Use Of Nuclear Magnetic Resonance Imaging Research Articles

Landmarks for the Location of the Subthalamic Nucleus Using Magnetic Resonance Imaging

AbstractDeep brain stimulation has become an option for advanced Parkinson's disease treatment since the 1990s, but the first reports are from Benabid's team, a French neurosurgeon, in the 1980s. The subthalamic nucleus (STN), more specifically its dorsolateral portion, is the most commonly stimulated brain area. One of the major aspects for a good surgical result is the accurate location of this target. Therefore, the present article aimed to identify landmarks that facilitate and refine the location of the STN using nuclear magnetic resonance imaging (NMRI) of the skull. In order to achieve this goal, a search for articles was performed using the PubMed and Science Direct online databases, and articles regarding the use of NMRI to target STN were included. The precise location of the dorsolateral portion of the STN is fundamental to achieve the best possible effect on motor symptoms and to minimize side effects. One of the most used location methods is the NMRI, associated or not with tomography or ventriculography. The location strategies can be classified as direct and indirect. Landmarks are among the indirect strategies, and the most important ones (red nucleus, Sukeroku sign, dent internal capsule sign, supramammillary commissure, mammillothalamic tract, and interpeduncular cistern) are described in the present article. The various landmarks can be combined to locate with more accuracy the dorsolateral portion of the STN and the ideal position of the electrodes to achieve the best possible clinical result.

Void structure in textiles by nuclear magnetic resonance, Part I. Imaging of imbibed fluids and image analysis by calculation of fluid density autocorrelation functions

Void structure in textiles may be characterized by a variety of methods, including many based on nuclear magnetic resonance (NMR). The NMR techniques are based on the measurement of fluid distribution or diffusion within porous media, and are therefore particularly relevant for characterizing the void space that governs fluid interactions and movement within textile substrates. In this article, we describe the use of NMR imaging, also known as magnetic resonance imaging, to measure average void dimensions in textile fabrics. In addition to direct visualization using NMR images, void space may be analyzed by calculating the fluid density autocorrelation function. The advantages of both types of data analysis are discussed. These NMR techniques are applied to a water-saturated nylon fabric and the results compared to void sizes measured from optical microscopy.

Rapid sample-mixing technique for transient NMR and photo-CIDNP spectroscopy: applications to real-time protein folding.

We describe the development and application of a novel rapid sample-mixing technique for real-time NMR (nuclear magnetic resonance) spectroscopy. The apparatus consists of an insert inside a conventional NMR tube coupled to a rapid injection syringe outside the NMR magnet. Efficient and homogeneous mixing of solutions in the NMR tube is achieved with a dead time of tens of milliseconds, without modification of the NMR probe or additional hardware inside the magnet. Provision is made for the inclusion of an optical fiber to allow in situ laser irradiation of samples, for example to generate photo-CIDNP (chemically induced dynamic nuclear polarization). An NMR water suppression method has been implemented to allow experiments in H(2)O as well as in deuterated solvents. The performance of the device has been tested and optimized by a variety of methods, including sensitive detection of residual pH gradients and the use of NMR imaging to monitor the extent of mixing in real time. The potential utility of this device, in conjunction with the sensitivity and selectivity of photo-CIDNP, is demonstrated by experiments on the protein hen lysozyme. These measurements involve the direct detection of spectra during real-time refolding, and the use of CIDNP pulse labeling to study a partially unfolded state of the protein under equilibrium conditions. Magnetization transfer from this disordered state to the well-characterized native state provides evidence for the remarkable persistence of nativelike elements of structure under conditions in which the protein is partially denatured and aggregation prone.

Spatially resolved adsorption isotherms of thermally polarized perfluorinated gases in yttria-stabilized tetragonal-zirconia polycrystal ceramic materials with NMR imaging

This paper presents the results obtained by nuclear magnetic resonance (NMR) imaging of perfluorinated gases in mesoporuous solids. NMR images of nuclear spin density as a function of gas pressure permits spatially resolved measurements that are analogous to conventional bulk Brunauer-Emmett-Teller adsorption isotherm measurements. The use of NMR imaging allows the nondestructive evaluation of macroscopic spatial variations in the underlying mesoporous structure, for materials such as partially sintered Y-TZP (yttria-stabilized tetragonal-zirconia polycrystal) ceramics. All NMR measurements were performed with octafluorocyclobutane (C4F8) gas, using only the thermal Boltzman nuclear magnetization.

