Charles G Cantrell¹, Parmede Vakil^1,2, Donald R Cantrell³, Yong Jeong¹, Sameer A Ansari³, and Timothy J Carroll^1,3
1Biomedical Engineering, Northwestern, Chicago, IL, United States, ²College of Medicine, University of Illinois, Chicago, IL, United States, ³Radiology, Northwestern, Chicago, IL, United States

We have found that MR-PARSE has detectable sensitivity to frequency shifts induced by transient alterations in de-oxyhemoglobin through the cardiac cycle.  Our initial studies have shown, through the use of ICA, a statistically significant hemispheric difference between healthy and compromised regions.  Our approach to quantifying cerebrovascular reactivity represents a new and simple, non contrast approach to stratifying patients toward therapies to prevent stroke.

Yuanliang Jiang¹, Chengcheng Zhu², Andrew J Degnan³, Wenjia Peng¹, Luguang Chen¹, Xinrui Wang¹, Qi Liu¹, Yang Wang⁴, Zhenzhen Xiang⁴, Zhongzhao Teng⁵, David Saloner², and Jianping Lu^1
1Radiology, Changhai Hospital, Shanghai, China, People's Republic of, ²Radiology, University of California, San Francisco, San Francisco, CA, United States, ³Radilogy, University of Pittsburgh, Pittsburgh, PA, United States, ⁴Pathology, Changhai Hospital, Shanghai, China, People's Republic of, ⁵Radiology, University of Cambridge, Cambridge, United Kingdom

The first ex vivo measurement of T1, T2, and T2* relaxation times of intracranial plaque components at 3T is reported. The ability of multi-contrast MRI to characterize plaque type was evaluated with histological validation. Plaque components could be differentiated based on relaxation times. Specifically, lipid core had significantly lower T2 values than fibrous cap. MRI and histology correlation was consistent across specimens and locations, and MRI showed a high sensitivity and specificity for identifying plaque features previously associated with high-risk. Therefore, MRI has the potential to characterize intracranial plaque composition and improve patient risk stratification.  

Osamu Togao¹, Akio Hiwatashi¹, Makoto Obara², Koji Yamashita¹, Kazufumi Kikuchi¹, and Hiroshi Honda^1
1Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan, ²Philips Electronics Japan, Tokyo, Japan

In this study, we demonstrated the utility of intracranial MR angiography (MRA) using acceleration-selective arterial spin labeling (AccASL) technique in Moyamoya disease. The AccASL-MRA markedly improved the visualization of arteries distal to the steno-occlusive site reflecting collateral flow via LMA in Moyamoya disease in comparison with time-of-flight (TOF)-MRA.

Alan J Stone¹, George WJ Harston², Davide Carone², Mmua Ngwako², Radim Licenik², James Kennedy ², and Nicholas P Blockley^1
1FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, ²Acute Stroke Programme, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom

Streamlined-qBOLD is applied to an exploratory cohort of acute stroke patients in a serial imaging study to map brain oxygen metabolism. Quantitative brain oxygenation parameters are demonstrated to vary between regions with different tissue outcomes and this imaging approach is shown to have the potential to refine the identification of the ischemic penumbra.

Seena Dehkharghani¹, Candace C. Fleischer², Deqiang Qiu¹, Sang-Eon Park², Junjie Wu¹, and Fadi Nahab^3
1Radiology and Imaging Sciences, Emory University, Atlanta, GA, United States, ²Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, United States, ³Neurology, Emory University, Atlanta, GA, United States

Methods for characterizing misery perfusion to predict stroke are largely limited to positron emission tomography, which suffers from high radiation exposure. Magnetic resonance imaging (MRI) and spectroscopy (MRS) offer non-invasive alternatives to explore cerebral hemodynamics and brain temperature regulation, a poorly understood physiologic variable at the intersection of perfusion and metabolism. We detail the first reported use of MRI/MRS to relate cerebrovascular reserve with temperature in patients following acetazolamide challenge, observing significant correlation between temperature changes and cerebrovascular reserve. These findings will be used to inform future MRI studies of perfusion and brain temperature among patients with chronic steno-occlusive disease.

