Nuclear magnetic resonance imaging (MRI) has became an unavoidable medical tool in spite of its poor sensitivity. This fact motivates the efforts to enhance the nuclear magnetic resonance (NMR) probe performance. Thus, the nuclear spin excitation and detection, classically performed using radio-frequency coils, are required to be highly sensitive and homogeneous. The space harmonics suppression (SHS) method, already demonstrated to construct coil producing homogenous static magnetic field, is used in this work to design radio-frequency coils. The SHS method is used to determine the distribution of the electrical conductive wires which are organized in a saddle-coil-like configuration. The theoretical study of these SHS coils allows one to expect an enhancement of the signal-to-noise ratio with respect to saddle coil. Coils prototypes were constructed and tested to measure 1H NMR signal at a low magnetic field (8 mT) and perform MRI acquired at a high magnetic field (3 T). The signal-to-noise ratios of these SHS coils are compared to the one of saddle coil and birdcage (in the 3 T case) of the same size under the same pulse sequence conditions demonstrating the performance enhancement allowed by the SHS coils.

Nuclear magnetic resonance (NMR) experiments are usually carried out at very high and homogenous magnetic fields. However, portable systems have emerged in recent years at low fields, offering many advantages like easier maintenance and open design that permit us to imagine a variety of coil configurations in order to maximize the homogeneity of the static field B0 and the radio-frequency field B1. The wire winding distribution based on space harmonics suppression (SHS) of the cosine current density distribution offers new possibilities of producing homogenous static fields B0. In this work, an extension of the SHS method, allowing homogeneity enhancement and flexibility of the coil design, is presented. The efficiency of the method is demonstrated through the construction of homogenous magnetic field coils dedicated to a very low magnetic field (8 mT) 1H NMR spectrometer. The performance of these coils in terms of magnetic field intensity and homogeneity as well as self-heating behavior is compliant with in planta experiments for agronomic studies.

The climate warming implies an increase of stress of plants (drought and torrential rainfall). The understanding of plant behavior, in this context, takes a major importance and sap flow measurement in plants remains a key issue for plant understanding. Magnetic Resonance Imaging (MRI) which is well known to be a powerful tool to access water quantity can be used to measure moving water. We describe a novel flow-MRI method which takes advantage of inflow slice sensitivity. The method involves the slice selectivity in the context of multi slice spin echo sequence. Two sequences such as a given slice is consecutively inflow and outflow sensitive are performed, offering the possiblility to perform slow flow sensitive imaging in a quite straigthforward way. The method potential is demonstrated by imaging both a slow flow measurement on a test bench (as low as 10 μm.s−1) and the Poiseuille’s profile of xylemian sap flow velocity in the xylematic tissues of a tomato plant stem.

THREE-DIMENSIONAL VISUALIZATION OF THE INTERNAL ARRANGEMENT OF ONCHOCERCAL (ONCHOCERCA VOLVULUS) NODULES USING HIGH-RESOLUTION MAGNETIC RESONANCE IMAGING

Electromagnetic coils are ubiquitously used in the modern world in motors, antennas, etc. In many applications (magnetic field coil calibration and nuclear magnetic resonance spectroscopy and imaging) there is a strong need for a homogeneous magnetic field. In this paper, we propose a simple modelling based on serial Fourier decomposition allowing the determination of the electrical conductor distribution to make the magnetic field homogeneous. The method is valid both for plane and axisymmetric geometries. The method allows the retrieval of the classical configurations of saddle coil for the plane geometry and Helmholtz coil for the axisymmetric one. The method is generalized for any number of electrical conductors and brings the perspective of new homogeneous magnetic resonance imaging (MRI) coil configuration.

