Directory of Open Access Journals (Sweden)
Mériam Ben Hamida-Rebaï
Full Text Available Small G-proteins of the superfamily Ras function as molecular switches, interacting with different cellular partners according to their activation state. G-protein activation involves the dissociation of bound GDP and its replacement by GTP, in an exchange reaction that is accelerated and regulated in the cell by guanine-nucleotide exchange factors (GEFs. Large conformational changes accompany the exchange reaction, and our understanding of the mechanism is correspondingly incomplete. However, much knowledge has been derived from structural studies of blocked or inactive mutant GEFs, which presumably closely represent intermediates in the exchange reaction and yet which are by design incompetent for carrying out the nucleotide exchange reaction. In this study we have used comparative modelling to recreate an exchange-competent form of a late, pre-GDP-ejection intermediate species in Arf1, a well-characterized small G-protein. We extensively characterized three distinct models of this intermediate using molecular dynamics simulations, allowing us to address ambiguities related to the mutant structural studies. We observed in particular the unfavorable nature of Mg2+ associated forms of the complex and the establishment of closer Arf1-GEF contacts in its absence. The results of this study shed light on GEF-mediated activation of this small G protein and on predicting the fate of the Mg ion at a critical point in the exchange reaction. The structural models themselves furnish additional targets for interfacial inhibitor design, a promising direction for exploring potentially druggable targets with high biological specificity.
The Emerging Role of Guanine Exchange Factors in ALS and other neurodegenerative diseases
Directory of Open Access Journals (Sweden)
Cristian eDroppelmann
2014-09-01
Full Text Available Small GTPases participate in a broad range of cellular processes such as proliferation, differentiation and migration. The exchange of GDP for GTP resulting in the activation of these GTPases is catalyzed by a group of enzymes called guanine nucleotide exchange factors (GEFs, of which two classes: Dbl-related exchange factors and the more recently described Dock family exchange factors. Increasingly, deregulation of normal GEF activity or function has been associated with a broad range of disease states, including neurodegeneration and neurodevelopmental disorders. In this review, we examine this evidence with special emphasis on the novel role of Rho guanine nucleotide exchange factor (RGNEF/p190RhoGEF in the pathogenesis of amyotrophic lateral sclerosis (ALS. RGNEF is the first neurodegeneration-linked GEF that regulates not only RhoA GTPase activation but also functions as an RNA binding protein that directly acts with low molecular weight neurofilament (NEFL mRNA 3’UTR to regulate its stability. This dual role for RGNEF, coupled with the increasing understanding of the key role for GEFs in modulating the GTPase function in cell survival suggests a prominent role for GEFs in mediating a critical balance between cytotoxicity and neuroprotection which, when disturbed, contributes to neuronal loss.
GEFs: Dual regulation of Rac1 signaling.
Marei, Hadir; Malliri, Angeliki
2017-04-03
GEFs play a critical role in regulating Rac1 signaling. They serve as signaling nodes converting upstream signals into downstream Rac1-driven cellular responses. Through associating with membrane-bound Rac1, GEFs facilitate the exchange of GDP for GTP, thereby activating Rac1. As a result, Rac1 undergoes conformational changes that mediate its interaction with downstream effectors, linking Rac1 to a multitude of physiological and pathological processes. Interestingly, there are at least 20 GEFs involved in Rac1 activation, suggesting a more complex role of GEFs in regulating Rac1 signaling apart from promoting the exchange of GDP for GTP. Indeed, accumulating evidence implicates GEFs in directing the specificity of Rac1-driven signaling cascades, although the underlying mechanisms were poorly defined. Recently, through conducting a comparative study, we highlighted the role of 2 Rac-specific GEFs, Tiam1 and P-Rex1, in dictating the biological outcome downstream of Rac1. Importantly, further proteomic analysis uncovered a GEF activity-independent function for both GEFs in modulating the Rac1 interactome, which results in the stimulation of GEF-specific signaling cascades. Here, we provide an overview of our recent findings and discuss the role of GEFs as master regulators of Rac1 signaling with a particular focus on GEF-mediated modulation of cell migration following Rac1 activation.
A Steric-inhibition model for regulation of nucleotide exchange via the Dock180 family of GEFs.
Lu, Mingjian; Kinchen, Jason M; Rossman, Kent L; Grimsley, Cynthia; Hall, Matthew; Sondek, John; Hengartner, Michael O; Yajnik, Vijay; Ravichandran, Kodi S
2005-02-22
CDM (CED-5, Dock180, Myoblast city) family members have been recently identified as novel, evolutionarily conserved guanine nucleotide exchange factors (GEFs) for Rho-family GTPases . They regulate multiple processes, including embryonic development, cell migration, apoptotic-cell engulfment, tumor invasion, and HIV-1 infection, in diverse model systems . However, the mechanism(s) of regulation of CDM proteins has not been well understood. Here, our studies on the prototype member Dock180 reveal a steric-inhibition model for regulating the Dock180 family of GEFs. At basal state, the N-terminal SH3 domain of Dock180 binds to the distant catalytic Docker domain and negatively regulates the function of Dock180. Further studies revealed that the SH3:Docker interaction sterically blocks Rac access to the Docker domain. Interestingly, ELMO binding to the SH3 domain of Dock180 disrupted the SH3:Docker interaction, facilitated Rac access to the Docker domain, and contributed to the GEF activity of the Dock180/ELMO complex. Additional genetic rescue studies in C. elegans suggested that the regulation of the Docker-domain-mediated GEF activity by the SH3 domain and its adjoining region is evolutionarily conserved. This steric-inhibition model may be a general mechanism for regulating multiple SH3-domain-containing Dock180 family members and may have implications for a variety of biological processes.
Vav1 GEF activity is required for T cell mediated allograft rejection.
Haubert, Dirk; Li, Jianping; Saveliev, Alexander; Calzascia, Thomas; Sutter, Esther; Metzler, Barbara; Kaiser, Daniel; Tybulewicz, Victor L J; Weckbecker, Gisbert
2012-06-01
The GDP exchange factor (GEF) Vav1 is a central signal transducer downstream of the T cell receptor and has been identified as a key factor for T cell activation in the context of allograft rejection. Vav1 has been shown to transduce signals both dependent and independent of its GEF function. The most promising approach to disrupt Vav1 activity by pharmacological inhibition would be to target its GEF function. However, the contribution of Vav1 GEF activity for allogeneic T cell activation has not been clarified yet. To address this question, we used knock-in mice bearing a mutated Vav1 with disrupted GEF activity but intact GEF-independent functions. T cells from these mice showed strongly reduced proliferation and activation in response to allogeneic stimulation. Furthermore, lack of Vav1 GEF activity strongly abrogated the in vivo expansion of T cells in a systemic graft-versus-host model. In a cardiac transplantation model, mice with disrupted Vav1 GEF activity show prolonged allograft survival. These findings demonstrate a strong requirement for Vav1 GEF activity for allogeneic T cell activation and graft rejection suggesting that disruption of Vav1 GEF activity alone is sufficient to induce significant immunosuppression. Copyright © 2012 Elsevier B.V. All rights reserved.
Kae, Helmut; Kortholt, Arjan; Rehmann, Holger; Insall, RobertH.; Van Haastert, Peter J. M.; Spiegelman, George B.; Weeks, Gerald
In general, mammalian Ras guanine nucleotide exchange factors (RasGEFs) show little substrate specificity, although they are often thought to regulate specific pathways. Here, we provide in vitro and in vivo evidence that two RasGEFs can each act on specific Ras proteins. During Dictyostelium
Goedhart, J.; Unen, J. van; Adjobo-Hermans, M.J.W.; Gadella, T.W.
2013-01-01
The p63RhoGEF and GEFT proteins are encoded by the same gene and both members of the Dbl family of guanine nucleotide exchange factors. These proteins can be activated by the heterotrimeric G-protein subunit Galphaq. We show that p63RhoGEF is located at the plasma membrane, whereas GEFT is confined
Goedhart, J.; van Unen, J.; Adjobo-Hermans, M.J.W.; Gadella (jr.), T.W.J.
2013-01-01
The p63RhoGEF and GEFT proteins are encoded by the same gene and both members of the Dbl family of guanine nucleotide exchange factors. These proteins can be activated by the heterotrimeric G-protein subunit Galphaq. We show that p63RhoGEF is located at the plasma membrane, whereas GEFT is confined
Family-wide characterization of the DENN domain Rab GDP-GTP exchange factors.
Yoshimura, Shin-ichiro; Gerondopoulos, Andreas; Linford, Andrea; Rigden, Daniel J; Barr, Francis A
2010-10-18
A key requirement for Rab function in membrane trafficking is site-specific activation by GDP-GTP exchange factors (GEFs), but the majority of the 63 human Rabs have no known GEF. We have performed a systematic characterization of the 17 human DENN domain proteins and demonstrated that they are specific GEFs for 10 Rabs. DENND1A/1B localize to clathrin patches at the plasma membrane and activate Rab35 in an endocytic pathway trafficking Shiga toxin to the trans-Golgi network. DENND2 GEFs target to actin filaments and control Rab9-dependent trafficking of mannose-6-phosphate receptor to lysosomes. DENND4 GEFs target to a tubular membrane compartment adjacent to the Golgi, where they activate Rab10, which suggests a function in basolateral polarized sorting in epithelial cells that compliments the non-DENN GEF Sec2 acting on Rab8 in apical sorting. DENND1C, DENND3, DENND5A/5B, MTMR5/13, and MADD activate Rab13, Rab12, Rab39, Rab28, and Rab27A/27B, respectively. Together, these findings provide a basis for future studies on Rab regulation and function.
Proteomic analysis of Rac1 signaling regulation by guanine nucleotide exchange factors.
Marei, Hadir; Carpy, Alejandro; Macek, Boris; Malliri, Angeliki
2016-08-02
The small GTPase Rac1 is implicated in various cellular processes that are essential for normal cell function. Deregulation of Rac1 signaling has also been linked to a number of diseases, including cancer. The diversity of Rac1 functioning in cells is mainly attributed to its ability to bind to a multitude of downstream effectors following activation by Guanine nucleotide Exchange Factors (GEFs). Despite the identification of a large number of Rac1 binding partners, factors influencing downstream specificity are poorly defined, thus hindering the detailed understanding of both Rac1's normal and pathological functions. In a recent study, we demonstrated a role for 2 Rac-specific GEFs, Tiam1 and P-Rex1, in mediating Rac1 anti- versus pro-migratory effects, respectively. Importantly, via conducting a quantitative proteomic screen, we identified distinct changes in the Rac1 interactome following activation by either GEF, indicating that these opposing effects are mediated through GEF modulation of the Rac1 interactome. Here, we present the full list of identified Rac1 interactors together with functional annotation of the differentially regulated Rac1 binding partners. In light of this data, we also provide additional insights into known and novel signaling cascades that might account for the GEF-mediated Rac1-driven cellular effects.
Structural Dynamics Control Allosteric Activation of Cytohesin Family Arf GTPase Exchange Factors
Energy Technology Data Exchange (ETDEWEB)
Malaby, Andrew W.; Das, Sanchaita; Chakravarthy, Srinivas; Irving, Thomas C.; Bilsel, Osman; Lambright, David G.
2018-01-01
Membrane dynamic processes including vesicle biogenesis depend on Arf guanosine triphosphatase (GTPase) activation by guanine nucleotide exchange factors (GEFs) containing a catalytic Sec7 domain and a membrane-targeting module such as a pleckstrin homology (PH) domain. The catalytic output of cytohesin family Arf GEFs is controlled by autoinhibitory interactions that impede accessibility of the exchange site in the Sec7 domain. These restraints can be relieved through activator Arf-GTP binding to an allosteric site comprising the PH domain and proximal autoinhibitory elements (Sec7-PH linker and C-terminal helix). Small-angle X-ray scattering and negative-stain electron microscopy were used to investigate the structural organization and conformational dynamics of cytohesin-3 (Grp1) in autoinhibited and active states. The results support a model in which hinge dynamics in the autoinhibited state expose the activator site for Arf-GTP binding, while subsequent C-terminal helix unlatching and repositioning unleash conformational entropy in the Sec7-PH linker to drive exposure of the exchange site.
Goedhart, Joachim; van Unen, Jakobus; Adjobo-Hermans, Merel J W; Gadella, Theodorus W J
2013-01-01
The p63RhoGEF and GEFT proteins are encoded by the same gene and both members of the Dbl family of guanine nucleotide exchange factors. These proteins can be activated by the heterotrimeric G-protein subunit Gαq. We show that p63RhoGEF is located at the plasma membrane, whereas GEFT is confined to the cytoplasm. Live-cell imaging studies yielded quantitative information on diffusion coefficients, association rates and encounter times of GEFT and p63RhoGEF. Calcium signaling was examined as a measure of the signal transmission, revealing more efficient signaling through the membrane-associated p63RhoGEF. A rapamycin dependent recruitment system was used to dynamically alter the subcellular location and concentration of GEFT, showing efficient signaling through GEFT only upon membrane recruitment. Together, our results show efficient signal transmission through membrane located effectors, and highlight a role for increased concentration rather than increased encounter times due to membrane localization in the Gαq mediated pathways to p63RhoGEF and PLCβ.
Role of Gd-DTPA enhanced fat-suppression MR imaging on ovarian tumors
International Nuclear Information System (INIS)
Kang, Heoung Keun; Moon, Woong Jae; Seo, Jeong Jin; Kim, Jae Kyu; Park, Jin Gyoon; Choi, Ho Sun
1995-01-01
To determine the value of Gd-DTPA enhanced fat-suppression (GEFS) MR imaging in the characterization and differentiation of benign from malignant ovarian tumors. MRI findings of thirty-seven patients with surgically proved 44 ovarian tumors (30 benign, 14 malignant) were studied retrospectively. MR imaging with conventional spin echo (CSE; T1-weighted image TR/TE 450/20, T2-weighted image TR/TE 3500/30, 90) and GEFS were performed with a 1.5T GE signa. MRI findings of tumors including cystic or solid, wall and septal thickness, necrosis, invasion to adjacent organ, ascites and lymphadenopathy were assessed separately by using CSE and GEFS images, and then tumors were characterized as benign or malignant. Compared with CSE image, GEFS MR image showed better visualization of solid component in 5 malignant lesions, wall thickness in 5 malignant and 1 benign lesions, septal thickness in 3 malignant and 1 benign lesions, necrosis in 1 malignant lesion, and adjacent soft tissue invasion in 5 malignant lesions. Correct characterization of malignant tumors was increased from 71% on CSE image to 93% on GEFS image. However, correct characterization of benign tumors was 93% on both images. GEFS MR imaging could be useful for characterization of ovarian tumors, especially in malignant cases, and employed for differentiation of benign from malignant tumors
Reichman, Melvin; Schabdach, Amanda; Kumar, Meera; Zielinski, Tom; Donover, Preston S; Laury-Kleintop, Lisa D; Lowery, Robert G
2015-12-01
Ras homologous (Rho) family GTPases act as molecular switches controlling cell growth, movement, and gene expression by cycling between inactive guanosine diphosphate (GDP)- and active guanosine triphosphate (GTP)-bound conformations. Guanine nucleotide exchange factors (GEFs) positively regulate Rho GTPases by accelerating GDP dissociation to allow formation of the active, GTP-bound complex. Rho proteins are directly involved in cancer pathways, especially cell migration and invasion, and inhibiting GEFs holds potential as a therapeutic strategy to diminish Rho-dependent oncogenesis. Methods for measuring GEF activity suitable for high-throughput screening (HTS) are limited. We developed a simple, generic biochemical assay method for measuring GEF activity based on the fact that GDP dissociation is generally the rate-limiting step in the Rho GTPase catalytic cycle, and thus addition of a GEF causes an increase in steady-state GTPase activity. We used the Transcreener GDP Assay, which relies on selective immunodetection of GDP, to measure the GEF-dependent stimulation of steady-state GTP hydrolysis by small GTPases using Dbs (Dbl's big sister) as a GEF for Cdc42, RhoA, and RhoB. The assay is well suited for HTS, with a homogenous format and far red fluorescence polarization (FP) readout, and it should be broadly applicable to diverse Rho GEF/GTPase pairs. © 2015 Society for Laboratory Automation and Screening.
Directory of Open Access Journals (Sweden)
Geldner Niko
2005-02-01
Full Text Available Abstract Background Small G proteins, which are essential regulators of multiple cellular functions, are activated by guanine nucleotide exchange factors (GEFs that stimulate the exchange of the tightly bound GDP nucleotide by GTP. The catalytic domain responsible for nucleotide exchange is in general associated with non-catalytic domains that define the spatio-temporal conditions of activation. In the case of small G proteins of the Arf subfamily, which are major regulators of membrane trafficking, GEFs form a heterogeneous family whose only common characteristic is the well-characterized Sec7 catalytic domain. In contrast, the function of non-catalytic domains and how they regulate/cooperate with the catalytic domain is essentially unknown. Results Based on Sec7-containing sequences from fully-annotated eukaryotic genomes, including our annotation of these sequences from Paramecium, we have investigated the domain architecture of large ArfGEFs of the BIG and GBF subfamilies, which are involved in Golgi traffic. Multiple sequence alignments combined with the analysis of predicted secondary structures, non-structured regions and splicing patterns, identifies five novel non-catalytic structural domains which are common to both subfamilies, revealing that they share a conserved modular organization. We also report a novel ArfGEF subfamily with a domain organization so far unique to alveolates, which we name TBS (TBC-Sec7. Conclusion Our analysis unifies the BIG and GBF subfamilies into a higher order subfamily, which, together with their being the only subfamilies common to all eukaryotes, suggests that they descend from a common ancestor from which species-specific ArfGEFs have subsequently evolved. Our identification of a conserved modular architecture provides a background for future functional investigation of non-catalytic domains.
Directory of Open Access Journals (Sweden)
Jesse E. Jun
2013-09-01
Full Text Available The Ras-MAPK signaling pathway is highly conserved throughout evolution and is activated downstream of a wide range of receptor stimuli. Ras guanine nucleotide exchange factors (RasGEFs catalyze GTP loading of Ras and play a pivotal role in regulating receptor-ligand induced Ras activity. In T cells, three families of functionally important RasGEFs are expressed: RasGRF, RasGRP, and SOS-family GEFs.Early on it was recognized that Ras activation is critical for T cell development and that the RasGEFs play an important role herein. More recent work has revealed that nuances in Ras activation appear to significantly impact T cell development and selection. These nuances include distinct biochemical patterns of analog versus digital Ras activation, differences in cellular localization of Ras activation, and intricate interplays between the RasGEFs during distinct T cell developmental stages as revealed by various new mouse models. In many instances, the exact nature of these nuances in Ras activation or how these may result from fine-tuning of the RasGEFs is not understood.One large group of biomolecules critically involved in the control of Ras-GEFs´functions are lipid second messengers. Multiple, yet distinct lipid products are generated following T cell receptor (TCR stimulation and bind to different domains in the RasGRP and SOS RasGEFs to facilitate the activation of the membrane-anchored Ras GTPases. In this review we highlight how different lipid-based elements are generated by various enzymes downstream of the TCR and other receptors and how these dynamic and interrelated lipid products may fine-tune Ras activation by RasGEFs in developing T cells.
International Nuclear Information System (INIS)
Thomas, Christoph; Weyand, Michael; Wittinghofer, Alfred; Berken, Antje
2006-01-01
Crystals of the catalytic PRONE domain of the guanine nucleotide exchange factor RopGEF8 and its complex with the Rho-family protein Rop4 from A. thaliana were obtained that diffract to 2.2 and 3.1 Å resolution, respectively. The PRONE domain of the guanine nucleotide exchange factor RopGEF8 (PRONE8) was purified and crystallized free and in complex with the Rho-family protein Rop4 using the hanging-drop vapour-diffusion method. PRONE8 crystals were obtained using NaCl as precipitating agent and belong to the hexagonal space group P6 5 22. Native and anomalous data sets were collected using synchrotron radiation at 100 K to 2.2 and 2.8 Å resolution, respectively. Crystals of the Rop4–PRONE8 complex belonging to space group P6 3 were obtained using Tacsimate and PEG 3350 as precipitating agents and diffracted to 3.1 Å resolution
Energy Technology Data Exchange (ETDEWEB)
Thomas, Christoph; Weyand, Michael; Wittinghofer, Alfred; Berken, Antje, E-mail: antje.berken@mpi-dortmund.mpg.de [Department of Structural Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund (Germany)
2006-06-01
Crystals of the catalytic PRONE domain of the guanine nucleotide exchange factor RopGEF8 and its complex with the Rho-family protein Rop4 from A. thaliana were obtained that diffract to 2.2 and 3.1 Å resolution, respectively. The PRONE domain of the guanine nucleotide exchange factor RopGEF8 (PRONE8) was purified and crystallized free and in complex with the Rho-family protein Rop4 using the hanging-drop vapour-diffusion method. PRONE8 crystals were obtained using NaCl as precipitating agent and belong to the hexagonal space group P6{sub 5}22. Native and anomalous data sets were collected using synchrotron radiation at 100 K to 2.2 and 2.8 Å resolution, respectively. Crystals of the Rop4–PRONE8 complex belonging to space group P6{sub 3} were obtained using Tacsimate and PEG 3350 as precipitating agents and diffracted to 3.1 Å resolution.
Directory of Open Access Journals (Sweden)
Hiroaki Kajiho
Full Text Available The Rab family of small guanosine triphosphatases (GTPases plays a vital role in membrane trafficking. Its active GTP-bound state is driven by guanine nucleotide-exchange factors (GEFs. Ras and Rab interactor (or Ras interaction/interference-like (RINL, which contains a conserved VPS9 domain critical for GEF action, was recently identified as a new Rab5 subfamily GEF in vitro. However, its detailed function and interacting molecules have not yet been fully elucidated. Here we found that RINL has GEF activity for the Rab5 subfamily proteins by measuring their GTP-bound forms in cultured cells. We also found that RINL interacts with odin, a member of the ankyrin-repeat and sterile-alpha motif (SAM domain-containing (Anks protein family. In addition, the Eph tyrosine kinase receptor EphA8 formed a ternary complex with both RINL and odin. Interestingly, RINL expression in cultured cells reduced EphA8 levels in a manner dependent on both its GEF activity and interaction with odin. In addition, knockdown of RINL increased EphA8 level in HeLa cells. Our findings suggest that RINL, as a GEF for Rab5 subfamily, is implicated in the EphA8-degradation pathway via its interaction with odin.
Structural Insights into Arl1-Mediated Targeting of the Arf-GEF BIG1 to the trans-Golgi
Directory of Open Access Journals (Sweden)
Antonio Galindo
2016-07-01
Full Text Available The GTPase Arf1 is the major regulator of vesicle traffic at both the cis- and trans-Golgi. Arf1 is activated at the cis-Golgi by the guanine nucleotide exchange factor (GEF GBF1 and at the trans-Golgi by the related GEF BIG1 or its paralog, BIG2. The trans-Golgi-specific targeting of BIG1 and BIG2 depends on the Arf-like GTPase Arl1. We find that Arl1 binds to the dimerization and cyclophilin binding (DCB domain in BIG1 and report a crystal structure of human Arl1 bound to this domain. Residues in the DCB domain that bind Arl1 are required for BIG1 to locate to the Golgi in vivo. DCB domain-binding residues in Arl1 have a distinct conformation from those in known Arl1-effector complexes, and this plasticity allows Arl1 to interact with different effectors of unrelated structure. The findings provide structural insight into how Arf1 GEFs, and hence active Arf1, achieve their correct subcellular distribution.
Singh, Nikhlesh K; Janjanam, Jagadeesh; Rao, Gadiparthi N
2017-08-25
Although the involvement of Rho proteins in the pathogenesis of vascular diseases is well studied, little is known about the role of their upstream regulators, the Rho guanine nucleotide exchange factors (RhoGEFs). Here, we sought to identify the RhoGEFs involved in monocyte chemotactic protein 1 (MCP1)-induced vascular wall remodeling. We found that, among the RhoGEFs tested, MCP1 induced tyrosine phosphorylation of p115 RhoGEF but not of PDZ RhoGEF or leukemia-associated RhoGEF in human aortic smooth muscle cells (HASMCs). Moreover, p115 RhoGEF inhibition suppressed MCP1-induced HASMC migration and proliferation. Consistent with these observations, balloon injury (BI) induced p115 RhoGEF tyrosine phosphorylation in rat common carotid arteries, and siRNA-mediated down-regulation of its levels substantially attenuated BI-induced smooth muscle cell migration and proliferation, resulting in reduced neointima formation. Furthermore, depletion of p115 RhoGEF levels also abrogated MCP1- or BI-induced Rac1-NFATc1-cyclin D1-CDK6-PKN1-CDK4-PAK1 signaling, which, as we reported previously, is involved in vascular wall remodeling. Our findings also show that protein kinase N1 (PKN1) downstream of Rac1-cyclin D1/CDK6 and upstream of CDK4-PAK1 in the p115 RhoGEF-Rac1-NFATc1-cyclin D1-CDK6-PKN1-CDK4-PAK1 signaling axis is involved in the modulation of vascular wall remodeling. Of note, we also observed that CCR2-G i/o -Fyn signaling mediates MCP1-induced p115 RhoGEF and Rac1 GTPase activation. These findings suggest that p115 RhoGEF is critical for MCP1-induced HASMC migration and proliferation in vitro and for injury-induced neointima formation in vivo by modulating Rac1-NFATc1-cyclin D1-CDK6-PKN1-CDK4-PAK1 signaling. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
Which Way In? The RalF Arf-GEF Orchestrates Rickettsia Host Cell Invasion
Rennoll-Bankert, Kristen E.; Rahman, M. Sayeedur; Gillespie, Joseph J.; Guillotte, Mark L.; Kaur, Simran J.; Lehman, Stephanie S.; Beier-Sexton, Magda; Azad, Abdu F.
2015-01-01
Bacterial Sec7-domain-containing proteins (RalF) are known only from species of Legionella and Rickettsia, which have facultative and obligate intracellular lifestyles, respectively. L. pneumophila RalF, a type IV secretion system (T4SS) effector, is a guanine nucleotide exchange factor (GEF) of ADP-ribosylation factors (Arfs), activating and recruiting host Arf1 to the Legionella-containing vacuole. In contrast, previous in vitro studies showed R. prowazekii (Typhus Group) RalF is a functional Arf-GEF that localizes to the host plasma membrane and interacts with the actin cytoskeleton via a unique C-terminal domain. As RalF is differentially encoded across Rickettsia species (e.g., pseudogenized in all Spotted Fever Group species), it may function in lineage-specific biology and pathogenicity. Herein, we demonstrate RalF of R. typhi (Typhus Group) interacts with the Rickettsia T4SS coupling protein (RvhD4) via its proximal C-terminal sequence. RalF is expressed early during infection, with its inactivation via antibody blocking significantly reducing R. typhi host cell invasion. For R. typhi and R. felis (Transitional Group), RalF ectopic expression revealed subcellular localization with the host plasma membrane and actin cytoskeleton. Remarkably, R. bellii (Ancestral Group) RalF showed perinuclear localization reminiscent of ectopically expressed Legionella RalF, for which it shares several structural features. For R. typhi, RalF co-localization with Arf6 and PI(4,5)P2 at entry foci on the host plasma membrane was determined to be critical for invasion. Thus, we propose recruitment of PI(4,5)P2 at entry foci, mediated by RalF activation of Arf6, initiates actin remodeling and ultimately facilitates bacterial invasion. Collectively, our characterization of RalF as an invasin suggests that, despite carrying a similar Arf-GEF unknown from other bacteria, different intracellular lifestyles across Rickettsia and Legionella species have driven divergent roles for Ral
Kutys, Matthew L; Yamada, Kenneth M
2014-09-01
Rho-family GTPases govern distinct types of cell migration on different extracellular matrix proteins in tissue culture or three-dimensional (3D) matrices. We searched for mechanisms selectively regulating 3D cell migration in different matrix environments and discovered a form of Cdc42-RhoA crosstalk governing cell migration through a specific pair of GTPase activator and inhibitor molecules. We first identified βPix, a guanine nucleotide exchange factor (GEF), as a specific regulator of migration in 3D collagen using an affinity-precipitation-based GEF screen. Knockdown of βPix specifically blocks cell migration in fibrillar collagen microenvironments, leading to hyperactive cellular protrusion accompanied by increased collagen matrix contraction. Live FRET imaging and RNAi knockdown linked this βPix knockdown phenotype to loss of polarized Cdc42 but not Rac1 activity, accompanied by enhanced, de-localized RhoA activity. Mechanistically, collagen phospho-regulates βPix, leading to its association with srGAP1, a GTPase-activating protein (GAP), needed to suppress RhoA activity. Our results reveal a matrix-specific pathway controlling migration involving a GEF-GAP interaction of βPix with srGAP1 that is critical for maintaining suppressive crosstalk between Cdc42 and RhoA during 3D collagen migration.
The Global Environment Facility (GEF): Right mechanism for improved implementation?
Energy Technology Data Exchange (ETDEWEB)
Andresen, Steinar; Rosendal, Kristin G.
2012-11-01
The purpose is to feed into the international discussions of environmental financial mechanisms such as for forestry and mercury by examining the performance of the GEF. We discuss performance against effectiveness and legitimacy and focus on institutional set-up and key actors as explanatory factors. Methodologically, we use document and literature analysis and interviews with key actors in organizations, state representatives and NGOs. The dominant position of the USA and the World Bank has probably contributed to the bias towards a northern environmental agenda and emphasis on effectiveness and climate change projects. The GEF has somewhat predictably diverted the flow of international money from the poorest countries to more rapidly developing countries. Still, despite turf battles between the organizations involved, the broad organisational and thematic composition of the GEF has comparative advantages. This enhances the score on legitimacy especially for biodiversity projects, although they receive less overall funding. The GEF may be seen as an indication of how, regardless of choosing established or new institutions, basic power structures and interests of dominating parties will be largely decisive for what can be achieved in global environmental governance.(auth)
Marei, Hadir; Carpy, Alejandro; Woroniuk, Anna; Vennin, Claire; White, Gavin; Timpson, Paul; Macek, Boris; Malliri, Angeliki
2016-01-01
The small GTPase Rac1 has been implicated in the formation and dissemination of tumours. Upon activation by guanine nucleotide exchange factors (GEFs), Rac1 associates with a variety of proteins in the cell thereby regulating various functions, including cell migration. However, activation of Rac1 can lead to opposing migratory phenotypes raising the possibility of exacerbating tumour progression when targeting Rac1 in a clinical setting. This calls for the identification of factors that influence Rac1-driven cell motility. Here we show that Tiam1 and P-Rex1, two Rac GEFs, promote Rac1 anti- and pro-migratory signalling cascades, respectively, through regulating the Rac1 interactome. In particular, we demonstrate that P-Rex1 stimulates migration through enhancing the interaction between Rac1 and the actin-remodelling protein flightless-1 homologue, to modulate cell contraction in a RhoA-ROCK-independent manner. PMID:26887924
Katrancha, Sara M; Wu, Yi; Zhu, Minsheng; Eipper, Betty A; Koleske, Anthony J; Mains, Richard E
2017-12-01
Bipolar disorder, schizophrenia, autism and intellectual disability are complex neurodevelopmental disorders, debilitating millions of people. Therapeutic progress is limited by poor understanding of underlying molecular pathways. Using a targeted search, we identified an enrichment of de novo mutations in the gene encoding the 330-kDa triple functional domain (TRIO) protein associated with neurodevelopmental disorders. By generating multiple TRIO antibodies, we show that the smaller TRIO9 isoform is the major brain protein product, and its levels decrease after birth. TRIO9 contains two guanine nucleotide exchange factor (GEF) domains with distinct specificities: GEF1 activates both Rac1 and RhoG; GEF2 activates RhoA. To understand the impact of disease-associated de novo mutations and other rare sequence variants on TRIO function, we utilized two FRET-based biosensors: a Rac1 biosensor to study mutations in TRIO (T)GEF1, and a RhoA biosensor to study mutations in TGEF2. We discovered that one autism-associated de novo mutation in TGEF1 (K1431M), at the TGEF1/Rac1 interface, markedly decreased its overall activity toward Rac1. A schizophrenia-associated rare sequence variant in TGEF1 (F1538Intron) was substantially less active, normalized to protein level and expressed poorly. Overall, mutations in TGEF1 decreased GEF1 activity toward Rac1. One bipolar disorder-associated rare variant (M2145T) in TGEF2 impaired inhibition by the TGEF2 pleckstrin-homology domain, resulting in dramatically increased TGEF2 activity. Overall, genetic damage to both TGEF domains altered TRIO catalytic activity, decreasing TGEF1 activity and increasing TGEF2 activity. Importantly, both GEF changes are expected to decrease neurite outgrowth, perhaps consistent with their association with neurodevelopmental disorders. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
In vitro guanine nucleotide exchange activity of DHR-2/DOCKER/CZH2 domains.
Côté, Jean-François; Vuori, Kristiina
2006-01-01
Rho family GTPases regulate a large variety of biological processes, including the reorganization of the actin cytoskeleton. Like other members of the Ras superfamily of small GTP-binding proteins, Rho GTPases cycle between a GDP-bound (inactive) and a GTP-bound (active) state, and, when active, the GTPases relay extracellular signals to a large number of downstream effectors. Guanine nucleotide exchange factors (GEFs) promote the exchange of GDP for GTP on Rho GTPases, thereby activating them. Most Rho-GEFs mediate their effects through their signature domain known as the Dbl Homology-Pleckstrin Homology (DH-PH) module. Recently, we and others identified a family of evolutionarily conserved, DOCK180-related proteins that also display GEF activity toward Rho GTPases. The DOCK180-family of proteins lacks the canonical DH-PH module. Instead, they rely on a novel domain, termed DHR-2, DOCKER, or CZH2, to exchange GDP for GTP on Rho targets. In this chapter, the experimental approach that we used to uncover the exchange activity of the DHR-2 domain of DOCK180-related proteins will be described.
Directory of Open Access Journals (Sweden)
Matthew J Spindler
Full Text Available A-kinase anchoring proteins (AKAPs are scaffolding molecules that coordinate and integrate G-protein signaling events to regulate development, physiology, and disease. One family member, AKAP13, encodes for multiple protein isoforms that contain binding sites for protein kinase A (PKA and D (PKD and an active Rho-guanine nucleotide exchange factor (Rho-GEF domain. In mice, AKAP13 is required for development as null embryos die by embryonic day 10.5 with cardiovascular phenotypes. Additionally, the AKAP13 Rho-GEF and PKD-binding domains mediate cardiomyocyte hypertrophy in cell culture. However, the requirements for the Rho-GEF and PKD-binding domains during development and cardiac hypertrophy are unknown.To determine if these AKAP13 protein domains are required for development, we used gene-trap events to create mutant mice that lacked the Rho-GEF and/or the protein kinase D-binding domains. Surprisingly, heterozygous matings produced mutant mice at Mendelian ratios that had normal viability and fertility. The adult mutant mice also had normal cardiac structure and electrocardiograms. To determine the role of these domains during β-adrenergic-induced cardiac hypertrophy, we stressed the mice with isoproterenol. We found that heart size was increased similarly in mice lacking the Rho-GEF and PKD-binding domains and wild-type controls. However, the mutant hearts had abnormal cardiac contractility as measured by fractional shortening and ejection fraction.These results indicate that the Rho-GEF and PKD-binding domains of AKAP13 are not required for mouse development, normal cardiac architecture, or β-adrenergic-induced cardiac hypertrophic remodeling. However, these domains regulate aspects of β-adrenergic-induced cardiac hypertrophy.
International Nuclear Information System (INIS)
Liao, Wei; Sharma, Sanjai
2016-01-01
Objective: Chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) cells over-express a guanine exchange factor (GEF), Rasgrf-1. This GEF increases active Ras as it catalyzes the removal of GDP from Ras so that GTP can bind and activate Ras. This study aims to study the mechanism of action of Rasgrf-1 in B-cell malignancies. Methods: N-terminus truncated Rasgrf-1 variants have a higher GEF activity as compared to the full-length transcript therefore a MCL cell line with stable over-expression of truncated Rasgrf-1 was established. The B-cell receptor (BCR) and chemokine signaling pathways were compared in the Rasgrf-1 over-expressing and a control transfected cell line. Results: Cells over-expressing truncated form of Rasgrf-1 have a higher proliferative rate as compared to control transfected cells. BCR was activated by lower concentrations of anti-IgM antibody in Rasgrf-1 over-expressing cells as compared to control cells indicating that these cells are more sensitive to BCR signaling. BCR signaling also phosphorylates Rasgrf-1 that further increases its GEF function and amplifies BCR signaling. This activation of Rasgrf-1 in over-expressing cells resulted in a higher expression of phospho-ERK, AKT, BTK and PKC-alpha as compared to control cells. Besides BCR, Rasgrf-1 over-expressing cells were also more sensitive to microenvironment stimuli as determined by resistance to apoptosis, chemotaxis and ERK pathway activation. Conclusions: This GEF protein sensitizes B-cells to BCR and chemokine mediated signaling and also upregulates a number of other signaling pathways which promotes growth and survival of these cells
Chaya, Taro; Shibata, Satoshi; Tokuhara, Yasunori; Yamaguchi, Wataru; Matsumoto, Hiroshi; Kawahara, Ichiro; Kogo, Mikihiko; Ohoka, Yoshiharu; Inagaki, Shinobu
2011-08-26
The T332I mutation in Rho guanine nucleotide exchange factor 10 (ARHGEF10) was previously found in persons with slowed nerve conduction velocities and thin myelination of peripheral nerves. However, the molecular and cellular basis of the T332I mutant is not understood. Here, we show that ARHGEF10 has a negative regulatory region in the N terminus, in which residue 332 is located, and the T332I mutant is constitutively active. An N-terminal truncated ARHGEF10 mutant, ARHGEF10 ΔN (lacking amino acids 1-332), induced cell contraction that was inhibited by a Rho kinase inhibitor Y27632 and had higher GEF activity for RhoA than the wild type. The T332I mutant also showed the phenotype similar to the N-terminal truncated mutant. These data suggest that the ARHGEF10 T332I mutation-associated phenotype observed in the peripheral nerves is due to activated GEF activity of the ARHGEF10 T332I mutant.
Chaya, Taro; Shibata, Satoshi; Tokuhara, Yasunori; Yamaguchi, Wataru; Matsumoto, Hiroshi; Kawahara, Ichiro; Kogo, Mikihiko; Ohoka, Yoshiharu; Inagaki, Shinobu
2011-01-01
The T332I mutation in Rho guanine nucleotide exchange factor 10 (ARHGEF10) was previously found in persons with slowed nerve conduction velocities and thin myelination of peripheral nerves. However, the molecular and cellular basis of the T332I mutant is not understood. Here, we show that ARHGEF10 has a negative regulatory region in the N terminus, in which residue 332 is located, and the T332I mutant is constitutively active. An N-terminal truncated ARHGEF10 mutant, ARHGEF10 ΔN (lacking amino acids 1–332), induced cell contraction that was inhibited by a Rho kinase inhibitor Y27632 and had higher GEF activity for RhoA than the wild type. The T332I mutant also showed the phenotype similar to the N-terminal truncated mutant. These data suggest that the ARHGEF10 T332I mutation-associated phenotype observed in the peripheral nerves is due to activated GEF activity of the ARHGEF10 T332I mutant. PMID:21719701
DEFF Research Database (Denmark)
Anders, Nadine; Nielsen, Michael M.; Keicher, Jutta
2008-01-01
vesicle formation by activating ARF GTPases on specific membranes in animals, plants, and fungi. However, apart from the catalytic exchange activity of the SEC7 domain, the functional significance of other conserved domains is virtually unknown. Here, we show that a distinct N-terminal domain of GNOM......The GNOM protein plays a fundamental role in Arabidopsis thaliana development by regulating endosome-to-plasma membrane trafficking required for polar localization of the auxin efflux carrier PIN1. GNOM is a family member of large ARF guanine nucleotide exchange factors (ARF-GEFs), which regulate...... mediates dimerization and in addition interacts heterotypically with two other conserved domains in vivo. In contrast with N-terminal dimerization, the heterotypic interaction is essential for GNOM function, as mutations abolishing this interaction inactivate the GNOM protein and compromise its membrane...
Chlamydial entry involves TARP binding of guanine nucleotide exchange factors.
Directory of Open Access Journals (Sweden)
B Josh Lane
2008-03-01
Full Text Available Chlamydia trachomatis attachment to cells induces the secretion of the elementary body-associated protein TARP (Translocated Actin Recruiting Protein. TARP crosses the plasma membrane where it is immediately phosphorylated at tyrosine residues by unknown host kinases. The Rac GTPase is also activated, resulting in WAVE2 and Arp2/3-dependent recruitment of actin to the sites of chlamydia attachment. We show that TARP participates directly in chlamydial invasion activating the Rac-dependent signaling cascade to recruit actin. TARP functions by binding two distinct Rac guanine nucleotide exchange factors (GEFs, Sos1 and Vav2, in a phosphotyrosine-dependent manner. The tyrosine phosphorylation profile of the sequence YEPISTENIYESI within TARP, as well as the transient activation of the phosphatidylinositol 3-kinase (PI3-K, appears to determine which GEF is utilized to activate Rac. The first and second tyrosine residues, when phosphorylated, are utilized by the Sos1/Abi1/Eps8 and Vav2, respectively, with the latter requiring the lipid phosphatidylinositol 3,4,5-triphosphate. Depletion of these critical signaling molecules by siRNA resulted in inhibition of chlamydial invasion to varying degrees, owing to a possible functional redundancy of the two pathways. Collectively, these data implicate TARP in signaling to the actin cytoskeleton remodeling machinery, demonstrating a mechanism by which C.trachomatis invades non-phagocytic cells.
Function of the Nucleotide Exchange Activity of Vav1 in T cell Development and Activation*
Saveliev, Alexander; Vanes, Lesley; Ksionda, Olga; Rapley, Jonathan; Smerdon, Stephen J.; Rittinger, Katrin; Tybulewicz, Victor L. J.
2012-01-01
The guanine nucleotide exchange factor (GEF) Vav1 is essential for transducing T cell antigen receptor (TCR) signals and therefore plays a critical role in the development and activation of T cells. It has been presumed that the GEF activity of Vav1 is important for its function; however, there has been no direct demonstration of this. Here, we generated mice expressing enzymatically inactive, but normally folded, Vav1 protein. Analysis of these mice showed that the GEF activity of Vav1 was necessary for the selection of thymocytes and for the optimal activation of T cells, including signal transduction to Rac1, Akt, and integrins. In contrast, the GEF activity of Vav1 was not required for TCR-induced calcium flux, activation of extracellular signal–regulated kinase (ERK) and protein kinase D1 (PKD1), and cell polarization. Thus, in T cells, the GEF activity of Vav1 is essential for some, but not all, of its functions. PMID:20009105
Function of the nucleotide exchange activity of vav1 in T cell development and activation.
Saveliev, Alexander; Vanes, Lesley; Ksionda, Olga; Rapley, Jonathan; Smerdon, Stephen J; Rittinger, Katrin; Tybulewicz, Victor L J
2009-12-15
The guanine nucleotide exchange factor (GEF) Vav1 is essential for transducing T cell antigen receptor (TCR) signals and therefore plays a critical role in the development and activation of T cells. It has been presumed that the GEF activity of Vav1 is important for its function; however, there has been no direct demonstration of this. Here, we generated mice expressing enzymatically inactive, but normally folded, Vav1 protein. Analysis of these mice showed that the GEF activity of Vav1 was necessary for the selection of thymocytes and for the optimal activation of T cells, including signal transduction to Rac1, Akt, and integrins. In contrast, the GEF activity of Vav1 was not required for TCR-induced calcium flux, activation of extracellular signal-regulated kinase and protein kinase D1, and cell polarization. Thus, in T cells, the GEF activity of Vav1 is essential for some, but not all, of its functions.
The Drosophila Arf GEF Steppke controls MAPK activation in EGFR signaling.
Hahn, Ines; Fuss, Bernhard; Peters, Annika; Werner, Tamara; Sieberg, Andrea; Gosejacob, Dominic; Hoch, Michael
2013-06-01
Guanine nucleotide exchange factors (GEFs) of the cytohesin protein family are regulators of GDP/GTP exchange for members of the ADP ribosylation factor (Arf) of small GTPases. They have been identified as modulators of various receptor tyrosine kinase signaling pathways including the insulin, the vascular epidermal growth factor (VEGF) and the epidermal growth factor (EGF) pathways. These pathways control many cellular functions, including cell proliferation and differentiation, and their misregulation is often associated with cancerogenesis. In vivo studies on cytohesins using genetic loss of function alleles are lacking, however, since knockout mouse models are not available yet. We have recently identified mutants for the single cytohesin Steppke (Step) in Drosophila and we could demonstrate an essential role of Step in the insulin signaling cascade. In the present study, we provide in vivo evidence for a role of Step in EGFR signaling during wing and eye development. By analyzing step mutants, transgenic RNA interference (RNAi) and overexpression lines for tissue specific as well as clonal analysis, we found that Step acts downstream of the EGFR and is required for the activation of mitogen-activated protein kinase (MAPK) and the induction of EGFR target genes. We further demonstrate that step transcription is induced by EGFR signaling whereas it is negatively regulated by insulin signaling. Furthermore, genetic studies and biochemical analysis show that Step interacts with the Connector Enhancer of KSR (CNK). We propose that Step may be part of a larger signaling scaffold coordinating receptor tyrosine kinase-dependent MAPK activation.
A software program for exchanging MR data
DEFF Research Database (Denmark)
Ring, P B; Jensen, J A; Henriksen, O
1993-01-01
of digital MR images of the human brain. Because there was no common data format, software package was developed for data exchange. This article describes the basic features of the developed software. The software package was written in the language of C and was successfully tested on an IBM-6150 UNIX...... workstation. The software is currently being tested on the following series of UNIX workstations: SUN SPARC, IBM RS6000, and HP 9000/700....
Uejima, Tamami; Ihara, Kentaro; Goh, Tatsuaki; Ito, Emi; Sunada, Mariko; Ueda, Takashi; Nakano, Akihiko; Wakatsuki, Soichi
2010-11-19
Many GTPases regulate intracellular transport and signaling in eukaryotes. Guanine nucleotide exchange factors (GEFs) activate GTPases by catalyzing the exchange of their GDP for GTP. Here we present crystallographic and biochemical studies of a GEF reaction with four crystal structures of Arabidopsis thaliana ARA7, a plant homolog of Rab5 GTPase, in complex with its GEF, VPS9a, in the nucleotide-free and GDP-bound forms, as well as a complex with aminophosphonic acid-guanylate ester and ARA7·VPS9a(D185N) with GDP. Upon complex formation with ARA7, VPS9 wedges into the interswitch region of ARA7, inhibiting the coordination of Mg(2+) and decreasing the stability of GDP binding. The aspartate finger of VPS9a recognizes GDP β-phosphate directly and pulls the P-loop lysine of ARA7 away from GDP β-phosphate toward switch II to further destabilize GDP for its release during the transition from the GDP-bound to nucleotide-free intermediates in the nucleotide exchange reaction.
Genetic screening of Scandinavian families with febrile seizures and epilepsy or GEFS+
DEFF Research Database (Denmark)
Selmer, K K; Egeland, T; Solaas, M H
2008-01-01
Background - Mutations in the three genes SCN1A, SCN1B and GABRG2, all encoding subunits of ion channels, have been known to cause generalized epilepsy with febrile seizures plus (GEFS+) in families of different origin. Objective - To study the occurrence of mutations in these genes in families...... with GEFS+ or a GEFS+ resembling phenotype of Scandinavian origin. Material and methods - We performed linkage analysis in 19 Scandinavian families with a history of febrile seizures (FS) and epilepsy or GEFS+. Where linkage could not be excluded, the genes of interest were sequenced. Results - We...... identified only one mutation in SCN1A, which seems to be a rare variant with no functional consequence. Conclusion - This suggests that mutations in these three genes are not a prevalent cause of familial cases of FS and epilepsy or GEFS+ in Scandinavia....
Moscatelli, D; Joseph-Silverstein, J; Manejias, R; Rifkin, D B
1987-01-01
A Mr 25,000 form of basic fibroblast growth factor (bFGF) has been isolated from guinea pig brain along with the typical Mr 18,000 form. Both forms were purified to homogeneity by a combination of heparin-affinity chromatography and ion-exchange chromatography on an FPLC Mono S column. The Mr 25,000 form, like the Mr 18,000 form, was not eluted from the heparin-affinity column with 0.95 M NaCl, but was eluted with 2 M NaCl. The Mr 25,000 guinea pig protein stimulated plasminogen activator pro...
Directory of Open Access Journals (Sweden)
Dulce Azevedo
Full Text Available Coordination of apical constriction in epithelial sheets is a fundamental process during embryogenesis. Here, we show that DRhoGEF2 is a key regulator of apical pulsation and constriction of amnioserosal cells during Drosophila dorsal closure. Amnioserosal cells mutant for DRhoGEF2 exhibit a consistent decrease in amnioserosa pulsations whereas overexpression of DRhoGEF2 in this tissue leads to an increase in the contraction time of pulsations. We probed the physical properties of the amnioserosa to show that the average tension in DRhoGEF2 mutant cells is lower than wild-type and that overexpression of DRhoGEF2 results in a tissue that is more solid-like than wild-type. We also observe that in the DRhoGEF2 overexpressing cells there is a dramatic increase of apical actomyosin coalescence that can contribute to the generation of more contractile forces, leading to amnioserosal cells with smaller apical surface than wild-type. Conversely, in DRhoGEF2 mutants, the apical actomyosin coalescence is impaired. These results identify DRhoGEF2 as an upstream regulator of the actomyosin contractile machinery that drives amnioserosa cells pulsations and apical constriction.
Brief introduction of GEF efficient industrial boiler project in China
Energy Technology Data Exchange (ETDEWEB)
Meijian, T.
1996-12-31
The present situation of installed industrial boilers, their efficiency and environmental impact are assessed. And the factors contribute to the low efficiency and serious pollution are summarized. Based on WB-assisted GEF project, {open_quotes}Efficient Industrial Boiler Project{close_quotes} aimed at CO{sub 2} mitigation in China, a series of effective measures to bring the GHG emission under control are addressed, in technology, system performance, and operation management aspects.
Linford, Andrea; Yoshimura, Shin-ichiro; Nunes Bastos, Ricardo; Langemeyer, Lars; Gerondopoulos, Andreas; Rigden, Daniel J; Barr, Francis A
2012-05-15
Rab GTPases define the vesicle trafficking pathways underpinning cell polarization and migration. Here, we find that Rab4, Rab11, and Rab14 and the candidate Rab GDP-GTP exchange factors (GEFs) FAM116A and AVL9 are required for cell migration. Rab14 and its GEF FAM116A localize to and act on an intermediate compartment of the transferrin-recycling pathway prior to Rab11 and after Rab5 and Rab4. This Rab14 intermediate recycling compartment has specific functions in migrating cells discrete from early and recycling endosomes. Rab14-depleted cells show increased N-cadherin levels at junctional complexes and cannot resolve cell-cell junctions. This is due to decreased shedding of cell-surface N-cadherin by the ADAM family protease ADAM10/Kuzbanian. In FAM116A- and Rab14-depleted cells, ADAM10 accumulates in a transferrin-positive endocytic compartment, and the cell-surface level of ADAM10 is correspondingly reduced. FAM116 and Rab14 therefore define an endocytic recycling pathway needed for ADAM protease trafficking and regulation of cell-cell junctions. Copyright © 2012 Elsevier Inc. All rights reserved.
Global Ensemble Forecast System (GEFS) [1 Deg.
National Oceanic and Atmospheric Administration, Department of Commerce — The Global Ensemble Forecast System (GEFS) is a weather forecast model made up of 21 separate forecasts, or ensemble members. The National Centers for Environmental...
Kanamarlapudi, Venkateswarlu; Thompson, Aiysha; Kelly, Eamonn; López Bernal, Andrés
2012-01-01
The luteinizing hormone chorionic gonadotropin receptor (LHCGR) is a Gs-coupled GPCR that is essential for the maturation and function of the ovary and testis. LHCGR is internalized following its activation, which regulates the biological responsiveness of the receptor. Previous studies indicated that ADP-ribosylation factor (ARF)6 and its GTP-exchange factor (GEF) cytohesin 2 regulate LHCGR internalization in follicular membranes. However, the mechanisms by which ARF6 and cytohesin 2 regulate LHCGR internalization remain incompletely understood. Here we investigated the role of the ARF6 signaling pathway in the internalization of heterologously expressed human LHCGR (HLHCGR) in intact cells using a combination of pharmacological inhibitors, siRNA and the expression of mutant proteins. We found that human CG (HCG)-induced HLHCGR internalization, cAMP accumulation and ARF6 activation were inhibited by Gallein (βγ inhibitor), Wortmannin (PI 3-kinase inhibitor), SecinH3 (cytohesin ARF GEF inhibitor), QS11 (an ARF GAP inhibitor), an ARF6 inhibitory peptide and ARF6 siRNA. However, Dynasore (dynamin inhibitor), the dominant negative mutants of NM23-H1 (dynamin activator) and clathrin, and PBP10 (PtdIns 4,5-P2-binding peptide) inhibited agonist-induced HLHCGR and cAMP accumulation but not ARF6 activation. These results indicate that heterotrimeric G-protein, phosphatidylinositol (PI) 3-kinase (PI3K), cytohesin ARF GEF and ARF GAP function upstream of ARF6 whereas dynamin and clathrin act downstream of ARF6 in the regulation of HCG-induced HLHCGR internalization and signaling. In conclusion, we have identified the components and molecular details of the ARF6 signaling pathway required for agonist-induced HLHCGR internalization. PMID:22523074
Ric-8A, a Gα protein guanine nucleotide exchange factor potentiates taste receptor signaling
Directory of Open Access Journals (Sweden)
Claire J Fenech
2009-10-01
Full Text Available Taste receptors for sweet, bitter and umami tastants are G-protein coupled receptors (GPCRs. While much effort has been devoted to understanding G-protein-receptor interactions and identifying the components of the signalling cascade downstream of these receptors, at the level of the G-protein the modulation of receptor signal transduction remains relatively unexplored. In this regard a taste-specific regulator of G-protein signaling (RGS, RGS21, has recently been identified. To study whether guanine nucleotide exchange factors (GEFs are involved in the transduction of the signal downstream of the taste GPCRs we investigated the expression of Ric-8A and Ric-8B in mouse taste cells and their interaction with G-protein subunits found in taste buds. Mammalian Ric-8 proteins were initially identified as potent GEFs for a range of Gα subunits and Ric-8B has recently been shown to amplify olfactory signal transduction. We find that both Ric-8A and Ric-8B are expressed in a large portion of taste bud cells and that most of these cells contain IP3R-3 a marker for sweet, umami and bitter taste receptor cells. Ric-8A interacts with Gα-gustducin and Gαi2 through which it amplifies the signal transduction of hTas2R16, a receptor for bitter compounds. Overall, these findings are consistent with a role for Ric-8 in mammalian taste signal transduction.
