis. SWI provides a direct measurement of angiogenesis, unlike indirect measurements of cerebral blood flow (CBF) and cerebral blood volume (CBV).

Victor E. Yushmanov¹, Alexander Kharlamov¹, Boris Yanovski¹, George LaVerde², Fernando E. Boada², Stephen C. Jones¹, ²

¹Allegheny-Singer Research Institute, Pittsburgh, Pennsylvania, USA; ²University of Pittsburgh, Pittsburgh, Pennsylvania, USA

ADC and ²³Na twisted projection MRI were compared and confirmed by histology and flame photometry in the rat brain after MCAO.  Within an ADC-homogeneous infarct region, sites with an elevated rate of ²³Na increase (slope, 22±4%/h, p<0.005 compared to 14%/h±1%/h in other ischemic regions) were observed.  In the ischemic regions, there was no slope/ADC correlation between and within brains (P>0.4).  Maximum slope was located near the stroke periphery in 7 animals.  Differences in collateral circulation in the cortex and caudate putamen were not slope determinants (P>0.3).  ²³Na MRI is more sensitive than ADC for assessing regional ischemic damage.

Tracy Deanne Farr¹, Jörg Seehafer², Mathias Hoehn²

¹Max-Plack Institute for Neurological Research , Cologne, Germany; ²Max-Plack Institute for Neurological Research, Cologne, Germany

There is concern that contrast in the ischemic brain, following systemic administration of iron oxide to label blood born macrophages, accumulates non-specifically. The results of this study support that. We administered contrast during a time of high peripheral macrophage activity following transient middle cerebral artery occlusion; an optimal model due to the delay in blood brain barrier breakdown, and the lack of erythrocyte accumulation and cerebral spinal fluid disruption. No changes in signal intensity that could be attributed to macrophage accumulation were observed in T2* or T1-weighted images and there were few iron positive macrophages in the histological sections.

Sheng-Ping Wu¹, Logi Vidarsson¹, Jeff Winter¹, David Mikulis², Andrea Kassner¹

¹The Hospital for Sick Children and the University of Toronto, Toronto, Canada; ²The Toronto Western Hospital, Toronto, Canada

Permeability MRI has the potential to objectively guide rt-PA treatment of stroke and thereby reducing the risk of hemorrhagic transformation (HT). However, one limitation is the long scan time (~5 min), which is problematic for stroke patients. In contrast, perfusion MRI is part of the routine stroke protocol and allows extraction of a parameters called relative recirculation (rR). The purpose of this study was to determine the relative efficacy of rR, compared with permeability (KPS), for prediction of HT. Our results demonstrated that KPS (p<0.01) and rR (p<0.01) were significantly increased in patients with HT, compared with patients without HT. Furthermore, a significant correlation was observed between KPS and rR (r=0.85, p<0.001). Both parameters effectively predict HT, although, rR is more clinically feasible

Andreas Harloff¹, Patrick Dudler¹, Alex Frydrychowicz¹, Christoph Strecker¹, Anna Lena Stroh¹, Annette Geibel¹, Andreas Hetzel¹, Cornelius Weiller¹, Jürgen Hennig¹, Michael Markl¹

¹Albert-Ludwigs Universität , Freiburg, Germany

The purpose of this study was to evaluate a new 3D MRI protocol for the reliable detection of aortic high-risk plaques compared to transesophageal echocardiography (TEE) and to test the reliability of additional MRI in stroke of undetermined etiology

Soren Christensen¹, ², Fernando Calamante³, Ona Wu⁴, Thomalla Götz⁵, Jens Fiehler⁵, Jachim Rother⁵, Thomas Kucinski⁵, Leif Ostergaard², Patricia Desmond¹, Stephen Davis¹

¹University of Melbourne, Parkville, Australia; ²University of Aarhus, Aarhus, Denmark; ³Brain Research Institute, Melbourne, Australia; ⁴Massachusetts General Hospital, Boston, USA; ⁵University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Two local AIF methods were compared to conventional processing (manual AIF selection from the contra lateral hemisphere) by ROC analysis in a retrospective study of 104 acute (<6h) stroke patients. The final infarct lesion was delineated on the follow up MRI and used as infarct/no infarct classifier on the acute PWI maps. Both local AIF techniques performed marginally inferior to conventional processing. We speculate that: 1) AIFs selected on distal branches signals of the arterial tree might not represent the true AIF. 2) Delay and dispersion provide predictive information that should not be discarded from local AIF estimates.

Fang Liu¹, George Tomlinson², David Mikulis³, Frank Silver³, Andrea Kassner¹

¹The Hospital for Sick Children and the University of Toronto, Toronto, Canada; ²The University of Toronto, Toronto, Canada; ³The Toronto Western Hospital, Toronto, Canada

Hemorrhagic transformation (HT) is a potentially fatal complication of thrombolytic therapy in acute ischemic stroke (AIS). Early prediction of HT could substantially improve the safety of this therapy, thereby improving patient outcome. Early Gadolinium (Gd) enhancement on post-contrast T1-weighted MRI has been used to predict HT in subacute stroke. However, assessment at earlier time points (< 4 hours from symptom onset) did not reliably predict HT. An alternative to visual inspection is texture analysis, which discriminates textural information related to higher-order statistics and spectral properties not obvious to even an expert eye (trained radiologist). This method can quantify dependencies between neighboring pixels as well as patterns of variation within a region-of-interest. In this study we performed texture analysis,based on a co-occurrence matrix of post-contrast T1w images, to assess the prediction of HT in AIS patients and to compare it with visual inspection of Gd enhancement. Our results show that texture analysis of post T1-weighted images is superior to visual inspection for the prediction of HT in early AIS. To our knowledge, this is the first application of texture analysis in AIS. Further studies are needed to validate our results.

Daniel M. Mandell¹, ², Jay S. Han, ²³, Julien Poublanc¹, Adrian P. Crawley¹, Jeff A. Stainsby, ¹, Joseph A. Fisher, ²³, David J. Mikulis¹, ²

¹Toronto Western Hospital, Toronto, Canada; ²University of Toronto, Toronto, Canada; ³Toronto General Hospital, Toronto, Canada

An emerging technique for mapping cerebrovascular reserve uses inhaled CO2 as a vasodilatory stimulus, and BOLD MR as an index of CBF changes. While BOLD MR signal reflects CBF, it also depends on cerebral blood volume, cerebral metabolic rate, arterial oxygenation, and hematocrit. We performed both BOLD and arterial spin labelling MR mapping of reserve in 25 patients with arterial steno-occlusive disease. ASL MR acted as a reference standard for measurement of CBF changes. BOLD and ASL MR measurements were highly correlated, suggesting BOLD MR is a reasonable surrogate for CBF imaging to map cerebrovascular reserve in this patient population.

Akash P. Kansagra¹, Eric C. Wong¹

¹University of California, San Diego, La Jolla, California , USA

Vessel encoded ASL allows quantitative and efficient imaging of cerebral vascular territories. Here, we discuss the application of vessel encoded ASL to reveal vertebral artery territories in five healthy subjects. In particular, we depict examples of vertebral artery territories and comment on unusual territorial morphology, with particular attention to asymmetry and mixing within the vertebrobasilar system.