Characterizing Transport and Sorption in Ion-Specific Resin Columns Using Nuclear Magnetic Resonance (NMR) Imaging

The goal of this work is to assess the physical transport properties of Gd through an ion exchange column while determining the sorption properties of the resin. By coupling the physical transport with the chemical sorption, further insight into the behavior of the ion exchange resin can be gained. NMR imaging provides a powerful, non-destructive, means to extract spatial information from complex systems on a near real-time basis. An important example is liquid flow through granular media. With the use of a chemically reactive NMR contrast agent, the chemical speciation can be traced along the physical flow path of the granular media. In this study, trivalent gadolinium (Gd 3+ ) was selected based on its chemical similarity to typical high-level waste components, 241 Am and 244 Cm, and for its paramagnetic contrasting abilities in NMR experiments. NMR imaging results of flow experiments are provided showing a characteristic flow phenomena and resin column loading profiles. ICP-AES data are provided to show resin ion exchange capacities (IECs) and breakthrough curves. The use of NMR imaging with a Gd 3+ tracer will lead to a better understanding of the transport and sorption properties of these ion-specific resins. This technique can be applied to other complex flow systems such as environmental transport.

Use of NMR imaging in the optimization of a compression-coated regulated release system

Nuclear magnetic resonance (NMR) imaging is routinely used to detect the protons of mobile water molecules within samples. In this investigation, this non-destructive, non-invasive technique was used to determine the cause for faster than predicted drug release from a dissolution-based regulated-release tablet. The NMR images of tablets, from two different formulations, taken at various intervals of time while immersed in static USP dissolution medium showed that the tablet with faster than predicted drug release had a porous coating. The porous coat exposed more of the core surface area to the dissolution medium than desired and this caused an increase in the rate of dissolution of the core. The data presented in this paper demonstrate the usefulness of NMR imaging in solid dosage form development.

Evaluation of effects of PAF on alveolar fluid clearance with use of NMR imaging

Autologous serum with or without platelet-activating factor (PAF) was instilled into one lung lobe of an anesthetized cat, and changes in the regional lung water content were monitored for 4 h with proton nuclear magnetic resonance (NMR) images and relaxation time measurements. With serum as an instillate, water was cleared with a half time of approximately 670 min; after 4 h, 86 +/- 6% of that instilled remained. With PAF added to the instillate, clearance was biphasic with an initial clearance half time of approximately 30 min followed by clearance similar to that observed after serum instillation; after 4 h, 35 +/- 4% of that instilled remained. In contrast, 4 h after instillation of serum or serum plus PAF, 91 +/- 3% and 82 +/- 5%, respectively, of the instilled 125I-labeled albumin remained in the lung (P = 0.06). From transverse magnetization relaxation curves we were able to resolve two relaxation components, which we have attributed to the instilled fluid in the air spaces (relaxation time = 177 +/- 7 ms) and the tissue-bound fluid (relaxation time = 25 +/- 1 ms).

Imaging the Vascular Continuity ofPrunus aviumPetioles During Leaf Senescence Using Nuclear Magnetic Resonance Spectroscopy

Nuclear magnetic resonance (NMR) micro-imaging was used to study the distribution of mobile protons in the petiole and stem of Prunus avium throughout the period of senescence of an attached leaf. The base of the NMR micro-imaging probe was modified to allow access to the coil from below, enabling a branch of the intact tree to be inserted into the probe which, in turn, was inserted into the base of the NMR cryomagnet. A multi-slice image was used to determine the final orientation of the petiole in the probe. NMR spin echo imaging parameters were investigated by using variable relaxation delays (D1) ranging from 0·1 to 4·0 s. Transverse slices of the petiole with a D1 ranging between 1·0 to 4·0 s produced bright images corresponding to the cortex and leaving the xylem vessels as a dark horseshoe-shaped area. Reducing D1 to 0·25 s or 0·1 s produced images with more detail, differentiating the phloem and xylem vessels from the surrounding cortex. A longitudinal slice, 0·5 mm thick, through the stem and subtending petiole was imaged repeatedly over 6 d, during which the leaf senesced and abscinded. The images showed details of the vascular strands in the stem with a section continuous with the petiole. During leaf senescence the development of the abscission zone in the petiole was observed. The petiole remained hydrated throughout leaf senescence, demonstrating the usefulness of NMR imaging to probe the vascular integrity of the intact plant.

