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NMR in Biomedicine

Ferdinand Schweser, Robert Zivadinov
Quantitative susceptibility mapping (QSM) aims to calculate the tissue's magnetic susceptibility distribution from its perturbing effect on the MRI static main magnetic field. The method is increasingly being applied to study iron and myelin in clinical and preclinical settings. However, recent experimental and theoretical findings have challenged the fundamental theoretical assumptions that form the basis of current numerical implementations of QSM algorithms. The present work introduces a new class of susceptibility mapping algorithms, termed quantitative susceptibility and residual mapping (QUASAR), which takes into account frequency contributions not related to the spatial variation of bulk magnetic susceptibility in the Lorentz sphere model...
September 24, 2018: NMR in Biomedicine
Elies Fuster-Garcia, Javier Juan-Albarracín, Germán A García-Ferrando, Luis Martí-Bonmatí, Fernando Aparici-Robles, Juan M García-Gómez
Advanced MRI and molecular markers have been raised as crucial to improve prognostic models for patients having glioblastoma (GBM) lesions. In particular, different MR perfusion based markers describing vascular intrapatient heterogeneity have been correlated with tumor aggressiveness, and represent key information to understand tumor resistance against effective therapies of these neoplasms. Recently, hemodynamic tissue signature (HTS) markers based on MR perfusion images have been demonstrated to be useful for describing the heterogeneity of GBM at the voxel level, as well as demonstrating significant correlations with the patient's overall survival...
September 21, 2018: NMR in Biomedicine
Peder E Z Larson, Hsin-Yu Chen, Jeremy W Gordon, Natalie Korn, John Maidens, Murat Arcak, Shuyu Tang, Mark Criekinge, Lucas Carvajal, Daniele Mammoli, Robert Bok, Rahul Aggarwal, Marcus Ferrone, James B Slater, Sarah J Nelson, John Kurhanewicz, Daniel B Vigneron
MRI using hyperpolarized (HP) carbon-13 pyruvate is being investigated in clinical trials to provide non-invasive measurements of metabolism for cancer and cardiac imaging. In this project, we applied HP [1-13 C]pyruvate dynamic MRI in prostate cancer to measure the conversion from pyruvate to lactate, which is expected to increase in aggressive cancers. The goal of this work was to develop and test analysis methods for improved quantification of this metabolic conversion. In this work, we compared specialized kinetic modeling methods to estimate the pyruvate-to-lactate conversion rate, kPL , as well as the lactate-to-pyruvate area-under-curve (AUC) ratio...
September 19, 2018: NMR in Biomedicine
Jiazheng Wang, Richard L Hesketh, Alan J Wright, Kevin M Brindle
Hyperpolarized MRI with 13 C-labeled metabolites has enabled metabolic imaging of tumors in vivo. The heterogeneous nature of tumors and the limited lifetime of the hyperpolarization require high resolution, both temporally and spatially. We describe two sequences that make more efficient use of the 13 C polarization than previously described single-shot 3D sequences. With these sequences, the target metabolite resonances were excited using spectral-spatial pulses and the data acquired using spiral readouts from a series of echoes created using a fast-spin-echo sequence employing adiabatic 180° pulses...
September 10, 2018: NMR in Biomedicine
Alexey Kulpanovich, Assaf Tal
Magnetic resonance fingerprinting has been proposed as a method for undersampling k-space while simultaneously yielding multiparametric tissue maps. In the context of single voxel spectroscopy, fingerprinting can provide a unified framework for parameter estimation. We demonstrate the utility of such a magnetic resonance spectroscopic fingerprinting (MRSF) framework for simultaneously quantifying metabolite concentrations, T1 and T2 relaxation times and transmit inhomogeneity for major singlets of N-acetylaspartate, creatine and choline...
September 3, 2018: NMR in Biomedicine
Shun Kishimoto, Nobu Oshima, Murali C Krishna, Robert J Gillies
Magnetic resonance-based approaches to obtain metabolic information on cancer have been explored for decades. Electron paramagnetic resonance (EPR) has been developed to pursue metabolic profiling and successfully used to monitor several physiologic parameters such as pO2 , pH, and redox status. All these parameters are associated with pathophysiology of various diseases. Especially in oncology, cancer hypoxia has been intensively studied because of its relationship with metabolic alterations, acquiring treatment resistance, or a malignant phenotype...
