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1

Magnetic resonance imaging of the elbow. Part I: Normal anatomy, imaging technique, and osseous abnormalities  

Microsoft Academic Search

Part I of this comprehensive review on magnetic resonance imaging of the elbow discusses normal elbow anatomy and the technical factors involved in obtaining high-quality magnetic resonance images of the elbow. Part I also discusses the role of magnetic resonance imaging in evaluating patients with osseous abnormalities of the elbow. With proper patient positioning and imaging technique, magnetic resonance imaging

Richard Kijowski; Michael Tuite; Matthew Sanford

2004-01-01

2

Visualization of coronary venous anatomy by cardiovascular magnetic resonance  

PubMed Central

Background Coronary venous imaging with whole-heart cardiovascular magnetic resonance (CMR) angiography has recently been described using developmental pulse sequences and intravascular contrast agents. However, the practical utility of coronary venous imaging will be for patients with heart failure in whom cardiac resynchronisation therapy (CRT) is being considered. As such complementary information on ventricular function and myocardial viability will be required. The aim of this study was to determine if the coronary venous anatomy could be depicted as part of a comprehensive CMR protocol and using a standard extracellular contrast agent. Methods and Results Thirty-one 3D whole heart CMR studies, performed after intravenous administration of 0.05 mmol/kg gadolinium DTPA, were reviewed. The cardiac venous system was visualized in all patients. The lateral vein of the left ventricle was present in 74%, the anterior interventricular vein in 65%, and the posterior interventricular vein in 74% of patients. The mean maximum distance of demonstrable cardiac vein on the 3D images was 81.5 mm and was dependent on the quality of the 3D data set. Five patients showed evidence of myocardial infarction on late gadolinium enhancement (LGE) images. Conclusion Coronary venous anatomy can be reliably demonstrated using a comprehensive CMR protocol and a standard extracellular contrast agent. The combination of coronary venous imaging, assessment of ventricular function and LGE may be useful in the management of patients with LV dysfunction being considered for CRT. PMID:19671132

Younger, John F; Plein, Sven; Crean, Andrew; Ball, Stephen G; Greenwood, John P

2009-01-01

3

Human tooth pulp anatomy visualization by 3D magnetic resonance microscopy  

PubMed Central

Background Precise assessment of dental pulp anatomy is of an extreme importance for a successful endodontic treatment. As standard radiographs of teeth provide very limited information on dental pulp anatomy, more capable methods are highly appreciated. One of these is 3D magnetic resonance (MR) microscopy of which diagnostic capabilities in terms of a better dental pulp anatomy assessment were evaluated in the study. Materials and methods Twenty extracted human teeth were scanned on a 2.35 T MRI system for MR microscopy using the 3D spin-echo method that enabled image acquisition with isotropic resolution of 100 ?m. The 3D images were then post processed by ImageJ program (NIH) to obtain advanced volume rendered views of dental pulps. Results MR microscopy at 2.35 T provided accurate data on dental pulp anatomy in vitro. The data were presented as a sequence of thin 2D slices through the pulp in various orientations or as volume rendered 3D images reconstructed form arbitrary view-points. Sequential 2D images enabled only an approximate assessment of the pulp, while volume rendered 3D images were more precise in visualization of pulp anatomy and clearly showed pulp diverticles, number of pulp canals and root canal anastomosis. Conclusions This in vitro study demonstrated that MR microscopy could provide very accurate 3D visualization of dental pulp anatomy. A possible future application of the method in vivo may be of a great importance for the endodontic treatment. PMID:22933973

Sustercic, Dusan; Sersa, Igor

2012-01-01

4

Assessment of Cardiovascular Anatomy in Patients with Congenital Heart Disease by Magnetic Resonance Imaging  

Microsoft Academic Search

.   The following discussion addresses the assessment of cardiovascular anatomy in patients with congenital heart disease by\\u000a magnetic resonance (MR). The focus of this review is on the techniques of performing the MR examination. In particular, individual\\u000a pulse sequences are described and illustrated with their strengths and weaknesses. Imaging strategies using the described\\u000a pulse sequences are proposed. The pulse sequences

T. Chung

2000-01-01

5

Magnetic resonance cholangiography in assessing biliary anatomy in living donors: A meta-analysis  

PubMed Central

AIM: To establish the role of magnetic resonance cholangiography (MRC) in diagnosis of biliary anatomy in living-donor liver transplantation (LDLT) donors. METHODS: A systematic review was performed by searching electronic bibliographic databases prior to March 2013. Studies with diagnostic results and fulfilled inclusion criteria were included. The methodological quality of the studies was assessed. Sensitivity, specificity and other measures of the accuracy of MRC for diagnosis of biliary anatomy in LDLT donors were summarized using a random-effects model or a fixed-effects model. Summary receiver operating characteristic (SROC) curves were used to summarize overall test performance. Publication bias was assessed using Deek’s funnel plot asymmetry test. Sensitivity analysis was adopted to explore the potential sources of heterogeneity. RESULTS: Twelve studies involving 869 subjects were eligible to the analysis. The scores of Quality Assessment of Diagnostic Accuracy Studies for the included studies ranged from 11 to 14. The summary estimates of sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic OR of MRC in diagnosis of biliary anatomy in LDLT donor were 0.88 (95%CI: 0.84-0.92), 0.95 (95%CI: 0.93-0.97), 15.33 (95%CI: 10.70-21.95), 0.15 (95%CI: 0.11-0.20) and 130.77 (95%CI: 75.91-225.27), respectively. No significant heterogeneity was detected in all the above four measures. Area under SROC curve was 0.971. Little publication bias was noted across the studies (P = 0.557). Sensitivity analysis excluding a study with possible heterogeneity got a similar overall result, which suggested the little influence of this study on the overall results. CONCLUSION: Our results suggest that MRC is a high specificity but moderate sensitivity technique in diagnosis of biliary anatomy in LDLT donors. PMID:24363536

Xu, Yu-Biao; Bai, Yu-Long; Min, Zhi-Gang; Qin, Shan-Yu

2013-01-01

6

Computed Tomography and Magnetic Resonance Anatomy of the Normal Orbit and Eye of the Horse.  

PubMed

Traumatic and infectious diseases of the eye and orbit can occur in horses. For diagnosis and monitoring of such diseases, medical imaging is useful including computed tomography (CT) and magnetic resonance imaging (MRI). The aim of the current study was to describe CT and MRI anatomy of the equine orbit and ocular globe. The heads from four adult horses were scanned with a 6-slice Emotion 6 CT (Siemens, Erlangen), and a 3.0 Tesla Siemens Verio 6 MRI using T1 and T2-weighted sequences. To validate CT and MR reference images, these were compared with anatomical models and gross anatomical sections. The bony limits of the orbital cavity, the relationship of the orbit with sinuses and foramina of the skull were well identified by CT. MRI was useful to observe soft tissues and was able to identify adnexae of the ocular globe (eyelids, periorbital fat, extraocular muscles, lacrymal and tarsal glands). Although MRI was able to identify all components of the eye (including the posterior chamber), it could not differentiate sclera from choroid and retina. The only nerve identified was the optic nerve. Vessels were not seen in this series of cadaver heads. This study showed that CT and MRI are useful techniques to image the equine orbit and eye that can have clinical applications. PMID:25294111

D'Août, C; Nisolle, J F; Navez, M; Perrin, R; Launois, T; Brogniez, L; Clegg, P; Hontoir, F; Vandeweerd, J M

2014-10-01

7

Solid-state nuclear magnetic resonance microscopy demonstrating human dental anatomy  

Microsoft Academic Search

Objective. Magnetic resonance imaging has become a common diagnostic tool in medical practice. It is a common view that solid-state material lacking a sufficient amount of unpaired nuclear spins, in particular proton spins, is impossible to depict with clinically used magnetic resonance devices. Characteristically rapid dephasing, caused by relatively short spin-spin relaxation (T2 time) also leads to broad resonance lines.

Thorsten R. Appel; Michael A. Baumann

2002-01-01

8

Systematic comparison and reconstruction of sea urchin (Echinoidea) internal anatomy: a novel approach using magnetic resonance imaging  

PubMed Central

Background Traditional comparative morphological analyses and subsequent three-dimensional reconstructions suffer from a number of drawbacks. This is particularly evident in the case of soft tissue studies that are technically demanding, time-consuming, and often prone to produce artefacts. These problems can partly be overcome by employing non-invasive, destruction-free imaging techniques, in particular micro-computed tomography or magnetic resonance imaging. Results Here, we employed high-field magnetic resonance imaging techniques to gather numerous data from members of a major marine invertebrate taxon, the sea urchins (Echinoidea). For this model study, 13 of the 14 currently recognized high-ranking subtaxa (orders) of this group of animals were analyzed. Based on the acquired datasets, interactive three-dimensional models were assembled. Our analyses reveal that selected soft tissue characters can even be used for phylogenetic inferences in sea urchins, as exemplified by differences in the size and shape of the gastric caecum found in the Irregularia. Conclusion The main focus of our investigation was to explore the possibility to systematically visualize the internal anatomy of echinoids obtained from various museum collections. We show that, in contrast to classical preparative procedures, magnetic resonance imaging can give rapid, destruction-free access to morphological data from numerous specimens, thus extending the range of techniques available for comparative studies of invertebrate morphology. PMID:18651948

Ziegler, Alexander; Faber, Cornelius; Mueller, Susanne; Bartolomaeus, Thomas

2008-01-01

9

Pulmonary artery anatomy in congenital heart disease with decreased pulmonary blood flow by magnetic resonance imaging  

Microsoft Academic Search

We performed magnetic resonance imaging (MRI) in 65 patients (ages 8 days to 17 years old) with congenital heart disease accompanied by pulmonary atresia or stenosis, who had not undergone radical or functional repair of the heart to assess the usefulness of MRI in evaluating the pulmonary artery (PA) tree and calculating the diameter of the pulmonary arteries. Imaging was

Koichiro Niwa; Mika Uchishiba; Hiroyuki Aotsuka; Shigeru Tateno; Kimimasa Tobita; Hiromichi Hamada; Tadashi Fujiwara; Kozo Matsuo

1997-01-01

10

Volume rendering based on magnetic resonance imaging: advances in understanding the three-dimensional anatomy of the human knee  

PubMed Central

The choice of medical imaging techniques, for the purpose of the present work aimed at studying the anatomy of the knee, derives from the increasing use of images in diagnostics, research and teaching, and the subsequent importance that these methods are gaining within the scientific community. Medical systems using virtual reality techniques also offer a good alternative to traditional methods, and are considered among the most important tools in the areas of research and teaching. In our work we have shown some possible uses of three-dimensional imaging for the study of the morphology of the normal human knee, and its clinical applications. We used the direct volume rendering technique, and created a data set of images and animations to allow us to visualize the single structures of the human knee in three dimensions. Direct volume rendering makes use of specific algorithms to transform conventional two-dimensional magnetic resonance imaging sets of slices into see-through volume data set images. It is a technique which does not require the construction of intermediate geometric representations, and has the advantage of allowing the visualization of a single image of the full data set, using semi-transparent mapping. Digital images of human structures, and in particular of the knee, offer important information about anatomical structures and their relationships, and are of great value in the planning of surgical procedures. On this basis we studied seven volunteers with an average age of 25 years, who underwent magnetic resonance imaging. After elaboration of the data through post-processing, we analysed the structure of the knee in detail. The aim of our investigation was the three-dimensional image, in order to comprehend better the interactions between anatomical structures. We believe that these results, applied to living subjects, widen the frontiers in the areas of teaching, diagnostics, therapy and scientific research. PMID:17645453

Anastasi, Giuseppe; Bramanti, Placido; Di Bella, Paolo; Favaloro, Angelo; Trimarchi, Fabio; Magaudda, Ludovico; Gaeta, Michele; Scribano, Emanuele; Bruschetta, Daniele; Milardi, Demetrio

2007-01-01

11

7 Tesla magnetic resonance imaging: a closer look at substantia nigra anatomy in Parkinson's disease.  

PubMed

A hallmark of Parkinson's disease (PD) is the progressive neurodegeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc). Dopaminergic denervation is commonly imaged using radiotracer imaging in target structures such as the striatum. Until recently, imaging made only a modest contribution to detecting neurodegenerative changes in the substantia nigra (SN) directly. Histologically, the SN is subdivided into the ventral pars reticulata and the dorsal pars compacta, which is composed of dopaminergic neurons. In humans, dopaminergic neurons, which are known to accumulate neuromelanin, form clusters of cells (nigrosomes) that penetrate deep into the SN pars reticulata (SNr). The SNr contains higher levels of iron than the SNc in normal subjects. Neuromelanin and T2*-weighted imaging therefore better detect the SNc and the SNr, respectively. The development of ultra-high field 7 Tesla (7T) magnetic resonance imaging (MRI) provided the increase in spatial resolution and in contrast that was needed to detect changes in SN morphology. 7T MRI allows visualization of nigrosome-1 as a hyperintense signal area on T2*-weighted images in the SNc of healthy subjects and its absence in PD patients, probably because of the loss of melanized neurons and the increase of iron deposition. This review is designed to provide a better understanding of the correspondence between the outlines and subdivisions of the SN detected using different MRI contrasts and the histological organization of the SN. The recent findings obtained at 7T will then be presented in relation to histological knowledge. PMID:25308960

Lehéricy, Stéphane; Bardinet, Eric; Poupon, Cyril; Vidailhet, Marie; François, Chantal

2014-11-01

12

Magnetic resonance imaging of the low rectum: defining the radiological anatomy.  

PubMed

Low rectal cancer provides a particular surgical challenge of local tumour control and sphincter preservation. Histopathological studies have shown that an involved circumferential resection margin (CRM) and depth of extramural invasion are independent markers of poor prognosis and correlate with high local recurrence rates due to residual microscopic disease [1]. Recent data suggests that a CRM at risk of tumour involvement can be reliably seen on the pre-operative magnetic resonance imaging (MRI) scan with good correlation with the histological specimen [2-5]. In published series, low rectal cancers have a higher incidence of involved resection margins, with rates up to 30% for abdomino-perineal excision (APE) vs 10% for low anterior resection (LAR) [6-9]. This has been attributed to narrow surgical planes deep within the pelvis as the mesorectum becomes narrowed and tapered, forming a bare muscle tube at the level of the anal sphincter complex. The challenge for the surgeon is to undertake careful removal of a cylinder of tissue beyond the rectal wall without perforating the tumour. An overall local recurrence rate of 10% after APE for all stages of rectal cancer has been reported and this low rate was attributed to the surgical technique that included a wide peri-anal dissection and lateral division of the levator ani. The abdominal dissection was stopped above the tumour, taking care to avoid separation of the tumour from the levator ani to reduce the risk of inadvertent tumour cell spillage [8]. Therefore, rates of involved surgical margins from APE specimens may be reduced when a cuff of levators is taken compared with standard resection. In this review, we will discuss how MRI of the low rectum can aid in the staging and optimization of the best treatment strategy for low rectal cancer. PMID:16813585

Salerno, G; Daniels, I R; Brown, G

2006-09-01

13

Magnetic resonance imaging  

SciTech Connect

The authors present a review of magnetic resonance imaging. Many topics are explored from instrumentation, spectroscopy, blood flow and sodium imaging to detailed clinical applications such as the differential diagnosis of multiple sclerosis or adrenal adenoma. The emphasis throughout is on descriptions of normal multiplanar anatomy and pathology as displayed by MRI.

Stark, D.D.; Bradley, W.G. Jr.

1988-01-01

14

Magnetic resonance imaging defines cervico-vaginal anatomy, cancer, and VEGF Trap antiangiogenic efficacy in estrogen-treated K14-HPV16 transgenic mice  

PubMed Central

Non-invasive detection of dysplasia provides a potential platform for monitoring the efficacy of chemopreventive therapy of premalignancy, imaging the tissue compartments comprising dysplasia: epithelium, microvasculature, and stromal inflammatory cells. Here, using respiratory-gated magnetic resonance imaging (MRI), the anatomy of premalignant and malignant stages of cervical carcinogenesis in estrogen-treated K14-HPV16 transgenic mice was noninvasively defined. Dynamic contrast enhanced (DCE) MRI was used to quantify leakage across premalignant dysplastic microvasculature. Vascular permeability as measured by DCE-MRI, Ktrans, was similar in transgenic (0.053 ± 0.020 min?1, n=32 mice) and nontransgenic (0.056 ± 0.029 min?1, n=17 mice) animals, despite a two-fold increase in microvascular area in the former compared with the latter. DCE-MRI did detect a significant decrease in vascular permeability accompanying diminution of dysplastic microvasculature by the anti-angiogenic agent, VEGF Trap (Ktrans =0.052 ± 0.013 min?1 pre-treatment; n=6 mice, vs. 0.019 +/? 0.008 min?1 post-treatment; n = 5 mice). Thus, we determined that the threshold of microvessel leakage associated with cervical dysplasia was below 17 kDa, and highlighted the potential of DCE-MRI to non-invasively monitor the efficacy of anti-angiogenic drugs or chemoprevention regimens targeting the vasculature, in premalignant cervical dysplasia. PMID:19789343

Garbow, Joel R.; Santeford, Andrea C.; Anderson, Jeff R.; Engelbach, John A.; Arbeit, Jeffrey M.

2009-01-01

15

Cross-sectional Anatomy, Computed Tomography and Magnetic Resonance Imaging of the Head of Common Dolphin (Delphinus delphis) and Striped Dolphin (Stenella coeruleoalba).  

PubMed

Computed tomography (CT) and low-field magnetic resonance imaging (MRI) were used to scan seven by-caught dolphin cadavers, belonging to two species: four common dolphins (Delphinus delphis) and three striped dolphins (Stenella coeruleoalba). CT and MRI were obtained with the animals in ventral recumbency. After the imaging procedures, six dolphins were frozen at -20°C and sliced in the same position they were examined. Not only CT and MRI scans, but also cross sections of the heads were obtained in three body planes: transverse (slices of 1 cm thickness) in three dolphins, sagittal (5 cm thickness) in two dolphins and dorsal (5 cm thickness) in two dolphins. Relevant anatomical structures were identified and labelled on each cross section, obtaining a comprehensive bi-dimensional topographical anatomy guide of the main features of the common and the striped dolphin head. Furthermore, the anatomical cross sections were compared with their corresponding CT and MRI images, allowing an imaging identification of most of the anatomical features. CT scans produced an excellent definition of the bony and air-filled structures, while MRI allowed us to successfully identify most of the soft tissue structures in the dolphin's head. This paper provides a detailed anatomical description of the head structures of common and striped dolphins and compares anatomical cross sections with CT and MRI scans, becoming a reference guide for the interpretation of imaging studies. PMID:24527804

Alonso-Farré, J M; Gonzalo-Orden, M; Barreiro-Vázquez, J D; Barreiro-Lois, A; André, M; Morell, M; Llarena-Reino, M; Monreal-Pawlowsky, T; Degollada, E

2015-02-01

16

Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Author's preface; 1. Introduction; 2. Basic theory; 3. Experimental methods; 4. Measurement of nuclear properties and general physical applications; 5. Nuclear magnetic resonance in liquids and gases; 6. Nuclear magnetic resonance in non-metallic solids; 7. Nuclear magnetic resonance in metals; 8. Quadrupole effects; Appendices 1-6; Glossary of symbols; Bibliography and author index; Subject index.

Andrew, E. R.

2009-06-01

17

Utility of Free-Breathing, Whole-Heart, Three-Dimensional Magnetic Resonance Imaging in the Assessment of Coronary Anatomy for Congenital Heart Disease  

Microsoft Academic Search

The incidence of coronary anomalies is increased in congenital heart disease (CHD). Whole-heart magnetic resonance imaging\\u000a (MRI) has been proposed as a robust approach to coronary artery imaging without ionizing radiation. The proximal coronary\\u000a arteries were imaged in 112 CHD patients (63 males) age 17 ± 13 years (range 11 days–68 years) using a navigator-gated, whole-heart,\\u000a three-dimensional (3D) technique at 1.5 T. Two observers assessed image

Prabhakar Rajiah; Randolph M. Setser; Milind Y. Desai; Scott D. Flamm; Janine L. Arruda

2011-01-01

18

Volume and planar gated cardiac magnetic resonance imaging: a correlative study of normal anatomy with thallium-201 SPECT and cadaver sections  

SciTech Connect

Magnetic resonance (MR) gated cardiac imaging was performed in ten subjects using a prototype 0.15-T resistive magnet imaging system. Volume and planar imaging techniques utilizing saturation recovery, proton Tl-weighted relaxation time pulse sequences produced images of the heart and great vessels with exquisite anatomic detail that showed excellent correlation with cadaver sections of the heart. The left ventricular myocardial segments also showed excellent correlation with the thallium-201 cardiac single photon emission computed tomography images. Volume acquisition allowed postprocessing selection of tomographic sections in various orientations to optimize visualization of a particular structure of interest. The excellent spatial and contrast resolution afforded by MR volume imaging, which does not involve the use of ionizing radiation and iodinated contrast material, should assure it a significant role in the diagnostic assessment of the cardiovascular system.

Go, R.T.; MacIntyre, W.J.; Yeung, H.N.; Kramer, D.M.; Geisinger, M.; Chilcote, W.; George, C.; O'Donnell, J.K.; Moodie, D.S.; Meaney, T.F.

1984-01-01

19

Volume and planar gated cardiac magnetic resonance imaging: a correlative study of normal anatomy with Thallium-201 SPECT and cadaver sections  

SciTech Connect

Magnetic resonance (MR) gated cardiac imaging was performed in ten subjects using a prototype 0.15-T resistive magnet imaging system. Volume and planar imaging techniques utilizing saturation recovery, proton TI-weighted relaxation time pulse sequences produced images of the heart and great vessels with exquisite anatomic detail that showed excellent correlation with cadaver sections of the heart. The left ventricular myocardial segments also showed excellent correlation with cadaver sections of the heart. The left ventricular myocardial segments also showed excellent correlation with the thallium-201 cardiac single photon emission computed tomography images. Volume acquisition allowed postprocessing selection of tomographic sections in various orientations to optimize visualization of a particular structure of interest. The excellent spatial and contrast resolution afforded by MR volume imaging, which does not involve the use of ionizing radiation and iodinated contrast material, should assure it a significant role in the diagnostic assessment of the cardiovascular system.

Go, R.T.; MacIntyre, W.J.; Yeung, H.N.

1984-01-01

20

Magnetic resonance imaging of the thorax  

SciTech Connect

Magnetic Resonance Imaging of the Thorax is an introductory text covering magnetic resources (MR) imaging of the heart, great vessels, mediastinum, hili, pulmonary nodules, pleura, and diaphragm. The book opens with a brief discussion of MR physics. This is followed by a larger section on normal mediastinal anatomy as viewed on axial, coronal, and sagittal MR images. This chapter suffers form several poor-quality images and inadequate labeling. The last section gives 13 cases for review and self-testing.

Sperber, M.; Kaiser, M.C.

1987-01-01

21

Advances in cardiac magnetic resonance imaging of congenital heart disease.  

PubMed

Due to advances in cardiac surgery, survival of patients with congenital heart disease has increased considerably during the past decades. Many of these patients require repeated cardiovascular magnetic resonance imaging to assess cardiac anatomy and function. In the past decade, technological advances have enabled faster and more robust cardiovascular magnetic resonance with improved image quality and spatial as well as temporal resolution. This review aims to provide an overview of advances in cardiovascular magnetic resonance hardware and acquisition techniques relevant to both pediatric and adult patients with congenital heart disease and discusses the techniques used to assess function, anatomy, flow and tissue characterization. PMID:25552386

Driessen, Mieke M P; Breur, Johannes M P J; Budde, Ricardo P J; van Oorschot, Joep W M; van Kimmenade, Roland R J; Sieswerda, Gertjan Tj; Meijboom, Folkert J; Leiner, Tim

2015-01-01

22

Cross-sectional anatomy, computed tomography and magnetic resonance imaging of the thoracic region of common dolphin (Delphinus delphis) and striped dolphin (Stenella coeruleoalba).  

PubMed

The aim of this study was to provide a detailed anatomical description of the thoracic region features in normal common (Delphinus delphis) and striped dolphins (Stenella coeruleoalba) and to compare anatomical cross-sections with computed tomography (CT) and magnetic resonance imaging (MRI) scans. CT and MRI were used to scan 7 very fresh by-caught dolphin cadavers: four common and three striped dolphins. Diagnostic images were obtained from dolphins in ventral recumbency, and after the examinations, six dolphins were frozen (-20°C) and sliced in the same position. As well as CT and MRI scans, cross-sections were obtained in the three body planes: transverse (slices of 1 cm thickness), sagittal (5 cm thickness) and dorsal (5 cm thickness). Relevant anatomical features of the thoracic region were identified and labelled on each section, obtaining a complete bi-dimensional atlas. Furthermore, we compared CT and MRI scans with anatomical cross-sections, and results provided a complete reference guide for the interpretation of imaging studies of common and striped dolphin's thoracic structures. PMID:23711289

Alonso-Farré, J M; Gonzalo-Orden, M; Barreiro-Vázquez, J D; Ajenjo, J M; Barreiro-Lois, A; Llarena-Reino, M; Degollada, E

2014-06-01

23

Magnetic resonance microscopy of embryos.  

PubMed

We demonstrate that magnetic resonance (MR) microscopy provides a mechanism to investigate normal and abnormal developmental anatomy in a non-destructive and distortion-free manner. Techniques for the fixation, embedding, perfusion and image acquisition of embryos between 3 and 30 mm crown rump length are described. We describe the perfusion of a contrast agent to enhance images of the developing embryonic vasculature. Data are acquired as three-dimensional isotropic arrays which permit images to be reformatted retrospectively in any plane. The data are available for archiving, distributing and for post-acquisition manipulations. MR microscopy is a fast technique for producing three-dimensional reconstructions and is free from registration and sectioning artifacts. PMID:9007215

Smith, B R; Linney, E; Huff, D S; Johnson, G A

1996-01-01

24

Nuclear magnetic resonance gyroscope  

SciTech Connect

A nuclear magnetic resonance gyro using two nuclear magnetic resonance gases, preferably xenon 129 and xenon 131, together with two alkaline metal vapors, preferably rubidium, potassium or cesium, one of the two alkaline metal vapors being pumped by light which has the wavelength of that alkaline metal vapor, and the other alkaline vapor being illuminated by light which has the wavelength of that other alkaline vapor.

Grover, B.C.

1984-02-07

25

Magnetic resonance imaging of the body  

SciTech Connect

This text provides reference to magnetic resonance imaging (MRI) of the body. Beginning with explanatory chapters on the physics, instrumentation, and interpretation of MRI, it proceeds to the normal anatomy of the neck, thorax, abdomen, and pelvis. Other chapters cover magnetic resonance imaging of blood flow, the larynx, the lymph nodes, and the spine, as well as MRI in obstetrics. The text features detailed coverage of magnetic resonance imaging of numerous disorders and disease states, including neck disease, thoracic disease; breast disease; congenital and acquired heart disease; vascular disease; diseases of the liver, pancreas, and spleen; diseases of the kidney, adrenals, and retroperitoneum; diseases of the male and female pelvis; and musculoskeletal diseases. Chapters on the biological and environmental hazards of MRI, the current clinical status of MRI in comparison to other imaging modalities, and economic considerations are also included.

Higgins, C.B.; Hricak, H.

1987-01-01

26

Magnetic Resonance Imaging  

NSDL National Science Digital Library

This lesson ties the preceding lessons together and brings students back to the grand challenge question on MRI safety. During this lesson, students focus on the logistics of magnetic resonance imaging as well as the MRI hardware. Students can then integrate this knowledge with their acquired knowledge on magnetic fields to solve the challenge question.

VU Bioengineering RET Program, School of Engineering,

27

Magnetic Resonance Online Texts  

NSDL National Science Digital Library

This well-organized and very thorough website was developed by the physicist Stanislav Sykora with the aim of providing free online texts, theses, and course materials on the subjects of magnetic resonance (MR), magnetic resonance imaging (MRI), nuclear-magnetic resonance (NMR) and other related topics. The amount of material on the site is impressive. At the top of the page are links to an "MR Blog", as well as to "MR Links" and the "Site Plan & SEARCH". The NMR/MRI Extras section on the right side of the page is particularly useful for visitors interested in all things about MR. Its links to "Events" provides an up-to-date list of symposia, conferences, and meetings, along with links to the events' sites. The "Societies" link offers at least 50 groups about MR, some of which are country-based, and others that are region- or application-based.

S�½kora, Stanislav

28

Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy in Dementias  

PubMed Central

This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in dementia, including Alzheimer's disease, frontotemporal dementia, dementia with Lewy bodies, idiopathic Parkinson's disease, Huntington's disease, and vascular dementia. Magnetic resonance imaging and magnetic resonance spectroscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential diagnosis and early detection of affected individuals, monitoring disease progression, and evaluation of therapeutic effect. PMID:11563438

Hsu, Yuan-Yu; Du, An-Tao; Schuff, Norbert; Weiner, Michael W.

2007-01-01

29

Anatomical Brain Magnetic Resonance Imaging of Typically Developing Children and Adolescents  

ERIC Educational Resources Information Center

Methodological issues relevant to magnetic resonance imaging studies of brain anatomy are discussed along with the findings on the neuroanatomic changes during childhood and adolescence. The development of the brain is also discussed.

Giedd, Jay N.; Lalonde, Francois M.; Celano, Mark J.; White, Samantha L.; Wallace, Gregory L.; Lee, Nancy R.; Lenroot, Rhoshel K.

2009-01-01

30

Magnetic Resonance Annual, 1985  

SciTech Connect

The inaugural volume of Magnetic Resonance Annual includes reviews of MRI of the posterior fossa, cerebral neoplasms, and the cardiovascular and genitourinary systems. A chapter on contrast materials outlines the mechanisms of paramagnetic contrast enhancement and highlights several promising contrast agents.

Kressel, H.Y.

1985-01-01

31

Magnetic Resonance Spectroscopy (MRS)  

E-print Network

does not require any ionizing radiation. It provides a wealth of information (in vivo) on variousMagnetic Resonance Spectroscopy (MRS) and Its Application in Alzheimer's Disease PRAVAT K. MANDAL1 alterations and the pathophysiology of disease. This article provides a comprehensive description of the MRS

Mandal, Pravat K.

32

Functional Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

Functional magnetic resonance imaging (fMRI), with its excellent spatial resolution and ability to visualize networks of neuroanatomical structures involved in complex information processing, has become the dominant technique for the study of brain function and its development. The accessibility of in-vivo pediatric brain-imaging techniques…

Voos, Avery; Pelphrey, Kevin

2013-01-01

33

Clinical magnetic resonance imaging  

SciTech Connect

This book presents clinical applications of magnetic resonance imaging with a strong clinical orientation. Covers technique, instrumentation, and contrast agents. Describes MRI of the neck, brain, heart, spine, TMJ and orbit, chest abdomen, pelvis, and the joints. Also includes a high field atlas of the central nervous system.

Brady, T.J.; Edelman, R.R.

1988-01-01

34

Introduction Magnetic Resonance Imaging (MRI)  

E-print Network

Introduction Statistics Magnetic Resonance Imaging (MRI) Statistics in the UK Statistics at UCL and Beyond #12;Introduction Statistics Magnetic Resonance Imaging (MRI) Statistics in the UK Statistics Magnetic Resonance Imaging (MRI) Statistics in the UK Statistics at UCL Outline Why do Statistics? Some

Wirosoetisno, Djoko

35

Magnetic Resonance and Computed Tomographic Image-Directed Stereotaxy for Animal Research  

Microsoft Academic Search

Current stereotactic frames for animal experimentation presume normal intracranial anatomy for atlas-directed probe placement. This is an invalid assumption for animal brain tumor models, where distortions of cerebral anatomy make image-directed stereotaxy necessary. To address this need, an accurate and reproducible magnetic resonance and computed tomographic compatible image-directed stereotactic apparatus for animal experimentation is presented.

Robert J. Maciunas; Robert L. Galloway

1989-01-01

36

Mediated Spatiotemporal Fusion of Multiple Cardiac Magnetic Resonance Datasets for Patient-specific Perfusion Analysis  

E-print Network

of my- ocardial anatomy, contractile function, perfusion, myocar- dial tissue viability, coronary artery anatomy and coronary blood-flow with accuracy similar or superior to that pro- vided by other established Magnetic Resonance Imaging (DCE-MRI) in patients with known or suspected Coronary Heart Disease (CHD) could

Magee, Derek

37

Magnetic Resonance Imaging  

PubMed Central

Magnetic resonance imaging (MRI) is an important new imaging modality just arriving on the clinical scene in Canada. MRI uses no ionizing radiation; images are derived from the interaction of hydrogen nuclei, a powerful magnetic field, and radio waves. Images are displayed as tomographic slices, much like CT. Direct transverse, sagittal, coronal or oblique slices can be obtained. Unlike CT, the MRI image does not reflect varying tissue densities. In MRI, tissues are differentiated by variation in the amount of hydrogen they contain and by differences in the magnetic environment at a molecular level. All parts of the body can be examined with MRI, although the CNS is particularly well visualized. In addition to providing high resolution images, MRI has the potential for performing non-invasive angiography and biochemical analysis through spectroscopy. To date, there are no known harmful effects of MRI. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5 PMID:21267205

Fache, J. Stephen

1986-01-01

38

Cross-Validation of Deformable Registration With Field Maps in Functional Magnetic Resonance Brain Imaging  

Microsoft Academic Search

The localization of brain functional activity with respect to brain anatomy requires registration between a functional image and a reference high-resolution anatomical image. The fast functional magnetic resonance brain images acquired via echo planar imaging (EPI) in functional magnetic resonance imaging (fMRI) suffer from local geometric distortions. After performing standard rigid or affine registration, local nonlinear distortions of up to

Ali Gholipour; Nasser Kehtarnavaz; Kaundinya Gopinath; Richard Briggs

2008-01-01

39

Nuclear Magnetic Resonance Gyroscope  

NASA Astrophysics Data System (ADS)

The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation is concluding the fourth and final phase of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. Traditional MEMS gyros utilize springs as an inherent part of the sensing mechanism, leading to bias and scale factor sensitivity to acceleration and vibration. As a result, they have not met performance expectations in real world environments and to date have been limited to tactical grade applications. The Nuclear Magnetic Resonance Gyroscope (NMRG) utilizes the fixed precession rate of a nuclear spin in a constant magnetic field as an inertial reference for determining rotation. The nuclear spin precession rate sensitivity to acceleration and vibration is negligible for most applications. Therefore, the application of new micro and batch fabrication methods to NMRG technology holds great promise for navigation grade performance in a low cost and compact gyro. This poster will describe the history, operational principles, and design basics of the NMRG including an overview of the NSD designs developed and demonstrated in the DARPA gyro development program. General performance results from phases 3 and 4 will also be presented.

Bulatowicz, Michael; Clark, Philip; Griffith, Robert; Larsen, Michael; Mirijanian, James

2012-06-01

40

Nuclear Magnetic Resonance Gyroscope  

NASA Astrophysics Data System (ADS)

The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation is currently in phase 4 of the DARPA Navigation Grade Integrated Micro Gyro (NGIMG) program. The micro-NMRG technology is pushing the boundaries of size, weight, power, and performance allowing new small platform applications of navigation grade Inertial Navigation System (INS) technology. Information on the historical development of the technology, basics of operation, task performance goals, application opportunities, and a phase 2 sample of earth rate measurement data will be presented.

Larsen, Michael

2011-06-01

41

[Utility of cardiovascular magnetic resonance in hypertrophic cardiomyopathy: When is it superior to echocardiography?].  

PubMed

The diagnosis of hypertrophic cardiomyopathy is usually established by echocardiography. Recently, there has been greatly increased use of cardiac magnetic resonance (CMR) because of its precise determination of myocardial anatomy and the depiction of myocardial fibrosis. In this review, we describe the role of echocardiography and magnetic resonance in the assessment of this complex disease. In conclusion, there is a complementarity between cardiovascular magnetic resonance imaging and echocardiography for the diagnosis and the management of HCM. PMID:24834991

Kammoun, I; Marrakchi, S; Zidi, A; Ibn ElHaj, Z; Naccache, S; Ben Amara, W; Jebri, F; Bennour, E; Kachboura, S

2015-02-01

42

nuclear magnetic resonance gyroscope  

SciTech Connect

A nuclear magnetic resonance gyroscope which derives angular rotation thereof from the phases of precessing nuclear moments utilizes a single-resonance cell situated in the center of a uniform DC magnetic field. The field is generated by current flow through a circular array of coils between parallel plates. It also utilizes a pump and read-out beam and associated electronics for signal processing and control. Encapsulated in the cell for sensing rotation are odd isotopes of Mercury Hg/sup 199/ and Hg/sup 201/. Unpolarized intensity modulated light from a pump lamp is directed by lenses to a linear polarizer, quarter wave plate combination producing circularly polarized light. The circularly polarized light is reflected by a mirror to the cell transverse to the field for optical pumping of the isotopes. Unpolarized light from a readout lamp is directed by lenses to another linear polarizer. The linearly polarized light is reflected by another mirror to the cell transverse to the field and orthogonal to the pump lamp light. The linear light after transversing the cell strikes an analyzer where it is converted to an intensity-modulated light. The modulated light is detected by a photodiode processed and utilized as feedback to control the field and pump lamp excitation and readout of angular displacement.

Karwacki, F. A.; Griffin, J.

1985-04-02

43

Magnetic resonance cell  

SciTech Connect

There is disclosed a nuclear magnetic alignment device for use in a nuclear magnetic resonance gyroscope and the like. One embodiment includes a container for gas having a layer of rubidium hydride on its inner surface. The container comprising a spherical portion and a tip portion, is rotationally symmetric about an axis of symmetry. Enclosed within the container is a nuclear moment gas having a nuclear electric quadrupole moment, such as xenon-131, and an optically pumpable substance, such as rubidium. A portion of the rubidium is a vapor. The remainder is a condensed pellet which is deposited in the tip of the container such that the pellet is also rotationally symmetric about the axis of symmetry of the container. A layer of rubidium hydride is deposited on the inner surface of the container. The device further includes means for orienting the symmetry axis of the container at an angle to an applied magnetic field such that the relaxation time constant of the aligned nuclear moment gas is substantially at a maximum.

Kwon, T.M.; Volk, C.H.

1984-05-01

44

The Anatomy of Plastic Events in Magnetic Amorphous Solids  

E-print Network

Plastic events in amorphous solids can be much more than just "shear transformation zones" when the positional degrees of freedom are coupled non-trivially to other degrees of freedom. Here we consider magnetic amorphous solids where mechanical and magnetic degrees of freedom interact, leading to rather complex plastic events whose nature must be disentangled. In this paper we uncover the anatomy of the various contributions to some typical plastic events. These plastic events are seen as Barkhausen Noise or other "serrated noises". Using theoretical considerations we explain the observed statistics of the various contributions to the considered plastic events. The richness of contributions and their different characteristics imply that in general the statistics of these "serrated noises" cannot be universal, but rather highly dependent on the state of the system and on its microscopic interactions.

H. George E. Hentschel; Itamar Procaccia; Bhaskar Sen Gupta

2015-01-25

45

Virtual magnetic resonance colonography  

PubMed Central

Colorectal cancer screening has vast potential. Beyond considerations for cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further increase patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. The review will describe the techniques underlying MR colonography and describe early clinical experience with fecal tagging techniques. PMID:12746264

Debatin, J; Lauenstein, T

2003-01-01

46

Nuclear Magnetic Resonance and Magnetic Field Measurements  

NSDL National Science Digital Library

This laboratory is designed for students to become familiar with the principles and detection techniques of Nuclear Magnetic Resonance (NMR), examine the relationship between current and magnetic field in an electromagnet, and gain experience in the use of magnetic field measurement techniques.

2012-01-04

47

Cranial and spinal magnetic resonance imaging: A guide and atlas  

SciTech Connect

This atlas provides a clinical guide to interpreting cranial and spinal magnetic resonance images. The book includes coverage of the cerebrum, temporal bone, and cervical, thoracic, and lumbar spine, with more than 400 scan images depicting both normal anatomy and pathologic findings. Introductory chapters review the practical physics of magnetic resonance (MR) imaging, offer guidelines for interpreting cranial MR scans, and provide coverage of each anatomic region of the cranium and spine. For each region, scans accompanied by captions, show normal anatomic sections matched with MR images. These are followed by MR scans depicting various disease states.

Daniels, D.L.; Haughton, V.M.

1987-01-01

48

Simple and Inexpensive Classroom Demonstrations of Nuclear Magnetic Resonance and Magnetic Resonance Imaging.  

ERIC Educational Resources Information Center

Describes a set of simple, inexpensive, classical demonstrations of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) principles that illustrate the resonance condition associated with magnetic dipoles and the dependence of the resonance frequency on environment. (WRM)

Olson, Joel A.; Nordell, Karen J.; Chesnik, Marla A.; Landis, Clark R.; Ellis, Arthur B.; Rzchowski, M. S.; Condren, S. Michael; Lisensky, George C.

2000-01-01

49

Nuclear magnetic resonance contrast agents  

DOEpatents

A family of contrast agents for use in magnetic resonance imaging and a method of enhancing the contrast of magnetic resonance images of an object by incorporating a contrast agent of this invention into the object prior to forming the images or during formation of the images. A contrast agent of this invention is a paramagnetic lanthanide hexaazamacrocyclic molecule, where a basic example has the formula LnC{sub 16}H{sub 14}N{sub 6}. Important applications of the invention are in medical diagnosis, treatment, and research, where images of portions of a human body are formed by means of magnetic resonance techniques. 10 figs.

Smith, P.H.; Brainard, J.R.; Jarvinen, G.D.; Ryan, R.R.

1997-12-30

50

Nuclear magnetic resonance contrast agents  

DOEpatents

A family of contrast agents for use in magnetic resonance imaging and a method of enhancing the contrast of magnetic resonance images of an object by incorporating a contrast agent of this invention into the object prior to forming the images or during formation of the images. A contrast agent of this invention is a paramagnetic lanthanide hexaazamacrocyclic molecule, where a basic example has the formula LnC.sub.16 H.sub.14 N.sub.6. Important applications of the invention are in medical diagnosis, treatment, and research, where images of portions of a human body are formed by means of magnetic resonance techniques.

Smith, Paul H. (Los Alamos, NM); Brainard, James R. (Los Alamos, NM); Jarvinen, Gordon D. (Los Alamos, NM); Ryan, Robert R. (Los Alamos, NM)

1997-01-01

51

Nuclear magnetic resonance imaging of the spine  

SciTech Connect

Forty subjects were examined to determine the accuracy and clinical usefulness of nuclear magnetic resonance (NMR) examination of the spine. The NMR images were compared with plain radiographs, high-resolution computed tomograms, and myelograms. The study included 15 patients with normal spinal cord anatomy and 25 patients whose pathological conditions included canal stenosis, herniated discs, metastatic tumors, primary cord tumor, trauma, Chiari malformations, syringomyelia, and developmental disorders. Saturation recovery images were best in differentiating between soft tissue and cerebrospinal fluid. NMR was excellent for the evaluation of the foramen magnum region and is presently the modality of choice for the diagnosis of syringomyelia and Chiari malformation. NMR was accurate in diagnosing spinal cord trauma and spinal canal block.

Modic, M.T.; Weinstein, M.A.; Pavlicek, W.; Starnes, D.L.; Duchesneau, P.M.; Boumphrey, F.; Hardy, R.J. Jr.

1984-01-01

52

Interventional magnetic resonance imaging.  

PubMed

The development of minimally invasive surgical and interventional techniques has created a need for more accurate and sensitive image guidance and monitoring. Magnetic resonance imaging, with its superior soft tissue discrimination and multiplanar facilities, seems the obvious choice for an ideal image-guidance tool. Until recently, the employment of MRI in this role has been prevented by the physical constraints of conventional, closed-configuration machines. The problem has now been overcome by the development of an open design allowing both horizontal and vertical access to the patient in the scanner so that procedures can be performed concurrent with image acquisition. This configuration, together with the use of fast gradient echo sequences which can scan at speeds close to real time, means that a wide range of interventional procedures can be performed with on-line image guidance and monitoring. In addition, the versatility of the open design means that patients can assume physiological positions to allow dynamic joint imaging to be performed. This opens up a whole new field in the understanding of joint pathophysiology. This review article discusses these recent technological developments and their clinical applications. In particular, the potential role in guidance of biopsies, monitoring of thermal ablation techniques and applications in endoscopic surgery is outlined. PMID:9534721

Lamb, G M; Gedroyc, W M

1997-11-01

53

Nuclear magnetic resonance readable sensors  

E-print Network

The monitoring of physiological biomarkers is fundamental to the diagnosis and treatment of disease. We describe here the development of molecular sensors which can be read by magnetic resonance (MR) relaxometry. MR is an ...

Ling, Yibo

2010-01-01

54

Magnetic Resonance Force Microscope Development  

SciTech Connect

Our objectives were to develop the Magnetic Resonance Force Microscope (MRFM) into an instrument capable of scientific studies of buried structures in technologically and scientifically important electronic materials such as magnetic multilayer materials. This work resulted in the successful demonstration of MRFM-detected ferromagnetic resonance (FMR) as a microscopic characterization tool for thin magnetic films. Strong FMR spectra obtained from microscopic Co thin films (500 and 1000 angstroms thick and 40 x 200 microns in lateral extent) allowed us to observe variations in sample inhomogeneity and magnetic anisotropy field. We demonstrated lateral imaging in microscopic FMR for the first time using a novel approach employing a spatially selective local field generated by a small magnetically polarized spherical crystallite of yttrium iron garnet. These successful applications of the MRFM in materials studies provided the basis for our successful proposal to DOE/BES to employ the MRF M in studies of buried interfaces in magnetic materials.

Hammel, P.C.; Zhang, Z.; Suh, B.J.; Roukes, M.L.; Midzor, M.; Wigen, P.E.; Childress, J.R.

1999-06-03

55

Noble gas magnetic resonator  

DOEpatents

Precise measurements of a precessional rate of noble gas in a magnetic field is obtained by constraining the time averaged direction of the spins of a stimulating alkali gas to lie in a plane transverse to the magnetic field. In this way, the magnetic field of the alkali gas does not provide a net contribution to the precessional rate of the noble gas.

