Liangdong Zhou¹, Thanh Nguyen², and Yi Li^2
1Radiology, Weill Cornell Medicine, New York, NY, United States, ²Weill Cornell Medicine, New York, NY, United States

We compared two free water methods, T2 relaxometry-based CSFF and DTI-based DTI-FW, by associating them with age, cognitive score RAVLT, amyloid beta deposition from PiB SUVr, tau deposition from MK6240, aqueduct CSF flow from PC-MRI and ventricle CSF clearance from MK-PET. Results show that CSFF outperforms DTI-FW in most relation pairs. CSFF works great for quantifying clearance related measures but DTI-FW failed.

Yicun Wang¹, Peter van Gelderen¹, Jacco A. de Zwart¹, Pinar S. Özbay¹, Hendrik Mandelkow¹, Dante Picchioni¹, and Jeff H. Duyn^1
1AMRI, LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States

We report a fast quantitative CSF flow imaging method based on the spatial-temporal perturbation patterns formed at the transition bands in balanced steady-state-free-precession (SSFP) images when combined with a background magnetic field gradient. By modeling CSF flow as a combination of a pulsatile (AC) and a constant (DC) flow component across the cardiac cycle, a dictionary was generated based on Bloch simulations and used to translate the observed patterns to flow velocities. Monte-Carlo simulations were performed to evaluate the accuracy of the approach. CSF flow resulting from different physiological mechanisms was quantified in selected regions in 12 healthy subjects.

Sunil Koundal¹, Zachary Gursky¹, Xinan Chen², Hedok Lee¹, Laura Santambrogio³, Jonathan Kipnis⁴, Allen Tannenbaum², and Helene Benveniste^1
1Anesthesiology, Yale University, New Haven, CT, United States, ²Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, United States, ³Department of Radiation Oncology, Weill Cornell Medicine, New York, NY, United States, ⁴Department of Pathology and Immunology, Washington University, St. Louis, MO, United States

The altered CNS fluid flow dynamics and homeostasis mechanisms in response to blockade of lymphatic drainage to deep cervical lymph nodes (dcLN)  is poorly understood. We used multi-modality MRI and computational fluid dynamics  approach to study the same in rats with electrocauterized afferent lymphatic vessels of  dcLN. The brain morphometry of Cauterized-dcLN rats showed localized volume expansion in Pons, Hippocampus and Corpus-callosum, while glymphatic speed maps showed hyperdynamic CSF flow in ambient and quadrigeminal cisterns. These results clearly show that the blockade of CSF drainage to dcLN alters CNS fluid homeostasis/flow dynamics, long-term may result in waste accumulation and neurodegeneration.

Yicun Wang¹, Peter van Gelderen¹, Jacco A. de Zwart¹, Pinar S. Özbay¹, Hendrik Mandelkow¹, Dante Picchioni¹, and Jeff H. Duyn^1
1AMRI, LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States

In addition to the well-established origin in cardiac and respiratory cycles, CSF pulsations may also result from the much slower variations in vascular tone associated with cerebral blood flow (CBF) autoregulation. Using a novel quantitative MRI approach, we measured CSF flow velocities and displaced volumes resulting from these three mechanisms in 12 healthy human controls. We found the autoregulatory effects to be a major factor, with associated CSF velocities comparable to and displaced volumes an order of magnitude larger than the cardio-respiratory effects. This may be an important mechanism underlying the CSF oscillations recently observed in resting-state fMRI.

Brandon Ojogho¹, Farzan Abdolahi², Xingfeng Shao¹, Samantha Ma³, Chenyang Zhao¹, Kay Jann¹, Xuejuan Jiang², and Danny JJ Wang^1
1Laboratory of FMRI Technology (LOFT) Mark & Mary Stevens Neuroimaging and Informatics Institute Keck School of Medicine University of Southern California (USC), Los Angeles, CA, United States, ²Department of Ophthalmology and Department of Preventive Medicine Keck School of Medicine University of Southern California (USC), Los Angeles, CA, United States, ³Siemens Healthcare, Los Angeles, CA, United States

This study evaluated CBF and BBB water exchange rate (kw) measured by diffusion prepared pseudo-continuous arterial spin labeling (DP-pCASL) in a cohort of aged African American individuals. The results showed decreasing CBF and kw with age, and higher CBF in females. Both CBF and kw were correlated with picture sequence memory test score. CBF was negatively correlated with white matter hyperintensities (WMH), free water (FW) and peak skeletonized mean diffusivity (PSMD), although age accounted for these correlations. These findings suggest the potential for CBF and kw as biomarkers of cerebral small vessel disease. 

