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Cover image Magnetic Resonance Imaging

Magnetic Resonance Imaging

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select article MRI visualization of shiitake mycelium growing in woodchip blocks used for shiitake mushroom cultivation

Research articleAbstract only

MRI visualization of shiitake mycelium growing in woodchip blocks used for shiitake mushroom cultivation

Kuniyasu Ogawa, Takeshi Yashima

In Press, Accepted Manuscript, Available online 11 January 2019

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Abstract

Abstract

In order to eliminate woodchip blocks where unwanted fungi have grown and select only blocks where shiitake mycelium are growing well, there is a need to develop a visualization technique for shiitake mycelium growing in woodchip blocks, and MRI is an obvious candidate technique. From the results of measurements of the woodchip bed in a small bottle (26 mm inside diameter) where shiitake mycelium was growing, the T1 relaxation time constant immediately after inoculation was 77.9 ± 5.5 ms, and the value after about 10 to 20 days increased to 135.0 ± 9.8 ms (the increase rate was 73%). The T1 maps of the wood-chip block (130 mm length, 75 mm height and 55 mm thickness) in which shiitake mycelium grew were calculated from T1 weighted images measured by changing TR from 28 to 400 ms. From the T1 maps of time series, it was found that the shiitake mycelium extended from the right-hand side to the left-hand side of the woodchip block in a planar manner. Furthermore, in a woodchip block in which penicillium was generated, since the T1 relaxation time constant of only the shiitake mycelium became longer, it was possible to visualize the shiitake mycelium distinctly from penicillium.

select article Quantification of pathophysiological alterations in venous oxygen saturation: A comparison of global MR susceptometry techniques

Short communicationAbstract only

Quantification of pathophysiological alterations in venous oxygen saturation: A comparison of global MR susceptometry techniques

Paula L. Croal, Jackie Leung, Charly L. Phillips, Malambing G. Serafin, Andrea Kassner

In Press, Accepted Manuscript, Available online 11 January 2019

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Abstract

Abstract

The purpose of this study was to compare the Infinite Cylinder and Forward Field methods of quantifying global venous oxygen saturation (Yv) in the superior sagittal sinus (SSS) from MRI phase data, and assess their applicability in systemic cerebrovascular disease.15 children with sickle cell disease (SCD) and 10 healthy age-matched controls were imaged on a 3.0 T MRI system. Anatomical and phase data around the superior sagittal sinus were acquired from a clinically available susceptibility weighted imaging sequence and converted to Yv using the Infinite Cylinder and Forward Field methods. Yv was significantly higher when calculated using the Infinite Cylinder method compared to the Forward Field method in both patients (p = 0.003) and controls (p < 0.001). A significant difference in Yv was observed between patients and controls for the Forward Field method only (p = 0.006). While various implementations of Yv quantification can be used in practice, the results can differ significantly. Simplistic models such as the Infinite Cylinder method may be easier to implement, but their dependence on broad assumptions can lead to an overestimation of Yv, and may reduce the sensitivity to pathophysiological changes in Yv.

select article The use of a binary chelate formulation: Could gadolinium based linear contrast agents be rescued by the addition of zinc selective chelates?

Research articleAbstract only

The use of a binary chelate formulation: Could gadolinium based linear contrast agents be rescued by the addition of zinc selective chelates?

