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1

Magnetic resonance and the human brain: anatomy, function and metabolism.  

PubMed

The introduction and development, over the last three decades, of magnetic resonance (MR) imaging and MR spectroscopy technology for in vivo studies of the human brain represents a truly remarkable achievement, with enormous scientific and clinical ramifications. These effectively non-invasive techniques allow for studies of the anatomy, the function and the metabolism of the living human brain. They have allowed for new understandings of how the healthy brain works and have provided insights into the mechanisms underlying multiple disease processes which affect the brain. Different MR techniques have been developed for studying anatomy, function and metabolism. The primary focus of this review is to describe these different methodologies and to briefly review how they are being employed to more fully appreciate the intricacies associated with the organ, which most distinctly differentiates the human species from the other animal forms on earth. PMID:16568243

Talos, I-F; Mian, A Z; Zou, K H; Hsu, L; Goldberg-Zimring, D; Haker, S; Bhagwat, J G; Mulkern, R V

2006-05-01

2

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

3

Sexual dimorphism in the human brain: evaluation of tissue volume, tissue composition and surface anatomy using magnetic resonance imaging  

Microsoft Academic Search

Magnetic resonance imaging (MRI) was used to evaluate sex differences in brain morphology by comparing measures of brain tissue volume, brain tissue composition (proportions of gray and white matter), and measures of cortical surface anatomy. A large and well-matched sample of healthy women (n=42) and healthy men (n=42) were evaluated. There was a significant gender effect on intracranial volume, males

Peg Nopoulos; Michael Flaum; Dan O’Leary; Nancy C Andreasen

2000-01-01

4

Prediction of transitional lumbosacral anatomy on magnetic resonance imaging of the lumbar spine  

PubMed Central

AIM: To evaluate two simple angle measurements for predicting lumbosacral transitional vertebra (LSTV) in magnetic resonance imaging (MRI) studies of the spine. METHODS: The lumbar spine MRI studies of 50 subjects with LSTV and 50 subjects with normal lumbosacral anatomy were retrospectively evaluated. In each study, the mid-sagittal T2-weighted image was used to measure the angle formed by a line parallel to the superior surface of the sacrum and a line perpendicular to the axis of the scan table (A-angle), as well as the angle formed by a line parallel to the superior endplate of the L3 vertebra and a line parallel to the superior surface of the sacrum (B-angle). RESULTS: The total study population consisted of 100 subjects (46 males, 54 females, 51 ± 16 years old). There were no differences in age and sex between the two groups. Both A-angle and B-angle were significantly increased in subjects with LSTV compared to controls (P < 0.05). The optimal cut-off values of A-angle and B-angle for the prediction of LSTV were 39.8° (sensitivity = 80%, specificity = 80%, accuracy = 83%; 95% confidence interval = 74%-89%, P = 0.0001) and 35.9° (sensitivity = 80%, specificity = 54%, accuracy = 69%; 95% confidence interval = 59%-78%, P = 0.0005), respectively. CONCLUSION: On sagittal MR images of the lumbar spine, an increased A-angle and/or B-angle should alert the radiologist to the presence of LSTV. PMID:22468190

Chalian, Majid; Soldatos, Theodoros; Carrino, John A; Belzberg, Alan J; Khanna, Jay; Chhabra, Avneesh

2012-01-01

5

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

6

Anatomy of a live invertebrate revealed by manganese-enhanced Magnetic Resonance Imaging  

Microsoft Academic Search

Non-invasive imaging technologies such as Magnetic Resonance Imaging (MRI) are increasingly in demand by researchers in many biological disciplines. However, when imaging small animals such as invertebrates, not only is the use of high-field magnets necessary to gain satisfactory spatial resolution, but the achievement of adequate contrast between tissues also requires the identification of applicable imaging parameters by means of

Jens Herberholz; Christopher J. Mims; X Xihang; Dh Edwards

2004-01-01

7

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

8

Anatomy, Variants, and Pathologies of the Superior Glenohumeral Ligament: Magnetic Resonance Imaging with Three-Dimensional Volumetric Interpolated Breath-Hold Examination Sequence and Conventional Magnetic Resonance Arthrography  

PubMed Central

The purpose of this review was to demonstrate magnetic resonance (MR) arthrography findings of anatomy, variants, and pathologic conditions of the superior glenohumeral ligament (SGHL). This review also demonstrates the applicability of a new MR arthrography sequence in the anterosuperior portion of the glenohumeral joint. The SGHL is a very important anatomical structure in the rotator interval that is responsible for stabilizing the long head of the biceps tendon. Therefore, a torn SGHL can result in pain and instability. Observation of the SGHL is difficult when using conventional MR imaging, because the ligament may be poorly visualized. Shoulder MR arthrography is the most accurately established imaging technique for identifying pathologies of the SGHL and associated structures. The use of three dimensional (3D) volumetric interpolated breath-hold examination (VIBE) sequences produces thinner image slices and enables a higher in-plane resolution than conventional MR arthrography sequences. Therefore, shoulder MR arthrography using 3D VIBE sequences may contribute to evaluating of the smaller intraarticular structures such as the SGHL. PMID:25053912

Ogul, Hayri; Karaca, Leyla; Can, Cahit Emre; Pirimoglu, Berhan; Tuncer, Kutsi; Topal, Murat; Okur, Aylin

2014-01-01

9

Magnetic resonance imaging of ankle ligaments. Emphasis on anatomy and injuries to lateral collateral ligaments.  

PubMed

Ankle ligament sprains are the most frequent sports injury, and radiographic evaluation of the ankle accounts for 10% or all radiographic examinations requested from an emergency department. This article reviews the diagnosis of the ankle sprain and the anatomy and injuries of the ankle ligaments. PMID:7584238

Mesgarzadeh, M; Schneck, C D; Tehranzadeh, J; Chandnani, V P; Bonakdarpour, A

1994-02-01

10

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

11

Altered human brain anatomy in chronic smokers: a review of magnetic resonance imaging studies.  

PubMed

Cigarette smoking is becoming more prevalent in developing countries, such as China, and is the largest single cause of preventable death worldwide. New emerging reports are highlighting how chronic cigarette smoking plays a role in neural dysfunctions, such as cognitive decline. Basic animal experimental studies have shown that rats undergo persistent pathological brain changes after being given chronic levels of nicotine. What is perhaps less appreciated is the fact that chronic cigarette smoking induces subtle anatomical changes in the human brain. Consequently, this chapter aims to summarize and integrate the existing magnetic resonance imaging studies on both gray- and white-matter marcostructural and microstructural changes. The reviewed studies demonstrate that chronic cigarette smoking results in discrete and localized alterations in brain region tissue (both the gray and white matter of different brain regions), which may, in part, be responsible for different neural dysfunctions. In addition, we further discuss the possible pathological and neurobiological mechanisms of these nicotinic effects on the brain tissue. We will also address the limitations of the current studies on this issue and identify opportunities for future research. PMID:25577510

Wang, Chao; Xu, Xiaojun; Qian, Wei; Shen, Zhujing; Zhang, Minming

2015-04-01

12

[Hypermedia software for teaching anatomy of the upper abdomen with computerized tomography and magnetic resonance].  

PubMed

The authors have developed a hypermedia program for creating a tutorial of CT and MR anatomy of the upper abdomen. The program was created on a Mcintosh computer, with the Supercard software: it is made up of a series of windows, each of them containing images, texts, schematic representations and sound. Moreover, each window contains buttons which are activated with the mouse and allow different kinds of function, all created by the authors to be displayed. In particular, navigation buttons allow the users to move in the program either sequentially or non-linearly, according to their needs. The possibility of obtaining information and schematic representations is given by specific buttons. There are also multiple buttons hidden in the images which, when activated, allow the name of the selected organ to be displayed. In conclusion, this program can be especially helpful since it allows different data sets to be integrated to provide the user with complete information. Moreover, the program allows learning to be controlled, that is the user to be informed on timing and methods for more effective studying. PMID:7505942

Pavone, P; Catalano, C; Laghi, A; Di Girolamo, M; Albertini Petroni, G; Campanella, V; Passariello, R

1993-11-01

13

Cardiac Magnetic Resonance Imaging  

Microsoft Academic Search

Magnetic resonance imaging (MRI) has proven to be extremely versatile and useful for studying cardiac anatomy and function,\\u000a both for providing a deeper understanding of cardiac physiology and as a means to diagnose cardiac diseases. The capabilities\\u000a of MRI as a tomographic imaging modality to capture, with high spatial resolution, the anatomy of 3D structures was already\\u000a well appreciated before

Michael Jerosch-Herold; Ravi Teja Seethamraju; Carsten Rickers

14

Pocket atlas of cranial magnetic resonance imaging  

SciTech Connect

This atlas illustrates normal cerebral anatomy in magnetic resonance images. From their studies in cerebral anatomy utilizing cryomicrotome and other techniques, the authors selected more than 100 high-resolution images that represent the most clinically useful scans.

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

1986-01-01

15

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

16

Magnetic Resonance  

Cancer.gov

Focus Group on Magnetic Resonance Spectroscopy (MRS) in Clinical Oncology(April 1999) To explore the technical requirements for MRS and the application of hydrogen and multinuclear spectroscopy for tumor response to therapy.

17

7-T magnetic resonance imaging of the inner ear's anatomy by using dual four-element radiofrequency coil arrays and the VIBE sequence  

NASA Astrophysics Data System (ADS)

An ultra-high-field magnetic resonance (MR) scanner and a specially-optimized radiofrequency (RF) coil and sequence protocol are required to obtain high-resolution images of the inner ear that can noninvasively confirm pathologic diagnoses. In phantom studies, the MR signal distribution of the gradient echo MR images generated by using a customized RF coil was compared with that of a commercial volume coil. The MR signal intensity of the customized RF coil decreases rapidly from near the RF coil plane toward the exterior of the phantom. However, the signal sensitivity of this coil is superior on both sides of the phantom, corresponding to the petrous pyramid. In in-vivo 7-T MR imaging, a customized RF coil and a volumetric-interpolated breath-hold examination imaging sequence are employed for visualization of the inner ear's structure. The entire membranous portion of the cochlear and the three semicircular canals, including the ductus reunions, oval window, and round window with associated nervous tissue, were clearly depicted with sufficient spatial coverage for adequate inspection of the surrounding anatomy. Developments from a new perspective to inner ear imaging using the 7-T modality could lead to further improved image sensitivity and, thus, enable ultra-structural MR imaging.

Kim, Kyoung-Nam; Heo, Phil; Kim, Young-Bo; Han, Gyu-Cheol

2015-02-01

18

Three-dimensional volume rendering of the ankle based on magnetic resonance images enables the generation of images comparable to real anatomy  

PubMed Central

We have applied high-quality medical imaging techniques to study the structure of the human ankle. Direct volume rendering, using specific algorithms, transforms conventional two-dimensional (2D) magnetic resonance image (MRI) series into 3D volume datasets. This tool allows high-definition visualization of single or multiple structures for diagnostic, research, and teaching purposes. No other image reformatting technique so accurately highlights each anatomic relationship and preserves soft tissue definition. Here, we used this method to study the structure of the human ankle to analyze tendon–bone–muscle relationships. We compared ankle MRI and computerized tomography (CT) images from 17 healthy volunteers, aged 18–30 years (mean 23 years). An additional subject had a partial rupture of the Achilles tendon. The MRI images demonstrated superiority in overall quality of detail compared to the CT images. The MRI series accurately rendered soft tissue and bone in simultaneous image acquisition, whereas CT required several window-reformatting algorithms, with loss of image data quality. We obtained high-quality digital images of the human ankle that were sufficiently accurate for surgical and clinical intervention planning, as well as for teaching human anatomy. Our approach demonstrates that complex anatomical structures such as the ankle, which is rich in articular facets and ligaments, can be easily studied non-invasively using MRI data. PMID:19678857

Anastasi, Giuseppe; Cutroneo, Giuseppina; Bruschetta, Daniele; Trimarchi, Fabio; Ielitro, Giuseppe; Cammaroto, Simona; Duca, Antonio; Bramanti, Placido; Favaloro, Angelo; Vaccarino, Gianluigi; Milardi, Demetrio

2009-01-01

19

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

20

Nectar formation and floral nectary anatomy of Anigozanthos flavidus: a combined magnetic resonance imaging and spectroscopy study  

PubMed Central

Metabolic processes underlying the formation of floral nectar carbohydrates, especially the generation of the proportions of fructose, glucose, and sucrose, are important for understanding ecological plant–pollinator interactions. The ratio of sucrose-derived hexoses, fructose and glucose, in the floral nectar of Anigozanthos flavidus (Haemodoraceae) was observed to be different from 1:1, which cannot be explained by the simple action of invertases. Various NMR techniques were used to investigate how such an unbalanced ratio of the two nectar hexoses can be formed. High-resolution 13C NMR spectroscopy in solution was used to determine the proportion of carbohydrates in vascular bundles of excised inflorescences fed with 13C-labelled carbohydrates. These experiments verified that feeding did not affect the metabolic processes involved in nectar formation. In vivo magnetic resonance imaging (e.g. cyclic J cross-polarization) was used to detect carbohydrates in vascular bundles and 1H spin echo imaging non-invasively displayed the architecture of tepal nectaries and showed how they are connected to the vascular bundles. A model of the carbohydrate metabolism involved in forming A. flavidus floral nectar was established. Sucrose from the vascular bundles is not directly secreted into the lumen of the nectary but, either before or after invertase-catalysed hydrolyses, taken up by nectary cells and cycled at least partly through glycolysis, gluconeogenesis, and the pentose phosphate pathway. Secretion of the two hexoses in the cytosolic proportion could elegantly explain the observed fructose:glucose ratio of the nectar. PMID:18653689

Wenzler, Michael; Hölscher, Dirk; Oerther, Thomas; Schneider, Bernd

2008-01-01

21

Magnetic resonance angiography  

MedlinePLUS

MRA; Angiography - magnetic resonance ... Kwong RY. Cardiovascular Magnetic Resonance Imaging. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine . ...

22

Roadmap: Radiologic Imaging Sciences Magnetic Resonance Imaging (with certification and ATS Radiologic Technology) -  

E-print Network

Roadmap: Radiologic Imaging Sciences ­ Magnetic Resonance Imaging (with certification and ATS Computed Tomography and Magnetic Resonance Imaging Sectional Anatomy I 2 C RIS 44031 Patient Management Credit Hours] RIS 34086 Computed Tomography and Magnetic Resonance Imaging Sectional Anatomy II 2 C RIS

Sheridan, Scott

23

MRI (Magnetic Resonance Imaging)  

MedlinePLUS

... Radiation-Emitting Products and Procedures Medical Imaging MRI (Magnetic Resonance Imaging) Description Uses Risks/Benefits Information for ... Regulations & Performance Standards Industry Guidance Other Resources Description Magnetic resonance imaging (MRI) is a medical imaging procedure ...

24

Optically Enhanced Magnetic Resonance  

E-print Network

Optically Enhanced Magnetic Resonance Dieter Suter Universit¨at Dortmund, Germany 1 Introduction 1.1 Motivation The physical mechanism of nuclear magnetic resonance spectroscopy, the excitation of transitions. In most magnetic resonance experiments, these couplings are used to monitor the environment of the nuclei

Suter, Dieter

25

Magnetic Resonance Spectroscopy (MRS)  

E-print Network

Magnetic Resonance Spectroscopy (MRS) and Its Application in Alzheimer's Disease PRAVAT K. MANDAL1, Pennsylvania ABSTRACT: Magnetic resonance spectroscopy (MRS) is a noninvasive tool to measure the chemical; PRESS; STEAM; 2D MRS; Alzheimer's disease I. INTRODUCTION Magnetic resonance spectroscopy (MRS) is a rap

Mandal, Pravat K.

26

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

27

[Magnetic resonance spectroscopy].  

PubMed

Life-time diagnosis of the initial pathological shifts in the organism remains an and still unsolved important problem of modern medicine. Magnetic resonance spectroscopy based on the nuclear magnetic resonance phenomenon is one of the methods which can help to solve this problem. Modern reports about the use of magnetic resonance spectroscopy in the diagnosis of various diseases are reviewed. PMID:11521591

Tsa?, I V; Kulikov, S A; Kozinets, G I

2001-06-01

28

Magnetic resonance imaging of the knee  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is an accepted non invasive modality for evaluation of soft tissue pathology without exposure to ionizing radiation. Current appli cations demonstrate excellent visualization of the anat omy and pathology of various organs. Preliminary stud ies in the knee reveal fine resolution of anatomy and pathology involving the meniscus. The purpose of this study is to determine

D. W. Jackson; L. D. Jennings; R. M. Maywood; P. E. Berger

1988-01-01

29

Magnetic Resonance Imaging of the Elbow  

Microsoft Academic Search

Elbow injuries are common, especially in the athlete, and can be basically classified into acute or chronic injuries. The\\u000a following discussion of magnetic resonance imaging (MRI) of the elbow will address variations in normal anatomy that represent\\u000a pitfalls in imaging diagnosis, and commonly encountered osseous and soft-tissue pathology.

C. Chung; L. Steinbach

30

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

31

Magnetic resonance imaging: prologue  

SciTech Connect

Magnetic resonance imaging is becoming an increasingly important method of diagnostic imaging. This new method can compete with computed tomography for several applications, especially those involving the central nervous system. Magnetic resonance imaging is rapidly evolving, and several advances can be anticipated in the near future.

Jacobson, H.G.

1987-12-11

32

Nuclear magnetic resonance gyroscope  

Microsoft Academic Search

A nuclear magnetic resonance gyroscope which derives angular rotation from the phases of precessing nuclear moments utilizes a single-resonance cel 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 readout beam and associated electronics for signal processing

F. A. Karwacki; J. Griffin

1985-01-01

33

Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy in Dementias  

Microsoft Academic Search

This article reviews recent studies of magnetic resonance imaging and magnetic resonance spectroscopy in demen tia, 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 spec troscopy can detect structural alteration and biochemical abnormalities in the brain of demented subjects and may help in the differential

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

2001-01-01

34

Roadmap: Radiologic Imaging Sciences Magnetic Resonance Imaging (with certification and ATS Radiologic Technology) -  

E-print Network

Roadmap: Radiologic Imaging Sciences ­ Magnetic Resonance Imaging (with certification and ATS courses. RIS 34084 Computed Tomography and Magnetic Resonance Imaging Sectional Anatomy I 2 C RIS 44031 Patient Management in MRI 2 C RIS 44035 MRI Clinical Education I 3 C RIS 44044 Magnetic Resonance

Sheridan, Scott

35

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

36

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.

2014-09-18

37

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

38

Resonant and non-resonant magnetic scattering  

SciTech Connect

The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

1991-01-01

39

Resonant and non-resonant magnetic scattering  

SciTech Connect

The tunability and the polarization of synchrotron radiation open upon new possibilities for the study of magnetism. Studies on magnetic materials performed at the National Synchrotron Light Source are reviewed, and thy fall into four areas: structure, evolution of magnetic order, separation of L and S, and resonance effects. In the vicinity of atomic absorption edges, the Faraday effect, magnetic circular dichroism, and resonant magnetic scattering are all related resonance effects which measure the spin polarized density of states. The production and analysis of polarized beams are discussed in the context of the study of magnetism with synchrotron radiation.

McWhan, D.B.; Hastings, J.B.; Kao, C.C.; Siddons, D.P.

1991-12-31

40

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

41

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

42

Nuclear magnetic resonance imaging  

SciTech Connect

A method of imaging a body by nuclear magnetic resonance wherein volume scanning of a region of the body is achieved by scanning a first planar slice of the region and at least one further slice of the region in the relaxation time for the scan of the first slice.

Young, I.R.

1984-07-03

43

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

44

Resonant Magnetic Vortices  

E-print Network

By using the complex angular momentum method, we provide a semiclassical analysis of electron scattering by a magnetic vortex of Aharonov-Bohm-type. Regge poles of the $S$-matrix are associated with surface waves orbiting around the vortex and supported by a magnetic field discontinuity. Rapid variations of sharp characteristic shapes can be observed on scattering cross sections. They correspond to quasibound states which are Breit-Wigner-type resonances associated with surface waves and which can be considered as quantum analogues of acoustic whispering-gallery modes. Such a resonant magnetic vortex could provide a new kind of artificial atom while the semiclassical approach developed here could be profitably extended in various areas of the physics of vortices.

Yves Décanini; Antoine Folacci

2002-12-23

45

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

46

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

47

Magnetic resonance urography in evaluation of duplicated renal collecting systems.  

PubMed

Duplex renal collecting systems are common congenital anomalies of the upper urinary tract. In most cases they are incidental findings and not associated with additional pathologies. They demonstrate, however, higher incidences of hydroureteronephrosis, ureteroceles, and ectopic ureters. The most comprehensive morphologic and functional evaluation of duplex systems can be achieved using magnetic resonance urography. Functional magnetic resonance urography allows better separation of the renal poles, thus more accurate calculation of the differential renal functions compared with renal scintigraphy. Magnetic resonance urography is the study of choice when upper urinary tract anatomy is complex or when functional evaluation is needed. PMID:24183522

Adeb, Melkamu; Darge, Kassa; Dillman, Jonathan R; Carr, Michael; Epelman, Monica

2013-11-01

48

Parallel Magnetic Resonance Imaging  

E-print Network

The main disadvantage of Magnetic Resonance Imaging (MRI) are its long scan times and, in consequence, its sensitivity to motion. Exploiting the complementary information from multiple receive coils, parallel imaging is able to recover images from under-sampled k-space data and to accelerate the measurement. Because parallel magnetic resonance imaging can be used to accelerate basically any imaging sequence it has many important applications. Parallel imaging brought a fundamental shift in image reconstruction: Image reconstruction changed from a simple direct Fourier transform to the solution of an ill-conditioned inverse problem. This work gives an overview of image reconstruction from the perspective of inverse problems. After introducing basic concepts such as regularization, discretization, and iterative reconstruction, advanced topics are discussed including algorithms for auto-calibration, the connection to approximation theory, and the combination with compressed sensing.

Uecker, Martin

2015-01-01

49

Magnetic resonance angiography for preoperative evaluation of potential kidney donors 1  

Microsoft Academic Search

BackgroundCareful evaluation of the renovascular anatomy for living kidney donors is essential to optimize donor and recipient outcomes. Arteriography has been the standard for delineating the renovascular anatomy. However, this procedure is invasive. Magnetic resonance angiography (MRA) is an attractive, noninvasive alternative. The aim of this study was to evaluate the accuracy of MRA in potential living kidney donors.

Amer Rajab; Hooman Khabiri; Ronald P. Pelletier; Mitchell L. Henry; Baris Akin; Elmahdi Elkhammas; Ginny L. Bumgardner; Ronald M. Ferguson

2004-01-01

50

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

51

Magnetic Resonance Facility (Fact Sheet)  

SciTech Connect

This fact sheet provides information about Magnetic Resonance Facility capabilities and applications at NREL's National Bioenergy Center. Liquid and solid-state analysis capability for a variety of biomass, photovoltaic, and materials characterization applications across NREL. NREL scientists analyze solid and liquid samples on three nuclear magnetic resonance (NMR) spectrometers as well as an electron paramagnetic resonance (EPR) spectrometer.

Not Available

2012-03-01

52

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

53

Cardiovascular Magnetic Resonance Imaging  

NASA Astrophysics Data System (ADS)

Cardiovascular diseases are a major source of morbidity and mortality in the United States. Early detection of disease can often be used to improved outcomes, either through direct interventions (e.g. surgical corrections) or by causing the patient to modify his or her behavior (e.g. smoking cessation or dietary changes). Ideally, the detection process should be noninvasive (i.e. it should not be associated with significant risk). Magnetic Resonance Imaging (MRI) refers to the formation of images by localizing NMR signals, typically from protons in the body. As in other applications of NMR, a homogeneous static magnetic field ( ~0.5 to 4 T) is used to create ``longitudinal" magnetization. A magnetic field rotating at the Larmor frequency (proportional to the static field) excites spins, converting longitudinal magnetization to ``transverse" magnetization and generating a signal. Localization is performed using pulsed gradients in the static field. MRI can produce images of 2-D slices, 3-D volumes, time-resolved images of pseudo-periodic phenomena such as heart function, and even real-time imaging. It is also possible to acquire spatially localized NMR spectra. MRI has a number of advantages, but perhaps the most fundamental is the richness of the contrast mechanisms. Tissues can be differentiated by differences in proton density, NMR properties, and even flow or motion. We also have the ability to introduce substances that alter NMR signals. These contrast agents can be used to enhance vascular structures and measure perfusion. Cardiovascular MRI allows the reliable diagnosis of important conditions. It is possible to image the blood vessel tree, quantitate flow and perfusion, and image cardiac contraction. Fundamentally, the power of MRI as a diagnostic tool stems from the richness of the contrast mechanisms and the flexibility in control of imaging parameters.

Pelc, Norbert

2000-03-01

54

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

55

Magnetic Resonance Imaging and Magnetic Resonance Angiography of Vertebrobasilar Dolichoectasia  

Microsoft Academic Search

We performed magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) in 16 patients with vertebrobasilar dolichoectasia (VBD). Five patients had compressive cranial nerve deficits and 11 patients presented with transient or permanent ischemic deficits related to the vertebrobasilar system. VBD did not present with distinct clinical findings and no clear correlation between basilar artery ectasia and the presence of

Franz T. Aichner; Stephan R. Felber; Günther G. Birbamer; Andrea Posch

1993-01-01

56

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

57

Travelling-wave nuclear magnetic resonance.  

PubMed

Nuclear magnetic resonance (NMR) is one of the most versatile experimental methods in chemistry, physics and biology, providing insight into the structure and dynamics of matter at the molecular scale. Its imaging variant-magnetic resonance imaging (MRI)-is widely used to examine the anatomy, physiology and metabolism of the human body. NMR signal detection is traditionally based on Faraday induction in one or multiple radio-frequency resonators that are brought into close proximity with the sample. Alternative principles involving structured-material flux guides, superconducting quantum interference devices, atomic magnetometers, Hall probes or magnetoresistive elements have been explored. However, a common feature of all NMR implementations until now is that they rely on close coupling between the detector and the object under investigation. Here we show that NMR can also be excited and detected by long-range interaction, relying on travelling radio-frequency waves sent and received by an antenna. One benefit of this approach is more uniform coverage of samples that are larger than the wavelength of the NMR signal-an important current issue in MRI of humans at very high magnetic fields. By allowing a significant distance between the probe and the sample, travelling-wave interaction also introduces new possibilities in the design of NMR experiments and systems. PMID:19225521

Brunner, David O; De Zanche, Nicola; Fröhlich, Jürg; Paska, Jan; Pruessmann, Klaas P

2009-02-19

58

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

59

NMR Nuclear Magnetic Resonance Nuclear magnetic resonance (NMR) is an effect whereby magnetic nuclei in  

E-print Network

NMR Nuclear Magnetic Resonance Nuclear magnetic resonance (NMR) is an effect whereby magnetic resonance frequency which depends on the strength of the magnetic field and other factors. This allows nuclei in a magnetic field absorb and re-emit electromagnetic (EM) energy. This energy is at a specific

Cavanagh, John

60

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

61

A nuclear magnetic resonance gyroscope  

Microsoft Academic Search

A nuclear magnetic resonance (NMR) gyroscope is under development for use as a low cost angle sensor in strapdown inertial measurement systems. The gyro operates on the principle that the magnetic moments of certain atoms precess at a known frequency in a magnetic field and that changes in phase of this frequency can be sensed to determine the inertial angular

E. Kanegsberg

1977-01-01

62

Low field magnetic resonance imaging  

DOEpatents

A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)

2010-07-13

63

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

64

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

65

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

66

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

67

Magnetic Resonance Imaging (MRI): Brain  

MedlinePLUS

KidsHealth > Parents > Doctors & Hospitals > Medical Tests & Exams > Magnetic Resonance Imaging (MRI): Brain Print A A A Text Size What's in this article? What It Is Why It's Done Preparation Procedure What ...

68

Magnetic resonance imaging of the knee.  

PubMed

Magnetic resonance imaging (MRI) is an accepted non-invasive modality for evaluation of soft tissue pathology without exposure to ionizing radiation. Current applications demonstrate excellent visualization of the anatomy and pathology of various organs. Preliminary studies in the knee reveal fine resolution of anatomy and pathology involving the meniscus. The purpose of this study is to determine a prospective correlation between MRI scans and actual meniscal pathology as documented at the time of arthroscopy. MRI scans were obtained in 155 patients, on 156 knees (one patient with bilateral scans), with 86 patients (87 knees) eventually undergoing diagnostic and operative videoarthroscopy performed by the same surgeon (DWJ). All images were obtained on the same high-resolution 1.5 Tesla GE Signa Magnetic Resonance Scanner with the same radiologist performing all readings (PEB). The knees were studied in the coronal and sagittal plane using a spin echo sequence and 5 mm slice thicknesses. The menisci were described as having Grade 1, 2, or 3 changes, with Grade 3 reserved for complete tears. Using arthroscopy as the diagnostic standard, the accuracy of MRI in diagnosing medial and lateral meniscal tears was 93.1% and 96.6%, respectively with a Grade 3 MRI reading. For tears of the ACL, the accuracy was 96.6% as confirmed at arthroscopy. Five tears of the PCL were also documented by MRI and correlated with clinical evaluation. Other abnormalities seen were articular cartilage and osteochondral defects, bone tumors, tibial plateau fractures, Baker's cysts, and meniscal cysts. The MRI scan is a highly accurate, noninvasive modality for documentation of meniscal pathology as well as cruciate ligament tears in the knee. PMID:3344877

Jackson, D W; Jennings, L D; Maywood, R M; Berger, P E

1988-01-01

69

Bayesian Optimization of Magnetic Resonance Imaging Sequences  

E-print Network

Bayesian Optimization of Magnetic Resonance Imaging Sequences Matthias Seeger MMCI Cluster SAARLANDES Seeger (MMCI) Bayesian MRI Optimization 28 November 2008 1 / 19 #12;Outline 1 Magnetic Resonance) Bayesian MRI Optimization 28 November 2008 2 / 19 #12;Magnetic Resonance Imaging Magnetic Resonance Imaging

Seeger, Matthias

70

JAMA Patient Page: Magnetic Resonance Imaging  

MedlinePLUS

... of the American Medical Association JAMA PATIENT PAGE Magnetic Resonance Imaging M agnetic resonance imaging (MRI) uses magnetic fields ... of magnetic fields processed with highly sophisticated computers, MRI scans produce detailed and clear pictures of body parts. ...

