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NMR in Biomedicine

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https://www.readbyqxmd.com/read/28643891/direct-comparison-of-high-temporal-resolution-cine-mri-with-doppler-ultrasound-for-assessment-of-diastolic-dysfunction-in-mice
#1
Thomas A Roberts, Anthony N Price, Laurence H Jackson, Valerie Taylor, Anna L David, Mark F Lythgoe, Daniel J Stuckey
Diastolic dysfunction is a sensitive early indicator of heart failure and can provide additional data to conventional measures of systolic function. Transmitral Doppler ultrasound, which measures the one-dimensional flow of blood through the mitral valve, is currently the preferred method for the measurement of diastolic function, but the measurement of the left ventricular volume changes using high-temporal-resolution cinematic magnetic resonance imaging (CINE MRI) is an alternative approach which is emerging as a potentially more robust and user-independent technique...
June 23, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28643354/diffusion-mri-microstructure-models-with-in-vivo-human-brain-connectome-data-results-from-a-multi-group-comparison
#2
Uran Ferizi, Benoit Scherrer, Torben Schneider, Mohammad Alipoor, Odin Eufracio, Rutger H J Fick, Rachid Deriche, Markus Nilsson, Ana K Loya-Olivas, Mariano Rivera, Dirk H J Poot, Alonso Ramirez-Manzanares, Jose L Marroquin, Ariel Rokem, Christian Pötter, Robert F Dougherty, Ken Sakaie, Claudia Wheeler-Kingshott, Simon K Warfield, Thomas Witzel, Lawrence L Wald, José G Raya, Daniel C Alexander
A large number of mathematical models have been proposed to describe the measured signal in diffusion-weighted (DW) magnetic resonance imaging (MRI). However, model comparison to date focuses only on specific subclasses, e.g. compartment models or signal models, and little or no information is available in the literature on how performance varies among the different types of models. To address this deficiency, we organized the 'White Matter Modeling Challenge' during the International Symposium on Biomedical Imaging (ISBI) 2015 conference...
June 23, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28632901/biexponential-t1%C3%AF-relaxation-mapping-of-human-knee-cartilage-in-vivo-at-3%C3%A2-t
#3
Azadeh Sharafi, Ding Xia, Gregory Chang, Ravinder R Regatte
The purpose of this study was to demonstrate the feasibility of biexponential T1ρ relaxation mapping of human knee cartilage in vivo. A three-dimensional, customized, turbo-flash sequence was used to acquire T1ρ -weighted images from healthy volunteers employing a standard 3-T MRI clinical scanner. A series of T1ρ -weighted images was fitted using monoexponential and biexponential models with two- and four-parametric non-linear approaches, respectively. Non-parametric Kruskal-Wallis and Mann-Whitney U-statistical tests were used to evaluate the regional relaxation and gender differences, respectively, with a level of significance of P = 0...
June 20, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28632306/analytical-modeling-provides-new-insight-into-complex-mutual-coupling-between-surface-loops-at-ultrahigh-fields
#4
N I Avdievich, A Pfrommer, I A Giapitzakis, A Henning
Ultrahigh-field (UHF) (≥7 T) transmit (Tx) human head surface loop phased arrays improve both the Tx efficiency (B1(+) /√P) and homogeneity in comparison with single-channel quadrature Tx volume coils. For multi-channel arrays, decoupling becomes one of the major problems during the design process. Further insight into the coupling between array elements and its dependence on various factors can facilitate array development. The evaluation of the entire impedance matrix Z for an array loaded with a realistic voxel model or phantom is a time-consuming procedure when performed using electromagnetic (EM) solvers...
June 20, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28590070/chemical-exchange-rotation-transfer-imaging-of-intermediate-exchanging-amines-at-2%C3%A2-ppm
#5
Zhongliang Zu, Elizabeth A Louie, Eugene C Lin, Xiaoyu Jiang, Mark D Does, John C Gore, Daniel F Gochberg
Chemical exchange saturation transfer (CEST) imaging of amine protons exchanging at intermediate rates and whose chemical shift is around 2 ppm may provide a means of mapping creatine. However, the quantification of this effect may be compromised by the influence of overlapping CEST signals from fast-exchanging amines and hydroxyls. We aimed to investigate the exchange rate filtering effect of a variation of CEST, named chemical exchange rotation transfer (CERT), as a means of isolating creatine contributions at around 2 ppm from other overlapping signals...
