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Magnetic Resonance Imaging

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https://www.readbyqxmd.com/read/29775663/free-breathing-ultrashort-echo-time-lung-magnetic-resonance-imaging-using-stack-of-spirals-acquisition-a-feasibility-study-in-oncology-patients
#1
Min Jae Cha, Hyun Jeong Park, Mun Young Paek, Alto Stemmer, Eun Sun Lee, Sung Bin Park, Yang Soo Kim
OBJECTIVES: To investigate the diagnostic accuracy of lung magnetic resonance imaging (MRI) with a free-breathing three-dimensional ultrashort echo time spoiled gradient echo sequence using a stack-of-spirals acquisition (spiral 3D UTE) for pulmonary nodule detection at 3 T in oncology patients. METHODS: The institutional review board approved this retrospective study. Between June and September of 2017, 32 oncology patients underwent both free-breathing spiral 3D UTE of the lungs and thin-section chest computed tomography (CT) for pulmonary metastasis workups...
May 15, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29747015/phase-matched-rf-pulse-design-for-imaging-a-reduced-field-of-excitation-with-a-fast-tse-acquisition
#2
Ronald Mooiweer, Alessandro Sbrizzi, Alexander J E Raaijmakers, Cornelis A T van den Berg, Peter R Luijten, Hans Hoogduin
A method is described to design parallel transmit (PTX) excitation pulses that are compatible with turbo spin echo (TSE) sequences, based on information available from conventional per-channel B1 + mapping. The excitation phase of PTX pulses that generate a reduced field of excitation (rFOX) is matched to the phase the quadrature mode of a PTX coil. This enables TSE imaging of a PTX-enabled rFOX excitation combined with standard nonselective refocusing pulses transmitted in the quadrature mode. In-vivo imaging experiments were performed at 7T using a dual channel parallel transmit head coil...
May 7, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29738802/intravoxel-incoherent-motion-mri-derived-parameters-and-t2-relaxation-time-for-noninvasive-assessment-of-renal-fibrosis-an-experimental-study-in-a-rabbit-model-of-unilateral-ureter-obstruction
#3
Sungmin Woo, Jeong Yeon Cho, Sang Youn Kim, Seung Hyup Kim
PURPOSE: To evaluate the association of apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM) MRI-derived parameters, and T2* relaxation time with histopathological changes observed during renal fibrogenesis in a rabbit model of unilateral ureter obstruction (UUO). METHODS: Twenty New Zealand White rabbits underwent baseline MRI followed by surgery (sham or UUO) and then follow-up MRI at postoperative day (POD) 0, 3, 7, and 14. Hematoxylin and eosin and Masson's trichrome staining was performed to evaluate cell density and area of fibrosis...
May 5, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29729951/pancreatic-stiffness-response-to-an-oral-glucose-load-in-obese-adults-measured-by-magnetic-resonance-elastography
#4
Ruoyun Ji, Jiahui Li, Ziying Yin, Yanqing Liu, Lizhuo Cang, Min Wang, Yu Shi
BACKGROUND: To test the feasibility of magnetic resonance elastography (MRE) for assessing changes in pancreatic stiffness of obese adults administered an oral glucose load. METHODS: MRE scans were performed on 21 asymptomatic obese volunteers (BMI ≥ 27 kg/m2 ) before and after receiving a 75-g oral glucose load, and repeated in 7 days without a glucose load. Shear waves at 40 and 60 Hz were introduced into the upper abdomen by a pneumatic drum driver (diameter of 12 cm)...
May 3, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29729438/amide-proton-transfer-imaging-can-predict-tumor-grade-in-rectal-cancer
#5
Akihiro Nishie, Yukihisa Takayama, Yoshiki Asayama, Kousei Ishigami, Yasuhiro Ushijima, Daisuke Okamoto, Nobuhiro Fujita, Daisuke Tsurumaru, Osamu Togao, Tatsuya Manabe, Eiji Oki, Yuichiro Kubo, Tomoyuki Hida, Minako Hirahashi-Fujiwara, Jochen Keupp, Hiroshi Honda
PURPOSE: To prospectively investigate the ability of amide proton transfer (APT) imaging, in comparison with that of diffusion-weighted imaging (DWI), to predict pathological factors in rectal cancer. MATERIALS AND METHODS: Twenty-two patients who underwent MR examination including APT imaging and DWI for evaluation of rectal cancer were enrolled. APT signal intensity (SI) was defined as the magnetization transfer asymmetry at 3.5 ppm and was mapped. An apparent diffusion coefficient (ADC) map was generated using b-values of 0, 500 and 1000 s/mm2 ...
