Strategies for Diagnosing and Alleviating Artifactual Attenuation Associated with Large Gradient Pulses in PGSE NMR Diffusion Measurements

Price, William S.; Hayamizu, Kikuko; Ide, Hiroyuki; Arata, Yoji

doi:10.1006/jmre.1999.1789

Cited by 70 publications

(67 citation statements)

References 15 publications

(30 reference statements)

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“…An often applied method for achieving better echo (and balancing) stability is the application of a permanent background gradient. 23 The background gradient should be parallel to the applied gradient pulses in order to be effective. 24 For economic reasons, low-field benchtop NMR spectrometers use permanent magnets, but these provide an inhomogeneous magnetic field B 0 .…”

Section: B 0 Field Homogeneitymentioning

confidence: 99%

Scope of droplet size measurements in food emulsions by pulsed field gradient NMR at low field

Duynhoven

Goudappel

Dalen

et al. 2002

Magnetic Reson in Chemistry

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Low-field NMR instrumentation offers a user-friendly and cost-effective means for assessment of water and oil droplet size measurements in food emulsions. Examples are given of major food application areas, and these are supported with validation data in terms of precision and equivalence to other methods. The NMR method gives the same results as other techniques, such as microscopy, laser diffraction and electric sensing, but with similar or better precision. NMR distinguishes itself by a simple and non-perturbing sample preparation procedure (in addition to the aforementioned advantages). For reliable results, the NMR parameters should be properly chosen and adjusted. A survey is given of experimental NMR parameters than can have an impact on the performance of water and oil droplet size determination. Copyright  2002 John Wiley & Sons, Ltd. KEYWORDS: NMR;1 H NMR; droplets; emulsion; foods; laser diffraction; microscopy INTRODUCTIONIn food research, the pressure to bring products faster to the market has become stronger, and the systems under investigation are becoming ever more complex both in structure and in chemical composition. 1 NMR spectroscopy has become an indispensable technique that can relate meso-and microstructural parameters to consumer-related features, such as shelf-life and mouthfeel.2 However, NMR is still considered an expert technique, whereas the rapid pace of product development requires understanding and/or control of food structures at the laboratory bench/kitchen table or manufacturing plant. In recent decades, low-cost and easy-to-handle benchtop NMR systems 3 have been developed which can determine phase-compositional 4 and microstructural 5 parameters of food materials. These systems operate at low field, typically 0.47 T (20 MHz for 1 H), and this poses intrinsic limitations on sensitivity and resolution. Nevertheless, these systems have gained a considerable position in food industry laboratories, with applications ranging from research and development to process and product control.The classical NMR application in the microstructural domain is the assessment of water droplet size distributions in food emulsions.6 -8 These methods are being used to explain and predict physical and microbiological stability of water-in-oil food emulsions, 9 such as margarines and low-calorie spreads. A more recent development is the assessment of oil droplet size distributions in oil-in-water systems.10 These systems also are fairly abundant as Ł Correspondence to: J. P. M. van Duynhoven, Unilever R&D Vlaardingen, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands. E-mail: john-van.duynhoven@unilever.com mayonnaises, cheese, dressings, spreads, etc. 11 Both the water and oil droplet size distribution measurements are based on the restricted diffusion of the liquid inside a droplet, a phenomenon that can be described analytically. The droplet size determination by low-field NMR has several significant advantages over other, and perhaps more obvious, methods. A summary of the typical ch...

