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The exchange interactions in the Cr3+–Cr3+ ion pairs in the isostructural ABO3 (A = Ga, In, Sc) diamagnetic compounds have been examined using the magnetic resonance technique. The values of bilinear and biquadratic exchange interactions have been determined. It is shown that the biquadratic exchange in the Cr3+–Cr3+ pair in these compounds is caused by the exchange striction.

Purpose Diffusion tensor imaging is a magnetic resonance technique that provides information about the orientation and anisotropy of the white matter tracts. The aim of this study was to analyse diffusion tensor imaging quantitative parameters in idiopathic normal pressure hydrocephalus patients, in order to determine whether this method could correlate to clinical scores and cerebrospinal fluid flowmetry data. Methods and materials Fifteen consecutive patients with idiopathic normal pressure hydrocephalus and 15 age-matched controls underwent cerebrospinal fluid flowmetry and diffusion tensor imaging using a 1.5 Tesla system. Fractional anisotropy, mean diffusivity, axial diffusivity and radial diffusivity values were calculated using region of interest atlas-based tract-mapping in nine cerebral areas and compared among the two groups. In addition, for idiopathic normal pressure hydrocephalus patients, diffusion tensor imaging parameters were correlated to clinical scores (mini mental state examination and frontal assessment battery) and cerebrospinal fluid flowmetry data. Results Mean fractional anisotropy was significantly lower for the idiopathic normal pressure hydrocephalus group than for the control group in the forceps minor and motor cortex; the idiopathic normal pressure hydrocephalus group had significantly higher mean axial diffusivity for the genu of the corpus callosum and forceps minor. We did not find significant correlation between diffusion tensor imaging parameters and cerebrospinal fluid flowmetry and mini mental state examination, while we observed a correlation between forceps minor fractional anisotropy and frontal assessment battery; no correlation between flowmetry and clinical scores was found. Conclusion Our findings suggest that diffusion tensor imaging provides a non-invasive biomarker of white matter changes in idiopathic normal pressure hydrocephalus patients. Forceps minor is the best site to analyse. As diffusion tensor imaging offers a better correlation to clinical status than cerebrospinal fluid flowmetry, it should be included in the routine idiopathic normal pressure hydrocephalus protocol.

Conventional morphological magnetic resonance imaging (MRI) represents the standard imaging method for neuro-oncologic assessment; its primary roles consist of initial brain tumor evaluation.

Diseases such as Alzheimer's and cancer have been linked to metabolic dysfunctions, and further understanding of metabolic pathways raises hope to develop cures for such diseases. To broaden the knowledge of metabolisms in vitro and in vivo, methods are desirable for direct probing of metabolic function. Here, we are introducing a pulsed nuclear magnetic resonance (NMR) approach to generate hyperpolarized metabolites within seconds, which act as metabolism probes. Hyperpolarization represents a magnetic resonance technique to enhance signals by over 10 000‐fold. We accomplished an efficient metabolite hyperpolarization by developing an isotopic labeling strategy for generating precursors containing a favorable nuclear spin system to add para‐hydrogen and convert its two‐spin longitudinal order into enhanced metabolite signals. The transfer is performed by an invented NMR experiment and 20 000‐fold signal enhancements are achieved. Our technique provides a fast way of generating hyperpolarized metabolites by using para‐hydrogen directly in a high magnetic field without the need for field cycling.

Introduction Recent data have suggested that myocardial oedema followed bimodal pattern early post ST-segment elevation myocardial infarction (STEMI). Yet, there was disagreement between oedema quantified by cardiac magnetic resonance (CMR) imaging and tissue desiccation. Using highly-sensitive T1 mapping we sought to study the temporal changes in the extent and intensity of injured myocardium within one week post STEMI. Methods A first group (n=31) underwent three 3 T-CMR scans (time-point (TP) Results The mean T1 relaxation time value within the AAR of the first group was reduced after 24 hours (p Conclusion The intensity of oedema post-STEMI followed a bimodal pattern; while the extent of AAR did not track the same course. This discrepancy has implications for use of CMR in this context and may explain the previously reported disagreement between oedema quantified by imaging and tissue desiccation.