Christian Federau¹, Soren Christensen¹, Michael Mlynash¹, Jenny Tsai¹, Sun Kim¹, Greg Zaharchuk¹, Matus Straka¹, Nishant Mishra¹, Maarten Lansberg¹, and Greg Albers^1
1Stanford University, Stanford, CA, United States

We studied the evolution of the infarct volume between an early post-revascularization scan (within 24 h of symptom onset) and day 5 in patients of the CRISP and DEFUSE 2 cohort studies.  On the early post-revascularization scan, FLAIR lesions were smaller compared to DWI, but were larger at day 5. The early post-revascularization stroke volume on DWI, compared to FLAIR, was closer, and correlated better with the day 5 DWI and FLAIR lesion volumes. Together, our findings suggest that DWI is a better early surrogate marker of stroke volume. 

Jingwei Zhang^1,2, Dong Zhou², Sarah Eskreis-Winkler², Thanh Nguyen², Pascal Spincemaille², Ajay Gupta², and Yi Wang^1,2
1Biomedical Engineering, Cornell University, New York, NY, United States, ²Radiology, Weill Cornell Medical College, New York, NY, United States

We propose a cerebral metabolic rate of oxygen consumption (CMRO2) mapping method without blood flow challenge using quantitative susceptibility mapping, cerebral blood flow and a regularization of minimal local variance (MLV) within the same type of tissue. Getting rid of blood flow challenge would vastly increase the clinical utility of MRI CMRO2. The MNV CMRO2 maps were very similar to CMRO2 maps using caffeine as challenge, with no significant bias in value. 

Jan Sedlacik¹, Andreas M. Frölich¹, Johanna Spallek², Nils D. Forkert³, Tobias D. Faizy¹, Franziska Werner^4,5, Tobias Knopp^4,5, Dieter Krause², Jens Fiehler¹, and Jan-Hendrik Buhk^1
1Neuroradiology, UKE, Hamburg, Germany, ²Product Development and Mechanical Engineering Design, TUHH, Hamburg, Germany, ³University of Calgary, Calgary, AB, Canada, ⁴Biomedical Imaging, UKE, Hamburg, Germany, ⁵Biomedical Imaging, TUHH, Hamburg, Germany

Magnetic particle imaging (MPI) was compared with dynamic magnetic resonance imaging (MRI) and dynamic subtraction angiography (DSA) in a realistic 3D printed aneurysm model. All three methods clearly depicted a distinct pulsatile flow pattern and a delayed contrast agent outflow from the aneurysm. Despite the disadvantages of a much lower temporal resolution of the dynamic MRI and the 2D projection of the DSA, all three methods are valid tools for characterizing the hemodynamics of aneurysms. Especially the radiation free, 3D, high temporal resolution MPI method seems to be a very promising tool for imaging and characterization of hemodynamics.

Elias Kellner¹, Karl Egger², Valerij G Kiselev², Horst Urbach², and Marco Reisert^1
1Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany, ²Department of Neuroradiology, University Medical Center Freiburg, Freiburg, Germany

In a recent study, we proposed a method for fast estimation of microstructural tissue parameters such as intra/extraaxonal volume fraction and diffusivities based on a Bayesian approach and machine learning. In this study, we report the application to cases of acute ischemic stroke. We show that the parameters are able to outline the infarct core qualitatively better than standard DTI. The results are in line with the currently accepted picture of axonal beading.

Yosuke Ishii^1,2, Tadashi Nariai¹, Yoji Tanaka¹, HIroshi Aihara², Yoshio Suyama², Shinichi Wakabayashi², and Taketoshi Maehara^1
1Neurosurgery, Tokyo Medial and Dental University, Tokyo, Japan, ²Neurosurgery, Suiseikai Kajikawa Hospital, Hiroshima, Japan

We used dynamic susceptibility contrast (DSC)-MRI to evaluate the chronological changes in hemodynamics after indirect bypass surgery for moyamoya disease. Twenty five patients who underwent indirect bypass surgery and repeated DSC–MRI measurement within the first 6 postoperative months were included. We analyzed mean transit time (MTT) delay using the cerebellum as control. Mean MTT delay in the anterior circulation area gradually decreased soon after surgery and stabilized after 3 postoperative months. Postoperative MTT delay values were significantly decreased compared with preoperative values from 1 to 2 weeks onwards. These results suggested DSC–MRI detected angiogenesis during the early postoperative stages.