71

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

72

Volumetric segmentation of magnetic resonance images  

NASA Astrophysics Data System (ADS)

Current computer graphics techniques can generate 3-D views of the human anatomy from magnetic resonance images. These techniques require that the images first be segmented into the various tissue types. However, there has been no fully automated system that can perform this task on a single set of high-resolution 3-D magnetic resonance images. We present a fully automated segmentation algorithm based on the 3-D difference of Gaussians (DOG) filter. A novel method for the classification of regions found by the DOG filter, as well as a correction procedure that detects errors from the DOG filter, is presented. Regions are classified based on the mean gray level of the voxels within closed contours. In previous work, the user had to manually split falsely merged regions. Our automated correction algorithm detects such errors and splits the merged regions. Spatial information is also incorporated to help discriminate between tissues. Encouraging results were obtained with an average of less than five percent error in each image. Integral shading is used to obtain a 3-D rendering of the data set.

Lee, James D.; Rodriguez, Jeffrey J.

1994-09-01

73

Optically Detected Magnetic Resonance Imaging  

E-print Network

Optically detected magnetic resonance (ODMR) provides ultrasensitive means to detect and image a small number of electron and nuclear spins, down to the single spin level with nanoscale resolution. Despite the significant recent progress in this field, it has never been combined with the power of pulsed magnetic resonance imaging (MRI) techniques. Here, we demonstrate for the first time how these two methodologies can be integrated using short pulsed magnetic field gradients to spatially-encode the sample. This results in what we denote as an "optically detected magnetic resonance imaging" (ODMRI) technique. It offers the advantage that the image is acquired in parallel from all parts of the sample, with well-defined three-dimensional point-spread function, and without any loss of spectroscopic information. In addition, this approach may be used in the future for parallel but yet spatially-selective efficient addressing and manipulation of the spins in the sample. Such capabilities are of fundamental importan...

Blank, Aharon; Fischer, Ran; London, Paz; Gershoni, David

2014-01-01

74

Optically detected magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Optically detected magnetic resonance provides ultrasensitive means to detect and image a small number of electron and nuclear spins, down to the single spin level with nanoscale resolution. Despite the significant recent progress in this field, it has never been combined with the power of pulsed magnetic resonance imaging techniques. Here, we demonstrate how these two methodologies can be integrated using short pulsed magnetic field gradients to spatially encode the sample. This result in what we denote as an "optically detected magnetic resonance imaging" technique. It offers the advantage that the image is acquired in parallel from all parts of the sample, with well-defined three-dimensional point-spread function, and without any loss of spectroscopic information. In addition, this approach may be used in the future for parallel but yet spatially selective efficient addressing and manipulation of the spins in the sample. Such capabilities are of fundamental importance in the field of quantum spin-based devices and sensors.

Blank, Aharon; Shapiro, Guy; Fischer, Ran; London, Paz; Gershoni, David

2015-01-01

75

Magnetic Resonance Imaging (MRI)  

MedlinePLUS

... addition, any credit cards or anything else with magnetic coding that is near the magnet will be erased by most MRI systems. MRI works by contrasting the differences present in the area being scanned. Different ... ways to the magnetic field that is applied; it is these differences ...

76

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

77

Applied Magnetic Resonance ISSN 0937-9347  

E-print Network

1 23 Applied Magnetic Resonance ISSN 0937-9347 Volume 42 Number 3 Appl Magn Reson (2012) 42:353-361 DOI 10.1007/s00723-011-0298-1 Transverse Relaxation of Scalar Coupled Protons in Magnetic Resonance Relaxation of Scalar Coupled Protons in Magnetic Resonance of Non-Deuterated Proteins Takuya F. Segawa

78

Use of Functional Magnetic Resonance Imaging (Blood Oxygenation Level-Dependent Imaging, Diffusion Tensor Imaging and Magnetic Resonance Spectroscopy) in Brain Development Research  

Microsoft Academic Search

The development of several new magnetic resonance imaging (MRI) techniques has facilitated serial observations of the developing human brain in utero. For example, the noninvasive technique of functional MRI, which is used to study brain anatomy, function and metabolism in both humans and animals, has already enhanced our understanding of brain development and behavior relations. Currently, three main kinds of

Fei Fei Yang; Shu Guang Yuan; David T. Yew

2008-01-01

79

Appl. Magn. Reson. 28, 1XXX (2005) Magnetic Resonance  

E-print Network

Appl. Magn. Reson. 28, 1XXX (2005) Applied Magnetic Resonance © Springer-Verlag 2005 Printed-based functional magnetic resonance imaging (fMRI) techniques have proven to be extremely robust and sensitive firing spatially and temporally integrates on the spatial scale of an MRI voxel to produce a magnetic

Baker, Chris I.

80

Magnetic Resonance Imaging (MRI)  

MedlinePLUS

... doctors use to see the body's organs and structures. MRI uses a magnetic field and radio waves to create detailed pictures of the body's insides. Unlike CAT scans or X-rays, MRI doesn't use radiation. An MRI scanner is a large doughnut-shaped magnet that often has a tunnel in the center. ...

81

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

82

Magnetic Resonance Cholangiopancreatography (MRCP)  

MedlinePLUS

... the magnet, radio waves redirect alignment of hydrogen atoms that naturally exist within the body without causing ... chemical changes in the tissues. As the hydrogen atoms return to their usual alignment, they emit energy ...

83

Nuclear magnetic resonance scanners  

SciTech Connect

This patent describes a medical NMR scanner comprising a primary field magnet assembly including: (a) a ferromagnetic frame defining a patient-receiving space adapted to receive a human body, the frame having a pair of opposed polar regions aligned on a polar axis and disposed on opposite sides of the patient-receiving space, and the frame including a substantially continuous ferro-magnetic flux return path extending between the polar regions remote from the patient-receiving space; (b) flux-generating means including superconductive windings and cryostat means for maintaining the windings at superconducting temperatures; and (c) support means for maintaining the windings in proximity to the frame so that when a current passes through the windings magnetic flux emanating from the windings produces a magnetic field within the patient-receiving space and at least a portion of the flux passes into the patient-receiving space by way of the polar regions.

Danby, G.T.; Hsieh, H.C.H.; Jackson, J.W.; Damadian, R.V.

1988-08-23

84

Magnetic Resonance Imaging of concrete  

E-print Network

1 Magnetic Resonance Imaging of concrete Dr Chris Burgoyne Department of Engineering University of Cambridge Assessment of Concrete Structures · How can we tell what is going on inside concrete? · We would like to know:- · Has the concrete hardened? · Is there corrosion? · Is there cracking? · Where

Burgoyne, Chris

85

International Society for Magnetic Resonance in Medicine  

MedlinePLUS

... full list. Of Special Note ISMRM Online Education Magnetic Resonance in Medicine 30th Anniversary (Password required) In ... archive Who We Are The International Society for Magnetic Resonance in Medicine is a nonprofit professional association ...

86

Magnetic Resonance Imaging (MRI) during Pregnancy  

MedlinePLUS

Magnetic Resonance Imaging (MRI) During Pregnancy Play Video Clip (00:02:58) Your Radiologist Explains MRI During ... during the exam? Contrast material MRI during pregnancy Magnetic resonance imaging (MRI) If you are pregnant and ...

87

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

88

Magnetically Tuned Spin Dynamics Resonance  

SciTech Connect

We present the experimental observation of a magnetically tuned resonance phenomenon in the spin mixing dynamics of ultracold atomic gases. In particular, we study the magnetic field dependence of spin conversion in F=2 {sup 87}Rb spinor condensates in the crossover from interaction dominated to quadratic Zeeman dominated dynamics. We discuss the observations in the framework of spin dynamics as well as matter wave four wave mixing. Furthermore, we show that the validity range of the single mode approximation for spin dynamics is significantly extended at high magnetic field.

Kronjaeger, J.; Becker, C.; Bongs, K.; Sengstock, K. [Institut fuer Laserphysik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Navez, P. [Labo Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); additional address: Universitaet Duisburg-Essen, Universitaetsstrasse 5, 45117 Essen (Germany)

2006-09-15

89

Magnetically tuned spin dynamics resonance.  

PubMed

We present the experimental observation of a magnetically tuned resonance phenomenon in the spin mixing dynamics of ultracold atomic gases. In particular, we study the magnetic field dependence of spin conversion in F=2 (87)Rb spinor condensates in the crossover from interaction dominated to quadratic Zeeman dominated dynamics. We discuss the observations in the framework of spin dynamics as well as matter wave four wave mixing. Furthermore, we show that the validity range of the single mode approximation for spin dynamics is significantly extended at high magnetic field. PMID:17025866

Kronjäger, J; Becker, C; Navez, P; Bongs, K; Sengstock, K

2006-09-15

90

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

91

Unentangling nuclear magnetic resonance Matthias Bechmann 1  

E-print Network

Unentangling nuclear magnetic resonance computing Matthias Bechmann 1 , John A. Clark 2 , Angelika of York, UK, YO10 5DD Abstract. Nuclear magnetic resonance (NMR) is typically thought of as a possible computer sciences and nuclear magnetic resonance (NMR) spectroscopy have emerged. From the point of view

Stepney, Susan

92

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

93

Human Cerebral Cortex: Localization, Parcellation, and Morphometry with Magnetic Resonance Imaging  

Microsoft Academic Search

We describe a system of parcellation of the human brain that is based on the functional anatomy of the cerebral cortex and that is applied to the analysis of magnetic resonance images. This system is designed to support investigations of hemispheric asymmetries and quantitative lesion localization studies in cognitive neuroscience. The system of cortical subdivision is a neural systems oriented

J. Rademacher; A. M. Galaburda; D. N. Kennedy; P. A. Filipek; V. S. Caviness

1992-01-01

94

Neuroanatomy of adult strabismus: a voxel-based morphometric analysis of magnetic resonance structural scans  

Microsoft Academic Search

Cerebral deficit has been implicated in the genesis of strabismus and in the mechanisms adopted to compensate for the visual disorder. Voxel-based morphometry (VBM) was applied to magnetic resonance images of strabismic adults to detect any abnormal brain anatomy, which could not be easily identified by simple inspection. The gray matter volume in strabismic adults was smaller than that in

Suk-tak Chan; Kwok-wing Tang; Kwok-cheung Lam; Lap-kong Chan; Janine D Mendola; Kenneth K Kwong

2004-01-01

95

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

96

Resonant magnetic fields from inflation  

E-print Network

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 order 10^{-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.

Christian T. Byrnes; Lukas Hollenstein; Rajeev Kumar Jain; Federico R. Urban

2012-03-06

97

Magnetic Resonance Connectome Automated Pipeline  

E-print Network

This manuscript presents a novel, tightly integrated pipeline for estimating a connectome, which is a comprehensive description of the neural circuits in the brain. The pipeline utilizes magnetic resonance imaging (MRI) data to produce a high-level estimate of the structural connectivity in the human brain. The Magnetic Resonance Connectome Automated Pipeline (MRCAP) is efficient and its modular construction allows researchers to modify algorithms to meet their specific requirements. The pipeline has been validated and over 200 connectomes have been processed and analyzed to date. This tool enables the prediction and assessment of various cognitive covariates, and this research is applicable to a variety of domains and applications. MRCAP will enable MR connectomes to be rapidly generated to ultimately help spur discoveries about the structure and function of the human brain.

Gray, William R; Vogelstein, Joshua T; Landman, Bennett A; Prince, Jerry L; Vogelstein, R Jacob

2011-01-01

98

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

99

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

100

Clinical applications of magnetic resonance imaging - current status  

SciTech Connect

Magnetic resonance imaging has far-reaching real and possible clinical applications. Its usefulness has been best explored and realized in the central nervous system, especially the posterior fossa and brain stem, where most abnormalities are better identified than with computed tomography. Its lack of ionizing radiation and extreme sensitivity to normal and abnormal patterns of myelination make magnetic resonance imaging advantageous for diagnosing many neonatal and pediatric abnormalities. New, reliable cardiac gating techniques open the way for promising studies of cardiac anatomy and function. The ability to image directly in three orthogonal planes gives us new insight into staging and follow-up of pelvic tumors and other pelvic abnormalities. Exquisite soft tissue contrast, far above that attainable by other imaging modalities, has made possible the early diagnosis of traumatic ligamentous knee injury, avascular necrosis of the hip and diagnosis, treatment planning and follow-up of musculoskeletal neoplasms. 59 references, 9 figures.

Cammoun, D.; Hendee, W.R.; Davis, K.A.

1985-12-01

101

Magnetic Resonance Imaging at Ultrahigh Fields  

PubMed Central

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, ultra-high 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

U?urbil, Kamil

2014-01-01

102

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

103

Nuclear magnetic resonance in magnets with a spiral magnetic structure  

NASA Astrophysics Data System (ADS)

Specific features of nuclear magnetic resonance (NMR) in a ferromagnet with a crystallographic magnetic anisotropy of the easy-plane type placed in a constant magnetic field have been studied. The symmetry of the magnet admits the existence of the Dzyaloshinskii-Moriya interaction, which leads to the formation of a new ground state, namely, a soliton lattice (spiral structure). Within the spin-wave approximation, the following basic local characteristics of the NMR of this structure have been calculated: resonance frequency, enhancement factor, and line broadening and their field dependences have been investigated. The magnetic resonance susceptibility of the electron-nucleus spin system has been calculated; the shape of the NMR absorption line has been analyzed. The problem of the evolution of the NMR absorption line upon the change in the magnitude of an external magnetic field has been solved. The possibility of the experimental detection and investigation of the structural and dynamic features of the spiral magnetic structure by the NMR method is discussed.

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

2014-03-01

104

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

105

Magnetic resonance in an elliptic magnetic field  

E-print Network

The behaviour of a particle with a spin 1/2 and a dipole magnetic moment in a time-varying magnetic field in the form $(h_0 cn(\\omega t,k), h_0 sn(\\omega t,k), H_0 dn(\\omega t,k))$, where $\\omega$ is the driving field frequency, $t$ is the time, $h_0$ and $H_0$ are the field amplitudes, $cn$, $sn$, $dn$ are Jacobi elliptic functions, $ k$ is the modulus of the elliptic functions has been considered. The variation parameter $k$ from zero to 1 gives rise to a wide set of functions from trigonometric shapes to exponential pulse shapes modulating the field. The problem was reduced to the solution of general Heun' equation. The exact solution of the wave function was found at resonance for any $ k$. It has been shown that the transition probability in this case does not depend on $k$. The present study may be useful for analysis interference experiments, improving magnetic spectrometers and the field of quantum computing.

E. A. Ivanchenko

2004-04-20

106

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

107

Motion Estimation in Static Magnetic Resonance Elastography  

E-print Network

Elastography is the imaging of the biomechanical properties of a tissue to detect and diagnose abnormal pathologies in a variety of disease conditions. Static Magnetic Resonance Elastography (MRE) is a modality of elastography that uses Magnetic...

Popel, Elena

2009-12-09

108

Magnetic resonance imaging of radiation optic neuropathy  

SciTech Connect

Three patients with delayed radiation optic neuropathy after radiation therapy for parasellar neoplasms underwent magnetic resonance imaging. The affected optic nerves and chiasms showed enlargement and focal gadopentetate dimeglumine enhancement. The magnetic resonance imaging technique effectively detected and defined anterior visual pathway changes of radionecrosis and excluded the clinical possibility of visual loss because of tumor recurrence.

Zimmerman, C.F.; Schatz, N.J.; Glaser, J.S. (Univ. of Miami, FL (USA))

1990-10-15

109

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

110

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

111

Functional Magnetic Resonance Imaging and Pediatric Anxiety  

ERIC Educational Resources Information Center

The use of functional magnetic resonance imaging in investigating pediatric anxiety disorders is studied. Functional magnetic resonance imaging can be utilized in demonstrating parallels between the neural architecture of difference in anxiety of humans and the neural architecture of attention-orienting behavior in nonhuman primates or rodents.…

Pine, Daniel S.; Guyer, Amanda E.; Leibenluft, Ellen; Peterson, Bradley S.; Gerber, Andrew

2008-01-01

112

Spread spectrum magnetic resonance imaging  

E-print Network

We propose a novel compressed sensing technique to accelerate the magnetic resonance imaging (MRI) acquisition process. The method, coined spread spectrum MRI or simply s2MRI, consists of pre-modulating the signal of interest by a linear chirp before random k-space under-sampling, and then reconstructing the signal with non-linear algorithms that promote sparsity. The effectiveness of the procedure is theoretically underpinned by the optimization of the coherence between the sparsity and sensing bases. The proposed technique is thoroughly studied by means of numerical simulations, as well as phantom and in vivo experiments on a 7T scanner. Our results suggest that s2MRI performs better than state-of-the-art variable density k-space under-sampling approaches

Puy, Gilles; Gruetter, Rolf; Thiran, Jean-Philippe; Van De Ville, Dimitri; Vandergheynst, Pierre; Wiaux, Yves; 10.1109/TMI.2011.2173698

2012-01-01

113

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

114

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

115

Magnetic resonance elastography of abdomen.  

PubMed

Many diseases cause substantial changes in the mechanical properties of tissue, and this provides motivation for developing methods to noninvasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate noninvasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed. PMID:25488346

Venkatesh, Sudhakar Kundapur; Ehman, Richard L

2015-04-01

116

Magnetic Resonance Imaging of Electrolysis.  

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

117

DEVELOPMENTAL NEUROIMAGING OF CHILDREN USING MAGNETIC RESONANCE TECHNIQUES  

E-print Network

DEVELOPMENTAL NEUROIMAGING OF CHILDREN USING MAGNETIC RESONANCE TECHNIQUES Michael J. Rivkin. Recently, powerful qualitative and quantita- tive magnetic resonance techniques have been developed, recent magnetic resonance imaging data related to human brain development during the fetal, neonatal

Stromswold, Karin

118

Thomas T. Liu Center for Functional Magnetic Resonance Imaging  

E-print Network

Thomas T. Liu Center for Functional Magnetic Resonance Imaging University of California, San Diego Engineering, Stanford University 1999-2001 Postgraduate Researcher, Magnetic Resonance Physics Group for Functional Magnetic Resonance Imaging 2007-Present Associate Professor of Radiology and Bioengineering

California at San Diego, University of

119

Quantification of Magnetic Resonance Spectroscopy signals with lineshape estimation  

E-print Network

Quantification of Magnetic Resonance Spectroscopy signals with lineshape estimation M.I Osorio - ESAT-SCD, Katholieke Universiteit Leuven b Biomedical Nuclear - Magnetic Resonance Unit, Katholieke Universiteit Leuven Abstract Quantification of Magnetic Resonance Spectroscopy (MRS) signals is required

120

Thomas T. Liu Center for Functional Magnetic Resonance Imaging  

E-print Network

Thomas T. Liu Center for Functional Magnetic Resonance Imaging University of California, San Diego Engineering, Stanford University 1999-2001 Postgraduate Researcher, Magnetic Resonance Physics Group for Functional Magnetic Resonance Imaging 2007-Present Associate Professor (with Tenure) of Radiology

California at San Diego, University of

121

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Magnetic resonance diagnostic device. 892... Diagnostic Devices § 892.1000 Magnetic resonance diagnostic device. (a) Identification. A magnetic resonance diagnostic device is...

2010-04-01

122

76 FR 58281 - Magnetic Resonance Imaging Safety; Public Workshop  

Federal Register 2010, 2011, 2012, 2013, 2014

...Docket No. FDA-2011-N-0640] Magnetic Resonance Imaging Safety; Public Workshop...announcing a public workshop entitled: ``Magnetic Resonance Imaging (MRI) Safety Public...discuss factors affecting the safe use of magnetic resonance imaging (MRI) and...

2011-09-20

123

Hosted by Yalin Wang Methods in Magnetic Resonance Imaging  

E-print Network

Hosted by Yalin Wang Methods in Magnetic Resonance Imaging Abstract: Magnetic Resonance Imaging for Magnetic Resonance in Medicine (ISMRM), and served on the ISMRM Board of Trustees and chaired their 20th Resonance Imaging and on the editorial boards of the journal Magnetic Resonance in Medicine. Dr. Pipe

Reisslein, Martin

124

Magnetic resonance imaging: Basic principles  

SciTech Connect

This book has been revised to reflect the past three years' technological developments and to meet the everyday needs of radiologists and clinicians who use MRI in routine practice. Among the new features are a lucid explanation of the gray scale and its significance; a complete atlas of normal MRI anatomy; and head-to-foot illustrations of pathologic MRI findings.

Young, S.W.

1987-01-01

125

Emergency Information Center for Magnetic Resonance Research  

E-print Network

Emergency Information for Center for Magnetic Resonance Research Dial 911 for Police, Fire Not Allow them to Enter the Magnet Room without being Screened and Briefed) Building: 180 Department. Remove subject from scanner and/or magnet room if possible (MR Safe wheelchair and gurney located in CTSI

Thomas, David D.

126

A Demonstration Model of Magnetic Resonance  

ERIC Educational Resources Information Center

Describes a simple and inexpensive model to demonstrate the pulsed magnetic resonance phenomenon. Gives the details of construction of the device which can provide a direct demonstration of the precessional motion of a magnetic moment in a steady magnetic field. (Author/GS)

Sandhu, H. S.; Peemoeller, H.

1974-01-01

127

Stepped Impedance Resonators for High Field Magnetic Resonance Imaging  

PubMed Central

Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high field magnetic resonance imaging (MRI). In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) multi-element transceiver coil consisting of microstrip resonators. In this paper, to further advance this design approach, a new microstrip resonator strategy in which the transmission line is segmented into alternating impedance sections referred to as stepped impedance resonators (SIRs) is investigated. Single element simulation results in free space and in a phantom at 7 tesla (298 MHz) demonstrate the rationale and feasibility of the SIR design strategy. Simulation and image results at 7 tesla in a phantom and human head illustrate the improvements in transmit magnetic field, as well as, RF efficiency (transmit magnetic field versus SAR) when two different SIR designs are incorporated in 8-element volume coil configurations and compared to a volume coil consisting of microstrip elements. PMID:23508243

Akgun, Can E.; DelaBarre, Lance; Yoo, Hyoungsuk; Sohn, Sung-Min; Snyder, Carl J.; Adriany, Gregor; Ugurbil, Kamil; Gopinath, Anand; Vaughan, J. Thomas

2014-01-01

128

Functional cardiac magnetic resonance microscopy  

NASA Astrophysics Data System (ADS)

The study of small animal models of human cardiovascular disease is critical to our understanding of the origin, progression, and treatment of this pervasive disease. Complete analysis of disease pathophysiology in these animal models requires measuring structural and functional changes at the level of the whole heart---a task for which an appropriate non-invasive imaging method is needed. The purpose of this work was thus to develop an imaging technique to support in vivo characterization of cardiac structure and function in rat and mouse models of cardiovascular disease. Whereas clinical cardiac magnetic resonance imaging (MRI) provides accurate assessment of the human heart, the extension of cardiac MRI from humans to rodents presents several formidable scaling challenges. Acquiring images of the mouse heart with organ definition and fluidity of contraction comparable to that achieved in humans requires an increase in spatial resolution by a factor of 3000 and an increase in temporal resolution by a factor of ten. No single technical innovation can meet the demanding imaging requirements imposed by the small animal. A functional cardiac magnetic resonance microscopy technique was developed by integrating improvements in physiological control, imaging hardware, biological synchronization of imaging, and pulse sequence design to achieve high-quality images of the murine heart with high spatial and temporal resolution. The specific methods and results from three different sets of imaging experiments are presented: (1) 2D functional imaging in the rat with spatial resolution of 175 mum2 x 1 mm and temporal resolution of 10 ms; (2) 3D functional imaging in the rat with spatial resolution of 100 mum 2 x 500 mum and temporal resolution of 30 ms; and (3) 2D functional imaging in the mouse with spatial resolution down to 100 mum2 x 1 mm and temporal resolution of 10 ms. The cardiac microscopy technique presented here represents a novel collection of technologies capable of acquiring routine high-quality images of murine cardiac structure and function with minimal artifacts and markedly higher spatial resolution compared to conventional techniques. This work is poised to serve a valuable role in the evaluation of cardiovascular disease and should find broad application in studies ranging from basic pathophysiology to drug discovery.

Brau, Anja Christina Sophie

2003-07-01

129

Artifacts in magnetic resonance imaging.  

PubMed

Artifacts in magnetic resonance imaging and foreign bodies within the patient's body may be confused with a pathology or may reduce the quality of examinations. Radiologists are frequently not informed about the medical history of patients and face postoperative/other images they are not familiar with. A gallery of such images was presented in this manuscript. A truncation artifact in the spinal cord could be misinterpreted as a syrinx. Motion artifacts caused by breathing, cardiac movement, CSF pulsation/blood flow create a ghost artifact which can be reduced by patient immobilization, or cardiac/respiratory gating. Aliasing artifacts can be eliminated by increasing the field of view. An artificially hyperintense signal on FLAIR images can result from magnetic susceptibility artifacts, CSF/vascular pulsation, motion, but can also be found in patients undergoing MRI examinations while receiving supplemental oxygen. Metallic and other foreign bodies which may be found on and in patients' bodies are the main group of artifacts and these are the focus of this study: e.g. make-up, tattoos, hairbands, clothes, endovascular embolization, prostheses, surgical clips, intraorbital and other medical implants, etc. Knowledge of different types of artifacts and their origin, and of possible foreign bodies is necessary to eliminate them or to reduce their negative influence on MR images by adjusting acquisition parameters. It is also necessary to take them into consideration when interpreting the images. Some proposals of reducing artifacts have been mentioned. Describing in detail the procedures to avoid or limit the artifacts would go beyond the scope of this paper but technical ways to reduce them can be found in the cited literature. PMID:25745524

Krupa, Katarzyna; Bekiesi?ska-Figatowska, Monika

2015-01-01

130

Artifacts in Magnetic Resonance Imaging  

PubMed Central

Summary Artifacts in magnetic resonance imaging and foreign bodies within the patient’s body may be confused with a pathology or may reduce the quality of examinations. Radiologists are frequently not informed about the medical history of patients and face postoperative/other images they are not familiar with. A gallery of such images was presented in this manuscript. A truncation artifact in the spinal cord could be misinterpreted as a syrinx. Motion artifacts caused by breathing, cardiac movement, CSF pulsation/blood flow create a ghost artifact which can be reduced by patient immobilization, or cardiac/respiratory gating. Aliasing artifacts can be eliminated by increasing the field of view. An artificially hyperintense signal on FLAIR images can result from magnetic susceptibility artifacts, CSF/vascular pulsation, motion, but can also be found in patients undergoing MRI examinations while receiving supplemental oxygen. Metallic and other foreign bodies which may be found on and in patients’ bodies are the main group of artifacts and these are the focus of this study: e.g. make-up, tattoos, hairbands, clothes, endovascular embolization, prostheses, surgical clips, intraorbital and other medical implants, etc. Knowledge of different types of artifacts and their origin, and of possible foreign bodies is necessary to eliminate them or to reduce their negative influence on MR images by adjusting acquisition parameters. It is also necessary to take them into consideration when interpreting the images. Some proposals of reducing artifacts have been mentioned. Describing in detail the procedures to avoid or limit the artifacts would go beyond the scope of this paper but technical ways to reduce them can be found in the cited literature.

Krupa, Katarzyna; Bekiesi?ska-Figatowska, Monika

2015-01-01

131

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

132

Cardiovascular magnetic resonance for amyloidosis.  

PubMed

Cardiac involvement drives the prognosis and treatment in systemic amyloid. Echocardiography, the mainstay of current cardiac imaging, defines cardiac structure and function. Echocardiography, in conjunction with clinical phenotype, electrocardiogram and biomarkers (brain natriuretic peptide and troponin), provides an assessment of the likelihood and extent of cardiac involvement. Two tests are transforming our understanding of cardiac amyloidosis, bone tracer scanning and cardiovascular magnetic resonance (CMR). CMR provides a "second opinion" on the heart's structure and systolic function with better accuracy and more precision than echocardiography but is unable to assess diastolic function and is not as widely available. Where CMR adds unique advantages is in evaluating myocardial tissue characterisation. With administration of contrast, the latest type of late gadolinium enhancement imaging (phase-sensitive inversion recovery sequence) is highly sensitive and specific with images virtually pathognomonic for amyloidosis. CMR is also demonstrating that the range of structural and functional changes in cardiac amyloid is broader than traditionally thought. CMR with T1 mapping, a relatively new CMR technique, can measure the amyloid burden and the myocyte response to infiltration (hypertrophy/cell loss) with advantages for tracking change (e.g. the wall thickness can stay the same but the composition can change) over time or during therapy. Such techniques hold great promise for advancing drug development in this arena and providing new prognostic insights. CMR with tissue characterisation is rewriting our understanding of cardiac amyloidosis and may lead to the development of new classification, therapies and prognostic systems. PMID:25549885

Fontana, Marianna; Chung, Robin; Hawkins, Philip N; Moon, James C

2015-03-01

133

Magnetic resonance imaging features of sinonasal disorders in horses.  

PubMed

Diseases of paranasal sinuses and nasal passages in horses can be a diagnostic challenge because of the complex anatomy of the head and limitations of many diagnostic modalities. Our hypothesis was that magnetic resonance (MR) imaging would provide excellent anatomical detail and soft tissue resolution, and would be accurate in the diagnosis of diseases of the paranasal sinuses and nasal passages in horses. Fourteen horses were imaged. Inclusion criteria were lesions located to the sinuses or nasal passages that underwent MR imaging and subsequent surgical intervention and/or histopathologic examination. A low field, 0.3 tesla open magnet was used. Sequences in the standard protocol were fast spin echo T2 sagittal and transverse, spin echo T1 transverse, short-tau inversion recovery (STIR) dorsal, gradient echo 3D T1 MPR dorsal (plain and contrast enhanced), spin echo T1 fatsat (contrast enhanced). Mean scan time to complete the examination was 53 min (range 39-99 min). Lesions identified were primary or secondary sinusitis (six horses), paranasal sinus cyst (four horses), progressive ethmoid hematoma (two horses), and neoplasia (two horses). The most useful sequences were fast spin echo T2 transverse and sagittal, STIR dorsal and FE3D MPR (survey and contrast enhanced). Fluid accumulation, mucosal thickening, presence of encapsulated contents, bone deformation, and thickening were common findings observed in MR imaging. In selected horses, magnetic resonance imaging is a useful tool in diagnosing lesions of the paranasal sinuses and nasal passages. PMID:22994147

Tessier, Caroline; Brühschwein, Andreas; Lang, Johann; Konar, Martin; Wilke, Markus; Brehm, Walter; Kircher, Patrick

2013-01-01

134

Magnetic Resonance at Short Distances  

SciTech Connect

The magnetic interactions between a fermion and an antifermion of opposite electric or color charges in the $^{1}S_{0}^{-+}$ and $^{3}P_{0}^{++}$ states with $J=0$ are very attractive and singular near the origin and may allow the formation of new bound and resonance states at short distances. In the two body Dirac equations formulated in constraint dynamics, the short-distance attraction for these states for point particles leads to a quasipotential that behaves near the origin as $-\\alpha ^{2}/r^{2}$, where $ \\alpha $ is the coupling constant. Representing this quasipotential at short distances as $\\lambda (\\lambda +1)/r^{2}$ with $\\lambda =(-1+\\sqrt{1-4\\alpha ^{2}})/2$, both $^{1}S_{0}^{-+}$ and $^{3}P_{0}^{++}$ states admit two types of eigenstates with drastically different behaviors for the radial wave function $u=r\\psi $. One type of states, with $u$ growing as $r^{\\lambda +1}$ at small $r$, will be called usual states. The other type of states with $u$ growing as $r^{-\\lambda }$ will be called peculiar states. Both of the usual and peculiar eigenstates have admissible behaviors at short distances. Remarkably, the solutions for both sets of $^{1}S_{0}$ states can be written out analytically. The usual bound $^{1}S_{0}$ states possess attributes the same as those one usually encounters in QED and QCD, with bound state energies explicitly agreeing with the standard perturbative results through order $\\alpha ^{4}$. In contrast, the peculiar bound $^{1}S_{0}$ states, yet to be observed, not only have different behaviors at the origin, but also distinctly different bound state properties (and scattering phase shifts). For the peculiar $^{1}S_{0}$ ground state of fermion-antifermion pair with fermion rest mass $m$, the root-mean-square radius is approximately $1/m$, binding energy is approximately $(2-\\sqrt{2})m$, and rest mass approximately $\\sqrt{2}m$. On the other hand, the $(n+1)$${}^{1}S_{0}$ peculiar state with principal quantum number $(n+1)$ is nearly degenerate in energy and approximately equal in size with the $n$$^{1}S_{0}$ usual states. For the $ {}^{3}P_{0}$ states, the usual solutions lead to the standard bound state energies and no resonance, but resonances have been found for the peculiar states whose energies depend on the description of the internal structure of the charges, the mass of the constituent, and the coupling constant. The existence of both usual and peculiar eigenstates in the same system leads to the non-self-adjoint property of the mass operator and two non-orthogonal complete sets. As both sets of states are physically admissible, the mass operator can be made self-adjoint with a single complete set of admissible states by introducing a new peculiarity quantum number and an enlarged Hilbert space that contains both the usual and peculiar states in different peculiarity sectors. Whether or not these newly-uncovered quantum-mechanically acceptable peculiar $^{1}S_{0}$ bound states and $^{3}P_{0}$ resonances for point fermion-antifermion systems correspond to physical states remains to be further investigated.

