A5039467196- Advanced Neuroimaging Techniques and Applications
- Advanced MRI Techniques and Applications
- MRI in cancer diagnosis
- Bone and Joint Diseases
- NMR spectroscopy and applications
- Functional Brain Connectivity Studies
- Traumatic Brain Injury and Neurovascular Disturbances
- Atomic and Subatomic Physics Research
- Glioma Diagnosis and Treatment
- Sports Dynamics and Biomechanics
- Experimental and Theoretical Physics Studies
- Advanced X-ray Imaging Techniques
- Fluid Dynamics and Vibration Analysis
- Metabolomics and Mass Spectrometry Studies
- Pituitary Gland Disorders and Treatments
- Photoacoustic and Ultrasonic Imaging
- Neurological disorders and treatments
- Physics of Superconductivity and Magnetism
- Cerebrospinal fluid and hydrocephalus
- Climate Change and Health Impacts
- Image and Signal Denoising Methods
- Tribology and Lubrication Engineering
- Blood properties and coagulation
- COVID-19 epidemiological studies
- Caveolin-1 and cellular processes
Athinoula A. Martinos Center for Biomedical Imaging
2021-2025
Massachusetts General Hospital
2021-2025
Harvard University
2021-2025
Advanced Imaging Research (United States)
2020-2021
New York University
2016-2021
National Yang Ming Chiao Tung University
2020
National Center for Theoretical Sciences
2012
National Taiwan University
2012
The dependence of the diffusion MRI signal on time t is a hallmark tissue microstructure at scale length. Here we measure time-dependence mean diffusivity D(t) and kurtosis K(t) in cortical gray matter 25 gray sub-regions, 10 healthy subjects. Significant observed for t=21.2-100 ms, characterized by power-law tail ∼t−ϑ with dynamical exponent ϑ. To interpret our measurements, systematize relevant scenarios mechanisms brain. Using effective medium theory formalism, derive an exact relation...
Abstract MRI provides a unique non-invasive window into the brain, yet is limited to millimeter resolution, orders of magnitude coarser than cell dimensions. Here, we show that diffusion sensitive micrometer-scale variations in axon caliber or pathological beading, by identifying signature power-law time-dependence along-fiber coefficient. We observe this human brain white matter and identify its origins Monte Carlo simulations realistic substrates from 3-dimensional electron microscopy...
Abstract To determine whether policies to limit transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) hinder spread other infectious diseases, we analyzed the National Health Insurance database in Taiwan. Rates infections were significantly lower after SARS-CoV-2 prevention measures announced. This finding can be applied cost-effectiveness prevention.
To study axonal microstructure with diffusion MRI, axons are typically modeled as straight impermeable cylinders, whereby the transverse MRI signal can be made sensitive to cylinder's inner diameter. However, shape of a real axon varies along direction, which couples longitudinal and overall direction. Here we develop theory intra-axonal based on coarse-graining by 3d diffusion. We demonstrate how estimate diameter is confounded variations (beading), local in direction (undulations) axon....
Abstract Purpose To overcome the major challenges in dMRI acquisition, including low SNR, distortion/blurring, and motion vulnerability. Methods A novel Romer-EPTI technique is developed to provide distortion-free with significant SNR gain, high motion-robustness, sharp spatial resolution, simultaneous multi-TE imaging. It introduces a ROtating-view Motion-robust supEr-Resolution (Romer) combined distortion/blurring-free EPTI encoding. Romer enhances by multi-thick-slice acquisition...
Abstract Biophysical modeling of diffusion MRI (dMRI) offers the exciting potential bridging gap between macroscopic resolution and microscopic cellular features, effectively turning scanner into a noninvasive in vivo microscope. In brain white matter, Standard Model (SM) interprets dMRI signal terms axon dispersion, intra- extra-axonal water fractions, diffusivities. However, for SM to be fully applicable correctly interpreted, it needs carefully evaluated using histology. Here, we perform...