June 7, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28574615/simultaneous-spin-echo-and-gradient-echo-bold-measurements-by-dynamic-mrs
#6
Peng Cao, Fahmeed Hyder, Iris Y Zhou, Jevin W Zhang, Victor B Xie, Adrian Tsang, Ed X Wu
This study aimed to dissociate the intravascular and extravascular contributions to spin-echo (SE) and gradient-echo (GE) blood oxygenation level-dependent (BOLD) signals at 7 T, using dynamic diffusion-weighted MRS. We simultaneously acquired SE and GE data using a point-resolved spectroscopy sequence with diffusion weightings of 0, 600, and 1200 s/mm(2) . The BOLD signals were quantified by fitting the free induction decays starting from the SE center to a mono-exponential decay function. Without diffusion weighting, BOLD signals measured with SE and GE increased by 1...
June 2, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28574604/boosting-the-snr-by-adding-a-receive-only-endorectal-monopole-to-an-external-antenna-array-for-high-resolution-t2-weighted-imaging-of-early-stage-cervical-cancer-with-7-t-mri
#7
I M L van Kalleveen, J P Hoogendam, A J E Raaijmakers, F Visser, C S Arteaga de Castro, R H M Verheijen, P R Luijten, R P Zweemer, W B Veldhuis, D W J Klomp
The aim of this study was to investigate the signal-to-noise ratio (SNR) gain in early-stage cervical cancer at ultrahigh-field MRI (e.g. 7 T) using a combination of multiple external antennas and a single endorectal antenna. In particular, we used an endorectal monopole antenna to increase the SNR in cervical magnetic resonance imaging (MRI). This should allow high-resolution, T2 -weighted imaging and magnetic resonance spectroscopy (MRS) for metabolic staging, which could facilitate the local tumor status assessment...
June 2, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28570014/metronomic-treatment-in-immunocompetent-preclinical-gl261-glioblastoma-effects-of-cyclophosphamide-and-temozolomide
#8
Laura Ferrer-Font, Nuria Arias-Ramos, Silvia Lope-Piedrafita, Margarida Julià-Sapé, Martí Pumarola, Carles Arús, Ana Paula Candiota
Glioblastoma (GBM) causes poor survival in patients even when applying aggressive treatment. Temozolomide (TMZ) is the standard chemotherapeutic choice for GBM treatment, but resistance always ensues. In previous years, efforts have focused on new therapeutic regimens with conventional drugs to activate immune responses that may enhance tumor regression and prevent regrowth, for example the "metronomic" approaches. In metronomic scheduling studies, cyclophosphamide (CPA) in GL261 GBM growing subcutaneously in C57BL/6 mice was shown not only to activate antitumor CD8(+) T-cell response, but also to induce long-term specific T-cell tumor memory...
June 1, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28548710/measurement-of-glycine-in-healthy-and-tumorous-brain-by-triple-refocusing-mrs-at-3%C3%A2-t-in-vivo
#9
Vivek Tiwari, Zhongxu An, Sandeep K Ganji, Jeannie Baxter, Toral R Patel, Edward Pan, Bruce E Mickey, Elizabeth A Maher, Marco C Pinho, Changho Choi
Glycine (Gly) has been implicated in several neurological disorders, including malignant brain tumors. The precise measurement of Gly is challenging largely as a result of the spectral overlap with myo-inositol (mI). We report a new triple-refocusing sequence for the reliable co-detection of Gly and mI at 3 T and for the evaluation of Gly in healthy and tumorous brain. The sequence parameters were optimized with density-matrix simulations and phantom validation. With a total TE of 134 ms, the sequence gave complete suppression of the mI signal between 3...