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Section: B 0 Field Homogeneitymentioning

confidence: 99%

Scope of droplet size measurements in food emulsions by pulsed field gradient NMR at low field

Duynhoven

Goudappel

Dalen

et al. 2002

Magnetic Reson in Chemistry

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“…Large amplitude pulsed field gradients induce physical vibrations and eddy currents, which are both detrimental to ADC measurements. To minimize these effects, the methods described by Price et al (17) were adopted. These include utilization of sine-modulated diffusion-sensitizing gradient pulse shapes and "steady-state" gradient prepulses.…”

Section: Mr Experimentsmentioning

confidence: 99%

Sodium ion apparent diffusion coefficient in living rat brain

Goodman

Kroenke

Bretthorst

et al. 2005

Magnetic Resonance in Med

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The apparent diffusion coefficient (ADC) of Na ؉ was determined in live rat brain. The brain extracellular-to-intracellular Na ؉ content ratio is ϳ8:2, which is the inverse of that for water in these spaces. Consequently, the ADC of Na ؉ is primarily affected by motion in the extracellular space, and Na ؉ can be viewed as a reporter molecule for motion in that space. Likewise, water ADC is dominated by intracellular motion. The brain Na The rate constant governing water incoherent displacement in tissue, the apparent diffusion coefficient (ADC), decreases markedly following various injuries to brain tissue (1-6). Although this phenomenon is exploited daily in the clinical setting to detect injury via diffusion-weighted images, the underlying biophysical mechanisms that cause the water ADC to change are not comprehensively understood. Characterization of water incoherent displacement motion in the intra-and extracellular compartments following injury would provide an important advance toward the elucidation of these mechanisms. Unfortunately, resolution of the water MR signal in each of these two compartments in the CNS remains a difficult problem, although progress toward this goal has been reported (7,8).One strategy for making inferences about the motion of the water in each of these compartments is to employ endogenous or exogenous MR-active chemical species (ions and molecules) that are present in the aqueous phase of either or both spaces and that can be compartmentally distinguished. The sodium ion is potentially one such species. In the normally functioning central nervous system, as in virtually all tissues, significant amounts of intracellular and extracellular sodium ion are present, and the concentration gradient across the plasma membrane is held fixed. The sodium ion concentration is roughly 140 mM (9) and 10 mM (10) in the extracellular and intracellular spaces, respectively. Since the extracellular space comprises about 20% of brain volume (9), there are about 3.5 times more sodium ions in the extracellular compartment than there are in the intracellular compartment. Thus, roughly 80% of the 23 Na MR signal (assuming similar T 1 and T 2 relaxation times in both compartments) is from the extracellular space, making the sodium ion an endogenous, compartment selective (although not entirely compartment specific) marker of the extracellular space. For this reason, we have developed a method for determining the ADC of total tissue sodium ("bulk" sodium) in rat brain.Many technical challenges must be overcome to perform in vivo diffusion measurements of tissue sodium ions by 23 Na MR. First, 23 Na has a magnetogyric ratio, ␥, that is about one fourth that of the 1 H nuclide. As a result (vide infra), much stronger (ϳ16ϫ) diffusion encoding magnetic field gradients are required relative to those employed for 1 H MR water diffusion measurements. Second, the brain bulk sodium ion concentration is about 40 mM, much less than the ϳ80 M 1 H concentration of tissue water. Thus, to achieve an acceptable signal-...

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“…It is important to confirm that the two strong PFG's are equivalent for short . 16 If the pulse duration,  were too long, the magnetization may decay during the PFG application. The accuracy of short  values is related to a rectangular shape of the PFG pulse.…”

Section: Methodsmentioning

confidence: 99%

“…16,19 In the limit of the slip condition (c = 4), no interaction is assumed between a particle and surrounding molecules. When a particle interacts strongly with solvent molecules, the stick condition holds (c = 6).…”

Section: Stokes-einstein Relationmentioning

confidence: 99%

Strategies for Diagnosing and Alleviating Artifactual Attenuation Associated with Large Gradient Pulses in PGSE NMR Diffusion Measurements

Cited by 70 publications

References 15 publications

Scope of droplet size measurements in food emulsions by pulsed field gradient NMR at low field

Scope of droplet size measurements in food emulsions by pulsed field gradient NMR at low field

Sodium ion apparent diffusion coefficient in living rat brain

Translational and Rotational Motions for TFSA-Based Ionic Liquids Studied by NMR Spectroscopy

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