Walker, Thad Gilbert; Lancor, Brian Robert; Wyllie, Robert

2014-04-15

56

Autotuning of the RF transmission line coil for high-fields magnetic resonance imaging (MRI) systems  

Microsoft Academic Search

RF coil with microstip transmission line elements have been used for high-fields magnetic resonance imaging (MRI) to inductively excite and receive the nuclear magnetic resonance signals in anatomy. These coil elements have narrow bandwidth due to its high quality factors (Qs). Although high signal-to-noise ratio (SNR) of RF coils is obtained from this property it has a critical drawback, loading

Sung-Min Sohn; John Thomas Vaughan; Anand Gopinath

2011-01-01

57

Interventional Cardiovascular Magnetic Resonance Imaging  

PubMed Central

Cardiovascular magnetic resonance (CMR) combines excellent soft-tissue contrast, multiplanar views, and dynamic imaging of cardiac function without ionizing radiation exposure. Interventional cardiovascular magnetic resonance (iCMR) leverages these features to enhance conventional interventional procedures or to enable novel ones. Although still awaiting clinical deployment, this young field has tremendous potential. We survey promising clinical applications for iCMR. Next, we discuss the technologies that allow CMR-guided interventions and, finally, what still needs to be done to bring them to the clinic. PMID:19909937

Saikus, Christina E.; Lederman, Robert J.

2010-01-01

58

Magnetic resonance image-guided biopsy and aspiration.  

PubMed

Recent advances in magnet design and magnetic resonance (MR) system technology coupled with the development of fast gradient-echo pulse sequences have contributed to the increasing interest in interventional magnetic resonance imaging (MRI). Minimally invasive diagnostic and therapeutic image-based intervention can now be performed under near real-time MR guidance, taking advantage of the high tissue contrast, spatial resolution, vascular conspicuity and multiplanar capabilities of MRI to achieve safe and precise needle placement. This is particularly advantageous for needle navigation in regions of complex anatomy, such as the suprahyoid neck. This article discusses the theoretical concepts and clinical applications of MR for guidance for biopsy and aspiration, and highlights the technical developments that provide the foundation for interventional MRI. PMID:11145209

Lewin, J S; Nour, S G; Duerk, J L

2000-06-01

59

Magnetic resonance assessment of aortic and mitral regurgitation.  

PubMed Central

Magnetic resonance imaging provides an accurate method for the measurement of left and right ventricular volume. The ratio of left ventricular stroke volume to right ventricular stroke volume was calculated from contiguous transverse magnetic resonance images and was used to measure the severity of regurgitation in 18 patients with aortic regurgitation and 10 with mitral regurgitation. Cardiac anatomy was well demonstrated, allowing an assessment of relative chamber volumes and associated abnormalities, although valve abnormality was not well seen. There was a weak correlation between magnetic resonance measurements of left ventricular end diastolic volume and stroke volume ratio. The stroke volume ratio differed significantly in four groups with increasing angiographic severity of regurgitation, and all but the group with trivial regurgitation differed significantly from normal. There was good correlation between magnetic resonance and radionuclide measurements of left ventricular ejection fraction and stroke volume ratio, although the stroke volume ratio was consistently overestimated by radionuclide ventriculography. Correlation was less good for the right ventricular ejection fraction, which was underestimated by radionuclide ventriculography. It is concluded that magnetic resonance imaging provides valuable information in patients with valvar regurgitation, and serves as a suitable standard by which to judge conventional techniques. Images Fig 1 Fig 2 Fig 3 PMID:3790381

Underwood, S R; Klipstein, R H; Firmin, D N; Fox, K M; Poole-Wilson, P A; Rees, R S; Longmore, D B

1986-01-01

60

Magnetic resonance apparatus  

DOEpatents

Means for producing a region of homogeneous magnetic field remote from the source of the field, wherein two equal field sources are arranged axially so their fields oppose, producing a region near the plane perpendicular to the axis midway between the sources where the radial component of the field goes through a maximum. Near the maximum, the field is homogeneous over prescribed regions.

Jackson, Jasper A. (Los Alamos, NM); Cooper, Richard K. (Los Alamos, NM)

1982-01-01

61

Magnetic resonance apparatus  

DOEpatents

The patent consists of means for producing a region of homogeneous magnetic field remote from the source of the field, wherein two equal field sources are arranged axially so their fields oppose, producing a region near the plane perpendicular to the axis midway between the sources where the radial correspondent of the field goes through a maximum. Near the maximum, the field is homogeneous over prescribed regions.

Jackson, J.A.; Cooper, R.K.

1980-10-10

62

Model-based 3-D segmentation of multiple sclerosis lesions in magnetic resonance brain images  

Microsoft Academic Search

Human investigators instinctively segment medical images into their anatomical components, drawing upon prior knowledge of anatomy to overcome image artifacts, noise, and lack of tissue contrast. The authors describe: 1) the development and use of a brain tissue probability model for the segmentation of multiple sclerosis (MS) lesions in magnetic resonance (MR) brain images, and 2) an empirical comparison of

Micheline Kamber; Rajjan Shinghal; D. L. Collins; Gordon S. Francis; Alan C. Evans

1995-01-01

63

The fundamentals of fetal magnetic resonance imaging: Part 2.  

PubMed

Careful assessment of fetal anatomy by a combination of ultrasound and fetal magnetic resonance imaging offers the clinical teams and counselors caring for the patient information that can be critical for the management of both the mother and the fetus. In the second half of this 2-part review, we focus on space-occupying lesions in the fetal body. Because developing fetal tissues are programmed to grow rapidly, mass lesions can have a substantial effect on the formation of normal adjacent organs. Congenital diaphragmatic hernia and lung masses, fetal teratoma, and intra-abdominal masses are discussed, with an emphasis on differential etiologies and on fundamental management considerations. PMID:24974309

Plunk, Matthew R; Chapman, Teresa

2014-01-01

64

Resonant magnetic fields from inflation  

SciTech Connect

We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the coupling is oscillating rather than growing or decaying exponentially. Despite these major advantages, we find that the backreaction is still far too large during inflation if the generated magnetic fields are required to have a strength of O(10{sup ?15} Gauss) today on observationally interesting scales. We provide a more general no-go argument, proving that this problem will apply to any model in which the magnetic fields are generated on subhorizon scales and freeze after horizon crossing.

Byrnes, Christian T. [CERN, PH-TH Division, CH-1211, Genève 23 (Switzerland); Hollenstein, Lukas; Jain, Rajeev Kumar [Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, 24, Quai Ernest Ansermet, CH-1211 Genève 4 (Switzerland); Urban, Federico R., E-mail: cbyrnes@cern.ch, E-mail: lukas.hollenstein@unige.ch, E-mail: rajeev.jain@unige.ch, E-mail: urban@phas.ubc.ca [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 (Canada)

2012-03-01

65

[31P magnetic-resonance spectroscopy in cardiac diseases].  

PubMed

Magnetic Resonant spectroscopy (MRS) in the nuclei of phosphorus is the only noninvasive method of studying the state of myocardial energy metabolism does not require the introduction of radiopharmaceuticals. This method uses the signals from the nuclei of 31P contained in such mattered phosphates like phosphocreatine and adenosine triphosphate. MRS can provide an answer to a variety of theoretical and clinical issues in the study of various cardiac diseases. The first is ischemic heart disease, as well as heart failure, hypertrophy of various origins, etc. In addition, the method can be used to control the various treatments, including therapeutic, interventional or surgical. Combined with magnetic resonance imaging of the heart gives information on the anatomy, size, function, perfusion defects, structural changes of the myocardium, as well as about the state of energy metabolism of myocardium. PMID:22839445

Mazaev, V V; Stukalova, O V; Ternovo?, S K; Chazova, I E

2012-01-01

66

Quantitative nuclear magnetic resonance spectrometry  

Microsoft Academic Search

The purities of the widely-used herbicide glyphosate (N-(phosphonomethyl)glycine), and the insecticide profenofos (O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate) were determined by 1H and 31P quantitative nuclear magnetic resonance (QNMR) spectrometry using an internal standard. QNMR does not need a standard reference of the same target analyte, in contrast to chromatographic methods, but only a compound containing the nucleus of interest. Sodium acetate

Tareq Saed Al Deen; D Brynn Hibbert; James M Hook; Robert J Wells

2002-01-01

67

Interventional cardiovascular magnetic resonance imaging  

PubMed Central

Magnetic resonance imaging (MRI) provides structural and functional cardiovascular information with excellent soft tissue contrast. Real-time MRI can guide transcatheter cardiovascular interventions in large animal models, and may prove superior to x-ray and adjunct modalities for peripheral vascular, structural heart and cardiac electrophysiology applications. We describe technical considerations, pre-clinical work and early clinical studies in this emerging field. PMID:17662914

Raman, Venkatesh K.; Lederman, Robert J.

2008-01-01

68

Magnetic resonance imaging at ultrahigh fields.  

PubMed

Since the introduction of 4 T human systems in three academic laboratories circa 1990, rapid progress in imaging and spectroscopy studies in humans at 4 T and animal model systems at 9.4 T have led to the introduction of 7 T and higher magnetic fields for human investigation at about the turn of the century. Work conducted on these platforms has demonstrated the existence of significant advantages in SNR and biological information content at these ultrahigh fields, as well as the presence of numerous challenges. Primary difference from lower fields is the deviation from the near field regime; at the frequencies corresponding to hydrogen resonance conditions at ultrahigh fields, the RF is characterized by attenuated traveling waves in the human body, which leads to image nonuniformities for a given sample-coil configuration because of interferences. These nonuniformities were considered detrimental to the progress of imaging at high field strengths. However, they are advantageous for parallel imaging for signal reception and parallel transmission, two critical technologies that account, to a large extend, for the success of ultrahigh fields. With these technologies, and improvements in instrumentation and imaging methods, ultrahigh fields have provided unprecedented gains in imaging of brain function and anatomy, and started to make inroads into investigation of the human torso and extremities. As extensive as they are, these gains still constitute a prelude to what is to come given the increasingly larger effort committed to ultrahigh field research and development of ever better instrumentation and techniques. PMID:24686229

Ugurbil, Kamil

2014-05-01

69

Magnetic Resonance Imaging of the Elbow  

PubMed Central

Context: The elbow is a complex joint and commonly injured in athletes. Evaluation of the elbow by magnetic resonance imaging (MRI) is an important adjunct to the physical examination. To facilitate accurate diagnosis, a concise structured approach to evaluation of the elbow by MRI is presented. Evidence Acquisition: A PubMed search was performed using the terms elbow and MR imaging. No limits were set on the range of years searched. Articles were reviewed for relevance with an emphasis of the MRI appearance of normal anatomy and common pathology of the elbow. Results: The spectrum of common elbow disorders varies from obvious acute fractures to chronic overuse injuries whose imaging manifestations can be subtle. MRI evaluation should include bones; lateral, medial, anterior, and posterior muscle groups; the ulnar and radial collateral ligaments; as well as nerves, synovium, and bursae. Special attention should be paid to the valgus extension overload syndrome and the MRI appearance of associated injuries when evaluating throwing athletes. Conclusion: MRI evaluation of the elbow should follow a structured approach to facilitate thoroughness, accuracy, and speed. Such an approach should cover bone, cartilage, muscle, tendons, ligaments, synovium, bursae, and nerves. PMID:24381699

Sampath, Srinath C.; Sampath, Srihari C.; Bredella, Miriam A.

2013-01-01

70

Bistable electron magnetic resonance in solids  

Microsoft Academic Search

This paper describes the phenomenon of Bistable Electron Magnetic Resonance, which manifests itself by a resonance line with a distorted shark fin-like shape. This effect requires only a fluctuating hyperfine interaction between electron spins and nuclear spins. It is demonstrated for shallow donors in semiconductors and conduction electrons in light metals. Bistability is an intrinsic property of electron magnetic resonance

Didier Gourier; Laurent Binet; Olivier Guillot-Noël

2004-01-01

71

Wide-range nuclear magnetic resonance detector  

NASA Technical Reports Server (NTRS)

Compact and easy to use solid state nuclear magnetic resonance detector is designed for measuring field strength to 20 teslas in cryogenically cooled magnets. Extremely low noise and high sensitivity make detector applicable to nearly all types of analytical nuclear magnetic resonance measurements and can be used in high temperature and radiation environments.

Sturman, J. C.; Jirberg, R. J.

1972-01-01

72

Integrated magnetic for LLC resonant converter  

Microsoft Academic Search

A new LLC resonant converter is proposed for front end DC\\/DC conversion in a distributed power system. This converter shows some potential benefits in this application. This paper proposes several integrated magnetic designs for LLC resonant converter. This converter has three magnetic components. With magnetic integration, first, a number of components can be reduced; secondly, flux ripple cancellation is achieved

Bo Yang; Rengang Chen; Fred C. Lee

2002-01-01

73

Introduction to Nuclear Magnetic Resonance  

NASA Technical Reports Server (NTRS)

The purpose of this paper is to try to give a short overview of what the status is on nuclear magnetic resonance (NMR). It's a subject where one really has to spend some time to look at the physics in detail to develop a proper working understanding. I feel it's not appropriate to present to you density matrices, Hamiltonians of all sorts, and differential equations representing the motion of spins. I'm really going to present some history and status, and show a few very simple concepts involved in NMR. It is a form of radio frequency spectroscopy and there are a great number of nuclei that can be studied very usefully with the technique. NMR requires a magnet, a r.f. transmitter/receiver system, and a data acquisition system.

Manatt, Stanley L.

1985-01-01

74

MAGNETIC RESONANCE ELASTOGRAPHY: A REVIEW  

PubMed Central

Magnetic Resonance Elastography (MRE) is a rapidly developing technology for quantitatively assessing the mechanical properties of tissue. The technology can be considered to be an imaging-based counterpart to palpation, commonly used by physicians to diagnose and characterize diseases. The success of palpation as a diagnostic method is based on the fact that the mechanical properties of tissues are often dramatically affected by the presence of disease processes such as cancer, inflammation, and fibrosis. MRE obtains information about the stiffness of tissue by assessing the propagation of mechanical waves through the tissue with a special magnetic resonance imaging (MRI) technique. The technique essentially involves three steps: generating shear waves in the tissue,acquiring MR images depicting the propagation of the induced shear waves andprocessing the images of the shear waves to generate quantitative maps of tissue stiffness, called elastograms. MRE is already being used clinically for the assessment of patients with chronic liver diseases and is emerging as a safe, reliable and noninvasive alternative to liver biopsy for staging hepatic fibrosis. MRE is also being investigated for application to pathologies of other organs including the brain, breast, blood vessels, heart, kidneys, lungs and skeletal muscle. The purpose of this review article is to introduce this technology to clinical anatomists and to summarize some of the current clinical applications that are being pursued. PMID:20544947

Mariappan, Yogesh K; Glaser, Kevin J; Ehman, Richard L

2011-01-01

75

Advances in mechanical detection of magnetic resonance  

PubMed Central

The invention and initial demonstration of magnetic resonance force microscopy (MRFM) in the early 1990s launched a renaissance of mechanical approaches to detecting magnetic resonance. This article reviews progress made in MRFM in the last decade, including the demonstration of scanned probe detection of magnetic resonance (electron spin resonance, ferromagnetic resonance, and nuclear magnetic resonance) and the mechanical detection of electron spin resonance from a single spin. Force and force-gradient approaches to mechanical detection are reviewed and recent related work using attonewton sensitivity cantilevers to probe minute fluctuating electric fields near surfaces is discussed. Given recent progress, pushing MRFM to single proton sensitivity remains an exciting possibility. We will survey some practical and fundamental issues that must be resolved to meet this challenge. PMID:18266413

Kuehn, Seppe; Hickman, Steven A.; Marohn, John A.

2008-01-01

76

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging  

E-print Network

-resolution non-invasive observation of the anatomy and function of intact organisms. However, previous MRI- netic resonance imaging (MRI) routinely delivers non-invasive images of anatomy at high resolution2 and biocompatible element distributes rapidly into tissues such as the lungs9 , brain10 , heart and kidneys11

Schaffer, David V.

77

Cadmium ferrite ionic magnetic fluid: Magnetic resonance investigation  

Microsoft Academic Search

In contrast to all magnetic resonance investigations previously performed using magnetic fluids (MFs) based on spinel ferrite nanoparticles, cadmium-ferrite-based MFs present an intense, relatively sharp resonance line near g=4, in addition to the typical, broad structure near g=2. The broad resonance structure is associated with larger cadmium-ferrite nanoparticles, whereas the sharp resonance line is associated with ultrasmall cadmium-ferrite nanoparticles. Transmission

O. Silva; E. C. D. Lima; P. C. Morais

2003-01-01

78

Cadmium ferrite ionic magnetic fluid: Magnetic resonance investigation  

Microsoft Academic Search

In contrast to all magnetic resonance investigations previously performed using magnetic fluids (MFs) based on spinel ferrite nanoparticles, cadmium–ferrite-based MFs present an intense, relatively sharp resonance line near g=4, in addition to the typical, broad structure near g=2. The broad resonance structure is associated with larger cadmium–ferrite nanoparticles, whereas the sharp resonance line is associated with ultrasmall cadmium–ferrite nanoparticles. Transmission

O. Silva; E. C. D. Lima; P. C. Morais

2003-01-01

79

Investigation of magnetic resonances for different split-ring resonator parameters and designs  

Microsoft Academic Search

We investigate the magnetic resonance of split-ring resonators (SRR) experimentally and numerically. The dependence of the geometrical parameters on the magnetic resonance frequency of SRR is studied. We further investigate the effect of lumped capacitors integrated to the SRR on the magnetic resonance frequency for tunable SRR designs. Different resonator structures are shown to exhibit magnetic resonances at various frequencies

Koray Aydin; Irfan Bulu; Kaan Guven; Maria Kafesaki; Costas M Soukoulis; Ekmel Ozbay

2005-01-01

80

Magnetic resonance sees lesions of multiple sclerosis  

SciTech Connect

The value of nuclear magnetic resonance imaging in the diagnosis and quantitation of the progression of multiple sclerosis is discussed. Magnetic resonance imaging generates images that reflect differential density and velocity of hydrogen nuclei between cerebral gray and white matter, as well as between white matter and pathological lesions of the disease.

Ziporyn, T.

1985-02-15

81

Chemical Principles Revisited. Proton Magnetic Resonance Spectroscopy.  

ERIC Educational Resources Information Center

Discusses how to interpret nuclear magnetic resonance (NMR) spectra and how to use them to determine molecular structures. This discussion is limited to spectra that are a result of observation of only the protons in a molecule. This type is called proton magnetic resonance (PMR) spectra. (CW)

McQuarrie, Donald A.

1988-01-01

82

Magnetic resonance imaging of glioblastoma using aptamer conjugated magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

Here we introduce a new class of smart imaging probes hybridizing polysorbate 80 coated-magnetic nanoparticles with vascular endothelial growth factor receptor 2 (VEGFR2)-targetable aptamer for specific magnetic resonance (MR) imaging of angiogenesis from glioblastoma.

Kim, Bongjune; Yang, Jaemoon; Hwang, Myeonghwan; Suh, Jin-Suck; Huh, Yong-Min; Haam, Seungjoo

2012-10-01

83

Magnetic resonance imaging of electrolysis.  

PubMed

This study explores the hypothesis that Magnetic Resonance Imaging (MRI) can image the process of electrolysis by detecting pH fronts. The study has relevance to real time control of cell ablation with electrolysis. To investigate the hypothesis we compare the following MR imaging sequences: T1 weighted, T2 weighted and Proton Density (PD), with optical images acquired using pH-sensitive dyes embedded in a physiological saline agar solution phantom treated with electrolysis and discrete measurements with a pH microprobe. We further demonstrate the biological relevance of our work using a bacterial E. Coli model, grown on the phantom. The results demonstrate the ability of MRI to image electrolysis produced pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E. Coli model grown on the phantom. The results are promising and invite further experimental research. PMID:25659942

Meir, Arie; Hjouj, Mohammad; Rubinsky, Liel; Rubinsky, Boris

2015-01-01

84

Magnetic Resonance Imaging of Electrolysis.  

PubMed Central

This study explores the hypothesis that Magnetic Resonance Imaging (MRI) can image the process of electrolysis by detecting pH fronts. The study has relevance to real time control of cell ablation with electrolysis. To investigate the hypothesis we compare the following MR imaging sequences: T1 weighted, T2 weighted and Proton Density (PD), with optical images acquired using pH-sensitive dyes embedded in a physiological saline agar solution phantom treated with electrolysis and discrete measurements with a pH microprobe. We further demonstrate the biological relevance of our work using a bacterial E. Coli model, grown on the phantom. The results demonstrate the ability of MRI to image electrolysis produced pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E. Coli model grown on the phantom. The results are promising and invite further experimental research. PMID:25659942

Meir, Arie; Hjouj, Mohammad; Rubinsky, Liel; Rubinsky, Boris

2015-01-01

85

[Cardiac magnetic resonance imaging (MRI)].  

PubMed

TECHNOLOGICAL PROGRESS: Although cardiac magnetic resonance imaging (MRI) is now recognised as the imaging method of choice for the morphological study of the heart, recent technological progress have widened its indications to functional analysis of the heart rate, perfusion and contractility. FUNCTIONAL ASSESSMENT: The possibility of conducting pharmacological stress tests enhances the functional exploration of cardiac perfusion and contractility. The rapid sequences in apnea, tissue marking and injection of contrast products are all elements that help to refine the study of the locoregional consequences of an ischemia: does the myocardial tissue contract normally? Is it sufficiently perfused? Is it still viable? THE BENEFITS OF A NON-INVASIVE TECHNIQUE: The MRI offers clinicians a non-invasive and non-radiating imaging technique that is the perfect supplement to echocardiography. A reliable angio-coronary LRI technique would, for the first time, permit exploration of the coronary vascularisation, tissue perfusion and resulting contractility. PMID:15387389

Vignaux, Olivier

2004-07-31

86

Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion  

Microsoft Academic Search

Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for clinical imaging. Velocities can be measured along single lines, in

Christopher J. Elkins; Marcus T. Alley

2007-01-01

87

Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion  

Microsoft Academic Search

Magnetic resonance velocimetry (MRV) is a non-invasive technique capable of measuring the three-component mean velocity field\\u000a in complex three-dimensional geometries with either steady or periodic boundary conditions. The technique is based on the\\u000a phenomenon of nuclear magnetic resonance (NMR) and works in conventional magnetic resonance imaging (MRI) magnets used for\\u000a clinical imaging. Velocities can be measured along single lines, in

Christopher J. Elkins; Marcus T. Alley

2007-01-01

88

Application of Advanced Magnetic Resonance Imaging Techniques in Evaluation of the Lower Extremity  

PubMed Central

Synopsis This article reviews current magnetic resonance imaging techniques for imaging the lower extremity, focusing on imaging of the knee, ankle, and hip joints. Recent advancements in MRI include imaging at 7 Tesla, using multiple receiver channels, T2* imaging, and metal suppression techniques, allowing more detailed visualization of complex anatomy, evaluation of morphological changes within articular cartilage, and imaging around orthopedic hardware. PMID:23622097

Braun, Hillary J.; Dragoo, Jason L.; Hargreaves, Brian A.; Levenston, Marc E.; Gold, Garry E.

2012-01-01

89

Evaluation of Hydatid Disease of the Heart with Magnetic Resonance Imaging  

SciTech Connect

Two patients with cardiac involvement of hydatid disease are presented: one with hydatid cyst of the interventricular septum and pulmonary arteries and the other with multiple pulmonary cysts associated with intracardiac and pericardial cysts. The ability of magnetic resonance imaging (MRI) to provide a global view of cardiac anatomy in any plane with high contrast between flowing blood and soft tissue ensures it an important role in the diagnosis and preoperative assessment of hydatid disease of the heart.

Kotoulas, Grigoris K.; Magoufis, George L.; Gouliamos, Athanasios D.; Athanassopoulou, Alexandra K.; Roussakis, Arcadios C.; Koulocheri, Dimitra P.; Kalovidouris, Angelos; Vlahos, Labros [Department of Radiology, CT-MRI Unit, Areteion Hospital, University of Athens, 76 Vas. Sophias Ave., GR-115 28 Athens (Greece)

1996-05-15

90

High resolution neurography of the lumbosacral plexus on 3T magneteic resonance imaging.  

PubMed

Magnetic resonance neurography is a technique that complements clinical and electrophysiological study of the peripheral nerves and brachial and lumbosacral plexuses. Numerous focal processes (inflammatory, traumatic, primary tumors, secondary tumors) and diffuse processes (diabetic polyneuropathy, chronic idiopathic demyelinating polyneuropathy due to amyloidosis or Charcot-Marie-Tooth disease) can involve the lumbosacral plexus. This article reviews the anatomy of the lumbosacral plexus, describes the technique for neurography of the plexus at our institution, and shows the diverse diseases that affect it. PMID:25447367

Cejas, C; Escobar, I; Serra, M; Barroso, F

2014-11-15

91

[Magnetic resonance imaging of the breasts].  

PubMed

Not even magnetic resonance imaging is a perfect method for imaging of the breasts. Quality of the equipment, imaging parameters as well as the experience and competence of radiographers and radiologists have a significant effect on the final outcome of the study. Since interpretation of magnetic resonance imaging of the breasts is challenging, the radiologist should have access to a comprehensive medical history and previous images, including the reports. Feedback from the reports made and multidisciplinary postoperative meetings are important. Since magnetic resonance imaging is expensive and has low availability, it should be targeted at the correct patient groups. PMID:24340717

Hukkinen, Katja

2013-01-01

92

Modern Miracle Medical Machines: Magnetic Resonance Imaging  

NSDL National Science Digital Library

This learning activity teaches the physics of magnetic resonance imaging and NMR. It begins with instruction on the basics of magnetism, electromagnetism, and resonance and applies these topics to the operation of magnetic resonance equipment for medical diagnostics. This activity includes both hands-on exercises and computer visualizations. Information on the construction of the measurement apparatus is available in the instructor resources for the Modern Miracle Medical Machines web site. This one of a growing set of activities developed by the Kansas State University Physics Education Research group on the physics of modern medicine.

Murphy, Sytil K.

2010-06-08

93

Quantitative Pulmonary Imaging Using Computed Tomography and Magnetic Resonance Imaging  

PubMed Central

Measurements of lung function, including spirometry and body plethesmography, are easy to perform and are the current clinical standard for assessing disease severity. However, these lung functional techniques do not adequately explain the observed variability in clinical manifestations of disease and offer little insight into the relationship of lung structure and function. Lung imaging and the image based assessment of lung disease has matured to the extent that it is common for clinical, epidemiologic, and genetic investigation to have a component dedicated to image analysis. There are several exciting imaging modalities currently being used for the non-invasive study of lung anatomy and function. In this review we will focus on two of them, x-ray computed tomography and magnetic resonance imaging. Following a brief introduction of each method we detail some of the most recent work being done to characterize smoking-related lung disease and the clinical applications of such knowledge. PMID:22142490

Washko, George R.; Parraga, Grace; Coxson, Harvey O.

2011-01-01

94

Magnetic resonance imaging in the evaluation of the brainstem  

SciTech Connect

Magnetic resonance (MR) images of the brainstem region from 100 normal or asymptomatic individuals were reviewed in addition to those of 17 patients with intra-axial brainstem lesions and 15 patients with extra-axial masses around the brainstem. MR was able to demonstrate consistently the normal anatomy of the brainstem and adjacent cisterns, though the distinction between gray and white matter was seldom possible with the present technology. Masses in and around the brainstem were all accurately identified on MR and its sensitivity was superior to that of x-ray computed tomography (CT). These study results show that despite its technical limitations, MR is presently the examination of choice for the evaluation of brainstem abnormalities and eventually it will undoubtedly replace metrizamide CT cisternography.

Han, J.S.; Bonstelle, C.T.; Kaufman, B.; Benson, J.E.; Alfidi, R.J.; Clampitt, M.; Van Dyke, C.; Huss, R.G.

1984-03-01

95

Gated magnetic resonance imaging of the normal and diseased heart  

SciTech Connect

Gated cardiac magnetic resonance (MR) images were obtained in two normal volunteers and 21 adults with a variety of cardiovascular abnormalities. The images were correlated with data from clinical examination, electrocardiograms, and cardiac catheterization. Gated cardiac images were superior to nongated images. Combined cardiac and respiratory gated images were superior to images obtained with cardiac gating only, but acquisition time was longer. Portions of the coronary arteries were visualized in seven of 23 examinations (30%), and subacute and old myocardial infarcts were seen in five of nine patients (55%) as areas of thinned myocardium. Normal cardiac anatomy (chambers, valves, and papillary muscles) was well visualized. Examples of aortic stenosis and atherosclerosis of the abdominal aorta are shown.

Lieberman, J.M.; Alfidi, R.J.; Nelson, A.D.; Botti, R.E.; Moir, T.W.; Haaga, J.R.; Kopiwoda, S.; Miraldi, F.D.; Cohen, A.M.; Butler, H.E.

1984-08-01

96

Magnetic resonance images in hanging.  

PubMed

Hanging is a devastating method of suicide and unfortunately is common in Japan. Although several CT findings of the head have been reported, there have not been any reports about magnetic resonance imaging (MRI) in hanging. We report here interesting MRI findings in a patient after hanging. A 39-year-old woman was transferred to our department after attempting suicide by hanging. Respiration had probably ceased for about three minutes but heart had not stopped when she was pulled down by her father. After her father performed cardiopulmonary resuscitation, she started to breathe immediately. She was treated conservatively in our intensive care unit for 14 days, her condition became stable. Ten days after admission, MRI demonstrated symmetrical hyperintensity on T1-weighted images and relative hyperintensity on T2 weighted images in bilateral lentiform nuclei and medial thalami. There have been several reports about characteristic MRI findings in the case of acute global cerebral ischaemia caused by severe hypoglycaemia or longstanding cardiopulmonary arrest. It was postulated that these specific findings reflected tissue degeneration, deposition of mineral substances, or lipid accumulation. These MRI findings suggest that severe acute global cerebral hypoperfusion also occurs in hanging in the same way as in long-standing cardiopulmonary arrest and that hanging has devastating sequelae. PMID:16458413

Matsuyama, Takeshi; Okuchi, Kazuo; Seki, Tadahiko; Higuchi, Takafumi; Ito, Shingo; Makita, Daisuke; Watanabe, Tomoo; Murao, Yoshinori

2006-05-01

97

Gradient characterization in magnetic resonance imaging  

E-print Network

Special magnetic resonance (MR) scans, such as spiral imaging and echo-planar imaging, require speed and gradient accuracy while putting high demands on the MR gradient system that may cause gradient distortion. Additionally, ...

Cheng, Joseph Yitan

2007-01-01

98

Parallel magnetic resonance imaging: characterization and comparison  

E-print Network

Magnetic Resonance Imaging (MRI) is now increasingly being used for fast imaging applications such as real-time cardiac imaging, functional brain imaging, contrast enhanced MRI, etc. Imaging speed in MRI is mainly limited by different imaging...

Rane, Swati Dnyandeo

2005-11-01

99

Magnetic Resonance Pulse Sequences for Fluorine-19  

E-print Network

. Magnetic resonance imaging (MRI) has the ability to noninvasively track the transplanted cells to ensure they are in the desired destination. Unlike other MRI contrast agents, fluorine-19 has the ability to provide unambiguous cell tracking for two reasons...

Terry, Robin

2014-07-11

100

Magnetic resonance imaging in cardiovascular disease   

E-print Network

Background Superparamagnetic particles of iron oxide (SPIO) are part of a novel and exciting class of ‘smart’ magnetic resonance imaging (MRI) contrast agents that are taken up by inflammatory cells. Ultrasmall SPIO ...

Richards, Jennifer Margaret Jane

2013-07-06

101

Miniature Magnet for Electron Spin Resonance Experiments  

ERIC Educational Resources Information Center

Describes commercially available permanent magnets that have been incorporated in a compact and inexpensive structure providing both field sweep and modulation suitable for electron spin resonance at microwave frequencies. (MLH)

Rupp, L. W.; And Others

1976-01-01

102

Coronary Computed Tomography and Magnetic Resonance Imaging  

PubMed Central

Cardiac computed tomography and magnetic resonance are relatively new imaging modalities that can exceed the ability of established imaging modalities to detect present pathology or predict patient outcomes. Coronary calcium scoring may be useful in asymptomatic patients at intermediate risk. Computed tomographic coronary angiography is a first-line indication to evaluate congenitally abnormal coronary arteries and, along with stress magnetic resonance myocardial perfusion imaging, is useful in symptomatic patients with nondiagnostic conventional stress tests. Cardiac magnetic resonance is indicated for visualizing cardiac structure and function, and delayed enhancement magnetic resonance is a first-line indication for assessing myocardial viability. Imaging plaque and molecular mechanisms related to plaque rupture holds great promise for the presymptomatic detection of patients at risk for coronary events but is not yet suitable for routine clinical use. PMID:19269527

Kantor, Birgit; Nagel, Eike; Schoenhagen, Paul; Barkhausen, Jörg; Gerber, Thomas C.

2009-01-01

103

Magnetic Resonance Imaging of Tissues Compatible with Supernumerary Extraocular Muscles  

PubMed Central

PURPOSE To determine by magnetic resonance imaging (MRI) the prevalence and anatomy of anomalous EOM bands. DESIGN Prospective, observational case series. METHODS High resolution, multi-positional, surface coil orbital MRI was performed using T1 or T2 fast spin echo weighting with target fixation control under a prospective protocol in normal adult subjects and a diverse group of strabismic patients between 1996 and 2009. Images demonstrating anomalous EOM bands were analyzed digitally to evaluate their sizes and paths, correlating findings with complete ophthalmic and motility examinations. RESULTS Among 118 orthotropic and 453 strabismic subjects, one (0.8%) orthotropic and 11 (2.4%) strabismic subjects exhibited unilateral or bilateral orbital bands having MRI signal characteristics identical to EOM. Most bands occurred without other EOM dysplasia and coursed in the retrobulbar space between rectus EOMs such as medial (MR) to lateral rectus (LR), or superior (SR) to inferior rectus (IR), or from one EOM to the globe. In two cases, horizontal bands from MR to LR immediately posterior to the globe apparently limited supraduction by collision with the optic nerve. All bands were too deep to be approached via conventional strabismus surgical approaches. CONCLUSIONS About 2% of humans exhibit on MRI deep orbital bands consistent with supernumerary EOMs. While band anatomy is non-oculorotary, some bands may cause restrictive strabismus. PMID:20801423

Khitri, Monica R.; Demer, Joseph L.

2010-01-01

104

Magnetic resonance studies of lunar samples  

Microsoft Academic Search

Electron spin resonance searches at 9.5 gigahertz on several fines samples and portions of several rocks have yielded signals whose lineshapes and temperature dependences show that the samples are principally ferromagnetic in nature. Proton magnetic resonance searches at 60 megahertz of these samples have not revealed any signals ascribable to water or any other types of hydrogen in concentrations greater

Stanley L. Manatt; Daniel D. Elleman; Robert W. Vaughan; Sunney I. Chan; Fun-Dow Tsay; Wesley T. Huntress Jr.

1970-01-01

105

Fano resonances in magnetic metamaterials  

SciTech Connect

We study the scattering of magnetoinductive plane waves by internal (external) capacitive (inductive) defects coupled to a one-dimensional split-ring resonator array. We examine a number of simple defect configurations where Fano resonances occur and study the behavior of the transmission coefficient as a function of the controllable external parameters. We find that for embedded capacitive defects, the addition of a small amount of coupling to second neighbors is necessary for the occurrence of Fano resonance. For external inductive defects, Fano resonances are commonplace, and they can be tuned by changing the relative orientation or distance between the defect and the SSR array.

Naether, Uta; Molina, Mario I. [Departmento de Fisica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile) and Center for Optics and Photonics (CEFOP), Casilla 4016, Concepcion (Chile)

2011-10-15

106

HOSPITAL PHYSICS: Magnetic resonance imaging and spectroscopy  

Microsoft Academic Search

Nuclear Magnetic Resonance (NMR) was first described in the scientific literature 50 years ago when Bloch and Purcell, working independently, showed how certain nuclei placed in a magnetic field absorbed energy in the radiofrequency range and re-emitted this energy during their transition back to the relaxed state (Bloch 1946, Purcell 1946). This phenomenon has since revolutionized medical imaging with its

Caroline Andrews; Andrew Simmons; Steve Williams

1996-01-01

107

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy  

E-print Network

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy B. J. Suh, P is similar to that used in magnetic force microscopy MFM ,4 where only the spin magnetization in the vicinity of microscopic ferromagnetic resonance FMR detected using the magnetic resonance force microscope MRFM

Hammel, P. Chris

108

Coherence of magnetic resonators in a metamaterial  

SciTech Connect

The coherence of periodic magnetic resonators (MRs) under oblique incidence is studied using simulations. The correlated phase of interaction including both the retardation effect and relative phase difference between two MRs is defined, and it plays a key role in the MR interaction. The correlated phase is anisotropic, as is the coherence condition. The coherence condition is the same as the Wood's anomaly and verified by the Fano resonance. This study shows that the applications of the Fano resonance of periodic MRs will become widespread owing to achieving the Fano resonance simply by tuning the incident angle.

Hou, Yumin, E-mail: ymhou@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)] [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)

2013-12-15

109

Wave-Particle Resonance in Magnetized Plasma  

NASA Astrophysics Data System (ADS)

We report the first observation of the wave-particle resonance line in a magnetized and weakly collisional plasma. The linear resonance satisfies the relation ?-n?ci = k||?|| and has a width which is related to the wave-particle coherence time. Both the in-phase (real) and quadrature (imaginary) parts of the resonant response are directly determined by a phased-lock laser induced fluorescence diagnostic. The wave-particle coherence time obtained by fitting the resonance line shape to a one-dimensional Poisson-Fokker-Planck model does not agree with a simple model of ion collisionality.

Sarfaty, M.; de Souza-Machado, S.; Skiff, F.

1998-04-01

110

Investigation of laser polarized xenon magnetic resonance  

NASA Technical Reports Server (NTRS)

Ground-based investigations of a new biomedical diagnostic technology: nuclear magnetic resonance of laser polarized noble gas are addressed. The specific research tasks discussed are: (1) Development of a large-scale noble gas polarization system; (2) biomedical investigations using laser polarized noble gas in conventional (high magnetic field) NMR systems; and (3) the development and application of a low magnetic field system for laser polarized noble gas NMR.

Walsworth, Ronald L.

1998-01-01

111

Magnetic material arrangement in oriented termites: a magnetic resonance study  

NASA Astrophysics Data System (ADS)

Temperature dependence of the magnetic resonance is used to study the magnetic material in oriented Neocapritermes opacus (N.o.) termite, the only prey of the migratory ant Pachycondyla marginata (P.m.). A broad line in the g=2 region, associated to isolated nanoparticles shows that at least 97% of the magnetic material is in the termite's body (abdomen + thorax). From the temperature dependence of the resonant field and from the spectral linewidths, we estimate the existence of magnetic nanoparticles 18.5 ± 0.3 nm in diameter and an effective magnetic anisotropy constant, Keff between 2.1 and 3.2 × 10 4 erg/cm 3. A sudden change in the double integrated spectra at about 100 K for N.o. with the long body axis oriented perpendicular to the magnetic field can be attributed to the Verwey transition, and suggests an organized film-like particle system.

Alves, O. C.; Wajnberg, E.; de Oliveira, J. F.; Esquivel, D. M. S.

2004-06-01

112

Planar Magnetic Metamaterial Slabs for Magnetic Resonance Imaging Applications  

NASA Astrophysics Data System (ADS)

A type of planar magnetic metamaterial is proposed with a square winding microstructure as a superlens for magnetic resonance imaging (MRI) applications. A direct magnetic field mapping measurement demonstrates that the radio-frequency magnetic field passing through the superlens is increased by as high as 46.9% at the position of about 3 cm behind the superlens. The resonance frequency of the fabricated slabs is found to be in good agreement with the target frequency (63.6 MHz) for a 1.5T MRI system. MRI experiments with the magnetic superlens show that the intensity of the image and the SNR (signal-to-noise ratio) are both enhanced, implying promising MRI applications of our planar magnetic superlens.

Li, Chun-Lai; Guo, Jie; Zhang, Peng; Yu, Quan-Qiang; Ma, Wei-Tao; Miao, Xi-Gen; Zhao, Zhi-Ya; Luan, Lin

2014-07-01

113

Magnetic resonance imaging by using nano-magnetic particles  

NASA Astrophysics Data System (ADS)

Magnetism and magnetic materials play a major role in various biological applications, such as magnetic bioseparation, magnetic resonance imaging (MRI), hyperthermia treatment of cancer and drug delivery. Among these techniques, MRI is a powerful method not only for diagnostic radiology but also for therapeutic medicine that utilizes a magnetic field and radio waves. Recently, this technique has contributed greatly to the promotion of the human quality life. Thus, this paper presents a short review of the physical principles and recent advances of MRI, as well as providing a summary of the synthesis methods and properties of contrast agents, like different core materials and surfactants.

Shokrollahi, H.; Khorramdin, A.; Isapour, Gh.

2014-11-01

114

Magnetic resonance in multilayer Gd/Si/Co magnetic films  

SciTech Connect

The magnetic properties of multilayer Gd/Si/Co magnetic films are experimentally studied by electron magnetic resonance and analyzed theoretically. The introduction of a semiconductor silicon interlayer is found to substantially affect the magnetic interlayer coupling and the magnetic dynamics of the system. The interlayer coupling is shown to be ferromagnetic for the (Gd/Si){sub n} films and to be antiferromagnetic for the (Gd/Si/Co/Si){sub n} films. The temperature dependences of the exchange parameters and the gyromagnetic ratios are determined. Possible mechanisms responsible for the formation of the interlayer coupling are discussed.

Patrin, G. S. [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Division (Russian Federation)], E-mail: patrin@iph.krasn.ru; Vas'kovskii, V. O.; Svalov, A. V. [Ural State University (Russian Federation); Eremin, E. V.; Panova, M. A.; Vasil'ev, V. N. [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Division (Russian Federation)

2006-01-15

115

Observation of 239Pu nuclear magnetic resonance.  

PubMed

In principle, the spin-½ plutonium-239 ((239)Pu) nucleus should be active in nuclear magnetic resonance spectroscopy. However, its signal has eluded detection for the past 50 years. Here, we report observation of a (239)Pu resonance from a solid sample of plutonium dioxide (PuO(2)) subjected to a wide scan of external magnetic field values (3 to 8 tesla) at a temperature of 4 kelvin. By mapping the external field dependence of the measured resonance frequency, we determined the nuclear gyromagnetic ratio (239)?(n)(PuO(2))/2? to be 2.856 ± 0.001 megahertz per tesla (MHz/T). Assuming a free-ion value for the Pu(4+) hyperfine coupling constant, we estimated a bare (239)?(n)/2? value of ~2.29 MHz/T, corresponding to a nuclear magnetic moment of ?(n) ? 0.15?(N) (where ?(N) is the nuclear magneton). PMID:22605773

Yasuoka, H; Koutroulakis, G; Chudo, H; Richmond, S; Veirs, D K; Smith, A I; Bauer, E D; Thompson, J D; Jarvinen, G D; Clark, D L

2012-05-18

116

Magnetic resonance lymphography in gynaecological malignancies  

PubMed Central

Abstract Following the submission of this article to Cancer Imaging, unfortunately the European manufacturer of ferumoxtran-10 (Guerbet) has withdrawn the product pending further phase III studies. This is secondary to the view of the Committee for Medicinal Products for Human Use that the phase III data did not provide adequate statistical demonstration of the product's efficacy. Magnetic resonance lymphography holds much promise for the non-invasive evaluation of lymph nodes. The technique utilizes ultrasmall superparamagnetic particles of iron oxide and has been shown to be highly sensitive and specific in the diagnosis of malignant lymph nodes. This article reviews the technique and the performance of magnetic resonance lymphography in studies to date; alternative newer methods of nodal assessment such as fluorodeoxyglucose-positron emission tomography/computed tomography and diffusion-weighted magnetic resonance imaging are also discussed, with emphasis on gynaecological malignancies. PMID:20233680

Narayanan, Priya; Rockall, Andrea

2010-01-01

117

Nuclear magnetic resonance offers new insights into Pu 239  

E-print Network

- 1 - Nuclear magnetic resonance offers new insights into Pu 239 May 29, 2012 Nuclear magnetic signal of plutonium 239's unique nuclear magnetic resonance signature has been detected by scientists on the subject, "Observation of 239 Pu Nuclear Magnetic Resonance," was published in the May 18 issue of Science

118

Functional magnetic resonance imaging in pediatrics.  

PubMed

Functional magnetic resonance imaging (fMRI) allows non-invasive assessment of human brain function in vivo by detecting blood flow differences. In this review, we want to illustrate the background and different aspects of performing functional magnetic resonance imaging (fMRI) in the pediatric age group. An overview over current and future applications of fMRI will be given, and typical problems, pitfalls, and benefits of doing fMRI in the pediatric age group are discussed. We conclude that fMRI can successfully be applied in children and holds great promise for both research and clinical purposes. PMID:14598227

Wilke, M; Holland, S K; Myseros, J S; Schmithorst, V J; Ball, W S

2003-06-01

119

Magnetic Microparticle Aggregation For Viscosity Determination By Magnetic Resonance  

PubMed Central

Micron-sized magnetic particles were induced to aggregate when placed in homogeneous magnetic fields, like those of magnetic resonance (MR) imagers and relaxometers, and then spontaneously returned to their dispersed state when removed from the field. Associated with the aggregation and dispersion of the magnetic particles were time dependent increases and decreases in the spin-spin relaxation time (T2) of the water. Magnetic nanoparticles, with far smaller magnetic moments per particle, did not undergo magnetically induced aggregation, and exhibited time independent values of T2. The rate of T2 change associated with magnetic micro-particle aggregation was used to determine the viscosity of liquid samples, providing a method that can be of particular advantage for determining the viscosity of small volumes of potentially biohazardous samples of blood or blood plasma. PMID:18306403

Hong, Rui; Cima, Michael J.; Weissleder, Ralph; Josephson, Lee

2009-01-01

120

Masticator space: imaging anatomy for diagnosis.  