Crater, H. W. [University of Tennessee Space Institute; Wong, Cheuk-Yin [ORNL

2012-01-01

135

Reducing Field Distortion in Magnetic Resonance Imaging  

NASA Technical Reports Server (NTRS)

A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

2010-01-01

136

Primate comparative neuroscience using magnetic resonance imaging: promises and challenges  

PubMed Central

Primate comparative anatomy is an established field that has made rich and substantial contributions to neuroscience. However, the labor-intensive techniques employed mean that most comparisons are often based on a small number of species, which limits the conclusions that can be drawn. In this review we explore how new developments in magnetic resonance imaging have the potential to apply comparative neuroscience to a much wider range of species, allowing it to realize an even greater potential. We discuss (1) new advances in the types of data that can be acquired, (2) novel methods for extracting meaningful measures from such data that can be compared between species, and (3) methods to analyse these measures within a phylogenetic framework. Together these developments will allow researchers to characterize the relationship between different brains, the ecological niche they occupy, and the behavior they produce in more detail than ever before. PMID:25339857

Mars, Rogier B.; Neubert, Franz-Xaver; Verhagen, Lennart; Sallet, Jérôme; Miller, Karla L.; Dunbar, Robin I. M.; Barton, Robert A.

2014-01-01

137

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

138

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

139

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

140

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

141

Magnetic moment of the Roper resonance  

E-print Network

The magnetic moment of the Roper resonance is calculated in the framework of a low-energy effective field theory of the strong interactions. A systematic power-counting procedure is implemented by applying the complex-mass scheme.

T. Bauer; J. Gegelia; S. Scherer

2012-08-13

142

Chronic liver disease: evaluation by magnetic resonance  

SciTech Connect

Magnetic resonance (MR) imaging distinguished hepatitis from fatty liver and cirrhosis in a woman with a history of alcohol abuse. Anatomic and physiologic manifestations of portal hypertension were also demonstrated by MR.

Stark, D.D.; Goldberg, H.I.; Moss, A.A.; Bass, N.M.

1984-01-01

143

Magnetic Resonance Imaging (MRI) (For Parents)  

MedlinePLUS

KidsHealth > Parents > Cancer Center > Diagnostic Tests > Magnetic Resonance Imaging (MRI) Print A A A Text Size What's in this article? What It Is Why It's Done Preparation Procedure What to Expect ...

144

Choledochocele: diagnosis by magnetic resonance imaging  

Microsoft Academic Search

The value of magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) is demonstrated in a\\u000a case of a 22-year-old female with a small choledochocele clinically presenting with acute cholecystitis and pancreatitis.\\u000a Previous abdominal sonography and computed tomography were not diagnostic. MRI and MRCP showed a cystic dilatation of the\\u000a distal common bile duct, intramurally located in the second portion

A. I. De Backer; K. Van den Abbeele; A. M. De Schepper; A. Van Baarle

2000-01-01

145

Manual of clinical magnetic resonance imaging  

SciTech Connect

This work is a guide to conducting magnetic resonance imaging (MRI) examinations. The manual presents specific imaging protocols for various MRI examinations of the body. An introductory section describes the physical principles and techniques of magnetic resonance imaging and describes the most commonly encountered artifacts. Guidelines are offered for selecting imaging protocols and conducting examinations of the head, spine, neck, chest, cardiovascular system, abdomen, pelvis, musculoskeletal system, and breast.

Heiken, J.P.; Glazer, H.S.; Lee, J.K.T.; Murphy, W.A.; Gado, M.

1986-01-01

146

4 Nuclear Magnetic Resonance and MRI February 26, 2008  

E-print Network

4 Nuclear Magnetic Resonance and MRI February 26, 2008 The technique of nuclear magnetic resonance at Harvard, for which they both received the 1952 Physics Nobel Prize. Magnetic resonance methods have found of Magnetic Resonance Imaging (MRI) by Paul Lauter- bur, then at SUNY Stony Brook, and Peter Mansfield

Thouless, David

147

Ferromagnetic resonance in ?-Co magnetic composites.  

PubMed

We investigate the electromagnetic properties of assemblies of nanoscale ?-cobalt crystals with size range between 5 to 35 nm, embedded in a polystyrene matrix, at microwave (1-12 GHz) frequencies. We investigate the samples by transmission electron microscopy imaging, demonstrating that the particles aggregate and form chains and clusters. By using a broadband coaxial-line method, we extract the magnetic permeability in the frequency range from 1 to 12 GHz, and we study the shift of the ferromagnetic resonance (FMR) with respect to an externally applied magnetic field. We find that the zero-magnetic field ferromagnetic resonant peak shifts towards higher frequencies at finite magnetic fields, and the magnitude of complex permeability is reduced. At fields larger than 2.5 kOe the resonant frequency changes linearly with the applied magnetic field, demonstrating the transition to a state in which the nanoparticles become dynamically decoupled. In this regime, the particles inside clusters can be treated as non-interacting, and the peak position can be predicted from Kittel's FMR theory for non-interacting uniaxial spherical particles combined with the Landau-Lifshitz-Gilbert equation. In contrast, at low magnetic fields this magnetic order breaks down and the resonant frequency in zero magnetic field reaches a saturation value reflecting the interparticle interactions as resulting from aggregation. Our results show that the electromagnetic properties of these composite materials can be tuned by external magnetic fields and by changes in the aggregation structure. PMID:25397945

Chalapat, Khattiya; Timonen, Jaakko V I; Huuppola, Maija; Koponen, Lari; Johans, Christoffer; Ras, Robin H A; Ikkala, Olli; Oksanen, Markku A; Seppälä, Eira; Paraoanu, G S

2014-12-01

148

Ferromagnetic resonance in ?-Co magnetic composites  

NASA Astrophysics Data System (ADS)

We investigate the electromagnetic properties of assemblies of nanoscale ?-cobalt crystals with size range between 5 to 35 nm, embedded in a polystyrene matrix, at microwave (1–12 GHz) frequencies. We investigate the samples by transmission electron microscopy imaging, demonstrating that the particles aggregate and form chains and clusters. By using a broadband coaxial-line method, we extract the magnetic permeability in the frequency range from 1 to 12 GHz, and we study the shift of the ferromagnetic resonance (FMR) with respect to an externally applied magnetic field. We find that the zero-magnetic field ferromagnetic resonant peak shifts towards higher frequencies at finite magnetic fields, and the magnitude of complex permeability is reduced. At fields larger than 2.5 kOe the resonant frequency changes linearly with the applied magnetic field, demonstrating the transition to a state in which the nanoparticles become dynamically decoupled. In this regime, the particles inside clusters can be treated as non-interacting, and the peak position can be predicted from Kittel?s FMR theory for non-interacting uniaxial spherical particles combined with the Landau–Lifshitz–Gilbert equation. In contrast, at low magnetic fields this magnetic order breaks down and the resonant frequency in zero magnetic field reaches a saturation value reflecting the interparticle interactions as resulting from aggregation. Our results show that the electromagnetic properties of these composite materials can be tuned by external magnetic fields and by changes in the aggregation structure.

Chalapat, Khattiya; Timonen, Jaakko V. I.; Huuppola, Maija; Koponen, Lari; Johans, Christoffer; Ras, Robin H. A.; Ikkala, Olli; Oksanen, Markku A.; Seppälä, Eira; Paraoanu, G. S.

2014-12-01

149

Multispectral magnetic resonance image analysis.  

PubMed

Multiecho magnetic resonance (MR) scanning produces tomographic images with approximately equal morphologic information but varying gray scales at the same anatomic level. Multispectral image classification techniques, originally developed for satellite imaging, have recently been applied to MR tissue characterization. Statistical assessment of multispectral tissue classification techniques has been used to select the most promising of several alternative methods. MR examinations of the head and body, obtained with a 0.35, 0.5, or 1.5T imager, comprised data sets with at least two pulse sequences yielding three images at each anatomical level: (1) TR = 0.3 sec, TE = 30 msec, (2) TR = 1.5, TE = 30, (3) TR = 1.5, TE = 120. Normal and pathological images have been analyzed using multispectral analysis and image classification. MR image data are first subjected to radiometric and geometric corrections to reduce error resulting from (1) instrumental variations in data acquisition, (2) image noise, and (3) misregistration. Training regions of interest (ROI) are outlined in areas of normal (gray and white matter, CSF) and pathological tissue. Statistics are extracted from these ROIs and classification maps generated using table lookup, minimum distance to means, maximum likelihood, and cluster analysis. These synthetic maps are then compared pixel by pixel with manually prepared classification maps of the same MR images. Using these methods, the authors have found that: (1) both supervised and unsupervised classification techniques yielded theme maps (class maps) which demonstrated tissue characteristic signatures and (2) tissue classification errors found in computer-generated theme maps were due to subtle gray scale changes present in the original MR data sets arising from radiometric inhomogeneity and spatial nonuniformity. PMID:3691157

Vannier, M W; Butterfield, R L; Rickman, D L; Jordan, D M; Murphy, W A; Biondetti, P R

1987-01-01

150

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 of microscopic ferromagnetic resonance FMR detected using the magnetic resonance force microscope MRFM of structural and magnetic properties of materials. The mag- netic resonance force microscope MRFM can

Hammel, P. Chris

151

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

E-print Network

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

Hammel, P. Chris

152

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

153

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

E-print Network

Observation of ferromagnetic resonance in a microscopic sample using magnetic resonance force can be measured. Employing magnetic resonance force microscopy MRFM we have observed a strong FMR the technologically important magnetic multilayer systems. MRFM, based on mechanical detection of magnetic resonance

Hammel, P. Chris

154

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

155

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

156

Nuclear Magnetic Resonance Technology for Medical Studies  

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance proton imaging provides anatomical definition of normal and abnormal tissues with a contrast and detection sensitivity superior to those of x-ray computed tomography in the human head and pelvis and parts of the cardiovascular and musculoskeletal systems. Recent improvements in technology should lead to advances in diagnostic imaging of the breast and regions of the abdomen. Selected-region nuclear magnetic resonance spectroscopy of protons, carbon-13, and phosphorus-31 has developed into a basic science tool for in vivo studies on man and a unique tool for clinical diagnoses of metabolic disorders. At present, nuclear magnetic resonance is considered safe if access to the magnet environment is controlled. Technological advances employing field strengths over 2 teslas will require biophysical studies of heating and static field effects.

Budinger, Thomas F.; Lauterbur, Paul C.

1984-10-01

157

Comparison of magnetic resonance angiography, magnetic resonance imaging and conventional angiography in cerebral arteriovenous malformation  

Microsoft Academic Search

10 patients with an AVM of the brain were examined by magnetic resonance angiography (MRA), magnetic resonance imaging (MRI) and conventional cerebral angiography (CCA). From MRA in 7\\/10 patients important information about vascular supply could be provided; in 3 patients, all with small AVM's it could be only suspected. CCA revealed the vascularisation of the AVM's in all patients and

F. Nüssel; H. Wegmüller; P. Huber

1991-01-01

158

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

159

Magnetic resonance of magnetic fluid and magnetoliposome preparations  

NASA Astrophysics Data System (ADS)

In this study, magnetic resonance was used to investigate lauric acid-coated magnetite-based magnetic fluid particles and particles which are surrounded by a double layer of phospholipid molecules (magnetoliposomes). The data reveal the presence of monomers and dimers in both samples. Whereas evidence for a thermally induced disruption of dimers is found in the magnetic fluid, apparently, the bilayer phospholipid envelop prevents the dissociation in the magnetoliposome samples.

Morais, Paulo C.; Santos, Judes G.; Skeff Neto, K.; Pelegrini, Fernando; De Cuyper, Marcel

2005-05-01

160

Euclidean resonance in a magnetic field  

E-print Network

An analogy between Wigner resonant tunneling and tunneling across a static potential barrier in a static magnetic field is found. Whereas in the process of Wigner tunneling an electron encounters a classically allowed regions, where a discrete energy level coincides with its energy, in the magnetic field a potential barrier is a constant in the direction of tunneling. Along the tunneling path the certain regions are formed, where, in the classical language, the kinetic energy of the motion perpendicular to tunneling is negative. These regions play a role of potential wells, where a discrete energy level can coincide with the electron energy. Such phenomenon, which occurs at the certain magnetic field, is called Euclidean resonance and substantially depends on a shape of potential forces in the direction perpendicular to tunneling. Under conditions of Euclidean resonance a long distance underbarrier motion is possible.

B. Ivlev

2007-05-19

161

Magnetic resonance signal moment determination using the Earth's magnetic field.  

PubMed

We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system. PMID:25700116

Fridjonsson, E O; Creber, S A; Vrouwenvelder, J S; Johns, M L

2015-03-01

162

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

163

Applications of Cardiac Magnetic Resonance in Electrophysiology  

PubMed Central

Contemporary methods for evaluation and treatment of arrhythmia are increasingly dependent upon characterization of the underlying myocardial substrate. Cardiovascular magnetic resonance offers unsurpassed soft tissue resolution capable of visualizing detailed cardiac anatomic features and intra-myocardial barriers to conduction. Non-invasive visualization of such anatomic detail has the potential to improve methods to diagnose, risk stratify, and treat patients with arrhythmia. This review describes a brief overview of the current knowledge on the applications of cardiac magnetic resonance for evaluation and treatment of patients with arrhythmia. PMID:19808444

Nazarian, Saman; Bluemke, David A.; Halperin, Henry R.

2012-01-01

164

Granular convection observed by magnetic resonance imaging  

SciTech Connect

Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here. 31 refs., 4 figs.

Ehrichs, E.E.; Jaeger, H.M.; Knight, J.B.; Nagel, S.R.; Karczmar, G.S.; Kuperman, V.Yu. [Univ. of Chicago, IL (United States)

1995-03-17

165

Granular convection observed by magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.

Ehrichs, E. E.; Jaeger, H. M.; Karczmar, Greg S.; Knight, James B.; Kuperman, Vadim Yu.; Nagel, Sidney R.

1995-03-01

166

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2006; 44: S206S212  

E-print Network

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2006; 44: S206­S212 Published online in Wiley 16 March 2006 Sample concentrations can be measured by nuclear magnetic resonance (NMR) spectroscopy Quantitative nuclear magnetic resonance (NMR) is an efficient method for the determination of concentrations

Wider, Gerhard

167

Magnetic force microscopy using tip magnetization modulated by ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

In magnetic force microscopy (MFM), the tip–sample distance should be reduced to analyze the microscopic magnetic domain structure with high spatial resolution. However, achieving a small tip–sample distance has been difficult because of superimposition of interaction forces such as van der Waals and electrostatic forces induced by the sample surface. In this study, we propose a new method of MFM using ferromagnetic resonance (FMR) to extract only the magnetic field near the sample surface. In this method, the magnetization of a magnetic cantilever is modulated by FMR to separate the magnetic field and topographic structure. We demonstrate the modulation of the magnetization of the cantilever and the identification of the polarities of a perpendicular magnetic medium.

Arima, Eiji; Naitoh, Yoshitaka; Li, Yan Jun; Yoshimura, Satoru; Saito, Hitoshi; Nomura, Hikaru; Nakatani, Ryoichi; Sugawara, Yasuhiro

2015-03-01

168

Magnetic Resonance Imaging (MRI) - Spine  

MedlinePLUS

... the magnet, radio waves redirect alignment of hydrogen atoms that naturally exist within the body without causing ... chemical changes in the tissues. As the hydrogen atoms return to their usual alignment, they emit energy ...

169

Magnetic elliptical polarization of Schumann resonances  

NASA Technical Reports Server (NTRS)

Measurements of orthogonal, horizontal components of the magnetic field in the ELF range obtained during September 1985 show that the Schumann resonance eigenfrequencies determined separately for the north-south and east-west magnetic components differ by as much as 0.5 Hz, suggesting that the underlying magnetic signal is not linearly polarized at such times. The high degree of magnetic ellipticity found suggests that the side multiplets of the Schumann resonances corresponding to azimuthally inhomogeneous normal modes are strongly excited in the highly asymmetric earth-ionosphere cavity. The dominant sense of polarization over the measurement passband is found to be right-handed during local daylight hours, and to be left-handed during local nighttime hours.

Sentman, D. D.

1987-01-01

170

JOURNAL OF MAGNETIC RESONANCE 99,495-506 ( 1992) Sensitivity of Optically Excited andDetectedMagnetic Resonance  

E-print Network

JOURNAL OF MAGNETIC RESONANCE 99,495-506 ( 1992) Sensitivity of Optically Excited andDetectedMagnetic forms of spectroscopy, the sensitivity of magnetic resonance exper- iments is relatively low, so some of this sensitivity advantage to the domain of magnetic resonance and gives numerical estimates

Suter, Dieter

171

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.

172

Magnetic resonance investigation of magnetic-labeled baker's yeast cells  

NASA Astrophysics Data System (ADS)

In this study, the interaction of DMSA-coated magnetite nanoparticles (5 and 10 nm core-size) with Saccharomyces cerevisae was investigated using magnetic resonance (MR) and transmission electron microscopy (TEM). The TEM micrographs revealed magnetite nanoparticles attached externally to the cell wall. The MR data support the strong interaction among the nanoparticles supported by the cells. A remarkable shift in the resonance field was used as signature of particle attachment to the cell wall.

Godoy Morais, J. P. M.; Azevedo, R. B.; Silva, L. P.; Lacava, Z. G. M.; Báo, S. N.; Silva, O.; Pelegrini, F.; Gansau, C.; Buske, N.; Safarik, I.; Safarikova, M.; Morais, P. C.

2004-05-01

173

Magnetic Resonance Connectome Automated Pipeline: An Overview  

Microsoft Academic Search

This article presents a novel, tightly integrated pipeline for estimating a connectome. The pipeline utilizes magnetic resonance (MR) imaging (MRI) data to produce a high-level estimate of the structural connectivity in the human brain. The MR connectome automated pipeline (MRCAP) is efficient, and its modular construction allows researchers to modify algorithms to meet their specific requirements. The pipeline has been

William R. Gray; John A. Bogovic; Joshua T. Vogelstein; Bennett A. Landman; Jerry L. Prince; R. Jacob Vogelstein

2012-01-01

174

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

175

Magnetic resonance imaging in cancer research  

Microsoft Academic Search

Non-invasive assessment of antineoplastic response and correlation of the location, magnitude and duration of transgene expression in vivo would be particularly useful for evaluating cancer gene therapy protocols. This review presents selected examples of how magnetic resonance (MR) has been used to assess therapeutic efficacy by non-invasive quantitation of cell kill, to detect a therapeutic response prior to a change

B. D. Ross; T. L. Chenevert; A. Rehemtulla

2002-01-01

176

Functional Magnetic Resonance Imaging of Pain Consciousness  

E-print Network

clinical pain states can be studied. Preliminary results are shown in patients suffering from chronicFunctional 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

177

Magnetic resonance urography in pediatric urology  

Microsoft Academic Search

Purpose of reviewMagnetic resonance urography (MRU) has emerged as a powerful diagnostic tool in the evaluation of the pediatric genitourinary tract. The purpose of this review is to familiarize the reader with the basic techniques, strengths and limitations, as well as the current and potential future applications of MRU in pediatric urology.

Wolfgang H. Cerwinka; J. Damien Grattan-Smith; Andrew J. Kirsch

2008-01-01

178

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

179

Nuclear magnetic resonance technology for medical studies  

Microsoft Academic Search

Nuclear magnetic resonance proton imaging provides anatomical definition of normal and abnormal tissues with a contrast and detection sensitivity superior to those of x-ray computed tomography in the human head and pelvis and parts of the cardiovascular and musculoskeletal systems. Recent improvements in technology should lead to advances in diagnostic imaging of the breast and regions of the abdomen. Selected-region

T. F. Budinger; P. C. Lauterbur

1984-01-01

180

Magnetic Resonance Imaging of the Postoperative Meniscus  

Microsoft Academic Search

Imaging of the postoperative meniscus is a challenge. Nevertheless, magnetic resonance imaging (MRI) of the symptomatic knee after meniscal surgery is a valuable diagnostic study of both the menisci and the entire joint. At present, symptomatic patients who have had partial meniscectomy of less than 25% may be evaluated by MRI. For those with partial meniscectomy of greater than 25%

Kennan Vance; Richard Meredick; Mark E. Schweitzer; James H. Lubowitz

2009-01-01

181

Cine magnetic resonance imaging of aqueductal stenosis  

Microsoft Academic Search

Cerebral aqueductal stenosis is one of the most common causes of congenital and acquired hydrocephalus, but the etiology, pathophysiology and cerebrospinal fluid (CSF) dynamics of aqueductal stenosis have yet to be clarified. Utilizing cardiac gated cine magnetic resonance (MR) imaging, we evaluated aqueductal configuration and pulsatile motion of brain and CSF flow stimulated by cardiac pulsation in five patients with

Chikafusa Kadowaki; Mitsuhiro Hara; Mitsuo Numoto; Kazuo Takeuchi; Isamu Saito

1995-01-01

182

The diabetic foot: magnetic resonance imaging evaluation  

Microsoft Academic Search

Fourteen diabetic patients with suspected foot infection and\\/or neuropathic joint (Charcot Joint) were evaluated with magnetic resonance imaging (MRI) in an attempt to assess the extent of the infection and also to distinguish infection from the changes seen with neuroarthropathy. The majority of patients with infection had more than one site of involvement and the following diagnoses were made by

Javier Beltran; D. Scott Campanini; Charles Knight; Melinda McCalla

1990-01-01

183

Magnetic resonance imaging in motor neuron disease  

Microsoft Academic Search

Magnetic resonance imaging (MRI) of the brain was evaluated in 20 patients with motor neuron disease (MND) and in a control group of 11 healthy people. Bilateral increased signal areas of various sizes in the centrum semiovale, corona radiata, internal capsule, pedunculi of midbrain, pons, medulla and even in the frontal lobe, topographically related with the corticospinal tract, were found

M. L. Sales Luís; A. Hormigo; C. Maurício; M. M. Alves; R. Serrão

1990-01-01

184

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

185

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

186

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2014 CFR

...distribution and/or magnetic resonance spectra which reflect frequency and distribution of nuclei exhibiting nuclear magnetic resonance. Other physical parameters derived from the images and/or spectra may also be produced. The...

2014-04-01

187

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2012 CFR

...distribution and/or magnetic resonance spectra which reflect frequency and distribution of nuclei exhibiting nuclear magnetic resonance. Other physical parameters derived from the images and/or spectra may also be produced. The...

2012-04-01

188

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2013 CFR

...distribution and/or magnetic resonance spectra which reflect frequency and distribution of nuclei exhibiting nuclear magnetic resonance. Other physical parameters derived from the images and/or spectra may also be produced. The...

2013-04-01

189

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2011 CFR

...distribution and/or magnetic resonance spectra which reflect frequency and distribution of nuclei exhibiting nuclear magnetic resonance. Other physical parameters derived from the images and/or spectra may also be produced. The...

2011-04-01

190

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

191

Musculoskeletal applications of magnetic resonance imaging: Council on Scientific Affairs  

SciTech Connect

Magnetic resonance imaging provides superior contrast, resolution, and multiplanar imaging capability, allowing excellent definition of soft-tissue and bone marrow abnormalities. For these reasons, magnetic resonance imaging has become a major diagnostic imaging method for the evaluation of many musculoskeletal disorders. The applications of magnetic resonance imaging for musculoskeletal diagnosis are summarized and examples of common clinical situations are given. General guidelines are suggested for the musculoskeletal applications of magnetic resonance imaging.

Harms, S.E.; Fisher, C.F.; Fulmer, J.M. (American Medical Association, Chicago, IL (USA))

1989-11-03

192

Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy in Parkinson’s Disease  

Microsoft Academic Search

At present, conventional magnetic resonance imaging (MRI) shows no convincing structural changes in Parkinson’s disease (PD)\\u000a itself, but it may be useful in helping to distinguish PD from other neurodegenerative parkinsonian syndromes. Magnetic resonance\\u000a spectroscopy (MRS) also may provide useful information in distinguishing PD from disorders such as multiple system atrophy.\\u000a The general field of MRI and MRS is evolving

W. R. Wayne Martin

193

1H Magnetic resonance imaging and 31P magnetic resonance spectroscopy in experimental filariasis  

Microsoft Academic Search

1H Magnetic resonance imaging and 31P magnetic resonance spectroscopy (MRS) have been carried out in experimental rodent filariasis, i.e., Acanthocheilonema viteae infection in the rodent host, Mastomys coucha. The T2-weighted image of the infected host shows fine hyperintense thread like structures of adult filariid nests in the cervical region. 31P MRS of normal and infected hosts, localized over the same

Amita Shukla-Dave; Nigar Fatma; Raja Roy; S. Srivastava; R. K. Chatterjee; V. Govindaraju; A. Kasi Viswanathan; P. Raghunathan

1997-01-01

194

Nuclear magnetic resonance properties of lunar samples.  

NASA Technical Reports Server (NTRS)

Nuclear magnetic resonance spectra of Na-23, Al-27, and P-31 in fines samples 10084,60 and 14163,168 and in crystalline rock samples 12021,55 and 14321,166, have been recorded over a range of frequencies up to 20 MHz. A shift in the field at which maximum absorption occurs for all of the spectra relative to the field at which maximum absorption occurs for terrestrial analogues is attributed to a sample-dependent magnetic field at the Na, Al, and P sites opposing the laboratory field. The magnitude of these fields internal to the samples is sample dependent and varies from 5 to 10 G. These fields do not correlate with the iron content of the samples. However, the presence of single-domain particles of iron distributed throughout the plagioclase fraction that contains the principal fraction of Na and Al is inferred from electron magnetic resonance spectra shapes.

Kline, D.; Weeks, R. A.

1972-01-01

195

Bipolar programmable current supply for superconducting nuclear magnetic resonance magnets  

Microsoft Academic Search

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

Jaakko Koivuniemi; Reeta Luusalo; Pertti Hakonen

1998-01-01

196

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging  

E-print Network

Genetically encoded reporters for hyperpolarized xenon magnetic resonance imaging Mikhail G Pines5,6, David V. Schaffer2,7 and Vikram S. Bajaj5,6 * Magnetic resonance imaging (MRI) enables high , such that its magnetic resonance signal in a saturated aqueous solution at millimolar concentrations

Schaffer, David V.

197

Magnetic Resonance Imaging Charles L. Epstein and Felix W. Wehrli  

E-print Network

Magnetic Resonance Imaging Charles L. Epstein and Felix W. Wehrli June 3, 2005 1 Introduction Nuclear magnetic resonance (NMR) is a subtle quantum mechanical phenomenon that, through magnetic resonance imaging (MRI), has played a major role in the revolution in medical imaging over the last 30 years

198

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

E-print Network

MBP 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 Course description: Nuclear Magnetic Resonance: The purpose of this course is to provide an understanding

Lennard, William N.

199

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 of a prototype of a portable NMR (nuclear magnetic resonance) spectrometer prototype. As the volume of the sample

Baudoin, Geneviève

200

Magnetic Resonance Imaging of Brain Function and Neurochemistry  

E-print Network

Magnetic Resonance Imaging of Brain Function and Neurochemistry KAMIL UGURBIL, DAE-SHIK KIM, TIM ANDERSEN, AND GREGOR ADRIANY Invited Paper In the past decade, magnetic resonance imaging (MRI) research approaches to map brain function. This capability, often referred to as functional magnetic resonance imaging

Duong, Timothy Q.

201

A Scalable Framework For Segmenting Magnetic Resonance Images  

E-print Network

A Scalable Framework For Segmenting Magnetic Resonance Images Prodip Hore, Lawrence O. Hall, Dmitry, accurate and fully automatic method of segmenting magnetic resonance images of the human brain a framework for auto- matically segmenting magnetic resonance images of the human brain. The framework

Hall, Lawrence O.

