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42
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Introduction
Current institution
Education
September 2016 - June 2021
Publications
Publications (42)
Cerebrospinal fluid (CSF) flow is a key component of the brain’s waste clearance system. However, our understanding of CSF flow in the human brain, particularly within the brain-wide subarachnoid space (SAS), is limited due to a lack of non-invasive tools for measuring slow flow. Here, we propose a CSF flowmetry technique using phase-contrast MRI c...
Purpose
To overcome the major challenges in diffusion MRI (dMRI) acquisition, including limited SNR, distortion/blurring, and susceptibility to motion artifacts.
Theory and Methods
A novel Romer‐EPTI technique is developed to achieve SNR‐efficient acquisition while providing distortion‐free imaging, minimal spatial blurring, high motion robustness...
Purpose
To develop a single‐shot SNR‐efficient distortion‐free multi‐echo imaging technique for dynamic imaging applications.
Methods
Echo planar time‐resolved imaging (EPTI) was first introduced as a multi‐shot technique for distortion‐free multi‐echo imaging. This work aims to develop single‐shot EPTI (ss‐EPTI) to achieve improved robustness to...
Purpose
Echo planar time‐resolved imaging (EPTI) is a new imaging approach that addresses the limitations of EPI by providing high‐resolution, distortion‐ and T2/T2*$$ {\mathrm{T}}_2^{\ast } $$ blurring–free imaging for functional MRI (fMRI). However, as in all multishot sequences, intershot phase variations induced by physiological processes can i...
Purpose: To overcome the major challenges in diffusion MRI acquisition, including low SNR, distortion/blurring, and motion vulnerability.
Methods: A novel Romer-EPTI technique is developed to provide high SNR, sharp spatial resolution, high motion-robustness, images free from distortion and slab-boundary artifacts, and simultaneous multi-TE imaging...
Purpose: To develop EPTI, a multi-shot distortion-free multi-echo imaging technique, into a single-shot acquisition to achieve improved robustness to motion and physiological noise, increased temporal resolution, and high SNR efficiency for dynamic imaging applications.
Methods: A new spatiotemporal encoding was developed to achieve single-shot EPT...
Purpose
Volumetric, high‐resolution, quantitative mapping of brain‐tissue relaxation properties is hindered by long acquisition times and SNR challenges. This study combines time‐efficient wave–controlled aliasing in parallel imaging (wave‐CAIPI) readouts with the 3D quantification using an interleaved Look‐Locker acquisition sequence with a T2 pre...
Purpose
To improve time‐resolved reconstructions by training auto‐encoders to learn compact representations of Bloch‐simulated signal evolution and inserting the decoder into the forward model.
Methods
Building on model‐based nonlinear and linear subspace techniques, we train auto‐encoders on dictionaries of simulated signal evolution to learn com...
Deep brain stimulation (DBS) to the fornix is an investigational treatment for patients with mild Alzheimer’s Disease. Outcomes from randomized clinical trials have shown that cognitive function improved in some patients but deteriorated in others. This could be explained by variance in electrode placement leading to differential engagement of neur...
Purpose: Volumetric, high resolution, quantitative mapping of brain tissues relaxation properties is hindered by long acquisition times and SNR challenges. This study, for the first time, combines the time efficient wave-CAIPI readouts into the 3D-QALAS acquisition scheme, enabling full brain quantitative T1, T2 and PD maps at 1.15 isotropic voxels...
Deep brain stimulation (DBS) to the fornix is an investigational treatment option for patients with mild Alzheimer's disease. Outcomes from randomised clinical trials have shown that cognitive function improved in some patients but deteriorated in others. One reason could be variance in electrode placement leading to differential engagement of neur...
Purpose: Training auto-encoders on simulated signal evolution and inserting the decoder into the forward model improves reconstructions through more compact, Bloch-equation-based representations of signal in comparison to linear subspaces. Methods: Building on model-based nonlinear and linear subspace techniques that enable reconstruction of signal...
Purpose
To develop a motion estimation and correction method for motion‐robust three‐dimensional (3D) quantitative imaging with 3D‐echo‐planar time‐resolved imaging.
Theory and Methods
The 3D‐echo‐planar time‐resolved imaging technique was designed with additional four‐dimensional navigator acquisition (x‐y‐z‐echoes) to achieve fast and motion‐rob...
Purpose
To develop an efficient acquisition technique for distortion‐free diffusion MRI and diffusion‐relaxometry.
Methods
A new accelerated echo‐train shifted echo‐planar time‐resolved imaging (ACE‐EPTI) technique is developed to achieve high‐SNR, distortion‐free diffusion, and diffusion‐relaxometry imaging. ACE‐EPTI uses a newly designed variabl...
