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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 imaging (MRI) anatomy of the ovine lumbar spine.  

PubMed

Although the ovine spine is a useful research model for intervertebral disc pathology and vertebral surgery, there is little peer-reviewed information regarding the MRI anatomy of the ovine spine. To describe the lumbar spine MRI anatomy, 10 lumbar segments of cadaver ewes were imaged by 1.5-Tesla MR. Sagittal and transverse sequences were performed in T1 and T2 weighting (T1W, T2W), and the images were compared to gross anatomic sagittal and transverse sections performed through frozen spines. MRI was able to define most anatomic structures of the ovine spine in a similar way as can be imaged in humans. In both T1W and T2W, the signals of ovine IVDs were similar to those observed in humans. Salient anatomic features were identified: (1) a 2- to 3-mm linear zone of hypersignal was noticed on both extremities of the vertebral body parallel to the vertebral plates in sagittal planes; (2) the tendon of the crura of the diaphragm appeared as a hypointense circular structure between hypaxial muscles and the aorta and caudal vena cava; (3) dorsal and ventral longitudinal ligaments and ligamentum flavum were poorly imaged; (4) no ilio-lumbar ligament was present; (5) the spinal cord ended between S1-S2 level, and the peripheral white matter and central grey matter were easily distinguished on T1W and T2W images. This study provides useful reference images to researchers working with ovine models. PMID:23668479

Nisolle, J F; Wang, X Q; Squélart, M; Hontoir, F; Kirschvink, N; Clegg, P; Vandeweerd, J M

2014-06-01

3

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.

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

2013-01-01

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.

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

Magnetic resonance microneurography of rabbit sciatic nerve on a 1.5-T clinical MR system correlated with gross anatomy.  

PubMed

This study was performed to investigate the feasibility and accuracy of magnetic resonance (MR) microneurography of the rabbit sciatic nerve on a 1.5-T clinical MR system by correlation with the gross anatomy. The 3D T2-weighted imaging (3D-T2WI), 3D T2-weighted imaging plus spectral presaturation with inversion recovery (SPIR), and T1-weighted imaging (T1WI) of the sciatic nerve in ten rabbits were performed on a 1.5-T MR system. The radiological anatomy of the sciatic nerve was observed and correlated with the gross anatomy. The anterior-posterior diameter of the sciatic nerve trunk was measured on 3D T2WI and on gross anatomy. The T1 and T2 relaxation times were also measured with multiecho spin echo and mixed sequence, respectively. The tibial nerve and peroneal nerve in the sciatic nerve trunk in all ten rabbits could be clearly displayed on T2WI and T2WI. The fine branches of the gastrocnemius nerve, posterior femoral cutaneous nerve, and the posterior gluteal nerve could be clearly depicted on T2WI. The T1 and T2 relaxation times of the sciatic nerves were 915 and 40 ms, respectively. The anterior-posterior diameter of sciatic nerve trunk was measured grossly, and on T2WI was 3.17 +/- 0.21 mm and 3.15 +/- 0.19 mm, respectively. There was no statistically significant difference (t = 0.768, P = 0.462). With the 1.5-T clinical MR system, the microneurography of the sciatic nerve could be revisualized, and the finer structure of the sciatic nerve trunk could be clearly and accurately delineated. PMID:17994593

Shen, Jun; Wang, Hua-Qiao; Zhou, Cui-Ping; Liang, Bi-Ling

2008-01-01

7

Changes of brain anatomy in patients with posttraumatic stress disorder: A pilot magnetic resonance imaging study  

Microsoft Academic Search

No abnormalities in magnetic resonance images were recorded in patients with posttraumatic stress disorder other than an increased incidence (50%) of a small cleft in the callosal-septal interface, a cavum of the septum pellucidum. A similar grade of cavum was obtained in 14% of normal volunteers matched for age, socioeconomic background, and military experience. The cavum is believed to have

Michael S. Myslobodsky; Joseph Glicksohn; Jaffa Singer; Max Stern; Jacob Bar-Ziv; Nehemia Friedland; Avi Bleich

1995-01-01

8

Magnetic Resonance Imaging (MRI).  

National Technical Information Service (NTIS)

Magnetic resonance imaging (MRI) is a method of graphically representing the distribution of water and other hydrogen-rich molecules in the human body. Imaging parameters are complex. Although MR images may demonstrate anatomy as do conventional radiograp...

E. Feigenbaum

1985-01-01

9

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.

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

2014-01-01

10

Anatomy of the perineal membrane as seen in magnetic resonance images of nulliparous women  

PubMed Central

Objective Recent cadaver research demonstrates the perineal membrane’s ventral and dorsal portions and close relationship to the levator ani muscle. This study seeks to show these relationships in women by magnetic resonance (MR) images. Methods The subjects were 20 asymptomatic nulliparous women with normal pelvic examinations. MR images were acquired in multiple planes. Anatomical relationships from cadaver studies were examined in these planes. Results In the coronal plane the ventral perineal membrane forms an interconnected complex with the compressor urethrae, vestibular bulb and levator ani. The dorsal part connects the levator ani and vaginal side wall via a distinct band to the ischiopubic ramus. In the sagittal plane the parallel position of perineal membrane and levator ani are seen. Conclusion The perineal membrane’s anatomical features can be seen in women with MR. The close relationship between the perineal membrane and levator ani is evident.

BRANDON, Catherine J.; LEWICKY-GAUPP, Christina; LARSON, Kindra A.; DeLANCEY, John O.L.

2009-01-01

11

Learning Relational Anatomy by Correlating Thin Plastinated Sections and Magnetic Resonance Images: Preparation of Specimens  

Microsoft Academic Search

Plastination is a process whereby the tissue water and part of the tissue fat of anatomical specimens is replaced with a curable polymer. Several variations of this technique are available, depending on both the type of specimen and polymer being used. In this study, the efficiency of BIODUR® PEM 11-prepared cross sections as a teaching aid for radiographic anatomy is

M. Magiros; M. Kekic; G. A. Doran

1997-01-01

12

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

PubMed Central

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

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

2007-01-01

13

Review: magnetic resonance imaging of male/female differences in human adolescent brain anatomy  

PubMed Central

Improvements in neuroimaging technologies, and greater access to their use, have generated a plethora of data regarding male/female differences in the developing brain. Examination of these differences may shed light on the pathophysiology of the many illnesses that differ between the sexes and ultimately lead to more effective interventions. In this review, we attempt to synthesize the anatomic magnetic resonance imaging (MRI) literature of male/female brain differences with emphasis on studies encompassing adolescence – a time of divergence in physical and behavioral characteristics. Across all ages total brain size is consistently reported to be about 10% larger in males. Structures commonly reported to be different between sexes include the caudate nucleus, amygdala, hippocampus, and cerebellum – all noted to have a relatively high density of sex steroid receptors. The direction and magnitude of reported brain differences depends on the methodology of data acquisition and analysis, whether and how the subcomponents are adjusted for the total brain volume difference, and the age of the participants in the studies. Longitudinal studies indicate regional cortical gray matter volumes follow inverted U shaped developmental trajectories with peak size occurring one to three years earlier in females. Cortical gray matter differences are modulated by androgen receptor genotyope and by circulating levels of hormones. White matter volumes increase throughout childhood and adolescence in both sexes but more rapidly in adolescent males resulting in an expanding magnitude of sex differences from childhood to adulthood.

2012-01-01

14

Review: magnetic resonance imaging of male/female differences in human adolescent brain anatomy.  

PubMed

Improvements in neuroimaging technologies, and greater access to their use, have generated a plethora of data regarding male/female differences in the developing brain. Examination of these differences may shed light on the pathophysiology of the many illnesses that differ between the sexes and ultimately lead to more effective interventions. In this review, we attempt to synthesize the anatomic magnetic resonance imaging (MRI) literature of male/female brain differences with emphasis on studies encompassing adolescence - a time of divergence in physical and behavioral characteristics. Across all ages total brain size is consistently reported to be about 10% larger in males. Structures commonly reported to be different between sexes include the caudate nucleus, amygdala, hippocampus, and cerebellum - all noted to have a relatively high density of sex steroid receptors. The direction and magnitude of reported brain differences depends on the methodology of data acquisition and analysis, whether and how the subcomponents are adjusted for the total brain volume difference, and the age of the participants in the studies. Longitudinal studies indicate regional cortical gray matter volumes follow inverted U shaped developmental trajectories with peak size occurring one to three years earlier in females. Cortical gray matter differences are modulated by androgen receptor genotyope and by circulating levels of hormones. White matter volumes increase throughout childhood and adolescence in both sexes but more rapidly in adolescent males resulting in an expanding magnitude of sex differences from childhood to adulthood. PMID:22908911

Giedd, Jay N; Raznahan, Armin; Mills, Kathryn L; Lenroot, Rhoshel K

2012-01-01

15

Perineal body anatomy in living women: 3-D analysis using thin-slice magnetic resonance imaging  

PubMed Central

Objective To describe a framework for visualizing the perineal body's complex anatomy using thin-slice MR imaging. Study Design Two mm-thick MR images were acquired in 11 women with normal pelvic support and no incontinence/prolapse symptoms. Anatomic structures were analyzed in axial, sagittal and coronal slices. 3-D models were generated from these images. Results Three distinct perineal body regions are visible on MRI: (1) a superficial region at the level of the vestibular bulb, (2) a mid region at the proximal end of the superficial transverse perineal muscle, and (3) a deep region at the level of the midurethra and puborectalis muscle. Structures are best visualized on axial scans while cranio-caudal relationships are appreciated on sagittal scans. The 3-D model further clarifies inter-relationships. Conclusion Advances in MR technology allow visualization of perineal body anatomy in living women and development of 3D models which enhance our understanding of its three different regions: superficial, mid and deep.

Larson, Kindra A.; Yousuf, Aisha; Lewicky-Gaupp, Christina; Fenner, Dee E.; DeLancey, John O.L.

2012-01-01

16

Magnetic resonance anatomy of the proximal metacarpal region of the horse described from images acquired from low- and high-field magnets.  

PubMed

While low-field magnetic resonance (MR) images can provide useful information in the investigation of proximal metacarpal region pain, an in-depth knowledge of anatomy and comparison with more detailed high-field images are essential to understand the meaning of different signal intensities within tissues. This anatomic description is based on low-field and high-field MR examination of 30 cadaver metacarpal regions of mature horses with no history of carpal or proximal metacarpal pain. Normal MR anatomy is described and is illustrated by high-field and low-field MR images in transverse, sagittal and dorsal planes. Normal anatomic variations of soft tissue and osseous structures are discussed. Differences between the signal intensity and definition of tissues on high-field and low-field MR images and in different pulse sequences are highlighted. Several structures could be evaluated in both high-field and low-field images that cannot easily be imaged using radiography and ultrasonography, including the abaxial margins of the suspensory ligament, the interosseous ligaments between the metacarpal bones and the carpometacarpal ligaments. Structures that have previously not been described in detail were also identified. PMID:19999342

Nagy, Annamaria; Dyson, Sue

2009-01-01

17

Magnetic resonance anatomy of the carpus of the horse described from images acquired from low-field and high-field magnets.  

PubMed

Cadaver carpi of 30 mature horses with no history of carpal or proximal metacarpal pain were examined using low-field (0.27?T) and high-field (1.5?T) magnetic resonance imaging (MRI). Normal MRI anatomy in transverse, sagittal, and dorsal plane images was determined by comparison with anatomical specimens and standard texts. Subchondral bone and cortical bone thickness measurements were obtained from standardised sites. There was variable subchondral bone thickness in the radius and carpal bones; subchondral bone thickness was consistently larger at dorsal compared with palmar sites in the proximal row of carpal bones. The endosteal surface of the subchondral bone was smooth. The shape of the ulnar carpal bone was variable and one or more small osseous fragments were identified palmar to the bone in 5/30 limbs. There was no evidence to suggest that these were pathological fractures or avulsions of the lateral palmar intercarpal ligament. The amount of muscle tissue in the superficial and deep digital flexor tendons in the proximal aspect of the carpus varied, but none was present at the level of the middle carpal joint and distally. Several structures could be evaluated that cannot be imaged using radiography, ultrasonography, or arthroscopy, including the transverse intercarpal ligaments, the radiocarpal ligament, the short palmar carpal ligaments, and the carpometacarpal ligaments. Anatomical variations not previously described were identified, including the layers of the medial aspect of the carpal fascia. Knowledge of the variation in MRI appearance of the carpus of nonlame horses is helpful for interpretation of MR images of lame horses. PMID:21554475

Nagy, Annamaria; Dyson, Sue

2011-01-01

18

High-resolution, high-throughput magnetic resonance imaging of mouse embryonic anatomy using a fast gradient-echo sequence  

Microsoft Academic Search

Embryonic development in normal and genetically modified mice is commonly analysed by histological sectioning. This procedure is time-consuming, prone to artefact, and results in the loss of three-dimensional (3D) information. Magnetic resonance imaging (MRI) of embryos has the potential of non-invasively acquiring a complete 3D data set. Published methods have used spin-echo techniques with inherently high signal-to-noise ratio (SNR); however,

Jürgen E. Schneider; Simon D. Bamforth; Stuart M. Grieve; Kieran Clarke; Shoumo Bhattacharya; Stefan Neubauer

2003-01-01

19

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.

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

2008-01-01

20

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.

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

21

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

22

Sports Health Magnetic Resonance Imaging Challenge  

PubMed Central

Injuries to the Lisfranc ligament complex are often suspected, particularly in the setting of midfoot pain without radiographic abnormality. Knowledge of the anatomy and magnetic resonance imaging findings of injuries to this region is helpful for the diagnosing and treating physicians.

Howell, Gary A.; Stadnick, Michael E.; Awh, Mark H.

2010-01-01

23

Pediatric magnetic resonance imaging  

SciTech Connect

This book defines the current clinical potential of magnetic resonance imaging and focuses on direct clinical work with pediatric patients. A section dealing with the physics of magnetic resonance imaging provides an introduction to enable clinicians to utilize the machine and interpret the images. Magnetic resonance imaging is presented as an appropriate imaging modality for pediatric patients utilizing no radiation.

Cohen, M.D.

1986-01-01

24

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

Microsoft Academic Search

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

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

2011-01-01

25

Temporal profile of the vascular anatomy evaluated by 9.4-T magnetic resonance angiography and histopathological analysis in mice lacking RNF213: a susceptibility gene for moyamoya disease.  

PubMed

Moyamoya disease (MMD) is a chronic occlusive cerebrovascular disease with unknown etiology. Recent genome-wide and locus-specific association studies identified RNF213 as an important MMD susceptibility gene. However, the exact mechanism by which an abnormality in RNF213 leads to MMD is unknown. To evaluate the role of RNF213 in the etiology of MMD, we generated RNF213-deficient mice (RNF213-/-) by deleting exon 32 of RNF213 by the Cre-lox system, and investigated whether they developed MMD. The temporal profile of cervical/intracranial arteries was evaluated by 9.4-T magnetic resonance angiography (MRA). The anatomy of the circle of Willis was analyzed by a trans-cardiac injection of carbon black dye. The common carotid arteries (CCA) were sectioned and the arterial wall thickness/thinness was evaluated by Elastica-Masson staining before and after CCA ligation, which selectively induced vascular hyperplasia. As a result, RNF213-/- grew normally, and no significant difference was observed in MRA findings, the anatomy of the circle of Willis, or vascular wall thickness/thinness between RNF-/- and wild-type littermates (Wt.) under normal conditions until 64 weeks of age. However, Elastica-Masson staining demonstrated that both the intima and medial layer were significantly thinner after CCA ligation in RNF213-/- than in Wt. after 14 days (P<0.01). In conclusion, mice lacking the RNF213 gene did not spontaneously develop MMD, indicating that a functional loss of RNF213 did not sufficiently induce MMD. Suppression of vascular remodeling in RNF213-/- requires further examination to clarify the role of RNF213. PMID:24440776

Sonobe, Shinya; Fujimura, Miki; Niizuma, Kuniyasu; Nishijima, Yasuo; Ito, Akira; Shimizu, Hiroaki; Kikuchi, Atsuo; Arai-Ichinoi, Natsuko; Kure, Shigeo; Tominaga, Teiji

2014-03-13

26

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

PubMed

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

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

2014-06-01

27

Mapping the anatomy of the immunodominant domain of the human immunodeficiency virus gp41 transmembrane protein: peptide conformation analysis using monoclonal antibodies and proton nuclear magnetic resonance spectroscopy.  

PubMed Central

Thirty-six monoclonal antibodies from mice and three from rats were raised against a peptide corresponding to the immunodominant domain of the transmembrane gp41 protein of human immunodeficiency virus (HIV) type 1 (LGLWGCSGKLIC; amino acid residues 598 to 609). Of these, three monoclonal antibodies from the mice and one from a rat also reacted with the corresponding peptide derived from the HIV type 2 transmembrane gp41 protein (amino acid residues 593 to 603; NSWGCAFRQVC). Immunochemical studies using a variety of synthetic peptides indicated that the cross-reactivity was due to antibody binding to CSGKLIC of HIV type 1 or CAFRQVC of HIV type 2. Single amino acid substitutions for a cysteine at either the amino or the carboxy end of the peptide interrupted antibody binding, indicating that the site recognized was the Cys-XXXXX-Cys loop. Similar results were obtained when the 11-mer HIV type 2 gp41 peptide (amino acids 593 to 603) was inoculated into mice to raise monoclonal antibodies. In this instance, of 30 monoclonal antibodies developed, 4 reacted with both HIV type 1 and HIV type 2 peptides. The conformation of a seven-residue peptide, CSGKLIC, corresponding to residues 603 to 609 of the gp41 immunodominant epitope of HIV-1 was investigated by proton nuclear magnetic resonance spectroscopy. The immunologically active form of CSGKLIC contains an intramolecular disulfide bond and maintains a preference for a folded conformation, apparently including a type I reverse turn about the residues SGKL. No such preference is observed for the reduced form of the peptide, which contains two thiol groups. The presence of the disulfide bond is thus integral to the formation of the structure of the loop in solution. In agreement with this finding, elimination of the possibility of loop formation by substitution of S for C at the amino or carboxy termini of the 7-mer is accompanied by the failure of antibody binding to this peptide.

Oldstone, M B; Tishon, A; Lewicki, H; Dyson, H J; Feher, V A; Assa-Munt, N; Wright, P E

1991-01-01

28

Left Ventricular Trabeculae and Papillary Muscles: Correlation With Clinical and Cardiac Characteristics and Impact on Cardiovascular Magnetic Resonance Measures of Left Ventricular Anatomy and Function  

PubMed Central

Objective We sought to assess the relationship of left ventricular (LV) trabeculae and papillary muscles (TPM) with clinical characteristics in a community-based, free living adult cohort and to determine the effect of TPM on quantitative measures of LV volume, mass and ejection fraction (EF). Background Hypertrabeculation has been associated with adverse cardiovascular events, but the distribution and clinical correlates of the volume and mass of the TPM in a normal left ventricle have not been well characterized. Methods Short-axis cine cardiovascular magnetic resonance (CMR) images, obtained using a steady-state free precession sequence, from 1494 members of the Framingham Offspring cohort were analyzed using software that automatically segments TPM. Absolute TPM volume, TPM as a fraction of end-diastolic volume (TPM/EDV), and TPM mass as a fraction of LV mass (TPMm/LVM) were determined on all Offspring and in a referent group of Offspring free of clinical cardiovascular disease and hypertension. Results In the referent group (aged 61±9 years, with 262 men and 423 women) TPM was 23±3 % of LV EDV in both sexes (p=0.9). TPM/EDV decreased with age (p<0.02) but was not associated with body mass index (BMI). TPMm/LVM was inversely correlated with age (p<0.0001), BMI (p<0.018) and systolic blood pressure (p<0.0001). Among all 1494 participants (699 men) LV volumes decreased 23%, LV mass increased 28% and EF increased by 7.5 EF units (p<0.0001) when TPM were considered myocardial mass rather than part of the LV blood pool. Conclusions Global CMR LV parameters are significantly affected by whether TPM are considered as part of the LV blood pool or as part of LV mass. Our cross-sectional data from a healthy referent group of adults free of clinical cardiovascular disease demonstrate that TPM/EDV decreases with increasing age in both sexes, but is not related to hypertension or obesity.

Chuang, Michael L.; Gona, Philimon; Hautvast, Gilion L.T.F.; Salton, Carol J.; Blease, Susan J.; Yeon, Susan B.; Breeuwer, Marcel; O'Donnell, Christopher J.; Manning, Warren J.

2012-01-01

29

Functional magnetic resonance imaging studies of language  

Microsoft Academic Search

Functional neuroimaging of language builds on almost 150 years of study in neurology, psychology, linguistics, anatomy, and\\u000a physiology. In recent years, there has been an explosion of research using functional imaging technology, especially positron\\u000a emission tomography (PET) and functional magnetic resonance imaging (fMRI), to understand the relationship between brain mechanisms\\u000a and language processing. These methods combine highresolution anatomic images with

Steven L. Small; Martha W. Burton

2002-01-01

30

Magnetic Resonance Facility.  

National Technical Information Service (NTIS)

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 anal...

2012-01-01

31

Magnetic resonance imaging  

SciTech Connect

This book contains the following four major sections: physics and chemistry, relaxation/relaxometry, instrumentation, research areas. The authors discuss instrumentation and technical approaches in magnetic resonance (MR) imaging.

Partain, C.L.; Price, R.R.; Patton, J.A.; Kulkarni, M.V.; James, A.E.

1988-01-01

32

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

33

Magnetic Resonance Imaging (MRI)  

MedlinePLUS

What is an MRI? MRI stands for Magnetic Resonance Imaging. It is an important tool used in many fields of medicine, and is capable of generating a detailed image of any part of the human body. As an analogy, think about a loaf of bread. You can’t see inside the loaf, so how would you go about finding ...

34

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

35

Magnetic resonance imaging of chest wall lesions.  

PubMed Central

Magnetic resonance imaging (MRI) demonstrates surface anatomy, nerves, and soft tissue pathology. Selective placement of the cursor lines in MRI displays specific anatomy. The MR images can then be used as adjunct in teaching surface anatomy to medical students and to other health professionals. Because the normal surface anatomy could be imaged at UCLA's radiology department, it was decided to image soft tissue abnormalities with MR to assist in patient care. Patients imaged were scheduled for special procedures of the chest or staging lymphangiograms. Patients were placed into categories depending on known diagnosis or interesting clinical presentation. The diagnostic categories included Hodgkin's disease, melanoma, carcinomas (eg, lung or breast), lymphedema, sarcomas, dermatological disorders, and neurological disorders. All images were orchestrated by the radiologist. This article discusses both the teaching and clinical impact on patient care. Images Figures 1A-B Figure 2 Figure 3 Figure 4 Figure 5 Figures 6A-B Figure 7 Figure 8 Figures 9A-B Figure 10

Collins, J. D.; Shaver, M.; Batra, P.; Brown, K.; Disher, A. C.

1991-01-01

36

Functional magnetic resonance imaging in medicine and physiology  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a well-established diagnostic tool that provides detailed information about macroscopic structure and anatomy. Recent advances in MRI allow the noninvasive spatial evaluation of various biophysical and biochemical processes in living systems. Specifically, the motion of water can be measured in processes such as vascular flow, capillary flow, diffusion, and exchange. In addition, the concentrations of

C. T. W. Moonen; P. C. M. van Zijl; J. A. Frank; D Le Bihan; E. D. Becker

1990-01-01

37

Magnetic Resonance Imaging of the Retina  

PubMed Central

This paper reviews recent developments in high-resolution magnetic resonance imaging (MRI) and its application to image anatomy, physiology, and function in the retina of animals. It describes technical issues and solutions in performing retinal MRI, anatomical MRI, blood oxygenation level-dependent functional MRI (fMRI), and blood-flow MRI both of normal retinas and of retinal degeneration. MRI offers unique advantages over existing retinal imaging techniques, including the ability to image multiple layers without depth limitation and to provide multiple clinically relevant data in a single setting. Retinal MRI has the potential to complement existing retinal imaging techniques.

Duong, Timothy Q.; Muir, Eric R.

2010-01-01

38

Magnetic Resonance Fingerprinting  

PubMed Central

Summary Magnetic Resonance (MR) is an exceptionally powerful and versatile measurement technique. The basic structure of an MR experiment has remained nearly constant for almost 50 years. Here we introduce a novel paradigm, Magnetic Resonance Fingerprinting (MRF) that permits the non-invasive quantification of multiple important properties of a material or tissue simultaneously through a new approach to data acquisition, post-processing and visualization. MRF provides a new mechanism to quantitatively detect and analyze complex changes that can represent physical alterations of a substance or early indicators of disease. MRF can also be used to specifically identify the presence of a target material or tissue, which will increase the sensitivity, specificity, and speed of an MR study, and potentially lead to new diagnostic testing methodologies. When paired with an appropriate pattern recognition algorithm, MRF inherently suppresses measurement errors and thus can improve accuracy compared to previous approaches.

Ma, Dan; Gulani, Vikas; Seiberlich, Nicole; Liu, Kecheng; Sunshine, Jeffrey L.; Duerk, Jeffrey L.; Griswold, Mark A.

2013-01-01

39

Advances in magnetic resonance imaging: cine MRI and flow velocity mapping  

Microsoft Academic Search

Magnetic resonance imaging is a powerful tool for evaluating the variety of abnormalities that occur in congenital heart disease. Specific morphological queries regarding arterial and venous connections, thoracic and visceral situs, valvar relationships and great vessel anatomy can be answered in great detail with standard spin-echo imaging techniques. The continuing technological development of magnetic resonance imaging, however, has allowed analysis

Scott D. Flamm; Douglas S. Moodie

1997-01-01

40

Nuclear Magnetic Resonance Gyroscope  

NASA Astrophysics Data System (ADS)

The navigation grade micro Nuclear Magnetic Resonance Gyroscope (micro-NMRG) being developed by the Northrop Grumman Corporation is 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

41

Breast magnetic resonance imaging.  

PubMed

Mammography has long been considered the gold standard for screening breast cancer. Although it reduces the risk of breast cancer mortality by enabling early diagnosis, it does not detect all breast cancers. Numerous breast imaging technologies are emerging as effective adjunctive diagnostic tools when mammography results are negative or inconclusive. Contrast-enhanced magnetic resonance (CE-MR) imaging, in particular, has demonstrated a high sensitivity and has proven to be most effective, especially with patients at high risk for developing breast cancer. This article discusses the clinical applications for breast MR imaging, use of CE-MR for breast cancer detection, and other emerging breast imaging technologies. PMID:22267704

Johnson, Marlene M

2012-01-01

42

Nuclear Magnetic Resonance Gyroscope  

NASA Astrophysics Data System (ADS)

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

Larsen, Michael

2011-06-01

43

Abdominal magnetic resonance elastography.  

PubMed

Magnetic resonance elastography (MRE) is a magnetic resonance imaging-based technique for quantitatively assessing the mechanical properties of tissues based on the propagation of shear waves. Multiple studies have described many potential applications of MRE, from characterizing tumors to detecting diffuse disease processes. Studies have shown that MRE can be successfully implemented to assess abdominal organs. The first clinical application of MRE to be well documented is the detection and characterization of hepatic fibrosis, which systematically increases the stiffness of liver tissue. In this diagnostic role, it offers a safer, less expensive, and potentially more accurate alternative to invasive liver biopsy. Emerging results suggest that measurements of liver and spleen stiffness may provide an indirect way to assess portal hypertension. Preliminary studies have demonstrated that it is possible to use MRE to evaluate the mechanical properties of other abdominal structures, such as the pancreas and kidneys. Steady technical progress in developing practical protocols for applying MRE in the abdomen and the pelvis provides opportunities to explore many other potential applications of this emerging technology. PMID:20010062

Yin, Meng; Chen, Jun; Glaser, Kevin J; Talwalkar, Jayant A; Ehman, Richard L

2009-04-01

44

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

45

Magnetic resonance venography and liver transplant complications.  

PubMed

Hepatic vein stenosis is a rare but serious complication following liver transplantation. Multiple modalities can be utilized to image the hepatic vasculature. Magnetic resonance venography (MRV) provides certain advantages over ultrasound, computed tomography angiography and digital subtraction venography. MRV utilizes the same imaging principles of magnetic resonance angiography in order to image the venous system. Blood pool contrast agents, specifically gadofosveset trisodium, allow for steady state imaging up to 1 h following injection, with improved visualisation of vital venous structures by utilising delayed steady state imaging. Additionally, the inherent physics properties of magnetic resonance imaging also provide excellent soft tissue detail and thus help define the extent of complications that often plague the post-liver transplant patient. This case report describes the use of gadofosveset trisodium in a patient with hepatic venous stenosis following liver transplantation. Initial venography failed to outline the stenoses and thus MRV using a blood pool contrast agent was utilised in order to delineate the anatomy and plan a therapeutic endovascular procedure. PMID:24106414

Strovski, Evgeny; Liu, Dave; Scudamore, Charles; Ho, Stephen; Yoshida, Eric; Klass, Darren

2013-09-28

46

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

47

Classification of magnetic resonance images  

Microsoft Academic Search

The aim of the paper is to compare classification error of the classifiers applied to magnetic resonance images for each descriptor used for feature extraction. We compared several Support Vector Machine (SVM) techniques, neural networks and k nearest neighbor classifier for classification of Magnetic Resonance Images (MRIs). Different descriptors are applied to provide feature extraction from the images. The dataset

Katarina Trojacanec; Gjorgji Madzarov; Dejan Gjorgjevikj; Suzana Loskovska

2010-01-01

48

Pelvic Floor Magnetic Resonance Imaging after Neonatal Single Stage Reconstruction in Male Patients With Classic Bladder Exstrophy  

Microsoft Academic Search

PurposeWe evaluate a magnetic resonance imaging (MRI) protocol used to study the pelvic floor anatomy in male patients following neonatal single stage complete bladder exstrophy and epispadias repair with osteotomies.

SAREL HALACHMI; WALID FARHAT; OSNAT KONEN; AZRA KHAN; JOHN HODAPP; DARIUS J. BAGLI; GORDON A. McLORIE; ANTOINE E. KHOURY

2003-01-01

49

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

50

Nuclear magnetic resonance contrast agents  

DOEpatents

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

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

1997-01-01

51

Nuclear magnetic resonance 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

52

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

53

Nuclear Magnetic Resonance Imaging of Vasculature of Abdominal Viscera: Normal and Pathologic  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) imaging of intraabdominal vascular anatomy and the effect of various lesions on retroperitoneal and splanchnic vessels was assessed in 67 patients and volunteers using a superconducting magnet (0.35 tesla) and the spin- echo imaging techniques. Because of the low signal generated by flowing blood in most images, blood vessels, including intraparenchymal vessels, were well demon- strated.

Charles B. Higgins; Henry Goldberg; Hedvig Hricak; Lawrence E. Crooks; Leon Kaufman; Robert Brasch

54

Magnetic Resonance Detection Method and and Apparatus.  

National Technical Information Service (NTIS)

A method and apparatus is described for detecting magnetic resonance of a sample. The apparatus uses an exceptionally stable tunnel diode rf oscillator incorporating a LC reentrant cavity resonator. The method entails measuring a magnetic resonance of the...

C. T. Van Degrift D. B. Utton

1977-01-01

55

Biological magnetic resonance: vol. 5  

SciTech Connect

This book discusses magnetic resonance techniques (NMR and ESR) as applied to biochemical research. Topics considered include the applications of carbon-13 NMR spectroscopy in investigations of metabolic pathways in vivo, the use of nitrogen-15 NMR in studies of systems of biological interest, phosphorus-31 NMR investigations of enzyme systems, the principles and state-of-the-art advances in the use of oxygen isotopes in phosphorus-31 and oxygen-17 NMR studies of biophosphates, and electron spin resonance and nuclear magnetic resonance studies of lipid-protein interactions in membranes.