May 26, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28543885/dce-mri-prediction-of-survival-time-for-patients-with-glioblastoma-multiforme-using-an-adaptive-neuro-fuzzy-based-model-and-nested-model-selection-technique
#10
Azimeh N V Dehkordi, Alireza Kamali-Asl, Ning Wen, Tom Mikkelsen, Indrin J Chetty, Hassan Bagher-Ebadian
This pilot study investigates the construction of an Adaptive Neuro-Fuzzy Inference System (ANFIS) for the prediction of the survival time of patients with glioblastoma multiforme (GBM). ANFIS is trained by the pharmacokinetic (PK) parameters estimated by the model selection (MS) technique in dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) data analysis, and patient age. DCE-MRI investigations of 33 treatment-naïve patients with GBM were studied. Using the modified Tofts model and MS technique, the following physiologically nested models were constructed: Model 1, no vascular leakage (normal tissue); Model 2, leakage without efflux; Model 3, leakage with bidirectional exchange (influx and efflux)...
May 25, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28543814/intra-and-interindividual-variability-of-fatty-acid-unsaturation-in-six-different-human-adipose-tissue-compartments-assessed-by-1-h-mrs-in-vivo-at-3%C3%A2-t
#11
Jürgen Machann, Norbert Stefan, Robert Wagner, Malte Bongers, Erwin Schleicher, Andreas Fritsche, Hans-Ulrich Häring, Konstantin Nikolaou, Fritz Schick
It is generally accepted that the amount and distribution of adipose tissue (AT) in the human body play an important role in the pathogenesis of metabolic diseases. In addition, metabolic effects of released saturated fatty acids (FAs) in blood are known to be more critical than those of unsaturated FAs. However, little is known about the variability in unsaturation of FAs in various AT compartments. The aim of this prospective study was the assessment of mono- and polyunsaturated FAs in various AT compartments by localized (1) H-MRS in order to obtain insight into the intra- and interindividual variability...
May 25, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28543797/simultaneous-use-of-linear-and-nonlinear-gradients-for-b1-inhomogeneity-correction
#12
Koray Ertan, Ergin Atalar
The simultaneous use of linear spatial encoding magnetic fields (L-SEMs) and nonlinear spatial encoding magnetic fields (N-SEMs) in B1(+) inhomogeneity problems is formulated and demonstrated with both simulations and experiments. Independent excitation k-space variables for N-SEMs are formulated for the simultaneous use of L-SEMs and N-SEMs by assuming a small tip angle. The formulation shows that, when N-SEMs are considered as an independent excitation k-space variable, numerous different k-space trajectories and frequency weightings differing in dimension, length, and energy can be designed for a given target transverse magnetization distribution...
May 25, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28543787/accurate-determination-of-brain-metabolite-concentrations-using-eretic-as-external-reference
#13
Niklaus Zoelch, Andreas Hock, Susanne Heinzer-Schweizer, Nikolai Avdievitch, Anke Henning
Magnetic Resonance Spectroscopy (MRS) can provide in vivo metabolite concentrations in standard concentration units if a reliable reference signal is available. For (1) H MRS in the human brain, typically the signal from the tissue water is used as the (internal) reference signal. However, a concentration determination based on the tissue water signal most often requires a reliable estimate of the water concentration present in the investigated tissue. Especially in clinically interesting cases, this estimation might be difficult...
May 25, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28544012/comments-on-tumor-apparent-diffusion-coefficient-as-an-imaging-biomarker-to-predict-tumor-aggressiveness
#14
LETTER
Li Xu, Rong-Pin Wang, SiWei Zhang, Zhi-Guang Chen
No abstract text is available yet for this article.
May 24, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28543921/correlations-of-low-field-nmr-and-variable-field-nmr-parameters-with-osteoarthritis-in-human-articular-cartilage-under-load
#15
Erik Rössler, Carlos Mattea, Simo Saarakkala, Petri Lehenkari, Mikko Finnilä, Lassi Rieppo, Sakari Karhula, Miika T Nieminen, Siegfried Stapf
NMR experiments carried out at magnetic fields below 1 T provide new relaxation parameters unavailable with conventional clinical scanners. Contrast of T1 generally becomes larger towards low fields, as slow molecular reorientation processes dominate relaxation at the corresponding Larmor frequencies. This advantage has to be considered in the context of lower sensitivity and frequently reduced spatial resolution. The layered structure of cartilage is one example where a particularly strong variation of T1 across the tissue occurs, being affected by degenerative diseases such as osteoarthritis (OA)...