Nuclear magnetic resonance imaging (NMRI) is a powerful tool for biological investigations. Nevertheless, the imaging resolution performance results in the combination of the magnetic field (B0) and the antenna efficiency. This latter one results in a compromise between the size of the sample, the location of the region of interest and the homogeneity requirement. In the context of spinal cord imaging on mice, a ribbon solenoid coil is used to enhance the efficiency of the MRI experiment. This paper details the calculation of the local magnetization contribution to the induced voltage of MRI coils. The modeling is illustrated on ribbon solenoid antennas used in emitter–receiver mode for the study. The analytical model, which takes into account the emitting mode, the receiving step and the imaging sequence, is compared to the measurement performed on a 9.4 T VARIAN MRI apparatus. The efficiency of the antenna, in terms of signal to noise ratio, is significantly enhanced with respect to a commercial quadrature volumic antenna, given a significant advantage for the study of spinal cord injuries.

THREE-DIMENSIONAL VISUALIZATION OF THE INTERNAL ARRANGEMENT OF ONCHOCERCAL (ONCHOCERCA VOLVULUS) NODULES USING HIGH-RESOLUTION MAGNETIC RESONANCE IMAGING

Nuclear Magnetic Resonance spectroscopy and imaging can be classified as inductive techniques working in the nearto far-field regimes. We investigate an alternative capacitive detection with the use of micrometer sized probes positioned at sub wavelength distances of the sample in order to characterize and model evanescent electromagnetic fields originating from NMR phenomenon. We report that in this experimental configuration the available NMR signal is one order of magnitude larger and follows an exponential decay inversely proportional to the size of the emitters. Those investigations open a new road to a better understanding of the evanescent waves component in NMR with the opportunity to perform localized spectroscopy and imaging. NMR principles and Evanescent Waves The principle of Nuclear Magnetic Resonance is based on the detection of the magnetization originating from an ensemble of spins located on the atomic nucleus [1–3]. In living sciences, NMR spectroscopy and imaging of H, C, Na and P are of great interest and extensively studied [4, 5]. The sample is polarized by a static magnetic field B0 and spatially encoded by pulse gradients, giving to the nuclear spin distinct precessional movements at well separated Larmor frequencies. Radiofrequency pulses are used to tilt the axis of the magnetization; when the spin system recovers its equilibrium, it generates an electromagnetic field which is classically detected using an inductive coupling in the radiative near-field regime [6]. Radio frequencies are usually emitted from the sample in the range from 1MHz to 1 GHz. A good receiving setup can be made generally from a coil wrapped around the sample, a loopless catheter antenna [7] with a tuning/matching circuit [8] or electric potential sensor capacitively coupled to the sample [9]. In this contribution, we propose a completely different approach, with the use of micrometer-sized Evanescent Waves probe (EW-probe) working in a capacitive mode [10] positioned in the vicinity of the object of interest at submillimetric distances, well shorter than the wavelength of the radiated radio-frequency signal. Over the past decades, near-field PLOSONE | DOI:10.1371/journal.pone.0144483 January 11, 2016 1 / 8 a11111

Nuclear Magnetic Resonance spectroscopy and imaging can be classified as inductive techniques working in the nearto far-field regimes. We investigate an alternative capacitive detection with the use of micrometer sized probes positioned at sub wavelength distances of the sample in order to characterize and model evanescent electromagnetic fields originating from NMR phenomenon. We report that in this experimental configuration the available NMR signal is one order of magnitude larger and follows an exponential decay inversely proportional to the size of the emitters. Those investigations open a new road to a better understanding of the evanescent waves component in NMR with the opportunity to perform localized spectroscopy and imaging. NMR principles and Evanescent Waves The principle of Nuclear Magnetic Resonance is based on the detection of the magnetization originating from an ensemble of spins located on the atomic nucleus [1–3]. In living sciences, NMR spectroscopy and imaging of H, C, Na and P are of great interest and extensively studied [4, 5]. The sample is polarized by a static magnetic field B0 and spatially encoded by pulse gradients, giving to the nuclear spin distinct precessional movements at well separated Larmor frequencies. Radiofrequency pulses are used to tilt the axis of the magnetization; when the spin system recovers its equilibrium, it generates an electromagnetic field which is classically detected using an inductive coupling in the radiative near-field regime [6]. Radio frequencies are usually emitted from the sample in the range from 1MHz to 1 GHz. A good receiving setup can be made generally from a coil wrapped around the sample, a loopless catheter antenna [7] with a tuning/matching circuit [8] or electric potential sensor capacitively coupled to the sample [9]. In this contribution, we propose a completely different approach, with the use of micrometer-sized Evanescent Waves probe (EW-probe) working in a capacitive mode [10] positioned in the vicinity of the object of interest at submillimetric distances, well shorter than the wavelength of the radiated radio-frequency signal. Over the past decades, near-field PLOSONE | DOI:10.1371/journal.pone.0144483 January 11, 2016 1 / 8 a11111