202

A Spectral-Scanning Magnetic Resonance Imaging (MRI) Integrated System  

E-print Network

A Spectral-Scanning Magnetic Resonance Imaging (MRI) Integrated System Arjang Hassibi1,2 , Aydin of Texas at Austin, Austin, TX 78712, USA Abstract- An integrated spectral-scanning magnetic resonance customized magnetic resonance (MR) excitation signals, and also recovering the MR response using a coherent

Hajimiri, Ali

203

Laser-Assisted Magnetic Resonance: Principles and Applications  

E-print Network

Laser-Assisted Magnetic Resonance: Principles and Applications D. Suter and J. Gutschank Universit radiation can be used in various magnetic resonance experiments. This chapter discusses a number of cases with the help of coherent optical radiation. 1 Introduction The interest in the field of magnetic resonance

Suter, Dieter

204

Classification of prostate magnetic resonance spectra using support vector machine  

E-print Network

that nuclear magnetic resonance spectra are sensitive enough to distinguish normal and cancer. In this paperClassification of prostate magnetic resonance spectra using support vector machine S. Parfait a, we propose a classification technique of spectra from magnetic resonance spectroscopy. We studied au

205

Principles of functional Magnetic Resonance Martin A. Lindquist  

E-print Network

1 Principles of functional Magnetic Resonance Imaging Martin A. Lindquist Department of Magnetic Resonance Signal Generation ............. 6 1.2.1.1 The MRI Scanner ...................................................... 40 1.1 Introduction Functional Magnetic Resonance Imaging (fMRI) is a non-invasive technique

206

Material Classification of Magnetic Resonance Volume Data David H. Laidlaw  

E-print Network

Material Classification of Magnetic Resonance Volume Data Thesis by David H. Laidlaw In Partial these traditional modeling methods. We use vector­valued magnetic resonance volume data in this thesis. The process and processing magnetic resonance data to meet the needs of the later steps. Our material classification

207

Hyperpolarized noble gas magnetic resonance imaging of the animal lung: Approaches and applications  

NASA Astrophysics Data System (ADS)

Hyperpolarized noble gas (HNG) magnetic resonance (MR) imaging is a very promising noninvasive tool for the investigation of animal models of lung disease, particularly to follow longitudinal changes in lung function and anatomy without the accumulated radiation dose associated with x rays. The two most common noble gases for this purpose are H3e (helium 3) and X129e (xenon 129), the latter providing a cost-effective approach for clinical applications. Hyperpolarization is typically achieved using spin-exchange optical pumping techniques resulting in ˜10 000-fold improvement in available magnetization compared to conventional Boltzmann polarizations. This substantial increase in polarization allows high spatial resolution (<1 mm) single-slice images of the lung to be obtained with excellent temporal resolution (<1 s). Complete three-dimensional images of the lungs with 1 mm slice thickness can be obtained within reasonable breath-hold intervals (<20 s). This article provides an overview of the current methods used in HNG MR imaging with an emphasis on ventilation studies in animals. Special MR hardware and software considerations are described in order to use the strong but nonrecoverable magnetization as efficiently as possible and avoid depolarization primarily by molecular oxygen. Several applications of HNG MR imaging are presented, including measurement of gross lung anatomy (e.g., airway diameters), microscopic anatomy (e.g., apparent diffusion coefficient), and a variety of functional parameters including dynamic ventilation, alveolar oxygen partial pressure, and xenon diffusing capacity.

Santyr, Giles E.; Lam, Wilfred W.; Parra-Robles, Juan M.; Taves, Timothy M.; Ouriadov, Alexei V.

2009-05-01

208

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

209

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

210

Diffusion magnetic resonance HE MAGNETIC resonance application that the rest of this thesis will be concerned with is that  

E-print Network

4 Diffusion magnetic resonance imaging T HE MAGNETIC resonance application that the rest of this thesis will be concerned with is that of diffusion magnetic resonance imaging (dMRI). This chapter provides a brief description of diffusion and how it can be examined in the brain with dMRI. Mathematical

Clayden, Jonathan D.

211

Magnetic resonance imaging of isolated single liposome by magnetic resonance force microscopy  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is very useful spectroscopy to visualize a three-dimensional (3D) real structure inside the sample without physical destruction. The spatial resolution of the readily available MRI spectrometer is, however, limited by a few ten to hundreds of microns due to a technological boundary of generating larger magnetic field gradient and to the insensitivity inherent to the inductive

S. Tsuji; T. Masumizu; Y. Yoshinari

2004-01-01

212

GARANT-a general algorithm for resonance assignment of multidimensional nuclear magnetic resonance spectra  

Microsoft Academic Search

A new program for automatic resonance assignment of nuclear magnetic resonance NMR spectra of proteins, GARANT General Algorithm for Resonance AssignmeNT, is introduced. Three principal elements used in this approach are: a. representation of resonance assignments as an optimal match of two graphs describing, respectively, peaks expected from combined knowledge of the primary structure and the magnetization transfer pathways in

Christian Bartels; Peter Güntert; Martin Billeter; Kurt Wüthrich

1997-01-01

213

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

E-print Network

with simultaneous nuclear magnetic resonance J. S. Colton1,a and L. R. Wienkes2 1 Department of Physics magnetic resonance ODMR experiments. The cylindrical quasi-TE011 mode cavity is designed to fit in a 1 in. magnet bore to allow the sample to be optically accessed and to have an adjustable resonant frequency

Hart, Gus

214

Spin echo magnetic resonance imaging.  

PubMed

The spin echo sequence is a fundamental pulse sequence in MRI. Many of today's applications in routine clinical use are based on this elementary sequence. In this review article, the principles of the spin echo formation are demonstrated on which the generation of the fundamental image contrasts T1, T2, and proton density is based. The basic imaging parameters repetition time (TR) and echo time (TE) and their influence on the image contrast are explained. Important properties such as the behavior in multi-slice imaging or in the presence of flow are depicted and the basic differences with gradient echo imaging are illustrated. The characteristics of the spin echo sequence for different magnetic field strengths with respect to clinical applications are discussed. PMID:23526758

Jung, Bernd André; Weigel, Matthias

2013-04-01

215

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2003; 41: S80S88  

E-print Network

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2003; 41: S80­S88 Published online in Wiley of Nuclear Magnetic Resonance, volume 9, Advances in NMR, D. M. Grant and R. K. Harris (eds), Wiley magnetic fields typically used for studies of proteins and nucleic acids, chemical shift anisotropy (CSA

Wider, Gerhard

216

Magnetic resonance of calcified tissues.  

PubMed

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. PMID:23414678

Wehrli, Felix W

2013-04-01

217

Magnetic resonance imaging characteristics of equine head disorders: 84 cases (2000-2013).  

PubMed

The equine head is an anatomically complex area, therefore advanced tomographic imaging techniques, such as computed tomography or magnetic resonance imaging (MRI), are often required for diagnosis and treatment planning. The purpose of this multicenter retrospective study was to describe MRI characteristics for a large sample of horses with head disorders. Horses imaged over a period of 13 years were recruited. Eighty-four horses met the inclusion criteria, having neurological (n = 65), sinonasal (n = 14), and soft tissue (n = 5) disorders. Magnetic resonance imaging accurately depicted the anatomy and allowed identification of the primary lesion and associated changes. There were good correlations between MRI findings and intraoperative or postmortem results. Magnetic resonance imaging showed the exact localization of the lesions, their size, and relation to surrounding structures. However, in the neurological group, there were 45 horses with no MRI abnormalities, 29 of which had a history of recurrent seizures, related to cryptogenic epilepsy. Magnetic resonance imaging was otherwise a valuable diagnostic tool, and can be used for studying a broad range of head disorders using either low-field or high-field magnets. PMID:25139131

Manso-Díaz, Gabriel; Dyson, Sue J; Dennis, Ruth; García-López, José M; Biggi, Marianna; García-Real, M Isabel; San Román, Fidel; Taeymans, Olivier

2015-03-01

218

A hyperpolarized equilibrium for magnetic resonance  

PubMed Central

Nuclear magnetic resonance spectroscopy and imaging (MRI) play an indispensable role in science and healthcare but use only a tiny fraction of their potential. No more than ?10?p.p.m. of all 1H nuclei are effectively detected in a 3-Tesla clinical MRI system. Thus, a vast array of new applications lays dormant, awaiting improved sensitivity. Here we demonstrate the continuous polarization of small molecules in solution to a level that cannot be achieved in a viable magnet. The magnetization does not decay and is effectively reinitialized within seconds after being measured. This effect depends on the long-lived, entangled spin-order of parahydrogen and an exchange reaction in a low magnetic field of 10?3 Tesla. We demonstrate the potential of this method by fast MRI and envision the catalysis of new applications such as cancer screening or indeed low-field MRI for routine use and remote application. PMID:24336292

Hövener, Jan-Bernd; Schwaderlapp, Niels; Lickert, Thomas; Duckett, Simon B.; Mewis, Ryan E.; Highton, Louise A. R.; Kenny, Stephen M.; Green, Gary G. R.; Leibfritz, Dieter; Korvink, Jan G.; Hennig, Jürgen; von Elverfeldt, Dominik

2013-01-01

219

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 that a particle with angular momentum I and magnetic moment µ = I placed in a uniform mag- netic field B0

Seager, Sara

220

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

221

Antiferromagnetic resonance excitation by terahertz magnetic field resonantly enhanced with split ring resonator  

SciTech Connect

Excitation of antiferromagnetic resonance (AFMR) in a HoFeO{sub 3} crystal combined with a split ring resonator (SRR) is studied using terahertz (THz) electromagnetic pulses. The magnetic field in the vicinity of the SRR is induced by the incident THz electric field component and excites spin oscillations that correspond to the AFMR, which are directly probed by the Faraday rotation of the polarization of a near-infrared probe pulse. The good agreement of the temperature-dependent magnetization dynamics with the calculation using the two-lattice Landau-Lifshitz-Gilbert equation confirms that the AFMR is excited by the THz magnetic field, which is enhanced at the SRR resonance frequency by a factor of 20 compared to the incident magnetic field.

Mukai, Y. [Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Hirori, H., E-mail: hirori@icems.kyoto-u.ac.jp [Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012 (Japan); Yamamoto, T. [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Kageyama, H. [Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Tanaka, K., E-mail: kochan@scphys.kyoto-u.ac.jp [Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012 (Japan)

2014-07-14

222

Antiferromagnetic resonance excitation by terahertz magnetic field resonantly enhanced with split ring resonator  

NASA Astrophysics Data System (ADS)

Excitation of antiferromagnetic resonance (AFMR) in a HoFeO3 crystal combined with a split ring resonator (SRR) is studied using terahertz (THz) electromagnetic pulses. The magnetic field in the vicinity of the SRR is induced by the incident THz electric field component and excites spin oscillations that correspond to the AFMR, which are directly probed by the Faraday rotation of the polarization of a near-infrared probe pulse. The good agreement of the temperature-dependent magnetization dynamics with the calculation using the two-lattice Landau-Lifshitz-Gilbert equation confirms that the AFMR is excited by the THz magnetic field, which is enhanced at the SRR resonance frequency by a factor of 20 compared to the incident magnetic field.

Mukai, Y.; Hirori, H.; Yamamoto, T.; Kageyama, H.; Tanaka, K.

2014-07-01

223

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

224

Field-focusing nuclear magnetic resonance (FONAR)  

NASA Astrophysics Data System (ADS)

A technique, field-focusing NMR (FONAR), is described for doing NMR scans in large samples. The method utilizes a shaped D.C. magnetic field that confines the NMR-signal-producing region of the sample to a small volume called the resonance aperture. The aperture contains the required values of the H o field to fully bracket the band of the r.f. pulse. The magnet system and r.f. pick-up coil that achieved the first human NMR scan is discussed.

Damadian, Raymond; Minkoff, Lawrence; Goldsmith, Michael; Koutcher, Jason A.

1978-05-01

225

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

226

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

227

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

228

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

229

Resonantly detecting axion-mediated forces with nuclear magnetic resonance.  

PubMed

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 10(9) and 10(12) GeV or axion masses between 10(-6) and 10(-3) eV, independent of the cosmic axion abundance. PMID:25361250

Arvanitaki, Asimina; Geraci, Andrew A

2014-10-17

230

Resonant detection of axion mediated forces with Nuclear Magnetic Resonance  

E-print Network

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 10^9 and 10^12 GeV or axion masses between 10^-6 and 10^-3 eV, independent of the cosmic axion abundance.

Asimina Arvanitaki; Andrew A. Geraci

2014-03-05

231

Resonantly Detecting Axion-Mediated Forces with Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 109 and 1012 GeV or axion masses between 10-6 and 10-3 eV, independent of the cosmic axion abundance.

Arvanitaki, Asimina; Geraci, Andrew A.

2014-10-01

232

Cardiovascular Magnetic Resonance in Heart Failure  

Microsoft Academic Search

Imaging has a central role in the evaluation of patients with heart failure (HF). Cardiovascular magnetic resonance (CMR)\\u000a is rapidly evolving as a versatile imaging modality that often provides additional information to echocardiography in patients\\u000a with suspected or known HF. CMR is the only imaging modality that has the ability to assess, without exposure to ionizing\\u000a radiation, cardiac function, structure

Theodoros D. Karamitsos; Stefan Neubauer

2011-01-01

233

Magnetic Resonance Imaging Guidance for Tumor Ablation  

Microsoft Academic Search

Since the late 1980s, magnetic resonance imaging (MRI) has been added to ultrasound (US) and computed tomography (CT) as a\\u000a cross-sectional imaging tool that can be used to guide the interventional diagnosis and treatment of a variety of disorders.\\u000a Due to its superior soft tissue contrast, multiplanar capabilities, lack of ionizing radiation, and, most importantly, ability\\u000a to image tissue function

Koenraad J. Mortele; Stuart G. Silverman; Vito Cantisani; Kemal Tuncali; Sridhar Shankar; Eric vanSonnenberg

234

Exploring brain function with magnetic resonance imaging  

Microsoft Academic Search

Since its invention in the early 1990s, functional magnetic resonance imaging (fMRI) has rapidly assumed a leading role among the techniques used to localize brain activity. The spatial and temporal resolution provided by state-of-the-art MR technology and its non-invasive character, which allows multiple studies of the same subject, are some of the main advantages of fMRI over the other functional

F. Di Salle; E. Formisano; D. E. J. Linden; R. Goebel; S. Bonavita; A. Pepino; F. Smaltino; G. Tedeschi

1999-01-01

235

Magnetic resonance imaging strategies for heart studies  

SciTech Connect

Given a suitable trigger signal, cardiac synchronized magnetic resonance (MR) imaging is simple to implement; however, single section techniques are not efficacious, especially when the heart rate sets the repetition interval. We demonstrate multi-section, double, and single-echo imaging, any of which rapidly covers the cardiac volume; 3-D modes capable of achieving very thin sections; and cycled multi-section imaging capable of efficaciously providing dynamic data on heart motion.

Crooks, L.E.; Barker, B.; Chang, H.; Feinberg, D.; Hoenninger, J.C.; Watts, J.C.; Arakawa, M.; Kaufman, L.; Sheldon, P.E.; Botvinick, E.

1984-11-01

236

Pharmaceutical applications of magnetic resonance imaging (MRI)  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a powerful imaging modality that provides internal images of materials and living organisms on a microscopic and macroscopic scale. It is non-invasive and non-destructive, and one of very few techniques that can observe internal events inside undisturbed specimens in situ. It is versatile, as a wide range of NMR modalities can be accessed, and 2D

J. Craig Richardson; Richard W. Bowtell; Karsten Mäder; Colin D. Melia

2005-01-01

237

Projective measurement in nuclear magnetic resonance  

E-print Network

It is demonstrated that nuclear magnetic resonance experiments using pseudopure spin states can give possible outcomes of projective quantum measurement and probabilities of such outcomes. The physical system is a cluster of six dipolar-coupled nuclear spins of benzene in a liquid-crystalline matrix. For this system with the maximum total spin S=3, the results of measuring $S_X$ are presented for the cases when the state of the system is one of the eigenstates of $S_Z$.

Jae-Seung Lee; A. K. Khitrin

2006-05-02

238

Magnetic Resonance Imaging of Acute Stroke  

Microsoft Academic Search

In the investigation of ischemic stroke, conventional structural magnetic resonance (MR) techniques (e.g., T1-weighted imaging, T2-weighted imaging, and proton density-weighted imaging) are valuable for the assessment of infarct extent and location beyond the first 12 to 24 hours after onset, and can be combined with MR angiography to noninvasively assess the intracranial and extracranial vasculature. However, during the critical first

Alison E. Baird; Steven Warach

1998-01-01

239

Adaptive Fuzzy Segmentation of Magnetic Resonance Images  

Microsoft Academic Search

An algorithm is presented for the fuzzy segmentation of two and three-dimensionalmultispectral magnetic resonance (MR) images that have been corrupted by intensity inhomogeneities,also known as shading artifacts. The algorithm is an extension of the two-dimensionaladaptive fuzzy C-means algorithm (2-D AFCM) presented in previous work by the authors. Thisalgorithm models the intensity inhomogeneities as a gain field that causes image intensities

Dzung L. Pham; Jerry L. Prince

1999-01-01

240

Nuclear magnetic resonance quantum information processing  

PubMed Central

For the past decade, nuclear magnetic resonance (NMR) has been established as a main experimental technique for testing quantum protocols in small systems. This Theme Issue presents recent advances and major challenges of NMR quantum information possessing (QIP), including contributions by researchers from 10 different countries. In this introduction, after a short comment on NMR-QIP basics, we briefly anticipate the contents of this issue. PMID:22946031

Serra, R. M.; Oliveira, I. S.

2012-01-01

241

Sensors for Applications in Magnetic Resonance Environments  

Microsoft Academic Search

This paper analyzes sensing methods compatible with magnetic resonance imaging (MRI) and functional MRI (fMRI) reported in the literature, and presents the three generations of MR-compatible force\\/torque sensors we have developed for robotic systems to interact with human motion. Conventional sensors such as camera-based measurement systems, strain gauges or commercial force\\/torque sensors, and optical encoders may be used, if placed

Roger Gassert; Dominique Chapuis; Hannes Bleuler; Etienne Burdet

2008-01-01

242

Magnetic resonance imaging: Principles and applications  

SciTech Connect

This text covers the physics underlying magnetic resonance (MR) imaging; pulse sequences; image production; equipment; aspects of clinical imaging; and the imaging of the head and neck, thorax, abdomen and pelvis, and musculoskeletal system; and MR imaging. The book provides about 150 examples of MR images that give an overview of the pathologic conditions imaged. There is a discussion of the physics of MR imaging and also on the spin echo.

Kean, D.; Smith, M.

1986-01-01

243

Magnetic resonance imaging in radiotherapy treatment planning  

Microsoft Academic Search

From its inception in the early 1970's up to the present, magnetic resonance imaging (MRI) has evolved into a sophisticated technique, which has aroused considerable interest in var-\\u000aious subelds of medicine including radiotherapy. MRI is capable of imaging in any plane\\u000aand does not use ionizing radiation by virtue of which MRI lends itself admirably to the\\u000apurpose of

Marinus Adriaan Moerland

1996-01-01

244

Rhinopharyngoscopy, computed tomography and magnetic resonance imaging.  

PubMed

Rhinitis is defined as nasal congestion, sneezing, itching and rhinorrhoea, recently classified as allergic, infective, structural or "other". The increasing employment of flexible rhynolaringoscopy may represent one of the most useful diagnostic tools in the complex differential diagnosis between allergic and nonallergic rhinitis. Furthermore, chronic allergic rhinitis, with secondary impairment of mucociliary clearance and the plethora of frequent anatomical variations, especially in the ostiomeatal complex, appear to predispose the patient to recurrent rhinosinusitis. In the last two decades, a better understanding of mucociliary clearance of nasal cavity and paranasal sinuses has shifted the attention from the maxillary sinuses to the area of the antherior ethmoid sinuses. Plain film radiographic examination, the historical standard, due to its inability to individualize ethmoid and sphenoid disease, is being rapidly supplanted by computed tomography and magnetic resonance imaging in the diagnosis of rhinosinusitis. In allergic and non-allergic rhinitis the diagnostic role of magnetic resonance imaging and computed tomography is still under debate. Computed tomography and magnetic resonance imaging are more efficient in demonstrating the bone wall, mucosal layer and sinus content than classical and computerized radiology; they have a higher diagnostic performance index in spite of a higher cost and, for computed tomography, a higher radiation dose. PMID:9188945

Bonifazi, F; Bilò, M B; Antonicelli, L; Bonetti, M G

1997-01-01

245

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

246

On the Dynamics of Magnetic Fluids in Magnetic Resonance Padraig J. Cantillon-Murphy  

E-print Network

On the Dynamics of Magnetic Fluids in Magnetic Resonance Imaging by Padraig J. Cantillon in Magnetic Resonance Imaging by Padraig J. Cantillon-Murphy B.E., Electrical and Electronic Engineering to be used in magnetic resonance imaging (MRI) where they have found application as contrast agents

247

Magnetic resonance imaging method based on magnetic susceptibility effects to estimate bubble size in alveolar products  

E-print Network

Magnetic resonance imaging method based on magnetic susceptibility effects to estimate bubble size-00454523,version1-8Feb2010 Author manuscript, published in "Magnetic Resonance Imaging 27, 4 (2009) p. 577 - p. 585" #12;Abstract18 19 20 21 22 23 24 25 26 27 28 29 30 Magnetic resonance imaging has proven its

Boyer, Edmond

248

The emerging clinical role of cardiovascular magnetic resonance imaging  

PubMed Central

Starting as a research method little more than a decade ago, cardiovascular magnetic resonance (CMR) imaging has rapidly evolved to become a powerful diagnostic tool used in routine clinical cardiology. The contrast in CMR images is generated from protons in different chemical environments and, therefore, enables high-resolution imaging and specific tissue characterization in vivo, without the use of potentially harmful ionizing radiation. CMR imaging is used for the assessment of regional and global ventricular function, and to answer questions regarding anatomy. State-of-the-art CMR sequences allow for a wide range of tissue characterization approaches, including the identification and quantification of nonviable, edematous, inflamed, infiltrated or hypoperfused myocardium. These tissue changes are not only used to help identify the etiology of cardiomyopathies, but also allow for a better understanding of tissue pathology in vivo. CMR tissue characterization may also be used to stage a disease process; for example, elevated T2 signal is consistent with edema and helps differentiate acute from chronic myocardial injury, and the extent of myocardial fibrosis as imaged by contrast-enhanced CMR correlates with adverse patient outcome in ischemic and nonischemic cardiomyopathies. The current role of CMR imaging in clinical cardiology is reviewed, including coronary artery disease, congenital heart disease, nonischemic cardiomyopathies and valvular disease. PMID:20548977

Kumar, Andreas; Patton, David J; Friedrich, Matthias G

2010-01-01

249

Simultaneous in vivo positron emission tomography and magnetic resonance imaging  

PubMed Central

Positron emission tomography (PET) and magnetic resonance imaging (MRI) are widely used in vivo imaging technologies with both clinical and biomedical research applications. The strengths of MRI include high-resolution, high-contrast morphologic imaging of soft tissues; the ability to image physiologic parameters such as diffusion and changes in oxygenation level resulting from neuronal stimulation; and the measurement of metabolites using chemical shift imaging. PET images the distribution of biologically targeted radiotracers with high sensitivity, but images generally lack anatomic context and are of lower spatial resolution. Integration of these technologies permits the acquisition of temporally correlated data showing the distribution of PET radiotracers and MRI contrast agents or MR-detectable metabolites, with registration to the underlying anatomy. An MRI-compatible PET scanner has been built for biomedical research applications that allows data from both modalities to be acquired simultaneously. Experiments demonstrate no effect of the MRI system on the spatial resolution of the PET system and <10% reduction in the fraction of radioactive decay events detected by the PET scanner inside the MRI. The signal-to-noise ratio and uniformity of the MR images, with the exception of one particular pulse sequence, were little affected by the presence of the PET scanner. In vivo simultaneous PET and MRI studies were performed in mice. Proof-of-principle in vivo MR spectroscopy and functional MRI experiments were also demonstrated with the combined scanner. PMID:18319342

Catana, Ciprian; Procissi, Daniel; Wu, Yibao; Judenhofer, Martin S.; Qi, Jinyi; Pichler, Bernd J.; Jacobs, Russell E.; Cherry, Simon R.

2008-01-01

250

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

251

Magnetic resonance imaging of live freshwater mussels (Unionidae)  

USGS Publications Warehouse

We examined the soft tissues of live freshwater mussels, Eastern elliptio Elliptio complanata, via magnetic resonance imaging (MRI), acquiring data with a widely available human whole-body MRI system. Anatomical features depicted in the profile images included the foot, stomach, intestine, anterior and posterior adductor muscles, and pericardial cavity. Noteworthy observations on soft tissue morphology included a concentration of lipids at the most posterior aspect of the foot, the presence of hemolymph-filled fissures in the posterior adductor muscle, the presence of a relatively large hemolymph-filled sinus adjacent to the posterior adductor muscle (at the ventral-anterior aspect), and segmentation of the intestine (a diagnostic description not reported previously in Unionidae). Relatively little is known about the basic biology and ecological physiology of freshwater mussels. Traditional approaches for studying anatomy and tissue processes, and for measuring sub-lethal physiological stress, are destructive or invasive. Our study, the first to evaluate freshwater mussel soft tissues by MRI, clarifies the body plan of unionid mussels and demonstrates the efficacy of this technology for in vivo evaluation of the structure, function, and integrity of mussel soft tissues. ?? 2008, The American Microscopical Society, Inc.

Michael, Holliman F.; Davis, D.; Bogan, A.E.; Kwak, T.J.; Gregory, Cope W.; Levine, J.F.

2008-01-01

252

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

253

Electron Spin Magnetic Resonance Force Microscopy of Nitroxide Spin Labels  

NASA Astrophysics Data System (ADS)

Nitroxide spin labels are widely used in electron spin resonance studies of biological and polymeric systems. Magnetic resonance force microscopy (MRFM) is a magnetic resonance technique that couples the high spatial resolution of a scanning probe microscope with the species selectivity of magnetic resonance. We report on our investigations of 4-amino TEMPO, a nitroxide spin label, by force-gradient MRFM. Our microscope operates at high vacuum in liquid helium, using a custom fabricated ultra-soft silicon cantilever in the magnet-on-cantilever geometry. An 18 GHz gap coupled microstripline resonator supplies the transverse field.

Moore, Eric W.; Lee, Sanggap; Hickman, Steven A.; Wright, Sarah J.; Marohn, John A.

2009-03-01

254

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

255

MAGNETIC RESONANCE ELECTRICAL IMPEDANCE TOMOGRAPHY (MR-EIT): A new technique for high resolution conductivity imaging  

E-print Network

MAGNETIC RESONANCE ELECTRICAL IMPEDANCE TOMOGRAPHY (MR-EIT): A new technique for high resolution field measurements are performed by using magnetic resonance imaging techniques. The conductivity resonance imaging (MRI) techniques, if the conductor contains magnetic resonance active nuclei [2

Eyüboðlu, Murat

256

Gadolinium-Enhanced Magnetic Resonance Angiography for Pulmonary Embolism  

PubMed Central

Background The accuracy of gadolinium-enhanced magnetic resonance pulmonary angiography and magnetic resonance venography for diagnosing pulmonary embolism has not been determined conclusively. Objective To investigate performance characteristics of magnetic resonance angiography, with or without magnetic resonance venography, for diagnosing pulmonary embolism. Design Prospective, multicenter study from 10 April 2006 to 30 September 2008. (ClinicalTrials.gov registration number: NCT00241826) Setting 7 hospitals and their emergency services. Patients 371 adults with diagnosed or excluded pulmonary embolism. Measurements Sensitivity, specificity, and likelihood ratios were measured by comparing independently read magnetic resonance imaging with the reference standard for diagnosing pulmonary embolism. Reference standard diagnosis or exclusion was made by using various tests, including computed tomographic angiography and venography, ventilation–perfusion lung scan, venous ultra-sonography, D-dimer assay, and clinical assessment. Results Magnetic resonance angiography, averaged across centers, was technically inadequate in 25% of patients (92 of 371). The proportion of technically inadequate images ranged from 11% to 52% at various centers. Including patients with technically inadequate images, magnetic resonance angiography identified 57% (59 of 104) with pulmonary embolism. Technically adequate magnetic resonance angiography had a sensitivity of 78% and a specificity of 99%. Technically adequate magnetic resonance angiography and venography had a sensitivity of 92% and a specificity of 96%, but 52% of patients (194 of 370) had technically inadequate results. Limitation A high proportion of patients with suspected embolism was not eligible or declined to participate. Conclusion Magnetic resonance pulmonary angiography should be considered only at centers that routinely perform it well and only for patients for whom standard tests are contraindicated. Magnetic resonance pulmonary angiography and magnetic resonance venography combined have a higher sensitivity than magnetic resonance pulmonary angiography alone in patients with technically adequate images, but it is more difficult to obtain technically adequate images with the 2 procedures. Primary Funding Source National Heart, Lung, and Blood Institute. PMID:20368649

Stein, Paul D.; Chenevert, Thomas L.; Fowler, Sarah E.; Goodman, Lawrence R.; Gottschalk, Alexander; Hales, Charles A.; Hull, Russell D.; Jablonski, Kathleen A.; Leeper, Kenneth V.; Naidich, David P.; Sak, Daniel J.; Sostman, H. Dirk; Tapson, Victor F.; Weg, John G.; Woodard, Pamela K.

2011-01-01

257

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

Microsoft Academic Search

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 in a cost function that minimizes the error

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

2008-01-01

258

Multifunctional magnetic nanoparticles for magnetic resonance imaging and cancer therapy  

Microsoft Academic Search

We have developed a multi-layer approach for the synthesis of water-dispersible superparamagnetic iron oxide nanoparticles for hyperthermia, magnetic resonance imaging (MRI) and drug delivery applications. In this approach, iron oxide core nanoparticles were obtained by precipitation of iron salts in the presence of ammonia and provided ?-cyclodextrin and pluronic polymer (F127) coatings. This formulation (F127250) was highly water dispersible which

Murali M. Yallapu; Shadi F. Othman; Evan T. Curtis; Brij K. Gupta; Meena Jaggi; Subhash C. Chauhan

2011-01-01

259

Southeastern Magnetic Resonance Conference October 11 -13, 2013  

E-print Network

42nd Southeastern Magnetic Resonance Conference October 11 - 13, 2013 Tallahassee, Florida The 42nd Southeastern Magnetic Resonance Conference will take place in the Florida capitol city of Tallahassee on the campus of T h e Florida State University. Additional information is located at http://semrc2013.magnet

McQuade, D. Tyler

260

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

261

Quantitative Neuromorphometry Using Magnetic Resonance Histology  

PubMed Central

Magnetic resonance imaging (MRI), now common in the clinical domain, has been adapted for use by the neuropathologist by increasing the spatial resolution over 100,000-times what is common in human clinical imaging. This increase in spatial resolution has been accomplished through a variety of technical advances—higher magnetic fields, more sensitive receivers, and clever encoding methods. Magnetic resonance histology (MRH), i.e. the application of MRI to study tissue specimens, now makes three-dimensional imaging of the fixed brain in the cranium routine. Active staining (perfusion fixation with a paramagnetic contrast agent) has allowed us to reduce the scan time by more than 8-times over earlier methods. The result is a three-dimensional isotropic image array that can be viewed along any direction without loss of spatial resolution. Homologous slices can be chosen interactively. Since the tissue is still fully hydrated in the cranium, tissue shrinkage and distortion are virtually eliminated. Volume measurements of neural structures can be made with a high degree of precision and accuracy. MRH will not replace more traditional methods, but it promises enormous value in choosing particular areas and times for more traditional sectioning and assessment. PMID:21119052

Johnson, G. Allan; Badea, Alexandra; Jiang, Yi

2010-01-01

262

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

263

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

264

Magnetic resonance-guided prostate interventions.  