Multi-parametric quantitative MRI has shown great potential to improve the sensitivity and specificity of clinical diagnosis and to enhance our understanding of complex brain processes, but suffers from long scan time especially at high spatial resolution. To address this long-standing challenge, we introduce a novel approach, termed 3D Echo Planar...
Strong gradient systems can improve the signal-to-noise ratio of diffusion MRI measurements and enable a wider range of acquisition parameters that are beneficial for microstructural imaging. We present a comprehensive diffusion MRI dataset of 26 healthy participants acquired on the MGH-USC 3 T Connectome scanner equipped with 300 mT/m maximum grad...
Spin-echo (SE) BOLD fMRI has high microvascular specificity, and thus provides a more reliable means to localize neural activity compared to conventional gradient-echo BOLD fMRI. However, the most common SE BOLD acquisition method, SE-EPI, is known to suffer from T2′ contrast contamination with undesirable draining vein bias. To address this, in th...
Purpose
To develop an efficient acquisition technique for distortion-free diffusion MRI and diffusion-relaxometry.
Methods
A new ACcelerated Echo-train shifted Echo-Planar Time-resolved Imaging (ACE-EPTI) technique is developed to achieve high-SNR, distortion- and blurring-free diffusion and diffusion-relaxometry imaging. ACE-EPTI employs a newly...
The first phase of the Human Connectome Project pioneered advances in MRI technology for mapping the macroscopic structural connections of the living human brain through the engineering of a whole-body human MRI scanner equipped with maximum gradient strength of 300 mT/m, the highest ever achieved for human imaging. While this instrument has made i...
Magnetic resonance imaging (MRI) is a widely used non-invasive imaging technology for both clinical diagnosis and neuroscientific research. However, the imaging sensitivity and specificity of brain MRI are limited by the well-known technical challenge of MRI acquisition—low image encoding efficiency, leading to limited acquisition speed, spatial re...
Spin-echo (SE) BOLD fMRI has high microvascular specificity, but its most common acquisition method, SE-EPI, suffers from T2' contrast contamination with undesirable draining vein bias. To address this, in this study, we extended a recently developed multi-shot EPI technique, Echo-Planar Time-resolved Imaging (EPTI), to laminar SE-fMRI at 7T to obt...
Multi-parametric quantitative MRI has shown great potential to improve the sensitivity and specificity of clinical diagnosis and to enhance our understanding of complex brain processes, but suffers from long scan time especially at high spatial resolution. To address this long-standing challenge, we introduce a novel approach, termed 3D Echo Planar...
We present a whole-brain in vivo diffusion MRI (dMRI) dataset acquired at 760 μm isotropic resolution and sampled at 1260 q-space points across 9 two-hour sessions on a single healthy participant. The creation of this benchmark dataset is possible through the synergistic use of advanced acquisition hardware and software including the high-gradient-...
Purpose
We combine SNR‐efficient acquisition and model‐based reconstruction strategies with newly available hardware instrumentation to achieve distortion‐free in vivo diffusion MRI of the brain at submillimeter‐isotropic resolution with high fidelity and sensitivity on a clinical 3T scanner.
Methods
We propose blip‐up/down acquisition (BUDA) for...
High-resolution diffusion tensor imaging (DTI) is beneficial for probing tissue microstructure in fine neuroanatomical structures, but long scan times and limited signal-to-noise ratio pose significant barriers to acquiring DTI at sub-millimeter resolution. To address this challenge, we propose a deep learning-based super-resolution method entitled...
Myelin water imaging techniques based on multi-compartment relaxometry have been developed as an important tool to measure myelin concentration in vivo, but are limited by the long scan time of multi-contrast multi-echo acquisition. In this work, a fast imaging technique, termed variable flip angle Echo Planar Time-Resolved Imaging (vFA-EPTI), is d...
We present a whole-brain in vivo diffusion MRI (dMRI) dataset acquired at 760 μm isotropic resolution and sampled at 1260 q-space points across 9 two-hour sessions on a single healthy subject. The creation of this benchmark dataset is possible through the synergistic use of advanced acquisition hardware and software including the high-gradient-stre...
Purpose
To develop new encoding and reconstruction techniques for fast multi‐contrast/quantitative imaging.
Methods
The recently proposed Echo Planar Time‐resolved Imaging (EPTI) technique can achieve fast distortion‐ and blurring‐free multi‐contrast/quantitative imaging. In this work, a subspace reconstruction framework is developed to improve th...