Berliner, L.J.; Reuben, J.

1983-01-01

56

Basics of magnetic resonance imaging  

SciTech Connect

Beginning with the behavior of a compass needle in a magnetic field, this text uses analogies from everyday experience to explain the phenomenon of nuclear magnetic resonance and how it is used for imaging. Using a minimum of scientific abbreviations and symbols, the basics of tissue visualization and characterization are presented. A description of the various types of magnets and scanners is followed by the practical advantages and limitations of MRI relative to x-ray CT scanning.

Oldendorf, W.; Oldendorf, W. Jr.

1988-01-01

57

Influence of X Chromosome and Hormones on Human Brain Development: A Magnetic Resonance Imaging and Proton Magnetic Resonance Spectroscopy Study of Turner Syndrome  

Microsoft Academic Search

Background: Women with Turner syndrome (TS; 45,X) lack a normal second X chromosome, and many are prescibed exogenous sex and growth hormones (GH). Hence, the allow its an opportunity to investigate genetic and endocrine influences on brain development. Methods: We examined brain anatomy and metabolism in 27 adult monosomic TS women and 21 control subjects with volumetric magnetic resonance imaging

William J. Cutter; Eileen M. Daly; Dene M. W. Robertson; Xavier A. Chitnis; Therese A. M. J. van Amelsvoort; Andrew Simmons; Virginia W. K. Ng; Benjamin S. Williams; Phillip Shaw; Gerard S. Conway; David H. Skuse; David A. Collier; Michael Craig; Declan G. M. Murphy

2006-01-01

58

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

59

Mechanical detection of magnetic resonance  

NASA Astrophysics Data System (ADS)

CONVENTIONAL techniques for measuring magnetic resonance involve the detection of electromagnetic signals induced in a coil or microwave cavity by the collective precession of magnetic moments (from nuclei or electrons) excited by an alternating magnetic field. In a different approach1, isolated electron spins have been detected by scanning tunnelling microscopy, with the spin precession inducing a radiofrequency modulation in the tunnelling current. Here, we describe a new and extremely sensitive method of detection, the principles of which derive from magnetic force microscopy2-5 and a recent proposal6,7 by one of us (J.A.S.). We measure the small, oscillatory magnetic force (10-14 N) acting on a paramagnetic sample (a few grains of diphenylpicrylhydrazil, weighing < 30 ng) which has been excited into magnetic resonance in the presence of an inhomogeneous magnetic field. This force is detected by optically sensing the angstrom-scale vibration of a micromechanical cantilever on which the sample is mounted. The sensitivity of this technique to the spatial distribution of the spins suggests that mechanical detection of magnetic resonance has the potential for imaging microscopic samples in three dimensions. So far, we have achieved a spatial resolution of 19 ?m in one dimension.

Rugar, D.; Yannoni, C. S.; Sidles, J. A.

1992-12-01

60

Clinical Applications of Cardiac Magnetic Resonance Imaging After Repair of Tetralogy of Fallot  

Microsoft Academic Search

.   In the past 15 years, cardiovascular magnetic resonance (MR) has evolved into an imaging technique that provides adequate,\\u000a and in part unique, information on residual problems in the follow-up of patients operated for tetralogy of Fallot. Spin-echo\\u000a or gradient-echo cine magnetic resonance imaging allow detailed assessment of intracardiac and large vessel anatomy, which\\u000a is particularly helpful in Fallot patients

W. A. Helbing; A. de Roos

2000-01-01

61

Magnetic resonance as an aid in the diagnosis of a transverse vaginal septum.  

PubMed

Transverse vaginal septum is a rare, often overlooked congenital abnormality that is typically not diagnosed until adolescence. We present the case of a transverse vaginal septum and partial bicornuate uterus in a 16-year-old adolescent girl with developmental delay and cerebral palsy. Magnetic resonance is an excellent diagnostic tool to delineate the specific anatomy before surgery. The effects of delayed diagnosis and the utility of magnetic resonance in diagnosis will be discussed. PMID:22325406

Krafft, Catherine; Hartin, Charles W; Ozgediz, Doruk E

2012-02-01

62

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

63

Nuclear Magnetic Resonance Massmetric Flowmeter.  

National Technical Information Service (NTIS)

Based on earlier research work in the measurement of jet and rocket propellants by means of Nuclear Magnetic Resonance (NMR), a propellant mass flow meter based on the NMR principle was designed and constructed. The mass flow measurement is derived by mul...

J. H. Battocletti W. H. Vander Heyden W. K. Genthe

1972-01-01

64

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.

Raman, Venkatesh K.; Lederman, Robert J.

2008-01-01

65

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

66

Magnetic Resonance Studies of Coal. Volume III.  

National Technical Information Service (NTIS)

Electron spin resonance (ESR) and Electron-Nuclear Double Resonance (ENDOR) techniques have been used to study natural radical centers in Alabama coals. Also Nuclear Magnetic Resonance (NMR) techniques have been used for a preliminary study of the hydroge...

I. Miyagawa C. Alexander

1981-01-01

67

Delta Relaxation Enhanced Magnetic Resonance  

NASA Astrophysics Data System (ADS)

Generally speaking, targeted molecular imaging has always been difficult to perform with magnetic resonance. The difficulty does not arise with the magnetic resonance imaging (MRI) technique or equipment itself, but rather with the targeted contrast agents, which the method requires. Also referred to as activatable contrast agents, or MRI probes, targeted contrast agents are pharmaceuticals that will selectively bind to a particular biological (target) molecule. They are used to highlight a certain tissue or the difference between healthy and diseased tissue. Unfortunately, nearly all MRI probes are non-specific, causing localized increases in MR image intensity in both the unbound and target-bound states. Therefore, brightening in a conventional MRI image, following probe injection, does not positively indicate the presence of the target molecule. Herein, a novel method known as delta relaxation enhanced magnetic resonance (dreMR, pronounced "dreamer") is presented that utilizes variable magnetic field technology to produce image contrast related to the dependence of the sample's longitudinal relaxation rates upon the strength of the main magnetic field of the MRI scanner. Since only bound contrast agent shows significant magnetic field dependence, it is an indicator of the bound probe, which is in turn a marker for the target molecule. This work details the development of the dreMR method, focusing on the specialized hardware necessary to provide a clinical, static-field MRI the ability to modulate its main magnetic field throughout an MRI sequence. All modifications were performed in such a manner that the host MRI system was not degraded or permanently modified in any way. The three parts of this technology are: the insertable electromagnet, the power supply system and the control system. The insertable electromagnet modifies the magnetic field, the power system drives the electromagnet, and the control system generates the magnetic field waveform envelope and synchronizes this waveform with the rest of the MRI pulse sequence. On two separate dreMR systems, images were obtained having contrast which was directly proportional to the magnetic field dependence of the sample's relaxation rates. This contrast unambiguously indicated the presence of the bound probe, and its imaging therefore yields a map of the targeted biological molecule. Keywords Magnetic Resonance Imaging; Field-Cycled MRI; MR Probe; Targeted Contrast Agent; Gadolinium; Insert Coil; Power Supply; Relaxation Rate; Relaxivity; Actively Shielded; dreMR; Delta Relaxation Enhanced MRI; MRI Hardware; Gradient Echo; Spin Echo; Spoiled Gradient; Echo iv

Alford, Jamu K.

68

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.

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

2012-01-01

69

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

70

Magnetic resonance as an aid in the diagnosis of a transverse vaginal septum  

Microsoft Academic Search

Transverse vaginal septum is a rare, often overlooked congenital abnormality that is typically not diagnosed until adolescence. We present the case of a transverse vaginal septum and partial bicornuate uterus in a 16-year-old female with developmental delay and cerebral palsy. Magnetic resonance (MR) is an excellent diagnostic tool to delineate the specific anatomy prior to surgery. The effects of delayed

Catherine Krafft; Charles W. Hartin; Doruk E. Ozgediz

71

Cardiovascular Magnetic Resonance Imaging in Experimental Models  

PubMed Central

Cardiovascular magnetic resonance (CMR) imaging is the modality of choice for clinical studies of the heart and vasculature, offering detailed images of both structure and function with high temporal resolution. Small animals are increasingly used for genetic and translational research, in conjunction with models of common pathologies such as myocardial infarction. In all cases, effective methods for characterising a wide range of functional and anatomical parameters are crucial for robust studies. CMR is the gold-standard for the non-invasive examination of these models, although physiological differences, such as rapid heart rate, make this a greater challenge than conventional clinical imaging. However, with the help of specialised magnetic resonance (MR) systems, novel gating strategies and optimised pulse sequences, high-quality images can be obtained in these animals despite their small size. In this review, we provide an overview of the principal CMR techniques for small animals for example cine, angiography and perfusion imaging, which can provide measures such as ejection fraction, vessel anatomy and local blood flow, respectively. In combination with MR contrast agents, regional dysfunction in the heart can also be identified and assessed. We also discuss optimal methods for analysing CMR data, particularly the use of semi-automated tools for parameter measurement to reduce analysis time. Finally, we describe current and emerging methods for imaging the developing heart, aiding characterisation of congenital cardiovascular defects. Advanced small animal CMR now offers an unparalleled range of cardiovascular assessments. Employing these methods should allow new insights into the structural, functional and molecular basis of the cardiovascular system.

Price, Anthony N.; Cheung, King K.; Cleary, Jon O; Campbell, Adrienne E; Riegler, Johannes; Lythgoe, Mark F

2010-01-01

72

High-resolution magnetic resonance neurography in upper extremity neuropathy.  

PubMed

The most common sites of nerve entrapment are in the upper extremity, commonly diagnosed based on clinical findings and electrophysiologic studies. Cross-sectional imaging modalities, such as ultrasonography and magnetic resonance (MR) imaging, have been used to enhance diagnostic accuracy and provide anatomic mapping of abnormalities. MR neurography offers multiplanar high-resolution imaging of upper extremity nerves as well as adjacent soft tissues, and provides an objective assessment of the neuromuscular anatomy and related abnormalities. This article reviews the normal 3-T MR neurographic appearance of the upper extremity nerves, and abnormal findings related to injury, entrapment, and other pathologic conditions. PMID:24210316

Chalian, Majid; Behzadi, Ashkan Heshmatzadeh; Williams, Eric H; Shores, Jaimie T; Chhabra, Avneesh

2014-02-01

73

3T magnetic resonance neurography of tibial nerve pathologies.  

PubMed

Diagnosis of tibial neuropathy has been traditionally based on clinical examination and electrodiagnostic studies; however, cross-sectional imaging modalities have been used to increase the diagnostic accuracy and provide anatomic mapping of the abnormalities. In this context, magnetic resonance neurography (MRN) offers high-resolution imaging of the tibial nerve (TN), its branches and the adjacent soft tissues, and provides an objective assessment of the neuromuscular anatomy, abnormality, and the surrounding pathology. This review describes the pathologies affecting the TN and illustrates their respective 3 Tesla (T) MRN appearances with relevant case examples. PMID:22243916

Chalian, Majid; Soldatos, Theodoros; Faridian-Aragh, Neda; Williams, Eric H; Rosson, Gedge D; Eng, John; Carrino, John A; Chhabra, Avneesh

2013-04-01

74

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

75

Magnetic resonance imaging in lissencephaly  

Microsoft Academic Search

In a patient with clinical manifestations suggestive of brain malformation, computer-assisted tomography (CT) showed lissencephaly:\\u000a agyria, pachygyria, absent opercularization, and colpocephaly. The patient did not have seizures or a typical EEG of hypsarrhythmia.\\u000a By magnetic resonance imaging (MRI), using a long inversion-recovery sequence, it was possible to verify the CT-findings and\\u000a to demonstrate heterotopic grey matter and missing claustrum. By

M. Krawinkel; H.-J. Steen; B. Terwey

1987-01-01

76

Magnetic resonance neurography: technical considerations.  

PubMed

Proper performance of magnetic resonance neurography (MRN) is essential not only to make the examination easier to interpret but also for its accurate evaluation. This article outlines the technical considerations of MRN, various imaging pulse sequences available on current scanners, as well as their relative advantages and disadvantages. In addition, a guide to the optimal use of high-resolution and high-contrast MRN technique is provided, which will aid clinicians in attaining a good-quality examination. PMID:24210313

Chhabra, Avneesh; Flammang, Aaron; Padua, Abraham; Carrino, John A; Andreisek, Gustav

2014-02-01

77

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

78

Magnetic resonance imaging at ultrahigh fields.  

PubMed

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

Ugurbil, Kamil

2014-05-01

79

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

80

Principles of nuclear magnetic resonance.  

PubMed

The basic principles of nuclear magnetic resonance (NMR) are discussed. The concepts presented include a qualitative quantum-mechanical approach to NMR spectroscopy and a classical-mechanical approach to time-dependent NMR phenomena (relaxation effects). The spectroscopic concepts discussed include absorption of radiation by matter, spin and energy quantization , chemical shift, and spin-spin splitting. The time-dependent phenomena include the concepts of T1 and T2, the spin-lattice and spin-spin relaxation time, and Fourier-transform NMR spectroscopy. PMID:6726415

Koutcher, J A; Burt, C T

1984-01-01

81

Magnetic resonance imaging of acquired cardiac disease.  

PubMed Central

Over the last 15 years, advances in magnetic resonance imaging techniques have increased the accuracy and applicability of cardiovascular magnetic resonance imaging. These advances have improved the utility of magnetic resonance imaging in evaluating cardiac morphology, blood flow, and myocardial contractility, all significant diagnostic features in the evaluation of the patient with acquired heart disease. Utilization of cardiovascular magnetic resonance imaging has been limited, primarily due to clinical reliance upon nuclear scintigraphy and echocardiography. Recent developments in fast and ultrafast imaging should continue to enhance the significance of magnetic resonance imaging in this field. Widespread use of magnetic resonance imaging in the evaluation of the cardiovascular system will ultimately depend upon its maturation into a comprehensive, noninvasive imaging technique for the varying manifestations of acquired heart disease, including cardiomyopathy, ischemic heart disease, and acquired valvular disease. Images

Carrol, C L; Higgins, C B; Caputo, G R

1996-01-01

82

Superconducting microwave resonator for millikelvin magnetic resonance force microscopy  

NASA Astrophysics Data System (ADS)

We have fabricated a superconducting resonator capable of generating a strong microwave magnetic field in a small (100 ?m) volume for low temperature magnetic resonance experiments. While the resonator was specifically developed for use at millikelvin temperatures in a dilution refrigerator, where the total cooling power is limited to a few hundred microwatts, it is also useful at temperatures up to 5 K. The resonator consists of a 220 ?m diameter, 2-1/2 turn niobium coil resonating with a short section of niobium microstripline. At a resonance frequency of 3 GHz, the loaded Q of the resonator was 780. The field strength was characterized by performing electron spin nutations. Operating at 100 mK with 320 ?W of dissipated power, the resonator generated a field of 4 G at a distance of 100 ?m from the coil.

Mamin, H. J.; Budakian, R.; Rugar, D.

2003-05-01

83

Society for Cardiovascular Magnetic Resonance guidelines for reporting cardiovascular magnetic resonance examinations  

PubMed Central

These reporting guidelines are recommended by the Society for Cardiovascular Magnetic Resonance (SCMR) to provide a framework for healthcare delivery systems to disseminate cardiac and vascular imaging findings related to the performance of cardiovascular magnetic resonance (CMR) examinations.

Hundley, W Gregory; Bluemke, David; Bogaert, Jan G; Friedrich, Matthias G; Higgins, Charles B; Lawson, Mark A; McConnell, Michael V; Raman, Subha V; van Rossum, Albert C; Flamm, Scott; Kramer, Christopher M; Nagel, Eike; Neubauer, Stefan

2009-01-01

84

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.

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

2011-01-01

85

Magnetic Resonance Force Microscopy with Magnetic Tiped Cantilevers  

Microsoft Academic Search

Magnetic resonance force microscopy has been performed, until recently, by attaching the sample under study to a fragile microcantilever. Increasing the resolution, force-sensitivity and practicality of the technique, demands both reducing the size of the magnetic particle and measuring magnetic resonance as an excitation of magnetic-tip cantilevers. To lift the sample-on-cantilever restriction we have succesfully attached and controllably magnetized a

John A. Marohn; Raul Fainchtein; Doran D. Smith

1998-01-01

86

A mechanical analog of nuclear magnetic resonance  

NSDL National Science Digital Library

A mechanical analog apparatus for teaching Nuclear Magnetic Resonance is assembled of PVC, an air-bearing, a magnetic sphere, two sheet magnets, and a pair of Helmholtz coils. The magnetic sphere spins in the air-bearing due to turbine torque and acts as an ensemble of protons in the NMR system. The Helmholtz coils allow us to supply an AC magnetic field to perturb the sphere and search for resonance. The sheet magnets are on a slide. By moving them closer or further from the air bearing, we adjust the magnetic field at the sphere. The field at the air bearing is relatively uniform.

Masters, Mark F.

2013-02-13

87

Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance Three Axis Vector Magnetometer  

NASA Astrophysics Data System (ADS)

The Northrop Grumman Corporation is leveraging the technology developed for the Nuclear Magnetic Resonance Gyroscope (NMRG) to build a combined Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance (EPR-NMR) magnetometer. The EPR-NMR approach provides a high bandwidth and high sensitivity simultaneous measurement of all three vector components of the magnetic field averaged over the small volume of the sensor's one vapor cell. This poster will describe the history, operational principles, and design basics of the EPR-NMR magnetometer including an overview of the NSD designs developed and demonstrated to date. General performance results will also be presented.

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

2012-06-01

88

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

89

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

90

[Cardiac magnetic resonance imaging (MRI)].  

PubMed

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

Vignaux, Olivier

2004-07-31

91

Coronary artery magnetic resonance angiography.  

PubMed

Coronary magnetic resonance angiography (coronary MRA) continues to advance rapidly from both a technical and clinical perspective. Coronary MRA has benefited directly from improvements in spatial resolution, contrast definition, and advances in motion correction, which have furthered its routine use in evaluating coronary artery bypass grafts and anomalous coronary arteries. Work in refining the techniques for more accurate identification of coronary artery disease (CAD) continues, with advances in navigator-gated and breath-hold motion correction techniques, novel k-space strategies (e.g., spiral and radial k-space filling), development and application of intravascular contrast agents, and imaging at higher field strengths. Ultimately, these developments may lead to the routine application of coronary MRA as a screening tool for CAD. This article reviews the development of coronary MRA, discusses the requirements and tools necessary for optimal visualization of the coronary arteries, and describes the application of coronary MRA to acquired and congenital CAD. PMID:15170777

Flamm, Scott D; Muthupillai, Raja

2004-06-01

92

Magnetic resonance imaging of cholangiocarcinoma.  

PubMed

Cholangiocarcinoma arises from the bile ducts and is the most common primary malignancy of the biliary tree. Cholangiocarcinoma is classified according to its growth pattern: mass-forming, periductal-infiltrating, or intraductal-growing type. The majority of cholangiocarcinomas occur at the common hepatic duct (CHD) and its bifurcation, also referred to as Klatskin's tumor, but they also can occur in more peripheral branches within the hepatic parenchyma. Microscopically, cholangiocarcinoma represents an adenocarcinoma with a glandular appearance arising from the epithelium of the bile ducts. On magnetic resonance (MR) images, cholangiocarcinomas appear hypointense on T1-weighted images, and hyperintense on T2-weighted images. Central hypointensity can be seen on T2-weighted images and correspond to fibrosis. On dynamic MR images, cholangiocarcinomas show moderate peripheral enhancement followed by progressive and concentric filling in the tumor with contrast material. Pooling of contrast within the tumor on delayed MR images is suggestive of peripheral cholangiocarcinoma. The role of MR imaging in hilar cholangiocarcinoma is to confirm/reach a diagnosis and to assess resectability. Hilar cholangiocarcinoma shows the same signal intensity pattern of peripheral tumors both on T1- and T2-weighted images. On magnetic resonance cholangiopancreatography (MRCP) images, hilar cholangiocarcinoma appears as a moderately irregular thickening of the bile duct wall (>/=5 mm) with symmetric upstream dilation of the intrahepatic bile ducts. The aim of preoperative investigation in Klatskin tumors typically requires the evaluation of the level of biliary obstruction, the intrahepatic tumor spread, and the vascular involvement; it also needs to show any atrophy-hypertrophy complex. Because of its intrinsic high tissue contrast and multiplanar capability, MR imaging and MRCP are able to detect and preoperatively assess patients with cholangiocarcinoma, investigating all involved structures such as bile ducts, vessels and hepatic parenchyma. The main reason for surgical/imaging discrepancy is represented by the microscopic diffusion along the mucosa and in the perineural space. PMID:15192788

Manfredi, Riccardo; Barbaro, Brunella; Masselli, Gabriele; Vecchioli, Amorino; Marano, Pasquale

2004-05-01

93

Magnetic resonance imaging of acetabular labral tears.  

PubMed

The acetabular labrum plays an important role in hip biomechanical function and stability. Labral tears can result in appreciable clinical symptoms and joint dysfunction and may predispose the hip to chondral damage and osteoarthritis. Magnetic resonance imaging is an effective tool for detecting and characterizing labral tears. Direct magnetic resonance arthrography is the most commonly used and validated technique for evaluating the labrum. However, indirect magnetic resonance arthrography and non-arthrographic magnetic resonance imaging are two less invasive and less resource-intensive techniques that should also be considered. Orthopaedic surgeons and radiologists should strive to develop and implement minimally and noninvasive diagnostic magnetic resonance imaging protocols for the investigation of labral pathology. PMID:21543685

Rakhra, Kawan S

2011-05-01

94

Magnetic resonance imaging of glioblastoma using aptamer conjugated magnetic nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

95

Multidimensionally encoded magnetic resonance imaging.  

PubMed

Magnetic resonance imaging (MRI) typically achieves spatial encoding by measuring the projection of a q-dimensional object over q-dimensional spatial bases created by linear spatial encoding magnetic fields (SEMs). Recently, imaging strategies using nonlinear SEMs have demonstrated potential advantages for reconstructing images with higher spatiotemporal resolution and reducing peripheral nerve stimulation. In practice, nonlinear SEMs and linear SEMs can be used jointly to further improve the image reconstruction performance. Here, we propose the multidimensionally encoded (MDE) MRI to map a q-dimensional object onto a p-dimensional encoding space where p > q. MDE MRI is a theoretical framework linking imaging strategies using linear and nonlinear SEMs. Using a system of eight surface SEM coils with an eight-channel radiofrequency coil array, we demonstrate the five-dimensional MDE MRI for a two-dimensional object as a further generalization of PatLoc imaging and O-space imaging. We also present a method of optimizing spatial bases in MDE MRI. Results show that MDE MRI with a higher dimensional encoding space can reconstruct images more efficiently and with a smaller reconstruction error when the k-space sampling distribution and the number of samples are controlled. PMID:22926830

Lin, Fa-Hsuan

2013-07-01

96

Correlating Sheet Plastinated Slices, Computed Tomography Images and Magnetic Resonance Images of the Pelvic Girdle: A Teaching Tool  

Microsoft Academic Search

Sheet plastination is currently used to produce anatomical slices of different body structures, allowing one to study and teach their topography in an anatomically correct state. Correlation with computed tomography (CT) and magnetic resonance imaging (MRI) techniques gives more insight into their anatomy. Using two female cadaver pelvises CT and MRI were performed. One pelvis was used to prepare 2-mm-thick

C. A. C. Entius; R. R. van Rijn; J. C. Holstege; R. Stoeckart; A. W. Zwamborn

1997-01-01

97

Magnetic resonance cholangiopancreatography: A novel approach to the evaluation of suspected pancreaticobiliary neoplasms  

Microsoft Academic Search

Background: Magnetic resonance cholangiopancreatography (MRCP) is a new noninvasive diagnostic method for pancreaticobiliary (PB) imaging\\u000a without endoscopy, sedation, or iodinated contrast. The purpose of this study was to evaluate the ability of MRCP to depict\\u000a pancreatic and biliary ductal anatomy compared to that of endoscopic retrograde cholangiopancreatography (ERCP) and to evaluate\\u000a the ability of MRCP to accurately diagnose PB neoplasms.

David R. Feldman; Daniel P. Kulling; Clive L. Kay; David J. Cole; John T. Cunningham; Robert H. Hawes; Paul R. Tarnasky; Peter B. Cotton; Paul L. Baron

1997-01-01

98

Anatomical observations on the renal veins and inferior vena cava at magnetic resonance angiography  

Microsoft Academic Search

Purpose: To describe the renal vein and inferior vena cava (IVC) anatomy found at abdominal magnetic resonance (MR) angiography. Methods: Gadolinium-enhanced, three-dimensional, time-of-flight MR angiograms of 150 patients were evaluated for the number and configuration of the renal veins, and the number, configuration, and dimensions of the IVC. Data were analyzed with the Student's ttest. Results: Retroaortic left renal veins

John A. Kaufman; Arthur C. Waltman; S. Mitchell Rivitz; Stuart C. Geller

1995-01-01

99

Magnetic nanostructures as amplifiers of transverse fields in magnetic resonance.  

PubMed

We introduce the concept of amplifying the transverse magnetic fields produced and/or detected with inductive coils in magnetic resonance settings by using the reversible transverse susceptibility properties of magnetic nanostructures. First, we describe the theoretical formalism of magnetic flux amplification through the coil in the presence of a large perpendicular DC magnetic field (typical of magnetic resonance systems) achieved through the singularity in the reversible transverse susceptibility in anisotropic single domain magnetic nanoparticles. We experimentally demonstrate the concept of transverse magnetic flux amplification in an inductive coil system using oriented nanoparticles with uni-axial magnetic anisotropy. We also propose a composite ferromagnetic/anti-ferromagnetic core/shell nanostructure system with uni-directional magnetic anisotropy that, in principle, provides maximal transverse magnetic flux amplification. PMID:16039099

Barbic, Mladen; Scherer, Axel

2005-09-01

100

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

101

Magnetic resonance elastometry using a single-sided permanent magnet  

NASA Astrophysics Data System (ADS)

In this paper, we describe a magnetic resonance method of measuring material elasticity using a single-sided magnet with a permanent static field gradient. This method encodes sample velocity in a reciprocal space using Hahn spin-echoes with variable timing. The experimental results show a strong correlation between magnetic resonance signal attenuation and elasticity when an oscillating force is applied on the sample. This relationship in turn provides us with information about the displacement velocity experienced by the sample, which is inversely proportional to Young's modulus. The proposed method shows promise in offering a portable and cost-effective magnetic resonance elastography system.

Tan, Carl S.; Marble, Andrew E.; Ono, Yuu

2012-04-01

102

Modern Miracle Medical Machines: Magnetic Resonance Imaging  

NSDL National Science Digital Library

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

Murphy, Sytil K.

2010-06-08

103

Magnetic Resonance Imaging of Glutamate  

PubMed Central

Glutamate (Glu) exhibits a pH and concentration dependent chemical exchange saturation transfer effect (CEST) between its -amine group and bulk water, here termed GluCEST. GluCEST asymmetry is observed at ~3 parts per million downfield from bulk water. Following middle cerebral artery occlusion in the rat brain, an approximately 100% elevation of GluCEST in the ipsilateral side compared to the contralateral side was observed, and is predominantly due to pH changes. In a rat brain tumor model with blood brain barrier disruption, intravenous Glu injection resulted in a clear elevation of GluCEST and a comparable increase in the proton magnetic resonance spectroscopy signal of Glu. GluCEST maps from healthy human brain at 7T were also obtained. These results demonstrate the feasibility and potential of GluCEST for mapping relative changes in Glu concentration as well as pH in vivo. Potential contributions from other brain metabolites to the GluCEST effect are also discussed.

Cai, Kejia; Haris, Mohammad; Singh, Anup; Kogan, Feliks; Greenberg, Joel H.; Hariharan, Hari; Detre, John A.; Reddy, Ravinder

2011-01-01

104

Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy achieves very high resolution three-dimensional imaging capabilities of magnetic resonance imaging by taking advantage of very high sensitivity mechanical force detection. This enables non-contacting, microscopic studies and imaging of a broad range of materials. As a consequence of the strong interactions between spins, the assumptions underlying conventional MRI are not applicable to FMR imaging. However, using a new approach to localizing the resonant volume in an FMR measurement founded on the strong, nonuniform magnetic field of the micromagnetic probe tip, we have demonstrated scanned probe Ferromagnetic Resonance (FMR) imaging [1]. The scanned probe FMR images obtained in patterned ferromagnetic films are well explained by detailed numerical modeling. In addition to illuminating the mechanisms underlying localized FMR, the model provides the basis for submicron scanned probe FMR imaging of films and buried ferromagnetic elements. This work was supported by the U.S. Department of Energy through Grant No. DE-FG02-03ER46054. [1] ``Local Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy,'' Yu. Obukhov, D.V. Pelekhov, J. Kim, P. Banerjee, I. Martin, E. Nazaretski, R. Movshovich, S. An, T.J. Gramila, S. Batra, and P. C. Hammel, Phys. Rev. Lett. 100(19), 197601 (2008).

Pelekhov, Denis

2009-03-01

105

Coronary computed tomography and magnetic resonance imaging.  

PubMed

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

2009-04-01

106

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.

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

2009-01-01

107

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

108

International Society for Magnetic Resonance in Medicine  

MedlinePLUS

... Links Workshop & Educational Course Series ISMRM Workshop on Functional MRI: Emerging Techniques & New Interpretations 22-25 June ... Are The International Society for Magnetic Resonance in Medicine is a nonprofit professional association dedicated to promoting ...

109

Mathematical Foundations for Magnetic Resonance Imaging.  

National Technical Information Service (NTIS)

Over the past decade, the technical development of Magnetic Resonance Imaging (MRI) has been very rapid. This report provides the theoretical framework for the understanding and the design of new imaging sequences, and points out limitations of achievable...

S. Mansson

1995-01-01

110

Magnetic resonance imaging and computer reconstruction of the velopharyngeal mechanism.  

PubMed

Further research is needed to fully understand the mechanics of the levator veli palatini muscle in coordination with surrounding structures in individuals born with a cleft palate. The purpose of this study was to combine magnetic resonance imaging (MRI) and three-dimensional computer modeling and animation to study the velopharyngeal mechanism in infants with and without a cleft palate. Two infants with a normal velopharyngeal anatomy (subjects 1 and 2) and 2 infants with a cleft lip and palate (subjects 3 and 4) were scheduled to receive a whole-head MRI for clinical reasons unrelated to the current study. This study demonstrated a successful method for combining MRI and three-dimensional computer technology to study the velopharyngeal mechanism in infants with and infants without a cleft palate. Subject 1 displayed a levator muscle sling arrangement that was shaped like a narrow U, whereas subject 2 had a wider U-shaped muscle arrangement. Subject 4 exhibited smaller angles of origin in the oblique coronal compared with that of subject 1. Both subjects with a normal anatomy showed steeper muscles compared with those of both subjects with a cleft palate. The current study enhances the body of literature in the area of MRI by acquiring MR images from infants before and after primary palatoplasty and combining the imaging with three-dimensional computer technology. The angles of the levator muscle may prove to be a significant factor in velar elevation for normal speech. PMID:19816343

Perry, Jamie L; Kuehn, David P

2009-09-01

111

Radiation therapy planning and simulation with magnetic resonance images  

NASA Astrophysics Data System (ADS)

We present a system which allows for use of magnetic resonance (MR) images as primary RT workflow modality alone and no longer limits the user to computed tomography data for radiation therapy (RT) planning, simulation and patient localization. The single steps for achieving this goal are explained in detail. For planning two MR data sets, MR1 and MR2 are acquired sequentially. For MR1 a standardized Ultrashort TE (UTE) sequence is used enhancing bony anatomy. The sequence for MR2 is chosen to get optimal contrast for the target and the organs at risk for each individual patient. Both images are naturally in registration, neglecting elastic soft tissue deformations. The planning software first automatically extracts skin and bony anatomy from MR1. The user can semi-automatically delineate target structures and organs at risk based on MR1 or MR2, associate all segmentations with MR1 and create a plan in the coordinate system of MR1. Projections similar to digitally reconstructed radiographs (DRR) enhancing bony anatomy are calculated from the MR1 directly and can be used for iso-center definition and setup verification. Furthermore we present a method for creating a Pseudo-CT data set which assigns electron densities to the voxels of MR1 based on the skin and bone segmentations. The Pseudo-CT is then used for dose calculation. Results from first tests under clinical conditions show the feasibility of the completely MR based workflow in RT for necessary clinical cases. It needs to be investigated in how far geometrical distortions influence accuracy of MR-based RT planning.

