Gongkai Liu¹, Hanzhang Lu¹, Yang Li¹, Binu Thomas², Marco Pinho², Judy Huang¹, Babu G. Welch², Denise C. Park³, and Peiying Liu^1
1Department of Radiology, Johns Hopkins University School of medicine, Baltimore, MD, United States, ²University of Texas Southwestern Medical Center, Dallas, TX, United States, ³The University of Texas at Dallas, Dallas, TX, United States

Cerebral vascular reserve, which indicates the potential of the tissue to receive more blood flow when needed, is desired to evaluate the ischemic risk of brain tissue. However, it is cumbersome to measure vascular reserve using the current methods with Diamox or hypercapnia challenges. Therefore there is a growing interest in using resting-state MRI data to measure cerebrovascular reactivity (CVR). Here, using CO2-inhalation MRI as a gold standard and capitalizing on a large cohort of healthy controls (N=170) and Moyamoya patients (N=50), we sought to identify the optimal strategies for resting-state CVR mapping and establish benchmarks for this new technique.

Mark Bitsch Vestergaard¹, Hashmat Ghanizada², Ulrich Lindberg¹, Nanna Arngrim², Olaf Paulson³, Messoud Ashina², and Henrik Bo Wiberg Larsson^1
1Functional Imaging Unit, Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Glostrup, Denmark, ²Danish Headache Center, Department of Neurology., Copenhagen University Hospital Rigshospitalet, Glostrup, Denmark, ³Neurobiology Research Unit, Department of Neurology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark

In present study we demonstrate that in healthy humans the cerebral lactate concentration increases during inhalation of hypoxic air but not after exposure to carbon monoxide. This suggests a regulatory mechanism of cerebral glycolytic activity possibly mediated by sensing of arterial oxygen pressure and that the lactate production is not solely a result of hindered oxidative metabolism, at least during non-threatening hypoxic exposure. Phase-contrast mapping and susceptibility-based oximetry were used to acquire global cerebral blood flow and oxygen consumption and MR-spectroscopy was used to measure the lactate concentration in the occipital lope in a total of 51 healthy humans.

David Yen-Ting Chen^1,2, Yosuke Ishii^1,3, Moss Yize Zhao¹, Audrey Peiwen Fan¹, and Greg Zaharchuk^1
1Radiology, Stanford University, Palo Alto, CA, United States, ²Medical Imaging, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan, ³Neurosurgery, Tokyo Medical and Dental University, Tokyo, Japan

Cerebrovascular reserve (CVR) is an important hemodynamic parameter for moyamoya disease. Acetazolamide (ACZ) test is often used to measure CVR clinically. However, ACZ is contraindicated in patients with sulfa allergies, severe kidney and liver disease and potentially has severe adverse side effect. Thus, there is a need to assess CVR without pharmacological vasodilation. We utilized a simultaneous [15O]-water PET/MRI dataset to train a convolutional neural network (CNN) to predict CVR. The CNN combined multi-contrast information from baseline perfusion and structural images to predict whole-brain PET-level CVR, with high image quality, quantification accuracy, and diagnostic accuracy for identifying impaired CVR.

Michael S Stringer^1,2, Nithya N Nair³, Una Clancy^1,2, Alasadir Morgan^1,2, Zahra Shirzadi^4,5, Yulu Shi^1,2,6, Francesca Chappell^1,2, Antoine Vallatos^1,2, Maria Valdes Hernandez^1,2, Dany Jaime Garcia^1,2, Gordon W Blair^1,2, Rosalind Brown^1,2, Bradley J MacIntosh^4,5, Ian Marshall^1,2, Fergus Doubal^1,2, Michael J Thrippleton^1,2, and Joanna M Wardlaw^1,2
1Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom, ²UK DRI at the University of Edinburgh, Edinburgh, United Kingdom, ³Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom, ⁴Department of Biomedical Physics, University of Toronto, Toronto, ON, Canada, ⁵Hurvitz Brain Sciences, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada, ⁶Beijing Tiantan Hospital, Capital Medical University, Beijing, China

Accurate cerebral blood flow (CBF) quantification using arterial spin labelling (ASL) depends on physiological and MR parameters. Labelling efficiency is particularly relevant given it may vary between vascular disease patients. We determined subject-specific labelling efficiency values using phase-contrast MRI scans in a mild stroke cohort. Bland-Altman plots suggested a bias in CBF, with nominal labelling efficiency values underestimating at low and overestimating at high CBF. Using subject-specific, but not nominal, labelling efficiency showed plausible associations between white matter CBF and smoking status, pulse pressure, and age. Subject-specific labelling efficiencies appear to mitigate variance and improve CBF quantification in clinical ASL.