Purpose
Spin‐echo functional MRI (SE‐fMRI) has the potential to improve spatial specificity when compared with gradient‐echo fMRI. However, high spatiotemporal resolution SE‐fMRI with large slice‐coverage is challenging as SE‐fMRI requires a long echo time to generate blood oxygenation level‐dependent (BOLD) contrast, leading to long repetition tim...
The interaction of the midbrain dopaminergic system and the striatum is implicated in reward processing; it is still unknown, however, how this interaction is altered in Major Depressive Disorder (MDD). In the current study, we related the dopamine release/binding inferred by [11C] Raclopride functional Positron Emission Tomography (fPET) to neural...
Purpose
To develop a motion‐robust extension to the recently developed echo‐planar time‐resolved imaging (EPTI) approach, referred to as PROPELLER EPTI with dynamic encoding (PEPTIDE), by incorporating rotations into the rapid, multishot acquisition to enable shot‐to‐shot motion correction.
Methods
Echo‐planar time‐resolved imaging is a multishot...
Purpose: To develop new encoding and reconstruction techniques for fast multi-contrast quantitative imaging. Methods: The recently proposed Echo Planar Time-resolved Imaging (EPTI) technique can achieve fast distortion- and blurring-free multi-contrast quantitative imaging. In this work, a subspace reconstruction framework is developed to improve t...
Spin-echo functional MRI (SE-fMRI) has the potential to improve spatial specificity when compared to gradient-echo fMRI. However, high spatiotemporal resolution SE-fMRI with large slice-coverage is challenging as SE-fMRI requires a long echo time (TE) to generate blood oxygenation level-dependent (BOLD) contrast, leading to long repetition times (T...
Purpose:
To propose a virtual coil (VC) acquisition/reconstruction framework to improve highly accelerated single-shot EPI (SS-EPI) and generalized slice dithered enhanced resolution (gSlider) acquisition in high-resolution diffusion imaging (DI).
Methods:
For robust VC-GRAPPA reconstruction, a background phase correction scheme was developed to...
Purpose
To develop an efficient distortion‐ and blurring‐free multi‐shot EPI technique for time‐resolved multiple‐contrast and/or quantitative imaging.
Methods
EPI is a commonly used sequence but suffers from geometric distortions and blurring. Here, we introduce a new multi‐shot EPI technique termed echo planar time‐resolved imaging (EPTI), which...
Purpose
To develop a method for fast distortion‐ and blurring‐free imaging.
Theory: EPI with point‐spread‐function (PSF) mapping can achieve distortion‐ and blurring‐free imaging at a cost of long acquisition time. In this study, an acquisition/reconstruction technique, termed “tilted‐CAIPI,” is proposed to achieve >20× acceleration for PSF‐EPI. Th...
Purpose:
Multishot interleaved echo-planar imaging (iEPI) can achieve higher image resolution than single-shot EPI for diffusion-tensor imaging (DTI), but its application is limited by the prolonged acquisition time. To reduce the acquisition time, a novel model-based reconstruction for simultaneous multislice (SMS) and parallel imaging (PI) accel...
Purpose
To develop an efficient MR technique for ultra‐high resolution diffusion MRI (dMRI) in the presence of motion.
Methods
gSlider is an SNR‐efficient high‐resolution dMRI acquisition technique. However, subject motion is inevitable during a prolonged scan for high spatial resolution, leading to potential image artifacts and blurring. In this...
Purpose:
To develop a new approach to correct for physiological and macroscopic motion in multishot, interleaved echo-planar diffusion imaging.
Theory:
This work built on the previous SPIRiT (iterative self-consistent parallel imaging reconstruction) based reconstruction for physiological motion correction in multishot diffusion-weighted imaging...
Purpose:
To develop a novel diffusion imaging reconstruction framework based on iterative self-consistent parallel imaging reconstruction (SPIRiT) for multishot interleaved echo planar imaging (iEPI), with computation acceleration by virtual coil compression.
Methods:
As a general approach for autocalibrating parallel imaging, SPIRiT improves th...
Purpose:
To develop an efficient acquisition for high-resolution diffusion imaging and allow in vivo whole-brain acquisitions at 600- to 700-μm isotropic resolution.
Methods:
We combine blipped-controlled aliasing in parallel imaging simultaneous multislice (SMS) with a novel slab radiofrequency (RF) encoding gSlider (generalized slice-dithered...
Purpose:
To accelerate MR temperature imaging using the proton resonance frequency (PRF) shift method for real time temperature monitoring during thermal ablation.
Materials and methods:
The proposed method estimates temperature changes from undersampled k-space with a fully sampled center. This proposed algorithm is based on the hybrid multi-ba...