Boettger, Thomas; Nyholm, Tufve; Karlsson, Magnus; Nunna, Chandrasekhar; Celi, Juan Carlos

2008-04-01

112

Magnetic resonance elastography of liver: clinical applications.  

PubMed

Magnetic resonance elastography (MRE) has been successfully implemented in the assessment of diffuse liver diseases. Currently, MRE is the most accurate noninvasive technique for detection and staging of liver fibrosis with a potential to replace liver biopsy. Magnetic resonance elastography is able to differentiate isolated fatty liver disease from steatohepatitis with or without fibrosis. Potential clinical applications include the differentiation of benign and malignant focal liver masses and the assessment of treatment response in diffuse liver diseases. PMID:24270110

Venkatesh, Sudhakar K; Yin, Meng; Ehman, Richard L

2013-01-01

113

Magnetic Resonance Elastography of Liver: Clinical Applications  

PubMed Central

Magnetic resonance elastography (MRE) has been successfully implemented in the assessment of diffuse liver diseases. Currently, MRE is the most accurate noninvasive technique for detection and staging of liver fibrosis with a potential to replace liver biopsy. Magnetic resonance elastography is able to differentiate isolated fatty liver disease from steatohepatitis with or without fibrosis. Potential clinical applications include the differentiation of benign and malignant focal liver masses and the assessment of treatment response in diffuse liver diseases.

Venkatesh, Sudhakar K.; Yin, Meng; Ehman, Richard L.

2014-01-01

114

Nuclear Magnetic Resonance in Liquid Crystal Solvents  

Microsoft Academic Search

Since the discovery by Saupe and Englert that a nematic phase is a satisfactory solvent for high resolution nuclear magnetic resonance (NMR) studies, the variety of liquid crystal phases which have been found useful in NMR experiments has greatly increased. The resonance studies have increased our understanding of the structure of the solvent mesophases, and of their interactions with solute

Lawrence C. Snyder; Saul Meiboom

1969-01-01

115

Magnetic-Resonance Studies of Coal. Volume IV.  

National Technical Information Service (NTIS)

As part of a continuing magnetic resonance characterization of geologically-selected coals, Electron Spin Resonance (ESR) and Nuclear Magnetic Resonance (NMR) studies have been conducted on coal seams which lie within the Pratt group of the Warrior Basin....

I. Miyagawa C. Alexander

1982-01-01

116

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

117

Magnetic resonance imaging of the pelvic floor: from clinical to biomechanical imaging.  

PubMed

This article reviews the current role of magnetic resonance imaging in the study of the pelvic floor anatomy and pelvic floor dysfunction. The application of static and dynamic magnetic resonance imaging in the clinical context and for biomechanical simulation modeling is assessed, and the main findings are summarized. Additionally, magnetic resonance-based diffusion tensor imaging is presented as a potential tool to evaluate muscle fiber morphology. In this article, focus is set on pelvic floor muscle damage related to urinary incontinence and pelvic organ prolapse, sometimes as a consequence of vaginal delivery. Modeling applications that evaluate anatomical and physiological properties of pelvic floor are presented to further illustrate their particular characteristics. Finally, finite element method is described as a method for modeling and analyzing pelvic floor structures' biomechanical performance, based on material and behavioral properties of the tissues, and considering pressure loads that mimic real-life conditions such as active contraction or Valsalva maneuver. PMID:24030164

Brandão, Sofia; Da Roza, Thuane; Parente, Marco; Ramos, Isabel; Mascarenhas, Teresa; Natal Jorge, Renato M

2013-12-01

118

Magnetic resonance in radiating or absorbing atoms  

Microsoft Academic Search

Investigation of atomic energy levels using magnetic resonance ; techniques is discussed. A review is presenied of some of the studies of atomic ; vapors in connection with level structures and the mutual interactions of light ; oscillating magnetic fields and the effects of collisions. (auth);

F. Bitter

1962-01-01

119

Homodyne detection in magnetic resonance imaging  

Microsoft Academic Search

Magnetic detection of complex images in magnetic resonance imaging (MRI) is immune to the effects of incidental phase variations, although in some applications information is lost or images are degraded. It is suggested that synchronous detection or demodulation can be used in MRI systems in place of magnitude detection to provide complete suppression of undesired quadrature components, to preserve polarity

Douglas C. Noll; Dwight G. Nishimura; Albert Macovski

1991-01-01

120

Pulse Shaping for Localized Magnetic Resonance Tagging.  

National Technical Information Service (NTIS)

Magnetic resonance tagging is usually achieved by means of a train of non-selective radio-frequency pulses separated by gradient pulses. Thus, the modulation of the M(sub z) magnetization component expands all over the imaging plane. It has been proposed ...

V. N. Ikonomidou G. D. Sergiadis

2001-01-01

121

Pressure Activated Driver for Magnetic Resonance Elastography.  

National Technical Information Service (NTIS)

A driver for use in applying an oscillating stress to a subject undergoing a magnetic resonance elastography (MRE) examination includes a passive actuator located in the bore of the magnet and in contact with the subject. A remotely located acoustic drive...

M. A. Dresner P. J. Rossman R. L. Ehman T. C. Hulshizer

2004-01-01

122

Designing dielectric resonators on substrates: combining magnetic and electric resonances.  

PubMed

High-performance integrated optics, solar cells, and sensors require nanoscale optical components at the surface of the device, in order to manipulate, redirect and concentrate light. High-index dielectric resonators provide the possibility to do this efficiently with low absorption losses. The resonances supported by dielectric resonators are both magnetic and electric in nature. Combined scattering from these two can be used for directional scattering. Most applications require strong coupling between the particles and the substrate in order to enhance the absorption in the substrate. However, the coupling with the substrate strongly influences the resonant behavior of the particles. Here, we systematically study the influence of particle geometry and dielectric environment on the resonant behavior of dielectric resonators in the visible to near-IR spectral range. We show the key role of retardation in the excitation of the magnetic dipole (MD) mode, as well as the limit where no MD mode is supported. Furthermore, we study the influence of particle diameter, shape and substrate index on the spectral position, width and overlap of the electric dipole (ED) and MD modes. Also, we show that the ED and MD mode can selectively be enhanced or suppressed using multi-layer substrates. And, by comparing dipole excitation and plane wave excitation, we study the influence of driving field on the scattering properties. Finally, we show that the directional radiation profiles of the ED and MD modes in resonators on a substrate are similar to those of point-dipoles close to a substrate. Altogether, this work is a guideline how to tune magnetic and electric resonances for specific applications. PMID:24216852

van de Groep, J; Polman, A

2013-11-01

123

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

124

Scanning ferromagnetic resonance microscopy and resonant heating of magnetite nanoparticles: Demonstration of thermally detected magnetic resonance  

NASA Astrophysics Data System (ADS)

We report a 9 GHz microwave scanning probe based on a slit aperture for spatially resolved magnetic resonance detection. We use patterned layers of dispersed magnetite Fe3O4 nanoparticles and demonstrate low-field ferromagnetic resonance images with a spatial resolution of 15 ?m. We also demonstrate localized heating of magnetite nanoparticles via ferromagnetic resonance absorption which can be controlled by an external dc magnetic field. Using our microwave probe as a transmitter and a temperature sensor (thermocouple or infrared detector), we show thermally detected magnetic resonance at room temperature.

Sakran, F.; Copty, A.; Golosovsky, M.; Davidov, D.; Monod, P.

2004-05-01

125

Magnetic resonance imaging and magnetic resonance spectroscopic imaging of prostate cancer  

Microsoft Academic Search

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) are evolving techniques that offer noninvasive evaluation of anatomic and metabolic features of prostate cancer. The ability of MRI to determine the location and extent of the tumor and to identify metastatic spread is useful in the pretreatment setting, enabling treatment decision-making that is evidence-based. MRSI of the prostate gland

Renata Huzjan; Evis Sala; Hedvig Hricak

2005-01-01

126

Magnetic resonance imaging: effects of magnetic field strength  

SciTech Connect

Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. For any one spin echo sequence, gray/white matter contrast decreases and muscle/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then change more slowly, actually dropping for muscle. The optimum field for magnetic resonance imaging depends on tissue type, body part, and imaging sequence, so that it does not have a unique value. Magnetic resonance systems that operate in the 3.0-5.0 kgauss range achieve most or all of the gains that can be achieved by higher magnetic fields.

Crooks, L.E.; Arakawa, M.; Hoenninger, J.; McCarten, B.; Watts, J.; Kaufman, L.

1984-04-01

127

Magnetic resonance elastography: Inversions in bounded media.  

PubMed

Magnetic resonance elastography 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, magnetic resonance elastography 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. Magnetic resonance elastography and finite element modeling of beam, plate, and spherical shell phantoms of various geometries were performed. Mechanical testing of the phantoms agreed with the stiffness values obtained from finite element modeling and magnetic resonance elastography data, and a linear correlation of r(2) >or= 0.99 was observed between the stiffness values obtained using magnetic resonance elastography and finite element modeling 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

2009-12-01

128

Magnetic Resonance Imaging of Dendrite Currents  

NASA Astrophysics Data System (ADS)

The action currents of active dendrites generate their own magnetic field, which can cause the phase of the spins to change. Many investigators have attempted to detect neural and dendritic currents directly using magnetic resonance imaging. Such a measurement of action currents would be remarkable, since it would allow functional imaging of neural activity using the high spatial resolution of MRI and avoid an ill-posed inverse problem to determine the current sources. Measurement of the magnetic field of neural currents would better follow the distribution of neural activity in time and space. Our goal in this presentation is to use the calculated magnetic field of a dendrite to estimate the resulting phase shift in the magnetic resonance signal. We find the phase shift produced by a collection of simultaneously active dendrites is below the threshold for detection using current MRI technology.

Jay, William; Dolasinski, Brian; Wijesinghe, Ranjith; Roth, Bradley

2011-10-01

129

Soft X-ray resonant magnetic scattering of magnetic nanostructures  

NASA Astrophysics Data System (ADS)

Soft X-ray resonant magnetic scattering offers a unique element-, site- and valence-specific probe to study magnetic structures on the nanoscopic length scale. This new technique, which combines X-ray scattering with X-ray magnetic circular and linear dichroism, is ideally suited to investigate magnetic superlattices and magnetic domain structures. The theoretical analysis of the polarization dependence to determine the vector magnetization profile is presented. This is illustrated with examples studying the closure domains in self-organising magnetic domain structures, the magnetic order in patterned samples, and the local configuration of magnetic nano-objects using coherent X-rays. To cite this article: G. van der Laan, C. R. Physique 9 (2008).

van der Laan, Gerrit

2008-06-01

130

The Diversity of Nuclear Magnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

The discovery of the physical phenomenon of Nuclear Magnetic Resonance (NMR) in 1946 gave rise to the spectroscopic technique that has become a remarkably versatile research tool. One could oversimplify NMR spectros-copy by categorizing it into the two broad applications of structure elucidation of molecules (associated with chemistry and biology) and imaging (associated with medicine). But, this certainly does not do NMR spectroscopy justice in demonstrating its general acceptance and utilization across the sciences. This manuscript is not an effort to present an exhaustive, or even partial review of NMR spectroscopy applications, but rather to provide a glimpse at the wide-ranging uses of NMR spectroscopy found within the confines of a single magnetic resonance research facility, the Stanford Magnetic Resonance Laboratory. Included here are summaries of projects involving protein structure determination, mapping of intermolecular interactions, exploring fundamental biological mechanisms, following compound cycling in the environmental, analysis of synthetic solid compounds, and microimaging of a model organism.

Liu, Corey W.; Alekseyev, Viktor Y.; Allwardt, Jeffrey R.; Bankovich, Alexander J.; Cade-Menun, Barbara J.; Davis, Ronald W.; Du, Lin-Shu; Garcia, K. Christopher; Herschlag, Daniel; Khosla, Chaitan; Kraut, Daniel A.; Li, Qing; Null, Brian; Puglisi, Joseph D.; Sigala, Paul A.; Stebbins, Jonathan F.; Varani, Luca

131

Stepped impedance resonators for high-field magnetic resonance imaging.  

PubMed

Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high-field magnetic resonance imaging. In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) 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 T (298 MHz) demonstrate the rationale and feasibility of the SIR design strategy. Simulation and image results at 7 T in a phantom and human head illustrate the improvements in a transmit magnetic field, as well as RF efficiency (transmit magnetic field versus specific absorption rate) 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

2014-02-01

132

Magnetic Resonance Imaging (MRI) -- Head  

MedlinePLUS Videos and Cool Tools

... x-ray contrast material, drugs, food, or the environment, or if you have asthma. The contrast material ... are also screened for safety in the magnetic environment. Children will be given appropriately sized earplugs or ...

133

Cardiovascular magnetic resonance for the clinical cardiologist  

PubMed Central

Cardiovascular magnetic resonance is a noninvasive imaging modality that provides superior anatomical and functional information in the absence of ionizing radiation. The cardiovascular magnetic resonance imaging program has been active at the Quebec Heart Institute at Laval Hospital for two years, now providing advanced imaging studies to over 42 referral centres from eastern and central Quebec as well as providing training for national and international fellows. The program benefits from the collborative work of cardiologists and radiologists, who both bring to the table their unique expertise. The following text reviews current clinical applications useful in the daily practice of the cardiovascular specialist.

Larose, Eric; Rodes-Cabau, Josep; Delarochelliere, Robert; Barbeau, Gerald; Noel, Bernard; Bertrand, Olivier

2007-01-01

134

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

135

Magnetic resonance imaging of shoulder arthropathies.  

PubMed

The role of magnetic resonance imaging in evaluating shoulder arthropathies is evolving. This article reviews 4 of the major arthropathies: septic arthritis, rheumatoid arthritis, calcium pyrophosphate dihydrate (CPPD) deposition disease, and hydroxyapatite disease (HAD), with special attention to their magnetic resonance imaging features. Comfort with identifying these entities allows appropriate and prompt treatment, which is critical for joint preservation in the case of infection, for maximal therapeutic efficacy of disease-modifying drugs in the case of rheumatoid arthritis, and for expediting symptomatic relief in the cases of CPPD deposition disease and HAD. PMID:22469408

Sussmann, A Ross; Cohen, Jodi; Nomikos, George C; Schweitzer, Mark E

2012-05-01

136

Functional magnetic resonance imaging in pediatrics  

PubMed Central

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

Wilke, Marko; Holland, Scott K.; Myseros, John S.; Schmithorst, Vincent J.; Ball, William S.

2005-01-01

137

Imaging in breast cancer: Magnetic resonance spectroscopy  

PubMed Central

A technique called in vivo magnetic resonance spectroscopy (MRS) can be performed along with magnetic resonance imaging (MRI) to obtain information about the chemical content of breast lesions. This information can be used for several clinical applications, such as monitoring the response to cancer therapies and improving the accuracy of lesion diagnosis. Initial MRS studies of breast cancer show promising results, and a growing number of research groups are incorporating the technique into their breast MRI protocols. This article introduces 1H-MRS of the breast, reviews the literature, discusses current methods and technical issues, and describes applications for treatment monitoring and lesion diagnosis.

Bolan, Patrick J; Nelson, Michael T; Yee, Douglas; Garwood, Michael

2005-01-01

138

Microwave Magnetic Resonance Spectrum of Oxygen  

Microsoft Academic Search

The complex magnetic-resonance spectrum of oxygen gas is observed at 9340 Mc\\/sec in magnetic fields up to 9000 oersted. Some 40 lines are resolved. A partial analysis of the spectrum is made with the help of Henry's recent Zeeman theory of O2. Other lines are identified by the temperature dependence of the relative intensities. Line widths are measured by several

Robert Beringer; J. G. Castle

1951-01-01

139

Video: Proton Nuclear Magnetic Resonance (NMR)  

NSDL National Science Digital Library

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

2011-06-03

140

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

ERIC Educational Resources Information Center

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

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

2001-01-01

141

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

ERIC Educational Resources Information Center

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

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

2011-01-01

142

An improved nuclear magnetic resonance spectrometer  

NASA Technical Reports Server (NTRS)

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

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

1967-01-01

143

Current technical development of magnetic resonance imaging  

Microsoft Academic Search

The impact of MRI continues to grow due to progress in all phases of the development cycle. Since its initial use for human imaging approximately 20 years ago, magnetic resonance imaging (MRI) has developed into a widely used clinical imaging modality. Now, at the start of the 21st century, the number of MRI systems worldwide is in excess of 10,800.

Stephen J. Riederer

2000-01-01

144

Nuclear Magnetic Resonance Technology for Medical Studies.  

ERIC Educational Resources Information Center

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

Budinger, Thomas F.; Lauterbur, Paul C.

1984-01-01

145

Clinical impact of shoulder magnetic resonance imaging  

Microsoft Academic Search

The clinical impact of magnetic resonance imaging (MRI) of the shoulder is dependent upon the clinical diagnosisand clinical indications for surgical management. MRI of the shoulder is very useful in defining the anatomic pathology associated with shoulder pain and disability. The clinical impact of MRI is improved when it is obtained under well defined criteria which should be based upon

Joseph P. Iannotti; Gerald R. Williams

1997-01-01

146

Magnetic resonance imaging of painful shoulder arthroplasty  

Microsoft Academic Search

Specialized magnetic resonance imaging (MRI) was performed in 42 painful shoulder arthroplasties, 22 of which underwent subsequent revision surgery, allowing surgical confirmation of the pathology identified on MRI. One hemiarthroplasty was excluded because of motion artifact, leaving 21 studies (19 patients) to be correlated retrospectively to the surgical findings. At the time of revision surgery, there were full-thickness rotator cuff

John W Sperling; Hollis G Potter; Edward V Craig; Evan Flatow; Russell F Warren

2002-01-01

147

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

148

Scatter-based magnetic resonance elastography  

Microsoft Academic Search

Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems.

Sebastian Papazoglou; Chao Xu; Uwe Hamhaber; Eberhard Siebert; Georg Bohner; Randolf Klingebiel; Jürgen Braun; Ingolf Sack

2009-01-01

149

Vibration safety limits for magnetic resonance elastography  

Microsoft Academic Search

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

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

2008-01-01

150

Image processing for magnetic-resonance elastography  

Microsoft Academic Search

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this

Armando Manduca; R. Muthupillai; P. J. Rossman; James F. Greenleaf; Richard L. Ehman

1996-01-01

151

Image analysis for magnetic resonance elastography  

Microsoft Academic Search

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this

A. Manduca; R. Muthupillai; P. J. Rossman; J. F. Greenleaf; R. L. Ehman

1996-01-01

152

Local wavelength estimation for magnetic resonance elastography  

Microsoft Academic Search

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this

A. Manduca; R. Muthupillai; P. J. Rossman; J. F. Greenleaf; R. L. Ehman

1996-01-01

153

Parallel Magnetic Resonance Imaging using Neural Networks  

Microsoft Academic Search

ABSTRACT Magnetic resonance imaging of dynamic,events such as cognitive tasks in the brain, requires high spatial and temporal resolution. In order to increase the resolution in both domains simultaneously, par- allel imaging schemes have been in existence, where multiple re- ceiver coils are used, each of which needs to acquire only a frac- tion of the total available signal. In

Neelam Sinha; Manojkumar Saranathan; Kalpathi R. Ramakrishnan; Sundaram Suresh

2007-01-01

154

The role of fetal magnetic resonance imaging  

Microsoft Academic Search

The role of magnetic resonance imaging (MRI) in fetal imaging is expanding. The depth of structural information provided by MRI means it is more than just a useful adjunct to ultrasound, as several structures are more clearly visualised and many of the limitations of ultrasound are avoided. Currently, MRI is most frequently utilised with reference to the fetal central nervous

C Wright; C P Sibley; P N Baker

2010-01-01

155

Coolant quality for magnetic resonance imaging systems  

Microsoft Academic Search

As radiologists demand increased power, speed and duty cycle from their magnetic resonance imaging (MRI) systems, thermal management of the gradient sub-system becomes more challenging. A heat exchanger in the MRI system cools heat-generating components by pumping water through hollow copper tubing, which also carries high electrical currents. Water is used as a coolant because of its high specific heat

Julie Wong; Garron K Morris

2008-01-01

156

Magnetic resonance elastography of the brain  

Microsoft Academic Search

The purpose of this study was to obtain normative data using magnetic resonance elastography (MRE) (a) to obtain estimates of the shear modulus of human cerebral tissue in vivo and (b) to assess a possible age dependence of the shear modulus of cerebral tissue in healthy adult volunteers. MR elastography studies were performed on tissue-simulating gelatin phantoms and 25 healthy

Scott A. Kruse; Gregory H. Rose; Kevin J. Glaser; Armando Manduca; Joel P. Felmlee; Clifford R. Jack; Richard L. Ehman

2008-01-01

157

Myocardial tissue tagging with cardiovascular magnetic resonance  

Microsoft Academic Search

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

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

2009-01-01

158

Magnetic resonance imaging of orbital tumors  

Microsoft Academic Search

This contribution provides an overview of diseases of eye and orbit and their appearance on magnetic resonance imaging. In recent years the diagnosis of eye and orbit pathology has profited significantly from increasingly sophisticated technical developments in the field of tomographic methods. Due to the small size of the examination area the improvement in spatial resolution and soft tissue contrast

A. J. Lemke; I. Kazi; R. Felix

2006-01-01

159

Magnetic resonance applications in atherosclerotic vascular disease  

Microsoft Academic Search

Magnetic resonance imaging of the cardiovascular system offers great promise in the detection and characterization of the\\u000a anatomic, physiologic, and biochemical consequences of atherosclerosis. This review will focus on the potential applications\\u000a of MRI for evaluating atherosclerosis of the abdominal aorta and iliofemoral vessels.

George E. Wesbey; Charles B. Higgins; James D. Hale; Peter E. Valk

1986-01-01

160

Magnetic Resonance Neurography in Extraspinal Sciatica  

Microsoft Academic Search

Background: Sciatica without evidence of lumbosa- cral root compression is often attributed to piriformis syndrome. However, specific diagnostic tools have not been available to demonstrate sciatic nerve entrapment by the piriformis muscle. Objective: To evaluate the use of magnetic resonance (MR) neurography in identifying abnormalities of the sciatic nerve in patients with unexplained sciatica. Design: Case series from a retrospective

Aaron M. Lewis; Robert Layzer; J. W. Engstrom; Nicholas M. Barbaro; Cynthia T. Chin

2006-01-01

161

Magnetic resonance imaging in patients with panhypopituitarism  

Microsoft Academic Search

Primary panhypopituitarism consists of functional deficiency of the anterior pituitary lobe, which appears during infancy or adolescence. The magnetic resonance findings in 10 patients with a history of primary hopopituitarism are presented. The findings include: reduced pituitary size in all cases: partially (8 cases) or totally (2 cases) empty sella; thin (4 cases), partially visible (3 cases) or absent (2

R. S. Pozzi Mucelli; F. Frezza; S. Magnaldi; G. Proto

1992-01-01

162

Magnetic resonance imaging of the carpal tunnel.  

PubMed

Eleven wrists in eight patients with carpal tunnel syndrome were investigated by electrophysiological studies and magnetic resonance imaging (M.R.I.). The operative findings in ten wrists correlated with the M.R.I. evidence of synovial disease, carpal tunnel stenosis and median nerve compression. PMID:2366024

Healy, C; Watson, J D; Longstaff, A; Campbell, M J

1990-05-01

163

Electrically detected magnetic resonance applied to polyaniline  

Microsoft Academic Search

The transport properties of polyaniline films have been investigated by electrically detected magnetic resonance (EDMR) in different protonation states. In polyaniline, a spin-dependent interchain tunneling involving a polaron-polaron transition is found. The EDMR signal in polyaniline is found to be dependent on the DC electric field, protonation level as well as the atmosphere. For low electric fields, and samples with

C. A. Brunello; R. M. Faria

1999-01-01

164

Off-center magnetic resonance imaging with permanent magnets  

NASA Astrophysics Data System (ADS)

Magnets for magnetic resonance imaging are currently designed as structures that are symmetric with respect to the geometric center O of the magnet cavity. This symmetry results in a symmetric field configuration, where point O coincides with the imaging center S defined as the point where the field gradient is zero. However, in many clinical applications such as breast or spine imaging, the region of interest is displaced from the geometric center. We present a design method for yokeless permanent magnets, where the position of point S is dictated by the imaging requirements. The magnet is composed of uniformly magnetized triangular prisms and it does not require a ferromagnetic yoke to channel the magnetic flux. Given an arbitrary polygonal cavity, the design depends on the position of point F, where the magnetostatic potential is assumed to be equal to the magnetostatic potential of the external medium. For a long magnet, the position of the imaging center S coincides with point F. As an example of the off-center design, we analyze a three-dimensional yokeless magnet with cavity of width=length=80 cm and height=45 cm. The magnet generates a field above 0.5 T when constructed using the NdFeB alloy of remanence larger than 1.3 T. The off-center configuration offers flexibility in magnet design that makes it possible to focus on a particular region of the human body, without increasing magnet cavity, magnet size, or its weight

Abele, Manlio G.; Rusinek, Henry

2008-04-01

165

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 3He (helium 3) and 129Xe (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

166

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

167

Nuclear Magnetic Resonance or Magnetic Resonance Imaging: Analysis of a New Technology.  

National Technical Information Service (NTIS)

The purpose of this study was to determine the need for nuclear magnetic resonance imaging in South Carolina. The study was conducted by (1) literature search, (2) contacts with vendors, (3) analysis of existing studies and (4) correspondence with physici...

1984-01-01

168

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

169

Magnetic resonance imaging of solid urethral and peri-urethral lesions.  

PubMed

Solid urethral and peri-urethral lesions are rare and encompass benign and malignant aetiologies. A diagnosis without imaging is often challenging secondary to non-specific clinical symptoms and overlapping findings at the time of physical examination. Magnetic resonance (MR) imaging may be helpful in confirming a diagnosis while providing anatomical detail and delineating disease extent. This article reviews the normal MR anatomy of the male and female urethra, the MR appearance of solid primary and secondary urethral lesions, and the MR appearance of solid urethral lesion mimics. Teaching points • MRI is an important imaging technique in the evaluation of the spectrum of solid urethral lesions.• With excellent soft tissue resolution, MR is accurate in staging primary urethral carcinoma.• Disruption of the zonal anatomy of the female urethral wall indicates peri-urethral extension.• Be aware of benign urethral lesions, particularly those that may mimic solid urethral masses. PMID:23686749

Del Gaizo, Andrew; Silva, Alvin C; Lam-Himlin, Dora M; Allen, Brian C; Leyendecker, John; Kawashima, Akira

2013-08-01

170

Magnetic resonance imaging with magnetic resonance cholangiopancreatography accurately predicts resectability of pancreatic carcinoma  

Microsoft Academic Search

Accurate preoperative staging of pancreatic malignancy aids in directing appropriate therapy and avoids unnecessary invasive\\u000a procedures. We evaluated the accuracy of magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography\\u000a (MRCP) in determining resectability of pancreatic malignancy. Twenty-one patients with suspected pancreatic malignancy underwent\\u000a dynamic, contrast-en-hanced breath-hold MRI with MRCP prior to surgical evaluation. Results of this study were correlated\\u000a with

Steven N. Hochwald; Neil M. Rofsky; Michael Dobryansky; Peter Shamamian; Stuart G. Marais

1999-01-01

171

Magnetic resonance in the differential diagnosis of dementia  

Microsoft Academic Search

Summary.   Magnetic resonance became an important tool for the differential diagnosis of dementia. Magnetic resonance imaging is the\\u000a preferred method to exclude treatable entities accompagnied by dementing symptoms. New techniques including diffusion and\\u000a perfusion magnetic resonance imaging are helpful for the differentiation between vascular dementia and degenerative disorders.\\u000a Magnetic Resonance spectroscopy evolves as a tool for the diagnosis of different

S. R. Felber

2002-01-01

172

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

173

Transcranial magnetic stimulation assisted by neuronavigation of magnetic resonance images  

NASA Astrophysics Data System (ADS)

Technological advance has improved the way scientists and doctors can learn about the brain and treat different disorders. A non-invasive method used for this is Transcranial Magnetic Stimulation (TMS) based on neuron excitation by electromagnetic induction. Combining this method with functional Magnetic Resonance Images (fMRI), it is intended to improve the localization technique of cortical brain structures by designing an extracranial localization system, based on Alcauter et al. work.

Viesca, N. Angeline; Alcauter, S. Sarael; Barrios, A. Fernando; González, O. Jorge J.; Márquez, F. Jorge A.

2012-10-01

174

Dipolar Broadening of Magnetic Resonance Lines in Magnetically Diluted Crystals  

Microsoft Academic Search

Calculations are given for the frequency moments associated with the dipolar broadening of magnetic resonance lines in crystals having lattice points populated at random by identical paramagnetic ions or nuclei. It is found that for fractional magnetic population f>0.1 the line shape is approximately Gaussian with a width proportional to f12; for f<0.01 the line shape is approximately Lorentzian with

C. Kittel; Elihu Abrahams

1953-01-01

175

Magnetic resonance imaging: effects of magnetic field strength  

Microsoft Academic Search

Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. For any one spin echo sequence, gray\\/white matter contrast decreases and muscle\\/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then

L. E. Crooks; M. Arakawa; J. Hoenninger; B. McCarten; J. Watts; L. Kaufman

1984-01-01

176

No association of abnormal cranial venous drainage with multiple sclerosis: a magnetic resonance venography and flow-quantification study  

Microsoft Academic Search

BackgroundRecent studies using colour-coded Doppler sonography showed that chronic impaired venous drainage from the central nervous system is almost exclusively found in multiple sclerosis (MS) patients. This study aimed to investigate the intracranial and extracranial venous anatomy and the intracerebral venous flow profile in patients with MS and healthy controls using magnetic resonance venography (MRV).MethodsTwenty patients with definite MS and

Mike P Wattjes; Bob W van Oosten; Wolter L de Graaf; Alexandra Seewann; Joseph C J Bot; René van den Berg; Bernard M J Uitdehaag; Chris H Polman; Frederik Barkhof

2010-01-01

177

Neonatal life support during magnetic resonance imaging.  

PubMed

Magnetic resonance techniques are required frequently for the assessment of the brain of ill neonates. In the present study, the effects of a 1.5 T MR scanner on devices for life support were assessed. A ventilator (Dräger Babylog 2000) was tested in the 1.5 T magnet, using a neonatal ventilation tester and 1.5-5 m tubes. In a special MR incubator, temperature and humidity were measured at 1-min intervals. Infusion was tested with the pump outside the magnet room: infusion rates and time to alarm were tested with 7-m tubes. The ventilator performed normally at a magnetic field line of 2 mT, although the alarms failed. The incubator created a temperature of 35.9 degrees C and humidity of 40.7%, which was acceptable for examinations of 45 min. The alarm limits of the infusion pump placed outside the magnet at 7 m were within company limits. The study indicates that magnetic resonance examinations can be performed safely in ill preterm neonates who require life-support devices. PMID:12102325

Groenendaal, F; Leusink, C; Nijenhuis, M; Janssen, M J H

2002-01-01

178

Magnetic resonance relaxation properties of superparamagnetic particles.  

