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Magnetic Resonance Imaging

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https://www.readbyqxmd.com/read/29103979/comparison-of-microvascular-perfusion-evaluation-among-ivim-dwi-ct-perfusion-imaging-and-histological-microvessel-density-in-rabbit-liver-vx2-tumors
#1
Jing-Lei Li, Wei-Tao Ye, Zai-Yi Liu, Li-Fen Yan, Wei Luo, Xi-Ming Cao, Changhong Liang
OBJECT: To explore microcirculation features with intravoxel incoherent motion (IVIM) and to compare IVIM with CT perfusion imaging (CTPI) and microvessel density (MVD). MATERIALS AND METHODS: Hepatic CTPI and IVIM were performed in 16 rabbit liver VX2 tumor models. Hepatic arterial perfusion (HAP), hepatic arterial perfusion index (HPI), Blood flow (BF), and blood volume (BV) from CTPI were measured. Apparent diffusion coefficient (ADC), true diffusion coefficient (D), perfusion fraction (f), and pseudo-diffusion coefficient (D*) from IVIM were measured...
November 9, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29128678/efficient-operator-splitting-algorithm-for-joint-sparsity-regularized-spirit-based-parallel-mr-imaging-reconstruction
#2
Jizhong Duan, Yu Liu, Peiguang Jing
Self-consistent parallel imaging (SPIRiT) is an auto-calibrating model for the reconstruction of parallel magnetic resonance imaging, which can be formulated as a regularized SPIRiT problem. The Projection Over Convex Sets (POCS) method was used to solve the formulated regularized SPIRiT problem. However, the quality of the reconstructed image still needs to be improved. Though methods such as NonLinear Conjugate Gradients (NLCG) can achieve higher spatial resolution, these methods always demand very complex computation and converge slowly...
November 8, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29103975/fast-quantitative-mri-as-a-nonlinear-tomography-problem
#3
Alessandro Sbrizzi, Oscar van der Heide, Martijn Cloos, Annette van der Toorn, Hans Hoogduin, Peter R Luijten, Cornelis A T van den Berg
Quantitative Magnetic Resonance Imaging (MRI) is based on a two-steps approach: estimation of the magnetic moments distribution inside the body, followed by a voxel-by-voxel quantification of the human tissue properties. This splitting simplifies the computations but poses several constraints on the measurement process, limiting its efficiency. Here, we perform quantitative MRI as a one step process; signal localization and parameter quantification are simultaneously obtained by the solution of a large scale nonlinear inversion problem based on first-principles...
November 8, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29122668/estimation-of-physiological-sources-of-nonlinearity-in-blood-oxygenation-level-dependent-contrast-signals
#4
Daehun Kang, Yul-Wan Sung, Satoshi Shioiri
Blood oxygenation level-dependent (BOLD) contrast appears through a variation in the transverse relaxation rate of magnetic resonance signals induced by neurovascular coupling and is known to have nonlinear characteristics along echo time (TE) due to the intra-vasculature. However, the physiological causes of this nonlinearity are unclear. We attempted to estimate the physiological information related to the nonlinearity of BOLD signals by using a two-compartment model. For this purpose, we used a multi-echo gradient-echo echo-planar imaging sequence and developed a computational method to estimate the physiological information from the TE-dependent BOLD signals...
November 6, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29122667/is-breast-mri-a-helpful-additional-diagnostic-test-in-suspicious-mammographic-microcalcifications
#5
Pascal A T Baltzer, Barbara Bennani-Baiti, Alexander Stöttinger, Alexander Bumberger, Panagiotis Kapetas, Paola Clauser
PURPOSE: Microcalcifications are a common finding in mammography and usually require invasive procedures to diagnose or exclude malignancy. As many microcalcifications are due to benign lesions, we wanted to assess whether breast MRI as an additional diagnostic tool may be used to distinguish benign from malignant in this setting. MATERIALS AND METHODS: Eligible for this retrospective, IRB-approved observational study were 858 consecutive patients (mean age 54±11years) undergoing stereotactically-guided biopsies of suspicious mammographic microcalcifications during three year at our institution...
