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Echo planar

Ki Hwan Kim, Hyo-Im Heo, Sung-Hong Park
Neuronal oscillations produce oscillating magnetic fields. There have been trials to detect neuronal oscillations using MRI, but the detectability in in vivo is still in debate. Major obstacles to detecting neuronal oscillations are (i) weak amplitudes, (ii) fast oscillations, which are faster than MRI temporal resolution, and (iii) random frequencies and on/off intervals. In this study, we proposed a new approach for direct detection of weak and fast oscillating magnetic fields. The approach consists of (i) dynamic acquisitions using multiple times to repeats (TRs) and (ii) an expanded frequency spectral analysis...
2018: PloS One
Ravi Kumar Lingam, Pravin Mundada, Vickie Lee
AIM: To examine the novel use of non-echo-planar diffusion weighted MRI (DWI) in depicting activity and treatment response in active Grave's orbitopathy (GO) by assessing, with inter-observer agreement, for a correlation between its apparent diffusion coefficients (ADCs) and conventional Short tau Inversion Recovery (STIR) MRI signal-intensity ratios (SIRs). METHOD AND MATERIALS: A total of 23 actively inflamed muscles and 30 muscle response episodes were analysed in patients with active GO who underwent medical treatment...
January 10, 2018: Orbit
Angela Albi, Antonio Meola, Fan Zhang, Pegah Kahali, Laura Rigolo, Chantal M W Tax, Pelin Aksit Ciris, Walid I Essayed, Prashin Unadkat, Isaiah Norton, Yogesh Rathi, Olutayo Olubiyi, Alexandra J Golby, Lauren J O'Donnell
BACKGROUND AND PURPOSE: Diffusion magnetic resonance imaging (dMRI) provides preoperative maps of neurosurgical patients' white matter tracts, but these maps suffer from echo-planar imaging (EPI) distortions caused by magnetic field inhomogeneities. In clinical neurosurgical planning, these distortions are generally not corrected and thus contribute to the uncertainty of fiber tracking. Multiple image processing pipelines have been proposed for image-registration-based EPI distortion correction in healthy subjects...
January 10, 2018: Journal of Neuroimaging: Official Journal of the American Society of Neuroimaging
Yi-Jui Liu, Yi-Hsiung Lee, Hing-Chiu Chang, Hui-Chu Chiu, Ta-Wei Chiu, Kang Hsu, Cheng-Ming Pen, Hsian-He Hsu, Chun-Jung Juan
The aim of this study was to investigate proton changes of the parotid gland after gustatory stimulation by semi-quantitative parameters and an empirical mathematical model (EMM) using high-temporal-resolution, double-echo, echo-planar imaging (EPI). Approved by a local institutional review board, this study examined 20 parotid glands from 10 healthy volunteers (male:female = 6: 4; age ± standard deviation =35.1 ± 14.1 years) with written informed consent obtained. All participants underwent 1.5-T, double-echo EPI with gustatory stimulation...
January 8, 2018: NMR in Biomedicine
Katharina Paul, Till Huelnhagen, Eva Oberacker, Daniel Wenz, André Kuehne, Helmar Waiczies, Sebastian Schmitter, Oliver Stachs, Thoralf Niendorf
This study shows that diffusion-weighted rapid acquisition with relaxation enhancement-echo planar imaging (RARE-EPI) has the capability to acquire distortion-free images of the eye and orbit with ample diffusion contrast. The results underpin the challenges of ocular imaging at 3.0 T and 7.0 T for EPI and demonstrate that these issues can be offset using accelerated RARE-based approaches. This benefit can be exploited for the assessment of spatial arrangements of the eye segments and their masses with the goal to provide guidance in the diagnostic assessment and treatment of ophthalmological diseases...
January 9, 2018: NMR in Biomedicine
Yayan Yin, Yaoyu Zhang, Jia-Hong Gao
PURPOSE: The oxygen extraction fraction (OEF), an important parameter for assessing brain oxygen metabolism, is a key marker of brain health. Dynamic measurement of the OEF is currently limited by the long acquisition time. In this study, a noninvasive method for rapidly and effectively assessing dynamic changes in the OEF during brain stimulation is proposed. METHODS: A novel pulse sequence using the multi-echo asymmetric spin echo with an echo-planar imaging acquisition scheme was developed to improve the temporal resolution of functional OEF measurements...
January 8, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Hansol Lee, Jae Eun Song, Jaewook Shin, Eunhae Joe, Chan Gyu Joo, Young-Suk Choi, Ho-Taek Song, Dong-Hyun Kim
PURPOSE: To test the feasibility of using the SPICE (SPectroscopic Imaging by exploiting spatiospectral CorrElation) technique, which uses the partial separability of spectroscopic data, for high resolution hyperpolarized (HP) 13 C spectroscopic imaging. METHODS: Numerical simulations were performed to investigate the impact of transient HP signals on SPICE reconstruction. Furthermore, spectroscopic imaging exams from SPICE and conventional EPSI (echo-planar spectroscopic imaging) were simulated for comparison...
