Takuya Urushihata¹, Hiroyuki Takuwa¹, Manami Takahashi¹, Yasuhiko Tachibana², Jeff Kershaw², Nobuhiro Nitta², Sayaka Shibata², Masato Yasui³, Makoto Higuchi¹, and Takayuki Obata^2
1Department of Functional Brain Imaging Research, National Institute of Radiological Sciences, QST, Chiba, Japan, ²Applied MRI Research, National Institute of Radiological Sciences, QST, Chiba, Japan, ³Keio Advanced Research Center for Water Biology and Medicine, Keio University, Tokyo, Japan

We measured multi-b-value multi-diffusion-time (MbMTd) DWI and compared ADCs in the ischemic focii of aquaporin4-knockout (AQP4-KO) and wild type (WT) mice. In the ischemic region, AQP4-KO mice showed lower ADCs compared to WT mice, whereas higher ADCs were observed in the contralateral region. In addition, we compared estimates of cell membrane water exchange time obtained by fitting a two-compartment exchange model to the DWI signal. The exchange-time was approximately 2.5 times longer for the AQP4-KO mice than for the WT mice. These results suggest that MbMTd DWI may be useful for in vivo research and clinical diagnosis of AQP4-related diseases.

Mira Liu¹, Yong Jeong¹, Gregory Christoforidis¹, Niloufar Saadat², Steven Roth³, Marek Niekrasz¹, and Timothy Carroll^1
1The University of Chicago, Chicago, IL, United States, ²Northwestern University, Chicago, IL, United States, ³University of Illinois at Chicago, Chicago, IL, United States

This is a retrospective validation study of intravoxel incoherent motion (IVIM) over a range of physiologic conditions: normocapnia, hypercapnia, and post middle cerebral artery occlusion. We performed controlled two-day experiments in a canine model (n=17) of ischemic stroke with baseline (normocapnia) and hypercapnia on the first day followed by occlusion on the second. We compared IVIM perfusion and diffusion images with neutron capture microsphere perfusion, DSC perfusion, and Apparent Diffusion Coefficient (ADC) from standard DWI. We found excellent agreement between IVIM for both perfusion and diffusion indicating IVIM may serve as a means of stratifying acute stroke patients for treatment. 

Andrew Crofts¹, Jessica J Steventon², Joseph R Whittaker³, Marcello Venzi¹, Hannah L Chandler⁴, Mahfoudha Al Shezawi⁵, Eric J Stohr⁶, Chris Pugh⁶, Barry McDonnell⁶, and Kevin Murphy^1
1Cardiff University Brain Research Imaging Centre (CUBRIC), School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom, ²CUBRIC, School of Medicine, Cardiff University, Cardiff, United Kingdom, ³Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, ⁴CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom, ⁵Cardiff Metropolitan University, Cardiff, United Arab Emirates, ⁶Cardiff Metropolitan University, Cardiff, United Kingdom

Cardiovascular risk factors have been linked with deteriorations in cerebrovascular function in the brain, causing cell loss, particularly in the white matter. The mechanisms by which cardiovascular risk factors influence the microvasculature is unclear. Increased blood pressure and associated arterial stiffness/morphological changes in larger cerebral vessels are thought to play a key role. Here, we demonstrate that central pulse pressure along with associated changes in carotid radius and tortuosity better predict the white matter lesion burden in the brain compared with other measures of blood pressure and systemic arterial stiffness.

Kyle Douglass Murray¹, Alan Finkelstein¹, Miriam Weber¹, Jianhui Zhong¹, and Giovanni Schifitto^1
1University of Rochester, Rochester, NY, United States

HIV-infected individuals are at increased risk of developing cerebrovascular diseases, such as cerebral small vessel disease (CSVD). Further, cognitive deficits as a result of chronic infection are common. In this abstract, we use a graph theoretical analysis of resting-state functional connectivity to show that functional and cognitive changes are driven by both HIV-infection and CSVD. We observed correlations between global and local graph theory metrics and cognitive scores derived from neuropsychological testing in the presence of HIV. We also describe potential compensatory changes in global brain function to combat functional deficits from HIV and CSVD.