PubMed

Nanometric crystals of maghemite are known to exhibit superparamagnetism. Because of the significance of their magnetic moment, maghemite nanoparticles are exceptional contrast agents and are used for magnetic resonance imaging (of the liver, spleen, lymph nodes), for magnetic resonance angiography and for molecular and cellular imaging. The relaxivity of these agents depends on their size, saturation magnetization and magnetic field and also on their degree of clustering. There are different types of maghemite particles whose relaxation characteristics are suited to a specific MRI application. The relaxation induced by maghemite particles is caused by the diffusion of water protons in the inhomogeneous field surrounding the particles. This is well described by a theoretical model that takes magnetite crystal anisotropy and Néel relaxation into account. Another type of superparamagnetic compound is ferritin, the iron-storing protein: it contains a superparamagnetic ferrihydrite core. Even if the resulting magnetic moment of ferritin is far smaller than for magnetite nanoparticles, its massive presence in different organs darkens T(2)-weighted MR images, allowing the noninvasive estimation of iron content, thanks to MRI. The relaxation induced by ferritin in aqueous solutions has been demonstrated to be caused by the exchange of protons between bulk water protons and the surface of the ferrihydrite crystal. However, in vivo, the relaxation properties of ferritin are still unexplained, probably because of protein clustering. PMID:20049798

Gossuin, Yves; Gillis, Pierre; Hocq, Aline; Vuong, Quoc L; Roch, Alain

2009-01-01

179

Magnetic resonance of calcified tissues  

NASA Astrophysics Data System (ADS)

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

Wehrli, Felix W.

2013-04-01

180

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

181

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

182

Magnetic resonance imaging of athletic pubalgia and the sports hernia: current understanding and practice.  

PubMed

Magnetic resonance imaging (MRI) has become the standard imaging modality for activity-related groin pain. Lesions, including rectus abdominis/adductor aponeurosis injury and osteitis pubis, can be accurately identified and delineated in patients with clinical conditions termed athletic pubalgia, core injury, and sports hernia. A dedicated noncontrast athletic pubalgia MRI protocol is easy to implement and should be available at musculoskeletal MR imaging centers. This article will review pubic anatomy, imaging considerations, specific lesions, and common MRI findings encountered in the setting of musculoskeletal groin pain. PMID:23168185

Khan, Waseem; Zoga, Adam C; Meyers, William C

2013-02-01

183

Magnetic resonance diagnostic markers in clinically sporadic prion disease: a combined brain magnetic resonance imaging and spectroscopy  

Microsoft Academic Search

The intra vitam diagnosis of prion disease is challenging and a definite diagnosis still requires neuropathological examination in non-familial cases. Magnetic resonance imaging has gained increasing importance in the diagnosis of prion disease. The aim of this study was to compare the usefulness of different magnetic resonance imaging sequences and proton magnetic resonance spectroscopy in the differential diagnosis of patients

Raffaele Lodi; Piero Parchi; Caterina Tonon; David Manners; Sabina Capellari; Rosaria Strammiello; Rita Rinaldi; Claudia Testa; Emil Malucelli; Barbara Mostacci; Giovanni Rizzo; Giulia Pierangeli; Pietro Cortelli; Pasquale Montagna; Bruno Barbiroli

2009-01-01

184

Magnetic resonance imaging with an optical atomicmagnetometer  

SciTech Connect

Magnetic resonance imaging (MRI) is a noninvasive andversatile methodology that has been applied in many disciplines1,2. Thedetection sensitivity of conventional Faraday detection of MRI depends onthe strength of the static magnetic field and the sample "fillingfactor." Under circumstances where only low magnetic fields can be used,and for samples with low spin density or filling factor, the conventionaldetection sensitivity is compromised. Alternative detection methods withhigh sensitivity in low magnetic fields are thus required. Here we showthe first use of a laser-based atomic magnetometer for MRI detection inlow fields. Our technique also employs remote detection which physicallyseparates the encoding and detection steps3-5, to improve the fillingfactor of the sample. Potentially inexpensive and using a compactapparatus, our technique provides a novel alternative for MRI detectionwith substantially enhanced sensitivity and time resolution whileavoiding the need for cryogenics.

Xu, Shoujun; Yashchuk, Valeriy V.; Donaldson, Marcus H.; Rochester, Simon M.; Budker, Dmitry; Pines, Alexander

2006-05-09

185

Magnetic resonance imaging: effects of magnetic field strength.  

PubMed

Magnetic resonance images of the head, abdomen, and pelvis of normal adult men were obtained using varying magnetic field strength, and measurements of T1 and T2 relaxations and of signal-to-noise (SN) ratios were determined. The T1 relaxation of gray matter, white matter, and muscle increases and T2 decreases with field strength, while T1 of fat remains relatively constant and T2 increases. As a consequence, for any one spin echo sequence, gray/white matter contrast decreases and muscle/fat contrast increases with field. SN levels rise rapidly up to 3.0 kgauss and then change more slowly, actually dropping for muscle. The optimum field for magnetic resonance imaging depends on tissue type, body part, and imaging sequence, so that it does not have a unique value. Magnetic resonance systems that operate in the 3.0-5.0 kgauss range achieve most or all of the gains that can be achieved by higher magnetic fields. PMID:6701302

Crooks, L E; Arakawa, M; Hoenninger, J; McCarten, B; Watts, J; Kaufman, L

1984-04-01

186

[Magnetic resonance tomography findings in adult patients with congenital corrected transposition of great arteries].  

PubMed

In four adult patients with congenitally corrected transposition (C-TGA) of the great arteries the typical anatomy and relevant additional lesions such as perimembranous ventricular septal defect (n = 3), secundum atrial septal defect (n = 2), sub-/valvular pulmonic stenosis (n = 3) and pulmonary artery dilatation (n = 4) and/or relevant tricuspid valve insufficiency (n = 3) were depicted by magnetic resonance imaging (MRI) using spin-echo and gradient-echo techniques. The severity of the additional lesions could be evaluated qualitatively. Therefore, in cases of C-TGA magnetic resonance imaging may provide additional information or in selected patients may serve as a useful alternative to conventional imaging techniques such as echocardiography and angiocardiography. PMID:7785305

Sünger, B; Sechtem, U; Schicha, H

1995-04-01

187

Simultaneous Measurement of Magnetic Resonance and Neuronal Signals  

Microsoft Academic Search

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) at ultra low magnetic fields (ULF, ˜ microT) have advantages over their counterparts at higher magnetic fields, despite the reduction in signal strength. Among these advantages are that the instrumentation uses superconducting quantum interference devices (SQUIDs), and is now compatible with simultaneous measurements of biomagnetic signals, such as magnetoencephalography (MEG). This

Michelle Espy

2007-01-01

188

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.

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

189

Nuclear magnetic resonance imaging in Marfan's syndrome.  

PubMed

Detection and evaluation of aortic root and other cardiovascular abnormalities in patients with Marfan's syndrome are important in determining appropriate therapy and preventing premature mortality. To evaluate the role of nuclear magnetic resonance imaging (NMR) in this syndrome, 10 patients were evaluated using a 0.35 tesla commercial nuclear magnetic resonance imaging system. Findings from these studies were compared with data from other noninvasive tests as well as surgical follow-up. Results from these examinations indicate that NMR-derived measurements of aortic root diameter agree closely with echocardiographic measurements. In addition, NMR provides more complete anatomic detail than does echocardiography and can be utilized to assess and follow up virtually all patients with this syndrome. PMID:3794112

Schaefer, S; Peshock, R M; Malloy, C R; Katz, J; Parkey, R W; Willerson, J T

1987-01-01

190

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

191

Cardiovascular magnetic resonance in heart failure.  

PubMed

Imaging has a central role in the evaluation of patients with heart failure (HF). Cardiovascular magnetic resonance (CMR) is rapidly evolving as a versatile imaging modality that often provides additional information to echocardiography in patients with suspected or known HF. CMR is the only imaging modality that has the ability to assess, without exposure to ionizing radiation, cardiac function, structure (tissue characterization), perfusion, and viability. Moreover, magnetic resonance spectroscopy techniques can assess the pathophysiologic role of deranged cardiac energetics in HF. In this review we discuss the role of CMR in the evaluation of patients with HF giving particular emphasis to recent developments and the additional information that can be obtained with this imaging modality, over and above standard echocardiography. PMID:21360113

Karamitsos, Theodoros D; Neubauer, Stefan

2011-06-01

192

Magnetic resonances in nano-scale metamaterials  

NASA Astrophysics Data System (ADS)

We have designed, fabricated, and optically measured several different kinds of nano-scale metamaterials. We make use e-beam nano-lithography technology at LBNL's Center for X-Ray Optics for fabricating these structures on extremely thin SiN substrates so that they are close to free-standing. Optical properties were measured as a function of incidence angle and polarization. We directly observe a strong magnetic resonance consistent with a negative magnetic permeability in our samples at mid- and near-IR optical frequencies. We will discuss the results in comparison with detailed simulations, and will discuss the electric dipole or quadrupole resonances observed in the samples. Finally, we will report on our progress towards constructing a fully negative index of refraction meta-material.

Hao, Zhao; Liddle, Alex; Martin, Michael

2006-03-01

193

Vibration criteria for a magnetic resonance imager  

NASA Astrophysics Data System (ADS)

One instrument used in clinical medicine to create a high-contrast image of the body's soft tissues involves the principle of nuclear magnetic resonance. The machine is called a magnetic resonance imager (MRI). The MRI scanning process is analogous to optical devices in that it is somewhat sensitive to vibration. This paper describes some field tests intended to quantify the effect of vibration upon image quality as heavy vehicles passed near two on-grade MRI installations. The measured field data are compared to recently published criteria and also are correlated with test images created by the MRI during the vibration events. The paper includes recommendations for improving the format of the manufacturer's vibration specification.

Nash, Anthony

1994-10-01

194

Nuclear magnetic resonance imaging of the pancreas  

SciTech Connect

Nuclear magnetic resonance (NMR) images were obtained from 12 patients with pancreatic disease, and from 40 patients in a control group. Correlation of the images with ultrasound examinations and with laparotomy in five cases indicates that NMR is accurate in the demonstration of pancreatic pathology. Though the images bear close similarity to those obtained by conventional computed tomography (CT), further investigations are needed to delineate the true accuracy of NMR.

Smith, F.W.; Reid, A.; Hutchison, J.M.S.; Mallard, J.R.

1980-03-01

195

Laser magnetic resonance of sulphur radicals  

Microsoft Academic Search

High rotational transitions of the radical NS have been observed using an FIR optically-pumped laser-magnetic-resonance (LMR) spectrometer. The spectra were recorded at wavelengths of 680 and 514 microns (from C2H3Br and DCOF lasers, respectively) and have been assigned to individual Zeeman components of the rotational transitions J = 8.5 to 9.5 and J = 11.5 to 12.5 in the lowest

J. R. Anacona; P. B. Davies

1985-01-01

196

Nuclear magnetic resonance imaging: Basic principles  

SciTech Connect

This book discusses the complicated physics of magnetic resonance imaging and explains the basic principles of data acquisition and image reconstruction techniques. The MR imaging photographs are provided with explanation and there are samples of images literally from head to toe. In this book, the author uses many analogies to more familiar physical phenomena, such as sound waves, to help explain NMR, and these are often ingenious and effective.

Young, S.W.

1985-01-01

197

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

198

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

199

Magnetic resonance urography: a pictorial overview  

Microsoft Academic Search

Magnetic resonance urography (MRU) can be performed on the basis of two different imaging strategies: static-fluid MRU, based on heavily T2 weighted turbo spin echo (TSE) sequences, and gadolinium-enhanced excretory MRU. Both MR urographic techniques in combination with standard MRI permit a comprehensive examination of the entire urinary tract. This pictorial review illustrates the MRU features of the a wide

R Garcia-Valtuille; A I GARCIA-VALTUILLE; F ABASCAL; L CEREZAL; M C ARGUELLO

2006-01-01

200

Wide-range dynamic magnetic resonance elastography  

Microsoft Academic Search

Tissue mechanical parameters have been shown to be highly sensitive to disease by elastography. Magnetic resonance elastography (MRE) in the human body relies on the low-dynamic range of tissue mechanics <100Hz. In contrast, MRE suited for investigations of mice or small tissue samples requires vibration frequencies 10–20 times higher than those used in human MRE. The dispersion of the complex

Kerstin Riek; Dieter Klatt; Hassan Nuzha; Susanne Mueller; Ulf Neumann; Ingolf Sack; Jürgen Braun

2011-01-01

201

Magnetic resonance imaging assessment of cardiac function  

Microsoft Academic Search

Measurements of left ventricular function at rest and during stress are useful for identifying myocardial ischemia, injury,\\u000a and the risk of subsequent myocardial infarction. Without ionizing radiation or intravascular contrast administration, magnetic\\u000a resonance imaging techniques can be used to acquire precise measurements of left ventricular function. This relatively new\\u000a development may enhance a physician’s ability to provide care to patients

W. Gregory Hundley; Craig A. Hamilton; Pairoj Rerkpattanapipat

2003-01-01

202

Cardiac Magnetic Resonance in Hypertrophic Cardiomyopathy  

Microsoft Academic Search

Hypertrophic cardiomyopathy is a fascinating and complex disorder with substantial variability in phenotypic expression and\\u000a natural progression. Recently, there has been substantial research demonstrating incremental utility of cardiac magnetic resonance in the diagnosis\\u000a and treatment of this disease. With the increasing utilization of multimodality imaging, our understanding of the subtle morphologic\\u000a differences and their prognostic implications is only going to

Milind Y. Desai; Ashwat Dhillon; Andrew C. Y. To

2011-01-01

203

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.

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

2012-01-01

204

Development of a Clinical Functional Magnetic Resonance Imaging Service  

PubMed Central

One of the limitations of anatomical based imaging approaches is its relative inability to identify whether specific brain functions may be compromised by the location of brain lesions or contemplated brain surgeries. For this reason, methods for identifying the regions of eloquent brain that should not be disturbed are absolutely critical to the surgeon. By accurately identifying these regions preoperatively, virtually every pre-surgical decision from the surgical approach, operative goals (biopsy, sub-total vs. gross-total resection), and the potential need for awake craniotomy with intraoperative cortical-mapping is affected. Of the many techniques available to the surgeon, functional magnetic resonance imaging (fMRI) has become the primary modality of choice due to the ability of MRI to serve as a “one-stop shop” for assessing both anatomy and functionality of the brain. Given their prevalence, brain tumors serve as the model pathology for the included discussion; however, a similar case can be made for the use of fMRI in other neurological conditions, most notably epilepsy. The value of fMRI was validated in 2007 when the Centers for Medicare and Medicaid Services (CMS) established three new current procedural terminology (CPT) codes for clinical fMRI based upon its use for pre-therapeutic planning. In this article we will discuss the specific requirements for establishing an fMRI program, including specific software and hardware requirements. In addition, the nature of the fMRI CPT codes will be discussed.

Rigolo, Laura; Stern, Emily; Deaver, Pamela; Golby, Alexandra J.; Mukundan, Srinivasan

2013-01-01

205

The cardiac magnetic resonance (CMR) approach to assessing myocardial viability.  

PubMed

Cardiac magnetic resonance (CMR) is a noninvasive imaging method that can determine myocardial anatomy, function, perfusion, and viability in a relative short examination. In terms of viability assessment, CMR can determine viability in a non-contrast enhanced scan using dobutamine stress following protocols comparable to those developed for dobutamine echocardiography. CMR can also determine viability with late gadolinium enhancement (LGE) methods. The gadolinium-based contrast agents used for LGE differentiate viable myocardium from scar on the basis of differences in cell membrane integrity for acute myocardial infarction. In chronic myocardial infarction, the scarred tissue enhances much more than normal myocardium due to increases in extracellular volume. LGE is well validated in pre-clinical and clinical studies that now span from almost a cellular level in animals to human validations in a large international multicenter clinical trial. Beyond infarct size or infarct detection, LGE is a strong predictor of mortality and adverse cardiac events. CMR can also image microvascular obstruction and intracardiac thrombus. When combined with a measure of area at risk like T2-weighted images, CMR can determine infarct size, area at risk, and thus estimate myocardial salvage 1-7 days after acute myocardial infarction. Thus, CMR is a well validated technique that can assess viability by gadolinium-free dobutamine stress testing or late gadolinium enhancement. PMID:21882082

Arai, Andrew E

2011-12-01

206

Heart valve disease: investigation by cardiovascular magnetic resonance  

PubMed Central

Cardiovascular magnetic resonance (CMR) has become a valuable investigative tool in many areas of cardiac medicine. Its value in heart valve disease is less well appreciated however, particularly as echocardiography is a powerful and widely available technique in valve disease. This review highlights the added value that CMR can bring in valve disease, complementing echocardiography in many areas, but it has also become the first-line investigation in some, such as pulmonary valve disease and assessing the right ventricle. CMR has many advantages, including the ability to image in any plane, which allows full visualisation of valves and their inflow/outflow tracts, direct measurement of valve area (particularly for stenotic valves), and characterisation of the associated great vessel anatomy (e.g. the aortic root and arch in aortic valve disease). A particular strength is the ability to quantify flow, which allows accurate measurement of regurgitation, cardiac shunt volumes/ratios and differential flow volumes (e.g. left and right pulmonary arteries). Quantification of ventricular volumes and mass is vital for determining the impact of valve disease on the heart, and CMR is the 'Gold standard' for this. Limitations of the technique include partial volume effects due to image slice thickness, and a low ability to identify small, highly mobile objects (such as vegetations) due to the need to acquire images over several cardiac cycles. The review examines the advantages and disadvantages of each imaging aspect in detail, and considers how CMR can be used optimally for each valve lesion.

2012-01-01

207

Magnetic Resonance Elastography of the Ex-vivo Bovine Globe  

PubMed Central

Purpose To evaluate the feasibility of using magnetic resonance elastography (MRE) to assess the mechanical properties of the eye. Methods The elastic properties of the corneoscleral shell of an intact, enucleated bovine globe specimen were estimated using MRE and finite element modeling (FEM), assuming linear, isotropic behavior. The two-dimensional (2D), axisymetric model geometry was derived from a segmented 2D MR image, and estimations of the Young’s modulus in both the cornea and sclera were made at various intraocular pressures using an iterative flexural wave speed matching algorithm. Results Estimated values of the Young’s moduli of the cornea and sclera varied from 40 to 185 kPa and 1 to 7 MPa, respectively, over an intraocular pressure range of 0.85 to 9.05 mmHg (1.2 to 12.3 cmH2O). They also varied exponentially as functions of both wave speed and intraocular dP/dV, an empirical measure of “ocular rigidity”. Conclusion These results show that it is possible to estimate the intrinsic elastic properties of the corneoscleral shell in an ex vivo bovine globe, suggesting that MRE may provide a useful means to assess the mechanical properties of the eye and its anatomy. Further development of the technique and modeling process will enhance its potential, and further investigations are needed to determine its clinical potential.

Litwiller, Daniel V.; Lee, Sung J.; Kolipaka, Arunark; Mariappan, Yogesh K.; Glaser, Kevin J.; Pulido, Jose S.; Ehman, Richard L.

2010-01-01

208

Magnetic resonance acoustic radiation force imaging  

PubMed Central

Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery.

McDannold, Nathan; Maier, Stephan E.

2008-01-01

209

Magnetic Resonance Microscopy of Collagen Mineralization  

PubMed Central

A model mineralizing system was subjected to magnetic resonance microscopy to investigate how water proton transverse (T2) relaxation times and magnetization transfer ratios can be applied to monitor collagen mineralization. In our model system, a collagen sponge was mineralized with polymer-stabilized amorphous calcium carbonate. The lower hydration and water proton T2 values of collagen sponges during the initial mineralization phase were attributed to the replacement of the water within the collagen fibrils by amorphous calcium carbonate. The significant reduction in T2 values by day 6 (p < 0.001) was attributed to the appearance of mineral crystallites, which were also detected by x-ray diffraction and scanning electron microscopy. In the second phase, between days 6 and 13, magnetic resonance microscopy properties appear to plateau as amorphous calcium carbonate droplets began to coalesce within the intrafibrillar space of collagen. In the third phase, after day 15, the amorphous mineral phase crystallized, resulting in a reduction in the absolute intensity of the collagen diffraction pattern. We speculate that magnetization transfer ratio values for collagen sponges, with similar collagen contents, increased from 0.25 ± 0.02 for control strips to a maximum value of 0.31 ± 0.04 at day 15 (p = 0.03) because mineral crystals greatly reduce the mobility of the collagen fibrils.

Chesnick, Ingrid E.; Mason, Jeffrey T.; Giuseppetti, Anthony A.; Eidelman, Naomi; Potter, Kimberlee

2008-01-01

210

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

211

Magnetic Field Effects on High Quality Factor Superconducting Coplanar Resonators  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

212

Comparative Anatomy of Dipole Magnets or the Magnet Designer's Coloring Book.  

National Technical Information Service (NTIS)

A collection of dipole magnet cross sections is presented together with an indication of how they are related geometrically. The relationships indicated do not necessarily imply the actual path of evolutionary development. Brief consideration is given to ...

R. B. Meuser

1983-01-01

213

Magnetic resonance spectroscopy of the human brain  

NASA Astrophysics Data System (ADS)

I give a brief description of the magnetic resonance spectroscopy (MRS) in the human brain examinations. MRS allows a noninvasive chemical analysis of the brain using a standard high field MR system. Nowadays, the dominant form of MR brain spectroscopy is proton spectroscopy. Two main techniques of MRS, which utilize the chemical shift of metabolites in the external magnetic field, are SVS (single voxel) and CSI (single slice). The major peaks in the spectrum of a normal brain include NAA, Cr, Cho and m-Ins, which are neuronal, energetic, membrane turnover and glial markers, respectively. In disease, two pathological metabolites can be found in the brain spectra: Lac, which is end product of anaerobic glycolysis and Lip, which is a marker of membrane breakdown, occurring in necrosis. The common way to analyze clinical spectra is to determine metabolite ratios, e.g. NAA/Cr, Cho/Cr, Cho/NAA. This analysis permits a safe and noninvasive examination of the brain tissue as each disease state has its own characteristic spectroscopic image. MRS is a valuable diagnostic tool in such clinical applications as detecting brain tumors and differentiating tumors from inflammatory and infectious processes. Proton MRS is also very helpful in diagnostic of ischemic lesions, Alzheimer's disease and hepatic encephalopathy. The MRS brain spectra should always be correlated with the Magnetic Resonance Imaging (MRI) results and alone cannot make neurological diagnosis.

Strózik-Kotlorz, D.

2014-01-01

214

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.

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

1999-01-01

215

Optimized wireless power transfer to RFID sensors via magnetic resonance  

Microsoft Academic Search

Wireless powering of sensors through the strongly coupled magnetic resonance (SCMR) method at the RFID frequency of 27.2 MHz is studied here. The proposed system comprises of two single resonant loops and two self-resonant helical coils, in contrast to the two resonant loops traditionally used in RFID systems. The system is designed using simulation software and is validated by measurements.

Stavros V. Georgakopoulos; Olutola Jonah

2011-01-01

216

Molecular structure and motion in zero field magnetic resonance  

SciTech Connect

Zero field magnetic resonance is well suited for the determination of molecular structure and the study of motion in disordered materials. Experiments performed in zero applied magnetic field avoid the anisotropic broadening in high field nuclear magnetic resonance (NMR) experiments. As a result, molecular structure and subtle effects of motion are more readily observed.

Jarvie, T.P.

1989-10-01

217

Nanodiamond graphitization: a magnetic resonance study.  

PubMed

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

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

2013-06-19

218

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

219

Effects of surgical implants on high-field magnetic resonance images of the normal canine stifle.  

PubMed

To determine the effect of surgical implants on the depiction of canine stifle anatomy in magnetic resonance (MR) images, three canine cadaver limbs were imaged at 1.5 T before and after tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), and extra-capsular stabilization (ECS), respectively. Susceptibility artifacts associated with implants were identified in MR images as a signal void and/or signal misregistration, which obscured or distorted the anatomy. Using the preoperative images as a reference, articular structures of the stifle in postoperative images were graded using an ordinal scale to describe to what degree each anatomic structure could be evaluated for clinical purposes. The TPLO implant, which contains ferromagnetic stainless steel, produced marked susceptibility artifacts that obscured or distorted most stifle anatomy. The titanium alloy TTA implants and the stainless steel crimps used for ECS produced susceptibility artifacts that mainly affected the lateral aspect of the stifle, but allowed the cruciate ligaments and medial meniscus to be evaluated satisfactorily. Susceptibility artifact was significantly less marked in images obtained using turbo spin-echo (TSE) sequences than in sequences employing spectral fat saturation. Clinical MR imaging of canine stifles containing certain metallic implants is feasible using TSE sequences without fat saturation. PMID:22372640

David, F H; Grierson, J; Lamb, C R

2012-01-01

220

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.

Fagan, Andrew J.

2012-01-01

221

Magnetic resonance imaging of the cervix  

PubMed Central

Abstract Due to deficiencies of clinical staging, magnetic resonance (MR) imaging is being increasingly used in the pre-treatment work-up of cervical cancer. Lymph node status, as evaluated by advanced imaging modalities, is also being incorporated into management algorithms. Familiarity with MR imaging features will lead to more accurate staging of cervical cancer. Awareness of impact of staging on management will enable the radiologists to tailor the report to clinically and surgically relevant information. This article emphasizes the guidelines on the MR staging criteria, dependence of newer treatments on imaging staging and lymph node involvement, and MR imaging in post-treatment surveillance of cervical cancer.

Zand, Khashayar Rafat; Reinhold, Caroline; Abe, Hisashi; Maheshwari, Sharad; Mohamed, Ahmed; Upegui, Daniel

2007-01-01

222

Nuclear magnetic resonance in intermetallic compounds  

Microsoft Academic Search

The nuclear magnetic resonance absorption of aluminium and cobalt has been studied in the intermetallic compounds NiAl, CoAl, FeAl, Al2NiCo, Al2FeCo, Al2FeNi and CoTi. The intensity measurements indicate a high degree of order in all the compounds studied, particularly NiAl and CoAl. The relatively large values of intensity at compositions appreciably different from the equiatomic value for these two series

G. W. West

1964-01-01

223

Applications for breast magnetic resonance imaging.  

PubMed

This article reviews the relevant data on breast magnetic resonance imaging (MRI) use in screening, the short-term surgical outcomes and long-term cancer outcomes associated with the use of MRI in breast cancer staging, the use of MRI in occult primary breast cancer, as well as MRI to assess eligibility for accelerated partial breast irradiation and to evaluate tumor response after neoadjuvant chemotherapy. MRI for screening is supported in specific high-risk populations, namely, women with BRCA1 or BRCA2 mutations, a family history suggesting a hereditary breast cancer syndrome, or a history of chest wall radiation. PMID:24882343

Pilewskie, Melissa; Morrow, Monica

2014-07-01

224

Multiparametric magnetic resonance imaging of prostate cancer  

PubMed Central

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

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

2012-01-01

225

[Magnetic resonance imaging of craniofacial pathology].  

PubMed

Effectiveness of nuclear magnetic resonance imaging (MRI) was compared with that of the CT scan in several cases involving different lesions: intracranial, base of skull, facial sinuses, parapharyngeal spaces. MRI provided excellent contrast in soft tissues with good detection of tumors and their limits, the condition of neighboring tissues and any local or regional tumor extension. Vessels were also visualized. It was not influenced by dental artefacts, and allowed three-dimensional sections to be obtained simply without manipulation of patients. In contrast, bone structures were analyzed less clearly than by the CT scan. Marked progress in MRI technical features and results obtained can be expected in the very near future. PMID:3030179

Bourdinière, J; Le Clech, G; Varene, A; Lavalou, J F; Galand, A; Bahu, P

1986-01-01

226

Clinical Applications of Magnetic Resonance Imaging  

PubMed Central

Magnetic resonance imaging (MRI) is a relatively new diagnostic imaging technique that has substantially affected the diagnosis of a multitude of diseases. It has become the imaging modality of choice for a number of pathologic processes, especially in the central nervous system. The authors discuss the clinical applications of MRI, its current status in radiologic investigations, and radiographic features of some of the common diseases of the central nervous system. ImagesFigure 1Figures 2-3Figure 4Figures 5-6Figure 7Figure 8Figure 9Figure 10Figure 11Figures 12-13

Kumar, Alka; Montanera, Walter; Terbrugge, Karel G.; Willinsky, Robert; Fenton, Paul V.

1992-01-01

227

Nanoplatforms for magnetic resonance imaging of cancer  

PubMed Central

Summary The application of biomedical nanotechnology in magnetic resonance imaging (MRI) is expect to have a major impact leading to the development of new contrast drug candidates on the nanoscale (1–100 nm) that are able to react with specific biological targets at a molecular level. One of the major challenges in this regard is the construction of nanomaterials, especially used in molecular MRI diagnostics of cancer in vivo, specialized antitumor drug delivery or real-time evaluation of the efficacy of the implemented cancer treatment. In this paper, we tried to gain further insights into current trends of nanomedicine, with special focus on preclinical MRI studies in translation cancer research.

Cywinska, Monika A.; Grudzinski, Ireneusz P.; Cieszanowski, Andrzej; Bystrzejewski, Michal; Poplawska, Magdalena

2011-01-01

228

Image processing for magnetic-resonance elastography  

NASA Astrophysics Data System (ADS)

A newly developed magnetic resonance imaging technique can directly visualize propagating acoustic strain waves in tissue-like materials. By estimating the local wavelength of the acoustic wave pattern, quantitative values of shear modulus can be calculated and images generated that depict tissue elasticity or stiffness. Since tumors are significantly stiffer than normal tissue (the basis of their detection by palpation), this technique may have potential for 'palpation by imaging,' with possible application to the detection of tumors in breast, liver, kidney, and prostate. We describe the local wavelength estimation algorithm, study its properties, and show a variety of sample results.

Manduca, Armando; Muthupillai, Raja; Rossman, P. J.; Greenleaf, James F.; Ehman, Richard L.

1996-04-01

229

Magnetic resonance imaging of perianal fistulas.  

PubMed

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

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

2014-02-01

230

Cardiovascular magnetic resonance in systemic hypertension  

PubMed Central

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

2012-01-01

231

Magnetic resonance imaging of small bowel neoplasms  

PubMed Central

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

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

2013-01-01

232

Proton-nuclear magnetic resonance study of water solvent magnetic fluid's phase separation  

Microsoft Academic Search

We report proton-nuclear magnetic resonance experiments on a diluted water solvent magnetic fluid of colloidal volume fraction phi=0.30%. By sweeping the external magnetic field strength, H0, applied to the magnetic fluid around 4000 Oe, we found one major resonant field, HM, and two satellite resonant fields, HS1 and HS2, which correspond to resonant protons in three different coexisting phases. HS1

Susamu Taketomi; Shin-Hachiro Saito

2000-01-01

233

Magnetic resonance cholangiopancreatography study of pancreaticobiliary maljunction and pancreaticobiliary diseases  

PubMed Central

AIM: To discuss the imaging anatomy about pancreaticobiliary ductal union, occurrence rate of pancreaticobiliary maljunction (PBM) and associated diseases in a Chinese population by using magnetic resonance cholangiopancreatography (MRCP). METHODS: Data were collected from 694 patients who underwent MRCP from January 2010 to December 2012. Three hundred and ninety-three patients were male and 301 patients were female. The age range was 16-92 years old and the average age was 51.8 years. The recruitment indication of all cases was patients who had clinical symptoms, such as abdominal pain, jaundice, nausea and vomiting, which thus were clinically suspected as relative pancreaticobiliary diseases. All cases were examined by MRCP using single-shot fast spin-echo sequences. In order to obtain MRCP images, the maximum intensity projection was used. RESULTS: According to the anatomy of pancreaticobiliary ductal union based on our analysis of MRCP images, all cases were classified into normal type and abnormal type according to the position of pancreaticobiliary ductal union. The abnormal type could be further divided into P-B type, B-P type and the duodenum type. By analyzing the incidence of biliary stone and inflammation, pancreatitis, biliary duct tumors and pancreatic tumors between normal and abnormal types, significant differences existed. The abnormal group was more likely to suffer from pancreaticobiliary diseases. Comparing three different types of PBM that were associated with pancreaticobiliary diseases by using Fisher’s method, the result showed that there was no significant difference in the incidence of biliary stones, cholecystitis and pancreatic tumors. The incidence of pancreatitis in B-P type and P-B type was higher than that in duodenum type; the incidence of biliary duct tumor in B-P type was higher than that in P-B type; the incidence of biliary duct tumor in duodenum type was lower than that in P-B type. The incidence of congenital choledochus dilatation in normal type and abnormal type was similar, and there was no significant difference between the two types. CONCLUSION: Types of PBM are closely related to the occurrence of pancreaticobiliary diseases. MRCP has important clinical value in the early diagnosis and preventive treatment of pancreaticobiliary diseases.