Wendell Gibby, Wes Parish, Ray M. Merrill, Diego Fernandez, ... Ryan Parr

In Press, Accepted Manuscript, Available online 10 January 2019

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Abstract

Abstract

Tissue and bone retention of gadolinium based contrast agents (GBCAs) has become a clinical concern because of the potential short and long term toxic effects of free gadolinium. This is a critical problem for most open-chain agents that more readily transmetallate in vivo, in comparison to macrocyclic compounds. Gadoliniumdiethylene tri-aminepentaacetic acid bis-glucosamide (Gd-DTPA-BIGA) is an experimental, open-chain contrast agent which has a significantly increased relaxivity coefficient in comparison to other GBCAs. This results in greater signal intensity and improved contrast enhancement. These superior imaging qualities initiated a search for a solution to the transmettalation of this agent. Plasma zinc is a well-known GBCA transmettalation agent. Since the base chelate of Gadodiamide (Gd-DPTA-Bis-Methylamide or Omniscan), DTPA-Bis-Methylamide (DTPA-BMA), readily transmettalates with and binds serum zinc, we hypothesized that a plasma "zinc sink," may significantly reduce transmettalation of linear agents. 5% DTPA-BMA was added to a formulation of Gd-DTPA-BIGA, which was tested against the original formulation of Gd-DTPA-BIGA with 0.2% of the base chelate DTPA-BIGA. These formulations, including gadodiamide, were labeled with 153GdCl3 followed by infusion into cohorts of Sprague Dawley rats which were sacrificed at 1, 30 and 60 days. Internal organs were harvested, along with blood, skin and femur, and analyzed for residual gadolinium. A subset of tissues were also interrogated with ICP-MS. Labeled Gadodiamide and saline where used as controls.

Conclusion: The addition of 5% DTPA-BMA, as a zinc binding agent, reduced the transmetallation of the linear agent Gd-DTPA-BIGA, in comparison to its original formulation supplemented with 0.2% BIGA. This result indicates that supplementing linear GBCAs with ancillary chelates may hold promise for reducing, or eliminating the biological archiving of gadolinium in tissues. In addition, this paper provides valuable animal data on the long term retention of gadolinium from linear based contrast agents.

select article NMR-based analysis of shear strength of weakly expansive clay in sodium chloride solution

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NMR-based analysis of shear strength of weakly expansive clay in sodium chloride solution

Haihao Yu, De'an Sun, Huihui Tian

In Press, Accepted Manuscript, Available online 7 January 2019

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Abstract

Abstract

A series of direct shear and nuclear magnetic resonance (NMR) tests were performed on a compacted weakly expansive clay saturated by sodium chloride (NaCl) solutions with different concentrations to study the effect of NaCl solution on the shear strength and its mechanism. Results from the direct shear tests show that the shear strength decreases slightly with increasing the NaCl solution concentration when the concentration is less than 1.0 mol/L. The results of NMR tests show that the smaller transverse relaxation times (T2) of specimens saturated by NaCl solutions with concentrations of 0.5 and 1.0 mol/L are less than that of the specimen saturated by deionized water. This means that the amount of smaller pores in the specimens saturated by deionized water is greater than that in specimens by NaCl solutions. That is, the specimen saturated by deionized water is denser than those by NaCl solutions under the same vertical pressure, and thus the shear strength of weakly expensive clay decreases with increasing the NaCl solution concentration.

select article Slow component apparent diffusion coefficient for prostate cancer: Comparison and correlation with pharmacokinetic evaluation from dynamic contrast-enhanced MR imaging

Research articleAbstract only

Slow component apparent diffusion coefficient for prostate cancer: Comparison and correlation with pharmacokinetic evaluation from dynamic contrast-enhanced MR imaging

Akio Ogura, Fumie Maeda, Seiji Yahata, Daisuke Koyama, ... Kenichiro Yamamura

In Press, Accepted Manuscript, Available online 7 January 2019

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Abstract

Abstract

Purpose

Dynamic contrast enhancement (DCE)-MRI has high diagnostic performance of prostate cancer. However, it is preferable to avoid the use of MRI contrast media. A study reported that the diagnosability of the wash-in index of DCE-MRI was equivalent to the intravoxel incoherent motion of the diffusion weighted image.

The purpose of this study was to examine the correlation between the slow component apparent diffusion coefficient (ADC) and the wash-out index of the DCE.

Materials and methods

Thirty-eight patients diagnosed with prostate cancer by biopsy were enrolled in this study. The fast and slow component ADCs of the DWI were calculated for 76 points of the tumor and the contralateral normal parts. Furthermore, the wash-in and wash-out indices of the DCE-MRI were calculated. The correlations for each calculated index were compared.