Osteoporosis, characterized by increased fracture risk and bone fragility, impacts millions of adults worldwide, but effective, non-invasive and easily accessible diagnostic tests of the disease remain elusive. We present a magnetic resonance (MR) technique that overcomes the motion limitations of traditional MR imaging to acquire high-resolution frequency-domain data to characterize the texture of biological tissues. This technique does not involve obtaining full two-dimensional or three-dimensional images, but can probe scales down to the order of 40 μm and in particular uncover structural information in trabecular bone. Using micro-computed tomography data of vertebral trabecular bone, we computationally validate this MR technique by simulating MR measurements of a ‘ratio metric’ determined from a few k -space values corresponding to trabecular thickness and spacing. We train a support vector machine classifier on ratio metric values determined from healthy and simulated osteoporotic bone data, which we use to accurately classify osteoporotic bone.

Objective: To compare a novel cardiovascular magnetic resonance technique for the assessment of left ventricular (LV) mechanical discoordination by characterizing the endocardial center motion (ECM) in short-axis cine MRI in healthy volunteers and heart failure patients with left bundle branch block (HF-LBBB). Approach: To evaluate ECM analysis as mechanical discoordination measure, we retrospectively compared spatial and temporal features of the ECM between a group of healthy volunteers (n = 14) and conduction defect patients (HF-LBBB, n = 31). We tracked the center of the endocardial borders on short-axis view MRI cine loops during the cardiac cycle. From the ECM trajectory we calculated the overall traveled distance, the enclosed area, the eccentricity of the trajectory, and the maximum traveled distance. The ECM can be visualized in spatial coordinates as well as by its temporal behavior. We evaluated the classification performance of these measures for LBBB detection. We also quantified the coherence of the ECM on the longitudinal direction by considering the variability of the ECM measures between different short-axis slices. Main results: Patients with LBBB showed significantly higher traveled distance (p < 0.0001), enclosed area (p < 0.002), eccentricity (p < 0.02), and peak displacement (p < 0.02) of the endocardial center. Patients with positive late gadolinium enhancement showed a higher variability of ECM measures across different slices (p < 0.05). Significance: ECM analysis is feasible and it allows the assessment of left ventricular mechanical discoordination. Differences in ECM measures permit one to distinguish between LBBB and healthy volunteers.

A method for determining the orientation of nitrogen-vacancy (NV) defect structure orientation in diamond crystals and nanodiamonds is proposed, which is based on the optically detected magnetic resonance technique with magnetic field modulation and microwave frequency scanning.

In the present study, thirty patients in the age range of 22 to 63 years of age were included after being diagnosed to be having brain tumour on CT scan or conventional MRI. In addition DWI, MRS, and PWI were carried out in these patients. All the patients with suspicious malignant lesions were then subjected to FDG-PET examination. Histopathological correlation was obtained in all the patients to serve as gold standard against which other modalities will be assessed for their sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy. Out of thirty patients selected for this study, twenty cases were found to be malignant and ten cases were benign on Histopathological evaluation. Majority of malignant lesions were glioblastoma multiforme. Amongst benign cases, majorities were meningioma, one was a Granulomatous lesion and one was a benign cystic lesion. MRI including the novel techniques showed high sensitivity and specificity in identifying malignant brain lesions and has a future role in better characterization of brain tumours. Wherever available, it should be integrated in routine workup of patients presenting with brain tumours or for follow up of patients undergone surgery / adjuvant chemotherapy.