Wang, Cheng-Lin; Ding, He-Yu; Dai, Yi; Xie, Ting-Ting; Li, Yong-Bin; Cheng, Lin; Wang, Bing; Tang, Run-Hui; Nie, Wei-Xia

2014-01-01

234

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

235

Magnetic resonance imaging of renal transplants.  

PubMed

Nineteen patients were examined to determine the clinical potential of magnetic resonance imaging (MRI) for evaluation of renal transplants. A 0.6-T cryogenic magnet and spin-echo technique with varying pulsing factors were used. T1-weighted images were best for differentiating the cortical and medullary parts of the transplanted kidney. Of the six living-related transplants with good renal function that were imaged, five demonstrated good corticomedullary differentiation (CMD) and one faint CMD. Three transplants with acute rejection were imaged, and all demonstrated a decrease in CMD and decrease in overall signal intensity compared with baseline. No CMD was seen in the three chronically rejecting transplants imaged. The appearance of cadaveric transplants and acute tubular necrosis was quite variable. All perinephric fluid collections were well depicted by MRI. Lymphoceles could be distinguished from hematomas. MRI may prove to be a useful adjunct in the evaluation of renal transplants and perinephric fluid collections. PMID:6388281

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

1984-12-01

236

In vivo nuclear magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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.

1986-05-01

237

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

238

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

Microsoft Academic Search

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

Zackary I. Cleveland

2008-01-01

239

Diffusion-weighted magnetic resonance imaging of the temporal bone  

Microsoft Academic Search

This paper summarizes the value of diffusion-weighted magnetic resonance imaging in the evaluation of temporal bone pathology.\\u000a It highlights the use of different types of diffusion-weighted magnetic resonance imaging in the different types of cholesteatoma,\\u000a prior to first stage surgery and prior to second look surgery. The value of diffusion-weighted magnetic resonance imaging\\u000a in the evaluation of pathology of the

B. De Foer; J. P. Vercruysse; M. Spaepen; T. Somers; M. Pouillon; E. Offeciers; J. W. Casselman

2010-01-01

240

Magnetic resonance studies of GaN-based LEDs  

Microsoft Academic Search

Electrically detected magnetic resonance (EDMR), electrically excited and optically detected magnetic resonance, photocurrent-detected magnetic resonance and the photo-quenching of EDMR are employed to study radiative and non-radiative recombination processes in single quantum well diodes. The effects of high current stress are studied in addition to recombination in unstressed devices. The signals are dominated by a broad line (g?2.01; ?B?13mT) which

William E Carlos; Shuji Nakamura

1998-01-01

241

Magnetic resonance elastography detected with a SQUID in microtesla magnetic fields  

Microsoft Academic Search

We have used a SQUID-based microtesla magnetic resonance imaging (MRI) system to perform magnetic resonance elastography (MRE) experiments in a measurement field of 132 microtesla. Magnetic resonance elastography is based on MRI and measures three-dimensional displacement and strain fields in a sample. With appropriate data processing this allows for a quantitative map of the physical response of a material to

Nathan Kelso; Kristie Koski; Jeffrey Reimer

2005-01-01

242

Pharynx Anatomy  

MedlinePLUS

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

243

Larynx Anatomy  

MedlinePLUS

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

244

Non-contrast-enhanced magnetic resonance angiography: techniques and applications.  

PubMed

Non-contrast-enhanced magnetic resonance angiography has gained renewed interest since the discovery of the association between gadolinium-based contrast agents and nephrogenic systemic fibrosis. The following article is an overview of the different magnetic resonance angiography sequences, the technical possibilities and new developments. Clinical options and recent advancements will be highlighted, and recommendations for non-contrast-enhanced magnetic resonance angiography techniques in different anatomical regions will be given. Furthermore, the authors seek to predict the future of non-contrast-enhanced magnetic resonance angiography, with special focus on patients at risk. PMID:22149527

Blankholm, Anne Dorte; Ringgaard, Steffen

2012-01-01

245

Measurement of acoustic streaming using magnetic resonance.  

PubMed

Magnetic resonance imaging (MRI) has been used to explore acoustic streaming caused in water under ultrasonic exposure conditions similar to those used for diagnostic applications. Streaming was established in an enclosed tube with acoustically transparent end windows, using a pulsed, weakly-focused transducer of acoustic frequency 3.5 MHz. Phase-detection MRI was used to image and quantify streaming profiles in the region of the acoustic focus. Acoustic powers in the range 0.4 mW to 100 mW were used. The sensitivity of the technique enabled streaming velocities down to 0. 1 mm s(-1) to be measured, generated by acoustic power less than 1 mW. In addition, acoustic streaming generated within open meshes with minimum pore dimensions of 3.0 mm and 2.0 mm was measured. The flow velocity in the coarser mesh reached 0.9 mm s(-1) at 95 mW total acoustic power. These observations demonstrate that acoustic streaming is probably a much more general phenomenon in diagnostic ultrasound (ultrasound) than previously recognised. The combination of magnetic resonance and ultrasound shows promise as a diagnostic method for the differentiation of cystic lesions in vivo, and for their characterisation, with sensitivity significantly greater than using ultrasound alone. PMID:10722922

Starritt, H C; Hoad, C L; Duck, F A; Nassiri, D K; Summers, I R; Vennart, W

2000-02-01

246

Magnetic Resonance Imaging Evaluation of Cardiac Masses  

PubMed Central

Background Cardiac tumors are extremely rare; however, when there is clinical suspicion, proper diagnostic evaluation is necessary to plan the most appropriate treatment. In this context, cardiovascular magnetic resonance imaging (CMRI) plays an important role, allowing a comprehensive characterization of such lesions. Objective To review cases referred to a CMRI Department for investigation of cardiac and paracardiac masses. To describe the positive case series with a brief review of the literature for each type of lesion and the role of cardiovascular magnetic resonance imaging in evaluation. Methods Between August 2008 and December 2011, all cases referred for CMRI with suspicion of tumor involving the heart were reviewed. Cases with positive histopathological diagnosis, clinical evolution or therapeutic response compatible with the clinical suspicion and imaging findings were selected. Results Among the 13 cases included in our study, eight (62%) had histopathological confirmation. We describe five benign tumors (myxomas, rhabdomyoma and fibromas), five malignancies (sarcoma, lymphoma, Richter syndrome involving the heart and metastatic disease) and three non-neoplastic lesions (pericardial cyst, intracardiac thrombus and infectious vegetation). Conclusion CMRI plays an important role in the evaluation of cardiac masses of non-neoplastic and neoplastic origin, contributing to a more accurate diagnosis in a noninvasive manner and assisting in treatment planning, allowing safe clinical follow-up with good reproducibility.

Braggion-Santos, Maria Fernanda; Koenigkam-Santos, Marcel; Teixeira, Sara Reis; Volpe, Gustavo Jardim; Trad, Henrique Simao; Schmidt, Andre

2013-01-01

247

Magnetic resonance imaging of adnexal masses.  

PubMed

Adnexal masses are common in women of all ages. A range of physiological and benign ovarian conditions that develop in women, especially in the reproductive age, and adnexal malignancies can be evaluated with magnetic resonance imaging (MRI). Management of women with adnexal masses is frequently guided by imaging findings; therefore, precise characterization of adnexal pathology should be performed whenever possible. Magnetic resonance imaging is useful in characterization of adnexal masses that are not completely evaluated by ultrasound because it can provide additional information on soft tissue composition of adnexal masses based on specific tissue relaxation times and allows multiplanar imaging at large field of view to define the origin and extent of pelvic pathology. The patients most likely to benefit from MRI are pregnant women and those who are premenopausal and have masses that have complex features on ultrasound but do not have raised cancer antigen 125 tumor marker levels. The overlap in imaging appearance among different cell type malignancies makes it difficult to predict exact histology based on MRI appearance; however, MRI has a high accuracy in differentiating benign from malignant masses. Teratomas, endometriomas, simple and hemorrhagic cysts, fibromas, exophytic or extrauterine fibroids, and hydrosalpinges can be diagnosed with high confidence. In this article, the authors review the histopathologic background and MRI features of adnexal masses and discuss the role of MRI in the differentiation of benign from malignant adnexal pathologies. PMID:17417086

Rajkotia, Kavita; Veeramani, Murugusundaram; Macura, Katarzyna J

2006-12-01

248

Metabolic tumor imaging using magnetic resonance spectroscopy.  

PubMed

The adaptability and the genomic plasticity of cancer cells, and the interaction between the tumor microenvironment and co-opted stromal cells, coupled with the ability of cancer cells to colonize distant organs, contribute to the frequent intractability of cancer. It is becoming increasingly evident that personalized molecular targeting is necessary for the successful treatment of this multifaceted and complex disease. Noninvasive imaging modalities such as magnetic resonance (MR), positron emission tomography (PET), and single-photon emission computed tomography (SPECT) are filling several important niches in this era of targeted molecular medicine, in applications that span from bench to bedside. In this review we focus on noninvasive magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) and their roles in future personalized medicine in cancer. Diagnosis, the identification of the most effective treatment, monitoring treatment delivery, and response to treatment are some of the broad areas into which MRS techniques can be integrated to improve treatment outcomes. The development of novel probes for molecular imaging--in combination with a slew of functional imaging capabilities--makes MRS techniques, especially in combination with other imaging modalities, valuable in cancer drug discovery and basic cancer research. PMID:21362514

Glunde, Kristine; Bhujwalla, Zaver M

2011-02-01

249

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

250

Reciprocity and gyrotropism in magnetic resonance transduction  

SciTech Connect

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

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

2006-12-15

251

Electron magnetic resonance of ferrofluids: Evidence for anisotropic resonance at 77 K in samples cooled in a magnetic field  

NASA Astrophysics Data System (ADS)

Evidence is presented from studies of electron magnetic resonance for the formation of linear chains in kerosene based Mn 0.1Fe 0.9Fe 2O 4 (MF1) ferrite ferrofluid cooled in a magnetic field. The resonance field at 77 K was found to depend on the field at which the sample was cooled. More interestingly, the samples cooled in a magnetic field exhibited anisotropy in a resonance field with 180° periodicity, giving evidence for frozen chains.

Sastry, M. D.; Babu, Y.; Goyal, P. S.; Mehta, R. V.; Upadhyay, R. V.; Srinivas, D.

1995-08-01

252

Proton Magnetic Resonance Imaging of Flowing Blood.  

NASA Astrophysics Data System (ADS)

A novel technique of making angiographic images non-invasively by NMR is introduced. In order to visualize the vascular structure, flowing blood must be labeled to achieve contrast against background static tissue. In this technique, a little surface coil is used as the labeling device in addition to a whole-body NMR imager. To label the flowing blood, a magnetic field gradient is applied along the long axis of a living subject. The labeling coil over a carotid artery in the neck is fed RF at the resonant frequency of the protons under the coil. Arterial flow moves blood protons from a field below resonance (at the heart), steadily passing through resonance (at the neck) to a field high above resonance (in the head); at the end of the event blood protons are inverted, or labeled by an adiabatic fast passage. Meanwhile, protons in stationary tissue feel only a constant field and remain unaffected. Blood retains this label as it flows downstream into the head and gives a negative signal, while protons in other tissue a positive signal. Two projection images of the head, with and without labeling, are obtained and subtracted digitally. The residue of the subtraction shows moving material only since signals arising from static material are identical and are cancelled in the subtraction process. Finally, the three dimensional vascular structure is presented in a projective format onto a two dimensional plane resembling an angiogram produced with dye injection and X-rays. Pulse sequences specially designed to image moving objects are presented and discussed. Experimental results on phantoms, volunteers and patients are demonstrated. Competing techniques by NMR are reviewed and compared.

Du, Leila Ning-Zhi

1987-09-01

253

Acoustic noise during functional magnetic resonance imaginga)  

PubMed Central

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

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

2007-01-01

254

Neurophysiological architecture of functional magnetic resonance images of human brain.  

PubMed

We investigated large-scale systems organization of the whole human brain using functional magnetic resonance imaging (fMRI) data acquired from healthy volunteers in a no-task or 'resting' state. Images were parcellated using a prior anatomical template, yielding regional mean time series for each of 90 regions (major cortical gyri and subcortical nuclei) in each subject. Significant pairwise functional connections, defined by the group mean inter-regional partial correlation matrix, were mostly either local and intrahemispheric or symmetrically interhemispheric. Low-frequency components in the time series subtended stronger inter-regional correlations than high-frequency components. Intrahemispheric connectivity was generally related to anatomical distance by an inverse square law; many symmetrical interhemispheric connections were stronger than predicted by the anatomical distance between bilaterally homologous regions. Strong interhemispheric connectivity was notably absent in data acquired from a single patient, minimally conscious following a brainstem lesion. Multivariate analysis by hierarchical clustering and multidimensional scaling consistently defined six major systems in healthy volunteers-- corresponding approximately to four neocortical lobes, medial temporal lobe and subcortical nuclei- - that could be further decomposed into anatomically and functionally plausible subsystems, e.g. dorsal and ventral divisions of occipital cortex. An undirected graph derived by thresholding the healthy group mean partial correlation matrix demonstrated local clustering or cliquishness of connectivity and short mean path length compatible with prior data on small world characteristics of non-human cortical anatomy. Functional MRI demonstrates a neurophysiological architecture of the normal human brain that is anatomically sensible, strongly symmetrical, disrupted by acute brain injury, subtended predominantly by low frequencies and consistent with a small world network topology. PMID:15635061

Salvador, Raymond; Suckling, John; Coleman, Martin R; Pickard, John D; Menon, David; Bullmore, Ed

2005-09-01

255

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.

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

2012-01-01

256

A desktop magnetic resonance imaging system.  

PubMed

Modern magnetic resonance imaging (MRI) systems consist of several complex, high cost subsystems. The cost and complexity of these systems often makes them impractical for use as routine laboratory instruments, limiting their use to hospitals and dedicated laboratories. However, advances in the consumer electronics industry have led to the widespread availability of inexpensive radio-frequency integrated circuits with exceptional abilities. We have developed a small, low-cost MR system derived from these new components. When combined with inexpensive desktop magnets, this type of MR scanner has the promise of becoming standard laboratory equipment for both research and education. This paper describes the development of a prototype desktop MR scanner utilizing a 0.21 T permanent magnet with an imaging region of approximately 2 cm diameter. The system uses commercially available components where possible and is programmed in LabVIEW software. Results from 3D data sets of resolution phantoms and fixed, newborn mice demonstrate the capability of this system to obtain useful images from a system constructed for approximately $13,500. PMID:11755094

Wright, Steven M; Brown, David G; Porter, Jay R; Spence, David C; Esparza, Emilio; Cole, David C; Huson, F Russell

2002-01-01

257

Permanent Magnet Structure for a Nuclear Magnetic Resonance Imager for Medical Diagnostics.  

National Technical Information Service (NTIS)

The present invention relates to the utilization of magnetic fields established by means of permanent magnets for use in medical diagnosis, particularly of the human body or torsi. Whole-body nuclear magnetic resonance diagnostics has been available in th...

H. A. Leupold E. Potenziani

1987-01-01

258

Medical image diagnostics based on computer-aided flow analysis using magnetic resonance images.  

PubMed

Most of the cardiac abnormalities have an implication on hemodynamics and affect cardiovascular health. Diagnostic imaging modalities such as computed tomography and magnetic resonance imaging provide excellent anatomical information on myocardial structures, but fail to show the cardiac flow and detect heart defects in vivo condition. The computerized technique for fluid motion estimation by pixel intensity tracking based on magnetic resonance signals represents a promising technique for functional assessment of cardiovascular disease, as it can provide functional information of the heart in addition to analysis of its anatomy. Cardiovascular flow characteristics can be measured in both normal controls and patients with cardiac abnormalities such as atrial septal defect, thus, enabling identification of the underlying causes of these flow phenomena. This review paper focuses on an overview of a flow analysis scheme based on computer-aided evaluation of magnetic resonance intensity images, in comparison with other commonly used medical imaging modalities. Details of the proposed technique are provided with validations being conducted at selected abnormal cardiovascular patients. It is expected that this new technique can potentially extend applications for characterizing cardiovascular defects and their hemodynamic behavior. PMID:22575846

Wong, Kelvin K L; Sun, Zhonghua; Tu, Jiyuan; Worthley, Stephen G; Mazumdar, Jagannath; Abbott, Derek

2012-10-01

259

Physiological monitoring of small animals during magnetic resonance imaging  

Microsoft Academic Search

Maintaining a stable physiologic state is essential when studying animal models of epilepsy with simultaneous electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI) or EEG and magnetic resonance spectroscopy (MRS). To achieve and maintain such stability in rats in the MRI environment, a minimally invasive but comprehensive system was developed to monitor body temperature, heart rate, blood pressure, blood oxygen

Seyed M. Mirsattari; Frank Bihari; L. Stan Leung; Ravi S. Menon; Zheng Wang; John R. Ives; Robert Bartha

2005-01-01

260

Physiological monitoring of small animals during magnetic resonance imaging  

Microsoft Academic Search

Maintaining a stable physiologic state is essential when studying animal models of epilepsy with simultaneous electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI) or EEG and magnetic resonance spectroscopy (MRS). To achieve and maintain such stability in rats in the MRI environment, a minimally invasive but comprehensive system was developed to monitor body temperature, heart rate, blood pressure, blood oxygen

Seyed M. Mirsattari; Frank Bihari; L. Stan Leung; Ravi S. Menon; Zheng Wang; John R. Ives; Robert Bartha

261

Convertible pneumatic actuator for magnetic resonance elastography of the brain  

Microsoft Academic Search

Here we present a novel pneumatic actuator design for brain magnetic resonance elastography (MRE). Magnetic resonance elastography is a phase contrast technique capable of tracing strain wave propagation and utilizing this information for the calculation of mechanical properties of materials and living tissues. In MRE experiments, the acoustic waves are generated in a synchronized way with respect to image acquisition,

Peter Latta; Marco L. H. Gruwel; Patricia Debergue; Brendon Matwiy; Uta N. Sboto-Frankenstein; Boguslaw Tomanek

2011-01-01

262

Shear Modulus Decomposition Algorithm in Magnetic Resonance Elastography  

Microsoft Academic Search

Magnetic resonance elastography (MRE) is an imaging modality capable of visualizing the elastic properties of an object using magnetic resonance imaging (MRI) measurements of transverse acoustic strain waves induced in the object by a harmonically oscillating mechanical vibration. Various algorithms have been designed to determine the mechanical properties of the object under the assumptions of linear elasticity, isotropic and local

Ohin Kwon; Hyun Soo Nam; Eung Je Woo; Jin Keun Seo; Kevin J. Glaser; Armando Manduca; Richard L. Ehman

2009-01-01

263

Gradient and RF Coil Issues in Magnetic Resonance Imaging  

Microsoft Academic Search

Techniques are presented for new analysis of coils in magnetic resonance imaging that should lead to faster and more accurate pictures of humans. Insertable planar, cylindrical or elliptical gradient coils offer the potential for significant performance increases in magnetic resonance imaging. Using variational methods to minimize inductance and thereby optimize switching speeds, we have analyzed coils with these three geometries.

Michael Alan Martens

1991-01-01

264

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

265

Graph theory based algorithm for magnetic resonance brain images segmentation  

Microsoft Academic Search

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

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

2008-01-01

266

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

267

Computed tomography and magnetic resonance findings in lipoid pneumonia.  

PubMed Central

A case of exogenous lipoid pneumonia was documented by computed tomography and magnetic resonance imaging. Although strongly suggesting the presence of fat on T1 weighted images, magnetic resonance does not produce images specific for this condition. Computed tomography is the best imaging modality for its diagnosis. Images

Brechot, J M; Buy, J N; Laaban, J P; Rochemaure, J

1991-01-01

268

Magnetic resonance imaging of fistula-in-ano  

Microsoft Academic Search

PURPOSE: Successful management of anal fistulas depends upon accurate assessment of the primary tract and any secondary extensions. Preoperative imaging has, to date, been disappointing. METHODS: A prospective study of 35 patients with a clinical diagnosis of fistula-in-ano was performed comparing magnetic resonance imaging with the independently documented operative findings. Magnetic resonance imaging was also compared with anal endosonography in

Peter J. Lunniss; Peter G. Barker; Abdul H. Sultan; Peter Armstrong; Rodney H. Reznek; Clive I. Bartram; Karen S. Cottam; Robin K. Phillips

1994-01-01

269

Rotational Resonance of Nonaxisymmetric Magnetic Braking in the KSTAR Tokamak  

NASA Astrophysics Data System (ADS)

One of the important rotational resonances in nonaxisymmetric neoclassical transport has been experimentally validated in the KSTAR tokamak by applying highly nonresonant n=1 magnetic perturbations to rapidly rotating plasmas. These so-called bounce-harmonic resonances are expected to occur in the presence of magnetic braking perturbations when the toroidal rotation is fast enough to resonate with periodic parallel motions of trapped particles. The predicted and observed resonant peak along with the toroidal rotation implies that the toroidal rotation in tokamaks can be controlled naturally in favorable conditions to stability, using nonaxisymmetric magnetic perturbations.

Park, J.-K.; Jeon, Y. M.; Menard, J. E.; Ko, W. H.; Lee, S. G.; Bae, Y. S.; Joung, M.; You, K.-I.; Lee, K.-D.; Logan, N.; Kim, K.; Ko, J. S.; Yoon, S. W.; Hahn, S. H.; Kim, J. H.; Kim, W. C.; Oh, Y.-K.; Kwak, J.-G.

2013-08-01

270

Rotational resonance of nonaxisymmetric magnetic braking in the KSTAR tokamak.  

PubMed

One of the important rotational resonances in nonaxisymmetric neoclassical transport has been experimentally validated in the KSTAR tokamak by applying highly nonresonant n=1 magnetic perturbations to rapidly rotating plasmas. These so-called bounce-harmonic resonances are expected to occur in the presence of magnetic braking perturbations when the toroidal rotation is fast enough to resonate with periodic parallel motions of trapped particles. The predicted and observed resonant peak along with the toroidal rotation implies that the toroidal rotation in tokamaks can be controlled naturally in favorable conditions to stability, using nonaxisymmetric magnetic perturbations. PMID:24033042

Park, J-K; Jeon, Y M; Menard, J E; Ko, W H; Lee, S G; Bae, Y S; Joung, M; You, K-I; Lee, K-D; Logan, N; Kim, K; Ko, J S; Yoon, S W; Hahn, S H; Kim, J H; Kim, W C; Oh, Y-K; Kwak, J-G

2013-08-30

271

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.

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

2008-01-01

272

[Magnetic resonance tomographic findings in cardiac tumors].  

PubMed

After ultrasound, magnetic resonance imaging (MRI) is the second noninvasive powerful method of examining the heart. The findings in 9 patients with cardiac tumors are reported, who were examined by means of MRI: There was little variance in the MRI signal behavior (with only one exception), although the tumor population examined was very heterogeneous. The MRI techniques used (T1-weighted spin echo, steady-state gradient echo) seem to allow no better tumor specification than ultrasound. Wince multiplanar reconstruction is possible with MRI, tumor size, localization, and the borders of the cardiac neoplasms can be depicted. The cine technique provides dynamic information. In addition, this method allows reliable discrimination between the flow effects and true space-occupying lesions. PMID:8480024

Guhl, L; Grawunder, H J; Arlart, I P

1993-03-01

273

Magnetic resonance spectroscopy of intact spermatozoa  

NASA Astrophysics Data System (ADS)

NMR and ESR techniques have been used to elucidate the cellular metabolism and maturation of goat spermatozoa. Due to electron transport chains in the mitochondrial part of the sperm, these cells reduce nitroxide spin labels such as TEMPO and the ESR signal intensity is a good measure of the reducing power of live cells. The use of 31P NMR helps in detecting changes in intracellular pH during metabolism as well as cellular capacity to generate ATP, while 13C NMR has been used to monitor metabolites generated by cells derived from different regions. The maturation of spermatozoa as it passes through the epididymal track has been characterized by magnetic resonance spectroscopy.

Govil, Girjesh; Phadke, Ratna S.; Srivastava, Sudha; Hegde, Umashashi C.; Fernandes, Elvyra J.

1992-12-01

274

Magnetic resonance spectroscopy in Alzheimer's disease  

PubMed Central

Aging is the primary risk factor for dementia. With increasing life expectancy and aging populations worldwide, dementia is becoming one of the significant public health problems of the century. The most common pathology underlying dementia in older adults is Alzheimer’s disease. Proton magnetic resonance spectroscopy (MRS) may provide a window into the biochemical changes associated with the loss of neuronal integrity and other neurodegenerative pathology that involve the brain before the manifestations of cognitive impairment in patients who are at risk for Alzheimer’s disease. This review focuses on proton MRS studies in normal aging, mild cognitive impairment, and dementia, and how proton MRS metabolite levels may be potential biomarkers for early diagnosis of dementia-related pathologic changes in the brain.

Graff-Radford, Jonathan; Kantarci, Kejal

2013-01-01

275

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

276

[Ophthalmoplegic migraine: value of magnetic resonance].  

PubMed

Ophthalmoplegic migraine is a rare entity, usually starting in childhood, and characterized by recurrent episodes of migrainous headaches associated with an oculomotor cranial nerve palsy, most commonly affecting the third nerve. Its physiopathology remains unknown, but the most recent theory, that considers it as a neuropathy, has led to its inclusion in the last International Headache Classification into the group of neuralgias. Diagnosis is reliant on clinical grounds and the exclusion of other disorders. The characteristic finding of enlargement and enhancement with contrast of the cisternal portion of the oculomotor nerve, observed in Magnetic Resonance Imaging (MRI) has supported its diagnosis. We describe a clinically compatible case, supported by typical MRI images that progressed favourably following corticoids treatment. PMID:19423405

Vecino López, R; Rivero, J Casas; Alvarez-Linera Prado, J; Noval Martín, S

2009-07-01

277

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.

Hash, Thomas W.

2013-01-01

278

Cardiovascular magnetic resonance in carotid atherosclerotic disease  

PubMed Central

Atherosclerosis is a chronic, progressive, inflammatory disease affecting many vascular beds. Disease progression leads to acute cardiovascular events such as myocardial infarction, stroke and death. The diseased carotid alone is responsible for one third of the 700,000 new or recurrent strokes occurring yearly in the United States. Imaging plays an important role in the management of atherosclerosis, and cardiovascular magnetic resonance (CMR) of the carotid vessel wall is one promising modality in the evaluation of patients with carotid atherosclerotic disease. Advances in carotid vessel wall CMR allow comprehensive assessment of morphology inside the wall, contributing substantial disease-specific information beyond luminal stenosis. Although carotid vessel wall CMR has not been widely used to screen for carotid atherosclerotic disease, many trials support its potential for this indication. This review summarizes the current state of knowledge regarding carotid vessel wall CMR and its potential clinical application for management of carotid atherosclerotic disease.

2009-01-01

279

Magnetic Earth Ionosphere Resonant Frequencies (MEIRF) project  

NASA Technical Reports Server (NTRS)

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

Spaniol, Craig

1993-01-01

280

Cardiovascular magnetic resonance in pulmonary hypertension  

PubMed Central

Pulmonary hypertension represents a group of conditions characterized by higher than normal pulmonary artery pressures. Despite improved treatments, outcomes in many instances remain poor. In recent years, there has been growing interest in the use of Cardiovascular Magnetic Resonance (CMR) in patients with pulmonary hypertension. This technique offers certain advantages over other imaging modalities since it is well suited to the assessment of the right ventricle and the proximal pulmonary arteries. Reflecting the relatively sparse evidence supporting its use, CMR is not routinely recommended for patients with pulmonary hypertension. However, it is particularly useful in patient with pulmonary arterial hypertension associated with congenital heart disease. Furthermore, it has proven informative in a number of ways; illustrating how right ventricular remodeling is favorably reversed by drug therapies and providing explicit confirmation of the importance of the right ventricle to clinical outcome. This review will discuss these aspects and practical considerations before speculating on future applications.

2012-01-01

281

Magnetic resonance imaging in pediatric stroke.  

PubMed

Pediatric stroke is a term that can be used to encompass everything from hypoxic-ischemic injury to the fetal central nervous system, and especially the premature neonate, to bland versus hemorrhagic infarction from arterial or venous causes in the infant and older child. Pediatric stroke is a chronically underrecognized and therefore underdiagnosed problem that may have significant economic implications. The risk factors for stroke in children are numerous and differ from those in adults. However, with adequate workup, the etiology can be identified in about 75% of cases. Cardiac disorders and hemoglobinopathy are the most common causes of ischemic infarction in children, whereas various congenital anomalies of the blood vessels or defects in coagulation or platelet function often are found in children with parenchymal hemorrhage. Magnetic resonance imaging provides a noninvasive method of investigating childhood stroke, aiding in both better diagnosis and management of this problem. PMID:11847499

Hunter, Jill Vanessa

2002-02-01

282

Magnetic resonance elastography of the brain.  

PubMed

The purpose of this study was to obtain normative data using magnetic resonance elastography (MRE) (a) to obtain estimates of the shear modulus of human cerebral tissue in vivo and (b) to assess a possible age dependence of the shear modulus of cerebral tissue in healthy adult volunteers. MR elastography studies were performed on tissue-simulating gelatin phantoms and 25 healthy adult volunteers. The data were analyzed using spatiotemporal filters and a local frequency estimating algorithm. Statistical analysis was performed using a paired t-test. The mean shear stiffness of cerebral white matter was 13.6 kPa (95% CI 12.3 to 14.8 kPa); while that of gray matter was lower at 5.22 kPa (95% CI 4.76 to 5.66 kPa). The difference was statistically significant (p<0.0001). PMID:17913514

Kruse, Scott A; Rose, Gregory H; Glaser, Kevin J; Manduca, Armando; Felmlee, Joel P; Jack, Clifford R; Ehman, Richard L

2008-01-01

283

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.

2013-01-01

284

Economic costs of nuclear magnetic resonance imaging.  

PubMed

The costs of nuclear magnetic resonance (NMR) imaging have been carefully accounted during its early use at one institution. Capital requirements total $2,250,000 ($750,000 for construction and $1,500,000 for equipment). The annual operational costs are estimated at $907,000. At the current estimated patient procedure volume of 1,500 per year, an economic break-even point analysis indicates a required charge of $775 per patient procedure. This compares with the current break-even point charge for computed tomography of $342. If patient throughout can be increased to 12 procedures per day, the NMR break-even point charge would be reduced to $402. PMID:6707263

Evens, R G

1984-04-01

285

Cardiovascular magnetic resonance: deeper insights through bioengineering.  