Results

There was a significant difference between the tumor and the contralateral normal parts for both fast (p = 0.03) and slow component (p < 0.01) ADCs. In addition, the slow component ADC was correlated with the wash-out index (r = 0.64).

Conclusion

The slow component ADC was correlated with the wash-out index, and may, therefore, be a suitable substitute for DCE-MRI.

select article Using functional magnetic resonance imaging to evaluate an acute allograft rejection model in rats

Research articleAbstract only

Using functional magnetic resonance imaging to evaluate an acute allograft rejection model in rats

Song Zeng, Lu Liang, Qiang Zhang, Yue Xu, ... Xiaopeng Hu

In Press, Accepted Manuscript, Available online 7 January 2019

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Abstract

Abstract

Purpose

To assess the longitudinal changes of allograft pathophysiology by intravoxel incoherent motion (IVIM) and blood oxygen level-dependent (BOLD) MRI in a rat model of acute renal allograft rejection.

Materials and methods

Acute rejection (AR) was induced by transplantation of Dark Agouti donor kidneys into Lewis recipients (n = 18). A Lewis-Lewis rat syngeneically transplanted (sTX) model served as the control (n = 6). Acute tubular necrosis (n = 6) and acute calcineurin inhibitor toxicity (n = 6) groups were established using Lewis rats. MRI was performed on postoperative day (POD) 1, 4 and 7 in the allogeneically transplanted (aTX) group and on POD4 in the other groups. Histological evaluation and PCR were performed.

Results

After the allogenic transplantation, all MRI parameters of allograft further decreased until POD7, and the D and ADC values in the cortex were significantly lower than that in the sTX group (1.03 ± 0.09 vs 1.52 ± 0.09 × 10−3 mm2/s, Padj < 0.05; 1.21 ± 0.03 vs 1.78 ± 0.07 × 10−3 mm2/s, Padj < 0.05). The D*, f and R2* values of the aTX group in the cortex and medulla were significantly lower than those in the sTX group on POD7 (cortex, D*: 25.60 ± 4.78 vs 69.32 ± 9.79 × 10−3 mm2/s, Padj < 0.05; f: 7.84 ± 1.83 vs 20.34 ± 3.08%, Padj < 0.05; R2*: 16.61 ± 4.18 vs 31.48 ± 6.43 1/s, Padj < 0.05; medulla, D*: 13.59 ± 6.08 vs 62.75 ± 9.20 × 10−3 mm2/s, Padj < 0.05; f: 7.46 ± 1.62 vs 14.68 ± 2.05%, Padj < 0.05; R2*: 21.59 ± 3.45 vs 39.53 ± 4.34 1/s, Padj < 0.05). AR grafts presented serve interstitial inflammation, tubulitis and infiltration of T-lymphocytes and macrophages. The MRI parameters, including D, ADC, D*, f and R2*, were significantly correlated with the histological changes, cell infiltration and inflammatory cytokine mRNA levels.

Conclusions

IVIM coupled with BOLD MRI allows longitudinal assessment of allograft diffusion, perfusion and oxygen consumption impairment caused by acute renal allograft rejection in rat model.

select article Water mobility spectral imaging of the spinal cord: Parametrization of model-free Laplace MRI

Research articleAbstract only

Water mobility spectral imaging of the spinal cord: Parametrization of model-free Laplace MRI

Dan Benjamini, Peter J. Basser

In Press, Corrected Proof, Available online 22 December 2018

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Abstract

Abstract

Diffusion magnetic resonance imaging (dMRI) of biological systems most often results in non-monoexponential signal, due to their complexity and heterogeneity. One approach to interpreting dMRI data without imposing tissue microstructural models is to fit the signal to a multiexponential function, which is sometimes referred to as an inverse Laplace transformation, and to display the coefficients as a distribution of the diffusivities, or water mobility spectra. Until recently, this method has not been used in a voxelwise manner, mainly because of heavy data requirements. With recent advancements in processing and experimental design, voxelwise Laplace MRI approaches are becoming feasible and attractive. The rich spectral information, combined with a three-dimensional image, presents a challenge because it tremendously increases the dimensionality of the data and requires a robust method for interpretation and analysis. In this work, we suggest parameterizing the empirically measured water mobility spectra using a bimodal lognormal function. This approach allows for a compact representation of the spectrum, and it also resolves overlapping spectral peaks, which allows for a robust extraction of their signal fraction. We apply the method on a fixed spinal cord sample and use it to generate robust intensity images of slow- and fast-diffusion components. Using the parametric variables, we create novel image contrasts, among them the information entropy of the water mobility spectrum, which pack unique features of the individual diffusion regimes in the investigated system.