BLOC-3 mutated in Hermansky-Pudlak syndrome is a Rab32/38 guanine nucleotide exchange factor.
Gerondopoulos, Andreas; Langemeyer, Lars; Liang, Jin-Rui; Linford, Andrea; Barr, Francis A
2012-11-20
Hermansky-Pudlak syndrome (HPS) is a human disease characterized by partial loss of pigmentation and impaired blood clotting. These symptoms are caused by defects in the biogenesis of melanosomes and platelet dense granules, often referred to as lysosome-related organelles. Genes mutated in HPS encode subunits of the biogenesis of lysosome-related organelles complexes (BLOCs). BLOC-1 and BLOC-2, together with the AP-3 clathrin adaptor complex, act at early endosomes to sort components required for melanin formation and melanosome biogenesis away from the degradative lysosomal pathway toward early stage melanosomes. However the molecular functions of the Hps1-Hps4 complex BLOC-3 remain mysterious. Like other trafficking pathways, melanosome biogenesis and transport of enzymes involved in pigmentation involves specific Rab GTPases, in this instance Rab32 and Rab38. We now demonstrate that BLOC-3 is a Rab32 and Rab38 guanine nucleotide exchange factor (GEF). Silencing of the BLOC-3 subunits Hps1 and Hps4 results in the mislocalization of Rab32 and Rab38 and reduction in pigmentation. In addition, we show that BLOC-3 can promote specific membrane recruitment of Rab32/38. BLOC-3 therefore defines a novel Rab GEF family with a specific function in the biogenesis of lysosome-related organelles. Copyright © 2012 Elsevier Ltd. All rights reserved.
WBSCR16 Is a Guanine Nucleotide Exchange Factor Important for Mitochondrial Fusion
Directory of Open Access Journals (Sweden)
Guorui Huang
2017-07-01
Full Text Available Regulated inter-mitochondrial fusion/fission is essential for maintaining optimal mitochondrial respiration and control of apoptosis and autophagy. In mammals, mitochondrial fusion is controlled by outer membrane GTPases MFN1 and MFN2 and by inner membrane (IM GTPase OPA1. Disordered mitochondrial fusion/fission contributes to various pathologies, and MFN2 or OPA1 mutations underlie neurodegenerative diseases. Here, we show that the WBSCR16 protein is primarily associated with the outer face of the inner mitochondrial membrane and is important for mitochondrial fusion. We provide evidence of a WBSCR16/OPA1 physical interaction in the intact cell and of a WBSCR16 function as an OPA1-specific guanine nucleotide exchange factor (GEF. Homozygosity for a Wbscr16 mutation causes early embryonic lethality, whereas neurons of mice heterozygous for the mutation have mitochondria with reduced membrane potential and increased susceptibility to fragmentation upon exposure to stress, suggesting roles for WBSCR16 deficits in neuronal pathologies.
Status of the general description of fission observables by the GEF code
Jurado, B
2014-01-01
The GEneral Fission (GEF) model treats spontaneous fission and fission up to an excitation energy of about 100 MeV of a wide range of heavy nuclei. GEF makes use of general laws of statistical and quantum mechanics, assuring a high predictive power. It is unique in providing a general description of essentially all fission observables in a consistent way while preserving the correlations between all of them. In this contribution we present some of the physical aspects on which the model is based, give an overview on the results that can be obtained with the code and show an example that illustrates how the GEF code can serve as a framework for revealing the sensitivity of the fission observables to some basic nuclear properties.
Breast MR imaging: correlation of high resolution dynamic MR findings with prognostic factors
International Nuclear Information System (INIS)
Lee, Shin Ho; Cho, Nariya; Chung, Hye Kyung; Kim, Seung Ja; Cho, Kyung Soo; Moon, Woo Kyung; Cho, Joo Hee
2005-01-01
We wanted to correlate the kinetic and morphologic MR findings of invasive breast cancer with the classical and molecular prognostic factors. Eighty-seven patients with invasive ductal carcinoma NOS underwent dynamic MR imaging at 1.5 T, and with using the T1-weighted 3D FLASH technique. The morphologic findings (shape, margin, internal enhancement of the mass or the enhancement distribution and the internal enhancement of any non-mass lesion) and the kinetic findings (the initial phase and the delayed phase of the time-signal. Intensity curve) were interpreted using a ACR BI-RADS-MRI lexicon. We correlate MR findings with histopathologic prognostic factors (tumor size, lymph node status and tumor grade) and the immunohistochemically detected biomarkers (ER, PR, ρ 53, c-erbB-2, EGFR and Ki-67). Univariate and multivariate statistical analyses were than performed. Among the MR findings, a spiculated margin, rim enhancement and washout were significantly correlated with the prognostic factors. A spiculated margin was independently associated with the established predictors of a good prognosis (a lower histologic and nuclear grade, positive ER and PR) and rim enhancement was associated with a poor prognosis (a higher histologic and nuclear grade, negative ER and PR). Wash out was a independent predictor of Ki-67 activity. Some of the findings of high resolution dynamic MR imaging were associated with the prognostic factors, and these findings may predict the prognosis of breast cancer
Global Ensemble Forecast System (GEFS) [2.5 Deg.
National Oceanic and Atmospheric Administration, Department of Commerce — The Global Ensemble Forecast System (GEFS) is a weather forecast model made up of 21 separate forecasts, or ensemble members. The National Centers for Environmental...
Improving GEFS Weather Forecasts for Indian Monsoon with Statistical Downscaling
Agrawal, Ankita; Salvi, Kaustubh; Ghosh, Subimal
2014-05-01
Weather forecast has always been a challenging research problem, yet of a paramount importance as it serves the role of 'key input' in formulating modus operandi for immediate future. Short range rainfall forecasts influence a wide range of entities, right from agricultural industry to a common man. Accurate forecasts actually help in minimizing the possible damage by implementing pre-decided plan of action and hence it is necessary to gauge the quality of forecasts which might vary with the complexity of weather state and regional parameters. Indian Summer Monsoon Rainfall (ISMR) is one such perfect arena to check the quality of weather forecast not only because of the level of intricacy in spatial and temporal patterns associated with it, but also the amount of damage it can cause (because of poor forecasts) to the Indian economy by affecting agriculture Industry. The present study is undertaken with the rationales of assessing, the ability of Global Ensemble Forecast System (GEFS) in predicting ISMR over central India and the skill of statistical downscaling technique in adding value to the predictions by taking them closer to evidentiary target dataset. GEFS is a global numerical weather prediction system providing the forecast results of different climate variables at a fine resolution (0.5 degree and 1 degree). GEFS shows good skills in predicting different climatic variables but fails miserably over rainfall predictions for Indian summer monsoon rainfall, which is evident from a very low to negative correlation values between predicted and observed rainfall. Towards the fulfilment of second rationale, the statistical relationship is established between the reasonably well predicted climate variables (GEFS) and observed rainfall. The GEFS predictors are treated with multicollinearity and dimensionality reduction techniques, such as principal component analysis (PCA) and least absolute shrinkage and selection operator (LASSO). Statistical relationship is
GEF small grants programme - overview
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-12-01
This paper describes the GEF small grants program which seeks to enhance the role of households and communities in conserving global biodiversity, mitigating global climate change, and protecting international waters. Grants up to $50k have been granted for projects in 33 countries, with plans for 12 other countries. The author describes the framework that the program works under, and the methodology followed in developing and planning projects. The approach to climate change concerns is to emphasize the development of non-carbon energy development activities to provide energy sources and economic development.
General Description of Fission Observables - JEFF Report 24. GEF Model
International Nuclear Information System (INIS)
Schmidt, Karl-Heinz; Jurado, Beatriz; Amouroux, Charlotte
2014-06-01
The Joint Evaluated Fission and Fusion (JEFF) Project is a collaborative effort among the member countries of the OECD Nuclear Energy Agency (NEA) Data Bank to develop a reference nuclear data library. The JEFF library contains sets of evaluated nuclear data, mainly for fission and fusion applications; it contains a number of different data types, including neutron and proton interaction data, radioactive decay data, fission yield data and thermal scattering law data. The General fission (GEF) model is based on novel theoretical concepts and ideas developed to model low energy nuclear fission. The GEF code calculates fission-fragment yields and associated quantities (e.g. prompt neutron and gamma) for a large range of nuclei and excitation energy. This opens up the possibility of a qualitative step forward to improve further the JEFF fission yields sub-library. This report describes the GEF model which explains the complex appearance of fission observables by universal principles of theoretical models and considerations on the basis of fundamental laws of physics and mathematics. The approach reveals a high degree of regularity and provides a considerable insight into the physics of the fission process. Fission observables can be calculated with a precision that comply with the needs for applications in nuclear technology. The relevance of the approach for examining the consistency of experimental results and for evaluating nuclear data is demonstrated. (authors)
Levine, Timothy P; Daniels, Rachel D; Gatta, Alberto T; Wong, Louise H; Hayes, Matthew J
2013-02-15
Fronto-temporal dementia (FTD) and amyotrophic lateral sclerosis (ALS, also called motor neuron disease, MND) are severe neurodegenerative diseases that show considerable overlap at the clinical and cellular level. The most common single mutation in families with FTD or ALS has recently been mapped to a non-coding repeat expansion in the uncharacterized gene C9ORF72. Although a plausible mechanism for disease is that aberrant C9ORF72 mRNA poisons splicing, it is important to determine the cellular function of C9ORF72, about which nothing is known. Sensitive homology searches showed that C9ORF72 is a full-length distant homologue of proteins related to Differentially Expressed in Normal and Neoplasia (DENN), which is a GDP/GTP exchange factor (GEF) that activates Rab-GTPases. Our results suggest that C9ORF72 is likely to regulate membrane traffic in conjunction with Rab-GTPase switches, and we propose to name the gene and its product DENN-like 72 (DENNL72).
Beck, Thomas; Fritz, Dominik; Biermann, Christina; Dillmann, Rüdiger
Bei der Befundung und Visualisierung von Blutgefäßen ist deren Centerline von zentraler Bedeutung. Die Unterscheidung zwischen unverzweigten Abschnitten des Gefäßes und Verzweigungsbereichen ermöglicht den Einsatz spezialisierter und sehr effizienter Algorithmen zur modellbasierten Extraktion der Centerline. In diesem Artikel wird ein robustes Verfahren zur Verzweigungserkennung vorgestellt. Das Verfahren beruht auf einem Front-Propagation-Ansatz mit dynamisch angepassten Schwellwerten und einer anschließenden Clusteranalyse. Die vorgestellte Methode zur Verzweigungserkennung wurde als Komponente einer Architektur zur Extraktion der Centerline auf handannotierten Datensätzen getestet. Erste Ergebnisse sind sehr vielversprechend und ermöglichen auch bei pathologischen Gefäßen eine robuste Detektion von Gefäßverzweigungen.
Hu, Shuang; Pawson, Tony; Steven, Robert M
2011-09-01
Rho-family GTPases play regulatory roles in many fundamental cellular processes. Caenorhabditis elegans UNC-73 RhoGEF isoforms function in axon guidance, cell migration, muscle arm extension, phagocytosis, and neurotransmission by activating either Rac or Rho GTPase subfamilies. Multiple differentially expressed UNC-73 isoforms contain a Rac-specific RhoGEF-1 domain, a Rho-specific RhoGEF-2 domain, or both domains. The UNC-73E RhoGEF-2 isoform is activated by the G-protein subunit Gαq and is required for normal rates of locomotion; however, mechanisms of UNC-73 and Rho pathway regulation of locomotion are not clear. To better define UNC-73 function in the regulation of motility we used cell-specific and inducible promoters to examine the temporal and spatial requirements of UNC-73 RhoGEF-2 isoform function in mutant rescue experiments. We found that UNC-73E acts within peptidergic neurons of mature animals to regulate locomotion rate. Although unc-73 RhoGEF-2 mutants have grossly normal synaptic morphology and weak resistance to the acetylcholinesterase inhibitor aldicarb, they are significantly hypersensitive to the acetylcholine receptor agonist levamisole, indicating alterations in acetylcholine neurotransmitter signaling. Consistent with peptidergic neuron function, unc-73 RhoGEF-2 mutants exhibit a decreased level of neuropeptide release from motor neuron dense core vesicles (DCVs). The unc-73 locomotory phenotype is similar to those of rab-2 and unc-31, genes with distinct roles in the DCV-mediated secretory pathway. We observed that constitutively active Gαs pathway mutations, which compensate for DCV-mediated signaling defects, rescue unc-73 RhoGEF-2 and rab-2 lethargic movement phenotypes. Together, these data suggest UNC-73 RhoGEF-2 isoforms are required for proper neurotransmitter signaling and may function in the DCV-mediated neuromodulatory regulation of locomotion rate.
Directory of Open Access Journals (Sweden)
Deng Xiaolu
2011-04-01
Full Text Available Abstract Background Tumor necrosis factor-α (TNF-α, a proinflammatory cytokine, is capable of activating the small GTPase RhoA, which in turn contributes to endothelial barrier dysfunction. However, the underlying signaling mechanisms remained undefined. Therefore, we aimed to determine the role of protein kinase C (PKC isozymes in the mechanism of RhoA activation and in signaling TNF-α-induced mouse brain microvascular endothelial cell (BMEC barrier dysfunction. Methods Bend.3 cells, an immortalized mouse brain endothelial cell line, were exposed to TNF-α (10 ng/mL. RhoA activity was assessed by pull down assay. PKC-α activity was measured using enzyme assasy. BMEC barrier function was measured by transendothelial electrical resistance (TER. p115RhoGEF phosphorylation was detected by autoradiography followed by western blotting. F-actin organization was observed by rhodamine-phalloidin staining. Both pharmacological inhibitors and knockdown approaches were employed to investigate the role of PKC and p115RhoGEF in TNF-α-induced RhoA activation and BMEC permeability. Results We observed that TNF-α induces a rapid phosphorylation of p115RhoGEF, activation of PKC and RhoA in BMECs. Inhibition of conventional PKC by Gö6976 mitigated the TNF-α-induced p115RhoGEF phosphorylation and RhoA activation. Subsequently, we found that these events are regulated by PKC-α rather than PKC-β by using shRNA. In addition, P115-shRNA and n19RhoA (dominant negative mutant of RhoA transfections had no effect on mediating TNF-α-induced PKC-α activation. These data suggest that PKC-α but not PKC-β acts as an upstream regulator of p115RhoGEF phosphorylation and RhoA activation in response to TNF-α. Moreover, depletion of PKC-α, of p115RhoGEF, and inhibition of RhoA activation also prevented TNF-α-induced stress fiber formation and a decrease in TER. Conclusions Taken together, our results show that PKC-α phosphorylation of p115RhoGEF mediates TNF
Directory of Open Access Journals (Sweden)
Donghoon M Lee
Full Text Available The recruitment of GDP/GTP exchange factors (GEFs to specific subcellular sites dictates where they activate small G proteins for the regulation of various cellular processes. Cytohesins are a conserved family of plasma membrane GEFs for Arf small G proteins that regulate endocytosis. Analyses of mammalian cytohesins have identified a number of recruitment mechanisms for these multi-domain proteins, but the conservation and developmental roles for these mechanisms are unclear. Here, we report how the pleckstrin homology (PH domain of the Drosophila cytohesin Steppke affects its localization and activity at cleavage furrows of the early embryo. We found that the PH domain is necessary for Steppke furrow localization, and for it to regulate furrow structure. However, the PH domain was not sufficient for the localization. Next, we examined the role of conserved PH domain amino acid residues that are required for mammalian cytohesins to bind PIP3 or GTP-bound Arf G proteins. We confirmed that the Steppke PH domain preferentially binds PIP3 in vitro through a conserved mechanism. However, disruption of residues for PIP3 binding had no apparent effect on GFP-Steppke localization and effects. Rather, residues for binding to GTP-bound Arf G proteins made major contributions to this Steppke localization and activity. By analyzing GFP-tagged Arf and Arf-like small G proteins, we found that Arf1-GFP, Arf6-GFP and Arl4-GFP, but not Arf4-GFP, localized to furrows. However, analyses of embryos depleted of Arf1, Arf6 or Arl4 revealed either earlier defects than occur in embryos depleted of Steppke, or no detectable furrow defects, possibly because of redundancies, and thus it was difficult to assess how individual Arf small G proteins affect Steppke. Nonetheless, our data show that the Steppke PH domain and its conserved residues for binding to GTP-bound Arf G proteins have substantial effects on Steppke localization and activity in early Drosophila embryos.
Hu, Shuang; Pawson, Tony; Steven, Robert M.
2011-01-01
Rho-family GTPases play regulatory roles in many fundamental cellular processes. Caenorhabditis elegans UNC-73 RhoGEF isoforms function in axon guidance, cell migration, muscle arm extension, phagocytosis, and neurotransmission by activating either Rac or Rho GTPase subfamilies. Multiple differentially expressed UNC-73 isoforms contain a Rac-specific RhoGEF-1 domain, a Rho-specific RhoGEF-2 domain, or both domains. The UNC-73E RhoGEF-2 isoform is activated by the G-protein subunit Gαq and is required for normal rates of locomotion; however, mechanisms of UNC-73 and Rho pathway regulation of locomotion are not clear. To better define UNC-73 function in the regulation of motility we used cell-specific and inducible promoters to examine the temporal and spatial requirements of UNC-73 RhoGEF-2 isoform function in mutant rescue experiments. We found that UNC-73E acts within peptidergic neurons of mature animals to regulate locomotion rate. Although unc-73 RhoGEF-2 mutants have grossly normal synaptic morphology and weak resistance to the acetylcholinesterase inhibitor aldicarb, they are significantly hypersensitive to the acetylcholine receptor agonist levamisole, indicating alterations in acetylcholine neurotransmitter signaling. Consistent with peptidergic neuron function, unc-73 RhoGEF-2 mutants exhibit a decreased level of neuropeptide release from motor neuron dense core vesicles (DCVs). The unc-73 locomotory phenotype is similar to those of rab-2 and unc-31, genes with distinct roles in the DCV-mediated secretory pathway. We observed that constitutively active Gαs pathway mutations, which compensate for DCV-mediated signaling defects, rescue unc-73 RhoGEF-2 and rab-2 lethargic movement phenotypes. Together, these data suggest UNC-73 RhoGEF-2 isoforms are required for proper neurotransmitter signaling and may function in the DCV-mediated neuromodulatory regulation of locomotion rate. PMID:21750262
Boulaiz, Houria; Aránega, Antonia; Cáceres, Blanca; Blanca, Cáceres; Alvarez, Pablo; Pablo, Alvarez; Serrano-Rodríguez, Fernando; Fernando, Rodríguez-Serrano; Carrillo, Esmeralda; Esmeralda, Carrillo; Melguizo, Consolación; Consolación, Melguizo; Prados, Jose; Jose, Prados
2014-02-01
Double-suicide gene therapy is a promising strategy for the treatment of advanced cancer. It has become an important research line in the development of gene therapy to overcome the drawbacks of single-gene therapy. The aim of this study was to investigate the usefulness of double-suicide gene therapy with the two suicide genes, gef and apoptin, in colon carcinoma. gef and apoptin genes were cloned into a doxycycline-regulated retrovirus-mediated gene expression system. Expression of both genes in the DLD-1 cell line was confirmed by reverse transcriptase polymerase chain reaction (RT-PCR). Cell viability was determined with the sulforhodamine B colorimetric assay, and the cell cycle was studied by propidium iodide (PI) staining. Annexin V-FITC and PI assays were used to evaluate apoptosis, and the results were confirmed by electron microscopy. The mitochondrial membrane potential was measured by JC-1 assay. Our results showed that the combined expression of gef and apoptin genes was strikingly more effective than the expression of either gene alone. Co-expression of gef and apoptin synergistically enhanced the decrease in cell viability, increasing necrosis and inducing apoptosis in colon cancer cells via the mitochondrial pathway, which can be deficient in advanced or metastatic colon cancer. Double-suicide gene therapy based on gef and apoptin genes may be a candidate for the development of new colon cancer strategies, and further studies are warranted to establish the usefulness of double-suicide gene therapy in vivo.
Preoperative diagnosis of N-factor by MR in primary lung cancer
International Nuclear Information System (INIS)
Akata, Soichi; Amino, Saburo; Abe, Kimihiko
1993-01-01
We compared the accuracies of preoperative diagnosis of N-factor by CT and MR in 71 cases of primary lung cancer. Lymph nodes larger than 10 mm in diameter were defined as positive. As a result, CT and MR both achieved an accuracy of more than 80%. MR was inefficient in detecting calcification and showed lower spatial resolution than CT; however, MR was useful in detecting hilar lymph nodes because of the signal loss of blood vessels. MR should be used to detect the contralateral hilar lymph nodes swelling because the sensitivity in the hilus is 20% higher in MR than in CT and the information about the contralateral hilar lymph nodes is more important than ipsilateral hilar lymph nodes for operation. (author)
Directory of Open Access Journals (Sweden)
Benno Gammerl
2015-08-01
Full Text Available Ausgehend von verschiedenen Ansätzen in der Forschung zu Gefühlen und Räumen umreißt der Artikel das theoretische, empirische und politische Potenzial des Spannungsfelds zwischen der affektiven Durchkreuzung geordneter Strukturen und der emotionalen Bearbeitung machtdurchwirkter Raumverhältnisse. Praktiken des urban gardening und Debatten über Gentrifizierung zeigen beispielhaft, wie Analysen der dynamischen Interaktionen zwischen Räumen und Gefühlen für eine kritische Perspektive auf Urbanität fruchtbar werden können. Die Beschäftigung mit der Körperlichkeit von Raumgefühlen und der Materialität von Gefühlsräumen bietet willkommene Gelegenheiten, nach Strategien zu suchen, die weder das beharrliche Wirken des Sozialen noch die widerständige Kraft des Materiellen in deterministischer Manier überbetonen, sondern sich stattdessen auf die ambivalenten Dynamiken und Effekte gefühlsräumlicher Prozesse konzentrieren.
Magnetoresistance of nanogranular Ni/NiO controlled by exchange anisotropy
International Nuclear Information System (INIS)
Del Bianco, L.; Spizzo, F.; Tamisari, M.; Allia, P.
2013-01-01
A link between exchange anisotropy and magnetoresistance has been found to occur in a Ni/NiO sample consisting of Ni nanocrystallites (mean size ∼13 nm, Ni content ∼33 vol%) dispersed in a NiO matrix. This material shows metallic-type electric conduction and isotropic spin-dependent magnetoresistance as well as exchange bias effect. The latter is the outcome of an exchange anisotropy arising from the contact interaction between the Ni phase and the NiO matrix. Combined analysis of magnetization M(H) and magnetoresistance MR(H) loops measured in the 5–250 K temperature range after zero-field-cooling (ZFC) and after field-cooling (FC) from 300 K reveals that the magnetoresistance is influenced by exchange anisotropy, which is triggered by the FC process and can be modified in strength by varying the temperature. Compared to the ZFC case, the exchange anisotropy produces a horizontal shift of the FC MR(H) loop along with a reduction of the MR response associated to the reorientation of the Ni moments. A strict connection between magnetoresistance and remanent magnetization of FC loops on one side and the exchange field on the other, ruled by exchange anisotropy, is indicated. - Highlights: • Nanogranular Ni/NiO with giant magnetoresistance (MR) and exchange bias effect. • Exchange anisotropy produces a shift of the field-cooled MR(H) loop and reduces MR. • MR, remanence of field-cooled loops and exchange field are three correlated quantities. • It is possible to control MR of nanogranular systems through the exchange anisotropy
Synthesis and properties of Rb2GeF6:Mn4+ red-emitting phosphors
Sakurai, Shono; Nakamura, Toshihiro; Adachi, Sadao
2018-02-01
Rb2GeF6:Mn4+ red-emitting phosphors were synthesized by coprecipitation and their structural and optical properties were investigated by laser microscopy observation, X-ray diffraction (XRD) analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and PL decay measurement. Single-crystalline ingots in the form of a hexagonal pyramid were prepared with a basal plane diameter of ˜2 mm. The XRD analysis suggested that Rb2GeF6 crystallizes in the hexagonal structure (C6v4 = P63mc) with a = 0.5955 nm and c = 0.9672 nm. The phosphor exhibited the strong Mn4+-related zero-phonon line (ZPL) emission peak typically observed in host crystals with piezoelectrically active lattices such as a hexagonal lattice. The quantum efficiencies of the bulk ingot and powdered samples were 87 and 74%, respectively, with nearly the same luminescence decay time of ˜6 ms. The exact ZPL energies and related crystal-field and Racah parameters were obtained from the PL and PLE spectra by Franck-Condon analysis. Temperature-dependent PL intensities were analyzed from T = 20 to 500 K using a thermal quenching model by considering Bose-Einstein phonon statistics. A comparative discussion on the phosphor properties of Rb2GeF6:Mn4+ and Rb2MF6:Mn4+ with M = Si and Ti was also given.
Protein Kinase A (PKA) Type I Interacts with P-Rex1, a Rac Guanine Nucleotide Exchange Factor
Chávez-Vargas, Lydia; Adame-García, Sendi Rafael; Cervantes-Villagrana, Rodolfo Daniel; Castillo-Kauil, Alejandro; Bruystens, Jessica G. H.; Fukuhara, Shigetomo; Taylor, Susan S.; Mochizuki, Naoki; Reyes-Cruz, Guadalupe; Vázquez-Prado, José
2016-01-01
Morphology of migrating cells is regulated by Rho GTPases and fine-tuned by protein interactions and phosphorylation. PKA affects cell migration potentially through spatiotemporal interactions with regulators of Rho GTPases. Here we show that the endogenous regulatory (R) subunit of type I PKA interacts with P-Rex1, a Rac guanine nucleotide exchange factor that integrates chemotactic signals. Type I PKA holoenzyme interacts with P-Rex1 PDZ domains via the CNB B domain of RIα, which when expressed by itself facilitates endothelial cell migration. P-Rex1 activation localizes PKA to the cell periphery, whereas stimulation of PKA phosphorylates P-Rex1 and prevents its activation in cells responding to SDF-1 (stromal cell-derived factor 1). The P-Rex1 DEP1 domain is phosphorylated at Ser-436, which inhibits the DH-PH catalytic cassette by direct interaction. In addition, the P-Rex1 C terminus is indirectly targeted by PKA, promoting inhibitory interactions independently of the DEP1-PDZ2 region. A P-Rex1 S436A mutant construct shows increased RacGEF activity and prevents the inhibitory effect of forskolin on sphingosine 1-phosphate-dependent endothelial cell migration. Altogether, these results support the idea that P-Rex1 contributes to the spatiotemporal localization of type I PKA, which tightly regulates this guanine exchange factor by a multistep mechanism, initiated by interaction with the PDZ domains of P-Rex1 followed by direct phosphorylation at the first DEP domain and putatively indirect regulation of the C terminus, thus promoting inhibitory intramolecular interactions. This reciprocal regulation between PKA and P-Rex1 might represent a key node of integration by which chemotactic signaling is fine-tuned by PKA. PMID:26797121
Koubek, Emily J; Santy, Lorraine C
2018-05-04
Hepatocyte growth factor (HGF) is a potent signaling factor that acts on epithelial cells, causing them to dissociate and scatter. This migration is coordinated by a number of small GTPases, such as ARF6 and Rac1. Active ARF6 is required for HGF-stimulated migration and intracellular levels of ARF6-GTP and Rac1-GTP increase following HGF treatment. During migration, cross talk between ARF6 and Rac1 occurs through formation of a multi-protein complex containing the ARF-GEF cytohesin-2, the scaffolding protein GRASP/Tamalin, and the Rac1-GEF Dock180. Previously, the role of ARF6 in this process was unclear. We have now found that ARF6 and ARF1 regulate trafficking of GRASP and Dock180 to the plasma membrane following HGF treatment. Trafficking of GRASP and Dock180 is impaired by blocking ARF6-mediated recycling pathways and is required for HGF-stimulated Rac1 activation. Finally, HGF treatment stimulates association of GRASP and Dock180. Inhibition of ARF6 trafficking pathways traps GRASP and Dock180 as a complex in the cell.
Evaluation of renal transplants with Gd-DOTA dynamic MR imaging with factor analysis
International Nuclear Information System (INIS)
Chabrials, J.; Frouin, F.; Helenon, O.; Benall, H.; Kreis, H.; Moreau, J.F.; Di Paola, R.
1990-01-01
This paper reports on renal and urinary excretion factors by means of Gd-DOTA dynamic MR imaging and using factor analysis of dynamic structure (FADS) to follow-up renal transplants. We examined 60 patients with renal transplants by use of dynamic MR imaging after administration of a Gd-DOTA bolus (0.2 ml/kg) on a 0.5-T system; 10--12 fast gradient-echo sequences (TR/TE = 40/14, flip angle = 45 degree, acquisition time = 13 seconds) with single images and a 32-second intersequence delay were used. Of these, 13 dynamic MR imaging sequences were processed with an extension to dynamic MR images of FADS, previously developed to analyze nuclear medicine dynamic studies. The results were compared with the results of biologic dosages, renal biopsy and Seldinger digital arteriography
International Nuclear Information System (INIS)
Birner, Sabrina; Martinot, Eric
2005-01-01
The Global Environment Facility (GEF) has allocated more than $90 million over the past 10 years to eight projects promoting energy-efficient products in developing and transition countries. We review the early experience from these projects and suggest lessons relevant to market transformation programs. Based on GEF project designs, we also propose a menu of generic supply-side and demand-side interventions useful for designing and analyzing market transformation programs. Experience suggests that institutional and policy changes, leading to sustained price reductions and higher market volumes, are important outcomes for market transformation; that market impacts can appear early in programs due to increased expectations and awareness; and that projects can have a catalytic effect. We recommend eight principles for designers of future projects but caution that no single approach guarantees success
DEFF Research Database (Denmark)
Llavero, Francisco; Urzelai, Bakarne; Osinalde, Nerea
2015-01-01
Recently, we have reported that the active form of Rac 1 GTPase binds to the glycogen phosphorylase muscle isoform (PYGM) and modulates its enzymatic activity leading to T cell proliferation. In the lymphoid system, Rac 1 and in general other small GTPases of the Rho family participate...... in the signaling cascades that are activated after engagement of the T cell antigen receptor. However, little is known about the IL-2-dependent Rac 1 activator molecules. For the first time, a signaling pathway leading to the activation of Rac 1/PYGM in response to IL-2-stimulated T cell proliferation is described....... More specifically, αPIX, a known guanine nucleotide exchange factor for the small GTPases of the Rho family, preferentially Rac 1, mediates PYGM activation in Kit 225 T cells stimulated with IL-2. Using directed mutagenesis, phosphorylation of αPIX Rho-GEF serines 225 and 488 is required for activation...
Epac : effectors and biological functions
Roscioni, Sara S.; Elzinga, Carolina R. S.; Schmidt, Martina
Epac1 (also known as cAMP-GEF-I) and Epac2 (also known as cAMP-GEF-II) are cyclic AMP-activated guanine nucleotide exchange factors for Ras-like GTPases. Since their discovery about 10 years ago, it is now accepted that Epac proteins are novel cAMP sensors that regulate several pivotal cellular
Directory of Open Access Journals (Sweden)
Alan M Eckler
Full Text Available Membrane trafficking is essential to eukaryotic life and is controlled by a complex network of proteins that regulate movement of proteins and lipids between organelles. The GBF1/GEA family of Guanine nucleotide Exchange Factors (GEFs regulates trafficking between the endoplasmic reticulum and Golgi by catalyzing the exchange of GDP for GTP on ADP Ribosylation Factors (Arfs. Activated Arfs recruit coat protein complex 1 (COP-I to form vesicles that ferry cargo between these organelles. To further explore the function of the GBF1/GEA family, we have characterized a fission yeast mutant lacking one copy of the essential gene gea1 (gea1+/-, the Schizosaccharomyces pombe ortholog of GBF1. The haploinsufficient gea1+/- strain was shown to be sensitive to the GBF1 inhibitor brefeldin A (BFA and was rescued from BFA sensitivity by gea1p overexpression. No overt defects in localization of arf1p or arf6p were observed in gea1+/- cells, but the fission yeast homolog of the COP-I cargo sac1 was mislocalized, consistent with impaired COP-I trafficking. Although Golgi morphology appeared normal, a slight increase in vacuolar size was observed in the gea1+/- mutant strain. Importantly, gea1+/- cells exhibited dramatic cytokinesis-related defects, including disorganized contractile rings, an increased septation index, and alterations in septum morphology. Septation defects appear to result from altered secretion of enzymes required for septum dynamics, as decreased secretion of eng1p, a β-glucanase required for septum breakdown, was observed in gea1+/- cells, and overexpression of eng1p suppressed the increased septation phenotype. These observations implicate gea1 in regulation of septum breakdown and establish S. pombe as a model system to explore GBF1/GEA function in cytokinesis.
Correlation between High Resolution Dynamic MR Features and Prognostic Factors in Breast Cancer
International Nuclear Information System (INIS)
Lee, Shin Ho; Cho, Nariya; Kim, Seung Ja; Cho, Kyung Soo; Ko, Eun Sook; Moon, Woo Kyung; Cha, Joo Hee
2008-01-01
To correlate high resolution dynamic MR features with prognostic factors in breast cancer. One hundred and ninety-four women with invasive ductal carcinomas underwent dynamic MR imaging using T1-weighted three dimensional fast low-angle shot (3D-FLASH) sequence within two weeks prior to surgery. Morphological and kinetic MR features were determined based on the breast imaging and reporting data system (BI-RADS) MR imaging lexicon. Histological specimens were analyzed for tumor size, axillary lymph node status, histological grade, expression of estrogen receptor (ER), expression of progesterone receptor (PR), and expression of p53, c-erbB-2, and Ki-67. Correlations between the MR features and prognostic factors were determined using the Pearson x 2 test, linear-by-linear association, and logistic regression analysis. By multivariate analysis, a spiculated margin was a significant, independent predictor of a lower histological grade (p < 0.001), and lower expression of Ki-67 (p = 0.007). Rim enhancement was significant, independent predictor of a higher histological grade (p < 0.001), negative expression of ER (p 0.001), negative expression of PR (p < 0.001) and a larger tumor size (p = 0.006). A washout curve may predict a higher level of Ki-67 (p = 0.05). Most of the parameters of the initial enhancement phase cannot predict the status of the prognostic factors. Only the enhancement ratio may predict a larger tumor size (p 0.05). Of the BI-RADS-MR features, a spiculated margin may predict favorable prognosis, whereas rim enhancement or washout may predict unfavorable prognosis of breast cancer
Photovoltaics in Africa and the GEF: the right path to sustainable development?
International Nuclear Information System (INIS)
Bacon, I.
1998-01-01
This paper explores the relevance of promoting photovoltaic (PV) projects within Africa by focusing on the issues arising from the GEF/Zimbabwe PV project 1992-1997. It questions the utility of such projects and the reasons for the continued promotion of this technology within Africa. It concludes that financial aid for PV technology needs to be thoroughly reviewed and redirected. (author)
Zhou, C; Li, C; Li, D; Wang, Y; Shao, W; You, Y; Peng, J; Zhang, X; Lu, L; Shen, X
2013-12-19
The elongation of neuron is highly dependent on membrane trafficking. Brefeldin A (BFA)-inhibited guanine nucleotide-exchange protein 1 (BIG1) functions in the membrane trafficking between the Golgi apparatus and the plasma membrane. BFA, an uncompetitive inhibitor of BIG1 can inhibit neurite outgrowth and polarity development. In this study, we aimed to define the possible role of BIG1 in neurite development and to further investigate the potential mechanism. By immunostaining, we found that BIG1 was extensively colocalized with synaptophysin, a marker for synaptic vesicles in soma and partly in neurites. The amount of both protein and mRNA of BIG1 were up-regulated during rat brain development. BIG1 depletion significantly decreased the neurite length and inhibited the phosphorylation of phosphatidylinositide 3-kinase (PI3K) and protein kinase B (AKT). Inhibition of BIG1 guanine nucleotide-exchange factor (GEF) activity by BFA or overexpression of the dominant-negative BIG1 reduced PI3K and AKT phosphorylation, indicating regulatory effects of BIG1 on PI3K-AKT signaling pathway is dependent on its GEF activity. BIG1 siRNA or BFA treatment also significantly reduced extracellular signal-regulated kinase (ERK) phosphorylation. Overexpression of wild-type BIG1 significantly increased ERK phosphorylation, but the dominant-negative BIG1 had no effect on ERK phosphorylation, indicating the involvement of BIG1 in ERK signaling regulation may not be dependent on its GEF activity. Our result identified a novel function of BIG1 in neurite development. The newly recognized function integrates the function of BIG1 in membrane trafficking with the activation of PI3K-AKT and ERK signaling pathways which are critical in neurite development. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.
La Theorie des Gefühls hegeliana in dialogo con le recenti teorie sulle emozioni
Directory of Open Access Journals (Sweden)
Caterina Maurer
2017-04-01
Full Text Available Considering the relevance of the interaction between neuroscience, psychology, and philosophy in the contemporary debate on emotions, this paper aims at establishing a fruitful dialogue between Hegel’s Philosophie des subjektiven Geistes and the most important neuroscientific and psychological research on emotions. By means of an analysis of the role of Empfindungen (sensations and Gefühle (feelings in the Enzyklopädie der philosophischen Wissenschaften (1830, we will show that Hegel developed a Theorie des Gefühls. The proposed dialogue between Hegel’s thought and contemporary theories is useful for distinguishing the various types of emotions and their cognitive and affective aspects. In fact, it will emerge that both Hegel and recent studies on emotion consider emotions to be characterized by a cognitive valence which enables a person to orient herself/himself in the world.
A continuous exchange factor method for radiative exchange in enclosures with participating media
International Nuclear Information System (INIS)
Naraghi, M.H.N.; Chung, B.T.F.; Litkouhi, B.
1987-01-01
A continuous exchange factor method for analysis of radiative exchange in enclosures is developed. In this method two types of exchange functions are defined, direct exchange function and total exchange function. Certain integral equations relating total exchange functions to direct exchange functions are developed. These integral equations are solved using Gaussian quadrature integration method. The results obtained based on the present approach are found to be more accurate than those of the zonal method
Energy Technology Data Exchange (ETDEWEB)
Glemarec, Yannick; Rickerson, Wilson; Waissbein, Oliver
2012-11-15
As a Global Environment Facility (GEF) founding implementing agency, UNDP has worked on over 230 GEF-supported clean energy projects in close to 100 developing countries since 1992. About 100 of these projects in 80 countries have focused on renewable energy, supported by approximately US $ 293 million in GEF funds and leveraging US $1.48 billion in associated co-financing from national governments, international organizations, the private sector and non-governmental organizations. As part of UNDP efforts to codify and share lessons learnt from these initiatives, this report addresses how scarce public resources can be used to catalyze larger private financial flows for renewable energy. It provides an overview of UNDP-GEF’s extensive work supporting development of national renewable energy policies such as feed-in tariffs. In these activities UNDP-GEF assists developing countries to assess key risks and barriers to technology diffusion and then to identify a mix of policy and financial de-risking measures to remove these barriers and drive investment. This approach is illustrated through three case studies in Uruguay, Mauritius and Kazakhstan. This report is complemented by a companion publication presenting an innovative UNDP financial modeling tool to assist policymakers in appraising different public instruments to promote clean energy.
A non-typical sequence of phase transitions in (NH4)3GeF7: optical and structural characterization.
Mel'nikova, S V; Molokeev, M S; Laptash, N M; Misyul, S V
2016-03-28
Single crystals of germanium double salt (NH4)3GeF7 = (NH4)2GeF6·NH4F = (NH4)3[GeF6]F were grown and studied by the methods of polarization optics and X-ray diffraction. The birefringence Δn = (no - ne), the rotation angle of the optical indicatrix ϕ(T) and unit cell parameters were measured in the temperature range 100-400 K. Three structural phase transitions were found at the temperatures: T1↓ = 279.2 K (T1↑ = 279.4 K), T2↑ = 270 K (T2↓ = 268.9 K), T3↓ = 218 K (T3↑ = 227 K). An unusual sequence of symmetry transformations with temperature change was established: P4/mbm (Z = 2) (G1) ↔ Pbam (Z = 4) (G2) ↔ P21/c (Z = 4) (G3) ↔ Pa3[combining macron] (Z = 8) (G4). The crystal structures of different phases were determined. The experimental data were additionally interpreted by a group-theoretical analysis of the complete condensate of order parameters taking into account the critical and noncritical atomic displacements. Strengthening of the N-HF hydrogen bonds can be a driving force of the observed phase transitions.
Hybrid MR-PET of brain tumours using amino acid PET and chemical exchange saturation transfer MRI.
da Silva, N A; Lohmann, P; Fairney, J; Magill, A W; Oros Peusquens, A-M; Choi, C-H; Stirnberg, R; Stoffels, G; Galldiks, N; Golay, X; Langen, K-J; Jon Shah, N
2018-06-01
PET using radiolabelled amino acids has become a promising tool in the diagnostics of gliomas and brain metastasis. Current research is focused on the evaluation of amide proton transfer (APT) chemical exchange saturation transfer (CEST) MR imaging for brain tumour imaging. In this hybrid MR-PET study, brain tumours were compared using 3D data derived from APT-CEST MRI and amino acid PET using O-(2- 18 F-fluoroethyl)-L-tyrosine ( 18 F-FET). Eight patients with gliomas were investigated simultaneously with 18 F-FET PET and APT-CEST MRI using a 3-T MR-BrainPET scanner. CEST imaging was based on a steady-state approach using a B 1 average power of 1μT. B 0 field inhomogeneities were corrected a Prametric images of magnetisation transfer ratio asymmetry (MTR asym ) and differences to the extrapolated semi-solid magnetisation transfer reference method, APT# and nuclear Overhauser effect (NOE#), were calculated. Statistical analysis of the tumour-to-brain ratio of the CEST data was performed against PET data using the non-parametric Wilcoxon test. A tumour-to-brain ratio derived from APT# and 18 F-FET presented no significant differences, and no correlation was found between APT# and 18 F-FET PET data. The distance between local hot spot APT# and 18 F-FET were different (average 20 ± 13 mm, range 4-45 mm). For the first time, CEST images were compared with 18 F-FET in a simultaneous MR-PET measurement. Imaging findings derived from 18 F-FET PET and APT CEST MRI seem to provide different biological information. The validation of these imaging findings by histological confirmation is necessary, ideally using stereotactic biopsy.
CEST and PARACEST MR contrast agents
International Nuclear Information System (INIS)
Hancu, Ileana; Dixon, W. Thomas; Woods, Mark; Sherry, A. Dean; Vinogradov, Elena; Lenkinski, Robert E.
2010-01-01
In this review we describe the status of development for a new class of magnetic resonance (MR) contrast agents, based on chemical exchange saturation transfer (CEST). The mathematics and physics relevant to the description of the CEST effect in MR are presented in an appendix published in the online version only. We discuss the issues arising when translating in vitro results obtained with CEST agents to using these MR agents in in vivo model studies and in humans. Examples are given on how these agents are imaged in vivo. We summarize the status of development of these CEST agents, and speculate about the next steps that may be taken towards the demonstration of CEST MR imaging in clinical applications
Energy Technology Data Exchange (ETDEWEB)
Yamaguchi, Kizashi [Institute for Nano Science Design Center, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan and TOYOTA Physical and Chemical Research Institute, Nagakute, Aichi, 480-1192 (Japan); Nishihara, Satomichi; Saito, Toru; Yamanaka, Shusuke; Kitagawa, Yasutaka; Kawakami, Takashi; Yamada, Satoru; Isobe, Hiroshi; Okumura, Mitsutaka [Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)
2015-01-22
First principle calculations of effective exchange integrals (J) in the Heisenberg model for diradical species were performed by both symmetry-adapted (SA) multi-reference (MR) and broken-symmetry (BS) single reference (SR) methods. Mukherjee-type (Mk) state specific (SS) MR coupled-cluster (CC) calculations by the use of natural orbital (NO) references of ROHF, UHF, UDFT and CASSCF solutions were carried out to elucidate J values for di- and poly-radical species. Spin-unrestricted Hartree Fock (UHF) based coupled-cluster (CC) computations were also performed to these species. Comparison between UHF-NO(UNO)-MkMRCC and BS UHF-CC computational results indicated that spin-contamination of UHF-CC solutions still remains at the SD level. In order to eliminate the spin contamination, approximate spin-projection (AP) scheme was applied for UCC, and the AP procedure indeed corrected the error to yield good agreement with MkMRCC in energy. The CC double with spin-unrestricted Brueckner's orbital (UBD) was furthermore employed for these species, showing that spin-contamination involved in UHF solutions is largely suppressed, and therefore AP scheme for UBCCD removed easily the rest of spin-contamination. We also performed spin-unrestricted pure- and hybrid-density functional theory (UDFT) calculations of diradical and polyradical species. Three different computational schemes for total spin angular momentums were examined for the AP correction of the hybrid (H) UDFT. HUDFT calculations followed by AP, HUDFT(AP), yielded the S-T gaps that were qualitatively in good agreement with those of MkMRCCSD, UHF-CC(AP) and UB-CC(AP). Thus a systematic comparison among MkMRCCSD, UCC(AP) UBD(AP) and UDFT(AP) was performed concerning with the first principle calculations of J values in di- and poly-radical species. It was found that BS (AP) methods reproduce MkMRCCSD results, indicating their applicability to large exchange coupled systems.
Reversible brain inactivation induces discontinuous gas exchange in cockroaches.
Matthews, Philip G D; White, Craig R
2013-06-01
Many insects at rest breathe discontinuously, alternating between brief bouts of gas exchange and extended periods of breath-holding. The association between discontinuous gas exchange cycles (DGCs) and inactivity has long been recognised, leading to speculation that DGCs lie at one end of a continuum of gas exchange patterns, from continuous to discontinuous, linked to metabolic rate (MR). However, the neural hypothesis posits that it is the downregulation of brain activity and a change in the neural control of gas exchange, rather than low MR per se, which is responsible for the emergence of DGCs during inactivity. To test this, Nauphoeta cinerea cockroaches had their brains inactivated by applying a Peltier-chilled cold probe to the head. Once brain temperature fell to 8°C, cockroaches switched from a continuous to a discontinuous breathing pattern. Re-warming the brain abolished the DGC and re-established a continuous breathing pattern. Chilling the brain did not significantly reduce the cockroaches' MR and there was no association between the gas exchange pattern displayed by the insect and its MR. This demonstrates that DGCs can arise due to a decrease in brain activity and a change in the underlying regulation of gas exchange, and are not necessarily a simple consequence of low respiratory demand.
cAMP signalling in the vasculature: the role of Epac (exchange protein directly activated by cAMP).
Roberts, Owain Llŷr; Dart, Caroline
2014-02-01
The second messenger cAMP plays a central role in mediating vascular smooth muscle relaxation in response to vasoactive transmitters and in strengthening endothelial cell-cell junctions that regulate the movement of solutes, cells and macromolecules between the blood and the surrounding tissue. The vasculature expresses three cAMP effector proteins: PKA (protein kinase A), CNG (cyclic-nucleotide-gated) ion channels, and the most recently discovered Epacs (exchange proteins directly activated by cAMP). Epacs are a family of GEFs (guanine-nucleotide-exchange factors) for the small Ras-related GTPases Rap1 and Rap2, and are being increasingly implicated as important mediators of cAMP signalling, both in their own right and in parallel with the prototypical cAMP target PKA. In the present paper, we review what is currently known about the role of Epac within blood vessels, particularly with regard to the regulation of vascular tone, endothelial barrier function and inflammation.
Yang, Long; Bashaw, Greg J
2006-11-22
Son of sevenless (Sos) is a dual specificity guanine nucleotide exchange factor (GEF) that regulates both Ras and Rho family GTPases and thus is uniquely poised to integrate signals that affect both gene expression and cytoskeletal reorganization. Here, using genetics, biochemistry, and cell biology, we demonstrate that Sos is recruited to the plasma membrane, where it forms a ternary complex with the Roundabout receptor and the SH3-SH2 adaptor protein Dreadlocks (Dock) to regulate Rac-dependent cytoskeletal rearrangement in response to the Slit ligand. Intriguingly, the Ras and Rac-GEF activities of Sos can be uncoupled during Robo-mediated axon repulsion; Sos axon guidance function depends on its Rac-GEF activity, but not its Ras-GEF activity. These results provide in vivo evidence that the Ras and RhoGEF domains of Sos are separable signaling modules and support a model in which Robo recruits Sos to the membrane via Dock to activate Rac during midline repulsion.
Lucato, Christina M; Halls, Michelle L; Ooms, Lisa M; Liu, Heng-Jia; Mitchell, Christina A; Whisstock, James C; Ellisdon, Andrew M
2015-08-21
The P-Rex (phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-dependent Rac exchanger) family (P-Rex1 and P-Rex2) of the Rho guanine nucleotide exchange factors (Rho GEFs) activate Rac GTPases to regulate cell migration, invasion, and metastasis in several human cancers. The family is unique among Rho GEFs, as their activity is regulated by the synergistic binding of PIP3 and Gβγ at the plasma membrane. However, the molecular mechanism of this family of multi-domain proteins remains unclear. We report the 1.95 Å crystal structure of the catalytic P-Rex1 DH-PH tandem domain in complex with its cognate GTPase, Rac1 (Ras-related C3 botulinum toxin substrate-1). Mutations in the P-Rex1·Rac1 interface revealed a critical role for this complex in signaling downstream of receptor tyrosine kinases and G protein-coupled receptors. The structural data indicated that the PIP3/Gβγ binding sites are on the opposite surface and markedly removed from the Rac1 interface, supporting a model whereby P-Rex1 binding to PIP3 and/or Gβγ releases inhibitory C-terminal domains to expose the Rac1 binding site. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.
Directory of Open Access Journals (Sweden)
Lina Guerra
Full Text Available BACKGROUND: Exposure of adherent cells to DNA damaging agents, such as the bacterial cytolethal distending toxin (CDT or ionizing radiations (IR, activates the small GTPase RhoA, which promotes the formation of actin stress fibers and delays cell death. The signalling intermediates that regulate RhoA activation and promote cell survival are unknown. PRINCIPAL FINDINGS: We demonstrate that the nuclear RhoA-specific Guanine nucleotide Exchange Factor (GEF Net1 becomes dephosphorylated at a critical inhibitory site in cells exposed to CDT or IR. Expression of a dominant negative Net1 or Net1 knock down by iRNA prevented RhoA activation, inhibited the formation of stress fibers, and enhanced cell death, indicating that Net1 activation is required for this RhoA-mediated responses to genotoxic stress. The Net1 and RhoA-dependent signals involved activation of the Mitogen-Activated Protein Kinase p38 and its downstream target MAPK-activated protein kinase 2. SIGNIFICANCE: Our data highlight the importance of Net1 in controlling RhoA and p38 MAPK mediated cell survival in cells exposed to DNA damaging agents and illustrate a molecular pathway whereby chronic exposure to a bacterial toxin may promote genomic instability.
International Nuclear Information System (INIS)
Sakata, Koh-ichi; Hareyama, Masato; Tamakawa, Mituharu; Oouchi, Atushi; Sido, Mitsuo; Nagakura, Hisayasu; Akiba, Hidenari; Koito, Kazumitsu; Himi, Tetsuo; Asakura, Kohji
1999-01-01
Purpose: To examine the usefulness of MR imaging for predicting local control of nasopharyngeal carcinoma (NPC) and the value of MR imaging in the newly published fifth edition of the TNM classification. Methods and Materials: We studied 29 patients with NPC with MR imaging and CT before and after treatment. Staging was done according to the fourth and newly published fifth editions of the International Union Against Cancer (UICC) staging system. The radiotherapy protocol was designed to deliver 66 to 68 Gy to the primary tumor and clinically involved nodes. Results: MR proved better than CT at identifying obliteration of the pharyngobasilar fascia, invasion of the sinus of Morgagni, through which the cartilaginous portion of the eustachian tube and the levator veli palatini muscle pass, invasion of the skull base, and metastases to lymph nodes in the carotid and retropharyngeal spaces. All seven patients without invasion of the pharyngobasilar fascia had local control. The local control rates of patients with invasion of the skull base were not good (60 to 73%). There was no apparent relationship between tumor volume determined by T1-weighted MR images and local control when the tumor volume was more than 20 cc. The newly published N staging system appears to successfully identify the high-risk group for distant metastasis as N3. In our series, four of five patients with N3 disease developed distant metastases. Conclusion: Deep infiltration of the tumor is a more important prognostic factor in NPC than tumor volume. Since the newly published T staging system requires a search for tumor invasion into soft tissue such as parapharyngeal space and bony structures, MR imaging may be indispensable for the newly published NPC staging system
Sinsky, E.; Zhu, Y.; Li, W.; Guan, H.; Melhauser, C.