November 6, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29109052/magnetic-resonance-imaging-with-rf-encoding-on-curved-natural-slices
#6
Gordon E Sarty, Logi Vidarsson
While the idea of using spatial encoding fields (SEM) for image formation has been proven, conventional wisdom still holds that a magnetic resonance imaging (MRI) system begins with a highly uniform magnetic field. In particular, radio frequency (RF) encoding MRIs designed and tested to date have largely used uniform magnetic fields. Here we demonstrate magnetic resonance imaging in a magnetic field with a built-in gradient that gives non-planar slices - curved surfaces - when the nuclear spins are excited with narrow band RF pulses...
November 4, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29109053/quantitative-assessment-of-liver-function-with-whole-liver-t1rho-mapping-at-3-0t
#7
Weibo Chen, Xin Chen, Li Yang, Guangbin Wang, Jianqi Li, Shanshan Wang, Queenie Chan, Dongrong Xu
OBJECTIVES: To assess the segmental liver function in healthy subjects and liver cirrhosis (LC) patients with different Child-Pugh grades using whole-liver T1rho mapping at 3.0T. METHODS: Thirty-three healthy volunteers and 33 patients with clinically diagnosed LC were examined using a three-dimensional (3D) whole-liver coverage T1rho mapping. T1rho maps were calculated from five respiratory-triggered sequences with different spin-lock durations (0, 10, 20, 40, and 60ms)...
November 3, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29103978/a-study-on-diffusion-and-kurtosis-features-of-cervical-cancer-based-on-non-gaussian-diffusion-weighted-model
#8
Panying Wang, Deepa Thapa, Guangyao Wu, Qunqi Sun, Hongbing Cai, Fei Tuo
OBJECTIVE: To explore the diffusion and kurtosis features of cervical cancer (CC) and study the feasibility of diffusion kurtosis imaging (DKI) based on the non-Gaussian diffusion-weighted model to differentiate the stage and grade of CC. METHODS: A total of 50 patients with pathologically confirmed CC were enrolled. MRI examinations including DKI (with 5b values 200, 500, 1000, 1500, and 2000smm(-2) were performed before any treatment. The apparent coefficient (Dapp) and the apparent kurtosis value (Kapp) were derived from the non-gaussian diffusion model, and the apparent diffusion coefficient (ADC) was derived from the Gaussian model...
November 2, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29103977/conventional-vs-reduced-field-of-view-diffusion-weighted-imaging-of-the-prostate-comparison-of-image-quality-correlation-with-histology-and-inter-reader-agreement
#9
Brent A Warndahl, Eric A Borisch, Akira Kawashima, Stephen J Riederer, Adam T Froemming
PURPOSE: To evaluate if Field of view Optimized and Constrained Undistorted Single shot (FOCUS) (GE Healthcare, Waukesha, WI) diffusion weighted images (DWI) provide more reliable imaging than conventional DWI, with non-inferior quantitative apparent diffusion coefficient (ADC) results. MATERIAL AND METHODS: IRB approval was obtained for this study of 43 patients (44 exams, one patient with two visits) that underwent multiparametric prostate MRI with two DWI sequences and subsequent radical prostatectomy with histology as the gold standard...
November 2, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29103976/accelerating-knee-mr-imaging-compressed-sensing-in-isotropic-three-dimensional-fast-spin-echo-sequence
#10
Seung Hyun Lee, Young Han Lee, Jin-Suck Suh
PURPOSE: To compare image quality between compressed sensing (CS)-3D-fast spin-echo (FSE) and conventional 3D-FSE sequences for knee magnetic resonance imaging (MRI). METHODS: Knee MRI of 43 patients (male:female, 14:29; mean age, 53years) were acquired using conventional and CS-3D-FSE with an acceleration factor of 1.5. Overall image quality was assessed by correlation coefficient, root-mean-square error (RMSE), and structural similarity (SSIM) index. Regional image quality was evaluated using signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs)...