Determining tomato fruit maturity with nondestructive in vivo nuclear magnetic resonance imaging

Nuclear magnetic resonance (NMR) images were taken of freshly harvested fruit ( Lycopersicon esculentum cv. Castlemart). Measurements were also made of the stage of repeness, rate of carbon dioxide and ethylene production, lycopene and chlorophyll content, density of the pericarp wall, and consistency of the locular tissue. An NMR image at 256 × 256 pixel per image and 16 levels of intensity per pixel clearly showed many structural details of the fruit. Increased intensity was associated with liquefaction of the placental tissue during ripening, while grainines of the pericarp wall was associated with a decrease in wall density. In vivo NMR imaging of mature-green fruit produced images in which differences in maturity could be seen. The long required to produce an image and the cost of operation currently precludes the use of NMR imaging to sort mature-green tomato fruit.

CORRELATION AMONG CHANGES IN THE NUCLEAR MAGNETIC RESONANCE IMAGE OF RIPENING TOMATO FRUIT AND OTHER RIPENING PARAMETERS

Tomato fruit undergo an orderly series of physiological and morphological changes as they progress from mature-green (MG) to red-ripe. Fruit are commercially harvested at the MG stage, a stage which often encompasses fruit of varying degrees of maturity. The ability to predict the time required for MG fruit to ripen would reduce variability in experiments and could be commercially used to pack fruit that would ripen uniformly. Nuclear magnetic resonance (NMR) imaging can nondestructively measure internal changes associated with plant growth and developmental. In this study, NMR images were taken of freshly harvested tomato fruit (Lycopersicum esculentum cv. Castlemart) at different stages of maturity and ripeness. Measurements were also made of the stage of ripeness, rate of respiration and ethylene production, lycopene and chlorophyll content, density of the pericarp wall, and condition of locular tissue. NMR images showed substantial charges in the pericarp wall and locular tissue during maturation and ripening of tomato fruit. However, it was difficult to objectively evaluate these visual changes with other ripening parameters. For example, increased lightness and graininess of the pericarp wall image was associated with a decrease in wall density; while lightening of the locular image was associated with tissue liquefacation. Use of NMR imaging in studies of tomato fruit ripening will be discussed.

NMR Imaging of the Interfaces of Epoxy Adhesive Joints

Abstract Nuclear magnetic resonance imaging (NMRI) is used to study epoxy adhesive bonded structures at a proton resonance frequency of 300 MHz. Oligomeric and almost pure monomeric diglycidyl ethers of bisphenol-A, triethylenetetramine and xylene representing typical raw materials of epoxy adhesives are imaged at 25 and 50°C with varying repetition times to optimize measurement conditions for the adhesives. NMR images with good signal-to-noise ratios from the liquid epoxy adhesives are obtained at 50°C using the shortest possible echo times and a repetition time of 1 s. Chemical shift images of the glue-lines are presented and their possible uses in adhesive studies are discussed. The use of NMRI to detect heterogenous resin/resin and resin/curing agent mixtures is demonstrated. A non-invasive glue-line analysis is made of an aluminium/epoxy/aluminium sample with a model debonding by recording cross-sectional NMR images and a proton shadowgram.

Evaluation of muscle degeneration in inherited muscular dystrophy by nuclear magnetic resonance techniques

Nuclear magnetic resonance (NMR) techniques were applied to study the muscular dystrophy in chicks. The water proton spin-lattice relaxation times ( T 1) of fast, slow, and mixed muscles and plasma were measured. The T 1 values of dystrophic pectoralis major and posterior latissimus dorsi (PLD) were significantly higher than those of the normal pectoralis and PLD muscles. The present results establish a direct relationship between the differences in T 1 values and the severity of muscle degeneration. Consistent with this conclusion, it was also found that the T 1 values of muscles unaffected in muscular dystrophy, namely, the gastrocnemius, and anterior latissimus dorsi (ALD), were not different between the normal and dystrophic chicks. Although the affected muscles of dystrophic chicks contained higher percent water and fat than those of normal chicks, the results show that the higher T 1 values is dystrophic muscles were not solely due to variations in their water content. The increase in the T 1 values is principally a result of altered interaction between cellular water and macromolecules in the diseased muscles. These data also point out the potential use of NMR imaging in evaluating muscle degeneration.