2017-12-01
Optimal forecast quality is crucial for the preservation of life and property. Improving monthly forecast performance over both the tropics and extra-tropics requires attention to various physical aspects such as the representation of the underlying SST, model physics and the representation of the model physics uncertainty for an ensemble forecast system. This work focuses on the impact of stochastic physics, SST and the convection scheme on forecast performance for the sub-seasonal scale over the tropics and extra-tropics with emphasis on the Madden-Julian Oscillation (MJO). A 2-year period is evaluated using the National Centers for Environmental Prediction (NCEP) Global Ensemble Forecast System (GEFS). Three experiments with different configurations than the operational GEFS were performed to illustrate the impact of the stochastic physics, SST and convection scheme. These experiments are compared against a control experiment (CTL) which consists of the operational GEFS but its integration is extended from 16 to 35 days. The three configurations are: 1) SPs, which uses a Stochastically Perturbed Physics Tendencies (SPPT), Stochastic Perturbed Humidity (SHUM) and Stochastic Kinetic Energy Backscatter (SKEB); 2) SPs+SST_bc, which uses a combination of SPs and a bias-corrected forecast SST from the NCEP Climate Forecast System Version 2 (CFSv2); and 3) SPs+SST_bc+SA_CV, which combines SPs, a bias-corrected forecast SST and a scale aware convection scheme. When comparing to the CTL experiment, SPs shows substantial improvement. The MJO skill has improved by about 4 lead days during the 2-year period. Improvement is also seen over the extra-tropics due to the updated stochastic physics, where there is a 3.1% and a 4.2% improvement during weeks 3 and 4 over the northern hemisphere and southern hemisphere, respectively. Improvement is also seen when the bias-corrected CFSv2 SST is combined with SPs. Additionally, forecast performance enhances when the scale aware
International Nuclear Information System (INIS)
Saito, Junki; Hashimoto, Kazuhito; Okamoto, Akihiro
2016-01-01
Microbial electrode catalysis such as microbial fuel cells or electrosynthesis involves electron exchange with the electrodes located at the cell exterior; i.e., extracellular electron transport (EET). Despite the vast amount of research on the kinetics of EET to optimize the catalysis rate, the relevance of other factors, including upstream metabolic reactions, has scarcely been investigated. Herein, we report an in vivo electrochemical assay to confirm whether EET limits anodic current production (j) for the lactate oxidation of Shewanella oneidensis MR-1. Addition of riboflavin, which specifically enhances the EET rate, increased j only in the early phase before j saturation. In contrast, when we removed a trace metal ion necessary for upstream reactions from the electrolyte, a significant decrease in j and the lactate consumption rate was observed only after j saturation. These data suggest that the limiting factor for j shifted from EET to upstream reactions, highlighting the general importance of enhancing, for example, microbial metabolism, especially for long-standing practical applications. Our concept to specifically control the rate of EET could be applicable to other bioelectrode catalysis systems as a strategy to monitor their rate-limiting factors.
Casey, F P; Baird, D; Feng, Q; Gutenkunst, R N; Waterfall, J J; Myers, C R; Brown, K S; Cerione, R A; Sethna, J P
2007-05-01
We apply the methods of optimal experimental design to a differential equation model for epidermal growth factor receptor signalling, trafficking and down-regulation. The model incorporates the role of a recently discovered protein complex made up of the E3 ubiquitin ligase, Cbl, the guanine exchange factor (GEF), Cool-1 (beta -Pix) and the Rho family G protein Cdc42. The complex has been suggested to be important in disrupting receptor down-regulation. We demonstrate that the model interactions can accurately reproduce the experimental observations, that they can be used to make predictions with accompanying uncertainties, and that we can apply ideas of optimal experimental design to suggest new experiments that reduce the uncertainty on unmeasurable components of the system.
Chávez-Vargas, Lydia; Adame-García, Sendi Rafael; Cervantes-Villagrana, Rodolfo Daniel; Castillo-Kauil, Alejandro; Bruystens, Jessica G H; Fukuhara, Shigetomo; Taylor, Susan S; Mochizuki, Naoki; Reyes-Cruz, Guadalupe; Vázquez-Prado, José
2016-03-18
Morphology of migrating cells is regulated by Rho GTPases and fine-tuned by protein interactions and phosphorylation. PKA affects cell migration potentially through spatiotemporal interactions with regulators of Rho GTPases. Here we show that the endogenous regulatory (R) subunit of type I PKA interacts with P-Rex1, a Rac guanine nucleotide exchange factor that integrates chemotactic signals. Type I PKA holoenzyme interacts with P-Rex1 PDZ domains via the CNB B domain of RIα, which when expressed by itself facilitates endothelial cell migration. P-Rex1 activation localizes PKA to the cell periphery, whereas stimulation of PKA phosphorylates P-Rex1 and prevents its activation in cells responding to SDF-1 (stromal cell-derived factor 1). The P-Rex1 DEP1 domain is phosphorylated at Ser-436, which inhibits the DH-PH catalytic cassette by direct interaction. In addition, the P-Rex1 C terminus is indirectly targeted by PKA, promoting inhibitory interactions independently of the DEP1-PDZ2 region. A P-Rex1 S436A mutant construct shows increased RacGEF activity and prevents the inhibitory effect of forskolin on sphingosine 1-phosphate-dependent endothelial cell migration. Altogether, these results support the idea that P-Rex1 contributes to the spatiotemporal localization of type I PKA, which tightly regulates this guanine exchange factor by a multistep mechanism, initiated by interaction with the PDZ domains of P-Rex1 followed by direct phosphorylation at the first DEP domain and putatively indirect regulation of the C terminus, thus promoting inhibitory intramolecular interactions. This reciprocal regulation between PKA and P-Rex1 might represent a key node of integration by which chemotactic signaling is fine-tuned by PKA. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.
Marcus-Gueret, Nancy; Schmidt, Kristopher L.; Stringham, Eve G.
2012-01-01
The cytoskeleton regulator UNC-53/NAV2 is required for both the anterior and posterior outgrowth of several neurons as well as that of the excretory cell while the kinesin-like motor VAB-8 is essential for most posteriorly directed migrations in Caenorhabditis elegans. Null mutations in either unc-53 or vab-8 result in reduced posterior excretory canal outgrowth, while double null mutants display an enhanced canal extension defect, suggesting the genes act in separate pathways to control this posteriorly directed outgrowth. Genetic analysis of putative interactors of UNC-53 or VAB-8, and cell-specific rescue experiments suggest that VAB-8, SAX-3/ROBO, SLT-1/Slit, and EVA-1 are functioning together in the outgrowth of the excretory canals, while UNC-53 appears to function in a parallel pathway with UNC-71/ADAM. The known VAB-8 interactor, the Rac/Rho GEF UNC-73/TRIO operates in both pathways, as isoform specific alleles exhibit enhancement of the phenotype in double-mutant combination with either unc-53 or vab-8. On the basis of these results, we propose a bipartite model for UNC-73/TRIO activity in excretory canal extension: a cell autonomous function that is mediated by the Rho-specific GEF domain of the UNC-73E isoform in conjunction with UNC-53 and UNC-71 and a cell nonautonomous function that is mediated by the Rac-specific GEF domain of the UNC-73B isoform, through partnering with VAB-8 and the receptors SAX-3 and EVA-1. PMID:21996675
Directory of Open Access Journals (Sweden)
Ma Hongqiang
2018-01-01
Full Text Available In this paper, the stresses of plate-fin structures at the different operation parameters were analyzed in actual operation process of LNG plate-fin heat exchanger based on finite element method and thermal elastic theory. Stress characteristics of plate-fin structures were investigated at the different operation parameters of that. The results show that the structural failure of plate-fin structures is mainly induced by the maximum shear stress at the brazing filler metal layer between plate and fin while by the maximum normal stress in the region of brazed joint near the fin side. And a crack would initiate in brazed joint near the fin side. The maximum normal stress is also main factor to result in the structural failure of plate-fin structures at the different temperature difference (between Natural Gas (NG and Mixture Refrigerant (MR, MR temperature and NG pressure of LNG heat exchanger. At the same time, the peak stresses obviously increase as the temperature difference, MR temperature and NG pressure increase. These results will provide some constructive instructions in the safe operation of LNG plate-fin heat exchanger in a large-scale LNG cold-box.
RADGEN: A radiation exchange factor generator for rod bundles
International Nuclear Information System (INIS)
Rector, D.R.
1987-10-01
The RADGEN computer program has been developed at Pacific Northwest Laboratory (PNL) to generate input required for the thermal radiation models used in the COBRA-SFS (Spent Fuel Storage) computer program. The COBRA-SFS program uses radiation exchange factors to describe the net amount of energy transferred from each surface to every other surface in an enclosure. The RADGEN program generates radiation exchange factors for arrays of rods on a square or triangular pitch as well as open channel geometries. This report describes the input requirements for the RADGEN code, which may be executed in a batch or interactive mode, and outlines the solution procedure used to obtain the exchange factors. 4 refs., 25 figs., 13 tabs
Closing the Gap GEF Experiences in Global Energy Efficiency
Yang, Ming
2013-01-01
Energy efficiency plays and will continue to play an important role in the world to save energy and mitigate greenhouse gas (GHG) emissions. However, little is known on how much additional capital should be invested to ensure using energy efficiently as it should be, and very little is known which sub-areas, technologies, and countries shall achieve maximum greenhouse gas emissions mitigation per dollar of investment in energy efficiency worldwide. Analyzing completed and slowly moving energy efficiency projects by the Global Environment Facility during 1991-2010, Closing the Gap: GEF Experiences in Global Energy Efficiency evaluates impacts of multi-billion-dollar investments in the world energy efficiency. It covers the following areas: 1. Reviewing the world energy efficiency investment and disclosing the global energy efficiency gap and market barriers that cause the gap; 2. Leveraging private funds with public funds and other resources in energy efficiency investments; using...
Polarized growth of pollen tubes is a critical step for successful reproduction in angiosperms and is controlled by ROP GTPases. Spatiotemporal activation of ROP (Rho GTPases of plants) necessitates a complex and sophisticated regulatory system, in which guanine nucleotide exchange factors (RopGEFs)...
What determines the exchange rate: economic factors or market sentiment?
Gregory P. Hopper
1997-01-01
Do economic factors influence exchange rates? Or does market sentiment play a bigger role? Are short-run exchange rates predictable? Greg Hopper reviews exchange-rate economics, focusing on what is predictable and what isn't. He also examines the practical implications of exchange-rate theories for currency option pricing, risk management, and portfolio selection.
Energy Technology Data Exchange (ETDEWEB)
Fritz, J.; Pereira, P.L. [Diagnostische Radiologie, Eberhard-Karls-Universitaet, Tuebingen (Germany)
2007-09-15
X-ray fluoroscopy and computed tomography are frequently used to perform percutaneous interventions in pain therapy. The development of MR-compatible therapy needles now allows these interventions to be performed under MR imaging guidance. MR-guided interventions may be performed using most clinical MR scanners; however, systems with an open configuration are advantageous. Multiplanar pre- and intra-procedural MR imaging provides the interventionalist with essential information, such as evaluation of anatomy and pathology, as well as the planning of the procedure and monitoring of fluid distribution without the use of contrast agents. With the use of non-ionizing radiation, interventional MR imaging is especially suited for the treatment of children and young adults as well as for serial injection therapy. For spinal MR interventions, passive needle visualization is an easily achievable and reliable method. The resulting needle artifact is influenced by several factors such as the alloy of the needle, the strength of the static magnetic field, the sequence type, the spatial orientation of the therapy needle as well as the echo time and may further be optimized during the intervention by alteration of the last three factors. Fast acquisition techniques and image processing allow for continuous, near real-time MR imaging (so-called MR fluoroscopy) and interactive needle navigations, comparable to X-ray fluoroscopy and CT fluoroscopy. The purpose of this review is to illustrate and discuss general concepts of interventional MR imaging. A spectrum of interventional MR imaging procedures in spinal pain therapy is described and illustrated, including procedures such as lumbar facet joint injections, sacroiliac joint injections, lumbar spinal nerve root infiltrations and drug delivery to the lumbar sympathetic chain. (orig.)
MR imaging of normal bone marrow; Obraz MR prawidlowego szpiku kostnego
Energy Technology Data Exchange (ETDEWEB)
Stajgis, M.; Paprzycki, W. [Osrodek Diagnostyki Obrazowej IR, Akademia Medyczna, Poznan (Poland)
1994-12-31
Principles of MR bone marrow imaging on the basis of retrospective analysis of MR examinations of bone marrow in different anatomic sites in 200 patients have been discussed. Significance of different physiologic factors and processes such as age, steatosis, osteoporosis, conversion and reconversion, which influence on MR bone marrow images, have been emphasized. T1-weighted images obtained with spin-echo sequences give the most of information about bone marrow structure in MR. Thorough knowledge of bone marrow physiology and clinical status of the patient is indispensable in correct interpretation of hypointensive lesions on T1-weighted images. When presence of disseminated bone marrow disease is suspected, authors propose routine imaging of lumbar vertebral column, pelvis and proximal parts of femoral bones. (author) 7 refs, 7 figs
Li, Zeng; Fu, Jingying; Jiang, Dong; Lin, Gang; Dong, Donglin; Yan, Xiaoxi
2017-11-21
Epidemiological studies conducted around the world have reported that the under-five mortality rate (U5MR) is closely associated with income and educational attainment. However, geographic elements should also remain a major concern in further improving child health issues, since they often play an important role in the survival environment. This study was undertaken to investigate the relationship between the U5MR, geographic, and socioeconomic factors, and to explore the associated spatial variance of the relationship in China using the geographically weighted regression (GWR) model. The results indicate that the space pattern of a high U5MR had been narrowed notably during the period from 2001 to 2010. Nighttime lights (NL) and the digital elevation model (DEM) both have obvious influences on the U5MR, with the NL having a negative impact and DEM having a positive impact. Additionally, the relationship between the NL and DEM varied over space in China. Moreover, the relevance between U5MR and DEM was narrowed in 2010 compared to 2001, which indicates that the development of economic and medical standards can overcome geographical limits.
Directory of Open Access Journals (Sweden)
Zeng Li
2017-11-01
Full Text Available Epidemiological studies conducted around the world have reported that the under-five mortality rate (U5MR is closely associated with income and educational attainment. However, geographic elements should also remain a major concern in further improving child health issues, since they often play an important role in the survival environment. This study was undertaken to investigate the relationship between the U5MR, geographic, and socioeconomic factors, and to explore the associated spatial variance of the relationship in China using the geographically weighted regression (GWR model. The results indicate that the space pattern of a high U5MR had been narrowed notably during the period from 2001 to 2010. Nighttime lights (NL and the digital elevation model (DEM both have obvious influences on the U5MR, with the NL having a negative impact and DEM having a positive impact. Additionally, the relationship between the NL and DEM varied over space in China. Moreover, the relevance between U5MR and DEM was narrowed in 2010 compared to 2001, which indicates that the development of economic and medical standards can overcome geographical limits.
Kaushik, S Sivaram; Freeman, Matthew S; Cleveland, Zackary I; Davies, John; Stiles, Jane; Virgincar, Rohan S; Robertson, Scott H; He, Mu; Kelly, Kevin T; Foster, W Michael; McAdams, H Page; Driehuys, Bastiaan
2013-09-01
Although some central aspects of pulmonary function (ventilation and perfusion) are known to be heterogeneous, the distribution of diffusive gas exchange remains poorly characterized. A solution is offered by hyperpolarized 129Xe magnetic resonance (MR) imaging, because this gas can be separately detected in the lung's air spaces and dissolved in its tissues. Early dissolved-phase 129Xe images exhibited intensity gradients that favored the dependent lung. To quantitatively corroborate this finding, we developed an interleaved, three-dimensional radial sequence to image the gaseous and dissolved 129Xe distributions in the same breath. These images were normalized and divided to calculate "129Xe gas-transfer" maps. We hypothesized that, for healthy volunteers, 129Xe gas-transfer maps would retain the previously observed posture-dependent gradients. This was tested in nine subjects: when the subjects were supine, 129Xe gas transfer exhibited a posterior-anterior gradient of -2.00 ± 0.74%/cm; when the subjects were prone, the gradient reversed to 1.94 ± 1.14%/cm (P exchange caused by differences in lung inflation and posture.
Fei, Baowei; Yang, Xiaofeng; Nye, Jonathon A.; Aarsvold, John N.; Raghunath, Nivedita; Cervo, Morgan; Stark, Rebecca; Meltzer, Carolyn C.; Votaw, John R.
2012-01-01
Purpose: Combined MR/PET is a relatively new, hybrid imaging modality. A human MR/PET prototype system consisting of a Siemens 3T Trio MR and brain PET insert was installed and tested at our institution. Its present design does not offer measured attenuation correction (AC) using traditional transmission imaging. This study is the development of quantification tools including MR-based AC for quantification in combined MR/PET for brain imaging. Methods: The developed quantification tools include image registration, segmentation, classification, and MR-based AC. These components were integrated into a single scheme for processing MR/PET data. The segmentation method is multiscale and based on the Radon transform of brain MR images. It was developed to segment the skull on T1-weighted MR images. A modified fuzzy C-means classification scheme was developed to classify brain tissue into gray matter, white matter, and cerebrospinal fluid. Classified tissue is assigned an attenuation coefficient so that AC factors can be generated. PET emission data are then reconstructed using a three-dimensional ordered sets expectation maximization method with the MR-based AC map. Ten subjects had separate MR and PET scans. The PET with [11C]PIB was acquired using a high-resolution research tomography (HRRT) PET. MR-based AC was compared with transmission (TX)-based AC on the HRRT. Seventeen volumes of interest were drawn manually on each subject image to compare the PET activities between the MR-based and TX-based AC methods. Results: For skull segmentation, the overlap ratio between our segmented results and the ground truth is 85.2 ± 2.6%. Attenuation correction results from the ten subjects show that the difference between the MR and TX-based methods was <6.5%. Conclusions: MR-based AC compared favorably with conventional transmission-based AC. Quantitative tools including registration, segmentation, classification, and MR-based AC have been developed for use in combined MR
Energy Technology Data Exchange (ETDEWEB)
Fei, Baowei, E-mail: bfei@emory.edu [Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1841 Clifton Road Northeast, Atlanta, Georgia 30329 (United States); Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia 30322 (United States); Department of Mathematics and Computer Sciences, Emory University, Atlanta, Georgia 30322 (United States); Yang, Xiaofeng; Nye, Jonathon A.; Raghunath, Nivedita; Votaw, John R. [Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia 30329 (United States); Aarsvold, John N. [Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia 30329 (United States); Nuclear Medicine Service, Atlanta Veterans Affairs Medical Center, Atlanta, Georgia 30033 (United States); Cervo, Morgan; Stark, Rebecca [The Medical Physics Graduate Program in the George W. Woodruff School, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Meltzer, Carolyn C. [Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, Georgia 30329 (United States); Department of Neurology and Department of Psychiatry and Behavior Sciences, Emory University School of Medicine, Atlanta, Georgia 30322 (United States)
2012-10-15
Purpose: Combined MR/PET is a relatively new, hybrid imaging modality. A human MR/PET prototype system consisting of a Siemens 3T Trio MR and brain PET insert was installed and tested at our institution. Its present design does not offer measured attenuation correction (AC) using traditional transmission imaging. This study is the development of quantification tools including MR-based AC for quantification in combined MR/PET for brain imaging. Methods: The developed quantification tools include image registration, segmentation, classification, and MR-based AC. These components were integrated into a single scheme for processing MR/PET data. The segmentation method is multiscale and based on the Radon transform of brain MR images. It was developed to segment the skull on T1-weighted MR images. A modified fuzzy C-means classification scheme was developed to classify brain tissue into gray matter, white matter, and cerebrospinal fluid. Classified tissue is assigned an attenuation coefficient so that AC factors can be generated. PET emission data are then reconstructed using a three-dimensional ordered sets expectation maximization method with the MR-based AC map. Ten subjects had separate MR and PET scans. The PET with [{sup 11}C]PIB was acquired using a high-resolution research tomography (HRRT) PET. MR-based AC was compared with transmission (TX)-based AC on the HRRT. Seventeen volumes of interest were drawn manually on each subject image to compare the PET activities between the MR-based and TX-based AC methods. Results: For skull segmentation, the overlap ratio between our segmented results and the ground truth is 85.2 ± 2.6%. Attenuation correction results from the ten subjects show that the difference between the MR and TX-based methods was <6.5%. Conclusions: MR-based AC compared favorably with conventional transmission-based AC. Quantitative tools including registration, segmentation, classification, and MR-based AC have been developed for use in combined MR/PET.
International Nuclear Information System (INIS)
Fei, Baowei; Yang, Xiaofeng; Nye, Jonathon A.; Raghunath, Nivedita; Votaw, John R.; Aarsvold, John N.; Cervo, Morgan; Stark, Rebecca; Meltzer, Carolyn C.
2012-01-01
Purpose: Combined MR/PET is a relatively new, hybrid imaging modality. A human MR/PET prototype system consisting of a Siemens 3T Trio MR and brain PET insert was installed and tested at our institution. Its present design does not offer measured attenuation correction (AC) using traditional transmission imaging. This study is the development of quantification tools including MR-based AC for quantification in combined MR/PET for brain imaging. Methods: The developed quantification tools include image registration, segmentation, classification, and MR-based AC. These components were integrated into a single scheme for processing MR/PET data. The segmentation method is multiscale and based on the Radon transform of brain MR images. It was developed to segment the skull on T1-weighted MR images. A modified fuzzy C-means classification scheme was developed to classify brain tissue into gray matter, white matter, and cerebrospinal fluid. Classified tissue is assigned an attenuation coefficient so that AC factors can be generated. PET emission data are then reconstructed using a three-dimensional ordered sets expectation maximization method with the MR-based AC map. Ten subjects had separate MR and PET scans. The PET with ["1"1C]PIB was acquired using a high-resolution research tomography (HRRT) PET. MR-based AC was compared with transmission (TX)-based AC on the HRRT. Seventeen volumes of interest were drawn manually on each subject image to compare the PET activities between the MR-based and TX-based AC methods. Results: For skull segmentation, the overlap ratio between our segmented results and the ground truth is 85.2 ± 2.6%. Attenuation correction results from the ten subjects show that the difference between the MR and TX-based methods was <6.5%. Conclusions: MR-based AC compared favorably with conventional transmission-based AC. Quantitative tools including registration, segmentation, classification, and MR-based AC have been developed for use in combined MR/PET.
Fundamentals of functional imaging II: emerging MR techniques and new methods of analysis.
Luna, A; Martín Noguerol, T; Mata, L Alcalá
2018-05-01
Current multiparameter MRI protocols integrate structural, physiological, and metabolic information about cancer. Emerging techniques such as arterial spin-labeling (ASL), blood oxygen level dependent (BOLD), MR elastography, chemical exchange saturation transfer (CEST), and hyperpolarization provide new information and will likely be integrated into daily clinical practice in the near future. Furthermore, there is great interest in the study of tumor heterogeneity as a prognostic factor and in relation to resistance to treatment, and this interest is leading to the application of new methods of analysis of multiparametric protocols. In parallel, new oncologic biomarkers that integrate the information from MR with clinical, laboratory, genetic, and histologic findings are being developed, thanks to the application of big data and artificial intelligence. This review analyzes different emerging MR techniques that are able to evaluate the physiological, metabolic, and mechanical characteristics of cancer, as well as the main clinical applications of these techniques. In addition, it summarizes the most novel methods of analysis of functional radiologic information in oncology. Copyright © 2018 SERAM. Publicado por Elsevier España, S.L.U. All rights reserved.
MR findings of cerebral palsy and clinical correlation
Energy Technology Data Exchange (ETDEWEB)
Kim, Sun Ho; Kim, In One; Kim, Woo Sun; Yeon, Kyung Mo [Seoul National Univ. College of Medicine, Seoul (Korea, Republic of)
1997-04-01
To demonstrate MR findings of cerebral palsy (CP), correlation with clinical findings, and differences between the full-term and pre-term group. Brain MRI of 94 patients with cerebral palsy (CP) were reviewed. The frequency of each MR finding, statistical correlation with clinical findings including type, severity and extent of CP, and differences between the full-term and pre-term group were analyzed. Abnormal MR findings were found in 83 patients(88%), and were as follows : diffuse brain atrophy(30%); periventricular leukomalacia(PVL)(28%); infarction(11%), basal ganglia abnormality(11%); delayed myelination(10%); nonspecific tissue loss or encephalomalacia(9%); and cortical dysplasia(7%). Hemiplegia was the most common condition among patients with infarction, and was found in 80% of this group; diplegia was found in 50% of cases with diffuse brain atrophy, while paraplegia was found in 36% of those with normal MR findings (p < .05). Mild symptoms were dominant in patients with normal MR findings(82%) and in those with infarctions(90%)(p < .05). PVL was the dominant finding in the pre-term group (65%) whereas findings in the full-term group varied; in this group, 38% of MR findings suggested prenatal insults. Possible causative factors were found in 66% of the full-term and 80% of the pre-term group. Perinatal factors were dominant in the pre-term group(81%), whereas prenatal and postnatal factors showed relatively higher frequencies in the full-term group(30% and 24%, respectively). Diffuse brain atrophy and PVL were the most common MR findings. The extent of CP the pre-term correlated well with MR findings. PVL and perinatal factors were dominant in the pre-term group, whereas variable MR findings and relatively higher frequencies of pre- and postnatal factors were found in the full-term group.
MR findings of cerebral palsy and clinical correlation
International Nuclear Information System (INIS)
Kim, Sun Ho; Kim, In One; Kim, Woo Sun; Yeon, Kyung Mo
1997-01-01
To demonstrate MR findings of cerebral palsy (CP), correlation with clinical findings, and differences between the full-term and pre-term group. Brain MRI of 94 patients with cerebral palsy (CP) were reviewed. The frequency of each MR finding, statistical correlation with clinical findings including type, severity and extent of CP, and differences between the full-term and pre-term group were analyzed. Abnormal MR findings were found in 83 patients(88%), and were as follows : diffuse brain atrophy(30%); periventricular leukomalacia(PVL)(28%); infarction(11%), basal ganglia abnormality(11%); delayed myelination(10%); nonspecific tissue loss or encephalomalacia(9%); and cortical dysplasia(7%). Hemiplegia was the most common condition among patients with infarction, and was found in 80% of this group; diplegia was found in 50% of cases with diffuse brain atrophy, while paraplegia was found in 36% of those with normal MR findings (p < .05). Mild symptoms were dominant in patients with normal MR findings(82%) and in those with infarctions(90%)(p < .05). PVL was the dominant finding in the pre-term group (65%) whereas findings in the full-term group varied; in this group, 38% of MR findings suggested prenatal insults. Possible causative factors were found in 66% of the full-term and 80% of the pre-term group. Perinatal factors were dominant in the pre-term group(81%), whereas prenatal and postnatal factors showed relatively higher frequencies in the full-term group(30% and 24%, respectively). Diffuse brain atrophy and PVL were the most common MR findings. The extent of CP the pre-term correlated well with MR findings. PVL and perinatal factors were dominant in the pre-term group, whereas variable MR findings and relatively higher frequencies of pre- and postnatal factors were found in the full-term group
MR imaging of spinal factors and compression of the spinal cord in cervical myelopathy
International Nuclear Information System (INIS)
Kokubun, Shoichi; Ozawa, Hiroshi; Sakurai, Minoru; Ishii, Sukenobu; Tani, Shotaro; Sato, Tetsuaki.
1992-01-01
Magnetic resonance (MR) images of surgical 109 patients with cervical spondylotic myelopathy were retrospectively reviewed to examine whether MR imaging would replace conventional radiological procedures in determining spinal factors and spinal cord compression in this disease. MR imaging was useful in determining spondylotic herniation, continuous type of ossification of posterior longitudinal ligament, and calcification of yellow ligament, probably replacing CT myelography, discography, and CT discography. When total defect of the subarachnoid space on T2-weighted images and block on myelograms were compared in determining spinal cord compression, the spinal cord was affected more extensively by 1.3 intervertebral distance (IVD) on T2-weighted images. When indentation of one third or more in anterior and posterior diameter of the spinal cord was used as spinal cord compression, the difference in the affected extension between myelography and MR imaging was 0.2 IVD on T1-weighted images and 0.6 IVD on T2-weighted images. However, when block was seen in 3 or more IVD on myelograms, the range of spinal cord compression tended to be larger on T1-weighted images. For a small range of spinal cord compression, T1-weighted imaging seems to be helpful in determining the range of decompression. When using T2-weighted imaging, the range of decompression becomes large, frequently including posterior decompression. (N.K.)
Lin, Changsheng; Ear, Jason; Midde, Krishna; Lopez-Sanchez, Inmaculada; Aznar, Nicolas; Garcia-Marcos, Mikel; Kufareva, Irina; Abagyan, Ruben; Ghosh, Pradipta
2014-01-01
A long-standing issue in the field of signal transduction is to understand the cross-talk between receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major and distinct signaling hubs that control eukaryotic cell behavior. Although stimulation of many RTKs leads to activation of trimeric G proteins, the molecular mechanisms behind this phenomenon remain elusive. We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins. Using a combination of homology modeling, protein–protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands. Using protein–protein interaction assays, we demonstrated that both SH2 and GEF domains of GIV are required for the formation of a ligand-activated ternary complex between GIV, Gαi, and growth factor receptors and for activation of Gαi after growth factor stimulation. Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV—Akt enhancement, actin remodeling, and cell migration. The mechanistic and structural insights gained here shed light on the long-standing questions surrounding RTK/G protein cross-talk, set a novel paradigm, and characterize a unique pharmacological target for uncoupling GIV-dependent signaling downstream of multiple oncogenic RTKs. PMID:25187647
Chang, Ho-Myung; Lim, Hye Su; Choe, Kun Hyung
2012-12-01
A thermodynamic study is carried out to investigate the effect of multi-stream heat exchanger on the performance of natural gas (NG) liquefaction with mixed refrigerant (MR). A cold stream (low-pressure MR) is in thermal contact with opposite flow of two hot streams (high-pressure MR and NG feed) at the same time. In typical process simulation with commercial software (such as Aspen HYSYS®), the liquefaction performance is estimated with a method of minimum temperature approach, simply assuming that two hot streams have the same temperature. In this study, local energy balance equations are rigorously solved with temperature-dependent properties of MR and NG feed, and are linked to the thermodynamic cycle analysis. The figure of merit (FOM) is quantitatively examined in terms of UA (the product of overall heat transfer coefficient and heat exchange area) between respective streams. In a single-stage MR process, it is concluded that the temperature profile from HYSYS is difficult to realize in practice, and the FOM value from HYSYS is an over-estimate, but can be closely achieved with a proper heat-exchanger design. It is also demonstrated that there exists a unique optimal ratio in three UA's, and no direct heat exchanger between hot streams is recommended.
Common factors and the exchange rate: results from the Brazilian case
Directory of Open Access Journals (Sweden)
Wilson Rafael de Oliveira Felício
2014-03-01
Full Text Available This paper studies the usefulness of factor models in explaining the dynamics of the exchange rate Real / Dollar from January 1999 to August 2011. The paper verifies that the inclusion of factors embedded on the common movements of exchange rates of a set of countries significantly improves the in-sample and out-of-sample predictive power of the models comprising only macroeconomic fundamentals commonly used in the literature to forecast the exchange rate. The paper also links the information contained in the factors to global shocks like the demand for dollars - a "dollar effect", volatility and liquidity of global financial markets.
Overhauser-enhanced MR imaging (OMRI)
DEFF Research Database (Denmark)
Golman, K; Leunbach, I; Ardenkjaer-Larsen, JH
1998-01-01
Purpose. To evaluate a new single-electron contrast agent for Overhauser-enhanced MR imaging. The contrast agents that are currently available give enhancement factors that are too low to make the technique a valid option for routine clinical use. Material and Methods. MR images were generated di...
2009-01-01
Abstract Purpose The potential use of combined therapy is under intensive study including the association between classical cytotoxic and genes encoding toxic proteins which enhanced the antitumour activity. The main aim of this work was to evaluate whether the gef gene, a suicide gene which has a demonstrated antiproliferative activity in tumour cells, improved the antitumour effect of chemotherapeutic drugs used as first-line treatment in the management...
Catana, Ciprian; van der Kouwe, Andre; Benner, Thomas; Michel, Christian J.; Hamm, Michael; Fenchel, Matthias; Fischl, Bruce; Rosen, Bruce; Schmand, Matthias; Sorensen, A. Gregory
2013-01-01
A number of factors have to be considered for implementing an accurate attenuation correction (AC) in a combined MR-PET scanner. In this work, some of these challenges were investigated and an AC method based entirely on the MR data obtained with a single dedicated sequence was developed and used for neurological studies performed with the MR-PET human brain scanner prototype. Methods The focus was on the bone/air segmentation problem, the bone linear attenuation coefficient selection and the RF coil positioning. The impact of these factors on the PET data quantification was studied in simulations and experimental measurements performed on the combined MR-PET scanner. A novel dual-echo ultra-short echo time (DUTE) MR sequence was proposed for head imaging. Simultaneous MR-PET data were acquired and the PET images reconstructed using the proposed MR-DUTE-based AC method were compared with the PET images reconstructed using a CT-based AC. Results Our data suggest that incorrectly accounting for the bone tissue attenuation can lead to large underestimations (>20%) of the radiotracer concentration in the cortex. Assigning a linear attenuation coefficient of 0.143 or 0.151 cm−1 to bone tissue appears to give the best trade-off between bias and variability in the resulting images. Not identifying the internal air cavities introduces large overestimations (>20%) in adjacent structures. Based on these results, the segmented CT AC method was established as the “silver standard” for the segmented MR-based AC method. Particular to an integrated MR-PET scanner, ignoring the RF coil attenuation can cause large underestimations (i.e. up to 50%) in the reconstructed images. Furthermore, the coil location in the PET field of view has to be accurately known. Good quality bone/air segmentation can be performed using the DUTE data. The PET images obtained using the MR-DUTE- and CT-based AC methods compare favorably in most of the brain structures. Conclusion An MR-DUTE-based AC
Energy Technology Data Exchange (ETDEWEB)
Brooun, A.; Foster, S.A.; Chrencik, H.E.; Chien, E.Y.T.; Kolatkar, A.R.; Streiff, M.; Ramage, P.; Widmer, H.; Weckbecker, G.; Kuhn, P.
2007-07-03
The signal transduction pathway involving the Vav1 guanine nucleotide exchange factor (GEF) and the Rac1 GTPase plays several key roles in the immune response mediated by the T cell receptor. Vav1 is also a unique member of the GEF family in that it contains a cysteine-rich domain (CRD) that is critical for Rac1 binding and maximal guanine nucleotide exchange activity, and thus may provide a unique protein-protein interface compared to other GEF/GTPase pairs. Here, we have applied a number of remedial structural proteomics strategies, such as construct and expression optimization, surface mutagenesis, limited proteolysis, and protein formulation to successfully express, purify, and crystallize the Vav1-DH-PH-CRD/Rac1 complex in an active conformation. We have also systematically characterized various Vav1 domains in a GEF assay and Rac1 in vitro binding experiments. In the context of Vav1-DH-PH-CRD, the zinc finger motif of the CRD is required for the expression of stable Vav1, as well as for activity in both a GEF assay and in vitro formation of a Vav1/Rac1 complex suitable for biophysical and structural characterization. Our data also indicate that the isolated CRD maintains a low level of specific binding to Rac1, appears to be folded based on 1D NMR analysis and coordinates two zinc ions based on ICP-MS analysis. The protein reagents generated here are essential tools for the determination of a three dimensional Vav1/Rac1 complex crystal structure and possibly for the identification of inhibitors of the Vav1/Rac1 protein-protein interaction with potential to inhibit lymphocyte activation.
Rational Design of Rho Protein Inhibitors
National Research Council Canada - National Science Library
Rojas, Rafael J
2006-01-01
... nucleotide exchange factors (RhoGEFs). We have developed a high throughput screening strategy identify novel inhibitors of Rho activation are currently following up on several compounds which appear to selectively inhibit Rho activation. These compounds may form the basis of future drug development strategies for the treatment of metastatic breast cancer.
Rational Design of Rho Protein Inhibitors
National Research Council Canada - National Science Library
Rojas, Rafael J
2005-01-01
... nucleotide exchange factors (RhoGEFs). We have developed a high throughput screening strategy identify novel inhibitors of Rho activation are currently following up on several compounds which appear to selectively inhibit Rho activation. These compounds may form the basis of future drug development strategies for the treatment of metastatic breast cancer.
MR imaging of avascular necrosis of the femoral head: Evaluation of the prognostic factors
Energy Technology Data Exchange (ETDEWEB)
Jin, Uk; Ryu, Kyung Nam; Yoo, Myung Chul; Yoon, Yup [Kyung Hee University Hospital, Seoul (Korea, Republic of)
1994-07-15
To evaluate the factors influencing the prognosis in avascular necrosis(AVN) of the femoral head by MR. Radiographic and MRI findings of twenty-three patients(30 cases, aged 23-67 years) with AVN identified clinically and radiologically were evaluated. The radiography included follow up study for at least 6 months. The mean age of these patients was 43 years and M : F ratio was 20 : 3. MR imaging was performed at 1.5 T unit using T1- and T2-weighted coronal and T1-weighted sagittal and axial spin echo sequences. We categorized the changes of the femoral head on radiographic follow-ups to three grades of mild , moderate and severe. We also analyzed the changes of the signal intensity and sizes of the lesion at sagittal and coronal MR images. On MR imaging we classified the extent of AVN of the femoral head to 2 grades according to the size of lesion. In the cases of mild changes in femoral head on radiography, the mean age of the patient was 37 years and the extent of AVN was below 1/2 in eleven out of seventeen cases. In the cases of moderate changes, the mean age was 43 years and the extent was above 1/2 in five out of seven cases. In the cases of severe changes, the mean age was 60 years and the extent was above 1/2 in all 6 cases. With 95% confidence coefficient, comparisons in the age and necrosis extent revealed statistical significance in severe versus moderate changes and in severe versus mild changes. Comparisons in the change of signal intensity on T1 and T2 weighted images showed no statistical relationship between each other. We conclude that if patient is younger and has smaller extent of the AVN, bone destruction is slower that these factors may be helpful in predicting the prognosis of AVN. However, the modes of the changes of the signal intensity on T1- and T2-weighted images may not be useful in predicting the prognosis of AVN.
International Nuclear Information System (INIS)
Baxter, R.C.; Martin, J.L.
1989-01-01
To determine the structure of the high molecular weight, growth hormone-dependent complex between the insulin-like growth factors (IGF-I and IGF-II) and their binding proteins in human serum, we have reconstituted the complex from its purified component proteins and analyzed it by gel electrophoresis and autoradiography after covalent cross-linking. The proteins tested in reconstitution mixtures were an acid-labile Mr 84,000-86,000 glycoprotein doublet (alpha subunit), an acid-stable Mr 47,000-53,000 glycoprotein doublet with IGF-binding activity (BP-53 or beta subunit), and IGF-I or IGF-II (gamma subunit). In incubations containing any one of the three subunits 125I-labeled and the other two unlabeled, identical 125I-labeled alpha-beta-gamma complexes of Mr 140,000 were formed. Minor bands of Mr 120,000 and 90,000 were also seen, thought to represent a partially deglycosylated form of the alpha-beta-gamma complex, and an alpha-gamma complex arising as a cross-linking artifact. When serum samples from subjects of various growth hormone status were affinity-labeled with IGF-II tracer, a growth hormone-dependent Mr 140,000 band was seen, corresponding to the reconstituted alpha-beta-gamma complex. Other growth hormone-dependent labeled bands, of Mr 90,000 (corresponding to alpha-gamma), Mr 55,000-60,000 (corresponding to labeled beta-subunit doublet), and smaller bands of Mr 38,000, 28,000, and 23,000-25,000 (corresponding to labeled beta-subunit degradation products), were also seen in the affinity-labeled serum samples and in the complex reconstituted from pure proteins. All were immunoprecipitable with an anti-BP-53 antiserum. We conclude that the growth hormone-dependent Mr 140,000 IGF-binding protein complex in human serum has three components: the alpha (acid-labile) subunit, the beta (binding) subunit, and the gamma (growth factor) subunit
MR plaque imaging of the carotid artery
International Nuclear Information System (INIS)
Watanabe, Yuji; Nagayama, Masako
2010-01-01
Atherosclerotic carotid plaque represents a major cause of cerebral ischemia. The detection of vulnerable plaque is important for preventing future cardiovascular events. The key factors in advanced plaque that are most likely to lead to patient complications are the condition of the fibrous cap, the size of the necrotic core and hemorrhage, and the extent of inflammatory activity within the plaque. Magnetic resonance (MR) imaging has excellent soft tissue contrast and can allow for a more accurate and objective estimation of carotid wall morphology and plaque composition. Recent advances in MR imaging techniques have permitted serial monitoring of atherosclerotic disease evolution and the identification of intraplaque risk factors for accelerated progression. The purpose of this review article is to review the current state of techniques of carotid wall MR imaging and the characterization of plaque components and surface morphology with MR imaging, and to describe the clinical practice of carotid wall MR imaging for the determination of treatment plan. (orig.)
DEFF Research Database (Denmark)
Ly, Donald L.; Waheed, Faiza; Lodyga, Monika
2013-01-01
Hyperosmotic stress initiates several adaptive responses, including the remodeling of the cytoskeleton. Besides maintaining structural integrity, the cytoskeleton has emerged as an important regulator of gene transcription. Myocardin-related transcription factor (MRTF), an actin-regulated coactiv......Hyperosmotic stress initiates several adaptive responses, including the remodeling of the cytoskeleton. Besides maintaining structural integrity, the cytoskeleton has emerged as an important regulator of gene transcription. Myocardin-related transcription factor (MRTF), an actin......-regulated coactivator of serum response factor, is a major link between the actin skeleton and transcriptional control. We therefore investigated whether MRTF is regulated by hyperosmotic stress. Here we show that hypertonicity induces robust, rapid, and transient translocation of MRTF from the cytosol to the nucleus...... in kidney tubular cells. We found that the hyperosmolarity-triggered MRTF translocation is mediated by the RhoA/Rho kinase (ROK) pathway. Moreover, the Rho guanine nucleotide exchange factor GEF-H1 is activated by hyperosmotic stress, and it is a key contributor to the ensuing RhoA activation and MRTF...
LOCUS MR: Localization of unaffected spins in MR tomography and MR spectroscopy
International Nuclear Information System (INIS)
Matthael, D.; Haase, A.
1986-01-01
Different pulse sequences have been proposed for localized in vivo MR spectroscopy. For localized MR tomography and MR spectroscopy, a method is proposed, dubbed LOCUS (LOCalization of Unaffected Spins) MR. The method uses the initial saturation of regions surrounding the region of interest (ROI) in the presence of gradients. This is followed by a conventional MR study of the unaffected ROI. In animals, human extremities, and phantoms, proton MR studies demonstrated that the method provides an optimal signal-to-noise ratio, an easily variable ROI, and ROI shim. The method can be combined with two- and three-dimensional imaging, and it allows localized measurement of MR parameters. The multinuclear capability is discussed
International Nuclear Information System (INIS)
Larsen, M.E.
1983-01-01
The exchange factor method (EFM) is introduced and compared to the zone method (ZM). In both the EFM and ZM the region of interest is discretized into volume and surface elements, each considered to be isothermal, which are small enough to give the required resolution. A suitable set of state variables for the system is composed of the surface element radiosities and the gas element emissive powers. The EFM defines exchange factors as dimensionless total-exchange areas for radiant interchange between volume and surface elements by all possible absorption/re-emission paths, but excluding wall reflections. In the EFM, the exchange factors replace the direct-exchange areas of the ZM and are used to write energy balances for each area and volume element in the system. As in the ZM, the radiant energy balance equations result in a set of algebraic equations linear in the system state variables. The distinguishing feature of the EFM is that exchange factors may be measurable quantities. Relationships between the EFM exchange factors and the ZM direct-exchange areas are presented. EFM conservation and reciprocity laws, analogous to those of the ZM, are also included. Temperature and heat flux distributions, predicted using the EFM, for two- and three-dimensional enclosures containing absorbing/emitting, isotropically scattering, and conducting media are included. An application of the EFM is proposed which calls for the measurement of exchange factors in a scale model of the enclosure to be analyzed. The measurement of these factors in an enclosure containing an isotropically scattering medium is discussed. The effects of isotropic scattering and absorption/re-emission processes are shown to be indistinguishable in their contribution to exchange factor paths
In Situ X-ray Diffraction Study of Cesium Exchange in Synthetic Umbite
International Nuclear Information System (INIS)
Fewox, C.; Clearfield, A.; Celestian, A.
2011-01-01
The exchange of Cs + into H 1.22 K 0.84 ZrSi 3 O 9 · 2.16H 2 O (umbite-(HK)) was followed in situ using time-resolved X-ray diffraction at the National Synchrotron Light Source. The umbite framework (space group P2 1 /c with cell dimensions of a = 7.2814(3) (angstrom), b = 10.4201(4) (angstrom), c = 13.4529(7) (angstrom), and β = 90.53(1) o ) consists of wollastonite-like silicate chains linked by isolated zirconia octahedra. Within umbite-(HK) there are two unique ion exchange sites in the tunnels running parallel to the a-axis. Exchange Site 1 is marked by 8 member-ring (MR) windows in the bc-plane and contains K + cations. Exchange Site 2 is marked by a larger 8-MR channel parallel to [100], and contains H 2 O molecules. The occupancy of the Cs + cations through these channels was modeled by Rietveld structure refinements of the diffraction data and demonstrated that there is a two-step exchange process. The incoming Cs + ions populated the larger 8-MR channel (Exchange Site 2) first and then migrated into the smaller 8-MR channel. During the exchange process a structural change occurs, transforming the exchanger from monoclinic P2 1 /c to orthorhombic P2 1 2 1 2 1 . This structural change occurs when Cs + occupancy in the small cavity becomes greater than 0.50. The final in situ ion exchange diffraction pattern was refined to yield umbite-(CsK) with the molecular formula H 0.18 K 0.45 Cs 1.37 ZrSi 3 O 9 · 0.98H 2 O and possessing an orthorhombic unit cell with dimensions a = 10.6668(8) (angstrom), b = 13.5821(11) (angstrom), c = 7.3946(6) (angstrom). Solid state 133 Cs MAS NMR showed there is only a slight difference between the two cavities electronically. Valence bond sums for the completely occupied Exchange Site 1 demonstrate that Cs-O bonds of up to 3.8 (angstrom) contribute to the coordination of the Cs + cation.
Vimar Is a Novel Regulator of Mitochondrial Fission through Miro.
Directory of Open Access Journals (Sweden)
Lianggong Ding
2016-10-01
Full Text Available As fundamental processes in mitochondrial dynamics, mitochondrial fusion, fission and transport are regulated by several core components, including Miro. As an atypical Rho-like small GTPase with high molecular mass, the exchange of GDP/GTP in Miro may require assistance from a guanine nucleotide exchange factor (GEF. However, the GEF for Miro has not been identified. While studying mitochondrial morphology in Drosophila, we incidentally observed that the loss of vimar, a gene encoding an atypical GEF, enhanced mitochondrial fission under normal physiological conditions. Because Vimar could co-immunoprecipitate with Miro in vitro, we speculated that Vimar might be the GEF of Miro. In support of this hypothesis, a loss-of-function (LOF vimar mutant rescued mitochondrial enlargement induced by a gain-of-function (GOF Miro transgene; whereas a GOF vimar transgene enhanced Miro function. In addition, vimar lost its effect under the expression of a constitutively GTP-bound or GDP-bound Miro mutant background. These results indicate a genetic dependence of vimar on Miro. Moreover, we found that mitochondrial fission played a functional role in high-calcium induced necrosis, and a LOF vimar mutant rescued the mitochondrial fission defect and cell death. This result can also be explained by vimar's function through Miro, because Miro's effect on mitochondrial morphology is altered upon binding with calcium. In addition, a PINK1 mutant, which induced mitochondrial enlargement and had been considered as a Drosophila model of Parkinson's disease (PD, caused fly muscle defects, and the loss of vimar could rescue these defects. Furthermore, we found that the mammalian homolog of Vimar, RAP1GDS1, played a similar role in regulating mitochondrial morphology, suggesting a functional conservation of this GEF member. The Miro/Vimar complex may be a promising drug target for diseases in which mitochondrial fission and fusion are dysfunctional.
Practical Considerations for Clinical PET/MR Imaging.
Galgano, Samuel; Viets, Zachary; Fowler, Kathryn; Gore, Lael; Thomas, John V; McNamara, Michelle; McConathy, Jonathan
2018-01-01
Clinical PET/MR imaging is currently performed at a number of centers around the world as part of routine standard of care. This article focuses on issues and considerations for a clinical PET/MR imaging program, focusing on routine standard-of-care studies. Although local factors influence how clinical PET/MR imaging is implemented, the approaches and considerations described here intend to apply to most clinical programs. PET/MR imaging provides many more options than PET/computed tomography with diagnostic advantages for certain clinical applications but with added complexity. A recurring theme is matching the PET/MR imaging protocol to the clinical application to balance diagnostic accuracy with efficiency. Copyright © 2017 Elsevier Inc. All rights reserved.
MR-guided MR arthrography of the shoulder
International Nuclear Information System (INIS)
Tratting, S.; Breitenseher, M.; Pretterklieber, M.; Kontaxis, G.; Rand, T.; Imhof, H.
1996-01-01
Purpose: To develop an MR-guided technique for joint puncture in MR arthrography of the shoulder and to confirm the intracapsular position of the needle tip by visualization of the flow of contrast media into the joint. Materials and methods: Three unfixed human shoulder joint specimens were examined on a 1.0 T unit. The optimal point of entrance and depth for joint puncture were estimated by means of MR-compatible markers on the skin. Needle orientation and localization of the needle tip (MR-compatible 22-gauge needle) in the shoulder joint were monitored by rapid localizer gradient-echo sequences in two orthogonal planes. To confirm the intracapsular position of the needle tip, diluted gadolinium-DTPA was administered via a long connecting tube and the flow of contrast media into the joint was viewed directly on an LCD screen using real-time MR imaging (local look technique). Results: The MR-compatible markers on the skin allowed determination of the optimal point of entrance and estimation of the depth for joint puncture. Passive visualization of the MR-compatible needle due to spin dephasing and signal loss provided adequate localization of the intra-articular needle tip position in all specimens, although significant artefacts were present on rapid localizer gradient-echo sequences with an increase in width of the apparent needle shaft. Real-time MR imaging of the flow of contrast media was possible using the local look technique and the LCD screen of the MR unit and allowed confirmation of the intracapsular position. Conclusion: MR-guided joint puncture and real-time MR-assisted contrast media application results in improved MR arthrography and may replace conventional fluoroscopic guidance. (orig.) [de
Directory of Open Access Journals (Sweden)
Mohammad Fathian
2012-04-01
Full Text Available In this paper, the problem of predicting the exchange rate time series in the foreign exchange rate market is going to be solved using a time-delayed multilayer perceptron neural network with gold price as external factor. The input for the learning phase of the artificial neural network are the exchange rate data of the last five days plus the gold price in two different currencies of the exchange rate as the external factor for helping the artificial neural network improving its forecast accuracy. The five-day delay has been chosen because of the weekly cyclic behavior of the exchange rate time series with the consideration of two holidays in a week. The result of forecasts are then compared with using the multilayer peceptron neural network without gold price external factor by two most important evaluation techniques in the literature of exchange rate prediction. For the experimental analysis phase, the data of three important exchange rates of EUR/USD, GBP/USD, and USD/JPY are used.
MR imaging of normal bone marrow
International Nuclear Information System (INIS)
Stajgis, M.; Paprzycki, W.
1994-01-01
Principles of MR bone marrow imaging on the basis of retrospective analysis of MR examinations of bone marrow in different anatomic sites in 200 patients have been discussed. Significance of different physiologic factors and processes such as age, steatosis, osteoporosis, conversion and reconversion, which influence on MR bone marrow images, have been emphasized. T1-weighted images obtained with spin-echo sequences give the most of information about bone marrow structure in MR. Thorough knowledge of bone marrow physiology and clinical status of the patient is indispensable in correct interpretation of hypointensive lesions on T1-weighted images. When presence of disseminated bone marrow disease is suspected, authors propose routine imaging of lumbar vertebral column, pelvis and proximal parts of femoral bones. (author)
MR-guided joint reconstruction of activity and attenuation in brain PET-MR
DEFF Research Database (Denmark)
Mehranian, Abolfazl; Zaidi, Habib; Reader, Andrew J
2017-01-01
by unknown scaling factors. We recently demonstrated that in hybrid PET-MR, the scaling issue of this algorithm can be effectively addressed by imposing MR spatial constraints on the estimation of attenuation maps using a penalized MLAA (P-MLAA(+)) algorithm. With the advent of simultaneous PET-MR systems......, MRI-guided PET image reconstruction has also gained attention for improving the quantitative accuracy of PET images, usually degraded by noise and partial volume effects. The aim of this study is therefore to increase the benefits of MRI information for improving the quantitative accuracy of PET...... as a reference. The simulation results showed that the proposed method can notably improve the visual quality of the PET images by reducing noise while preserving structural boundaries and at the same time improving the quantitative accuracy of the PET images. Our clinical reconstruction results showed...
Directory of Open Access Journals (Sweden)
Alexander eStaruschenko
2012-05-01
Full Text Available Small GTPases function as molecular switches in cell signaling, alternating between an inactive, GDP-bound state, and active GTP-bound state. βPix is one of guanine nucleotide exchange factors (GEFs that catalyze the exchange of bound GDP for ambient GTP. The central goal of this review article is to summarize recent findings on βPix and the role it plays in kidney pathology and physiology. Recent studies shed new light on several key questions concerning the signaling mechanisms mediated by βPix. This manuscript provides a review of the various mechanisms whereby βPix has been shown to function within the kidney through a wide range of actions. Both canonical GEF activity and non-canonical signaling pathways mediated by βPix are discussed. Distribution patterns of βPix in the kidney will be also covered. Much has yet to be discerned, but it is clear that βPix plays a significant role in the kidney.
Scambio, a novel guanine nucleotide exchange factor for Rho
Directory of Open Access Journals (Sweden)
Groffen John
2004-04-01
Full Text Available Abstract Background Small GTPases of the Rho family are critical regulators of various cellular functions including actin cytoskeleton organization, activation of kinase cascades and mitogenesis. For this reason, a major objective has been to understand the mechanisms of Rho GTPase regulation. Here, we examine the function of a novel protein, Scambio, which shares homology with the DH-PH domains of several known guanine nucleotide exchange factors for Rho family members. Results Scambio is located on human chromosome 14q11.1, encodes a protein of around 181 kDa, and is highly expressed in both heart and skeletal muscle. In contrast to most DH-PH-domain containing proteins, it binds the activated, GTP-bound forms of Rac and Cdc42. However, it fails to associate with V14RhoA. Immunofluorescence studies indicate that Scambio and activated Rac3 colocalize in membrane ruffles at the cell periphery. In accordance with these findings, Scambio does not activate either Rac or Cdc42 but rather, stimulates guanine nucleotide exchange on RhoA and its close relative, RhoC. Conclusion Scambio associates with Rac in its activated conformation and functions as a guanine nucleotide exchange factor for Rho.
