Cerebral blood flow, transit time, and apparent diffusion coefficient in moyamoya disease before and after acetazolamide.

Introduction: The goal of this study was to assess the changes in arterial spin labeling (ASL) cerebral blood flow (CBF) and arterial transit time (ATT), and in apparent diffusion coefficient (ADC), before and after an acetazolamide challenge in moyamoya patients, as function of arterial stenosis severity.

Methods: Pre-operative patients diagnosed with moyamoya disease who could undergo MRI at 3.0T were recruited for this study.

Early Non-invasive Detection of Acute 1,2-Dichloroethane-induced Toxic Encephalopathy in Rats.

Aim: To assess the acute effect of 1,2-dichloroethane (1,2-DCE) on rat brain using diffusion magnetic resonance imaging (dMRI).

Materials And Methods: We performed dMRI on 30 male Sprague-Dawley rats, microstructural alterations were investigated by calculating the mean fractional anisotropy (FA) and apparent diffusion coefficient (ADC) changes in eight selected brain regions of interest. For the whole brain, clusters of 20+ voxels that differed significantly in FA and ADC between groups were marked.

Using automatically extracted information from mammography reports for decision-support.

Objective: To evaluate a system we developed that connects natural language processing (NLP) for information extraction from narrative text mammography reports with a Bayesian network for decision-support about breast cancer diagnosis. The ultimate goal of this system is to provide decision support as part of the workflow of producing the radiology report.

Materials And Methods: We built a system that uses an NLP information extraction system (which extract BI-RADS descriptors and clinical information from mammography reports) to provide the necessary inputs to a Bayesian network (BN) decision support system (DSS) that estimates lesion malignancy from BI-RADS descriptors.

FRET Imaging of Enzymatic Activities Using Smart Probes.

Tumor-related enzymes are extensively involved in the occurrence, development, invasion, and metastasis of tumors, indicating they hold the potential to serve as biomarkers for tumor diagnosis and treatment. Smart probes based on characteristic activities of these enzymes and fluorescence resonance energy transfer (FRET) have been widely developed for fluorescent imaging of enzymatic activities. Here, we describe the detailed chemical strategies for construction of smart probe and its application for FRET imaging of fibroblast activation protein alpha in vitro and in vivo.

3D Cartesian MRI with compressed sensing and variable view sharing using complementary poisson-disc sampling.

Purpose: To enable robust, high spatio-temporal-resolution three-dimensional Cartesian MRI using a scheme incorporating a novel variable density random k-space sampling trajectory allowing flexible and retrospective selection of the temporal footprint with compressed sensing (CS).

Methods: A complementary Poisson-disc k-space sampling trajectory was designed to allow view sharing and varying combinations of reduced view sharing with CS from the same prospective acquisition. These schemes were used for two-point Dixon-based dynamic contrast-enhanced MRI (DCE-MRI) of the breast and abdomen.

Mitigation of partial volume effects in susceptibility-based oxygenation measurements by joint utilization of magnitude and phase (JUMP).

Purpose: Susceptibility-based blood oxygenation measurements in small vessels of the brain derive from gradient echo (GRE) phase and can provide localized assessment of brain function and pathology. However, when vessel diameter becomes smaller than the acquisition voxel size, partial volume effects compromise these measurements. The purpose of this study was to develop a technique to improve the reliability of vessel oxygenation estimates in the presence of partial volume effects.

Susceptibility-based time-resolved whole-organ and regional tissue oximetry.

The magnetism of hemoglobin - being paramagnetic in its deoxy and diamagnetic in its oxy state - offers unique opportunities to probe oxygen metabolism in blood and tissues. The magnetic susceptibility χ of blood scales linearly with blood oxygen saturation, which can be obtained by measuring the magnetic field ΔB of the intravascular MR signal relative to tissue. In contrast to χ, the induced field ΔB is non-local.

Amplified magnetic resonance imaging (aMRI).

Purpose: This work describes a new method called amplified MRI (aMRI), which uses Eulerian video magnification to amplify the subtle spatial variations in cardiac-gated brain MRI scans and enables better visualization of brain motion.

Methods: The aMRI method takes retrospective cardiac-gated cine MRI data as input, applies a spatial decomposition, followed by temporal filtering and frequency-selective amplification of the MRI cardiac-gated frames before synthesizing a motion-amplified cine data set.