PubMed

Heart disease is the main cause of morbidity and mortality worldwide, with coronary artery disease, diabetes, and obesity being major contributing factors. Cardiovascular magnetic resonance (CMR) can provide a wealth of quantitative information on the performance of the heart, without risk to the patient. Quantitative analyses of these data can substantially augment the diagnostic quality of CMR examinations and can lead to more effective characterization of disease and quantification of treatment benefit. This review provides an overview of the current state of the art in CMR with particular regard to the quantification of motion, both microscopic and macroscopic, and the application of bioengineering analysis for the evaluation of cardiac mechanics. We discuss the current clinical practice and the likely advances in the next 5-10 years, as well as the ways in which clinical examinations can be augmented by bioengineering analysis of strain, compliance, and stress. PMID:23662778

Young, A A; Prince, J L

2013-01-01

286

Morphometric magnetic resonance imaging in psychiatry.  

PubMed

Although advances in the clinical criteria of various axis I psychiatric disorders are continually being made, there is still considerable overlap in the clinical features, and diagnosis is often challenging. As a result, there has been substantial interest in using morphometric magnetic resonance imaging to better characterize these diseases and inform diagnosis. Region of interest and voxel-based morphometry studies are reviewed herein to examine the extent to which these goals are being met across various psychiatric disorders. It is concluded based on the studies reviewed that specific patterns of regional loss, although present in certain axis I disorders, are not, as yet, diagnostically useful. However, advances in outcome and treatment monitoring show considerably more promise for rapid application in psychiatry. PMID:19363434

Fleck, David E; Nandagopal, Jayasree; Cerullo, Michael A; Eliassen, James C; DelBello, Melissa P; Adler, Caleb M; Strakowski, Stephen M

2008-04-01

287

Nuclear magnetic resonance imaging of atherosclerotic disease  

SciTech Connect

Nuclear magnetic resonance (NMR) images of 93 patients undergoing studies of the abdomen and pelvis were studied for evidence of lesions of the aorta and the iliac and femoral arteries; atherosclerotic lesions were present in 13 of them. The lesions consisted of eccentric and concentric mural thickening with luminal narrowing and discrete plaques protruding into the vessel lumen. This appearance was distinctly different from the morphology of the internal vessel surface and uniformly thin vessel wall in normal patients and volunteers under the age of 30 years. Intraluminal flow signals observed in atherosclerotic and nonatherosclerotic subjects could be distinguished from mural lesions because of their lack of contiguity with the vessel wall and variation in appearance on multiple images obtained with the first and second spin echo. This initial experience suggests a potential role for NMR in the noninvasive imaging of atherosclerotic lesions. The natural contrast between flowing blood and the vessel wall indicates a distinct advantage of NMR for vascular imaging.

Herfkens, R.J.; Higgins, C.B.; Hricak, H.; Lipton, M.J.; Crooks, L.E.; Sheldon, P.E.; Kaufman, L.

1983-07-01

288

Magnetic Resonance Elastography of the Brain  

PubMed Central

The purpose of this study was to obtain normative data using magnetic resonance elastography (MRE) to: [a] obtain estimates of the shear modulus of human cerebral tissue in vivo, and [b] assess a possible age dependence of the shear modulus of cerebral tissue in healthy adult volunteers. MR elastography studies were performed on tissue-simulating gelatin phantoms and 25 healthy adult volunteers. The data were analyzed using spatio-temporal filters and a local frequency estimating algorithm. Statistical analysis was performed using a paired t-test. The mean shear stiffness of cerebral white matter was 13.6 kPa (95% CI 12.3 to 14.8 kPa); while that of gray matter was lower at 5.22 kPa (95% CI 4.76 to 5.66 kPa). The difference was statistically significant (p < 0.0001).

Kruse, Scott A.; Rose, Gregory H.; Glaser, Kevin J.; Manduca, Armando; Felmlee, Joel P.; Jack, Clifford R.; Ehman, Richard L.

2008-01-01

289

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

290

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

291

Magnetic resonance spectroscopy in common dementias.  

PubMed

Neurodegenerative dementias are characterized by elevated myoinositol and decreased N-acetylaspartate (NAA) levels. The increase in myoinositol seems to precede decreasing NAA levels in Alzheimer's diseases. NAA/myo-inositol ratio in the posterior cingulate gyri decreases with increasing burden of Alzheimer's disease pathologic conditions. Proton magnetic resonance spectroscopy ((1)H MRS) is sensitive to the pathophysiologic processes associated with the risk of dementia in patients with mild cognitive impairment. Although significant progress has been made in improving the acquisition and analysis techniques in (1)H MRS, translation of these technical developments to clinical practice have not been effective because of the lack of standardization for multisite applications and normative data and an insufficient understanding of the pathologic basis of (1)H MRS metabolite changes. PMID:23928196

Kantarci, Kejal

2013-08-01

292

Magnetic penetration depth measurements with the microstrip resonator technique  

Microsoft Academic Search

The microstrip resonator technique is a convenient way to sensitively measure the temperature dependence of the magnetic penetration depth ?(T) in superconducting thin films. Because the method relies on measuring the resonant frequency of a high-Q transmission line resonator at microwave frequencies, one can very precisely measure small changes in ?(T). This technique is applied to studying the low-temperature dependence

S. M. Anlage; B. W. Langley; H. J. Snortland; C. B. Eom; T. H. Geballe; M. R. Beasley

1990-01-01

293

Dipole Resonances in a Homogeneous Plasma in a Magnetic Field  

Microsoft Academic Search

Radar observations recently made from a satellite orbiting above the ionosphere provide evidence for resonances of a plasma in a magnetic field which may be excited and detected by a dipole. The plasma may be said to be resonant, for a particular mode and frequency, if the group velocity is zero. These resonances are studied theoretically on the assumption that

Peter A. Sturrock

1965-01-01

294

Magnetic Resonance Studies of Energy Storage Materials  

NASA Astrophysics Data System (ADS)

In today's society there is high demand to have access to energy for portable devices in different forms. Capacitors with high performance in small package to achieve high charge/discharge rates, and batteries with their ability to store electricity and make energy mobile are part of this demand. The types of internal dielectric material strongly affect the characteristics of a capacitor, and its applications. In a battery, the choice of the electrolyte plays an important role in the Solid Electrolyte Interphase (SEI) formation, and the cathode material for high output voltage. Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) spectroscopy are research techniques that exploit the magnetic properties of the electron and certain atomic nuclei to determine physical and chemical properties of the atoms or molecules in which they are contained. Both EPR and NMR spectroscopy technique can yield meaningful structural and dynamic information. Three different projects are discussed in this dissertation. First, High energy density capacitors where EPR measurements described herein provide an insight into structural and chemical differences in the dielectric material of a capacitor. Next, as the second project, Electrolyte solutions where an oxygen-17 NMR study has been employed to assess the degree of preferential solvation of Li+ ions in binary mixtures of EC (ethylene carbonate) and DMC (dimethyl carbonate) containing LiPF6 (lithium hexafluo-rophosphate) which may be ultimately related to the SEI formation mechanism. The third project was to study Bismuth fluoride as cathode material for rechargeable batteries. The objective was to study 19F and 7Li MAS NMR of some nanocomposite cathode materials as a conversion reaction occurring during lithiation and delithation of the BiF3/C nanocomposite.

Vazquez Reina, Rafael

295

Magnetic resonance characterization of silicon nanowires  

NASA Astrophysics Data System (ADS)

Silicon nanowires (SiNWs) have been extensively investigated in the last decades. The interest in these nanostructures stems from both fundamental and applied research motivations. The functional properties of one- and zero-dimensional silicon structures are significantly different, at least below a certain critical dimension, from those well known in the bulk. The key and peculiar functional properties of SiNWs find applications in nanoelectronics, classical and quantum information processing and storage, optoelectronics, photovoltaics, thermoelectric, battery technology, nano-biotechnology, and neuroelectronics. We report our work on the characterization by continuous wave (CW) and pulse electron spin resonance (CW, FT-EPR) and electrically detected magnetic resonance (EDMR) measurements of silicon nanowires (SiNWs) produced by different top-down processes. SiNWs were fabricated starting from SOI wafers using standard e-beam lithography and anisotropic wet etching or by metal-assisted chemical etching. Further oxidation was used to reduce the wire cross section. Different EDMR implementations were used to address the electronic wave function of donors (P, As) and to characterize point defects at the SiNWs/SiO2 interface.

Fanciulli, Marco; Belli, Matteo; Vellei, Antonio; Canevali, Carmen; Rotta, Davide; Paleari, Stefano; Basini, Martina

2012-02-01

296

The electrically detected magnetic resonance microscope: Combining conductive atomic force microscopy with electrically detected magnetic resonance  

NASA Astrophysics Data System (ADS)

We present the design and implementation of a scanning probe microscope, which combines electrically detected magnetic resonance (EDMR) and (photo-)conductive atomic force microscopy ((p)cAFM). The integration of a 3-loop 2-gap X-band microwave resonator into an AFM allows the use of conductive AFM tips as a movable contact for EDMR experiments. The optical readout of the AFM cantilever is based on an infrared laser to avoid disturbances of current measurements by absorption of straylight of the detection laser. Using amorphous silicon thin film samples with varying defect densities, the capability to detect a spatial EDMR contrast is demonstrated. Resonant current changes as low as 20 fA can be detected, allowing the method to realize a spin sensitivity of 8 × 10^6spins/?Hz at room temperature.

Klein, Konrad; Hauer, Benedikt; Stoib, Benedikt; Trautwein, Markus; Matich, Sonja; Huebl, Hans; Astakhov, Oleksandr; Finger, Friedhelm; Bittl, Robert; Stutzmann, Martin; Brandt, Martin S.

2013-10-01

297

Magnetic resonance imaging and magnetic resonance spectroscopy assessment of brain function in experimental animals and man  

Microsoft Academic Search

This paper introduces the basic principles and techniques of functional magnetic resonance imaging (fMRI) and spectroscopy (MRS). Examples are given of single event human fMRI studies on control subjects, and a graded activation protocol applied to Parkinsonian patients. Possibilities are discussed for using fMRI techniques to study the neural substrate of various pharmacological agents, including drugs of abuse.The application of

Peter G. Morris

1999-01-01

298

Multi-dimensionally encoded magnetic resonance imaging  

PubMed Central

Magnetic resonance imaging typically achieves spatial encoding by measuring the projection of a q-dimensional object over q-dimensional spatial bases created by linear spatial encoding magnetic fields (SEMs). Recently, imaging strategies using nonlinear SEMs have demonstrated potential advantages for reconstructing images with higher spatiotemporal resolution and reducing peripheral nerve stimulation. In practice, nonlinear SEMs and linear SEMs can be used jointly to further improve the image reconstruction performance. Here we propose the multi-dimensionally encoded (MDE) MRI to map a q-dimensional object onto a p-dimensional encoding space where p > q. MDE MRI is a theoretical framework linking imaging strategies using linear and nonlinear SEMs. Using a system of eight surface SEM coils with an eight-channel RF coil array, we demonstrate the five-dimensional MDE MRI for a two-dimensional object as a further generalization of PatLoc imaging and O-space imaging. We also present a method of optimizing spatial bases in MDE MRI. Results show that MDE MRI with a higher dimensional encoding space can reconstruct images more efficiently and with a smaller reconstruction error when the k-space sampling distribution and the number of samples are controlled.

Lin, Fa-Hsuan

2013-01-01

299

Microrobotic navigable entities for Magnetic Resonance Targeting.  

PubMed

Magnetic Resonance Targeting (MRT) uses MRI for gathering tracking data to determine the position of microscale entities with the goal of guiding them towards a specific target in the body accessible through the vascular network. At full capabilities, a MRT platform designed to treat a human would consist of a clinical MRI scanner running special algorithms and upgraded to provide propulsion gradient up to approximately 400mT/m to enable entities as small as a few tens of micrometers in diameter and containing magnetic nanoparticles (MNP) to be steered at vessel bifurcations based on tracking information. Indeed, using a clinical MRI system, we showed that such single entity with a diameter as small as 15microm is detectable in gradient-echo scans. Among many potential interventions, targeted cancer therapy is a good initial application for such new microrobotic approach since secondary toxicity for the patient could be reduced while increasing therapeutic efficacy using lower dosages. Although many types of such entities are needed to provide a larger set of tools, here, only three initial types designed with different functionalities and for different types of cancer are briefly described. Initially designed for targeted chemo-embolization of liver tumors, the first type known as Therapeutic Magnetic Micro-Carriers (TMMC) consists in its present form of approximately 50 microm PLGA microparticles containing therapeutics and approximately 180 nm FeCo MNP. For the second type, MNP are not only used for propulsion and tracking, but also actuation based on a local elevation of the temperature. In its simplest form, it consists of approxiamtely 20 nm MNP embedded in a thermo-sensitive hydrogel known as PNIPA, allowing additional functionalities such as computer triggered drug release and targeted hyperthermia. The third type initially considered to target colorectal tumors, consists of 1-2 microm MR-trackable and controllable MC-1 Magnetotactic Bacteria (MTB) with propelling thrust force provided by two flagella bundles per cell exceeding 4 pN. PMID:21097003

Martel, Sylvain

2010-01-01

300

Computer simulation of magnetic resonance spectra employing homotopy.  

PubMed

Multidimensional homotopy provides an efficient method for accurately tracing energy levels and hence transitions in the presence of energy level anticrossings and looping transitions. Herein we describe the application and implementation of homotopy to the analysis of continuous wave electron paramagnetic resonance spectra. The method can also be applied to electron nuclear double resonance, electron spin echo envelope modulation, solid-state nuclear magnetic resonance, and nuclear quadrupole resonance spectra. PMID:9799683

Gates, K E; Griffin, M; Hanson, G R; Burrage, K

1998-11-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

302

Giant magnetic modulation of a planar, hybrid metamolecule resonance  

NASA Astrophysics Data System (ADS)

Coupling magnetic elements to metamaterial structures creates hybrid metamolecules with new opportunities. Here we report on the magnetic control of a metamolecule resonance, by utilizing the interaction between a single split ring resonator (SRR) and a magnetic thin film of permalloy. To suppress eddy current shielding, the permalloy films are patterned into arrays of 30–500 ?m diameter discs. Strong hybridized resonances were observed at the anticrossing between the split ring resonance and the ferromagnetic resonance (FMR) of the permalloy. In particular, it is possible to achieve 40 dB modulation of the electric (symmetric) mode of the SRR on sweeping the applied magnetic field through the SRR/FMR anticrossing. The results open the way to the design of planar metamaterials, with potential applications in nonlinear metamaterials, tunable metamaterials and spintronics.

Gregory, Simon A.; Stenning, Gavin B. G.; Bowden, Graham J.; Zheludev, Nikolay I.; de Groot, Peter A. J.

2014-06-01

303

Self-sensing magnetic levitation using a LC resonant circuit  

Microsoft Academic Search

A self-sensing magnetic levitation system utilizing a LC resonant circuit is proposed by using the characteristic that the inductance of the magnetic system is varied with respect to the air gap displacement. An external capacitor is added into the electric system to make the levitation system statically stable, which much relieves the control effort required to stabilize the magnetic levitation

Changhwan Choi

1999-01-01

304

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

NASA Astrophysics Data System (ADS)

A half-century quest for improving resolution in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) has enabled the study of molecular structures, biological interactions, and fine details of anatomy. This progress largely relied on the advent of sophisticated superconducting magnets that can provide stable and homogeneous fields with temporal and spatial variations below ?B0/B0<0.01ppm. In many cases however, inherent properties of the objects under investigation, pulsating arteries, breathing lungs, tissue-air interfaces, surgical implants, etc., lead to fluctuations and losses of local homogeneity. A new method dubbed “long-lived-coherence correlation spectroscopy” (LLC-COSY) opens the way to overcome both inhomogeneous and homogeneous broadening, which arise from local variations in static fields and fluctuating dipole-dipole interactions, respectively. LLC-COSY makes it possible to obtain ultrahigh resolution two-dimensional spectra, with linewidths on the order of ??=0.1 to 1 Hz, even in very inhomogeneous fields (?B0/B0>10ppm or 5000 Hz at 9.7 T), and can improve resolution by a factor up to 9 when the homogeneous linewidths are determined by dipole-dipole interactions. The resulting LLC-COSY spectra display chemical shift differences and scalar couplings in two orthogonal dimensions, like in “J spectroscopy.” LLC-COSY does not require any sophisticated gradient switching or frequency-modulated pulses. Applications to in-cell NMR and to magnetic resonance spectroscopy (MRS) of selected volume elements in MRI appear promising, particularly when susceptibility variations tend to preclude high resolution.

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

2012-07-01

305

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

PubMed Central

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

Bresch, Erik; Narayanan, Shrikanth

2010-01-01

306

Magnetic resonance imaging of penile cancer.  

PubMed

Penile cancer is a rare neoplasm that, although rare in the developed world, has devastating physical and psychological consequences for the patient. Novel MR imaging techniques such as lymphotropic nanoparticle-enhanced MR imaging may help identify metastatic lymph node disease. This article reviews the normal penile anatomy and MR imaging techniques and features of primary and metastatic penile cancer. Recent advances in penile cancer imaging are discussed. PMID:24792677

Gupta, Sumit; Rajesh, Arumugam

2014-05-01

307

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.

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

2011-01-01

308

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

309

Pancoast Tumor: The Role of Magnetic Resonance Imaging  

PubMed Central

We report imaging techniques in the definition of the therapeutic planning of a 65-year-old man with a diagnosis of Pancoast tumor. Computed Tomography has a pivotal role in the assessment of nodes involvement and distant metastasis. Magnetic Resonance allows a detailed study of locoregional extension for its high soft tissue resolution. We particularly highlight the actual importance of Magnetic Resonance Neurography, Diffusion-Weighted Imaging, and Magnetic Resonance Angiography techniques in the assessment of the superior sulcus vascular and nervous structures involvement. Their integrity has been showed in our patient with a complete surgical excision of the lesion.

Manenti, Guglielmo; Raguso, Mario; D'Onofrio, Silvia; Altobelli, Simone; Scarano, Angela Lia; Vasili, Erald; Simonetti, Giovanni

2013-01-01

310

Nuclear magnetic resonance spectrometric assay of beta-lactamase.  

PubMed Central

Beta-Lactam antibiotics and the crude enzyme were mixed in deuterium oxide and placed in a nuclear magnetic resonance tube. The change of the nuclear magnetic resonance spectrum during the enzymatic reaction was then analyzed to determine beta-lactamase activity. By using beta-lactam antibiotics such as penicillins, cephalosporins, and cephamycins as substrates, a comparison of the beta-lactamase activities was made between the nuclear magnetic resonance spectrometric assay and the iodometric assay. There was a close correlation between these two methods.

Kono, M; O'Hara, K; Shiomi, Y

1980-01-01

311

Resonant microwave cavity for 8.5-12 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

We present a newly developed microwave resonant cavity for use in optically detected 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 between 8.5 and 12 GHz. The cavity uses cylinders of high dielectric material, so-called ``dielectric resonators,'' in a double-stacked configuration to determine the resonant frequency. Wires in a pseudo-Helmholtz configuration are incorporated into the cavity to provide frequencies for simultaneous nuclear magnetic resonance (NMR). The system was tested by measuring cavity absorption as microwave frequencies were swept, by performing ODMR on a zinc-doped InP sample, and by performing optically detected NMR on a GaAs sample. The results confirm the suitability of the cavity for ODMR with simultaneous NMR.

Colton, J. S.; Wienkes, L. R.

2009-03-01

312

The Role of Cardiovascular Magnetic Resonance in Pediatric Congenital Heart Disease  

PubMed Central

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

2011-01-01

313

[High resolution 3T magnetic resonance neurography of the peroneal nerve].  

PubMed

Peroneal neuropathy is the most common mononeuropathy of the lower limbs. The causes of peroneal neuropathy include trauma, tumors of the nerve and nerve sheath, entrapment, and others like perineurioma, fibromatosis, lymphoma, and intraneural and externeural ganglia. The diagnosis is based on clinical manifestations and electrophysiological studies. Nowadays, however, magnetic resonance (MR) neurography is a complementary diagnostic technique that can help determine the location and cause of peroneal neuropathy. In this article, we describe the MR anatomy of the peroneal nerve, its relations, and the muscles it innervates. We also discuss the clinical and electrophysiological manifestations of peroneal neuropathy, describe the technical parameters used at our institution, and illustrate the MR appearance of various diseases that involve the peroneal nerve. PMID:24508057

Pineda, D; Barroso, F; Cháves, H; Cejas, C

2014-01-01

314

Anatomic magnetic resonance imaging studies of attention-deficit/hyperactivity disorder  

PubMed Central

Neuroimaging techniques are increasingly being applied to the study of attention-deficit/hyperactivity disorder (ADHD). This review focuses on magnetic resonance imaging studies of the brain anatomy of ADHD. Such studies were first conducted over a decade ago, and most focus on frontal-striatal regions and tend to find smaller volumes in ADHD children than in controls. Recently published analyses with the largest sample so far of patients and controls found that ADHD is associated with a statistically significant 3% to 4% global reduction in brain volume in both boys and girls, with abnormally small caudate nuclei only being found in younger patients. After adjusting for global brain differences, only cerebellar hemispheric volumes remained significantly smaller in ADHD, and these differences continued throughout childhood and adolescence. Pathophysiological models of ADHD need take into account cerebellar dysfunction, as well as prefrontal-striatal dysregulation.

Castellanos, Francisco Xavier

2002-01-01

315

Evaluation of magnetic resonance imaging in the diagnosis of osteomyelitis in diabetic foot infections.  

PubMed

To assess the role of magnetic resonance imaging (MRI) in diagnosing osteomyelitis in diabetic foot infections, 47 diabetic patients with clinical suspicion of osteomyelitis, nonhealing foot ulcer, or soft tissue infection of the foot were examined prospectively by MRI and plain radiographs. Pathological confirmation of diagnosis was obtained in 62 bones from 32 patients. In addition, 14 patients with pathological confirmation of diagnosis underwent technetium-99 MDP triple-phase bone and gallium-67 citrate scans. MRI was significantly more sensitive and accurate (P < .01), with equal specificity in comparison to plain radiographs and technetium and gallium scans. MRI also provided a more detailed and accurate depiction of the anatomy. At early clinical follow-up, complete resection of abnormal bone on an MRI scan correlated with clinical healing. In summary, MRI is indicated when plain radiographs are negative for osteomyelitis or when the extent and accurate depiction of the infective process will facilitate surgical planning. PMID:8425726

Weinstein, D; Wang, A; Chambers, R; Stewart, C A; Motz, H A

1993-01-01

316

Multifrequency inversion in magnetic resonance elastography.  

PubMed

Time-harmonic shear wave elastography is capable of measuring viscoelastic parameters in living tissue. However, finite tissue boundaries and waveguide effects give rise to wave interferences which are not accounted for by standard elasticity reconstruction methods. Furthermore, the viscoelasticity of tissue causes dispersion of the complex shear modulus, rendering the recovered moduli frequency dependent. Therefore, we here propose the use of multifrequency wave data from magnetic resonance elastography (MRE) for solving the inverse problem of viscoelasticity reconstruction by an algebraic least-squares solution based on the springpot model. Advantages of the method are twofold: (i) amplitude nulls appearing in single-frequency standing wave patterns are mitigated and (ii) the dispersion of storage and loss modulus with drive frequency is taken into account by the inversion procedure, thereby avoiding subsequent model fitting. As a result, multifrequency inversion produces fewer artifacts in the viscoelastic parameter map than standard single-frequency parameter recovery and may thus support image-based viscoelasticity measurement. The feasibility of the method is demonstrated by simulated wave data and MRE experiments on a phantom and in vivo human brain. Implemented as a clinical method, multifrequency inversion may improve the diagnostic value of time-harmonic MRE in a large variety of applications. PMID:22460134

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

2012-04-21

317

Automated lung segmentation in magnetic resonance images  

NASA Astrophysics Data System (ADS)

Segmentation of the lungs within magnetic resonance (MR) scans is a necessary preprocessing step in the computerized analysis of thoracic MR images. This task is complicated by potentially significant cardiac and pulmonary motion artifacts, partial volume effect, and morphological deformation from disease. We have developed an automated segmentation method to account for these complications. First, the thorax is segmented using a threshold obtained from analysis of the cumulative gray-level histogram constructed along a diagonal line through the center of the image. Next two separate lung-thresholded images are created. The first lung-thresholded image is created using histogram-based gray-level thresholding techniques applied to the segmented thorax. To include lung areas that may be adversely affected by artifact or disease, a second lung-thresholded image is created by applying a grayscale erosion operator to the first lung-thresholded image. After a rolling ball filter is applied to the lung contour to eliminate non-lung pixels from the thresholded lung regions, a logical OR operation is used to combine the two lung-thresholded images into the final segmented lung regions. Modifications to this approach were required to properly segment sections in the lung bases. In a preliminary evaluation, the automated method was applied to 10 MR scans, an observer evaluated the segmented lung regions using a five-point scale ("highly accurate segmentation" to "highly inaccurate segmentation"). Eighty-five percent of the segmented lung regions were rated as highly or moderately accurate.

Sensakovic, William F.; Armato, Samuel G., III; Starkey, Adam

2005-04-01

318

Nuclear magnetic resonance studies of biological molecules  

SciTech Connect

A number of biological systems are investigated using a variety of nuclear magnetic resonance (NMR) techniques. The first two studies are applications of the technique to systems in solution. Proton NMR and lanthanide shift agents are used to determine the outside to inside ratio of lipids in large unilamellar vesicles produced by the method of reverse-phase evaporation. The observed ratio of 1.1 is indicative of the unilamellar nature of the vesicles. In order to facilitate the study of motions of the carbohydrate moiety of glycoproteins, a method of enzymatically attaching a carbon-13 (/sup 13/C) enriched galactopyranose onto the nonreducing end of the carbohydrate chain has been developed. The overall reaction is followed using /sup 31/P and /sup 13/C NMR relaxation parameters permits the modeling of motions characteristic of the attached galactose residue. The third study is an application of the technique to live animals. Non-invasive, real time observation of changes in brain energy phosphates in young, middle age and old rats taken into and recovered from mild hypoxic stress has been accomplished in vivo with phosphorus-31 NMR. Age related changes in brain oxidative metabolism apparently are manifest significantly only under physiological or pharmacological stress. Each age group displayed somewhat different patterns of phosphate metabolite alterations during the time course of the hypoxic episode and subsequent recovery.

Perry, C.

1985-01-01

319

Scatter-based magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

Elasticity is a sensitive measure of the microstructural constitution of soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows in vivo measurement of the shear elasticity of brain tissue. However, the spatial resolution of MRE is inherently limited as the transformation of shear wave patterns into elasticity maps requires the solution of inverse problems. Therefore, an MRE method is introduced that avoids inversion and instead exploits shear wave scattering at elastic interfaces between anatomical regions of different shear compliance. This compliance-weighted imaging (CWI) method can be used to evaluate the mechanical consistency of cerebral lesions or to measure relative stiffness differences between anatomical subregions of the brain. It is demonstrated that CWI-MRE is sensitive enough to reveal significant elasticity variations within inner brain parenchyma: the caudate nucleus (head) was stiffer than the lentiform nucleus and the thalamus by factors of 1.3 ± 0.1 and 1.7 ± 0.2, respectively (P < 0.001). CWI-MRE provides a unique method for characterizing brain tissue by identifying local stiffness variations.

Papazoglou, Sebastian; Xu, Chao; Hamhaber, Uwe; Siebert, Eberhard; Bohner, Georg; Klingebiel, Randolf; Braun, Jürgen; Sack, Ingolf

2009-04-01

320

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

321

Magnetic resonance elastography of skeletal muscle.  

PubMed

While the contractile properties of skeletal muscle have been studied extensively, relatively little is known about the elastic properties of muscle in vivo. Magnetic resonance elastography (MRE) is a phase contrast-based method for observing shear waves propagating in a material to determine its stiffness. In this work, MRE is applied to skeletal muscle under load to quantify the change in stiffness with loading. A mathematical model of muscle is developed that predicts a linear relationship between shear stiffness and muscle load. The MRE technique was applied to bovine muscle specimens (N = 10) and human biceps brachii in vivo (N = 5). Muscle stiffness increased linearly for both passive tension (14.5 +/- 1.77 kPa/kg) and active tension, in which the increase in stiffness was dependent upon muscle size, as predicted by the model. A means of noninvasively assessing the viscoelastic pro-perties of skeletal muscle in vivo may provide a useful method for studying muscle biomechanics in health and disease. PMID:11169834

Dresner, M A; Rose, G H; Rossman, P J; Muthupillai, R; Manduca, A; Ehman, R L

2001-02-01

322

Vibration safety limits for magnetic resonance elastography  

PubMed Central

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

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

2010-01-01

323

Small animal imaging with magnetic resonance microscopy.  

PubMed

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 noninvasive biomedical investigations. MRM now increasingly provides functional information about living animals, with images of the beating heart, breathing lung, and functioning brain. Unlike clinical MRI, where the focus is on diagnosis, MRM is used to reveal fundamental biology or to noninvasively measure subtle changes in the structure or function of organs during disease progression or in response to experimental therapies. High-resolution anatomical imaging reveals increasingly exquisite detail in healthy animals and subtle architectural aberrations that occur in genetically altered models. Resolution of 100 mum in all dimensions is now routinely attained in living animals, and (10 mum)(3) is feasible in fixed specimens. Such images almost rival conventional histology while allowing the object to be viewed interactively in any plane. In this review we describe 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 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, and brain-and the emerging field of MR histology. 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

2008-01-01

324

Nuclear magnetic resonance methods for metabolic fluxomics.  

PubMed

Fluxomics, through its core methodology of metabolic flux analysis (MFA), enables quantification of carbon traffic through cellular biochemical pathways. Isotope labeling experiments aid MFA by providing information on intracellular fluxes, especially through parallel and cyclic pathways. Nuclear magnetic resonance (NMR) and mass spectrometry (MS) are two complementary methods to measure abundances of isotopomers generated in these experiments. 2-D [(13)C, (1)H] heteronuclear correlation NMR spectra can detect (13)C isotopes coupled to protons and thus noninvasively separate molecules and atoms with a specific isotopic content from a mixture of molecular species. Furthermore, the fine structures of the peaks in these spectra can reveal scalar couplings between chemically bonded carbon atoms in the sample, from which isotopomer abundances can be quantified. This chapter introduces methods for NMR sample preparation and spectral acquisition of 2-D [(13)C, (1)H] correlation maps, followed by a detailed presentation of methods to process the spectra and quantify isotopomer abundances. We explain the use of the software NMRViewJ for spectral visualization and processing, as well as MATLAB scripts developed by us for peak extraction, deconvolution of overlapping peaklets, and isotopomer abundance quantification. Finally, we discuss the applications of NMR-derived isotopomer data toward quantitatively understanding metabolic pathways. PMID:23417811

Nargund, Shilpa; Joffe, Max E; Tran, Dennis; Tugarinov, Vitali; Sriram, Ganesh

2013-01-01

325

Multifrequency inversion in magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

326

Moderne Entwicklung der NMR (Nuclear Magnetic Resonance)  

NASA Astrophysics Data System (ADS)

Die NMR-Spektroskopie kann sich altersmäßig nicht mit den Annalen der Physik messen; sie entstand vor rd. 45 Jahren. Ihre Entwicklung wurde und wird durch unterschiedliche Erfahrungen, Erkenntnisse und Techniken bestimmt; sie zeigt, daß auch heute noch die Fortschritte von Spezialgebieten Impulse aus weiten Bereichen der Physik, der Naturwissenschaften und Technik beziehen. In entsprechender Weise machen Spezialzeitschriften das Erscheinen allgemeiner Fachzeitschriften nicht überflüssig. Diese Zusammenhänge sollen an einigen Beispielen der NMR demonstriert werden.Translated AbstractModern Development of NMR (Nuclear Magnetic Resonance)The age of NMR-spectroscopy is not comparable with that of the Annalen der Physik; NMR was established only about 45 years ago. Its development was promoted by different experience, knowledge and techniques; it shows that also in these days the progress of a special topic depends on stimulations by other parts of physics, of natural and technical science. In an analogous way general scientific journals are not made superfluous by the existence of special papers. These relations are demonstrated with some examples in NMR.

