71 research outputs found
Finite difference simulation of diffusion behaviors under inter- and intra-molecular multiple-quantum coherences in liquid NMR
No full textThe Successful Mechanical Lipectomy Treatment of Cerebral Fat Embolism following Autologous Fat Injection
No full textFlat pancake distant dipolar fields for enhancement of intermolecular multiple-quantum coherence signals
No full textIntermolecular multiple-quantum coherences (iMQCs) originated from distant dipolar field (DDF) possess some appealing unique properties for magnetic resonance imaging (MRI). DDF is usually induced with continuous wave (i.e., sine- or square-wave) magnetization modulation in the whole sample. In this article, a spatially localized and enhanced DDF was optimally tailored in a thin slice with an adiabatic inversion pulse. Evidence was provided to show that careful tailoring of the spatially localized DDF can generate highly efficient iMQC signals, with more than two-fold enhancement compared to the conventional sine-wave magnetization modulation method, and 1.5 times of that with the square-wave modulation under the similar condition. Theoretical predictions, simulation results, and experimental verifications agree well with each other. Practical implementation of this approach for efficient iMQC MRI was explored. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3690110]National Natural Science Foundation (NNSF) of China [81171331, 10974164, 11074209]; Fundamental Research Funds for the Central Universities [2010121101
Apparent diffusion behaviors of spins in the presence of distant dipolar field in two-component solution NMR
No full textThe diffusion behaviors of spins in the presence of distant dipolar field in two-component spin systems during the second evolution period of a modified CRAZED sequence before acquisition were investigated. Theoretical formulas were deduced based on the distant dipolar field model. The simulation results and experimental observations are consistent with the theoretical predictions. This study shows that the relative intensities of signals from intermolecular zero-quantum coherences (iZQCs) and intermolecular double-quantum coherences (iDQCs) have the same diffusion attenuation characteristic under the combined effect of diffusion weighting gradients and distant dipolar field during the second evolution period. This diffusion attenuation may be different from that of conventional single-quantum coherence signal, depending on the relative orientation of the diffusion weighting gradients to the coherence selection gradients. The results presented herein are helpful for understanding the effect of distant dipolar field from a spin system on the diffusion behavior of other spin system and the signal properties in the iZQC or iDQC magnetic resonance imaging.NNSF of China[10875101, 11074209]; Research Fund for the Doctoral Program of Higher Education of China[20090121110030
Software: SPROM - an efficient program for NMR/MRI simulations of inter- and intra-molecular multiple quantum coherences
No full textA software package has been designed to simulate nuclear magnetic resonance spectra and images. Combining the product operator matrix with the non-linear Bloch equations, the software can efficiently simulate classical and quantum effects including scalar coupling, dipolar coupling, translational diffusion, chemical shift, radiation damping, transverse relaxation, and longitudinal relaxation.</p
The Successful Mechanical Lipectomy Treatment of Cerebral Fat Embolism following Autologous Fat Injection
No full textSummary:. Autologous fat injection is becoming a more and more widely accepted procedure in plastic surgery nowadays. Concomitantly, there are many complications. The most serious one is arterial fat embolism, for which there is only poor prognosis and no effective treatment. Here, we report the first case of successful treatment of cerebral fat embolization with the help of mechanical lipectomy. Our patient was found unconscious with left-sided hemiparesis after a facial fat injection surgery 4 hours before. Cerebral artery computed tomography angiography indicated it was multiple fat embolism. Then Solitaire stent (4 × 20 mm) and Solumbra (continuously negative pressure attraction) were utilized for the mechanical extraction of fat emboli. The patient recovered from left-side hemiparesis to muscle strength of Medical Research Council scale grade 4, and National Institutes of Health Stroke Scale score was 0 after 3 months visit. In the cerebral infarction after fat transplantation, mechanical lipectomy can be a novel and significant treatment
Observation of true and pseudo NOE signals using CEST‐MRI and CEST‐MRS sequences with and without lipid suppression
No full textSpatial-Temporal Characteristics of Brain Activity in Autism Spectrum Disorder Based on Hidden Markov Model and Dynamic Graph Theory: A Resting-State fMRI Study
No full textAutism spectrum disorder (ASD) is a common neurodevelopmental disorder. Functional magnetic resonance imaging (fMRI) can be used to measure the temporal correlation of blood-oxygen-level-dependent (BOLD) signals in the brain to assess the brain’s intrinsic connectivity and capture dynamic changes in the brain. In this study, the hidden Markov model (HMM) and dynamic graph (DG) theory are used to study the spatial-temporal characteristics and dynamics of brain networks based on dynamic functional connectivity (DFC). By using HMM, we identified three typical brain states for ASD and healthy control (HC). Furthermore, we explored the correlation between HMM time-varying properties and clinical autism scale scores. Differences in brain topological characteristics and dynamics between ASD and HC were compared by DG analysis. The experimental results indicate that ASD is more inclined to enter a strongly connected HMM brain state, leading to the isolation of brain networks and alterations in the topological characteristics of brain networks, such as default mode network (DMN), ventral attention network (VAN), and visual network (VN). This work suggests that using different data-driven methods based on DFC to study brain network dynamics would have better information complementarity, which can provide a new direction for the extraction of neuro-biomarkers in the early diagnosis of ASD
Modeling and simulation of magnetic resonance imaging based on intermolecular multiple quantum coherences
No full textCompressed sensing MRI based on nonsubsampled contourlet transform
No full textHow to reduce acquisition time is very important in magnetic resonance imaging (MRI). Compressed sensing MRI emerges recently to suppress the aliasing when undersampling k-space data is employed However, typical sparse transform for compressed sensing MRI ever used is wavelet, which only captures limited directional information with decay rate M(1). In this paper, we introduce contourlet into compressed sensing to obtain a sparse expansion for smooth contours with decay rate C(logM)(3)M(2) and employ nonsubsampled contourlet to increase the redundancy of basis for magnetic resonance images. We propose compressed sensing MRI based on nonsubsampled contourlet transform (NSCT). Experimental results demonstrate that NSCT outperforms wavelet on suppressing the aliasing and improves the visual appearance of magnetic resonance images
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