August 31, 2018: NMR in Biomedicine
Maryam Vareth, Janine Lupo, Peder Larson, Sarah Nelson
The goal of this study was to find the most robust algorithm for a phase-sensitive coil combination of 3D single-cycle and lactate-edited, multi-channel H-1 point-resolved spectroscopy (PRESS) localized echo planar spectroscopic imaging (EPSI) data for clinical applications in the brain. Data were acquired over 5-10 minutes at 3T using 8- or 32-channel array coils. Peak referencing with residual water and N-acetyl-aspartate, first-point phasing, generalized least squared (GLS) and whitened singular-value decomposition (WSVD) combination algorithms were evaluated relative to unsuppressed water with data from a phantom, six volunteers and 55 patients with brain tumors...
August 31, 2018: NMR in Biomedicine
Dickson Wong, Amy L Schranz, Robert Bartha
A short echo time (TE ) is commonly used for brain glutamate measurement by 1 H MRS to minimize drawbacks of long TE such as signal modulation due to J evolution and T2 relaxation. However, J coupling causes the spectral patterns of glutamate to change with TE , and the shortest achievable TE may not produce the optimal glutamate measurement. The purpose of this study was to determine the optimal TE for glutamate measurement at 7 T using semi-LASER (localization by adiabatic selective refocusing). Time-domain simulations were performed to model the TE dependence of glutamate signal energy, a measure of glutamate signal strength, and were verified against measurements made in the human sensorimotor cortex (five subjects, 2 × 2 × 2 cm3 voxel, 16 averages) on a 7 T MRI scanner...
August 24, 2018: NMR in Biomedicine
M Muge Karaman, Xiaohong Joe Zhou
The purpose of this study was to develop an analytical expression for a fractional motion (FM) diffusion model to characterize diffusion-induced signal attenuation in a twice-refocused spin-echo (TRSE) sequence that is resilient to eddy currents, and to demonstrate its applicability to human brain imaging in vivo. Based on the FM theory, which provides a unified statistical description for Langevin motions, the diffusion-weighted (DW) MR signal was measured with a TRSE sequence that balances the concomitant gradients...
August 22, 2018: NMR in Biomedicine
Ralph Sinkus
No abstract text is available yet for this article.
August 20, 2018: NMR in Biomedicine
Flavio Dell'Acqua, J-Donald Tournier
Since the realization that diffusion MRI can probe the microstructural organization and orientation of biological tissue in vivo and non-invasively, a multitude of diffusion imaging methods have been developed and applied to study the living human brain. Diffusion tensor imaging was the first model to be widely adopted in clinical and neuroscience research, but it was also clear from the beginning that it suffered from limitations when mapping complex configurations, such as crossing fibres. In this review, we highlight the main steps that have led the field of diffusion imaging to move from the tensor model to the adoption of diffusion and fibre orientation density functions as a more effective way to describe the complexity of white matter organization within each brain voxel...
August 16, 2018: NMR in Biomedicine
Shu Xing, Carolyn R Freeman, Sungmi Jung, Robert Turcotte, Ives R Levesque
The purpose of this work is to propose a method to characterize tumour heterogeneity on MRI, using probabilistic classification based on a reference tissue. The method uses maps of the apparent diffusion coefficient (ADC), T2 relaxation, and a calculated map representing high-b-value diffusion-weighted MRI (denoted simDWI) to identify up to five habitats (i.e. sub-regions) of tumours. In this classification method, the parameter values (ADC, T2 , and simDWI) from each tumour voxel are compared against the corresponding parameter probability distributions in a reference tissue...
August 16, 2018: NMR in Biomedicine
A Manduca, T L Rossman, D S Lake, K J Glaser, A Arani, S P Arunachalam, P J Rossman, J D Trzasko, R L Ehman, D Dragomir-Daescu, P A Araoz
Magnetic resonance elastography (MRE) is increasingly being applied to thin or small structures in which wave propagation is dominated by waveguide effects, which can substantially bias stiffness results with common processing approaches. The purpose of this work was to investigate the importance of such biases and artifacts on MRE inversion results in: (i) various idealized 2D and 3D geometries with one or more dimensions that are small relative to the shear wavelength; and (ii) a realistic cardiac geometry...
August 13, 2018: NMR in Biomedicine
Martin Schwartz, Petros Martirosian, Günter Steidle, Michael Erb, Alto Stemmer, Bin Yang, Fritz Schick
The purpose of this work was assessment of volumetric characteristics of spontaneous mechanical activities in musculature (SMAMs) by diffusion-weighted simultaneous multi-slice (DW-SMS) imaging and spatial correlation to anatomical structure, as revealed by fusion to fiber tractographic information derived from diffusion-tensor imaging (DTI). The feasibility of using DW-SMS to image spontaneous events in human musculature was assessed by phantom measurements. Series of DW-SMS images and DTI datasets were recorded from the resting calf of three human subjects...