May 2, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29729437/influence-of-k-space-trajectory-corrections-on-proton-density-mapping-with-ultrashort-echo-time-imaging-application-for-imaging-of-short-t2-components-in-white-matter
#6
Peter Latta, Zenon Starčuk, Marco L H Gruwel, Barbora Lattova, Petra Lattova, Pavel Štourač, Boguslaw Tomanek
PURPOSE: To evaluate the impact of MR gradient system imperfections and limitations for the quantitative mapping of short T2* signals performed by ultrashort echo time (UTE) acquisition approach. MATERIALS AND METHODS: The measurement of short T2* signals from a phantom and a healthy volunteer study (8 subjects of average age 28 ± 4 years) were performed on a 3T scanner. The characteristics of the gradient system were obtained using calibration method performed directly on the measured subject or phantom...
May 2, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29729436/compressive-sensing-based-on-l-1-and-hessian-regularizations-for-mri-denoising
#7
Jianjun Yuan, Jianjun Wang
Compressive sensing can be used to reduce noise. However, some details also are sparsified. This paper presents a new denoising model based on compressive sensing with L1 and Hessian regularizations for magnetic resonance images denoising. Firstly, the proposed model can make an image more sparse through L1 regularization and reduce noise. Secondly, Hessian regularization is introduced to protect some details from being over-smoothed. Experimental results demonstrate that the proposed method is efficient, and has better denoising capability...
May 2, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29709464/dynamic-contrast-enhanced-mri-of-orbital-and-anterior-visual-pathway-lesions
#8
Nutchawan Jittapiromsak, Ping Hou, Ho-Ling Liu, Jia Sun, Jade S Schiffman, T Linda Chi
PURPOSE: The accurate diagnosis of orbital and anterior visual pathway lesions has clinical significance. We determined whether dynamic contrast-enhanced MRI could differentiate benign from malignant lesions and compared model-independent and model-dependent methods of data analysis. METHODS: We retrospectively reviewed dynamic contrast-enhanced MRI studies of 37 enhancing orbital and anterior visual pathway lesions. The data were processed using model-independent analysis and model-dependent analysis using a 2-compartment pharmacokinetic model...
April 27, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29704561/oral-carcinoma-clinical-evaluation-using-diffusion-kurtosis-imaging-and-its-correlation-with-histopathologic-findings
#9
Ichiro Yamada, Norio Yoshino, Keigo Hikishima, Junichiro Sakamoto, Misaki Yokokawa, Yu Oikawa, Hiroyuki Harada, Tohru Kurabayashi, Yukihisa Saida, Ukihide Tateishi, Akane Yukimori, Toshiyuki Izumo, Shun Asahina
PURPOSE: In this study, we aimed to determine the usefulness of diffusion kurtosis imaging (DKI) as a noninvasive method for evaluation of the histologic grade and lymph node metastasis in patients with oral carcinoma. MATERIALS AND METHODS: Twenty-seven patients with oral carcinoma were examined with a 3-T MR system and 16-channel coil. DKI data were obtained by a single-shot echo-planar imaging sequence with repetition time, 10,000 ms; echo time, 94 ms; field of view, 250 × 204...
April 25, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29704560/identification-of-an-optimal-threshold-for-detecting-human-brown-adipose-tissue-using-receiver-operating-characteristic-analysis-of-ideal-mri-fat-fraction-maps
#10
Terence A Jones, Sarah C Wayte, Narendra L Reddy, Oludolapo Adesanya, George K Dimitriadis, Thomas M Barber, Charles E Hutchinson
PURPOSE: Lower fat fraction (FF) in brown adipose tissue (BAT) than white adipose tissue (WAT) has been exploited using Dixon-based Magnetic Resonance Imaging (MRI) to differentiate these tissues in rodents, human infants and adults. We aimed to determine whether an optimal FF threshold could be determined to differentiate between BAT and WAT in adult humans in vivo. METHODS: Sixteen volunteers were recruited (9 females, 7 males; 44.2 ± 19.2 years) based on BAT uptake on 18 F-FDG PET/CT...