Radiotracer and spin-labeled magnetic resonance technique development has greatly advanced in the last two decades providing myriad new targeted ligands and biologics for targeting a multitude of receptors, enzymes, saccharides, metabolites, and cellular processes. The majority of these new ligands have been validated in cancer models, reflecting the distribution of funding from federal and other sources. However, infections remain a prevalent scourge in developing nations and are re-emerging as a serious threat in developed nations in the form of antibiotic-resistant infections. The need to confirm and locate infections, especially in inaccessible anatomic locations, should be high priority both to understand the biological processes involved and as an aid to clinicians. Imaging the host response, in particular, can help scientists understand how effector and innate immune cells respond and understand the impact of antimicrobial treatments.

Arterial spin labeling (ASL) is a non-invasive magnetic resonance technique for tissue perfusion quantification working without contrast media application. The method uses magnetically labeled blood protons as intrinsic tracer. Perfusion-weighted images are obtained by the signal difference between an image with proximal labeling of the arterial water protons and a control image. Initially designed for cerebral perfusion measurement, the ASL technique is increasingly being used for the evaluation of extracranial organs which might be attributed to the improvements in scanner, coil and sequence technology but also to the elaboration of postprocessing tools. In this review, the basic principles of ASL are explained. Technical difficulties in ASL sequence design are discussed. To illustrate the potential role of ASL in clinical research and diagnostics, comparison of ASL with other methods currently applied for perfusion assessment is performed. Finally, a variety of clinical applications of ASL is presented with respect to the current literature.

Introduction:There is a clear clinical need to reliably detect residual cholesteatoma after canal wall up mastoid surgery. Ideally, this would be achieved through non-invasive radiological means rather than second-look surgery, thus preventing morbidity in those patients in whom no residual disease is found.Case report:We describe a case in which non-echo-planar, diffusion-weighted magnetic resonance imaging sequences were used pre-operatively, and compared with subsequent surgical findings. This case highlights both the potential of this increasingly popular magnetic resonance technique and also its current limitations.Discussion:Various magnetic resonance sequencing types have been employed to try to reliably detect residual cholesteatoma, each with varying success. Non-echo-planar, fast-spin echo, diffusion-weighted sequences currently appear to be the most reliable at detecting even the smallest pearl of cholesteatoma, down to 2 mm in diameter. In our unit, a propeller, diffusion-weighted image sequence is employed on a GE Signa scanner. However, both this case study and other reports show that the accuracy of the technique is not 100 per cent. This begs the question of how much one can rely on the findings of such techniques when deciding whether second-look surgery is indicated. Scan-negative patients will require continued follow up as, at the time of imaging, residual disease may not have reached a detectable size.

Diffusion-weighted imaging is a noninvasive magnetic resonance technique that is capable of measuring icroscopic movement of water molecules (ie, random or Brownian motion) within biologic tissues. Diffusion weighting is achieved with a pulsed-field gradient that leaves "static" spins unaffected but causes dephasing of spin ensembles that experience different motion histories according to their diffusion paths, with respect to the direction of the gradient. This article focuses on the interesting opportunities of the use of diffusion weighted imaging in the diagnosis of musculoskeletal diseases, including trauma, tumor, and inflammation.

Sensitivity encoding (SENSE) is a magnetic resonance technique that unifies gradient and receive coil encoding. SENSE reconstructs the image by solving a large, ill-conditioned inverse problem, which generally requires regularization and preconditioning. The present study suggests a simple heuristic for determining the regularization parameter. Also discussed are the use of density weighting and intensity correction as preconditioners and the role that coil sensitivity estimation has in regularization. A modification to the intensity correction is proposed for use with a phase constraint.