select article Two-dimensional nuclear magnetic resonance method for wettability determination of tight sand

Research articleAbstract only

Two-dimensional nuclear magnetic resonance method for wettability determination of tight sand

Can Liang, Lizhi Xiao, Cancan Zhou, Yan Zhang, ... Zijian Jia

In Press, Corrected Proof, Available online 5 December 2018

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Abstract

Abstract

The wettability of reservoir rocks is important for oil recovery and reserve calculations. However, current methods for evaluating the wettability of rocks are time-consuming and expensive. Previous work has shown that low-field nuclear magnetic resonance (NMR) is a potentially useful and non-invasive technique for rock wettability determination. However, for rocks with strong internal magnetic field gradients, the current method is less efficient. In this study, the bipolar pulsed field gradient (PFG)-Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was applied to the study of rock wettability. This method can suppress the effect of the internal magnetic field gradient in rocks and accurately extract wettability information. The diffusion-transverse relaxation time (D-T2) method was employed to quantitatively estimate the wettability of rocks. Results of Amott wettability tests and NMR T1-T2 maps were combined to provide a more complete wettability characterization of tight sand. The results demonstrate the feasibility of the new method for characterizing wettability. The proposed method and workflow is of significance to the development of oil fields.

select article Influence of excess ligand on Nephrogenic Systemic Fibrosis associated with nonionic, linear gadolinium-based contrast agents

Research articleAbstract only

Influence of excess ligand on Nephrogenic Systemic Fibrosis associated with nonionic, linear gadolinium-based contrast agents

Richard C. Semelka, John P. Prybylski, Miguel Ramalho

In Press, Accepted Manuscript, Available online 22 November 2018

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Abstract

Abstract

Background

The molecular structure, charge, thermodynamic and kinetic stability are approximately the same for gadodiamide and gadoversetamide, the main substantive difference is that gadodiamide is manufactured with 5% free ligand to form Omniscan® and gadoversetamide with 10% free ligand to form OptiMARK®.

Purpose

To determine the relative risk of Nephrogenic Systemic Fibrosis (NSF) between gadodiamide (Omniscan®) and gadoversetamide (OptiMARK®) and to explore the potential contribution of the amount of excess ligand added to their commercial formulations.

Materials and methods

In this retrospective observational study, the number of doses and NSF cases associated with these agents were calculated based on two different approaches: the number of doses was determined based on pharmaceutical companies' information, and the number of unconfounded NSF cases was obtained from the previously published literature based on a legal database. A second analysis estimates the number of doses and NSF cases from the Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS).

Results

Approximately 87 million and 12 million doses of Omniscan® and OptiMARK®, respectively, have been administered worldwide since their original approval for use in the various countries throughout the world. A total of 197 and 8 unconfounded cases of NSF have been reported with Omniscan® and OptiMARK®, rendering an incidence of 2.3/million and 0.7/million for these agents, respectively. The FAERS analysis suggested reported incidences of 13.1/million and 5.0/million.