Study on influencing factors for hydrogen isotopic exchange
International Nuclear Information System (INIS)
Gu Mei; Liu Jun; Luo Yangming
2013-01-01
Background: Hydrogen-water catalytic exchange reaction offers an approach to hydrogen isotope separation, which can be applied in heavy water detritiation. Purpose: To optimize the operating condition for hydrogen-water catalytic exchange reaction, we analysed the influence of different factors on the transfer coefficient. Methods: In detail, the isotope exchange experiments of H-D system were carried out in a self-designed catalytic bed loaded with hydrophobic catalyst and hydrophilic packing with certain volume ratio. The experiments showed the changes of both the transfer coefficient and the pressure drop of column with the changing of the operational temperatures (29℃, 45℃, 60℃ and 75℃), the ratios of gas to liquid (0.58, 1.17, 2.65, 3.54) and the deuterium concentrations (5.05×10 -3 , 1.0144×10 -2 , 2.01×10 -2 ). Results: Results showed that 45℃ is the optimal temperature for operating. The transfer coefficient increases with the increasing of the ratio of gas to liquid in the ranges of 0.58 to 1.17 and 2.65 to 3.56, while decreases with the deuterium concentration increases from 5.05×10 -3 to 2.01×10 -2 . The pressure drop of column increases with increasing of gas flow rate. Conclusions: The experiment proves that the ratio of gas to liquid, the reaction temperature and the deuterium concentration are all important factors, which influence the transfer coefficient of deuterium obviously. The optimal operating condition for hydrogen-water catalytic exchange reaction are as follows: the temperature is 45℃, the ratio of gas to liquid is 3.56, and the deuterium concentration is 2.01×10 -2 . (authors)
Investigation of ambient temperature on the performance of GE-F5 gas turbine
International Nuclear Information System (INIS)
Ghazikhani, M.; Taffazoli, D.; Manshori, N.
2002-01-01
The role of ambient temperature in determining the performance of GE-F5 gas turbine is analysed by investigating the Shirvan gas turbine power plant 10 MW , 15 MW and 20 MW power output. These parameters have been brought as a function of ambient temperature. The results show when ambient temperature increases 1 deg C, The compressor pressure decreases about 20 k Pa, compressor outlet temperature increases about 1.13 deg C and exhaust temperature increases about 2.5 deg C. It is revealed that variations are due to decreasing the efficiency of compressor and less due to mass flow rate of air reduction as ambient temperature increases at constant power output. The results shows cycle efficiency reduces 3% with increasing 50 of ambient temperature, also the m increases as ambient temperature increase for constant turbine work. These are also because of reducing the compressor efficiency as ambient temperature increases
International Nuclear Information System (INIS)
Tsoumpas, C.; Mackewn, J.E.; Halsted, P.; King, A.P.; Buerger, C.; Totman, J.J.; Schaeffter, T.; Marsden, P.K.
2010-01-01
Positron emission tomography (PET) provides an accurate measurement of radiotracer concentration in vivo, but performance can be limited by subject motion which degrades spatial resolution and quantitative accuracy. This effect may become a limiting factor for PET studies in the body as PET scanner technology improves. In this work, we propose a new approach to address this problem by employing motion information from images measured simultaneously using a magnetic resonance (MR) scanner. The approach is demonstrated using an MR-compatible PET scanner and PET-MR acquisition with a purpose-designed phantom capable of non-rigid deformations. Measured, simultaneously acquired MR data were used to correct for motion in PET, and results were compared with those obtained using motion information from PET images alone. Motion artefacts were significantly reduced and the PET image quality and quantification was significantly improved by the use of MR motion fields, whilst the use of PET-only motion information was less successful. Combined PET-MR acquisitions potentially allow PET motion compensation in whole-body acquisitions without prolonging PET acquisition time or increasing radiation dose. This, to the best of our knowledge, is the first study to demonstrate that simultaneously acquired MR data can be used to estimate and correct for the effects of non-rigid motion in PET. (author)
Time-motion analysis of factors affecting patient throughput in an MR imaging center
International Nuclear Information System (INIS)
O'Donohue, J.; Enzmann, D.R.
1986-01-01
The high cost of MR imaging makes efficient use essential. In an effort to increase patient throughput, attention has been focused on shortening the imaging time through reductions in matrix size and number of excitations, and through the use of newer ''fast imaging'' techniques. Less attention has been given to other time-consuming aspects not directly related to imaging time. The authors undertook a time-motion study using a daily log of minute-by-minute activities associated with an MR imaging examination. The times required for the following components of the examination were measured: total study time, examination set-up time, intrastudy physician ''image review'' time, and interstudy patient turnover time. The time lost to claustrophobic reactions, patients' failure to appear for scheduled examinations, unanticipated patient care (sedation, reassurance), and equipment malfunction was also analyzed. Actual imaging time accounted for a relatively small proportion (42%) of total study time. Other factors such as intrastudy image review time (15%), interstudy patient turnover time (11%), and time lost due to claustrophobic reactions, patients' failure to appear for scheduled examinations, and equipment malfunction contributed significantly to the total study time. Simple solutions to these problems can contribute greatly to increasing patient throughput
International Nuclear Information System (INIS)
1985-06-01
The French Rules of Mechanical equipments of Fast Neutron nuclear Reactors (RCC-MR) aims at equipments included in a safety classification. The equipments concerned are those of the nuclear boiler and its auxiliaries: tanks, vessels, internal equipments of the reactor, exchangers, pumps, fittings, pipes, and supports. The present edition of the RCC-MR comprises 12 books presented in the present one in the volume A. The chapter RA 3000 defines the documents to be established in application of the RCC-MR rules. The chapter RA 5000 defines the requirements to take into account to establish and carry out quality Assurance programs according to the RCC-MR rules [fr
A survey analysis of acoustic trauma related to MR scans
International Nuclear Information System (INIS)
Nakai, Toshiharu; Kamiya, Naoki; Sone, Michihiko; Muranaka, Hiroyuki; Tsuchihashi, Toshio; Yamada, Naoki; Yamaguchi, Sachiko
2012-01-01
The maximum limit of MR scanner noise and necessity of ear protection is defined in the IEC standard (IEC60601-2-33) of MR safety. With improvements in MR scanner performance, pulse sequences generating higher scanning noise have been used clinically. In this study, we investigated the factors significantly related to potential acoustic trauma cases (PATC) after MR examinations. To consider the future direction for MR safety and prevention of acoustic trauma, issues related to noise generation by MR scanners and acoustic trauma were systematically reviewed. A statistical analysis was performed using the data set from a survey (n=974) conducted in 2010 by the Japanese Society for Magnetic Resonance in Medicine (JSMRM) safety committee. Hierarchical clustering analysis was used to extract the characteristics of the responders. With this classification as a reference, tests of independence and a residual analysis were employed to evaluate the factors related to PATC. No significant relationship was observed between the ear protection policy and the incidence or the reported outcome of PATC. While the two main clusters out of the six clusters extracted were associated with who reported the PATC and the confirmation process of the acoustic noise level of MR scanners, no cluster was associated with the frequency of PATC. An absence of PATC was significantly less reported (p=0.03) and more PATC was reported (p=0.04) by facilities with 3T MR systems. Although the total frequency was 4 cases, it should be noted that persistent hearing disturbances are a possible consequence of MR examinations. Neither the condition of the subjects nor the ear protection method was significantly related to the probability of PATC, suggesting the difficulty of predicting the potential risk of acoustic trauma. It is recommended to more systematically follow up PATC cases and clarify the risk factors. (author)
Directory of Open Access Journals (Sweden)
Jennifer A Corcoran
2015-01-01
Full Text Available Kaposi's sarcoma-associated herpesvirus (KSHV is the infectious cause of several AIDS-related cancers, including the endothelial cell (EC neoplasm Kaposi's sarcoma (KS. KSHV-infected ECs secrete abundant host-derived pro-inflammatory molecules and angiogenic factors that contribute to tumorigenesis. The precise contributions of viral gene products to this secretory phenotype remain to be elucidated, but there is emerging evidence for post-transcriptional regulation. The Kaposin B (KapB protein is thought to contribute to the secretory phenotype in infected cells by binding and activating the stress-responsive kinase MK2, thereby selectively blocking decay of AU-rich mRNAs (ARE-mRNAs encoding pro-inflammatory cytokines and angiogenic factors. Processing bodies (PBs are cytoplasmic ribonucleoprotein foci in which ARE-mRNAs normally undergo rapid 5' to 3' decay. Here, we demonstrate that PB dispersion is a feature of latent KSHV infection, which is dependent on kaposin protein expression. KapB is sufficient to disperse PBs, and KapB-mediated ARE-mRNA stabilization could be partially reversed by treatments that restore PBs. Using a combination of genetic and chemical approaches we provide evidence that KapB-mediated PB dispersion is dependent on activation of a non-canonical Rho-GTPase signaling axis involving MK2, hsp27, p115RhoGEF and RhoA. PB dispersion in latently infected cells is likewise dependent on p115RhoGEF. In addition to PB dispersion, KapB-mediated RhoA activation in primary ECs caused actin stress fiber formation, increased cell motility and angiogenesis; these effects were dependent on the activity of the RhoA substrate kinases ROCK1/2. By contrast, KapB-mediated PB dispersion occurred in a ROCK1/2-independent manner. Taken together, these observations position KapB as a key contributor to viral reprogramming of ECs, capable of eliciting many of the phenotypes characteristic of KS tumor cells, and strongly contributing to the post
Factors contributing to troponin exchange in myofibrils and in solution.
She, M; Trimble, D; Yu, L C; Chalovich, J M
2000-01-01
The troponin complex in a muscle fiber can be replaced with exogenous troponin by using a gentle exchange procedure in which the actin-tropomyosin complex is never devoid of a full complement of troponin (Brenner et al. (1999) Biophys J 77: 2677-2691). The mechanism of this exchange process and the factors that influence this exchange are poorly understood. In this study, the exchange process has now been examined in myofibrils and in solution. In myofibrils under rigor conditions, troponin exchange occurred preferentially in the region of overlap between actin and myosin when the free Ca2+ concentration was low. At higher concentrations of Ca2+, the exchange occurred uniformly along the actin. Ca2+ also accelerated troponin exchange in solution but the effect of S1 could not be confirmed in solution experiments. The rate of exchange in solution was insensitive to moderate changes in pH or ionic strength. Increasing the temperature resulted in a two-fold increase in rate with each 10 degrees C increase in temperature. A sequential two step model of troponin binding to actin-tropomyosin could simulate the observed association and dissociation transients. In the absence of Ca2+ or rigor S1, the following rate constants could describe the binding process: k1 = 7.12 microM(-1) s(-1), k(-1) = 0.65 s(-1), k2 = 0.07 s(-1), k(-2) = 0.0014 s(-1). The slow rate of detachment of troponin from actin (k(-2)) limits the rate of exchange in solution and most likely contributes to the slow rate of exchange in fibers.
On factors influencing air-water gas exchange in emergent wetlands
Ho, David T.; Engel, Victor C.; Ferron, Sara; Hickman, Benjamin; Choi, Jay; Harvey, Judson W.
2018-01-01
Knowledge of gas exchange in wetlands is important in order to determine fluxes of climatically and biogeochemically important trace gases and to conduct mass balances for metabolism studies. Very few studies have been conducted to quantify gas transfer velocities in wetlands, and many wind speed/gas exchange parameterizations used in oceanographic or limnological settings are inappropriate under conditions found in wetlands. Here six measurements of gas transfer velocities are made with SF6 tracer release experiments in three different years in the Everglades, a subtropical peatland with surface water flowing through emergent vegetation. The experiments were conducted under different flow conditions and with different amounts of emergent vegetation to determine the influence of wind, rain, water flow, waterside thermal convection, and vegetation on air-water gas exchange in wetlands. Measured gas transfer velocities under the different conditions ranged from 1.1 cm h−1 during baseline conditions to 3.2 cm h−1 when rain and water flow rates were high. Commonly used wind speed/gas exchange relationships would overestimate the gas transfer velocity by a factor of 1.2 to 6.8. Gas exchange due to thermal convection was relatively constant and accounted for 14 to 51% of the total measured gas exchange. Differences in rain and water flow among the different years were responsible for the variability in gas exchange, with flow accounting for 37 to 77% of the gas exchange, and rain responsible for up to 40%.
[Chemical Exchange Saturation Transfer Imaging of Creatine Metabolites: a 3.0 T MRI Pilot].
Guo, Ying-kun; Li, Zhen-lin; Rong, Yu; Xia, Chun-chao; Zhang, Li-zhi; Peng, Wan-ling; Liu, Xi; Xu, Hua-yan; Zhang, Ti-jiang; Zuo, Pan-li; Schmitt, Benjamin
2016-03-01
To determine the feasibility of using chemical exchange saturation transfer (CEST) imaging to measure creatine (Cr) metabolites with 3.0 T MR. Phantoms containing different concentrations of Cr under various pH conditions were studied with CEST sequence on 3.0 T MR imaging. CEST effect and Z spectra were analyzed. Cr exhibited significant CEST effect (± 1.8 ppm, F = 99.08, P 3.0 T MR imaging, and positive correlation was found between the signal intensity and concentration of Cr (r = 0.963, P 3.0 T MR imaging. Creatine concentrations and pH influence CEST effect.
Advanced MR methods at ultra-high field (7 Tesla) for clinical musculoskeletal applications
Energy Technology Data Exchange (ETDEWEB)
Trattnig, Siegfried [Medical University of Vienna/Vienna General Hospital, MR Centre - High Field MR, Department of Radiology, Vienna (Austria); Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Austrian Cluster for Tissue Regeneration, Vienna (Austria); Zbyn, Stefan; Schmitt, Benjamin; Friedrich, Klaus; Bogner, Wolfgang [Medical University of Vienna/Vienna General Hospital, MR Centre - High Field MR, Department of Radiology, Vienna (Austria); Juras, Vladimir; Szomolanyi, Pavol [Medical University of Vienna/Vienna General Hospital, MR Centre - High Field MR, Department of Radiology, Vienna (Austria); Slovak Academy of Sciences, Department of Imaging Methods, Institute of Measurement Science, Bratislava (Slovakia)
2012-11-15
This article provides an overview of the initial clinical results of musculoskeletal studies performed at 7 Tesla, with special focus on sodium imaging, new techniques such as chemical exchange saturation transfer (CEST) and T2* imaging, and multinuclear MR spectroscopy. Sodium imaging was clinically used at 7 T in the evaluation of patients after cartilage repair procedures because it enables the GAG content to be monitored over time. Sodium imaging and T2* mapping allow insights into the ultra-structural composition of the Achilles tendon and help detect early disease. Chemical exchange saturation transfer was, for the first time, successfully applied in the clinical set-up at 7 T in patients after cartilage repair surgery. The potential of phosphorus MR spectroscopy in muscle was demonstrated in a comparison study between 3 and 7 T, with higher spectral resolution and significantly shorter data acquisition times at 7 T. These initial clinical studies demonstrate the potential of ultra-high field MR at 7 T, with the advantage of significantly improved sensitivity for other nuclei, such as {sup 23}Na (sodium) and {sup 31}P (phosphorus). The application of non-proton imaging and spectroscopy provides new insights into normal and abnormal physiology of musculoskeletal tissues, particularly cartilage, tendons, and muscles. (orig.)
Chemical Exchange Saturation Transfer (CEST): what is in a name and what isn’t?
van Zijl, Peter C.M.; Yadav, Nirbhay N.
2011-01-01
Chemical exchange saturation transfer (CEST) imaging is a relatively new MRI contrast approach in which exogenous or endogenous compounds containing either exchangeable protons or exchangeable molecules are selectively saturated and, after transfer of this saturation, detected indirectly through the water signal with enhanced sensitivity. The focus of this review is on basic MR principles underlying CEST and similarities to and differences with conventional magnetization transfer contrast (MTC). In CEST MRI, transfer of magnetization is studied in mobile compounds instead of semisolids. Similar to MTC, CEST has contributions of both chemical exchange and dipolar cross-relaxation, but the latter can often be neglected if exchange is fast. Contrary to MTC, CEST imaging requires sufficiently slow exchange on the MR time scale to allow selective irradiation of the protons of interest. As a consequence, magnetic labeling is not limited to radio-frequency saturation but can be expanded with slower frequency-selective approaches such as inversion, gradient dephasing and frequency labeling. The basic theory, design criteria, and experimental issues for exchange transfer imaging are discussed. A new classification for CEST agents based on exchange type is proposed. The potential of this young field is discussed, especially with respect to in vivo application and translation to humans. PMID:21337419
Shih, I-Lun; Yen, Ruoh-Fang; Chen, Chi-An; Chen, Bang-Bin; Wei, Shwu-Yuan; Chang, Wen-Chun; Sheu, Bor-Ching; Cheng, Wen-Fang; Tseng, Yao-Hui; Chen, Xin-Jia; Chen, Chi-Hau; Wei, Lin-Hung; Chiang, Ying-Cheng; Torng, Pao-Ling; Yen, Men-Luh; Shih, Tiffany Ting-Fang
2015-12-01
To evaluate the correlation between maximum standardized uptake value (SUVmax ) and minimum apparent diffusion coefficient (ADCmin ) of endometrial cancer derived from an integrated positron emission tomography / magnetic resonance (PET/MR) system and to determine their correlation with pathological prognostic factors. This prospective study was approved by the Institutional Review Board of the hospital, and informed consent was obtained. Between April and December 2014, 47 consecutive patients with endometrial cancer were enrolled and underwent simultaneous PET/MR examinations before surgery. Thirty-six patients with measurable tumors on PET/MR were included for image analysis. Pearson's correlation coefficient was used to evaluate the correlation between SUVmax and ADCmin of the tumors. The Mann-Whitney U-test was utilized to evaluate relationships between these two imaging biomarkers and pathological prognostic factors. The mean SUVmax and ADCmin were 14.7 ± 7.1 and 0.48 ± 0.13 × 10(-3) mm(2) /s, respectively. A significant inverse correlation was found between SUVmax and ADCmin (r = -0.53; P = 0.001). SUVmax was significantly higher in tumors with advanced stage, deep myometrial invasion, cervical invasion, lymphovascular space involvement, and lymph node metastasis (P correlated and are associated with pathological prognostic factors. © 2015 Wiley Periodicals, Inc.
Energy Technology Data Exchange (ETDEWEB)
Haller, Joerg [Department of Radiology, Hanusch Hospital, Heinrich Collin-Strasse 30, A-1140 Vienna (Austria); Ludwig Boltzmann Institute for Osteology, Hanusch Hospital, Heinrich Collin-Strasse 30, A-1140 Vienna (Austria); Bernt, Reinhard [Department of Radiology, Hanusch Hospital, Heinrich Collin-Strasse 30, A-1140 Vienna (Austria)]. E-mail: reinhard.bernt@wgkk.sozvers.at; Seeger, Thomas [Department of Trauma Surgery, Hanusch Hospital, Heinrich Collin-Strasse 30, A-1140 Vienna (Austria); Weissenbaeck, Alexander [Department of Trauma Surgery, Hanusch Hospital, Heinrich Collin-Strasse 30, A-1140 Vienna (Austria); Tuechler, Heinrich [Ludwig Boltzmann Institute for Hematology, Hanusch Hospital, Heinrich Collin-Strasse 30, A-1140 Vienna (Austria); Resnick, Donald [Department of Radiology, VA Medical Center, UCSD, 3350 La Jolla Village Dr, San Diego, CA 92161 (United States)
2006-06-15
Objective: To clarify the role of MR-imaging in the diagnosis of anterior ankle impingement syndromes. Materials and methods: We prospectively examined 51 consecutive patients with chronic ankle pain by MR-imaging. Arthroscopy was performed in 29 patients who previously underwent non-enhanced MR-imaging; in 11 patients, indirect MR-arthrography additionally was performed. MR-examinations were correlated with clinical findings; MR and arthroscopy scores were statistically compared, agreement was measured. Results: Arthroscopy demonstrated granulation tissue in the lateral gutter (38%) and anterior recess (31%), lesions of the anterior tibiofibular (31%) and the anterior talofibular ligament (21%) as well as intraarticular bodies (10%). Stenosing tenosynovitis and a ganglionic cyst were revealed as extraarticular causes for chronic ankle pain by MR-examination (17%). Agreement of MR-imaging and arthroscopy was fair for the anterior talofibular ligament and the anterior joint cavity (kappa 0.40). Major discrepancy was found for non-enhanced MR scans (kappa 0.49) when compared with indirect MR-arthrography (kappa 0.03) in the anterior cavity. The sensitivity for lesions of the anterior talofibular and calcaneofibular ligament and the anterior cavity (0.91-0.87) detected by MR-imaging was superior in comparison to lesions of the anterior tibiofibular ligament and anteromedial cavity (0.50-0.24). Conclusion: MR-imaging provides additional information about the mechanics of chronic ankle impingement rather than an accurate diagnosis of this clinical entity. The method is helpful in differentiating extra- from intra-articular causes of ankle impingement. Indirect MR-arthrography has little or no additional value in patients with ankle impingement syndrome.
International Nuclear Information System (INIS)
Haller, Joerg; Bernt, Reinhard; Seeger, Thomas; Weissenbaeck, Alexander; Tuechler, Heinrich; Resnick, Donald
2006-01-01
Objective: To clarify the role of MR-imaging in the diagnosis of anterior ankle impingement syndromes. Materials and methods: We prospectively examined 51 consecutive patients with chronic ankle pain by MR-imaging. Arthroscopy was performed in 29 patients who previously underwent non-enhanced MR-imaging; in 11 patients, indirect MR-arthrography additionally was performed. MR-examinations were correlated with clinical findings; MR and arthroscopy scores were statistically compared, agreement was measured. Results: Arthroscopy demonstrated granulation tissue in the lateral gutter (38%) and anterior recess (31%), lesions of the anterior tibiofibular (31%) and the anterior talofibular ligament (21%) as well as intraarticular bodies (10%). Stenosing tenosynovitis and a ganglionic cyst were revealed as extraarticular causes for chronic ankle pain by MR-examination (17%). Agreement of MR-imaging and arthroscopy was fair for the anterior talofibular ligament and the anterior joint cavity (kappa 0.40). Major discrepancy was found for non-enhanced MR scans (kappa 0.49) when compared with indirect MR-arthrography (kappa 0.03) in the anterior cavity. The sensitivity for lesions of the anterior talofibular and calcaneofibular ligament and the anterior cavity (0.91-0.87) detected by MR-imaging was superior in comparison to lesions of the anterior tibiofibular ligament and anteromedial cavity (0.50-0.24). Conclusion: MR-imaging provides additional information about the mechanics of chronic ankle impingement rather than an accurate diagnosis of this clinical entity. The method is helpful in differentiating extra- from intra-articular causes of ankle impingement. Indirect MR-arthrography has little or no additional value in patients with ankle impingement syndrome
MR-fluid yield surface determination in disc-type MR rotary brakes
International Nuclear Information System (INIS)
Farjoud, Alireza; Vahdati, Nader; Fah, Yap Fook
2008-01-01
Magneto-rheological (MR) fluids are currently attracting a great deal of attention because of their unique rheological behavior. Many devices have been designed using MR fluids, and of potential interest here are disc-type MR rotary brakes. The plug flow region in MR devices is defined as the region where the fluid is not flowing. The plug flow region plays an important role in design and analysis of MR devices. In MR dampers, the damping coefficient is a function of the plug thickness. In MR valves, the plug thickness is used to control the flow rate through, and the pressure drop across, the MR valve. A MR clutch is performing at the highest efficiency when the entire MR gap is the plug region. For an MR rotary brake, the highest restraining torque is obtained when the entire gap is the plug region as far as there are no wall slip effects. In this paper, using the Bercovier and Engelman constitutive model, the MR fluid flow in disc-type MR brakes is modeled to determine the plug flow region. The resulting system of equations is solved numerically. It is shown that the existence of a plug flow region in the brake will affect the control torque ratio. Better estimation of the plug flow region results in better estimation of the viscous torque
MR Measurement Technique of Rapidly Switched Gradient Magnetic Fields in MR Tomography
Czech Academy of Sciences Publication Activity Database
Bartušek, Karel; Gescheidtová, E.
2005-01-01
Roč. 29, č. 4 (2005), s. 675-686 ISSN 0937-9347 Institutional research plan: CEZ:AV0Z20650511 Keywords : MR tomography * gradiernt magnet ic field * IF method * IFSE method * IFSES method * spin echo Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.743, year: 2005
MR findings of bowlegs in toddlers
International Nuclear Information System (INIS)
Iwasawa, Tae; Inaba, Yutaka; Kameshita, Kikuo; Nishimura, Gen; Aida, Noriko; Matsubara, Sho
1999-01-01
Background. Toddlers with severe physiologic tibial bowing are considered to be at risk for the development of Blount's disease. Objective. To correlate MR findings of the knee with the clinical outcome in toddlers with severe physiological tibial bowing. Materials and methods. MR findings were evaluated in 22 affected legs of 14 children with severe tibial bowing (mean age 1.9 years). In 18 affected legs, MR findings were compared with the transition of the tibial metaphyseal-diaphyseal angle (MDA) and tibiofemoral angle (TFA) measured serially between 2 and 3 years of age. Results. MR findings of severe tibial bowing comprised undulation of the posteromedial physis of the tibia (3/22), signal alterations in the medial tibial metaphysis (10/22), T2 prolongation in the posteromedial tibial epiphyseal cartilage (14/22) and signal changes in the medial menisci (18/22). The decrease in the TFA was different in the legs with and without increased signal in the epiphyseal cartilage, and the decrease in the MDA was different in the legs with and without physeal undulation. Conclusion. MR imaging findings can predict the retarded resolution of tibial bowing, which may be a risk factor for the development of Blount's disease. (orig.)
Goerke, Steffen; Zaiss, Moritz; Bachert, Peter
2014-05-01
Chemical exchange saturation transfer (CEST) enables indirect detection of small metabolites in tissue by MR imaging. To optimize and interpret creatine-CEST imaging we characterized the dependence of the exchange-rate constant k(sw) of creatine guanidinium protons in aqueous creatine solutions as a function of pH and temperature T in vitro. Model solutions in the low pH range (pH = 5-6.4) were measured by means of water-exchange (WEX)-filtered ¹H NMR spectroscopy on a 3 T whole-body MR tomograph. An extension of the Arrhenius equation with effective base-catalyzed Arrhenius parameters yielded a general expression for k(sw) (pH, T). The defining parameters were identified as the effective base-catalyzed rate constant k(b,eff) (298.15 K) = (3.009 ± 0.16) × 10⁹ Hz l/mol and the effective activation energy E(A,b,eff) = (32.27 ± 7.43) kJ/mol at a buffer concentration of c(buffer) = (1/15) M. As expected, a strong dependence of k(sw) on temperature was observed. The extrapolation of the exchange-rate constant to in vivo conditions (pH = 7.1, T = 37 °C) led to the value of the exchange-rate constant k(sw) = 1499 Hz. With the explicit function k(sw) (pH, T) available, absolute-pH CEST imaging could be realized and experimentally verified in vitro. By means of our calibration method it is possible to adjust the guanidinium proton exchange-rate constant k(sw) to any desired value by preparing creatine model solutions with a specific pH and temperature. Copyright © 2014 John Wiley & Sons, Ltd.
Synthesis and characterization of magneto-rheological (MR fluids for MR brake application
Directory of Open Access Journals (Sweden)
Bhau K. Kumbhar
2015-09-01
Full Text Available Magneto rheological (MR fluid technology has been proven for many industrial applications like shock absorbers, actuators, etc. MR fluid is a smart material whose rheological characteristics change rapidly and can be controlled easily in presence of an applied magnetic field. MR brake is a device to transmit torque by the shear stress of MR fluid. However, MR fluids exhibit yield stress of 50–90 kPa. In this research, an effort has been made to synthesize MR fluid sample/s which will typically meet the requirements of MR brake applications. In this study, various electrolytic and carbonyl iron powder based MR fluids have been synthesized by mixing grease as a stabilizer, oleic acid as an antifriction additive and gaur gum powder as a surface coating to reduce agglomeration of the MR fluid. MR fluid samples based on sunflower oil, which is bio-degradable, environmentally friendly and abundantly available have also been synthesized. These MR fluid samples are characterized for determination of magnetic, morphological and rheological properties. This study helps identify most suitable localized MR fluid meant for MR brake application.
MrGrid: a portable grid based molecular replacement pipeline.
Directory of Open Access Journals (Sweden)
Jason W Schmidberger
Full Text Available BACKGROUND: The crystallographic determination of protein structures can be computationally demanding and for difficult cases can benefit from user-friendly interfaces to high-performance computing resources. Molecular replacement (MR is a popular protein crystallographic technique that exploits the structural similarity between proteins that share some sequence similarity. But the need to trial permutations of search models, space group symmetries and other parameters makes MR time- and labour-intensive. However, MR calculations are embarrassingly parallel and thus ideally suited to distributed computing. In order to address this problem we have developed MrGrid, web-based software that allows multiple MR calculations to be executed across a grid of networked computers, allowing high-throughput MR. METHODOLOGY/PRINCIPAL FINDINGS: MrGrid is a portable web based application written in Java/JSP and Ruby, and taking advantage of Apple Xgrid technology. Designed to interface with a user defined Xgrid resource the package manages the distribution of multiple MR runs to the available nodes on the Xgrid. We evaluated MrGrid using 10 different protein test cases on a network of 13 computers, and achieved an average speed up factor of 5.69. CONCLUSIONS: MrGrid enables the user to retrieve and manage the results of tens to hundreds of MR calculations quickly and via a single web interface, as well as broadening the range of strategies that can be attempted. This high-throughput approach allows parameter sweeps to be performed in parallel, improving the chances of MR success.
Energy Technology Data Exchange (ETDEWEB)
Dąbrowski, P., E-mail: piotr_dabrowski@sggw.pl [Department of Environmental Improvement, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Kalaji, M.H., E-mail: hazem@kalaji.pl [Department of Plant Physiology, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); SI TECHNOLOGY Sp. z o. o., Górczewska 226C/26, 01-460 Warsaw (Poland); Baczewska, A.H., E-mail: a.baczewska@obpan.pl [Polish Academy of Sciences Botanical Garden-Center for Biological Diversity Conservation in Powsin, 2 Prawdziwka St., 02-973 Warsaw (Poland); Pawluśkiewicz, B. [Department of Environmental Improvement, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Mastalerczuk, G., E-mail: grazyna_mastalerczuk@sggw.pl [Department of Agronomy, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Borawska-Jarmułowicz, B., E-mail: barbara_borawska_jarmulowicz@sggw.pl [Department of Agronomy, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Paunov, M. [Department Biophysics and Radiobiology, St. Kl. Ohridski Sofia University, 8 Dragan Tsankov Blvd., 1164 Sofia (Bulgaria); Goltsev, V., E-mail: goltsev@biofac.uni-sofia.bg [Department Biophysics and Radiobiology, St. Kl. Ohridski Sofia University, 8 Dragan Tsankov Blvd., 1164 Sofia (Bulgaria)
2017-03-15
Perennial ryegrass (Lolium perenne L.) is one of the more popular grass species in Europe. It is commonly used for starting lawns in urban areas, where plant growth is limited by many environmental conditions. The contamination of soils by salt is one of the major problems in urban green areas, as well as in natural areas. The basic aim of this study is to provide a detailed in vivo analysis of the changes in the delayed chlorophyll fluorescence and MR 820 signals (induced by salt stress) of two lawn varieties of perennial ryegrass, and to find out if there are correlations between these parameters and gas exchange. Two lawn varieties of Lolium perenne L. were used: Nira and Roadrunner. Salinization was performed at 8 weeks after sowing by adding NaCl in water solution (0, 0.15, and 0.30 M). There were 8 terms of measurement: 0 h, 24 h, 48 h, 96 h, 144 h, 192 h, 240 h, and 288 h after salinization. Our results showed that delayed fluorescence is a tool that can bring completely new opportunities for detecting stress in plants caused by salt. Our work allowed us to identify various limitation patterns in the photosynthetic efficiency of perennial ryegrass lawn varieties grown under salt stress conditions. Significant differences between the two tested varieties in response to salt stress were confirmed.
International Nuclear Information System (INIS)
Dąbrowski, P.; Kalaji, M.H.; Baczewska, A.H.; Pawluśkiewicz, B.; Mastalerczuk, G.; Borawska-Jarmułowicz, B.; Paunov, M.; Goltsev, V.
2017-01-01
Perennial ryegrass (Lolium perenne L.) is one of the more popular grass species in Europe. It is commonly used for starting lawns in urban areas, where plant growth is limited by many environmental conditions. The contamination of soils by salt is one of the major problems in urban green areas, as well as in natural areas. The basic aim of this study is to provide a detailed in vivo analysis of the changes in the delayed chlorophyll fluorescence and MR 820 signals (induced by salt stress) of two lawn varieties of perennial ryegrass, and to find out if there are correlations between these parameters and gas exchange. Two lawn varieties of Lolium perenne L. were used: Nira and Roadrunner. Salinization was performed at 8 weeks after sowing by adding NaCl in water solution (0, 0.15, and 0.30 M). There were 8 terms of measurement: 0 h, 24 h, 48 h, 96 h, 144 h, 192 h, 240 h, and 288 h after salinization. Our results showed that delayed fluorescence is a tool that can bring completely new opportunities for detecting stress in plants caused by salt. Our work allowed us to identify various limitation patterns in the photosynthetic efficiency of perennial ryegrass lawn varieties grown under salt stress conditions. Significant differences between the two tested varieties in response to salt stress were confirmed.
Overhauser-enhanced MR imaging (OMRI)
International Nuclear Information System (INIS)
Golman, K.; Leunbach, I.; Ardenkjaer-Larsen, J.H.; Wistrand, L.G.; Petersson, J.S.; Ehnholm, G.J.; Jaervi, A.; Vahasalo, S.
1998-01-01
Purpose: To evaluate a new single-electron contrast agent for Overhauser-enhanced MR imaging. The contrast agents that are currently available give enhancement factors that are too low to make the technique a valid option for routine clinical use. Material and Methods: MR images were generated directly following the injection of the substance into rats. The MR scanner was operated at a main magnetic field of 0.01 T and equipped with a separate rf-transmitter tuned to the electron paramagnetic resonance frequency of the contrast agent. Results: As expected, the images generated show a high level of enhancement in areas where the contrast agent was present, and a maximum enhancement of 60 times the normal proton signal was obtained in the vascular area. The signal-to-noise ratios in the images were superior to those previously attained. Conclusion: The new contrast agent makes it possible to generate MR images with both morphological and functional information at 0.01 T. The signal-to-noise ratios found in the generated images were of the same order as, or better than, those obtained with the standard clinical routine. (orig.)
Influence of market factors on the pricing of exchange traded metals in the medium term
Bogdanov, S. V.; Shevelev, I. M.; Chernyi, S. A.
2017-06-01
On the basis of comparison of the influence of the stock exchange factors on the pricing of nonferrous metals for medium term with similar results for short term, it has been established that the main attention should be paid to the changes in the pricing environment on the metal market as a function of the prices of exchange traded metals. The situation on the market of energy carriers (hydrocarbons) and the European, American, and Asian stock exchanges can be based on parity and even significantly influence the variation of the metal prices. In the medium term, constructive development of metal trade should be reasonably promoted by changing the elasticity of supply with regard to prices for exchange traded metals and by applying the stock exchange factors that positively influence the pricing on commodity and stock markets.
Using Mason number to predict MR damper performance from limited test data
Becnel, Andrew C.; Wereley, Norman M.
2017-05-01
The Mason number can be used to produce a single master curve which relates MR fluid stress versus strain rate behavior across a wide range of shear rates, temperatures, and applied magnetic fields. As applications of MR fluid energy absorbers expand to a variety of industries and operating environments, Mason number analysis offers a path to designing devices with desired performance from a minimal set of preliminary test data. Temperature strongly affects the off-state viscosity of the fluid, as the passive viscous force drops considerably at higher temperatures. Yield stress is not similarly affected, and stays relatively constant with changing temperature. In this study, a small model-scale MR fluid rotary energy absorber is used to measure the temperature correction factor of a commercially-available MR fluid from LORD Corporation. This temperature correction factor is identified from shear stress vs. shear rate data collected at four different temperatures. Measurements of the MR fluid yield stress are also obtained and related to a standard empirical formula. From these two MR fluid properties - temperature-dependent viscosity and yield stress - the temperature-corrected Mason number is shown to predict the force vs. velocity performance of a full-scale rotary MR fluid energy absorber. This analysis technique expands the design space of MR devices to high shear rates and allows for comprehensive predictions of overall performance across a wide range of operating conditions from knowledge only of the yield stress vs. applied magnetic field and a temperature-dependent viscosity correction factor.
Value of new MR techniques in MR-PET; Stellenwert neuer MR-Techniken in der MR-PET
Energy Technology Data Exchange (ETDEWEB)
Attenberger, U.I.; Schoenberg, S.O. [Universitaetsmedizin Mannheim, Medizinische Fakultaet Mannheim der Universitaet Heidelberg, Institut fuer klinische Radiologie und Nuklearmedizin, Mannheim (Germany); Quick, H.H. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Institut fuer Medizinische Physik, Erlangen (Germany); Guimaraes, A. [Massachusetts General Hospital, Martinos Center for Biomedical Imaging, Department of Radiology, Charlestown (United States); Catalano, O. [University of Naples Federico II, Naples (Italy); Morelli, J.N. [The Johns Hopkins Hospital, The Russell H. Morgan Department of Radiology and Radiological Science, Baltimore (United States)
2013-12-15
The unparalleled soft tissue contrast of magnetic resonance imaging (MRI) and the functional information obtainable with 18-F fluorodeoxyglucose positron emission tomography (FDG-PET) render MR-PET well-suited for oncological and psychiatric imaging. The lack of ionizing radiation with MRI also makes MR-PET a promising modality for oncology patients requiring frequent follow-up and pediatric patients. Lessons learned with PET computed tomography (CT) over the last few years do not directly translate to MR-PET. For example, in PET-CT the Hounsfield units derived from CT are used for attenuation correction (AC). As 511 keV photons emitted in PET examinations are attenuated by the patient's body CT data are converted directly to linear attenuation coefficients (LAC); however, proton density measured by MRI is not directly related to the radiodensity or LACs of biological tissue. Thus, direct conversion to LAC data is not possible making AC more challenging in simultaneous MRI-PET scanning. In addition to these constraints simultaneous MRI-PET acquisitions also improve on some solutions to well-known challenges of hybrid imaging techniques, such as limitations in motion correction. This article reports on initial clinical experiences with simultaneously acquired MRI-PET data, focusing on the potential benefits and limitations of MRI with respect to motion correction as well as metal and attenuation correction artefacts. (orig.) [German] Die klinische Implementierung der neuen Hybridtechnologie MR-Positronenemissionstomographie (MR-PET) bietet durch die Kombination aus hochaufloesender Morphologie, Funktion und Metabolismus bisher ungeahnte diagnostische Moeglichkeiten, die nicht nur fuer die Diagnose und die Verlaufskontrolle onkologischer und psychiatrischer Erkrankungen von hoher Bedeutung sind. Verglichen mit der PET-CT wird dies mit reduzierter Strahlenbelastung fuer den Patienten moeglich, was wiederum insbesondere fuer Patienten in der Tumornachsorge, die
Bimodal MR-PET agent for quantitative pH imaging
Frullano, Luca; Catana, Ciprian; Benner, Thomas; Sherry, A. Dean; Caravan, Peter
2010-01-01
Activatable or “smart” magnetic resonance contrast agents have relaxivities that depend on environmental factors such as pH or enzymatic activity, but the MR signal depends on relaxivity and agent concentration – two unknowns. A bimodal approach, incorporating a positron emitter, solves this problem. Simultaneous positron emission tomography (PET) and MR imaging with the biomodal, pH-responsive MR-PET agent GdDOTA-4AMP-F allows direct determination of both concentration (PET) and T1 (MRI), and hence pH. PMID:20191650
Kroon, Jeffrey; Heemskerk, Niels; Kalsbeek, Martin J T; de Waard, Vivian; van Rijssel, Jos; van Buul, Jaap D
2017-07-01
Endothelial cells line the lumen of the vessel wall and are exposed to flow. In linear parts of the vessel, the endothelial cells experience laminar flow, resulting in endothelial cell alignment in the direction of flow, thereby protecting the vessel wall from inflammation and permeability. In order for endothelial cells to align, they undergo rapid remodeling of the actin cytoskeleton by local activation of the small GTPase Rac1. However, it is not clear whether sustained and local activation of Rac1 is required for long-term flow-induced cell alignment. Using a FRET-based DORA Rac1 biosensor, we show that local Rac1 activity remains for 12 h upon long-term flow. Silencing studies show that the RhoGEF Trio is crucial for keeping active Rac1 at the downstream side of the cell and, as a result, for long-term flow-induced cell alignment. Surprisingly, Trio appears to be not involved in flow-induced activation of Rac1. Our data show that flow induces Rac1 activity at the downstream side of the cell in a Trio-dependent manner and that Trio functions as a scaffold protein rather than a functional GEF under long-term flow conditions. © 2017 Kroon et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).
MR-based source localization for MR-guided HDR brachytherapy
Beld, E.; Moerland, M. A.; Zijlstra, F.; Viergever, M. A.; Lagendijk, J. J. W.; Seevinck, P. R.
2018-04-01
For the purpose of MR-guided high-dose-rate (HDR) brachytherapy, a method for real-time localization of an HDR brachytherapy source was developed, which requires high spatial and temporal resolutions. MR-based localization of an HDR source serves two main aims. First, it enables real-time treatment verification by determination of the HDR source positions during treatment. Second, when using a dummy source, MR-based source localization provides an automatic detection of the source dwell positions after catheter insertion, allowing elimination of the catheter reconstruction procedure. Localization of the HDR source was conducted by simulation of the MR artifacts, followed by a phase correlation localization algorithm applied to the MR images and the simulated images, to determine the position of the HDR source in the MR images. To increase the temporal resolution of the MR acquisition, the spatial resolution was decreased, and a subpixel localization operation was introduced. Furthermore, parallel imaging (sensitivity encoding) was applied to further decrease the MR scan time. The localization method was validated by a comparison with CT, and the accuracy and precision were investigated. The results demonstrated that the described method could be used to determine the HDR source position with a high accuracy (0.4–0.6 mm) and a high precision (⩽0.1 mm), at high temporal resolutions (0.15–1.2 s per slice). This would enable real-time treatment verification as well as an automatic detection of the source dwell positions.
Coman, Daniel; Kiefer, Garry E; Rothman, Douglas L; Sherry, A Dean; Hyder, Fahmeed
2011-12-01
Responsive contrast agents (RCAs) composed of lanthanide(III) ion (Ln3R) complexes with a variety of1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA4S) derivatives have shown great potential as molecular imaging agents for MR. A variety of LnDOTA–tetraamide complexes have been demonstrated as RCAs for molecular imaging using chemical exchange saturation transfer (CEST). The CEST method detects proton exchange between bulk water and any exchangeable sites on the ligand itself or an inner sphere of bound water that is shifted by a paramagnetic Ln3R ion bound in the core of the macrocycle. It has also been shown that molecular imaging is possible when the RCA itself is observed (i.e. not its effect on bulk water) using a method called biosensor imaging of redundant deviation in shifts (BIRDS). The BIRDS method utilizes redundant information stored in the nonexchangeable proton resonances emanating from the paramagnetic RCA for ambient factors such as temperature and/or pH.Thus, CEST and BIRDS rely on exchangeable and nonexchangeable protons, respectively, for biosensing. We posited that it would be feasible to combine these two biosensing features into the same RCA (i.e. dual CEST and BIRDS properties). A complex between europium(III) ion (Eu3R) and DOTA–tetraglycinate [DOTA–(gly)S4] was used to demonstrate that its CEST characteristics are preserved, while its BIRDS properties are also detectable. The in vitro temperature sensitivity of EuDOTA–(gly)S4 was used to show that qualitative MR contrast with CEST can be calibrated using quantitative MR mapping with BIRDS, thereby enabling quantitative molecular imaging at high spatial resolution.
Generation of structural MR images from amyloid PET: Application to MR-less quantification.
Choi, Hongyoon; Lee, Dong Soo
2017-12-07
Structural magnetic resonance (MR) images concomitantly acquired with PET images can provide crucial anatomical information for precise quantitative analysis. However, in the clinical setting, not all the subjects have corresponding MR. Here, we developed a model to generate structural MR images from amyloid PET using deep generative networks. We applied our model to quantification of cortical amyloid load without structural MR. Methods: We used florbetapir PET and structural MR data of Alzheimer's Disease Neuroimaging Initiative database. The generative network was trained to generate realistic structural MR images from florbetapir PET images. After the training, the model was applied to the quantification of cortical amyloid load. PET images were spatially normalized to the template space using the generated MR and then standardized uptake value ratio (SUVR) of the target regions was measured by predefined regions-of-interests. A real MR-based quantification was used as the gold standard to measure the accuracy of our approach. Other MR-less methods, a normal PET template-based, multi-atlas PET template-based and PET segmentation-based normalization/quantification methods, were also tested. We compared performance of quantification methods using generated MR with that of MR-based and MR-less quantification methods. Results: Generated MR images from florbetapir PET showed visually similar signal patterns to the real MR. The structural similarity index between real and generated MR was 0.91 ± 0.04. Mean absolute error of SUVR of cortical composite regions estimated by the generated MR-based method was 0.04±0.03, which was significantly smaller than other MR-less methods (0.29±0.12 for the normal PET-template, 0.12±0.07 for multiatlas PET-template and 0.08±0.06 for PET segmentation-based methods). Bland-Altman plots revealed that the generated MR-based SUVR quantification was the closest to the SUVR values estimated by the real MR-based method. Conclusion
Ionization chamber correction factors for MR-linacs.
Pojtinger, Stefan; Dohm, Oliver Steffen; Kapsch, Ralf-Peter; Thorwarth, Daniela
2018-06-07
Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor k B . The purpose of this study is to systematically investigate k B for a typical reference setup for commercially available ionization chambers with different magnetic field strengths. The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0-2.5 T. To validate the simulation, the influence of the magnetic field was experimentally determined for a PTW30013 Farmer-type chamber for magnetic flux densities between 0 and 1.425 T. Changes in the detector response of up to 8% depending on the magnetic flux density, on the chamber geometry and on the chamber orientation were obtained. In the experimental setup, a maximum deviation of less than 2% was observed when comparing measured values with simulated values. Dedicated values for two MR-linac systems (ViewRay MRIdian, ViewRay Inc, Cleveland, United States, 0.35 T/ 6 MV and Elekta Unity, Elekta AB, Stockholm, Sweden, 1.5 T/7 MV) were determined for future use in reference dosimetry. Simulated values for thimble-type chambers are in good agreement with experiments as well as with the results of previous publications. After further experimental validation, the results can be considered for definition of standard protocols for purposes of reference dosimetry in MRgRT.
Ionization chamber correction factors for MR-linacs
Pojtinger, Stefan; Steffen Dohm, Oliver; Kapsch, Ralf-Peter; Thorwarth, Daniela
2018-06-01
Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor k B. The purpose of this study is to systematically investigate k B for a typical reference setup for commercially available ionization chambers with different magnetic field strengths. The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0–2.5 T. To validate the simulation, the influence of the magnetic field was experimentally determined for a PTW30013 Farmer-type chamber for magnetic flux densities between 0 and 1.425 T. Changes in the detector response of up to 8% depending on the magnetic flux density, on the chamber geometry and on the chamber orientation were obtained. In the experimental setup, a maximum deviation of less than 2% was observed when comparing measured values with simulated values. Dedicated values for two MR-linac systems (ViewRay MRIdian, ViewRay Inc, Cleveland, United States, 0.35 T/ 6 MV and Elekta Unity, Elekta AB, Stockholm, Sweden, 1.5 T/7 MV) were determined for future use in reference dosimetry. Simulated values for thimble-type chambers are in good agreement with experiments as well as with the results of previous publications. After further experimental validation, the results can be considered for definition of standard protocols for purposes of reference dosimetry in MRgRT.
Schuette, W; Eberhardt, W E E; Waller, C; Schirmacher, P; Dietel, M; Zirrgiebel, U; Radke, S; Thomas, M
2016-09-01
Assessment of several clinical factors on progression-free (PFS) and overall survival (OS) in NSCLC patients (pts.) (stage IV) with mutated epidermal growth factor receptor (EGFRm+) treated with gefitinib (gef) or with chemotherapy (CT) under real-world conditions. 285 EGFRm+ pts. of the non-interventional REASON study treated with gef (n = 206) or CT (n = 79) as first-line therapy or with gef (n = 213) or CT (n = 61) in any line throughout the course of therapy were analyzed according to age, gender, smoking history and histology. Compared with CT, patients treated with gef showed prolongation of PFS and OS in all subgroups. PFS was significantly increased in women and non-smokers. OS was significantly increased in women, non-smokers, (ex)-smokers, patients with adenocarcinoma and elderly patients when treated with gef compared to CT. Female gender turned out to be an independent positive predictive factor for OS in patients treated with gef (HRmale: 1.74, p = 0.0009). A clinical benefit of gef was shown for all analyzed clinical subgroups of EGFRm+ pts. This was confirmed for the female gender in a multivariate analysis. © Georg Thieme Verlag KG Stuttgart · New York.
Prognostic value of contrast-enhanced MR mammography in patients with breast cancer.
Fischer, U; Kopka, L; Brinck, U; Korabiowska, M; Schauer, A; Grabbe, E
1997-01-01
The objective of this study was to evaluate the prognostic value of contrast-enhanced MR mammography in patients with breast cancer. A total of 190 patients with breast cancer (37 noninvasive carcinomas, 153 invasive carcinomas) underwent dynamic contrast-enhanced MR mammography preoperatively. Using 1.5-T unit, T1-weighted sequences (2D FLASH) were obtained repeatedly one time before and five times after IV administration of 0.1 mmol gadopentetate-dimeglumine per kilogram body weight. The findings on MR imaging were correlated with histopathologically defined prognostic factors (histological type, tumor size, tumor grading, metastasis in lymph nodes). In addition, immunohistochemically defined prognostic factors (c-erbB-1, c-erbB-2, p53, Ki-67) were correlated with the signal increase on MR mammogram in 40 patients. There was no significant correlation between the findings on MR mammography and the histopathological type of carcinoma, the grading, and the lymphonodular status. Noninvasive carcinomas showed a higher rate of moderate (38 %) or low (27 %) enhancement on MR imaging than invasive carcinomas (6 and 3 %). The results on MR mammography and the results of immunohistochemical stainings did not correlate significantly. Noninvasive carcinomas showed significantly lower enhancement than invasive carcinomas. However, the signal behavior of contrast-enhanced MR mammography is not related to established histopathological prognostic parameters as subtyping, grading, nodal status, and the expression of certain oncogenes/tumor suppressor genes.
Imaging Human Brain Perfusion with Inhaled Hyperpolarized 129Xe MR Imaging.
Rao, Madhwesha R; Stewart, Neil J; Griffiths, Paul D; Norquay, Graham; Wild, Jim M
2018-02-01
Purpose To evaluate the feasibility of directly imaging perfusion of human brain tissue by using magnetic resonance (MR) imaging with inhaled hyperpolarized xenon 129 ( 129 Xe). Materials and Methods In vivo imaging with 129 Xe was performed in three healthy participants. The combination of a high-yield spin-exchange optical pumping 129 Xe polarizer, custom-built radiofrequency coils, and an optimized gradient-echo MR imaging protocol was used to achieve signal sensitivity sufficient to directly image hyperpolarized 129 Xe dissolved in the human brain. Conventional T1-weighted proton (hydrogen 1 [ 1 H]) images and perfusion images by using arterial spin labeling were obtained for comparison. Results Images of 129 Xe uptake were obtained with a signal-to-noise ratio of 31 ± 9 and demonstrated structural similarities to the gray matter distribution on conventional T1-weighted 1 H images and to perfusion images from arterial spin labeling. Conclusion Hyperpolarized 129 Xe MR imaging is an injection-free means of imaging the perfusion of cerebral tissue. The proposed method images the uptake of inhaled xenon gas to the extravascular brain tissue compartment across the intact blood-brain barrier. This level of sensitivity is not readily available with contemporary MR imaging methods. © RSNA, 2017.
International Nuclear Information System (INIS)
Ohtomi, S; Matsui, M; Mochizuki, Y; Suga, A; Kato, H; Hoshino, M; Tanaka, H; Duflot, D; Limão-Vieira, P
2015-01-01
We report on the measurements of the electron impact electronic excitation cross sections for XF 4 (X = C, Si and Ge) molecules at 100 eV, 5° scattering angle and 30 eV, 30° in the electron energy loss range 8.0 - 18 eV. For a target of GeF 4 molecule, the optically-forbidden behavior has been observed in the lower electron energy loss range. (paper)
Hadzi-Vaskov, M.; Kool, C.J.M.
2007-01-01
This paper presents evidence of the stochastic discount factor approach to international risk-sharing applied to fixed exchange rate regimes. We calculate risk-sharing indices for two episodes of fixed or very rigid exchange rates: the Eurozone before and after the introduction of the Euro, and
International Nuclear Information System (INIS)
Kinosada, Yasutomi; Okuda, Yasuyuki; Ono, Mototsugu
1993-01-01
We developed a new noninvasive technique to visualize the anatomical structure of the nerve fiber system in vivo, and named this technique magnetic resonance (MR) tractography and the acquired image an MR tractogram. MR tractography has two steps. One is to obtain diffusion-weighted images sensitized along axes appropriate for depicting the intended nerve fibers with anisotropic water diffusion MR imaging. The other is to extract the anatomical structure of the nerve fiber system from a series of diffusion-weighted images by the maximum intensity projection method. To examine the clinical usefulness of the proposed technique, many contiguous, thin (3 mm) coronal two-dimensional sections of the brain were acquired sequentially in normal volunteers and selected patients with paralyses, on a 1.5 Tesla MR system (Signa, GE) with an ECG-gated Stejskal-Tanner pulse sequence. The structure of the nerve fiber system of normal volunteers was almost the same as the anatomy. The tractograms of patients with paralyses clearly showed the degeneration of nerve fibers and were correlated with clinical symptoms. MR tractography showed great promise for the study of neuroanatomy and neuroradiology. (author)
Silencing MR-1 attenuates inflammatory damage in mice heart induced by AngII
International Nuclear Information System (INIS)
Dai, Wenjian; Chen, Haiyang; Jiang, Jiandong; Kong, Weijia; Wang, Yiguang
2010-01-01
Myofibrillogenesis regulator-1(MR-1) can aggravate cardiac hypertrophy induced by angiotensin(Ang) II in mice through activation of NF-κB signaling pathway, and nuclear transcription factor (NF)-κB and activator protein-1(AP-1) regulate inflammatory and immune responses by increasing the expression of specific inflammatory genes in various tissues including heart. Whether inhibition of MR-1 expression will attenuate AngII-induced inflammatory injury in mice heart has not been explored. Herein, we monitored the activation of NF-κB and AP-1, together with expression of pro-inflammatory of interleukin(IL)-6, tumor necrosis factor(TNF)-α, vascular-cell adhesion molecule (VCAM)-1, platelet endothelial cell adhesion molecule (PECAM), and inflammatory cell infiltration in heart of mice which are induced firstly by AngII (PBS),then received MR-1-siRNA or control-siRNA injecting. We found that the activation of NF-κB and AP-1 was inhibited significantly, together with the decreased expression of IL-6, TNF-α, VCAM-1, and PECAM in AngII-induced mice myocardium in MR-1-siRNA injection groups compared with control-siRNA injecting groups. However, the expression level of MR-1 was not an apparent change in PBS-infused groups than in unoperation groups, and MR-1-siRNA do not affect the expression of MR-1 in PBS-infused mice. Our findings suggest that silencing MR-1 protected mice myocardium against inflammatory injury induced by AngII by suppression of pro-inflammatory transcription factors NF-κB and AP-1 signaling pathway.