PubMed

Masticator space anatomy and pathologic conditions are illustrated examples from computed tomography and magnetic resonance imaging. Characteristic imaging features of various disease processes are presented to aid the otolaryngologist (head and neck surgeon) in diagnosis. The article describes infection, primary neoplasm, metastatic disease, Osteonecrosis, and vascular anomalies. PMID:23153747

Meltzer, Daniel E; Shatzkes, Deborah R

2012-12-01

121

Observation of ferromagnetic resonance in a microscopic sample using magnetic resonance force microscopy  

E-print Network

can be measured. Employing magnetic resonance force microscopy MRFM we have observed a strong FMRObservation of ferromagnetic resonance in a microscopic sample using magnetic resonance force resonance force microscopy MRFM . The large signal intensity in the resonance spectra suggests that MRFM

Hammel, P. Chris

122

Video: Proton Nuclear Magnetic Resonance (NMR)  

NSDL National Science Digital Library

This video, distributed on YouTube by the Royal Society of Chemistry, describes the basic principles of Nuclear Magnetic Resonance. This video is a good primer and would be very useful to supplement introductory lectures on NMR. The video covers the basic theory behind a 1H spectrum and goes through actually acquiring a spectrum. The top-off look of the instrument is useful and how the superconducting magnet is mounted. Running time for the video is 8:43.

2011-06-03

123

Nuclear Magnetic Resonance Technology for Medical Studies.  

ERIC Educational Resources Information Center

Reports on the status of nuclear magnetic resonance (NMR) from theoretical and clinical perspectives, reviewing NMR theory and relaxation parameters relevant to NMR imaging. Also reviews literature related to modern imaging strategies, signal-to-noise ratio, contrast agents, in vivo spectroscopy, spectroscopic imaging, clinical applications, and…

Budinger, Thomas F.; Lauterbur, Paul C.

1984-01-01

124

Myocardial tissue tagging with cardiovascular magnetic resonance  

Microsoft Academic Search

Cardiovascular magnetic resonance (CMR) is currently the gold standard for assessing both global and regional myocardial function. New tools for quantifying regional function have been recently developed to characterize early myocardial dysfunction in order to improve the identification and management of individuals at risk for heart failure. Of particular interest is CMR myocardial tagging, a non-invasive technique for assessing regional

Monda L Shehata; Susan Cheng; Nael F Osman; David A Bluemke; João AC Lima

2009-01-01

125

STROBOSCOPIC ARTICULOGRAPHY USING FAST MAGNETIC RESONANCE IMAGING  

Microsoft Academic Search

A method to display dynamic aspects of vocal tract configuration during speech production by means of fast magnetic resonance imaging (MRI) is presented. Data acquisition during repetitive movement relies on a stroboscopy-like procedure. The time res- olution achieved is 120 images per second in a selected plane. As compared to other techniques of kinematic measurements of speech motor processes, this

K. Mathiak; U. Klose; H. Ackermann; I. Hertrich; W.-E. Kincses; W. Grodd

126

Magnetic resonance images of chronic patellar tendinitis  

Microsoft Academic Search

Chronic patellar tendinitis can be a frustrating diagnostic and therapeutic problem. This report evaluates seven tendons in five patients with chronic patellar tendinitis. The etiologies included “jumper's knee” and Osgood-Schlatter disease. In all cases magnetic resonance images (MRI) showed thickening of the tendon. Some of the tendons had focal areas of thickening which helped establish the etiology. All cases had

David Bodne; Stephen F. Quinn; William T. Murray; Thomas Bolton; Steven Rudd; Kirk Lewis; Peter Daines; John Bishop; Courtney Cochran

1988-01-01

127

Brain Morphometry Using Anatomical Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

The efficacy of anatomical magnetic resonance imaging (MRI) in studying the morphological features of various regions of the brain is described, also providing the steps used in the processing and studying of the images. The ability to correlate these features with several clinical and psychological measures can help in using anatomical MRI to…

Bansal, Ravi; Gerber, Andrew J.; Peterson, Bradley S.

2008-01-01

128

Magnetic Resonance Imaging in Lewy Body Dementias  

Microsoft Academic Search

Dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD) share common clinical, neuropsychological and pathological features. In clinical diagnosis, distinguishing between these conditions and other dementia subtypes such as Alzheimer’s disease (AD) can be difficult. Despite the development of consensus diagnostic criteria, sensitivity for diagnosis remains low, especially outside specialist centres. Neuroimaging techniques using magnetic resonance (MR) can assess

Rosie Watson; Andrew M. Blamire; John T. O’Brien

2009-01-01

129

Analytical Methods for Characterizing Magnetic Resonance Probes  

PubMed Central

SUMMARY The efficiency of Gd(III) contrast agents in magnetic resonance image enhancement is governed by a set of tunable structural parameters. Understanding and measuring these parameters requires specific analytical techniques. This Feature describes strategies to optimize each of the critical Gd(III) relaxation parameters for molecular imaging applications and the methods employed for their evaluation. PMID:22624599

Manus, Lisa M.; Strauch, Renee C.; Hung, Andy H.; Eckermann, Amanda L.; Meade, Thomas J.

2012-01-01

130

Magnetic resonance imaging in prostate cancer  

Microsoft Academic Search

With the recently published National Institute of Clinical Excellence guidelines, it is now generally accepted that magnetic resonance imaging (MRI) is the imaging method of choice for staging prostate cancer in patients for whom radical treatment is being considered. MRI offers the single most accurate assessment of local disease and regional metastatic spread. As well as detecting extraprostatic extension, this

S D Heenan

2004-01-01

131

Magnetic Resonance Imaging in Endodontic Treatment Prediction  

Microsoft Academic Search

The necessary condition for successful endodontic treatment is the precise mapping of the shape of dental cavities. The aim of this work has been an elaboration and verification of the possibility of using three-dimensional (3D) spin echo magnetic resonance imaging (MRI) techniques in dentistry. Six extracted molar teeth were used for measurements without additional preparation and after endodontic preparation. MRI

Marta Tanasiewicz

2010-01-01

132

Imaging Intelligence with Proton Magnetic Resonance Spectroscopy  

ERIC Educational Resources Information Center

Proton magnetic resonance spectroscopy ([to the first power]H-MRS) is a technique for the assay of brain neurochemistry "in vivo." N-acetylaspartate (NAA), the most prominent metabolite visible within the [to the first power]H-MRS spectrum, is found primarily within neurons. The current study was designed to further elucidate NAA-cognition…

Jung, Rex E.; Gasparovic, Charles; Chavez, Robert S.; Caprihan, Arvind; Barrow, Ranee; Yeo, Ronald A.

2009-01-01

133

An improved nuclear magnetic resonance spectrometer  

NASA Technical Reports Server (NTRS)

Cylindrical sample container provides a high degree of nuclear stabilization to a nuclear magnetic resonance /nmr/ spectrometer. It is placed coaxially about the nmr insert and contains reference sample that gives a signal suitable for locking the field and frequency of an nmr spectrometer with a simple audio modulation system.

Elleman, D. D.; Manatt, S. L.

1967-01-01

134

Sample spinner for nuclear magnetic resonance spectrometer  

SciTech Connect

A sample spinner for a nuclear magnetic resonance spectrometer having improved operating characteristics is described comprising a rotor supported at both ends by support gas bearings and positioned by a thrust gas bearing. Improved support gas bearings are also described which result in a spinner exhibiting long-term stable operation characteristics.

Stejskal, E.O.

1984-05-01

135

Nuclear magnetic resonance in rare earth metals  

Microsoft Academic Search

This article describes the study, by nuclear magnetic resonance, of both static and dynamical aspects of the hyperfine interaction in rare earth metals, and illustrates the categories of information that can be obtained by using nuclei as microscopic probes in metallic media. The systems discussed include not only the pure rare earth metals but also their alloys and their metallic

M. A. H. McCausland; I. S. Mackenzie

1979-01-01

136

Functional Magnetic Resonance Imaging of Pain Consciousness  

E-print Network

reflex sympathetic dystrophy (RSD) and chronic back pain. The review emphasizes that differentFunctional Magnetic Resonance Imaging of Pain Consciousness: Cortical Networks of Pain Critically Depend on What is Implied by "Pain" A. Vania Apkarian, PhD Address SUNY Health Science Center, Department

Apkarian, A. Vania

137

Quantum electrodynamic equations for magnetic resonance- and optical spectroscopic transitions  

E-print Network

Quantum electrodynamic equations for magnetic resonance- and optical spectroscopic transitions have been for the first time obtained. New phenomena - stochastic electrical and magnetic spin wave resonances are predicted to be the effects of EM-field quantization.

D. Yearchuck; Y. Yerchak; A. Alexandrov

2009-03-02

138

Multidimensionally Encoded Magnetic Resonance Imaging  

E-print Network

algorithm. As an alternative to linear SEMs, nonlinear SEMs have been used to improve the dynamic range-dimensional spatial bases created by linear spa- tial encoding magnetic fields (SEMs). Recently, imaging strat- egies and linear SEMs can be used jointly to further improve the image reconstruction performance. Here, we propose

139

Magnetic Layer in Neutron Wave Resonator  

NASA Astrophysics Data System (ADS)

Expressions for the neutron density and the neutron reflection amplitude are given in the case of a non-collinear magnetic layer inside of the neutron wave resonator subject to a static or a rotating magnetic fields. It is shown that the enhancement of the spin-flip reflection intensity and density of neutrons in opposite to initial spin state are enhanced in second and third degree relatively of enhancement of neutron density in the initial spin state, correspondently. Conditions are defined for high sensitive measurements of the magnetic layer parameters.

Nikitenko, Yu. V.

140

Interaction of magnetic resonators studied by the magnetic field enhancement  

SciTech Connect

It is the first time that the magnetic field enhancement (MFE) is used to study the interaction of magnetic resonators (MRs), which is more sensitive than previous parameters–shift and damping of resonance frequency. To avoid the coherence of lattice and the effect of Bloch wave, the interaction is simulated between two MRs with same primary phase when the distance is changed in the range of several resonance wavelengths, which is also compared with periodic structure. The calculated MFE oscillating and decaying with distance with the period equal to resonance wavelength directly shows the retardation effect. Simulation also shows that the interaction at normal incidence is sensitive to the phase correlation which is related with retardation effect and is ultra-long-distance interaction when the two MRs are strongly localized. When the distance is very short, the amplitude of magnetic resonance is oppressed by the strong interaction and thus the MFE can be much lower than that of single MR. This study provides the design rules of metamaterials for engineering resonant properties of MRs.

Hou, Yumin, E-mail: ymhou@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)] [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China)

2013-12-15

141

Browsing Software of the Visible Korean Data Used for Teaching Sectional Anatomy  

ERIC Educational Resources Information Center

The interpretation of computed tomographs (CTs) and magnetic resonance images (MRIs) to diagnose clinical conditions requires basic knowledge of sectional anatomy. Sectional anatomy has traditionally been taught using sectioned cadavers, atlases, and/or computer software. The computer software commonly used for this subject is practical and…

Shin, Dong Sun; Chung, Min Suk; Park, Hyo Seok; Park, Jin Seo; Hwang, Sung Bae

2011-01-01

142

The Functional Anatomy of Inspection Time: A Pilot fMRI Study.  

ERIC Educational Resources Information Center

Studied the functional anatomy of inspection time (IT) through functional magnetic resonance imaging of the brain while seven healthy adults performed an IT task. Pilot data encourage further studies of the functional anatomy of inspection time and its relation to psychometric intelligence. (SLD)

Deary, Ian J.; Simonotto, Enrico; Marshall, Alan; Marshall, Ian; Goddard, Nigel; Wardlaw, Joanna M.

2001-01-01

143

Magnetic resonance properties of some lunar material.  

PubMed

Paramagnetic resonance spectra of Apollo 11 fines and rocks were measured at 9 and 35 gigahertz and at 4 degrees , 80 degrees , and 300 degrees K. At both frequencies the material has an intense absorption at g = 2, with a line width of approximately 950 gauss. Fe ions with strong exchange interactions produce this resonance. A comparison of the resonance absorption due to Fe(3+) showed that the energy of the crystal field interaction was approximately 0.1 per centimeter. Mn(2+) was identified in several samples, and an absorption at g = 1.89 was tentatively attributed to Ti(3+). The nuclear magnetic resonance spectra of (27)Al had a distribution of asymmetry parameters eta ranging from 0.25 to 0.75 and had nuclear quadrupole coupling constants e(2)qQ/h of approximately 3 megahertz. PMID:17781555

Weeks, R A; Chatelain, A; Kolopus, J L; Kline, D; Castle, J G

1970-01-30

144

Magnetic resonance imaging of the heart: positioning and gradient angle selection for optimal imaging planes  

SciTech Connect

Electrocardiographically gated magnetic resonance images were acquired in 20 subjects using a spin-echo pulse sequence. For optimizing the display of cardiac anatomy, a technique was developed which uses patients positioning in addition to alteration of gradient angle to select image planes. High-quality images were acquired in three basic cardiac projections: (1) the long axis of the left ventricle, through the aortic valve and apex, parallel to the interventricular septum, (2) the long axis of the left ventricle, perpendicular to the septum, and (3) the short axis of the left ventricle at multiple levels including outflow, papillary muscle, and apex. Images of the aorta included axial images at multiple levels and long-axis images oriented to display the plane of the aortic arch. Images of these planes are easily achieved and, in contrast to standard images orthogonal to the chest wall, provide a reproductible and logical display of cardiac anatomy.

Dinsmore, R.E.; Wismer, G.L.; Levine, R.A.; Okada, R.D.; Brady, T.J.

1984-12-01

145

Magnetic Earth Ionosphere Resonant Frequencies  

NASA Technical Reports Server (NTRS)

The Community College Division is pleased to report progress of NASA funded research at West Virginia State College. During this reporting period, the project research group has continued with activities to develop instrumentation capability designed to monitor resonant cavity frequencies in the atmospheric region between the Earth's surface and the ionosphere. In addition, the project's principal investigator, Dr. Craig Spaniol, and NASA technical officer, Dr. John Sutton, have written and published technical papers intended to expand the scientific and technical framework needed for project research. This research continues to provide an excellent example of government and education working together to provide significant research in the college environment. This cooperative effort has provided many students with technical project work which compliments their education.

Spaniol, Craig

1994-01-01

146

Magnetic resonance studies of lunar samples.  

PubMed

Electron spin resonance searches at 9.5 gigahertz on several fines samples and portions of several rocks have yielded signals whose lineshapes and temperature dependences show that the samples are principally ferromagnetic in nature. Proton magnetic resonance searches at 60 megahertz of these samples have not revealed any signals ascribable to water or any other types of hydrogen in concentrations greater than 0.0001 percent by weight contained in narrow lines (5 oersteds wide or less) and 0.01 percent by weight in wide lines (as wide as 100 oersteds). PMID:17781557

Manatt, S L; Elleman, D D; Vaughan, R W; Chan, S I; Tsay, F D; Huntress, W T

1970-01-30

147

Cadmium ferrite ionic magnetic fluid: Magnetic resonance investigation  

NASA Astrophysics Data System (ADS)

In contrast to all magnetic resonance investigations previously performed using magnetic fluids (MFs) based on spinel ferrite nanoparticles, cadmium-ferrite-based MFs present an intense, relatively sharp resonance line near g=4, in addition to the typical, broad structure near g=2. The broad resonance structure is associated with larger cadmium-ferrite nanoparticles, whereas the sharp resonance line is associated with ultrasmall cadmium-ferrite nanoparticles. Transmission electron microscopy (TEM) data confirm the bimodal particle size distribution in the sample investigated. The temperature T dependence of the resonance field HR is almost linear, for both high-field (HF) and low-field (LF) resonance lines, in the range of 100-300 K. In support of the identification of the HF line (around g=2) and LF line (around g=4) with larger and smaller Cd-ferrite nanoparticles, respectively, the slope of the HR versus T curve is lower for the HF line (1.3 G/K) compared to the LF line (1.69 G/K), whereas the intercept constant of the HF line (3050 G) is higher than the intercept constant of the LF line (1130 G).

Silva, O.; Lima, E. C. D.; Morais, P. C.

2003-05-01

148

Differentiation of radiation fibrosis from recurrent pulmonary neoplasm by magnetic resonance imaging  

SciTech Connect

Recent reports have shown the value of magnetic resonance imaging (MRI) in demonstrating normal and abnormal mediastinal and hilar anatomy. The potential role of MRI in evaluating patients who have undergone prior chest irradiation for pulmonary neoplasm has not been emphasized. The MRI appearance of mediastinal fibrosis after treatment of a patient with Hodgkin disease has been illustrated. Although plain chest radiographs and CT can demonstrate radiation-induced changes within the thorax, it is often difficult to distinguish radiation fibrosis from residual tumor. The authors report a case in which MRI differentiated fibrosis from recurrent tumor, thus confirming both the conventional radiographic and CT suspicions of recurrent neoplasm.

Glazer, H.S.; Levitt, R.G.; Lee, J.K.T.; Emami, B.; Gronemeyer, S.; Murphy, W.A.

1984-10-01

149

Magnetic resonance of calcified tissues  

NASA Astrophysics Data System (ADS)

MRI of the human body is largely made possible by the favorable relaxation properties of protons of water and triacyl glycerides prevalent in soft tissues. Hard tissues - key among them bone - are generally less amenable to measurement with in vivo MR imaging techniques, not so much as a result of the lower proton density but rather due to the extremely short life-times of the proton signal in water bound to solid-like entities, typically collagen, or being trapped in micro-pores. Either mechanism can enhance T2 relaxation by up to three orders of magnitude relative to their soft-tissue counterparts. Detection of these protons requires solid-state techniques that have emerged in recent years and that promise to add a new dimension to the study of hard tissues. Alternative approaches to probe calcified tissues exploit their characteristic magnetic properties. Bone, teeth and extra-osseous calcium-containing biomaterials are unique in that they are more diamagnetic than all other tissues and thus yield information indirectly by virtue of the induced magnetic fields present in their vicinity. Progress has also been made in methods allowing very high-resolution structural imaging of trabecular and cortical bone relying on detection of the surrounding soft-tissues. This brief review, much of it drawn from work conducted in the author's laboratory, seeks to highlight opportunities with focus on early-stage developments for image-based assessment of structure, function, physiology and mechanics of calcified tissues in humans via liquid and solid-state approaches, including proton, deuteron and phosphorus NMR and MRI.

Wehrli, Felix W.

2013-04-01

150

Multiplane magnetic resonance imaging of the heart and major vessels: studies in normal volunteers  

SciTech Connect

The feasibility of magnetic resonance imaging for defining anatomy of internal cardiac structures and major blood vessels was assessed in 14 normal subjects. Both electrocardiogram-gated and standard spin-echo images were obtained. Gated images provided better visualization of internal cardiac morphology and of upper mediastinal vessels than did nongated images. Trabecular detail and components of the mitral valve could be resolved. All segments of the left ventricular wall could be evaluated by combining axial, coronal, and sagittal images. Gated acquisition of magnetic resonance images did not increase imaging time; five transverse slices of the left ventricle were obtained in 6.0-8.5 min. The good image quality, ease of gated acquisition, large field of view, capability of direct imaging in multiple planes, and noninvasiveness of the technique suggest that it will be an important imaging method in cardiovascular disease.

Higgins, C.B.; Stark, D.; McNamara, M.; Lanzer, P.; Crooks, L.E.; Kaufman, L.

1984-04-01

151

Journal of Magnetism and Magnetic Materials 286 (2005) 324328 Light-free magnetic resonance force microscopy for studies of  

E-print Network

Journal of Magnetism and Magnetic Materials 286 (2005) 324­328 Light-free magnetic resonance force for Physical Sciences, College Park, MD, USA Available online 4 November 2004 Abstract Magnetic resonance force microscopy is a scanned probe technique capable of three-dimensional magnetic resonance imaging. Its

152

Foundations of Advanced Magnetic Resonance Imaging  

PubMed Central

Summary: During the past decade, major breakthroughs in magnetic resonance imaging (MRI) quality were made by means of quantum leaps in scanner hardware and pulse sequences. Some advanced MRI techniques have truly revolutionized the detection of disease states and MRI can now—within a few minutes—acquire important quantitative information noninvasively from an individual in any plane or volume at comparatively high resolution. This article provides an overview of the most common advanced MRI methods including diffusion MRI, perfusion MRI, functional MRI, and the strengths and weaknesses of MRI at high magnetic field strengths. PMID:15897944

Bammer, Roland; Skare, Stefan; Newbould, Rexford; Liu, Chunlei; Thijs, Vincent; Ropele, Stefan; Clayton, David B.; Krueger, Gunnar; Moseley, Michael E.; Glover, Gary H.

2005-01-01

153

Proton magnetic resonance spectroscopy in multiple sclerosis  

SciTech Connect

Regional in vivo proton magnetic resonance spectroscopy provides quantitative data on selected chemical constituents of brain. We imaged 16 volunteers with clinically definite multiple sclerosis on a 1.5 tesla magnetic resonance scanner to define plaque-containing volumes of interest, and obtained localized water-suppressed proton spectra using a stimulated echo sequence. Twenty-five of 40 plaque-containing regions provided spectra of adequate quality. Of these, 8 spectra from 6 subjects were consistent with the presence of cholesterol or fatty acids; the remainder were similar to those obtained from white matter of normal volunteers. This early experience with regional proton spectroscopy suggests that individual plaques are distinct. These differences likely reflect dynamic stages of the evolution of the demyelinative process not previously accessible to in vivo investigation.

Wolinsky, J.S.; Narayana, P.A.; Fenstermacher, M.J. (Univ. of Texas Health Science Center, Houston (USA))

1990-11-01

154

Contrast testing for magnetic resonance imaging.  

PubMed

A test phantom for evaluating magnetic resonance image contrast was constructed using separate chambers filled with manganese chloride (MnCl2) solutions of different concentrations. The concentrations were chosen so that the relaxation times produced were distributed over the range appropriate for human tissues in brain imaging. Specific solutions had relaxation properties similar to those of white matter, gray matter, and brain tumors. The region surrounding the chambers was filled with a sodium chloride solution with conductivity similar to that of brain tissue so that radiofrequency signal absorption would be appropriate. When magnetic resonance relaxation response curves were obtained with the phantom, relaxation contrast and latitude could be compared for different imaging pulse sequences. Contrast responses for gradient echo sequences differed considerably when the flip angle was changed. PMID:2720266

Anderson, D W; Yamanashi, W S; Stanley, D W; Wohler, J B

1989-01-01

155

Magnetic resonance spectroscopy in myocardial disease.  

PubMed

31-phosphorous ((31)P) magnetic resonance spectroscopy (MRS) is a technique that allows the noninvasive characterization of the biochemical and metabolic state of the myocardium in vivo. MRS is a pure form of molecular imaging using magnetic resonance signals from nuclei with nuclear spin to assess cardiac metabolism without the need for external radioactive tracers. (31)P MRS provides information on the underlying metabolic abnormalities that are fundamental to common conditions including ischemic heart disease, cardiomyopathy, hypertrophy and valvular disease. (31)P MRS could potentially also have a role to play in assessing response to therapy as well as the effectiveness of metabolic modulating agents. However, the use of MRS is currently limited to research due to its poor reproducibility, low spatial and temporal resolution, and long acquisition times. With technical advances in both the spectrometers and postprocessing, MRS is likely to play a role in the future of multimodal noninvasive cardiac assessment. PMID:20136613

Beadle, Roger; Frenneaux, Michael

2010-02-01

156

Combined Confocal and Magnetic Resonance Microscopy  

SciTech Connect

Confocal and magnetic resonance microscopy are both used to study live cells in a minimally invasive way. Both techniques provide complementary information. Therefore, by examining cells simultaneously with both methodologies, more detailed information is obtained than is possible with each of the microscopes individually. In this paper two configurations of a combined confocal and magnetic resonance microscope described. In both cases the sample compartment is part of a temperature regulated perfusion system. The first configuration is capable of studying large single cells or three-dimensional cell agglomerates, whereas with the second configuration monolayers of mammalian cells can be investigated . Combined images are shown of Xenopus laevis frog oocytes, model JB6 tumor spheroids, and a single layer of Chinese hamster ovary cells. Finally, potential applications of the combined microscope are discussed.

Wind, Robert A.; Majors, Paul D.; Minard, Kevin R.; Ackerman, Eric J.; Daly, Don S.; Holtom, Gary R.; Thrall, Brian D.; Weber, Thomas J.

2002-05-12

157

Diagnostic Magnetic Resonance Imaging of the Breast  

PubMed Central

Contrast enhanced breast magnetic resonance imaging is a modality that is frequently used into the breast radiologist’s daily clinical practice. MRI examination should have optimal technical proficiency in order to attain diagnostic quality avoiding false positive and negative diagnoses. Furthermore, due to increasing usage fields of the examinations uniting with high sensitivity phenomenon, excessive usage and excision/interventional procedures are inevitable. Therefore, we hope to highlight the appropriate usage of the MRI technique and it’s clinical applications.

Kilic, Fahrettin; Ogul, Hayri; Bayraktutan, Ummugulsum; Gumus, Hatice; Unal, Ozlem; Kantarci, Mecit; Yilmaz, M. Halit

2012-01-01

158

Neurosurgical uses for intraprocedural magnetic resonance imaging.  

PubMed

Neurosurgical procedures demand precision, and efforts to create accurate neurosurgical navigation have been central to the profession through its history. Magnetic resonance image (MRI)-guided navigation offers the possibility of real-time, image-based stereotactic information for the neurosurgeon, which makes possible a number of diagnostic and therapeutic procedures. This article will review both current options for intraoperative MRI operative suite arrangements and the current therapeutic/diagnostic uses of intraoperative MRI. PMID:16924171

Mutchnick, Ian S; Moriarty, Thomas M

2005-10-01

159

Musculoskeletal magnetic resonance imaging: importance of radiography  

Microsoft Academic Search

ObjectiveTo determine the usefulness of radiography for interpretation of musculoskeletal (MSK) magnetic resonance imaging (MRI) studies.Designs and patientsIn a 1-year period, 1,030 MSK MRI studies were performed in 1,002 patients in our institution. For each study, the interpreting radiologist completed a questionnaire regarding the availability and utility of radiographs, radiological reports and clinical information for the interpretation of the MRI

Mihra S. Taljanovic; Tim B. Hunter; Kimberly A. Fitzpatrick; Elizabeth A. Krupinski; Thomas L. Pope

2003-01-01

160

Diffusion tensor magnetic resonance image regularization  

Microsoft Academic Search

As multi-dimensional complex data become more common, new regularization schemes tailored to those data are needed. In this paper we present a scheme for regularising diffusion tensor magnetic resonance (DT-MR) data, and more generally multi-dimen- sional data defined by a direction map and one or several magnitude maps. The scheme is divided in two steps. First, a variational method is

Olivier Coulon; Daniel C. Alexander; Simon R. Arridge

2004-01-01

161

Magnetic Resonance Imaging of Hepatocellular Carcinoma  

Microsoft Academic Search

In hepatocellular carcinomas (HCCs), T1 shortening occurs due to internal protein, fat, copper, iron, hypercellularity, or a combination thereof. T1-weighted magnetic resonance imaging (MRI) is obtained with a non-fat-suppressed phase shift [in- (4 ms) and opposed- (2 ms) phase] gradient-echo sequence. Internal fat deposition is often (36%) seen in well-differentiated HCCs between 1.1 and 1.5 cm in size. T2-weighted MRI

Masayuki Kanematsu; Hiroshi Kondo; Satoshi Goshima; Yusuke Tsuge; Haruo Watanabe

2008-01-01

162

Magnetic resonance imaging and contrast enhancement. Scientific report  

SciTech Connect

Chapters II through VI of this report discuss: Relaxation of Nuclear Spins; Echo Techniques; Basic Imaging Pulse Sequences; Partial Saturation Recovery; Inversion Recovery; Spin Echo; Effects of Pulse Sequence on Image Contrast; Contrast Agents; Theoretical Aspects; Pharmacokinetics and Toxicity; and Physiological Rationale for Agent Selection. One of the major goals in all medical imaging techniques is to maximize one's ability to visualize and differentiate adjacent tissue regions in the body on the basis of differences in anatomy, physiology, or various pathological processes. Magnetic resonance (MR) imaging offers distinct advantages over conventional x-ray imaging because of the possibility of selecting specific pulse sequences that can differentiate adjacent structures on the basis of differences in proton density, T/sub 1/ or T/sub 2/ relaxation rates, or flow. As a result of applying these various pulse sequences, numerous images have been obtained of the brain and other organs that demonstrate considerably more-detailed anatomical structure than had previously been available with computerized tomography, ultrasound, or nuclear medicine techniques. In some situations it is clearly superior, such as in the diagnosis of multiple sclerosis.

Swenberg, C.E.; Movius, E.G.

1988-01-01

163

Magnetic resonance imaging of primary intracranial tumors: a review  

SciTech Connect

The experience in magnetic resonance (MR) imaging of primary intracranial neoplasia at University of California, San Francisco is reviewed. Seventy patients have been evaluated by MR and computerized tomography (CT). MR scans were performed using a multi-slice spin echo technique with a long pulse repetition time (TR = 2000 msec), and long echo sampling delay (TE = 56 msec). This method was most sensitive in differentiating normal gray and white matter and in detecting both cerebral edema and abnormal tissue with prolonged T/sub 2/ characteristics. More sensitive to slight alterations in normal tissue, MR may detect a focal lesion in cases in which CT shows only mass effect. Moreover, MR may demonstrate more thoroughly the extent of tumor infiltration and broaden the characterization of abnormal tissue. Posterior fossa and brainstem anatomy are invariably better depicted by MR. The major limitations of MR include its inability to detect foci of tumor calcification, demonstrate the severity of bone destruction, or reliably distinguish tumor nidus from surrounding edema.

Holland, B.A.; Brant-Zawadzki, M.; Norman, D.; Newton, T.H.

1985-02-01

164

Magnetic resonance imaging in patients with congenital heart disease.  

PubMed

Magnetic resonance imaging (MRI) was conducted with use of the spin-echo technique (0.35 Tesla) in 22 patients with a variety of congenital and cardiovascular anomalies and in 16 normal volunteers. Electrocardiographic (ECG) synchronization of the data acquisition produced transverse, parasagittal, and coronal tomograms that were used to define size and relationship of the great vessels and internal cardiac structures. MRI findings were corroborated by angiography and sector-scan echocardiography. In most patients the diagnosis had been established before the MRI study. MRI detected all of 11 abnormalities at the level of the great vessels, all of six atrial septal abnormalities, and 10 of 11 ventricular septal defects. Images of poor quality resulting from patient motion were obtained in the one instance in which a small ventricular septal defect was not imaged. Of two patients with Ebstein's anomaly, the displacement of the tricuspid leaflets was shown in one patient but was not evident in another. Complex anomalies such as double-outlet right ventricle, uncorrected L-transposition, single atrioventricular valve, single ventricle, and common ventricle were clearly shown by MRI. Initial experience with MRI has indicated the effectiveness of this technique for defining great vessel and internal cardiac anatomy in patients with congenital heart disease. This is accomplished without the use of contrast media and is thus a completely noninvasive technique for cardiovascular diagnosis. PMID:6488498

Higgins, C B; Byrd, B F; Farmer, D W; Osaki, L; Silverman, N H; Cheitlin, M D

1984-11-01

165

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) enables high-resolution non-invasive observation of the anatomy and function of intact organisms. However, previous MRI reporters of key biological processes tied to gene expression have been limited by the inherently low molecular sensitivity of conventional 1H MRI. This limitation could be overcome through the use of hyperpolarized nuclei, such as in the noble gas xenon, but previous reporters acting on such nuclei have been synthetic. Here, we introduce the first genetically encoded reporters for hyperpolarized 129Xe MRI. These expressible reporters are based on gas vesicles (GVs), gas-binding protein nanostructures expressed by certain buoyant microorganisms. We show that GVs are capable of chemical exchange saturation transfer interactions with xenon, which enables chemically amplified GV detection at picomolar concentrations (a 100- to 10,000-fold improvement over comparable constructs for 1H MRI). We demonstrate the use of GVs as heterologously expressed indicators of gene expression and chemically targeted exogenous labels in MRI experiments performed on living cells.

Shapiro, Mikhail G.; Ramirez, R. Matthew; Sperling, Lindsay J.; Sun, George; Sun, Jinny; Pines, Alexander; Schaffer, David V.; Bajaj, Vikram S.

2014-07-01

166

Fluctuating magnetic field induced resonant activation.  

PubMed

In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field. PMID:25494726

Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

2014-12-14

167

Fluctuating magnetic field induced resonant activation  

NASA Astrophysics Data System (ADS)

In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field.

Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

2014-12-01

168

Magnetic resonance imaging of prosthetic heart valves.  

PubMed

To evaluate the safety of magnetic resonance (MR) imaging of prosthetic heart valves, nine different synthetic and tissue valves were studied ex vivo. Deflection was measured in 0.35-tesla (T) and 1.5-T superconducting magnets and at the edge of the bore of a 2.35-T electromagnet in field gradients of 5, 1.1, and 6.3 mT/cm, respectively. No valve deflected in the 0.35-T magnet; six synthetic valves deflected 0.25 degrees-3 degrees in the 1.5-T magnet; all valves deflected 1 degree-27 degrees at the edge of the 2.35-T magnet. Each valve was then submerged in a vial of water and the temperature was measured immediately before and after each of two spin-echo imaging sequences in the two superconducting magnets. No significant temperature rise followed exposure in either magnet. Image distortion varied from negligible to severe in both imagers; magnitude of distortion paralleled magnitude of deflection. These data suggest that patients with present-day prosthetic heart valves can be safely imaged in present-day MR imagers and that prosthesis-induced artifacts will not interfere with interpretation in most instances. PMID:3969474

Soulen, R L; Budinger, T F; Higgins, C B

1985-03-01

169

Superconducting Magnet Safety Nuclear Magnetic Resonance (NMR) facilities present unique hazards not found in most  

E-print Network

Superconducting Magnet Safety Nuclear Magnetic Resonance (NMR) facilities present unique hazards not found in most laboratory environments. The NMR facilities maintain superconducting magnets which have associated with installation and operation. Temperature, structural support and magnetic field isolation

Maroncelli, Mark

170

Nuclear Magnetic Resonance: Portable and integrated Lead: P. Poulichet.  

E-print Network

Nuclear Magnetic Resonance: Portable and integrated Lead: P. Poulichet. Permanent members: L. Rousseau, A. Fakri. Associated researchers: C. Delabie, A. Exertier. Portable Nuclear Magnetic Resonance : our work in the field of nuclear magneto resonance is focused on the design and the realization

Baudoin, Geneviève

171

Compact low field magnetic resonance imaging magnet: Design and optimization  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.

2000-03-01

172

Magnetic Field Effects on High Quality Factor Superconducting Coplanar Resonators  

NASA Astrophysics Data System (ADS)

Superconducting coplanar waveguide resonators have proven to be invaluable tools in studying some of the same decoherence mechanisms as those found in superconducting qubits. Prior improvements in fabrication led to resonator internal quality factors (Qi's) in excess of 10 million at high power, enabling us to sensitively probe environmental effects on the resonance frequency and Qi. We have found these resonators to be very susceptible to applied and stray magnetic fields, with measurable changes in the resonator's Qi and resonance frequency from fields as small as a few milligauss. I will present more recent measurements of resonators in magnetic fields.

Megrant, Anthony; Neill, Charles; Barends, Rami; Chen, Yu; Chiaro, Ben; Kelly, Julian; Mariantoni, Matteo; Mutus, Josh; O'Malley, Peter; Sank, Daniel; Vainsencher, Amit; Wenner, James; White, Ted; Low, David; Ohya, Shinobu; Palmstrom, Christopher; Martinis, John; Cleland, Andrew

2013-03-01

173

CARBON-13 Nuclear Magnetic Resonance in Solids.  

NASA Astrophysics Data System (ADS)

The rotational resonance phenomena induced by the modulation of the interactions in magnetic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments have been demonstrated for the first time. In the study of chemical shielding, the rotational resonance occurs when a spin-lock field with an amplitude of nomega _{rm r} (n = 1,2) is applied where omega_{rm r} is the spinning speed. The magnetization, which nutates in the rotating frame at a frequency related to the chemical shift anisotropy (CSA), allows for the retrieval of the CSA from MAS NMR spectra at a high spinning speed. In addition, a similar rotational resonance phenomenon was studied in a homonuclear spin coupled system. The resonance occurs when the separation of the isotropic chemical shifts of the two spins equal omega_{ rm r}. The rotational resonance restores a splitting pattern in the MAS spectra and enhances the flip-flop motion of the two spins. Also, the sample spinning NMR of homonuclear coupled systems has been analyzed by a pseudo-spin model. In the case of the ^ {13}C dilabelled phthalic anhydride, the analyses at different spinning speeds lead to the determination of the orientation of the chemical shielding tensor. The quadrupolar effect in ^{13 }C-^{14}N coupled spins is manifested in the ^{13 }C MAS spectra by the appearance of an asymmetric doublet. A simple analytical solution to this quadrupolar effect was developed to study ^{13 }C-^{14}N systems for information on both the electric field gradient (EFG) tensor of the nitrogen and the ^{13 }C-^{14}N bond distance. Furthermore, the variable angle sample spinning technique has been applied to determine of the chemical shielding tensors with their orientation for these systems. The molecules studied include tetramethyl-pyrazine, dimethylglyoxime and triethylenediamine. The effect of relaxation in solid state NMR dipolar spectra was studied. The cross relaxation terms introduce a peak in the center of the expected Pake doublet. The dipolar spectra of methyl phosphonic acid at room temperature and methyl fluoride at low temperature (25 K) were used to study this effect.

Gan, Zhehong

174

Portal biliopathy, magnetic resonance imaging and magnetic resonance cholangiopancreatography findings: a case series.  

PubMed

Portal biliopathy (PB) is a rare disorder, characterized by biliary ductal and gallbladder wall abnormalities seen in patients with portal hypertension. It most commonly occurs due to idiopathic extrahepatic portal vein obstruction (EHPVO). The abnormalities consist mainly of bile duct compression, stenoses, fibrotic strictures and dilation of both extrahepatic and intrahepatic bile ducts, as well as gallbladder varices. PB may mimic cholangiocarcinoma, sclerosing cholangitis, or choledocholithiasis. Misdiagnosis can be avoided using appropriate imaging modalities to prevent complications. We present the magnetic resonance imaging (MRI) and magnetic resonance cholangiography (MRCP) features of three patients with PB. PMID:25216728

Baskan, Ozdil; Erol, Cengiz; Sahingoz, Yusuf

2014-09-12

175

Magnetic Field Gradient Calibration as an Experiment to Illustrate Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

A nuclear magnetic resonance (NMR) spectroscopy experiment for the undergraduate physical chemistry laboratory is described that encompasses both qualitative and quantitative pedagogical goals. Qualitatively, the experiment illustrates how images are obtained in magnetic resonance imaging (MRI). Quantitatively, students experience the…

Seedhouse, Steven J.; Hoffmann, Markus M.

2008-01-01

176

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics  

E-print Network

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics (Dated: February 5, 2014) In this experiment, the phenomenon of Nuclear Magnetic Resonance (NMR) is used to determine the magnetic moments-factor in atomic spectroscopy and is given by g = (µ/µN )/I, (2) and µN is the nuclear magneton, e /2mp

Seager, Sara

177

Magnetic resonance imaging of male and female genitals during coitus and female sexual arousal  

PubMed Central

Objective To find out whether taking images of the male and female genitals during coitus is feasible and to find out whether former and current ideas about the anatomy during sexual intercourse and during female sexual arousal are based on assumptions or on facts. Design Observational study. Setting University hospital in the Netherlands. Methods Magnetic resonance imaging was used to study the female sexual response and the male and female genitals during coitus. Thirteen experiments were performed with eight couples and three single women. Results The images obtained showed that during intercourse in the “missionary position” the penis has the shape of a boomerang and 1/3 of its length consists of the root of the penis. During female sexual arousal without intercourse the uterus was raised and the anterior vaginal wall lengthened. The size of the uterus did not increase during sexual arousal. Conclusion Taking magnetic resonance images of the male and female genitals during coitus is feasible and contributes to understanding of anatomy. PMID:10600954

Schultz, Willibrord Weijmar; van Andel, Pek; Sabelis, Ida; Mooyaart, Eduard

1999-01-01

178

Atlas of the developing brain of the marmoset monkey constructed using magnetic resonance histology.  

PubMed

The developmental anatomy of the brain is largely directed by neural-based cues. Despite this knowledge, the developmental trajectory of the primate brain has not yet been fully characterized. To realize this goal, the advance in noninvasive imaging methods and new brain atlases are essential. The common marmoset (Callithrix jacchus), a small New World primate, is widely used in neuroscience research. The recent introduction of transgenic techniques has enabled the marmoset to be used as a genetically modifiable primate model for brain development. Here, a magnetic resonance histology technique involving the use of ultra-high-resolution ex vivo magnetic resonance imaging (MRI) was performed to identify the developmental anatomy of the marmoset brain at different time points from gestational week 8 through to birth. The data allowed the generation of a multidimensional atlas of brain structures at different developmental stages. Furthermore, in utero MRI techniques were developed to noninvasively monitor brain development during the embryonic and fetal stages. The multidimensional atlas and the MRI tools developed herein are anticipated to further our understanding of the developing primate brain. PMID:23047019

Hikishima, K; Sawada, K; Murayama, A Y; Komaki, Y; Kawai, K; Sato, N; Inoue, T; Itoh, T; Momoshima, S; Iriki, A; Okano, H J; Sasaki, E; Okano, H

2013-01-29

179

Nanodiamond graphitization: a magnetic resonance study  

NASA Astrophysics Data System (ADS)

We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. 1H, 13C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800?° C were measured. For the samples annealed at 600 to 800?° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp2 carbon content with increased annealing temperature. Such quantitative experimental data were recorded for the first time. These findings correlate with EPR data on the sensitivity of the dangling bond EPR line width to air content, progressing with rising annealing temperature, that evidences consequent graphitization of the external layers of the diamond core. The sample annealed at 1800?° C shows complete conversion of nanodiamond particles into carbon onions.

Panich, A. M.; Shames, A. I.; Sergeev, N. A.; Olszewski, M.; McDonough, J. K.; Mochalin, V. N.; Gogotsi, Y.

2013-06-01

180

Nanodiamond graphitization: a magnetic resonance study.  

PubMed

We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. (1)H, (13)C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800 ° C were measured. For the samples annealed at 600 to 800 ° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp(2) carbon content with increased annealing temperature. Such quantitative experimental data were recorded for the first time. These findings correlate with EPR data on the sensitivity of the dangling bond EPR line width to air content, progressing with rising annealing temperature, that evidences consequent graphitization of the external layers of the diamond core. The sample annealed at 1800 ° C shows complete conversion of nanodiamond particles into carbon onions. PMID:23709490

Panich, A M; Shames, A I; Sergeev, N A; Olszewski, M; McDonough, J K; Mochalin, V N; Gogotsi, Y

2013-06-19

181

Cardiac magnetic resonance imaging: artefacts for clinicians.  

PubMed

In recent years, the clinical importance of cardiac magnetic resonance (CMR) imaging has increased dramatically. As a consequence, more clinicians need to become familiar with this imaging modality, including its technical challenges. MR images are obtained through a physical process of proton excitation and the reception of resonating signals. Besides these physical principles, the motion of the heart and diaphragm, together with the presence of fast flowing blood in the vicinity, pose challenges to the acquisition of high-quality diagnostic images and are an important cause of image artefacts. Artefacts may render images non-diagnostic and measurements unreliable, and most artefacts can only be corrected during the acquisition itself. Hence, timely and accurate recognition of the type of artefact is crucial. This paper provides a concise description of the CMR acquisition process and the underlying MR physics for clinical cardiologists and trainees. Frequently observed CMR artefacts are illustrated and possible adjustments to minimise or eliminate these artefacts are explained. PMID:25339204

van der Graaf, A W M; Bhagirath, P; Ghoerbien, S; Götte, M J W

2014-12-01

182

Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance force microscopy  

E-print Network

The signal intensity of electron spin resonance in magnetic resonance force microscopy MRFM experiments that magnetic resonance force microscopy MRFM is a new 3D imaging technique8,9 with the potential of achieving force microscopy Z. Zhanga) Condensed Matter and Thermal Physics Group, Materials Science and Technology

Hammel, P. Chris

183

Collective electric and magnetic plasmonic resonances in spherical nanoclusters  

E-print Network

with the electric dipole efficiency Q sca indicating thatthe electric resonance the p e scattering efficiency Q scaelectric and magnetic resonances, previously identified from the analysis of the extinction and scattering efficiencies,

Vallecchi, Andrea; Albani, Matteo; Capolino, Filippo

2011-01-01

184

Cardiovascular magnetic resonance imaging in small animals.  

PubMed

Noninvasive imaging studies involving small animals are becoming increasingly important in preclinical pharmacological, genetic, and biomedical cardiovascular research. Especially small animal magnetic resonance imaging (MRI) using high field and clinical MRI systems has gained significant importance in recent years. Compared to other imaging modalities, like computer tomography, MRI can provide an excellent soft tissue contrast, which enables the characterization of different kinds of tissues without the use of contrast agents. In addition, imaging can be performed with high spatial and temporal resolution. Small animal MRI cannot only provide anatomical information about the beating murine heart; it can also provide functional and molecular information, which makes it a unique imaging modality. Compared to clinical MRI examinations in humans, small animal MRI is associated with additional challenges. These included a smaller size of all cardiovascular structures and a up to ten times higher heart rate. Dedicated small animal monitoring devices make a reliable cardiac triggering and respiratory gating feasible. MRI in combination with molecular probes enables the noninvasive imaging of biological processes at a molecular level. Different kinds of iron oxide or gadolinium-based contrast agents can be used for this purpose. Compared to other molecular imaging modalities, like single photon emission computed tomography (SPECT) and positron emission tomography (PET), MRI can also provide imaging with high spatial resolution, which is of high importance for the assessment of the cardiovascular system. The sensitivity for detection of MRI contrast agents is however lower compared to sensitivity of radiation associated techniques like PET and SPECT. This chapter is divided into the following sections: (1) "Introduction," (2) "Principals of Magnetic Resonance Imaging," (3) "MRI Systems for Preclinical Imaging and Experimental Setup," and (4) "Cardiovascular Magnetic Resonance Imaging." PMID:22137434

Botnar, René M; Makowski, Marcus R

2012-01-01

185

Magnetic Resonance Imaging of the Pediatric Knee.  

PubMed

In pediatric patients, the high resolution and excellent soft-tissue contrast of magnetic resonance (MR) imaging allows for complete evaluation of osseous and soft-tissue structures around the knee joint, and its lack of ionizing radiation makes it a preferred modality for advanced imaging. Older children and adolescents are most commonly imaged to evaluate athletic and traumatic injuries, whereas in infants and school age children MR imaging is used to evaluate developmental conditions such as Blount disease or assess for causes of atraumatic pain such as infection or inflammatory arthritis. A thorough understanding of normal skeletal development is necessary to avoid misdiagnoses. PMID:25442031

Gill, Kara G; Nemeth, Blaise A; Davis, Kirkland W

2014-11-01

186

Magnetic resonance imaging of perianal fistulas.  