Since the discovery that lithium (Li) is efficacious for the treatment of manic depressive illness, the brain Li distribution of mammals treated with lithium has been of interest. However, the spatial relationship of lithium in the brain regions to its function remains largely unknown. Knowledge of Li distribution in the brain is necessary to localize its action in the brain. Both the therapeutic and neurotoxic side effects of Li are centered mainly in the central nervous system and hence there is considerable interest in understanding the extent of lithium penetration into the central nervous system. The mechanism by which neurotoxic side effects are generated is not known and may, in part, be related to the particular distribution of lithium in the brain. The regional specificity in lithium's brain distribution could underlie important steps on its action. Li levels in various brain regions for autopsied rats and humans have been reported. However, many results are conflicting due to ion redistribution at death or during sample preparation. A direct nondestructive measurement of Li levels in the brain where the drug exerts its effects is certainly desirable. Because magnetic resonance technique can be used to observe Li, it can be an appropriate method to monitor and map the distribution in the brain. The application of MR technology to rat brain regions has provided information on lithium distribution in a non-invasive manner. The earlier development work at lower field strengths provided brain lithium information at high dose of Li administration. Here we demonstrate the feasibility of quantitative spectroscopic imaging on rat brain under therapeutic doses.

AIM: To compare the objective and subjective image quality of non-contrast three-dimensional (3D) navigator-gated balanced steady state free precession magnetic resonance angiography (NC-MRA) and contrast-enhanced magnetic resonance angiography (CE-MRA) along the entire thoracic aorta. MATERIALS AND METHODS: Fifty consecutive patients with thoracic aortic disease underwent NC-MRA and CE-MRA using a 1.5 T MRI system. Vessel sharpness was assessed using signal intensity profiles at five predefined levels of the thoracic aorta. Two readers scored subjective quality. Manual diameter measurements of both readers were used for calculation of interobserver variation. RESULTS: NC-MRA resulted in significantly sharper delineation of the aortic root, ascending aorta, and distal descending aorta compared to CE-MRA. Sharpness was comparable at the level of the arch and proximal descending aorta. NC-MRA resulted in significantly better subjective image quality. Interobserver agreement for diameter measurements was excellent for both techniques. CONCLUSION: NC-MRA resulted in superior image quality for assessment of the thoracic aorta and in better vessel sharpness for assessment of the aortic root and ascending aorta, when compared to CE-MRA. NC-MRA can be considered the MRA technique of choice for the assessment of the thoracic aorta diameters in clinical practice. (C) 2017 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved

In this study, we aimed to determine the relationship between the size of cerebral structures evaluated by quantitative magnetic resonance technique and the ability of performing rapid-velocity limb movements. Forty-seven healthy women with a mean age of 43.4 years (range 22–68) were included. Exclusion criteria were systemic diseases including alcoholism. Finger and ankle tapping were quantitatively recorded for both right and left extremities. A mean value for the right and left side was calculated. To determine atrophy, we measured the area of the corpus callosum, the cerebrum and the cerebellum on midline sagittal sections. On transverse images, the ventricle-to-brain ratio, the bifrontal ratio and the bicaudate ratio were selected as atrophy parameters. Also, the prevalence of white matter hyperintensities was assessed. Fifteen (32%) had hyperintense white matter lesions. Using simple regression analysis, the frequencies of both finger (r = 0.37, β = –0.002, p = 0.022) and ankle (r = 0.35, β = –0.001, p = 0.032) tapping were associated with reduced cerebellar size. No association was found for other atrophy parameters or the number of hyperintense white matter lesions. This study indicates that impaired ability to perform fast limb movements may be related to a relative cerebellar atrophy.

A new magnetic resonance technique to measure perfusion is described in detail. The means by which this is done is to invert all the spins in the radiofrequency RF coil with a non-spatially selective pulse and immediately re-invert the spins in the imaging plane. The net effect is that the spins in the imaging plane experience minimal perturbation of their magnetization while the spins outside the plane (extraslice) are inverted, or tagged. Tagged spins that flow into the imaging plane before image data are acquired decrease the signal intensity in the imaging plane when compared with an image in which the inflowing spins are not tagged. This decrease in signal can be used to calculate the number of spins that have flowed into the imaging plane, i.e., can be used to calculate the perfusion in mL · 100 gtissue−1 · min−1. The extraslice spin tagging (EST) magnetization preparation period was coupled with a fast imaging sequence to obtain perfusion maps for normal volunteers. J. Magn. Reson. Imaging 1999;9:146–150 © 1999 Wiley-Liss, Inc.