Taghi Rostami¹, Moss Y Zhao², Audry P Fan³, David Yen-Ting Chen⁴, Magdalina J Sokolska⁵, Jia Guo⁶, Yosuke Ishii⁷, David D Shin⁸, Mohamad Mehdi Khalighi², Dawn Holley², Kim Halbert², Andrea Otte², Brittney Williams², Jun-Hyung Park², Bin Shen², and Greg Zaharchuk^2
1Bioengineering, Stanford University, Stanford, CA, United States, ²Radiology, Stanford University, Stanford, CA, United States, ³Medical Imaging, UC Davis, Davis, CA, United States, ⁴Taipei Medical University, Taipei, Taiwan, ⁵University College London Hospitals, London, United Kingdom, ⁶University of California Riverside, Riverside, CA, United States, ⁷Tokyo Medical. and Dental University, Tokyo, Japan, ⁸GE Healthcare, Menlo Park, CA, United States

In this study, we examined repeatability of labeling efficiency of single- and multi-PLD arterial spin labeling (ASL) MRI before and after vasodilation in 15 normal subjects. Individual measurements of hematocrit and flow velocity in the carotid and vertebral arteries, obtained by phase-contrast (PC) MRI, were used to assess the labeling efficiency for both ASL methods. Our results showed that both labeling techniques achieved high repeatability before and after vasodilation (within-subject Coefficient of Variance pre-ACZ: 0.82 and 1.23%, and post-ACZ: 0.51 % and 1.00%).

Anuja Sharma¹, Clint Frandsen¹, Ganesh Adluru¹, and Edward DiBella^1
1UCAIR, Dept. of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States

We investigate the potential advantages of using distribution-valued variables to capture image information instead of the conventional techniques which use mean values to represent entire regions-of-interest. Using distribution-based distances in comparison with a mean-based approach, we explore various models to predict motor performance recovery in stroke patients. Our experiments indicate that for predictor variables Orientation Dispersion index and the Restricted Diffusion Index (diffusion scalars derived from the NODDI model), the distribution representations can lead to significantly improved regression models, over the respective mean values. Additionally, using the baseline Fugl-Meyer scores to predict follow-up Fugl-Meyer scores further enhances the model statistics.

Shoko Hara^1,2, Masaaki Hori^2,3, Yoji Tanaka¹, Taketoshi Maehara¹, Shigeki Aoki², and Tadashi Nariai^1
1Neurosurgery, Tokyo Medical and Dental University, Tokyo, Japan, ²Radiology, Juntendo University, Tokyo, Japan, ³Radiology, Toho University Omori Medical Center, Tokyo, Japan

To investigate specific microstructural change after the revascularization surgery, we evaluated 13 patients with moyamoya disease and 13 age-sex matched normal controls using multishell diffusion MRI. By NODDI and free-water imaging analysis, preoperative hemispheres showed significant increase of extracellular fluid compared to controls, and subsequent significant decrease after the surgery. Only free-water eliminated parameter (orientation dispersion index) showed significant difference between patients with and without cognitive improvement after the surgery. Increased parenchymal free water observed in moyamoya disease may decrease after the surgery, and free-water elimination might be useful to detect true neuronal change related to postoperative cognitive improvement.

Kunjian Chen¹, Weiqiang Dou², Xinyi Wang¹, Weiyin Vivian Liu², Xinyu Wang¹, Huimin Mao¹, and Yu Guo^1
1The First Affiliated Hospital of Shandong First Medical University, Jinan, China, ²MR Research China, GE Healthcare, Beijing, China

The main purpose was to explore the feasibility of amide proton transfer weighted (APTw) imaging in diagnosing patients with symptomatic intracranial artery stenosis (SIAS). 27 patients with severe intracranial artery stenosis (≥ 70%) or occlusion diagnosed by DSA but without infarction were recruited for MRI measurement. Compared to the contralateral area, higher APT relevant MTR_asym ratio and lower cerebral-blood-flow (CBF) measured by 3D arterial-spin-labeling imaging were found in the abnormal blood supply area by the corresponding ipsilateral vessels. With these findings, APTw imaging may thus be used as an effective method providing added clinical value in diagnosing of SIAS.

Mingzhu Fu¹, Chao Xia², Miaoqi Zhang¹, Yutao Ren², Shuo Chen¹, Rui Tian², Yi Liu², and Rui Li^1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China, ²Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, China

In this study, we utilized 4D Flow MRI to assessed and compared the change of cerebral blood flow in patients with MMD before and after STA-MCA bypass surgery. Statistics indicated that BFV_total significantly increased after bypass surgery while no differences were found in BFV_iICA, BFV_cICA and BFV_BA. This is probably because the STA-MCA bypass could directly compensate for blood flow supply and play a role in flow augmentation for the whole brain. The results of this study suggested that STA-MCA bypass could improve the cerebral blood supply without affecting the hemodynamics of other arteries, such as BA and ICA.