PubMed

Perianal fistulization is the result of a chronic inflammation of the perianal tissues. A wide spectrum of clinical manifestations, ranging from simple to complex fistulas, can be seen, the latter especially in patients with Crohn disease. Failure to detect secondary tracks and hidden abscesses may lead to therapeutic failure, such as insufficient response to medical treatment and relapse after surgery. Currently, magnetic resonance (MR) imaging is the preferred technique for evaluating perianal fistulas and associated complications. Initially used most often in the preoperative setting, MR imaging now also plays an important role in evaluating the response to medical therapy. PMID:24238135

Vanbeckevoort, Dirk; Bielen, Didier; Vanslembrouck, Ragna; Van Assche, Gert

2014-02-01

187

Review: Magnetic resonance imaging techniques in ophthalmology  

PubMed Central

Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye’s propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due to the resulting motion artifacts. However, advances in MRI technology help to mitigate such drawbacks, enabling the acquisition of high spatiotemporal resolution images with a variety of contrast mechanisms. This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this may inform on ocular pathophysiology. PMID:23112569

Fagan, Andrew J.

2012-01-01

188

Multiparametric magnetic resonance imaging of prostate cancer.  

PubMed

In India, prostate cancer has an incidence rate of 3.9 per 100,000 men and is responsible for 9% of cancer-related mortality. It is the only malignancy that is diagnosed with an apparently blind technique, i.e., transrectal sextant biopsy. With increasing numbers of high-Tesla magnetic resonance imaging (MRI) equipment being installed in India, the radiologist needs to be cognizant about endorectal MRI and multiparametric imaging for prostate cancer. In this review article, we aim to highlight the utility of multiparamteric MRI in prostate cancer. It plays a crucial role, mainly in initial staging, restaging, and post-treatment follow-up. PMID:23599562

Hedgire, Sandeep S; Oei, Tamara N; McDermott, Shaunagh; Cao, Kai; Patel M, Zena; Harisinghani, Mukesh G

2012-07-01

189

Magnetic resonance imaging of small bowel neoplasms  

PubMed Central

Abstract Magnetic resonance (MR) imaging is rapidly increasing clinical acceptance to evaluate the small bowel and can be the initial imaging method to investigate small bowel diseases. MR examinations may provide the first opportunity to detect and characterize tumours of the small bowel. Intra- and extraluminal MR findings, combined with contrast enhancement and functional information, help to make an accurate diagnosis and consequently characterize small bowel neoplasms. MR enteroclysis should be recommended for the initial investigation in patients suspected of having small bowel tumours. In this article, the MR findings of primary small bowel neoplasms are described and the MR findings for the differential diagnosis are discussed. PMID:23524074

Casciani, Emanuele; Polettini, Elisabetta; Laghi, Francesca; Gualdi, Gianfranco

2013-01-01

190

Magnetic resonance imaging of the postoperative spine.  

PubMed

Magnetic resonance (MR) imaging is an excellent technique for evaluating the postoperative spine when the patient has chronic or recurrent symptoms. Potential causes of pain following lumbar surgery include arachnoiditis, stenosis, epidural fibrosis and disc herniations, pseudomeningocele, and infection. The postoperative cervical spine may be complicated by hematoma, canal or foraminal stenosis, disc herniation, and cord abnormality. This article reviews standard imaging protocols, the normal postoperative appearance of the spine, and the characteristic imaging findings for each of the abnormal postoperative conditions. PMID:11371319

Ross, J S

2000-01-01

191

Cardiac magnetic resonance in clinical cardiology  

PubMed Central

Over the last decades, cardiac magnetic resonance (CMR) has transformed from a research tool to a widely used diagnostic method in clinical cardiology. This method can now make useful, unique contributions to the work-up of patients with ischemic and non-ischemic heart disease. Advantages of CMR, compared to other imaging methods, include very high resolution imaging with a spatial resolution up to 0.5 mm × 0.5 mm in plane, a large array of different imaging sequences to provide in vivo tissue characterization, and radiation-free imaging. The present manuscript highlights the relevance of CMR in the current clinical practice and new perspectives in cardiology. PMID:25632313

Kumar, Andreas; Bagur, Rodrigo

2015-01-01

192

Magnetic resonance imaging of the immature skeleton.  

PubMed

Magnetic resonance (MR) is unique in its ability to allow assessment of bone marrow, epiphyseal, physeal, and articular cartilage as well as tendons and ligaments. An understanding of skeletal maturation and the accompanying changes on MR is of utmost importance in pediatric radiology. In particular, it is important to recognize the normal spectrum related to ossification and marrow transformation. This review will include a brief description of main indications and common pitfalls in musculoskeletal MR in children. Also, we will focus on the MR appearance of the growing pediatric skeleton on the most commonly used sequences. PMID:24179233

Boavida, Peter; Muller, Lil-Sofie; Rosendahl, Karen

2013-11-01

193

Cardiovascular magnetic resonance in systemic hypertension  

PubMed Central

Systemic hypertension is a highly prevalent potentially modifiable cardiovascular risk factor. Imaging plays an important role in the diagnosis of underlying causes for hypertension, in assessing cardiovascular complications of hypertension, and in understanding the pathophysiology of the disease process. Cardiovascular magnetic resonance (CMR) provides accurate and reproducible measures of ventricular volumes, mass, function and haemodynamics as well as uniquely allowing tissue characterization of diffuse and focal fibrosis. In addition, CMR is well suited for exclusion of common secondary causes for hypertension. We review the current and emerging clinical and research applications of CMR in hypertension. PMID:22559053

2012-01-01

194

Pleural endometriosis: findings on magnetic resonance imaging.  

PubMed

Endometriosis is a benign gynecological disorder associated with pelvic pain and infertility, primarily affecting women of reproductive age. Thoracic endometriosis affects the pulmonary parenchyma or pleura. We report the cases of two patients with pleural endometriosis who presented with recurrent pneumothorax. In both cases, magnetic resonance imaging (MRI) of the chest showed right hydropneumothorax and well-defined, rounded nodules on the pleural surface in the right hemithorax. We conclude that MRI is a good option for the characterization of pleural endometriotic nodules and hemorrhagic pleural effusion. PMID:23288127

Marchiori, Edson; Zanetti, Gláucia; Rodrigues, Rosana Souza; Souza, Luciana Soares; Souza Junior, Arthur Soares; Francisco, Flávia Angélica Ferreira; Hochhegger, Bruno

2012-01-01

195

Multiparametric magnetic resonance imaging of prostate cancer  

PubMed Central

In India, prostate cancer has an incidence rate of 3.9 per 100,000 men and is responsible for 9% of cancer-related mortality. It is the only malignancy that is diagnosed with an apparently blind technique, i.e., transrectal sextant biopsy. With increasing numbers of high-Tesla magnetic resonance imaging (MRI) equipment being installed in India, the radiologist needs to be cognizant about endorectal MRI and multiparametric imaging for prostate cancer. In this review article, we aim to highlight the utility of multiparamteric MRI in prostate cancer. It plays a crucial role, mainly in initial staging, restaging, and post-treatment follow-up. PMID:23599562

Hedgire, Sandeep S; Oei, Tamara N; Mcdermott, Shaunagh; Cao, Kai; Patel M, Zena; Harisinghani, Mukesh G

2012-01-01

196

Magnetic resonance imaging of fibrosing mediastinitis  

SciTech Connect

Magnetic resonance imaging (MRI) was performed in seven patients with fibrosing mediastinitis. Comparison was made in each case to standard chest radiography and computed tomography (CT). Angiography was performed in three cases. Although MRI and CT were found to be equivalent in defining the extent of adenopathy, CT was superior at demonstrating calcifications, often important in making the diagnosis of fibrosing mediastinitis. MRI, however, offered complementary information, particularly in assessing vascular patency without the need for intravenous contrast media. On T2-weighted images, the adenopathy associated with fibrosing mediastinitis was noted to be of relatively low signal intensity, possibly indicating its benign nature.

Rholl, K.S.; Levitt, R.G.; Glazer, H.S.

1985-08-01

197

Magnetic Resonance Imaging of Cartilage Repair Procedures.  

PubMed

Cartilage injuries in the knee are common and can be a persistent source of pain or dysfunction. Many new surgical strategies have been developed to treat these lesions. It is important for the radiologist to have an understanding of these procedures and their appearance on magnetic resonance (MR) imaging. This article provides the radiologist with an overview of the surgical strategies for repairing cartilage lesions in the knee followed by a discussion of their postoperative appearance on MR imaging in normal and abnormal cases. Guidelines for adequate reporting of the MR imaging findings after cartilage repair in the knee are also included. PMID:25442028

Forney, Michael C; Gupta, Amit; Minas, Tom; Winalski, Carl S

2014-11-01

198

Creating a magnetic resonance imaging ontology.  

PubMed

The goal of this work is to build an ontology of Magnetic Resonance Imaging. The MRI domain has been analysed regarding MRI simulators and the DICOM standard. Tow MRI simulators have been analysed: JEMRIS, which is developed in XML and C++, has a hierarchical organisation and SIMRI, which is developed in C, has a good representation of MRI physical processes. To build the ontology we have used Protégé 4, owl2 that allows quantitative representations. The ontology has been validated by a reasoner (Fact++) and by a good representation of DICOM headers and of MRI processes. The MRI ontology would improved MRI simulators and eased semantic interoperability. PMID:21893854

Lasbleiz, Jérémy; Saint-Jalmes, Hervé; Duvauferrier, Régis; Burgun, Anita

2011-01-01

199

Creating a magnetic resonance imaging ontology  

PubMed Central

The goal of this work is to build an ontology of Magnetic Resonance Imaging. The MRI domain has been analysed regarding MRI simulators and the DICOM standard. Tow MRI simulators have been analysed: JEMRIS, which is developed in XML and C++, has a hierarchical organisation and SIMRI, which is developed in C, has a good representation of MRI physical processes. To build the ontology we have used Protégé 4, owl2 that allows quantitative representations. The ontology has been validated by a reasoner (Fact++) and by a good representation of DICOM headers and of MRI processes. The MRI ontology would improved MRI simulators and eased semantic interoperability. PMID:21893854

Lasbleiz, Jérémy; Saint-Jalmes, Hervé; Duvauferrier, Régis; Burgun, Anita

2011-01-01

200

Fano resonance generated by magnetic scatterer in micro metal slit  

NASA Astrophysics Data System (ADS)

A micro metal slit/magnetic scatterer structure is proposed to generate electromagnetic Fano resonance. The magnetic scatterer is formed by infinite long split cylinder resonator array. The analytical transmissivity formulas are deduced from Maxwell electromagnetic theory and the Fano resonance transmission is achieved by the theoretical calculations. The enhancement of environment refractive index leads to an ultrasensitive and linear red shift of resonance peak in the THz range.

Zhou, Yun-Song; Wang, Pei-Jie; Wang, Hai; Feng, Sheng-Fei

2014-09-01

201

Science Drivers and Technical Challenges for Advanced Magnetic Resonance  

SciTech Connect

This report recaps the "Science Drivers and Technical Challenges for Advanced Magnetic Resonance" workshop, held in late 2011. This exploratory workshop's goal was to discuss and address challenges for the next generation of magnetic resonance experimentation. During the workshop, participants from throughout the world outlined the science drivers and instrumentation demands for high-field dynamic nuclear polarization (DNP) and associated magnetic resonance techniques, discussed barriers to their advancement, and deliberated the path forward for significant and impactful advances in the field.

Mueller, Karl T.; Pruski, Marek; Washton, Nancy M.; Lipton, Andrew S.

2013-03-07

202

Metabolite specific proton magnetic resonance imaging.  

PubMed Central

An imaging method is described that makes use of proton double quantum nuclear magnetic resonance (NMR) to construct images based on selected metabolites such as lactic acid. The optimization of the method is illustrated in vitro, followed by in vivo determination of lactic acid distribution in a solid tumor model. Water suppression and editing of lipid signals are such that two-dimensional spectra of lactic acid may be obtained from a radiation-induced fibrosarcoma (RIF-1) tumor in under 1 min and lactic acid images from the same tumor in under 1 hr at 2.0 T. This technique provides a fast and reproducible method at moderate magnetic field strength for mapping biologically relevant metabolites. Images PMID:2734292

Hurd, R E; Freeman, D M

1989-01-01

203

In vivo nuclear magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

During the past year the Woodlands Baylor Magnetic Resonance Imaging (MRI) facility became fully operational. A detailed description of this facility is given. One significant instrument addition this year was the 100 MHz, 40cm bore superconducting imaging spectrometer. This instrument gives researchers the capability to acquire high energy phosphate spectra. This will be used to investigate ATP, phosphocreatinine and inorganic phosphate changes in normal and atrophied muscle before, during and after exercise. An exercise device for use within the bore of the imaging magnet is under design/construction. The results of a study of T sub 1 and T sub 2 changes in atrophied muscle in animals and human subjects are given. The imaging and analysis of the lower leg of 15 research subjects before and after 5 weeks of complete bedrest was completed. A compilation of these results are attached.

Leblanc, A.

1986-01-01

204

Resonant microwave cavity for 8.512 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance  

E-print Network

Resonant microwave cavity for 8.5­12 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance J. S. Colton1,a and L. R. Wienkes2 1 Department of Physics online 16 March 2009 We present a newly developed microwave resonant cavity for use in optically detected

Hart, Gus

205

Breast anatomy for the interventionalist.  

PubMed

Normal breast anatomy can be seen on a variety of imaging modalities. Knowledge of normal breast anatomy on imaging examinations is important for an interventionalist, primarily to avoid mistaking normal anatomy for a pathologic disorder, so as not to harm a patient with an unnecessary intervention. Knowledge of breast anatomy is also critical in planning safe breast interventions and unwanted procedural complications. The key anatomical structures in the breast include skin, fat, fascial layers, Cooper ligaments, fibroglandular tissue, lymphatics, and neurovascular structures, all positioned over the chest wall. In men, the breast parenchyma is usually only composed of fat, with absence of fibroglandular tissue. In women, fibroglandular tissue volumes vary with age, with many women having a predominance of fat within the breasts after menopause. Embryologically, the breast develops under genetic and hormonal influence from skin precursor cells during the fourth through twelfth weeks of gestation, and the resulting breast bud continues to lengthen and branch throughout the remainder of gestation, forming a complex network of radially arranged breast ducts that connect the nipple with the mammary lobules. The key arterial blood supply to the breast arises from the internal thoracic artery, but additional arterial blood supply is seen from intercostal and lateral thoracic arteries. The venous anatomy and lymphatic drainage of the breast generally parallels the arterial anatomy, with presence of variation in communicating channels between deep and superficial venous and lymphatic channels. Tools that assess breast vascular structures (eg, contrast-enhanced breast magnetic resonance imaging) and lymphatic structures (nuclear medicine lymphoscintigraphy) are routinely used to assess extent of breast disease and help guide breast interventions. PMID:24636325

Jesinger, Robert A

2014-03-01

206

Methods for chemical exchange saturation transfer magnetic resonance imaging  

E-print Network

Chemical exchange saturation transfer (CEST) is a relatively new magnetic resonance imaging (MRI) acquisition technique that generates contrast dependent on tissue microenvironment, such as protein concentration and ...

Scheidegger, Rachel Nora

2013-01-01

207

Multimodal neuroimaging integrating functional magnetic resonance Imaging and electroencephalography.  

E-print Network

??Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are two widely used neuroimaging modalities with complementary merits and limitations. FMRI has low temporal resolution but… (more)

Liu, Zhongming

2009-01-01

208

Nuclear magnetic resonance in magnets with a helicoidal magnetic structure in an external magnetic field  

NASA Astrophysics Data System (ADS)

In this review, the static and dynamic properties of a magnet with a helicoidal magnetic structure placed in an external magnetic field are discussed. The results of the investigation of its ground state and spectra, as well as the amplitudes of the spin excitations are presented. The temperature and field dependences of the basic thermodynamic characteristics (heat capacity, magnetization, and magnetic susceptibility) have been calculated in the spin-wave approximation. The results of calculating the local and integral dynamic magnetic susceptibility are given. This set of data represents a methodical basis for constructing a consistent (in the framework of unified approximations) picture of the NMR absorption in the magnet under consideration. Both local NMR characteristics (resonance frequency, line broadening, enhancement coefficient) and integral characteristics (resultant shape of the absorption line with its specific features) have been calculated. The effective Hamiltonian of the Suhl-Nakamura interaction of nuclear spins through spin waves has been constructed. The second moment and the local broadening of the line of the NMR absorption caused by this interaction have been calculated. The role of the basic local inhomogeneities in the formation of the integral line of the NMR absorption has been analyzed. The opportunities for the experimental NMR investigations in magnets with a chiral spin structure are discussed.

Tankeyev, A. P.; Borich, M. A.; Smagin, V. V.

2014-11-01

209

Magnetic resonance imaging. Application to family practice.  

PubMed Central

OBJECTIVE: To review indications, contraindications, and risks of using magnetic resonance imaging (MRI) in order to help primary care physicians refer patients appropriately for MRI, screen for contraindications to using MRI, and educate patients about MRI. QUALITY OF EVIDENCE: Recommendations are based on classic textbooks, the policies of our MRI group, and a literature search using MEDLINE with the MeSH headings magnetic resonance imaging, brain, musculoskeletal, and spine. The search was limited to human, English-language, and review articles. Evidence in favour of using MRI for imaging the head, spine, and joints is well established. For cardiac, abdominal, and pelvic conditions, MRI has been shown useful for certain indications, usually to complement other modalities. MAIN MESSAGE: For demonstrating soft tissue conditions, MRI is better than computed tomography (CT), but CT shows bone and acute bleeding better. Therefore, patients with trauma or suspected intracranial bleeding should have CT. Tumours, congenital abnormalities, vascular structures, and the cervical or thoracic spine show better on MRI. Either modality can be used for lower back pain. Cardiac, abdominal, and pelvic abnormalities should be imaged with ultrasound or CT before MRI. Contraindications for MRI are mainly metallic implants or shrapnel, severe claustrophobia, or obesity. CONCLUSIONS: With the increasing availability of MRI scanners in Canada, better understanding of the indications, contraindications, and risks will be helpful for family physicians and their patients. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 PMID:10509224

Goh, R. H.; Somers, S.; Jurriaans, E.; Yu, J.

1999-01-01

210

Stress reconfigurable tunable magnetoelectric resonators as magnetic sensors  

NASA Astrophysics Data System (ADS)

Magnetoelectric multiferroic materials are extremely attractive due to their potential in sensing, filtering and energy transduction applications. We report a magnetoelastic effect in doubly-clamped ferromagnetic magnetostrictive Metglas resonators, as well as the magnetic field dependence of the resonance frequency as a function of uniaxial stress. Magnetostrictive strain results in a resonance frequency shift when the resonator is exposed to a magnetic field. The resonance frequency can be tracked in real time as a function of magnetic field bias using a feedback loop based on the quadrature of the excited motion. This magnetically reconfigurable resonance response can be used as a simple, tunable, magnetoelectric (ME) magnetic field sensor. The effect of sample pre-tension on the field dependent magnetostrictive constant and the sensor sensitivity is examined, and the resolution of such a sensor is estimated.

Kiser, Jillian; Finkel, Peter; Dolabdjian, Christophe

2013-03-01

211

Reciprocity and gyrotropism in magnetic resonance transduction  

SciTech Connect

We give formulas for transduction in magnetic resonance - i.e., the appearance of an emf due to Larmor precession of spins - based upon the modified Lorentz reciprocity principle for gyrotropic (also called 'nonreciprocal') media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e. (H{sub 1x}{+-}iH{sub 1y}), where, e.g., for a single transceive antenna, the H's are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are swapped between the two antenna ports--giving in one instance a signal intensity pattern whose form resembles an umbrella (i.e., with a central column of moderate intensity surmounted by a bright canopy), and in the other, a distorted oval with slight concavities at its horizontal extremes, whose outline suggests that of a cat's eye. The relation between image patterns and drive scheme can be shown to reverse if the static polarizing field is reversed. Electromagnetic and circuit calculations, together with the modified reciprocity principle, allow us to reproduce these pattern changes in numerical simulations, closely and convincingly. Although the imaging experiments are performed at a static field of 3.0 T, and consequently a Larmor frequency of 128 MHz, the nonreciprocal effects are not related to the shortness of the wavelength in aqueous medium, but appear equally in simulations based in either the quasistatic or full electromagnetic regimes. Finally, we show that although antenna patterns for transmission and reception are swapped with reversal of the polarizing field, meaning that the receive pattern equals the transmit pattern with the field reversed, this in no way invalidates the familiar rotating wave model of spin dynamics in magnetic resonance.

Tropp, James [General Electric Healthcare Technologies, 47697 Westinghouse Drive, Fremont, California 94539 (United States)

2006-12-15

212

Reciprocity and gyrotropism in magnetic resonance transduction  

NASA Astrophysics Data System (ADS)

We give formulas for transduction in magnetic resonance—i.e., the appearance of an emf due to Larmor precession of spins—based upon the modified Lorentz reciprocity principle for gyrotropic (also called “nonreciprocal”) media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e., (H1x±iH1y) , where, e.g., for a single transceive antenna, the H ’s are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are swapped between the two antenna ports—giving in one instance a signal intensity pattern whose form resembles an umbrella (i.e., with a central column of moderate intensity surmounted by a bright canopy), and in the other, a distorted oval with slight concavities at its horizontal extremes, whose outline suggests that of a cat’s eye. The relation between image patterns and drive scheme can be shown to reverse if the static polarizing field is reversed. Electromagnetic and circuit calculations, together with the modified reciprocity principle, allow us to reproduce these pattern changes in numerical simulations, closely and convincingly. Although the imaging experiments are performed at a static field of 3.0T , and consequently a Larmor frequency of 128MHz , the nonreciprocal effects are not related to the shortness of the wavelength in aqueous medium, but appear equally in simulations based in either the quasistatic or full electromagnetic regimes. Finally, we show that although antenna patterns for transmission and reception are swapped with reversal of the polarizing field, meaning that the receive pattern equals the transmit pattern with the field reversed, this in no way invalidates the familiar rotating wave model of spin dynamics in magnetic resonance.

Tropp, James

2006-12-01

213

Purely electric and magnetic dipole resonances in metamaterial dielectric resonators through perturbation theory inspired geometries  

E-print Network

In this paper we describe a methodology for tailoring the design of metamaterial dielectric resonators, which represent a promising path toward low-loss metamaterials at optical frequencies. We first describe a procedure to decompose the far field scattered by subwavelength resonators in terms of multipolar field components, providing explicit expressions for the multipolar far fields. We apply this formulation to confirm that an isolated high-permittivity cube resonator possesses frequency separated electric and magnetic dipole resonances, as well as a magnetic quadrupole resonance in close proximity to the electric dipole resonance. We then introduce multiple dielectric gaps to the resonator geometry in a manner suggested by perturbation theory, and demonstrate the ability to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering by satisfying the first Kerker condition. We further demonstrate the ability to push the quadrupole resonance away from the degenerate dipole ...

Campione, Salvatore; Warne, Larry K; Sinclair, Michael B

2014-01-01

214

Sample-detector coupling in atomic resolution magnetic resonance diffraction  

NASA Astrophysics Data System (ADS)

A technique for potential realization of atomic resolution magnetic resonance diffraction was recently proposed for the case of a crystalline sample in proximity of a ferromagnetic sphere [M. Barbic, J. Appl. Phys. 91, 9987 (2002)]. This article predicted the detection of distinct peaks in the number of resonant spin sites at different magnetic field values for specific sphere and crystal configurations. Here, the focus is on the specific detection coupling mechanisms between the resonant spin population of the sample and the magnetic sphere probe. We investigate and compare the force, torque, and flux detection mechanisms in order to provide guidance to the experimental efforts towards the realization of the atomic resolution magnetic resonance diffraction. We also investigate the dependence of the magnetic resonance diffraction spectrum on the relative position of the magnetic sphere with respect to the crystal lattice.

Barbic, Mladen; Scherer, Axel

2002-12-01

215

Acoustic noise during functional magnetic resonance imaginga)  

PubMed Central

Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For studies of the auditory system, acoustic noise generated during fMRI can interfere with assessments of this activation by introducing uncontrolled extraneous sounds. As a first step toward reducing the noise during fMRI, this paper describes the temporal and spectral characteristics of the noise present under typical fMRI study conditions for two imagers with different static magnetic field strengths. Peak noise levels were 123 and 138 dB re 20 ?Pa in a 1.5-tesla (T) and a 3-T imager, respectively. The noise spectrum (calculated over a 10-ms window coinciding with the highest-amplitude noise) showed a prominent maximum at 1 kHz for the 1.5-T imager (115 dB SPL) and at 1.4 kHz for the 3-T imager (131 dB SPL). The frequency content and timing of the most intense noise components indicated that the noise was primarily attributable to the readout gradients in the imaging pulse sequence. The noise persisted above background levels for 300-500 ms after gradient activity ceased, indicating that resonating structures in the imager or noise reverberating in the imager room were also factors. The gradient noise waveform was highly repeatable. In addition, the coolant pump for the imager’s permanent magnet and the room air handling system were sources of ongoing noise lower in both level and frequency than gradient coil noise. Knowledge of the sources and characteristics of the noise enabled the examination of general approaches to noise control that could be applied to reduce the unwanted noise during fMRI sessions. PMID:11051496

Ravicz, Michael E.; Melcher, Jennifer R.; Kiang, Nelson Y.-S.

2007-01-01

216

BROADBAND EXCITATION IN NUCLEAR MAGNETIC RESONANCE  

SciTech Connect

Theoretical methods for designing sequences of radio frequency (rf) radiation pulses for broadband excitation of spin systems in nuclear magnetic resonance (NMR) are described. The sequences excite spins uniformly over large ranges of resonant frequencies arising from static magnetic field inhomogeneity, chemical shift differences, or spin couplings, or over large ranges of rf field amplitudes. Specific sequences for creating a population inversion or transverse magnetization are derived and demonstrated experimentally in liquid and solid state NMR. One approach to broadband excitation is based on principles of coherent averaging theory. A general formalism for deriving pulse sequences is given, along with computational methods for specific cases. This approach leads to sequences that produce strictly constant transformations of a spin system. The importance of this feature in NMR applications is discussed. A second approach to broadband excitation makes use of iterative schemes, i.e. sets of operations that are applied repetitively to a given initial pulse sequences, generating a series of increasingly complex sequences with increasingly desirable properties. A general mathematical framework for analyzing iterative schemes is developed. An iterative scheme is treated as a function that acts on a space of operators corresponding to the transformations produced by all possible pulse sequences. The fixed points of the function and the stability of the fixed points are shown to determine the essential behavior of the scheme. Iterative schemes for broadband population inversion are treated in detail. Algebraic and numerical methods for performing the mathematical analysis are presented. Two additional topics are treated. The first is the construction of sequences for uniform excitation of double-quantum coherence and for uniform polarization transfer over a range of spin couplings. Double-quantum excitation sequences are demonstrated in a liquid crystal system. The second additional topic is the construction of iterative schemes for narrowband population inversion. The use of sequences that invert spin populations only over a narrow range of rf field amplitudes to spatially localize NMR signals in an rf field gradient is discussed.

Tycko, R.

1984-10-01

217

Automated Analysis of Craniofacial Morphology Using Magnetic Resonance Images  

PubMed Central

Quantitative analysis of craniofacial morphology is of interest to scholars working in a wide variety of disciplines, such as anthropology, developmental biology, and medicine. T1-weighted (anatomical) magnetic resonance images (MRI) provide excellent contrast between soft tissues. Given its three-dimensional nature, MRI represents an ideal imaging modality for the analysis of craniofacial structure in living individuals. Here we describe how T1-weighted MR images, acquired to examine brain anatomy, can also be used to analyze facial features. Using a sample of typically developing adolescents from the Saguenay Youth Study (N?=?597; 292 male, 305 female, ages: 12 to 18 years), we quantified inter-individual variations in craniofacial structure in two ways. First, we adapted existing nonlinear registration-based morphological techniques to generate iteratively a group-wise population average of craniofacial features. The nonlinear transformations were used to map the craniofacial structure of each individual to the population average. Using voxel-wise measures of expansion and contraction, we then examined the effects of sex and age on inter-individual variations in facial features. Second, we employed a landmark-based approach to quantify variations in face surfaces. This approach involves: (a) placing 56 landmarks (forehead, nose, lips, jaw-line, cheekbones, and eyes) on a surface representation of the MRI-based group average; (b) warping the landmarks to the individual faces using the inverse nonlinear transformation estimated for each person; and (3) using a principal components analysis (PCA) of the warped landmarks to identify facial features (i.e. clusters of landmarks) that vary in our sample in a correlated fashion. As with the voxel-wise analysis of the deformation fields, we examined the effects of sex and age on the PCA-derived spatial relationships between facial features. Both methods demonstrated significant sexual dimorphism in craniofacial structure in areas such as the chin, mandible, lips, and nose. PMID:21655288

Chakravarty, M. Mallar; Aleong, Rosanne; Leonard, Gabriel; Perron, Michel; Pike, G. Bruce; Richer, Louis; Veillette, Suzanne; Pausova, Zdenka; Paus, Tomáš

2011-01-01

218

Pharynx Anatomy  

MedlinePLUS

... Pictures Browse Search Quick Search Image Details Pharynx Anatomy View/Download: Small: 720x576 View Download Add to My Pictures Title: Pharynx Anatomy Description: Anatomy of the pharynx; drawing shows the ...

219

Larynx Anatomy  

MedlinePLUS

... Pictures Browse Search Quick Search Image Details Larynx Anatomy View/Download: Small: 648x576 View Download Add to My Pictures Title: Larynx Anatomy Description: Anatomy of the larynx; drawing shows the ...

220

Vulva Anatomy  

MedlinePLUS

... Pictures Browse Search Quick Search Image Details Vulva Anatomy View/Download: Small: 720x634 View Download Add to My Pictures Title: Vulva Anatomy Description: Anatomy of the vulva; drawing shows the ...

221

A computer model based on real anatomy for electrophysiology study  

Microsoft Academic Search

In order to investigate the pattern of wave propagation on atria in both sinus rhythm and arrhythmia, we constructed a computational model based on real anatomy. The original anatomic data which encompasses morphological and geometrical knowledge was created from a whole-body set of 2mm interval magnetic resonance imaging (MRI) images of a male volunteer and represented in stl format. The

Weijia Lu; Daming Wei; Xin Zhu; Wenxi Chen

2011-01-01

222

Magnetic Resonance Imaging as a Tool to Predict Meniscal Reparability  

Microsoft Academic Search

One hundred six patients who underwent high field strength magnetic resonance imaging and subsequent arthroscopy of the knee were evaluated to determine the accuracy of magnetic resonance imaging in predicting meniscal tear reparability. Each scan was independently read by three examiners with varying degrees of expertise: a musculoskeletal radiologist, a senior orthopaedic surgeon, and a general radiologist. Each suspected tear

Matthew J. Matava; Kevin Eck; William Totty; Rick W. Wright; Robert A. Shively

1999-01-01

223

Midinfrared Resonant Magnetic Nanostructures Exhibiting a Negative Permeability  

Microsoft Academic Search

We experimentally demonstrate the first midinfrared (mid-IR) resonant magnetic nanostructures exhibiting a strong magnetic response corresponding to a negative permeability. This result is an important step toward the achievement of a negative refractive index in the IR. The possibility of extending negative permeability to higher frequencies is discussed; a structure with a negative effective permeability at a near-IR resonance frequency

Shuang Zhang; Wenjun Fan; B. K. Minhas; Andrew Frauenglass; K. J. Malloy; S. R. Brueck

2005-01-01

224

Magnetic resonance imaging in entomology: a critical review  

Microsoft Academic Search

Magnetic resonance imaging (MRI) enables in vivo imaging of organisms. The recent development of the magnetic resonance microscope (MRM) has enabled organisms within the size range of many insects to be imaged. Here, we introduce the principles of MRI and MRM and review their use in entomology. We show that MRM has been successfully applied in studies of parasitology, development,

Ratnieks F. L. W

225

The Nobel Prize in Medicine for Magnetic Resonance Imaging  

ERIC Educational Resources Information Center

Nobel Prize in Medicine awarded in December 2003 to chemist Paul C. Lauterbur and physicist Peter Mansfield for the development of magnetic resonance imaging (MRI), a long overdue recognition of the huge impact MRI has had in medical diagnostics and research is mentioned. MRI was derived, and remains an extension of nuclear magnetic resonance

Fry, Charles G.

2004-01-01

226

Graph theory based algorithm for magnetic resonance brain images segmentation  

Microsoft Academic Search

Image segmentation is often required as a preliminary and indispensable stage in the computer aided medical image process, particularly during the clinical analysis of magnetic resonance (MR) brain images. The segmentation of magnetic resonance image (MRI) is a challenging problem that has received an enormous amount of attention lately. In this paper, we propose a simple and effective segmentation method

Jianzhong Wang; Di Liu; Lili Dou; Baoxue Zhang; Jun Kong; Yinghua Lu

2008-01-01

227

Magnetic Resonance Imaging of Electroconvection in a Polar Organic Solvent  

E-print Network

Magnetic Resonance Imaging of Electroconvection in a Polar Organic Solvent Scott A. Riley, California 95616 Received October 20, 1999; revised February 2, 2000 Molecular motion in the polar organic solvent nitrobenzene induced by an electric field is studied by magnetic resonance imaging. Rf pulse

Augustine, Mathew P.

228

Magnetic resonance imaging of brain function and neurochemistry  

Microsoft Academic Search

In the past decade, magnetic resonance imaging (MRI) research has been focused on the acquisition of physiological and biochemical information noninvasively. Probably the most notable accomplishment in this general effort has been the introduction of the MR approaches to map brain function. This capability, often referred to as functional magnetic resonance imaging, or fMRI, is based on the sensitivity of

KAMIL UGURBIL; DAE-SHIK KIM; TIM DUONG; XIAOPING HU; SEIJI OGAWA; ROLF GRUETTER; WEI CHEN; SEONG-GI KIM; XIAO-HUNG ZHU; ESSA YACOUB; PIERRE-FRANCOIS VAN DE MOORTELE; AMIR SHMUEL; JOSEF PFEUFFER; HELLMUT MERKLE; PETER ANDERSEN; GREGOR ADRIANY

2001-01-01

229

Nuclear magnetic resonance in environmental engineering: Principles and applications  

Microsoft Academic Search

This paper gives an introduction to nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) in relation to applications in the field of environmental science and engineering. The underlying principles of high resolution solution and solid state NMR, relaxation time measurements and imaging are presented. Then, the use of NMR is illustrated and reviewed in studies of biodegradation and

P. N. L. Lens; M. A. Hemminga

1998-01-01

230

Design of LLC resonant converter using planar magnetic component  

Microsoft Academic Search

This paper presents the design and implementation of LLC resonant converter using planar magnetic component. In the LLC resonant converter, ZVS turn-on and ZCS turn-off of MOSFETs and diode rectifiers can be achieved over the entire operating range, respectively. Therefore, the switching loss is reduced and we can operate the converter at higher switching frequency. At that frequency, planar magnetic

Sihun Yang; Seiya Abe; Masahito Shoyama

2009-01-01

231

MBP 9662a: Nuclear Magnetic Resonance Prof. Blaine A. Chronik  

E-print Network

of Physics and Astronomy Office: Room 241, Physics & Astronomy Building Phone: 661-2111 x24067 (phone mailMBP 9662a: Nuclear Magnetic Resonance Prof. Blaine A. Chronik Fall Semester, 2010 1 of 3 Medical Biophysics 9662a "Introductory Nuclear Magnetic Resonance" or "MRI 1: no gradients" Fall Semester, 2010

Lennard, William N.

232

Functional magnetic resonance imaging (FMRI) of the human brain  

Microsoft Academic Search

Functional magnetic resonance imaging (FMRI) can provide detailed images of human brain that reflect localized changes in cerebral blood flow and oxygenation induced by sensory, motor, or cognitive tasks. This review presents methods for gradient-recalled echo-planar functional magnetic resonance imaging (FMRI). Also included is a discussion of the hypothesized basis of FMRI, imaging hardware, a unique visual stimulation apparatus, image

Edgar A. DeYoe; Peter Bandettini; Jay Neitz; David Miller; Paula Winans

1994-01-01

233

Global resonances in the evolution of solar magnetic fields  

Microsoft Academic Search

Decomposition of the pattern of solar magnetic fields in spherical harmonics for a data set of 25 years and power spectrum analysis of the harmonic coefficients reveals a strikingly resonant modal structure. The resonances for the modes of odd and even parity are decoupled from each other, indicating an underlying selection rule. This new 'emission line' spectrum of solar magnetic

J. O. Stenflo; M. Vogel

1986-01-01

234

Anatomy of the Heart and Great Arteries  

Microsoft Academic Search

Magnetic resonance imaging (MRI) techniques produce high spatial, contrast, and temporal resolution image data for evaluation\\u000a of cardiac and great vessel anatomy, regional tissue characterization, vascular blood flow, cardiac chamber filling and contraction,\\u000a regional myocardial dynamics, and myocardial perfusion. MRI produces series of tomographic images of the heart and great arteries\\u000a in arbitrary section, allowing tailoring of an examination to

Lawrence M. Boxt; Martin J. Lipton

235

Magnet driver for producing ultra-high gradient magnetic fields for magnetic resonance imaging  

Microsoft Academic Search

Pulsed gradient magnetic fields are required for magnetic resonance imaging (MRI). Many imaging sequences (e.g., echo planar imaging, diffusion tensor imaging) could be improved with shorter gradient pulses. MRI systems currently available typically require ramp times of hundreds of microseconds. The goal of the work described here is to achieve very high gradient fields, with very short rise times to

Howard D. Sanders; Steven C. Glidden; Daniel M. Warnow; Irving N. Weinberg; Pavel Stepanov; Roland Probst; Alan McMillan; Rao Gullapalli; Piotr M. Starewicz; William F. B. Punchard; Kai-Ming Lo; Stanley Thomas Fricke

2011-01-01

236

[Magnetic resonance imaging in multiple sclerosis].  

PubMed

The contribution of magnetic resonance imaging techniques to the clinical prognosis of multiple sclerosis. Magnetic resonance imaging (MRI) is a diagnostic technique with a high sensitivity for the detection of lesions, but with a poor pathological specificity. In the case of multiple sclerosis (MS), the improvement of diagnostic efficacy depends on a careful analysis of the clinical presentation and the use of increasingly stringent MRI criteria aimed at improving the specificity of the conventional MRI T2 sequences. New sequences such as fast spin-echo (also called turbo spin-echo) and FLAIR (fluid attenuated inversion recovery, a method derived from inversion recovery) have improved the visualization of lesions. MRI can under certain conditions be used to monitor the evolution of MS. Acute-phase monitoring is focused on observed changes in disease activity such as the appearance, recurrence or extension of lesions after i.v. injection of contrast medium, i.e., gadolinium (Gd)-enhanced MRI. In the chronic phase, the lesions is the aspect used as the monitoring criterion. However, MRI is still only a secondary criterion in phase III therapeutic trials due to its insufficient correlation with the disability. In neurological daily practice, conventional MRI is only of limited interest at the individual level in patient follow-up, as its prognostic value is poor. Moreover, the difficulty in determining the lesion load can only be excluded in the context of clinical trials, in which certain methodological precautions are taken. This is why techniques other than MRI are being investigated to obtain a better correlation with the clinical course of the disease, for instance the quantification of 'black holes' on T1 weighted images, and the measurement of cerebral and spinal atrophy. Adapted MRI techniques allow a weighted signal to be obtained via the movement (diffusion imaging), by the complexity of the molecular structure (magnetization transfer imaging), by chemical shift (spectroscopic imaging), or by local oxygenation (functional MRI). These new MRI techniques allow a more precise assessment of the pathological mechanisms involved in MS, such as edema, blood brain barrier break-down, demyelinisation, gliosis, cellular infiltration and axonal loss; they provide a better means of establishing the correlation between clinical impact and the destructive nature of the MS lesion. The importance of axonal loss has recently been confirmed in MS by analyzing MRI spectroscopic and neuropathological findings. In addition to magnetization transfer imaging, MR diffusion imaging and functional MRI are being intensively studied in order to assess their contribution to the study of reversibility of the degenerative process. PMID:10815291

Tourbah, A; Berry, I

2000-03-01

237

Plasma-induced magnetic responses during nonlinear dynamics of magnetic islands due to resonant magnetic perturbations  

NASA Astrophysics Data System (ADS)

Resonant magnetic perturbations (RMPs) produce magnetic islands in toroidal plasmas. Self-healing (annihilation) of RMP-induced magnetic islands has been observed in helical systems, where a possible mechanism of the self-healing is shielding of RMP penetration by plasma flows, which is well known in tokamaks. Thus, fundamental physics of RMP shielding is commonly investigated in both tokamaks and helical systems. In order to check this mechanism, detailed informations of magnetic island phases are necessary. In experiments, measurement of radial magnetic responses is relatively easy. In this study, based on a theoretical model of rotating magnetic islands, behavior of radial magnetic fields during the self-healing is investigated. It is confirmed that flips of radial magnetic fields are typically observed during the self-healing. Such behavior of radial magnetic responses is also observed in LHD experiments.

Nishimura, Seiya

2014-12-01

238

The magnetic resonance imaging-linac system.  

PubMed

The current image-guided radiotherapy systems are suboptimal in the esophagus, pancreas, kidney, rectum, lymph node, etc. These locations in the body are not easily accessible for fiducials and cannot be visualized sufficiently on cone-beam computed tomographies, making daily patient set-up prone to geometrical uncertainties and hinder dose optimization. Additional interfraction and intrafraction uncertainties for those locations arise from motion with breathing and organ filling. To allow real-time imaging of all patient tumor locations at the actual treatment position a fully integrated 1.5-T, diagnostic quality, magnetic resonance imaging with a 6-MV linear accelerator is presented. This system must enable detailed dose painting at all body locations. PMID:24931095

Lagendijk, Jan J W; Raaymakers, Bas W; van Vulpen, Marco

2014-07-01

239

Magnetic resonance imaging of renal transplants  

SciTech Connect

Nineteen patients were examined to determine the clinical potential of magnetic resonance imaging (MRI) for evaluation of renal transplants. Of the six living-related transplants with good renal function that were imaged, five demonstrated good corticomedullary differentiation (CMD) and one faint CMD. Three transplants with acute rejection were imaged, and all demonstrated a decrease in CMD and decrease in overall signal intensity compared with baseline. No CMD was seen in the three chronically rejecting transplants imaged. The appearance of cadaveric transplants and acute tubular necrosis was quite variable. All perinephric fluid collections were well depicted by MRI. Lymphoceles could be distinguished from hematomas. MRI may prove to be a useful adjunct in the evaluation of renal transplant and perinephric fluid collections.

Geisinger, M.A.; Risius, B.; Jordan, M.L.; Zelch, M.G.; Novick, A.C.; George, C.R.

1984-12-01

240

Interactive Course on Magnetic Resonance Imagining  

NSDL National Science Digital Library

As the health care professions continue to attract talented individuals, online resources have become an attractive way to learn new skills and supplement classroom learning. This website offers interested parties a step-by-step, interactive course on magnetic resonance imaging (MRI). It's worth noting that the site has received several awards from organizations such as the Radiological Society of North America. The course is divided into 16 sections, including Cardiac MRI, Image Formation, and Functional MRI. Each section contains a table of contents and a detailed list of learning objectives. As a whole, the site is a great way to get acquainted with this important medical tool and it is a resource that educators will want to share with friends and colleagues. [KMG

2013-01-01

241

Oxygenation-sensitive cardiovascular magnetic resonance  

PubMed Central

Oxygenation-sensitive cardiovascular magnetic resonance (CMR) is a non-contrast technique that allows the non-invasive assessment of myocardial oxygenation. It capitalizes on the fact that deoxygenated hemoglobin in blood can act as an intrinsic contrast agent, changing proton signals in a fashion that can be imaged to reflect the level of blood oxygenation. Increases in O2 saturation increase the BOLD imaging signal (T2 or T2*), whereas decreases diminish it. This review presents the basic concepts and limitations of the BOLD technique, and summarizes the preclinical and clinical studies in the assessment of myocardial oxygenation with a focus on recent advances. Finally, it provides future directions and a brief look at emerging techniques of this evolving CMR field. PMID:23706167

2013-01-01

242

Magnetic Resonance Imaging of the Knee  

PubMed Central

Context: Magnetic resonance imaging (MRI) affords high-resolution visualization of the soft tissue structures (menisci, ligaments, cartilage, etc) and bone marrow of the knee. Evidence Acquisition: Pertinent clinical and research articles in the orthopaedic and radiology literature over the past 30 years using PubMed. Results: Ligament tears can be accurately assessed with MRI, but distinguishing partial tears from ruptures of the anterior cruciate ligament (ACL) can be challenging. Determining the extent of a partial tear is often extremely difficult to accurately assess. The status of the posterolateral corner structures, menisci, and cartilage can be accurately evaluated, although limitations in the evaluation of certain structures exist. Patellofemoral joint, marrow, tibiofibular joint, and synovial pathology can supplement physical examination findings and provide definitive diagnosis. Conclusions: MRI provides an accurate noninvasive assessment of knee pathology. PMID:24381701

Hash, Thomas W.

2013-01-01

243

Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project  

NASA Technical Reports Server (NTRS)

The West Virginia State College Community College Division NASA Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) study is described. During this contract period, the two most significant and professionally rewarding events were the presentation of the research activity at the Sir Isaac Newton Conference in St. Petersburg, Russia, and the second Day of Discovery Conference, focusing on economic recovery in West Virginia. An active antenna concept utilizing a signal feedback principle similar to regenerative receivers used in early radio was studied. The device has potential for ELF research and other commercial applications for improved signal reception. Finally, work continues to progress on the development of a prototype monitoring station. Signal monitoring, data display, and data storage are major areas of activity. In addition, we plan to continue our dissemination of research activity through presentations at seminars and other universities.

Spaniol, Craig

1993-01-01

244

Magnetic resonance enterography of Crohn's disease.  