Lösche, Artur

327

Compression-sensitive magnetic resonance elastography  

NASA Astrophysics Data System (ADS)

Magnetic resonance elastography (MRE) quantifies the shear modulus of biological tissue to detect disease. Complementary to the shear elastic properties of tissue, the compression modulus may be a clinically useful biomarker because it is sensitive to tissue pressure and poromechanical interactions. In this work, we analyze the capability of MRE to measure volumetric strain and the dynamic bulk modulus (P-wave modulus) at a harmonic drive frequency commonly used in shear-wave-based MRE. Gel phantoms with various densities were created by introducing CO2-filled cavities to establish a compressible effective medium. The dependence of the effective medium's bulk modulus on phantom density was investigated via static compression tests, which confirmed theoretical predictions. The P-wave modulus of three compressible phantoms was calculated from volumetric strain measured by 3D wave-field MRE at 50 Hz drive frequency. The results demonstrate the MRE-derived volumetric strain and P-wave modulus to be sensitive to the compression properties of effective media. Since the reconstruction of the P-wave modulus requires third-order derivatives, noise remains critical, and P-wave moduli are systematically underestimated. Focusing on relative changes in the effective bulk modulus of tissue, compression-sensitive MRE may be useful for the noninvasive detection of diseases involving pathological pressure alterations such as hepatic hypertension or hydrocephalus.

Hirsch, Sebastian; Beyer, Frauke; Guo, Jing; Papazoglou, Sebastian; Tzschaetzsch, Heiko; Braun, Juergen; Sack, Ingolf

2013-08-01

328

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.

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

2009-01-01

329

Brain magnetic resonance in hepatic encephalopathy.  

PubMed

The term hepatic encephalopathy (HE) covers a wide spectrum of neuropsychiatric abnormalities caused by portal-systemic shunting. The diagnosis requires demonstration of liver dysfunction or portal-systemic shunts and exclusion of other neurologic disorders. Most patients with this condition have liver dysfunction caused by cirrhosis, but it also occurs in patients with acute liver failure and less commonly, in patients with portal-systemic shunts that are not associated with hepatocellular disease. Various magnetic resonance (MR) techniques have improved our knowledge about the pathophysiology of HE. Proton MR spectroscopy and T1-weighted imaging can detect and quantify accumulations of brain products that are normally metabolized or eliminated such as glutamine and manganese. Other MR techniques such as T2-weighted and diffusion-weighted imaging can identify white matter abnormalities resulting from disturbances in cell volume homeostasis secondary to brain hyperammonemia. Partial or complete recovery of these abnormalities has been observed with normalization of liver function or after successful liver transplantation. MR studies have undoubtedly improved our understanding of the mechanisms involved in the pathogenesis of HE, and some findings can be considered biomarkers for monitoring the effects of therapeutic measures focused on correcting this condition. PMID:24745889

Alonso, Juli; Córdoba, Juan; Rovira, Alex

2014-04-01

330

Magnetic resonance imaging of feline hippocampal necrosis.  

PubMed

The clinical, neuropathologic, and magnetic resonance (MR) imaging features in four cats with necrosis of the hippocampus and piriform lobe are described. All cats had acute generalized seizures and behavioral changes including aggression, salivation, polyphagia, and disorientation. Routine hematologic, serum chemistry, and cerebrospinal fluid analyses were normal. MR imaging abnormalities were restricted to the area of the hippocampus and piriform lobe. The lesions were T2-hyperintense, T1-hypointense, and were characterized by various degrees of contrast enhancement. Lesions were consistent with necrotizing encephalitis. Two cats were euthanized and underwent postmortem examination within a week after MR imaging due to the lack of response to antiepileptic drug therapy and progressive encephalopathy [corrected] The remaining two cats lived for about four months and were then euthanized because of persistent behavioral and neurologic signs; only one of these cats underwent postmortem examination with histopathologic examination. Histopathological findings were typical of severe, diffuse, bilateral symmetric necrosis, and degeneration of neurons in the hippocampus and piriform lobe, but an etiologic agent was not apparent. This apparently unique feline syndrome, now reported in Switzerland and Italy, has no known cause at this time. PMID:18720764

Schmied, Oliver; Scharf, Gernot; Hilbe, Monika; Michal, Ulrike; Tomsa, Kamil; Steffen, Frank

2008-01-01

331

Magnetic resonance force microscopy with a permanent magnet on the cantilever  

SciTech Connect

The magnetic resonance force microscope (MRFM) is a microscopic 3-D imaging instrument based on a recent proposal to detect magnetic resonance signals mechanically using a micro-mechanical resonator. MRFM has been successfully demonstrated in various magnetic resonance experiments including electron spin resonance, ferromagnetic resonances and nuclear magnetic resonance. In order to apply this ultra-high, 3-D spatial resolution technique to samples of arbitrary size and shape, the magnetic particle which generates the field gradient {del}{bold B}, (and, therefore, the force {bold F = (m {center_dot} {del}B)} between itself and the spin magnetization {bold m} of the sample) will need to be mounted on the mechanical resonator. Up to the present, all experiments have been performed with the sample mounted on the resonator. This is done, in part, to avoid the spurious response of the mechanical resonator which is generated by the variation of the magnetization of the magnetic particle as the external field is varied.

Zhang, Z.; Hammel, P.C.

1997-02-01

332

Sensitive magnetic force detection with a carbon nanotube resonator  

NASA Astrophysics Data System (ADS)

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; Haapamaki, Chris; Baugh, Jonathan

2014-03-01

333

Cardiac magnetic resonance imaging of a patient with an magnetic resonance imaging conditional permanent pacemaker  

PubMed Central

Cardiac magnetic resonance imaging (MRI) is increasingly used as the optimum modality for cardiac imaging. An aging population and rising numbers of patients with permanent pacemakers means many such individuals may require cardiac MRI scanning in the future. Whilst the presence of a permanent pacemaker is historically regarded as a contra-indication to MRI scanning, pacemaker systems have been developed to limit any associated risks. No reports have been published regarding the use of such devices with cardiac MRI in a clinical setting. We present the safe, successful cardiac MRI scan of a patient with an MRI-conditional permanent pacing system.

Hogarth, Andrew J.; Artis, Nigel J.; Sivananthan, U. Mohan; Pepper, Chris B.

2011-01-01

334

Paraganglioma Anatomy  

MedlinePLUS

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

335

Eye Anatomy  

MedlinePLUS

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

336

Element Selective X-ray Detected Magnetic Resonance  

SciTech Connect

Element selective X-ray Detected Magnetic Resonance (XDMR) was measured on exciting the Fe K-edge in a high quality YIG thin film. Resonant pumping at high microwave power was achieved in the nonlinear foldover regime and X-ray Magnetic Circular Dichroism (XMCD) was used to probe the time-invariant change of the magnetization {delta}Mz due to the precession of orbital magnetization densities of states (DOS) at the Fe sites. This challenging experiment required us to design a specific instrumentation which is briefly described.

Goulon, J.; Rogalev, A.; Wilhelm, F.; Jaouen, N.; Goulon-Ginet, C.; Goujon, G. [European Synchrotron Radiation Facility (ESRF), B.P. 220, 38043 Grenoble Cedex (France); Youssef, J. Ben; Indenbom, M. V. [Laboratoire de Magnetisme de Bretagne, CNRS FRE 2697, UFR Sciences et Techniques, 29328 Brest Cedex 03 (France)

2007-01-19

337

Magnetic Resonance Studies of the Structure of Glasses.  

National Technical Information Service (NTIS)

Nuclear magnetic resonance techniques have been used to study atomic arrangements and chemical bonds in glasses. The principal results are as follows: (1) NMR distinguishes between BO3 and BO4, configurations; quantitative measures of each configuration i...

P. J. Bray

1970-01-01

338

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

339

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

340

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

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

2014-04-01

341

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2011 CFR

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

2011-04-01

342

Nuclear Magnetic Double Resonance Using Weak Perturbing RF Fields  

ERIC Educational Resources Information Center

Describes a nuclear magnetic resonance experimental example of spin tickling; also discusses a direct approach for verifying the relative signs of coupling constants in three-spin cyclopropyl systems. (SL)

Reynolds, G. Fredric

1977-01-01

343

Nuclear magnetic resonance data of C36H80BN  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

344

Nuclear magnetic resonance data of C30H22OSe  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

345

Nuclear magnetic resonance data of C30H68BN  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

346

Nuclear magnetic resonance data of C30H50Si  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

347

Nuclear magnetic resonance data of C30H25Sb  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

348

Nuclear magnetic resonance data of C35H35As  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

349

Nuclear magnetic resonance data of C35H35Sb  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

350

Nuclear magnetic resonance data of C30H25As  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

351

Nuclear magnetic resonance data of C30H22SSe  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

352

Nuclear magnetic resonance data of CF2Se  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

353

Nuclear magnetic resonance data of CF3NSe  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

354

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.

355

Nuclear magnetic resonance data of C28 H56  

NASA Astrophysics Data System (ADS)

This document is part of Part 1 `Aliphatic Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Kalinowski, H.-O.; Kumar, M.; Gupta, V.; Gupta, R.

356

Nuclear magnetic resonance tomography with a toroid cavity detector.  

National Technical Information Service (NTIS)

A new type of nuclear magnetic resonance (NMR) tomography has been developed at Argonne National Laboratory. The method uses the strong radio frequency field gradient within a cylindrical toroid cavity to provide high-resolution NMR spectral information w...

K. Woelk J. W. Rathke R. J. Klingler

1995-01-01

357

Prediction of Chemotherapy Response by Magnetic Resonance Spectroscopy.  

National Technical Information Service (NTIS)

This research seeks to validate the use of MRS to assess therapeutic response in patients with locally-advanced breast cancer receiving primary Systemic therapy (PST), or neoadjuvant chemotherapy. 35 women were enrolled in this study. Magnetic resonance s...

M. Garwood

2004-01-01

358

Magnetic resonance imaging of cavernous sinus cavernous hemangiomas  

Microsoft Academic Search

Radiological findings of surgically verified cavernous hemangiomas of the cavernous sinus are presented with special reference to the appearance in magnetic resonance imaging. Differences in radiological features of the cavernous sinus cavernous hemangiomas and intracerebral cavernous hemangiomas are discussed.

Y. Katayama; T. Tsubokawa; S. Miyazaki; K. Yoshida; K. Himi

1991-01-01

359

Organic Pollutants in Soils, as Studied by Nuclear Magnetic Resonance.  

National Technical Information Service (NTIS)

This three-year project focussed on the development and application of state-of-the art NMR (nuclear magnetic resonance) techniques to elucidate the fundamental behaviors of certain organic pollutants (e.g., benzene, CCl, trichloroethylene, ethylene glyco...

G. E. Maciel W. L. Lindsay

1998-01-01

360

21 CFR 892.1000 - Magnetic resonance diagnostic device.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

361

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

362

Evaluation of adult congenital heart disease by cardiac magnetic resonance imaging.  

PubMed

Cardiovascular magnetic resonance (CMR) imaging plays an essential role in the evaluation and follow-up of adult congenital heart disease (ACHD), providing safe, high-resolution imaging of some of the most complex anatomies encountered. Unlimited by acoustic windows and capable of tissue characterization, CMR is devoid of ionizing radiation and provides superior three-dimensional spatial resolution to transthoracic echocardiography and superior temporal resolution to computed tomography, making it the gold standard for various cardiac and great vessel imaging indications in ACHD. In this state-of-the art review, we provide an overview of CMR examination methods and detail the various approaches and classical findings in the more common forms of ACHD. Although this review touches upon technical aspects of CMR imaging in ACHD, it is primarily geared toward the adult congenital caregiver (i.e., clinical, interventional, or surgical), highlighting relevant practical considerations. To enhance the clinical utility of this review, numerous examples with intraoperative correlates are provided to highlight our imaging approaches for various defects. As CMR image acquisition may be time consuming and requires patient collaboration (e.g., intermittent breath holding), a systemic approach is required to maximize efficiency. A thorough knowledge of ACHD anatomy and natural history is essential in maximizing image interpretation. Proficient scanning is further enabled by clearly outlined study objectives with prior documentation of interventional and surgical procedures, where applicable. PMID:19664024

Marcotte, François; Poirier, Nancy; Pressacco, Josephine; Paquet, Eléonore; Mercier, Lise-Andrée; Dore, Annie; Ibrahim, Reda; Khairy, Paul

2009-01-01

363

Magnetic field induced properties of type II superconducting microstrip resonators  

NASA Astrophysics Data System (ADS)

The vortex effects of high temperature superconducting (HTS) microstrip resonators have been studied using the theoretical approach developed by Coffey and Clem (CC). A rectangular HTS strip resonator printed on sapphire substrate and subjected to a static magnetic field is considered, where the HTS strip is in the mixed state. An impedance type Green’s function is derived which connects the strip current to the electric field around the resonator, in the Fourier transformed domain. Galerkin’s procedure is used in the spectral domain to determine the resonant frequency and the unloaded Q value, both of which are computed for different applied fields, reduced temperatures and superconducting strip thicknesses. The results reveal considerable influence of applied field on resonant frequency and quality factor due to vortex motion, which should be considered when designing resonators which operate under external magnetic field.

Andrews, Jolly; Mathew, Vincent

2012-02-01

364

Anomalous magnetic field effects in high Q superconducting resonators  

NASA Astrophysics Data System (ADS)

Superconducting coplanar wave guide resonators are an important tool in quantum computing for use as memory elements. Recent process improvements have allowed for quality factors in excess of 1.5 million at single photon excitations. While allowing for more sensitive experiments, the most recent group of resonators exhibit very high sensitivity to magnetic fields. Ordinarily Abrikosov vortex physics is expected to govern the magnetic response of the resonators. During field cooling, vortices begin to form at a threshold field, Bth, that depends quadratically on the width of the resonator. However these resonators show an observed Bth two orders of magnitude lower than predicted by theory and without any scaling with resonator width. We explore increased sensitivity to frequency fluctuations at nonzero field as a possible explanation for reduced quality factor long before vortices are expected to form.

Lenander, M.; Barends, R.; Chen, Yu; Kelly, J.; Lucero, Erik; Mariantoni, Matteo; Megrant, A.; O'Malley, P. J. J.; Neill, C.; Sank, D.; Vainsencher, A.; Wang, H.; Wenner, J.; White, T. C.; Yin, Y.; Zhao, J.; Palmstrom, C.; Cleland, A. N.; Martinis, John M.

2012-02-01

365

Assessment of coronary artery stenosis by magnetic resonance imaging.  

PubMed Central

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

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

1996-01-01

366

Magnetic resonance-compatible-spirometry: principle, technical evaluation and application  

Microsoft Academic Search

The aim of this study was to assess the feasibility and accuracy of a novel magnetic resonance-compatible (MRc)-spirometer. The influence of body posture, magnetic resonance (MR)-setting and image acquisition on lung function was evaluated. Dynamic MR imaging (dMRI) was compared with simultaneously measured lung function. The development of the MRc-spirometer was based on a commercial spirometer and evaluated by flow-generator

M. Eichinger; M. Puderbach; H. J. Smith; R. Tetzlaff; A. Kopp-Schneider; M. Bock; J. Biederer; H. U. Kauczor

2007-01-01

367

Plasma currents induced by resonant magnetic field perturbations in tokamaks  

SciTech Connect

The plasma response on externally applied resonant magnetic field perturbations is studied by means of numerical simulations. It is shown that dependent on collisionality and perturbation strength, plasma currents build up which can compensate the external field. These plasma currents are accompanied by out-of-phase currents and poloidal flows at the resonant surfaces. With an increasing perturbation field the screening of the externally applied field decreases and at a certain level, the vacuum field approximation holds for the total magnetic field.

Reiser, D. [EURATOM Association, Institut fuer Energieforschung-Plasmaphysik, Forschungszentrum Juelich GmbH, Trilateral Euregio Cluster, D-52425 Juelich (Germany); Chandra, D. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

2009-04-15

368

Functional magnetic resonance imaging: Clinical applications and potential  

Microsoft Academic Search

Demonstration that contrast in magnetic resonance images can be generated based on differences in blood oxygenation has led\\u000a to an explosion of interest in so-called functional magnetic resonance imaging (FMRI). FMRI can be used to map increases in\\u000a blood flow that accompany local synaptic activity in the brain. The technique has proved remarkably sensitive and has been\\u000a used to map

P. M. Matthews; S. Clare; J. Adcock

1999-01-01

369

Detection of fungal wood decay using Magnetic Resonance Imaging  

Microsoft Academic Search

Fagus sylvatica   L.) infected with the brown rot fungus Coniophora puteana (Schum.) Karst was examined 12 and 26 days after incubation using magnetic resonance imaging. We were able to detect areas\\u000a containing free water attributed to fungal activity 12 days after incubation. Magnetic resonance imaging was found to be a\\u000a useful tool for determining early stages of fungal decay in

Ulrich Müller; Roland Bammer; Erhard Halmschlager; Rudolf Stollberger; Rupert Wimmer

2001-01-01

370

Magnetic Resonance Imaging of Adhesive Capsulitis: Correlation with Clinical Staging  

Microsoft Academic Search

The purpose of this study was to evaluate non-contrast magnetic resonance imaging (MRI) findings of adhesive capsulitis and\\u000a correlate them with clinical stages of adhesive capsulitis. This will hopefully define a role for shoulder MR imaging in the\\u000a diagnosis of adhesive capsulitis as well as in potentially directing appropriate treatment. Forty-seven consecutive non-contrast\\u000a magnetic resonance imaging examinations of 46 patients

Carolyn M. Sofka; Gina A. Ciavarra; Jo A. Hannafin; Frank A. Cordasco; Hollis G. Potter

2008-01-01

371

Cardiac Sarcoidosis Detected by Delayed-Hyperenhancement Magnetic Resonance Imaging  

PubMed Central

We report the case of a patient with sarcoidosis and ventricular tachycardia in whom cardiac magnetic resonance imaging provided supportive evidence of cardiac involvement by delineating regions of myocardial inflammation and fibrosis inconsistent with ischemic injury. The identification of cardiac involvement in patients with sarcoidosis is problematic, and the true incidence is unknown. Cardiac magnetic resonance imaging may help establish the actual incidence of cardiac involvement and allow further advances in monitoring and treatment options.

Nemeth, Margit A.; Muthupillai, Raja; Wilson, James M.; Awasthi, Mukta; Flamm, Scott D.

2004-01-01

372

Cardiac sarcoidosis detected by delayed-hyperenhancement magnetic resonance imaging.  

PubMed

We report the case of a patient with sarcoidosis and ventricular tachycardia in whom cardiac magnetic resonance imaging provided supportive evidence of cardiac involvement by delineating regions of myocardial inflammation and fibrosis inconsistent with ischemic injury. The identification of cardiac involvement in patients with sarcoidosis is problematic, and the true incidence is unknown. Cardiac magnetic resonance imaging may help establish the actual incidence of cardiac involvement and allow further advances in monitoring and treatment options. PMID:15061637

Nemeth, Margit A; Muthupillai, Raja; Wilson, James M; Awasthi, Mukta; Flamm, Scott D

2004-01-01

373

Magnetic resonance assessment of acute and chronic stroke  

Microsoft Academic Search

This article describes the important role of magnetic resonance imaging (MRI) in noninvasively assessing human focal ischemic stroke. Conventional MRI, diffusion-weighted and\\/or perfusion-weighted imaging have been used to facilitate both the qualitative and quantitative evaluation of heterogeneity of ischemic brain tissue. Further, by combining 2 or more magnetic resonance parameters, tissue-signature models have been developed that may be used as

K. M. A. Welch; Yue Cao; Vijaya Nagesh

2000-01-01

374

[Magnetic resonance cholangiopancreatography (MRCP) from a radiological and gastroenterological perspective].  

PubMed

Magnetic resonance imaging (MRI) in combination with magnetic resonance cholangiopancreatography (MRCP) is an integrated part in the diagnosis of bile-duct diseases and requires a standaridized complex examination technique. Radiologic and gastroenterologic indications are the diagnosis of anomalies, concrements, chronic inflammations and tumor diagnosis, especially of cholangiocarinoma such as Klatskin tumor and pancreatic cancer. MRCP is integrated in the preinterventional concept for performing invasive endoscopic retrograde cholangiopancreatography (ERCP) and for follow-up post intervention and for diagnosing complications. PMID:19401971

Vogl, T J; Zeuzem, S; Zangos, S; Hammerstingl, R

2009-05-01

375

Assessment of coronary artery stenosis by magnetic resonance imaging  

Microsoft Academic Search

OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient

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

1996-01-01

376

Computed tomography and magnetic resonance imaging of cerebral coenurosis.  

PubMed

A case of Coenurus cerebralis involving both cerebral hemispheres and the interpeduncular cistern is presented to illustrate the computed tomography (CT) and magnetic resonance imaging (MRI) features. In CT scans viable cysts appear as lucent lesions surrounded by a contrast-enhanced peripheral rim. By using multiple echo sequences the cyst content is characterized in magnetic resonance images by a cerebrospinal fluid-like intensity pattern. PMID:3576430

Pau, A; Turtas, S; Brambilla, M; Leoni, A; Rosa, M; Viale, G L

1987-06-01

377

Perfluoro-crown ethers in fluorine magnetic resonance spectroscopy  

SciTech Connect

This patent describes a method for obtaining a {sup 19}F-fluorine magnetic resonance spectrum from body cavities, organs or tissue by administering to a mammal a fluorine-containing agent in a diagnostically effective amount to provide a fluorine magnetic resonance spectrum from such cavities, organs or tissues, the improvement comprising using as the fluorine-containing agent an aqueous isotonic emulsion of perfluoro 15-crown-5 ether.

Schweighardt, F.K.; Rubertone, J.A.

1991-11-26

378

Magnetic Resonance Imaging of Neoplasms of the Pancreatobiliary System  

Microsoft Academic Search

Magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) are noninvasive imaging techniques\\u000a that can detect, characterize, and stage neoplasms of the biliary system and pancreas. In patients with suspected pancreatic\\u000a cancer, MRI\\/MRCP can help distinguish those patients who are unresectable from those who are potentially resectable. In patients\\u000a with pancreatic cysts, MRI assists in the distinction among pseudocysts, benign

Evan S. Siegelman; Wendy C. Hsu

379

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

380

Complementary role of magnetic resonance imaging after ultrasound examination in assessing fetal renal agenesis: a case report  

PubMed Central

Introduction Ultrasonography is used routinely during pregnancy to screen and detect fetal abnormalities. However, there are some conditions like anhydramnios (a prevalent state in renal agenesis) or maternal obesity that may limit the diagnostic accuracy of ultrasonography. Magnetic resonance imaging has proven to be useful when ultrasound alone is insufficient to make a correct diagnosis. Case presentation We present the case of a 22-year-old Caucasian woman who was admitted to our unit at the 26th week of gestation for a detailed anatomy scan. Anhydramnios and failure to visualize the kidneys, bladder and renal vessels were confirmed with the use of sonography in our department. Since the lack of amniotic fluid limited the acoustic window for fetal ultrasonography, a magnetic resonance imaging scan was requested to confirm suspected renal agenesis. A fetal magnetic resonance imaging scan was performed and confirmed the suspected diagnosis. A baby boy was born by breech vaginal delivery after spontaneous onset of labor at the 34th week of gestation. The boy weighed 1690g, with Apgar scores of 6 and 4 at two and five minutes respectively, and died one hour after delivery. The diagnosis of bilateral renal agenesis was confirmed on autopsy. Conclusions The aim of this study was to evaluate the potential contribution of magnetic resonance imaging in diagnostic procedure after inconclusive ultrasound examination during the assessment of fetal urinary tract abnormalities in the third trimester.

2014-01-01

381

Functional magnetic resonance imaging of the lung.  

PubMed

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

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

2014-02-01

382

Tools for cardiovascular magnetic resonance imaging.  

PubMed

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; Muthupillai, Raja

2014-04-01

383

PACS-based functional magnetic resonance imaging.  

PubMed

The picture archiving and communication system (PACS) technology reaches its 10th anniversary. Retrospectively no one could foresee the impact the PACS would have to the health care enterprise, but it is common consent today, that PACS is the key technology crucial to daily clinical image operations and especially to image related basic and clinical research. During the past 10 years the PACS has been matured from a research and developmental stage into commercial products which are provided by all major modality and health care equipment vendors. The PACS, originally implemented in the Radiology Department, needs to grow and has already carried well beyond departmental limits conquering all image relevant areas inside the hospital. During the past 10 years a dramatic development in imaging techniques especially within MRI emerged. Advanced 3D- and 4D-MR imaging techniques result in much more images and more complex data objects than ever before which need to be implemented into the existing PACS. These new imaging techniques require intensive post-processing apart from the imaging modality which need to be integrated into the image workflow and the PACS implementation. Along with these new imaging techniques new clinical applications, e.g. stroke detection, and research applications, e.g. study of heart and brain function, in Neurology and Cardiology require changes to the traditional PACS concept. Therefore inter-disciplinary image distribution will become the high-water mark for the next 10 years in the PACS endeavor. This paper focuses on one new advanced imaging technique, functional magnetic resonance imaging (fMRI), and discusses how fMRI data is defined, what fMRI requires in terms of clinical and research applications and how to implement fMRI in the existing PACS. PMID:12620313

Erberich, Stephan G

2003-01-01

384

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.

Krishnamurthy, Ramkumar; Cheong, Benjamin

2014-01-01

385

Use of magnetic resonance imaging in pharmacogenomics.  

PubMed

Because of the large variation in the response to psychoactive medication, many studies have attempted to uncover genetic factors that determine response. While considerable knowledge exists on the large effects of genetic polymorphisms on pharmacokinetics and plasma concentrations of drugs, effects of the concentration at the target site and pharmacodynamic effects on brain functions in disease are much less known. This article reviews the role of magnetic resonance imaging (MRI) to visualize response to medication in brain behaviour circuits in vivo in humans and assess the influence of pharmacogenetic factors. Two types of studies have been used to characterize effects of medication and genetic variation. In task-related activation studies the focus is on changes in the activity of a neural circuit associated with a specific psychological process. The second type of study investigates resting state perfusion. These studies provide an assessment of vascular changes associated with bioavailability of drugs in the brain, but may also assess changes in neural activity after binding of centrally active agents. Task-related pharmacogenetic studies of cognitive function have characterized the effects in the prefrontal cortex of genetic polymorphisms of dopamine receptors (DRD2), metabolic enzymes (COMT) and in the post-synaptic signalling cascade under the administration of dopamine agonists and antagonists. In contrast, pharmacogenetic imaging with resting state perfusion is still in its infancy. However, the quantitative nature of perfusion imaging, its non-invasive character and its repeatability might be crucial assets in visualizing the effects of medication in vivo in man during therapy. PMID:23802603

Viviani, Roberto; Lehmann, Marie-Louise; Stingl, Julia C

2014-04-01

386

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.

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

2007-01-01

387

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

388

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

389

MRI findings of acute turf toe. A case report and review of anatomy.  

PubMed

Normal anatomy of the metatarsophalangeal joint of the hallux has been well described. However, the pathologic anatomy of turf toe, a common injury among football and rugby players, has not been documented in detail. Magnetic resonance images (MRI) of a classic case of turf toe were examined and the findings were compared with MRI of a normal specimen and correlated with known features of gross anatomy. MRI findings confirmed that turf toe involves a sprain or tear of the plantar metatarsophalangeal joint capsule. PMID:8020216

Tewes, D P; Fischer, D A; Fritts, H M; Guanche, C A

1994-07-01

390

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

391

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

392

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

393

Spin Dynamics and Magnetic Resonance in Some Disordered Crystals  

Microsoft Academic Search

This thesis is a theoretical study of three problems involving impure and disordered crystals, which have been probed experimentally by magnetic resonance techniques. First we examine the local mode produced by a single substitutional Mn impurity (in practice, low enough concentration that the impurities act independently) in the uniaxial antiferromagnet FeF(,2). With increasing magnetic field the upgoing Zeeman branch of

Pradeep Thayamballi

1981-01-01

394

Study of Superconducting Hg by Nuclear Magnetic Resonance Techniques  

Microsoft Academic Search

Since nuclear magnetic resonance techniques can provide rather microscopic information about conduction electrons in metals, their application to the study of superconducting metals is of considerable interest. The difficulties associated with the failure of magnetic fields to penetrate inside superconductors can be overcome by the use of dense colloids consisting of particles mostly less than 500 A in diameter. The

F. Reif

1957-01-01

395

What Have We Learned From Magnetic Resonance Imaging Studies?  

Microsoft Academic Search

e review studies that have examined the relationship between magnetic reso- nance imaging findings and clinical disability, postmortem observations, and cog- nitive dysfunction in patients with multiple sclerosis. We also review the use of magnetic resonance imaging findings as an outcome measure in clinical trials assessing the efficacy of new therapeutic agents for the treatment of multiple sclerosis. More ad-

Samia J. Khoury; Howard L. Weiner

1998-01-01

396

Magnetic resonance studies of GaN-based LEDs  

NASA Astrophysics Data System (ADS)

Electrically detected magnetic resonance (EDMR), electrically excited and optically detected magnetic resonance, photocurrent-detected magnetic resonance and the photo-quenching of EDMR are employed to study radiative and non-radiative recombination processes in single quantum well diodes. The effects of high current stress are studied in addition to recombination in unstressed devices. The signals are dominated by a broad line ( g?2.01; ? B?13 mT) which can be optically quenched by absorption in the quantum well of the diode. Measurements on diodes which have been subjected to high current stressing reveal another resonance located in an area of the diode in series with the quantum well and these results also indicate that the broad line is due to more than one defect level.

Carlos, William E.; Nakamura, Shuji

1998-06-01

397

Ferromagnetic resonance of transversally magnetized amorphous microwires and nanowires  

NASA Astrophysics Data System (ADS)

Ferromagnetic resonance of very thin glass covered wires with diameters ranging from 25 ?m down to 133 nm was investigated at microwave frequencies 49.1 and 69.7 GHz at room temperature. The static magnetic field was applied perpendicular to the wire axis. The resonance spectra substantially change when the wire diameter decreases below the electromagnetic skin depth. Depending on the wire thickness and the experimental arrangement, various resonance modes can be excited. In thick wires, an inhomogeneously broadened resonance curve, with two distinct peaks at minimum and maximum resonance fields, can be seen. In submicron wires, generally three narrow resonances can be observed. The weak central resonance peak corresponds to the uniform precession (Kittel) resonance mode and is excited by the uniform component of microwave magnetic field. The other two belong to non-uniform magnetostatic modes, which are excited by the strong circumferential magnetic field due to electric polarization of the wire. The experimental results are explained using a strong skin effect limit and a quasistatic approximation for the bulk and submicron wires, respectively.

Kraus, Lud?k; Frait, Zden?k; Ababei, Gabriel; Chiriac, Horia

2013-05-01

398

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

399

Magnetic resonance imaging in scaphoid fractures.  

PubMed

The use of a 1.5 tesla superconducting M.R. imager and surface coil was found to enhance the ability of M.R.I. to depict the fine anatomy of the wrist. Five healthy volunteers and 28 patients with scaphoid fractures underwent M.R.I., which made possible a definitive diagnosis of scaphoid fractures at an early stage. A fresh fracture was identified by decreased or iso signal intensity on the T1-weighted image and increased signal intensity on the T2-weighted image. This increase continued until bony union was apparent on radiographs. On the T2-weighted image, high signal intensity was characteristic of fresh fractures and suggested that bony union was possible. When bony union was complete, the intensity of the signal for the scaphoid on both T1- and T2-weighted images returned to normal. M.R.I. should thus prove useful in the diagnosis of scaphoid fractures. PMID:1640140

Imaeda, T; Nakamura, R; Miura, T; Makino, N

1992-02-01

400

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

401

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

402

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

403

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

PubMed

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

404

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.