Pei-pei Chang ¹, 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

This study prospectively compared the differences of fluid-attenuated inversion recovery vascular hyperintensity (FVH) score and MR measurements between patients with mild-to-moderate and severe vascular stenosis, and analyzed the relationship between the FVH score and MRI measurements. It was found that the FVH score in severe-occlusion group were higher than those in mild-to-moderate stenosis group. In addition, FVH scores were positively correlated with the ratio of relative CBF2.5 value, and negatively correlated with the ADC value, indicating FVH score was correlated with collateral circulation and brain edema. No significant correlation was observed between the FVH score and amide-proton-transfer weighted measurement, suggesting that FVH had little effect on acid-base metabolism.

Young Ro Kim¹ and Jerrold L Boxerman^2
1Radiology, MGH, Charlestown, MA, United States, ²Neuroradiology, Brown University, Providence, RI, United States

Previously, water exchange index (WEI) was proposed to quantify the rate of water movement across the blood-brain barrier (BBB). Although efficient and clinically applicable, the technique could not reliably provide voxelwise WEI maps due to the inadequate signal to noise ratio (SNR). In remedy of this shortcoming, we here present the relative WEI (rWEI) method, which enables voxelwise mapping of BBB water exchange while significantly reducing the acquisition time (< 10 min). To confirm the validity of the technique, the rWEI maps were acquired in post thrombectomy patients with unilateral infarct and compared with the WEI values. 

Greg O Cron¹, Rafael Glikstein², Jean Francois Thibodeau³, Anthony Carter³, Chet E Holterman³, Alexey Gutsol³, Lihua Zhu³, Baptiste Lacoste³, and Chris Kennedy^3
1Ottawa Hospital Research Institute, Ottawa, ON, Canada, ²The Ottawa Hospital, Ottawa, ON, Canada, ³University of Ottawa, Ottawa, ON, Canada

For hypertensive patients taking low-dose aspirin, there may be risk of kidney injury. NSAIDs block vasoactive prostaglandin production, potentially blunting the reopening of hypertension-constricted renal vessels, thereby decreasing renal blood flow. We hypothesized that hypertension would predispose rats to low-dose aspirin induced kidney and cerebrovascular injury.  Hypertensive rats who received low-dose daily aspirin appeared to have decreased cerebral blood flow, however the data must be interpreted with caution, as statistical power was lacking. Of interest, rats given both AngII and ASA developed significant kidney and cerebrovascular injury, suggesting a possible deleterious effect of this drug combination on the vasculature.

David C. Hike^1,2, Taylor A. Ariko^1,2, Frederick A. Bagdasarian^1,2, Shannon Helsper^1,2, and Samuel Colles Grant^1,2
1National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, United States, ²Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, United States

This research utilizes DTI and graph theory to provide a method for monitoring the progression of structural stroke recovery at 21.1 T. Edema that occurs for multiple days post the initial ischemic limits the ability for tractography to be used for any meaningful connectivity analysis before day 5. After this initial phase, graph theory provides metrics for determining the progression of recovery in major white matter regions of the ischemic brain. This method could be utilized as a means for determining the efficacies of different treatments compare with standard stroke recovery.

Jacqueline Chen¹, Mark Lowe¹, Ken Sakaie¹, Kenneth Baker², Andre Machado³, and Stephen Jones^1
1Cleveland Clinic Imaging Institute, Cleveland, OH, United States, ²Cleveland Clinic Lerner Research Institute, Cleveland, OH, United States, ³Cleveland Clinic Neurological Institute, Cleveland, OH, United States

Accurate white-matter tractography maps can be a useful clinical tool for assessing neurological disorders, however, incorrect assumptions within tractography algorithms can yield non-physiological results. We have developed a tractography methodology based on probability theory that uses both local and global information to improve accuracy, and standard partial differential equation solvers for fast whole-brain mapping. In this abstract we demonstrate: 1) the accuracy of the method by comparing a topographical map of the corpus callosum (CC) generated from a symmetrized human data phantom to published maps; 2) how differences in CC topography may be associated with stroke location and functional disability.