PubMed

Magnetic resonance enterography (MRE) has been reported to be a useful modality for the evaluation of luminal inflammation and extraintestinal complications in Crohn's disease (CD). A recent study indicated that the diagnostic ability of MRE was comparable to the diagnostic ability of other devices, such as ileocolonoscopy. MRE can be performed repeatedly because there is no radiation exposure. Therefore, MRE is useful as a method of follow-up for younger patients with established CD. It is useful for evaluating the efficacy of medical treatments, such as biologics. MRE can detect small intestinal lesions even if the endoscope does not pass through the stenosis. The concerns of availability of expertise and the costs associated with MRE should be addressed so MRE can be widely used for CD patients in the near future. PMID:25186521

Naganuma, Makoto; Hisamatsu, Tadakazu; Kanai, Takanori; Ogata, Haruhiko

2015-01-01

245

Cranial magnetic resonance imaging findings in kwashiorkor.  

PubMed

Protein energy malnutrition (PEM) is an important public health problem in the developing countries, although it is becoming uncommon in South West Nigeria. Cerebral changes have been associated with severe PEM. This study evaluated the neurological changes using Magnetic Resonance Imaging (MRI) in Ibadan south west Nigeria. The 5 children evaluated had a median age of 16 months and all the children had brain changes compatible with cerebral atrophy. In addition two of the children had periventricular white matter changes, while one these two had mega cisterna magna in addition. Though this study did not re-evaluate the brains of these children after nutritional rehabilitation, it is possible that changes are reversible as demonstrated in earlier studies. PMID:20128668

Atalabi, Omolola Mojisola; Lagunju, Ikeoluwa Abiola; Tongo, Olukemi Oluwatoyin; Akinyinka, Olusegun Olusina

2010-01-01

246

Magnetic resonance imaging of pancreatitis: an update.  

PubMed

Magnetic resonance (MR) imaging plays an important role in the diagnosis and staging of acute and chronic pancreatitis and may represent the best imaging technique in the setting of pancreatitis due to its unmatched soft tissue contrast resolution as well as non-ionizing nature and higher safety profile of intravascular contrast media, making it particularly valuable in radiosensitive populations such as pregnant patients, and patients with recurrent pancreatitis requiring multiple follow-up examinations. Additional advantages include the ability to detect early forms of chronic pancreatitis and to better differentiate adenocarcinoma from focal chronic pancreatitis. This review addresses new trends in clinical pancreatic MR imaging emphasizing its role in imaging all types of acute and chronic pancreatitis, pancreatitis complications and other important differential diagnoses that mimic pancreatitis. PMID:25356038

Manikkavasakar, Sriluxayini; AlObaidy, Mamdoh; Busireddy, Kiran K; Ramalho, Miguel; Nilmini, Viragi; Alagiyawanna, Madhavi; Semelka, Richard C

2014-10-28

247

Magnetic resonance imaging of atherosclerotic vascular disease.  

PubMed

Atherosclerosis is a chronic, progressive, and often widespread arterial disorder in which the morphology and composition of the arterial segments containing atheroma are of considerable importance. Magnetic resonance imaging (MRI) allows non-invasive assessment of early arterial disease without the use of ionizing radiation. Arterial compliance, flow-wave velocity, and the pattern of flow within the aorta may all be disturbed by the disease, but these parameters are all accessible to MRI. In addition, atheroma can be directly imaged. Thus, MRI is valuable not only in the detection of disease, but also in the study of its natural history and the effects of interventions such as the control of risk factors and the use of lipid-lowering agents. PMID:8297541

Underwood, R S; Mohiaddin, R H

1993-11-01

248

Bilateral filtering of magnetic resonance phase images.  

PubMed

High-pass filtering is required for the removal of background field inhomogeneities in magnetic resonance phase images. This high-pass filtering smooths across boundaries between areas with large differences in phase. The most prominent boundary is the surface of the brain where areas with large phase values inside the brain are located close to areas outside the brain where the phase is, on average, zero. Cortical areas, which are of great interest in brain MRI, are therefore often degraded by high-pass filtering. Here, we propose the use of the bilateral filter for the high-pass filtering step. The bilateral filter is essentially a Gaussian filter that stops smoothing at boundaries. We show that the bilateral filter improves image quality at the brain's surface, without sacrificing contrast within the brain. PMID:21664782

McPhee, Kelly C; Denk, Christian; Al-Rekabi, Zeinab; Rauscher, Alexander

2011-09-01

249

Magnetic resonance imaging after exposure to microgravity  

NASA Technical Reports Server (NTRS)

A number of physiological changes were demonstrated in bone, muscle, and blood from exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long-duration space missions is an important NASA goal. Historically, NASA has had to rely on tape measures, x-ray, and metabolic balance studies with collection of excreta and blood specimens to obtain this information. The development of magnetic resonance imaging (MRI) offers the possibility of greatly extending these early studies in ways not previously possible; MRI is also non-invasive and safe; i.e., no radiation exposure. MRI provides both superb anatomical images for volume measurements of individual structures and quantification of chemical/physical changes induced in the examined tissues. This investigation will apply MRI technology to measure muscle, intervertebral disc, and bone marrow changes resulting from exposure to microgravity.

Leblanc, Adrian

1993-01-01

250

Small-volume nuclear magnetic resonance spectroscopy.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is one of the most information-rich analytical techniques available. However, it is also inherently insensitive, and this drawback precludes the application of NMR spectroscopy to mass- and volume-limited samples. We review a particular approach to increase the sensitivity of NMR experiments, namely the use of miniaturized coils. When the size of the coil is reduced, the sample volume can be brought down to the nanoliter range. We compare the main coil geometries (solenoidal, planar, and microslot/stripline) and discuss their applications to the analysis of mass-limited samples. We also provide an overview of the hyphenation of microcoil NMR spectroscopy to separation techniques and of the integration with lab-on-a-chip devices and microreactors. PMID:21391818

Fratila, Raluca M; Velders, Aldrik H

2011-01-01

251

In vivo nuclear magnetic resonance imaging  

NASA Technical Reports Server (NTRS)

A number of physiological changes have been demonstrated in bone, muscle and blood after exposure of humans and animals to microgravity. Determining mechanisms and the development of effective countermeasures for long duration space missions is an important NASA goal. The advent of tomographic nuclear magnetic resonance imaging (NMR or MRI) gives NASA a way to greatly extend early studies of this phenomena in ways not previously possible; NMR is also noninvasive and safe. NMR provides both superb anatomical images for volume assessments of individual organs and quantification of chemical/physical changes induced in the examined tissues. The feasibility of NMR as a tool for human physiological research as it is affected by microgravity is demonstrated. The animal studies employed the rear limb suspended rat as a model of mucle atrophy that results from microgravity. And bedrest of normal male subjects was used to simulate the effects of microgravity on bone and muscle.

Leblanc, A.; Evans, H.; Bryan, R. N.; Johnson, P.; Schonfeld, E.; Jhingran, S. G.

1984-01-01

252

Endometriosis: the role of magnetic resonance imaging.  

PubMed

Several imaging options are available today to diagnose endometriosis. Currently, the two techniques most used are sonography and magnetic resonance imaging (MRI). Three-dimensional (3D) sonography has proved to be particularly sensitive in the diagnosis of endometriosis. In recent years, MRI has emerged as a high reproducible method to explore endometriosis; moreover, its capability to evaluate tissue signal is an extremely powerful system in the differential diagnosis with other pathologies and for the identification of malignant degeneration. The purpose of this paper is to present the state-of-the-art of MRI of endometriosis by performing a review of the literature and showing the epidemiology, pathogenesis, and classification of endometriosis. In this work, the technique that should be used, MR findings of endometriosis and the principles of differential diagnosis are explained. PMID:24676084

Saba, Luca; Sulcis, Rosa; Melis, Gian Benedetto; Cecco, Carlo Nicola de; Laghi, Andrea; Piga, Mario; Guerriero, Stefano

2014-03-27

253

Rotating-frame gradient fields for magnetic resonance imaging and nuclear magnetic resonance in low fields  

DOEpatents

A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.

Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki

2014-01-21

254

Could magnetic resonance provide in vivo histology?  

PubMed Central

The diagnosis of a suspected tumor lesion faces two basic problems: detection and identification of the specific type of tumor. Radiological techniques are commonly used for the detection and localization of solid tumors. Prerequisite is a high intrinsic or enhanced contrast between normal and neoplastic tissue. Identification of the tumor type is still based on histological analysis. The result depends critically on the sampling sites, which given the inherent heterogeneity of tumors, constitutes a major limitation. Non-invasive in vivo imaging might overcome this limitation providing comprehensive three-dimensional morphological, physiological, and metabolic information as well as the possibility for longitudinal studies. In this context, magnetic resonance based techniques are quite attractive since offer at the same time high spatial resolution, unique soft tissue contrast, good temporal resolution to study dynamic processes and high chemical specificity. The goal of this paper is to review the role of magnetic resonance techniques in characterizing tumor tissue in vivo both at morphological and physiological levels. The first part of this review covers methods, which provide information on specific aspects of tumor phenotypes, considered as indicators of malignancy. These comprise measurements of the inflammatory status, neo-vascular physiology, acidosis, tumor oxygenation, and metabolism together with tissue morphology. Even if the spatial resolution is not sufficient to characterize the tumor phenotype at a cellular level, this multiparametric information might potentially be used for classification of tumors. The second part discusses mathematical tools, which allow characterizing tissue based on the acquired three-dimensional data set. In particular, methods addressing tumor heterogeneity will be highlighted. Finally, we address the potential and limitation of using MRI as a tool to provide in vivo tissue characterization. PMID:24454320

Dominietto, Marco; Rudin, Markus

2014-01-01

255

Selectivity in multiple quantum nuclear magnetic resonance  

SciTech Connect

The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible.

Warren, W.S.

1980-11-01

256

Controlling interactions between highly-magnetic atoms with Feshbach resonances  

E-print Network

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic $^7$S$_3$ chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on Dysprosium and Erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.

Svetlana Kotochigova

2014-10-14

257

Controlling interactions between highly magnetic atoms with Feshbach resonances  

NASA Astrophysics Data System (ADS)

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic 7S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin–orbit coupling exists.

Kotochigova, Svetlana

2014-09-01

258

Controlling interactions between highly magnetic atoms with Feshbach resonances.  

PubMed

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists. PMID:25221938

Kotochigova, Svetlana

2014-09-01

259

Designing Magnetic Resonance Imaging Curriculum for Undergraduates  

NSDL National Science Digital Library

A new hands-on curriculum developed at Vanderbilt University focuses on teaching medical imaging, specifically magnetic resonance imaging(MRI). This material was designed to engage students in real world applications of biomedical engineering through challenge based activities. These activities include homework, quizzes, and hands-on experiments. The materials for each activity are easy to find and can be purchased for under $25. The curriculum begins with a Grand Challenge that presents a medical case in order to interest the students. The challenge questions allow the students to play the role of the patient, technician, and physician. The material was organized in five modules: Electromagnetic Fields and Magnetic Moments, Spin Behavior: Excitation and Relaxation, Spatial Encoding and Detecting Signals, Image Reconstruction, and Image Characteristics. In addition, there are expert interviews that provide the students with multiple perspectives on the information. The material was tested in the summer of 2007 on five students in order to gain feedback, correct errors, and gauge student understanding. Testing showed that the curriculum had a positive impact on student interest in biomedical imaging and resulted in several improvements and additions to the curriculum. During the academic year, the materials will be field-tested at the undergraduate and high school level. Additionally, the materials are being adapted for high school level implementation.

260

Cardiac imaging using gated magnetic resonance  

SciTech Connect

To overcome the limitations of magnetic resonance (MR) cardiac imaging using nongated data acquisition, three methods for acquiring a gating signal, which could be applied in the presence of a magnetic field, were tested; an air-filled plethysmograph, a laser-Doppler capillary perfusion flowmeter, and an electrocardiographic gating device. The gating signal was used for timing of MR imaging sequences (IS). Application of each gating method yielded significant improvements in structural MR image resolution of the beating heart, although with both plethysmography and laser-Doppler velocimetry it was difficult to obtain cardiac images from the early portion of the cardiac cycle due to an intrinsic delay between the ECG R wave and peripheral detection of the gating signal. Variations in the temporal relationship between the R wave and plethysmographic and laser-Doppler signals produced inconsistencies in the timing of IS. Since the ECG signal is virtually free of these problems, the preferable gating technique is IS synchronization with an electrocardiogram. The gated images acquired with this method provide sharp definition of internal cardiac morphology and can be temporarily referenced to end diastole and end systole or intermediate points.

Lanzer, P.; Botvinick, E.H.; Schiller, N.B.

1984-01-01

261

MAGNETIC RESONANCE IMAGE SYNTHESIS THROUGH PATCH REGRESSION.  

PubMed

Magnetic resonance imaging (MRI) is widely used for analyzing human brain structure and function. MRI is extremely versatile and can produce different tissue contrasts as required by the study design. For reasons such as patient comfort, cost, and improving technology, certain tissue contrasts for a cohort analysis may not have been acquired during the imaging session. This missing pulse sequence hampers consistent neuroanatomy research. One possible solution is to synthesize the missing sequence. This paper proposes a data-driven approach to image synthesis, which provides equal, if not superior synthesis compared to the state-of-the-art, in addition to being an order of magnitude faster. The synthesis transformation is done on image patches by a trained bagged ensemble of regression trees. Validation was done by synthesizing T 2-weighted contrasts from T 1-weighted scans, for phantoms and real data. We also synthesized 3 Tesla T 1-weighted magnetization prepared rapid gradient echo (MPRAGE) images from 1.5 Tesla MPRAGEs to demonstrate the generality of this approach. PMID:24443686

Jog, Amod; Roy, Snehashis; Carass, Aaron; Prince, Jerry L

2013-12-31

262

Resonance magnetic x-ray-scattering study of erbium  

Microsoft Academic Search

The magnetic phases of erbium have been studied by resonance x-ray-scattering techniques. When the incident x-ray energy is tuned near the LIII absorption edge, large resonant enhancements of the magnetic scattering are observed above 18 K. We have measured the energy and polarization dependence of this magnetic scattering and analyzed it using a simple model based on electric dipole and

M. K. Sanyal; Doon Gibbs; J. Bohr; M. Wulff

1994-01-01

263

Magnetic Transitions of Multiferroic Frustrated Magnets Revealed by Resonant Soft X-ray Magnetic Scattering  

NASA Astrophysics Data System (ADS)

The coexistence of magnetism and ferroelectricity with cross coupling, termed multiferroicity, rarely occurs. The discovery of gigantic magnetoelectric coupling in frustrated magnets has revived interest in their multiferroic behavior. Here, we review the measurements of resonant soft-X-ray magnetic scattering in the multiferroic frustrated magnets TbMn2O5, LiCu2O2, and CoCr2O4. In addition to the experimental technique used, the evolution of the wave vector of magnetic ordering about the temperature of multiferroic transitions is discussed. We proffer scattering evidence of multiferroicity and a pathway for understanding the intricate coupling between magnetism and ferroelectricity in magnets with spin spirals. Our results also reveal the low-dimension nature of a quantum spin-chain multiferroics and the evolution of the interrelation between the polarization P, the magnetization M, and the spiral wave vector Q.

Huang, Di-Jing; Okamoto, Jun; Huang, Shih-Wen; Mou, Chung-Yu

2010-01-01

264

[Diagnosis of atrial septal defect using magnetic resonance imaging].  

PubMed

We studied the morphological features of defects of the interatrial septum using magnetic resonance imaging (MRI) to determine the sizes of defects and other abnormalities. MR images were obtained in 28 patients with atrial septal defect, including five cases with complicated anomalies (two with Ebstein's anomaly, one pentalogy of Fallot, and one anomalous pulmonary vein connection and azygos continuation). Images were also obtained in the control subjects including seven normal volunteers and 142 patients with various acquired heart diseases. The diagnosis of atrial septal defect was established by cardiac catheterization, angiography and two-dimensional echocardiography prior to the MRI studies, and in 14 patients, the diagnosis was confirmed by surgery. The MRI unit had a superconducting magnet and operated at 0.25 or 0.50 Tesla. A spin echo pulse sequence was used with an echo time of 40 or 60 msec. At the beginning of this study, non-gated MRI images were obtained in the 28 controls and in three patients with atrial septal defect. Nongated MRI could not image the anatomical structure of the interatrial septa of 12 of the 28 controls, or any of the three patients with atrial septal defect. Nongated MRI was, therefore, inadequate for visualizing cardiac anatomy. Gated MRI images were obtained in 141 controls and in 25 patients with atrial septal defect. Gated MRI revealed the interatrial septum, interventricular septum, atrioventricular septum, mitral valve, tricuspid valve and other intracardiac structures in most subjects. In 17 control subjects (12%), however, there was a very faint signal from the central portion of the interatrial septum. In these instances, there was a gradual fading of the signal of the interatrial septum, so that they could be distinguished from the atrial septal defect. The sudden disappearance of the signal from the interatrial septum was observed by gated MRI in all 25 patients with atrial septal defect. The sizes of the defects by MRI coincided with the findings at surgery in all 14 patients. MRI showed right atrial dilatation, right ventricular hypertrophy and dilatation, and pulmonary artery dilatation in most of the patients having atrial septal defect. Complex anomalies associated with atrial septal defect were also clearly shown by MRI, such as displacement of the tricuspid leaflets in two patients with Ebstein's anomaly, and anomalous pulmonary venous connection and persistent left superior vena cava in one patient. These results indicated that gated MRI is a valuable noninvasive method of diagnosing atrial septal defect and complicating anomalies. PMID:3506607

Sakakibara, M; Kobayashi, S; Imai, H; Watanabe, S; Masuda, Y; Inagaki, Y

1987-12-01

265

Ultrahigh-resolution magnetic resonance in inhomogeneous magnetic fields: two-dimensional long-lived-coherence correlation spectroscopy.  

PubMed

A half-century quest for improving resolution in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) has enabled the study of molecular structures, biological interactions, and fine details of anatomy. This progress largely relied on the advent of sophisticated superconducting magnets that can provide stable and homogeneous fields with temporal and spatial variations below ?B(0)/B(0)<0.01 ppm. In many cases however, inherent properties of the objects under investigation, pulsating arteries, breathing lungs, tissue-air interfaces, surgical implants, etc., lead to fluctuations and losses of local homogeneity. A new method dubbed "long-lived-coherence correlation spectroscopy" (LLC-COSY) opens the way to overcome both inhomogeneous and homogeneous broadening, which arise from local variations in static fields and fluctuating dipole-dipole interactions, respectively. LLC-COSY makes it possible to obtain ultrahigh resolution two-dimensional spectra, with linewidths on the order of ??=0.1 to 1 Hz, even in very inhomogeneous fields (?B(0)/B(0)>10 ppm or 5000 Hz at 9.7 T), and can improve resolution by a factor up to 9 when the homogeneous linewidths are determined by dipole-dipole interactions. The resulting LLC-COSY spectra display chemical shift differences and scalar couplings in two orthogonal dimensions, like in "J spectroscopy." LLC-COSY does not require any sophisticated gradient switching or frequency-modulated pulses. Applications to in-cell NMR and to magnetic resonance spectroscopy (MRS) of selected volume elements in MRI appear promising, particularly when susceptibility variations tend to preclude high resolution. PMID:23006108

Chinthalapalli, Srinivas; Bornet, Aurélien; Segawa, Takuya F; Sarkar, Riddhiman; Jannin, Sami; Bodenhausen, Geoffrey

2012-07-27

266

Design of matrix shim coils system for nuclear magnetic resonance  

Microsoft Academic Search

A high purity magnetic field matrix shim system for Nuclear Magnetic Resonance has been designed and constructed. The stochastic methods, suitably determined by the parameters obtained from the theoretical analysis, are used for optimization of its coils. The approach to the design ensures the high purity of correcting magnetic fields and minimizes the total shim system power consumption. The measuring

Pavel Konzbul; K. Sveda; A. Srnka

2000-01-01

267

Quantifying Mixing using Magnetic Resonance Imaging  

PubMed Central

Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media 1, 2. The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile 1H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for imaging process flows. Here, MRI provides spatially resolved component concentrations at different axial locations during the mixing process. This work documents real-time mixing of highly viscous fluids via distributive mixing with an application to personal care products. PMID:22314707

Tozzi, Emilio J.; McCarthy, Kathryn L.; Bacca, Lori A.; Hartt, William H.; McCarthy, Michael J.

2012-01-01

268

Quantifying mixing using magnetic resonance imaging.  

PubMed

Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device. Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media (1, 2). The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile (1)H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for imaging process flows. Here, MRI provides spatially resolved component concentrations at different axial locations during the mixing process. This work documents real-time mixing of highly viscous fluids via distributive mixing with an application to personal care products. PMID:22314707

Tozzi, Emilio J; McCarthy, Kathryn L; Bacca, Lori A; Hartt, William H; McCarthy, Michael J

2012-01-01

269

Nuclear magnetic double resonance based on strong rf magnetic-field-induced coupling between spin systems  

Microsoft Academic Search

The origin of the rf magnetic-field-induced coupling between spin systems is discussed. A new nuclear-double-resonance technique employing this coupling is proposed, which has particular value in measuring pure nuclear-quadrupole-resonance spectra of integer-spin nuclei by nuclear double resonance. The sensitivity of the new technique is discussed for the case of 1H-14N double resonance in zero static magnetic field, as well as

J. Seliger; R. Blinc; M. Mali; R. Osredkar; A. Prelesnik

1975-01-01

270

Real-time magnetic resonance imaging investigation of resonance tuning in soprano singing  

PubMed Central

This article investigates using real-time magnetic resonance imaging the vocal tract shaping of 5 soprano singers during the production of two-octave scales of sung vowels. A systematic shift of the first vocal tract resonance frequency with respect to the fundamental is shown to exist for high vowels across all subjects. No consistent systematic effect on the vocal tract resonance could be shown across all of the subjects for other vowels or for the second vocal tract resonance. PMID:21110548

Bresch, Erik; Narayanan, Shrikanth

2010-01-01

271

Resonant x-ray magnetic scattering in holmium  

SciTech Connect

We review the results of resonant x-ray magnetic scattering experiments on the rare earth metal holmium. When the incident incident x-ray energy is tuned near the L{sub III} absorption edge, large resonant enhancements of the magnetic scattering and resonant integer harmonics are observed. These results are analyzed within the theory of x-ray resonance exchange scattering assuming electric dipole (2p {yields} 5d) and quadrupole (2p {yields} 4f) transitions among atomic orbitals. 30 refs., 5 figs.

Gibbs, D.

1991-01-01

272

Bipolar programmable current supply for superconducting nuclear magnetic resonance magnets  

NASA Astrophysics Data System (ADS)

In high resolution continuous-wave nuclear magnetic resonance (NMR) work well-reproducible, linear sweeps of current are needed. We have developed a microcontroller based programmable current supply, tested with superconducting magnets with inductance of 10 mH and 10 H. We achieved a resolution and noise of 4 ppm. The supply has an internal sweep with programmable ramping rate and a possibility for remote operation from a computer with either GPIB or RS232 interface. It is based on an 18-bit D/A converter. The maximum output current is ±10 A, the sweep rate can be set between 1 ?A/s-140 mA/s, and the maximum output voltage is ±2.5 V. In work at ultralow temperatures, especially in superconducting quantum interference device NMR, all rf interference to the experiment should be avoided. One of the sources of this kind of unwanted input is the digital switching noise of fast logic devices. We discuss this problem in the context of our design.

Koivuniemi, Jaakko; Luusalo, Reeta; Hakonen, Pertti

1998-09-01

273

Magnetic resonance beacon to detect intracellular microRNA during neurogenesis.  

PubMed

Magnetic resonance imaging (MRI) offers great spatial resolution for viewing deep tissues and anatomy. We developed a self-assembling signal-on magnetic fluorescence nanoparticle to visualize intracellular microRNAs (miRNAs or miRs) during neurogenesis using MRI. The self-assembling nanoparticle (miR124a MR beacon) was aggregated by the incubation of three different oligonucleotides: a 3' adaptor, a 5' adaptor, and a linker containing miR124a-binding sequences. The T2-weighted magnetic resonance (MR) signal of the self-assembled nanoparticle was quenched when miR124a was absent from test tubes or was minimally expressed in cells and tissues. When miR124a was present in test tubes or highly expressed in vitro and in vivo during P19 cell neurogenesis, it hybridized with the miR124a MR beacon, causing the linker to detach, resulting in increased signal-on MRI intensity. This MR beacon can be used as a new imaging probe to monitor the miRNA-mediated regulation of cellular processes. PMID:25522966

Lee, Jonghwan; Jin, Yeon A; Ko, Hae Young; Lee, Yong Seung; Heo, Hyejung; Cho, Sujeong; Kim, Soonhag

2015-02-01

274

Sensitive magnetic force detection with a carbon nanotube resonator  

SciTech Connect

We propose a technique for sensitive magnetic point force detection using a suspended carbon nanotube (CNT) mechanical resonator combined with a magnetic field gradient generated by a ferromagnetic gate electrode. Numerical calculations of the mechanical resonance frequency show that single Bohr magneton changes in the magnetic state of an individual magnetic molecule grafted to the CNT can translate to detectable frequency shifts, on the order of a few kHz. The dependences of the resonator response to device parameters such as length, tension, CNT diameter, and gate voltage are explored and optimal operating conditions are identified. A signal-to-noise analysis shows that, in principle, magnetic switching at the level of a single Bohr magneton can be read out in a single shot on timescales as short as 10??s. This force sensor should enable new studies of spin dynamics in isolated single molecule magnets, free from the crystalline or ensemble settings typically studied.

Willick, Kyle [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Haapamaki, Chris [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Baugh, Jonathan, E-mail: baugh@iqc.ca [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2014-03-21

275

The Role of Cardiovascular Magnetic Resonance in Pediatric Congenital Heart Disease  

PubMed Central

Cardiovascular magnetic resonance (CMR) has expanded its role in the diagnosis and management of congenital heart disease (CHD) and acquired heart disease in pediatric patients. Ongoing technological advancements in both data acquisition and data presentation have enabled CMR to be integrated into clinical practice with increasing understanding of the advantages and limitations of the technique by pediatric cardiologists and congenital heart surgeons. Importantly, the combination of exquisite 3D anatomy with physiological data enables CMR to provide a unique perspective for the management of many patients with CHD. Imaging small children with CHD is challenging, and in this article we will review the technical adjustments, imaging protocols and application of CMR in the pediatric population. PMID:21936913

2011-01-01

276

Value of magnetic resonance imaging in patients with penile induration (Peyronie's disease).  

PubMed

Magnetic resonance imaging (MRI) is a noninvasive procedure that enables exact imaging of penile anatomy. A total of 34 patients with clinical Peyronie's disease underwent palpation, ultrasound and MRI after intracavernous injection of 10 micrograms. prostaglandin E1. MRI images were obtained before and after intravenous application of gadolinium-diethylenetriaminepentaacetic acid. In 34 patients 45 plaques were palpable. Ultrasound revealed evidence of lesions in 66.6% of the cases. On MRI 36 of 45 palpable plaques (80%) were detected. Not palpable or sonographically revealed indurations could be shown in 4 cases. After intravenous application of gadolinium-diethylenetriaminepentaacetic acid 4 plaques demonstrated contrast enhancement, thus indicating local inflammatory activity. The combination of clinical examination and sonography remains the method of choice for diagnosis and observation of patients with Peyronie's disease. MRI enables exact imaging of penile structures but it does not provide a significant advantage over standard investigative procedures. PMID:7869479

Vosshenrich, R; Schroeder-Printzen, I; Weidner, W; Fischer, U; Funke, M; Ringert, R H

1995-04-01

277

Partial volume effect modeling for segmentation and tissue classification of brain magnetic resonance images: A review.  

PubMed

Quantitative analysis of magnetic resonance (MR) brain images are facilitated by the development of automated segmentation algorithms. A single image voxel may contain of several types of tissues due to the finite spatial resolution of the imaging device. This phenomenon, termed partial volume effect (PVE), complicates the segmentation process, and, due to the complexity of human brain anatomy, the PVE is an important factor for accurate brain structure quantification. Partial volume estimation refers to a generalized segmentation task where the amount of each tissue type within each voxel is solved. This review aims to provide a systematic, tutorial-like overview and categorization of methods for partial volume estimation in brain MRI. The review concentrates on the statistically based approaches for partial volume estimation and also explains differences to other, similar image segmentation approaches. PMID:25431640

Tohka, Jussi

2014-11-28

278

Advancing magnetic resonance imaging in Crohn's disease.  

PubMed

Crohn's disease (CD) is a lifelong chronic inflammatory bowel disease associated with diarrhea, abdominal pain, bloody stool and often perianal fistulae. Inflammation in CD involves the entire gastrointestinal tract, especially including the small and large bowels, causing irreversible bowel damage. Frequent imaging examinations are necessary to monitor disease activity and to evaluate response to therapeutic interventions, and, furthermore, to predict recurrence in order to provide appropriate treatment. The suitable imaging modality should be reproducible, well tolerated, safe and free of ionizing radiation. In recent years, imaging used in CD has dramatically changed. Cross-sectional imaging techniques such as computed tomography and magnetic resonance imaging (MRI) are used to investigate not only extraluminal abnormalities, but also intraluminal changes. Recently, new techniques such as MR enteroclysis, enterography, colonography and enterocolonography have been developed. These recent advances enable the use of MRI to assess bowel disorders with high sensitivity, specificity and accuracy. MRI can evaluate simultaneously the bowel surface, bowel wall, abdominal abscesses and perianal lesions, such as perianal fistulae and perianal abscesses, without the problem of overlapping bowel loops. Therefore, MRI has the potential for evaluation of the overall disease activity of CD without radiation exposure. We believe that MRI is a suitable first choice imaging modality in the assessment of CD. PMID:24458109

Fujii, Toshimitsu; Naganuma, Makoto; Kitazume, Yoshio; Saito, Eiko; Nagahori, Masakazu; Ohtsuka, Kazuo; Watanabe, Mamoru

2014-01-01

279

Fast noniterative registration of magnetic resonance images  

NASA Astrophysics Data System (ADS)

EvIdent (EVent IDENTification) is an exploratory data analysis system for the detection and investigation of novelty, identified for a region of interest and its characteristics, within a set of images. For functional magnetic resonance imaging, for instance, a characteristic of the region of interest is a time course, which represents the intensity value of voxels over several discrete instances in time. An essential preprocessing step is the rapid registration of these images prior to analysis. Two dimensional image registration coefficients are obtained within EvIdent by solving a regression problem based on integration of a linearized matching equation over a set of patches in the image space. The registration method is robust to noise, offers a flexible hierarchical procedure, is easily generalizable to 3D registration, and is well suited to parallel processing. EvIdent, written in Java and C++, offers a sophisticated data model, an extensible algorithm framework, and a suite of graphical user interface constructs. We describe the registration algorithm and its implementation within the EvIdent software.

Pizzi, Nicolino J.; Alexander, Murray; Vivanco, Rodrigo A.; Somorjai, Raymond L.

2001-07-01

280

Hybrid sparse regularization for magnetic resonance spectroscopy.  

PubMed

Magnetic resonance spectroscopy imaging (MRSI) is a powerful non-invasive tool for characterising markers of biological processes. This technique extends conventional MRI by providing an additional dimension of spectral information describing the abnormal presence or concentration of metabolites of interest. Unfortunately, in vivo MRSI suffers from poor signal-to-noise ratio limiting its clinical use for treatment purposes. This is due to the combination of a weak MR signal and low metabolite concentrations, in addition to the acquisition noise. We propose a new method that handles this challenge by efficiently denoising MRSI signals without constraining the spectral or spatial profiles. The proposed denoising approach is based on wavelet transforms and exploits the sparsity of the MRSI signals both in the spatial and frequency domains. A fast proximal optimization algorithm is then used to recover the optimal solution. Experiments on synthetic and real MRSI data showed that the proposed scheme achieves superior noise suppression (SNR increase up to 60%). In addition, this method is computationally efficient and preserves data features better than existing methods. PMID:24111297

Laruelo, Andrea; Chaari, Lotfi; Batatia, Hadj; Ken, Soleakhena; Rowland, Ben; Laprie, Anne; Tourneret, Jean-Yves

2013-01-01

281

Prenatal Imaging: Ultrasonography and Magnetic Resonance Imaging  

PubMed Central

The Eunice Kennedy Shriver National Institute of Child Health and Human Development held a workshop on September 18–19, 2006, to summarize the available evidence on the role and performance of current fetal imaging technology and to establish a research agenda. Ultrasonography is the imaging modality of choice for pregnancy evaluation due to its relatively low cost, real-time capability, safety, and operator comfort and experience. First-trimester ultrasonography extends the available window for fetal observation and raises the possibility of performing an early anatomic survey. Three-dimensional ultrasonography has the potential to expand the clinical application of ultrasonography by permitting local acquisition of volumes and remote review and interpretation at specialized centers. New advances allow performance of fetal magnetic resonance imaging (MRI) without maternal or fetal sedation, with improved characterization and prediction of prognosis of certain fetal central nervous system anomalies such as ventriculomegaly when compared with ultrasonography. Fewer data exist on the usefulness of fetal MRI for non–central nervous system anomalies. PMID:18591320

Reddy, Uma M.; Filly, Roy A.; Copel, Joshua A.

2009-01-01

282

Magnetic resonance enterography: state of the art.  

PubMed

: Crohn's disease is a chronic inflammatory bowel disease of the gastrointestinal tract manifested by frequent periods of relapses and remissions of symptoms. The small bowel is most frequently affected. Progression of transmural inflammation can lead to stricturing or penetrating complications. At the time of diagnosis, approximately 10% of patients have disease beyond the reach of the colonoscope. Imaging can aid in clinical evaluation by depicting small bowel involvement and extraenteric disease. Magnetic resonance enterography (MRE) has emerged as a valuable tool and is being used with increasing frequency for the diagnosis and management of Crohn's disease. This article will discuss the current state of the art in MRE. In addition to reviewing the literature reporting its utility, we will present case examples illustrating how MRE best depicts the various findings of Crohn's disease within 4 imaging categories of disease: active inflammatory, fibrostenotic, fistulizing/perforating, and reparative or regenerative. We will present additional important clinical considerations in routine use of MRE, including implications for monitoring disease activity and response to treatment, cost-effectiveness, and appropriate use in the context of the American College of Radiology Appropriateness Criteria. PMID:25222657

Stoddard, Paul B; Ghazi, Leyla J; Wong-You-Cheong, Jade; Cross, Raymond K; Vandermeer, Fauzia Q

2015-01-01

283

[Magnetic resonance imaging of cardiovascular thrombi].  

PubMed

Magnetic resonance imaging (MRI) was performed for 10 patients with cardiovascular thrombi using a 0.1-Tesla resistive type apparatus (ASAHI MARK-J). In all cases thrombi were clearly imaged by NMR and their shapes closely resembled those imaged by X-ray CT. Mural thrombi located within left ventricular aneurysms of two patients with old anteroseptal myocardial infarction were semilunar in form. A mural thrombus in the right ventricle of a patient with cardiovascular Behcet's disease was also clearly imaged. Mural thrombi within the enlarged left atrium of two patients with mitral valve stenosis and insufficiency were clearly demonstrated in both cross- and longitudinal sections. In three patients with thoracic aortic aneurysm, mural thrombi were recognized within the local dilatations of the aorta. In two patients with dissecting aortic aneurysm, mural thrombi were visualized within false lumen using MRI. Mean T1 values and standard deviations for the left ventricular cavity, the left ventricular wall, and the thrombi were 639 +/- 49, 349 +/- 17 and 316 +/- 84 msec, respectively. Mean T1 values of the thrombi were usually shorter than those of the left ventricular wall. Some supposedly fresh thrombi had longer T1 values, however. PMID:3837061

Imai, H; Sakakibara, M; Yoshida, K; Watanabe, S; Masuda, Y; Inagaki, Y; Ikehira, H; Fukuda, N; Tateno, Y

1985-09-01

284

Vibration safety limits for magnetic resonance elastography  

PubMed Central

Magnetic resonance elastography (MRE) has been demonstrated to have potential as a clinical tool for assessing the stiffness of tissue in vivo. An essential step in MRE is the generation of acoustic mechanical waves within tissue via a coupled mechanical driver. Motivated by an increasing volume of human imaging trials using MRE, the objectives of this study were to audit the vibration amplitude of exposure for our IRB-approved human MRE studies, to compare these values to a conservative regulatory standard for vibrational exposure, and to evaluate the applicability and implications of this standard for MRE. MRE displacement data were examined from 29 MRE exams, including the liver, brain, kidney, breast, and skeletal muscle. Vibrational acceleration limits from a European Union directive limiting occupational exposure to whole-body and extremity vibrations (EU 2002/44/EC) were adjusted for time and frequency of exposure, converted to maximum displacement values, and compared to the measured in vivo displacements. The results indicate that the vibrational amplitudes used in MRE studies are below the EU whole-body vibration limit and the EU guidelines represent a useful standard that could be readily accepted by Institutional Review Boards to define standards for vibrational exposures for MRE studies in humans. PMID:18263949

Ehman, E C; Rossman, P J; Kruse, S A; Sahakian, A V; Glaser, K J

2010-01-01

285

Magnetic resonance imaging of the skin.  

PubMed

A thorough examination of the skin is essential to screen various diseases accurately, evaluate the effectiveness of topically applied drugs and assess the results of dermatological surgeries such as skin grafts. The assessment of skin properties is also crucial in the cosmetics industry, where it is important to evaluate the effects skin care products have on these properties. The simplest and most widely used method of skin evaluation, the 'naked eye' assessment, enables researchers to assess only the skin surface and involves a large amount of inter-observer variability. Thanks to a great progress that has been made in physics, electronics and computer engineering in recent years, sophisticated imaging methods are increasingly available in day-to-day studies. The aim of this review was to present one of these techniques, namely the magnetic resonance imaging (MRI), and to discuss its possible use in skin examination and analysis. We present basic principles of MRI, as well as several interesting applications in the field of dermatology, and discuss the advantages and limitations of this method. PMID:20180890

Stefanowska, J; Zakowiecki, D; Cal, K

2010-08-01

286

Multifrequency inversion in magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

Time-harmonic shear wave elastography is capable of measuring viscoelastic parameters in living tissue. However, finite tissue boundaries and waveguide effects give rise to wave interferences which are not accounted for by standard elasticity reconstruction methods. Furthermore, the viscoelasticity of tissue causes dispersion of the complex shear modulus, rendering the recovered moduli frequency dependent. Therefore, we here propose the use of multifrequency wave data from magnetic resonance elastography (MRE) for solving the inverse problem of viscoelasticity reconstruction by an algebraic least-squares solution based on the springpot model. Advantages of the method are twofold: (i) amplitude nulls appearing in single-frequency standing wave patterns are mitigated and (ii) the dispersion of storage and loss modulus with drive frequency is taken into account by the inversion procedure, thereby avoiding subsequent model fitting. As a result, multifrequency inversion produces fewer artifacts in the viscoelastic parameter map than standard single-frequency parameter recovery and may thus support image-based viscoelasticity measurement. The feasibility of the method is demonstrated by simulated wave data and MRE experiments on a phantom and in vivo human brain. Implemented as a clinical method, multifrequency inversion may improve the diagnostic value of time-harmonic MRE in a large variety of applications.

Papazoglou, Sebastian; Hirsch, Sebastian; Braun, Jürgen; Sack, Ingolf

2012-04-01

287

Magnetic resonance imaging: present and future applications  

PubMed Central

Magnetic resonance (MR) imaging has created considerable excitement in the medical community, largely because of its great potential to diagnose and characterize many different disease processes. However, it is becoming increasingly evident that, because MR imaging is similar to computed tomography (CT) scanning in identifying structural disorders and because it is more costly and difficult to use, this highly useful technique must be judged against CT before it can become an accepted investigative tool. At present MR imaging has demonstrated diagnostic superiority over CT in a limited number of important, mostly neurologic, disorders and is complementary to CT in the diagnosis of certain other disorders. For most of the remaining organ systems its usefulness is not clear, but the lack of ionizing radiation and MR's ability to produce images in any tomographic plane may eventually prove to be advantageous. The potential of MR imaging to display in-vivo spectra, multinuclear images and blood-flow data makes it an exciting investigative technique. At present, however, MR imaging units should be installed only in medical centres equipped with the clinical and basic research facilities that are essential to evaluate the ultimate role of this technique in the care of patients. ImagesFig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11Fig. 12Fig. 13Fig. 14 PMID:3884120

Johnston, Donald L.; Liu, Peter; Wismer, Gary L.; Rosen, Bruce R.; Stark, David D.; New, Paul F.J.; Okada, Robert D.; Brady, Thomas J.

1985-01-01

288

Monitoring tissue engineering using magnetic resonance imaging.  

PubMed

Assessment of tissue regeneration is essential to optimize the stages of tissue engineering (cell proliferation, tissue development and implantation). Optical and X-ray imaging have been used in tissue engineering to provide useful information, but each has limitations: for example, poor depth penetration and radiation damage. Magnetic resonance imaging (MRI) largely overcomes these restrictions, exhibits high resolution (approximately 100 microm) and can be applied both in vitro and in vivo. Recently, MRI has been used in tissue engineering to generate spatial maps of tissue relaxation times (T(1), T(2)), water diffusion coefficients, and the stiffness (shear moduli) of developing engineered tissues. In addition, through the use of paramagnetic and superparamagnetic contrast agents, MRI can quantify cell death, assess inflammation, and visualize cell trafficking and gene expression. After tissue implantation MRI can be used to observe the integration of a tissue implant with the surrounding tissues, and to check for early signs of immune rejection. In this review, we describe and evaluate the growing role of MRI in the assessment of tissue engineered constructs. First, we briefly describe the underlying principles of MRI and the expected changes in relaxation times (T(1), T(2)) and the water diffusion coefficient that are the basis for MR contrast in developing tissues. Next, we describe how MRI can be applied to evaluate the tissue engineering of mesenchymal tissues (bone, cartilage, and fat). Finally, we outline how MRI can be used to monitor tissue structure, composition, and function to improve the entire tissue engineering process. PMID:19134545

Xu, Huihui; Othman, Shadi F; Magin, Richard L

2008-12-01

289

Autologous breast reconstruction: preoperative magnetic resonance angiography for perforator flap vessel mapping.  

PubMed

Background?Selection of a vascular pedicle for autologous breast reconstruction is time consuming and depends on visual evaluation during the surgery. Preoperative imaging of donor site for mapping the perforator artery anatomy greatly improves the efficiency of perforator selection and significantly reduces the operative time. In this article, we present our experience with magnetic resonance angiography (MRA) for perforator vessel mapping including MRA technique and interpretation. Methods?We have performed over 400 MRA examinations from August 2008 to August 2013 at our institution for preoperative imaging of donor site for mapping the perforator vessel anatomy. Using our optimized imaging protocol with blood pool magnetic resonance imaging contrast agents, multiple donor sites can be imaged in a single MRA examination. Following imaging using the postprocessing and reporting tool, we estimated incidence of commonly used perforators for autologous breast reconstruction. Results?In our practice, anterior abdominal wall tissue is the most commonly used donor site for perforator flap breast reconstruction and deep inferior epigastric artery perforators are the most commonly used vascular pedicle. A thigh flap, based on the profunda femoral artery perforator has become the second most used flap at our institution. In addition, MRA imaging also showed evidence of metastatic disease in 4% of our patient subset. Conclusion?Our MRA technique allows the surgeons to confidently assess multiple donor sites for the best perforator and flap design. In conclusion, a well-performed MRA with specific postprocessing provides an accurate method for mapping perforator vessel, at the same time avoiding ionizing radiation. PMID:24875438

Agrawal, Mukta D; Thimmappa, Nanda Deepa; Vasile, Julie V; Levine, Joshua L; Allen, Robert J; Greenspun, David T; Ahn, Christina Y; Chen, Constance M; Hedgire, Sandeep S; Prince, Martin R

2015-01-01

290

Linear electro-optic effect for nuclear magnetic resonance coil  

NASA Astrophysics Data System (ADS)

An electrooptic transduction is here used to perform a low invasive characterization of the magnetic field in the context of magnetic resonance imaging. A resonant coil is coupled to a passive electrooptic crystal and the electromotive force of the magnetic field sensor is converted into a polarization state modulation of a laser probe beam. The optical conversion is demonstrated and lead to a fiber remote measurement of the magnetic field. The setup sensitivity and dynamics are finally dramatically enhanced using a LiNbO3 integrated waveguide. The minimum detectable field is as low as 60 fT.Hz-1/2 and the dynamics exceeds 100 dB.

Ayde, R.; Gaborit, Gwenaël.; Dahdah, Jean; Duvillaret, Lionel; Sablong, Raphaël.; Perrier, Anne-Laure; Beuf, Olivier

2014-05-01

291

Stress reconfigurable tunable magnetoelectric resonators as magnetic sensors  

NASA Astrophysics Data System (ADS)

We report a magnetoelastic effect in doubly clamped ferromagnetic magnetostrictive Metglas resonators with electrically and magnetically reconfigurable frequency response. The field-induced resonance frequency shift is due to magnetostrictive strain, which is shown to have a strong dependence on uniaxial stress. Here, we demonstrate that this magnetic field induced behavior can be used as the basis for a simple, tunable, magnetoelectric magnetic field sensor. The effect of tension on the field dependent magnetostrictive constant and the sensor sensitivity is examined, and the equivalent magnetic noise floor of such a sensor is estimated.

Kiser, Jillian; Finkel, Peter; Gao, Junqi; Dolabdjian, Christophe; Li, Jiefang; Viehland, D.

2013-01-01

292

Design algorithms for parallel transmission in magnetic resonance imaging  

E-print Network

The focus of this dissertation is on the algorithm design, implementation, and validation of parallel transmission technology in Magnetic Resonance Imaging (MRI). Novel algorithms are proposed which yield excellent excitation ...

Setsompop, Kawin

2008-01-01

293

Detection of brain metabolites in magnetic resonance spectroscopy  

E-print Network

While magnetic resonance imaging (MRI) derives its signal from protons in water, additional and potentially important biochemical compounds are detectable in vivo within the proton spectrum. The detection and mapping of ...

Kok, Trina

2009-01-01

294

Monitoring Locally Induced Hyperthermia with Magnetic Resonance Imaging.  

E-print Network

??abstract__Abstract__ Magnetic resonance thermometry is a relatively new and unique technology for non-invasive monitoring of (local) therapeutic temperature changes that is not yet in common… (more)

M.W. Vogel (M.)

2005-01-01

295

Acoustic ringing effects in pulsed nuclear magnetic resonance probes  

Microsoft Academic Search

The troublesome spurious ringing phenomenon found in pulsed nuclear magnetic resonance probes is explained in terms of the electromagnetic generation and detection of ultrasonic waves. A few techniques for eliminating this problem are discussed.

M. L. Buess; G. L. Petersen

1978-01-01

296

Acoustic ringing effects in pulsed nuclear magnetic resonance probes.  