August 1, 2018: NMR in Biomedicine
Saeed Jerban, Yajun Ma, Amin Nazaran, Erik W Dorthe, Esther Cory, Michael Carl, Darryl D'Lima, Robert L Sah, Eric Y Chang, Jiang Du
Bone stress injury (BSI) incidents have been increasing amongst athletes in recent years as a result of more intense sporting activities. Cortical bone in the tibia and fibula is one of the most common BSI sites. Nowadays, clinical magnetic resonance imaging (MRI) is the recommended technique for BSI diagnosis at an early stage. However, clinical MRI focuses on edema observations in surrounding soft tissues, rather than the injured components of the bone. Specifically, both normal and injured bone are invisible in conventional clinical MRI...
July 30, 2018: NMR in Biomedicine
Eduardo Coello, Ralph Noeske, Brian L Burns, Jeremy W Gordon, Angela Jakary, Bjoern Menze, Axel Haase, Peder E Z Larson, Yan Li, Rolf F Schulte
MR spectroscopic imaging (MRSI) at ultra-high field (≥7 T) benefits from improved sensitivity that allows the detection of low-concentration metabolites in the brain. However, optimized acquisition techniques are required to overcome inherent limitations of MRSI at ultra-high field. This work describes an optimized method for fast high-resolution 1 H-MRSI of the brain at 7 T. The proposed acquisition sequence combines precise volume localization using semi-localization by adiabatic selective refocusing, fast spatial encoding using high-bandwidth symmetric echo-planar spectroscopic imaging (EPSI), and robust water suppression with variable power and optimized relaxation delays...
July 27, 2018: NMR in Biomedicine
Alberto De Luca, Alexander Leemans, Alessandra Bertoldo, Filippo Arrigoni, Martijn Froeling
The diffusion-weighted magnetic resonance imaging (dMRI) signal measured in vivo arises from multiple diffusion domains, including hindered and restricted water pools, free water and blood pseudo-diffusion. Not accounting for the correct number of components can bias metrics obtained from model fitting because of partial volume effects that are present in, for instance, diffusion tensor imaging (DTI) and diffusion kurtosis imaging (DKI). Approaches that aim to overcome this shortcoming generally make assumptions about the number of considered components, which are not likely to hold for all voxels...
July 27, 2018: NMR in Biomedicine
Tangi Roussel, Jens T Rosenberg, Samuel C Grant, Lucio Frydman
This study explores opportunities opened up by ultrahigh fields for in vivo saturation transfer brain magnetic resonance imaging experiments. Fast spin-echo images weighted by chemical exchange saturation transfer (CEST) effects were collected on Sprague-Dawley rats at 21.1 T, focusing on two neurological models. One involved a middle cerebral artery occlusion emulating ischemic stroke; the other involved xenografted glioma cells that were followed over the course of several days as they developed into brain tumors...
July 27, 2018: NMR in Biomedicine
Jessie E Lee, Chris J Diederich, Robert Bok, Renuka Sriram, Romelyn Delos Santos, Susan M Noworolski, Vasant A Salgaonkar, Matthew S Adams, Daniel B Vigneron, John Kurhanewicz
The goal of the study was to establish early hyperpolarized (HP) 13 C MRI metabolic and perfusion changes that predict effective high-intensity focused ultrasound (HIFU) ablation and lead to improved adjuvant treatment of partially treated regions. To accomplish this a combined HP dual-agent (13 C pyruvate and 13 C urea) 13 C MRI/multiparametric 1 H MRI approach was used to measure prostate cancer metabolism and perfusion 3-4 h, 1 d, and 5 d after exposure to ablative and sub-lethal doses of HIFU within adenocarcinoma of mouse prostate tumors using a focused ultrasound applicator designed for murine studies...
July 18, 2018: NMR in Biomedicine
Chunlei Liu, Evren Özarslan
The contrast in diffusion-weighted MR images is due to variations of diffusion properties within the examined specimen. Certain microstructural information on the underlying tissues can be inferred through quantitative analyses of the diffusion-sensitized MR signals. In the first part of the paper, we review two types of approach for characterizing diffusion MRI signals: Bloch's equations with diffusion terms, and statistical descriptions. Specifically, we discuss expansions in terms of cumulants and orthogonal basis functions, the confinement tensor formalism and tensor distribution models...
July 16, 2018: NMR in Biomedicine
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