Tianxiao Zhang¹, Rong Guo^2,3, Tianyao Wang⁴, Zengping Lin¹, Yudu Li^2,3, Yibo Zhao^2,3, Jun Liu⁴, Danhong Wu⁵, Zheng Jin⁶, Xin Yu⁷, Zhi-Pei Liang^2,3, and Yao Li^1
1School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ²Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁴Radiology Department, The Fifth People's Hospital of Shanghai, Fudan University, Shanghai, China, ⁵Neurology Department, The Fifth People's Hospital of Shanghai, Fudan University, Shanghai, China, ⁶Shanghai Minhang Hospital of Integrated Traditional Chinese and Western Medicine Hospital, Shanghai, China, ⁷Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

Elevated oxygen extraction fraction and impaired neurometabolic metabolism are hallmarks of at-risk tissue in acute ischemic stroke. This study investigated the concurrent changes of oxygen and neuronal metabolisms. In an 8-min scan using SPICE, we simultaneously obtained 3D maps of neurometabolites (2.0 x 3.0 x 3.0 mm³ nominal spatial resolution) and T₂'/oxygen extraction fraction (1.0 x 1.0 x 1.9 mm³ nominal resolution). Our results showed the expected changes in oxygenation and neurometabolite markers individually, and also their coupling. This study may lay a foundation for prediction of tissue viability in acute stroke using noninvasive multimodal high-resolution metabolic imaging.

Sina Straub¹, Janis Stiegeler^1,2, Edris El-Sanosy³, and Till M. Schneider^4
1Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, ³Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ⁴4Department of Neuroradiology, University of Heidelberg, Heidelberg, Germany

Generating whole-brain vein segmentations can be very time-consuming. In this abstract, a method is proposed that can segment brain veins from a single-echo or multi-echo gradient echo scan. The segmentation algorithm combines classical vessel enhancement filtering and local thresholding methods with a shearlet-based multi-scale approach. Compared with a ground truth, the algorithm performs better for multi-echo data when R₂^* information is included in the segmentation. Moreover, the combination of venous segmentation with masks for deep and superficial venous territories yields higher susceptibility values for the superficial venous vasculature which is in accordance with a higher oxygen consumption of the cortex.

Siddhant Dogra¹, Xiuyuan Wang², Jelle Veraart³, Alejandro Gupta³, Koto Ishida³, Deqiang Qiu⁴, and Seena Dehkharghani^3
1Radiology, New York University Langone Health, New York, NY, United States, ²Weill Cornell, New York, NY, United States, ³New York University Langone Health, New York, NY, United States, ⁴Emory University, Atlanta, GA, United States

Cerebrovascular reactivity (CVR) is conventionally assessed by comparing discrete cerebral blood flow measurements obtained prior to and following a hemodynamic stimulus. Blood-oxygen-level-dependent (BOLD)-MRI provides potentially continuous, dynamic CVR characterization when coupled to stimuli such as acetazolamide (ACZ), but poor signal-to-noise generally limits its analysis to an analogous comparison of arbitrarily defined terminal BOLD signals relative to baseline. We present a novel framework incorporating temporal and spatial denoising to pre-condition the dynamic time-signal course for robust voxel-level maximal and terminal CVR, and novel CVR time-to-peak and related kinetic features, disambiguating confounders related to potentially non-optimal terminal CVR assignment in conventional use. 

Pei-pei chang¹, Yan-wei Miao¹, Yu-han Jiang¹, Yi-wei Che¹, Bing-bing Gao¹, Li-hua Chen¹, Qing-wei Song¹, Ren-wang Pu¹, Ai-lian Liu¹, Liang-jie Lin², and Jia-zheng Wang^2
1The First Affiliated Hospital of Dalian Medical University, Da Lian, China, ²Philips Healthcare, Bei Jing, China

Previous studies have suggested that fluid-attenuated inversion recovery vascular hyperintensity (FVH) and asymmetrical prominent cortical veins (APCVs) may be related with collateral flow in cerebral ischemia. Some studies showed susceptibility-weighted imaging (SWI) can reflect oxygenation fraction (OEF) in venous blood. Here, we prospectively compared the differences of FVH and APCVs scores in different types of vascular stenosis, and analyzed the relationships of the FVH score with the APCVs score, the venous-oxygen-saturation related MR measurements as well as the NIHSS score in patients with cerebral infarction. It was found that FVH and APCVs scores in severe-occlusion group were significantly higher than those in mild-to-moderate group. In addition, FVH score was positively correlated with APCVs score, rΔφ (phase value) and NIHSSadmission. It suggests that the occurrence of FVH is related to cerebral oxygen metabolism.