PubMed

The troublesome spurious ringing phenomenon found in pulsed nuclear magnetic resonance probes is explained in terms of the electromagnetic generation and detection of ultrasonic waves. A few techniques for eliminating this problem are discussed. PMID:18699271

Buess, M L; Petersen, G L

1978-08-01

297

Target-specific contrast agents for magnetic resonance microscopy  

E-print Network

High-resolution ex vivo magnetic resonance microscopy (MRM) can be used to delineate prominent architectonic features in the human brain, but increased contrast is required to visualize more subtle distinctions. The goal ...

Hepler Blackwell, Megan Leticia

2007-01-01

298

Designing and characterizing hyperpolarizable silicon nanoparticles for magnetic resonance imaging  

E-print Network

Magnetic Resonance Imaging (MRI) is one of the most powerful noninvasive tools for diagnosing human disease, but its utility is limited because current contrast agents are ineffective when imaging air-tissue interfaces, ...

Anahtar, Melis Nuray

2008-01-01

299

LASER-POLARIZED 129Xe MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING;  

E-print Network

LASER-POLARIZED 129Xe MAGNETIC RESONANCE SPECTROSCOPY AND IMAGING; THE DEVELOPMENT OF A METHOD.....................................................................13 2.2 Spin Exchange Polarization of 129 Xe......................................................................................19 3 129 Xe polarization and delivery system

Rosen, Matthew S

300

Improvements in magnetic resonance imaging excitation pulse design  

E-print Network

This thesis focuses on the design of magnetic resonance imaging (MRI) radio-frequency (RF) excitation pulses, and its primary contributions are made through connections with the novel multiple-system single-output (MSSO) ...

Zelinski, Adam Charles

2008-01-01

301

Magnetic Resonance Imaging Method For Estimating Cone Of Uncertainty  

Cancer.gov

The National Institute of Child Health and Human Development (NICHD), Section on Tissue Biophysics and Biomimetics, is seeking statements of capability or interest from parties interested in collaborative research to further develop, evaluate, or commercialize magnetic resonance imaging techniques.

302

Profile of compressive myelopathy as evaluated by magnetic resonance imaging.  

PubMed

To evaluate spectrum of diseases causing compressive myelopathy and accuracy of magnetic resonance imaging in diagnosing these conditions, a total of 69 clinically diagnosed cases of compressive myelopathy were evaluated by magnetic resonance imaging and results were tabulated. Caries spine was the commonest condition (24.6%) followed by metastasis spine (17.4%), ossified posterior longitudinal ligament (7.8%), primary bone tumours, nerve sheath tumours, intramedullary tumours and rare conditions like epidural abscess, spontaneous epidural haematoma, subdural haematoma, epidural lipomatosis, etc. Sensitivity, specificity and accuracy for diagnosing caries by magnetic resonance imaging was found to be 94%, 98% and 97% while that of metastasis spine was 91%, 98% and 97% respectively. Magnetic resonance imaging is the modality of choice for diagnosing compressive myelopathy. PMID:18705249

Yadav, Rohtas K; Agarwal, Shalini; Saini, Jitender

2008-02-01

303

Imaging agents for in vivo magnetic resonance and scintigraphic imaging  

DOEpatents

Methods are provided for in vivo magnetic resonance imaging and/or scintigraphic imaging of a subject using chelated transition metal and lanthanide metal complexes. Novel ligands for these complexes are provided.

Engelstad, Barry L. (Orinda, CA); Raymond, Kenneth N. (Berkeley, CA); Huberty, John P. (Corte Madera, CA); White, David L. (Oakland, CA)

1991-01-01

304

Fast magnetic resonance spectroscopic imaging using RF coil arrays  

E-print Network

Conventional Magnetic Resonance Spectroscopic Imaging (MRSI) suffers from both low signal-to-noise (SNR), as well as long acquisition times. The development of high-fidelity gradient coils has opened opportunities for fast ...

Gagoski, Borjan Aleksandar

2006-01-01

305

Model-based reconstruction of magnetic resonance spectroscopic imaging  

E-print Network

Magnetic resonance imaging (MRI) is a medical imaging technique that is used to obtain images of soft tissue throughout the body. Since its development in the 1970s, MRI has gained tremendous importance in clinical practice ...

Chatnuntawech, Itthi

2013-01-01

306

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2012 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2012-04-01

307

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2014-04-01

308

Imaging agents for in vivo magnetic resonance and scintigraphic imaging  

DOEpatents

Methods are provided for in vivo magnetic resonance imaging and/or scintigraphic imaging of a subject using chelated transition metal and lanthanide metal complexes. Novel ligands for these complexes are provided. No Drawings

Engelstad, B.L.; Raymond, K.N.; Huberty, J.P.; White, D.L.

1991-04-23

309

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2011 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2011-04-01

310

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2013 CFR

... Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification....

2013-04-01

311

Magnetic resonance imaging contrast agents for chemical sensing  

E-print Network

Magnetic resonance imaging (MRI) is frequently used for examining the human body. MRI contrast agents currently used in the clinic assist physicians in locating problematic areas, but other tools are needed to interrogate ...

Liu, Vincent Hok

2014-01-01

312

Assessment of coronary artery stenosis by magnetic resonance imaging.  

PubMed Central

OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient echo imaging technique incorporating fat suppression was used in 39 patients (55 coronary stenoses) with known coronary artery disease. RESULTS: Overall, 47 stenoses (85%) were assessed by magnetic resonance (29 of 33 stenoses in the left anterior descending artery, one of one in the left main stem, 14 of 17 in the right coronary artery, and three of four in the left circumflex artery were detected). There was close agreement between magnetic resonance and x-ray angiography for the distance of the stenosis from the arterial origin (magnetic resonance mean (SD) 27 (16) mm versus x-ray angiography 27 (16) mm, P = NS, mean difference -0.2 mm). The distance to 39 stenoses (83%) agreed to within 5 mm, with increased scatter for more distal stenoses. The severity of magnetic resonance signal loss, assessed visually at the site of stenosis, varied significantly according to the percentage diameter stenosis (F = 30, P < 0.0001); stenosis severity with severe signal loss was 89 (7)%, with partial signal was 70 (16)%, and with irregular wall only 37 (11)%, with significant differences among the three groups (P < 0.001). A significant correlation was found between the proportional magnetic resonance signal loss at the stenosis and the percentage diameter stenosis severity (r = -0.67, P < 0.0001). The length of stenosis measured by magnetic resonance (6 (3) mm) was greater than by x-ray angiography (5 (2) mm, P < 0.006, mean difference +1.1 mm). Spearman's rank test showed that there was significant overestimation of stenosis length by magnetic resonance as stenosis severity increased (rs = 0.34, P < 0.02). CONCLUSIONS: Accurate localisation of coronary stenosis and a qualitative assessment of stenosis severity are possible by magnetic resonance, but stenosis length is overestimated as severity increases, probably because of disturbed patterns of flow with turbulence distal to severe stenoses. Reasonable results for the detection of coronary artery stenosis by magnetic resonance were achieved in this highly selected population, but further progress in imaging techniques is necessary before moving towards appreciable clinical application. Images PMID:8673749

Pennell, D. J.; Bogren, H. G.; Keegan, J.; Firmin, D. N.; Underwood, S. R.

1996-01-01

313

Functional magnetic resonance imaging at 0.2 Tesla  

Microsoft Academic Search

Functional magnetic resonance imaging of healthy human volunteers was carried out at 0.2 T, using proton-density weighted (TE = 24 ms) spin-echo imaging, in order to eliminate any contribution from the blood oxygenation-level dependent (BOLD) effect. The purpose of the study was to verify the existence of a proton-density change contribution to spin-echo functional magnetic resonance imaging (fMRI) data. Results

P. W Stroman; K. L Malisza; M Onu

2003-01-01

314

A dataset comprising 141 magnetic resonance imaging scans of 98 extant sea urchin species  

PubMed Central

Background Apart from its application in human diagnostics, magnetic resonance imaging (MRI) can also be used to study the internal anatomy of zoological specimens. As a non-invasive imaging technique, MRI has several advantages, such as rapid data acquisition, output of true three-dimensional imagery, and provision of digital data right from the onset of a study. Of particular importance for comparative zoological studies is the capacity of MRI to conduct high-throughput analyses of multiple specimens. In this study, MRI was applied to systematically document the internal anatomy of 98 representative species of sea urchins (Echinodermata: Echinoidea). Findings The dataset includes raw and derived image data from 141 MRI scans. Most of the whole sea urchin specimens analyzed were obtained from museum collections. The attained scan resolutions permit differentiation of various internal organs, including the digestive tract, reproductive system, coelomic compartments, and lantern musculature. All data deposited in the GigaDB repository can be accessed using open source software. Potential uses of the dataset include interactive exploration of sea urchin anatomy, morphometric and volumetric analyses of internal organs observed in their natural context, as well as correlation of hard and soft tissue structures. Conclusions The dataset covers a broad taxonomical and morphological spectrum of the Echinoidea, focusing on ‘regular’ sea urchin taxa. The deposited files significantly expand the amount of morphological data on echinoids that are electronically available. The approach chosen here can be extended to various other vertebrate and invertebrate taxa. We argue that publicly available digital anatomical and morphological data gathered during experiments involving non-invasive imaging techniques constitute one of the prerequisites for future large-scale genotype—phenotype correlations. PMID:25356198

2014-01-01

315

Ferromagnetic resonance of a magnetic dimer with dipolar coupling  

NASA Astrophysics Data System (ADS)

We develop a general formalism for analyzing the ferromagnetic resonance characteristics of a magnetic dimer consisting of two magnetic elements (in a horizontal or vertical configuration) coupled by dipolar interaction, taking account of their finite-size and aspect ratio. We study the effect on the resonance frequency and resonance field of the applied magnetic field (in amplitude and direction), the inter-element coupling, and the (uniaxial) anisotropy in various configurations. We obtain analytical expressions for the resonance frequency in various regimes of the interlayer coupling. We (numerically) investigate the behavior of the resonance field in the corresponding regimes. The critical value of the applied magnetic field at which the resonance frequency vanishes may be an increasing or a decreasing function of the dimer's coupling, depending on the anisotropy configuration. It is also a function of the nanomagnets aspect ratio in the case of in-plane anisotropy. This and several other results of this work, when compared with experiments using the standard ferromagnetic resonance with fixed frequency, or the network analyzer with varying frequency and applied magnetic field, provide a useful means for characterizing the effective anisotropy and coupling within systems of stacked or assembled nanomagnets. Comparing with the experimental data for the frequency splitting of coupled FeV nano disks, we find that our theory provides the same order of magnitude for the dipolar coupling.

Franco, A. F.; Déjardin, J. L.; Kachkachi, H.

2014-12-01

316

Magnetic Resonance Force Microscopy Measurement of Entangled Spin States  

E-print Network

We simulate magnetic resonance force microscopy measurements of an entangled spin state. One of the entangled spins drives the resonant cantilever vibrations, while the other remote spin does not interact directly with the quasiclassical cantilever. The Schr\\"odinger cat state of the cantilever reveals two possible outcomes of the measurement for both entangled spins.

G. P. Berman; F. Borgonovi; G. Chapline; P. C. Hammel; V. I. Tsifrinovich

2001-10-10

317

Design guideline for magnetic integration in LLC resonant converters  

Microsoft Academic Search

The aim of this paper is to present a comprehensive design methodology for the magnetic integration of the series and shunt inductances of the resonant tank in an LLC resonant converter within the transformer. The design procedure applies to symmetrical core-bobbin structures with two separate slots for the primary and secondary windings. A specific leakage inductance Asigma. (per square turn)

S. De Simone; C. Adragna; C. Spini

2008-01-01

318

Spin wave resonance detection using magnetic tunnel junction structure  

Microsoft Academic Search

We have demonstrated that spin wave resonance in a permalloy microstrip can be detected by an electrical method based on magnetic tunnel junction structures. The detection method promises high spatial resolution and sensitivity. Both even and odd spin wave resonance modes can be clearly observed in a permalloy microstrip. The spin wave induced voltage is proportional to the input microwave

Chong Bi; Xin Fan; Liqing Pan; Xiaoming Kou; Jun Wu; Qinghui Yang; Huaiwu Zhang; John Q. Xiao

2011-01-01

319

Characterization of microwave magnetic narrow band filters by ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

Ferromagnetic resonance cavity and microstrip excitation experiments have been performed on a straight edge yttrium iron garnet resonator. Both excitation systems have been modeled as band-stop configurations and a mapping from the swept bias magnetic field domain to the frequency domain has been elaborated to compare them in terms of the dispersion and the amplitude of the magnetostatic wave modes.

Bousbahi, Khaled; Marcelli, Romolo

2000-05-01

320

Simultaneous Measurement of Magnetic Resonance and Neuronal Signals  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at ultra low magnetic fields (ULF, ˜ microT) have advantages over their counterparts at higher magnetic fields, despite the reduction in signal strength. Among these advantages are that the instrumentation uses superconducting quantum interference devices (SQUIDs), and is now compatible with simultaneous measurements of biomagnetic signals, such as magnetoencephalography (MEG). This presents a new opportunity for noninvasive simultaneous functional and anatomical brain imaging. We present here the physical basis and experimental evidence for a variety of ULF-MRI techniques being developed at Los Alamos to enable simultaneous anatomical and functional imaging of the human brain. We conclude by presenting a novel technique, based on the resonant interaction between the magnetic fields such as those that arise from neural activity and the spin population in ULF-MRI experiments, that may enable direct tomographic imaging of the consequences of neural activity.

Espy, Michelle

2007-03-01

321

Chapter 1 Magnetic Resonance Contributions to Other Sciences  

NASA Astrophysics Data System (ADS)

In 1947, I.I. Rabi invented the molecular beam magnetic resonance method for the important, but limited purpose, of measuring nuclear magnetic moments and five of us working in his laboratory immediately began such experiments. The first experiments with LiCl gave the expected single resonance for each nucleus, but we were surprised to discover six resonances for the proton in H2, which we soon showed was due to the magnetic effects of the other proton and the rotating charged molecule: from these measurements we could also obtain new information on molecular structure. We had another shock when we studied D2 and found the resonance curves were spread more widely for D2 than H2 even though the magnetic interactions should have been much smaller. We found we could explain this by assuming that the deuteron had an electric quadrupole moment and J. Schwinger pointed out that this would require the existence of a previously unsuspected electric tensor force between the neutron and the proton. With this, the resonance method was giving new fundamental information about nuclear forces. In 1944, Rabi and I pointed out that it should be possible by the Dirac theory and our past resonance experiments to calculate exactly the hyperfine interaction between the electron and the proton in the hydrogen atom and we had two graduate students, Nafe and Nelson do the experiment and they found a disagreement which led J. Schwinger to develop the first successful relativistic quantum field theory and QED. In 1964, Purcell, Bloch and others detected magnetic resonance transitions by the effect of the transition on the oscillator, called NMR, making possible measurements on liquids, solids and gases and giving information on chemical shifts and thermal relaxation times T1 and T2. I developed a magnetic resonance method for setting a limit to the EDM of a neutron in a beam and with others for neutrons stored in a suitably coated bottle. Magnetic resonance measurements provide high stability atomic clocks. Both the second and the meter are now defined in terms of atomic clocks. Lauterbuhr, Mansfield, Damadian and others developed the important methods of using inhomogeneous magnetic fields to localize the magnetic resonance in a tissue sample producing beautiful and valuable magnetic resonance images, MRI's, and fMRI's.

Ramsey, Norman F.

322

Fetal magnetic resonance imaging in obstetric practice  

PubMed Central

Ultrasonography (USG) is the primary imaging method for prenatal diagnosis of fetal abnormalities since its discovery. Although it is the primary method of fetal imaging, it cannot provide sufficient information about the fetus in some conditions such as maternal obesity, oligohydramnios and engagement of the fetal head. At this stage, magnetic resonance imaging (MRI) facilitates examination by providing more specific information. The need and importance of fetal MRI applications further increased by the intrauterine surgery which is currently gaining popularity. Some advantages of fetal MRI over USG are the good texture of contrast, a greater study area and visualization of the lesion and neighbourhood relations, independence of the operators. Also it is not affected by maternal obesity and severe oligohydramnios. However, MRI is inadequate in detecting fetal limb and cardiac abnormalities when compared to USG. MRI is not used routinely in pregnancy. It is used in situations where nonionizing imaging methods are inadequate or ionizing radiation is required in pregnant women. It is not recommended during the first trimester. Contrast agent (Godalinium) is not used during pregnancy. It is believed that MRI is not harmful to the fetus, although the biological risk of MRI application is not known. MRI technique is superior to USG in the detection of corpus callosum dysgenesis, third-trimester evaluation of posterior fossa malformations, bilateral renal agenesis, diaphragmatic hernia and assessment of lung maturation. Especially, it is the method of choice for evaluation of central nervous system (CNS) abnormalities. Fetal MRI has a complementary role with USG. It provides important information for prenatal diagnosis, increases diagnostic accuracy, and in turn affects the prenatal treatment, prenatal interventions and birth plan. PMID:24591956

Kö?ü?, Ayd?n; Kö?ü?, Nermin; Usluo?ullar?, Betül; Duran, Müzeyyen; Turhan, Nilgün Öztürk; Tek?am, Mehmet

2011-01-01

323

Magnetic Resonance Imaging in Postprostatectomy Radiotherapy Planning  

SciTech Connect

Purpose: To investigate whether the use of magnetic resonance imaging (MRI) in prostate bed treatment planning could influence definition of the clinical target volume (CTV) and organs at risk. Methods and Materials: A total of 21 consecutive patients referred for prostate bed radiotherapy were included in the present retrospective study. The CTV was delineated according to the European Organization for Research and Treatment of Cancer recommendations on computed tomography (CT) and T{sub 1}-weighted (T{sub 1}w) and T{sub 2}-weighted (T{sub 2}w) MRI. The CTV magnitude, agreement, and spatial differences were evaluated on the planning CT scan after registration with the MRI scans. Results: The CTV was significantly reduced on the T{sub 1}w and T{sub 2}w MRI scans (13% and 9%, respectively) compared with the CT scans. The urinary bladder was drawn smaller on the CT scans and the rectum was smaller on the MRI scans. On T{sub 1}w MRI, the rectum and urinary bladder were delineated larger than on T{sub 2}w MRI. Minimal agreement was observed between the CT and T{sub 2}w images. The main spatial differences were measured in the superior and superolateral directions in which the CTV on the MRI scans was 1.8-2.9 mm smaller. In the posterior and inferior border, no difference was seen between the CT and T{sub 1}w MRI scans. On the T{sub 2}w MRI scans, the CTV was larger in these directions (by 1.3 and 1.7 mm, respectively). Conclusions: The use of MRI in postprostatectomy radiotherapy planning resulted in a reduction of the CTV. The main differences were found in the superior part of the prostate bed. We believe T{sub 2}w MRI enables more precise definition of prostate bed CTV than conventional planning CT.

Sefrova, Jana, E-mail: sefrova@post.cz [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Odrazka, Karel [Department of Clinical and Radiation Oncology, Multiscan and Pardubice Regional Hospital, Pardubice (Czech Republic); First and Third Faculty of Medicine, Charles University in Prague, Prague (Czech Republic); Paluska, Petr [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Belobradek, Zdenek [Department of Radiology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Brodak, Milos [Department of Urology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Dolezel, Martin [Department of Clinical and Radiation Oncology, Multiscan and Pardubice Regional Hospital, Pardubice (Czech Republic); First and Third Faculty of Medicine, Charles University in Prague, Prague (Czech Republic); Prosvic, Petr [Department of Urology, Regional Hospital Nachod, Nachod (Czech Republic); Macingova, Zuzana; Vosmik, Milan [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Hoffmann, Petr [Department of Radiology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Louda, Miroslav [Department of Urology, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic); Nejedla, Anna [Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove (Czech Republic)

2012-02-01

324

Small Animal Imaging with Magnetic Resonance Microscopy  

PubMed Central

Small animal magnetic resonance microscopy (MRM) has evolved significantly from testing the boundaries of imaging physics to its expanding use today as a tool in non-invasive biomedical investigations. This review is intended to capture the state-of-the-art in MRM for scientists who may be unfamiliar with this modality, but who want to apply its capabilities to their research. We therefore include a brief review of MR concepts and methods of animal handling and support before covering a range of MRM applications including the heart, lung, brain, and the emerging field of MR histology. High-resolution anatomical imaging reveals increasingly exquisite detail in healthy animals and subtle architectural aberrations that occur in genetically altered models. Resolution of 100 µm in all dimensions is now routinely attained in living animals, and 10 µm3 is feasible in fixed specimens. Such images almost rival conventional histology while allowing the object to be viewed interactively in any plane. MRM is now increasingly used to provide functional information in living animals. Images of the beating heart, breathing lung, and functioning brain can be recorded. While clinical MRI focuses on diagnosis, MRM is used to reveal fundamental biology or to non-invasively measure subtle changes in the structure or function of organs during disease progression or in response to experimental therapies. The ability of MRM to provide a detailed functional and anatomical picture in rats and mice, and to track this picture over time, makes it a promising platform with broad applications in biomedical research. PMID:18172332

Driehuys, Bastiaan; Nouls, John; Badea, Alexandra; Bucholz, Elizabeth; Ghaghada, Ketan; Petiet, Alexandra; Hedlund, Laurence W.

2009-01-01

325

Tools for cardiovascular magnetic resonance imaging  

PubMed Central

In less than fifteen years, as a non-invasive imaging option, cardiovascular MR has grown from a being a mere curiosity to becoming a widely used clinical tool for evaluating cardiovascular disease. Cardiovascular magnetic resonance imaging (CMRI) is now routinely used to study myocardial structure, cardiac function, macro vascular blood flow, myocardial perfusion, and myocardial viability. For someone entering the field of cardiac MR, this rapid pace of development in the field of CMRI might make it difficult to identify a cohesive starting point. In this brief review, we have attempted to summarize the key cardiovascular imaging techniques that have found widespread clinical acceptance. In particular, we describe the essential cardiac and respiratory gating techniques that form the backbone of all cardiovascular imaging methods. It is followed by four sections that discuss: (I) the gradient echo techniques that are used to assess ventricular function; (II) black-blood turbo spin echo (SE) methods used for morphologic assessment of the heart; (III) phase-contrast based techniques for the assessment of blood flow; and (IV) CMR methods for the assessment of myocardial ischemia and viability. In each section, we briefly summarize technical considerations relevant to the clinical use of these techniques, followed by practical information for its clinical implementation. In each of those four areas, CMRI is considered either as the benchmark imaging modality against which the diagnostic performance of other imaging modalities are compared against, or provides a complementary capability to existing imaging techniques. We have deliberately avoided including cutting-edge CMR imaging techniques practiced at few academic centers, and restricted our discussion to methods that are widely used and are likely to be available in a clinical setting. Our hope is that this review would propel an interested reader toward more comprehensive reviews in the literature. PMID:24834409

Krishnamurthy, Ramkumar; Cheong, Benjamin

2014-01-01

326

Magnetic resonance imaging evaluation of myocardial perfusion.  

PubMed

Noninvasive qualitative/quantitative assessment of myocardial perfusion is considered to be fundamental in the management of known and suspected coronary artery disease patients, as shown by the widespread utilization of thallium-201- and technetium-99m-labeled agents in myocardial single-photon emission computed tomography (SPECT) scintigraphy for diagnostic as well as prognostic purposes. Recently, the availability of subsecond ultrafast magnetic resonance imaging (MRI) sequences (FLASH, TurboFLASH, EPI) has provided new avenues for assessing myocardial perfusion by MRI in conjunction with contrast-agent bolus administration (contrast-enhanced first-pass MRI). MRI contrast agents can be classified into relaxation agents (T1 "positive") and susceptibility agents (T2 star [T2*] "negative"). All the commercially available MRI contrast agents used in clinical practice are relaxation agents employing the T1 shortening effect of metal ions like gadolinium (paramagnetism), thus producing a tissue signal-intensity increase on T1-weighted images (positive enhancement). On the other hand, T2* agents induce mainly susceptibility effects, i.e., rapid dephasing of spins with resultant signal loss on T2*-sensitive sequences (negative enhancement). Unfortunately, both relaxation and susceptibility agents are, by definition, "extracellular" contrast media, as they rapidly diffuse into the interstitial space, thus hampering the simple application of indicator-dilution kinetics for myocardial perfusion assessment. Blood pool agents are therefore needed to obtain predictable relations between the concentration of contrast medium in the myocardium and the change in signal intensity. In addition, newer MRI techniques for tissue perfusion quantitation have been recently reported, based on blood-sensitive sequences, thus without intravenous contrast administration. PMID:9662231

Passariello, R; De Santis, M

1998-06-18

327

Functional magnetic resonance imaging of the lung.  

PubMed

Beyond being a substitute for X-ray, computed tomography, and scintigraphy, magnetic resonance imaging (MRI) inherently combines morphologic and functional information more than any other technology. Lung perfusion: The most established method is first-pass contrast-enhanced imaging with bolus injection of gadolinium chelates and time-resolved gradient-echo (GRE) sequences covering the whole lung (1 volume/s). Images are evaluated visually or semiquantitatively, while absolute quantification remains challenging due to the nonlinear relation of T1-shortening and contrast material concentration. Noncontrast-enhanced perfusion imaging is still experimental, either based on arterial spin labeling or Fourier decomposition. The latter is used to separate high- and low-frequency oscillations of lung signal related to the effects of pulsatile blood flow. Lung ventilation: Using contrast-enhanced first-pass perfusion, lung ventilation deficits are indirectly identified by hypoxic vasoconstriction. More direct but still experimental approaches use either inhalation of pure oxygen, an aerosolized contrast agent, or hyperpolarized noble gases. Fourier decomposition MRI based on the low-frequency lung signal oscillation allows for visualization of ventilation without any contrast agent. Respiratory mechanics: Time-resolved series with high background signal such as GRE or steady-state free precession visualize the movement of chest wall, diaphragm, mediastinum, lung tissue, tracheal wall, and tumor. The assessment of volume changes allows drawing conclusions on regional ventilation. With this arsenal of functional imaging capabilities at high spatial and temporal resolution but without radiation burden, MRI will find its role in regional functional lung analysis and will therefore overcome the sensitivity of global lung function analysis for repeated short-term treatment monitoring. PMID:24481761

Biederer, J; Heussel, C P; Puderbach, M; Wielpuetz, M O

2014-02-01

328

Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design  

SciTech Connect

Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."

Paulsen, Jeffrey L; Franck, John; Demas, Vasiliki; Bouchard, Louis-S.

2008-03-27

329

Cardiac magnetic resonance imaging in children.  

PubMed

MRI is an important additional tool in the diagnostic work-up of children with congenital heart disease. This review aims to summarise the role MRI has in this patient population. Echocardiography remains the main diagnostic tool in congenital heart disease. In specific situations, MRI is used for anatomical imaging of congenital heart disease. This includes detailed assessment of intracardiac anatomy with 2-D and 3-D sequences. MRI is particularly useful for assessment of retrosternal structures in the heart and for imaging large vessel anatomy. Functional assessment includes assessment of ventricular function using 2-D cine techniques. Of particular interest in congenital heart disease is assessment of right and single ventricular function. Two-dimensional and newer 3-D techniques to quantify flow in these patients are or will soon become an integral part of quantification of shunt size, valve function and complex flow patterns in large vessels. More advanced uses of MRI include imaging of cardiovascular function during stress and tissue characterisation of the myocardium. Techniques used for this purpose need further validation before they can become part of the daily routine of MRI assessment of congenital heart disease. PMID:25552387

Helbing, Willem A; Ouhlous, Mohamed

2015-01-01

330

Eye Anatomy  

MedlinePLUS

Eye Anatomy en Español email Send this article to a friend by filling out the fields below: Your name: ... You at Risk For Glaucoma? Childhood Glaucoma Eye Anatomy Five Common Glaucoma Tests Glaucoma Facts and Stats ...

331

Paraganglioma Anatomy  

MedlinePLUS

... Pictures Browse Search Quick Search Image Details Paraganglioma Anatomy View/Download: Small: 648x576 View Download Add to My Pictures Title: Paraganglioma Anatomy Description: Paraganglioma of the head and neck; drawing ...

332

Nasal Anatomy  

MedlinePLUS

... Devyani Lal, MD Jayakar V. Nayak, MD, PhD anatomy The nose is the organ of smell, and ... sinuses drain into the nose, and their detailed anatomy is discussed in another Patient Education section. Smell ...

333

Magnetic resonance imaging (MRI) of inflammation in stroke  

Microsoft Academic Search

Magnetic resonance imaging (MRI) of inflammation is based on the in vivo magnetic labelling of macrophages, the most abundant cells involved in the post-ischemic inflammatory response, by nanoparticles of iron oxides. Such approach has been successfully applied to study experimental rodent models of focal cerebral ischemia and has proved feasible in pioneer clinical studies. Despite current limitations, MRI of inflammation

Marlène Wiart; Nathalie Davoust; Jean-Baptiste Pialat; Yves Berthezène; Norbert Nighoghossian

2007-01-01

334

PERTURBING A SYMMETRIC RESONANCE: THE MAGNETIC SPHERICAL PENDULUM  

E-print Network

PERTURBING A SYMMETRIC RESONANCE: THE MAGNETIC SPHERICAL PENDULUM JAMES MONTALDI Institut Non, such as the spherical pendulum. Perturbing such a system by breaking the symmetry (e.g. adding a magnetic term) creates. Introduction The spherical pendulum is a 2-degree of freedom Hamiltonian system with O(2) symmetry. The stable

Montaldi, James

335

Manganese-enhanced magnetic resonance microscopy of mineralization  

Microsoft Academic Search

Paramagnetic manganese (II) can be employed as a calcium surrogate to sensitize magnetic resonance microscopy (MRM) to the processing of calcium during bone formation. At high doses, osteoblasts can take up sufficient quantities of manganese, resulting in marked changes in water proton T1, T2 and magnetization transfer ratio values compared to those for untreated cells. Accordingly, inductively coupled plasma mass

Ingrid E. Chesnick; Todor I. Todorov; Jose A. Centeno; Dale E. Newbury; John A. Small; Kimberlee Potter

2007-01-01

336

Automatic Segmentation of Adipose Tissue from Thigh Magnetic Resonance Images  

E-print Network

, such as connective, neu- ral, adipose, skeletal and muscle tissue. They pose various challenges to standard imageAutomatic Segmentation of Adipose Tissue from Thigh Magnetic Resonance Images Senthil Purushwalkam1, Manchester Metropolitan University, UK Abstract. Automatic segmentation of adipose tissue in thigh magnetic

Li, Baihua

337

Resonant Magnetic Field Sensors Based On MEMS Technology  

Microsoft Academic Search

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to

Agustín L. Herrera-May; Luz A. Aguilera-Cortés; Pedro J. García-Ramírez; Elías Manjarrez

2009-01-01

338

Spin microscope based on optically detected magnetic resonance  

Microsoft Academic Search

We propose a scanning magnetic microscope which has a photoluminescence nanoprobe implanted in the tip of an atomic force microscope, (AFM) scanning tunneling microscope (STM), or near-field scanning optical microscope, and exhibits optically detected magnetic resonance. The proposed spin microscope has nanoscale lateral resolution and the single spin sensitivity for AFM and STM.

Boris M. Chernobrod; Gennady P. Berman

2005-01-01

339

Spin Microscope Based on Optically Detected Magnetic Resonance  

E-print Network

We propose a scanning magnetic microscope which has a photoluminescence nanoprobe implanted in the tip of an AFM or STM, or NSOM, and exhibits optically detected magnetic resonance (ODMR). The proposed spin microscope has nanoscale lateral resolution and the single spin sensitivity for AFM and STM.

Chernobrod, B M; Chernobrod, Boris M.; Berman, Gennady P.

2004-01-01

340

Spin Microscope Based on Optically Detected Magnetic Resonance  

E-print Network

We propose a scanning magnetic microscope which has a photoluminescence nanoprobe implanted in the tip of an AFM or STM, or NSOM, and exhibits optically detected magnetic resonance (ODMR). The proposed spin microscope has nanoscale lateral resolution and the single spin sensitivity for AFM and STM.

Boris M. Chernobrod; Gennady P. Berman

2004-05-24

341

A model to assess SAR for surface coil magnetic resonance spectroscopy measurements.  

PubMed

Surface coils are widely used in magnetic resonance (MR) studies due to their superior signal to noise properties. Application of excessive power levels to transmit surface coils may result in local tissue damage. A homogeneous muscle tissue model for the conservative prediction of surface coil specific absorption rate (SAR) is introduced. Based on this model, sequence parameters can be limited to provide operational levels within safety guidelines. It is demonstrated that this model provides worst-case SAR estimates at MR frequencies of 25.75 MHz and 63.6 MHz. The dependence of SAR on model structure and geometry is analysed and conclusions on the relationship between SAR levels and local anatomy are drawn. By making a worst-case assumption for the tissue parameters the model provides safe operational levels for all tissue types. Power-demanding proton-decoupled 31P magnetic resonance spectroscopy experiments are possible based on the SAR estimates provided. To date SAR values are calculated for 1 g of tissue. Changes in regulations to calculate SAR values for 10 g tissue masses, and the according averaging of local SAR over a larger volume, have been proposed by the International Electrotechnical Commission. A comparative study shows that up to 100% more energy may be applied to surface coils if SAR values are determined for 10 g tissue masses rather than 1 g tissue masses. PMID:12069095

Prock, T; Collins, D J; Leach, M O

2002-05-21

342

[Laparoscopic and general surgery guided by open interventional magnetic resonance].  

PubMed

Interventional magnetic resonance (IMR) machines have produced unique opportunity for image-guided surgery. The open configuration design and fast pulse sequence allow virtual real time intraoperative scanning to monitor the progress of a procedure, with new images produced every 1.5 sec. This may give greater appreciation of anatomy, especially deep to the 2-dimensional laparoscopic image, and hence increase safety, reduce procedure magnitude and increase confidence in tumour resection surgery. The aim of this paper was to investigate the feasibility of performing IMR-image-guided general surgery, especially in neoplastic and laparoscopic field, reporting a single center -- St. Mary's Hospital (London, UK) -- experience. Procedures were carried out in a Signa 0.5 T General Elettric SP10 Interventional MR (General Electric Medical Systems, Milwaukee, WI, USA) with magnet-compatible instruments (titanium alloy instruments, plastic retractors and ultrasonic driven scalpel) and under general anesthesia. There were performed 10 excision biopsies of palpable benign breast tumors (on female patients), 3 excisions of skin sarcoma (dermatofibrosarcoma protuberans), 1 right hemicolectomy and 2 laparoscopic cholecystectomies. The breast lesions were localized with pre- and postcontrast (intravenous gadolinium DPTA) sagittal and axial fast multiplanar spoiled gradient recalled conventional Signa sequences; preoperative real time fast gradient recalled sequences were also obtained using the flashpoint tracking device. During right hemicolectomy intraoperative single shot fast spin echo (SSFSE) and fast spoiled gradient recalled (FSPGR) imaging of right colon were performed after installation of 150 cc of water or 1% gadolinium solution, respectively, through a Foley catheter; imaging was also obtained in an attempt to identify mesenteric lymph nodes intraoperatively. Concerning laparoscopic procedures, magnetic devices (insufflator, light source) were positioned outside scan room, the tubing and light head being passed through penetration panels. Intraoperative MR-cholangiography was performed using fast spin echo (SSFSE) techniques with minimal intensity projection 3-dimensional reconstruction. About skin sarcomas, 2 of them were skin recurrences of previously surgically treated sarcomas (all of them received preoperative biopsy) and the extent of the lesion was then determined using short tau inversion recovery (STIR) sequence. The skin was closed in each case without need for any plastic reconstruction. The breast lesions were visualized with both Signa and real-time imaging and all enhanced with contrast: 2 (20%) were visualized only after contrast enhancement; intraoperative real time imaging clearly demonstrated a resection margin in all cases. Maximum dimensions of breast specimens (range 8-50 mm, median 24.5 mm) were not significantly different from those measured by Signa (p>0.17, Student's paired t-test) or real time images (p>0.4): also there was no significant difference in lesion size between Signa and real time images (p>0.25). All postprocedure scans clearly demonstrated complete excision. The extent of the tumor at MR imaging was greater in each case than suggested by clinical examination. Adequate resection margins were planned using STIR sequences. Histological examination confirmed clear surgical margins of at least 1 cm in each case. During right hemicolectomy, both intraoperative SSFSE and FSPGR contrast imaging revealed the lesion and details of the colonic surface; imaging of the lymph node draining right colon was only partially successful, due to movement artifact. Concerning laparoscopic procedures, both FSE and SSFSE techniques produced reasonable images of the gallbladder and intrahepatic ducts, but the FSE imaging was of poor quality due to respiration artifact; however, SSFSE allowed visualization of the gallbladder and part of the common bile duct. About skin sarcomas, the extent of the tumor at MR imaging was greater in each case than suggested by clinical examination and in each case the com

Lauro, A; Gould, S W T; Cirocchi, R; Giustozzi, G; Darzi, A

2004-10-01

343

Net electromagnetic torque induced by multiple neighboring resonant magnetic perturbations  

NASA Astrophysics Data System (ADS)

In this work, previous calculations [1,2] of the electromagnetic torque exerted by coupled resonant magnetic perturbations on a toroidal plasma are expanded to include many resonant surfaces in close proximity. We are interested in the possibility of a simplified torque expression in the limit that the distance between resonant surfaces collapses, i.e. as in the edge region where the q-profile is steep and their singular layers might overlap. Such a case is relevant to the ELM control community when resonant magnetic perturbation (RMP) fields are applied. Present analytic estimates of the shielding or penetration of an applied RMP field are done using single surface models, while in practice multiple neighboring resonances exist. [4pt] [1] J.W. Connor, S.C. Cowley, R.J. Hastie, et al., Phys. Fluids 31, 577 (1988).[0pt] [2] R. Fitzpatrick, Phys. Plasmas 16, 032502 (2009).

Cole, A. J.; Hegna, C. C.; Callen, J. D.

2011-11-01

344

Magnetic multi-domain resonance in single crystal ferrite platelets  

NASA Astrophysics Data System (ADS)

We have observed ferromagnetic resonance (FMR) on single crystal platelets of Zn and Co substituted M-type hexagonal ferrites. FMR was observed with both swept field and swept frequency measurements. The results were compared, and agreed well, with calculations of resonance frequencies based on periodic arrays of stripes and bubble domains. In addition to the resonance parameters necessary to describe the results in the magnetically saturated regime, our calculations take into account the wall energy, which results in a field dependence of the domain spacing, which in turn strongly affects the resonances near saturating fields.

Rachford, F. J.; Lubitz, P.; Vittoria, C.

1981-03-01

345

Long-lived localization in magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

The longitudinal nuclear relaxation time, T1, sets a stringent limit on the range of information that can be obtained from magnetic resonance imaging (MRI) experiments. Long-lived nuclear spin states provide a possibility to extend the timescale over which information can be encoded in magnetic resonance. We introduce a strategy to localize an ensemble of molecules for a significantly extended duration (?30 times longer than T1 in this example), using a spatially selective conversion between magnetization and long-lived singlet order. An application to tagging and transport is proposed.

Dumez, Jean-Nicolas; Hill-Cousins, Joseph T.; Brown, Richard C. D.; Pileio, Giuseppe

2014-09-01

346

Magnetically tunable Mie resonance-based dielectric metamaterials  

NASA Astrophysics Data System (ADS)

Electromagnetic materials with tunable permeability and permittivity are highly desirable for wireless communication and radar technology. However, the tunability of electromagnetic parameters is an immense challenge for conventional materials and metamaterials. Here, we demonstrate a magnetically tunable Mie resonance-based dielectric metamaterials. The magnetically tunable property is derived from the coupling of the Mie resonance of dielectric cube and ferromagnetic precession of ferrite cuboid. Both the simulated and experimental results indicate that the effective permeability and permittivity of the metamaterial can be tuned by modifying the applied magnetic field. This mechanism offers a promising means of constructing microwave devices with large tunable ranges and considerable potential for tailoring via a metamaterial route.

Bi, Ke; Guo, Yunsheng; Liu, Xiaoming; Zhao, Qian; Xiao, Jinghua; Lei, Ming; Zhou, Ji

2014-11-01

347

Magnetic Resonance Properties of Some Lunar Material  

Microsoft Academic Search

Paramagnetic resonance spectra of Apollo 11 fines and rocks were measured at 9 and 35 gigahertz and at 4 degrees, 80 degrees, and 300 degrees K. At both frequencies the material has an intense absorption at g = 2, with a line width of ~ 950 gauss. Fe ions with strong exchange interactions produce this resonance. A comparison of the

A. Chatelain; J. L. Kolopus; D. Kline; J. G. Castle

1970-01-01

348

One-pot synthesis of magnetic nanoclusters enabling atherosclerosis-targeted magnetic resonance imaging  

PubMed Central

In this study, dextran-encrusted magnetic nanoclusters (DMNCs) were synthesized using a one-pot solution phase method for detection of atherosclerosis by magnetic resonance imaging. Pyrenyl dextran was used as a surfactant because of its electron-stabilizing effect and its amphiphilic nature, rendering the DMNCs stable and water-dispersible. The DMNCs were 65.6±4.3 nm, had a narrow size distribution, and were superparamagnetic with a high magnetization value of 60.1 emu/g. Further, they showed biocompatibility and high cellular uptake efficiency, as indicated by a strong interaction between dextran and macrophages. In vivo magnetic resonance imaging demonstrated the ability of DMNCs to act as an efficient magnetic resonance imaging contrast agent capable of targeted detection of atherosclerosis. In view of these findings, it is concluded that DMNCs can be used as magnetic resonance imaging contrast agents to detect inflammatory disease. PMID:24904209

Kukreja, Aastha; Lim, Eun-Kyung; Kang, Byunghoon; Choi, Yuna; Lee, Taeksu; Suh, Jin-Suck; Huh, Yong-Min; Haam, Seungjoo

2014-01-01

349

A Model for Quantum Jumps in Magnetic Resonance Force Microscopy  

E-print Network

We propose a simple model which describes the statistical properties of quantum jumps in a single-spin measurement using the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. Our computer simulations based on this model predict the average time interval between two consecutive quantum jumps and the correlation time to be proportional to the characteristic time of the magnetic noise and inversely proportional to the square of the magnetic noise amplitude.

G. P. Berman; F. Borgonovi; V. I. Tsifrinovich

2004-02-09

350

A Model for Quantum Jumps in Magnetic Resonance Force Microscopy  

E-print Network

We propose a simple model which describes the statistical properties of quantum jumps in a single-spin measurement using the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. Our computer simulations based on this model predict the average time interval between two consecutive quantum jumps and the correlation time to be proportional to the characteristic time of the magnetic noise and inversely proportional to the square of the magnetic noise amplitude.

Berman, G P; Tsifrinovich, V I

2004-01-01

351

Spin microscope based on optically detected magnetic resonance  

DOEpatents

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2010-06-29

352

Design of LLC resonant converter with integrated magnetic technology  

Microsoft Academic Search

Under the condition of 300-400 V input voltage and 48 V output voltages, this paper presents a thin-film integrated magnetic converter based on LLC resonant converter. In this paper, equivalent circuit of integrated magnetic components was gained and its working modes were discussed, then its design results were given. Thin-film technology was used to design integrated magnetic components. At last,

Cheng Ruijun; Yang Yugang; Jiang Ying

2005-01-01

353

Coplanar probe microwave current injection ferromagnetic resonance of magnetic nanostructures  

Microsoft Academic Search

The non-uniform standing spin-wave modes in thin magnetic films and nanostructures provide important information about their magnetic properties. Very often they are lacking in the recorded ferromagnetic resonance spectra for symmetry reasons. In this work we experimentally demonstrate that by direct injection of microwave currents into a magnetic nanostructure using a sub-millimetre sized microwave coaxial to coplanar adaptor one can

C. S. Chang; M. Kostylev; A. O. Adeyeye; M. Bailleul; S. Samarin

2011-01-01

354

Spin microscope based on optically detected magnetic resonance  

DOEpatents

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2007-12-11

355

Nuclear magnetic resonance spectroscopy with single spin sensitivity.  

PubMed

Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen-vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four (29)Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503

Müller, C; Kong, X; Cai, J-M; Melentijevi?, K; Stacey, A; Markham, M; Twitchen, D; Isoya, J; Pezzagna, S; Meijer, J; Du, J F; Plenio, M B; Naydenov, B; McGuinness, L P; Jelezko, F

2014-01-01

356

Nuclear magnetic resonance spectroscopy with single spin sensitivity  

PubMed Central

Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen–vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four 29Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503

Müller, C.; Kong, X.; Cai, J.-M.; Melentijevi?, K.; Stacey, A.; Markham, M.; Twitchen, D.; Isoya, J.; Pezzagna, S.; Meijer, J.; Du, J. F.; Plenio, M. B.; Naydenov, B.; McGuinness, L. P.; Jelezko, F.

2014-01-01

357

Magnetic Resonance Imaging of Surgical Implants Made from Weak Magnetic Materials  

NASA Astrophysics Data System (ADS)

Materials with high magnetic susceptibility cause local inhomogeneities in the main field of the magnetic resonance (MR) tomograph. These inhomogeneities lead to loss of phase coherence, and thus to a rapid loss of signal in the image. In our research we investigated inhomogeneous field of magnetic implants such as magnetic fibers, designed for inner suture during surgery. The magnetic field inhomogeneities were studied at low magnetic planar phantom, which was made from four thin strips of magnetic tape, arranged grid-wise. We optimized the properties of imaging sequences with the aim to find the best setup for magnetic fiber visualization. These fibers can be potentially exploited in surgery for internal stitches. Stitches can be visualized by the magnetic resonance imaging (MRI) method after surgery. This study shows that the imaging of magnetic implants is possible by using the low field MRI systems, without the use of complicated post processing techniques (e.g., IDEAL).

Gogola, D.; Kraf?ík, A.; Štrbák, O.; Frollo, I.

2013-08-01

358

Sensitivity of Optically Enhanced Magnetic Resonance While magnetic resonance is one of the less sensitive spectroscopic techniques, there are a number  

E-print Network

Sensitivity of Optically Enhanced Magnetic Resonance While magnetic resonance is one of the less sensitive spectroscopic techniques, there are a number of possible means to correct this deficiency. Optical electronic or nuclear spins. Compared to conventional magnetic resonance, the sensitivity can be increased

Suter, Dieter

359

Spatially coherent surface resonance states derived from magnetic resonances  

NASA Astrophysics Data System (ADS)

A thin metamaterial slab comprising a dielectric spacer sandwiched between a metallic grating and a ground plane is shown to possess spatially coherent surface resonance states that span a large frequency range and can be tuned by structural and material parameters. They give rise to nearly perfect angle-selective absorption and thus exhibit directional thermal emissivity. Direct numerical simulations show that the metamaterial slab supports spatially coherent thermal emission in a wide frequency range that is robust against structural disorder.