Uniformity factor of temperature difference in heat exchanger networks
International Nuclear Information System (INIS)
Chen, Shang; Cui, Guo-min
2016-01-01
Highlights: • A uniformity factor of temperature (UFTD) is proposed to heat exchanger network (HEN). • A novel stage-wise superstructure with inner utilities is presented based on UFTD. • New model and DE method is combined as an optimization method. • Optimal HEN structures with inner utilities can be obtained with new method. - Abstract: A uniformity factor of temperature difference (UFTD) is proposed and set up to guide the optimization of Heat exchanger network (HEN). At first, the factor is presented to evaluate the whole enhancement of HEN by handling the logical mean temperature difference as two-dimensional discrete temperature field in system. Then, the factor is applied to different HENs, of which the comparison indicates that a more uniform discrete temperature field leads to a lower UFTD which correlated with a better whole enhancement to improve the optimization level of HEN. A novel stage-wise superstructure model where inner utility can be generated is presented for further analysis of correlation between UFTD and the efficiency of HEN, and more optimal HEN structures can be obtained as inner utility added. Inner utility appears to violate the thermodynamic law, but it makes the discrete temperature field more uniform and improves the heat transfer efficiency of the whole HEN, which brings much more profit than the side effect of inner utility. In sum, the UFTD can not only evaluate the optimization level of the HEN, but also be an optimization object to design new HEN with higher efficiency of energy utilization and lower total annual cost.
Vav1: Friend and Foe of Cancer.
Guo, Fukun; Zheng, Yi
2017-12-01
A recent study shows that the protumorigenic guanine nucleotide exchange factor (GEF) Vav1 functions as a tumor suppressor in T cell acute lymphoblastic leukemia (T-ALL) through its ability to complex with the Cbl-b ubiquitin ligase and the intracellular domain of Notch1 (ICN1) and to promote ICN1 degradation. Vav1can act as a double-edged sword in tumorigenesis. Copyright © 2017 Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Gehl, H.B.; Frahm, C.
1998-01-01
Biopsies were the first 'intervention' under MR guidance. After initial difficulties concerning ferromagnetic biopsy instruments and the design of MR scanners, the latest technological improvements rendered MR guidance for biopsies more feasible. In this article we illustrate present-day clinical experience in the field of abdominal, breast and bone biopsy. Important aspects regarding the different designs of 'interventional' MR scanners and the visualization of instruments for biopsy are discussed. (orig.) [de
Authentically radiolabelled Mn(II) complexes as bimodal PET/MR tracers
Energy Technology Data Exchange (ETDEWEB)
Vanasschen, Christian; Brandt, Marie; Ermert, Johannes [Institute of Neuroscience and Medicine, INM-5 - Nuclear Chemistry, Forschungszentrum Jülich (Germany); Neumaier, Bernd [Institute for Radiochemistry and Experimental Molecular Imaging, Medical Clinics, University of Cologne (Germany); Coenen, Heinz H [Institute of Neuroscience and Medicine, INM-5 - Nuclear Chemistry, Forschungszentrum Jülich (Germany)
2015-05-18
The development of small molecule bimodal PET/MR tracers is mainly hampered by the lack of dedicated preparation methods. Authentic radiolabelling of MR contrast agents ensures easy access to such probes: a ligand, chelating a paramagnetic metal ion (e.g. Mn2+) and the corresponding PET isotope (e.g. 52gMn), leads to a “cocktail mixture” where both imaging reporters exhibit the same pharmacokinetics. Paramagnetic [55Mn(CDTA)]2- shows an excellent compromise between thermodynamic stability, kinetic inertness and MR contrast enhancement. Therefore, the aim of this study was to develop new PET/MR tracers by labelling CDTA ligands with paramagnetic manganese and the β+-emitter 52gMn. N.c.a. 52gMn (t1/2: 5.6 d; Eβ+: 575.8 keV (29.6%)) was produced by proton irradiation of a natCr target followed by cation-exchange chromatography. CDTA was radiolabelled with n.c.a. 52gMn2+ in NaOAc buffer (pH 6) at RT. The complex was purified by RP-HPLC and its stability tested in PBS and blood plasma at 37°C. The redox stability was assessed by monitoring the T1 relaxation (20 MHz) in HEPES buffer (pH 7.4). A functionalized CDTA ligand was synthesized in 5 steps. [52gMn(CDTA)]2- was quantitatively formed within 30 min at RT. The complex was stable for at least 6 days in PBS and blood plasma at 37°C and no oxidation occurred within 7 months storage at RT. Labelling CDTA with an isotopic 52g/55Mn2+ mixture led to the corresponding bimodal PET/MR tracer. Furthermore, a functionalized CDTA ligand was synthesized with an overall yield of 18-25%. [52g/55Mn(CDTA)]2-, the first manganese-based bimodal PET/MR tracer prepared, exhibits excellent stability towards decomplexation and oxidation. This makes the functionalized CDTA ligand highly suitable for designing PET/MR tracers with high relaxivity or targeting properties.
Authentically radiolabelled Mn(II) complexes as bimodal PET/MR tracers
International Nuclear Information System (INIS)
Vanasschen, Christian; Brandt, Marie; Ermert, Johannes; Neumaier, Bernd; Coenen, Heinz H
2015-01-01
The development of small molecule bimodal PET/MR tracers is mainly hampered by the lack of dedicated preparation methods. Authentic radiolabelling of MR contrast agents ensures easy access to such probes: a ligand, chelating a paramagnetic metal ion (e.g. Mn2+) and the corresponding PET isotope (e.g. 52gMn), leads to a “cocktail mixture” where both imaging reporters exhibit the same pharmacokinetics. Paramagnetic [55Mn(CDTA)]2- shows an excellent compromise between thermodynamic stability, kinetic inertness and MR contrast enhancement. Therefore, the aim of this study was to develop new PET/MR tracers by labelling CDTA ligands with paramagnetic manganese and the β+-emitter 52gMn. N.c.a. 52gMn (t1/2: 5.6 d; Eβ+: 575.8 keV (29.6%)) was produced by proton irradiation of a natCr target followed by cation-exchange chromatography. CDTA was radiolabelled with n.c.a. 52gMn2+ in NaOAc buffer (pH 6) at RT. The complex was purified by RP-HPLC and its stability tested in PBS and blood plasma at 37°C. The redox stability was assessed by monitoring the T1 relaxation (20 MHz) in HEPES buffer (pH 7.4). A functionalized CDTA ligand was synthesized in 5 steps. [52gMn(CDTA)]2- was quantitatively formed within 30 min at RT. The complex was stable for at least 6 days in PBS and blood plasma at 37°C and no oxidation occurred within 7 months storage at RT. Labelling CDTA with an isotopic 52g/55Mn2+ mixture led to the corresponding bimodal PET/MR tracer. Furthermore, a functionalized CDTA ligand was synthesized with an overall yield of 18-25%. [52g/55Mn(CDTA)]2-, the first manganese-based bimodal PET/MR tracer prepared, exhibits excellent stability towards decomplexation and oxidation. This makes the functionalized CDTA ligand highly suitable for designing PET/MR tracers with high relaxivity or targeting properties.
Correction of distortion of MR pictures for MR-guided robotic sterotactic procedures
International Nuclear Information System (INIS)
Jonckheere, E.A.; Kwoh, Y.S.
1988-01-01
Ever since magnetic resonance (MR) invaded the medical imaging field, it has played an increasingly important role and is even currently being considered for stereotactic guidance of probes in the brain. While MR pictures indeed convey more clinical information than CT, the geometry of MR pictures is, unfortunately, not as accurate as the geometry of CT pictures. In other words, if a square grid phantom is scanned, then the CT picture will show a square grid, while the MR picture will rather reveal a distorted grid. This distortion is primarily due to small variations in the static magnetic field. This small distortion does not impede radiological diagnosis; however, it is a source of concern if one contemplates utilizing the MR pictures for accurate stereotactic positioning of a probe at a very precise point in the brain. Another area of application where the distortion of the MR picture should be compensated for is the superposition of CT and MR pictures so that both informations could be used for diagnosis or stereotactic purposes. This paper essentially addresses the nonlinear distortion of MR pictures and how it could be compensated for through software manipulation of the MR picture
Haris, Mohammad; Nanga, Ravi Prakash Reddy; Singh, Anup; Cai, Kejia; Kogan, Feliks; Hariharan, Hari; Reddy, Ravinder
2012-11-01
Creatine (Cr), phosphocreatine (PCr) and adenosine-5-triphosphate (ATP) are major metabolites of the enzyme creatine kinase (CK). The exchange rate of amine protons of CK metabolites at physiological conditions has been limited. In the current study, the exchange rate and logarithmic dissociation constant (pKa) of amine protons of CK metabolites were calculated. Further, the chemical exchange saturation transfer effect (CEST) of amine protons of CK metabolites with bulk water was explored. At physiological temperature and pH, the exchange rate of amine protons in Cr was found to be 7-8 times higher than PCr and ATP. A higher exchange rate in Cr was associated with lower pKa value, suggesting faster dissociation of its amine protons compared to PCr and ATP. CEST MR imaging of these metabolites in vitro in phantoms displayed predominant CEST contrast from Cr and negligible contribution from PCr and ATP with the saturation pulse parameters used in the current study. These results provide a new method to perform high-resolution proton imaging of Cr without contamination from PCr. Potential applications of these finding are discussed. Copyright © 2012 John Wiley & Sons, Ltd.
Application Summary Report 22: LED MR16 Lamps
Energy Technology Data Exchange (ETDEWEB)
Royer, Michael P.
2014-07-23
This report analyzes the independently tested photometric performance of 27 LED MR16 lamps. It describes initial performance based on light output, efficacy, distribution, color quality, electrical characteristics, and form factor, with comparisons to a selection of benchmark halogen MR16s and ENERGY STAR qualification thresholds. Three types of products were targeted. First, CALiPER sought 3000 K lamps with the highest rated lumen output (i.e., at least 500 lm) or a claim of equivalency to a 50 W halogen MR16 or higher. The test results indicate that while the initial performance of LED MR16s has improved across the board, market-available products still do not produce the lumen output and center beam intensity of typical 50 W halogen MR16 lamps. In fact, most of the 18 lamps in this category had lower lumen output and center beam intensity than a typical 35 W halogen MR16 lamp. Second, CALiPER sought lamps with a CRI of 90 or greater. Only four manufacturers were identified with a product in this category. CALiPER testing confirmed the performance of these lamps, which are a good option for applications where high color fidelity is needed. A vast majority of the LED MR16 lamps have a CRI in the low 80s; this is generally acceptable for ambient lighting, but may not always be acceptable for focal lighting. For typical LED packages, there is a fundamental tradeoff between CRI and efficacy, but the lamps in the high-CRI group in this report still offer comparable performance to the rest of the Series 22 products in other performance areas. Finally, CALiPER sought lamps with a narrow distribution, denoted as a beam angle less than 15°. Five such lamps were purchased. Notably, no lamp was identified as having high lumen output (500 lumens or greater), high CRI (90 or greater), a narrow distribution (15° or less), and an efficacy greater than 60 lm/W. This would be an important achievement for LED MR16s especially if output could reach approximately 700 800 lumens
Prognostic value of contrast-enhanced MR mammography in patients with breast cancer
International Nuclear Information System (INIS)
Fischer, U.; Kopka, L.; Brinck, U.; Korabiowska, M.; Schauer, A.; Grabbe, E.
1997-01-01
The objective of this study was to evaluate the prognostic value of contrast-enhanced MR mammography in patients with breast cancer. A total of 190 patients with breast cancer (37 noninvasive carcinomas, 153 invasive carcinomas) underwent dynamic contrast-enhanced MR mammography preoperatively. Using 1.5-T unit, T1-weighted sequences (2D FLASH) were obtained repeatedly one time before and five times after IV administration of 0.1 mmol gadopentetate-dimeglumine per kilogram body weight. The findings on MR imaging were correlated with histopathologically defined prognostic factors (histological type, tumor size, tumor grading, metastasis in lymph nodes). In addition, immunohistochemically defined prognostic factors (c-erbB-1,c-erbB-2, p53, Ki-67) were correlated with the signal increase on MR mammogram in 40 patients. There was no significant correlation between the findings on MR mammography and the histopathological type of carcinoma, the grading, and the lymphonodular status. Noninvasive carcinomas showed a higher rate of moderate (38 %) or low (27 %) enhancement on MR imaging than invasive carcinomas (6 and 3 %). The results on MR mammography and the results of immunohistochemical stainings did not correlate significantly. Noninvasive carcinomas showed significantly lower enhancement than invasive carcinomas. However, the signal behavior of contrast-enhanced MR mammography is not related to established histopathological prognostic parameters as subtyping, grading, nodal status, and the expression of certain oncogenes/tumor suppressor genes. (orig.). With 5 tabs
Pulmonary MR angiography and perfusion imaging—A review of methods and applications
Energy Technology Data Exchange (ETDEWEB)
Johns, Christopher S.; Swift, Andrew J.; Hughes, Paul J.C. [University of Sheffield (United Kingdom); Ohno, Yoshiharu [Division of Functional and Diagnostic Imaging Research, Department of Radiology, KobeUniversity Graduate School of Medicine, Kobe, Hyogo (Japan); Schiebler, Mark [UW-Madison School of Medicine and Public Health, Madison, WI (United States); Wild, Jim M., E-mail: j.m.wild@sheffield.ac.uk [University of Sheffield (United Kingdom)
2017-01-15
Highlights: • This article represents an overview of the methodology and clinical applications of pulmonary MRA and perfusion imaging. • Both contrast enhanced and non-contrast enhanced metholodology for MRA and perfusion are covered. • The current clinical uses and future directions of MRA and MR perfusion are discussed. - Abstract: The pulmonary vasculature and its role in perfusion and gas exchange is an important consideration in many conditions of the lung and heart. Currently the mainstay of imaging of the vasculature and perfusion of the lungs lies with CT and nuclear medicine perfusion scans, both of which require ionizing radiation exposure. Improvements in MRI techniques have increased the use of MRI in pulmonary vascular imaging. Here we review MRI methods for imaging the pulmonary vasculature and pulmonary perfusion, both using contrast enhanced and non-contrast enhanced methodology. In many centres pulmonary MR angiography and dynamic contrast enhanced perfusion MRI are now well established in the routine workflow of patients particularly with pulmonary hypertension and thromboembolic disease. However, these imaging modalities offer exciting new directions for future research and clinical use in other respiratory diseases where consideration of pulmonary perfusion and gas exchange can provide insight in to pathophysiology.
Pulmonary MR angiography and perfusion imaging—A review of methods and applications
International Nuclear Information System (INIS)
Johns, Christopher S.; Swift, Andrew J.; Hughes, Paul J.C.; Ohno, Yoshiharu; Schiebler, Mark; Wild, Jim M.
2017-01-01
Highlights: • This article represents an overview of the methodology and clinical applications of pulmonary MRA and perfusion imaging. • Both contrast enhanced and non-contrast enhanced metholodology for MRA and perfusion are covered. • The current clinical uses and future directions of MRA and MR perfusion are discussed. - Abstract: The pulmonary vasculature and its role in perfusion and gas exchange is an important consideration in many conditions of the lung and heart. Currently the mainstay of imaging of the vasculature and perfusion of the lungs lies with CT and nuclear medicine perfusion scans, both of which require ionizing radiation exposure. Improvements in MRI techniques have increased the use of MRI in pulmonary vascular imaging. Here we review MRI methods for imaging the pulmonary vasculature and pulmonary perfusion, both using contrast enhanced and non-contrast enhanced methodology. In many centres pulmonary MR angiography and dynamic contrast enhanced perfusion MRI are now well established in the routine workflow of patients particularly with pulmonary hypertension and thromboembolic disease. However, these imaging modalities offer exciting new directions for future research and clinical use in other respiratory diseases where consideration of pulmonary perfusion and gas exchange can provide insight in to pathophysiology.
Exchange bias effect and intragranular magnetoresistance in Nd0.84Sr0.16CoO3
International Nuclear Information System (INIS)
Patra, M; Majumdar, S; Giri, S
2009-01-01
Electrical transport properties as a function of magnetic field and time have been investigated in polycrystalline, Nd 0.84 Sr 0.16 CoO 3 . A strong exchange bias (EB) effect is observed associated with the fairly large intragranular magnetoresistance (MR). The EB effect observed in the MR curve is compared with the EB effect manifested in the magnetic hysteresis loop. A training effect, described as the decrease of EB effect when the sample is successively field cycled at a particular temperature, has been observed in the shift of the MR curve. The training effect could be analyzed by successful models. The EB effect, MR and a considerable time dependence in MR are attributed to the intrinsic nanostructure giving rise to varieties of magnetic interfaces in the grain interior.
MR Imaging-Guided Attenuation Correction of PET Data in PET/MR Imaging.
Izquierdo-Garcia, David; Catana, Ciprian
2016-04-01
Attenuation correction (AC) is one of the most important challenges in the recently introduced combined PET/magnetic resonance (MR) scanners. PET/MR AC (MR-AC) approaches aim to develop methods that allow accurate estimation of the linear attenuation coefficients of the tissues and other components located in the PET field of view. MR-AC methods can be divided into 3 categories: segmentation, atlas, and PET based. This review provides a comprehensive list of the state-of-the-art MR-AC approaches and their pros and cons. The main sources of artifacts are presented. Finally, this review discusses the current status of MR-AC approaches for clinical applications. Copyright © 2016 Elsevier Inc. All rights reserved.
Do exchange rates follow random walks? A variance ratio test of the ...
African Journals Online (AJOL)
Kirstam
However, emerging markets in sub-Saharan Africa have ... C.J. Auret and Mr L. Chiliba are at the School of Economic and Business Sciences, University ... follow the exchange rate, as this helps them to manage or guard their exposures.
Ankle ligamints : comparison of MR arthrography with conventional MR imaging in amputated feet
International Nuclear Information System (INIS)
Yoo, Jae Sung; Lee, Sang Yong; Lee, Jeong Min; Han, Young Min; Chung, Kyung Ho; Kim, CHong Soo
2001-01-01
To compare magnetic resonance (MR) arthrography with conventional MR imaging in the evaluation of ankle ligaments. Eight freshly amputated human feet underwent conventional MR imaging and MR arthrography. For the former, 1.5-T magnets in the axial, coronal and sagittal planes were used, and T1-weighted sequences were obtained. Following the injection of 6-10 ml of diluted contrast media (Gd-DTPA 1:250), T1-weighted images were obtained in the same positions as conventional MR images. Paired conventional MR imaging and MR arthrography of each ankle ligament were rated on a five-point scale, and to reflect inter-group differences a Wilcoxon singed-rank test was used to compare the different measurements (p<0.05). In two ankles, MR images of the ligaments were correlated with ankle dissection. Anterior and posterior talofibular ligaments were more clearly revealed by MR arthrography than by conventional MR imaging, while calcaneofibular ligaments showed no difference between these two modalities. With regard to deltoid ligaments, visualization of the anterior and posterior tibiotalar ligament was much improved when contrast material was used to outline the ligament's articular aspect. Visualization of the posterior inferior tibiofibular ligament and inferior transverse ligament were also improved when the use of contrast material provided delineation of the articular side of the ligaments and separated them from adjacent bone. In addition, MR arthography was very useful for indentification of the posterior intermalleolar ligament, though its use did not enhance visualization of the calcaneofibular, tibiocalcaneal, spring or tibiospring ligaments. MR arthrography accurately revealed the anatomic details of ankle ligaments, and may therefore be more useful than conventional Mr imaging for evaluation of these structures
The striated MR nephrogram, not a reflection of pathology
Energy Technology Data Exchange (ETDEWEB)
Trout, Andrew T.; Care, Marguerite M.; Towbin, Alexander J. [Cincinnati Children' s Hospital Medical Center, Department of Radiology - MLC 5031, Cincinnati, OH (United States); Zhang, Bin [Cincinnati Children' s Hospital Medical Center, Division of Biostatistics and Epidemiology, Cincinnati, OH (United States)
2015-10-15
We have intermittently observed low signal striations in the kidneys on delayed post-contrast MR exams of the spine. While we suspected these striations were due to concentrated gadolinium, the clinical importance of this finding was uncertain. To describe the striated MR nephrogram (low signal striations in the kidney) and assess its clinical relevance. Retrospective review of delayed post-contrast MRIs of the spine (mean: 45 min after contrast administration). The presence of the striated MR nephrogram was correlated with imaging parameters (field strength, time since contrast), and findings (gadolinium in the bladder, inferior vena cava and aorta diameters) and with clinical factors (history of renal disease, laboratory values). Seven hundred seventy-three exams performed on 229 patients, 8.3 ± 5.3 years of age, were reviewed. The striated MR nephrogram was observed in 102/773 examinations (13.2%) and was present on at least one study in 54/229 patients (23.6%). The presence of striations was associated with the specific magnet on which the exam was performed (P < 0.01) but not with magnet field strength. Serum creatinine was minimally lower in patients with striations (0.43 ± 0.12 vs. 0.49 ± 0.18 mg/dL, P = 0.002), but no other clinical or historical data, including time from contrast administration (P = 0.54), fluid status (P = 0.17) and clinical history of renal disease (P = 0.14), were predictive of the presence of striations. The striated MR nephrogram was observed in 13% of delayed post-contrast MR exams of the spine. Precipitating factors are unclear, but the striated nephrogram does not appear to be a marker of clinically apparent renal dysfunction. (orig.)
Do carotid MR surface coils affect PET quantification in PET/MR imaging?
International Nuclear Information System (INIS)
Willemink, Martin J; Eldib, Mootaz; Leiner, Tim; Fayad, Zahi A; Mani, Venkatesh
2015-01-01
To evaluate the effect of surface coils for carotid MR imaging on PET quantification in a clinical simultaneous whole-body PET/MR scanner. A cylindrical phantom was filled with a homogeneous 2L water-FDG mixture at a starting dose of 301.2MBq. Clinical PET/MR and PET/CT systems were used to acquire PET-data without a coil (reference standard) and with two carotid MRI coils (Siemens Special Purpose 8-Channel and Machnet 4-Channel Phased Array). PET-signal attenuation was evaluated with Osirix using 51 (PET/MR) and 37 (PET/CT) circular ROIs. Mean and maximum standardized uptake values (SUVs) were quantified for each ROI. Furthermore, SUVs of PET/MR and PET/CT were compared. For validation, a patient was scanned with an injected dose of 407.7MBq on both a PET/CT and a PET/MR system without a coil and with both coils. PET/MR underestimations were -2.2% (Siemens) and -7.8% (Machnet) for SUVmean, and -1.2% (Siemens) and -3.3% (Machnet) for SUVmax, respectively. For PET/CT, underestimations were -1.3% (Siemens) and -1.4% (Machnet) for SUVmean and -0.5% (both Siemens and Machnet) for SUVmax, respectively using no coil data as reference. Except for PET/CT SUVmax values all differences were significant. SUVs differed significantly between PET/MR and PET/CT with SUVmean values of 0.51-0.55 for PET/MR and 0.68-0.69 for PET/CT, respectively. The patient examination showed that median SUVmean values measured in the carotid arteries decreased from 0.97 without a coil to 0.96 (Siemens) and 0.88 (Machnet). Carotid surface coils do affect attenuation correction in both PET/MR and PET/CT imaging. Furthermore, SUVs differed significantly between PET/MR and PET/CT.
International Nuclear Information System (INIS)
Huang, Chuan; Petibon, Yoann; Ouyang, Jinsong; El Fakhri, Georges; Reese, Timothy G.; Ahlman, Mark A.; Bluemke, David A.
2015-01-01
Purpose: Degradation of image quality caused by cardiac and respiratory motions hampers the diagnostic quality of cardiac PET. It has been shown that improved diagnostic accuracy of myocardial defect can be achieved by tagged MR (tMR) based PET motion correction using simultaneous PET-MR. However, one major hurdle for the adoption of tMR-based PET motion correction in the PET-MR routine is the long acquisition time needed for the collection of fully sampled tMR data. In this work, the authors propose an accelerated tMR acquisition strategy using parallel imaging and/or compressed sensing and assess the impact on the tMR-based motion corrected PET using phantom and patient data. Methods: Fully sampled tMR data were acquired simultaneously with PET list-mode data on two simultaneous PET-MR scanners for a cardiac phantom and a patient. Parallel imaging and compressed sensing were retrospectively performed by GRAPPA and kt-FOCUSS algorithms with various acceleration factors. Motion fields were estimated using nonrigid B-spline image registration from both the accelerated and fully sampled tMR images. The motion fields were incorporated into a motion corrected ordered subset expectation maximization reconstruction algorithm with motion-dependent attenuation correction. Results: Although tMR acceleration introduced image artifacts into the tMR images for both phantom and patient data, motion corrected PET images yielded similar image quality as those obtained using the fully sampled tMR images for low to moderate acceleration factors (<4). Quantitative analysis of myocardial defect contrast over ten independent noise realizations showed similar results. It was further observed that although the image quality of the motion corrected PET images deteriorates for high acceleration factors, the images were still superior to the images reconstructed without motion correction. Conclusions: Accelerated tMR images obtained with more than 4 times acceleration can still provide
Energy Technology Data Exchange (ETDEWEB)
Huang, Chuan, E-mail: chuan.huang@stonybrookmedicine.edu [Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Department of Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115 (United States); Departments of Radiology, Psychiatry, Stony Brook Medicine, Stony Brook, New York 11794 (United States); Petibon, Yoann [Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Department of Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Ouyang, Jinsong; El Fakhri, Georges [Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Department of Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115 (United States); Reese, Timothy G. [Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115 and Martinos Center for Biomedical Imaging, Charlestown, Massachusetts 02129 (United States); Ahlman, Mark A.; Bluemke, David A. [Radiology and Imaging Sciences, National Institutes of Health Clinical Center, Bethesda, Maryland 20892 (United States)
2015-02-15
Purpose: Degradation of image quality caused by cardiac and respiratory motions hampers the diagnostic quality of cardiac PET. It has been shown that improved diagnostic accuracy of myocardial defect can be achieved by tagged MR (tMR) based PET motion correction using simultaneous PET-MR. However, one major hurdle for the adoption of tMR-based PET motion correction in the PET-MR routine is the long acquisition time needed for the collection of fully sampled tMR data. In this work, the authors propose an accelerated tMR acquisition strategy using parallel imaging and/or compressed sensing and assess the impact on the tMR-based motion corrected PET using phantom and patient data. Methods: Fully sampled tMR data were acquired simultaneously with PET list-mode data on two simultaneous PET-MR scanners for a cardiac phantom and a patient. Parallel imaging and compressed sensing were retrospectively performed by GRAPPA and kt-FOCUSS algorithms with various acceleration factors. Motion fields were estimated using nonrigid B-spline image registration from both the accelerated and fully sampled tMR images. The motion fields were incorporated into a motion corrected ordered subset expectation maximization reconstruction algorithm with motion-dependent attenuation correction. Results: Although tMR acceleration introduced image artifacts into the tMR images for both phantom and patient data, motion corrected PET images yielded similar image quality as those obtained using the fully sampled tMR images for low to moderate acceleration factors (<4). Quantitative analysis of myocardial defect contrast over ten independent noise realizations showed similar results. It was further observed that although the image quality of the motion corrected PET images deteriorates for high acceleration factors, the images were still superior to the images reconstructed without motion correction. Conclusions: Accelerated tMR images obtained with more than 4 times acceleration can still provide
PDZ Protein Regulation of G Protein-Coupled Receptor Trafficking and Signaling Pathways.
Dunn, Henry A; Ferguson, Stephen S G
2015-10-01
G protein-coupled receptors (GPCRs) contribute to the regulation of every aspect of human physiology and are therapeutic targets for the treatment of numerous diseases. As a consequence, understanding the myriad of mechanisms controlling GPCR signaling and trafficking is essential for the development of new pharmacological strategies for the treatment of human pathologies. Of the many GPCR-interacting proteins, postsynaptic density protein of 95 kilodaltons, disc large, zona occludens-1 (PDZ) domain-containing proteins appear most abundant and have similarly been implicated in disease mechanisms. PDZ proteins play an important role in regulating receptor and channel protein localization within synapses and tight junctions and function to scaffold intracellular signaling protein complexes. In the current study, we review the known functional interactions between PDZ domain-containing proteins and GPCRs and provide insight into the potential mechanisms of action. These PDZ domain-containing proteins include the membrane-associated guanylate-like kinases [postsynaptic density protein of 95 kilodaltons; synapse-associated protein of 97 kilodaltons; postsynaptic density protein of 93 kilodaltons; synapse-associated protein of 102 kilodaltons; discs, large homolog 5; caspase activation and recruitment domain and membrane-associated guanylate-like kinase domain-containing protein 3; membrane protein, palmitoylated 3; calcium/calmodulin-dependent serine protein kinase; membrane-associated guanylate kinase protein (MAGI)-1, MAGI-2, and MAGI-3], Na(+)/H(+) exchanger regulatory factor proteins (NHERFs) (NHERF1, NHERF2, PDZ domain-containing kidney protein 1, and PDZ domain-containing kidney protein 2), Golgi-associated PDZ proteins (Gα-binding protein interacting protein, C-terminus and CFTR-associated ligand), PDZ domain-containing guanine nucleotide exchange factors (GEFs) 1 and 2, regulator of G protein signaling (RGS)-homology-RhoGEFs (PDZ domain-containing RhoGEF and
Mr imaging and mr spectroscopy of brain metastases by mr perfusion
International Nuclear Information System (INIS)
Weber, Marc-Andre; Lichy, M.P.; Thilmann, C.; Guenther, M.; Bachert, P.; Delorme, S.; Schad, L.R.; Debus, J.; Schlemmer, H.P.; Maudsley, A.A.
2003-01-01
In follow-up examinations of irradiated brain metastases conventional contrast-enhanced morphological MR imaging is often unable to distinguish between transient radiation effects, radionecrosis, and tumor recurrence. To evaluate changes of relative cerebral blood flow (rCBF) in irradiated brain metastases arterial spin-labeling techniques (ASL) were applied and compared to the outcome of 1 H MR spectroscopy and spectroscopic imaging ( 1 H MRS, SI). Patients and methods In 2 patients follow-up examinations of irradiated brain metastases were performed on a 1.5-T tomograph (average single dose: 20 Gy/80% isodose). Relative CBF values of gray matter (GM), white matter (WM), and metastases (Met) were measured by means of the ASL techniques ITS-FAIR and Q2TIPS. 1 H MRS was performed with PRESS 1500/135. In both patients with initially hyperperfused metastases (Met/GM >1) the reduction of rCBF after stereotactic radiosurgery indicated response to treatment - even if the contrast-enhancing region increased - while increasing rCBF values indicated tumor progression. The findings were confirmed by 1 H MRS, SI and subsequent follow-up. The ASL techniques ITS-FAIR and Q2TIPS are able to monitor changes of rCBF in irradiated brain metastases. The two cases imply a possible role for ASL-MR perfusion imaging and 1 H MR spectroscopy in differentiating radiation effects from tumor progression. (orig.) [de
Deep Learning MR Imaging-based Attenuation Correction for PET/MR Imaging.
Liu, Fang; Jang, Hyungseok; Kijowski, Richard; Bradshaw, Tyler; McMillan, Alan B
2018-02-01
Purpose To develop and evaluate the feasibility of deep learning approaches for magnetic resonance (MR) imaging-based attenuation correction (AC) (termed deep MRAC) in brain positron emission tomography (PET)/MR imaging. Materials and Methods A PET/MR imaging AC pipeline was built by using a deep learning approach to generate pseudo computed tomographic (CT) scans from MR images. A deep convolutional auto-encoder network was trained to identify air, bone, and soft tissue in volumetric head MR images coregistered to CT data for training. A set of 30 retrospective three-dimensional T1-weighted head images was used to train the model, which was then evaluated in 10 patients by comparing the generated pseudo CT scan to an acquired CT scan. A prospective study was carried out for utilizing simultaneous PET/MR imaging for five subjects by using the proposed approach. Analysis of covariance and paired-sample t tests were used for statistical analysis to compare PET reconstruction error with deep MRAC and two existing MR imaging-based AC approaches with CT-based AC. Results Deep MRAC provides an accurate pseudo CT scan with a mean Dice coefficient of 0.971 ± 0.005 for air, 0.936 ± 0.011 for soft tissue, and 0.803 ± 0.021 for bone. Furthermore, deep MRAC provides good PET results, with average errors of less than 1% in most brain regions. Significantly lower PET reconstruction errors were realized with deep MRAC (-0.7% ± 1.1) compared with Dixon-based soft-tissue and air segmentation (-5.8% ± 3.1) and anatomic CT-based template registration (-4.8% ± 2.2). Conclusion The authors developed an automated approach that allows generation of discrete-valued pseudo CT scans (soft tissue, bone, and air) from a single high-spatial-resolution diagnostic-quality three-dimensional MR image and evaluated it in brain PET/MR imaging. This deep learning approach for MR imaging-based AC provided reduced PET reconstruction error relative to a CT-based standard within the brain compared
Factors Influencing Electronic Clinical Information Exchange in Small Medical Group Practices
Kralewski, John E.; Zink, Therese; Boyle, Raymond
2012-01-01
Purpose: The purpose of this study was to identify the organizational factors that influence electronic health information exchange (HIE) by medical group practices in rural areas. Methods: A purposive sample of 8 small medical group practices in 3 experimental HIE regions were interviewed to determine the extent of clinical information exchange…
MR imaging of prostate cancer; MR-Tomographie des Prostatakarzinoms
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Heuck, A.; Scheidler, J.; Sommer, B.; Graser, A. [Radiologisches Zentrum Muenchen-Pasing (Germany); Mueller-Lisse, U.G. [Institut fuer Klinische Radiologie, Universitaet Muenchen (Germany); Massmann, J. [Gemeinschaftspraxis Pathologie, Muenchen (Germany)
2003-06-01
Accurate diagnosis and staging of prostate cancer (PC) is developing into an important health care issue in light of the high incidence of PC and the improvements in stage-adapted therapy. The purpose of this paper is to provide an overview on the current role of MR imaging and MR spectroscopy in the diagnosis and staging of PC.Material and methods Pertinent literature was searched and evaluated to collect information on current clinical indications, study techniques, diagnostic value, and limitations of magnetic resonance imaging and spectroscopy. Major indications for MR imaging of patients with supected PC are to define tumor location before biopsy when clinical or TRUS findings are inconclusive, and to provide accurate staging of histologically proven PC to ascertain effective therapy. Current MR imaging techniques for the evaluation of PC include multiplanar high-resolution T2-weighted FSE and T1-weighted SE sequences using combined endorectal and phased-array coils. Using these techniques, the reported accuracy of MR imaging for the diagnosis of extracapsular tumor extension ranges between 82 and 88% with sensitivities between 80 and 95%, and specificities between 82 and 93%. Typical MR findings of PC in different stages of disease, as well as diagnostic problems, such as chronic prostatitis, biopsy-related hemorrhage and therapy-related changes of prostatic tissue are discussed. In addition, the current perspectives and limitations of MR spectroscopy in PC are summarized. Current MR imaging techniques provide important diagnostic information in the pretherapeutic workup of PC including a high staging accuracy, and is superior to TRUS. (orig.) [German] Der Diagnostik des Prostatakarzinoms kommt wegen seiner hohen Inzidenz und den verbesserten stadienadaptierten Therapiemoeglichkeiten eine grosse Bedeutung zu. Dabei spielen bildgebende Verfahren bei den klinisch oft unzureichend diagnostizierbaren Faellen eine wesentliche Rolle fuer die praetherapeutische
Factors affecting the determination of the isotopically exchangeable phosphorus in soils
International Nuclear Information System (INIS)
Morales, L.E.M.
1981-06-01
In order to evaluate the factors that affect the determination of the isotopically exchangeable phosphorus in soils (L value), various greenhouse experiments were carried out. The following factors were considered: carrier level; plant species; harvest time; nitrogen doses; nitrogen sources; culture conditions and soil type. A radioactive solution with an activity level of approximately 10 μCi 32 p/3 kg soil with different carrier levels was located in layers or mixed completely with the soil depending upon the experiment. (author)
Interventional MR: vascular applications.
Smits, H F; Bos, C; van der Weide, R; Bakker, C J
1999-01-01
Three strategies for visualisation of MR-dedicated guidewires and catheters have been proposed, namely active tracking, the technique of locally induced field inhomogeneity and passive susceptibility-based tracking. In this article the pros and cons of these techniques are discussed, including the development of MR-dedicated guidewires and catheters, scan techniques, post-processing tools, and display facilities for MR tracking. Finally, some of the results obtained with MR tracking are discussed.
Curran, Janet A; Murphy, Andrea L; Sinclair, Douglas; McGrath, Patrick
2013-01-01
Rural emergency departments (EDs) generally have limited access to continuing education and are typically staffed by clinicians without pediatric emergency specialty training. Emergency care of children is complex and the majority of children receive emergency care in non-pediatric tertiary care centers. In recent decades, there has been a call to action to improve quality and safety in the emergency care of children. Of the one million ED visits by children in Ontario in 2005-2006, one in three visited more than once in a year and one in 15 returned to the ED within 72 hours of the index visit. This study explored factors influencing rural and urban ED clinicians' participation in a Web-based knowledge exchange intervention that focused on best practice knowledge about pediatric emergency care. The following questions guided the study: (i) What are the individual, context of practice or knowledge factors which impact a clinician's decision to participate in a Web-based knowledge exchange intervention?; (ii) What are clinicians' perceptions of organizational expectations regarding knowledge and information sources to be used in practice?; and (iii) What are the preferred knowledge sources of rural and urban emergency clinicians? A Web-based knowledge exchange intervention, the Pediatric Emergency Care Web Based Knowledge Exchange Project, for rural and urban ED clinicians was developed. The website contained 12 pediatric emergency practice learning modules with linked asynchronous discussion forums. The topics for the modules were determined through a needs assessment and the module content was developed by known experts in the field. A follow-up survey was sent to a convenience sample of 187 clinicians from nine rural and two urban Canadian EDs participating in the pediatric emergency Web-based knowledge exchange intervention study. The survey response rate was 56% (105/187). Participation in the knowledge exchange intervention was related to individual
International Nuclear Information System (INIS)
Catalano, C.; Pavone, P.; Laghi, A.; Panebianco, V.; Scipioni, A.; Fanelli, F.; Brillo, R.; Passariello, R.
1998-01-01
The purpose of this study was to determine the possibility of integrating MR cholangiopancreatography (MRCP) and MR angiography (MRA) to conventional MR images in the diagnosis and assessment of resectability of pancreatic adenocarcinoma. Twenty-three patients with pancreatic adenocarcinoma were prospectively examined with MR. Conventional MR images were acquired in all patients. Three-dimensional MRCP and MRA images were acquired in all patients with suspected biliary and vascular involvement. Acquisition time was less than 45 min in all cases. Images were independently evaluated by two radiologists, with final reading decided by consensus among readers. Diagnosis was confirmed with surgery in 16 patients and with percutaneous biopsy in 7. Concordance among readers was high with a kappa value of 0.83. Pancreatic adenocarcinoma was observed in all patients. Correct assessment of unresectability due to vascular involvement was found in 22 of 23 patients. Biliary obstruction was evident in 13 patients, involving the biliary and pancreatic ducts in 9 and the biliary ducts only in 4. Technical advances permit extensive use of MRI in the evaluation of abdominal pathologies. The combination of MR imaging, MRCP, and MRA can provide sufficient information for the diagnosis and assessment of resectability of pancreatic adenocarcinoma, which otherwise would require three different exams. (orig.)
MR anatomy of the joints: an MR-cadaveric correlative study: part I. wrist
Energy Technology Data Exchange (ETDEWEB)
Kang, Heung Sik [Seoul National University College of Medicine, Seoul (Korea, Republic of); Donald Resnick [University of California, San Diego (United States)
1991-07-15
To acquire the anatomic information necessary for correct interpretation of MR images of the wrist, transverse, coronal, and sagittal MR images of 3 fresh cadaveric wrists were obtained and, subsequently, sectioned along the MR imaging planes. For the precise correlation of anatomic features depicted with MR and with specimen section, cadaveric wrists were fixed in a rectangular cardboard box using paraffin and frozen after MR imaging. High contrast and spatial resolution enabled delineation of small structures including tendons, nerves, vessels, and ligaments, as well as osseous structures. Transverse images provided the best delineation of the carpal tunnel, tendons, nerves, and vessels. Coronal images permitted optimal visualization of triangular fibrocartilage and lunotriquetral and scapholunate ligaments. We conclude that MR imaging accurately and reliably displays the anatomy of the wrist.
PET/MR in oncology: an introduction with focus on MR and future perspectives for hybrid imaging
Balyasnikova, Svetlana; Löfgren, Johan; de Nijs, Robin; Zamogilnaya, Yanna; Højgaard, Liselotte; Fischer, Barbara M
2012-01-01
After more than 20 years of research, a fully integrated PET/MR scanner was launched in 2010 enabling simultaneous acquisition of PET and MR imaging. Currently, no clinical indication for combined PET/MR has been established, however the expectations are high. In this paper we will discuss some of the challenges inherent in this new technology, but focus on potential applications for simultaneous PET/MR in the field of oncology. Methods and tracers for use with the PET technology will be familiar to most readers of this journal; thus this paper aims to provide a short and basic introduction to a number of different MRI techniques, such as DWI-MR (diffusion weighted imaging MR), DCE-MR (dynamic contrast enhanced MR), MRS (MR spectroscopy) and MR for attenuation correction of PET. All MR techniques presented in this paper have shown promising results in the treatment of patients with solid tumors and could be applied together with PET increasing the amount of information about the tissues of interest. The potential clinical benefit of applying PET/MR in staging, radiotherapy planning and treatment evaluation in oncology, as well as the research perspectives for the use of PET/MR in the development of new tracers and drugs will be discussed. PMID:23145362
Radiochemical analysis of the body of the late Mr. Kuboyama
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Kimura, K; Ikedo, N; Kimura, K; Kawanishi, H; Kimura, M
1956-01-01
Analyses were carried out of various organs of Mr. Kuboyama 200 days after he had exposed himself to radiation of the atomic bomb explosion on Bikini Atoll, March, 1954. By ion-exchange chromatography, the presence of the following nuclides was indicated: /sup 144/Ce, and /sup 144/Pr in the bone (I) (20 x 10/sup -12/ counts/g. fresh wt.). Liver (II), and Kidneys (III); /sup 95/Zr and /sup 95/Nb in II and III; /sup 106/Rh, /sup 129m/Te, and /sup 129/Te in I, III, and muscles; and /sup 89/Sr, /sup 90/Sr, and /sup 90/Y in I, II, and III. Activities found in these organs were decidedly higher than those found in the control samples obtained from individuals who died of other than the so-called radiation sickness. Radiation dose received by the bones of Mr. Kuboyama was calculated to be approximately 8 r.e.p.
Effects of core polarization and meson exchange currents on electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Arima, Akito [Tokyo Univ. (Japan). Dept. of Physics; Ikegami, Hidetsugu; Muraoka, Mitsuo [eds.; Osaka Univ., Suita (Japan). Research Center for Nuclear Physics
1980-01-01
Magnetic form factors observed by electron scattering provide good evidence for core polarization and meson exchange currents. Their effects are discussed by taking /sup 17/O, /sup 51/V, /sup 207/Pb /sup 208/Pb, /sup 209/Bi and /sup 12/C.
Fujiwara, Sachiko; Ohashi, Kazumasa; Mashiko, Toshiya; Kondo, Hiroshi; Mizuno, Kensaku
2016-01-01
Mechanical force–induced cytoskeletal reorganization is essential for cell and tissue remodeling and homeostasis; however, the underlying cellular mechanisms remain elusive. Solo (ARHGEF40) is a RhoA-targeting guanine nucleotide exchange factor (GEF) involved in cyclical stretch–induced human endothelial cell reorientation and convergent extension cell movement in zebrafish gastrula. In this study, we show that Solo binds to keratin-8/keratin-18 (K8/K18) intermediate filaments through multiple sites. Solo overexpression promotes the formation of thick actin stress fibers and keratin bundles, whereas knockdown of Solo, expression of a GEF-inactive mutant of Solo, or inhibition of ROCK suppresses stress fiber formation and leads to disorganized keratin networks, indicating that the Solo-RhoA-ROCK pathway serves to precisely organize keratin networks, as well as to promote stress fibers. Of importance, knockdown of Solo or K18 or overexpression of GEF-inactive or deletion mutants of Solo suppresses tensile force–induced stress fiber reinforcement. Furthermore, knockdown of Solo or K18 suppresses tensile force-induced RhoA activation. These results strongly suggest that the interplay between Solo and K8/K18 filaments plays a crucial role in tensile force–induced RhoA activation and consequent actin cytoskeletal reinforcement. PMID:26823019
Directory of Open Access Journals (Sweden)
Stefano Delli Pizzi
Full Text Available To prospectively evaluate the feasibility of using magnetic resonance (MR techniques for in-vivo assessing a rat diabetic model of limb ischemia. Unilateral hind limb ischemia was induced by ligation of the iliac-femoral artery in male streptozotocin-treated and non-diabetic control rats. Four weeks after ligation, rats underwent MR Angiography (MRA, T(1-weighted and Short Time Inversion Recovery (STIR sequences and muscle Proton MR Spectroscopy ((1H-MRS on both hind limbs. After MR examinations, immunoblotting and immunofluorescence analysis were performed. MRA showed a signal void due to flow discontinuation distal to the artery ligation. T(1-weighted and STIR images showed, respectively, the presence of tissue swelling (p = 0.018 for non-diabetic; p = 0.027 for diabetic rats and signal hyperintensity in tissue affected by occlusion. Mean total creatine/water for the occluded limb was significantly lower than for the non-occluded limbs in both non-diabetic (5.46×10(-4 vs 1.14×10(-3, p = 0.028 and diabetic rats (1.37×10(-4 vs 1.10×10(-3; p = 0.018. MR Imaging and (1H-MRS changes were more pronounced in diabetic than in non-diabetic occluded limbs (p = 0.032. MR findings were confirmed by using histological findings. Combined MR techniques can be used to demonstrate the presence of structural and metabolic changes produced by iliac-femoral artery occlusion in rat diabetic model of limb ischemia.
MR and MR arthrography to identify degenerative and posttraumatic diseases in the shoulder joint
International Nuclear Information System (INIS)
Lee, Shi-Uk; Lang, Philipp
2000-01-01
MR imaging provides a comprehensive evaluation of a wide spectrum of both intraarticular and extraarticular pathology of the shoulder. MR imaging enables the detection or exclusion of degenerative and posttraumatic diseases of the shoulder with a reasonable accuracy. MR arthrography is useful in the visualization of subtle anatomic details and further improves the differentiation. In this article, findings of MR imaging and MR arthrography of degenerative and posttraumatic shoulder diseases (impingement syndrome, rotator cuff tears, and glenohumeral instability) has been reviewed
International Nuclear Information System (INIS)
Gupta, V.; Goyal, M.; Mishra, N.; Gaikwad, S.; Sharma, A.
1997-01-01
Purpose: To evaluate the role of MR imaging in the localisation of cerebrospinal fluid (CSF) fistulae. Material and Methods: A total of 36 consecutive unselected patients with either clincally proven CSF leakage (n=26) or suspected CSF fistula (n=10) were prospectively evaluated by MR. All MR examinations included fast spin-echo T2-weighted images in the 3 orthogonal planes. Thin-section CT was performed following equivocal or negative MR examination. MR and CT findings were correlated with surgical results in 33 patients. Results: CSF fistula was visualised as a dural-bone defect with hyperintense fluid signal continuous with that in the basal cisterns on T2-weighted images. MR was positive in 26 cases, in 24 of which the fistula was confirmed surgically. In 2 patients the CSF leakage was directly demonstrated on MR. MR sensitivity of 80% compared favourably with the reported 46-81% of CT cisternography (CTC). No significant difference in MR sensitivity in detecting CSF fistula was found between active and inactive leaks. (orig.)
Lee, Jong-Yeon; Park, Sanghoon
2017-01-01
This study identifies the factors influencing the success of online international learning exchange (ILE) among Korean school pupils who partnered with American and Australian pupils. In particular, it examined the effects of self-efficacy (SE), exchange infrastructure (EI) and quality of exchange activities (QEA) on the students' learning…
MR elastography: high rate of technical success in pediatric and young adult patients
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Joshi, Madalsa [British Columbia Children' s Hospital, Department of Radiology, Vancouver, BC (Canada); Dillman, Jonathan R.; Towbin, Alexander J.; Serai, Suraj D.; Trout, Andrew T. [Cincinnati Children' s Hospital Medical Center, Department of Radiology, MLC 5031, Cincinnati, OH (United States)
2017-06-15
Magnetic resonance (MR) elastography allows the noninvasive assessment of liver stiffness, which is a surrogate for fibrosis. The purpose of this study was to describe our experience using liver MR elastography in a large pediatric population with attention to the frequency and causes of exam failure. Imaging records were searched for patients ≤18 years of age who underwent 2-D gradient recalled echo (GRE) MR elastography of the liver between September 2011 and August 2015 on one of two 1.5-T MRI platforms. Imaging reports and clinical records were reviewed for failed MR elastography acquisitions, factor(s) resulting in failure and whether a subsequent successful examination had been performed. Four hundred sixty-eight MR elastography examinations were performed in 372 patients between 1.5 months and 18 years of age during the study period. Ninety-six percent (450/468) of the examinations were successful. There was no significant difference in mean age (12.6±3.6 vs. 11.2±4.1 years, P=0.12) or body mass index (BMI) (28.2±12.4 vs. 29.5±10 kg/m{sup 2}, P=0.6) between patients with and without successful examinations. MR elastography failures were due to poor paddle positioning resulting in inadequate generation of hepatic shear waves (n=5), iron overload (n=4), patient inability to tolerate MRI (n=3), patient breathing/motion (n=3), artifact from implanted hardware (n=1) and technical malfunction (n=2). Seven of nine (78%) repeat examinations were successful (78%). Hepatic 2-D GRE MR elastography at 1.5 T is technically robust in children. Exam failure is infrequent and largely reflects patient specific factors, some of which can be mitigated with careful technique. (orig.)