PubMed

We review our experience using an open 0.5-T magnetic resonance (MR) interventional unit to guide procedures in the prostate. This system allows access to the patient and real-time MR imaging simultaneously and has made it possible to perform prostate biopsy and brachytherapy under MR guidance. We review MR imaging of the prostate and its use in targeted therapy, and describe our use of image processing methods such as image registration to further facilitate precise targeting. We describe current developments with a robot assist system being developed to aid radioactive seed placement. PMID:16924169

Haker, Steven J; Mulkern, Robert V; Roebuck, Joseph R; Barnes, Agnieska Szot; Dimaio, Simon; Hata, Nobuhiko; Tempany, Clare M C

2005-10-01

265

Magnetic resonance imaging of primary breast lymphoma  

Microsoft Academic Search

Purpose  Primary lymphomas of the breast (PBNHL) are uncommon. Magnetic resonance imaging (MRI) features of these malignancies can\\u000a be relevant in establishing the extent of disease and planning the appropriate therapeutic strategy, usually represented by\\u000a chemo- and radiotherapy, rather than surgery. The purpose of this study was to assess MRI features of PBNHL.\\u000a \\u000a \\u000a \\u000a Materials and methods  MRI examinations performed on seven patients

S. Rizzo; L. Preda; G. Villa; S. Brambilla; G. Pruneri; A. Alietti; E. Cassano; G. Martinelli; M. Bellomi

2009-01-01

266

[Magnetic resonance imaging of atherosclerotic plaque].  

PubMed

Recent advances in terms of spatial and temporal resolution have enabled magnetic resonance imaging (MRI) to be used to display atherosclerotic plaque. MRI permits not only to detect atherosclerotic lesions but also enables determination of plaque volume and plaque characterization. It allows to display different plaque components such as lipid core, fibrous cap, calcium, and thrombus. To improve the spatial resolution, different invasive approaches based on intravascular coils have been evaluated. Novel contrast agent developments aim at the detection of inflammatory plaque activity in order to identify lesions with a high vascular risk (vulnerable plaque). PMID:14564414

Ruehm, Stefan G

2003-09-01

267

Approach to breast magnetic resonance imaging interpretation.  

PubMed

With the increasing use of breast magnetic resonance (MR) imaging comes the expectation that the breast radiologist is as fluent in its interpretation as in that of mammography and breast ultrasonography. Knowledge of who should be included for imaging and how to perform the imaging are as essential as interpreting the images. When reading the examination, the radiologist should approach the images from both a global and focused perspective, synthesizing findings into a report that includes a management plan. This article reviews a systematic and organized approach to breast MR imaging interpretation. PMID:24792657

Palestrant, Sarah; Comstock, Christopher E; Moy, Linda

2014-05-01

268

Magnetic resonance imaging of the elbow.  

PubMed

Magnetic resonance imaging (MRI) provides useful information regarding the elbow joint. Many abnormalities seen in the elbow are a result of trauma, often from sports such as baseball and tennis. Elbow problems are frequently related to the medial tension-lateral compression phenomenon where repeated valgus stress produces flexor-pronator strain, ulnar collateral ligament sprain, ulnar traction spurring, and ulnar neuropathy. The lateral compression causes osteochondritis dissecans of the capitellum and radial head, degenerative arthritis, and loose bodies. Other elbow abnormalities seen on MRI include radial collateral ligament injuries, biceps and triceps tendon injuries, other nerve entrapment syndromes, loose bodies, osseous and soft tissue trauma, arthritis, and masses, including bursae. PMID:9430831

Steinbach, L S; Fritz, R C; Tirman, P F; Uffman, M

1997-11-01

269

New magnetic resonance imaging methods in nephrology  

PubMed Central

Established as a method to study anatomic changes, such as renal tumors or atherosclerotic vascular disease, magnetic resonance imaging (MRI) to interrogate renal function has only recently begun to come of age. In this review, we briefly introduce some of the most important MRI techniques for renal functional imaging, and then review current findings on their use for diagnosis and monitoring of major kidney diseases. Specific applications include renovascular disease, diabetic nephropathy, renal transplants, renal masses, acute kidney injury and pediatric anomalies. With this review, we hope to encourage more collaboration between nephrologists and radiologists to accelerate the development and application of modern MRI tools in nephrology clinics. PMID:24067433

Zhang, Jeff L.; Morrell, Glen; Rusinek, Henry; Sigmund, Eric; Chandarana, Hersh; Lerman, Lilach O.; Prasad, Pottumarthi Vara; Niles, David; Artz, Nathan; Fain, Sean; Vivier, Pierre H.; Cheung, Alfred K.; Lee, Vivian S.

2013-01-01

270

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

271

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

272

Three-Magnet Arrays for Unilateral Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Unilateral Magnetic Resonance (UMR) has become, in different research areas, a powerful tool to interrogate samples of arbitrary size. The three-magnet array developed by the MRI Centre of the University of New Brunswick has features that make it a simple and robust approach for UMR. This thesis introduces a group of solutions to broaden the range of application of this design. Practical applications for non-destructive testing and reservoir core plug characterization are presented. We have shown that it is also possible to monitor the curing process of an epoxy/polyamidoamine system by employing a three-magnet array. A new version of the three-magnet array which features extended constant magnetic field gradients is also introduced. Constant gradients of more than 3 cm extent can be achieved in a very simple, compact and safe design. The application of the three-magnet array in combination with a solenoid as the RF probe for analysis of long core plugs has been presented. Core plugs of different diameter can be analyzed by simply changing the diameter of the RF probe employed for the measurement. Results of an initial survey of selective excitation in UMR are presented. The low SNR and inhomogeneities in the selective spot reduce the effectiveness of selective excitation for UMR.

Garcia Naranjo, Juan Carlos

273

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

274

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

275

Metabolite specific proton magnetic resonance imaging  

SciTech Connect

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.

Hurd, R.E.; Freeman, D.M.

1989-06-01

276

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

277

Nuclear magnetic resonance imaging of liver hemangiomas  

SciTech Connect

Nine patients with cavernous hemangioma of the liver were examined by nuclear magnetic resonance imaging (MRI) with a 0.5 T superconductive magnet. Spin-echo technique was used with varying time to echo (TE) and repetition times (TR). Results were compared with /sup 99m/Tc red blood cell (RBC) scintigraphy, computed tomography (CT), echography, and arteriography. Four illustrated cases are reported. It was possible to establish a pattern for MRI characteristics of cavernous hemangiomas; rounded or smooth lobulated shape, marked increase in T1 and T2 values as compared with normal liver values. It is concluded that, although more experience is necessary to compare the specificity with that of ultrasound and CT, MRI proved to be very sensitive for the diagnosis of liver hemangioma, especially in the case of small ones which may be missed by /sup 99m/Tc-labeled RBC scintigraphy.

Sigal, R.; Lanir, A.; Atlan, H.; Naschitz, J.E.; Simon, J.S.; Enat, R.; Front, D.; Israel, O.; Chisin, R.; Krausz, Y.

1985-10-01

278

THE USE OF MAGNETIC RESONANCE SPECTROSCOPY AND MAGNETIC RESONANCE IMAGING IN ALCOHOL RESEARCH  

Microsoft Academic Search

he recent emergence of magnetic resonance (MR)­ based neuroimaging techniques has dramatically improved researchers' ability to understand the neuro­ pathology of alcoholism. These techniques range from those that directly monitor the metabolism and the biochemical and physiological effects (i.e., the pharmacodynamics) of alcohol within the brain to techniques that examine the impact of heavy alcohol use on brain structure and

Bonnie J. Nagel; Christopher D. Kroenke

2008-01-01

279

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

280

Magnetic resonance imaging in acute mastoiditis  

PubMed Central

Background In cases of suspected mastoiditis, imaging is used to evaluate the extent of mastoid destruction and possible complications. The role of magnetic resonance imaging (MRI) in mastoiditis has not been systematically evaluated. Purpose To assess the diagnostic performance of MRI in patients with suspected acute mastoiditis. Material and Methods Twenty-three patients with suspected acute mastoiditis were included in this retrospective study (15 boys, 8 girls; mean age, 2 years 11 months). All patients were examined on a 1.5?T MRI system. The MRI examination included both enhanced and non-enhanced turbo spin echo (TSE), diffusion-weighted images, and venous time-of-flight magnetic resonance angiography (TOF MRA) for the evaluation of the venous sinuses. Surgical findings, as well as clinical and imaging follow-up were used as the standard of reference. The sensitivity and accuracy of MRI for mastoiditis and subperiosteal abscesses was calculated. Results Twenty (87%) of 23 patients had mastoiditis, and 12 (52%) of 23 patients had a subperiosteal abscess in addition to mastoiditis. Mastoiditis and subperiosteal abscesses were identified by MRI in all cases. Sensitivity for mastoiditis was 100%, specificity was 66%, and accuracy was 86%. Sensitivity for subperiosteal abscesses was 100% and accuracy was 100%. Conclusion Multiparametric MRI has high accuracy for mastoiditis and subperiosteal abscesses. PMID:24778805

Kitzler, Hagen H; Gudziol, Volker; Laniado, Michael; Hahn, Gabriele

2014-01-01

281

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

282

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

283

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

284

Directly Mapping Magnetic Field Effects of Neuronal Activity by Magnetic Resonance  

E-print Network

Directly Mapping Magnetic Field Effects of Neuronal Activity by Magnetic Resonance Imaging Jinhu Center at San Antonio, San Antonio, Texas Abstract: Magnetic resonance imaging (MRI) of brain functional functional activity by directly detecting magnetic fields induced by neuronal firing. Using a well

Gabrieli, John

285

Assessment of Myocardial Infarction by Cardiac Magnetic Resonance Imaging and Long-Term Mortality  

PubMed Central

Background Cardiac magnetic resonance imaging provides detailed anatomical information on infarction. However, few studies have investigated the association of these data with mortality after acute myocardial infarction. Objective To study the association between data regarding infarct size and anatomy, as obtained from cardiac magnetic resonance imaging after acute myocardial infarction, and long-term mortality. Methods A total of 1959 reports of “infarct size” were identified in 7119 cardiac magnetic resonance imaging studies, of which 420 had clinical and laboratory confirmation of previous myocardial infarction. The variables studied were the classic risk factors – left ventricular ejection fraction, categorized ventricular function, and location of acute myocardial infarction. Infarct size and acute myocardial infarction extent and transmurality were analyzed alone and together, using the variable named “MET-AMI”. The statistical analysis was carried out using the elastic net regularization, with the Cox model and survival trees. Results The mean age was 62.3 ± 12 years, and 77.3% were males. During the mean follow-up of 6.4 ± 2.9 years, there were 76 deaths (18.1%). Serum creatinine, diabetes mellitus and previous myocardial infarction were independently associated with mortality. Age was the main explanatory factor. The cardiac magnetic resonance imaging variables independently associated with mortality were transmurality of acute myocardial infarction (p = 0.047), ventricular dysfunction (p = 0.0005) and infarcted size (p = 0.0005); the latter was the main explanatory variable for ischemic heart disease death. The MET-AMI variable was the most strongly associated with risk of ischemic heart disease death (HR: 16.04; 95%CI: 2.64-97.5; p = 0.003). Conclusion The anatomical data of infarction, obtained from cardiac magnetic resonance imaging after acute myocardial infarction, were independently associated with long-term mortality, especially for ischemic heart disease death.

Petriz, João Luiz Fernandes; Gomes, Bruno Ferraz de Oliveira; Rua, Braulio Santos; Azevedo, Clério Francisco; Hadlich, Marcelo Souza; Mussi, Henrique Thadeu Periard; Taets, Gunnar de Cunto; do Nascimento, Emília Matos; Pereira, Basílio de Bragança; e Silva, Nelson Albuquerque de Souza

2015-01-01

286

Assessment of Myocardial Infarction by Cardiac Magnetic Resonance Imaging and Long-Term Mortality.  

PubMed

Background: Cardiac magnetic resonance imaging provides detailed anatomical information on infarction. However, few studies have investigated the association of these data with mortality after acute myocardial infarction. Objective: To study the association between data regarding infarct size and anatomy, as obtained from cardiac magnetic resonance imaging after acute myocardial infarction, and long-term mortality. Methods: A total of 1959 reports of "infarct size" were identified in 7119 cardiac magnetic resonance imaging studies, of which 420 had clinical and laboratory confirmation of previous myocardial infarction. The variables studied were the classic risk factors - left ventricular ejection fraction, categorized ventricular function, and location of acute myocardial infarction. Infarct size and acute myocardial infarction extent and transmurality were analyzed alone and together, using the variable named "MET-AMI". The statistical analysis was carried out using the elastic net regularization, with the Cox model and survival trees. Results: The mean age was 62.3 ± 12 years, and 77.3% were males. During the mean follow-up of 6.4 ± 2.9 years, there were 76 deaths (18.1%). Serum creatinine, diabetes mellitus and previous myocardial infarction were independently associated with mortality. Age was the main explanatory factor. The cardiac magnetic resonance imaging variables independently associated with mortality were transmurality of acute myocardial infarction (p = 0.047), ventricular dysfunction (p = 0.0005) and infarcted size (p = 0.0005); the latter was the main explanatory variable for ischemic heart disease death. The MET-AMI variable was the most strongly associated with risk of ischemic heart disease death (HR: 16.04; 95%CI: 2.64-97.5; p = 0.003). Conclusion: The anatomical data of infarction, obtained from cardiac magnetic resonance imaging after acute myocardial infarction, were independently associated with long-term mortality, especially for ischemic heart disease death. PMID:25424161

Petriz, João Luiz Fernandes; Gomes, Bruno Ferraz de Oliveira; Rua, Braulio Santos; Azevedo, Clério Francisco; Hadlich, Marcelo Souza; Mussi, Henrique Thadeu Periard; Taets, Gunnar de Cunto; Nascimento, Emília Matos do; Pereira, Basílio de Bragança; Silva, Nelson Albuquerque de Souza E

2014-11-21

287

Magnetic Resonance Imaging Methods in Soil Science  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Imaging (MRI) is a powerful technique to study water content, dynamics and transport in natural porous media. However, MRI systems and protocols have been developed mainly for medical purposes, i.e. for media with comparably high water contents and long relaxation times. In contrast, natural porous media like soils and rocks are characterized by much lower water contents, typically 0 < theta < 0.4, and much faster T1 and T2 relaxation times. So, the usage of standard medical scanners and protocols is of limited benefit. Three strategies can be applied for the monitoring of water contents and dynamics in natural porous media: i) Dedicated high-field scanners (with vertical bore) allowing stronger gradients and faster switching so that shorter echo times can be realized. ii) Special measurement sequences using ultrashort rf- and gradient-pulses like single point imaging derivates (SPI, SPRITE)(1) and multi-echo methods, which monitor series of echoes and allow for extrapolation to zero time(2). Hence, the loss of signal during the first echo period may be compensated to determine the initial magnetization (= water content) as well as relaxation time maps simultaneously. iii) Finally low field( < 1T) scanners also provide longer echo times and hence detect larger fractions of water, since the T2 relaxation time of water in most porous media increases with decreasing magnetic field strength(3). In the presentation examples for all three strategies will be given. References 1) Pohlmeier et al. Vadose Zone J. 7, 1010-1017 (2008) 2) Edzes et al., Magn. Res. Imag. 16, 185-196 (1998) 3) Raich H, and Blümler P, Concepts in Magn. Reson. B 23B, 16-25 (2004) 4) Pohlmeier et al. Magn. Res. Imag. doi:10.1016/j.mri.2008.06.007 (2008)

Pohlmeier, A.; van Dusschoten, D.; Blümler, P.

2009-04-01

288

Immobilization of iron oxide magnetic nanoparticles for enhancement of vessel wall magnetic resonance imaging--an ex vivo feasibility study.  

PubMed

Emerging data supports a role for negative wall remodeling in the failure of vascular interventions such as vein grafts, yet clinicians/researchers currently lack the ability to temporally/efficiently investigate adventitial surface topography/total vascular wall anatomy in vivo. We established a strategy of immobilizing commercially available iron oxide magnetic nanoparticles (Fe-NPs) onto the surface of human vein conduits to facilitate high-throughput total vascular wall demarcation with magnetic resonance (MR). Binding of activated Fe-NPs to amine groups on the surface of the veins induced a thin layer of negative contrast that differentiated the adventitia from surrounding saline signal in all MR images, enabling delineation of total wall anatomy; this was not possible in simultaneously imaged unlabeled control veins. Under the conditions of this ex vivo experiment, stable covalent binding of Fe-NPs can be achieved (dose-dependent) on human vein surface for MR detection, suggesting a potential strategy for enhancing the ability of MRI to investigate total wall adaptation and remodeling in vein graft failure. PMID:20608720

Nguyen, Binh Thai; Vemula, Praveen Kumar; Mitsouras, Dimitrios; Yu, Peng; Tao, Ming; Campagna, Christina; Mulkern, Robert V; Rybicki, Frank J; Karp, Jeffrey M; Ozaki, C Keith

2010-08-18

289

Functional magnetic resonance imaging using RASER  

PubMed Central

Although functional imaging of neuronal activity by magnetic resonance imaging (fMRI) has become the primary methodology employed in studying the brain, significant portions of the brain are inaccessible by this methodology due to its sensitivity to macroscopic magnetic field inhomogeneities induced near air filled cavities in the head. In this paper, we demonstrate that this sensitivity is eliminated by a novel pulse sequence, RASER (rapid acquisition by sequential excitation and refocusing) (Chamberlain et al., 2007), that can generate functional maps. This is accomplished because RASER acquired signals are purely and perfectly T2 weighted, without any T2*-effects that are inherent in the other image acquisition schemes employed to date. T2-weighted fMRI sequences are also more specific to the site of neuronal activity at ultrahigh magnetic fields than T2*-variations since they are dominated by signal components originating from the tissue in the capillary bed. The RASER based fMRI response is quantified; it is shown to have inherently less noisy time series and to provide fMRI in brain regions, such as the orbitofrontal cortex, which are challenging to image with conventional techniques. PMID:20699123

Goerke, Ute; Garwood, Michael; Ugurbil, Kamil

2010-01-01

290

Ultrahigh-Resolution Magnetic Resonance in Inhomogeneous Magnetic Fields: Two-Dimensional Long-Lived-Coherence Correlation Spectroscopy  

E-print Network

Ultrahigh-Resolution Magnetic Resonance in Inhomogeneous Magnetic Fields: Two-Dimensional Long resolution in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) has enabled the study.56.Fk, 82.56.Pp, 82.56.Jn Nuclear magnetic resonance (NMR) is often regarded as one of the most

291

Magnetic resonance tracking of fluorescent nanodiamond fabrication  

NASA Astrophysics Data System (ADS)

Magnetic resonance techniques (electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR)) are used for tracking the multi-stage process of the fabrication of fluorescent nanodiamonds (NDs) produced by high-energy electron irradiation, annealing, and subsequent nano-milling. Pristine commercial high pressure and high temperature microdiamonds (MDs) with mean size 150??m contain ~5? × ?1018?spins/g of singlet (S = 1/2) substitutional nitrogen defects P1, as well as sp3 C–C dangling bonds in the crystalline lattice. The half-field X-band EPR clearly shows (by the appearance of the intense ‘forbidden’ g = 4.26 line) that high-energy electron irradiation and annealing of MDs induce a large amount (~5? × ?1017?spins/g) of triplet (S = 1) magnetic centers, which are identified as negatively charged nitrogen vacancy defects (NV?). This is supported by EPR observations of the ‘allowed’ transitions between Zeeman sublevels of the triplet state. After progressive milling of the fluorescent MDs down to an ultrasubmicron scale (?100?nm), the relative abundance of EPR active NV? defects in the resulting fluorescent NDs (FND) substantially decreases and, vice versa, the content of C-inherited singlet defects correlatively increases. In the fraction of the finest FNDs (mean particle size <20?nm), which are contained in the dried supernatant of ultracentrifuged aqueous dispersion of FNDs, the NV? content is found to be reduced by one order of magnitude whereas the singlet defects content increases up to ~2? × ?1019?spins/g. In addition, another triplet-type defect, which is characterized by the g = 4.00 ‘forbidden’ line, appears. On reduction of the particle size below the 20?nm limit, the ‘allowed’ EPR lines become practically unobservable, whereas the ‘forbidden’ lines remain as a reliable fingerprint of the presence of NV? centers in small ND systems. The same size reduction causes the disappearance of the characteristic hyperfine satellites in the spectra of the P1 centers. We discuss the mechanisms that cause both the strong reduction of the peak intensity of the ‘allowed’ lines in EPR spectra of triplet defects and the transformation of the P1 spectra.

Shames, A. I.; Osipov, V. Yu; Boudou, J. P.; Panich, A. M.; von Bardeleben, H. J.; Treussart, F.; Vul’, A. Ya

2015-04-01

292

Towards magnetic resonance imaging guided radiation therapy (MRIgRT)  

NASA Astrophysics Data System (ADS)

The goal of this work is to address key aspects of the magnetic resonance imaging guided radiation therapy (MRIgRT) process of cancer sites. MRIgRT is implemented by using a system comprised of a magnetic resonance imaging (MRI) scanner coupled with a radiation source, in our case a radiotherapy accelerator (Linac). The potential benefits of MRIgRT are the real-time tracking of the tumor and neighbouring healthy anatomy during treatment irradiation leading to on-line treatment plan optimization. Ultimately, this results in an increased accuracy and efficiency of the overall treatment process. A large research effort is conducted at Cross Cancer Institute to develop a hybrid MRI-Linac system consisting of a bi-planar 0.2 T permanent magnet coupled with a 6 MV Linac. The present work is part of this project and aims to address the following key components: (a) magnetic shielding and dosimetric effects of the MRI-Linac system, (b) measure and correction of scanner-related MR image distortions, and (c) MRI-based treatment planning procedure for intracranial lesions. The first two components are essential for the optimal construction and operation of the MRI-Linac system while the third one represents a direct application of the system. The linac passive shielding was achieved by (a) adding two 10 cm thick steel (1020) plates placed at a distance of 10 cm from the structure on opposite sides of the magnet; and (b) a box lined with a 1 mm MuMetal(TM) wall surrounding the Linac. For our proposed MRI-Linac configuration (i.e. 0.2 T field and rotating bi-planar geometry) the maximum dose difference from zero magnetic field case was found to be within 6% and 12% in a water and water-lung-water phantom, respectively. We developed an image system distortion correction method for MRI that relies on adaptive thresholding and an iterative algorithm to determine the 3D distortion field. Applying this technique the residual image distortions were reduced to within the voxel resolution of the raw imaging data. We investigated a procedure for the MRI Simulation of brain lesions which consists of (a) correction of MR images for 3D distortions, (b) automatic segmentation of head sub-structures (i.e. scalp, bone, and brain) relevant for dosimetric calculations, (c) conversion of MRI datasets into CT-like images by assigning bulk CT values to head sub-structures and MRI-based dose calculations, and (d) RT plan evaluation based on isodose distributions, dosimetric parameters, dose volume histograms, and an RT ranking tool. The proposed MRI-based treatment planning procedure performed similarly to the standard clinical technique, which relies on both CT and MR imaging modalities, and is suitable for the radiotherapy of brain cancer.

Stanescu, Teodor Marius

293

PTFOS: Flexible and Absorbable Intracranial Electrodes for Magnetic Resonance Imaging  

PubMed Central

Intracranial electrocortical recording and stimulation can provide unique knowledge about functional brain anatomy in patients undergoing brain surgery. This approach is commonly used in the treatment of medically refractory epilepsy. However, it can be very difficult to integrate the results of cortical recordings with other brain mapping modalities, particularly functional magnetic resonance imaging (fMRI). The ability to integrate imaging and electrophysiological information with simultaneous subdural electrocortical recording/stimulation and fMRI could offer significant insight for cognitive and systems neuroscience as well as for clinical neurology, particularly for patients with epilepsy or functional disorders. However, standard subdural electrodes cause significant artifact in MRI images, and concerns about risks such as cortical heating have generally precluded obtaining MRI in patients with implanted electrodes. We propose an electrode set based on polymer thick film organic substrate (PTFOS), an organic absorbable, flexible and stretchable electrode grid for intracranial use. These new types of MRI transparent intracranial electrodes are based on nano-particle ink technology that builds on our earlier development of an EEG/fMRI electrode set for scalp recording. The development of MRI-compatible recording/stimulation electrodes with a very thin profile could allow functional mapping at the individual subject level of the underlying feedback and feed forward networks. The thin flexible substrate would allow the electrodes to optimally contact the convoluted brain surface. Performance properties of the PTFOS were assessed by MRI measurements, finite difference time domain (FDTD) simulations, micro-volt recording, and injecting currents using standard electrocortical stimulation in phantoms. In contrast to the large artifacts exhibited with standard electrode sets, the PTFOS exhibited no artifact due to the reduced amount of metal and conductivity of the electrode/trace ink and had similar electrical properties to a standard subdural electrode set. The enhanced image quality could enable routine MRI exams of patients with intracranial electrode implantation and could also lead to chronic implantation solutions. PMID:22984396

Bonmassar, Giorgio; Fujimoto, Kyoko; Golby, Alexandra J.

2012-01-01

294

PTFOS: flexible and absorbable intracranial electrodes for magnetic resonance imaging.  

PubMed

Intracranial electrocortical recording and stimulation can provide unique knowledge about functional brain anatomy in patients undergoing brain surgery. This approach is commonly used in the treatment of medically refractory epilepsy. However, it can be very difficult to integrate the results of cortical recordings with other brain mapping modalities, particularly functional magnetic resonance imaging (fMRI). The ability to integrate imaging and electrophysiological information with simultaneous subdural electrocortical recording/stimulation and fMRI could offer significant insight for cognitive and systems neuroscience as well as for clinical neurology, particularly for patients with epilepsy or functional disorders. However, standard subdural electrodes cause significant artifact in MRI images, and concerns about risks such as cortical heating have generally precluded obtaining MRI in patients with implanted electrodes. We propose an electrode set based on polymer thick film organic substrate (PTFOS), an organic absorbable, flexible and stretchable electrode grid for intracranial use. These new types of MRI transparent intracranial electrodes are based on nano-particle ink technology that builds on our earlier development of an EEG/fMRI electrode set for scalp recording. The development of MRI-compatible recording/stimulation electrodes with a very thin profile could allow functional mapping at the individual subject level of the underlying feedback and feed forward networks. The thin flexible substrate would allow the electrodes to optimally contact the convoluted brain surface. Performance properties of the PTFOS were assessed by MRI measurements, finite difference time domain (FDTD) simulations, micro-volt recording, and injecting currents using standard electrocortical stimulation in phantoms. In contrast to the large artifacts exhibited with standard electrode sets, the PTFOS exhibited no artifact due to the reduced amount of metal and conductivity of the electrode/trace ink and had similar electrical properties to a standard subdural electrode set. The enhanced image quality could enable routine MRI exams of patients with intracranial electrode implantation and could also lead to chronic implantation solutions. PMID:22984396

Bonmassar, Giorgio; Fujimoto, Kyoko; Golby, Alexandra J

2012-01-01

295

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

296

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 electronic or nuclear spins. Compared to conventional magnetic resonance, the sensitivity can be increased. Polarization Figure 1: Spin polarization The magnetic resonance signal is generally proportional to the degree

Suter, Dieter

297

RESEARCH Open Access H low field nuclear magnetic resonance  

E-print Network

produced by a chemical reaction named transesterification (TE), where a lipid is reacted with an alcoholRESEARCH Open Access Novel 1 H low field nuclear magnetic resonance applications for the field Field Nuclear Magnetic Resonance (LF-NMR) applications, which offer great potential to the field

Stanford University

298

Hybrid Magnetic Resonance Angiography and Quantitative Volume Flow Measurement  

Microsoft Academic Search

Volume blood flow rate correlates directly with oxygen delivery for aerobic metabolism and is thus clinically more significant than velocity in the diagnosis of vascular diseases. In this dissertation, an magnetic resonance imaging (MRI) technique has been developed to directly measure flow rate. A two echo hybrid magnetic resonance angiography (MRA) pulse sequence has been designed and implemented to obtain

Ping Hou

1993-01-01

299

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

300

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

301

Improved Preparation of Chick Embryonic Samples for Magnetic Resonance Microscopy  

E-print Network

Improved Preparation of Chick Embryonic Samples for Magnetic Resonance Microscopy Xiaowei Zhang,1 T voxels for three stages of chick embryos (day 4, day 5.5, and day 9), and com- pared to histological words: magnetic resonance microscopy; heart develop- ment; embryo; contrast; chick The developmental

302

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

303

Designing and tuning magnetic resonance with exchange interaction.  

PubMed

Exchange interaction at the interface between magnetic layers exhibits significant contribution to the magnetic resonance frequency. The in situ tuning of the resonance frequency, as large as 10 GHz, is demonstrated in a spintronics microwave device through manipulating the interface exchange interaction. PMID:25572962

Chen, Yunpeng; Fan, Xin; Zhou, Yang; Xie, Yunsong; Wu, Jun; Wang, Tao; Chui, Siu Tat; Xiao, John Q

2015-02-01

304

Bioengineering 278: Magnetic Resonance Imaging Laboratory Winter 2010  

E-print Network

Bioengineering 278: Magnetic Resonance Imaging Laboratory Winter 2010 Lab 4 1. EPI. In this exercise, you will observe and correct the effects of time shifts and resonance offset in EPI. Place, in units of the sampling period. (6 points) b. Off resonance effects in EPI. In addition to the time shift

California at San Diego, University of

305

Small-Volume Nuclear Magnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Fratila, Raluca M.; Velders, Aldrik H.

2011-07-01

306

Magnetic resonance imaging of pancreatitis: An update  

PubMed Central

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

2014-01-01

307

Two-dimensional nuclear magnetic resonance petrophysics.  

PubMed

Two-dimensional nuclear magnetic resonance (2D NMR) opens a wide area for exploration in petrophysics and has significant impact to petroleum logging technology. When there are multiple fluids with different diffusion coefficients saturated in a porous medium, this information can be extracted and clearly delineated from CPMG measurements of such a system either using regular pulsing sequences or modified two window sequences. The 2D NMR plot with independent variables of T2 relaxation time and diffusion coefficient allows clear separation of oil and water signals in the rocks. This 2D concept can be extended to general studies of fluid-saturated porous media involving other combinations of two or more independent variables, such as chemical shift and T1/T2 relaxation time (reflecting pore size), proton population and diffusion contrast, etc. PMID:15833623

Sun, Boqin; Dunn, Keh-Jim

2005-02-01

308

Magnetic resonance imaging of knee cartilage repair.  

