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Magnetic Resonance Imaging

A Reci, M I Ainte, A J Sederman, M D Mantle, L F Gladden
A recently reported method, based on the Cramér-Rao Lower Bound theory, for optimising sampling patterns for a wide range of nuclear magnetic resonance (NMR) experiments is applied to the problem of optimising sampling patterns for bi-exponentially decaying signals. Sampling patterns are optimised by minimizing the percentage error in estimating the most difficult to estimate parameter of the bi-exponential model, termed the objective function. The predictions of the method are demonstrated in application to pulsed field gradient NMR data recorded for the two-component diffusion of a binary mixture of methane/ethane in a zeolite...
November 6, 2018: Magnetic Resonance Imaging
Clifford R Bowers, Sergey Vasenkov
No abstract text is available yet for this article.
November 1, 2018: Magnetic Resonance Imaging
Zhenxiong Wang, Shun Zhang, Chengxia Liu, Yihao Yao, Jingjing Shi, Ju Zhang, Yuanyuan Qin, Wenzhen Zhu
OBJECTIVES: To demonstrate the feasibility of the neurite orientation dispersion and density imaging (NODDI) technique in characterizing the microstructural changes in brain tissues during ischemic stroke and to compare its sensitivity with diffusion tensor imaging (DTI) and diffusion kurtosis imaging (DKI). METHODS: Seventy-one patients with hyperacute/acute/subacute ischemic stroke were enrolled in the study. A multishell diffusion magnetic resonance imaging (dMRI) protocol was performed for each subject...
October 29, 2018: Magnetic Resonance Imaging
Pawel Brzozowski, Kalin I Penev, Francisco M Martinez, Timothy J Scholl, Kibret Mequanint
OBJECT: The research follows the analysis of gellan gum-based gels as novel MRI phantom material with the implementation of a design of experiments model to obtain tunable relaxation properties. MATERIALS AND METHODS: Gellan gum gels doped with newly synthesized superparamagnetic iron oxide nanoparticles (SPIONs) and either MnCl2 or GdCl3 were prepared and scanned from 230 μT to 3 T. Nineteen gel samples were formulated with varying concentrations of contrast agents to determine the linear, quadratic, and interactive effects of the contrast agents by a central composite design of experiment...
October 28, 2018: Magnetic Resonance Imaging
S Mangione, R Acquaviva, G Garbo
This paper describes an automated method for extracting the apparent positions of fiducial points from 2D or 3D images of a phantom. We consider a 3D-lattice phantom for two main reasons: first, ease of manufacture and isotropy of its structure with respect to coordinate projections; second, a connected structure allowing to uniquely assess the adjacency relationship between fiducial points even if geometric distortions arising from main magnet inhomogeneity and gradient fields non-linearity is severe as observed in open-bore systems...
October 25, 2018: Magnetic Resonance Imaging
Hanjing Kong, Chengyan Wang, Fei Gao, Xiaodong Zhang, Min Yang, Li Yang, Xiaoying Wang, Jue Zhang
Acute kidney injury (AKI) is a common complication in various clinical settings. In recent years, AKI diagnostics have been investigated intensively showing the emerging need for early characterization of this disease. To verify whether targeted field-of-view diffusion-weighted imaging (tFOV-DWI) is feasible to significantly improve the performance of traditional full field-of-view diffusion-weighted imaging (fFOV-DWI) in the early assessment of AKI. 14 rabbits with unilateral AKI were induced by injection of microspheres under the guidance of digital subtraction angiography (DSA)...
October 25, 2018: Magnetic Resonance Imaging
Hans-Jonas Meyer, Peter Gundermann, Anne Kathrin Höhn, Gordian Hamerla, Alexey Surov
OBJECTIVE: Diffusion weighted imaging (DWI) can be quantified by apparent diffusion coefficient (ADC) and can predict tissue microstructure. The aim of the present study was to analyze possible associations between ADC histogram based parameters with different histopathological parameters in cervical squamous cell carcinoma. MATERIALS AND METHODS: 18 female patients (age range 32-79 years) with squamous cell cervical carcinoma were retrospectively enrolled. In all cases, pelvic MRI was performed with a DWI (b-values 0 and 1000 s/mm2 )...