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

2014-01-01

405

Impedance magnetic resonance imaging: A method for imaging of impedance distributions based on magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging (MRI) techniques have become important tools in medicine and biology. Conventional MRI, however, produces no information about the electrical properties of the body. This article proposes a new and noninvasive method for imaging electrical properties such as conductivity and impedance based on MRI techniques. The basic idea is to use the shielding effects of induced eddy currents in the body on spin precession. Two types of methods are introduced; (i) a large flip angle method, and (ii) a third coil method. The large flip angle method enhances the shielding effects of conducting tissues at the given Larmor frequency. The third coil method detects the shielding effects of conducting tissues at an arbitrary frequency. Both phantom and animal experiments have been carried out to verify this concept using a MRI system of 7.05 T with a bore size of 183 mm in diameter.

Ueno, S.; Iriguchi, N.

1998-06-01

406

Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy Characterize a Rodent Model of Covert Stroke  

NASA Astrophysics Data System (ADS)

Covert stroke (CS) comprises lesions in the brain often associated by risk factors such as a diet high in fat, salt, cholesterol and sugar (HFSCS). Developing a rodent model for CS incorporating these characteristics is useful for developing and testing interventions. The purpose of this thesis was to determine if magnetic resonance (MR) can detect brain abnormalities to confirm this model will have the desired anatomical effects. Ex vivo MR showed brain abnormalities for rats with the induced lesions and fed the HFSCS diet. Spectra acquired on the fixed livers had an average percent area under the fat peak relative to the water peak of (20+/-4)% for HFSCS and (2+/-2)% for control. In vivo MR images had significant differences between surgeries to induce the lesions (p=0.04). These results show that applying MR identified abnormalities in the rat model and therefore is important in the development of this CS rodent model.

Herrera, Sheryl Lyn

407

Computer-assisted learning in anatomy at the international medical school in Debrecen, Hungary: a preliminary report.  

PubMed

The University of Debrecen's Faculty of Medicine has an international, multilingual student population with anatomy courses taught in English to all but Hungarian students. An elective computer-assisted gross anatomy course, the Computer Human Anatomy (CHA), has been taught in English at the Anatomy Department since 2008. This course focuses on an introduction to anatomical digital images along with clinical cases. This low-budget course has a large visual component using images from magnetic resonance imaging and computer axial tomogram scans, ultrasound clinical studies, and readily available anatomy software that presents topics which run in parallel to the university's core anatomy curriculum. From the combined computer images and CHA lecture information, students are asked to solve computer-based clinical anatomy problems in the CHA computer laboratory. A statistical comparison was undertaken of core anatomy oral examination performances of English program first-year medical students who took the elective CHA course and those who did not in the three academic years 2007-2008, 2008-2009, and 2009-2010. The results of this study indicate that the CHA-enrolled students improved their performance on required anatomy core curriculum oral examinations (P < 0.001), suggesting that computer-assisted learning may play an active role in anatomy curriculum improvement. These preliminary results have prompted ongoing evaluation of what specific aspects of CHA are valuable and which students benefit from computer-assisted learning in a multilingual and diverse cultural environment. PMID:22837191

Kish, Gary; Cook, Samuel A; Kis, Gréta

2013-01-01

408

Spin relaxation mechanism in graphene: resonant scattering by magnetic impurities.  

PubMed

We propose that the observed small (100 ps) spin relaxation time in graphene is due to resonant scattering by local magnetic moments. At resonances, magnetic moments behave as spin hot spots: the spin-flip scattering rates are as large as the spin-conserving ones, as long as the exchange interaction is greater than the resonance width. Smearing of the resonance peaks by the presence of electron-hole puddles gives quantitative agreement with experiment, for about 1 ppm of local moments. Although magnetic moments can come from a variety of sources, we specifically consider hydrogen adatoms, which are also resonant scatterers. The same mechanism would also work in the presence of a strong local spin-orbit interaction, but this would require heavy adatoms on graphene or a much greater coverage density of light adatoms. To make our mechanism more transparent, we also introduce toy atomic chain models for resonant scattering of electrons in the presence of a local magnetic moment and Rashba spin-orbit interaction. PMID:24702397

Kochan, Denis; Gmitra, Martin; Fabian, Jaroslav

2014-03-21

409

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

410

Magnetic resonance imaging with an optical atomic magnetometer.  

PubMed

We report an approach for the detection of magnetic resonance imaging without superconducting magnets and cryogenics: optical atomic magnetometry. This technique possesses a high sensitivity independent of the strength of the static magnetic field, extending the applicability of magnetic resonance imaging to low magnetic fields and eliminating imaging artifacts associated with high fields. By coupling with a remote-detection scheme, thereby improving the filling factor of the sample, we obtained time-resolved flow images of water with a temporal resolution of 0.1 s and spatial resolutions of 1.6 mm perpendicular to the flow and 4.5 mm along the flow. Potentially inexpensive, compact, and mobile, our technique provides a viable alternative for MRI detection with substantially enhanced sensitivity and time resolution for various situations where traditional MRI is not optimal. PMID:16885210

Xu, Shoujun; Yashchuk, Valeriy V; Donaldson, Marcus H; Rochester, Simon M; Budker, Dmitry; Pines, Alexander

2006-08-22

411

[Neoplasms of the glomus caroticum: magnetic resonance angiography versus magnetic resonance].  

PubMed

This work was aimed at investigating the diagnostic role of Magnetic Resonance angiography (MRA) versus spin-echo images in the study of carotid paragangliomas. Ten patients affected with carotid paragangliomas were studied; surgery was the gold standard. MR examinations were performed with a superconductive 1.5 T magnet and a linear head coil. T1-weighted (TR 500 ms, TE 15 ms, 256 x 256 matrix) and T2-weighted (TR 2000 ms, TE 15/90 ms, 256 x 256 matrix) spin-echo sequences were acquired. TOF 3D (flash: FA 25 degrees, TR 30 ms, TE 7 ms) MRA images were acquired; coronal and sagittal images were rotated according to the MIP. Spin-echo images demonstrated the typical "salt and pepper" pattern in all cases. In 6 cases (lesion diameter > 3 cm) the vascular structures of the paragangliomas and carotid dislocation were clearly demonstrated by MRA. MRA also depicted carotid dislocation in all cases. In conclusion, in the evaluation of carotid paragangliomas > 3 cm diameter, MRA yields complementary information on vascular structures and dislocation of carotid vessels to spin-echo MR sequences. PMID:8128036

Carriero, A; Tonni, A G; D'Ettorre, L; Iezzi, A; Tartaro, A; Bonomo, L

1994-01-01

412

Magnetic resonance imaging (MRI): effects of electro-magnetic radiation and safety aspects  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is a widely used noninvasive imaging modality for obtaining diagnostic radiological images. An MRI scanner consists of several diverse technological components such as powerful static magnetic field, rapidly varying local gradient magnetic fields, pulsed radiofrequency (RF) field and liquid helium and\\/or liquid nitrogen. At present, there is no conclusive evidence for adverse biological effects in patients

N. R JAGANNATECAN

1999-01-01

413

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.

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

2009-01-01

414

Low field strength magnetic resonance imaging of the neonatal brain  

PubMed Central

Background: Magnetic resonance (MR) imaging of the neonate has been restricted by the need to transport the sick baby to the large magnetic resonance scanners and often the need for sedation or anaesthesia in order to obtain good quality images. Ultrasound is the reference standard for neonatal imaging. Objective: To establish a dedicated neonatal MR system and compare the clinical usefulness of MR imaging with ultrasound imaging. Design: Prospective double blind trial. Setting: Neonatal intensive care unit, Sheffield. Main outcome measures: Imaging reports. Patients: 134 premature and term babies. Results: In 56% of infants with pathology suspected on clinical grounds, MR provided additional useful clinical information over and above that obtained with ultrasound. Conclusion: Infants can be safely imaged by dedicated low field magnetic resonance on the neonatal intensive care unit without the need for sedation at a cost equivalent to ultrasound.

Whitby, E; Paley, M; Smith, M; Sprigg, A; Woodhouse, N; Griffiths, P

2003-01-01

415

Silicon Nanoparticles as Hyperpolarized Magnetic Resonance Imaging Agents  

PubMed Central

Magnetic resonance imaging of hyperpolarized nuclei provides high image contrast with little or no background signal. To date, in-vivo applications of pre-hyperpolarized materials have been limited by relatively short nuclear spin relaxation times. Here, we investigate silicon nanoparticles as a new type of hyperpolarized magnetic resonance imaging agent. Nuclear spin relaxation times for a variety of Si nanoparticles are found to be remarkably long, ranging from many minutes to hours at room temperature, allowing hyperpolarized nanoparticles to be transported, administered, and imaged on practical time scales. Additionally, we demonstrate that Si nanoparticles can be surface functionalized using techniques common to other biologically targeted nanoparticle systems. These results suggest that Si nanoparticles can be used as a targetable, hyperpolarized magnetic resonance imaging agent with a large range of potential applications.

Aptekar, Jacob W.; Cassidy, Maja C.; Johnson, Alexander C.; Barton, Robert A.; Lee, Menyoung; Ogier, Alexander C.; Vo, Chinh; Anahtar, Melis N.; Ren, Yin; Bhatia, Sangeeta N.; Ramanathan, Chandrasekhar; Cory, David G.; Hill, Alison L.; Mair, Ross W.; Rosen, Matthew S.; Walsworth, Ronald L.

2014-01-01

416

Renal relevant radiology: renal functional magnetic resonance imaging.  

PubMed

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; Lerman, Lilach O

2014-02-01

417

A platform for designing hyperpolarized magnetic resonance chemical probes  

PubMed Central

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

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

2013-01-01

418

Grain Sizing in Porous Media using Bayesian Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We introduce a Bayesian inference approach to analyze magnetic resonance data of granular solids. To characterize structure using magnetic resonance, it is usual to acquire data in k space which are then Fourier transformed to obtain an image. An alternative approach, adopted here, is to utilize the Rayleigh distribution observed in the signal intensity for a given k when a random selection of grains is measured in k space, to define a likelihood function for Bayesian analysis. This Bayesian likelihood function is used to noninvasively characterize grains within a porous medium on length scales below the practical resolution of magnetic resonance imaging. A pore size distribution is then calculated from the measured grain size distribution using a Monte Carlo approach. We demonstrate this general technique with specific examples of water-saturated rock cores.

Holland, D. J.; Mitchell, J.; Blake, A.; Gladden, L. F.

2013-01-01

419

Magnetic resonance study of a vanadium pentoxide gel  

Microsoft Academic Search

In this work we report results from continuous-wave (CW) and pulsed electron paramagnetic resonance (EPR) and proton nuclear\\u000a magnetic resonance (NMR) studies of the vanadium pentoxide xerogel V2O5:nH2O (n ? 1.6). The low temperature CW-EPR spectrum shows hyperfine structure due to coupling of unpaired V4+ electron with the vanadium nucleus. The analysis of the spin Hamiltonian parameters suggests that the V4+ ions

Otaciro R. Nascimento; Claudio J. Magon; Jose Fernando Lima; Jose Pedro Donoso; Eglantina Benavente; Jaime Paez; Vladimir Lavayen; Maria Angelica Santa Ana; Guillermo Gonzalez

2008-01-01

420

Deuteron Magnetic Resonance of Ferroelectric Potassium Ferrocyanide Trihydrate  

Microsoft Academic Search

The quadrupolar splittings and linewidths of the deuteron magnetic resonance of single crystals of ferroelectric K4Fe(CN)6·3D2O(KFCT) have been measured from ?100° to 58°C. At low temperatures eight pairs of resonance lines are observed corresponding to four types of water molecules A, B, C, D, and their ac plane enantiomorphs A+, B+, C+, D+. The molecules are undergoing a fast 180°

Tung Tsang; D. E. O'Reilly

1965-01-01

421

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

422

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

423

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.

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

2003-01-01

424

Magnetic resonance, nuclear orientation and antiferromagnetism  

Microsoft Academic Search

A small range of compounds contain ions from two transition groups, 3d and 4f. Most of these enter an ordered antiferromagnetic state only at liquid helium temperatures, and the internal fields are 1 tesla or less. Experiments are suggested on various single crystals. Measurements by electron spin resonance on impurity ions in antiferromagnetic dysprosium phosphate show that similar compounds could

B. Bleaney

1998-01-01

425

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

426

lac repressor: 3-fluorotyrosine substitution for nuclear magnetic resonance studies.  

PubMed Central

This paper describes the isolation of 3-fluorotyrosine-substituted lac repressor, and its 19F nuclear magnetic resonance spectrum. From the spectrum, one can conclude that for each of the four identical subunits of the repressor there are four or five surface tyrosines, two buried or internal tyrosines, and one tyrosine with an phenolic group ionized or involved in a hydrogen bond. Conditions are described that can be used for the 3-fluorotyrosine substitution of a variety of Escherichia coli proteins for 19F nuclear magnetic resonance studies.

Lu, P; Jarema, M; Mosser, K; Daniel, W E

1976-01-01

427

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

428

Magnetic resonance imaging and spectroscopy of the murine cardiovascular system  

PubMed Central

Magnetic resonance imaging (MRI) has emerged as a powerful and reliable tool to noninvasively study the cardiovascular system in clinical practice. Because transgenic mouse models have assumed a critical role in cardiovascular research, technological advances in MRI have been extended to mice over the last decade. These have provided critical insights into cardiac and vascular morphology, function, and physiology/pathophysiology in many murine models of heart disease. Furthermore, magnetic resonance spectroscopy (MRS) has allowed the nondestructive study of myocardial metabolism in both isolated hearts and in intact mice. This article reviews the current techniques and important pathophysiological insights from the application of MRI/MRS technology to murine models of cardiovascular disease.

Akki, Ashwin; Gupta, Ashish

2013-01-01

429

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

430

Computed tomography and magnetic resonance imaging in spinal hydatidosis.  

PubMed

Computed tomography and magnetic resonance imaging in patients with spinal hydatidosis provide comprehensive evaluation of the actual extent of the disease. Paravertebral uncalcified cysts, hardly recognizable by conventional radiologic examinations, are clearly shown by both methods. Initial involvement of the spongy bone is evident in computed tomography scans, in contrast to what usually appears to be normal in plain films or tomograms. Occurrence of cysts within the spinal canal is revealed by both types of computed scans, with magnetic resonance imaging being able to provide further information on the involvement of the spinal cord. PMID:3824143

Pau, A; Simonetti, G; Tortori-Donati, P; Turtas, S; Viale, G L

1987-04-01

431

Electrically detected magnetic resonance studies of phosphorus doped diamond  

NASA Astrophysics Data System (ADS)

Phosphorus doped n-type epitaxial diamond films have been studied by electron spin resonance (ESR) and electrically detected magnetic resonance (EDMR). At low electric field, the dominant defects influencing the electronic transport are carbon dangling bonds, while at higher fields the anisotropic spin resonance signal of a new phosphorus-related center with g?=2.0026, g||=2.0042, Aiso=17.6 G, and Aaniso=1.8 G is observed. These results indicate that room temperature conductivity in this film is dominated by hopping via phosphorus-related defect centers rather than via hydrogenic donor states of phosphorus atoms on substitutional sites.

Graf, T.; Brandt, M. S.; Nebel, C. E.; Stutzmann, M.; Koizumi, S.

2001-12-01

432

Electrically Detected Magnetic Resonance in Undoped Polyacetylene and Polyaniline  

NASA Astrophysics Data System (ADS)

The transport properties of polyacetylene and polyaniline films have been investigated by electrically detected magnetic resonance (EDMR) at room temperature. In polyacetylene, a spin-dependent interchain tunneling involving a polaron and a soliton is detected. In polyaniline, a similar process is found but involving a polaron-polaron transition. The EDMR signal in polyaniline is found to be dependent on the dc electric field. For low electric fields (F < 1000 V/cm), one resonance line is observed, for higher fields, two resonance lines are observed, having similar g-factors but different linewidths.

Graeff, C. F. O.; Brandt, M. S.; Faria, R. M.; Leising, G.

1997-08-01

433

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

434

In vivo anatomy of the Neer and Hawkins sign positions for shoulder impingement  

Microsoft Academic Search

The Neer and Hawkins impingement signs are com- monly used to diagnose subacromial pathology, but the anatomy of these maneuvers has not been well elucidated in vivo. This 3-dimensional open magnetic resonance imaging study characterized shoulder anat- omy and rotator cuff impingement in 8 normal volun- teers placed in the Neer and Hawkins positions. Sub- acromial and intraarticular contact of

George P. Pappas; Silvia S. Blemker; Christopher F. Beaulieu; Timothy R. McAdams; Sean T. Whalen; Garry E. Gold

435

The veins of the medulla oblongata: MRI cross-sectional anatomy  

Microsoft Academic Search

Magnetic resonance imaging (MRI) has progressively become the major or even the only imaging procedure for displaying the vascular relationships of the brainstem in the context of infra-tentorial lesions. In order to assess the MR sectional anatomy of the bulbar vv. 40 normal patients were examined in the MR axial, frontal and sagittal planes after gadolinium IV injection. The bulbar

M. Braun; S. Bracard; R. Anxionnat; J. Roland; L. Picard

1996-01-01

436

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.

437

Probing arrays of circular magnetic microdots by ferromagnetic resonance.  

SciTech Connect

X-band ferromagnetic resonance (FMR) was used to characterize in-plane magnetic anisotropies in rectangular and square arrays of circular nickel and Permalloy microdots. In the case of a rectangular lattice, as interdot distances in one direction decrease, the in-plane uniaxial anisotropy field increases, in good agreement with a simple theory of magnetostatically interacting uniformly magnetized dots. In the case of a square lattice a four-fold anisotropy of the in-plane FMR field H(r) was found when the interdot distance a gets comparable to the dot diameter D. This anisotropy, not expected in the case of uniformly magnetized dots, was explained by a non-uniform magnetization m(r) in a dot in response to dipolar forces in the patterned magnetic structure. It is well described by an iterative solution of a continuous variation procedure. In the case of perpendicular magnetization multiple sharp resonance peaks were observed below the main FMR peak in all the samples, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR spectra was given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account. It was demonstrated that ferromagnetic resonance force microscopy (FMRFM) can be used to determine both local and global properties of patterned submicron ferromagnetic samples. Local spectroscopy together with the possibility to vary the tip-sample spacing enables the separation of those two contributions to a FMRFM spectrum. The global FMR properties of circular submicron dots determined using magnetic resonance force microscopy are in a good agreement with results obtained using conventional FMR and with theoretical descriptions.

Kakazei, G. N.; Mewes, T.; Wigen, P. E.; Hammel, P. C.; Slavin, A. N.; Pogorelov, Y. G.; Costa, M. D.; Golub, V. O.; Guslienko, K. Y.; Novosad, V. (Materials Science Division); (Univ. of Porto); (National Academy of Sciences Ukraine); (Univ. of Alabama); (Ohio State Univ.); (Oakland Univ.)

2008-06-01

438

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

439

The University of Hull: Magnetic Resonance Imaging (MRI)  

NSDL National Science Digital Library

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

Liney, Gary P.

2008-01-22

440

Resonance-Field Dependence in Electrically Detected Magnetic Resonance: Effects of Exchange Interaction  

Microsoft Academic Search

Resonance-field dependence of signal intensity in electronically detected magnetic resonance (EDMR) has been investigated both theoretically and experimentally. Theoretical expressions presenting the field dependence of EDMR signal intensity are obtained from a quantum mechanical treatment of the Kaplan–Solomon–Mott model, where it is assumed that recombination only occurs through recombination pairs in the singlet spin state. In this study, effects of

Kôichi Fukui; Toshiyuki Sato; Hidekatsu Yokoyama; Hiroaki Ohya; Hitoshi Kamada

2001-01-01

441

Transfer efficiency analysis of magnetic resonance wireless power transfer with intermediate resonant coil  

NASA Astrophysics Data System (ADS)

Generally, for the magnetic resonance coupling wireless power transfer (WPT) system, the transfer efficiency and the transmission distance are contradictory. In order to simultaneously achieve the high transfer efficiency and the far transmission distance, some researchers have successfully proposed to use intermediate coils system to improve efficiency of WPT. In this paper, the expression for the efficiency of intermediate WPT system is obtained by applying coupled-mode theory. System efficiency is improved by optimizing key parameters of system. The intermediate WPT system via magnetic resonance coupling is designed. Simulation and experimental results validate the proposed optimization method.

Huang, S. D.; Li, Z. Q.; Li, Y.

2014-05-01

442

Magnetization exchange observed in human skeletal muscle by non-water-suppressed proton magnetic resonance spectroscopy.  

PubMed

Many metabolites in the proton magnetic resonance spectrum undergo magnetization exchange with water, such as those in the downfield region (6.0-8.5 ppm) and the upfield peaks of creatine, which can be measured to reveal additional information about the molecular environment. In addition, these resonances are attenuated by conventional water suppression techniques complicating detection and quantification. To characterize these metabolites in human skeletal muscle in vivo at 3 T, metabolite cycled non-water-suppressed spectroscopy was used to conduct a water inversion transfer experiment in both the soleus and tibialis anterior muscles. Resulting median exchange-independent T1 times for the creatine methylene resonances were 1.26 and 1.15 s, and for the methyl resonances were 1.57 and 1.74 s, for soleus and tibialis anterior muscles, respectively. Magnetization transfer rates from water to the creatine methylene resonances were 0.56 and 0.28 s(-1), and for the methyl resonances were 0.39 and 0.30 s(-1), with the soleus exhibiting faster transfer rates for both resonances, allowing speculation about possible influences of either muscle fibre orientation or muscle composition on the magnetization transfer process. These water magnetization transfer rates observed without water suppression are in good agreement with earlier reports that used either postexcitation water suppression in rats, or short CHESS sequences in human brain and skeletal muscle. PMID:23172828

MacMillan, Erin L; Boesch, Chris; Kreis, Roland

2013-10-01

443

Imaging of the dielectric resonance effect in high field magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

At a high field magnetic resonance imaging (MRI), the interactions between the RF pulse and the high permittivity samples, which cause the B1 field inhomogeneity, can no longer be negligible. We present a postprocessing method of compensating the B1 field inhomogeneity mainly caused by the dielectric resonance. The intensity of the transmitted B1 field is calculated using two spin echo images of the water phantom obtained with different flip angles 45° and 90°. Applying the proposed method, the dielectric resonance of the water in high field MRI is visualized as a quantitative map of the B1 field. The corrected image compensating the B1 field inhomogeneity was also calculated.

Mihara, Hiroaki; Iriguchi, Norio; Ueno, Shoogo

2005-05-01

444

Magnetic resonance imaging systems: evaluation of 1.5-Tesla systems.  

PubMed

Magnetic resonance imaging (MRI) systems manipulate magnetic fields and radio-frequency signals to create diagnostic images of human anatomy. An MR system is an essential clinical tool, but the cost of buying and installing one is high, so it's crucial that hospitals choose a model carefully. The selection process is made more complex by the numerous options available: different field strengths, gradient systems, coils, and channels, to name just a few. Also, some systems are better than others at facilitating specialized imaging, such as breast and cardiac studies. Our Evaluation is intended to help clarify the choices. We tested three 1.5-tesla systems from three suppliers--GE, Siemens, and Toshiba. We rate the systems for two different uses: inpatient imaging (performed in hospitals) and outpatient imaging (most often performed in imaging centers). For inpatient facilities, which are likely to have less responsive patients and to treat more complex medical problems, the most important purchase considerations will be patient positioning features, advanced imaging capabilities, and system integration. For outpatient facilities, the ability to perform routine exams efficiently and comfortably will be most important. We also provide separate ratings for each system's ability to meet the needs of three specialized applications--breast imaging, cardiac imaging, and functional MRI. PMID:16893049

2006-06-01

445

Neuromagnetic localization using magnetic resonance images  

Microsoft Academic Search

Ionic flow associated with neural activation of the brain produces a magnetic field, called the neuromagnetic field, that can be measured outside the head using a highly sensitive superconducting quantum interference device (SQUID)-based neuromagnetometer. Under certain conditions, the sources producing the neuromagnetic field can be localized from a sampling of the neuromagnetic field. Neuromagnetic measurements alone, however, do not contain

Manbir Singh; R. Ricardo Brechner; Victor W. Henderson

1992-01-01

446

Magnetic Resonance Studies of Coal. Volume II.  

National Technical Information Service (NTIS)

The ESR signal of a coal sample has at least four components differing in phase angle of the magnetic modulation. The ENDOR technique was greatly improved by taking advantage of this fact, e.g., a coal sample was shown to have at least five different grou...

I. Miyagawa C. Alexander

1980-01-01

447

Real-Time Functional Magnetic Resonance Imaging  

Microsoft Academic Search

A recursive algorithm suitable for functional magnetic reso- nance imaging (FMRI) calculations is presented. The correla- tion coefficient of a time course of images with a reference time series, with the mean and any linear trend projected out, may be computed with 22 operations per voxel, per image; the storage overhead is four numbers per voxel. A statistical model for

Robert W. Cox; Andrzej Jesmanowicz; James S. Hyde

1995-01-01

448

Microstructured magnetic materials for RF flux guides in magnetic resonance imaging.  

PubMed

Magnetic resonance imaging and spectroscopy systems use coils, either singly or as arrays, to intercept radio-frequency (RF) magnetic flux from regions of interest, often deep within the body. Here, we show that a new magnetic material offers novel possibilities for guiding RF flux to the receiver coil, permitting a clear image to be obtained where none might otherwise be detectable. The new material contains microstructure designed according to concepts taken from the field of photonic band gap materials. In the RF range, it has a magnetic permeability that can be produced to specification while exhibiting negligible direct-current magnetism. The latter property is vital to avoid perturbing the static and audio-frequency magnetic fields needed to obtain image and spectral data. The concept offers a new paradigm for the manipulation of RF flux in all nuclear magnetic resonance systems. PMID:11157159

Wiltshire, M C; Pendry, J B; Young, I R; Larkman, D J; Gilderdale, D J; Hajnal, J V

2001-02-01

449

Nuclear magnetic resonance of iron and copper disease states  

Microsoft Academic Search

The tissue levels of paramagnetic ions are an important factor in the determination of T⁠values as observed by nuclear magnetic resonance (NMR) imaging. The increased levels of iron present in human disease states such as hemochromatosis lead to decreased T⁠values. The mean liver T⁠of three patients with iron storage disease was determined to be 130 msec, significantly

V. M. Runge; J. A. Clanton; F. W. Smith; J. Hutchison; J. Mallard; C. L. Partain; A. E. Jr. James

1983-01-01

450

Signal and noise estimation from magnetic resonance images  

Microsoft Academic Search

This thesis deals with the estimation of noise and signal from Magnetic Resonance (MR) images with a special reference to magnitude MR images. Furthermore, the estimation and improvement of the image signal-to-noise ratio (SNR) and an application to 3D segmentation is discussed. In order to process experimental data in a scientifically justified manner, knowledge of the underlying probability density function

Jan Sijbers

1998-01-01

451

Ultrasound to Magnetic Resonance Volume Registration for Brain Sinking Measurement  

Microsoft Academic Search

This paper addresses the registration of ultrasound scans and magnetic resonance (MR ) volume datasets of the same patient. During a neurosurgery intervention, pre-operative MR images are often employed as a guide despite the fact that they do not show the actual state of the brain, which sometimes has sunk up to 1 cm. By means of a standard ecographer

David Lloret; Joan Serrat; Antonio M. López; Juan José Villanueva

2003-01-01

452

Concepts in Biochemistry: Nuclear Magnetic Resonance Spectroscopy in Biochemistry.  

ERIC Educational Resources Information Center

Discusses the nature of a nuclear magnetic resonance (NMR) experiment, the techniques used, the types of structural and dynamic information obtained, and how one can view and refine structures using computer graphics techniques in combination with NMR data. Provides several spectra and a computer graphics image from B-form DNA. (MVL)

Cheatham, Steve

1989-01-01

453

Magnetic resonance imaging to diagnose breast implant rupture  

Microsoft Academic Search

The purpose of this study was to prospectively evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) as a method to discover an implant rupture in patients with breast augmentation or reconstruction. From January 1997 to February 1998, 20 breast implants in 12 patients (mean age 52.5 years) were removed surgically. Indications included local pain after reconstructive breast surgery (n=5

V. Wedler; C. Meuli-Simmen; R. Kubik-Huch; W. Künzi; V. Meyer

2002-01-01

454

New approach for analyzing magnetic resonance elastography images  

Microsoft Academic Search

A new method for evaluating Magnetic Resonance Elastography (MRE) wave images is introduced, which consists of both local frequency estimation (LFE) and simulation of wave patterns by a coupled harmonic oscillator (CHO) approach. It is shown that i) LFE performs improved reconstruction by use of Gauss filters and ii) CHO calculations can help to refine the resulting wave speed or

Ingolf Sack; Gerd Buntkowsky; Johannes Bernarding; Thomas Tolxdorff; Juergen Braun

2001-01-01

455

Magnetic resonance elastography and inverse problem solution in elasticity  

Microsoft Academic Search

Visualization of mechanical properties of soft tissues using nuclear magnetic resonance imaging (MRI) with mechanical compression is introduced. Then, reconstruction of the elasticity distribution by the linear perturbation method is explained. Simulation results show that the elasticity distribution of soft tissues can be reconstructed by utilizing the phase images obtained from MRI so that the biomechanical properties of soft tissues

Z. Akalin; B. M. Eyuboglu

1999-01-01

456

Peak wireless power transfer using magnetically coupled series resonators  

Microsoft Academic Search

Wireless power transfer can create the illusion of portable devices with infinite power supplies. Power transfer using magnetically coupled series resonators is maximized when the load presented to the sender is matched to the series impedance of the source. This determines an optimal separation distance between the sender and the receiver. However, the maximum power transferred only depends on the

José Oscar Mur-Miranda; Giulia Fanti

2010-01-01

457

Controllable Magnetic Metamaterial Using Digitally Addressable Split-Ring Resonators  

Microsoft Academic Search

An ideal metamaterial is composed of identical elements in a uniformly structured array so that the material response is a single magnetic or electric resonance. Variations in the metamaterial particle characteristics or array assembly result in undesirable broadening of the effective material response. When lumped circuit elements are used in metamaterial particles, this effect can be significant due to element

Thomas H. Hand; Steven A. Cummer

2009-01-01

458

Magnetic resonance imaging in obstructive M?llerian anomalies  

PubMed Central

Herlyn-Werner-Wunderlich (HWW) syndrome is a very rare congenital anomaly of the urogenital tract involving Müllerian ducts and Wolffian structures. It is characterized by the triad of didelphys uterus, obstructed hemivagina, and ipsilateral renal agenesis. Magnetic resonance imaging (MRI) is a sensitive, non-invasive diagnostic modality for demonstrating anatomic variation and associated complications.

Sen, Kamal Kumar; Balasubramaniam, Dhivya; Kanagaraj, Vikrant

2013-01-01

459

Nuclear Magnetic Resonance Coupling Constants and Electronic Structure in Molecules.  

ERIC Educational Resources Information Center

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

Venanzi, Thomas J.

1982-01-01

460

Volume measurement of multiple sclerosis lesions with magnetic resonance images  

Microsoft Academic Search

The ability to visualise multiple selerosis lesions in vivo with magnetic resonance imaging suggests and important role in monitoring the course of the disease. In order to help the long-term assessment of prospective treatments, a semi-automated technique for measuring lesion volume has been developed to provide a quantitative index of disease progression. Results are presented from a preliminary study with

D. A. G. Wicks; P. S. Tofts; D. H. Miller; G. H. Boulay; A. Feinstein; R. P. Sacares; I. Harvey; R. Brenner; W. I. McDonald

1992-01-01