PubMed

Cartilage injury resulting in osteoarthritis is a frequent cause of disability in young people. Osteoarthritis, based on either cartilage injury or degeneration, is a leading cause of disability in the United States. Over the last several decades, much progress has been made in understanding cartilage injury and repair. Magnetic resonance (MR) imaging, with its unique ability to noninvasively image and characterize soft tissue, has shown promise in assessment of cartilage integrity. In addition to standard MR imaging methods, MR imaging contrast mechanisms under development may reveal detailed information regarding the physiology and morphology of cartilage. MR imaging will play a crucial role in assessing the success or failure of therapies for cartilage injury and degeneration. PMID:9894740

Gold, G E; Bergman, A G; Pauly, J M; Lang, P; Butts, R K; Beaulieu, C F; Hargreaves, B; Frank, L; Boutin, R D; Macovski, A; Resnick, D

1998-12-01

309

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

310

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

311

Magnetic resonance imaging of placenta accreta  

PubMed Central

Placenta accreta (PA) is a severe pregnancy complication which occurs when the chorionic villi (CV) invade the myometrium abnormally. Optimal management requires accurate prenatal diagnosis. Ultrasonography (USG) and magnetic resonance imaging (MRI) are the modalities for prenatal diagnosis of PA, although USG remains the primary investigation of choice. MRI is a complementary technique and reserved for further characterization when USG is inconclusive or incomplete. Breath-hold T2-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) and balanced steady-state free precession imaging in the three orthogonal planes is the key MRI technique. Markedly heterogeneous placenta, thick intraplacental dark bands on half-Fourier acquisition single-shot turbo spin-echo (HASTE), and disorganized abnormal intraplacental vascularity are the cardinal MRI features of PA. MRI is less reliable in differentiating between different degrees of placental invasion, especially between accreta vera and increta. PMID:24604945

Varghese, Binoj; Singh, Navdeep; George, Regi A.N; Gilvaz, Sareena

2013-01-01

312

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; de Cecco, Carlo Nicola; Laghi, Andrea; Piga, Mario; Guerriero, Stefano

2015-03-01

313

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

314

Magnetic resonance imaging for acute pancreatitis  

PubMed Central

Acute pancreatitis is characterized by acute chemical injury of the pancreatic parenchyma and peripancreatic tissue. The increased frequency of death in acute pancreatitis is directly correlated with the degree and progress of pancreatic necrosis. Moreover, the occurrence of some local complications in acute pancreatitis, such as pancreatic hemorrhage, peripancreatic abscess or large pseudocyst, and pseudoaneurysm, could influence the choice of treatment for these patients. Magnetic resonance imaging (MRI) can be used to help evaluate the presence and degree of pancreatic necrosis, and is crucial for identifying complications of acute pancreatitis and predicting prognosis. The purpose of this article is to describe MRI techniques for acute pancreatitis, to review the spectrum of pancreatic and peripancreatic patterns, as well as to survey various complications secondary to acute pancreatitis on MRI. The role of MRI in the initial evaluation and staging of acute pancreatitis is emphasized. PMID:21160684

Xiao, Bo; Zhang, Xiao-Ming

2010-01-01

315

Claustrophobia and the magnetic resonance imaging procedure.  

PubMed

We examined fear induced by the magnetic resonance imaging (MRI) procedure in 80 adult patients who were undergoing the procedure for the first time. Participants completed self-report measures of claustrophobia, anxiety sensitivity, thoughts about the scan, and pain. Participants were assessed pre- and postscan, and at 1-month follow-up. Twenty-five percent of the participants experienced moderate to severe anxiety during the MRI scan. Prescan scores on the Claustrophobia Questionnaire (CLQ: Rachman and Taylor, 1993) significantly predicted participants' distress during the scan: pain and anxeity sensitivity did not. Furthermore, CLQ scores discriminated between participants who reported panic during the scan and participants who did not report panic. A brief screening instrument consisting of six items from the 29-item CLQ is suggested. This brief screening instrument administered prior to the scan may help identify in advance those people who are most likely to experience claustrophobic fear and, in particular, those who panic during the MRI procedure. PMID:9642571

McIsaac, H K; Thordarson, D S; Shafran, R; Rachman, S; Poole, G

1998-06-01

316

Functional magnetic resonance imaging in schizophrenia  

PubMed Central

The integration of functional magnetic resonance imaging (fMRI) with cognitive and affective neuroscience paradigms enables examination of the brain systems underlying the behavioral deficits manifested in schizophrenia; there have been a remarkable increase in the number of studies that apply fMRI in neurobiological studies of this disease. This article summarizes features of fMRI methodology and highlights its application in neurobehavioral studies in schizophrenia. Such work has helped elucidate potential neural substrates of deficits in cognition and affect by providing measures of activation to neurobehavioral probes and connectivity among brain regions. Studies have demonstrated abnormalities at early stages of sensory processing that may influence downstream abnormalities in more complex evaluative processing. The methodology can help bridge integration with neuropharmacologic and genomic investigations. PMID:20954429

Gur, Raquel E.; Gur, Ruben C.

2010-01-01

317

Musculoskeletal applications of nuclear magnetic resonance  

SciTech Connect

Thirty healthy subjects and 15 patients with a variety of musculoskeletal disorders were examined by conventional radiography, computed tomography (CT), and nuclear magnetic resonance (NMR). NMR proved capable of demonstrating important anatomic structures in the region of the lumbosacral spine. Lumbar disk protrusion was demonstrated in three patients with CT evidence of the disease. NMR appeared to differentiate annulus fibrosus from nucleus pulposus in intervertebral disk material. Avascular necrosis of the femoral head was demonstrated in two patients. The cruciate ligaments of the knee were well defined by NMR. Musceles, tendons and ligaments, and blood vessels could be reliably differentiated, and the excellent soft-tissue contrast of NMR proved useful in the evaluation of bony and soft-tissue tumors. NMR holds promise in the evaluation of musculoskeletal disorders.

Moon, K.L. Jr.; Genant, H.K.; Helms, C.A.; Chafetz, N.I.; Crooks, L.E.; Kaufman, L.

1983-04-01

318

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

319

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

320

Overview of Functional Magnetic Resonance Imaging  

PubMed Central

Synopsis Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) depicts changes in deoxyhemoglobin concentration consequent to task-induced or spontaneous modulation of neural metabolism. Since its inception in 1990, this method has been widely employed in thousands of studies of cognition for clinical applications such as surgical planning, for monitoring treatment outcomes, and as a biomarker in pharmacologic and training programs. Technical developments have solved most of the challenges of applying fMRI in practice. These challenges include low contrast to noise ratio of BOLD signals, image distortion, and signal dropout. More recently, attention is turning to the use of pattern classification and other statistical methods to draw increasingly complex inferences about cognitive brain states from fMRI data. This paper reviews the methods, some of the challenges and the future of fMRI. PMID:21435566

Glover, Gary H.

2010-01-01

321

Simulations of pulsed nuclear magnetic resonance experiments  

SciTech Connect

In order to help elucidate various aspects of pulsed nuclear magnetic resonance (NMR) experiments in the liquid state, a consistent mathematical treatment based on density matrix formalism was developed and implemented in a computer program, RELAX. Relaxation effects stemming from dipolar, chemical shift anisotropy (CSA), and random field mechanisms are accounted for, including contributions from dipole-CSA cross-correlation. The program was utilized to study para-fluorophenyl spin systems in dynamical regimes characteristic of both small and large molecules. Theory demonstrates that dipole-CSA cross-correlation can have pronounced effects in these systems and suggests that analysis of these effects will be useful in the study of protein conformation and dynamics.

Smith, S.A.

1991-01-01

322

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

323

The Multisensory Attentional Consequences of Tool Use: A Functional Magnetic Resonance Imaging Study  

E-print Network

The Multisensory Attentional Consequences of Tool Use: A Functional Magnetic Resonance Imaging of Oxford Centre for Clinical Magnetic Resonance Research, John Radcliffe Hospital, Headington, Oxford functional magnetic resonance imaging, while they used a simple tool to discriminate between target

Hansen, Peter

324

Magnetic resonance imaging of live freshwater mussels (Unionidae) F. Michael Holliman,1,a  

E-print Network

Magnetic resonance imaging of live freshwater mussels (Unionidae) F. Michael Holliman,1,a Denise 2 Magnetic Resonance Research Center, University of Pittsburgh Medical Center, Pittsburgh, Eastern elliptio Elliptio complanata, via magnetic resonance imaging (MRI), acquiring data with a widely

Kwak, Thomas J.

325

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

326

ASA monitoring standards and magnetic resonance imaging.  

PubMed

Some patients, often because of age or altered mental state, require general anesthesia or monitored anesthesia care and sedation if adequate magnetic resonance imaging (MRI) is to be accomplished. This study evaluated whether patients can be monitored during MRI with 1.5-tesla scanners in a manner which complies with ASA monitoring standards without causing degradation of image quality. Ten volunteers were scanned in the MRI without sedation. Monitors meeting ASA standards were placed and electronic artifact produced by the magnetic resonance (MR) scanner was evaluated, after which two scans of the head and two of the chest were performed. One of each pair of scans was obtained with the monitors functioning and one with them turned off. Four radiologists, blinded as to whether the monitors were turned on or off, independently evaluated the 20 pairs of scans. Differences in diagnostic quality and image degradation between the scans were evaluated and scores assigned. All monitors functioned appropriately during the scans, with the exception of the electrocardiogram (ECG) which was grossly distorted to the extent that only ventricular rate could be evaluated. None of the head or body scans was nondiagnostic; however, images with the monitors off were of better quality overall than with them on. Two types of noise were generated and are described. During the head scans, three of seven monitoring combinations caused degradation of the images, while four were judged clinically adequate. During the body scans, two of six monitoring combinations created noticeable noise, while four introduced no significant noise. Ungated cardiac scans were nondiagnostic.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7978439

Jorgensen, N H; Messick, J M; Gray, J; Nugent, M; Berquist, T H

1994-12-01

327

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

328

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

PubMed Central

Background Temperatures below the freezing point of water and the ensuing ice crystal formation pose serious challenges to cell structure and function. Consequently, species living in seasonally cold environments have evolved a multitude of strategies to reorganize their cellular architecture and metabolism, and the underlying mechanisms are crucial to our understanding of life. In multicellular organisms, and poikilotherm animals in particular, our knowledge about these processes is almost exclusively due to invasive studies, thereby limiting the range of conclusions that can be drawn about intact living systems. Methodology Given that non-destructive techniques like 1H Magnetic Resonance (MR) imaging and spectroscopy have proven useful for in vivo investigations of a wide range of biological systems, we aimed at evaluating their potential to observe cold adaptations in living insect larvae. Specifically, we chose two cold-hardy insect species that frequently serve as cryobiological model systems–the freeze-avoiding gall moth Epiblema scudderiana and the freeze-tolerant gall fly Eurosta solidaginis. Results In vivo MR images were acquired from autumn-collected larvae at temperatures between 0°C and about ?70°C and at spatial resolutions down to 27 µm. These images revealed three-dimensional (3D) larval anatomy at a level of detail currently not in reach of other in vivo techniques. Furthermore, they allowed visualization of the 3D distribution of the remaining liquid water and of the endogenous cryoprotectants at subzero temperatures, and temperature-weighted images of these distributions could be derived. Finally, individual fat body cells and their nuclei could be identified in intact frozen Eurosta larvae. Conclusions These findings suggest that high resolution MR techniques provide for interesting methodological options in comparative cryobiological investigations, especially in vivo. PMID:19057644

Mietchen, Daniel; Manz, Bertram; Volke, Frank; Storey, Kenneth

2008-01-01

329

Novel Detection Schemes of Nuclear Magnetic Resonance and Magnetic Resonance Imaging: Applications from Analytical Chemistry to Molecular Sensors  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) is a well-established analytical technique in chemistry. The ability to precisely control the nuclear spin interactions that give rise to the NMR phenomenon has led to revolutionary advances in fields as diverse as protein structure determination and medical diagnosis. Here, we discuss methods for increasing the sensitivity of magnetic resonance experiments, moving away from the paradigm

Elad Harel; Leif Schröder; Shoujun Xu

2008-01-01

330

Relationship of Structural Magnetic Resonance Imaging, Magnetic Resonance Perfusion, and Other Disease Factors to Neuropsychological Outcome in Sickle Cell Disease  

Microsoft Academic Search

Objective To investigate the relationship between neuropsychological functioning and radiographic findings in children with sickle cell disease (SCD) with no history of clinical neurological events. Methods Thirty-one patients with SCD randomly selected from a regional treatment center underwent neuropsychological and disease severity assessments. Of these, 22 also had structural magnetic resonance imaging and magnetic resonance perfusion studies performed. Results Forty-five

Royal Grueneich; M. Douglas Ris; William Ball; Karen A. Kalinyak; Robert Noll; Kathy Vannatta; Robert Wells

2004-01-01

331

[Isoflurane in angiography with magnetic resonance].  

PubMed

The authors investigated if the use of vasodilating drugs could increase Magnetic Resonance angiography (MRA) capabilities in demonstrating intracranial vessels. Twenty patients (mean age: 10 years) were examined with MRA: a vasodilating drug (isoflurane) was administered to 10 of them and 10 matched-pair subjects were selected as controls and submitted to MRA without receiving any drug known to increase cerebral blood flow. MRA was performed with a 1.5-T superconductive magnet; FISP 3D sequences were used in all cases. A multiple choice card was used by a reader reporting the following diagnostic information for the different segments of the intracranial vessels: 1) hyperintense and homogeneous vessel with high signal-to-noise (S/N) ratio; 2) hyperintense and heterogeneous vessel with high S/N ratio; 3) hyperintense vessel with low S/N ratio; 4) poor vessels depiction. Small vessels (ophthalmic arteries, A3, M3, M4, anterior communicating arteries and P2 segments) were better demonstrated with isoflurane than with conventional MRA. The results were compared with the Mann-Withney test: isoflurane MRA allowed good vessel depiction in 127 cases, versus 83 of conventional MRA; the difference was statistically significant. To conclude, the use of vasodilating drugs represents a new research field in MRA of the intracranial vessels. PMID:7569104

Carriero, A; Villa, A; Iezzi, A; Tamburri, L; Bosco, G; Bonomo, L

1995-01-01

332

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.

333

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

334

Thoracic magnetic resonance imaging: pulmonary thromboembolism.  

PubMed

Ongoing technical developments have substantially improved the potential of magnetic resonance imaging (MRI) in the assessment of the pulmonary circulation. These developments includes improved magnet and hardware design, new k-space sampling techniques (ie, parallel imaging), and alternative contrast materials. With these techniques, not only can pulmonary vessels be visualized by MR angiography with high spatial resolution but also the perfusion of the lungs and its changes in relation to pulmonary thromboembolism (PE) can be assessed. Considering venous thromboembolism as a systemic disease, MR venography might be added for the diagnosis of underlying deep venous thrombosis. A unique advantage of MRI over other imaging tests is its potential to evaluate changes in cardiac function as a result of obstruction of the pulmonary circulation, which may have a significant impact on patient monitoring and treatment. Finally, MRI does not involve radiation, which is advantageous, especially in young patients. Over the years, a number of studies have shown promising results not only for MR angiography but also for MRI of lung perfusion and for MR venography. This review article summarizes and discusses the current evidence on pulmonary MRI for patients with suspected PE. PMID:23545949

Fink, Christian; Henzler, Thomas; Shirinova, Aysel; Apfaltrer, Paul; Wasser, Klaus

2013-05-01

335

In vivo Off-Resonance Saturation Magnetic Resonance Imaging of AvB3-Targeted Superparamagnetic Nanoparticles  

E-print Network

#12;In vivo Off-Resonance Saturation Magnetic Resonance Imaging of AvB3-Targeted Superparamagnetic of Texas Southwestern Medical Center, Dallas, Texas Abstract Magnetic resonance imaging is a powerful mechanisms and imaging probes have been actively pursued for cancer molecular imaging by magnetic resonance

Gao, Jinming

336

[Magnetic resonance contract agents and perfusion imaging].  

PubMed

Contrast agents may be categorised as non-specific or specific agents. Non-specific agents are freely diffusible in the extracellular and extravascular compartment with the exception of the brain where only blood brain barrier lesions enables the contrast agent to pass. In the specific agent group, a new class of products has been developed, that of blood pool contrast agent, which are distributed in the total intravascular volume and are slowly cleared from the blood. Crossing the healthy capillary wall is limited and depends both on the pathological state of the endothelial permeability tissue of the organ under interest and on the characteristics of the contrast agent (size, charge, molecular shape...). The diagnostic efficacy in perfusion imaging including cerebral perfusion is modulated by the pharmacokinetic profile of the blood pool contrast agent. One way to improve the vascular residence time, consists in binding a vector such as synthetic polymer or a biological macromolecule and a lanthanide like Gd3+, Mn2+, Dy3+ or metal ions. A second way is the synthesis of ultrasmall iron oxide nanoparticles which could escape rapid recognition by the monocyte macrophage phagocytic system mainly of liver and spleen. Because of their cristalline structure and the large number of non-paired spins, five electrons for the iron metal, the nanoparticles behave as magnetic domain when an external field is applied. They consequently have a high dipolar magnetic moment, and can produce a T2 effect in vivo, resulting in a drop in the magnetic resonance signal. Possible interests and developments toward perfusion imaging are demonstrated in experimental models studies. PMID:8656086

Benderbous, S; Bonnemain, B

1996-01-01

337

DIABETIC RETINOPATHY UPDATE Magnetic resonance imaging of the retina: A brief  

E-print Network

DIABETIC RETINOPATHY UPDATE Magnetic resonance imaging of the retina: A brief historical and future KEYWORDS MRI; Magnetic resonance imaging; Diabetic retinopathy; Retinitis pigmentosa; Glaucoma Abstract

Duong, Timothy Q.

338

Bridging the Gap: Integrating Cellular and Functional Magnetic Resonance Imaging Studies  

E-print Network

Bridging the Gap: Integrating Cellular and Functional Magnetic Resonance Imaging Studies and interpreting experimental results. The temporal and spatial resolution of functional magnetic resonance imaging

Rotstein, Horacio G.

339

Identifying patients with obsessivecompulsive disorder using whole-brain anatomy  

E-print Network

Identifying patients with obsessive­compulsive disorder using whole-brain anatomy Carles Soriano a variety of brain alterations between groups of obsessive­compulsive disorder (OCD) patients and healthy brain structure are common in magnetic resonance imaging (MRI) studies of obsessive­compulsive disorder

Gaser, Christian

340

Advanced Magnetic Resonance Imaging and Spectroscopy (AMRIS) Facility  

E-print Network

1 Advanced Magnetic Resonance Imaging and Spectroscopy (AMRIS) Facility Progress and Research Report #3, April 2000 R E P O R T SThe National High Magnetic Field Laboratory FLOR IDA STATE UNIVER SITY ALAMOS NATIONAL LABORATORY AMRIS continued on page 7 World's Most Powerful Magnet Tested -- Ushers in New

Weston, Ken

341

Stress reconfigurable tunable magnetoelectric resonators as magnetic Jillian Kiser,1  

E-print Network

coupling coeffi- cients for low frequency passive magnetometry, establishing equivalent magnetic noise approach in double-clamped ME structures.18 As will be seen, the magnetic field frequency dependenceStress reconfigurable tunable magnetoelectric resonators as magnetic sensors Jillian Kiser,1 Peter

Paris-Sud XI, Université de

342

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

343

Magnetic Field Gradient Waveform Monitoring for Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Linear magnetic field gradients have played a central role in Magnetic Resonance Imaging (MRI) since Fourier Transform MRI was proposed three decades ago. Their primary function is to encode spatial information into MR signals. Magnetic field gradients are also used to sensitize the image contrast to coherent and/or incoherent motion, to selectively enhance an MR signal, and to minimize image artifacts. Modern MR imaging techniques increasingly rely on the implementation of complex gradient waveforms for the manipulation of spin dynamics. However, gradient system infidelities caused by eddy currents, gradient amplifier imperfections and group delays, often result in image artifacts and other errors (e.g., phase and intensity errors). This remains a critical problem for a wide range of MRI techniques on modern commercial systems, but is of particular concern for advanced MRI pulse sequences. Measuring the real magnetic field gradients, i.e., characterizing eddy currents, is critical to addressing and remedying this problem. Gradient measurement and eddy current calibration are therefore a general topic of importance to the science of MRI. The Magnetic Field Gradient Monitor (MFGM) idea was proposed and developed specifically to meet these challenges. The MFGM method is the heart of this thesis. MFGM methods permit a variety of magnetic field gradient problems to be investigated and systematically remedied. Eddy current effects associated with MR compatible metallic pressure vessels were analyzed, simulated, measured and corrected. The appropriate correction of eddy currents may enable most MR/MRI applications with metallic pressure vessels. Quantitative imaging (1D/2D) with model pressure vessels was successfully achieved by combining image reconstruction with MFGM determined gradient waveform behaviour. Other categories of MR applications with metallic vessels, including diffusion measurement and spin echo SPI T2 mapping, cannot be realized solely by MFGM guided image reconstruction. A new 'demand compensation' gradient waveform adjustment method was proposed to address this particular challenge. This idea was verified in this thesis. It should also be noted that, in a general sense, this new waveform compensation method will potentially provide a novel solution to a variety of gradient related problems in MRI.

Han, Hui

344

Optically Detected Magnetic Resonance (ODMR) of photoexcited triplet states.  

PubMed

Optically Detected Magnetic Resonance (ODMR) is a double resonance technique which combines optical measurements (fluorescence, phosphorescence, absorption) with electron spin resonance spectroscopy. After the first triplet-state ODMR experiments in zero magnetic field reported in 1968 by Schmidt and van der Waals, the number of double resonance studies on excited triplet states grew rapidly. Photosynthesis has proven to be a fruitful field of application due to the intrinsic possibility of forming photo-induced pigment triplet states in many sites of the photosynthetic apparatus. The basic principles of this technique are described and examples of application in Photosynthesis are reported. PMID:19238576

Carbonera, Donatella

2009-01-01

345

Purcell factor of Mie resonators featuring electric and magnetic modes  

E-print Network

We present a modal approach to compute the Purcell factor in Mie resonators exhibiting both electric and magnetic resonances. The analytic expressions of the normal modes are used to calculate the effective volumes. We show that important features of the effective volume can be predicted thanks to the translation-addition coefficients of a displaced dipole. Using our formalism, it is easy to see that, in general, the Purcell factor of Mie resonators is not dominated by a single mode, but rather by a large superposition. Finally we consider a silicon resonator homogeneously doped with electric dipolar emitters, and we show that the average electric Purcell factor dominates over the magnetic one.

Zambrana-Puyalto, Xavier

2015-01-01

346

MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2001; 39: 137140  

E-print Network

-coupling constant for the I­S connection, fI is the resonance frequency of the I-nucleus, and fSi is the resonance frequency of the ith S-nucleus. This signal generates an expected HMQC peak for each I­S connection at (fSi, fI), where fSi and

Collum, David B.

347

Magnetic resonance imaging in cardiac amyloidosis  

SciTech Connect

Primary amyloidosis (AL) involves the myocardium in 90% of cases and may present as apparent ischemia, vascular disease, or congestive heart failure. Two-dimensional echocardiography (echo) has proven useful in the diagnosis, particularly in differentiating AL from constrictive pericarditis. The findings of thickened RV and LV myocardium, normal LV cavity dimension, and a diffuse hyperrefractile ''granular sparkling'' appearance are virtually diagnostic. Magnetic resonance (MR) imaging may improve the resolution of anatomic changes seen in cardiac AL and has the potential to provide more specific information based on biochemical tissue alterations. In this preliminary study, the authors obtained both MR and echo images in six patients with AL and biopsy-proven myocardial involvement. 5/6 patients also had Tc-99 PYP myocardial studies including emission tomography (SPECT). MR studies utilized a 0.6 Tesla superconductive magnet. End diastolic gated images were obtained with TE=30msec and TR=R-R interval on the ECG. 6/6 pts. showed LV wall thickening which was concentric and included the septum. Papillary muscles were identified in all and were enlarged in 3/6. 4/6 pts. showed RV wall thickening but to a lesser degree than LV. Pericardial effusions were present in 4 cases. These findings correlated well with the results of echo although MR gave better RV free wall resolution. PYP scans were positive in 3 pts. but there was no correlation with degree of LV thickening. The authors conclude that there are no identifiable MR findings in patients with cardiac AL which encourage further attempts to characterize myocardial involvement by measurement of MR relaxation times in vivo.

O'Donnell, J.K.; Go, R.T.; Bott-Silverman, C.; Feiglin, D.H.; Salcedo, E.; MacIntyre, W.J.

1984-01-01

348

Microscopic magnetic resonance elastography (?MRE) applications  

NASA Astrophysics Data System (ADS)

Microscopic magnetic resonance elastography (?MRE) is a phase contrast based imaging technique that is capable of mapping the acoustic shear waves resulting from low amplitude cyclic displacement in tissue-like materials. This new technique has proven successful in imaging gel phantoms mimicking soft biological tissues with shear moduli ranging from 0.7 to 40 kPa. The 4-dimensional (4D) spatial-temporal shear wave vector can be measured, which in turn can be used to identify material properties with high spatial resolution. Experiments were conducted using 5 and 10 mm RF saddle coils in the 10 mm vertical imaging bore of an 11.74 Tesla magnet. The field-of-view ranged from 4 to 14 mm, with in plane resolution up to 34 ?m x 34 ?m and slice thickness up to 100 ?m using shear wave excitation of 550 to 580 Hz. In this study, the capability and constraints of ?MRE are investigated. The constraints include the range of measured shear moduli, excitation frequency, and minimum physical sample volume. Applications investigated include: 1) late-stage frog oocytes with typical diameter from 1 to 1.5 mm; and 2) tissue engineered constructs at different growth stages. Mesenchymal stem cells (MSCs) extracted from bone marrow can serve as progenitor cells that differentiate into specific types of tissues such as bone, adipose tissue, cartilage and muscle. ?MRE can monitor the growth of such tissues and evaluate their mechanical properties. Also, a silicon-based tissue phantom material (CF-11-2188, Nusil Technologies) is tested in order to address challenges associated with excitation frequency and the dispersive nature of the media.

Othman, Shadi F.; Xu, Huihui; Royston, Thomas J.; Magin, Richard L.

2005-04-01

349

Nuclear magnetic resonance for cultural heritage.  

PubMed

Nuclear magnetic resonance (NMR) portable devices are now being used for nondestructive in situ analysis of water content, pore space structure and protective treatment performance in porous media in the field of cultural heritage. It is a standard procedure to invert T(1) and T(2) relaxation data of fully water-saturated samples to get "pore size" distributions, but the use of T(2) requires great caution. It is well known that dephasing effects due to water molecule diffusion in a magnetic field gradient can affect transverse relaxation data, even if the smallest experimentally available half echo time tau is used in Carr-Purcell-Meiboom-Gill experiments. When a portable single-sided NMR apparatus is used, large field gradients due to the instrument, at the scale of the sample, are thought to be the dominant dephasing cause. In this paper, T(1) and T(2) (at different tau values) distributions were measured in natural (Lecce stone) and artificial (brick samples coming from the Greek-Roman Theatre of Taormina) porous media of interest for cultural heritage by a standard laboratory instrument and a portable device. While T(1) distributions do not show any appreciable effect from inhomogeneous fields, T(2) distributions can show strong effects, and a procedure is presented based on the dependence of 1/T(2) on tau to separate pore-scale gradient effects from sample-scale gradient effects. Unexpectedly, the gradient at the pore scale can be, in some cases, strong enough to make negligible the effects of gradients at the sample scale of the single-sided device. PMID:17466764

Brai, Maria; Camaiti, Mara; Casieri, Cinzia; De Luca, Francesco; Fantazzini, Paola

2007-05-01

350

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

351

[Magnetic resonance angiography of the renal arteries].  

PubMed

Initially, the clinical use of magnetic resonance angiography (MRA) in the abdomen has been restricted because of motion and flow related artifacts. The advent of high performance gradient systems made possible the development of 3D gadolinium-enhanced MRA techniques and expanded the clinical applications of MRA into the abdominal area, particularly for the investigation of renal arteries. This technique is safe, because the administered contrast agent (gadolinium) is free of clinically detectable nephrotoxicity and has a low incidence of allergic reactions. Moreover, contrast MRA also eliminates the risks of ionizing radiation which allows repeating the examination without the accumulation of radiation exposure. The main disadvantages of the technique are its low availability and the fact that the use of contrast agents for this procedure is still not reimbursed by the social security. Many studies demonstrated that contrast MRA allows for the reliable assessment of renal artery morphology and pathologic states. Furthermore, within a single MR examination a comprehensive approach including renal artery morphology, hemodynamic significance of any stenosis and kidney perfusion is available. In this paper, we provide a review of the literature concerning the clinical performance of contrast MRA for the renal arteries and suggest its rationale for the investigation of patients suspected of renovascular disease in our specific environment. PMID:10523920

Matos, C; Metens, T; Nicaise, N; Golzarian, J; Dussaussois, L; Struyven, J

1999-09-01

352

Magnetic resonance imaging of the kidneys  

SciTech Connect

A study of the magnetic resonance imaging (MRI) appearance of the kidneys in six normal volunteers and 52 patients is reported. Corticomedullary differentiation was seen with the inversion-recovery (IR 1400/400) sequence in the normal volunteers and in patients with functioning transplanted kidneys and acute tubular necrosis. Partial or total loss of corticomedullary differentiation was seen in glomerulonephritis, acute and chronic renal failure, renal artery stenosis, and transplant rejection. The T1 of the kidneys was increased in glomerulonephritis with neuphrotic syndrome, but the T1 was within the normal range for renal medulla in glomerulonephritis without nephrotic syndrome, renal artery stenosis, and chronic renal failure. A large staghorn calculus was demonstrated with MRI, but small calculi were not seen. Fluid within the hydonephrosis, simple renal cysts, and polycystic kidneys displayed very low signal intensity and long T1 values. Tumors displayed varied appearances. Hypernephromas were shown to be hypo- or hyperintense with the renal medulla on the IR 1400/400 sequence. After intravenous injection of gadolinium-DTPA, there was marked decrease in the tumor T1.

Leung, A.W.L.; Bydder, G.M.; Steinter, R.E.; Bryant, D.J.; Young, I.R.

1984-12-01

353

Magnetic Resonance Elastography: Inversions in Bounded Media  

PubMed Central

Magnetic resonance elastography (MRE) is a noninvasive imaging technique capable of quantifying and spatially resolving the shear stiffness of soft tissues by visualization of synchronized mechanical wave displacement fields. However, MRE inversions generally assume that the measured tissue motion consists primarily of shear waves propagating in a uniform, infinite medium. This assumption is not valid in organs such as the heart, eye, bladder, skin, fascia, bone and spinal cord in which the shear wavelength approaches the geometric dimensions of the object. The aim of this study was to develop and test mathematical inversion algorithms capable of resolving shear stiffness from displacement maps of flexural waves propagating in bounded media such as beams, plates and spherical shells using geometry-specific equations of motion. MRE and finite element modeling (FEM) of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from FEM and MRE data and a linear correlation of r2 ? 0.99 was observed between the stiffness values obtained using MRE and FEM data. In conclusion, we have demonstrated new inversion methods for calculating shear stiffness that may be more appropriate for waves propagating in bounded media. PMID:19780146

Kolipaka, Arunark; McGee, Kiaran P.; Manduca, Armando; Romano, Anthony J.; Glaser, Kevin J.; Araoz, Philip A.; Ehman, Richard L.