Muneeb A Faiq¹, Anoop Sainulabdeen¹, Vishnu Adi¹, Thajunnisa A Sajitha¹, Sophia Khoja¹, Carlos Parra¹, Choong H Lee², Jiangyang Zhang², and Kevin C Chan^1,2
1Department of Ophthalmology, New York University Grossman School of Medicine, NYU Langone Health, New York, NY, United States, ²Department of Radiology, New York University Grossman School of Medicine, NYU Langone Health, New York, NY, United States

Recent evidence suggests the existence of a functional glymphatic system in the optic nerve. Insulin resistance in the central nervous system (CNS-IR) has been implicated in neurodegenerative conditions. Its mechanism remains unclear though one candidate involves dysregulation of the cerebrospinal fluid (CSF). Here, we investigated if CNS-IR affects CSF flow in the visual pathway by measuring the spatiotemporal profiles of CSF dynamics using gadolinium-enhanced MRI following intrathecal administration of the specific insulin receptor blocker, S961. Our results suggested that central insulin function may play an imperative role in CSF dynamics for the homeostasis of the visual system.

Md Nasir Uddin¹, Abrar Faiyaz², Alan Finkelstein³, and Giovanni Schifitto^1,2
1Department of Neurology, University of Rochester, Rochester, NY, United States, ²Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY, United States, ³Department of Biomedical Engineering, University of Rochester, Rochester, NY, United States

HIV-infected individuals are at increased risk of developing cerebral small vessel disease (CSVD).  Myelin damage is a feature in CSVD, and can be quantified using myelin water imaging. In this work, we investigated if MWI can be used to quantify myelin related changes in white matter in an HIV cohort at risk of CSVD. Our results lend support to the use of MHI to track myelin related abnormalities in the white matter.

Emanuele Camerucci¹, Benjamin Elder¹, Jeffrey Gunter¹, John Huston¹, Clifford Jack¹, and Petrice Cogswell^1
1Mayo Clinic, Rochester, MN, United States

We compared the artifact induced by the Certas Plus at 3.0T vs 1.5T in 9 patients with idiopathic normal pressure hydrocephalus (iNPH) on six sequences (3D MPRAGE, Sagittal T1, axial DWI, axial GRE, axial T2 FLAIR, axial T2 FSE) at three levels (atria of the lateral ventricles, cerebral aqueduct, and cerebellum hemispheres). The 1.5T scans had a significantly greater area of artifact on DWI (all levels) and GRE (cerebellar level) sequences, and a smaller area of artifact on T2 FLAIR (cerebellar level). Post-shunt imaging at 3T with the Certas plus valve is feasible and with lesser artifact than on 1.5T.

Azadeh Nazemorroaya¹, Ali Aghaeifar², Hildegard Schulz³, Klaus Scheffler ^3,4, Thomas Shiozawa-Bayer⁵, Bernhard Hirt⁵, and Gisela Hagberg^3,4
1High Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²Wellcome Centre for Human Neuroimaging, London, United Kingdom, ³High Field Magnetic Resonance,, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ⁴Biomedical Magnetic Resonance, University Hospital Tuebingen, Tuebingen, Germany, ⁵Clinical Anatomy, University Hospital Tübingen, Tuebingen, Germany

Post-mortem brain MRI can yield valuable information. However, tissue preservation requires substitution of the CSF-fluid by fixation agents, which is time-consuming for large samples. R₂*  maps, dominated by R₂-effects, were measured at several timepoints during fixation of pig-brain tissue samples using formalin-based fixatives.

Benjamin Sylvanus¹, Susie Yi Huang^2,3, and Hong Hsi Lee^2,3
1Northeastern University, Boston, MA, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Department of Radiology, Harvard Medical School, Boston, MA, United States

The 1.4 petabyte electron microscopy volume with fully segmented cells in the human cerebral cortex is publicly available, serving as a valuable resource of building numerical phantoms of MRI. However, even few neurite interruptions in cell segmentations can lead to substantial biases in numerical simulations of diffusion inside cells. Here we propose a user interface to automatically correct most of the neurite interruptions and manually edit the corrections. Combing the proposed user interface with Trees toolbox and SpinDoctor for quantitative cell analysis and diffusion simulations, we provide a convenient platform to validate biophysical modeling of MRI evaluating tissue microstructure.