Nuclear Magnetic Resonance spectroscopy and imaging can be classified as inductive techniques working in the near- to far-field regimes. We investigate an alternative capacitive detection with the use of micrometer sized probes positioned at sub wavelength distances of the sample in order to characterize and model evanescent electromagnetic fields originating from NMR phenomenon. We report that in this experimental configuration the available NMR signal is one order of magnitude larger and follows an exponential decay inversely proportional to the size of the emitters. Those investigations open a new road to a better understanding of the evanescent waves component in NMR with the opportunity to perform localized spectroscopy and imaging.

Cyano-bridged Gd(3+)/[Fe(CN)6](3-) coordination polymer nanoparticles of 3-4 nm stabilized with D-mannitol presenting a high r1 relaxivity value of 11.4 mM(-1) s(-1) were investigated in vivo as contrast agents (CA) for Magnetic Resonance Imaging (MRI). They allow an increase of the MR image contrast and can act as an efficient intravascular T1 CA with a relatively long blood-circulation lifetime (60 min) without specific toxicity.

Nondestructive studies of physiological processes in agronomic products require increasingly higher spatial and temporal resolutions. Nuclear Magnetic Resonance (NMR) imaging is a non-invasive technique providing physiological and morphological information on biological tissues. The aim of this study was to design a robust and accurate quantitative measurement method based on NMR imaging combined with contrast agent (CA) for mapping and quantifying water transport in growing cherry tomato fruits. A multiple flip-angle Spoiled Gradient Echo (SGE) imaging sequence was used to evaluate the intrinsic parameters maps M0 and T1 of the fruit tissues. Water transport and paths flow were monitored using Gd(3+)/[Fe(CN)6](3-)/D-mannitol nanoparticles as a tracer. This dynamic study was carried out using a compartmental modeling. The CA was preferentially accumulated in the surrounding tissues of columella and in the seed envelopes. The total quantities and the average volume flow of water estimated are: 198 mg, 1.76 mm(3)/h for the columella and 326 mg, 2.91 mm(3)/h for the seed envelopes. We demonstrate in this paper that the NMR imaging technique coupled with efficient and biocompatible CA in physiological medium has the potential to become a major tool in plant physiology research.

Background No reliable biomarkers are identified in KLS. However, few functional neuroimaging studies suggested hypoactivity in thalamic and hypothalamic regions during symptomatic episodes. Here, we investigated relative changes in regional brain metabolism in Kleine-Levin syndrome (KLS) during symptomatic episodes and asymptomatic periods, as compared to healthy controls. Methods Four drug-free male patients with typical KLS and 15 healthy controls were included. 18-F-fluorodeoxy glucose positron emission tomography (PET) was obtained in baseline condition in all participants, and during symptomatic episodes in KLS patients. All participants were asked to remain fully awake during the whole PET procedure. Results Between state-comparisons in KLS disclosed higher metabolism in paracentral, precentral, and postcentral areas, supplementary motor area, medial frontal gyrus, thalamus and putamen during symptomatic episodes, and decreased metabolism in occipital and temporal gyri. As compared to healthy control subjects, KLS patients in the asymptomatic phase consistently exhibited significant hypermetabolism in a wide cortical network including frontal and temporal cortices, posterior cingulate and precuneus, with no detected hypometabolism. In symptomatic KLS episodes, hypermetabolism was additionally found in orbital frontal and supplementary motor areas, insula and inferior parietal areas, and right caudate nucleus, and hypometabolism in the middle occipital gyrus and inferior parietal areas. Conclusion Our results demonstrated significant hypermetabolism and few hypometabolism in specific but widespread brain regions in drug-free KLS patients at baseline and during symptomatic episodes, highlighting the behavioral state-dependent nature of changes in regional brain activity in KLS.