Hui Wang¹, Chuili Kong², Quanzhi Feng¹, Yi Liu¹, Yutian Li¹, Jinli Li¹, Josef Pfeuffer³, Xianchang Zhang⁴, and Tong Han^1
1Radiology, Tianjin Huanhu Hospital, Tianjin, China, ²Radiology, Liaocheng People’s Hospital, Liaocheng, China, ³Siemens Healthcare, Erlangen, Germany, ⁴MR Collaboration, Siemens Healthcare Ltd, Beijing, China

This study proposed a new method that can directly visualize and assess the collateral status by post-processing multiphase perfusion-weighted images (PWI) generated by multi-inversion time arterial spin labeling (mTI-ASL), and evaluate its performance by comparison with digital subtraction angiography (DSA) in patients with ischemic stroke. Comparison of the results of 28 patients showed that the collateral status assessed by the 3D mTI-ASL grading system was greatly consistent (kappa coefficient k = 0.854) with DSA. This technique is promising for the noninvasive assessment of the collateral status in stroke patients.

Sophie Schauman¹, Thomas W Okell¹, and Mark Chiew^1
1Wellcome Centre for Integrative Neuroimaging, NDCN, University of Oxford, Oxford, United Kingdom

Arterial spin labeling methods can be used to produce vessel selective angiograms. However, to do this in 3D or 4D is extremely time consuming as many encodings of high spatial (and temporal) resolution images are needed. We propose an optimized acquisition and reconstruction method to create high quality angiogams is five minutes or less. For the acquisition protocol we explore different sampling patterns across encoded images, and for the reconstruction method different ways of constraining the signal temporally.

Ravi Varma Dandu¹, Karthick Raj Rajendran², Rithika Varma Dandu³, Sivakanth Nalubolu⁴, Kiran Barla¹, Narayana Rolla⁵, and Indrajit Saha^6
1Citi Neuro Centre, Hyderabad, India, ²Philips Healthcare, Eindhoven, Netherlands, ³RV College of Engineering, Bengaluru, India, ⁴Narayana Health City, Bangalore, India, ⁵Philips Healthcare, Bangalore, India, ⁶Philips Healthcare, Gurgaon, India

This study compares the performance of Time of Flight MR angiography (ToF-MRA) with spiral k-space filling and ToF-MRA with cartesian filling, for evaluation of the cervicocerebral circulation in 16 healthy volunteers. The imaging protocols were adjusted to give similar coverage and scan times for both techniques. Spiral ToF-MRA showed better visualization of almost all arteries of the cervicocerebral circulation – especially in the small distal intracranial arteries. Artefactual signal drops in segments with slow flow were also fewer with spiral ToF-MRA. Spiral ToF-MRA can potentially evaluate the cervicocerebral arterial system with higher spatial resolution than Cartesian ToF-MRA.

Qing Fu¹, Xiao-yong Zhang², and Ding-xi Liu^1
1Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, ²MR Collaborations, Siemens Healthcare Ltd., Shenzhen, China

Jilei Zhang¹, Weibo Chen¹, Jianqing Sun¹, Queenie Chan¹, Maoxue Wang², and Bing Zhang^2
1Clinical Science, Philips Healthcare, Shanghai, China, ²Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China

The non-contrast enhanced 4D MRA is time-consuming because of the needs to acquire high resolution data at multi-timepoints, which limited its clinical application.In current study, 4D-PACK combined with C-SENSE=6.5 can reduce 23% acquisition time(4 min 42s) for non-contrast enhanced 4D-MRA compared with 4D-PACK with SENSE acceleration, and the excellent acceleration advantage of C-SENSE can improve the clinical application for 4D MRA. the proposed acquisition scheme of 4DMRA with C-SENSE acceleration can be potentially used for evaluating arteriovenous malformation (AVM), arteriovenous fistulas (AVF), moyamoya disease, and stroke patients.