Wei, Zeyong; Li, Hongqiang; Cao, Yang; Wu, Chao; Ren, Jinzhi; Hang, Zhihong; Chen, Hong; Zhang, Daozhong; Chan, C. T.

2010-09-01

360

Anatomy Corner  

NSDL National Science Digital Library

This fascinating and informative website was created by a high school teacher in Granite City, Missouri. It brings together a wide range of resources designed to help students learn about anatomy. The materials are divided into three sections: Anatomy Galleries, Anatomy Topics, and Virtual Cat Dissection. The Anatomy Galleries area provides slides, photos, and illustrative materials related to eye dissection, sheep heart dissection, and cat muscles. The Anatomy Topics area includes overviews of the major body systems, including the nervous, circulatory, and endocrine systems. The site also includes a Virtual Cat Dissection, which walks interested parties through this process.

2013-01-01

361

Voltage-Induced Ferromagnetic Resonance in Magnetic Tunnel Junctions  

NASA Astrophysics Data System (ADS)

Excitation of sub-nanosecond magnetic dynamics by an electric field is a grand challenge in the field of spintronics. The ability to perform high-speed manipulation of magnetization by electric fields rather than by current-induced spin torques or magnetic fields would greatly improve energy efficiency of spintronic devices such as nonvolatile magnetic memory and logic. In this talk, I will discuss our experiments on excitation of ferromagnetic resonance in CoFeB/ MgO/ CoFeB magnetic tunnel junctions by the combined action of voltage-controlled magnetic anisotropy (VCMA) and spin transfer torque [1]. Our measurements reveal that GHz-frequency VCMA torque and spin torque in low resistance (resistance-area product of a few Ohm . ?m^2) CoFeB-based magnetic tunnel junctions have similar magnitudes, and thus that both torques are equally important for understanding high-speed voltage-driven magnetization dynamics in CoFeB magnetic tunnel junctions such as magnetization switching and auto-oscillations induced by spin torque. As an example, we show that VCMA can increase the sensitivity of a microwave signal detector based on a magnetic tunnel junction to the sensitivity level of semiconductor Schottky diodes. Our measurements also demonstrate that ferromagnetic resonance in high resistance magnetic tunnel junctions can be excited by VCMA alone without a significant contribution from the spin torque drive. I will conclude this talk with a discussion on how voltage-induced ferromagnetic resonance can be used for quantitative measurements of various voltage-dependent torques in magnetic tunnel junctions: in-plane and perpendicular spin torques as well as VCMA torque. [4pt] [1] J. Zhu et al., Phys. Rev. Lett. 108, 197203 (2012)

Krivorotov, Ilya

2013-03-01

362

LA-UR-97-40 Magnetic Resonance Force Microscopy With a  

E-print Network

LA-UR-97-40 Magnetic Resonance Force Microscopy With a Ferromagnetic Tip Mounted on the Force Resonance Force Microscope (MRFM) presents the oppor- tunity for a magnetic resonance imaging probe MRFM techniques. A crucial remaining challenge in the development of the magnetic resonance force

Hammel, P. Chris

363

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy  

SciTech Connect

Lateral one-dimensional imaging of cobalt (Co) films by means of microscopic ferromagnetic resonance (FMR) detected using the magnetic resonance force microscope (MRFM) is demonstrated. A novel approach involving scanning a localized magnetic probe is shown to enable FMR imaging in spite of the broad resonance linewidth. We introduce a spatially selective local field by means of a small, magnetically polarized spherical crystallite of yttrium iron garnet (YIG). Using MRFM-detected FMR signals from a sample consisting of two Co films, we can resolve the {approximately}20 {mu}m lateral separation between the films. The results can be qualitatively understood by consideration of the calculated spatial profiles of the magnetic field generated by the YIG sphere. {copyright} {ital 1998 American Vacuum Society.}

Suh, B.J.; Hammel, P.C.; Zhang, Z. [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Midzor, M.M.; Roukes, M.L. [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States)] [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States); Childress, J.R. [University of Florida, Gainesville, Florida 32611 (United States)] [University of Florida, Gainesville, Florida 32611 (United States)

1998-07-01

364

A prototype manipulator for magnetic resonance-guided interventions inside standard cylindrical magnetic resonance imaging scanners.  

PubMed

The aim of this work is to develop a remotely controlled manipulator to perform minimally invasive diagnostic and therapeutic interventions in the abdominal and thoracic cavities, with real-time magnetic resonance imaging (MRI) guidance inside clinical cylindrical MR scanners. The manipulator is composed of a three degree of freedom Cartesian motion system, which resides outside the gantry of the scanner, and serves as the holder and global positioner of a three degree of freedom arm which extends inside the gantry of the scanner At its distal end, the arm's end-effector can carry an interventional tool such as a biopsy needle, which can be advanced to a desired depth by means of a seventh degree of freedom. These seven degrees of freedom, provided by the entire assembly, offer extended manipulability to the device and a wide envelope of operation to the user, who can select a trajectory suitable for the procedure. The device is constructed of nonmagnetic and nonconductive fiberglass, and carbon fiber composite materials, to minimize artifacts and distortion on the MR images as well as eliminate effects on its operation from the high magnetic field and the fast switching magnetic field gradients used in MR imaging. A user interface was developed for man-in-the-loop control of the device using real-time MR images. The user interface fuses all sensor signals (MR and manipulator information) in a visualization, planning, and control command environment. Path planning is performed with graphical tools for setting the trajectory of insertion of the interventional tool using multislice and/or three dimensional MR images which are refreshed in real time. The device control is performed with an embedded computer which runs real-time control software. The manipulator compatibility with the MR environment and image-guided operation was tested on a 1.5 T MR scanner. PMID:16438235

Tsekos, Nikolaos V; Ozcan, Alpay; Christoforou, Eftychios

2005-11-01

365

Magnetic anisotropy of polycrystalline magnetoferritin investigated by SQUID and electron magnetic resonance  

NASA Astrophysics Data System (ADS)

Magnetoferritin molecules with an average inorganic core diameter of 5.7±1.6 nm and polycrystalline internal structure were investigated by a combination of transmission electron microscopy, magnetic susceptibility, magnetization, and electron magnetic resonance (EMR) experiments. The temperature and frequency dependence of the magnetic susceptibility allowed for the determination of the magnetic anisotropy on an experimental time scale which spans from seconds to nanoseconds. In addition, angle-dependent EMR experiments were carried out for the determination of the nanoparticle symmetry and internal magnetic field. Due to the large surface to volume ratio, the nanoparticles show larger and uniaxial rather than cubic magnetic anisotropies compared to bulk maghemite and magnetite.

Moro, F.; de Miguel, R.; Jenkins, M.; Gómez-Moreno, C.; Sells, D.; Tuna, F.; McInnes, E. J. L.; Lostao, A.; Luis, F.; van Slageren, J.

2014-06-01

366

Coplanar probe microwave current injection ferromagnetic resonance of magnetic nanostructures  

NASA Astrophysics Data System (ADS)

The non-uniform standing spin-wave modes in thin magnetic films and nanostructures provide important information about their magnetic properties. Very often they are lacking in the recorded ferromagnetic resonance spectra for symmetry reasons. In this work we experimentally demonstrate that by direct injection of microwave currents into a magnetic nanostructure using a sub-millimetre sized microwave coaxial to coplanar adaptor one can efficiently excite non-uniform standing spin wave modes with odd symmetry. The proposed method is quick and allows easy spatial mapping of magnetic properties with the resolution down to 100 ?m. We have validated this method using an example from a periodical array of nanostripes.

Chang, C. S.; Kostylev, M.; Adeyeye, A. O.; Bailleul, M.; Samarin, S.

2011-12-01

367

Illustrated Speech Anatomy.  

ERIC Educational Resources Information Center

Written for students in the fields of speech correction and audiology, the text deals with the following: structures involved in respiration; the skeleton and the processes of inhalation and exhalation; phonation and pitch, the larynx, and esophageal speech; muscles involved in articulation; muscles involved in resonance; and the anatomy of the…

Shearer, William M.

368

A platform for designing hyperpolarized magnetic resonance chemical probes  

PubMed Central

Hyperpolarization is a highly promising technique for improving the sensitivity of magnetic resonance chemical probes. Here we report [15N, D9]trimethylphenylammonium as a platform for designing a variety of hyperpolarized magnetic resonance chemical probes. The platform structure shows a remarkably long 15N spin–lattice relaxation value (816?s, 14.1 T) for retaining its hyperpolarized spin state. The extended lifetime enables the detection of the hyperpolarized 15N signal of the platform for several tens of minutes and thus overcomes the intrinsic short analysis time of hyperpolarized probes. Versatility of the platform is demonstrated by applying it to three types of hyperpolarized chemical probes: one each for sensing calcium ions, reactive oxygen species (hydrogen peroxide) and enzyme activity (carboxyl esterase). All of the designed probes achieve high sensitivity with rapid reactions and chemical shift changes, which are sufficient to allow sensitive and real-time monitoring of target molecules by 15N magnetic resonance. PMID:24022444

Nonaka, Hiroshi; Hata, Ryunosuke; Doura, Tomohiro; Nishihara, Tatsuya; Kumagai, Keiko; Akakabe, Mai; Tsuda, Masashi; Ichikawa, Kazuhiro; Sando, Shinsuke

2013-01-01

369

[Diagnostic approach to cardiopathies by means of magnetic resonance imaging].  

PubMed

Cardiomyopathies encompass a broad spectrum of heart pathologies having a basic principle, the intrinsic injury of the myocardial fiber. By definition, cardiomyopathies could be primary (dilated cardiomyopathy), or can be a consequence of another cardiovascular illness (high blood pressure), or of genetic anomalies, such as hypertrophic cardiomyopathy, or due to alterations in myocytes due to fibrolipidic material as occurs in right ventricle arrhythmogenic dysplasia. Currently, magnetic resonance imaging is the best method to approach the diagnosis of these pathologies. Magnetic resonance imaging has allowed us to study histological sections through adequate sequences and using gadolinium as contrast agent. We present herein a simple way to approach the diagnosis of cardiomyopathies by means of magnetic resonance imaging methods. PMID:15909747

Gutiérrez Zamora, Agustín

2005-01-01

370

Synthesis, magnetic resonance and microwave absorption properties of cobalt nanospheres  

NASA Astrophysics Data System (ADS)

By using a simple and low-cost liquid reduction method, we have synthesized cobalt nanospheres on a large scale. The materials were characterized, and the result showed that as-prepared products were cobalt nanospheres, assembled by nanosheets in parallel, with a size of around 100 nm. The electromagnetic behaviors of the cobalt nanospheres, including permittivity ({{\\varepsilon }r}=\\varepsilon '-j\\varepsilon '') and permeability ({{? }r}=? '-j? ''), were also investigated as a function of frequency in the microwave frequency range of 2–18 GHz. The permittivity presented multiple dielectric resonance peaks whilst the permeability displayed dual obvious magnetic resonance peaks, manifestly different from other cobalt particles in comparison. The calculated reflection loss (RL) indicated there were two strong microwave absorption peaks over the microwave frequency range of 2–18 GHz, which was in accord with the magnetic resonance peaks. The result revealed that the magnetic loss contributed even more than dielectric loss to the microwave absorption for the cobalt nanospheres.

Wen, S. L.; Liu, Y.; Zhao, X. C.; Cheng, J. W.; Li, H.

2014-12-01

371

Magnetic resonance imaging of transplanted stem cell fate in stroke  

PubMed Central

Nowadays, scientific findings in the field of regeneration of nervous system have revealed the possibility of stem cell based therapies for damaged brain tissue related disorders like stroke. Furthermore, to achieve desirable outcomes from cellular therapies, one needs to monitor the migration, engraftment, viability, and also functional fate of transplanted stem cells. Magnetic resonance imaging is an extremely versatile technique for this purpose, which has been broadly used to study stroke and assessment of therapeutic role of stem cells. In this review we searched in PubMed search engine by using following keywords; “Stem Cells”, “Cell Tracking”, “Stroke”, “Stem Cell Transplantation”, “Nanoparticles”, and “Magnetic Resonance Imaging” as entry terms and based on the mentioned key words, the search period was set from 1976 to 2012. The main purpose of this article is describing various advantages of molecular and magnetic resonance imaging of stem cells, with focus on translation of stem cell research to clinical research. PMID:25097631

Aghayan, Hamid Reza; Soleimani, Masoud; Goodarzi, Parisa; Norouzi-Javidan, Abbas; Emami-Razavi, Seyed Hasan; Larijani, Bagher; Arjmand, Babak

2014-01-01

372

Cardiovascular magnetic resonance guided electrophysiology studies  

PubMed Central

Catheter ablation is a first line treatment for many cardiac arrhythmias and is generally performed under x-ray fluoroscopy guidance. However, current techniques for ablating complex arrhythmias such as atrial fibrillation and ventricular tachycardia are associated with suboptimal success rates and prolonged radiation exposure. Pre-procedure 3D CMR has improved understanding of the anatomic basis of complex arrhythmias and is being used for planning and guidance of ablation procedures. A particular strength of CMR compared to other imaging modalities is the ability to visualize ablation lesions. Post-procedure CMR is now being applied to assess ablation lesion location and permanence with the goal of indentifying factors leading to procedure success and failure. In the future, intra-procedure real-time CMR, together with the ability to image complex 3-D arrhythmogenic anatomy and target additional ablation to regions of incomplete lesion formation, may allow for more successful treatment of even complex arrhythmias without exposure to ionizing radiation. Development of clinical grade CMR compatible electrophysiology devices is required to transition intra-procedure CMR from pre-clinical studies to more routine use in patients. PMID:19580654

Kolandaivelu, Aravindan; Lardo, Albert C; Halperin, Henry R

2009-01-01

373

Magnetic resonance images of neuronal migration anomalies.  

PubMed

Neuronal migration anomalies are a spectrum of brain malformations caused by insults to migrating neuroblasts during the sixth week to fifth month of gestation. To study the characteristics of MRI findings in migration anomalies, MR images of 36 patients (28 children and 8 adults) with migration anomalies were evaluated. Five patients had lissencephaly, eight had pachygyria, twelve had schizencephaly, six had heterotopias of gray matter, three had hemimegalencephaly, and two had polymicrogyria. The frequency of migration anomalies was 0.51% of all cranial MRI studies and 1.21% of pediatric cranial MRI studies at our hospital. The major clinical presentations of these patients were seizure (64%), development delay (42%), motor deficits (42%) and mental retardation (25%). Twenty-five patients (69%) associated with other brain anomalies, including: other migration anomalies in 12 cases (33%), absence of the septum pellucidum in 10 cases (28%), Dandy-Walker malformation/variant in 5 cases, arachnoid cyst in 4 cases, agenesis of the corpus callosum in 3 cases, holoprosencephaly in 2 cases, mega cisterna magna in 1 case and cephalocele in 1 case. Some of them presented with multiple complicated anomalies. As MR imaging provides superb gray-white matter distinction, details of cortical anatomy and multiplanar capability, it can clearly delineate the detail morphologic changes of the brain caused by neuronal migration disorders as well as the associated anomalies. PMID:9780601

Jaw, T S; Sheu, R S; Liu, G C; Chou, M S

1998-08-01

374

Duffing oscillation-induced reversal of magnetic vortex core by a resonant perpendicular magnetic field  

PubMed Central

Nonlinear dynamics of the magnetic vortex state in a circular nanodisk was studied under a perpendicular alternating magnetic field that excites the radial modes of the magnetic resonance. Here, we show that as the oscillating frequency is swept down from a frequency higher than the eigenfrequency, the amplitude of the radial mode is almost doubled to the amplitude at the fixed resonance frequency. This amplitude has a hysteresis vs. frequency sweeping direction. Our result showed that this phenomenon was due to a Duffing-type nonlinear resonance. Consequently, the amplitude enhancement reduced the vortex core-switching magnetic field to well below 10?mT. A theoretical model corresponding to the Duffing oscillator was developed from the Landau–Lifshitz–Gilbert equation to explore the physical origin of the simulation result. This work provides a new pathway for the switching of the magnetic vortex core polarity in future magnetic storage devices. PMID:25145837

Moon, Kyoung-Woong; Chun, Byong Sun; Kim, Wondong; Qiu, Z. Q.; Hwang, Chanyong

2014-01-01

375

Duffing oscillation-induced reversal of magnetic vortex core by a resonant perpendicular magnetic field  

NASA Astrophysics Data System (ADS)

Nonlinear dynamics of the magnetic vortex state in a circular nanodisk was studied under a perpendicular alternating magnetic field that excites the radial modes of the magnetic resonance. Here, we show that as the oscillating frequency is swept down from a frequency higher than the eigenfrequency, the amplitude of the radial mode is almost doubled to the amplitude at the fixed resonance frequency. This amplitude has a hysteresis vs. frequency sweeping direction. Our result showed that this phenomenon was due to a Duffing-type nonlinear resonance. Consequently, the amplitude enhancement reduced the vortex core-switching magnetic field to well below 10 mT. A theoretical model corresponding to the Duffing oscillator was developed from the Landau-Lifshitz-Gilbert equation to explore the physical origin of the simulation result. This work provides a new pathway for the switching of the magnetic vortex core polarity in future magnetic storage devices.

Moon, Kyoung-Woong; Chun, Byong Sun; Kim, Wondong; Qiu, Z. Q.; Hwang, Chanyong

2014-08-01

376

Magnetic resonance imaging findings in Axenfeld–Rieger syndrome  

PubMed Central

Axenfeld–Rieger syndrome (ARS) is a genetic disorder representing a disease spectrum resulting from neural crest cell maldevelopment. Glaucoma is a common complication from the incomplete formation of the iridocorneal angle structures. Neural crest cells also form structures of the forebrain and pituitary gland, dental papillae, aortic arch walls, genitalia, and long bones; therefore, patients with ARS manifest a wide range of systemic findings. To our knowledge, detailed magnetic resonance imaging findings have not been previously reported. We report a case of a 19-month-old Indian male diagnosed with ARS with emphasis on magnetic resonance imaging findings of the globes, brain, teeth, and skull base. PMID:23723681

Whitehead, Matthew T; Choudhri, Asim F; Salim, Sarwat

2013-01-01

377

Nuclear Magnetic Resonance (NMR) And Its Impact On Medical Imaging  

NASA Astrophysics Data System (ADS)

Not since the advent of x-ray transmission computed tomography a decade ago has an innovation in medical imaging generated as much interest as that currently directed to nuclear magnetic resonance. This technique, long a standby in chemistry and physics laboratories, promises to provide images of reasonable spatial resolution and exquisite contrast sensitivity. In addition, quantitative analysis of specific elements in selected regions of tissue may be possible. In developing a strategy for the acquisition of nuclear magnetic resonance, cost factors must be considered together with a realistic appraisal of a clinical facility as primarily a research or clinical unit.

Hendee, William R.

1982-12-01

378

Magnetic damping of a carbon nanotube nano-electromechanical resonator  

NASA Astrophysics Data System (ADS)

A suspended, doubly clamped single-wall carbon nanotube is characterized at cryogenic temperatures. We observe specific switching effects in dc-current spectroscopy of the embedded quantum dot. These have been identified previously as nano-electromechanical self-excitation of the system, where positive feedback from single-electron tunneling drives mechanical motion. A magnetic field suppresses this effect, by providing an additional damping mechanism. This is modeled by eddy current damping, and confirmed by measuring the resonance quality factor of the radio-frequency-driven nano-electromechanical resonator in an increasing magnetic field.

Schmid, D. R.; Stiller, P. L.; Strunk, Ch; Hüttel, A. K.

2012-08-01

379

On transition from Alfvén resonance to forced magnetic reconnection  

SciTech Connect

We revisit the transition from Alfvén resonance to forced magnetic reconnection with a focus on the property of their singularities. As the driven frequency tends to zero, the logarithmic singularity of Alfvén resonance shifts to the power-law singularity of forced reconnection, due to merging of the two resonance layers. The transition criterion depends on either kinetic effects or dissipations that resolve the singularity. As an example, a small but finite resistivity ? is introduced to investigate the transition process. The transition threshold is then obtained as the driven frequency reaches a level of ?O((?/k){sup 1/3})

Luan, Q. [MOE Key Lab of Materials Modification by Beams and School of Physics and Optoelectrical Technology, Dalian University of Technology, Dalian 116024 (China); Wang, X., E-mail: xgwang@hit.edu.cn [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China)

2014-07-15

380

Field line resonances in general magnetic topology  

Microsoft Academic Search

We examine the spatial and temporal characteristics of dispersive field line resonances observed by the CANOPUS chain of magnetometers and by all-sky cameras in the NORSTAR array. We pay particular attention to small dispersive scale properties of Alfven waves excited on field lines that are stretched and distorted out of the meridional plane, and address similarities between some auroral arcs

R. Rankin; K. Kabin; R. Marchand; J. Y. Lu; V. T. Tikhonchuk

2004-01-01

381

Wireless Energy Transfer Using Magnetic Resonance  

Microsoft Academic Search

In 1899, Nikola Tesla, who had devised a type of resonant transformer called the Tesla coil, achieved a major breakthrough in his work by transmitting 100 million volts of electric power wirelessly over a distance of 26 miles to light up a bank of 200 light bulbs and run one electric motor. Tesla claimed to have achieved 95% efficiency, but

Rohan Bhutkar; Sahil Sapre

2009-01-01

382

Open magnetic resonance imaging (MRI) scanners.  

PubMed

(1) In most MRI scanners, the patient examination table fits inside a long cylindrical tube. Large patients cannot be accommodated, and some persons experience claustrophobic reactions. Open MRI systems, in which the patient is placed between two plates, overcome these disadvantages. (2) Open MRI scanners are widely used in health care. High-field closed MRI systems are preferred for many examinations. (3) Early versions of open MRI scanners had low magnetic field strength, gave poorer image quality than most closed systems, and required longer examination times. Newer open scanners include machines with higher magnetic field strengths and improved image quality. (4) Closed high magnetic field scanners with short magnets and wide bore tubes offer improved comfort to patients, and may be an alternative to open scanners. (5) There is interest in using open systems for intra-operative and image-guided interventions. PMID:17086657

Hailey, D

2006-11-01

383

Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance  

NASA Technical Reports Server (NTRS)

We pursued advanced technology development of laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This new multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation-as well as studies of tissue perfusion. In addition, laser-polarized noble gases (3He and 129Xe) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We pursued two technology development specific aims: (1) development of low-field (less than 0.01 T) noble gas MRI of humans; and (2) development of functional MRI of the lung using laser-polarized noble gas and related techniques.

Walsworth, Ronald L.

2003-01-01

384

Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance  

NASA Technical Reports Server (NTRS)

We are developing laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI) (e.g., of lung ventilation) as well as studies of tissue perfusion. In addition, laser-polarized noble gases (He-3 and Xe-129) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We are pursuing two specific aims in this research. The first aim is to develop a low-field (< 0.01 T) instrument for noble gas MRI of humans, and the second aim is to develop functional MRI of the lung using laser-polarized Xe-129 and related techniques.

Walsworth, Ronald L.

2001-01-01

385

The University of Hull: Magnetic Resonance Imaging (MRI)  

NSDL National Science Digital Library

Gary P. Liney, at the University of Hull, offers an introduction to magnetic resonance physics and techniques. Users can download presentations about spin-echo and Fourier Transformation. The website discusses a host of artifacts such as Gibbs Ringing, chemical shift, and susceptibility. Students and educators can learn about the magnet, RF Coils, gradients, and other instruments used to produce MRIs. The many animations and figures help users learn about the difficult physical concepts.

Liney, Gary P.

386

Nuclear magnetic resonance imaging of water motion in plants  

Microsoft Academic Search

This Thesis treats one of the new techniques in plant science i.e. nuclear magnetic resonance imaging (NMRi) applied to water motion in plants. It is a challenge, however, to measure this motion in intact plants quantitatively, because plants impose specific problems when studied using NMRi. At high magnetic field strength air-filled intercellular spaces in the plant tissue cause susceptibility-related local

T. W. J. Scheenen

2001-01-01

387

The Underpinnings of the BOLD Functional Magnetic Resonance Imaging Signal  

Microsoft Academic Search

The good coverage and high resolution afforded by functional mag-netic resonance imaging (fMRI) make it an excellent tool for the noninvasive imaging of the human brain. Equally interesting, how-ever, is the use of this technique in animal studies using high mag-netic fields. In the latter case, highly spatiotemporally resolved fMRI can reveal how widespread neural networks are organized, and ac-companying

Nikos K. Logothetis

2003-01-01

388

Hybrid microparticles for drug delivery and magnetic resonance imaging.  

PubMed

In this work, we report the synthesis, characterization, and possible application as drug-delivery system magnetically triggered, of hybrid microparticles formed by magnetic nanoparticles embedded within poly(?-caprolactone). The magnetism of the microparticles permits their localization within the body using magnetic resonance imaging, and the biodegradable polymer layer allows entrapping drugs that can be released when temperature increases. The synthesis of the hybrid material was performed using "grafting from" technique of conveniently modified magnetic nanoparticles. Subsequently, the resulting hybrid nanoparticles were assembled into spherical particles of 138 ± 49 nm via precipitation technique. The produced hybrid material was evaluated as stimuli-responsive drug delivery system in which the release of the drug was triggered by magnetic induction. Furthermore, the microparticles were injected in rats and their localization within the animal was monitored using the local field inhomogeneities generated by the particles. PMID:22915497

Serrano-Ruiz, David; Laurenti, Marco; Ruiz-Cabello, Jesús; López-Cabarcos, Enrique; Rubio-Retama, Jorge

2013-05-01

389

Nuclear magnetic resonance spectroscopy. Principles and applications in neuroophthalmology.  

PubMed

Magnetic resonance spectroscopy is a valuable method for the non-invasive investigation of metabolic processes and can now be combined with conventional magnetic resonance imaging in patients. This article gives a brief introduction into the principles and physiological and clinical applications of in vivo proton magnetic resonance spectroscopy, surveys experiences in healthy volunteers and presents exemplary results in patients suffering from cortical blindness or visual field defects. The causes of visual loss include brain trauma, cerebral ischemia, and brain tumors. In traumatic, ischemic and neoplastic lesions, an important spectral finding is an elevated lactate resonance which has been explained by increased anaerobic glycolysis of ischemic brain tissue and macrophages invading necrotic tissue. In our investigations using a clinical spectroscopy protocol on a 1.5 T MR system, a significant lactate signal was absent in spectra obtained from the visual cortex of normal volunteers, even during photic stimulation with a stroboscope. Other spectral changes in the patients include a decreased N-acetyl-aspartate resonance which indicates a decreased number of viable neurons in the examined brain region. PMID:7852025

Ettl, A; Fischer-Klein, C; Chemelli, A; Daxer, A; Felber, S

1994-01-01

390

Bi-exponential magnetic resonance signal model for partial volume computation  

PubMed Central

Accurate quantification of small structures in magnetic resonance (MR) images is often limited by partial volume (PV) effects which arise when more than one tissue type is present in a voxel. PV may be critical when dealing with changes in brain anatomy as the considered structures such as gray matter (GM) are of the similar size as the MR spatial resolution. To overcome the limitations imposed by PV effects and achieve subvoxel accuracy different methods have been proposed. Here, we describe a method to compute PV by modeling the MR signal with a biexponential linear combination representing the contribution of at most two tissues in each voxel. In a first step, we estimated the parameters (T1, T2 and Proton Density) per tissue. Then, based on the bi-exponential formulation one can retrieve fractional contents by solving a linear system of two equations with two unknowns, namely tissue magnetizations. Preliminary tests were conducted on images acquired on a specially designed physical phantom for the study of PV effects. Further, the model was tested on BrainWeb simulated brain images to estimate GM and white matter (WM) PV effects. Root Mean Squared Error was computed between the BrainWeb ground truth and the obtained GM and WM PV maps. The proposed method outperformed traditionally used methods by 33% and 34% in GM and WM, respectively. PMID:23285556

Duché, Quentin; Acosta, Oscar; Gambarota, Giulio; Merlet, Isabelle; Salvado, Olivier; Saint-Jalmes, Hervé

2012-01-01

391

5.4 Magnetic Resonance Imaging, Diagnostic Ultrasound  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A 'Fundamentals and Data in Radiobiology, Radiation Biophysics, Dosimetry and Medical Radiological Protection' of Volume 7 'Medical Radiological Physics' of Landolt-Börnstein - Group VIII 'Advanced Materials and Technologies'. It contains the Section '5.4 Magnetic Resonance Imaging, Diagnostic Ultrasound' of the Chapter '5 Medical Radiological Protection' with the contents:

Bernhardt, J. H.

392

Three-Dimensional Magnetic Resonance Imaging of Velopharyngeal Structures  

ERIC Educational Resources Information Center

Purpose: To report the feasibility of using a 3-dimensional (3D) magnetic resonance imaging (MRI) protocol for examining velopharyngeal structures. Using collected 3D MRI data, the authors investigated the effect of sex on the midsagittal velopharyngeal structures and the levator veli palatini (levator) muscle configurations. Method: Ten Caucasian…

Bae, Youkyung; Kuehn, David P.; Sutton, Bradley P.; Conway, Charles A.; Perry, Jamie L.

2011-01-01

393

Functional Connectivity Magnetic Resonance Imaging Classification of Autism  

ERIC Educational Resources Information Center

Group differences in resting state functional magnetic resonance imaging connectivity between individuals with autism and typically developing controls have been widely replicated for a small number of discrete brain regions, yet the whole-brain distribution of connectivity abnormalities in autism is not well characterized. It is also unclear…

Anderson, Jeffrey S.; Nielsen, Jared A.; Froehlich, Alyson L.; DuBray, Molly B.; Druzgal, T. Jason; Cariello, Annahir N.; Cooperrider, Jason R.; Zielinski, Brandon A.; Ravichandran, Caitlin; Fletcher, P. Thomas; Alexander, Andrew L.; Bigler, Erin D.; Lange, Nicholas; Lainhart, Janet E.

2011-01-01

394

Human Brain Language Areas Identified by Functional Magnetic Resonance Imaging  

Microsoft Academic Search

Functional magnetic resonance imaging (FMRI) was used to identify candidate language processing areas in the intact hu- man brain. Language was defined broadly to include both phonological and lexical-semantic functions and to exclude sensory, motor, and general executive functions. The language activation task required phonetic and semantic analysis of aurally presented words and was compared with a control task involving

Jeffrey R. Binder; Julie A. Frost; Thomas A. Hammeke; Robert W. Cox; Stephen M. Rao; Thomas Prieto

1997-01-01

395

Permutation Testing Made Practical for Functional Magnetic Resonance Image Analysis  

Microsoft Academic Search

We describe an efficient algorithm for the step-down permutation test, applied to the analysis of functional magnetic resonance images. The algorithm's time bound is nearly linear, making it feasible as an interactive tool. Results of the permutation test algorithm applied to data from a cognitive activation paradigm are compared with those of a standard parametric test corrected for multiple comparisons.

Matthew Belmonte; Deborah Yurgelun-todd

2001-01-01

396

UNIVERSITY OF OREGON CAMCOR Nuclear Magnetic Resonance Spectroscopy Facility  

E-print Network

Probe (liquids); CP/MAS solids Varian INOVA 500 MHz NMR Spectrometer Varian INOVA 300 MHz NMR Spectrometer 1 HUNIVERSITY OF OREGON CAMCOR Nuclear Magnetic Resonance Spectroscopy Facility INSTRUMENTS NMR 1H/19F SAMPLES FOR ROUTINE 1H NMR $30 each + materials SOLID STATE NMR surcharge 25% + rotors, caps, & staff time

397

Cognitive-Pharmacologic Functional Magnetic Resonance Imaging in Tourette Syndrome  

E-print Network

Cognitive-Pharmacologic Functional Magnetic Resonance Imaging in Tourette Syndrome: A Pilot Study and vocalizations (tics) in Tourette syndrome (TS); however, dopamine-responsive abnormal function in specific brain dopamine antagonists and agonists alleviate tics. Key Words: Tourette syndrome, physiopathology, dopamine

398

C-13 nuclear magnetic resonance in organic geochemistry.  

NASA Technical Reports Server (NTRS)

Study of C-13 nuclear magnetic resonance (NMR) spectra of polycyclic fused systems. The fingerprint qualities of the natural abundance in C-13 NMR spectra permitting unequivocal identification of these compounds is discussed. The principle of structural additivity of C-13 NMR information is exemplified on alpha and beta androstanes, alpha and beta cholestanes, ergostanes, sitostanes, and isodecanes.

Balogh, B.; Wilson, D. M.; Burlingame, A. L.

1972-01-01

399

Image Processing for Diffusion Tensor Magnetic Resonance Imaging  

Microsoft Academic Search

This paper1 describes image processing techniques for Diffusion Ten- sor Magnetic Resonance. In Diffusion Tensor MRI, a tensor describing local wa- ter diffusion is acquired for each voxel. The geometric nature of the diffusion tensors can quantitatively characterize the local structure in tissues such as bone, muscles, and white matter of the brain. The close relationship between local im- age

Carl-fredrik Westin; S. E. Maier; B. Khidhir; Peter Everett; Ferenc A. Jolesz; Ron Kikinis

1999-01-01

400

Blood Flow Magnetic Resonance Imaging of Retinal Degeneration  

E-print Network

Blood Flow Magnetic Resonance Imaging of Retinal Degeneration Yingxia Li,1 Haiying Cheng,1 Qiang. Duong1,2,3,4,5,6,7 PURPOSE. This study aims to investigate quantitative basal blood flow as well as hypercapnia- and hyperoxia-induced blood flow changes in the retinas of the Royal College of Surgeons (RCS

Duong, Timothy Q.

401

Toward Measuring Program Comprehension with Functional Magnetic Resonance Imaging  

E-print Network

. This way, we hope to relate program comprehension to other cognitive processes (e.g., reading comprehensionToward Measuring Program Comprehension with Functional Magnetic Resonance Imaging Janet Siegmund Program comprehension is an often evaluated, internal cog- nitive process. In neuroscience, functional

Kaestner, Christian

402

RECONSTRUCTION OF HUMAN LUNG MORPHOLOGY MODELS FROM MAGNETIC RESONANCE IMAGES  

EPA Science Inventory

Reconstruction of Human Lung Morphology Models from Magnetic Resonance Images T. B. Martonen (Experimental Toxicology Division, U.S. EPA, Research Triangle Park, NC 27709) and K. K. Isaacs (School of Public Health, University of North Carolina, Chapel Hill, NC 27514) ...

403

Proton magnetic resonance spectroscopy in youth with severe mood dysregulation  

Microsoft Academic Search

Increasing numbers of youth are presenting for psychiatric evaluation with markedly irritable mood plus “hyperarousal” symptoms. Diagnostically homeless in current nosology, the syndrome (as well as its underlying neurobiology) is little understood. To address this problem, we conducted an exploratory proton magnetic resonance spectroscopy (MRS) study in a large sample of youth with chronic, functionally disabling irritability accompanied by hyperarousal,

Daniel P. Dickstein; Jan Willem van der Veen; Lisa Knopf; Kenneth E. Towbin; Daniel S. Pine; Ellen Leibenluft

2008-01-01

404

Diagnosis of orbital myositis by nuclear magnetic resonance imaging.  

PubMed Central

Two cases of orbital myositis are reported in which precise identification of the involved muscle was possible with the use of surface coil nuclear magnetic resonance (NMR) imaging. A clinical response to oral steroids in both cases coincided with a marked reduction in the abnormal thickening of the muscles as seen on the NMR images. Images PMID:3814571

Dua, H S; Smith, F W; Singh, A K; Forrester, J V

1987-01-01

405

Detection of Prostate Cancer from Multiparametric Magnetic Resonance Imaging  

E-print Network

050 051 052 053 Detection of Prostate Cancer from Multiparametric Magnetic Resonance Imaging Anonymous (MRI) based technique of detecting prostate cancer is developed. A machine learning algorithm, based. The classifier is trained to detect prostate cancer in the peripheral zone and using the trained classifier

de Freitas, Nando

406

Antimyosin Scintigraphy Compared With Magnetic Resonance Imaging in Inflammatory Myopathies  

Microsoft Academic Search

Objective: To compare indium In 111 altumomab pen- tetate-labeled antimyosin scintigraphy with magnetic resonance imaging (MRI) in the diagnosis and fol- low-up of patients with myositis. Design and Methods: Sixteen patients with polymyo- sitis and 1 patient with dermatomyositis, all verified with biopsy samples, were examined during diagnostic evalu- ation with antimyosin antibody scintigraphy and low- field MRI of the

Mervi Lofberg; Kristian Liewendahl; Antti Lamminen; Ossi Korhola; Hannu Somer

1998-01-01

407

Applications of proton magnetic resonance to functional group analysis  

Microsoft Academic Search

The application of proton magnetic resonance spectrometry to functional group analysis is discussed. Two examples are given viz. the distinction and simultaneous determination of primary, secondary, and tertiary functional groups in aliphatic monocarboxylic acids and in monovalent alcohols. Binary mixtures of acid types, and binary and ternary mixtures of alcohol types can be analysed with an accuracy of 5%m absolute

N. Meurs

1964-01-01

408

Nuclear Magnetic Resonance Experiments using Laser-Polarized Noble Gas  

E-print Network

Patrick Teen Chung Wong to The Department of Physics in partial fulfillment of the requirements 2001 #12;c 2001 by Glenn Patrick Teen Chung Wong All rights reserved #12;Advisor: Dr. Ronald Walsworth Author: Glenn Patrick Teen Chung Wong Nuclear Magnetic Resonance Experiments using Laser-Polarized Noble

Walsworth, Ronald L.

409

Oxymetry by magnetic resonance: applications to animal biology and medicine  

Microsoft Academic Search

In vivo oxygen concentration measurements are of crucial importance for monitoring the energetic metabolism from a physiological and pathological point of view. Magnetic resonance methods based on the paramagnetism of oxygen have the advantage of using great electromagnetic wavelengths, which present an important penetration in aqueous samples, and display no scattering in condensed matter. The transverse relaxation time (T2) of

D. Grucker

2000-01-01

410

A resonant switching write driver for magnetic recording  

Microsoft Academic Search

This paper describes a high-speed circuit for driving magnetic recording write heads. Resonant current switching enables a reduction in power consumption without compromising switching speed. With a 100 nH load and 120 mApp write currents, a rise time of 1.6 ns was achieved with a 7 V power supply

Richard J. Reay; Klaas B. Klaassen; Calvin S. Nomura

1997-01-01

411

Original Research In Vivo Magnetic Resonance Imaging of the Human  

E-print Network

Original Research In Vivo Magnetic Resonance Imaging of the Human Cervical Spinal Cord at 3 Tesla is feasible at 3 T. Key Words: MRI; 3 Tesla; cervical spinal cord; gradient echo; gray matter; white matter J, and pulsatile flow (9,10). Deficits in motor and sensory function from damage to the spinal cord are mainly due

Gorassini, Monica

412

Using Nuclear Magnetic Resonance Spectroscopy for Measuring Ternary Phase Diagrams  

ERIC Educational Resources Information Center

A laboratory experiment is presented for the upper-level undergraduate physical chemistry curriculum in which the ternary phase diagram of water, 1-propanol and n-heptane is measured using proton nuclear magnetic resonance (NMR) spectroscopy. The experiment builds upon basic concepts of NMR spectral analysis, typically taught in the undergraduate…

Woodworth, Jennifer K.; Terrance, Jacob C.; Hoffmann, Markus M.

2006-01-01

413

Nuclear Magnetic Resonance Coupling Constants and Electronic Structure in Molecules.  

ERIC Educational Resources Information Center

Theory of nuclear magnetic resonance spin-spin coupling constants and nature of the three types of coupling mechanisms contributing to the overall spin-spin coupling constant are reviewed, including carbon-carbon coupling (neither containing a lone pair of electrons) and carbon-nitrogen coupling (one containing a lone pair of electrons).…

Venanzi, Thomas J.

1982-01-01

414

A Scalable Framework For Segmenting Magnetic Resonance Images  

PubMed Central

A fast, accurate and fully automatic method of segmenting magnetic resonance images of the human brain is introduced. The approach scales well allowing fast segmentations of fine resolution images. The approach is based on modifications of the soft clustering algorithm, fuzzy c-means, that enable it to scale to large data sets. Two types of modifications to create incremental versions of fuzzy c-means are discussed. They are much faster when compared to fuzzy c-means for medium to extremely large data sets because they work on successive subsets of the data. They are comparable in quality to application of fuzzy c-means to all of the data. The clustering algorithms coupled with inhomogeneity correction and smoothing are used to create a framework for automatically segmenting magnetic resonance images of the human brain. The framework is applied to a set of normal human brain volumes acquired from different magnetic resonance scanners using different head coils, acquisition parameters and field strengths. Results are compared to those from two widely used magnetic resonance image segmentation programs, Statistical Parametric Mapping and the FMRIB Software Library (FSL). The results are comparable to FSL while providing significant speed-up and better scalability to larger volumes of data. PMID:20046893

Hore, Prodip; Goldgof, Dmitry B.; Gu, Yuhua; Maudsley, Andrew A.; Darkazanli, Ammar

2009-01-01

415

Mapping strain in biological tissues using magnetic resonance  

Microsoft Academic Search

Diffusion tensor magnetic resonance (MR) images reflect structure of cell membranes as well as the self-diffusion coefficient of water. A change in the geometry of cell membrane affects diffusion tensor images, which suggests a potential for a new method of strain mapping. In this study, we investigated the effect of strain on diffusion tensor images of muscles using numerical simulation

M. Sekino; A. Kaneko; S. Ueno

2005-01-01

416

Image processing for diffusion tensor magnetic resonance imaging  

Microsoft Academic Search

Abstract. This paper, describes image processing techniques for Diffusion Tensor Magnetic Resonance. In Diffusion Tensor MRI, a tensor describing local water diffusion is acquired for each voxel. The geometric nature of the diffusion tensors can quantitatively characterize the local structure in tissues such as bone, muscles, and white matter of the brain. The close relationship between local image structure and

C. F Westin; S. Peled; H. Gubjartsson; R. Kikinis; F. Jolesz

1997-01-01

417

Diagnosis of paraesophageal omental hiatal hernia by magnetic resonance imaging.  

PubMed

We present a case of an enlarging retrocardiac mass lesion in which we observed the magnetic resonance imaging (MRI) finding of a fatty tumor with contiguous blood vessels extending from the abdominal portion into the thoracic portion of the tumor. These surgically verified findings provide an MRI indication of the presence of a paraesophageal omental hiatal hernia. PMID:8417901

Rockoff, S D; Aaron, B L; Black, C; Kathuria, R; Biben, L

1993-01-01

418

Applications of nuclear magnetic resonance imaging in process engineering  

Microsoft Academic Search

During the past decade, the application of nuclear magnetic resonance (NMR) imaging techniques to problems of relevance to the process industries has been identified. The particular strengths of NMR techniques are their ability to distinguish between different chemical species and to yield information simultaneously on the structure, concentration distribution and flow processes occurring within a given process unit. In this

Lynn F. Gladden; Paul Alexander

1996-01-01

419

Magnetic resonance imaging of bovine ovaries in vitro  

Microsoft Academic Search

A sample of 20 bovine ovaries were imaged in vitro using nuclear magnetic resonance (NMR) techniques to determine the visibility of various physiologic structures. In particular, the possibility of using NMR imaging to differentiate atretic follicles from physiologically selected and ovulatory follicles was examined. Five of the 20 ovaries were preserved in formalin, whereas the remaining 15 were preserved in

G. E. Sarty; E. J. Kendall; R. A. Pierson

1996-01-01

420

GEOMETRIC COMPUTATION OF HUMAN GYRIFICATION INDEXES FROM MAGNETIC RESONANCE IMAGES  

E-print Network

University 3 Division of Child and Adolescent Psychiatry 4 Center for Neurobehavioral Development 5 Center for Magnetic Resonance Research University of Minnesota 6 Department of Child and Adolescent Psychiatry in typically developing children and adolescents. Using this novel approach, we provide evidence

421

MAGNETIC RESONANCE SCREENING FORM Name Height Weight  

E-print Network

or ear implant Prosthesis (eye/orbital, penile, etc.) Implant held in place by a magnet Heart valve or neurological illness Head Trauma Migraine Headache Panic attack Stroke Please remove all metallic objects-9082 Sign only during the inform-consent process and in the presence of a researcher. #12;

Biederman, Irving

422

An atlas of radiological anatomy  

SciTech Connect

This book contains a wealth of radiologic images of normal human anatomy; plain radiographs, contrast-enhanced radiographs, and computed tomography (CT) scans. There are 18 pages of magnetic resonance (MR) images, most on the brain and spinal cord, so that there are only two pages on MR imaging of the heart and two pages on abdominal and pelvic MR imaging. Twelve pages of ultrasound (US) images are included. This book has the radiologic image paired with an explanatory drawing; the image is on the left with a paragraph or two of text, and the drawing is on the right with legends. This book includes images of the brain and spinal cord obtained with arteriography, venography, myelography, encephalography, CT, and MR imaging.

Weir, J.; Abrahams, P.

1986-01-01

423

Double-outlet right ventricle: morphologic demonstration using nuclear magnetic resonance imaging.  