Conclusion

There is an approximately 3-fold greater incidence of NSF from Omniscan® than OptiMARK®. The difference in incidence might reflect the lesser quantity of added free ligand to the formulation of Omniscan®.

select article Optimising sampling patterns for bi-exponentially decaying signals

Research articleAbstract only

Optimising sampling patterns for bi-exponentially decaying signals

A. Reci, M.I. Ainte, A.J. Sederman, M.D. Mantle, L.F. Gladden

In Press, Corrected Proof, Available online 6 November 2018

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Abstract

Abstract

A recently reported method, based on the Cramér-Rao Lower Bound theory, for optimising sampling patterns for a wide range of nuclear magnetic resonance (NMR) experiments is applied to the problem of optimising sampling patterns for bi-exponentially decaying signals. Sampling patterns are optimised by minimizing the percentage error in estimating the most difficult to estimate parameter of the bi-exponential model, termed the objective function. The predictions of the method are demonstrated in application to pulsed field gradient NMR data recorded for the two-component diffusion of a binary mixture of methane/ethane in a zeolite. It is shown that the proposed method identifies an optimal sampling pattern with the predicted objective function being within 10% of that calculated from the experiment dataset. The method is used to advise on the number of sampled points and the noise level needed to resolve two-component systems characterised by a range of ratios of populations and diffusion coefficients. It is subsequently illustrated how the method can be used to reduce the experiment acquisition time while still being able to resolve a given two-component system.

select article Editorial: The Fourteenth International Bologna Conference on Magnetic Resonance in Porous Media (MRPM14)

EditorialNo access

Editorial: The Fourteenth International Bologna Conference on Magnetic Resonance in Porous Media (MRPM14)

Clifford R. Bowers, Sergey Vasenkov

In Press, Corrected Proof, Available online 1 November 2018

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select article High temperature/pressure MAS-NMR for the study of dynamic processes in mixed phase systems

Research articleOpen access

High temperature/pressure MAS-NMR for the study of dynamic processes in mixed phase systems

Ali Chamas, Long Qi, Hardeep S. Mehta, Jesse A. Sears, ... David W. Hoyt

In Press, Corrected Proof, Available online 25 October 2018

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Abstract

Abstract

A new MAS-NMR rotor (the WHiMS rotor) has been developed which can reach pressures of 400 bar at 20 °C or 225 bar at 250 °C. These rotors are ideal for mixed phase systems such as a reaction using a solid catalyst with a liquid/supercritical solvent topped with high pressure gas in the head space. After solid and liquid portions of the sample are loaded, the rotor is capped with an o-ring equipped polymer bushing that snaps into a mating groove in the rotor. The bushings incorporate a check valve into the sealing mechanism which allows for pressurization without mechanical manipulation – they will allow gas to flow in but not out. This WHiMS rotor design has enabled experiments on a wide variety of biotic and abiotic mixed-phase systems. Geochemical systems have also been studied, for example, adsorption and confinement studies of supercritical methane/CO2 in clays and other minerals which display pressure dependent 13C chemical shifts. Example data from other mixed-phase chemical and microbial systems are reported. These include monitoring metabolite conversion of extremophilic bacteria found in subsurface systems at elevated pressures and real-time operando reactions in catalysis systems - with liquid-quality resolution for 1H and 13C NMR spectra.

select article Preliminary evaluation of accelerated microscopic diffusional kurtosis imaging (μDKI) in a rodent model of epilepsy

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Preliminary evaluation of accelerated microscopic diffusional kurtosis imaging (μDKI) in a rodent model of epilepsy

Yang Ji, Dongshuang Lu, Limin Wu, Bensheng Qiu, ... Phillip Zhe Sun

In Press, Corrected Proof, Available online 20 October 2018

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Abstract

Abstract

Purpose

Our study aimed to develop accelerated microscopic diffusional kurtosis imaging (μDKI) and preliminarily evaluated it in a rodent model of chronic epilepsy.

Methods

We investigated two μDKI acceleration schemes of reduced sampling density and angular range in a phantom and wild-type rats, and further tested μDKI method in pilocarpine-induced epilepsy rats using a 4.7 Tesla MRI. Single slice average μDapp and μKapp maps were derived, and Nissl staining was obtained.

Results

The kurtosis maps from two accelerated μDKI sampling schemes (sampling density and range) are very similar to that using fully sampled data (SSIM > 0.95). For the epileptic models, μDKI showed noticeably different contrast from those obtained with conventional DKI. Specifically, the average μKapp was significantly less than that of the average of Kapp (0.15 ± 0.01 vs. 0.47 ± 0.02) in the ventricle.