January 8, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Máté Kiss, Petra Hermann, Zoltán Vidnyánszky, Viktor Gál
PURPOSE: To maintain alertness and to remain motionless during scanning represent a substantial challenge for patients/subjects involved in both clinical and research functional magnetic resonance imaging (fMRI) examinations. Therefore, availability and application of new data acquisition protocols allowing the shortening of scan time without compromising the data quality and statistical power are of major importance. METHODS: Higher order category-selective visual cortical areas were identified individually, and rapid event-related fMRI design was used to compare three different sampling rates (TR = 2000, 1000, and 410 ms, using state-of-the-art simultaneous multislice imaging) and four different scanning lengths to match the statistical power of the traditional scanning methods to high sampling-rate design...
January 4, 2018: Neuroradiology
Rita G Nunes, Joseph V Hajnal
OBJECTIVE: Point spread function (PSF) mapping enables estimating the displacement fields required for distortion correction of echo planar images. Recently, a highly accelerated approach was introduced for estimating displacements from the phase slope of under-sampled PSF mapping data. Sampling schemes with varying spacing were proposed requiring stepwise phase unwrapping. To avoid unwrapping errors, an alternative approach applying the concept of finite rate of innovation to PSF mapping (FRIP) is introduced, using a pattern search strategy to locate the PSF peak, and the two methods are compared...
January 3, 2018: Magma
Hakyoung Yoon, Won-Jin Moon, Sang-Soep Nahm, Jaehwan Kim, Kidong Eom
The use of diffusion tensor imaging (DTI) for the characterization of various lesion types in dogs with spinal cord injury (SCI) has not been investigated. The purpose of this study was to characterize scarring [loose immature scarring (LIMS), intermediate mature scarring (IMS), and dense mature scarring (DMS)], necrosis, cavitation, and acute hemorrhage using multiple DTI parameters and determine the correlations between the DTI parameters and histopathological finding in dogs with controlled SCI. All imaging data were obtained from the lumbar spinal cord (from L1 to L3) of normal and SCI dogs using a 3-Tesla magnetic resonance imaging scanner...
January 3, 2018: Journal of Neurotrauma
András Jakab, Ruth L Tuura, Raimund Kottke, Nicole Ochsenbein-Kölble, Giancarlo Natalucci, Thi Dao Nguyen, Christian Kellenberger, Ianina Scheer
BACKGROUND: In utero intravoxel incoherent motion magnetic resonance imaging (IVIM-MRI) provides a novel method for examining microvascular perfusion fraction and diffusion in the developing human fetus. PURPOSE: To characterize gestational changes in the microvascular perfusion fraction of the placenta, fetal liver, and lungs using IVIM-MRI. STUDY TYPE: Retrospective, cross-sectional study. SUBJECTS: Fifty-five datasets from 33 singleton pregnancies were acquired (17-36 gestational weeks)...
December 27, 2017: Journal of Magnetic Resonance Imaging: JMRI
Jesper L R Andersson, Mark S Graham, Ivana Drobnjak, Hui Zhang, Jon Campbell
Because of their low bandwidth in the phase-encode (PE) direction, the susceptibility-induced off-resonance field causes distortions in echo planar imaging (EPI) images. It is therefore crucial to correct for susceptibility-induced distortions when performing diffusion studies using EPI. The susceptibility-induced field is caused by the object (head) disrupting the field and it is typically assumed that it remains constant within a framework defined by the object, (i.e. it follows the object as it moves in the scanner)...
December 22, 2017: NeuroImage
Hiroki Togo, Jaroslav Rokicki, Kenji Yoshinaga, Tatsuhiro Hisatsune, Hiroshi Matsuda, Nobuhiko Haga, Takashi Hanakawa
Magnetic field inhomogeneities cause geometric distortions of echo planar images used for functional magnetic resonance imaging (fMRI). To reduce this problem, distortion correction (DC) with field map is widely used for both task and resting-state fMRI (rs-fMRI). Although DC with field map has been reported to improve the quality of task fMRI, little is known about its effects on rs-fMRI. Here, we tested the influence of field-map DC on rs-fMRI results using two rs-fMRI datasets derived from 40 healthy subjects: one with DC (DC+) and the other without correction (DC-)...
2017: Frontiers in Neuroscience
Rajakumar Nagarajan, Catherine L Carpenter, Cathy C Lee, Navin Michael, Manoj K Sarma, Raissa Souza, Edward Xu, S Sendhil Velan, Theodore J Hahn, Vay-Liang Go, M Albert Thomas
Obesity-related conditions including heart disease, stroke, and type 2 diabetes are leading causes of preventable death. Recent evidence suggests that altered myocellular lipid metabolism in obesity may lead to increased insulin resistance (IR) that predisposes to these disorders. To test the hypothesis that muscles rich in type I vs. type II muscle fibers would exhibit similar changes in intramyocellular lipid (IMCL) and extramyocellular lipid (EMCL) content in obesity, we utilized a new four-dimensional multi echo echo-planar correlated spectroscopic imaging technique that allows separate determination of IMCL and EMCL content in individual calf muscles in obese vs...