International Nuclear Information System (INIS)
Amouroux, Charlotte
2014-01-01
The study of fission yields has a major impact on the characterization and understanding of the fission process and is mandatory for reactor applications. While the yields are known for the major actinides (U-235, Pu-239) in the thermal neutron-induced fission, only few measurements were performed on Am-242. Moreover, the two main data libraries do not agree among each other on the light peak. Am-241 and Am-242 are nuclei of interest for the MOX-fuel reactors and for the reduction of nuclear waste radiotoxicity using transmutation reactions. Thus, a campaign of precise measurement of the fission mass yields from the reaction Am-241(2n,f) was performed at the Lohengrin mass spectrometer (ILL, France) for both the light and the heavy peak. Forty-one masses were measured. Moreover, the measurement of the isotopic fission yields on the heavy peak by gamma-ray spectrometry led to the extraction of 20 independent isotopic yields. Our measurement was also meant to determine whether there is a difference in fission yields between the Am-242 isomeric state and its ground state as it exists in fission cross sections. The experimental method used to answer this question is based on the measurement a set of fission mass yields as a function of the ratio of Am-242gs to Am-242m fission rate. Results show that the mass yields are independent of the fission rate ratio. A future experimental campaign is proposed to observe a possible influence on the isomeric yields. The theoretical models are nowadays unable to predict the fission yields with enough accuracy and therefore we have to rely on experimental data and phenomenological models. The accuracy of the predictions of the semi empirical GEF fission model predictions makes it a useful tool for evaluation. This thesis also presents the physical content and part of the development of this model. Validation of the kinetic energy distributions, isomeric yields and fission yields predictions was performed. The extension of the GEF
Normal anatomy and MR findings of fetal main organs at MR imaging
International Nuclear Information System (INIS)
Xia Liming; Zou Mingli; Feng Dingyi; Hu Junwu; Qi Jianpin; Wang Chengyuan
2005-01-01
Objective: To investigate normal anatomy and MR findings of fetal main organs. Methods: Forty-seven fetus underwented fast MR imaging, SSFSE sequence was used, the normal anatomy and MR findings of fetal main organs was observed in different gestational age. The organs included: brain, lungs, heart, liver, spleen, gastrointestinal tract, urinary collecting systems, bladder, bones, spine, and subcutaneous fat. Results: Results of MR in 47 fetus showed that the main organs had developed by 20-week-old fetus, about 20 weeks gestation, cerebral cortical surface was smooth, no cortical gyri and sulci, then cortical gyri and sulci developed slowly. The lungs, trachea, bronchus, gastrointestinal tract, renal collecting system and bladder showed high signal intensity; the heart, great vessels, liver, spleen, bones and muscles appeared hypointense; the kidneys appeared isointense, the spine had developed and subcutaneous fat was seen in 20-week-old fetus, the subcutaneous fat increased with fetus maturating. Conclusion: Normal anatomy and MR findings of fetal main organs were clearly showed by fast MR imaging, and they are different from the newborns. (authors)
International Nuclear Information System (INIS)
Date, Shuji
1998-01-01
The main purpose of this study was to investigate pathohistological factors that affect the MR findings of intraductal spread (IDS) of breast cancer. The subjects of the present study were 42 breast cancer patients who were examined by MR imaging. Fat-suppressed high-resolution T1-weighted spin-echo images (350/13/1 (TR/TE/excitations), 16-cm FOV, 5-mm section thickness, and 512 x 256 matrix) were obtained one minute after the intravenous administration of Gd-DTPA. In this protocol, contrast determination time was 1 min 48 sec. Of the 42 cases, IDS was found to be located more than 1 cm from the primary focus in 22 cases (52%). Rates of sensitivity, specificity and accuracy of MR imaging for the detection of IDS were 82%, 80%, and 81%, respectively. The probable cause of misdiagnosis was parenchymal enhancement due to severe fibrocystic disease and normal menstrual cycle. In 21 of 42 cases, the MR findings were precisely correlated with the pathohistologic findings of almost the same cross-section. The MR findings of IDS varied greatly with observation of linear, band-like, branch-like, plate-like and minute ring enhancements. These findings closely reflected the size, aggregation pattern, and distribution of intraductal lesions. In particular, minute ring enhancement was only observed in 4 comedo-type lesions. This pattern of enhancement is considered to reflect elevated intraductal cellular density with necrosis in the central region. (author)
Energy Technology Data Exchange (ETDEWEB)
Date, Shuji [Hiroshima City Hospital (Japan)
1998-04-01
The main purpose of this study was to investigate pathohistological factors that affect the MR findings of intraductal spread (IDS) of breast cancer. The subjects of the present study were 42 breast cancer patients who were examined by MR imaging. Fat-suppressed high-resolution T1-weighted spin-echo images (350/13/1 (TR/TE/excitations), 16-cm FOV, 5-mm section thickness, and 512 x 256 matrix) were obtained one minute after the intravenous administration of Gd-DTPA. In this protocol, contrast determination time was 1 min 48 sec. Of the 42 cases, IDS was found to be located more than 1 cm from the primary focus in 22 cases (52%). Rates of sensitivity, specificity and accuracy of MR imaging for the detection of IDS were 82%, 80%, and 81%, respectively. The probable cause of misdiagnosis was parenchymal enhancement due to severe fibrocystic disease and normal menstrual cycle. In 21 of 42 cases, the MR findings were precisely correlated with the pathohistologic findings of almost the same cross-section. The MR findings of IDS varied greatly with observation of linear, band-like, branch-like, plate-like and minute ring enhancements. These findings closely reflected the size, aggregation pattern, and distribution of intraductal lesions. In particular, minute ring enhancement was only observed in 4 comedo-type lesions. This pattern of enhancement is considered to reflect elevated intraductal cellular density with necrosis in the central region. (author)
MR imaging of articular cartilage; Gelenkknorpel in der MR-Tomographie
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Schaefer, F.K.W.; Muhle, C.; Heller, M.; Brossmann, J. [Kiel Univ. (Germany). Klinik fuer Diagnostische Radiologie
2001-04-01
MR imaging has evolved to the best non-invasive method for the evaluation of articular cartilage. MR imaging helps to understand the structure and physiology of cartilage, and to diagnose cartilage lesions. Numerous studies have shown high accuracy and reliability concerning detection of cartilage lesions and early changes in both structure and biochemistry. High contrast-to-noise ratio and high spatial resolution are essential for analysis of articular cartilage. Fat-suppressed 3D-T{sub 1} weighted gradient echo and T{sub 2}-weighted fast spin echo sequences with or without fat suppression are recommended for clinical routine. In this article the anatomy and pathology of hyaline articular cartilage and the complex imaging characteristics of hyaline cartilage will be discussed. (orig.) [German] Die MR-Tomographie hat sich zur besten nichtinvasiven bildgebenden Methode fuer die Untersuchung von Gelenkknorpel entwickelt. Die MR-Tomographie liefert einen Beitrag zum Verstaendnis der Knorpelstruktur und der Physiologie sowie zur Diagnostik von Knorpelschaeden. Zahlreiche MR-Studien konnten eine hohe Genauigkeit und Zuverlaessigkeit bei der Detektion chondraler Laesionen sowie frueher Veraenderungen struktureller und biochemischer Natur zeigen. Neben einem hohen Kontrast/Rausch-Verhaeltnis ist fuer die Gelenkknorpelanalyse eine hohe raeumliche Aufloesung erforderlich. Im klinischen Routinebetrieb empfehlen sich fuer die Erkennung von Knorpellaesionen besonders fettunterdrueckte 3D-T{sub 1}-gewichtete Gradientenecho- und T{sub 2}-gewichtete Fastspinecho-Sequenzen mit oder ohne Fettunterdrueckung. Die vorliegende Arbeit geht auf die Anatomie und Pathologie des hyalinen Gelenkknorpels ein und diskutiert das komplexe MR-Signalverhalten. (orig.)
Blood flow measurement of transverse sinuses by using MR: a phantom study of its influence factors
International Nuclear Information System (INIS)
Gao Gejun; Feng Xiaoyuan; Li Yuan; Geng Daoying; Yao Zhengyu
2003-01-01
Objective: (1) To determine the relationship between the MR signal intensity and the actual flow velocity under steady flow condition. (2) to analyze the influence produced by the angle (θ) between the flow direction and the velocity-encoded gradient direction, and flip angle as well as section thickness on the velocity measurement under oblique flow condition. (3) to develop a suitable protocol for using this method to measure volumetric flow rate in the transverse sinus system. Methods: Flow phantom, which simulated blood-flow conditions in the transverse sinus system, consisted of a fluid-filled cylinder and a bent tube with a 3.4 mm internal diameter. A 1.5 T superconductive MR imager and VIGRE sequence were used for these studies. A suitable protocol was based on consideration of the effects of (1) the accuracy of velocity and transverse area measurement of flow, and (2) signal-to-noise ratio (SNR). Results: (1) Signal intensity (y) determined by MR and the actual flow velocity (x) showed straight-line correlation, y=68.914x + 357.206, R 2 =0.998. (2) As the angle (θ) increased, the transverse area of the signal determined by MR also increased, but the value of flow velocity decreased. (3) As the flip angle increased, the SNR varied from 5.7 to 11.2. The maximum SNR was obtained with 30 degree flip angle. (4) As the section thickness increased, the SNR and the transverse area of the signal determined by MR slightly increased. Conclusions: Phase-contrast MR imaging is a practical method for measuring volumetric flow rates. The angle (θ influenced the accuracy of flow velocity and the measurement of transverse area of flow whereas the flip angle and the section thickness substantially influenced the signal-to-noise ratio and the transverse area of flow
Energy Technology Data Exchange (ETDEWEB)
Bae, Won C.; Chang, Eric Y.; Chung, Christine B. [VA San Diego Healthcare System, Radiology Service, San Diego, CA (United States); University of California-San Diego, Department of Radiology, San Diego, CA (United States); Ruangchaijatuporn, Thumanoon [Mahidol University, Department of Diagnostic and Therapeutic Radiology, Faculty of Medicine Ramathibodi Hospital, Rachathewi, Bangkok (Thailand); Biswas, Reni; Du, Jiang; Statum, Sheronda [University of California-San Diego, Department of Radiology, San Diego, CA (United States)
2016-04-15
To evaluate pathology of the triangular fibrocartilage complex (TFCC) using high-resolution morphologic magnetic resonance (MR) imaging, and compare with quantitative MR and biomechanical properties. Five cadaveric wrists (22-70 years) were imaged at 3 T using morphologic (proton density weighted spin echo, PD FS, and 3D spoiled gradient echo, 3D SPGR) and quantitative MR sequences to determine T2 and T1rho properties. In eight geographic regions, morphology of TFC disc and laminae were evaluated for pathology and quantitative MR values. Samples were disarticulated and biomechanical indentation testing was performed on the distal surface of the TFC disc. On morphologic PD SE images, TFC disc pathology included degeneration and tears, while that of the laminae included degeneration, degeneration with superimposed tear, mucinous transformation, and globular calcification. Punctate calcifications were highly visible on 3D SPGR images and found only in pathologic regions. Disc pathology occurred more frequently in proximal regions of the disc than distal regions. Quantitative MR values were lowest in normal samples, and generally higher in pathologic regions. Biomechanical testing demonstrated an inverse relationship, with indentation modulus being high in normal regions with low MR values. The laminae studied were mostly pathologic, and additional normal samples are needed to discern quantitative changes. These results show technical feasibility of morphologic MR, quantitative MR, and biomechanical techniques to characterize pathology of the TFCC. Quantitative MRI may be a suitable surrogate marker of soft tissue mechanical properties, and a useful adjunct to conventional morphologic MR techniques. (orig.)
International Nuclear Information System (INIS)
Bae, Won C.; Chang, Eric Y.; Chung, Christine B.; Ruangchaijatuporn, Thumanoon; Biswas, Reni; Du, Jiang; Statum, Sheronda
2016-01-01
To evaluate pathology of the triangular fibrocartilage complex (TFCC) using high-resolution morphologic magnetic resonance (MR) imaging, and compare with quantitative MR and biomechanical properties. Five cadaveric wrists (22-70 years) were imaged at 3 T using morphologic (proton density weighted spin echo, PD FS, and 3D spoiled gradient echo, 3D SPGR) and quantitative MR sequences to determine T2 and T1rho properties. In eight geographic regions, morphology of TFC disc and laminae were evaluated for pathology and quantitative MR values. Samples were disarticulated and biomechanical indentation testing was performed on the distal surface of the TFC disc. On morphologic PD SE images, TFC disc pathology included degeneration and tears, while that of the laminae included degeneration, degeneration with superimposed tear, mucinous transformation, and globular calcification. Punctate calcifications were highly visible on 3D SPGR images and found only in pathologic regions. Disc pathology occurred more frequently in proximal regions of the disc than distal regions. Quantitative MR values were lowest in normal samples, and generally higher in pathologic regions. Biomechanical testing demonstrated an inverse relationship, with indentation modulus being high in normal regions with low MR values. The laminae studied were mostly pathologic, and additional normal samples are needed to discern quantitative changes. These results show technical feasibility of morphologic MR, quantitative MR, and biomechanical techniques to characterize pathology of the TFCC. Quantitative MRI may be a suitable surrogate marker of soft tissue mechanical properties, and a useful adjunct to conventional morphologic MR techniques. (orig.)
Bae, Won C; Ruangchaijatuporn, Thumanoon; Chang, Eric Y; Biswas, Reni; Du, Jiang; Statum, Sheronda; Chung, Christine B
2016-04-01
To evaluate pathology of the triangular fibrocartilage complex (TFCC) using high-resolution morphologic magnetic resonance (MR) imaging, and compare with quantitative MR and biomechanical properties. Five cadaveric wrists (22-70 years) were imaged at 3 T using morphologic (proton density weighted spin echo, PD FS, and 3D spoiled gradient echo, 3D SPGR) and quantitative MR sequences to determine T2 and T1rho properties. In eight geographic regions, morphology of TFC disc and laminae were evaluated for pathology and quantitative MR values. Samples were disarticulated and biomechanical indentation testing was performed on the distal surface of the TFC disc. On morphologic PD SE images, TFC disc pathology included degeneration and tears, while that of the laminae included degeneration, degeneration with superimposed tear, mucinous transformation, and globular calcification. Punctate calcifications were highly visible on 3D SPGR images and found only in pathologic regions. Disc pathology occurred more frequently in proximal regions of the disc than distal regions. Quantitative MR values were lowest in normal samples, and generally higher in pathologic regions. Biomechanical testing demonstrated an inverse relationship, with indentation modulus being high in normal regions with low MR values. The laminae studied were mostly pathologic, and additional normal samples are needed to discern quantitative changes. These results show technical feasibility of morphologic MR, quantitative MR, and biomechanical techniques to characterize pathology of the TFCC. Quantitative MRI may be a suitable surrogate marker of soft tissue mechanical properties, and a useful adjunct to conventional morphologic MR techniques.
Sogani, Julie; Morris, Elizabeth A; Kaplan, Jennifer B; D'Alessio, Donna; Goldman, Debra; Moskowitz, Chaya S; Jochelson, Maxine S
2017-01-01
Purpose To assess the extent of background parenchymal enhancement (BPE) at contrast material-enhanced (CE) spectral mammography and breast magnetic resonance (MR) imaging, to evaluate interreader agreement in BPE assessment, and to examine the relationships between clinical factors and BPE. Materials and Methods This was a retrospective, institutional review board-approved, HIPAA-compliant study. Two hundred seventy-eight women from 25 to 76 years of age with increased breast cancer risk who underwent CE spectral mammography and MR imaging for screening or staging from 2010 through 2014 were included. Three readers independently rated BPE on CE spectral mammographic and MR images with the ordinal scale: minimal, mild, moderate, or marked. To assess pairwise agreement between BPE levels on CE spectral mammographic and MR images and among readers, weighted κ coefficients with quadratic weights were calculated. For overall agreement, mean κ values and bootstrapped 95% confidence intervals were calculated. The univariate and multivariate associations between BPE and clinical factors were examined by using generalized estimating equations separately for CE spectral mammography and MR imaging. Results Most women had minimal or mild BPE at both CE spectral mammography (68%-76%) and MR imaging (69%-76%). Between CE spectral mammography and MR imaging, the intrareader agreement ranged from moderate to substantial (κ = 0.55-0.67). Overall agreement on BPE levels between CE spectral mammography and MR imaging and among readers was substantial (κ = 0.66; 95% confidence interval: 0.61, 0.70). With both modalities, BPE demonstrated significant association with menopausal status, prior breast radiation therapy, hormonal treatment, breast density on CE spectral mammographic images, and amount of fibroglandular tissue on MR images (P spectral mammographic and MR images. © RSNA, 2016.
Recent developments of MR imaging system and future trends
International Nuclear Information System (INIS)
Fujieda, Kunimi
1996-01-01
Because MR imaging technique has no limitation of slice direction, uses none of mechanically moving components and can employ electronic scanning method for data acquisition, the most advanced electronics and CPU techniques have been applied to develop MR imaging systems. Along with pursuance of better equipment performance as clinical diagnostic equipment, cost reduction, improvement of operability and safety, easy siting, comfortable examination and economical operation cost by remarkable reduction of running cost have become important factors in development of MR imaging system. From this viewpoint, MR imaging systems incorporating an open gantry with a relatively low field strength and of vertical field system have been developed recently and they are being accepted as clinically useful equipment. The vertical field, open gantry system has an optimum structure capable of performing interventional imaging, thus clinical application of the system have been actively attempted. Thanks to recent development of various MRI techniques, image quality quite acceptable for routine clinical diagnosis can now be obtained by using the systems with permanent magnet and resistive magnet. Thus, it is considered that evaluation of not only equipment performance but also the total performances of the MR imaging system as described above will become important. The MR imaging technique has a possibility to substitute itself for other conventional imaging modalities because the technique can visualize physiological and metabolic functions in addition to morphological imaging. It is expected that application of MR imaging modality will be further expanded by continuous investigation of applicable clinical fields and development of imaging technologies. (J.P.N.)
International Nuclear Information System (INIS)
Abdel-Ghany, Ahmed M.; Kozai, Toyoki
2006-01-01
General mathematical relations are presented for the specular exchange factors, F S , of diffuse radiation exchange between the inner surfaces of a rectangular enclosure. Three of these surfaces are specular reflectors, diffuse emitters and the fourth surface is a diffuse reflector, diffuse emitter. This enclosure can be used as a transplant production unit with artificial lighting for electric energy saving purposes. An image system and the crossed string method are used to derive these relations. The resulting expressions are conceptually simple and similar to the commonly known expressions of the exchange factors between diffuse surfaces, F. The accuracy of the presented F S relations was examined for different numbers of multiple reflections, N, on the specular surfaces and for different aspect ratios (ratio of the width, w to the height, h). The results proved that the relations are accurate and strongly satisfy the well-known relation of the radiation exchange between enclosure surfaces and satisfy the reciprocity relation. For any aspect ratio, considering N of 150 between highly reflective surfaces (ρ = 0.99) is sufficient to estimate the F S factors without any possible error. Using specular reflecting surfaces in such cases significantly reduces the electric energy consumption used for lighting
MR evaluation of postmenopausal ovarian size. Comparison with surgical specimen
International Nuclear Information System (INIS)
Joja, Ikuo; Ishida, Kana; Matsushita, Toshi; Mimura, Seiichi; Yamaguchi, Takuya; Akagi, Noriaki; Miyagi, Yasunari; Hara, Takeshi; Kanazawa, Susumu
2008-01-01
We investigated ovarian size after menopause using magnetic resonance (MR) imaging and gross specimens obtained from patients with uterine cancer after menopause in whom normal ovaries were confirmed at the time of surgery. The relationships between size of ovarian long axis and age, the number of years since menopause, and age at menopause were statistically evaluated for 130 ovaries observed in short-axis T 2 -weighted MR images of the uterine corpus and in 147 ovarian gross specimens. No significant relationships were found between size of ovarian long axis and these 3 factors. When the sizes of the ovaries in MR images were compared with those in gross specimens, the latter were larger, with a statistically significant difference. Similarly, when the sizes of the ovaries observed or not observed in MR images were compared in gross specimens, the former were larger, with a statistically significant difference. These results indicate that the size of the ovarian long axis observed in MR images does not accurately reflect the true size of the long axis, but ovarian size strongly affects visualization of the ovaries in MR images after menopause. In addition, these results indicate that there are no significant relationships between ovarian size after menopause and age, the number of years since menopause, or age at menopause. (author)
Gain-of-function SOS1 mutations cause a distinctive form of noonansyndrome
Energy Technology Data Exchange (ETDEWEB)
Tartaglia, Marco; Pennacchio, Len A.; Zhao, Chen; Yadav, KamleshK.; Fodale, Valentina; Sarkozy, Anna; Pandit, Bhaswati; Oishi, Kimihiko; Martinelli, Simone; Schackwitz, Wendy; Ustaszewska, Anna; Martin, Joes; Bristow, James; Carta, Claudio; Lepri, Francesca; Neri, Cinzia; Vasta,Isabella; Gibson, Kate; Curry, Cynthia J.; Lopez Siguero, Juan Pedro; Digilio, Maria Cristina; Zampino, Giuseppe; Dallapiccola, Bruno; Bar-Sagi, Dafna; Gelb, Brude D.
2006-09-01
Noonan syndrome (NS) is a developmental disordercharacterized by short stature, facial dysmorphia, congenital heartdefects and skeletal anomalies1. Increased RAS-mitogenactivated proteinkinase (MAPK) signaling due to PTPN11 and KRAS mutations cause 50 percentof NS2-6. Here, we report that 22 of 129 NS patients without PTPN11 orKRAS mutation (17 percent) have missense mutations in SOS1, which encodesa RAS-specific guanine nucleotide exchange factor (GEF). SOS1 mutationscluster at residues implicated in the maintenance of SOS1 in itsautoinhibited form and ectopic expression of two NS-associated mutantsinduced enhanced RAS activation. The phenotype associated with SOS1defects is distinctive, although within NS spectrum, with a highprevalence of ectodermal abnormalities but generally normal developmentand linear growth. Our findings implicate for the first timegain-of-function mutations in a RAS GEF in inherited disease and define anew mechanism by which upregulation of the RAS pathway can profoundlychange human development.
Lee, Young Kwang; Low-Nam, Shalini T; Chung, Jean K; Hansen, Scott D; Lam, Hiu Yue Monatrice; Alvarez, Steven; Groves, Jay T
2017-04-28
The guanine nucleotide exchange factor (GEF) Son of Sevenless (SOS) plays a critical role in signal transduction by activating Ras. Here we introduce a single-molecule assay in which individual SOS molecules are captured from raw cell lysate using Ras-functionalized supported membrane microarrays. This enables characterization of the full-length SOS protein, which has not previously been studied in reconstitution due to difficulties in purification. Our measurements on the full-length protein reveal a distinct role of the C-terminal proline-rich (PR) domain to obstruct the engagement of allosteric Ras independently of the well-known N-terminal domain autoinhibition. This inhibitory role of the PR domain limits Grb2-independent recruitment of SOS to the membrane through binding of Ras·GTP in the SOS allosteric binding site. More generally, this assay strategy enables characterization of the functional behaviour of GEFs with single-molecule precision but without the need for purification.
International Nuclear Information System (INIS)
Zagoria, R.J.; Karstaedt, N.; Koubek, T.D.
1986-01-01
The use of magnetic resonance (MR) imaging in two cases of rhabdomyolysis, one resulting from prolonged muscle compression and one from electrical burns, is described. The involved muscles were clearly demonstrated with MR. Recognition and assessment of the extent of rhabdomyolysis are important since life-threatening sequelae including severe metabolic disorders are possible. In one case, spin-echo and inversion-recovery MR imaging provided greater detail of muscle abnormalities than did 99mTc-pyrophosphate radionuclide scanning. Both cases illustrate the usefulness of MR in evaluation of skeletal muscle disorders
Contribution of abdoscan using MR cholangio-pancreatography and MR urography
International Nuclear Information System (INIS)
Lecesne, R.; Drouillard, J.; Cisse, R.; Schiratti, M.
1998-01-01
MR cholangio-pancreatography (MRCP) and MR Urography (MRU) are promising recent imaging modalities. Oral magnetic particles (Abdoscan, Nycomed SA, Oslo, Norway) is an negative contrast agent eliminating signal intensity of the gastro-intestinal tract thus improvising image quality at MRCP and MRU. (author)
MR imaging and MR angiography in popliteal artery entrapment syndrome
International Nuclear Information System (INIS)
Atilla, S.; Akpek, S.; Yuecel, C.; Tali, E.T.; Isik, S.; Ilgit, E.T.
1998-01-01
Popliteal artery entrapment (PAE) syndrome is an uncommon congenital anomaly seen in young adults causing ischemic symptoms in the lower extremities. It is the result of various types of anomalous relationships between the popliteal artery and the neighboring muscular structures. The purpose of this study was to define the role of MR imaging combined with MR angiography in the diagnosis of PAE cases. Four cases with segmental occlusion and medial displacement of popliteal artery in digital subtraction angiography (DSA) examinations were diagnosed as PAE syndrome by MR imaging and MR angiography. The DSA and MRA images are compared. All of the cases showed various degrees of abnormal intercondylar insertion of the medial head of the gastrocnemius muscle. The MR images showed detailed anatomy of the region revealing the cause of the arterial entrapment. Subclassification of the cases were done and fat tissue filling the normal localization of the muscle was evaluated. The DSA and MRA images demonstrated the length and localization of the occluded segment and collateral vascular developments equally. It is concluded that angiographic evaluation alone in PAE syndrome might result in overlooking the underlying cause of the arterial occlusion, which in turn leads to unsuccessful therapy procedures such as balloon angioplasty. Magnetic resonance imaging combined with MR angiography demonstrates both the vascular anatomy and the variations in the muscular structures in the popliteal fossa successfully, and this combination seems to be the most effective way of evaluating young adults with ischemic symptoms suggesting PAE syndrome. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Magee, Thomas [NSI, Merritt Island, FL (United States); University of Central Florida School of Medicine, Orlando, FL (United States)
2014-08-15
This study assesses the accuracy of 3-Tesla (3-T) conventional MR imaging, 3-T MR arthrography, and the combined use of conventional MR and MR arthrography in the diagnosis of meniscal retears as compared with arthroscopy. The study also assess whether there are false-negative cases in which injected contrast does not extend into the meniscus despite a meniscal retear being seen on arthroscopy. One hundred consecutive knee MR arthrograms performed on patients with previous knee surgery were reviewed retrospectively. 3-T conventional MR imaging, 3-T MR arthrography, and the combined use of conventional MR and MR arthrography were assessed for meniscal retears as compared with arthroscopy. The criterion used to diagnose a meniscal retear on MR arthrogram was injected contrast tracking into the meniscus. All patients underwent second-look arthroscopy. Seventy-four patients had conventional MR findings consistent with a meniscal retear. In 83 of the 100 patients, intraarticular contrast helped in demonstrating a retear. In ten patients, there were MR findings consistent with a meniscal retear despite intra-articular contrast not tracking into the meniscus. Ninety-four of the 100 patients had meniscal retears on second-look arthroscopy. Three-Tesla conventional MR examination was 78 % sensitive and 75 % specific, MR arthrogram examination was 88 % sensitive and 100 % specific, and the combined use of MR and MR arthrogram imaging was 98 % sensitive and 75 % specific in the diagnosis of a meniscal retear. The combined use of 3-T MR and MR arthrography allows for high sensitivity and specificity in meniscal retear detection. In some patients, intraarticular contrast will not track into a meniscal retear. When MR findings are consistent with a meniscal retear but contrast does not extend into the meniscus, a meniscal retear is likely. (orig.)
Von Mr Classic zu Mr Nerd: Wie Forschende soziale Medien nutzen
Directory of Open Access Journals (Sweden)
Doreen Siegfried
2014-12-01
Full Text Available Unter Wissenschaftlerinnen und Wissenschaftlern lassen sich vier Typen differenzieren, die ein signifikant unterschiedliches Verhalten in ihrer Nutzung und ihrer Einstellung gegenüber Social-Web-Anwendungen zeigen: Ms Maker, Mr Tech, Mr Classic und Mr Nerd. Grundlage für die Identifizierung dieser Social-Media-Typen ist die Auswertung von 778 Online-Fragebögen, die von Anfang September bis Mitte Oktober 2013 erhoben wurden. Erfragt wurde die Nutzung von Social-Media-Instrumenten für die tägliche Arbeit in Forschung, Lehre, Administration und Wissenschaftskommunikation. Neben Intensität und Kontext der Nutzung von Web-2.0-Diensten wurden auch die Gründe für Nutzung bzw. Nicht-Nutzung einzelner Kanäle sowie generelle Einstellungen gegenüber Social-Media-Werkzeugen erfragt. Among scientists, four types of personality can be identified whose usage and attitude towards social web applications show significant variations: Ms Maker, Mr Tech, Mr Classic and Mr Nerd. This typification is based on 778 online questionnaires received between September and October 2013. The survey sampled the usage of social media tools for daily routines in research, teaching, administrative work and scholarly communication. The survey asked questions about the intensity and the context in which Web 2.0 services are used, about the reasons for (not using certain channels, and about general attitudes towards social media tools.
van de Giessen, E.; Groot, P. F. C.; Booij, J.; van den Brink, W.; Veltman, D. J.; Nederveen, A. J.
2011-01-01
Open MR imaging scanners are designed for imaging of specific patient groups that cannot be routinely scanned with conventional MR imaging scanners (eg, patients with obesity and claustrophobia). This study aims to determine whether BOLD sensitivity on an open 1T scanner is adequate for fMRI for
MR imaging of the normal pancreas
International Nuclear Information System (INIS)
Itoh, Hisao; Takahashi, Norio; Uchida, Yoshie; Nakayama, Gen; Bito, Kaoru; Haba, Hirotsugu; Kawamura, Masashi; Kataoka, Masaaki; Hamamoto, Ken.
1989-01-01
To evaluate current 1.5-T MR imaging with respiratory ordered phase encoding (ROPE) technique in the identification of pancreatic contour and main pancreatic duct, 100 normal subjects examined with spin echo technique including transaxial scans of T 1 -WI,T 2 -WI, and proton density (PD)-WI were reviewed. The results of MR imaging were then compared with computed tomography (CT). Pancreatic contour was divided into 3 parts; head, body, and tail. T 1 -WI was the best pulse sequence in describing pancreas and the rates of specific identification of head, body, and tail were 69%, 97%, and 92%, respectively. While these rates were 62%, 90%, and 92% with plain CT and 69%, 94%, and 94% with contrast-enhanced CT, respectively. A combination of MR imaging and CT yielded better rates of identification. The main pancreatic duct was visible in 44% as a low intensity line on T 1 -WI and in 16% on plain CT. Dorsal to pancreas, all of the major vessels were seen in every patients. Ventrally, retroperitoneal fat was important, however, it was not a limiting factor. When respiratory compensation using ROPE functioned well, it was possible to differentiate bowel from pancreas in patients with sparse fat because signal intensity of the pancreas tended to be higher than that of gastrointestinal wall and its contents on T 1 -WI. Current MR imaging seemed to be a complementary method with CT in the identification of the pancreas. (author)
Directory of Open Access Journals (Sweden)
Zeller, Stefanie
2014-09-01
Full Text Available Die zur Familie der Brassicaceae gehörende Gartenkresse wird in Deutschland überwiegend im biologischen Anbau vermehrt. Seit einigen Jahren werden diese Gartenkressebestände von Erregern des Falschen Mehltaus (Hyaloperonospora parasitica, Perofascia lepidii befallen, was zu einem Totalausfall des Pflanzenbestandes führen kann. Daher ist die biologische Saatgutproduktion von Gartenkresse gefährdet, was eine Beeinträchtigung der Saatgutversorgung für die Keimsprossenerzeugung zur Folge hat. In den laufenden Untersuchungen wird der Einfluss von nicht chemischen Saatgutbehandlungsmaßnahmen (Wasserdampf, Elektronen, sowie Wachstumsbedingungen (Feuchte, Boden auf die Infektion mit Falschem Mehltau untersucht.
MR spectroscopy in dementia; MR-Spektroskopie bei Demenz
Energy Technology Data Exchange (ETDEWEB)
Hauser, T.; Gerigk, L.; Giesel, F.; Schuster, L.; Essig, M. [Deutsches Krebsforschungszentrum (DKFZ) Heidelberg, Abteilung E010, Radiologie, Heidelberg (Germany)
2010-09-15
With an increasingly aging population we are faced with the problem of an increasing number of dementia patients. In addition to clinical, neuropsychological and laboratory procedures, MRI plays an important role in the early diagnosis of dementia. In addition to various morphological changes functional changes can also help in the diagnosis and differential diagnosis of dementia. Overall the diagnosis of dementia can be improved by using parameters from MR spectroscopy. This article focuses on MR spectroscopic changes in the physiological aging process as well as on changes in mild cognitive impairment a precursor of Alzheimer's dementia, in Alzheimer's dementia, frontotemporal dementia, vascular dementia and Lewy body dementia. (orig.) [German] Angesichts einer immer aelter werdenden Bevoelkerung sind wir mit dem Problem einer zunehmenden Zahl an Demenzerkrankungen konfrontiert. Neben klinischen, neuropsychologischen und laborchemischen Verfahren spielt die MRT zur Fruehdiagnostik einer Demenz eine wichtige Rolle. Morphologische Veraenderungen wie auch verschiedene funktionelle Verfahren helfen bei der Diagnostik und Differenzialdiagnostik einer Demenz. Insgesamt kann mittels MR-spektroskopischer Parameter die Diagnostik einer Demenz verbessert werden. In diesem Artikel soll auf MR-spektroskopische Veraenderungen im Rahmen des physiologischen Alterungsprozesses eingegangen werden. Ferner werden speziell Veraenderungen bei leichter kognitiver Beeintraechtigung, einer Vorform der Alzheimer-Demenz, bei Alzheimer-, frontotemporaler, vaskulaerer und Lewy-Koerper-Demenz eroertert. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Tian, Chun-Yan [Department of Radiology, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191 (China); Wang, Jian-Quan [Department of Sports Medicine, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191,PR China (China); Zheng, Zhuo-Zhao, E-mail: zzhuozhao@aliyun.com [Department of Radiology, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191 (China); Ren, A.-Hong [Department of Radiology, Beijing Daxing Hospital, 26 West Huangcun Road, Daxing District, Beijing 102600 (China)
2014-10-15
Highlights: • MR is the preferred imaging modality for diagnosing acetabular labral tears. • The diagnostic performance of MR arthrography are superior than conventional hip MR. • The hip MR arthrography is recommended for diagnosing acetabular labral lesions. - Abstract: Objective: To evaluate the value of hip MR for diagnosing acetabular labrum tears, and to further compare the diagnostic performances of conventional MR with MR arthrography in acetabular labrum tears. Methods: 90 patients undergoing both hip MR examination and subsequent hip arthroscopy were retrospectively evaluated. Of these patients, 34 accepted both conventional MR and MR arthrography; while the other 56 only underwent conventional MR examination. All hip MR images were independently reviewed by two radiologists, and further compared with the results of hip arthroscopy. Results: 59 of 90 patients were confirmed with acetabular labral tears by hip arthroscopy and 31 without tears. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of conventional MR for evaluating the acetabular labral tears were 61.0%, 77.4%, 83.7% and 51.1% (radiologist A), and 66.1%, 74.2%, 82.9% and 53.4% (radiologist B), respectively, with good consistency between the two observers (K = 0.645). The sensitivity, specificity, PPV and NPV of MR arthrography for assessing the acetabular labral tears were 90.5%, 84.6%, 90.5% and 84.6% (radiologist A), and 95.2%, 84.6%, 90.9% and 91.7% (radiologist B), respectively, with excellent good consistency between the two observers (K = 0.810). The sensitivity and NPV of MR arthrography for diagnosing the acetabular labral tears were significantly higher than those of conventional MR (both P < 0.05). Conclusion: Hip MR arthrography is a reliable evaluation modality for diagnosing the acetabular labral tears, and its diagnostic performance is superior to that of conventional MR at 3.0 T.
MR imaging of colorectal carcinomas using an MR endoscopic coil
International Nuclear Information System (INIS)
Murano, Akihiko; Kido, Choichiro; Sasaki, Fumio; Nakamura, Tsuneya; Kobayashi, Semi; Katoh, Tomoyuki; Hirai, Takashi
1994-01-01
Diagnosis of the depth of wall invasion by rectal carcinoma using MR endoscopy was performed in ten resected specimens, including five rectal carcinomas, three colon carcinomas, two normal gastric wall. In addition, the gastric wall of a pig was examined. MR imaging was done with a 1.5-T Signa Advantage (GE Medical System) system, with the surface coil of the MR endoscope acting as the receiver coil. Five layers could be distinguished in the bowel wall: mucosa, submucosa and muscularis propria divided into circular muscle, longitudinal muscle and intervening connective tissue. Tumors had almost the same signal intensity as muscle. The MR images of colon carcinomas, rectal carcinomas, and extrinsically metastatic involvement of the sigmoid colon by rectal carcinoma all correlated well with the pathological findings. The normal structure of the gastric wall was similar to that of the colon. 3D-fast Spoiled Grass (SPGR) sequence has a fairly short scanning time. Thus, the possibility of precise clinical diagnosis by this method was suggested. (author)
Current status of MR colonography.
LENUS (Irish Health Repository)
Thornton, Eavan
2010-01-01
The search for an acceptable colorectal cancer screening examination has led to the development of virtual colonoscopy, which includes both computed tomographic (CT) colonography and magnetic resonance (MR) colonography. As indicated by the much larger number of published studies on CT colonography than on MR colonography, multidetector CT appears to be more suitable for colorectal screening than does MR colonography, in part reflecting the ease and speed of performing CT, as well as the increased spatial resolution, decreased cost, and wider availability of CT colonography. The main advantage of MR colonography over CT colonography is that it does not use ionizing radiation, which has important implications for colorectal cancer screening. The use of dark-lumen MR colonography to screen patients for colorectal cancer as well as other abdominopelvic disease could make it more attractive than CT. With the integration of 3.0-T MR colonography, fecal tagging, and parallel imaging into research and clinical settings, new MR colonography protocols must be optimized. Future MR colonography research should address issues such as image characteristics, presence of artifacts, management of specific absorption rate, and hardware-related modifications.
MR-assisted PET Motion Correction for eurological Studies in an Integrated MR-PET Scanner
Catana, Ciprian; Benner, Thomas; van der Kouwe, Andre; Byars, Larry; Hamm, Michael; Chonde, Daniel B.; Michel, Christian J.; El Fakhri, Georges; Schmand, Matthias; Sorensen, A. Gregory
2011-01-01
Head motion is difficult to avoid in long PET studies, degrading the image quality and offsetting the benefit of using a high-resolution scanner. As a potential solution in an integrated MR-PET scanner, the simultaneously acquired MR data can be used for motion tracking. In this work, a novel data processing and rigid-body motion correction (MC) algorithm for the MR-compatible BrainPET prototype scanner is described and proof-of-principle phantom and human studies are presented. Methods To account for motion, the PET prompts and randoms coincidences as well as the sensitivity data are processed in the line or response (LOR) space according to the MR-derived motion estimates. After sinogram space rebinning, the corrected data are summed and the motion corrected PET volume is reconstructed from these sinograms and the attenuation and scatter sinograms in the reference position. The accuracy of the MC algorithm was first tested using a Hoffman phantom. Next, human volunteer studies were performed and motion estimates were obtained using two high temporal resolution MR-based motion tracking techniques. Results After accounting for the physical mismatch between the two scanners, perfectly co-registered MR and PET volumes are reproducibly obtained. The MR output gates inserted in to the PET list-mode allow the temporal correlation of the two data sets within 0.2 s. The Hoffman phantom volume reconstructed processing the PET data in the LOR space was similar to the one obtained processing the data using the standard methods and applying the MC in the image space, demonstrating the quantitative accuracy of the novel MC algorithm. In human volunteer studies, motion estimates were obtained from echo planar imaging and cloverleaf navigator sequences every 3 seconds and 20 ms, respectively. Substantially improved PET images with excellent delineation of specific brain structures were obtained after applying the MC using these MR-based estimates. Conclusion A novel MR-based MC
Factors influencing intentions to use social recommender systems: a social exchange perspective.
Chang, Tsung-Sheng; Hsiao, Wei-Hung
2013-05-01
This study employs the perspective of social exchange theory and seeks to understand users' intentions to use social recommender systems (SRS) through three psychological factors: trust, shared values, and reputation. We use structural equation modeling to analyze 221 valid questionnaires. The results show that trust has a direct positive influence on the intention to use SRS, followed by shared values, whereas reputation has an indirect influence on SRS use. We further discuss specific recommendations concerning these factors for developing SRS.
International Nuclear Information System (INIS)
Hricak, H.
1987-01-01
MR imaging, CT, and US should be viewed as complementary studies for imaging the pelvis. MR imaging is relatively expensive, not widely available, and requires special facilities. However, it is noninvasive and offers a large field-of-view, direct imaging in all three orthogonal planes and excellent soft-tissue contrast. Surgical clips, which present a problem with other imaging modalities, do not create significant MR image artifacts. Image degradation due to bowel motion can be minimized by bowel preparation and/or the administration of glucagon. The value of MR imaging of the pelvis is in staging rather than diagnosis of pelvic neoplasms. The accuracy, sensitivity, and specificity of MR imaging in staging prostate or bladder tumors exceed those of US and CT. In prostate carcinoma, MR imaging can be used to evaluate periprostatic tumor extension, especially to the bladder base, rectum, or seminal vesicles. For early transcapsular extension, however, the accuracy of transrectal US reportedly surpasses that of MR imaging. In bladder carcinoma, the value of MR imaging is in direct tumor visualization, the ability to differentiate between tumor and normal bladder wall, and the evaluation of bladder tumors located at the dome of the bladder base, where imaging in the sagittal plane is essential. In the evaluation of benign entities of the female pelvis, US remains the preferred screening modality. The use of MR imaging is reserved for cases of infertility or for planning myomectomy when knowledge of the exact number, size, and location of tumors is essential. MR imaging is useful in evaluating patients with amenorrhea or any suspected congenital anomalies. The main application of MR imaging of the female pelvis is in the staging of neoplasms, including endometrial and cervical carcinomas
MR imaging of the brain: tumors
International Nuclear Information System (INIS)
Sartor, K.
1999-01-01
The radiologic modality that most likely provides the imaging information needed in a patient suspected of having a brain tumor is MR imaging. A brain tumor can be reliably ruled out if the MR examination is performed properly and experts interpret the results as negative. If there is a tumor, however, its exact location and topography must be determined. Important for therapy and prognosis are also tumor properties such as histologic type and grade, as well as effects on adjacent brain structures. Although potentially a noninvasive method of in vivo neuropathology, MR is still far from being sufficiently specific, as dissimilar lesions may look the same despite the use of refined imaging protocols. The evolution of MR imaging continues, however, making further methodologic improvement likely. Presently, advanced methods, such as diffusion- and perfusion-weighted MR imaging, functional MR imaging, neuronavigation based on MR imaging data, and the use of MR imaging during surgery (intraoperative MR imaging), influence the way patients are treated. Likewise, follow-up imaging (monitoring) of tumor patients by MR has become more effective, and experience has shown how to distinguish reactive changes from recurrent tumor. In the future, MR imaging may gain importance in the development of novel therapeutic concepts. (orig.)
MR in phenylketonuria-related brain lesions
Czech Academy of Sciences Publication Activity Database
Dezortová, M.; Hájek, M.; Tintěra, J.; Hejcmanová, L.; Syková, Eva
2001-01-01
Roč. 42, - (2001), s. 459-466 ISSN 0284-1851 R&D Projects: GA ČR GV309/97/K048; GA ČR GA309/99/0657; GA MŠk VS96130 Institutional research plan: CEZ:AV0Z5039906 Keywords : brain phenylketonuria MR imaging Subject RIV: FH - Neurology Impact factor: 0.914, year: 2001
Safety issues and updates under MR environments
Energy Technology Data Exchange (ETDEWEB)
Kim, Soo Jung; Kim, Kyung Ah, E-mail: bellenina@daum.net
2017-04-15
Highlights: • Unexpected biological effects can occur within stronger magnetic fields. • MR safety for MR conditional items is not guaranteed beyond the tested conditions. • Updated knowledge about MR-related safety is important for a safe MR environment. - Abstract: Magnetic resonance (MR) imaging is a useful imaging tool with superior soft tissue contrast for diagnostic evaluation. The MR environments poses unique risks to patients and employees differently from ionizing radiation exposure originated from computed tomography and plain x-ray films. The technology associated with MR system has evolved continuously since its introduction in the late 1970s. MR systems have advanced with static magnetic fields, faster and stronger gradient magnetic fields and more powerful radiofrequency transmission coils. Higher field strengths of MR offers greater signal to noise capability and better spatial resolution, resulting in better visualization of anatomic detail, with a reduction in scan time. With the rapid evolution of technology associated with MR, we encounter new MR-related circumstances and unexpected dangerous conditions. A comprehensive update of our knowledge about MR safety is necessary to prevent MR-related accidents and to ensure safety for patients and staff associated with MR. This review presents an overview about MR-related safety issues and updates.
Lam, Mie K; Huisman, Merel; Nijenhuis, Robbert J; van den Bosch, Maurice; Viergever, Max A; Moonen, Chrit Tw; Bartels, LW
2015-01-01
BACKGROUND: Magnetic resonance (MR)-guided high-intensity focused ultrasound has emerged as a clinical option for palliative treatment of painful bone metastases, with MR thermometry (MRT) used for treatment monitoring. In this study, the general image quality of the MRT was assessed in terms of
Motion correction in simultaneous PET/MR brain imaging using sparsely sampled MR navigators
DEFF Research Database (Denmark)
Keller, Sune H; Hansen, Casper; Hansen, Christian
2015-01-01
BACKGROUND: We present a study performing motion correction (MC) of PET using MR navigators sampled between other protocolled MR sequences during simultaneous PET/MR brain scanning with the purpose of evaluating its clinical feasibility and the potential improvement of image quality. FINDINGS......: Twenty-nine human subjects had a 30-min [(11)C]-PiB PET scan with simultaneous MR including 3D navigators sampled at six time points, which were used to correct the PET image for rigid head motion. Five subjects with motion greater than 4 mm were reconstructed into six frames (one for each navigator...
Energy Technology Data Exchange (ETDEWEB)
Leeuwenburgh, Marjolein M.N., E-mail: m.m.leeuwenburgh@amc.uva.nl [Department of Surgery, Academic Medical Center, University of Amsterdam (Netherlands); Department of Radiology, Academic Medical Center, University of Amsterdam (Netherlands); Wiarda, Bart M. [Department of Radiology, Alkmaar Medical Center, Alkmaar (Netherlands); Jensch, Sebastiaan [Department of Radiology, Sint Lucas Andreas Hospital, Amsterdam (Netherlands); Wouter van Es, H. [Department of Radiology, Sint Antonius Hospital, Nieuwegein (Netherlands); Stockmann, Hein B.A.C. [Department of Surgery, Kennemer Gasthuis, Haarlem (Netherlands); Gratama, Jan Willem C. [Department of Radiology, Gelre Hospitals, Apeldoorn (Netherlands); Cobben, Lodewijk P.J. [Department of Radiology, Haaglanden Medical Center, Leidschendam (Netherlands); Bossuyt, Patrick M.M. [Department of Clinical Epidemiology, Academic Medical Center, University of Amsterdam (Netherlands); Boermeester, Marja A. [Department of Surgery, Academic Medical Center, University of Amsterdam (Netherlands); Stoker, Jaap [Department of Radiology, Academic Medical Center, University of Amsterdam (Netherlands)
2014-01-15
Objective: To compare accuracy and interobserver agreement between radiologists with limited experience in the evaluation of abdominal MRI (non-experts), and radiologists with longer MR reading experience (experts), in reading MRI in patients with suspected appendicitis. Methods: MR imaging was performed in 223 adult patients with suspected appendicitis and read independently by two members of a team of eight MR-inexperienced radiologists, who were trained with 100 MR examinations previous to this study (non-expert reading). Expert reading was performed by two radiologists with a larger abdominal MR experience (>500 examinations) in consensus. A final diagnosis was assigned after three months based on all available information, except MRI findings. We estimated MRI sensitivity and specificity for appendicitis and for all urgent diagnoses separately. Interobserver agreement was evaluated using kappa statistics. Results: Urgent diagnoses were assigned to 147 of 223 patients; 117 had appendicitis. Sensitivity for appendicitis was 0.89 by MR-non-expert radiologists and 0.97 in MR-expert reading (p = 0.01). Specificity was 0.83 for MR-non-experts versus 0.93 for MR-expert reading (p = 0.002). MR-experts and MR-non-experts agreed on appendicitis in 89% of cases (kappa 0.78). Accuracy in detecting urgent diagnoses was significantly lower in MR-non-experts compared to MR-expert reading: sensitivity 0.84 versus 0.95 (p < 0.001) and specificity 0.71 versus 0.82 (p = 0.03), respectively. Agreement on urgent diagnoses was 83% (kappa 0.63). Conclusion: MR-non-experts have sufficient sensitivity in reading MRI in patients with suspected appendicitis, with good agreement with MR-expert reading, but accuracy of MR-expert reading was higher.
International Nuclear Information System (INIS)
Leeuwenburgh, Marjolein M.N.; Wiarda, Bart M.; Jensch, Sebastiaan; Wouter van Es, H.; Stockmann, Hein B.A.C.; Gratama, Jan Willem C.; Cobben, Lodewijk P.J.; Bossuyt, Patrick M.M.; Boermeester, Marja A.; Stoker, Jaap
2014-01-01
Objective: To compare accuracy and interobserver agreement between radiologists with limited experience in the evaluation of abdominal MRI (non-experts), and radiologists with longer MR reading experience (experts), in reading MRI in patients with suspected appendicitis. Methods: MR imaging was performed in 223 adult patients with suspected appendicitis and read independently by two members of a team of eight MR-inexperienced radiologists, who were trained with 100 MR examinations previous to this study (non-expert reading). Expert reading was performed by two radiologists with a larger abdominal MR experience (>500 examinations) in consensus. A final diagnosis was assigned after three months based on all available information, except MRI findings. We estimated MRI sensitivity and specificity for appendicitis and for all urgent diagnoses separately. Interobserver agreement was evaluated using kappa statistics. Results: Urgent diagnoses were assigned to 147 of 223 patients; 117 had appendicitis. Sensitivity for appendicitis was 0.89 by MR-non-expert radiologists and 0.97 in MR-expert reading (p = 0.01). Specificity was 0.83 for MR-non-experts versus 0.93 for MR-expert reading (p = 0.002). MR-experts and MR-non-experts agreed on appendicitis in 89% of cases (kappa 0.78). Accuracy in detecting urgent diagnoses was significantly lower in MR-non-experts compared to MR-expert reading: sensitivity 0.84 versus 0.95 (p < 0.001) and specificity 0.71 versus 0.82 (p = 0.03), respectively. Agreement on urgent diagnoses was 83% (kappa 0.63). Conclusion: MR-non-experts have sufficient sensitivity in reading MRI in patients with suspected appendicitis, with good agreement with MR-expert reading, but accuracy of MR-expert reading was higher
A 31-channel MR brain array coil compatible with positron emission tomography.
Sander, Christin Y; Keil, Boris; Chonde, Daniel B; Rosen, Bruce R; Catana, Ciprian; Wald, Lawrence L
2015-06-01
Simultaneous acquisition of MR and positron emission tomography (PET) images requires the placement of the MR detection coil inside the PET detector ring where it absorbs and scatters photons. This constraint is the principal barrier to achieving optimum sensitivity on each modality. Here, we present a 31-channel PET-compatible brain array coil with reduced attenuation but improved MR sensitivity. A series of component tests were performed to identify tradeoffs between PET and MR performance. Aspects studied include the remote positioning of preamplifiers, coax size, coil trace size/material, and plastic housing. We then maximized PET performance at minimal cost to MR sensitivity. The coil was evaluated for MR performance (signal to noise ratio [SNR], g-factor) and PET attenuation. The coil design showed an improvement in attenuation by 190% (average) compared with conventional 32-channel arrays, and no loss in MR SNR. Moreover, the 31-channel coil displayed an SNR improvement of 230% (cortical region of interest) compared with a PET-optimized 8-channel array with similar attenuation properties. Implementing attenuation correction of the 31-channel array successfully removed PET artifacts, which were comparable to those of the 8-channel array. The design of the 31-channel PET-compatible coil enables higher sensitivity for PET/MR imaging, paving the way for novel applications in this hybrid-imaging domain. © 2014 Wiley Periodicals, Inc.
PET/MR Imaging in Gynecologic Oncology.
Ohliger, Michael A; Hope, Thomas A; Chapman, Jocelyn S; Chen, Lee-May; Behr, Spencer C; Poder, Liina
2017-08-01
MR imaging and PET using 2-Deoxy-2-[ 18 F]fluoroglucose (FDG) are both useful in the evaluation of gynecologic malignancies. MR imaging is superior for local staging of disease whereas fludeoxyglucose FDG PET is superior for detecting distant metastases. Integrated PET/MR imaging scanners have great promise for gynecologic malignancies by combining the advantages of each modality into a single scan. This article reviews the technology behind PET/MR imaging acquisitions and technical challenges relevant to imaging the pelvis. A dedicated PET/MR imaging protocol; the roles of PET and MR imaging in cervical, endometrial, and ovarian cancers; and future directions for PET/MR imaging are discussed. Copyright © 2017 Elsevier Inc. All rights reserved.
A 16-channel MR coil for simultaneous PET/MR imaging in breast cancer
International Nuclear Information System (INIS)
Dregely, Isabel; Lanz, Titus; Mueller, Matthias F.; Metz, Stephan; Kuschan, Marika; Nimbalkar, Manoj; Ziegler, Sibylle I.; Nekolla, Stephan G.; Schwaiger, Markus; Bundschuh, Ralph A.; Haase, Axel
2015-01-01
To implement and evaluate a dedicated receiver array coil for simultaneous positron emission tomography/magnetic resonance (PET/MR) imaging in breast cancer. A 16-channel receiver coil design was optimized for simultaneous PET/MR imaging. To assess MR performance, the signal-to-noise ratio, parallel imaging capability and image quality was evaluated in phantoms, volunteers and patients and compared to clinical standard protocols. For PET evaluation, quantitative 18 F-FDG PET images of phantoms and seven patients (14 lesions) were compared to images without the coil. In PET image reconstruction, a CT-based template of the coil was combined with the MR-acquired attenuation correction (AC) map of the phantom/patient. MR image quality was comparable to clinical MR-only examinations. PET evaluation in phantoms showed regionally varying underestimation of the standardised uptake value (SUV; mean 22 %) due to attenuation caused by the coil. This was improved by implementing the CT-based coil template in the AC (<2 % SUV underestimation). Patient data indicated that including the coil in the AC increased the SUV values in the lesions (21 ± 9 %). Using a dedicated PET/MR breast coil, state-of-the-art MRI was possible. In PET, accurate quantification and image homogeneity could be achieved if a CT-template of this coil was included in the AC for PET image reconstruction. (orig.)
Basic MR relaxation mechanisms and contrast agent design.
De León-Rodríguez, Luis M; Martins, André F; Pinho, Marco C; Rofsky, Neil M; Sherry, A Dean
2015-09-01
The diagnostic capabilities of magnetic resonance imaging (MRI) have undergone continuous and substantial evolution by virtue of hardware and software innovations and the development and implementation of exogenous contrast media. Thirty years since the first MRI contrast agent was approved for clinical use, a reliance on MR contrast media persists, largely to improve image quality with higher contrast resolution and to provide additional functional characterization of normal and abnormal tissues. Further development of MR contrast media is an important component in the quest for continued augmentation of diagnostic capabilities. In this review we detail the many important considerations when pursuing the design and use of MR contrast media. We offer a perspective on the importance of chemical stability, particularly kinetic stability, and how this influences one's thinking about the safety of metal-ligand-based contrast agents. We discuss the mechanisms involved in MR relaxation in the context of probe design strategies. A brief description of currently available contrast agents is accompanied by an in-depth discussion that highlights promising MRI contrast agents in the development of future clinical and research applications. Our intention is to give a diverse audience an improved understanding of the factors involved in developing new types of safe and highly efficient MR contrast agents and, at the same time, provide an appreciation of the insights into physiology and disease that newer types of responsive agents can provide. © 2015 Wiley Periodicals, Inc.
Leader-Member Exchange (LMX) and Psychosocial Factors at Work Among Healthcare Professionals
DEFF Research Database (Denmark)
Johansson Hanse, Jan; Harlin, Ulrika; Jarebrant, Caroline
2014-01-01
Aim: The study aims to examine the associations between leader–member exchange (LMX) and psychosocial factors at work. Methods: A questionnaire-based cross-sectional study was undertaken at four units in two not-for-profit hospitals in southwestern Sweden. The study sample included 240 employees.......-quality LMX was associated with good psychosocial work conditions experienced by the employees. Conclusions: The results support possible ways for managers and employees to strengthen their relationships and this may in turn lead to more sustainable systems in health care.......Aim: The study aims to examine the associations between leader–member exchange (LMX) and psychosocial factors at work. Methods: A questionnaire-based cross-sectional study was undertaken at four units in two not-for-profit hospitals in southwestern Sweden. The study sample included 240 employees....... Results: Significant correlations were found between LMX items and most of the psychosocial domains and dimensions. The strongest correlations were found between the LMX item affect and rewards/recognition, role clarity and predictability, and the LMX item loyalty and rewards/recognition. In sum, high...