April 25, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29698668/foca-a-new-framework-of-coupled-geometric-active-contours-for-segmentation-of-3d-cardiac-magnetic-resonance-images
#11
Mohammad-Bagher Khamechian, Mahdi Saadatmand-Tarzjan
In this paper, a new framework of coupled active contours (FoCA) is proposed for segmentation of the left ventricle myocardium, in cardiac magnetic resonance (CMR) images, without primary learning and user-driven segmentation. Primarily, we suggest a pair of coupled geometric active contours (GACs) for segmentation of the endo- and epicardial boundaries of the left ventricle in every CMR slice. The energy functional of each active contour includes the edge and shape terms of the STACS energy functional, regulator term of the local binary fitting (LBF), and new region and coupling terms...
April 23, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29680454/effect-of-echo-time-and-t-2-weighting-on-grase-based-t-1-w-t-2-w-ratio-measurements-at-3t
#12
Md Nasir Uddin, Teresa D Figley, Chase R Figley
Tissue contrast can be enhanced by dividing T1 -weighted (T1 w) images by T2 -weighted (T2 w) images to map the so-called T1 w/T2 w ratio, which has become an increasingly popular technique for quantifying brain tissue changes associated with neurodevelopment, aging, and a variety of neurodegenerative diseases. However, although it is self-evident that T1 w/T2 w ratios increase with the amount of T2 -weighting in the T2 w image - which is determined by the echo time (TE), all else being equal - longer TEs also reduce the signal-to-noise ratio (SNR) of the T2 w images, and it is not clear how these SNR characteristics affect the reliability of T1 w/T2 w measurements...
April 19, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29679635/a-multi-purpose-electromagnetic-actuator-for-magnetic-resonance-elastography
#13
Yuan Feng, Mo Zhu, Suhao Qiu, Ping Shen, Shengyuan Ma, Xuefeng Zhao, Chun-Hong Hu, Liang Guo
An electromagnetic actuator was designed for magnetic resonance elastography (MRE). The actuator is unique in that it is simple, portable, and capable of brain, abdomen, and phantom imagings. A custom-built control unit was used for controlling the vibration frequency and synchronizing the trigger signals. An actuation unit was built and mounted on the specifically designed clamp and holders for different imaging applications. MRE experiments with respect to gel phantoms, brain, and liver showed that the actuator could produce stable and consistent mechanical waves...
April 18, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29679634/ex-vivo-mouse-brain-microscopy-at-15t-with-loop-gap-rf-coil
#14
Ouri Cohen, Jerome L Ackerman
The design of a loop-gap-resonator RF coil optimized for ex vivo mouse brain microscopy at ultra high fields is described and its properties characterized using simulations, phantoms and experimental scans of mouse brains fixed in 10% formalin containing 4 mM Magnevist™. The RF (B1 ) and magnetic field (B0 ) homogeneities are experimentally quantified and compared to electromagnetic simulations of the coil. The coil's performance is also compared to a similarly sized surface coil and found to yield double the sensitivity...
April 18, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29678542/effect-of-intravascular-contrast-agent-on-diffusion-and-perfusion-fraction-coefficients-in-the-peripheral-zone-and-prostate-cancer
#15
Yousef Mazaheri, Andreas M Hötker, Amita Shukla-Dave, Oguz Akin, Hedvig Hricak
PURPOSE: To determine whether water diffusion and the perfusion fraction coefficients in prostate peripheral zone (PZ) and prostate cancer (PCa) are affected by intravenous contrast injection and explore the potential mechanism behind previously reported differences between pre- and post-contrast ADC values. METHODS: Our institutional review board waived informed consent for this HIPAA-compliant, retrospective study, which included 32 patients (median age, 63 years; range, 47-77 years) with biopsy-proven, untreated PCa who underwent 3-Tesla MRI, including DW-MRI at b-values 0, 400, 700, 1000 s/mm2 before and after gadolinium injection...