Yue Ma^1,2, Maria Aristova¹, Sameer Ansari^1,3,4, Ann Ragin¹, Michael Markl¹, and Susanne Schnell^5
1Radiology, Northwestern University, Chicago, IL, United States, ²Radiology, Shengjing Hospital of China Medical University, Shenyang, China, ³Neurology, Northwestern University, Chicago, IL, United States, ⁴Neurosurgery, Northwestern University, Chicago, IL, United States, ⁵Radiology, University of Greifswald, Chicago, IL, United States

Symptomatic intracranial atherosclerotic disease (ICAD) patients who present with stenosis and hemodynamic abnormalities are at higher risk of recurrent stroke. We propose a methodology that creates patient-specific ‘heat maps’ of abnormal hemodynamic parameters, based on intracranial dual-venc 4D flow MRI. The heat maps were created by detecting and highlighting outlier measurements from 95% confidence interval of normative parameter estimates in healthy controls. Elevated peak velocity (PV) was found in 75% of patients and 58.3% of them with abnormal PV in the uninvolved hemisphere. This novel approach to characterize intracranial hemodynamic impact may allow making patient-specific risk stratification and treatment strategies.

Leonardo A Rivera-Rivera¹, Grant S Roberts¹, Laura B Eisenmenger², Oliver Wieben^1,2, Sterling C Johnson³, and Kevin M Johnson^1,2
1Department of Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, ²Department of Radiology, University of Wisconsin - Madison, Madison, WI, United States, ³Department of Medicine, University of Wisconsin - Madison, Madison, WI, United States

The coupling of brain biomechanics and hemodynamics is complex as it includes arterial pressure pulsations, venous and CSF flow, and tissue compliance. Experimental evidence has demonstrated alterations of each the multiple compartments in disease; however, the relationships and coupling between brain biomechanics (e.g. strain and stiffness) and vascular flow dynamics is not well characterized. This study investigates the relationships between brain blood flow, stiffness, and strain using a multi-scale brain imaging platform that includes 4D flow, MRE, and DENSE MRI. Results suggest strong correlations between blood flow, strain, and stiffness and age-related changes in these parameters.

Ang Zhou¹, Sean Moen², Bharathi Jagadeesan^2,3,4, and Pierre-Francois Van de Moortele^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Department of Neurosurgery, University of Minnesota, Minneapolis, MN, United States, ³Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ⁴Department of Neurology, University of Minnesota, Minneapolis, MN, United States

Asymptomatic small intracranial aneurysms affect about 1 in 50 people and are often considered at a low risk of rupture. There are no effective hemodynamic parameters accurately predicting the evolution of small aneurysms. Three dimensional vortex motion is observed in aneurysms which reflects the hemodynamic environment and potentially impact the development of small aneurysms. We propose an approach to describe the three dimensional main vortex motion as a whole inside small aneurysms based on 4D Flow MRI at 7 Tesla. This approach defines the high vortex motion region and gives the direction of the main vortex motion and its center.

Osamu Togao¹, Akio Hiwatashi², Makoto Obara³, Michael Helle⁴, Kazufumi Kikuchi¹, Daichi Momosaka¹, Yoshitomo Kikuchi¹, Tatsuhiro Wada⁵, Hiroo Murazaki⁵, and Marc Van Cauteren^3
1Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan, ²Department of Molecular Imaging & Diagnosis, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan, ³Philips Japan, Tokyo, Japan, ⁴Philips Research, Hamburg, Germany, ⁵Division of Radiology, Department of Medical Technology, Kyushu University Hospital, Fukuoka, Japan

In this study, we demonstrated the ability of 4D-S-PACK (4D-MRA based on superselective pCASL with CENTRA-keyhole and view-sharing) to visualize intracranial DAVFs. 4D-S-PACK enables a time-resolved and vessel-selective angiography within 5 minutes without a use of contrast agents. It was shown that good vessel selectivity for the internal and external carotid arteries was achieved with 4D-S-PACK. 4D-S-PACK enabled accurate identification of feeding arteries. Although the superselective labelling in 4D-S-PACK caused a slight reduction in CNR, compared to full labelling in 4D-PACK, this was acceptable since visualization was well preserved. 4D-PACK can be a non-invasive clinical tool for assessing intracranial DAVFs.