The Common Factor of Bilateral U.S. Exchange Rates: What is it Related to?
Ponomareva, Natalia; Sheen, Jeffrey; Wang, Ben
2015-01-01
We identify a common factor driving a panel of fifteen monthly bilateral exchange rates against the U.S. dollar. We find this factor is closely related to U.S. nominal and real macroeconomic variables, financial market variables and commodity prices. Our results suggest this common factor is broadly related to the macroeconomic fundamentals in the Taylor rule and uncovered interest parity models. However, the set of fundamentals relevant to these models changes over time.
International Nuclear Information System (INIS)
Kramer, J.
2006-01-01
abnormalities shown with MR arthrography. Only the accurate detection of these lesions may allow early therapeutic intervention and, therefore relief of pain, and prevent or delay the development of arthritis. Avascular necrosis (AVN) also known as (ischemic) osteonecrosis, or aseptic osteonecrosis is a condition resulting from insufficient blood supply to the richly vascularized subchondral bone. AVN may be idiopathic, but is often secondary to trauma, exogenous steroid use or Cushing syndrome, alcoholism, pancreatitis, HIV, Gaucher, rheumatoid arthritis, Caisson's disease, etc. Symptoms are very much dependent on subchondral location. On T1-weighted images a low signal intensity line of demarcation is seen in over 90% of cases. On T2-weighted sequences a high signal intensity line appears within the low signal intensity in the majority of cases. This is referred to as the double line sign. This highly specific sign for AVN is secondary to a combination of factors including chemical shift artifact, presence of granulation tissue and sclerosis. The double line sign may be absent in early AVN. The signal intensity of the central zone may look like fat (early AVN), blood (rare), edema (not specific), or fibrotic tissue (advanced AVN). Marrow edema can also be seen in transient osteoporosis, osteomyelitis, and secondary to occult (subchondral) fractures or tumors like osteoid osteoma, osteoblastoma and chondroblastoma. The relationship between transient osteoporosis and AVN is controversial. Patients with edema without initial demarcation that develop AVN have subchondral abnormalities in the initial phase. Not rarely avascular necrosis is bilateral. The size of the necrotic area is the most important prognostic factor. When the necrotic volume is small, patients often are asymptomatic and collapse or fractures are uncommon. MRI is the most sensitive imaging modality in the early detection of AVN. The reported MR sensitivities of 85-97 % are superior to those of bone scintigraphy
International Nuclear Information System (INIS)
Wegmueller, H.; Vock, P.
1993-01-01
The two techniques currently most often used for MR angiography, those based on time-of-flight effects and on phase-contrast, are introduced, and our results with three-dimensional phase contrast angiography of the abdomen are presented. Several basic differences from other imaging procedures render MR angiography clinically useful for screening for renal artery stenosis in critical situations, such as renal failure or intolerance to contrast agents. In the future, the spectrum of applications of MR angiography will broaden and include other indications, such as portal venous hypertension and follow-up studies after surgical portal systemic shunting. (orig.) [de
ASME and RCC-MR comparison for the prevention of fatigue analysis
International Nuclear Information System (INIS)
Autrusson, B.; Acker, D.
1989-01-01
The purpose of this survey is to compare the simplified methods, without reference to the safety factor allowed for the mechanical properties. An application of both codes, RCC-MR and ASME, on the design of the wall mock-up of the NET project is made and also an estimation with an elastoplastic analysis. In the case of fatigue analysis according to ASME in the plastic field, the elastic stress is magnified by a K e factor derived from stress variation, S n , disregarding geometrical discontinuities. According to RCC-MR, the elastic maximum strain will magnified by two coefficients accounting for plasticity and variation of Poisson ratio
Laurent Guiraud
2000-01-01
Visit of Mr. Susumu Yoda, Japanese Atomic Energy Commission, Mr. Nobuo Natsume, Vice-President, Central Research Institute of Electric Power Industry, Japan (CRIEPI), Mr. Nobuya Yoshiki, CRIEPI, Mrs. Seiko Ichikawa, Interpreter, with Mr. Taylor of CERN, visiting SM18
MR myelography of sacral meningeal cysts
International Nuclear Information System (INIS)
Tsuchiya, K.; Katase, S.; Hachiya, J.
1999-01-01
Purpose: To describe the findings of sacral meningeal cysts (SMCs) on MR myelography and assess its value for the diagnosis of SMCs. Material and Methods: We evaluated the MR images and MR myelograms obtained from 10 patients with SMC. MR myelograms were obtained using a 2D or 3D single-shot fast spin-echo sequence. In 5 patients, X-ray myelograms and postmyelographic CT images were compared with the MR myelograms. Results: A total of 33 SMCs were diagnosed within the spinal canal and/or sacral foramen. MR myelograms clearly revealed each cyst as a well-defined mass showing hyperintensity (10 cysts) or isointensity (23 cysts) compared to cerebrospinal fluid. MR myelograms demonstrated SMCs better than X-ray myelograms and postmyelographic CT images in 3 of the 5 patients. Conclusion: MR myelography can be an adjunct to conventional imaging techniques when surgical treatment is indicated, because it can precisely delineate the extent of SMCs. (orig.)
Characterization of a prototype MR-compatible Delta4 QA system in a 1.5 tesla MR-linac
de Vries, J. H. W.; Seravalli, E.; Houweling, A. C.; Woodings, S. J.; van Rooij, R.; Wolthaus, J. W. H.; Lagendijk, J. J. W.; Raaymakers, B. W.
2018-01-01
To perform patient plan quality assurance (QA) on a newly installed MR-linac (MRL) it is necessary to have an MR-compatible QA device. An MR compatible device (MR-Delta4) has been developed together with Scandidos AB (Uppsala, Sweden). The basic characteristics of the detector response, such as short-term reproducibility, dose linearity, field size dependency, dose rate dependency, dose-per-pulse dependency and angular dependency, were investigated for the clinical Delta4-PT as well as for the MR compatible version. All tests were performed with both devices on a conventional linac and the MR compatible device was tested on the MRL as well. No statistically significant differences were found in the short-term reproducibility (tesla magnetic field of the Elekta MR-linac
International Nuclear Information System (INIS)
Fritts, H.M.; Craig, E.; Kyle, R.; Strefling, M.; Miller, D.; Heithoff, K.; Schellhas, K.
1988-01-01
Magnetic resonance (MR) imaging (1.5-T unit) was performed in over 600 shoulders to evaluate shoulder pain. Ultrasound (US) and arthrography were performed in over 100 patients. Surgery was performed in over 75 patients. MR imaging offers information not well evaluated with other modalities, including bony impingement, tendinitis, bursitis, and osseous abnormalities, such as primary arthritis, avascular necrosis, occult fractures, and tumors. US and MR findings correlate well with surgical findings for medium to large rotator cuff tears. MR imaging with T2 weighting is superior for differentiating small tears from associated tendinitis. An algorithm for cost-effective shoulder imaging integrating US, MR imaging, arthrography, and computed tomographic arthrography are presented
MR appearance of central neurocytoma
International Nuclear Information System (INIS)
Chang, K.H.; Han, M.H.; Kim, D.G.; Chi, J.G.; Suh, D.C.; Kim, S.J.; Cha, S.H.; Han, M.C.
1993-01-01
To provide a detailed description of the MR appearances of central neurocytoma, MR images of 13 patients with central neurocytoma were retrospectively reviewed and compared with CT examinations. The histology was confirmed by ultrastructural and immunohistochemical studies. In 12 patients the tumors were histologically benign and located in the anterior part of the lateral ventricle, 6 of which extended to the 3rd ventricle. There was one case of a histologically malignant variant involving the thalamus and lateral ventricle. The tumors were primarily solid, but contained cysts (85%, 11/13), calcifications (69%, 9/13), and signal void from tumor vessels (62%, 8/13), frequently producing heterogeneous signal intensity on both T1- and T2-weighted images. Most of the solid portion appeared isointense or slightly hyperintense relative to the cerebral cortex on all MR pulse sequences. Calcifications were iso- or hypointense on MR, making them difficult to characterize with MR alone. Intratumoral hemorrhage was seen in 2 patients on MR but not on CT. Contrast enhancement was variable in degree and pattern. Coronal and sagittal MR images were valuable in evaluating the tumor extent and origin site, and in planning the surgical approach. It is concluded that MR imaging appears to be more useful than CT in the overall evaluation of central neurocytoma, even though calcification is better characterized with CT. (orig.)
International Nuclear Information System (INIS)
Fallone, B. G.; Murray, B.; Rathee, S.; Stanescu, T.; Steciw, S.; Vidakovic, S.; Blosser, E.; Tymofichuk, D.
2009-01-01
The authors report the first magnetic resonance (MR) images produced by their prototype MR system integrated with a radiation therapy source. The prototype consists of a 6 MV linac mounted onto the open end of a biplanar 0.2 T permanent MR system which has 27.9 cm pole-to-pole opening with flat gradients (40 mT/m) running under a TMX NRC console. The distance from the magnet isocenter to the linac target is 80 cm. The authors' design has resolved the mutual interferences between the two devices such that the MR magnetic field does not interfere with the trajectory of the electron in the linac waveguide, and the radiofrequency (RF) signals from each system do not interfere with the operation of the other system. Magnetic and RF shielding calculations were performed and confirmed with appropriate measurements. The prototype is currently on a fixed gantry; however, in the very near future, the linac and MR magnet will rotate in unison such that the linac is always aimed through the opening in the biplanar magnet. MR imaging was found to be fully operational during linac irradiation and proven by imaging a phantom with conventional gradient echo sequences. Except for small changes in SNR, MR images produced during irradiation were visually and quantitatively very similar to those taken with the linac turned off. This prototype system provides proof of concept that the design has decreased the mutual interferences sufficiently to allow the development of real-time MR-guided radiotherapy. Low field-strength systems (0.2-0.5 T) have been used clinically as diagnostic tools. The task of the linac-MR system is, however, to provide MR guidance to the radiotherapy beam. Therefore, the 0.2 T field strength would provide adequate image quality for this purpose and, with the addition of fast imaging techniques, has the potential to provide 4D soft-tissue visualization not presently available in image-guided radiotherapy systems. The authors' initial design incorporates a
Characterization of a prototype MR-compatible Delta4 QA-system in a 1.5 tesla MR-linac
de Vries, Wilfred J H; Seravalli, Enrica; Houweling, Anette; Woodings, Simon J; van Rooij, Rob; Wolthaus, Jochem W H; Lagendijk, JJW; Raaymakers, Bas W
2018-01-01
To perform patient plan-quality assurance (QA) on the newly installed MR-Linac (MRL) there was a need for having an MR-compatible QA-device. An MR compatible device (MR-Delta4) was developed together with Scandidos AB (Uppsala, Sweden). The basic characteristics of the detector response
Kogan, Feliks; Singh, Anup; Cai, Keija; Haris, Mohammad; Hariharan, Hari; Reddy, Ravinder
2011-01-01
Proton exchange imaging is important as it allows for visualization and quantification of the distribution of specific metabolites with conventional MRI. Current exchange mediated MRI methods suffer from poor contrast as well as confounding factors that influence exchange rates. In this study we developed a new method to measure proton exchange which combines chemical exchange saturation transfer (CEST) and T1ρ magnetization preparation methods (CESTrho). We demonstrated that this new CESTrho sequence can detect proton exchange in the slow to intermediate exchange regimes. It has a linear dependence on proton concentration which allows it to be used to quantitatively measure changes in metabolite concentration. Additionally, the magnetization scheme of this new method can be customized to make it insensitive to changes in exchange rate while retaining its dependency on solute concentration. Finally, we showed the feasibility of using CESTrho in vivo. This sequence is able to detect proton exchange at intermediate exchange rates and is unaffected by the confounding factors that influence proton exchange rates thus making it ideal for the measurement of metabolites with exchangeable protons in this exchange regime. PMID:22009759
Kogan, Feliks; Singh, Anup; Cai, Keija; Haris, Mohammad; Hariharan, Hari; Reddy, Ravinder
2012-07-01
Proton exchange imaging is important as it allows for visualization and quantification of the distribution of specific metabolites with conventional MRI. Current exchange mediated MRI methods suffer from poor contrast as well as confounding factors that influence exchange rates. In this study we developed a new method to measure proton exchange which combines chemical exchange saturation transfer and T(1)(ρ) magnetization preparation methods (CESTrho). We demonstrated that this new CESTrho sequence can detect proton exchange in the slow to intermediate exchange regimes. It has a linear dependence on proton concentration which allows it to be used to quantitatively measure changes in metabolite concentration. Additionally, the magnetization scheme of this new method can be customized to make it insensitive to changes in exchange rate while retaining its dependency on solute concentration. Finally, we showed the feasibility of using CESTrho in vivo. This sequence is able to detect proton exchange at intermediate exchange rates and is unaffected by the confounding factors that influence proton exchange rates thus making it ideal for the measurement of metabolites with exchangeable protons in this exchange regime. Copyright © 2011 Wiley Periodicals, Inc.
A study of artefacts in simultaneous PET and MR imaging using a prototype MR compatible PET scanner
International Nuclear Information System (INIS)
Slates, R.B.; Farahani, K.; Marsden, P.K.; Taylor, J.; Summers, P.E.; Williams, S.; Beech, J.
1999-01-01
We have assessed the possibility of artefacts that can arise in attempting to perform simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) using a small prototype MR compatible PET scanner (McPET). In these experiments, we examine MR images for any major artefacts or loss in image quality due to inhomogeneities in the magnetic field, radiofrequency interference or susceptibility effects caused by operation of the PET system inside the MR scanner. In addition, possible artefacts in the PET images caused by the static and time-varying magnetic fields or radiofrequency interference from the MR system were investigated. Biological tissue and a T 2 -weighted spin echo sequence were used to examine susceptibility artefacts due to components of the McPET scanner (scintillator, optical fibres) situated in the MR field of view. A range of commonly used MR pulse sequences was studied while acquiring PET data to look for possible artefacts in either the PET or MR images. Other than a small loss in signal-to-noise using gradient echo sequences, there was no significant interaction between the two imaging systems. Simultaneous PET and MR imaging of simple phantoms was also carried out in different MR systems with field strengths ranging from 0.2 to 4.7 T. The results of these studies demonstrate that it is possible to acquire PET and MR images simultaneously, without any significant artefacts or loss in image quality, using our prototype MR compatible PET scanner. (author)
Wagner, Mathilde; Corcuera-Solano, Idoia; Lo, Grace; Esses, Steven; Liao, Joseph; Besa, Cecilia; Chen, Nelson; Abraham, Ginu; Fung, Maggie; Babb, James S; Ehman, Richard L; Taouli, Bachir
2017-08-01
Purpose To assess the determinants of technical failure of magnetic resonance (MR) elastography of the liver in a large single-center study. Materials and Methods This retrospective study was approved by the institutional review board. Seven hundred eighty-one MR elastography examinations performed in 691 consecutive patients (mean age, 58 years; male patients, 434 [62.8%]) in a single center between June 2013 and August 2014 were retrospectively evaluated. MR elastography was performed at 3.0 T (n = 443) or 1.5 T (n = 338) by using a gradient-recalled-echo pulse sequence. MR elastography and anatomic image analysis were performed by two observers. Additional observers measured liver T2* and fat fraction. Technical failure was defined as no pixel value with a confidence index higher than 95% and/or no apparent shear waves imaged. Logistic regression analysis was performed to assess potential predictive factors of technical failure of MR elastography. Results The technical failure rate of MR elastography at 1.5 T was 3.5% (12 of 338), while it was higher, 15.3% (68 of 443), at 3.0 T. On the basis of univariate analysis, body mass index, liver iron deposition, massive ascites, use of 3.0 T, presence of cirrhosis, and alcoholic liver disease were all significantly associated with failure of MR elastography (P analysis, only body mass index, liver iron deposition, massive ascites, and use of 3.0 T were significantly associated with failure of MR elastography (P technical failure rate of MR elastography with a gradient-recalled-echo pulse sequence was low at 1.5 T but substantially higher at 3.0 T. Massive ascites, iron deposition, and high body mass index were additional independent factors associated with failure of MR elastography of the liver with a two-dimensional gradient-recalled-echo pulse sequence. © RSNA, 2017.
Macroeconomics factors and the balanced value of the Czech Koruna/Euro Exchange rate
Czech Academy of Sciences Publication Activity Database
Brůha, J.; Derviz, Alexis
2006-01-01
Roč. 56, 7-8 (2006), s. 318-343 ISSN 0015-1920 R&D Projects: GA ČR GA402/05/0671 Institutional research plan: CEZ:AV0Z10750506 Keywords : exchange rate * latent risk * order flow pricing kernel Subject RIV: AH - Economics Impact factor: 0.190, year: 2006
International Nuclear Information System (INIS)
Barrera, M. C.; Recondo, J. A.; Aperribay, M.; Gervas, C.; Fernandez, E.; Alustiza, J. M.
2003-01-01
To evaluate the efficiency of magnetic resonance (MR) in the diagnosis of knee lesions and how the results are influenced by the time interval between MR and arthroscopy. 248 knees studied by MR were retrospectively analyzed, as well as those which also underwent arthroscopy. Arthroscopy was considered to be the gold standard, MR diagnostic capacity was evaluated for both meniscal and cruciate ligament lesions. Sensitivity, specificity and Kappa index were calculated for the set of all knees included in the study (248), for those in which the time between MR and arthroscopy was less than or equal to three months (134) and for those in which the time between both procedures was less than or equal to one month. Sensitivity, specificity and Kappa index of the MR had global values of 96.5%, 70% and 71%, respectively. When the interval between MR and arthroscopy was less than or equal to three months, sensitivity, specificity and Kappa index were 95.5%, 75% and 72%, respectively. When it was less than or equal to one month, sensitivity was 100%, specificity was 87.5% and Kappa index was 91%. MR is an excellent tool for the diagnosis of knee lesions. Higher MR values of sensitivity, specificity and Kappa index are obtained when the time interval between both procedures is kept to a minimum. (Author) 11 refs
Exchange enhancement of the electron g-factor in a two-dimensional semimetal in HgTe quantum wells
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Bovkun, L. S., E-mail: bovkun@ipmras.ru; Krishtopenko, S. S.; Zholudev, M. S.; Ikonnikov, A. V.; Spirin, K. E. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Dvoretsky, S. A.; Mikhailov, N. N. [Russian Academy of Sciences, Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation); Teppe, F.; Knap, W. [Universite Montpellier II, Laboratoire Charles Coulomb (L2C), UMR CNRS 5221, GIS-TERALAB (France); Gavrilenko, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)
2015-12-15
The exchange enhancement of the electron g-factor in perpendicular magnetic fields to 12 T in HgTe/CdHgTe quantum wells 20 nm wide with a semimetal band structure is studied. The electron effective mass and g-factor at the Fermi level are determined by analyzing the temperature dependence of the amplitude of Shubnikov–de Haas oscillation in weak fields and near odd Landau-level filling factors ν ≤ 9. The experimental values are compared with theoretical calculations performed in the one-electron approximation using the eight-band kp Hamiltonian. The found dependence of g-factor enhancement on the electron concentration is explained by changes in the contributions of hole- and electron-like states to exchange corrections to the Landau-level energies in the conduction band.
Gadolinium-enhanced excretory MR urography: comparison with MR urography using HASTE technique
International Nuclear Information System (INIS)
Jin, Gong Yong; Lee, Jeong Min; Han, Young Min; Cheong, Gyung Ho; Oh, Hee Sul; Kim, Chong Soo; Park, Sung Kwang; Kim, Young Gon
2000-01-01
To compare the feasibility of gadolinium-enhanced excretory MR urography (GEMRU) and conventional MR urography using the half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in patients with hydronephrosis or non-visualized kidney. Fifteen patients with hydronephrosis or non-visualized kidney, as demonstrated by ultrasonography or intravenous urography, were enrolled in this study. Nine were men and six were women, and their age ranged from 18 to 77 (mean, 60.6) years. For all MR examinations, a 1.5T MR unit was employed. For breath-hold MR urography, the HASTE technique (MRU) was used, and reconstruction involved the use of a maximum intensity-projection (MIP) algorithm. For gadolinium-enhanced excretory MR urography, the fast low angle shot (FLASH) 3-D method was used and images were obtained at 5, 10, 20, and 30 minutes, and reconstruction again involved the use of MIP algorithm. In some cases, additional GEMRU was obtained 24 hour after contrast material injection, and an MIP algorithm was used for reconstruction. MRU and GEMRU were independently interpreted by two radiologists who for quantitative analysis compared SNR with CNR, and at each anatomic level qualitatively analyzed morphologic accuracy and diagnostic value of the lesions. In quantitative analysis, SNR and CNR differences between the two sequences at the renal pelvis and the level of the ureter were not significant (p greater than 0.05). In qualitative analysis, GEMRU was superior to MRU for the assessment of evaluated ureter at each level (p less than 0.05), anatomic anomaly and intrinsic tumor. Ureteral stones, however, were more easily diagnosed with MRU. For assessment of the ureter GEMRU is superior to MRU and has the advantage of evaluating renal function. We believe that for evaluation of the urinary tract, especially the distal ureter, GEMRU may be a valuable adjunct to routine MR urography. (author)
MR cholangiography: usefulness in obstructive jaundice
International Nuclear Information System (INIS)
Bae, Sang Hoon; Lee, In Jae; Nam, Kung Sook; Hong, Myung Sun; Lee, Kyung Hwan; Yun, Ku Sub
1994-01-01
Three-dimensional(3D) magnetic resonance(MR) projection imaging was evaluated as a noninvasive alternative to direct cholangiography for the assessment of its reliability in patients with obstructive jaundice. A heavily T2-weighted gradient-echo sequence(PSIF) was used for 3D MR projection imaging of the biliary system in five healthy volunteers and 25 patients with obstructive jaundice. The 3D images of the bile ducts were formed by stacking consecutive coronal MR images obtained with a fast imaging method to a maximum-intensity projection algorithm. In the volunteers, MR cholangiography could demonstrate the anatomy of the biliary tract in only two subjects. The extrahepatic and intrahepatic bile ducts were well visualized in 23 patients with obstructive jaundice. The leve of obstruction and the grade of dilatation were depicted with MR cholangiography in all cases. And the cause of obstruction could be determined with MR cholangiography in 18 cases, MR cholangiography wa successful in two patients in whom ERCP failed. The gallbladder or dilated pancreatic duct not demonstrated by means of direct cholangiography was demonstrated with MR cholangiography in six cases. MR cholangiography may be a useful adjunctive tool for the noninvasive evaluation of patients with obstructive Jaundice
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Dohan, Anthony, E-mail: anthony.dohan@lrb.aphp.fr [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Université Paris-Diderot, Sorbonne Paris Cité, 10 Rue de Verdun, 75010 Paris (France); UMR INSERM 965, Hôpital Lariboisière, 2 Rue Amboise Paré, 75010 Paris (France); Gavini, Jean-Philippe, E-mail: jpgavini@gmail.com [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Université Paris-Diderot, Sorbonne Paris Cité, 10 Rue de Verdun, 75010 Paris (France); Placé, Vinciane, E-mail: vinciane.place@gmail.com [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Sebbag, Delphine, E-mail: delphinesebbag@gmail.com [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Université Paris-Diderot, Sorbonne Paris Cité, 10 Rue de Verdun, 75010 Paris (France); Vignaud, Alexandre, E-mail: alexandre.vignaud@cea.fr [LRMN, Neurospin, CEA-SACLAY, Bâtiment 145, 91 191 Gif-sur-Yvette Cedex (France); and others
2013-11-01
Objective: To qualitatively and quantitatively compare T2-weighted MR imaging of the liver using volumetric spin-echo with sampling perfection with application-optimized contrast using different flip angle evolutions (SPACE) with conventional turbo spin-echo (TSE) sequence for fat-suppressed T2-weighted MR imaging of the liver. Materials and methods: Thirty-three patients with suspected focal liver lesions had SPACE MR imaging and conventional fat-suppressed TSE MR imaging. Images were analyzed quantitatively by measuring the lesion-to-liver contrast-to-noise ratio (CNR), and the signal-to-noise ratio (SNR) of main focal hepatic lesions, hepatic and splenic parenchyma and qualitatively by evaluating the presence of vascular, respiratory motion and cardiac artifacts. Wilcoxon signed rank test was used to search for differences between the two sequences. Results: SPACE MR imaging showed significantly greater CNR for focal liver lesions (median = 22.82) than TSE MR imaging (median = 14.15) (P < .001). No differences were found for SNR of hepatic parenchyma (P = .097), main focal hepatic lesions (P = .35), and splenic parenchyma (P = .25). SPACE sequence showed less artifacts than TSE sequence (vascular, P < .001; respiratory motion, P < .001; cardiac, P < .001) but needed a longer acquisition time (228.4 vs. 162.1 s; P < .001). Conclusion: SPACE MR imaging provides a significantly increased CNR for focal liver lesions and less artifacts by comparison with the conventional TSE sequence. These results should stimulate further clinical studies with a surgical standard of reference to compare the two techniques in terms of sensitivity for malignant lesions.
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Tagliafico, Alberto; Neumaier, Carlo Emanuele; Calabrese, Massimo [National Institute for Cancer Research, Department of Radiology, Genova (Italy); Succio, Giulia; Serafini, Giovanni; Ghidara, Matteo [Santa Corona Hospital, Radiology Department, Savona (Italy); Martinoli, Carlo [Universita di Genova, Radiology Department, Genova (Italy)
2011-06-15
To compare 1.5-T and 3-T magnetic resonance (MR) imaging of the brachial plexus. Institutional review board approval and informed consent were obtained from 30 healthy volunteers and 30 consecutive patients with brachial plexus disturbances. MR was prospectively performed with comparable sequence parameters and coils with a 1.5-T and a 3-T system. Imaging protocols at both field strengths included T1-weighted turbo spin-echo (tSE) sequences and T2-weighed turbo spin-echo (tSE) sequences with fat saturation. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) between muscle and nerve were calculated for both field strengths. The visibility of brachial plexus nerve at various anatomic levels (roots, interscalene area, costoclavicular space, and axillary level) was analyzed with a four-point grading scale by two radiologists. MR imaging diagnoses and pathological findings were also compared qualitatively. SNR and CNRs were significantly higher on 3-T MR images than on 1.5-T MR images (Friedman test) for all sequences. Nerve visibility was significantly better on 3-T MR images than on 1.5-T MR images (paired sign test). Pathological findings (n = 30/30) were seen equally well with both field strengths. MR imaging diagnoses did not differ for the 1.5- and 3-T protocols. High-quality MR images of the brachial plexus can be obtained with 3-T MR imaging by using sequences similar to those used at 1.5-T MR imaging. In patients and healthy volunteers, the visibility of nerve trunks and cords at 3-T MR imaging appears to be superior to that at 1.5-T MR imaging. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Schoenberg, S.O.; Knopp, M.V.; Bock, M.; Floemer, F.; Essig, M.; Hawighorst, H.; Kaick, G. van [Deutsches Krebsforschungszentrum, Heidelberg (Germany). Forschungsschwerpunkt Radiologische Diagnostik; Kallinowski, F. [Heidelberg Univ. (Germany). Chirurgische Universitaetsklinik; Just, A. [Heidelberg Univ. (Germany). 1. Physiologisches Inst.; Laub, G. [Siemens AG, Erlangen (Germany). Unternehmensbereich Medizinische Technik; Prince, M.R [Michigan Univ., Ann Arbor, MI (United States). Dept. of Radiology
1999-05-01
Aim: New diagnostic strategies for evaluation of the kidney by fast MR imaging of renal morphology, multiphase 3D gadolinium MR angiography, MR urography and MR flow measurements. A signal MR examination is designed to grade renovascular disease and assess the hemodynamic and functional significance, detect and characterize renal lesions and evaluate the urinary tract. Results: The combined analysis of morphologic and functional data allows reliable assessment of renal artery stenosis, benign and malignant renal masses and diseases of the renal collecting system and ureters, as well as congenital abnormalities in good agreement to the results of conventional imaging modalities. The improved tissue contrast and additional functional information compensates for the disadvantage of a lower spatial resolution. Conclusion: Combined morphologic and functional MR examination represents a reliable, non-invasive and cost-effective alternative imaging modality for comprehensive diagnostic evaluation of renal disease. (orig.) [Deutsch] Fragestellung: Darstellung neuer diagnostischer Moeglichkeiten im Bereich der Niere mittels schneller Magnetresonanz (MR)-Bildgebung. Methodik: Vorgestellt wird ein kombiniertes morphologisches und funktionelles Untersuchungskonzept bestehend aus schneller morphologischer Bildgebung, multiphasischer 3D-Gadolinium-MR-Angiographie, MR-Urographie und MR-Flussmessung. In einer einzigen MR-Untersuchung sollen vaskulaere Erkrankungen erfasst, eingestuft und auf ihre haemodynamische und funktionelle Signifikanz ueberprueft werden, renale Laesionen detektiert und differenziert sowie die Harnabflusswege beurteilt werden. Ergebnisse: Durch Integration der gewonnenen morphologischen und funktionellen Daten lassen sich Nierenarterienstenosen, benigne und maligne renale Tumoren, Harnabflussstoerungen und kongenitale Fehlbildungen mit aehnlicher Genauigkeit wie in den konventionellen radiologischen Verfahren erfassen. Der Nachteil der geringeren raeumlichen
MR-guided lumbar sympathicolysis
Energy Technology Data Exchange (ETDEWEB)
Koenig, Claudius W.; Schott, Ulrich G.; Pereira, Philippe L.; Truebenbach, Jochen; Claussen, Claus D.; Duda, Stephan H. [Department of Diagnostic Radiology, University of Tuebingen (Germany); Schneider, Wilke [Department of Vascular Surgery, University of Tuebingen (Germany)
2002-06-01
The aim of this study was to demonstrate the feasibility of MR-guided lumbar sympathicolysis (LSL) in a non-selected patient population. One hundred one MR-guided LSL procedures were performed in 89 patients according to Haaga's technique using a horizontally open clinical MR system (0.2 T) and non-ferromagnetic 20-G cannulas (neurolysis, n=93; blockade, n=8). Only gradient-recalled sequences in either single or multislice mode [fast imaging with steady-state precession (FISP) and fast low-angle shot] were applied for anatomical survey and needle guiding. Bupivacaine injection was monitored with MR fluoroscopically. Fluid distribution was subsequently documented in a CT scan in 65 patients. Ninety-one LSL procedures could be successfully completed. Ten patients were not treated using MR due to patient inconvenience, severe motion artifacts (n=4 each), excessive spondylophytes, and retroperitoneal hematoma (n=1 each). One case of ureteral necrosis occurred. Motion artifacts were rated less severe in single-slice FISP sequences and in obese patients. An average of 3.48 sequence measurements were required for definitive needle placement. Average table time was 32.3 min. An MR-guided LSL is feasible and can be performed with acceptable safety and time effort. It can be recommended for repeated sympathetic blockades in younger patients to avoid cumulative irradiation associated with CT guidance. (orig.)
MR-guided lumbar sympathicolysis
International Nuclear Information System (INIS)
Koenig, Claudius W.; Schott, Ulrich G.; Pereira, Philippe L.; Truebenbach, Jochen; Claussen, Claus D.; Duda, Stephan H.; Schneider, Wilke
2002-01-01
The aim of this study was to demonstrate the feasibility of MR-guided lumbar sympathicolysis (LSL) in a non-selected patient population. One hundred one MR-guided LSL procedures were performed in 89 patients according to Haaga's technique using a horizontally open clinical MR system (0.2 T) and non-ferromagnetic 20-G cannulas (neurolysis, n=93; blockade, n=8). Only gradient-recalled sequences in either single or multislice mode [fast imaging with steady-state precession (FISP) and fast low-angle shot] were applied for anatomical survey and needle guiding. Bupivacaine injection was monitored with MR fluoroscopically. Fluid distribution was subsequently documented in a CT scan in 65 patients. Ninety-one LSL procedures could be successfully completed. Ten patients were not treated using MR due to patient inconvenience, severe motion artifacts (n=4 each), excessive spondylophytes, and retroperitoneal hematoma (n=1 each). One case of ureteral necrosis occurred. Motion artifacts were rated less severe in single-slice FISP sequences and in obese patients. An average of 3.48 sequence measurements were required for definitive needle placement. Average table time was 32.3 min. An MR-guided LSL is feasible and can be performed with acceptable safety and time effort. It can be recommended for repeated sympathetic blockades in younger patients to avoid cumulative irradiation associated with CT guidance. (orig.)
Skeletal MR imaging: Correlation with skeletal scintigraphy
International Nuclear Information System (INIS)
Colletti, P.M.; Raval, J.K.; Ford, P.V.; Benson, R.C.; Kerr, R.M.; Boswell, W.D.; Siegel, M.E.; Ralls, P.W.
1987-01-01
Skeletal MR images bone marrow while skeletal scintigraphy uses bone metabolism to demonstrate abnormalities. The purpose of this paper is to correlate these MR and scintigraphic findings. T1 and T2 MR images at 0.5 T were correlated with planar bone scintigraphy (RN) using Tc-99m MDP in 56 patients. Of 23 cases with suspected spinal metastases, 19 were positive by MR imaging, 16 by RN. Individual lesions were shown better by MR imaging in five and by RN in two. These two cases had scoliosis, a potential difficulty with MR imaging. In 14 cases of suspected avascular necrosis (AVN), MR imaging was positive in 13 while RN was positive in ten. One negative case by RN had bilateral AVN by MR imaging. Four skull lesions shown easily by RN were seen only in retrospect on MR images. MR imaging is advantageous in evaluating bones with predominant marrow such as vertebrae or the femoral head, while RN is superior in areas primarily composed of cortical bone such as the skull
International Nuclear Information System (INIS)
Davis, W.L.; Blatter, D.D.; Parker, D.L.; Robison, R.O.; Harnsberger, H.R.
1991-01-01
This paper compares the more traditional three-dimensional (3D) time-of-flight MR angiography with a novel new technique, MOTSA, in the evaluation of both normal and abnormal intracranial anatomy. The authors performed sequential, location-matched 3D TOF and MOTSA MR angiography in 10 subjects with normal and 25 with abnormal intracranial anatomy. Images were evaluated for visualization of specific vessels and depiction of pathologic anatomy. All images were subjected to an objective scoring system. Digital angiography was available in 15 of 25 abnormal cases. In the normal cases, large- and small-vessel visualization was improved. Significant improvement in visualization of venous anatomy was also observed. In the abnormal cases, pathologic anatomy was better visualized, providing important diagnostic information. Multiple overlapping thin-slab-acquisition MR angiography demonstrates vessel visualization that is increased over that of 3D TOF MR angiography in both normal and abnormal cases. Because of the decrease in saturation effects and phase dispersion, MOTSA is especially useful in the evaluation of complex intracranial vascular abnormalities
MR of acute subarachnoid hemorrhage
International Nuclear Information System (INIS)
Spickler, E.; Lufkin, R.; Frazee, J.; Lylyk, P.; Vinuela, F.; Bentson, J.; Dion, J.
1987-01-01
Subarachnoid hemorrhage was produced in four Macaca nemestrina monkeys using the technique of Frazee. CT and MR imaging was performed immediately after the procedure and at frequent intervals up to 2 weeks after hemorrhage. The imaging studies were compared with clinical evaluations and pathologic specimens of all animals. Additional human clinical CT/MR studies of subarachnoid hemorrhage were also studied. Acute hemorrhage was recognized on MR images as an increase in signal in the region of clot compared with surrounding cerebrospinal fluid. This most likely reflects T1 shortening due to proton binding rather than a pure paramagnetic effect. While CT is sensitive to the hemoglobin protein in acute hemorrhage, the superior resolution of MR of the basal cisterns results in equal or better definition of acute subarachnoid hemorrhage on MR studies in many cases
Magnetic Resonance (MR) Defecography
... to a CD or uploaded to a digital cloud server. Magnetic resonance (MR) defecography is a special ... with you. top of page What are the benefits vs. risks? Benefits MR defecography helps assess pelvic ...
Energy Technology Data Exchange (ETDEWEB)
Kreitner, K.F. [Mainz Univ. (Germany). Klinik mit Poliklinik fuer Radiologie; Grebe, P. [Mainz Univ. (Germany). Klinik mit Poliklinik fuer Radiologie; Kersjes, W. [Mainz Univ. (Germany). Klinik mit Poliklinik fuer Radiologie; Runkel, M. [Mainz Univ. (Germany). Klinik fuer Unfallchirurgie; Kirschner, P. [Elisabeth-Hospital, Mainz (Germany). Abt. fuer Unfall- und Wiederherstellungschirurgie St. Vincenz; Schild, H.H. [Mainz Univ. (Germany). Klinik mit Poliklinik fuer Radiologie
1994-02-01
In a prospective study possible indications for MR arthrography of the shoulder were evaluated. 37 patients were examined before and after intraarticular administration of a 2-mmolar solution of Gd-DTPA. MR arthrography was performed if there was no joint effusion and/or an uncertain finding concerning the rotator cuff or the capsulolabral complex on plain MR images. MR arthrography leads to a better demonstration of labrum pathology in 11/22 patients and to a superior delineation of the capsuloligamentous apparatus in 20/22 cases. In 9/15 patients with impingement lesions MR arthrography allowed a differentiation of severe tendinitis from partial and small full-thickness tears of the rotator cuff. MR arthrography of the shoulder joint enhances the accuracy of MR in case of an uncertain finding on plain MR images. (orig.) [Deutsch] In einer prospektiven Studie sollten Einsatzmoeglichkeiten der MR-Arthrographie bei Erkrankungen des Schultergelenkes herausgearbeitet werden. 37 Patienten wurden sowohl nativ als auch nach intraartikulaerer Gabe einer 2mmolaren Gd-DTPA-Loesung untersucht. Voraussetzungen fuer die KM-Gabe waren ein fehlender Gelenkerguss und/oder ein unklarer Befund des Labrum-Kapsel-Komplexes oder der Rotatorenmanschette in der Nativuntersuchung. Durch die MR-Arthrographie wurde bei 11/22 Patienten eine verbesserte Darstellung der Labrumpathologie erzielt; in 20/22 Faellen ergabe sich eine zuverlaessige Beurteilung der Gelenkkapsel. Bei 9/15 Patienten mit Erkrankungen der Rotatorenmanschette konnten Tendinitiden von partiellen und kleinen kompletten Rotatorenmanschettenrupturen sicher differenziert werden. Die MR-Arthrographie des Schultergelenkes fuehrt bei nicht eindeutigen Befunden in der Nativuntersuchung zu einer verbesserten Treffsicherheit der MR-Diagnostik. (orig.)
US and MR imaging of pelvic masses
International Nuclear Information System (INIS)
Angtuaco, T.L.; Boyd, C.M.; Mattison, D.R.; Williamson, M.R.; Sanders, M.M.; Bard, D.S.
1987-01-01
US and MR imaging were compared in benign and malignant pelvic masses to determine where MR imaging may replace US. With regard to benign masses, MR imaging showed a significant advantage only in the imaging of teratomas. In malignancy, US was better than MR imaging in delineating internal architecture. MR imaging was superior in suggesting the origin and extent of masses, especially in large neoplasms. US remains a reliable tool in the initial evaluation of pelvic masses. When US studies are suboptimal, MR imaging should be performed as complementary study. MR imaging may replace US in the initial examination of large masses where US cannot depict the origin and extent
Patrice Loïez
2003-01-01
Photo 01: Mr Ansar Shamsi, Member Finance, Pakistan Atomic Energy Commission (centre), visiting the ATLAS Tile Calorimeter in building 191 with, from left to right, Mr Syed Shaukat Hussain, Pakistan Mission in Geneva and Dr Peter Jenni, ATLAS Spokesperson. Photo 02: Mr Ansar Shamsi, Member Finance, Pakistan Atomic Energy Commission (2nd form left), visiting the ATLAS Tile Calorimeter in building 191 with, from left to right, Mr Syed Shaukat Hussain, Pakistan Mission in Geneva; Dr Peter Jenni, ATLAS Spokesperson; Dr David Jacobs and Dr Philip Bryant, Joint Pakistan-CERN Committee.
International Nuclear Information System (INIS)
Heuck, A.; Scheidler, J.; Sommer, B.; Graser, A.; Mueller-Lisse, U.G.; Massmann, J.
2003-01-01
Accurate diagnosis and staging of prostate cancer (PC) is developing into an important health care issue in light of the high incidence of PC and the improvements in stage-adapted therapy. The purpose of this paper is to provide an overview on the current role of MR imaging and MR spectroscopy in the diagnosis and staging of PC.Material and methods Pertinent literature was searched and evaluated to collect information on current clinical indications, study techniques, diagnostic value, and limitations of magnetic resonance imaging and spectroscopy. Major indications for MR imaging of patients with supected PC are to define tumor location before biopsy when clinical or TRUS findings are inconclusive, and to provide accurate staging of histologically proven PC to ascertain effective therapy. Current MR imaging techniques for the evaluation of PC include multiplanar high-resolution T2-weighted FSE and T1-weighted SE sequences using combined endorectal and phased-array coils. Using these techniques, the reported accuracy of MR imaging for the diagnosis of extracapsular tumor extension ranges between 82 and 88% with sensitivities between 80 and 95%, and specificities between 82 and 93%. Typical MR findings of PC in different stages of disease, as well as diagnostic problems, such as chronic prostatitis, biopsy-related hemorrhage and therapy-related changes of prostatic tissue are discussed. In addition, the current perspectives and limitations of MR spectroscopy in PC are summarized. Current MR imaging techniques provide important diagnostic information in the pretherapeutic workup of PC including a high staging accuracy, and is superior to TRUS. (orig.) [de
Directory of Open Access Journals (Sweden)
Tanya Baycheva-Merger
2018-03-01
Full Text Available Adequate and accessible expert-based forest information has become increasingly in demand for effective decisions and informed policies in the forest and forest-related sectors in Europe. Such accessibility requires a collaborative environment and constant information exchange between various actors at different levels and across sectors. However, information exchange in complex policy environments is challenging, and is often constrained by various institutional, actor-oriented, and technical factors. In forest policy research, no study has yet attempted to simultaneously account for these multiple factors influencing expert-based forest information exchange. By employing a policy analysis from an actor-centred institutionalist perspective, this paper aims to provide an overview of the most salient institutional and actor-oriented factors that are perceived as constraining forest information exchange at the national level across European countries. We employ an exploratory research approach, and utilise both qualitative and quantitative methods to analyse our data. The data was collected through a semi-structured survey targeted at forest and forest-related composite actors in 21 European countries. The results revealed that expert-based forest information exchange is constrained by a number of compound and closely interlinked institutional and actor-oriented factors, reflecting the complex interplay of institutions and actors at the national level. The most salient institutional factors that stand out include restrictive or ambiguous data protection policies, inter-organisational information arrangements, different organisational cultures, and a lack of incentives. Forest information exchange becomes even more complex when actors are confronted with actor-oriented factors such as issues of distrust, diverging preferences and perceptions, intellectual property rights, and technical capabilities. We conclude that expert-based forest information
International Nuclear Information System (INIS)
Ordejon, B.; Seijo, L.; Barandiaran, Z.
2007-01-01
Complete text of publication follows: Excitons trapped at impurity centres in highly ionic crystals were first described by McClure and Pedrini [Phys. Rev. B 32, 8465 (1985)] as excited states consisting of a bound electron-hole pair with the hole localized on the impurity and the electron on nearby lattice sites, and a very short impurity-ligand bond length. In this work we present a detailed microscopic characterization of an impurity - trapped exciton in Cs 2 GeF 6 doped with U 4+ . Its electronic structure has been studied by means of CASSCF/CASPT2/SOCI relativistic ab initio model potential (AIMP) embedded-cluster calculations on (UF 6 ) 2- and (UF 6 Cs 8 ) 6+ clusters embedded in Cs 2 GeF 6 . The local geometry of the impurity-trapped exciton, the potential energy curves, and the multi electronic wavefunctions, have been obtained as direct, non-empirical results of the methods. The calculated excited states appear to be significantly delocalized outside the UF 6 volume and their U-F bond length turns out to be very short, closer to that of a pentavalent uranium defect than to that of a tetravalent uranium defect. The wavefunctions of these excited states show a dominant U 5f 1 7s 1 configuration character. This result has never been anticipated by simpler models and reveals the unprecedented ability of diffuse orbitals of f-element impurities to act as electron traps in ionic crystals
Mr. Wolfgang Petritsch, Austrian Ambassador
Patrice Loïez
2002-01-01
Dr.Peter Schmid/CERN/EP, Dr.Wolfgang Petritsch, Austrian Ambassador, Permanent representative at UN, Mrs.Nora Petritsch, Dr.Kurt Hubner/CERN/AC, Mrs. Frederike Klaus-Salesin, Adviser, Mrs.Andrea Strohmeier, Secretary of the Ambassador, Mr.Heinz Klaus, Attaché, Dr.Theodor Tortschanoff/CERN/LHC, Mr.Peter Storer, Advisor. Dr.Peter Schmid/CERN/EP, Dr.Wolfgang Petritsch, Austrian Ambassador, Permanent representative at UN, Mrs.Nora Petritsch, Dr.Kurt Hubner/CERN/AC, Mrs. Frederike Klaus-Salesin, Adviser, Mrs.Andrea Strohmeier, Secretary of the Ambassador, Mr.Heinz Klaus, Attaché, Dr.Theodor Tortschanoff/CERN/LHC, Mr.Peter Storer, Advisor.
Intracranial tuberculoma: MR imaging
Energy Technology Data Exchange (ETDEWEB)
Salgado, P; Zenteno, M A; Rodriguez-Carbajal, J; Brutto, O.H. del; Talamas, O
1989-09-01
MR studies of 6 patients with intracranial tuberculoma are reviewed. All patients also underwent CT scans which showed hypo- or isodense lesions with abnormal enhancement following contrast administration. MR showed lesions with prolongation of the T1 relaxation time in every case. On the T2-weighted sequences, the signal properties of the tuberculoma varied according to the stage of evolution of the lesion. Incipient tuberculomas appeared as scattered areas of hypointensity surrounded by edema. Mature tuberculomas were composed of a dark necrotic center surrounded by an isointense capsule which was, in turn, surrounded by edema. In one patient, the center of the lesion was hyperintense probably because of liquefaction and pus formation (tuberculous abscess). While both, CT and MR, were equally sensitive in visualizing the intracranial tuberculoma in every patient, MR was slightly superior in demonstrating the extent of the lesion, especially for brainstem tuberculomas. Nevertheless, the potential role for MR diagnosis of intracranial tuberculoma is limited by the fact that other infectious or neoplasic diseases may present similar findings. The diagnosis of intracranial tuberculoma should rest on a proper integration of data from clinical manifestations, cerebrospinal fluid analysis, and neuroimaging studies. (orig.).
Intracranial tuberculoma: MR imaging
International Nuclear Information System (INIS)
Salgado, P.; Zenteno, M.A.; Rodriguez-Carbajal, J.; Brutto, O.H. del; Talamas, O.
1989-01-01
MR studies of 6 patients with intracranial tuberculoma are reviewed. All patients also underwent CT scans which showed hypo- or isodense lesions with abnormal enhancement following contrast administration. MR showed lesions with prolongation of the T1 relaxation time in every case. On the T2-weighted sequences, the signal properties of the tuberculoma varied according to the stage of evolution of the lesion. Incipient tuberculomas appeared as scattered areas of hypointensity surrounded by edema. Mature tuberculomas were composed of a dark necrotic center surrounded by an isointense capsule which was, in turn, surrounded by edema. In one patient, the center of the lesion was hyperintense probably because of liquefaction and pus formation (tuberculous abscess). While both, CT and MR, were equally sensitive in visualizing the intracranial tuberculoma in every patient, MR was slightly superior in demonstrating the extent of the lesion, especially for brainstem tuberculomas. Nevertheless, the potential role for MR diagnosis of intracranial tuberculoma is limited by the fact that other infectious or neoplasic diseases may present similar findings. The diagnosis of intracranial tuberculoma should rest on a proper integration of data from clinical manifestations, cerebrospinal fluid analysis, and neuroimaging studies. (orig.)
Gagliardi, J A; Chung, E M; Chandnani, V P; Kesling, K L; Christensen, K P; Null, R N; Radvany, M G; Hansen, M F
1994-09-01
Chondromalacia patellae is a condition characterized by softening, fraying, and ulceration of patellar articular cartilage. We compare the sensitivity, specificity, and accuracy of conventional MR imaging, MR arthrography, and CT arthrography in detecting and staging this abnormality. Twenty-seven patients with pain in the anterior part of the knee were prospectively examined with MR imaging, including T1-weighted (650/16), proton density-weighted (2000/20), T2-weighted (2000/80), and spoiled two-dimensional gradient-recalled acquisition in the steady state (SPGR/)/35 degrees (51/10) with fat saturation pulse sequences. All were also examined with T1-weighted MR imaging after intraarticular injection of dilute gadopentetate dimeglumine and with double-contrast CT arthrography. Each imaging technique was evaluated independently by two observers, who reached a consensus interpretation. The signal characteristics of cartilage on MR images and contour abnormalities noted with all imaging techniques were evaluated and graded according to a modification of the classification of Shahriaree. Twenty-six of the 54 facets examined had chondromalacia shown by arthroscopy, which was used as the standard of reference. The sensitivity, specificity, and accuracy of each imaging technique in the diagnosis of each stage of chondromalacia patellae were determined and compared by using the McNemar two-tailed analysis. Arthroscopy showed that 28 facets were normal. Grade 1 chondromalacia patellae was diagnosed only with MR and CT arthrography in two (29%) of seven facets. Intermediate (grade 2 or 3) chondromalacia patellae was detected in two (13%) of 15 facets with T1-weighted and SPGR MR imaging, in three (20%) of 15 facets with proton density-weighted MR imaging, in seven (47%) of 15 facets with T2-weighted MR imaging, in 11 (73%) of 15 facets with CT arthrography, and in 12 (80%) of 15 facets with MR arthrography. Grade 4 was detected in three (75%) of four facets with T1-, proton
International Nuclear Information System (INIS)
Ha, Hong Il; Kim, Ah Young; Park, Seong Ho; Ha, Hyun Kwon; Yu, Chang Sik
2013-01-01
To evaluate DW MR tumour volumetry and post-CRT ADC in rectal cancer as predicting factors of CR using high b values to eliminate perfusion effects. One hundred rectal cancer patients who underwent 1.5-T rectal MR and DW imaging using three b factors (0, 150, and 1,000 s/mm 2 ) were enrolled. The tumour volumes of T2-weighted MR and DW images and pre- and post-CRT ADC 150-1000 were measured. The diagnostic accuracy of post-CRT ADC, T2-weighted MR, and DW tumour volumetry was compared using ROC analysis. DW MR tumour volumetry was superior to T2-weighted MR volumetry comparing the CR and non-CR groups (P z = 0.910) was superior to that of T2-weighed MR tumour volumetry (A z = 0.792) and post-CRT ADC (A z = 0.705) in determining CR (P = 0.015). Using a cutoff value for the tumour volume reduction rate of more than 86.8 % on DW MR images, the sensitivity and specificity for predicting CR were 91.4 % and 80 %, respectively. DW MR tumour volumetry after CRT showed significant superiority in predicting CR compared with T2-weighted MR images and post-CRT ADC. (orig.)
Ha, Hong Il; Kim, Ah Young; Yu, Chang Sik; Park, Seong Ho; Ha, Hyun Kwon
2013-12-01
To evaluate DW MR tumour volumetry and post-CRT ADC in rectal cancer as predicting factors of CR using high b values to eliminate perfusion effects. One hundred rectal cancer patients who underwent 1.5-T rectal MR and DW imaging using three b factors (0, 150, and 1,000 s/mm(2)) were enrolled. The tumour volumes of T2-weighted MR and DW images and pre- and post-CRT ADC150-1000 were measured. The diagnostic accuracy of post-CRT ADC, T2-weighted MR, and DW tumour volumetry was compared using ROC analysis. DW MR tumour volumetry was superior to T2-weighted MR volumetry comparing the CR and non-CR groups (P volumetry (Az = 0.910) was superior to that of T2-weighed MR tumour volumetry (Az = 0.792) and post-CRT ADC (Az = 0.705) in determining CR (P = 0.015). Using a cutoff value for the tumour volume reduction rate of more than 86.8 % on DW MR images, the sensitivity and specificity for predicting CR were 91.4 % and 80 %, respectively. DW MR tumour volumetry after CRT showed significant superiority in predicting CR compared with T2-weighted MR images and post-CRT ADC.
Chondromalacia patellae: diagnosis with MR imaging.
McCauley, T R; Kier, R; Lynch, K J; Jokl, P
1992-01-01
Most previous studies of MR imaging for detection of chondromalacia have used T1-weighted images. We correlated findings on axial MR images of the knee with arthroscopic findings to determine MR findings of chondromalacia patellae on T2-weighted and proton density-weighted images. The study population included 52 patients who had MR examination of the knee with a 1.5-T unit and subsequent arthroscopy, which documented chondromalacia patellae in 29 patients and normal cartilage in 23. The patellar cartilage was assessed retrospectively for MR signal and contour characteristics. MR diagnosis based on the criteria of focal signal or focal contour abnormality on either the T2-weighted or proton density-weighted images yielded the highest correlation with the arthroscopic diagnosis of chondromalacia. When these criteria were used, patients with chondromalacia were detected with 86% sensitivity, 74% specificity, and 81% accuracy. MR diagnosis based on T2-weighted images alone was more sensitive and accurate than was diagnosis based on proton density-weighted images alone. In conclusion, most patients with chondromalacia patellae have focal signal or focal contour defects in the patellar cartilage on T2-weighted MR images. These findings are absent in most patients with arthroscopically normal cartilage.
