Bragi Sveinsson^1,2, Robert Barry^1,2,3, Olivia Rowe^1,2, Jason Stockmann^1,2, Daniel Park¹, Peter Lally⁴, Matthew S Rosen^1,2,5, and Reza Sadjadi^6
1Radiology, A. A. Martinos Center, Massachusetts General Hospital, Boston, MA, United States, ²Radiology, Harvard Medical School, Boston, MA, United States, ³Harvard-MIT Health Sciences and Technology, Cambridge, MA, United States, ⁴Brain Sciences, Imperial College London, London, United Kingdom, ⁵Physics, Harvard University, Cambridge, MA, United States, ⁶Neurology, Massachusetts General Hospital, Boston, MA, United States

The ability to estimate neurological disease progression based on objective quantitative measurements could be of great value for assessing treatment efficacy. Here, we demonstrate the feasibility of acquiring high-resolution anatomic and quantitative images at 7T in the sciatic, tibial, and fibular nerves, allowing quantitative assessment of individual fascicles. We also measure the quantities of fascicle cross-sectional area, T2, ADC, and fat fraction for CMT1A patients and healthy controls and investigate any between-group differences.

Isaiah Ailes¹, KiChang Kang¹, Anish Sathe¹, Jingya Miao¹, Leonard A. Frizon², Laura Krisa¹, Kristen Fleming¹, Peter Natale¹, Kiran Talekar¹, Devon Middleton¹, Feroze Mohamed¹, Ashwini Sharan¹, and Mahdi Alizadeh^1
1Thomas Jefferson University, Philadelphia, PA, United States, ²Faculdades Pequeno Príncipe, Curitiba, Brazil

Spinal cord stimulation (SCS) in patients with failed back surgery syndrome aims to reduce neuropathic pain. However, minimal studies show a safe procedure using 3T diffusion weighted imaging (DWI) MRI for patients with SCS. Additionally, more studies looking at the neurological SCS treatment responses can lead to better optimization of SCS. It was our objective to safely develop a systematic procedure for 3T DWI MRI while also generating a map of the neural network connectivity in structures associated with pain. Long term application of this protocol aims to provide an objective assessment to SCS treatment.

Yael Jacob¹, Gaurav Verma¹, Judy Alper¹, Bradley Delman¹, Alan Seifert¹, Raj Shrivastava¹, and Priti Balchandani^1
1Icahn School of Medicine at Mount Sinai, New York, NY, United States

Trigeminal neuralgia (TN) is a physically and mentally incapacitating disorder characterized by extreme, sporadic, sudden facial pain. TN is associated with the trigeminal sensory pathway, however, the etiology of TN remains unclear. Implementing a graph-theory analysis using diffusion MRI we tested whether whole brain network structural connectivity hierarchies differentiate between TN patients and healthy controls. We found aberrant centrality measures of various brain regions in TN. Specifically, this whole-brain data-driven network analysis was able to depict two major regions of the trigeminal sensory circuit, the brainstem and thalamus, and highlight their dysfunction role in the whole brain network.  

Ki Sueng Choi¹, Martijn Figee², Robert Marc Lebel³, Maggie Fung⁴, Suchandrima Banerjee⁵, Helen S Maybeg⁶, and Jaemin Shin^4
1Radiology / Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ³GE Healthcare, Alberta, AB, Canada, ⁴GE Healthcare, New York, NY, United States, ⁵GE Healthcare, Menlo Park, CA, United States, ⁶Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, United States

The connectomic DBS approach, stimulation tractographically defined white mater pathways, has been successfully employed in functional neurosurgery, and it demonstrated the feasibility of clinical utility. However, this approach is limited in the clinical environment due to low SNR and various artifacts of DWI. The recent development of deep learning-based MR reconstruction allows us to improve SNR and reduce artifacts. This study evaluated the DL reconstruction method in the field of connectomic DBS using deterministic and probabilistic tractography. Tractography results from DL reconstruction show higher sensitivity for delineating WM pathways in specific DBS targets.  

Tyler Robinson¹, Paul Chang¹, and Jean Chen^1
1Rotman Research Institute, Baycrest, Toronto, ON, Canada

We examined differences in median tract length with age across eighteen major white matter tracts in 541 subjects of the Human Connectome Project in Aging. We observed a significant negative age effect on tract length in the forceps minor, left cingulum angular bundle, right superior longitudinal fasciculus parietal, and right uncinate fasciculus. Paradoxically, we also report a significant positive age effect on tract length in the forceps major and right cingulate gyrus. Restricted analyses suggest that these effects are driven by female subjects.