Yasheng Chen¹, Chunwei Ying², Peter Kang¹, Slim Fellah¹, Amy Mirro³, Melanie Fields³, Kristin Guilliams¹, Jin-Moo Lee¹, Andria Ford¹, and Hongyu An^4
1Neurology, Washington University School of Medicine, St. Louis, MO, United States, ²Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States, ³Pediatrics Hematology, Washington University School of Medicine, St. Louis, MO, United States, ⁴Washington University School of Medicine, St. Louis, MO, United States

Measurement of oxygen extraction fraction (OEF) provides important information about tissue oxygen utilization. OEF maps can be obtained using a double echo asymmetric spin echo (ASE) sequence. Partial volume effect may lead to inaccurate OEF measurements in regions with mixed tissue types. We introduced a local linear regression algorithm to correct for partial volume effect. The PVC OEF method reduced model fitting errors and signal contamination of CSF, and it improved the association between OEF and WMH lesion burden.

Takayuki YAMAMOTO¹, Hikaru FUKUTOMI¹, Vincent DOUSSET^1,2, Igor SIBON³, and Thomas TOURDIAS^1,2
1Institut de Bio-imagerie IBIO, Université de Bordeaux, Bordeaux, France, ²Neuroimagerie diagnostique et thérapeutique, CHU de Bordeaux, Bordeaux, France, ³Unité de soins intensifs neurovasculaires, CHU de Bordeaux, Bordeaux, France

We investigated remote effects of brain infarction. We previously demonstrated higher iron content (higher R2* values) in deep nuclei as a consequence of their disconnection. Here, we aimed at predicting such long term remote degeneration from the acute stage. Through a disconnectivity approach, we mapped the fibers that were likely to be disconnected by projecting the acute stroke masks on tractograms from 180 healthy volunteers. We showed that disconnected areas based on this approach were likely to show significantly higher iron content at follow-up. This validates the prediction of deep nuclei disconnection from acute stage through a disconnectivity approach. 

Suk-tak Chan¹, Karleyton C. Evans², Tian-yue Song¹, Andre van der Kouwe¹, Bruce R. Rosen¹, Yong-ping Zheng³, and Kenneth K. Kwong^1
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Biogen, Inc., Cambridge, MA, United States, ³Department of Biomedical Engineering, Hong Kong Polytechnic University, Kowloon, Hong Kong

Regional cerebraovascular reactivity (CVR) to endogenous carbon dioxide (CO₂) during spontaneous breathing (i.e. end-tidal partial pressure of CO2 (P_ETCO₂) measured at rest), was substantially different from that obtained under externally applied CO₂ challenge. Individual maps of CVR to endogenous CO₂ showed significant inter-subject variability while CVR maps under hypercapnic challenge did not.  Such inter-subject variability was not reduced by correction of respiratory effects.   In addition, the CVR to end-tidal partial pressure of oxygen (P_ETO₂) during spontaneous breathing shows less inter-subject variability.  Our findings question the compatibility of using CVR during spontaneous breathing as a surrogate of CVR under hypercapnic challenge.

Jyun-Ru Chen¹, Chun-Jen Lin^2,3, I-Hui Lee^2,3,4, and Chia-Feng Lu^1
1National Yang-Ming University, Taipei, Taiwan, ²School of Medicine, National Yang-Ming University, Taipei, Taiwan, ³Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan, ⁴Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan

Previous studies reported that the patients with asymptomatic internal carotid stenosis (aICS) had a higher risk of stroke and neurocognitive impairment. However, whether the side of aICS could cause different neurocognitive outcomes was less explored. In this study, significant difference of functional connectivity (FC) was found between the left and right aICS groups. The association between FC and neuropsychological measures (dizziness, immediate and delayed recall verbal memory) revealed by the correlation analysis also presented different profiles between two aICS groups.