2009-01-01

354

Vibration safety limits for magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

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 a 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.

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

2008-02-01

355

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

356

Magnetic Resonance Image Example Based Contrast Synthesis  

PubMed Central

The performance of image analysis algorithms applied to magnetic resonance images is strongly influenced by the pulse sequences used to acquire the images. Algorithms are typically optimized for a targeted tissue contrast obtained from a particular implementation of a pulse sequence on a specific scanner. There are many practical situations, including multi-institution trials, rapid emergency scans, and scientific use of historical data, where the images are not acquired according to an optimal protocol or the desired tissue contrast is entirely missing. This paper introduces an image restoration technique that recovers images with both the desired tissue contrast and a normalized intensity profile. This is done using patches in the acquired images and an atlas containing patches of the acquired and desired tissue contrasts. The method is an example-based approach relying on sparse reconstruction from image patches. Its performance in demonstrated using several examples, including image intensity normalization, missing tissue contrast recovery, automatic segmentation, and multimodal registration. These examples demonstrate potential practical uses and also illustrate limitations of our approach. PMID:24058022

Roy, Snehashis; Carass, Aaron; Prince, Jerry L.

2013-01-01

357

Magnetic resonance imaging of spinal dysraphism.  

PubMed

Spinal cord development occurs through three consecutive periods. Gastrulation (weeks 2-3) is characterized by conversion of the embryonic disk from a bilaminar to a trilaminar arrangement and establishment of a notochord. Primary neurulation (weeks 3-4) produces the uppermost nine tenths of the spinal cord. Secondary neurulation and retrogressive differentiation (weeks 5-6) result in formation of the conus tip and filum terminale. Defects in these early embryonic stages produce spinal dysraphisms, which are characterized by anomalous differentiation and fusion of dorsal midline structures. Spinal dysraphisms may be categorized clinically into two subsets. In open spinal dysraphisms, the placode (non-neurulated neural tissue) is exposed to the environment. These disorders include myelomeningocele, myeloschisis, hemimyelomeningocele, and hemimyelocele, and are always associated with a Chiari II malformation. Closed spinal dysraphisms are covered by intact skin, although cutaneous stigmata usually indicate their presence. Two subsets may be identified based on whether a subcutaneous mass is present in the low back. Closed spinal dysraphisms with mass comprise lipomyeloschisis, lipomyelomeningocele, meningocele, and myelocystocele. Closed spinal dysraphisms without mass comprise complex dysraphic states (ranging from complete dorsal enteric fistula to neurenteric cysts, split cord malformations, dermal sinuses, caudal regression, and spinal segmental dysgenesis), bony spina bifida, tight filum terminale, filar and intradural lipomas, and persistent terminal ventricle. Magnetic resonance imaging is the imaging method of choice for investigation of this complex group of disorders. PMID:11744877

Tortori-Donati, P; Rossi, A; Biancheri, R; Cama, A

2001-12-01

358

Magnetic Resonance Imaging of Intercranial Plasmocytic Granuloma  

PubMed Central

The objective of this study is to determine characteristic magnetic resonance imaging (MRI) features of intracranial plasmocytic granulomas. Pathological confirmation of three patients with intracranial pathologically confirmed plasmocytic granuloma are presented. Clinical records as well pre- and postgadolinium-enhanced images from each patient are reviewed. The location of the abnormalities is compared with previous reported cases of plasmocytic granulomas, to determine if there is a characteristic finding in this disense. The predominance of this abnormality in the pediatric and young adult patient was striking. On T1-weighted MRI, plasmocytic granulomas appear as hypointense lesions, with isointense appearance on T2 images, and significant, variable patterns of enhancement after the infusion of gadolinium. Typically, the lesion is infiltrating, and causes little mass effect. A dural based lesion, as well as a sellar region abnormality and an infiltrating cortical lesion with little mass effect in the pediatric or young adult age group may lead the observer to suspect the diagnosis of plasmocytic granuloma. ImagesFigure 1Figure 2Figure 3 PMID:17171115

Wilner, Harvey I.; Vinas, Federico C.; Duffy, Colleen; Kupsky, William J.; Guthikonda, Murali

1999-01-01

359

TOPICAL REVIEW: Endovascular interventional magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Minimally invasive interventional radiological procedures, such as balloon angioplasty, stent placement or coiling of aneurysms, play an increasingly important role in the treatment of patients suffering from vascular disease. The non-destructive nature of magnetic resonance imaging (MRI), its ability to combine the acquisition of high quality anatomical images and functional information, such as blood flow velocities, perfusion and diffusion, together with its inherent three dimensionality and tomographic imaging capacities, have been advocated as advantages of using the MRI technique for guidance of endovascular radiological interventions. Within this light, endovascular interventional MRI has emerged as an interesting and promising new branch of interventional radiology. In this review article, the authors will give an overview of the most important issues related to this field. In this context, we will focus on the prerequisites for endovascular interventional MRI to come to maturity. In particular, the various approaches for device tracking that were proposed will be discussed and categorized. Furthermore, dedicated MRI systems, safety and compatibility issues and promising applications that could become clinical practice in the future will be discussed.

Bartels, L. W.; Bakker, C. J. G.

2003-07-01

360

Magnetic resonance imaging of triangular fibrocartilage.  

PubMed

Due to their small size and complex structure, diagnosing injury of the proximal wrist ligamentous structures can be challenging. The triangular fibrocartilage complex (TFCC) is an example of one such structure, for which lesions may be missed unless high-resolution magnetic resonance imaging (MRI) obtained via a standard matrix with a small field of view or high-resolution imaging matrix (small spatial scale matrix elements/large matrix size) is utilized. While there have been recent advances in increasing MRI spatial resolution, attempts at improved visualization by isolated increase in the spatial resolution will be ineffective if the signal-to-noise ratio (SNR) of the images obtained is low. Additionally, high contrast resolution is important to facilitate a more precise visualization of these structures and their pathology. Thus, a balance of the three important imaging factor qualifications of high spatial resolution, high SNR, and high contrast resolution must be struck for optimized TFCC and wrist imaging. The goal of this article, then, is to elucidate the theory and techniques of effective high-resolution imaging of the proximal ligamentous structures of the wrist, balancing SNR and high contrast resolution constraints, and focusing on imaging of the TFCC as a prototypical example. PMID:22434698

Yoshioka, Hiroshi; Burns, Joseph E

2012-04-01

361

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

362

Imaging intelligence with proton magnetic resonance spectroscopy  

PubMed Central

Proton magnetic resonance spectroscopy (1H-MRS) is a technique for the assay of brain neurochemistry in vivo. N-acetylaspartate (NAA), the most prominent metabolite visible within the 1H-MRS spectrum, is found primarily within neurons. The current study was designed to further elucidate NAA–cognition relationships, particularly whether such relationships are moderated by sex, or tissue type (gray or white matter). We administered standard measures of intelligence to 63 young, healthy subjects and obtained spectroscopic imaging data within a slab of tissue superior to the lateral ventricles. We found that lower NAA within right anterior gray matter predicted better performance VIQ (F=6.83, p=.011, r2=.10), while higher NAA within the right posterior gray matter region predicted better PIQ (F=8.175, p=.006, r2=.12). These findings add to the small but growing body of literature linking brain biochemistry to intelligence in normal healthy subjects using 1H-MRSI. PMID:19936275

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

2009-01-01

363

The developing role of fetal magnetic resonance imaging in the diagnosis of congenital cardiac anomalies: A systematic review  

PubMed Central

Advances in the fetal magnetic resonance imaging (MRI) over the last few years have resulted in the exploring the use of fetal MRI to detect congenital cardiac anomalies. Early detection of congenital cardiac anomalies can help more appropriately manage the infant's delivery and neonatal management. MRI offers anatomical and functional studies and is a safe adjunct that can help more fully understand a fetus’ cardiac anatomy. It is important for the obstetricians and pediatric cardiologists to be aware of the recent advancements in fetal MRI and it`s potential utility in diagnosing congenital cardiac anomalies. PMID:21976881

Loomba, Rohit S; Chandrasekar, Suraj; Shah, Parinda H; Sanan, Prateek

2011-01-01

364

The developing role of fetal magnetic resonance imaging in the diagnosis of congenital cardiac anomalies: A systematic review.  

PubMed

Advances in the fetal magnetic resonance imaging (MRI) over the last few years have resulted in the exploring the use of fetal MRI to detect congenital cardiac anomalies. Early detection of congenital cardiac anomalies can help more appropriately manage the infant's delivery and neonatal management. MRI offers anatomical and functional studies and is a safe adjunct that can help more fully understand a fetus' cardiac anatomy. It is important for the obstetricians and pediatric cardiologists to be aware of the recent advancements in fetal MRI and it`s potential utility in diagnosing congenital cardiac anomalies. PMID:21976881

Loomba, Rohit S; Chandrasekar, Suraj; Shah, Parinda H; Sanan, Prateek

2011-07-01

365

Effect of peripheral nerve action currents on magnetic resonance imaging.  

PubMed

Many researchers have attempted to detect neural currents directly using magnetic resonance imaging (MRI). The action currents of a peripheral nerve create their own magnetic field that can cause the phase of the spins to change. Our goal in this paper is to use the measured magnetic field of a nerve to estimate the resulting phase shift in the magnetic resonance signal. We examine three cases: the squid giant axon, the frog sciatic nerve, and the human median nerve. In each case, the phase shift is much less than one degree, and will be very difficult to measure with current technology. PMID:19963781

Wijesinghe, Ranjith; Roth, Bradley J

2009-01-01

366

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

367

Magnetic resonance imaging of the maxilla and mandible: signal characteristics and features in the differential diagnosis of common lesions.  

PubMed

The maxilla and mandible are among the most difficult areas of the body to image with magnetic resonance techniques owing to the geometry of the jaws as well as the frequent susceptibility artifacts from dental restorations or appliances. This chapter briefly reviews the essentials of imaging techniques and basic anatomy and discusses the most common inflammatory conditions, benign and malignant lesions of the jaws, and temporomandibular joint. This review emphasizes and illustrates specific magnetic resonance features that facilitate characterization and diagnostic differentiation of these lesions. As the focus of this review is on the differentiation of infection and benign and malignant disease, a discussion of internal derangements and associated inflammatory disorders of the temporomandibular joint is beyond the scope of this review and is not discussed. PMID:25654419

Mosier, Kristine M

2015-02-01

368

High-Resolution Magnetic Resonance Angiography of the Mouse Brain: Application to Murine Focal Cerebral Ischemia Models  

NASA Astrophysics Data System (ADS)

Three-dimensional time-of-flight high-resolution magnetic resonance angiography was applied to visualize the cerebral vasculature of the mouse brain. In normal mice, angiograms of good quality, showing the essential details of the arterial cerebrovascular anatomy, could be obtained in only 2.5 min without the use of contrast agents. Signals from slowly flowing blood, e.g., in veins, could also be detected after administration of a blood pool contrast agent. The technique was applied to mouse models of permanent and transient brain ischemia, involving the occlusion of the middle cerebral artery. High-resolution magnetic resonance angiography proved to be a very useful tool for verifying the success of the occlusion in these models.

Beckmann, Nicolau; Stirnimann, Roger; Bochelen, Damien

1999-10-01

369

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

PubMed Central

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

2014-01-01

370

Magnetic resonance imaging of sellar and juxtasellar abnormalities in the paediatric population: an imaging review.  

PubMed

The sellar and juxtasellar regions in the paediatric population are complex both anatomically and pathologically, with magnetic resonance imaging (MRI) being the "gold standard" imaging modality due to the high contrast of detail. Assessment requires a detailed understanding of the anatomy, embryology, pathophysiology and normal signal characteristics of the pituitary gland and surrounding structures in order to appropriately characterise abnormalities. This article aims to provide an overview of the imaging characteristics of developmental/congenital and acquired disease processes which affect the sellar and juxtasellar region in the paediatric population. Main Messages • The sellar region is anatomically complex and covers a wide pathology spectrum. • MRI is the key imaging modality to assess sellar and juxtasellar pathology. • Numerous developmental anomalies may not be discovered until adulthood. • Knowledge of pathology alerts and guides the clinician towards appropriate management. PMID:25794595

Shields, Rachel; Mangla, Rajiv; Almast, Jeevak; Meyers, Steven

2015-04-01

371

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

372

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

373

Magnetic resonance spectroscopic imaging using parallel transmission at 7T  

E-print Network

Conventional magnetic resonance spectroscopic imaging (MRSI), also known as phase-encoded (PE) chemical shift imaging (CSI), suffers from both low signal-to-noise ratio (SNR) of the brain metabolites, as well as inflexible ...

Gagoski, Borjan Aleksandar

2011-01-01

374

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

375

Magnetic resonance image enhancement using V-filter  

SciTech Connect

The purpose of this study is to present a method of boundary enhancement algorithms for magnetic resonance images using a V-filter. The boundary of the brain tumor was precisely extracted by the region segmentation techniques.

Yamamoto, H.; Sugita, K. (School of Health Sciences, Okayama Univ., Shikata, Okayama 700 (JP)); Kanzaki, N.; Johja, I.; Hiraki, Y. (Okayama Univ. (Japan). School of Medicine); Kuwahara, M. (Osaka Industrial Univ., Nakagaito, Daito 574 (JP))

1990-06-01

376

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

377

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.

378

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

379

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

380

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

381

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

382

Microfluidically Cryo-Cooled Planar Coils for Magnetic Resonance Imaging  

E-print Network

High signal-to-noise ratio (SNR) is typically required for higher resolution and faster speed in magnetic resonance imaging (MRI). Planar microcoils as receiver probes in MRI systems offer the potential to be configured into array elements for fast...

Koo, Chiwan

2013-08-09

383

Magnetic resonance imaging of papillary renal cell carcinoma  

Microsoft Academic Search

The authors report magnetic resonance (MR) studies in a case of papillary renal cell carcinoma. The preoperative ultrasound\\u000a and computed tomographic scans suggested either a hemorrhagic cyst or a carcinoma, but the angiogram demonstrated avascularity.\\u000a The magnetic resonance scan was more consistent with carcinoma than complicated cyst. We report the MR findings with pathologic\\u000a correlation.

Steven D. Herman; Arnold C. Friedman; Marc Siegelbaum; Parvati Ramchandani; Paul D. Radecki

1985-01-01

384

Magnetic Resonance Imaging: From Spin Physics to Medical Diagnosis  

Microsoft Academic Search

Two rather similar historical evolutions are evoked, each one originating in fundamental spin studies by physicists, and ending\\u000a as magnetic resonance imaging (MRI), a set of invaluable tools for clinical diagnosis in the hands of medical doctors. The\\u000a first one starts with the early work on nuclear magnetic resonance, the founding stone of the usual proton-based MRI, of which\\u000a the

Pierre-Jean Nacher

2009-01-01

385

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

386

Carbon13 nuclear magnetic resonance spectra of keto steroids  

Microsoft Academic Search

Fourier transform C-13 nuclear magnetic resonance spectra were obtained ; and assigned for a complete series of keto steroids -the steroid skeletons being ; those of androstane and cholestane. The assignments were performed by comparing ; the spectra of these closely related compounds and correlating the shifts due to ; differences in structure, and by use of off-resonance decoupled spectra.

Hanne Eggert; Carl Djerassi

1973-01-01

387

Passive Shim Design and a Shimming Approach for Biplanar Permanent Magnetic Resonance Imaging Magnets  

Microsoft Academic Search

This paper presents a new passive shim design method and a novel shimming procedure to correct the magnetic field inhomogeneities generated by C-shape permanent biplanar magnetic resonance imaging magnets. The method expresses the shim distribution as a sum of orthogonal functions multiplied by unknown amplitudes. The oscillating modes of the shim magnetization-thickness function are normalized within a finite disk. By

Hector Sanchez Lopez; Feng Liu; Ewald Weber; Stuart Crozier

2008-01-01

388

Magnetic resonance imaging of the elbow. Part II: Abnormalities of the ligaments, tendons, and nerves  

Microsoft Academic Search

Part II of this comprehensive review on magnetic resonance imaging of the elbow discusses the role of magnetic resonance imaging in evaluating patients with abnormalities of the ligaments, tendons, and nerves of the elbow. Magnetic resonance imaging can yield high-quality multiplanar images which are useful in evaluating the soft tissue structures of the elbow. Magnetic resonance imaging can detect tears

Richard Kijowski; Michael Tuite; Matthew Sanford

2005-01-01

389

Patellar tendinitis: the significance of magnetic resonance imaging findings.  

PubMed

We evaluated the significance of magnetic resonance imaging findings in patients with patellar tendinitis. Midline sagittal magnetic resonance images were taken of 12 knees from 10 patients and of 17 knees from 15 age- and activity-matched subjects who underwent imaging for reasons other than patellar tendinitis. Of the 12 magnetic resonance imaging scans of knees with clinical patellar tendinitis, 3 (25%) exhibited no defect and only 7 (58%) had unequivocal intratendinous lesions. Among the 17 scans of subjects without clinical patellar tendinitis, 5 (34%) showed no defect and 4 (24%) had unequivocal intratendinous lesions. Proximal tendon width was significantly larger for the tendinitis patient group (5.0 +/- 1.7 mm versus 3.9 +/- 1.0 mm), although considerable overlap was present. All subjects with unequivocal intratendinous signal changes had a significantly longer nonarticular inferior patellar pole and were significantly older (38.1 years versus 26.8 years). Only Blazina stage III lesions were associated with abnormal findings on magnetic resonance imaging. As a whole, the sensitivity and specificity of magnetic resonance imaging was 75% and 29%, respectively. In younger patients with relatively mild symptoms, magnetic resonance imaging did not show significant changes; in older, active patients changes may be present in asymptomatic knees. PMID:10352771

Shalaby, M; Almekinders, L C

1999-01-01

390

Ferromagnetic resonance in $\\epsilon$-Co magnetic composites  

E-print Network

We investigate the electromagnetic properties of assemblies of nanoscale $\\epsilon$-cobalt crystals with size range between 5 nm to 35 nm, embedded in a polystyrene (PS) matrix, at microwave (1-12 GHz) frequencies. We investigate the samples by transmission electron microscopy (TEM) imaging, demonstrating that the particles aggregate and form chains and clusters. By using a broadband coaxial-line method, we extract the magnetic permeability in the frequency range from 1 to 12 GHz, and we study the shift of the ferromagnetic resonance with respect to an externally applied magnetic field. We find that the zero-magnetic field ferromagnetic resonant peak shifts towards higher frequencies at finite magnetic fields, and the magnitude of complex permeability is reduced. At fields larger than 2.5 kOe the resonant frequency changes linearly with the applied magnetic field, demonstrating the transition to a state in which the nanoparticles become dynamically decoupled. In this regime, the particles inside clusters can ...

Chalapat, Khattiya; Huuppola, Maija; Koponen, Lari; Johans, Christoffer; Ras, Robin H A; Ikkala, Olli; Oksanen, Markku A; Seppälä, Eira; Paraoanu, G S

2014-01-01

391

Magnetic resonance imaging of the adrenal gland.  

PubMed

The authors review their experience with magnetic resonance imaging (MRI) of the adrenal gland and discuss the appearance of adrenal diseases where MRI is clinically useful. A basic description of some of the newer pulse sequences is provided. Fat-suppressed MRI is advantageous because of reduction of cardiac and respiratory motion induced artifacts, accentuation of small differences in tissue contrast, and elimination of chemical shift artifacts. These advantages far outweigh the disadvantages of inhomogeneity of fat suppression and the fewer slices obtained per acquisition. Chemical shift imaging is used to differentiate benign from malignant adrenal diseases based on a gradient echo phase cycling technique. Detailed descriptions of MRI findings in adrenal pheochromocytomas, hemorrhage, cysts, adenomas, myelolipomas, and metastases are provided. Most pheochromocytomas appear markedly hyperintense to the liver on T2-weighted images. However, this appearance is not specific as adrenal metastases and adrenal adenomas may occasionally produce a similar appearance. In addition, pheochromocytomas may occasionally be isointense or hypointense to the liver on T2-weighted images. Differentiation of adrenal metastases from adrenal adenomas with MRI is problematic using signal intensity ratios (33% overlap) or T2 calculations. The future of discriminating between adrenal metastases and adenomas may rest with chemical shift MRI, which uses in- and out-of-phase gradient echo pulse sequences for differentiation. This approach relies on the fact that adrenal adenomas contain fat, while adrenal metastases do not. The reported accuracy of chemical shift imaging in differentiating between adrenal adenomas and adrenal metastases ranges from 96 to 100%. An algorithmic approach to differentiating benign from malignant adrenal diseases is presented that relies on an initial noncontrast CT with CT attenuation values obtained from the adrenal mass. If CT attenuation values are less than zero, the mass is characterized as benign. If the mass remains indeterminate after CT, chemical shift MR is performed. If the mass remains indeterminate after MR, biopsy is required. PMID:7612177

Boland, G W; Lee, M J

1995-01-01

392

Magnetic Resonance Imaging–guided Vascular Interventions  

PubMed Central

Magnetic resonance imaging (MRI), which provides superior soft-tissue imaging and no known harmful effects, has the potential as an alternative modality to guide various medical interventions. This review will focus on MR-guided endovascular interventions and present its current state and future outlook. In the first technical part, enabling technologies such as developments in fast imaging, catheter devices, and visualization techniques are examined. This is followed by a clinical survey that includes proof-of-concept procedures in animals and initial experience in human subjects. In preclinical experiments, MRI has already proven to be valuable. For example, MRI has been used to guide and track targeted cell delivery into or around myocardial infarctions, to guide atrial septal puncture, and to guide the connection of portal and systemic venous circulations. Several investigational MR-guided procedures have already been reported in patients, such as MR-guided cardiac catheterization, invasive imaging of peripheral artery atheromata, selective intraarterial MR angiography, and preliminary angioplasty and stent placement. In addition, MR-assisted transjugular intrahepatic portosystemic shunt procedures in patients have been shown in a novel hybrid double-doughnut x-ray/MRI system. Numerous additional investigational human MR-guided endovascular procedures are now underway in several medical centers around the world. There are also significant hurdles: availability of clinical-grade devices, device-related safety issues, challenges to patient monitoring, and acoustic noise during imaging. The potential of endovascular interventional MRI is great because as a single modality, it combines 3-dimensional anatomic imaging, device localization, hemodynamics, tissue composition, and function. PMID:16924170

Ozturk, Cengizhan; Guttman, Michael; McVeigh, Elliot R.; Lederman, Robert J.

2007-01-01

393

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

394

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

395

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

396

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

397

An improved discrete configuration of a cylinder magnet for portable nuclear magnetic resonance instruments  

NASA Astrophysics Data System (ADS)

The continuous magnetization profile approximated by a discrete source is the main reason for the deteriorating magnetic field homogeneity in Halbach magnet. It is identified by comparing the two-dimensional (2D) field solutions of an ideal cylinder magnet with those of a cylinder magnet constructed from several segment magnets. To improve the magnetic field homogeneity, a cylinder magnet from several crescent-shaped magnets is therefore presented. The programed 2D field solutions of the magnet from the crescent-shaped segments verify that the configuration effectively improves the homogeneity inside the cylinder magnet compared to that of a magnet built from simpler segments. For a small magnet with a required field uniformity and magnitude, the configuration has more advantages than a configuration from typical segments. Hence, the magnet is more appropriate for a portable nuclear magnetic resonance instruments.

Chen, Jizhong; Xu, Chunyan

2007-06-01

398

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

399

Magnetic-field measurements using an integrated resonant magnetic-field sensor  

Microsoft Academic Search

The present paper introduces a magnetic-field sensor based on a resonating single-crystal silicon structure. The excitation of the resonator is achieved by the Lorentz force generated by a sinusoidal current flowing through a rectangular coil deposited on the surface of the structure. The amplitude of the vibration, which is proportional to the magnetic field, is detected by sensing capacitors. Because

Zs. Kádár; A. Bossche; P. M. Sarro; J. R. Mollinger

1998-01-01

400

Narrow band deformable registration of prostate magnetic resonance imaging, magnetic resonance spectroscopic imaging, and computed tomography studies  

Microsoft Academic Search

Purpose: Endorectal (ER) coil-based magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) is often used to obtain anatomic and metabolic images of the prostate and to accurately identify and assess the intraprostatic lesions. Recent advancements in high-field (3 Tesla or above) MR techniques affords significantly enhanced signal-to-noise ratio and makes it possible to obtain high-quality MRI data. In

Eduard Schreibmann; Lei Xing

2005-01-01

401

In Vivo Phenotyping of the ob\\/ob Mouse by Magnetic Resonance Imaging and 1H-Magnetic Resonance Spectroscopy  

Microsoft Academic Search

Objective: We studied ob\\/ob and wild-type (WT) mice to characterize the adipose tissues depots and other visceral organs and to establish an experimental paradigm for in vivo phenotyping.Research Methods and Procedures: An in vivo evaluation was conducted using magnetic resonance imaging and 1H-magnetic resonance spectroscopy (1H-MRS). We used T1-weighted images and three-dimensional spin echo T1-weighted images for the morphological analysis

Laura Calderan; Pasquina Marzola; Elena Nicolato; Paolo F. Fabene; Chiara Milanese; Paolo Bernardi; Antonio Giordano; Saverio Cinti; Andrea Sbarbati

2006-01-01

402

Electron paramagnetic resonance of nitroxide-doped magnetic fluids  

NASA Astrophysics Data System (ADS)

Electron paramagnetic resonance was used to investigate surface-coated magnetite-based magnetic fluids doped with TEMPOL. Two magnetic fluid samples, having magnetite nanoparticles with average diameter of 94 Å and coated with different coating layers (lauric acid plus ethoxylated polyalcohol in one case and oleoylsarcosine in the other case), were doped with TEMPOL (6 mM and pH 7.4) and investigated as a function of the nanoparticle concentration. The resonance field and the resonance linewidth both scale linearly with the nanoparticle concentration.

Morais, P. C.; Alonso, A.; Silva, O.; Buske, N.

2002-11-01

403

Stochastic Resonance in a simple model of magnetic reversals  

E-print Network

We discuss the effect of stochastic resonance in a simple model of magnetic reversals. The model exhibits statistically stationary solutions and bimodal distribution of the large scale magnetic field. We observe a non trivial amplification of stochastic resonance induced by turbulent fluctuations, i.e. the amplitude of the external periodic perturbation needed for stochastic resonance to occur is much smaller than the one estimated by the equilibrium probability distribution of the unperturbed system. We argue that similar amplifications can be observed in many physical systems where turbulent fluctuations are needed to maintain large scale equilibria.

Roberto Benzi; Jean-Francois Pinton

2011-04-22

404

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

405

Magnetic Resonance Imaging System Based on Earth's Magnetic Field  

E-print Network

magnetic field can be partly compensated by the receiving coil design and shielding of electromagnetic pick magnetic fields. Common sources of static magnetic fields are super conducting coils, electromagnets, and permanent magnets. The induced magnetization, and thus the signal, is proportional to the magnitude

StepiÂ?nik, Janez

406

Permanent magnet electron cyclotron resonance plasma source with remote window  

Microsoft Academic Search

An electron cyclotron resonance (ECR) plasma has been used in conjunction with a solid metal sputter target for Cu deposition over 200 mm diameters. The goal is to develop a deposition system and process suitable for filling submicron, high-aspect ratio ULSI features. The system uses a permanent magnet for creation of the magnetic field necessary for ECR, and is significantly

Lee A. Berry; S. M. Gorbatkin

1995-01-01

407

High-Resolution Nuclear Magnetic Resonance of Solids.  

ERIC Educational Resources Information Center

Examines recent developments in techniques for obtaining high-resolution nuclear magnetic resonance (NMR) spectra on solid samples, discussing the kinds of applications for which these techniques are well suited. Also discusses the characteristics of NMR of solids and generating magnetization for NMR in solids. (JN)

Maciel, Gary E.

1984-01-01

408

Magnetic Resonance Imaging in Experimental Models of Brain Disorders  

Microsoft Academic Search

This review gives an overview of the application of magnetic resonance imaging (MRI) in experimental models of brain disorders. MRI is a noninvasive and versatile imaging modality that allows longitudinal and three-dimensional assessment of tissue morphology, metabolism, physiology, and function. MRI can be sensitized to proton density, T1, T2, susceptibility contrast, magnetization transfer, diffusion, perfusion, and flow. The combination of

Rick M. Dijkhuizen; Klaas Nicolay

2003-01-01

409

Disclosure of Unknown Harms in Magnetic Resonance Imaging Research  

Microsoft Academic Search

Unknown harms are by their nature difficult to communicate. While magnetic resonance imaging (MRI) has known risks (e.g., metal projectiles, dislodgement of medical implants), this imaging modality also has potential unknown long-term negative health effects associated with its static magnetic fields. We carried out a research ethics board (REB) file review of previously approved MRI research studies and found that

Jennifer Marshall

2010-01-01

410

Artificial magnetic metamaterial design by using spiral resonators  

Microsoft Academic Search

A metallic planar particle, that will be called spiral resonator (SR), is introduced as a useful artificial atom for artificial magnetic media design and fabrication. A simple theoretical model which provides the most relevant properties and parameters of the SR is presented. The model is validated by both electromagnetic simulation and experiments. The applications of SR's include artificial negative magnetic

Juan D. Baena; Ricardo Marqués; Francisco Medina; Jesús Martel

2004-01-01

411

NMR-0Fessler, Univ. of Michigan Nuclear Magnetic Resonance Imaging  

E-print Network

NMR-0Fessler, Univ. of Michigan Nuclear Magnetic Resonance Imaging Jeffrey A. Fessler EECS Department The University of Michigan NSS-MIC: Fundamentals of Medical Imaging Oct. 20, 2003 #12;NMR-1Fessler, Univ. of Michigan Outline · Background · Basic physics · 4 magnetic fields · Bloch equation

Fessler, Jeffrey A.

412

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

413

Magnetic Resonance Imaging 1 A new global optimization algorithm and its application to a  

E-print Network

Magnetic Resonance Imaging 1 A new global optimization algorithm and its application to a Magnetic-cost, low-field multipolar magnet for Magnetic Resonance Imaging with a high field uniformity with probability one. Key Words: Magnetic Resonance Imaging, global optimization, simulated annealing, derivative

Neumaier, Arnold

414

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

415

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

416

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

417

Visualization of Rabi oscillations in a magnetic resonance  

E-print Network

A visualization scheme for dynamics of a qudit polarization vector in a time-dependent magnetic field is presented by solving equations for a density matrix in Hermitian basis. This is realized by means of mapping solution for the polarization vector on the three-dimensional spherical curve (vector hodograph). The obtained results obviously display the interference of precessional and nutational effects on the polarization vector in a magnetic resonance. The study can find the practical applications in a magnetic resonance and 3D visualization of computational data.