Alexandra Ereni King¹, Paul D Teal², Yu-Chieh Tzeng³, Annabel Jain Sorby-Adams⁴, Isabella Megan Bilecki⁴, Renée Jade Turner⁴, and Sergei Obruchkov^5
1School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, ²School of Engineering and Computer Science, Victoria University of Wellington, Wellington, New Zealand, ³Centre for Translational Physiology, University of Otago, Wellington, New Zealand, ⁴Discipline of Anatomy and Pathology, University of Adelaide, Adelaide, Australia, ⁵Robinson Research Institute, Victoria University of Wellington, Wellington, New Zealand

Following a surgical model of transient and ischaemic stroke, 20 sheep (24-36 months; 65-75kg; 10M, 10F) underwent 2h middle cerebral artery occlusion (MCAO). Dynamic Contrast Enhanced (DCE) MRI datasets were obtained capturing the healthy animal, and progression of the infarct at 24h, 3d, 6d and 28 d post-stroke. Based on established pharmacokinetic models, analysis of these DCE-MRI images allows for calculation of perfusion parameters. The surgical procedure used is standardised and reproducible, meaning that this dataset provides an opportunity for quantitative in vivo analysis of stroke evolution in a clinically-relevant, gyrencephalic large animal model.

Xiaodong Zhang¹, Chunxia Li¹, Xiaohuan Gu², Doty Kempf¹, Ling Wei², and Shan Ping Yu^2
1Yerkes Imaging Center, Emory University, Atlanta, GA, United States, ²Department of Anesthesiology, Emory University, Atlanta, GA, United States

Previous studies have demonstrated that pharmacological hypothermia could protect the brain from ischemia or traumatic brain injury in rodent models. However, it remains unknown how the brain is affected by the hypothermia in patients as the physiology and brain metabolism of human are very different from rodents. Large animal models have been recommended to improve clinical translation in the study of ischemia . In the present study,  the effects of drug-induced hypothermia on the brain of adult macaque monkeys were examined using diffusion MRI. The results suggested  large animals play an important role in neuroprotection research of stroke.

Maoxue Wang¹, Yongbo Yang¹, Fei Zhou¹, Ming Li¹, Jilei Zhang², and Bing Zhang^1,3
1The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China, ²Philips Healthcare, Shanghai, China, ³Institute of Brain Science, Nanjing University Nanjing, Nanjing, China

Predictive value of perfusion reduction on ASL for the occurrence of cerebrovascular events in patients with bilateral moyamoya angiography

Aude Pavilla^1,2, Giulio Gambarota¹, Alessandro Arrigo², Mehdi Mejdoubi², and Hervé Saint-Jalmes^1,3
1Inserm, UMR 1099, Université de Rennes 1, LTSI, Rennes, France, ²Department of Neuroradiology, Pierre-Zobda-Quitman Hospital, University Hospital of Martinique, French West Indies, France, Fort-de-France, France, ³CRLCC, Centre Eugène Marquis, Rennes, France

This study aims to investigate the feasibility of simultaneously measuring perfusion and diffusion in the acute phase of ischemic stroke with the combined IntraVoxel Incoherent Motion and non-gaussian Diffusional Kurtosis Imaging (DKI-IVIM). For the fifteen patients enrolled, a significant decrease for the diffusion coefficient D and a significant increase in the kurtosis coefficient was observed in the infarcted lesions. Regarding the perfusion, the perfusion fraction f significantly decreased. Enhanced tissues heterogeneity was observable on reconstructed K maps. DKI-IVIM can provide with a clinically acceptable acquisition time both  diffusion and perfusion  characterization that might be of great interest for stroke diagnosis.

Shuai Yang¹, Jiuqing Guo¹, Lirong Ouyang¹, and Weiyin Vivian Liu^2
1Department of Radiology, Xiangya Hospital, Central South University, Changsha, China, ²MR Research, GE Healthcare, Beijing, China

Altered cognition and emotion-related brain regions in patients with asymptomatic carotid vulnerable plaques : preliminary whole-brain voxel-wise analysis of intravoxel incoherent motion imaging 

Luis Hernandez-Garcia¹, Anish Lahiri², Scott Peltier², Jon Fredrik Nielsen², and Benjamin Hampstead^2
1FMRI Laboratory, University of Michigan, Ann Arbor, MI, United States, ²University of Michigan, Ann Arbor, MI, United States

Partial Volume  effects (PVE) in ASL have been shown to lead to significant quantification errors.  PVE in ASL fingerprinting data have not been previously investigated but are also likely to introduce significant errors in quantification, given their typically coarse resolution.  A simple algorithm is presented to calculate tissue fraction maps from ASL MRF timeseries data without collection of additional anatomical images.  These fraction maps can be used to implement partial volume corrections as well as identify tissue abnormalities.