May 24, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28543840/imaging-of-nuclear-overhauser-enhancement-at-7-and-3%C3%A2-t
#16
Yuanyu Shen, Gang Xiao, Zhiwei Shen, Xiaolei Zhang, Xiangyong Tang, Wei Hu, Zhiyan Zhang, Jitian Guan, Renhua Wu
Nuclear Overhauser enhancement (NOE) is a type of magnetization transfer using cross-relaxation. It originates from mobile macromolecules, which may have relevance to the evaluation of tumor features. We studied the value of NOE imaging at 7 and 3 T and suggest a utility for diagnosing human brain tumors. Two types of protein solution at different concentrations and pH values, and six normal Sprague Dawley (SD) rats, were used to detect NOE signal with a 7 T scanner. Then, six healthy volunteers and 11 patients with brain tumors (six gliomas and five meningiomas) were included at 3 T...
May 24, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28543640/electric-properties-tomography-biochemical-physical-and-technical-background-evaluation-and-clinical-applications
#17
REVIEW
Ulrich Katscher, Cornelius A T van den Berg
Electric properties tomography (EPT) derives the patient's electric properties, i.e. conductivity and permittivity, using standard magnetic resonance (MR) systems and standard MR sequences. Thus, EPT does not apply externally mounted electrodes, currents or radiofrequency (RF) probes, as is the case in competing techniques. EPT is quantitative MR, i.e. it yields absolute values of conductivity and permittivity. This review summarizes the physical equations underlying EPT, the corresponding basic and advanced reconstruction techniques and practical numerical aspects to realize these reconstruction techniques...
May 24, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28544286/early-regional-cuprizone-induced-demyelination-in-a-rat-model-revealed-with-mri
#18
Wendy Oakden, Nicholas A Bock, Alia Al-Ebraheem, Michael J Farquharson, Greg J Stanisz
The cuprizone model of demyelination is well established in the mouse as a tool for the study of the mechanisms of both demyelination and remyelination. It is often desirable, however, to have a larger model, such as the rat, especially for imaging-based studies, yet initial work has failed to show demyelination in cuprizone-fed rats. Several recent studies have demonstrated demyelination in the rat, but only in the corpus callosum. In this study, we acquired high-resolution, three-dimensional images of the whole brain every 2 weeks, using a T1 -weighted magnetization-prepared rapid acquisition gradient echo imaging sequence, optimized for myelin contrast, in order to assess myelination across the entire rat brain over a period of 8 weeks on a 1% cuprizone diet...
May 22, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28544159/simultaneous-measurement-of-t1-b1-and-pharmacokinetic-model-parameters-using-active-contrast-encoding-ace-mri
#19
Jin Zhang, Kerryanne Winters, Olivier Reynaud, Sungheon Gene Kim
The aim of this study was to assess the feasibility of combining dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) with the measurement of the radiofrequency (RF) transmit field B1 and pre-contrast longitudinal relaxation time T10 . A novel approach has been proposed to simultaneously estimate B1 and T10 from a modified DCE-MRI scan that actively encodes the washout phase of the curve with different amounts of T1 and B1 weighting using multiple flip angles and repetition times, hence referred to as active contrast encoding (ACE)-MRI...
May 22, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28544035/chemical-exchange-sensitive-mri-of-amide-amine-and-noe-at-9-4%C3%A2-t-versus-15-2%C3%A2-t
#20
Julius Juhyun Chung, Wonmin Choi, Tao Jin, Jung Hee Lee, Seong-Gi Kim
Chemical exchange (CE)-sensitive MRI benefits greatly from stronger magnetic fields; however, field effects on CE-sensitive imaging have not yet been studied well in vivo. We have compared CE-sensitive Z-spectra and maps obtained at the fields of 9.4 T and 15.2 T in phantoms and rats with off-resonance chemical-exchange-sensitive spin lock (CESL), which is similar to conventional chemical exchange saturation transfer. At higher fields, the background peak at water resonance has less spread and the exchange rate relative to chemical shift decreases, thus CESL intensity is dependent on B0 ...
May 22, 2017: NMR in Biomedicine
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