November 2, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29100989/single-shot-late-gd-enhancement-imaging-of-myocardial-infarction-with-retrospectively-adjustable-contrast-and-heart-phase
#11
Tobias Wech, Johannes Tran-Gia, Felix Rützel, Thorsten Klink, Thorsten A Bley, Herbert Köstler
OBJECT: To enable a retrospective adjustment of image contrast and heart phase in inversion recovery prepared late gadolinium enhancement (LE) imaging in the myocardium. MATERIALS AND METHODS: After one inversion pulse, unsegmented data were acquired over multiple cardiac cycles using a radial spoiled gradient-echo sequence with golden angle increments between subsequent readouts. Model-based acceleration of parameter mapping (MAP) was combined with an image registration technique ("MOCO-MAP") to enable the reconstruction of images with arbitrary inversion time TI...
October 31, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29100988/fast-b1-mapping-using-three-consecutive-rf-pulses-and-balanced-gradients-for-improved-bssfp-imaging
#12
Min-Oh Kim, Taehwa Hong, Dong-Hyun Kim
PURPOSE: To develop a B1(+) mapping during the transient phase of balanced steady state free precession (bSSFP) imaging which can be used for subsequent B1(+) inhomogeneity compensation. METHODS: Two images with different flip angles (FA) are acquired using single-shot spiral technique during the transient phase of bSSFP with three consecutive RF pulses and balanced gradients. Under the assumptions that the transmit (B1(+)) field varies slowly in spatial domain and T1 and T2 relaxation effects are negligible during 2·TR, B1(+) was estimated using the two magnitude images and bSSFP data was sequentially acquired...
October 31, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29066294/semi-parametric-arterial-input-functions-for-quantitative-dynamic-contrast-enhanced-magnetic-resonance-imaging-in-mice
#13
Torfinn Taxt, Rolf K Reed, Tina Pavlin, Cecilie Brekke Rygh, Erling Andersen, Radovan Jiřík
OBJECTIVE: An extension of single- and multi-channel blind deconvolution is presented to improve the estimation of the arterial input function (AIF) in quantitative dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). METHODS: The Lucy-Richardson expectation-maximization algorithm is used to obtain estimates of the AIF and the tissue residue function (TRF). In the first part of the algorithm, nonparametric estimates of the AIF and TRF are obtained. In the second part, the decaying part of the AIF is approximated by three decaying exponential functions with the same delay, giving an almost noise free semi-parametric AIF...
October 21, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29061370/strategically-acquired-gradient-echo-stage-imaging-part-ii-correcting-for-rf-inhomogeneities-in-estimating-t1-and-proton-density
#14
Yu Wang, Yongsheng Chen, Dongmei Wu, Ying Wang, Sean K Sethi, Guang Yang, Haibin Xie, Shuang Xia, E Mark Haacke
PURPOSE: To develop a method for mapping the B1 transmit (B1t) and B1 receive (B1r) fields from two gradient echo datasets each with a different flip angle and from these two images obtain accurate T1 and proton density (PD) maps of the brain. METHODS: A strategically acquired gradient echo (STAGE) data set is collected using two flip angles each with multiple echoes. The B1t field extraction was based on forcing cortical gray matter and white matter to have specific T1 values and fitting the resulting B1t field to a quadratic function...
October 20, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29056394/strategically-acquired-gradient-echo-stage-imaging-part-i-creating-enhanced-t1-contrast-and-standardized-susceptibility-weighted-imaging-and-quantitative-susceptibility-mapping
#15
Yongsheng Chen, Saifeng Liu, Yu Wang, Yan Kang, E Mark Haacke
PURPOSE: To provide whole brain grey matter (GM) to white matter (WM) contrast enhanced T1W (T1WE) images, multi-echo quantitative susceptibility mapping (QSM), proton density (PD) weighted images, T1 maps, PD maps, susceptibility weighted imaging (SWI), and R2* maps with minimal misregistration in scanning times <5min. METHODS: Strategically acquired gradient echo (STAGE) imaging includes two fully flow compensated double echo gradient echo acquisitions with a resolution of 0...