October 24, 2018: Magnetic Resonance Imaging
Binbin Nie, Di Wu, Shengxiang Liang, Hua Liu, Xi Sun, Panlong Li, Qi Huang, Tianhao Zhang, Ting Feng, Songtao Ye, Zhijun Zhang, Baoci Shan
PURPOSE: Manganese-enhanced magnetic resonance imaging (MEMRI) can help us trace the active neurons and neuronal pathway in transgenic mouse AD model. 5XFAD has been widespread accepted as a valuable model system for studying brain dysfunction progresses in the courses of AD. To further understand the development of AD at early stages, an effective and objective data analysis platform for MEMRI studies should be constructed. MATERIALS AND METHODS: A set of stereotaxic templates of mouse brain in Paxinos and Franklin space, "the Institute of High Energy Physics Mouse Template", or IMT for short, was constructed by iteratively registration and averaging...
October 22, 2018: Magnetic Resonance Imaging
Sagar Buch, Yongsheng Chen, E Mark Haacke
Quantitative susceptibility mapping (QSM) is a means to obtain direct measurements of local tissue susceptibility distribution. Usually the focus is on imaging tissues in the brain, and the region of the brain studied is dictated by an eroded skull stripped mask. Producing the pristine local phase behavior for regions at the edge of the brain has been difficult in the past. For structures such as the superior sagittal sinus (SSS) that run alongside the surface of the brain and under the skull bones, a considerable part of the external phase from the dipole effect is lost due to the short T2* of the bones...
October 21, 2018: Magnetic Resonance Imaging
Francesco Giganti, Clare Allen, Jonathan W Piper, David Mirando, Armando Stabile, Shonit Punwani, Alex Kirkham, Mark Emberton, Caroline M Moore
BACKGROUND AND OBJECTIVES: There is interest in using sequential multiparametric magnetic resonance imaging (mpMRI) to assess men on active surveillance (AS) for prostate cancer. The Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) recommendations propose standardised reporting mpMRI data for these men. This includes accurate size measurements of lesions over time, but such approach is time consuming for the radiologist and there is a strong need of dedicated tools to report serial scans in a systematic manner...
October 20, 2018: Magnetic Resonance Imaging
Yang Ji, Dongshuang Lu, Limin Wu, Bensheng Qiu, Yi-Qiao Song, Phillip Zhe Sun
PURPOSE: Our study aimed to develop accelerated microscopic diffusional kurtosis imaging (μDKI) and preliminarily evaluated it in a rodent model of chronic epilepsy. METHODS: We investigated two μDKI acceleration schemes of reduced sampling density and angular range in a phantom and wild-type rats, and further tested μDKI method in pilocarpine-induced epilepsy rats using a 4.7 Tesla MRI. Single slice average μDapp and μKapp maps were derived, and Nissl staining was obtained...
October 20, 2018: Magnetic Resonance Imaging
M E Komlosh, D Benjamini, N W Williamson, F Horkay, E B Hutchinson, P J Basser
The glymphatic system is a recently discovered transport system, mediated by cerebral spinal fluid (CSF), that clears metabolic and cellular waste products in the brain. This system's function in the brain is analogous to that of the lymphatic system in the rest of the mammalian body. It is hypothesized that CSF clears harmful chemicals from the brain by flowing through interstitial spaces in the brain during sleep. While there is growing recognition of the critical role the glymphatic system plays in maintaining normal brain health and in explaining pathology, there are few noninvasive imaging methods that measure and characterize the efficacy of glymphatic transport in vivo...
October 19, 2018: Magnetic Resonance Imaging
Wei Liu, Lizhi Xiao, Guangzhi Liao, Yan Zhang, Sihui Luo
The downhole circumferential scanning magnetic resonance logging is able to image saturation distribution and fluid properties of stratum around a borehole, thus providing relevant and abundant information for formation evaluation. The device employs a phase-controlled excitation device based on combined array structure to accomplish three dimensional data acquisition from axial, radial and circumferential directions. This paper focuses on the design principle of device and the structure of electronic control system...
October 18, 2018: Magnetic Resonance Imaging
J Beau W Webber, Pavel Demin
The tools for developing systems for NMR improve each year. Some firmware based designs based on Field Programmable Gate Arrays (FPGAs) have been developed to implement both the core and peripheral apparatus for NMR Relaxometers and NMR Cryoporometers. Hand held in size they are particularly suitable for desktop, mobile and field use. Software tools now enable the writing of firmware that enable the rapid design of digital and digitised R.F. data and control systems. This firmware can then be loaded into and run on hardware that often is only the size of a credit-card...