E. A. Ivanchenko

2013-11-11

418

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

419

Detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor  

E-print Network

We report detection of nuclear magnetic resonance (NMR) using an anisotropic magnetoresistive (AMR) sensor. A ``remote-detection'' arrangement was used, in which protons in flowing water were pre-polarized in the field of a superconducting NMR magnet, adiabatically inverted, and subsequently detected with an AMR sensor situated downstream from the magnet and the adiabatic inverter. AMR sensing is well suited for NMR detection in microfluidic ``lab-on-a-chip'' applications.

Verpillat, F; Budker, D; Xu, S; Michalak, D; Hilty, C; Antonijevic, S; Pines, A; Bouchard, L -S

2007-01-01

420

Cardiovascular magnetic resonance with an MR compatible pacemaker  

PubMed Central

Magnetic resonance imaging (MRI) within FDA guidelines for the MRI-conditional pacemaker precludes placing the heart at the center of the magnet’s bore. This in effect appears to preclude cardiovascular MR. In this manuscript, we describe a protocol for cardiovascular MR of patients with a Revo pacemaker system while operating within FDA guidelines, and the first US case of cardiovascular MR in a patient with a Revo MRI-conditional pacing system despite position constraints. PMID:23409835

2013-01-01

421

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

422

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)

2009-10-27

423

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

424

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 impaired 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)

2009-11-10

425

Exploring effects of magnetic field on the Hadron Resonance Gas  

E-print Network

We present a study of the effects of magnetic fields on various physical quantities in hadron resonance gas model. We find significant non-trivial dependence of particle ratios on the magnetic field. Depending on the charge and spin, some of the particle ratios are even getting inverted due to the magnetic field. There is also significant changes in the fluctuations of net baryon number, electric charge and strangeness. This is also reflected in various fluctuation ratios along the freezeout curve.

Bhattacharyya, Abhijit; Ray, Rajarshi; Samanta, Subhasis

2015-01-01

426

Computed tomography and magnetic resonance imaging of the coronary sinus: anatomic variants and congenital anomalies.  

PubMed

The coronary sinus (CS) is an important vascular structure that allows for access into the coronary veins in multiple interventional cardiology procedures, including catheter ablation of arrhythmias, pacemaker implantation and retrograde cardioplegia. The success of these procedures is facilitated by the knowledge of the CS anatomy, in particular the recognition of its variants and anomalies. This pictorial essay reviews the spectrum of CS anomalies, with particular attention to the distinction between clinically benign variants and life-threatening defects. Emphasis will be placed on the important role of cardiac CT and cardiovascular magnetic resonance in providing detailed anatomic and functional information of the CS and its relationship to surrounding cardiac structures. Teaching Points • Cardiac CT and cardiovascular magnetic resonance offer 3D high-resolution mapping of the coronary sinus in pre-surgical planning.• Congenital coronary sinus enlargement occurs in the presence or absence of a left-to-right shunt.• Lack of recognition of coronary sinus anomalies can lead to adverse outcomes in cardiac procedures.• In coronary sinus ostial atresia, coronary venous drainage to the atria occurs via Thebesian or septal veins.• Coronary sinus diverticulum is a congenital outpouching of the coronary sinus and may predispose to cardiac arrhythmias. PMID:25048808

Chen, Yingming Amy; Nguyen, Elsie T; Dennie, Carole; Wald, Rachel M; Crean, Andrew M; Yoo, Shi-Joon; Jimenez-Juan, Laura

2014-10-01

427

Nuclear magnetic resonance spectroscopy with single spin sensitivity  

NASA Astrophysics Data System (ADS)

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.

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.

2014-08-01

428

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

429

Spatially coherent surface resonance states derived from magnetic resonances  

E-print Network

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; Cao, Yang; Wu, Chao; Ren, Jinzhi; Hang, Zhihong; Chen, Hong; Zhang, Daozhong; Chan, C T

2010-01-01

430

Brain Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy Findings of Children with Kernicterus  

PubMed Central

Summary Background The term kernicterus, or bilirubin encephalopathy, is used to describe pathological bilirubin staining of the basal ganglia, brain stem, and cerebellum, and is associated with hyperbilirubinemia. Kernicterus generally occurs in untreated hyperbilirubinemia or cases where treatment is delayed. Magnetic resonance imaging (MRI)-based studies have shown characteristic findings in kernicterus. The objective of our study was to describe the role of 1H magnetic resonance spectroscopy (MRS) in demonstrating these metabolic changes and to review conventional MRI findings of kernicterus. Material/Methods Forty-eight pediatric cases with kernicterus were included in this study. MRI and MRS examinations were performed on variable dates (10–29 days after birth). NAA, Cr, Cho, NAA/Cr, NAA/Cho, and Cho/Cr values were evaluated visually and by computer analysis. Results There was no statistically significant difference between the NAA and Cho levels in the acute kernicterus patients and the control group (healthy patients), whereas both were significantly elevated in the chronic kernicterus patients. Both the mean NAA/Cr and Cho/Cr ratio values were significantly higher in the acute and chronic cases compared to the control group. The NAA/Cho ratio value was statistically lower in the acute cases than in the control group while it was similar in the chronic cases. Conclusions Conventional MR imaging and 1H-MRS are important complementary tools in the diagnostics of neonatal bilirubin encephalopathy. This study provided important information for applying these MR modalities in the evaluation of neonates with bilirubin encephalopathy. PMID:25745520

Sar?, Sahabettin; Yavuz, Alpaslan; Batur, Aabdussamet; Bora, Ayd?n; Caksen, Huseyin

2015-01-01

431

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

432

Raspberry-like Metamolecules Exhibiting Strong Magnetic Resonances.  

PubMed

We report a synthetic approach to produce raspberry-like plasmonic nanostructures with unusually strong magnetic resonances, termed raspberry-like metamolecules (raspberry-MMs). The synthesis based on the surfactant-assisted templated seed-growth method allows for the simultaneous one-step synthesis and assembly of well-insulated gold nanoparticles. The aromatic surfactant used for the syntheses forms a thin protective layer around the nanoparticles, preventing them from touching each other and making it possible to pack discrete nanoparticles at close distances in a single cluster. The resulting isotropic gold nanoparticle clusters (i.e., raspberry-MMs) exhibit unusually broad extinction spectra in the visible and near-IR region. Finite-difference time-domain (FDTD) modeling showed that the raspberry-MMs support strong magnetic resonances that contribute significantly to the broadband spectra. The strong magnetic scattering was also verified by far-field scattering measurements, which show that in the near-IR region the magnetic dipole resonance can be even stronger than the electric dipole resonance in these raspberry-MMs. Structural parameters such as the size and the number of gold nanoparticles composing raspberry-MMs can be readily tuned in our synthetic method. A series of syntheses with varying structure parameters, along with FDTD modeling and mode analyses of corresponding model structures, showed that the close packing of a large number of metal nanoparticles in raspberry-MMs is responsible for the unusually strong magnetic resonances observed here. PMID:25621502

Qian, Zhaoxia; Hastings, Simon P; Li, Chen; Edward, Brian; McGinn, Christine K; Engheta, Nader; Fakhraai, Zahra; Park, So-Jung

2015-02-24

433

Optical pumping magnetic resonance in high magnetic fields: Characterization of nuclear relaxation during pumping  

E-print Network

Optical pumping magnetic resonance in high magnetic fields: Characterization of nuclear relaxation during pumping Matthew P. Augustine and Kurt W. Zilm Department of Chemistry, Yale University, New Haven exchange with optically pumped Rb vapor is investigated in high magnetic field. Operation in a high field

Augustine, Mathew P.

434

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- tection of nuclear magnetic, electron-spin and ferromagnetic resonance (FMR) highlights its significant

Hammel, P. Chris

435

Resonance Free Regions in Magnetic Scattering by Two Solenoidal Fields at Large Separation  

E-print Network

Resonance Free Regions in Magnetic Scattering by Two Solenoidal Fields at Large Separation Ivana the problem of quantum resonances in magnetic scattering by two solenoidal fields at large separation in two : Resonances for scattering by solenoidal fields Keywords : Resonances; magnetic scattering; solenoidal fields

Alexandrova, Ivana

436

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

437

Peripheral nerve stimulation by gradient switching fields in magnetic resonance imaging.  

PubMed

A heterogeneous model of the human body and the scalar potential finite difference method are used to compute electric fields induced in tissue by magnetic field exposures. Two types of coils are considered that simulate exposure to gradient switching fields during magnetic resonance imaging (MRI). These coils producing coronal (y axis) and axial (z axis) magnetic fields have previously been used in experiments with humans. The computed fields can, therefore, be directly compared to human response data. The computed electric fields in subcutaneous fat and skin corresponding to peripheral nerve stimulation (PNS) thresholds in humans in simulated MRI experiments range from 3.8 to 5.8 V/m for the fields exceeded in 0.5% of tissue volume (skin and fat of the torso). The threshold depends on coil type and position along the body, and on the anatomy and resolution of the human body model. The computed values are in agreement with previously established thresholds for neural stimulation. PMID:15536892

So, Poman P M; Stuchly, Maria A; Nyenhuis, John A

2004-11-01

438

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

439

Magnetic resonance imaging in lateral sinus hypoplasia and thrombosis.  

PubMed

Lateral sinus thrombosis may be difficult to differentiate angiographically from lateral sinus hypoplasia, which mainly affects its proximal transverse portion. Using magnetic resonance imaging, we evaluated six patients who demonstrated poor filling or lack of filling of one or both lateral sinuses at angiography. In each patient, magnetic resonance imaging unambiguously demonstrated either lateral sinus thrombosis or lateral sinus hypoplasia. The latter was characterized by a frank asymmetry in size (surface of section) of the transverse portion of the lateral sinuses on parasagittal images without any abnormal signal in the course of the sinus. Lateral sinus thrombosis was indicated by increased intraluminal signal on all planes and with all pulse sequences. By virtue of its freedom from bone-related artifact, its multiplanar imaging capability, and its sensitivity to both blood flow and thrombus formation, magnetic resonance imaging is an excellent tool for the evaluation of lateral sinus thrombosis or hypoplasia. PMID:2396274

Mas, J L; Meder, J F; Meary, E; Bousser, M G

1990-09-01

440

[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

441

Renal Relevant Radiology: Renal Functional Magnetic Resonance Imaging  

PubMed Central

Summary Because of its noninvasive nature and provision of quantitative measures of a wide variety of physiologic parameters, functional magnetic resonance imaging (MRI) shows great potential for research and clinical applications. Over the past decade, application of functional MRI extended beyond detection of cerebral activity, and techniques for abdominal functional MRI evolved. Assessment of renal perfusion, glomerular filtration, interstitial diffusion, and parenchymal oxygenation turned this modality into an essential research and potentially diagnostic tool. Variations in many renal physiologic markers can be detected using functional MRI before morphologic changes become evident in anatomic magnetic resonance images. Moreover, the framework of functional MRI opened a window of opportunity to develop novel pathophysiologic markers. This article reviews applications of some well validated functional MRI techniques, including perfusion, diffusion-weighted imaging, and blood oxygen level–dependent MRI, as well as some emerging new techniques such as magnetic resonance elastography, which might evolve into clinically useful tools. PMID:24370767

Ebrahimi, Behzad; Textor, Stephen C.

2014-01-01

442

Spin torque ferromagnetic resonance with magnetic field modulation  

NASA Astrophysics Data System (ADS)

We demonstrate a technique of broadband spin torque ferromagnetic resonance (ST-FMR) with magnetic field modulation for measurements of spin wave properties in magnetic nanostructures. This technique gives great improvement in sensitivity over the conventional ST-FMR measurements, and application of this technique to nanoscale magnetic tunnel junctions (MTJs) reveals a rich spectrum of standing spin wave eigenmodes. Comparison of the ST-FMR measurements with micromagnetic simulations of the spin wave spectrum allows us to explain the character of low-frequency magnetic excitations in nanoscale MTJs.

Gonçalves, A. M.; Barsukov, I.; Chen, Y.-J.; Yang, L.; Katine, J. A.; Krivorotov, I. N.

2013-10-01

443

Solid State Nuclear Magnetic Resonance 29 (2006) 105117 Electron-nuclear cross polarization  

E-print Network

Solid State Nuclear Magnetic Resonance 29 (2006) 105­117 Electron-nuclear cross polarization V. Weis1 , R.G. Griffin� MIT/Harvard Center for Magnetic Resonance, Francis Bitter Magnet Laboratory magnetic resonance (SSNMR), it differs in significant respects. In particular, eNCP requires an alternative

Griffin, Robert G.

444

Current and future applications of in vitro magnetic resonance spectroscopy in hepatobiliary disease  

Microsoft Academic Search

Nuclear magnetic resonance spectroscopy allows the study of cellular biochemistry and metabolism, both in the whole body in vivo and at higher magnetic fi eld strengths in vitro . Since the technique is non-invasive and non-selective, magnetic resonance spectroscopy methodologies have been widely applied in biochemistry and medicine. In vitro magnetic resonance spectroscopy studies of cells, body fl uids and

I Jane Cox; Amar Sharif; Jeremy FL Cobbold; Howard C Thomas; Simon D Taylor-Robinson

445

Optimal Classification of Long Echo Time In Vivo Magnetic Resonance Spectra in the  

E-print Network

Optimal Classification of Long Echo Time In Vivo Magnetic Resonance Spectra in the Detection magnetic resonance spectra, and assess the benefits and limitations of automated methods as diagnostic aids, Benchmark, Magnetic Resonance Spectroscopy, Human Brain Tumor 1 #12;1 Introduction In vivo nuclear magnetic

Hamprecht, Fred A.

446

Pocket atlas of head and neck MRI anatomy  

SciTech Connect

This pocket atlas depicts the anatomy of the head and neck as seen in magnetic resonance (MR) images. The collection of 140 high-resolution images covers all major areas - neck, larynx, oropharynx, tongue, nasopharynx, skull base, sinuses, and temporal bone - displayed in sagittal, axial, and coronal MR image planes. The images show maximum fat/muscle contrast for better visualization of fascial planes. In certain areas of the anatomy, such as the neck and temporal bone, surface coils were used to achieve significant advantages in image quality over standard head or body coils.

Lufkin, R.B.; Hanafee, W.N.

1989-01-01

447

Magnetic Resonance–Visible Meshes for Laparoscopic Ventral Hernia Repair  

PubMed Central

Background and Objectives: We aimed to evaluate the first human use of magnetic resonance–visible implants for intraperitoneal onlay repair of incisional hernias regarding magnetic resonance presentability. Methods: Ten patients were surgically treated with intraperitoneally positioned superparamagnetic flat meshes. A magnetic resonance investigation with a qualified protocol was performed on postoperative day 1 and at 3 months postoperatively to assess mesh appearance and demarcation. The total magnetic resonance–visible mesh surface area of each implant was calculated and compared with the original physical mesh size to evaluate potential reduction of the functional mesh surfaces. Results: We were able to show a precise mesh demarcation, as well as accurate assessment of the surrounding tissue, in all 10 cases. We documented a significant decrease in the magnetic resonance–visualized total mesh surface area after release of the pneumoperitoneum compared with the original mesh size (mean, 190 cm2 vs 225 cm2; mean reduction of mesh area, 35 cm2; P < .001). At 3 months postoperatively, a further reduction of the surface area due to significant mesh shrinkage could be observed (mean, 182 cm2 vs 190 cm2; mean reduction of mesh area, 8 cm2; P < .001). Conclusion: The new method of combining magnetic resonance imaging and meshes that provide enhanced signal capacity through direct integration of iron particles into the polyvinylidene fluoride base material allows for detailed mesh depiction and quantification of structural changes. In addition to a significant early postoperative decrease in effective mesh surface area, a further considerable reduction in size occurred within 3 months after implantation.

Pallwein-Prettner, Leo; Koch, Oliver Owen; Luketina, Ruzica Rosalia; Lechner, Michael; Emmanuel, Klaus

2015-01-01

448

Travelling wave magnetic resonance imaging at 3 T  

NASA Astrophysics Data System (ADS)

Waveguides have been successfully used to generate magnetic resonance images at 7 T with whole-body systems. The bore diameter limits the magnetic resonance signal transmitted because its specific cut-off frequency is greater than the majority of resonant frequencies in magnetic resonance imaging and spectroscopy. This restriction can be overcome by using a parallel-plate waveguide whose cut-off frequency is zero for the transverse electromagnetic modes and it can propagate any frequency. To study the potential benefits of travelling-wave excitation for whole-body imaging at 3 T, we compare numerical simulations of the principal mode propagation for a parallel-plate waveguide filled with a cylindrical phantom and two surface coils for all simulations at 1.5 T, 3 T, 4.7, 7 T, and 9.4 T. The principal mode shows very little variation of the field magnitude along the propagation direction at 3 T when compared to other higher resonant frequencies. Unlike the standard method for travelling-wave magnetic resonance imaging, a parallel-plate waveguide prototype was built and used together with a whole-body birdcage coil for signal transmission and a pair of circular coils for reception. Experimental B1 mapping was computed to investigate the feasibility of this approach and, the point spread function method was used to measure the imager performance. Human leg images were acquired to experimentally validate this approach. The numerical magnetic field and specific absorption rate of a simulated leg were computed and results are within the safety limits. The B1 mapping and point spread function results showed that it is possible to conduct travelling-wave imaging experiments with good imager performance. Human leg images were also obtained with the whole-body birdcage coil for comparison purposes. The simulated and in vivo travelling-wave results of the human leg correspond very well for the signal received. A similar image signal-to-noise ratio was observed for the travelling-wave approach and the conventional one. We have demonstrated the feasibility of travelling-wave magnetic resonance imaging at 3 T and whole-body magnetic resonance systems, using a parallel-plate waveguide with standard pulse sequences and only one coil array. This extends the use of the waveguide approach to a wider range of resonant frequencies.

Vazquez, F.; Martin, R.; Marrufo, O.; Rodriguez, A. O.

2013-08-01

449

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

PubMed

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

450

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

451

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

452

Magnetic resonance imaging in entomology: a critical review  

PubMed Central

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, metabolism, biomagnetism and morphology, and the advantages and disadvantages relative to other imaging techniques are discussed. In addition, we illustrate the images that can be obtained using MRM. We conclude that although MRM has significant potential, further improvements to the technique are still desirable if it is to become a mainstream imaging technology in entomology. Abbreviation: CSI chemical shift imaging. The dependence of the resonance frequency of a nucleus on the chemical binding of the atom or molecule in which it is contained. (N)MRI (nuclear) magnetic resonance imaging MRM magnetic resonance microscopy Voxel A contraction for volume element, which is the basic unit of MR reconstruction; represented as a pixel in the display of the MR image. PMID:15841222

Hart, A.G.; Bowtell, R.W.; Köckenberger, W.; Wenseleers, T.; Ratnieks, F.L.W.

2003-01-01

453

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

454

Magnetic resonance imaging as a tool for extravehicular activity analysis  

NASA Technical Reports Server (NTRS)

The purpose of this research is to examine the value of magnetic resonance imaging (MRI) as a means of conducting kinematic studies of the hand for the purpose of EVA capability enhancement. After imaging the subject hand using a magnetic resonance scanner, the resulting 2D slices were reconstructed into a 3D model of the proximal phalanx of the left hand. Using the coordinates of several landmark positions, one is then able to decompose the motion of the rigid body. MRI offers highly accurate measurements due to its tomographic nature without the problems associated with other imaging modalities for in vivo studies.

Dickenson, R.; Lorenz, C.; Peterson, S.; Strauss, A.; Main, J.

1992-01-01

455

Development of magnetic resonance technology for noninvasive boron quantification  

SciTech Connect

Boron magnetic resonance imaging (MRI) and spectroscopy (MRS) were developed in support of the noninvasive boron quantification task of the Idaho National Engineering Laboratory (INEL) Power Burst Facility/Boron Neutron Capture Therapy (PBF/BNCT) program. The hardware and software described in this report are modifications specific to a GE Signa{trademark} MRI system, release 3.X and are necessary for boron magnetic resonance operation. The technology developed in this task has been applied to obtaining animal pharmacokinetic data of boron compounds (drug time response) and the in-vivo localization of boron in animal tissue noninvasively. 9 refs., 21 figs.

Bradshaw, K.M.

1990-11-01

456

High-resolution nuclear magnetic resonance in paramagnetic complexes  

NASA Astrophysics Data System (ADS)

The features of the phenomenon of nuclear magnetic resonance in paramagnetic systems are considered. Specific character of detection of high-resoluton NMR spectra modified by hyperfine coupling is analyzed. Examples of the use of specific features of nuclear magnetic resonance in paramagnetic complexes in studies of the structure and dynamics of multielectron systems are given. The need for further experimental investigations of the nature of paramagnetic shifts (especially, contact ones) of NMR signals not only of 1H and 13C, but also of other nuclei is emphasized.

Voronov, Vladimir K.; Ushakov, Igor A.

2010-12-01

457

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

458

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

459

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

460

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

461

Magnetic Resonance (MR)-Guided Breast Biopsy  

MedlinePLUS

... the magnet, radio waves redirect alignment of hydrogen atoms that naturally exist within the body without causing ... chemical changes in the tissues. As the hydrogen atoms return to their usual alignment, they emit energy ...

462

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

463

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

464

Developing hyperpolarized krypton-83 for nuclear magnetic resonance spectroscopy and magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

This dissertation discusses the production of highly nonequilibrium nuclear spin polarization, referred to as hyperpolarization or hp, in the nuclear spin I = 9/2 noble gas isotope krypton-83 using spin exchange optical pumping (SEOP). This nonequilibrium polarization yields nuclear magnetic resonance (NMR) signals that are enhanced three or more orders of magnitude above those of thermally polarized krypton and enables experiments that would otherwise be impossible. Krypton-83 possesses a nuclear electric quadrupole moment that dominates the longitudinal (T1) relaxation due to coupling of the quadrupole moment to fluctuating electric field gradients generated by distortions to the spherical symmetry of the electronic environment. Relaxation slows polarization buildup and limits the maximum signal intensity but makes krypton-83 a sensitive probe of its environment. The gas-phase krypton-83 longitudinal relaxation rate increases linearly with total gas density due to binary collisions. Density independent relaxation, caused by the formation of krypton-krypton van der Waals molecules and surface adsorption, also contributes to the observed rate. Buffer gases suppress van der Waals molecule mediated relaxation by breaking apart the weakly bound krypton dimers. Surface relaxation is gas composition independent and therefore more difficult to suppress. However, this relaxation mechanism makes hp krypton-83 sensitive to important surface properties including surface-to-volume ratio, surface chemistry, and surface temperature. The presence of surfaces with high krypton adsorption affinities (i.e. hydrophobic surfaces) accelerates the relaxation times and can produce T1 contrast in hp krypton-83 magnetic resonance imaging (MRI). Tobacco smoke deposited on surfaces generates strong T1 contrast allowing the observation of smoke deposition with spatial resolution. Conversely, water adsorption on surfaces significantly lengths the T1 times due competitive surface adsorption. Finally, this work demonstrates that hp krypton-83 MRI of intact, excised lungs is feasible. No attempts have been made to observe pathology specific contrast, but this work represents the first steps in developing hp krypton into a useful biomedical tool. Although the signal must be improved for biomedical applications, additional enhancements of up to 180 times greater than the currently obtained signal are possible through improved SEOP, and another order of magnitude increase can be obtained through isotopic enrichment.

Cleveland, Zackary I.

465

Impurity effects in tungsten phosphate glasses. I. Magnetic resonance properties  

Microsoft Academic Search

The magnetic effects of small quantities of V2O5, MoO3 and CuO acting as impurities in a 67 mol% WO3:33 mol% P2O5 semiconducting glass have been investigated. The four paramagnetic species that were produced have been attributed to W5+, V4+, Mo5+ and Cu2+ and the magnetic resonance spectrum of each has been characterized at low impurity concentrations. At high impurity concentrations

G. F. Lynch; M. Sayer

1973-01-01

466

Magnetic resonance imaging and cochlear implants: Compatibility and safety aspects  

Microsoft Academic Search

With cochlear implants, magnetic resonance imaging (MRI) has until recently been contraindicated due to excessive magnetic and electromagnetic interference. The aim of this study was to determine the MRI compatibility of the Med-El Combi 40\\/401 cochlear implant, within a wide range of clinical MRI applications. In vitro experiments on a 1.5 T MR scanner were performed. Torque, force, demag- netization,

Christian Teissl; Christian Kremser; Erwin S. Hochmair; Ingeborg J. Hochmair-Desoyer

1999-01-01

467

Magnetic Resonance Image Tissue Classification Using a Partial Volume Model  

Microsoft Academic Search

We describe a sequence of low-level operations to isolate and classify brain tissue within T1-weighted magnetic resonance images (MRI). Our method first removes nonbrain tissue using a combination of anisotropic diffusion filtering, edge detection, and mathematical morphology. We compensate for image nonuniformities due to magnetic field inhomogeneities by fitting a tricubic B-spline gain field to local estimates of the image

David W. Shattuck; Stephanie R. Sandor-Leahy; Kirt A. Schaper; David A. Rottenberg; Richard M. Leahy

2001-01-01

468

Magnetic resonance cardiac tagging: visualization of LV function parameters  

Microsoft Academic Search

Magnetic Resonance Imaging (MRI) tissue tagging allows the non-invasive placement of magnetic markers into the myocardium. These tags appear as black lines and remain visible on the myocardium during the cardiac cycle. A semi-automatic segmentation tool is used to delineate the tags. A tagging analysis program calculates from these time-varying tag coordinates several LV functional parameters: e.g. radius of curvature,

P. Plets; F. Rademakers; J. Van Cleynenbreugel; J. Bogaert; P. Suetens; G. Marchal

1996-01-01

469

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.

470

Magnetic resonance imaging without field cycling at less than earth's magnetic field  

NASA Astrophysics Data System (ADS)

A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a ? / 2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 ?T static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

2015-03-01

471

A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., ?-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies.

Eguchi, Haruki; Umemura, Masanari; Kurotani, Reiko; Fukumura, Hidenobu; Sato, Itaru; Kim, Jeong-Hwan; Hoshino, Yujiro; Lee, Jin; Amemiya, Naoyuki; Sato, Motohiko; Hirata, Kunio; Singh, David J.; Masuda, Takatsugu; Yamamoto, Masahiro; Urano, Tsutomu; Yoshida, Keiichiro; Tanigaki, Katsumi; Yamamoto, Masaki; Sato, Mamoru; Inoue, Seiichi; Aoki, Ichio; Ishikawa, Yoshihiro

2015-03-01

472

A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging.  

PubMed

Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., ?-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies. PMID:25779357

Eguchi, Haruki; Umemura, Masanari; Kurotani, Reiko; Fukumura, Hidenobu; Sato, Itaru; Kim, Jeong-Hwan; Hoshino, Yujiro; Lee, Jin; Amemiya, Naoyuki; Sato, Motohiko; Hirata, Kunio; Singh, David J; Masuda, Takatsugu; Yamamoto, Masahiro; Urano, Tsutomu; Yoshida, Keiichiro; Tanigaki, Katsumi; Yamamoto, Masaki; Sato, Mamoru; Inoue, Seiichi; Aoki, Ichio; Ishikawa, Yoshihiro

2015-01-01

473

A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging  

PubMed Central

Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., ?-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies. PMID:25779357

Eguchi, Haruki; Umemura, Masanari; Kurotani, Reiko; Fukumura, Hidenobu; Sato, Itaru; Kim, Jeong-Hwan; Hoshino, Yujiro; Lee, Jin; Amemiya, Naoyuki; Sato, Motohiko; Hirata, Kunio; Singh, David J.; Masuda, Takatsugu; Yamamoto, Masahiro; Urano, Tsutomu; Yoshida, Keiichiro; Tanigaki, Katsumi; Yamamoto, Masaki; Sato, Mamoru; Inoue, Seiichi; Aoki, Ichio; Ishikawa, Yoshihiro

2015-01-01

474

Resonant Magnetization Tunneling in Single-Molecule Magnets  

Microsoft Academic Search

Data are presented for three different types of single-molecule magnets (SMM's): [Mn12O12(O2CR)16(H2O)4],[Cation][Mn12O12(O2CR)16(H2O)4], and the distorted cubane [Mn Mn 3O3X(O2CR)3L3] complexes. All three types of complexes exhibit slow magnetization relaxation at temperatures below 5 K. Each molecule can change the direction of its magnetization only slowly at these low temperatures. Manisfetations of this are seen in magnetization hysteresis loops and in

Sheila M. J. Aubin; Daniel Ruiz; Evan Rumberger; Ziming Sun; Belen Albela; Michael W. Wemple; Neil R. Dilley; Joan Ribas; M. Brian Maple; George Christou; David N. Hendrickson

1999-01-01

475

Magnetic resonance imaging of the inner ear by using a hybrid radiofrequency coil at 7 T  

NASA Astrophysics Data System (ADS)

Visualization of the membranous structures of the inner ear has been limited to the detection of the normal fluid signal intensity within the bony labyrinth by using magnetic resonance imaging (MRI) equipped with a 1.5 Tesla (T) magnet. High-field (HF) MRI has been available for more than a decade, and numerous studies have documented its significant advantages over conventional MRI with regards to its use in basic scientific research and routine clinical assessments. No previous studies of the inner ear by using HF MRI have been reported, in part because high-quality resolution of mastoid pneumatization is challenging due to artifacts generated in the HF environment and insufficient performance of radiofrequency (RF) coils. Therefore, a hybrid RF coil with integrated circuitry was developed at 7 T and was targeted for anatomical imaging to achieve a high resolution image of the structure of the human inner ear, excluding the bony portion. The inner-ear's structure is composed of soft tissues containing hydrogen ions and includes the membranous labyrinth, endolymphatic space, perilymphatic space, and cochlear-vestibular nerves. Visualization of the inner-ear's anatomy was performed in-vivo with a custom-designed hybrid RF coil and a specific imaging protocol based on an interpolated breath-held examination sequence. The comparative signal intensity value at 30-mm away from the phantom side was 88% higher for the hybrid RF coil and 24% higher for the 8-channel transmit/receive (Tx/Rx) coil than for the commercial birdcage coil. The optimized MRI protocol employed a hybrid RF coil because it enabled high-resolution imaging of the inner-ear's anatomy and accurate mapping of structures including the cochlea and the semicircular canals. These results indicate that 7 T MRI achieves high spatial resolution visualization of the inner-ear's anatomy. Therefore, MRI imaging using a hybrid RF coil at 7 T could provide a powerful tool for clinical investigations of petrous pathologies of the inner ear.

Kim, Kyoung-Nam; Heo, Phil; Kim, Young-Bo; Han, Gyu-Cheol

2015-01-01

476

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 la