December 11, 2017: Scientific Reports
Matthew J Courtemanche, Carolyn J Sparrey, Xiaowei Song, Alex MacKay, Ryan C N D'Arcy
Detection of functional magnetic resonance imaging (fMRI) activation in white matter has been increasingly reported despite historically being controversial. Much of the development work to-date has used high-field 4 T MRI and specialized pulse sequences. In the current study, we utilized conventional 3 T MRI and a commonly applied gradient-echo-planar imaging sequence to evaluate white matter (WM) fMRI sensitivity within a common framework. Functional WM activity was replicated in target regions of interest within the corpus callosum, at the group and individual levels...
December 8, 2017: NeuroImage
Ali M Golestani, Zahra Faraji-Dana, M Aras Kayvanrad, Kawin Setsompop, Simon Graham, J Jean Chen
Simultaneous multi-slice echo-planar imaging (EPI) can enhance the spatiotemporal resolution of resting-state functional MRI (rs-fMRI) by encoding and simultaneously imaging "groups" of slices. However, phenomena including respiration, cardiac pulsatility, respiration volume per time (RVT) and cardiac-rate variation (CRV), referred to as "physiological processes", impact SMS-EPI rs-fMRI in a manner that has yet to be well characterized. In particular, physiological noise may incur aliasing and introduce spurious signals from one slice into another within the "slice-group" in rs-fMRI data, resulting in a deleterious effect on resting-state functional connectivity MRI (rs-fcMRI) maps...
December 10, 2017: Brain Connectivity
Jiazheng Wang, Alan J Wright, Richard L Hesketh, De-En Hu, Kevin M Brindle
Single-shot echo planar imaging (EPI), which allows an image to be acquired using a single excitation pulse, is used widely for imaging the metabolism of hyperpolarized 13 C-labelled metabolites in vivo as the technique is rapid and minimizes the depletion of the hyperpolarized signal. However, EPI suffers from Nyquist ghosting, which normally is corrected for by acquiring a reference scan. In a dynamic acquisition of a series of images, this results in the sacrifice of a time point if the reference scan involves a full readout train with no phase encoding...
December 7, 2017: NMR in Biomedicine
Atsushi Tachibana, Yasuhiko Tachibana, Jeff Kershaw, Hiromi Sano, Masahiro Fukushi, Takayuki Obata
PURPOSE: The purpose of this study was to evaluate the suitability of two phantoms, one made of capillary plates and the other polyethylene fibers, for assessing the quality of diffusion tensor imaging (DTI). METHODS: The first phantom was a stack of glass capillary plates with many parallel micropores (CP). The second phantom was a bundle of polyethylene fiber Dyneema held together with a thermal shrinkage tube (Dy). High resolution multi-shot echo planar imaging (EPI) DTI acquisitions were performed at b-values of 0 and 1000 s/mm2 and diffusion-times (Tdiff) of 37...
December 5, 2017: Magnetic Resonance in Medical Sciences: MRMS
Yi-Cheng Hsu, Ying-Hua Chu, Shang-Yueh Tsai, Wen-Jui Kuo, Chun-Yuan Chang, Fa-Hsuan Lin
Ultrafast functional magnetic resonance imaging (fMRI) can measure blood oxygen level dependent (BOLD) signals with high sensitivity and specificity. Here we propose a novel method: simultaneous multi-slice inverse imaging (SMS-InI) - a combination of simultaneous multi-slice excitation, simultaneous echo refocusing (SER), blipped controlled aliasing in parallel imaging echo-planar imaging (EPI), and regularized image reconstruction. Using a 32-channel head coil array on a 3 T scanner, SMS-InI achieves nominal isotropic 5-mm spatial resolution and 10 Hz sampling rate at the whole-brain level...
December 5, 2017: Scientific Reports
Alexander M Puckett, Saskia Bollmann, Benedikt A Poser, Jake Palmer, Markus Barth, Ross Cunnington
The nuclei of the basal ganglia pose a special problem for functional MRI, especially at ultra-high field, because T2* variations between different regions result in suboptimal BOLD sensitivity when using gradient-echo echo-planar imaging (EPI). Specifically, the iron-rich lentiform nucleus of the basal ganglia, including the putamen and globus pallidus, suffers from substantial signal loss when imaging is performed using conventional single-echo EPI with echo times (TE) optimized for the cortex. Multi-echo EPI acquires several echoes at different echo times for every imaging slice, allowing images to be reconstructed with a weighting of echo times that is optimized individually for each voxel according to the underlying tissue or T2* properties...
December 2, 2017: NeuroImage
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