Results: This approach reveals deformations of the brain parenchyma and displacements of arteries due to cardiac pulsatility, especially in the brainstem, cerebellum, and spinal cord.

Direct Visualization and Mapping of the Spatial Course of Fiber Tracts at Microscopic Resolution in the Human Hippocampus.

While hippocampal connectivity is essential to normal memory function, our knowledge of human hippocampal circuitry is largely inferred from animal studies. Using polarized light microscopy at 1.3 µm resolution, we have directly visualized the 3D course of key medial temporal pathways in 3 ex vivo human hemispheres and 2 ex vivo vervet monkey hemispheres.

Characterization of Axonal Disease in Patients with Multiple Sclerosis Using High-Gradient-Diffusion MR Imaging.

Purpose To evaluate the ability of high-gradient-diffusion magnetic resonance (MR) imaging by using gradient strengths of up to 300 mT/m to depict axonal disease in lesions and normal-appearing white matter (NAWM) in patients with multiple sclerosis (MS) and to compare high-gradient-diffusion MR findings in these patients with those in healthy control subjects. Materials and Methods In this HIPAA-compliant institutional review board-approved prospective study in which all subjects provided written informed consent, six patients with relapsing-remitting MS and six healthy control subjects underwent diffusion-weighted imaging with a range of diffusion weightings performed with a 3-T human MR imager by using gradient strengths of up to 300 mT/m. A model of intra-axonal, extra-axonal, and free water diffusion was fitted to obtain estimates of axon diameter and density.

Accelerating functional MRI using fixed-rank approximations and radial-cartesian sampling.

Purpose: Recently, k-t FASTER (fMRI Accelerated in Space-time by means of Truncation of Effective Rank) was introduced for rank-constrained acceleration of fMRI data acquisition. Here we demonstrate improvements achieved through a hybrid three-dimensional radial-Cartesian sampling approach that allows posthoc selection of acceleration factors, as well as incorporation of coil sensitivity encoding in the reconstruction.

Methods: The multicoil rank-constrained reconstruction used hard thresholding and shrinkage on matrix singular values of the space-time data matrix, using sensitivity encoding and the nonuniform Fast Fourier Transform to enforce data consistency in the multicoil non-Cartesian k-t domain.

Trade-off between angular and spatial resolutions in in vivo fiber tractography.

Tractography is becoming an increasingly popular method to reconstruct white matter connections in vivo. The diffusion MRI data that tractography is based on requires a high angular resolution to resolve crossing fibers whereas high spatial resolution is required to distinguish kissing from crossing fibers. However, scan time increases with increasing spatial and angular resolutions, which can become infeasible in clinical settings.

Q-space truncation and sampling in diffusion spectrum imaging.

Purpose: To characterize the q-space truncation and sampling on the spin-displacement probability density function (PDF) in diffusion spectrum imaging (DSI).

Methods: DSI data were acquired using the MGH-USC connectome scanner (G  = 300 mT/m) with b  = 30,000 s/mm , 17 × 17 × 17, 15 × 15 × 15 and 11 × 11 × 11 grids in ex vivo human brains and b  = 10,000 s/mm , 11 × 11 × 11 grid in vivo. An additional in vivo scan using b =7,000 s/mm , 11 × 11 × 11 grid was performed with a derated gradient strength of 40 mT/m.

Baseline oxygenation in the brain: Correlation between respiratory-calibration and susceptibility methods.

New MRI methods for noninvasive imaging of baseline oxygen extraction fraction (OEF) in the brain show great promise. Quantitative O2 imaging (QUO2) applies a biophysical model to measure OEF in tissue from BOLD, cerebral blood flow (CBF), and end-tidal O2 (ETO2) signals acquired during two or more gas manipulations. Alternatively, quantitative susceptibility mapping (QSM) maps baseline OEF along cerebral vessels based on the deoxyhemoblogin (dHb) susceptibility shift between veins and water.

The Structural Connectome of the Human Central Homeostatic Network.

Homeostatic adaptations to stress are regulated by interactions between the brainstem and regions of the forebrain, including limbic sites related to respiratory, autonomic, affective, and cognitive processing. Neuroanatomic connections between these homeostatic regions, however, have not been thoroughly identified in the human brain. In this study, we perform diffusion spectrum imaging tractography using the MGH-USC Connectome MRI scanner to visualize structural connections in the human brain linking autonomic and cardiorespiratory nuclei in the midbrain, pons, and medulla oblongata with forebrain sites critical to homeostatic control.