Hemidystonia is usually 'secondary' to structural lesions within the cortico-striato-pallido-thalamic or the cerebello-thalamo-cortical loops. Globus pallidus internus Deep Brain Stimulation (GPi DBS) is a validated technique in the treatment of primary dystonia and still under assessment for secondary dystonia. Results of DBS in hemidystonia are limited and heterogeneous. Further knowledge concerning motor network organization after focal brain lesions might contribute to the understanding of this mitigated response to DBS and to the refinement of DBS indications and techniques in secondary dystonia. This study aimed to identify movement-related functional magnetic resonance imaging (fMRI) activation patterns in a group of hemidystonic patients in comparison to healthy controls (HC). Further analysis assessed recruitment pattern in different patient subgroups defined according to clinical and radiological criteria relevant to GPi DBS eligibility (hyperkinetic/hypokinetic and prepallidal/postpallidal). Eleven patients and nine HC underwent fMRI with a block-design alternating active and rest conditions. The motor paradigm consisted of self-paced elbow flexion-extension movements. The main results were as follows: single-subject studies revealed several activation patterns involving motor-related network regions; both ipsilesional and contralesional hemispheres showed abnormal patterns of activity; compared with HC, hemidystonic patients showed decreased brain activity in ipsilesional thalamus, pallidal and temporal areas during affected arm task execution; 'hypokinetic' subgroup was commonly related to widespread bilateral overactivity. This study provides additional arguments for case-by-case assessment of DBS surgery indication and target selection in hemidystonia. Single-lead approach might be unable to modulate a highly disorganized network activity in certain patients with this clinical syndrome.

In this paper, we report the synthesis of size-controlled (6 and 18nm) monodisperse magnetic iron oxide nanoparticles, from the pyrolysis of iron oxyhydroxide with oleic acid in high temperature solvents. Superconducting Quantum Interface Device (SQUID) measurements revealed that the iron oxide nanoparticles exhibit a superparamagnetic behavior at room temperature. In order to evaluate their potential applications as contrast agents in Nuclear Magnetic Resonance (NMR) imaging, we investigated using 1H NMR spectroscopy (at a magnetic field 4.7T) the changes in T1 and T2 relaxation times in the colloidal aqueous solution at various concentration of nanoparticles. The following transverse (r2) and longitudinal (r1) relaxivities were found: (r2=17.85mM−1s−1, r1=6.90mM−1s−1) and (r2=9.20mM−1s−1, r1=4.30mM−1s−1) for nanoparticle sizes of 18 and 6nm, respectively. These results confirm that the synthesized nanoparticles have both high r1 and r2 relaxivities and thus the capacity for positive or negative contrast enhancement. This effect increases with the nanoparticle size. We also developed a new recognition motif of a saccharide type (mannose coating) for targeting biological models (plants) at the tissue and cellular levels in order to track the flow of the water and saccharide (which are the main drivers of plant growth) in NMR imaging. Moreover, we demonstrated that this saccharide motif provides good biocompatibility and biodistribution in a physiological medium.

We present the case of a 43-year-old man with acute visual loss due to an optic chiasm cavernoma. Our clinical and imaging findings quickly led us to this diagnosis. As a clinical improvement spontaneously occurred soon after the initial diagnosis, we decided not to perform any surgical treatment. The visual evolution was satisfactory and, to date after a 36-months follow-up, no clinical worsening has been reported. We present this clinical case regarding our approach, primarily a close follow-up, as well as a review of the literature.Nous présentons le cas d’un homme de 43 ans présentant une baisse d’acuité visuelle brutale due à une hémorragie d’un cavernome chiasmatique. Puisqu’une amélioration spontanée significative survint rapidement après le saignement, nous décidions de ne pas traiter chirurgicalement la lésion. L’évolution visuelle fut satisfaisante et, à ce jour, après 36 mois de suivi, aucune aggravation ou récidive n’est survenue. Nous présentons ce cas pour l’approche clinique que nous avons choisi, c’est-à-dire une surveillance rapprochée, ainsi qu’une revue de la littérature.