Conclusions

Our study demonstrated the feasibility of accelerated in vivo μDKI. Our work revealed that μDKI provides complementary information to conventional DKI method, suggesting that advanced DKI sequences are promising to elucidate tissue microstructure in neurological diseases.

select article A novel MRI phantom to study interstitial fluid transport in the glymphatic system

Research articleAbstract only

A novel MRI phantom to study interstitial fluid transport in the glymphatic system

M.E. Komlosh, D. Benjamini, N.W. Williamson, F. Horkay, ... P.J. Basser

In Press, Corrected Proof, Available online 19 October 2018

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Abstract

Abstract

The glymphatic system is a recently discovered transport system, mediated by cerebral spinal fluid (CSF), that clears metabolic and cellular waste products in the brain. This system's function in the brain is analogous to that of the lymphatic system in the rest of the mammalian body. It is hypothesized that CSF clears harmful chemicals from the brain by flowing through interstitial spaces in the brain during sleep. While there is growing recognition of the critical role the glymphatic system plays in maintaining normal brain health and in explaining pathology, there are few noninvasive imaging methods that measure and characterize the efficacy of glymphatic transport in vivo. In this study we designed, constructed, and tested a glymphatic transport magnetic resonance imaging (MRI) flow phantom, which combines regions that mimic CSF-filled ventricles and brain interstitial space. We tested high- and low-q space diffusion MRI and diffusion tensor imaging (DTI) acquisitions to determine if they could detect, measure, and map interstitial glymphatic flows. The results suggest that, under certain flow conditions, diffusion-weighted MRI can detect the enhanced mixing that occurs during glymphatic clearance.

select article The downhole circumferential scanning magnetic resonance imaging tool

Research articleAbstract only

The downhole circumferential scanning magnetic resonance imaging tool

Wei Liu, Lizhi Xiao, Guangzhi Liao, Yan Zhang, Sihui Luo

In Press, Corrected Proof, Available online 19 October 2018

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Abstract

Abstract

The downhole circumferential scanning magnetic resonance logging is able to image saturation distribution and fluid properties of stratum around a borehole, thus providing relevant and abundant information for formation evaluation. The device employs a phase-controlled excitation device based on combined array structure to accomplish three dimensional data acquisition from axial, radial and circumferential directions. This paper focuses on the design principle of device and the structure of electronic control system. A mutual coupling analysis with array antenna was carried out using inductance coupling principle, and realize the decoupling and energy discharge compensation of array antennas. The circumferential scanning nuclear magnetic resonance technique has a potential of overcoming the weakness of two dimensional measurements and raising new applications that it determines the azimuth of the fluid in the borehole and realizes the imaging measurement of the pore structure and the reservoir fluid.

select article Characterization of porous media by <em>T</em>₂-<em>T</em>₂ correlation beyond fast diffusion limit

Research articleAbstract only

Characterization of porous media by T2-T2 correlation beyond fast diffusion limit

Zhou Yu, Yan Zhang, Lizhi Xiao, Guangzhi Liao

In Press, Corrected Proof, Available online 19 October 2018

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Abstract

Abstract

Pore size distribution and surface relaxivity are two important properties of porous media such as rock samples and can be obtained by NMR methods. However, it is difficult to obtain these information beyond the fast diffusion limit. Here we present a new method to directly characterize the averaged pore size of a porous sample with a narrow pore size distribution. This method is based on the parallel plates pore model and the T2-T2 correlation sequence. The pore size (a) - surface relaxivity (ρ) correlation maps were obtained using the non-negative least squares method. Three kinds of glass bead samples were measured and the averaged pore size and surface relaxivity were extracted.

select article Credit-card sized field and benchtop NMR relaxometers using field programmable gate arrays

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Credit-card sized field and benchtop NMR relaxometers using field programmable gate arrays

J. Beau W. Webber, Pavel Demin

In Press, Corrected Proof, Available online 18 October 2018

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Abstract

Abstract

The tools for developing systems for NMR improve each year. Some firmware based designs based on Field Programmable Gate Arrays (FPGAs) have been developed to implement both the core and peripheral apparatus for NMR Relaxometers and NMR Cryoporometers. Hand held in size they are particularly suitable for desktop, mobile and field use.