October 18, 2018: Magnetic Resonance Imaging
Zhou Yu, Yan Zhang, Lizhi Xiao, Guangzhi Liao
Pore size distribution and surface relaxivity are two important properties of porous media such as rock samples and can be obtained by NMR methods. However, it is difficult to obtain these information beyond the fast diffusion limit. Here we present a new method to directly characterize the averaged pore size of a porous sample with a narrow pore size distribution. This method is based on the parallel plates pore model and the T2 -T2 correlation sequence. The pore size (a) - surface relaxivity (ρ) correlation maps were obtained using the non-negative least squares method...
October 18, 2018: Magnetic Resonance Imaging
Sihui Luo, Lizhi Xiao, Xin Li, Guangzhi Liao, Huabing Liu, Zhengduo Wang, Zhe Sun, Wei Liu, Yangyang Xu
In low-field NMR, depth information and radial profile information of downhole formation can be easily acquired with the help of static gradient magnetic field produced by permanent magnets, called downhole NMR imaging. Based on the hypothesis that the formation is homogeneous, average signals detected by centralized or decentralized sensors can provide enough information for petrophysical parameters. In fact, the inhomogeneity of formation may have serious impact on description of the characteristics of formation and oil/gas location which is rarely studied in NMR well-logging...
October 16, 2018: Magnetic Resonance Imaging
Daan W de Kort, Stefan A Hertel, Matthias Appel, Hilko de Jong, Michael D Mantle, Andrew J Sederman, Lynn F Gladden
A method for under-sampling and compressed sensing of 3D spatially-resolved propagators is presented and demonstrated for flow in a packed bed and a heterogeneous carbonate rock. By sampling only 12.5% of q,k-space, the experimental acquisition time was reduced by almost an order of magnitude. In particular, for both systems studied, a 3D image was acquired at 1 mm isotropic spatial resolution such that 134,400 local propagators were obtained. Data were acquired in ~1 h and ~11 h for the packed bed and rock, respectively...
October 15, 2018: Magnetic Resonance Imaging
Henrik N Sørgård, Christian Totland, Willy Nerdal, John Georg Seland
We have applied diffusion and relaxation Nuclear Magnetic Resonance experiments to investigate the translational and rotational mobility of adsorbents on quartz and calcite mineral surfaces. On both surfaces it was found that water is the dominant molecule. On the quartz surface the majority of water molecules have a relatively high degree of both rotational and translational mobility, while a minor fraction of water molecules, and all hydrocarbon molecules, have a significantly lower mobility. On the calcite surface the translational mobility is very low for all the adsorbed molecules, while there is a large diversity in rotational mobility, indicating that the hydrocarbon molecules are strongly attached to the surface, but that some part of each molecule still have a large degree of rotational mobility...
October 15, 2018: Magnetic Resonance Imaging
Yunyun Yang, Dongcai Tian, Wenjing Jia, Xiu Shu, Boying Wu
At present, magnetic resonance (MR) images have gradually become a major aid for clinical medicine, which has greatly improved the doctor's diagnosis rate. Accurate and fast segmentation of MR images plays an extremely important role in medical research. However, due to the influence of external factors and the defects of imaging devices, the MR images have severe intensity inhomogeneity, which poses a great challenge to accurately segment MR images. To deal with this problem, this paper presents an improved active contour model by combining the level set evolution model (LSE) and the split Bregman method, and gives the two-phase, the multi-phase and the vector-valued formulations of our model, respectively...
October 13, 2018: Magnetic Resonance Imaging
Sean K Sethi, Shawn J Kisch, Kiarash Ghassaban, Ali Rajput, Alex Rajput, Paul S Babyn, Saifeng Liu, Peter Szkup, E Mark Haacke
BACKGROUND: Elevated brain iron has been observed in Idiopathic Parkinson's disease (IPD) within the deep gray matter. Using quantitative susceptibility mapping (QSM) and a thresholded high-iron region, we quantified iron content in the midbrain of patients with Parkinson's disease as a function of age. METHODS: We used MRI to scan 24 IPD patients at 3-Tesla. Susceptibility-weighted images were collected with the following parameters, TE: 6 and 20 ms, TR: 30 ms, FA: 15°, and resolution: 0...
October 13, 2018: Magnetic Resonance Imaging
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