Arjun Patel¹, Jordan A. Chad^1,2, and J. Jean Chen^1,2
1Rotman Research Institute, Baycrest Health Sciences, Toronto, ON, Canada, ²Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

White matter microstructural degeneration is an early marker of declining brain health, and vascular risk factors such as high blood pressure and adipose fat deposition have been found to be significantly associated with white matter microstructural degeneration in healthy adults. In this study, using diffusion tensor imaging, we find that the vascular-risk influences on white matter are more pronounced in women than in men. This study therefore calls attention to the consideration of sex differences in studying brain vulnerability to vascular risk factors. 

Matthew C Murphy¹, Prashanthi Vemuri¹, Matthew L Senjem¹, Clifford R Jack, Jr.¹, Richard L Ehman¹, and John Huston, III^1
1Mayo Clinic, Rochester, MN, United States

Vascular health is a predictor of cognitive outcomes, but the relationship between the two remains incompletely understood. Here we tested the hypothesis that brain stiffness is significantly associated with vascular health as assessed by white matter hyperintensity (WMH) load and the presence of systemic risk factors. Through voxel-wise mapping, WMH was associated with decreased stiffness in periventricular regions, while systemic risk factors were associated with widespread, lower-amplitude stiffness decreases. Examining the partial correlations between stiffness, WMH and vascular risk factors, stiffness was significantly associated with both measures, while WMH and vascular risk were not significantly correlated after controlling for stiffness.

Robert Shih^1,2, Ante Zhu³, J Kevin DeMarco^1,2, H Douglas Morris^1,2, Maureen Hood^1,2, Nastaren Abad³, Radhika Madhavan³, Luca Marinelli³, Thomas Foo³, and Vincent Ho^1,2
1Uniformed Services University, Bethesda, MD, United States, ²Walter Reed National Military Medical Center, Bethesda, MD, United States, ³GE Research, Niskayuna, NY, United States

The MAGNUS ultra-high-performance gradient coil delivers simultaneous 200 mT/m and 500 T/m/s performance on each axis, with higher PNS thresholds than whole-body gradient coils, which is particularly useful for diffusion microstructure imaging. Our initial clinical experience with the MAGNUS research scanner has successfully identified white matter abnormalities (? intra-axonal edema) using multi-shell DTI (b_max = 4000 s/mm²) and OGSE (f_max = 100 Hz) in an acute symptomatic mTBI subject. It has also successfully identified differences in intracellular volume fraction using multi-shell multi-frequency OGSE (b_max = 2000 s/mm², f_max = 100 Hz) between a low-grade diffuse astrocytoma and a high-grade glioblastoma.

Jae Eun Song¹, Shreyas Vasanawala², and Dong-Hyun Kim^3
1Radiology, Stanford University, Stanford, CA, United States, ²Department of Radiology, Stanford University, Stanford, CA, United States, ³Department of Electrical and Electronic Engineering, Yonsei University, Seoul, Korea, Republic of

Multi-echo gradient-echo (mGRE)-based myelin water fraction (MWF) mapping is a promising myelin water imaging (MWI) modality but is vulnerable to noise and artifact corruption. The linear dimensionality reduction (LDR) method has recently shown improvements with regard to these challenges. However, the magnitude value based low rank operators have been shown to misestimate the MWF for regions with T2* anisotropy. This paper presents a nonlinear dimensionality reduction (NLDR) method to estimate the MWF map better by encouraging nonlinear low dimensionality of mGRE signal sources.

Sohae Chung¹, Els Fieremans¹, Dmitry S. Novikov¹, Prin X. Amorapanth², Joseph F. Rath², Steven R. Flanagan², and Yvonne W. Lui^1
1Department of Radiology, NYU Grossman School of Medicine, New York, NY, United States, ²Department of Rehabilitation Medicine, NYU Grossman School of Medicine, New York, NY, United States

Primary and secondary injury are both believed to play important roles in the pathogenesis of disease after mild traumatic brain injury (MTBI). Here we investigate the relationships between white matter microstructure and deep gray matter iron deposition after MTBI, which may shed light on primary WM injuries and potential secondary changes in brain iron. Our results show different patterns of correlation between deep gray matter iron content as measured by QSM and WM microstructure as measured by diffusion MRI in MTBI compared with normal controls.