Abstract Purpose Introduce a unified acquisition and modeling strategy to simultaneously quantify magnetization transfer (MT), tissue susceptibility () . Theory Methods Magnetization is induced through the application of off‐resonance irradiation between excitation an RF‐spoiled gradient‐echo scheme, where free pool spin–lattice relaxation (), macromolecular proton fraction exchange rate were calculated by magnitude MR signal using binary spin‐bath MT model with inhomogeneity correction via...
Purpose To investigate and remove Gibbs‐ringing artifacts caused by partial Fourier (PF) acquisition zero filling interpolation in MRI data. Theory Methods Gibbs ringing of fully sampled data, leading to oscillations around tissue boundaries, is the symmetric truncation k ‐space. Such can be removed conventional methods, with local subvoxel shifts method being state‐of‐the‐art. However, asymmetric ‐space routinely used PF acquisitions leads additional ringings wider intervals sampling...
Various diffusion MRI (dMRI) preprocessing pipelines are currently available to yield more accurate parameters. Here, we evaluated accuracy and robustness of the optimized Diffusion parameter EStImation with Gibbs NoisE Removal (DESIGNER) pipeline in a large clinical dMRI dataset using ground truth phantoms. DESIGNER has been modified improve denoising target ringing for partial Fourier acquisitions. We compared revisited (Dv2) (including denoising, removal, correction motion, EPI...
The increasing availability of high‐performance gradient systems in human MRI scanners has generated great interest diffusion microstructural imaging applications such as axonal diameter mapping. Practically, sensitivity to axon is attained at strong weightings , where the deviation from expected scaling white matter yields a finite transverse diffusivity, which then translated into an estimate. While axons are usually modeled perfectly straight, impermeable cylinders, local variations...
Abstract Diffusion magnetic resonance imaging is an important tool for mapping tissue microstructure and structural connectivity non‐invasively in the vivo human brain. Numerous diffusion signal models are proposed to quantify microstructural properties. Nonetheless, accurate estimation of model parameters computationally expensive impeded by image noise. Supervised deep learning‐based approaches exhibit efficiency superior performance but require additional training data may be not...
Noninvasive mapping of cellular pathology can provide critical diagnostic and prognostic information. Recent advances in diffusion magnetic resonance imaging enabled vivo examination tissue microstructures well beyond the resolution. Here, we proposed to use time–dependent kurtosis ( t DKI) simultaneously assess morphology transmembrane permeability hypoxic-ischemic (HI) brain injury. Through numerical simulations organoid imaging, demonstrated feasibility capturing effective size changes...
Abstract The human brain undergoes age‐related microstructural alterations across the lifespan. Soma and Neurite Density Imaging (SANDI), a novel biophysical model of diffusion MRI, provides estimates cell body (soma) radius density, neurite density in gray matter. goal this cross‐sectional study was to assess sensitivity high‐gradient MRI toward cortical microstructure adult lifespan using SANDI. Seventy‐two cognitively unimpaired healthy subjects (ages 19–85 years; 40 females) were scanned...
To overcome the major challenges in diffusion MRI (dMRI) acquisition, including limited SNR, distortion/blurring, and susceptibility to motion artifacts. A novel Romer-EPTI technique is developed achieve SNR-efficient acquisition while providing distortion-free imaging, minimal spatial blurring, high robustness, simultaneous multi-TE imaging. It introduces a ROtating-view Motion-robust supEr-Resolution (Romer) combined with distortion/blurring-free Echo Planar Time-resolved Imaging (EPTI)...
Purpose The ultimate intrinsic signal‐to‐noise ratio (UISNR) is normally calculated using electrodynamic simulations with a complete basis of modes. Here, we provide an exact solution for the UISNR at center dielectric sphere and assess how accurately this approximates away from center. Methods We performed mode analysis to determine which modes contribute central – . then derived analytic expression calculate analyzed its dependence on main magnetic field strength, sample geometry,...