October 19, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29054737/a-novel-dti-qa-tool-automated-metric-extraction-exploiting-the-sphericity-of-an-agar-filled-phantom
#16
Sofia Chavez, Joseph Viviano, Mojdeh Zamyadi, Peter B Kingsley, Peter Kochunov, Stephen Strother, Aristotle Voineskos
PURPOSE: To develop a quality assurance (QA) tool (acquisition guidelines and automated processing) for diffusion tensor imaging (DTI) data using a common agar-based phantom used for fMRI QA. The goal is to produce a comprehensive set of automated, sensitive and robust QA metrics. METHODS: A readily available agar phantom was scanned with and without parallel imaging reconstruction. Other scanning parameters were matched to the human scans. A central slab made up of either a thick slice or an average of a few slices, was extracted and all processing was performed on that image...
October 17, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29038047/joint-groupwise-registration-and-adc-estimation-in-the-liver-using-a-b-value-weighted-metric
#17
Santiago Sanz-Estébanez, Iñaki Rabanillo-Viloria, Javier Royuela-Del-Val, Santiago Aja-Fernández, Carlos Alberola-López
PURPOSE: The purpose of this work is to develop a groupwise elastic multimodal registration algorithm for robust ADC estimation in the liver on multiple breath hold diffusion weighted images. METHODS: We introduce a joint formulation to simultaneously solve both the registration and the estimation problems. In order to avoid non-reliable transformations and undesirable noise amplification, we have included appropriate smoothness constraints for both problems. Our metric incorporates the ADC estimation residuals, which are inversely weighted according to the signal content in each diffusion weighted image...
October 14, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29031584/validation-of-diffusion-measurements-obtained-on-a-0-35t-mr-in-malawi-important-insights-for-radiologists-in-low-income-settings-with-low-field-mri
#18
Yuchuan Zhuang, Michael J Potchen, Samuel D Kampondeni, Madalina Tivarus, Gretchen L Birbeck, Jianhui Zhong
PURPOSE: To investigate the reliability of diffusion weighted image (DWI) measurements obtained on a 0.35T MR scanner in Malawi for malaria research. MATERIALS AND METHODS: The same healthy volunteers (n=6) were scanned on a 0.35T MR scanner in Malawi and a 3T scanner in the US. Three subjects had two repeated DWI scans at 0.35T. Due to scanner constraints, only three diffusion gradient directions for DWI on 0.35T could be obtained. An apparent diffusion coefficient (ADC) map was reconstructed from the 0...
October 12, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29031583/model-selection-for-high-b-value-diffusion-weighted-mri-of-the-prostate
#19
Yousef Mazaheri, Andreas M Hötker, Amita Shukla-Dave, Oguz Akin, Hedvig Hricak
PURPOSE: To assess the abilities of the standard mono-exponential (ME), bi-exponential (BE), diffusion kurtosis (DK) and stretched exponential (SE) models to characterize diffusion signal in malignant and prostatic tissues and determine which of the four models best characterizes these tissues on a per-voxel basis. MATERIALS AND METHODS: This institutional-review-board-approved, HIPAA-compliant, retrospective study included 55 patients (median age, 61years; range, 42-77years) with untreated, biopsy-proven PCa who underwent endorectal coil MRI at 3-Tesla, diffusion-weighted MRI acquired at eight b-values from 0 to 2000s/mm(2)...
October 12, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29017799/automated-segmentation-of-abdominal-subcutaneous-adipose-tissue-and-visceral-adipose-tissue-in-obese-adolescent-in-mri
#20
Steve C N Hui, Teng Zhang, Lin Shi, Defeng Wang, Chei-Bing Ip, Winnie C W Chu
PURPOSE: To develop a reliable and reproducible automatic technique to segment and measure SAT and VAT based on MRI. MATERIALS AND METHODS: Chemical-shift water-fat MRI were taken on twelve obese adolescents (mean age: 16.1±0.6, BMI: 31.3±2.3) recruited under the health monitoring program. The segmentation applied a spoke template created using Midpoint Circle algorithm followed by Bresenham's Line algorithm to detect narrow connecting regions between subcutaneous and visceral adipose tissues...
October 7, 2017: Magnetic Resonance Imaging
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