We investigate theoretically the use of time-varying magnetic fields to selectively create and manipulate quasiparticles in magnetically trapped Bose condensates. To maximize the transition matrix element connecting two desired quasiparticle states, the spatial symmetry of the applied magnetic field must be tailored to exploit the different spatial distributions of magnetization in the two quasiparticle states. This ‘‘spatial magnetic resonance’’ effect is analogous to the Franck-Condon factor in electric dipole transitions in diatomic molecules. Experimentally, the spatial magnetic resonance technique may allow the creation of coherences between quasiparticle states, the inversion of quasiparticle state populations, the measurement of quasiparticle lifetimes ~T1! and decoherence times ~T2!, the creation of quasiparticle echoes, etc., in analogy with conventional spin magnetic resonance. @S1050-2947~97!04306-0#

Rate constants k1, k2, and k3 have been measured at 298 K by means of a laser photolysis-laser magnetic resonance technique and (or) by a laser photolysis-infrared chemiluminescence detection technique (LMR and IRCL, respectively). \hfill\hbox to 12em{$\rm Cl+I_2\longrightarrow ICl+I;$}\hbox to 8em{$\rm {\it k}_1=(2.5\pm 0.7)\times 10^{-10}(IRCL)$}\hfill(1)\\\hfill\hbox to 12em{}\hbox to 8em{$\rm {\it k}_1=(2.8\pm 0.8)\times 10^{-10}(LMR)$}\hfill \\\hfill\hbox to 12em{$\rm SiCl_3+I_2\longrightarrow SiCl_3I+I;$}\hbox to 8em{$\rm {\it k}_2=(5.8\pm 1.8)\times 10^{-10}(IRCL)$}\hfill (2)\\\hfill\hbox to 12em{$\rm SiH_3+I_2\longrightarrow SiIH_3+I;$}\hbox to 8em{$\rm {\it k}_3=(1.8\pm 0.46)\times 10^{-10}(LMR)$}\hfill (3)\\ As an average of the LMR and IRCL results we offer the value k1 = (2.7 ± 0.6) × 10−10. Units are cm3 molecule−1 s−1; uncertainties are 2σ including precision and estimated systematic errors. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 25–33, 1997.

Synthetic polymers belong to the vast realm of soft matter and are one of the key types of materials to address societal needs at the beginning of the twenty-first century. Polymer science progressively addresses questions that deal with tuning mesoscopic and macroscopic structures and functions of polymers by understanding the effects that govern these systems on the nanoscopic level. EPR spectroscopy as a local, sensitive, and extremely specific magnetic resonance technique in many cases shows sensitivity on well-suited length- (0–10 nm) and time scales (μs–ps) and can deliver unique information on structure, dynamics, and in particular function of polymeric systems. A short review of recent literature is given and the power of simple EPR methods, especially CW EPR performed on a low-cost benchtop spectrometer, to elucidate complex polymeric materials is shown with specific examples from thermoresponsive polymer systems. These bear great potential in molecular transport and biomedical applications (e.g., drug delivery) and insights into interactions between carrier and small molecule are fundamental for designing and tuning these materials.

Workers attending patients diagnosed by magnetic resonance technique are exposed to strong static magnetic field (SMF) in the vicinity of magnets of scanners (MRI scanners). Currents induced in the body of worker moving in strong, heterogeneous SMF in the vicinity of MRI scanner magnet should be consider among risk factors related to such exposure. Registration of magnetic field at the surface of body of worker performing normal activities with patients can be used for assessment of induced currents hazards. Examples of results of such investigations in MRI centers in Poland are presented. Proposal for the use of standardized basic simple movements and measurements of exposure pattern related to such movements for evaluation of induced currents hazards is discussed.

(1991). MRI and Breast Cancer: A New Magnetic Resonance Technique Specifically Designed for the Breast. Baylor University Medical Center Proceedings: Vol. 4, No. 4, pp. 13-16.