Kristina M. Zvolanek^1,2, Rachael C. Stickland², Stefano Moia^3,4, Apoorva Ayyagari^1,2, César Caballero-Gaudes³, and Molly G. Bright^1,2
1Biomedical Engineering, Northwestern University, Evanston, IL, United States, ²Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, United States, ³Basque Center on Cognition, Brain and Language, Donostia, [Gipuzkoa], Spain, ⁴University of the Basque Country EHU/UPV, Donostia, [Gipuzkoa], Spain

The addition of a breath-hold or deep breathing task to the beginning of a resting state fMRI scan is a feasible method for cerebrovascular reactivity (CVR) mapping. However, these two tasks rely on different physiological mechanisms with different temporal properties. We used a bespoke analysis method to account for voxelwise hemodynamic lag and assessed its impact on agreement between CVR measurements from each breathing task. Good agreement was observed both across the brain and across subjects, regardless of hemodynamic lag correction, indicating both tasks are comparable options for BOLD CVR measurements in healthy subjects.

Elizabeth Dao¹, Roger Tam¹, Ging-Yuek R Hsiung¹, Lisanne ten Brinke¹, Rachel Crockett¹, Cindy K Barha¹, Youngjin Yoo¹, Walid al Keridy², Stephanie H Doherty¹, Alex L MacKay¹, Cornelia Laule¹, and Teresa Liu-Ambrose^1
1University of British Columbia, Vancouver, BC, Canada, ²King Saud University, Riyadh, Saudi Arabia

Pathology studies report myelin damage as a salient feature in cerebral small vessel disease (cSVD). Currently, the role of myelin content in-vivo on cognition is poorly understood. Thus, the main purpose of this study was to investigate the association between myelin content and cognitive function in cSVD. Normal appearing white matter (NAWM) myelin water fraction (MWF) was quantified in 55 people with cSVD with spin-echo myelin water imaging. After accounting for age, education, and white matter hyperintensity volume, lower NAWM MWF was significantly associated with slower processing speed and poorer working memory, but not with set shifting or inhibitory control.

Suk-tak Chan¹, Nathaniel Mercaldo², Kenneth K. Kwong¹, Steven M. Hersch³, and Herminia D. Rosas^3
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ²Department of Radiology, Massachusetts General Hospital, Boston, MA, United States, ³Department of Neurology, Massachusetts General Hospital, Boston, MA, United States

Multiple subcortical white matter areas showing impaired cerebrovascular reactivity (CVR) in our pre-symptomatic and early Huntington Disease (HD) subjects overlap with the white matter areas and tracts that have been reported to demonstrate altered microstructural integrity. They are also adjacent to cortical brain regions that atrophy as disease progresses in HD.  Our findings support that abnormal cerebrovascular function contributes to the neuropathology of HD.

Zhangyan yang^1,2, Feng Wang^1,3, Chaohui Tang¹, Li Min Chen^1,3, and Gore C. John^1,2,3
1Institute of Imaging Science, Vanderbilt University, Nashiville, TN, United States, ²Biomedical Engineering, Vanderbilt University, Nashiville, TN, United States, ³Department of Radiology and Radiological Science, Vanderbilt University, Nashiville, TN, United States

Cerebral blood volume (CBV) is a fundamental hemodynamic characteristic of brain related to blood flow and metabolism. High resolution (sub-millimeter) maps of relative values of CBV (rCBV) provide important information for studies of brain function and changes that occur in brain structure and organization. In this study, by using an intravascular superparamagnetic contrast agent in non-human primates, we quantified high-resolution rCBV maps across subjects, identified alterations of rCBV across regions, and created an rCBV atlas using a brain template.

Chunwei Ying¹, Michael M. Binkley², Peter Kang², Yasheng Chen², Jin-Moo Lee^2,3, Andria L. Ford², and Hongyu An^3
1Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States, ²Department of Neurology, Washington University School of Medicine, St. Louis, MO, United States, ³Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, United States

We evaluated the test-retest repeatability of MR-measurement of CBF, OEF and CMRO₂ in whole brain, gray matter, white matter, and watershed regions in healthy subjects. The inter-session wCV was 2.20% in white matter and 2.76% in watershed region for OEF measured with ASE, 15.02% in white matter and 28.73% in watershed region for CBF measured with 2D multi-slice pCASL, and 9.11% in white matter and 17.14% in watershed region for CBF measured with background suppressed 3D pCASL. CMRO₂ had similar test-retest repeatability to CBF.