A Self-Assembled DNA Origami-Gold Nanorod Complex for Cancer Theranostics.

A self-assembled DNA origami (DO)-gold nanorod (GNR) complex, which is a dual-functional nanotheranostics constructed by decorating GNRs onto the surface of DNA origami, is demonstrated. After 24 h incubation of two structured DO-GNR complexes with human MCF7 breast cancer cells, significant enhancement of cell uptake is achieved compared to bare GNRs by two-photon luminescence imaging. Particularly, the triangle shaped DO-GNR complex exhibits optimal cellular accumulation.

Activated iron-containing microglia in the human hippocampus identified by magnetic resonance imaging in Alzheimer disease.

Although amyloid plaques and neurofibrillary pathology play important roles in Alzheimer disease (AD), our understanding of AD is incomplete, and the contribution of microglia and iron to neurodegeneration is unknown. High-field magnetic resonance imaging (MRI) is exquisitely sensitive to microscopic iron. To explore iron-associated neuroinflammatory AD pathology, we studied AD and control human brain specimens by (1) performing ultra-high resolution ex vivo 7 Tesla MRI, (2) coregistering the MRI with successive histologic staining for iron, microglia, amyloid beta, and tau, and (3) quantifying the relationship between magnetic resonance signal intensity and histological staining.

Intensity-Corrected Dual-Echo Echo-Planar Imaging (DE-EPI) for Improved Pediatric Brain Diffusion Imaging.

Here we investigate the utility of a dual-echo Echo-Planar Imaging (DE-EPI) Diffusion Weighted Imaging (DWI) approach to improve lesion conspicuity in pediatric imaging. This method delivers two 'echo images' for one diffusion-preparation period. We also demonstrate how the echoes can be utilized to remove transmit/receive coil-induced and static magnetic field intensity modulations on both echo images, which often mimic pathology and thereby pose diagnostic challenges.

Reduced field of view imaging using a static second-order gradient for functional MRI applications.

Purpose: Imaging using reduced FOV excitation allows higher resolution or signal-to-noise ratio (SNR) per scan time but often requires long radiofrequency pulses. The goal of this study was to improve a recent reduced field of view (FOV) method that uses a second-order shim gradient to decrease pulse length and evaluate its use in functional MRI (fMRI) applications.

Theory And Methods: The method, which was initially limited to excite thin disc-shaped regions at the isocenter, was extended to excite thicker regions off the isocenter and produced accurate excitation profiles on a grid phantom.

Fast quantitative susceptibility mapping using 3D EPI and total generalized variation.

Quantitative susceptibility mapping (QSM) allows new insights into tissue composition and organization by assessing its magnetic property. Previous QSM studies have already demonstrated that magnetic susceptibility is highly sensitive to myelin density and fiber orientation as well as to para- and diamagnetic trace elements. Image resolution in QSM with current approaches is limited by the long acquisition time of 3D scans and the need for high signal to noise ratio (SNR) to solve the dipole inversion problem.

2-Cyanobenzothiazole (CBT) condensation for site-specific labeling of proteins at the terminal cysteine residues.

Site specificity is pivotal in obtaining homogeneously labeled proteins without batch-to-batch variations. More importantly, precisely controlled modification at specific sites avoids potential pitfalls that could otherwise interfere with protein folding, structure, and function. Inspired by the chemical synthesis of D-luciferin, we have developed an efficient strategy (second-order rate constant k 2 = 9.

Right arcuate fasciculus abnormality in chronic fatigue syndrome.

Purpose: To identify whether patients with chronic fatigue syndrome (CFS) have differences in gross brain structure, microscopic structure, or brain perfusion that may explain their symptoms.

Materials And Methods: Fifteen patients with CFS were identified by means of retrospective review with an institutional review board-approved waiver of consent and waiver of authorization. Fourteen age- and sex-matched control subjects provided informed consent in accordance with the institutional review board and HIPAA.

Regionally-specified second trimester fetal neural stem cells reveals differential neurogenic programming.

Neural stem/progenitor cells (NSC) have the potential for treatment of a wide range of neurological diseases such as Parkinson Disease and multiple sclerosis. Currently, NSC have been isolated only from hippocampus and subventricular zone (SVZ) of the adult brain. It is not known whether NSC can be found in all parts of the developing mid-trimester central nervous system (CNS) when the brain undergoes massive transformation and growth.