April 17, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29678541/b-1-non-uniformity-correction-of-phased-array-coils-without-measuring-coil-sensitivity
#16
Frederick C Damen, Kejia Caic
Parallel imaging can be used to increase SNR and shorten acquisition times, albeit, at the cost of image non-uniformity. B1 - non-uniformity correction techniques are confounded by signal that varies not only due to coil induced B1 - sensitivity variation, but also the object's own intrinsic signal. Herein, we propose a method that makes minimal assumptions and uses only the coil images themselves to produce a single combined B1 - non-uniformity-corrected complex image with the highest available SNR. A novel background noise classifier is used to select voxels of sufficient quality to avoid the need for regularization...
April 17, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29678540/quantitative-diffusion-mri-using-reduced-field-of-view-and-multi-shot-acquisition-techniques-validation-in-phantoms-and-prostate-imaging
#17
Yuxin Zhang, James Holmes, Iñaki Rabanillo, Arnaud Guidon, Shane Wells, Diego Hernando
PURPOSE: To evaluate the reproducibility of quantitative diffusion measurements obtained with reduced Field of View (rFOV) and Multi-shot EPI (msEPI) acquisitions, using single-shot EPI (ssEPI) as a reference. METHODS: Diffusion phantom experiments, and prostate diffusion-weighted imaging in healthy volunteers and patients with known or suspected prostate cancer were performed across the three different sequences. Quantitative diffusion measurements of apparent diffusion coefficient, and diffusion kurtosis parameters (healthy volunteers), were obtained and compared across diffusion sequences (rFOV, msEPI, and ssEPI)...
April 17, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29673894/anisotropy-of-anomalous-diffusion-improves-the-accuracy-of-differentiating-low-and-high-grade-cerebral-gliomas
#18
Boyan Xu, Lu Su, Zhenxiong Wang, Yang Fan, Gaolang Gong, Wenzhen Zhu, Peiyi Gao, Jia-Hong Gao
BACKGROUND: Anomalous diffusion model has been introduced and shown to be beneficial in clinical applications. However, only the directionally averaged values of anomalous diffusion parameters were investigated, and the anisotropy of anomalous diffusion remains unexplored. The aim of this study was to demonstrate the feasibility of using anisotropy of anomalous diffusion for differentiating low- and high-grade cerebral gliomas. METHODS: Diffusion MRI images were acquired from brain tumor patients and analyzed using the fractional motion (FM) model...
April 16, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29673893/a-new-discrete-dipole-kernel-for-quantitative-susceptibility-mapping
#19
Carlos Milovic, Julio Acosta-Cabronero, José Miguel Pinto, Hendrik Mattern, Marcelo Andia, Sergio Uribe, Cristian Tejos
PURPOSE: Most approaches for quantitative susceptibility mapping (QSM) are based on a forward model approximation that employs a continuous Fourier transform operator to solve a differential equation system. Such formulation, however, is prone to high-frequency aliasing. The aim of this study was to reduce such errors using an alternative dipole kernel formulation based on the discrete Fourier transform and discrete operators. METHODS: The impact of such an approach on forward model calculation and susceptibility inversion was evaluated in contrast to the continuous formulation both with synthetic phantoms and in vivo MRI data...
April 16, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29649574/detection-of-high-gs-risk-group-prostate-tumors-by-diffusion-tensor-imaging-and-logistic-regression-modelling
#20
Gokhan Ertas
PURPOSE: To assess the value of joint evaluation of diffusion tensor imaging (DTI) measures by using logistic regression modelling to detect high GS risk group prostate tumors. MATERIALS AND METHODS: Fifty tumors imaged using DTI on a 3 T MRI device were analyzed. Regions of interests focusing on the center of tumor foci and noncancerous tissue on the maps of mean diffusivity (MD) and fractional anisotropy (FA) were used to extract the minimum, the maximum and the mean measures...
April 9, 2018: Magnetic Resonance Imaging
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