PubMed

Sixteen patients with double-outlet right ventricle, aged 1 week to 29 years (median 5 months), were studied with a 1.5 tesla nuclear magnetic resonance (NMR) imaging scanner. Two-dimensional echocardiography was performed in all patients. Thirteen patients underwent angiography, including nine who underwent subsequent surgical correction. Three patients underwent postmortem examination. Small children and infants were scanned inside a 32 cm diameter proton head coil. Multiple 5 mm thick sections separated by 0.5 mm and gated to the patient's electrocardiogram were acquired with a spin-echo sequence and an echo time of 30 ms. A combination of standard and oblique imaging planes was used. Imaging times were less than 90 min. The NMR images were technically unsuitable in one patient because of excessive motion artifact. In the remaining patients, the diagnosis of double outlet right ventricle was confirmed and correlated with surgical and postmortem findings. The NMR images were particularly valuable in demonstrating the interrelations between the great arteries and the anatomy of the outlet septum and the spatial relations between the ventricular septal defect and the great arteries. Although the atrioventricular (AV) valves were not consistently demonstrated, NMR imaging in two patients identified abnormalities of the mitral valve that were not seen with two-dimensional echocardiography. In one patient who had a superoinferior arrangement of the ventricles, NMR imaging was the most useful imaging technique for demonstrating the anatomy. In patients with double-outlet right ventricle, NMR imaging can provide clinically relevant and accurate morphologic information that may contribute to future improvement in patient management. PMID:2050920

Parsons, J M; Baker, E J; Anderson, R H; Ladusans, E J; Hayes, A; Fagg, N; Cook, A; Qureshi, S A; Deverall, P B; Maisey, M N

1991-07-01

424

Towards the invisible cryogenic system for Magnetic Resonance Imaging  

NASA Astrophysics Data System (ADS)

With about 10,000 Magnetic Resonance Imaging (MRI) systems installed worldwide, helium cooled magnets have become familiar equipment in hospitals and imaging centers. Patients and operators are only aware of the hissing sound of the Gifford-MacMahon refrigerator. Service technicians, however, still work with cryogenic fluids and cold gases, e.g. for replenishing the helium reservoir, inserting retractable current leads for magnet ramps, or replacing burst disks after a magnet quench. We will describe the steps taken at Oxford Magnet Technology towards the ultimate goal of a superconducting magnet being as simple as a household fridge. Early steps included the development of resealing quench valves, as well as permanently installed transfer siphons that only open when fully cooled to 4K. On recently launched 1.5 Tesla solenoid magnets, 500 A current leads are permanently fixed into the service turret, with hardly any boil-off penalty (40-50 cc/hr total). Ramping of the magnet has been fully automated, including electronic supervision of the gas-cooled current leads. One step ahead, the 1 Tesla High Field Open magnet is refrigerated by a single 4K Gifford MacMahon coldhead, relieving the user from the necessity to refill with helium. Our conduction cooled 0.2 Tesla HTS magnet testbed does not require liquid cryogens at any time in its life, including initial cool-down.

Steinmeyer, F.; Retz, P. W.; White, K.; Lang, A.; Stautner, W.; Smith, P. N.; Gilgrass, G.

2002-05-01

425

Microstrip resonator for GHz measurements of microscale magnetic objects (abstract)  

NASA Astrophysics Data System (ADS)

The integration of thin ferromagnetic films for applications above 1 GHz is expected to require micron scale, thin film objects (˜100 ?m×100 ?m×0.1 ?m) with volumes less than ˜10-15 m3. With maximum relative susceptibilities of ˜100, the measurement of these micro-objects by small perturbative techniques is experimentally challenging. Here, we describe the design, calibration, and performance of a microstrip resonator with a cavity volume of <10-6 m3 and a cross-sectional area <1 mm2. We have designed and built a gap-coupled, transmission-type, linear microstrip resonator. At even (odd) harmonics of the fundamental resonance, maxima of the electric (magnetic) field are established at the midpoint of the linear resonator. This resonator was designed to measure the magnetic responses of ensembles of micron scale ferromagnetic objects in the 0.4-10 GHz frequency range. The lowest resonant frequency (400 MHz) intentionally overlapped the upper operating frequency range of our lower frequency measurement systems, to permit comparison and calibration. The center conductor of the microstrip was photolithographically patterned in a 6 ?m thick gold film electroplated on a high quality microwave alumina substrate. A quasi transverse electric mode (TEM) was launched on the microstrip from a well-matched transition to a 3.5 mm coaxial connector. The microstrip resonator was excited by coupling to the microstrip transmission line through two 50 ?m capacitive gaps (˜0.07 pF) in the center conductor. The measurements were performed with HP 8510 network analyzer. The equivalent circuit of the microstrip transmission resonator and coupling capacitors were used to compute the 22 transmission resonances expected in the 0.4-10 GHz range. The results compare well with the measured resonances indicating the applicability of the quasi static approximation to 6 GHz. A perturbation theory for calculating the permeability from the measured cavity parameters was formulated for the microstrip resonator. Initial measurements on microscale magnetic objects are in good agreement with those obtained from other measurements.

Valanju, A. P.; Win, W.; Yun, E. J.; Walser, R. M.

1997-04-01

426

Selective actuation of arrays of carbon nanotubes using magnetic resonance.  

PubMed

We introduce the use of ferromagnetic resonance (FMR) to actuate mechanical resonances in as grown arrays of carbon nanotubes (CNTs) loaded with Ni particles (Ni-CNTs). This contactless method is closely related to the magnetic resonance force microscopy technique and provides spatial selectivity of actuation along the array. The Ni-CNT arrays are grown by chemical vapor deposition and are composed of homogeneous CNTs with uniform length (~600 nm) and almost equal diameter (~20 nm), which are loaded with Ni catalyst particles at their tips due to the tip growth mode. The vibrations of the Ni-CNTs are actuated by relying on the driving force that appears due to the FMR excited at about 2 GHz in the Ni particles (diameter ~100 nm). The Ni-CNT oscillations (frequency ~40 MHz) are detected mechanically by atomic force microscopy. The acquired oscillation images of the Ni-CNT uniform array reveal clear maxima in the spatial distribution of the oscillation amplitudes. We attribute these maxima to the "sensitive slices", i.e., the spatial regions of the Ni-CNT array where the FMR condition is met. Similar to magnetic resonance imaging, the sensitive slice is determined by the magnetic field gradient and moves along the Ni-CNT array as the applied magnetic field is ramped. Our excitation method does not require the presence of any additional microfabricated electrodes or coils near the CNTs and is particularly advantageous in cases where the traditional electrical actuation methods are not effective or cannot be implemented. The remote actuation can be effectively implemented also for arrays of other magnetic nanomechanical resonators. PMID:23742039

Volodin, Alexander; Santini, Claudia A; De Gendt, Stefan; Vereecken, Philippe M; Van Haesendonck, Chris

2013-07-23

427

Feshbach resonances in cesium at ultralow static magnetic fields  

NASA Astrophysics Data System (ADS)

We have observed Feshbach resonances for 133Cs atoms in two different hyperfine states at static magnetic fields of a few milligauss. These resonances are unusual for two main reasons. First, they are the lowest static-field resonances investigated up to now, and we explain their multipeak structure in these ultralow fields. Second, they are robust with respect to temperature effects. We have measured them using an atomic fountain clock and reproduced them using coupled-channels calculations, which are in excellent agreement with our measurements. We show that these are s-wave resonances due to a very weakly bound state of the triplet molecular Hamiltonian. We also describe a model explaining their asymmetric shape in the regime where the kinetic energy dominates over the coupling strength.

Papoular, D. J.; Bize, S.; Clairon, A.; Marion, H.; Kokkelmans, S. J. J. M. F.; Shlyapnikov, G. V.

2012-10-01

428

Kondo resonance lineshape of magnetic adatoms on decoupling layers  

NASA Astrophysics Data System (ADS)

The zero-bias resonance in the dI/dV tunneling spectrum recorded using a scanning tunneling microscope above a spin-1/2 magnetic adatom (such as Ti) adsorbed on a decoupling layer on a metal surface can be accurately fitted using the universal spectral function of the Kondo impurity model both at zero field and at finite external magnetic field. Excellent agreement is found both for the asymptotic low-energy part and for the high-energy logarithmic tails of the Kondo resonance. For finite magnetic field, the nonlinear fitting procedure consists of repeatedly solving the impurity model for different Zeeman energies in order to obtain accurate spectral functions which are compared with the experimental dI/dV curves. The experimental results at zero field are sufficiently restraining to enable an unprecedented reliability in the determination of the Kondo temperature, while at finite fields the results are more ambiguous and two different interpretations are proposed.

Žitko, Rok

2011-11-01

429

Magnetically tunable Mie resonance-based dielectric metamaterials.  

PubMed

Electromagnetic materials with tunable permeability and permittivity are highly desirable for wireless communication and radar technology. However, the tunability of electromagnetic parameters is an immense challenge for conventional materials and metamaterials. Here, we demonstrate a magnetically tunable Mie resonance-based dielectric metamaterials. The magnetically tunable property is derived from the coupling of the Mie resonance of dielectric cube and ferromagnetic precession of ferrite cuboid. Both the simulated and experimental results indicate that the effective permeability and permittivity of the metamaterial can be tuned by modifying the applied magnetic field. This mechanism offers a promising means of constructing microwave devices with large tunable ranges and considerable potential for tailoring via a metamaterial route. PMID:25384397

Bi, Ke; Guo, Yunsheng; Liu, Xiaoming; Zhao, Qian; Xiao, Jinghua; Lei, Ming; Zhou, Ji

2014-01-01

430

Magnetically tunable Mie resonance-based dielectric metamaterials  

PubMed Central

Electromagnetic materials with tunable permeability and permittivity are highly desirable for wireless communication and radar technology. However, the tunability of electromagnetic parameters is an immense challenge for conventional materials and metamaterials. Here, we demonstrate a magnetically tunable Mie resonance-based dielectric metamaterials. The magnetically tunable property is derived from the coupling of the Mie resonance of dielectric cube and ferromagnetic precession of ferrite cuboid. Both the simulated and experimental results indicate that the effective permeability and permittivity of the metamaterial can be tuned by modifying the applied magnetic field. This mechanism offers a promising means of constructing microwave devices with large tunable ranges and considerable potential for tailoring via a metamaterial route. PMID:25384397

Bi, Ke; Guo, Yunsheng; Liu, Xiaoming; Zhao, Qian; Xiao, Jinghua; Lei, Ming; Zhou, Ji

2014-01-01

431

NMR Spectroscopy for Thin Films by Magnetic Resonance Force Microscopy  

PubMed Central

Nuclear magnetic resonance (NMR) is a fundamental research tool that is widely used in many fields. Despite its powerful applications, unfortunately the low sensitivity of conventional NMR makes it difficult to study thin film or nano-sized samples. In this work, we report the first NMR spectrum obtained from general thin films by using magnetic resonance force microscopy (MRFM). To minimize the amount of imaging information inevitably mixed into the signal when a gradient field is used, we adopted a large magnet with a flat end with a diameter of 336??m that generates a homogeneous field on the sample plane and a field gradient in a direction perpendicular to the plane. Cyclic adiabatic inversion was used in conjunction with periodic phase inversion of the frequency shift to maximize the SNR. In this way, we obtained the 19F NMR spectrum for a 34?nm-thick CaF2 thin film. PMID:24217000

Won, Soonho; Saun, Seung-Bo; Lee, Soonchil; Lee, SangGap; Kim, Kiwoong; Han, Yunseok

2013-01-01

432

Magnetic resonance imaging safety of deep brain stimulator devices.  

PubMed

Magnetic resonance imaging (MRI) has become the standard of care for the evaluation of different neurological disorders of the brain and spinal cord due to its multiplanar capabilities and excellent soft tissue resolution. With the large and increasing population of patients with implanted deep brain stimulation (DBS) devices, a significant proportion of these patients with chronic neurological diseases require evaluation of their primary neurological disease processes by MRI. The presence of an implanted DBS device in a magnetic resonance environment presents potential hazards. These include the potential for induction of electrical currents or heating in DBS devices, which can result in neurological tissue injury, magnetic field-induced device migration, or disruption of the operational aspects of the devices. In this chapter, we review the basic physics of potential interactions of the MRI environment with implanted DBS devices, summarize results from phantom studies and clinical series, and discuss present recommendations for safe MRI in patients with implanted DBS devices. PMID:24112886

Oluigbo, Chima O; Rezai, Ali R

2013-01-01

433

Nuclear magnetic resonance investigations of the structure and magnetic properties of metallic multilayers and nanocomposites  

Microsoft Academic Search

Nuclear Magnetic Resonance (NMR) is a popular analysis technique in chemistry or biology but it is much less used in condensed matter physics and even less when the systems under investigation are ferromagnetic materials. However as a probe of the short-range chemical and topological order, NMR has proved useful to investigate the nanostructure of magnetic multilayers or granular systems and,

C. Mény

2010-01-01

434

In Vivo Assessment of Cold Adaptation in Insect Larvae by Magnetic Resonance Imaging and Magnetic  

E-print Network

crystal formation pose serious challenges to cell structure and function. Consequently, species livingIn Vivo Assessment of Cold Adaptation in Insect Larvae by Magnetic Resonance Imaging and Magnetic systems, we aimed at evaluating their potential to observe cold adaptations in living insect larvae

Hammerton, James

435

Solid-State Carbon-13 Nuclear Magnetic Resonance of Humic Acids at High Magnetic Field Strengths  

E-print Network

for cross state 13 C NMR spectra obtained with modern high-field spectrometers, polarization (CP). Similarly magnetic resonance (NMR) spectros- 1 H, 25 MHz 13 C) and low sample reorientation frequen-copy has become NMR spectra of humic acids at high magnetic width of the chemical shift anisotropy (CSA

Hemminga, Marcus A.

436

Oxygenation-sensitive contrast in magnetic resonance image of rodent brain at high magnetic fields  

Microsoft Academic Search

At high magnetic fields (7 and 8.4 T), water proton magnetic resonance images of brains of live mice and rats under pentobarbital anesthetization have been measured by a gradient echo pulse sequence with a spatial resolution of 65 x 65-microns pixel size and 700-microns slice thickness. The contrast in these images depicts anatomical details of the brain by numerous dark

S. Ogawa; T. M. Lee; A. S. Nayak; P. Glynn

1990-01-01

437

Biodegradation 9: 391, 1998. Nuclear Magnetic Resonance (NMR) Spectroscopy and Magnetic Resonance Imaging (MRI) are techniques of  

E-print Network

Biodegradation 9: 391, 1998. 391 Editorial Nuclear Magnetic Resonance (NMR) Spectroscopy applications. This special issue of Biodegradation is directed at presenting examples of applications of NMR with an introductionary paper about NMR and MRI in environmental science and engineering by Lens and Hemminga. With regard

Hemminga, Marcus A.

438

Co-Funding for the Conference on Magnetic Resonance in Biological Systems  

Microsoft Academic Search

The XXIst International Conference on Magnetic Resonance in Biological Systems (ICMRBS 2005), '60th anniversary of the discovery of Nuclear Magnetic Resonance,' was held between 16 and 21 January 2005 in Hyderabad, India. The meeting focused on a broad range of magnetic resonance methods as applied to studies of biological processes related to human health. The biennial ICMRBS has become the

Alan McLaughlin

2008-01-01

439

A GLRT AND BOOTSTRAP APPROACH TO DETECTION IN MAGNETIC RESONANCE FORCE MICROSCOPY  

E-print Network

A GLRT AND BOOTSTRAP APPROACH TO DETECTION IN MAGNETIC RESONANCE FORCE MICROSCOPY Pei­Jung Chung, USA moura@ece.cmu.edu ABSTRACT Magnetic resonance force microscopy (MRFM) is a tech- nology = 0.05, at SNR= -20 dB. 1. MOTIVATION Magnetic resonance force microscopy (MRFM), [3], and single spin

Moura, José

440

Single-spin measurement and decoherence in magnetic-resonance force microscopy G. P. Berman,1  

E-print Network

Single-spin measurement and decoherence in magnetic-resonance force microscopy G. P. Berman,1 F inversion CAI technique in magnetic-resonance force microscopy MRFM . We study the problem: What component.67.Lx I. INTRODUCTION Magnetic-resonance force microscopy MRFM is striv- ing for its ultimate goal

Goan, Hsi-Sheng

441

Theory of spin relaxation in magnetic resonance force microscopy D. Mozyrsky and I. Martina)  

E-print Network

Theory of spin relaxation in magnetic resonance force microscopy D. Mozyrsky and I. Martina; accepted 31 December 2002 We study relaxation of a spin in magnetic resonance force microscopy MRFM fluctuations. © 2003 American Institute of Physics. DOI: 10.1063/1.1554769 Magnetic resonance force microscopy

Hammel, P. Chris

442

Application of Magnetic Resonance Force Microscopy Cyclic Adiabatic Inversion for a Single-Spin Measurement  

E-print Network

Application of Magnetic Resonance Force Microscopy Cyclic Adiabatic Inversion for a Single using magnetic resonance force microscopy (MRFM) with a cyclic adiabatic inversion (CAI). This technique, 14].) One of them is based on a magnetic resonance force microscopy (MRFM). A MRFM was first proposed

Hammel, P. Chris

443

State-selective Rabi and Ramsey magnetic resonance line shapes G. Xu and D. J. Heinzen  

E-print Network

State-selective Rabi and Ramsey magnetic resonance line shapes G. Xu and D. J. Heinzen Department-selective Rabi and Ramsey magnetic-resonance experiments on ground-state 133 Cs(F 4) atoms. Novel line shapes-selective Rabi and Ramsey magnetic-resonance experiments on 133 Cs at- oms in their 62 S1/2 , F 4 ground

Heinzen, Daniel J.

444

PREDICTIVE THERMAL MODEL FOR INDIRECT TEMPERATURE MEASUREMENT INSIDE ATOMIC CELL OF NUCLEAR MAGNETIC RESONANCE GYROSCOPE  

E-print Network

MAGNETIC RESONANCE GYROSCOPE M. Salleras* , E.J. Eklund, I.P. Prikhodko, and A.M. Shkel Microsystems. The device under study is a nuclear magnetic resonance gyroscope, an instrument that is highly sensitive of the temperature inside the atomic cell. KEYWORDS Predictive models, atomic gyroscope, nuclear magnetic resonance

Tang, William C

445

ON THE CONVERGENCE OF THE HARMONIC Bz ALGORITHM IN MAGNETIC RESONANCE ELECTRICAL IMPEDANCE TOMOGRAPHY  

E-print Network

the convergence of the harmonic Bz algorithm in magnetic resonance electrical impedance tomography J.J. Liu J.K. Seo M. Sini E.J. Woo § May 31, 2006 Abstract. Magnetic Resonance Electrical Impedance Tomography Introduction Magnetic Resonance Electrical Impedance Tomography (MREIT) is an electrical conduc- tivity imaging

446

Nuclear magnetic resonance investigations of the structure and magnetic properties of metallic multilayers and nanocomposites  

Microsoft Academic Search

As a probe of the short-range chemical and topological order, nuclear magnetic resonance (NMR) has proved useful to investigate\\u000a the nanostructure of magnetic multilayers or granular systems and, in particular, to evaluate the nature, sharp or diffuse,\\u000a of interfaces in such nanocomposites. These structural aspects are shortly reviewed in the paper. A larger emphasis is given\\u000a to the magnetic properties

P. Panissod; C. Mény

2000-01-01

447

Paramagnetic and ferromagnetic resonance imaging with a tip-on-cantilever magnetic resonance force microscope  

NASA Astrophysics Data System (ADS)

A magnetic resonance force microscope with a "tip-on-cantilever" configuration was used to compare imaging characteristics of paramagnetic and ferromagnetic samples. Three-dimensional electron paramagnetic resonance (EPR) imaging of diphenylpicrylhydrazil (DPPH) particles was accomplished by scanning the sample in two dimensions while stepping an external field. The EPR force map showed broad response reflecting the size and shape of the sample, allowing a three-dimensional real-space magnetization image to be successfully reconstructed. In contrast to the EPR case, ferromagnetic resonance imaging of a micron-scale yttrium iron garnet sample showed no significant line broadening despite the strong field gradient (˜10 G/?m). Two-dimensional force maps revealed spatial dependence of magnetostatic and magnetoelastic modes.

Wago, K.; Botkin, D.; Yannoni, C. S.; Rugar, D.

1998-05-01

448

Travelling Wave Magnetic Resonance Imaging at 3 Tesla  

E-print Network

Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transversal electric modes and it can propagate any frequency. To investigate the potential benefits for whole-body imaging at 3 T, we compare numerical simulations at 1.5 T, 3 T, 7 T, and 9 T via the propagation of the parallel-plate waveguide principal mode filled with a cylindrical phantom and two surface coils. B1 mapping was computed to investigate the feasibility of this approach at 3T. The point spread function method was used to measure the imager performance for the traveling-wave magnetic resonance imaging experiment. Human leg images were acquired to experimentally validate this approach. The principal mode shows very little field magni...

Vazquez, F; Marrufo, O; Rodriguez, A O

2013-01-01

449

Probing electric field control of magnetism using ferromagnetic resonance.  

PubMed

Exchange coupled CoFe/BiFeO3 thin-film heterostructures show great promise for power-efficient electric field-induced 180° magnetization switching. However, the coupling mechanism and precise qualification of the exchange coupling in CoFe/BiFeO3 heterostructures have been elusive. Here we show direct evidence for electric field control of the magnetic state in exchange coupled CoFe/BiFeO3 through electric field-dependent ferromagnetic resonance spectroscopy and nanoscale spatially resolved magnetic imaging. Scanning electron microscopy with polarization analysis images reveal the coupling of the magnetization in the CoFe layer to the canted moment in the BiFeO3 layer. Electric field-dependent ferromagnetic resonance measurements quantify the exchange coupling strength and reveal that the CoFe magnetization is directly and reversibly modulated by the applied electric field through a ~180° switching of the canted moment in BiFeO3. This constitutes an important step towards robust repeatable and non-volatile voltage-induced 180° magnetization switching in thin-film multiferroic heterostructures and tunable RF/microwave devices. PMID:25631924

Zhou, Ziyao; Trassin, Morgan; Gao, Ya; Gao, Yuan; Qiu, Diana; Ashraf, Khalid; Nan, Tianxiang; Yang, Xi; Bowden, S R; Pierce, D T; Stiles, M D; Unguris, J; Liu, Ming; Howe, Brandon M; Brown, Gail J; Salahuddin, S; Ramesh, R; Sun, Nian X

2015-01-01

450

Contour-based brain segmentation method for magnetic resonance imaging human head scans.  

PubMed

The high-resolution magnetic resonance brain images often contain some nonbrain tissues (ie, skin, fat, muscle, neck, eye balls, etc) compared with the functional images such as positron emission tomography, single-photon emission computed tomography, and functional magnetic resonance imaging (MRI) scans, which usually contain few nonbrain tissues. Automatic segmentation of brain tissues from MRI scans remains a challenging task due to the variation in shape and size, use of different pulse sequences, overlapping signal intensities and imaging artifacts. This article presents a contour-based automatic brain segmentation method to segment the brain regions from T1-, T2-, and proton density-weighted MRI of human head scans. The proposed method consists of 2 stages. In stage 1, the brain regions in the middle slice is extracted. Many of the existing methods failed to extract brain regions in the lower and upper slices of the brain volume, where the brain appears in more than 1 connected region. To overcome this problem, in the proposed method, a landmark circle is drawn at the center of the extracted brain region of a middle slice and is likely to pass through all the brain regions in the remaining lower and upper slices irrespective of whether the brain is composed of 1 or more connected components. In stage 2, the brain regions in the remaining slices are extracted with reference to the landmark circle obtained in stage 1. The proposed method is robust to the variability of brain anatomy, image orientation, and image type, and it extracts the brain regions accurately in T1-, T2-, and proton density-weighted normal and abnormal brain images. Experimental results by applying the proposed method on 100 volumes of brain images show that the proposed method exhibits best and consistent performance than by the popular existing methods brain extraction tool, brain surface extraction, watershed algorithm, hybrid watershed algorithm, and skull stripping using graph cuts. PMID:23674005

Somasundaram, K; Kalavathi, P

2013-01-01

451

Spectrally Resolved Magnetic Resonance Imaging of the XenonBiosensor  

SciTech Connect

Due to its ability to non-invasively record images, as well as elucidate molecular structure, nuclear magnetic resonance is the method of choice for applications as widespread as chemical analysis and medical diagnostics. Its detection threshold is, however, limited by the small polarization of nuclear spins in even the highest available magnetic fields. This limitation can, under certain circumstances, be alleviated by using hyper-polarized substances. Xenon biosensors make use of the sensitivity gain of hyperpolarized xenon to provide magnetic resonance detection capability for a specific low-concentration target. They consist of a cryptophane cage, which binds one xenon atom, and which has been connected via a linker to a targeting moiety such as a ligand or antibody. Recent work has shown the possibility of using the xenon biosensor to detect small amounts of a substance in a heterogeneous environment by NMR. Here, we demonstrate that magnetic resonance (MR) provides the capability to obtain spectrally and spatially resolved images of the distribution of immobilized biosensor, opening the possibility for using the xenon biosensor for targeted imaging.

Hilty, Christian; Lowery, Thomas; Wemmer, David; Pines, Alexander

2005-07-15

452

Specific pathogen detection using bioorthogonal chemistry and diagnostic magnetic resonance.  

PubMed

The development of faster and more sensitive detection methods capable of identifying specific bacterial species and strains has remained a longstanding clinical challenge. Thus to date, the diagnosis of bacterial infections continues to rely on the performance of time-consuming microbiological cultures. Here, we demonstrate the use of bioorthogonal chemistry for magnetically labeling specific pathogens to enable their subsequent detection by nuclear magnetic resonance. Antibodies against a bacterial target of interest were first modified with trans-cyclooctene and then coupled to tetrazine-modified magnetic nanoprobes, directly on the bacteria. This labeling method was verified by surface plasmon resonance as well as by highly specific detection of Staphylococcus aureus using a miniaturized diagnostic magnetic resonance system. Compared to other copper-free bioorthogonal chemistries, the cycloaddition reaction reported here displayed faster kinetics and yielded higher labeling efficiency. Considering the short assay times and the portability of the necessary instrumentation, it is feasible that this approach could be adapted for clinical use in resource-limited settings. PMID:22043803

Liong, Monty; Fernandez-Suarez, Marta; Issadore, David; Min, Changwook; Tassa, Carlos; Reiner, Thomas; Fortune, Sarah M; Toner, Mehmet; Lee, Hakho; Weissleder, Ralph

2011-12-21

453

Specific Pathogen Detection Using Bioorthogonal Chemistry and Diagnostic Magnetic Resonance  

PubMed Central

The development of faster and more sensitive detection methods capable of identifying specific bacterial types and strains has remained a longstanding clinical challenge. Thus to date, the diagnosis of bacterial infections continues to rely on the performance of time-consuming cultures. Here, we demonstrate the use of bioorthogonal chemistry for magnetically labeling specific pathogens to enable their subsequent detection by nuclear magnetic resonance. Antibodies against a bacterial target of interest were first modified with trans-cyclooctene and then coupled to tetrazine-modified magnetic nanoprobes, directly on the bacteria. This labeling method was verified using surface plasmon resonance as well as by using a miniaturized diagnostic magnetic resonance device capable of highly specific detection of Staphylococcus aureus. Compared to other copper-free bioorthogonal chemistries, the cycloaddition reaction described displayed faster kinetics and yielded higher labeling efficiency. Considering the short assay times and the portability of the necessary instrumentation, it is feasible that this approach could be adapted for clinical use in resource-limited settings. PMID:22043803

Liong, Monty; Fernandez-Suarez, Marta; Issadore, David; Min, Changwook; Tassa, Carlos; Reiner, Thomas; Fortune, Sarah M.; Toner, Mehmet; Lee, Hakho; Weissleder, Ralph

2011-01-01

454

Magnetic field sensor based on anti-resonant reflecting guidance in the magnetic gel-coated hollow core fiber.  

PubMed

A compact all-fiber magnetic field sensor based on the magnetic gel coated hollow core fiber (HCF) has been proposed and experimentally demonstrated. A double-layered Fabry-Perot resonator is formed by coating a magnetic gel layer on the surface of the HCF. Anti-resonant reflecting guidance of light can be achieved in the HCF, and leaky mode is induced at resonant wavelength of the double-layered Fabry-Perot resonator, which results in lossy dips in the transmission spectrum of the HCF. Due to the tunable magneto-elastic effect, the shape of the magnetic gel is deformed with the external magnetic field, which results in a change of the resonate condition for the double-layered Fabry-Perot resonator. The magnetic field can be measured by interrogating the wavelength of the lossy dip. The experimental results show that a magnetic field sensitivity of 245??pm/Oe is achieved. PMID:25361337

Gao, R; Jiang, Y; Zhao, Yang

2014-11-01

455

Neuronavigation using an articulated arm with a bayonet probe on a computer graphic composite of magnetic resonance and computerized tomography images.  

PubMed

This report describes a neurosurgical navigational system using a newly-designed articulated arm with an interchangeable probe shaped like a bayonet, which can be used in deep structures through narrow openings. This system enables three-dimensional integration of magnetic resonance and computed tomographical images, and thereby yields computer graphic composites of the scalp, brain, skull, and vessels. The arm was used in 15 patients during open brain surgery, including 5 skull base procedures. This system was useful for comprehension of skull base anatomy and could conveniently be used in microscopic neurosurgical procedures without limiting the operative field. PMID:9802038

Hayashi, N; Endo, S; Ikeda, H; Takaku, A

1998-09-01

456

Precise wavefunction engineering with magnetic resonance  

E-print Network

Controlling quantum fluids at their fundamental length scale will yield superlative quantum simulators, precision sensors, and spintronic devices. This scale is typically below the optical diffraction limit, precluding precise wavefunction engineering using optical potentials alone. We present a protocol to rapidly control the phase and density of a quantum fluid down to the healing length scale using strong time-dependent coupling between internal states of the fluid in a magnetic field gradient. We demonstrate this protocol by simulating the creation of a single stationary soliton and double soliton states in a Bose-Einstein condensate with control over the individual soliton positions and trajectories, using experimentally feasible parameters. Such states are yet to be realized experimentally, and are a path towards engineering soliton gases and exotic topological excitations.

L. M. Bennie; P. B. Wigley; S. S. Szigeti; M. Jasperse; J. J. Hope; L. D. Turner; R. P. Anderson

2014-12-22

457

Diamond based single molecule magnetic resonance spectroscopy  

E-print Network

The detection of a nuclear spin in an individual molecule represents a key challenge in physics and biology whose solution has been pursued for many years. The small magnetic moment of a single nucleus and the unavoidable environmental noise present the key obstacles for its realization. Here, we demonstrate theoretically that a single nitrogen-vacancy (NV) center in diamond can be used to construct a nano-scale single molecule spectrometer that is capable of detecting the position and spin state of a single nucleus and can determine the distance and alignment of a nuclear or electron spin pair. The proposed device will find applications in single molecule spectroscopy in chemistry and biology, such as in determining protein structure or monitoring macromolecular motions and can thus provide a tool to help unravelling the microscopic mechanisms underlying bio-molecular function.

Jianming Cai; Fedor Jelezko; Martin B. Plenio; Alex Retzker

2012-12-07

458

High-field magnetic resonance imaging.  

PubMed

This article explores the role of high-field (HF) MR imaging in medicine. It analyzes advantages of HF MR imaging in application to human subjects and how best they can be used to unravel the secrets of diseases, such as multiple sclerosis. Special emphasis is placed on morphologic imaging to highlight the role of soft tissue contrast, MR spectroscopy to showcase the ability of detecting biochemical information, and functional MR imaging as an emerging technology for assessing tissue function with the possibility of eventual introduction to the clinical arena. In this article, hardware issues, such as RF coils for HF systems with a static magnetic field of 3.0 T or higher are also discussed. PMID:19064204

Kangarlu, Alayar

2009-02-01

459

Magnetic resonance imaging and aneurysm clips.  

PubMed

The problem of implanted metals causing tissue damage by movement in patients exposed to MRI fields has produced a confusing welter of erroneous, pseudoscientific publications about magnetics, metals, medical equipment, and tissue compatibility. Quite simply, among the devices made for implantation, only those fabricated of stainless steel have the ferromagnetic properties capable of causing such accidents. The author, who introduced the basic design of the modern aneurysm clip in the late 1960s and then a cobalt nickel alloy as an improvement over steel, while chairing the neurosurgical committee assigned to the task of establishing neurosurgical standards at American Society for Testing and Materials, exposes this flawed information and offers clear guidelines for avoiding trouble. PMID:22503120

McFadden, Joseph T

2012-07-01

460

Instant Anatomy  

NSDL National Science Digital Library

There might not be such a thing as "instant" anatomy, but this nice site does offer up some podcasts on the matter that can provide a pathway to anatomical enlightenment. The site was created by Robert Whitaker, a professor of clinically applied topographical anatomy in the United Kingdom. Visitors can wander through a range of useful instructional materials here, and the nine free podcasts are some of the best items available. The titles include "Surface Anatomy," "Classification of the Joints," "Venous Drainage of the Limbs," and "Principles of Movements at Joints in the Upper Limb." Also, users have access to several free podcast apps, including a series of flashcards and embryology diagrams.

Whitaker, Robert

461

Human Anatomy  

NSDL National Science Digital Library

Please find links below: Human Anatomy Human Anatomy Online Human Body - Gray s Anatomy - Digestive Aparatus MEDtropolis - Virtual Body - can be viewed in English or Spanish. Contains tours of the Human Brain, Skeleton, Human Heart, and Digestive Tract. Respiratory System National Heart, Lung, and Blood Institute HealthTalk COPD (chronic obstructive pulmonary disease) American Lung Association - Disease Finder Association of Legal Aid Attorneys/UAW 2325 Canadian Lung Association Kids Health Family Living and Personal Living - Ms. Schultz added this link because on this page there is CDC, American ...

Schultz, Ms.

2007-11-09

462

Magnetic damping: domain wall dynamics versus local ferromagnetic resonance.  

PubMed

Magnetic relaxation is one of the dominating features of magnetization dynamics. Depending on the magnetic structure and the experimental approach, different magnitudes of the damping parameter are reported even for a given material. In this study, we experimentally address this issue by accessing the damping parameter in the same magnetic nanotracks using different approaches: local ferromagnetic resonance (?=0.0072) and field-driven domain wall dynamics (?=0.023). The experimental results cannot fully be accounted for by modeling only roughness in micromagnetic simulations. Consequently, we have included nonlocal texture induced damping to the micromagnetic code. We find excellent agreement with the observed increased damping in the vortex structures for the same input Gilbert alpha when texture-induced nonlocal damping is included. PMID:25526154

Weindler, T; Bauer, H G; Islinger, R; Boehm, B; Chauleau, J-Y; Back, C H

2014-12-01

463

Synthesis of gadolinium oxide magnetoliposomes for magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

A method for the synthesis of gadolinium oxide magnetoliposomes, i.e., nanosized gadolinium oxide magnetic particles coated by a phospholipid membrane, is presented. Magnetoliposomes were prepared by reacting lauric acid coated gadolinium oxide nanoparticles with dimyristoylphosphatidylcholine liposomes prepared using a direct injection method. The gadolinium oxide magnetoliposomes were characterized using transmission electron microscopy imaging, x-ray diffraction, and fluorescence. The magnetic properties of the magnetoliposomes were investigated with a superconducting quantum interference device magnetometer and nuclear magnetic resonance (NMR) spectrometry. Our results indicate that the magnetoliposomes contain approximately spherical nanoparticles averaging 20 nm in diameter. The occurrence of a phospholipid bilayer surrounding the magnetic particles is confirmed both by transmission electron micrographs of samples negatively stained with uranyl acetate and by digital fluorescence imaging microscopy measurements of magnetoliposomes labeled with fluorescein. The particles are paramagnetic at room temperature. NMR measurements show that the ratio between the relaxivities of the particles depends largely on their preparation.

Roberts, Danielle; Zhu, Weibe L.; Frommen, Christoph M.; Rosenzweig, Zeev

2000-05-01

464

Magnetic Damping: Domain Wall Dynamics versus Local Ferromagnetic Resonance  

NASA Astrophysics Data System (ADS)

Magnetic relaxation is one of the dominating features of magnetization dynamics. Depending on the magnetic structure and the experimental approach, different magnitudes of the damping parameter are reported even for a given material. In this study, we experimentally address this issue by accessing the damping parameter in the same magnetic nanotracks using different approaches: local ferromagnetic resonance (? =0.0072 ) and field-driven domain wall dynamics (? =0.023 ). The experimental results cannot fully be accounted for by modeling only roughness in micromagnetic simulations. Consequently, we have included nonlocal texture induced damping to the micromagnetic code. We find excellent agreement with the observed increased damping in the vortex structures for the same input Gilbert alpha when texture-induced nonlocal damping is included.

Weindler, T.; Bauer, H. G.; Islinger, R.; Boehm, B.; Chauleau, J.-Y.; Back, C. H.

2014-12-01

465

Neutron magnetic resonance and non-specular reflection from a magnetic film placed in an oscillating magnetic field  

NASA Astrophysics Data System (ADS)

Experimental results on neutron reflection from a magnetic film placed in an oscillating magnetic field are reported. We found evidence for neutron spin resonance in the film and observed a spatial beam-splitting. The beam-splitting finds its origin in the exchange of an energy quantum hslash? between the oscillating field and the neutron.

Kozhevnikov, S. V.; Ignatovich, V. K.; Nikitenko, Yu V.; Ott, F.; Radu, F.; Rühm, A.; Major, J.

2012-02-01

466

Resonant Magnetic Field Sensors Based On MEMS Technology.  

PubMed

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration. PMID:22408480

Herrera-May, Agustín L; Aguilera-Cortés, Luz A; García-Ramírez, Pedro J; Manjarrez, Elías

2009-01-01

467

MRI (Magnetic Resonance Imaging) : tour an MRI machine  

NSDL National Science Digital Library

In this resource, appropriate for students in high school and beyond, the user navigates through a five-page illustrated explanation of MRI (magnetic resonance imaging). Each page profiles a different step in the MRI process. The resource addresses the science behind how MRI works, revealing how a strong magnet and radio wave pulses affect the targeted area of the body and allow that area to be imaged. As part of a set of materials about brain scanning technologies, this resource focuses on brain MRI. Copyright 2005 Eisenhower National Clearinghouse

David Grubin Productions

2001-01-01

468

Nuclear magnetic resonance in the Condon domain state  

NASA Astrophysics Data System (ADS)

Calculations of splittings of nuclear magnetic resonance (NMR) lines at diamagnetic phase transitions are carried out for a three-dimensional electron gas. There is a good agreement between the theory and the experimental results in silver. The size of the Condon domains and the width of the domain walls are estimated. Experimental results on the de Haas-van Alphen effect in silver are analyzed with the help of the temperature-magnetic-field diagram. The results of the analysis are in agreement with the NMR data. The NMR splitting in a two-dimensional electron gas due to Condon domains is calculated.

Gordon, A.; Grushko, B.; Vagner, I. D.; Wyder, P.

1991-11-01

469

General Magnetic Transition Dipole Moments for Electron Paramagnetic Resonance  

NASA Astrophysics Data System (ADS)

We present general expressions for the magnetic transition rates in electron paramagnetic resonance (EPR) experiments of anisotropic spin systems in the solid state. The expressions apply to general spin centers and arbitrary excitation geometry (Voigt, Faraday, and intermediate). They work for linear and circular polarized as well as unpolarized excitation, and for crystals and powders. The expressions are based on the concept of the (complex) magnetic transition dipole moment vector. Using the new theory, we determine the parities of ground and excited spin states of high-spin (S =5 /2 ) FeIII in hemin from the polarization dependence of experimental EPR line intensities.

Nehrkorn, Joscha; Schnegg, Alexander; Holldack, Karsten; Stoll, Stefan

2015-01-01

470

High-field small animal magnetic resonance oncology studies  

NASA Astrophysics Data System (ADS)

This review focuses on the applications of high magnetic field magnetic resonance imaging (MRI) and spectroscopy (MRS) to cancer studies in small animals. High-field MRI can provide information about tumor physiology, the microenvironment, metabolism, vascularity and cellularity. Such studies are invaluable for understanding tumor growth and proliferation, response to treatment and drug development. The MR techniques reviewed here include 1H, 31P, chemical exchange saturation transfer imaging and hyperpolarized 13C MRS as well as diffusion-weighted, blood oxygen level dependent contrast imaging and dynamic contrast-enhanced MRI. These methods have been proven effective in animal studies and are highly relevant to human clinical studies.

Bokacheva, Louisa; Ackerstaff, Ellen; LeKaye, H. Carl; Zakian, Kristen; Koutcher, Jason A.

2014-01-01

471

The Alfvén resonance in a magnetized dusty plasma  

NASA Astrophysics Data System (ADS)

Wave propagation in a dusty magnetized plasma at frequencies below and of the order of the ion-cyclotron frequency, and with a non-zero electron temperature is considered. The general dispersion relation for waves propagating at an arbitrary angle with respect to the external magnetic field and for finite ion-cyclotron frequency is derived and discussed. Modification of the Alfvén resonance absorption mechanism due to the presence of a finite proportion of the negative charge of the plasma on stationary dust grains is investigated.

Cramer, N. F.; Vladimirov, S. V.

1996-05-01

472

General magnetic transition dipole moments for electron paramagnetic resonance.  

PubMed

We present general expressions for the magnetic transition rates in electron paramagnetic resonance (EPR) experiments of anisotropic spin systems in the solid state. The expressions apply to general spin centers and arbitrary excitation geometry (Voigt, Faraday, and intermediate). They work for linear and circular polarized as well as unpolarized excitation, and for crystals and powders. The expressions are based on the concept of the (complex) magnetic transition dipole moment vector. Using the new theory, we determine the parities of ground and excited spin states of high-spin (S=5/2) Fe^{III} in hemin from the polarization dependence of experimental EPR line intensities. PMID:25615456

Nehrkorn, Joscha; Schnegg, Alexander; Holldack, Karsten; Stoll, Stefan

2015-01-01

473

Innovative computing for diagnoses from medical, magnetic-resonance imaging  

SciTech Connect

The author presents a final report on a Laboratory-Directed Research and Development (LDRD) project, Innovative Computing for Diagnoses from Medical, Magnetic-Resonance Imaging, performed during fiscal years 1992 and 1993. The project defined a role for high-performance computing in surgery: the supercomputer can automatically summarize the three-dimensional extents of lesions and other clinically-relevant structures, and can deliver these summaries to workstation-based, augmented-reality environments at the clinical site. The author developed methods and software to make these summaries from the digital data already acquired using clinical, magnetic-resonance machines. In joint work with Albuquerque`s Department of Veterans Affairs Hospital, the author applied this work, and obtained a basis for planning, for rehearsal, and for guidance during surgery.

Diegert, C.

1997-01-01

474

Computed tomography and magnetic resonance imaging comparisons in boxers  

SciTech Connect

The efficacy of computed tomography (CT) and magnetic resonance imaging (MRI) in identifying traumatic injuries of the brain was compared in a referred population of 21 amateur and professional boxers. Three boxers displayed CT scans with equivocal findings that were verified as artifacts by MRI. Eleven boxers had both CT and MRI scans with normal findings, and 7 boxers had both CT and MRI scans with abnormal findings. There were no instances where abnormalities demonstrated on CT scanning were not detected by MRI. However, some abnormalities detected on MRI were not detected on CT scans. These included a subdural hematoma, white-matter changes, and a focal contusion. Magnetic resonance imaging appears to be the neuroradiodiagnostic test of choice compared with CT.

Jordan, B.D. (Hospital for Special Surgery, New York, NY (USA)); Zimmerman, R.D. (New York Hospital-Cornell Medical Center, NY (USA))

1990-03-23

475

Time-resolved reaction yield detected magnetic resonance (RYDMR)  

NASA Astrophysics Data System (ADS)

Novel time-resolved reaction yield detected magnetic resonance studies are reported on exciplex systems consisting of pyrene and dicyanobenzene. It is shown that the fluorescence from the systems, observed under the action of a static and a resonant magnetic field, exhibits a marked variation in time, including oscillations, after the creation of the exciplex. This variation is characteristically different between the three isomers of the dicyanobenzene molecule. In a theoretical analysis, the major experimental features are reproduced and it is suggested that oscillations observed in the fluorescence decay curves may correlate with ST 0 mixing quantum beats. This experiment provides a new method for studying the spin evolution inside radical pair systems and for estimating the lifetime of the spin-correlated radical pair.

Batchelor, S. N.; McLauchlan, K. A.; Shkrob, I. A.

1991-06-01

476

Basic principles of magnetic resonance imaging--an update.  

PubMed

Magnetic resonance (MR) imaging technology has undergone many technologic advances over the past few years. Many of these advances were stimulated by the wealth of information emerging from nuclear magnetic resonance research in the areas of new and optimal scanning methods and radio-frequency coil design. Other changes arose from the desire to improve image quality, ease siting restrictions and generally facilitate the clinical use of MR equipment. Many questions, however, remain unanswered. Perhaps the most controversial technologic question involves the optimal field strength required for imaging or spectroscopic applications or both. Other issues include safety and clinical efficacy. Technologic issues affect all aspects of MR use including the choice of equipment, examination procedure and image interpretation. Thus, an understanding of recent changes and their theoretic basis is necessary. PMID:3911591

Scherzinger, A L; Hendee, W R

1985-12-01

477

Basic principles of magnetic resonance imaging - an update  

SciTech Connect

Magnetic resonance (MR) imaging technology has undergone many technologic advances over the past few years. Many of these advances were stimulated by the wealth of information emerging from nuclear magnetic resonance research in the areas of new and optimal scanning methods and radio-frequency coil design. Other changes arose from the desire to improve image quality, ease siting restrictions and generally facilitate the clinical use of MR equipment. Many questions, however, remain unanswered. Perhaps the most controversial technologic question involves the optimal field strength required for imaging or spectroscopic applications or both. Other issues include safety and clinical efficacy. Technologic issues affect all aspects of MR use including the choice of equipment, examination procedure and image interpretation. Thus, an understanding of recent changes and their theoretic basis is necessary. 92 references, 10 figures, 1 table.

Scherzinger, A.L.; Hendee, W.R.

1985-12-01

478

[Fetal magnetic resonance imaging evaluation of congenital diaphragmatic hernia].  

PubMed

A diaphragmatic hernia is defined as the protrusion of abdominal viscera into the thoracic cavity through a normal or pathological orifice. The herniated viscera compress the lungs, resulting in pulmonary hypoplasia and secondary pulmonary hypertension, which are the leading causes of neonatal death in patients with congenital diaphragmatic hernia. Congenital diaphragmatic hernia is diagnosed by sonography in routine prenatal screening. Although magnetic resonance imaging is fundamentally used to determine whether the liver is located within the abdomen or has herniated into the thorax, it also can provide useful information about other herniated structures and the degree of pulmonary hypoplasia. The aim of this article is to review the fetal magnetic resonance findings for congenital diaphragmatic hernia and the signs that enable us to establish the neonatal prognosis when evaluating pulmonary hypoplasia. PMID:23523414

Sebastià, C; Garcia, R; Gomez, O; Paño, B; Nicolau, C

2014-01-01

479

Use of contrast agents in oncological imaging: magnetic resonance imaging  

PubMed Central

Abstract Magnetic resonance plays a leading role in the management of oncology patients, providing superior contrast resolution and greater sensitivity compa