Software tools now enable the writing of firmware that enable the rapid design of digital and digitised R.F. data and control systems. This firmware can then be loaded into and run on hardware that often is only the size of a credit-card. These devices can include a single-chip Linux computer with an FPGA capable of processing digital RF on the same chip. These can generate RF signals digitally, process RF signals for up- and down-conversion, and can provide an on chip NMR pulse sequencer.

An extremely well tested NMR digital transmitter has been upgraded to use the latest surface-mount Bipolar and Field Effect Transistors. The circuitry is now the size of a book of matches, and interfaces to credit-card sized FPGA modules for RF generation, phase shifting and drive signals. This NMR transmitter design uses digital logic principles rather than conventional tuned R.F. techniques Offering both active-damping and active-quench, a very square R.F. Pulse with fast turn off is achieved, with Mark 1 giving 2.6 μs π/2 and 4.8 μs π pulses into a 5 mm diameter NMR sample (2.7 mT B1) at 20 MHz for Protons. T1ρ pulses are stable and consistent.

select article New magnet array design for downhole NMR azimuthal measurement

Research articleAbstract only

New magnet array design for downhole NMR azimuthal measurement

Sihui Luo, Lizhi Xiao, Xin Li, Guangzhi Liao, ... Yangyang Xu

In Press, Corrected Proof, Available online 16 October 2018

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Abstract

Abstract

In low-field NMR, depth information and radial profile information of downhole formation can be easily acquired with the help of static gradient magnetic field produced by permanent magnets, called downhole NMR imaging. Based on the hypothesis that the formation is homogeneous, average signals detected by centralized or decentralized sensors can provide enough information for petrophysical parameters. In fact, the inhomogeneity of formation may have serious impact on description of the characteristics of formation and oil/gas location which is rarely studied in NMR well-logging. To improve this, we design and implement a new quadrupolar magnet array aimed at achieving azimuthal measurement in this paper. A new quadrupolar magnet array is consisted of four bread-shaped magnets combined with additional small hexangular magnets to produce enough strength and high homogeneity of static field along with circumferential direction at deeper DOI (depth of investigation). Azimuthal measurements are achieved by using coil array combined with quadrupolar magnet array.

select article Investigating mobility of crude oil adsorbates on mineral surfaces by NMR

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Investigating mobility of crude oil adsorbates on mineral surfaces by NMR

Henrik N. Sørgård, Christian Totland, Willy Nerdal, John Georg Seland

In Press, Corrected Proof, Available online 15 October 2018

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Abstract

Abstract

We have applied diffusion and relaxation Nuclear Magnetic Resonance experiments to investigate the translational and rotational mobility of adsorbents on quartz and calcite mineral surfaces. On both surfaces it was found that water is the dominant molecule. On the quartz surface the majority of water molecules have a relatively high degree of both rotational and translational mobility, while a minor fraction of water molecules, and all hydrocarbon molecules, have a significantly lower mobility. On the calcite surface the translational mobility is very low for all the adsorbed molecules, while there is a large diversity in rotational mobility, indicating that the hydrocarbon molecules are strongly attached to the surface, but that some part of each molecule still have a large degree of rotational mobility. Diffusion and relaxation experiments give a detailed description of both the molecular mobility of adsorbed species on these mineral surfaces, which leads to new insight with respect to aging processes on a molecular level.

select article Under-sampling and compressed sensing of 3D spatially-resolved displacement propagators in porous media using APGSTE-RARE MRI

Research articleAbstract only

Under-sampling and compressed sensing of 3D spatially-resolved displacement propagators in porous media using APGSTE-RARE MRI

Daan W. de Kort, Stefan A. Hertel, Matthias Appel, Hilko de Jong, ... Lynn F. Gladden

In Press, Corrected Proof, Available online 15 October 2018

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Abstract

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