Jonathan Taylor¹, Oun Al-iedani^2,3, Saadallah Ramadan^3,4, Neil Spratt¹, and Sarah Valkenborghs^5
1School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle, Australia, ²School of Health Sciences, University of Newcastle, Newcastle, Australia, ³Hunter Medical Research Institute, Newcastle, Australia, ⁴Faculty of Health and Medicine, University of Newcastle, Newcastle, Australia, ⁵University of Newcastle, Newcastle, Australia

Using Magnetic Resonance (MR) data acquired as part of a feasibility study in stroke rehabilitation, a novel post-processing pipeline was designed and implemented to explore metabolic factors with MR Spectroscopy (MRS). The stroke study looked at the effect of aerobic exercise performed immediately prior to the usual task-specific rehabilitation training. Examining the clinical motor function results in relation to the metabolic data revealed by the MRS pipeline showed some interesting correlations among metabolites and rehabilitation outcomes.

Emilie Sleight^1,2, Michael S Stringer^1,2, Ian Marshall^1,2, Joanna M Wardlaw^1,2, Sotirios A Tsaftaris³, and Michael J Thrippleton^1,2
1Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom, ²UK Dementia Research Institute, Edinburgh, United Kingdom, ³Institute for Digital Communications, University of Edinburgh, Edinburgh, United Kingdom

The BOLD response to a hypercapnic challenge, i.e. cerebrovascular reactivity (CVR), may vary between individuals and tissue types. Linear regression (GLM) between the BOLD signal and the end-tidal CO₂ is the most common CVR processing method but does not allow for different haemodynamic responses across the brain. We propose to use shift-invariant dictionary learning (SIDL) as a promising method to enable data-driven extraction of BOLD response(s). We show that CVR and delay estimates from SIDL are comparable to estimates from GLM. Future work will focus on reducing the effect of drift on SIDL estimates.

Bejoy Thomas¹, Jithin S S¹, Sabarish S Sekar¹, Santhosh Kannath¹, and Ramshekhar N Menon^2
1Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, India, ²Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, India

Cognitive decline is a common non-hemorrhagic complication of intracranial dural arteriovenous fistula (DAVF).  Increase in cerebral circulation time (CCT)  can be related to significant resting-state functional changes in the brain. 30 DAVF patients and a similar cohort of age-matched  controls underwent resting-state functional MRI (rsfMRI) and the results were correlated with CCT and neuropsychological profile. Patients with high CCT showed  decreased connectivity at DMN seed regions and less compensatory pre-frontal connectivity (pFDR < 0.05), which showed a trend in reversal after a month of embolisation therapy.  These findings may be of significance in formulating treatment strategies in DAVF.

Rama Jayasundar¹, Dushyant Kumar¹, Rajesh Mishra¹, Priyanka Jain², Jaideep Sachdeva³, Chahat Kumar¹, Priyanka Bhagat⁴, and Padma Srivastava^4
1Department of NMR, All India Institute of Medical Sciences, New Delhi, India, ²Centre for Development of Advanced Computing, New Delhi, India, ³Manipal University, Jaipur, India, ⁴Department of Neurology, All India Institute of Medical Sciences, New Delhi, India

This fMRI study has evaluated for the first time, the functional changes effected by yoga in post-stroke (ischemic) recovery. Left hemisphere stroke patients (n=13) with motor deficits practiced Hatha yoga for one hour daily for six months under the supervision of certified yoga trainers. Pre-intervention, and 3 and 6 months post-yoga intervention assessments were carried out using fMRI at 3T and also clinically evaluated using NIHSS score. Results show positive response to yoga, reflected both in the significantly reduced NIHSS scores and the increased BOLD activity in the left pre-central gyrus region in the stroke patients.  

Lijuan Zhang¹, Siqi Cai^1,2, Chunxiang Jiang^1,2, Shihui Zhou^1,2, and Li Yi^3
1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China, ²University of Chinese Academy of Sciences, Beijing, China, ³Peking University Shenzhen Hospital, Shenzhen, China

The clinical profile of motor deficit after ischemic stroke may vary greatly, which are not fully attributable to the lesion topography. Investigation of the clinical phenotype polymorphism is promising to provide new insights to infer the relevance of functional remodeling to the refinement of the disease characterization and management of ischemic stroke. 

Jian Shen¹ and John Wood^1,2
1University of Southern California, Los Angeles, CA, United States, ²Children's Hospital Los Angeles, Los Angeles, CA, United States

Asymmetric spin echo (ASE) sequence is a technique for mapping oxygen extraction fraction (OEF) and venous cerebral blood volume (vCBV). However, there might be an overestimation of vCBV due to the diffusion effect related to vessel size. In this study, we use Monte Carlo simulation to study this effect and investigate the feasibility of estimating vessel size index from ASE data.