Background Transthoracic Doppler-echocardiography (TTE) is the standard clinical method for diagnosis and staging of aortic stenosis (AS). AS staging is based on measurement of aortic peak velocity, transvalvular gradient, and calculation of aortic valve area. Unidirectional throughplane phase-contrast magnetic resonance imaging (1DPC-MRI) has been widely applied in clinical imaging to quantify aortic peak velocities and flow. Nonetheless, 1DPC-MRI requires accurate positioning of imaging planes perpendicular to flow direction in order to avoid peak velocity underestimation, which can be challenging in patients with multiple or eccentric jets. Therefore PC techniques with multi-directional velocity quantification would likely improve the accuracy of velocity determination, and allow for more accurate grading of AS severity. The aim of this study is to determine whether a rapid technique that is able to capture 3 directions of velocity in a 2D image plane in a single breath-hold (3DPCMRI) provides more accurate estimation of diagnostic parameters compared with the traditional 1DPC-MRI, using TTE as the reference standard.

Purpose: To measure 3-dimensional (3D) posterior cranial fossa (PCF) crowdedness and to evaluate the effect of age, sex, and body height on PCF. Material and Methods: Fifty-two healthy volunteers (24 M and 28 F; mean age 55.4±17.2 years; range 24–82 years) were recruited. Using a semi-automated magnetic resonance technique, we calculated a PCF crowdedness index (CI) as the ratio of hindbrain (HB) volume to PCF volume ×100% and correlated this index with age, sex, body height, and other crowdedness parameters. Results: The mean PCF CI was 93.7±2.7%. Women had a more crowded PCF than men (95.0±1.7% versus 92.1±2.7%; P Conclusion: Our study shows that PCF CI is associated with age and sex, and can therefore be used as a surrogate to assess hindbrain atrophy in a cross-sectional sample. Moreover, sex- and age-specific normal ranges may be needed to evaluate the PCF CI in clinical practice.

Important grown‐in nonradiative defects in Si epilayers and SiGe/Si heterostructures prepared by molecular beam epitaxy are studied by the optically detected magnetic resonance technique. Several nonradiative defects are observed that have been introduced by ion bombardment during growth or by the low surface adatom mobility during low‐temperature growth. These defects are shown to provide efficient nonradiative channels for carrier recombination and, to a large extent, control the carrier lifetime.

Purpose To assess tissue iron concentrations by the use of a gradient echo T2* multiecho technique. Materials and Methods We compared the results of measurements of heart T2* from 32 patients using the established multiple breath-hold variable TR technique with a new multiecho sequence that acquires all images within a single breath-hold with constant TR. Results There was good agreement of myocardial T2* values between both methods in the abnormal range of T2* < 20 msec (mean difference 0.2msec, 95% CI −1.3 to 0.9 msec, r = 0.97, P < 0.0001). The coefficient of variability between the methods was 3.5%. The interstudy reproducibility using the multiecho sequence had a variability coefficient of 2.3% in the abnormal T2* range and 5.8% over all T2* values. There was good agreement between the techniques for the liver T2* values. Conclusions The use of the single breath-hold, multiecho acquisition allowed reliable quantification of myocardial T2*. The good reproducibility, speed, and T1 independence of this technique allows greater accuracy, faster patient throughput, and, therefore, reduced costs (which is important in developing countries where thalassemia is most prevalent). J. Magn. Reson. Imaging 2003;18:33–39. © 2003 Wiley-Liss, Inc.

Oxygenation (pO2) is a major variable in many types of cancer treatment. This includes radiation therapy1–6, photodynamic therapy7–9 and certain chemotherapeutic agents10–17. The pO2 level can affect the response of tumors to therapy, especially in the critical range below 10 mmHg, where increasing hypoxia results in increased resistance to radiotherapy18. If it were possible to measure pO2 in tumors, then it might be possible to optimize the type and timing of treatment.