MR imaging of septic sacroiliitis
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Stuerzenbecher, A.; Hamm, B.; Bollow, M. [Humboldt-Universitaet, Berlin (DD). Bereich Medizin (Charite); Braun, J. [Freie Univ. Berlin (Germany). Universitaetsklinikum Benjamin Franklin; Paris, S. [Unfallkrankenhaus Berlin (Germany). Dept. of Radiology; Biedermann, T. [Krankenhaus Berlin-Buch (Germany). II. Kinderklinik
2000-08-01
Objective. To investigate the diagnostic value of magnetic resonance (MR) imaging in detecting septic sacroiliitis and to determine whether the MR characteristics allow this entity to be differentiated from sacroiliitis in spondylarthropathy (SpA).Patients and design. The imaging findings of 11 patients with septic sacroiliitis were retrospectively analyzed by two experienced radiologists. Radiographic surveys of the pelvis as well as computed tomography (CT) and MR images of the sacroiliac joints were available in all cases. Seven of the patients additionally underwent a follow-up MR examination. The MR imaging protocol comprised combinations of coronal and transverse T1-weighted spin-echo (SE) or fast SE sequences, T2-weighted gradient-echo (GE) sequences and short tau inversion recovery sequence (STIR) sequences as well as dynamic contrast- enhanced T1-weighted acquisitions.Results. Three patients with a short disease history showed anterior and/or posterior subperiosteal infiltrations (''lava cleft phenomenon''), transcapsular infiltrations of juxta-articular muscle layers, which obscured the fasciae, and periarticular bone marrow edema. The eight patients with more advanced stages of sacroiliitis additionally showed abscess formation, sequestration, and erosion. At follow-up MR examination (n=7) under systemic antibiotic treatment, the morphologic characteristics showed progression (n=1), regression (n=4), unchanged findings (n=1), or a mixed response (n=1). Clinical improvement precedes resolution of the MR findings.Conclusions. Anterior and/or posterior subperiosteal infiltrations and transcapsular infiltrations of juxta-articular muscle layers were depicted in all patients. These MR imaging findings are characteristic of septic sacroiliitis and may be used to differentiate this entity from sacroiliitis in SpA. (orig.)
MR arthrography of the ankle joint
International Nuclear Information System (INIS)
Trattnig, S.; Rand, T.; Breitenseher, M.; Ba-Ssalamah, A.; Schick, S.; Imhof, H.
1999-01-01
Due to its superior soft tissue contrast conventional MRI is the imaging method of choice in the evaluation of ankle joint disorders. Conventional MR imaging can accurately demonstrate normal or acutely injured ligaments; however, in subacute and chronic injury joint fluid necessary for delineation of injured ligaments is absent and MR arthrography should be performed. MR arthrography uses the intraarticular injection of contrast material to distend the joint, yielding improved discrimination of intraarticular structures. This joint distension with MR arthrography is also helpful in the staging of osteochondritis dissecans, since in cases of unstable lesions tracking of contrast material into the interface can be more easily demonstrated. Finally, high contrast and joint distension by MR arthrography improves the detection of intraarticular loose bodies, which often require surgery. MR artrography, although invasive, may provide additional information in various ankle joint disorders. (orig.) [de
π-exchange NN interaction model with overlapping nucleon form factors
International Nuclear Information System (INIS)
Bagnoud, X.
1986-01-01
The nucleon-nucleon (NN) interaction model includes a π-exchange and takes into account the first excited state Δ(1232) of the nucleon. It is supplemented by a short-range repulsion which has been derived from the nucleon form factor (rms radius b/sub f/) combined with the three-quark wave function (rms radius b/sub q/). The optimization of the model on empirical scattering phase shifts below 300 MeV gives, for a minimum chi 2 , the root-mean-square radii b/sub f/ = b/sub q/ = 0.51 fm and a coupling constant G/sub π/ 2 /4π = 13
International Nuclear Information System (INIS)
Kramer, J. Jr.; Engel, A. Jr.; Stiglbauer, R.; Prayer, L. Jr.; Hajek, P. Jr.; Imhof, H.
1991-01-01
This paper reports on MR imaging which has gained increasing importance as a diagnostic instrument in orthopedics. The key to joint diagnostics - the evaluation of hyaline articular cartilage - however, has not been touched sufficiently by this development. Fundamental studies were done and 140 patients were examined with MR imaging after intraarticular administration of contrast agent. Hyaline cartilage, cruciate ligaments, and menisci were assessed before and after injection of a 2-mmol/L Gd-DTPA solution, and the results were compared with those of arthroscopy/arthrotomy. MR arthrography provided superior image quality compared with plain MR imaging. This resulted in an improved delineation of intraarticular structures, especially of cartilage defects
International Nuclear Information System (INIS)
Schwenzer, N.F.; Stegger, L.; Bisdas, S.; Schraml, C.; Kolb, A.; Boss, A.; Müller, M.
2012-01-01
Objectives: The present work illustrates the current state of image quality and diagnostic accuracy in a new hybrid BrainPET/MR. Materials and methods: 50 patients with intracranial masses, head and upper neck tumors or neurodegenerative diseases were examined with a hybrid BrainPET/MR consisting of a conventional 3T MR system and an MR-compatible PET insert. Directly before PET/MR, all patients underwent a PET/CT examination with either [ 18 F]-FDG, [ 11 C]-methionine or [ 68 Ga]-DOTATOC. In addition to anatomical MR scans, functional sequences were performed including diffusion tensor imaging (DTI), arterial spin labeling (ASL) and proton-spectroscopy. Image quality score of MR imaging was evaluated using a 4-point-scale. PET data quality was assessed by evaluating FDG-uptake and tumor delineation with [ 11 C]-methionine and [ 68 Ga]-DOTATOC. FDG uptake quantification accuracy was evaluated by means of ROI analysis (right and left frontal and temporo-occipital lobes). The asymmetry indices and ratios between frontal and occipital ROIs were compared. Results: In 45/50 patients, PET/MR examination was successful. Visual analysis revealed a diagnostic image quality of anatomical MR imaging (mean quality score T2 FSE: 1.27 ± 0.54; FLAIR: 1.38 ± 0.61). ASL and proton-spectroscopy was possible in all cases. In DTI, dental artifacts lead to one non-diagnostic dataset (mean quality score DTI: 1.32 ± 0.69; ASL: 1.10 ± 0.31). PET datasets of PET/MR and PET/CT offered comparable tumor delineation with [ 11 C]-methionine; additional lesions were found in 2/8 [ 68 Ga]-DOTATOC-PET in the PET/MR. Mean asymmetry index revealed a high accordance between PET/MR and PET/CT (1.5 ± 2.2% vs. 0.9 ± 3.6%; mean ratio (frontal/parieto-occipital) 0.93 ± 0.08 vs. 0.96 ± 0.05), respectively. Conclusions: The hybrid BrainPET/MR allows for molecular, anatomical and functional imaging with uncompromised MR image quality and a high accordance of PET results between PET/MR and PET
Energy Technology Data Exchange (ETDEWEB)
Schwenzer, N.F., E-mail: nina.schwenzer@med.uni-tuebingen.de [Department of Diagnostic and Interventional Radiology, Eberhard-Karls University Tuebingen, Tuebingen (Germany); Stegger, L., E-mail: stegger@gmx.net [Department of Nuclear Medicine and European Institute for Molecular Imaging, University of Muenster, Muenster (Germany); Bisdas, S., E-mail: sbisdas@gmail.com [Department of Diagnostic and Interventional Neuroradiology, Eberhard-Karls University Tuebingen, Tuebingen (Germany); Schraml, C., E-mail: christina.schraml@med.uni-tuebingen.de [Department of Diagnostic and Interventional Radiology, Eberhard-Karls University Tuebingen, Tuebingen (Germany); Kolb, A., E-mail: armin.kolb@med.uni-tuebingen.de [Laboratory for Preclinical Imaging and Imaging Technology of the Werner Siemens-Foundation, Department of Preclinical Imaging and Radiopharmacy, Eberhard-Karls University Tuebingen, Tuebingen (Germany); Boss, A., E-mail: Andreas.Boss@usz.ch [Department of Diagnostic and Interventional Radiology, Eberhard-Karls University Tuebingen, Tuebingen (Germany); Institute of Diagnostic and Interventional Radiology, University Hospital Zuerich, Zuerich (Switzerland); Mueller, M., E-mail: mark.mueller@med.uni-tuebingen.de [Department of Nuclear Medicine, Eberhard-Karls University Tuebingen, Tuebingen (Germany); and others
2012-11-15
Objectives: The present work illustrates the current state of image quality and diagnostic accuracy in a new hybrid BrainPET/MR. Materials and methods: 50 patients with intracranial masses, head and upper neck tumors or neurodegenerative diseases were examined with a hybrid BrainPET/MR consisting of a conventional 3T MR system and an MR-compatible PET insert. Directly before PET/MR, all patients underwent a PET/CT examination with either [{sup 18}F]-FDG, [{sup 11}C]-methionine or [{sup 68}Ga]-DOTATOC. In addition to anatomical MR scans, functional sequences were performed including diffusion tensor imaging (DTI), arterial spin labeling (ASL) and proton-spectroscopy. Image quality score of MR imaging was evaluated using a 4-point-scale. PET data quality was assessed by evaluating FDG-uptake and tumor delineation with [{sup 11}C]-methionine and [{sup 68}Ga]-DOTATOC. FDG uptake quantification accuracy was evaluated by means of ROI analysis (right and left frontal and temporo-occipital lobes). The asymmetry indices and ratios between frontal and occipital ROIs were compared. Results: In 45/50 patients, PET/MR examination was successful. Visual analysis revealed a diagnostic image quality of anatomical MR imaging (mean quality score T2 FSE: 1.27 {+-} 0.54; FLAIR: 1.38 {+-} 0.61). ASL and proton-spectroscopy was possible in all cases. In DTI, dental artifacts lead to one non-diagnostic dataset (mean quality score DTI: 1.32 {+-} 0.69; ASL: 1.10 {+-} 0.31). PET datasets of PET/MR and PET/CT offered comparable tumor delineation with [{sup 11}C]-methionine; additional lesions were found in 2/8 [{sup 68}Ga]-DOTATOC-PET in the PET/MR. Mean asymmetry index revealed a high accordance between PET/MR and PET/CT (1.5 {+-} 2.2% vs. 0.9 {+-} 3.6%; mean ratio (frontal/parieto-occipital) 0.93 {+-} 0.08 vs. 0.96 {+-} 0.05), respectively. Conclusions: The hybrid BrainPET/MR allows for molecular, anatomical and functional imaging with uncompromised MR image quality and a high accordance
MR investigation of recurrent cholesteatomas
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Doyon, D.; Chan, K.Y.; Attia, M.; Halimi, P.; Sigal, R.; Bobin, S.; Sterkers, J.M.
1989-03-01
Nine cases of recurrent petrous cholesteatomas have been studied by a 1.5 T MR unit. Gadolinium was injected in 1 case. In all cases, comparison between MR, CT and clinical findings were made. MR allows for accurate topographic study and assessment of cholesteatomas extension, in particular in the posterior fossa and skull base. Relationships with the internal carotid artery and the jugular vein are clearly depicted.
MR imaging of heterotopic gray matter; Heterotopia istoty szarej mozgu w obrazie MR
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Kryst-Widzgowska, T.; Kozlowski, P.; Poniatowska, R. [Instytut Psychiatrii i Neurologii, Warsaw (Poland)
1994-12-31
Six patients with heterotopic gray matter were evaluated with MR. 5 patients had history of seizures. 4 cases were suspected of the cerebral tumor. In the MR examination areas of heterotopic gray matter were found along the posterior horn of the lateral ventricle on the one side in 4 cases and bilateraly in 2 cases. In 3 cases another brain abnormalities were also detected including: hypoplasia of corpus callosum, hypoplasia of brain hemisphere, cavum septi pellucidi. MR is a modality of choice in the assessment of abnormal gray matter migration. (author). 6 refs, 4 figs.
Serial MR imaging and 1H-MR spectroscopy in monozygotic twins with Tay-Sachs disease.
Imamura, A; Miyajima, H; Ito, R; Orii, K O
2008-10-01
Four-year-old monozygotic female twins with early onset Tay-Sachs disease are described. The sisters showed similar slowly progressive clinical symptoms and deterioration, however the younger sister also demonstrated intractable myoclonus in the right leg. The serial MR images and (1)H-MR spectroscopy of the brain were obtained in both twins. MR images showed high intensity on T (2)-weighted image in the bilateral white matter, however there were no signal changes in the basal ganglia and thalamus during any of the phases. The ratio of N-acetylaspartate (NAA)/creatine (Cr) was decreased in the both white matter lesions and the corpus striatum, and that of myoinositol (mI)/Cr was increased in the damaged white matter on MR spectroscopy. The elevation of the lactate peak was clearly demonstrated in the left basal ganglia of the younger sister; however it was not shown in cerebral lesions of the elder sister. Changes in metabolites on MR spectroscopy were closely linked to the respective clinical features of each twin. Follow-up examination by (1)H-MR spectroscopy is useful for the evaluation of neuronal changes in children with Tay-Sachs disease.
Common injuries related to weightlifting: MR imaging perspective.
Yu, Joseph S; Habib, Paula A
2005-12-01
Weightlifting has evolved to become a ubiquitous form of exercise. Resistance training has been shown to have beneficial effects on both muscle and osseous maintenance and development. Competitive weightlifting sports continue to enjoy tremendous popularity, with participants striving to establish new standards in performance and more demanding personal goals. Thus, it is not surprising that we have also seen an increase in injuries related to weightlifting. Many of these injuries are radiographically occult and are best suited for evaluation by magnetic resonance (MR) imaging because many involve the soft tissues. In this article, we discuss some of the factors that contribute to these injuries and address the mechanisms of injury and the MR imaging manifestations of the more common injuries.
Classification of bones from MR images in torso PET-MR imaging using a statistical shape model
International Nuclear Information System (INIS)
Reza Ay, Mohammad; Akbarzadeh, Afshin; Ahmadian, Alireza; Zaidi, Habib
2014-01-01
There have been exclusive features for hybrid PET/MRI systems in comparison with its PET/CT counterpart in terms of reduction of radiation exposure, improved soft-tissue contrast and truly simultaneous and multi-parametric imaging capabilities. However, quantitative imaging on PET/MR is challenged by attenuation of annihilation photons through their pathway. The correction for photon attenuation requires the availability of patient-specific attenuation map, which accounts for the spatial distribution of attenuation coefficients of biological tissues. However, the lack of information on electron density in the MR signal poses an inherent difficulty to the derivation of the attenuation map from MR images. In other words, the MR signal correlates with proton densities and tissue relaxation properties, rather than with electron density and, as such, it is not directly related to attenuation coefficients. In order to derive the attenuation map from MR images at 511 keV, various strategies have been proposed and implemented on prototype and commercial PET/MR systems. Segmentation-based methods generate an attenuation map by classification of T1-weighted or high resolution Dixon MR sequences followed by assignment of predefined attenuation coefficients to various tissue types. Intensity-based segmentation approaches fail to include bones in the attenuation map since the segmentation of bones from conventional MR sequences is a difficult task. Most MR-guided attenuation correction techniques ignore bones owing to the inherent difficulties associated with bone segmentation unless specialized MR sequences such as ultra-short echo (UTE) sequence are utilized. In this work, we introduce a new technique based on statistical shape modeling to segment bones and generate a four-class attenuation map. Our segmentation approach requires a torso bone shape model based on principle component analysis (PCA). A CT-based training set including clearly segmented bones of the torso region
Breast cancer staging with MR imaging
International Nuclear Information System (INIS)
Smathers, R.L.; D'Amelio, F.; Stockdale, F.
1989-01-01
Forty-three patients with biopsy-proved breast cancer underwent MR staging of the cervicothoracic spine, lumbosacral spine, liver, and thorax. In all cases, these findings have been compared with the results of clinical staging, laboratory tests, chest radiography, and radionuclide bone scanning. MR imaging was a valuable staging tool for patients with more than minimal breast cancer and indications for radionuclide bone scanning. MR imaging had the greatest clinical importance when it identified thoracic soft-tissue abnormalities, including axillary., lateral thoracic, supraclavicular, and mediastinal lymphadenopathy. The coronal and sagittal views were very valuable for detection of chest wall invasion, sternal involvement, and internal mammary adenopathy. Negative MR staging clinically reassured patients that aggressive local therapy bad curative potential. Positive MR staging avoided inappropriate aggressive local therapy and mastectomy. MR imaging can be recommended for improved breast cancer staging in patients with newly diagnosed breast cancer who have more than minimal disease
The importance of social exchange to nurses and nurse assistants: impact on retention factors.
Trybou, Jeroen; De Pourcq, Kaat; Paeshuyse, Michel; Gemmel, Paul
2014-07-01
The purpose of this study was to test the norm of reciprocity by examining relationships between perceived organisational support (POS), the quality of leader-member exchange (LMX) and psychological contract breach (PCB) and important nurse retention factors identified in the literature. A major cause of turnover among nurses is related to unsatisfying workplaces. Previous research, mainly outside the nursing setting, found that social exchange affects employees' work-related attitudes. A cross-sectional survey was conducted on 217 nurses and nursing assistants to test and refine a model linking POS, LMX, PCB with job satisfaction, trust and turnover intentions. Hierarchical multiple linear regression revealed that POS, PCB and LMX explained significant variance in all three retention factors: job satisfaction (adjusted R² = 0.502), trust (adjusted R² = 0.462) and turnover intentions (adjusted R² = 0.196). POS and PCB predicted most strongly job satisfaction (P < 0.001) and trust (P < 0.001 and P < 0.01, respectively). LMX predicted most strongly intention to leave (P < 0.01). In our study, POS, the quality of LMX and PCB were strongly related to job satisfaction, trust and turnover intentions. Nursing managers and leaders should recognize the importance of social exchange within their organisation to build trust, satisfy and retain scarce nurses and nursing assistants. © 2013 John Wiley & Sons Ltd.
Zhang, Jingbo; Hricak, Hedvig; Shukla-Dave, Amita; Akin, Oguz; Ishill, Nicole M; Carlino, Lauren J; Reuter, Victor E; Eastham, James A
2009-11-01
To assess the diagnostic accuracy of endorectal magnetic resonance (MR) imaging and MR spectroscopic imaging for prediction of the pathologic stage of prostate cancer and the presence of clinically nonimportant disease in patients with clinical stage T1c prostate cancer. The institutional review board approved-and waived the informed patient consent requirement for-this HIPAA-compliant study involving 158 patients (median age, 58 years; age range, 40-76 years) who had clinical stage T1c prostate cancer, had not been treated preoperatively, and underwent combined 1.5-T endorectal MR imaging-MR spectroscopic imaging between January 2003 and March 2004 before undergoing radical prostatectomy. On the MR images and combined endorectal MR-MR spectroscopic images, two radiologists retrospectively and independently rated the likelihood of cancer in 12 prostate regions and the likelihoods of extracapsular extension (ECE), seminal vesicle invasion (SVI), and adjacent organ invasion by using a five-point scale, and they determined the probability of clinically nonimportant prostate cancer by using a four-point scale. Whole-mount step-section pathology maps were used for imaging-pathologic analysis correlation. Receiver operating characteristic curves were constructed and areas under the curves (AUCs) were estimated nonparametrically for assessment of reader accuracy. At surgical-pathologic analysis, one (0.6%) patient had no cancer; 124 (78%) patients, organ-confined (stage pT2) disease; 29 (18%) patients, ECE (stage pT3a); two (1%) patients, SVI (stage pT3b); and two (1%) patients, bladder neck invasion (stage pT4). Forty-six (29%) patients had a total tumor volume of less than 0.5 cm(3). With combined MR imaging-MR spectroscopic imaging, the two readers achieved 80% accuracy in disease staging and AUCs of 0.62 and 0.71 for the prediction of clinically nonimportant cancer. Clinical stage T1c prostate cancers are heterogeneous in pathologic stage and volume. MR imaging may
Directory of Open Access Journals (Sweden)
Shakizada Uteulievna Niyazbekova
2016-12-01
Full Text Available This article describes the influence of macroeconomic factors on Kazakhstan Stock Exchange Market by using data from 2005 to 2014. Engle-Granger cointegration test has shown that stock index is cointegrated with the exchange rate, interest rate, CPI and oil price. Vector error correction model has confirmed that macroeconomic variables and the stock index has a long-term equilibrium relationship. Moreover, empirical results have shown that stock index can be used as a leading indicator of the economic situation in Kazakhstan. Therefore, the authors decided to consider the impact of major macroeconomic indicators to the dynamics of the stock market of the Republic of Kazakhstan. The Engle-Granger cointegration test results show that the following variables such as exchange rate, 10-years long-term bond rate, the consumer price index and the Brent oil price are cointegrated with stock index, which means that there is a long-term relationship between this stock market index and these variables. With the help of econometric models, the authors have found the factors such as the exchange rate, the 10-year long-term bonds rate, the consumer price index and the Brent oil price (these factors have the long-term relationship with stock market index. Changes in the dynamics of the stock market index in Kazakhstan are caused by changes in the dynamics of Central bank's reserves and export. The analysis has shown that the economy of the Republic of Kazakhstan (the index reflects the situation in the real sector of the economy remains dependent on world oil prices, the volume of exports and the rate of the national currency
International Nuclear Information System (INIS)
Ecklund, K.; Jaramillo, D.; Doria, A.S.
1999-01-01
Background. The pathologic changes at the physis in patients with rickets have been well demonstrated histologically. Radiographs can depict only the associated osseous abnormalities. Patients and methods. We report two children in whom MR imaging demonstrated rachitic changes in the physeal cartilage beyond the well-recognized bony features. Results. The striking appearance of the physes and the physes of the secondary ossification centers confirm that MR imaging can successfully evaluate the cartilaginous structures of the developing skeleton. Conclusion. Though MR imaging is clearly unnecessary for the diagnosis of rickets, it is important that the typical features are not misinterpreted as other pathology. (orig.)
DEFF Research Database (Denmark)
Balyasnikova, Svetlana; Löfgren, Johan; de Nijs, Robin
2012-01-01
of the challenges inherent in this new technology, but focus on potential applications for simultaneous PET/MR in the field of oncology. Methods and tracers for use with the PET technology will be familiar to most readers of this journal; thus this paper aims to provide a short and basic introduction to a number...... be applied together with PET increasing the amount of information about the tissues of interest. The potential clinical benefit of applying PET/MR in staging, radiotherapy planning and treatment evaluation in oncology, as well as the research perspectives for the use of PET/MR in the development of new...
MR investigation of recurrent cholesteatomas
International Nuclear Information System (INIS)
Doyon, D.; Chan, K.Y.; Attia, M.; Halimi, P.; Sigal, R.; Bobin, S.; Sterkers, J.M.
1989-01-01
Nine cases of recurrent petrous cholesteatomas have been studied by a 1.5 T MR unit. Gadolinium was injected in 1 case. In all cases, comparison between MR, CT and clinical findings were made. MR allows for accurate topographic study and assessment of cholesteatomas extension, in particular in the posterior fossa and skull base. Relationships with the internal carotid artery and the jugular vein are clearly depicted [fr
Czech Academy of Sciences Publication Activity Database
Marek, Michal V.; Janouš, Dalibor; Taufarová, Klára; Havránková, Kateřina; Pavelka, Marian; Kaplan, Věroslav; Marková, I.
2011-01-01
Roč. 159, č. 5 (2011), s. 1035-1039 ISSN 0269-7491 R&D Projects: GA MŽP(CZ) SP/1A6/108/07; GA MŠk 2B06068 Institutional research plan: CEZ:AV0Z60870520 Keywords : carbon fluxes * net ecosystem exchange * spruce forest * beech forest * Grassland * agroecosystem * wetland * climate factors Subject RIV: EH - Ecology, Behaviour Impact factor: 3.746, year: 2011
MR imaging of pituitary dwarfism
International Nuclear Information System (INIS)
Kashimada, Akio; Machida, Kikuo; Honda, Norinari; Mamiya, Toshio; Takahashi, Taku; Kamano, Tsuyoshi; Muramatsu, Masayuki; Inoue, Yusuke
1993-01-01
Pituitary MR imaging was performed in 32 patients with clinically diagnosed pituitary dwarfism and 12 normal controls. The patients were divided into two groups according to the severity of pituitary dwarfism based on endocrinological data. The two patients with severe dwarfism showed transection of the pituitary stalk, ectopic posterior lobe and atrophy of the anterior lobe on MR imaging, while the 27 patients with mild dwarfism showed no abnormal MR findings of the pituitary gland. The former group corresponds to typical pituitary dwarfism and the latter to partial GH deficiency, which was recently proposed as another type of pituitary dwarfism. In conclusion, pituitary MR imaging may differentiate partial GH deficiency from typical (stalk-transected) pituitary dwarfism. (author)
MR imaging of pituitary dwarfism
Energy Technology Data Exchange (ETDEWEB)
Kashimada, Akio; Machida, Kikuo; Honda, Norinari; Mamiya, Toshio; Takahashi, Taku; Kamano, Tsuyoshi; Muramatsu, Masayuki; Inoue, Yusuke (Saitama Medical School, Kawagoe (Japan). Medical Center)
1993-02-01
Pituitary MR imaging was performed in 32 patients with clinically diagnosed pituitary dwarfism and 12 normal controls. The patients were divided into two groups according to the severity of pituitary dwarfism based on endocrinological data. The two patients with severe dwarfism showed transection of the pituitary stalk, ectopic posterior lobe and atrophy of the anterior lobe on MR imaging, while the 27 patients with mild dwarfism showed no abnormal MR findings of the pituitary gland. The former group corresponds to typical pituitary dwarfism and the latter to partial GH deficiency, which was recently proposed as another type of pituitary dwarfism. In conclusion, pituitary MR imaging may differentiate partial GH deficiency from typical (stalk-transected) pituitary dwarfism. (author).
MR imaging of breast implants.
Gorczyca, D P
1994-11-01
MR imaging has proved to be an excellent imaging modality in locating free silicone and evaluating an implant for rupture, with a sensitivity of approximately 94% and specificity of 97%. Silicone has a unique MR resonance frequency and long T1 and T2 relaxation times, which allows several MR sequences to provide excellent diagnostic images. The most commonly used sequences include T2-weighted, STIR, and chemical shift imaging (Figs. 3, 13, and 14). The T2-weighted and STIR sequences are often used in conjunction with chemical water suppression. The most reliable findings on MR images for detection of implant rupture include identification of the collapsed implant shell (linguine sign) and free silicone within the breast parenchyma.
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Noguchi, Tomoyuki, E-mail: tnogucci@radiol.med.kyushu-u.ac.jp [Department of Radiology, Faculty of Medicine, Saga University, 5-1-1, Nabeshima, Saga 849-8501 (Japan); Kawashima, Masatou [Department of Neurosurgery, Faculty of Medicine, Saga University, 5-1-1, Nabeshima, Saga 849-8501 (Japan); Nishihara, Masashi; Hirai, Tetsuyoshi [Department of Radiology, Faculty of Medicine, Saga University, 5-1-1, Nabeshima, Saga 849-8501 (Japan); Matsushima, Toshio [Department of Neurosurgery, Faculty of Medicine, Saga University, 5-1-1, Nabeshima, Saga 849-8501 (Japan); Irie, Hiroyuki [Department of Radiology, Faculty of Medicine, Saga University, 5-1-1, Nabeshima, Saga 849-8501 (Japan)
2013-12-01
Purpose: Our purpose was to identify the causal factors for the perfusion distribution obtained with ASL-MRI by comparing ASL-MRI with clinical information and other MRI findings in moyamoya disease. Methods: Seventy-one patients with moyamoya disease underwent ASL-MRI and other MRI, including fluid-attenuated inversion recovery imaging (FLAIR) and three-dimensional time-of-flight magnetic resonance angiography (MRA) on 3.0-Tesla MRI system. Cerebral blood flow (CBF) values (ASL values) for the cerebral hemispheres (142 sides) were measured on CBF maps generated by ASL-MRI. Relationships between the ASL values and the following 9 factors were assessed: sex, family history, revascularization surgery, age at MR exam, age at onset, the steno-occlusive severity on MRA (MRA score), degree of basal collaterals, degree of leptomeningeal high signal intensity seen on FLAIR, and size of ischemic or hemorrhagic cerebrovascular accident lesion (CVA score). Results: Patients with a family history had significantly higher ASL values than those without such a history. There were significant negative correlations between ASL values and age at MR exam, MRA score, and CVA score. Conclusions: ASL-MRI may have cause-and-effect or mutual associations with family history, current patient age, size of CVA lesion, and intracranial arterial steno-occlusive severity in Moyamoya disease.
International Nuclear Information System (INIS)
Noguchi, Tomoyuki; Kawashima, Masatou; Nishihara, Masashi; Hirai, Tetsuyoshi; Matsushima, Toshio; Irie, Hiroyuki
2013-01-01
Purpose: Our purpose was to identify the causal factors for the perfusion distribution obtained with ASL-MRI by comparing ASL-MRI with clinical information and other MRI findings in moyamoya disease. Methods: Seventy-one patients with moyamoya disease underwent ASL-MRI and other MRI, including fluid-attenuated inversion recovery imaging (FLAIR) and three-dimensional time-of-flight magnetic resonance angiography (MRA) on 3.0-Tesla MRI system. Cerebral blood flow (CBF) values (ASL values) for the cerebral hemispheres (142 sides) were measured on CBF maps generated by ASL-MRI. Relationships between the ASL values and the following 9 factors were assessed: sex, family history, revascularization surgery, age at MR exam, age at onset, the steno-occlusive severity on MRA (MRA score), degree of basal collaterals, degree of leptomeningeal high signal intensity seen on FLAIR, and size of ischemic or hemorrhagic cerebrovascular accident lesion (CVA score). Results: Patients with a family history had significantly higher ASL values than those without such a history. There were significant negative correlations between ASL values and age at MR exam, MRA score, and CVA score. Conclusions: ASL-MRI may have cause-and-effect or mutual associations with family history, current patient age, size of CVA lesion, and intracranial arterial steno-occlusive severity in Moyamoya disease
International Nuclear Information System (INIS)
Mitsui, Hideaki; Saito, Haruo; Ishibashi, Tadashi; Takahashi, Shoki; Zuguchi, Masayuki; Yamada, Shogo
2002-01-01
We evaluated the accuracy of Whole Heart Cine (WHC) magnetic resonance (MR) imaging in the depiction of pulmonary veins (PVs) in patients with congenital heart disease (CHD) compared to that of spin echo (SE) MR imaging. Among our 35 patients, 4 patients had anomalous PV return. Detectability of four PVs on each MR examination images were evaluated. MR imaging is an effective modality for the clarification of PVs, and WHC MR imaging is more useful in delineating PV anomalies than SE MR imaging. (author)
MR and CT for malignant hypernephromas
International Nuclear Information System (INIS)
Uhlenbrock, D.; Fischer, C.; Ruehl, G.; Beyer, H.K.; Hummelsheim, P.; Bochum Univ.; Marienhospital, Herne; Bochum Univ.
1987-01-01
Forty patients with histologically confirmed hypernephromas were examined by MR and CT. As regards T-staging, MR had an accuracy of 97 % and CT of 91%; for N-staging, MR had an accuracy of 85% and CT of 91% and, with regard to infiltration of the renal vein, MR was correct in 88% of cases and CT in 81%. MR was most accurate in the pre-operative assessment of tumour spread, demonstrating caval involvement in 100% and lymph node metastases in 97%. On the other hand, infiltration of the renal pelvis could be assessed in only 65% of cases; in 27% the assessment was not possible and in 8% one could not be certain. CT proved to be at its best for staging of lymph nodes, but in 15% it was not possible to identify infiltration of the renal vein. MR was not greatly superior to CT in the preoperative diagnosis and staging of hypernephromas. (orig.) [de
Fast high-resolution MR imaging using the snapshot-FLASH MR sequence
International Nuclear Information System (INIS)
Matthaei, D.; Haase, A.; Henrich, D.; Duhmke, E.
1990-01-01
Snapshot, fast low-angle short (FLASH) MR imaging using an accelerated FLASH-MR sequence provides MR images with measuring times far below 1 second. The short TE of this sequence prevents susceptibility artifacts in gradient-echo imaging. In this paper variations of the sequence are shown that provide high resolution images with T1-weighted IR, T2-weighted SE, and chemical shift (CHESS) contrast sequences. METHODS AND MATERIALS: A whole-body 2-T system (Bruker-Medizintechnik) were used in combination with a 60-cm gradient system (providing gradient strength of 5 mT/m) to study healthy volunteers. The measuring time for a 256 x 256 image matrix was 800 msec. This sequence has been used in combination with T1-weighted IR, T2-weighted SE, and CHESS variations
MR-guided direct arthrography of the glenohumeral joint
International Nuclear Information System (INIS)
Soh, E.; Bearcroft, P.W.P.; Graves, M.J.; Black, R.; Lomas, D.J.
2008-01-01
Aim: To evaluate the feasibility of magnetic resonance (MR)-guided direct arthrography of the glenohumeral joint with a 1.5 T MR system, performing the entire procedure in a single MR examination. Materials and methods: MR-guided direct arthrography was performed on 11 patients. MR imaging guidance and interactive MR fluoroscopy, with in-room control and display system, were used for needle placement and contrast medium injection. The outcome measures were success or failure of joint puncture, the time taken for introduction of contrast medium, and the diagnostic quality of the subsequent MR arthrography images. Results: Contrast medium was successfully instilled into the joint and diagnostic quality MR arthrography images were obtained in all cases. The median time from initial placement of the skin marker to introduction of the contrast medium was 17 min (range 11-29 min). There were no immediate post-procedure complications. Conclusion: Accurate needle placement is feasible in a single MR examination on a commercial 1.5 T closed-bore MR system, using an in-room control and display system together with interactive fluoroscopic imaging, and this was used to provide direct MR arthrography in this study
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Hattingen, E.; Raab, P.; Lanfermann, H.; Zanella, F.E.; Weidauer, S. [Johann-Wolfgang-Goethe-Universitaet Frankfurt/Main, Institut fuer Neuroradiologie, Frankfurt (Germany)
2008-11-15
Postictal MR findings are analyzed in the context of MR morphological differential diagnoses. Postictal MRI was performed in 11 patients. The patterns of MR changes and their differential diagnoses were analyzed. Focal accentuation of signal increase in the cortex was found on T2-weighted images in 90% of these cases, pial enhancement in 70% and signal changes of the pulvinar/thalamus in 40%. The most common differential diagnoses were encephalitis, and in tumor patients carcinomatous involvement of the meninges. Postictal MR changes vary widely and are difficult to differentiate from illnesses such as encephalitis and carcinomatosis involving the meninges. Nevertheless, knowledge of the typical pattern of postictal MR findings and the clinical course may help to avoid mistaken diagnoses. (orig.) [German] Postiktale MR-Veraenderungen werden im Kontext ihrer Differenzialdiagnosen analysiert. Elf Patienten wurden postiktal im MRT untersucht. Ausgewertet wurden die MR-tomographischen Befundmuster und ihre Differenzialdiagnosen. Bei 90% der Patienten fanden sich fokale kortikal betonte Signalsteigerungen in der T2-Wichtung, bei 90% Diffusionseinschraenkungen, bei 70% piale Anreicherungen und bei 40% Signalalterationen des Pulvinars/Thalamus. Haeufigste Differenzialdiagnosen waren die Enzephalitis und bei entsprechender Tumoranamnese die Meningeosis carcinomatosa. Postiktale MR-Veraenderungen sind vielgestaltig und nicht immer leicht von Erkrankungen wie insbesondere der Enzephalitis oder der Meningeosis carcinomatosa zu unterscheiden. Dennoch helfen die Kenntnis typischer postiktaler Befallsmuster und der klinische Verlauf, Fehldiagnosen zu vermeiden. (orig.)
International Nuclear Information System (INIS)
Wu Honglin; Chen Junkun; Zhang Zongjun; Lu Guangming; Chen Ziqian; Wang Wei; Ji Xueman; Tang Xiaojun; Li Lin
2005-01-01
Objective: To compare the accuracy of MR imaging scores with MR perfusion imaging in pre-operative grading of intracranial gliomas. Methods: Thirty patients with intracranial gliomas (8 low-grade and 22 high-grade, according to WHO criteria) were examined with MR perfusion imaging pre-operatively. The lesions were evaluated by using an MR imaging score based on nine criteria. rCBV of the lesions were calculated by comparing the CBV of the lesion and that of contralateral normal white matter. The scores and ratios in high-grade and low-grade tumours were compared. Results: The MR imaging score of low grade (grades I and II) gliomas (0.67±0.29) were significantly lower than that of grades III (1.32 ± 0.47) (t=-3.48, P=0.003) and IV (1.56 ± 0.20) (t=-7.36, P=0.000) gliomas. There was no statistical difference when MR imaging scores of grades III and IV gliomas (t=-1.39, P=0.182) were compared. The maximum rCBV ratio of low grade (grades I and II) gliomas (2.38 ± 0.66 ) were significantly lower than that of grades III (5.81 ± 3.20) (t=-3.57, P=0.003) and IV (6.99 ± 2.47) (t=-5.09, P=0.001). There was no statistical difference when rCBV ratios of grades III and IV (t =-0.93, P=0.365) gliomas were compared. The accuracy of MR imaging scores in the noninvasive grading of untreated gliomas was all most the same as that of MR perfusion imaging (90.00% vs 89.29%). Conclusion: The MR imaging scores and MR perfusion imaging are two very useful tools in the evaluation of the histopathologic grade of cerebral gliomas. The overall accuracy in the noninvasive grading of gliomas may be imp roved if MR imaging scores and MR perfusion imaging are combined. (authors)
Theory and design of heat exchanger : air cooled plate, spiral heat exchanger
International Nuclear Information System (INIS)
Min, Ui Dong
1960-02-01
This book deals with air cooled heat exchanger, which introduces heat rejection system, wet surface cooler in new from, explanation of structure and design, materials, basic design like plenums chambers and fan ring, finned tube fouling factor, airflow in forced draft and fan design. It also tells of plate heat exchanger and spiral heat exchanger giving descriptions of summary, selection, basic design, device and safety function, maintenance, structure of plate heat exchanger, frames and connector plate and, basic things of spiral tube heat exchanger.
MR imaging of persistent primitive trigeminal artery
International Nuclear Information System (INIS)
Ashikaga, Ryuichiro; Araki, Yutaka; Ono, Yukihiko; Ishida, Osamu; Mabuchi, Nobuhisa.
1997-01-01
The persistent trigeminal artery is the most common anomaly of the primitive carotid-vertebrobasilar anastomoses. We reviewed MR images and MR angiographies of 11 patients with primitive trigeminal artery. In 8 of the 11 cases, PTA were identified with conventional long TR spin-echo images. In 8 of 11 cases, a hypoplastic basilar trunk associated with PTA was seen on both MR images and MR angiographies. In 7 of 11 cases, a hypoplasia or agenesis of the ipsilateral posterior communicating artery was seen on MR angiographies. (author)
77 FR 65545 - Mr. Jesse S. Capel and Mr. Hilton J. Cochran; EWP LLC; Notice of Transfer of Exemption
2012-10-29
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 4815-009] Mr. Jesse S. Capel and Mr. Hilton J. Cochran; EWP LLC; Notice of Transfer of Exemption 1. By application filed on July 30, 2012 and supplemented on August 14, 2012, Mr. Jesse S. Capel and Mr. Hilton J. Cochran and EWP...
MAHMOOD, UMAR; JOSEPHSON, LEE
2005-01-01
Magnetic resonance imaging (MRI) has been successfully applied to many of the applications of molecular imaging. This review discusses by example some of the advances in areas such as multimodality MR-optical agents, receptor imaging, apoptosis imaging, angiogenesis imaging, noninvasive cell tracking, and imaging of MR marker genes.
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Staatz, G.; Nolte-Ernsting, C.C.A.; Haage, P.; Tacke, J.; Guenther, R.W. [Technische Hochschule Aachen (Germany). Klinik fuer Radiologische Diagnostik; Rohrmann, D. [Technische Hochschule Aachen (Germany). Urologische Klinik; Stollbrink, C. [Technische Hochschule Aachen (Germany). Kinderklinik
2001-11-01
Purpose: To evaluate gadolinium-enhanced T{sub 1}-weighted excretory MR urography (EMRU) versus T{sub 2}-weighted (HASTE) MR urography in children with upper urinary tract abnormalities. Patients and Methods: In a prospective study 63 children, aged from 3 weeks to 15 years, underwent MR urography in a 1.5-T scanner. Before and after an intravenous injection of 0.05 mg/kg body weight of furosemide, respiratory-triggered HASTE images were obtained for T{sub 2}-weighted MR urography. EMRU was performed subsequent to i.v. gadolinium injection with respiratory-gated, coronal 3D-gradient-echo sequences. Results: Compared to T{sub 2}-weighted (HASTE) MR urography, gadolinium-enhanced MR urography revealed a superior diagnostic accuracy in non-dilated collecting systems (horseshoe kidneys, ectopic kidneys, duplex systems, single ectopic ureters, ureteroceles). EMRU and T{sub 2}-weighted (HASTE) MRU turned out to be equivalent in the assessment of obstructed but normal functioning upper urinary tracts (UPJ obstructions, megaureters). Non-functioning dilated collecting systems and multicystic dysplastic kidneys were best visualized with use of T{sub 2}-weighted (HASTE) MR urography. Conclusion: Respiratory-gated gadolinium-enhanced T{sub 1}-weighted MRU allows accurate evaluation of most upper urinary tract abnormalities. T{sub 2}-weighted (HASTE) MRU complements GMRU in the evaluation of non-functioning renal units and cystic disease of the kidneys. (orig.) [German] Ziel: Vergleich der kontrastangehobenen T{sub 1}-gewichteten MR-Urographie mit der T{sub 2}-gewichteten (HASTE) MR-Urographie bei Kindern mit Anomalien des oberen Harntraktes. Methoden: In einer prospektiven Studie wurde bei 63 Kindern (3 Wo. - 15J.) eine MR-Urographie (MRU) in einem 1,5-Tesla-Magneten durchgefuehrt. Die T{sub 2}-gewichtete MRU erfolgte vor und nach intravenoeser Injektion von 0,05 mg/kg KG Furosemid mit atemgetriggerten HASTE-Sequenzen. Fuer die T{sub 1}-gewichtete MRU wurden nach
MR-based field-of-view extension in MR/PET: B0 homogenization using gradient enhancement (HUGE).
Blumhagen, Jan O; Ladebeck, Ralf; Fenchel, Matthias; Scheffler, Klaus
2013-10-01
In whole-body MR/PET, the human attenuation correction can be based on the MR data. However, an MR-based field-of-view (FoV) is limited due to physical restrictions such as B0 inhomogeneities and gradient nonlinearities. Therefore, for large patients, the MR image and the attenuation map might be truncated and the attenuation correction might be biased. The aim of this work is to explore extending the MR FoV through B0 homogenization using gradient enhancement in which an optimal readout gradient field is determined to locally compensate B0 inhomogeneities and gradient nonlinearities. A spin-echo-based sequence was developed that computes an optimal gradient for certain regions of interest, for example, the patient's arms. A significant distortion reduction was achieved outside the normal MR-based FoV. This FoV extension was achieved without any hardware modifications. In-plane distortions in a transaxially extended FoV of up to 600 mm were analyzed in phantom studies. In vivo measurements of the patient's arms lying outside the normal specified FoV were compared with and without the use of B0 homogenization using gradient enhancement. In summary, we designed a sequence that provides data for reducing the image distortions due to B0 inhomogeneities and gradient nonlinearities and used the data to extend the MR FoV. Copyright © 2011 Wiley Periodicals, Inc.
International Nuclear Information System (INIS)
Zhou, Nan; Chu, Chen; Dou, Xin; Li, Ming; Liu, Song; Zhu, Lijing; Liu, Baorui; Guo, Tingting; Chen, Weibo; He, Jian; Yan, Jing; Zhou, Zhengyang; Yang, Xiaofeng; Liu, Tian
2016-01-01
Radiation-induced parotid damage is one of the most common complications in patients with nasopharyngeal carcinoma (NPC) undergoing radiotherapy (RT). Intravoxel incoherent motion (IVIM) magnetic resonance (MR) imaging has been reported for evaluating irradiated parotid damage. However, the changes of IVIM perfusion-related parameters in irradiated parotid glands have not been confirmed by conventional perfusion measurements obtained from dynamic contrast-enhanced (DCE) MR imaging. The purposes of this study were to monitor radiation-induced parotid damage using IVIM and DCE MR imaging and to investigate the correlations between changes of these MR parameters. Eighteen NPC patients underwent bilateral parotid T1-weighted, IVIM and DCE MR imaging pre-RT (2 weeks before RT) and post-RT (4 weeks after RT). Parotid volume; IVIM MR parameters, including apparent diffusion coefficient (ADC), pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f); and DCE MR parameters, including maximum relative enhancement (MRE), time to peak (TTP), Wash in Rate, and the degree of xerostomia were recorded. Correlations of parotid MR parameters with mean radiation dose, atrophy rate and xerostomia degree, as well as the relationships between IVIM and DCE MR parameters, were investigated. From pre-RT to post-RT, all of the IVIM and DCE MR parameters increased significantly (p < 0.001 for ADC, D, f, MRE, Wash in Rate; p = 0.024 for D*; p = 0.037 for TTP). Change rates of ADC, f and MRE were negatively correlated with atrophy rate significantly (all p < 0.05). Significant correlations were observed between the change rates of D* and MRE (r = 0.371, p = 0.026) and between the change rates of D* and TTP (r = 0.396, p = 0.017). The intra- and interobserver reproducibility of IVIM and DCE MR parameters was good to excellent (intraclass correlation coefficient, 0.633–0.983). Early radiation-induced changes of parotid glands could be evaluated by IVIM and
Ma, Yan-Qing; Venugopalan, Raju; Watanabe, Kazuhiro; Zhang, Hong-Fei
2018-01-01
We argue that the large suppression of the ψ (2 S ) inclusive cross section relative to the J /ψ inclusive cross section in proton-nucleus (p+A) collisions can be attributed to factorization breaking effects in the formation of quarkonium. These factorization breaking effects arise from soft color exchanges between charm-anticharm pairs undergoing hadronization and comoving partons that are long lived on time scales of quarkonium formation. We compute the short distance pair production of heavy quarks in the color glass condensate (CGC) effective field theory and employ an improved color evaporation model (ICEM) to describe their hadronization into quarkonium at large distances. The combined CGC+ICEM model provides a quantitative description of J /ψ and ψ (2 S ) data in proton-proton (p+p) collisions from both RHIC and the LHC. Factorization breaking effects in hadronization, due to additional parton comovers in the nucleus, are introduced heuristically by imposing a cutoff Λ , representing the average momentum kick from soft color exchanges, in the ICEM. Such soft exchanges have no perceptible effect on J /ψ suppression in p+A collisions. In contrast, the interplay of the physics of these soft exchanges at large distances, with the physics of semihard rescattering at short distances, causes a significant additional suppression of ψ (2 S ) yields relative to that of the J /ψ . A good fit of all RHIC and LHC J /ψ and ψ (2 S ) data, for transverse momenta P⊥≤5 GeV in p+p and p+A collisions, is obtained for Λ ˜10 MeV.
Energy Technology Data Exchange (ETDEWEB)
Ecklund, K.; Jaramillo, D. [Department of Radiology, Children`s Hospital, Boston, MA (United States); Doria, A.S. [Department of Radiology, Instituto da Crianca - Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo (Brazil)
1999-09-01
Background. The pathologic changes at the physis in patients with rickets have been well demonstrated histologically. Radiographs can depict only the associated osseous abnormalities. Patients and methods. We report two children in whom MR imaging demonstrated rachitic changes in the physeal cartilage beyond the well-recognized bony features. Results. The striking appearance of the physes and the physes of the secondary ossification centers confirm that MR imaging can successfully evaluate the cartilaginous structures of the developing skeleton. Conclusion. Though MR imaging is clearly unnecessary for the diagnosis of rickets, it is important that the typical features are not misinterpreted as other pathology. (orig.) With 6 figs., 6 refs.
Sun, Ying-Jie; Nishikawa, Kaori; Yuda, Hideki; Wang, Yu-Lai; Osaka, Hitoshi; Fukazawa, Nobuna; Naito, Akira; Kudo, Yoshihisa; Wada, Keiji; Aoki, Shunsuke
2006-09-01
With DNA microarrays, we identified a gene, termed Solo, that is downregulated in the cerebellum of Purkinje cell degeneration mutant mice. Solo is a mouse homologue of rat Trio8-one of multiple Trio isoforms recently identified in rat brain. Solo/Trio8 contains N-terminal sec14-like and spectrin-like repeat domains followed by a single guanine nucleotide exchange factor 1 (GEF1) domain, but it lacks the C-terminal GEF2, immunoglobulin-like, and kinase domains that are typical of Trio. Solo/Trio8 is predominantly expressed in Purkinje neurons of the mouse brain, and expression begins following birth and increases during Purkinje neuron maturation. We identified a novel C-terminal membrane-anchoring domain in Solo/Trio8 that is required for enhanced green fluorescent protein-Solo/Trio8 localization to early endosomes (positive for both early-endosome antigen 1 [EEA1] and Rab5) in COS-7 cells and primary cultured neurons. Solo/Trio8 overexpression in COS-7 cells augmented the EEA1-positive early-endosome pool, and this effect was abolished via mutation and inactivation of the GEF domain or deletion of the C-terminal membrane-anchoring domain. Moreover, primary cultured neurons transfected with Solo/Trio8 showed increased neurite elongation that was dependent on these domains. These results suggest that Solo/Trio8 acts as an early-endosome-specific upstream activator of Rho family GTPases for neurite elongation of developing Purkinje neurons.
Variable stiffness and damping MR isolator
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Zhang, X Z; Wang, X Y; Li, W H; Kostidis, K [University of Wollongong, School of Mechanical, Materials and Mechatronic Engineering, NSW 2522 (Australia)], E-mail: weihuali@uow.edu.au
2009-02-01
This paper presents the development of a magnetorheological (MR) fluid-based variable stiffness and damping isolator for vibration suppressions. The MR fluid isolator used a sole MR control unit to achieve the variable stiffness and damping in stepless and relative large scope. A mathematical model of the isolator was derived, and a prototype of the MR fluid isolator was fabricated and its dynamic behavior was measured in vibration under various applied magnetic fields. The parameters of the model under various magnetic fields were identified and the dynamic performances of isolator were evaluated.
MR imaging of hemimegalencephaly in children
International Nuclear Information System (INIS)
Kalifa, G.; Sellier, N.; Demange, P.; Ponsot, G.; Chiron, C.; Robain, O.
1986-01-01
Hemimegalencephaly is a rare brain malformation characterized by cerebral asymmetry and cortical dysplasia. Affected infants are seen initially with early seizures and a severe encephalopathy. The author report five new cases studied with MR imaging. MR imaging clearly demonstrated brain hemihypertrophy, abnormal gyration, and poor differentiation between gray and white matter. A highly abnormal disposition of the cellular layers was observed. MR imaging turned out to be the most efficient diagnostic method for hemimegalencephaly. The examination may facilitate understanding and classification of this rare entity. Autopsy findings correlated well with MR imaging appearances
Minimizing Back Exchange in the Hydrogen Exchange-Mass Spectrometry Experiment
Walters, Benjamin T.; Ricciuti, Alec; Mayne, Leland; Englander, S. Walter
2012-12-01
The addition of mass spectrometry (MS) analysis to the hydrogen exchange (HX) proteolytic fragmentation experiment extends powerful HX methodology to the study of large biologically important proteins. A persistent problem is the degradation of HX information due to back exchange of deuterium label during the fragmentation-separation process needed to prepare samples for MS measurement. This paper reports a systematic analysis of the factors that influence back exchange (solution pH, ionic strength, desolvation temperature, LC column interaction, flow rates, system volume). The many peptides exhibit a range of back exchange due to intrinsic amino acid HX rate differences. Accordingly, large back exchange leads to large variability in D-recovery from one residue to another as well as one peptide to another that cannot be corrected for by reference to any single peptide-level measurement. The usual effort to limit back exchange by limiting LC time provides little gain. Shortening the LC elution gradient by 3-fold only reduced back exchange by ~2 %, while sacrificing S/N and peptide count. An unexpected dependence of back exchange on ionic strength as well as pH suggests a strategy in which solution conditions are changed during sample preparation. Higher salt should be used in the first stage of sample preparation (proteolysis and trapping) and lower salt (<20 mM) and pH in the second stage before electrospray injection. Adjustment of these and other factors together with recent advances in peptide fragment detection yields hundreds of peptide fragments with D-label recovery of 90 % ± 5 %.
Minimizing back exchange in the hydrogen exchange-mass spectrometry experiment.
Walters, Benjamin T; Ricciuti, Alec; Mayne, Leland; Englander, S Walter
2012-12-01
The addition of mass spectrometry (MS) analysis to the hydrogen exchange (HX) proteolytic fragmentation experiment extends powerful HX methodology to the study of large biologically important proteins. A persistent problem is the degradation of HX information due to back exchange of deuterium label during the fragmentation-separation process needed to prepare samples for MS measurement. This paper reports a systematic analysis of the factors that influence back exchange (solution pH, ionic strength, desolvation temperature, LC column interaction, flow rates, system volume). The many peptides exhibit a range of back exchange due to intrinsic amino acid HX rate differences. Accordingly, large back exchange leads to large variability in D-recovery from one residue to another as well as one peptide to another that cannot be corrected for by reference to any single peptide-level measurement. The usual effort to limit back exchange by limiting LC time provides little gain. Shortening the LC elution gradient by 3-fold only reduced back exchange by ~2%, while sacrificing S/N and peptide count. An unexpected dependence of back exchange on ionic strength as well as pH suggests a strategy in which solution conditions are changed during sample preparation. Higher salt should be used in the first stage of sample preparation (proteolysis and trapping) and lower salt (<20 mM) and pH in the second stage before electrospray injection. Adjustment of these and other factors together with recent advances in peptide fragment detection yields hundreds of peptide fragments with D-label recovery of 90% ± 5%.
MR appearance of hypothalamic hamartoma
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Hahn, F.J.; Leibrock, L.G.; Huseman, C.A.; Makos, M.M.
1988-02-01
Hypothalamic hamartoma is the most common detectable cerebral lesion causing precocious puberty. Two histologically confirmed cases were studied by computerized tomography (CT) and magnetic resonance (MR) imaging. T2 weighted, sagittal MR images were superior to CT in delineating the tumor from surrounding grey matter. The lesion was isointense to grey matter on T1 weighted images allowing exclusion of other hypothalamic tumors. MR will undoubtedly become the imaging modality of choice in the detection of hypothalamic hamartoma.
International Nuclear Information System (INIS)
Chan, S.H.; Cho, D.H.
1984-01-01
A reactor core filled with an emitting-absorbing mixture (like steam, hydrogen gas and fission gases) is considered. Analysis is provided to evaluate axial radiative heat exchange of a rod bundle with a nonuniform axial temperature distribution. The necessary radiation exchange shape factors (geometric mean absorptance, emittance and transmittance) between segments of the complex rod bundle arrangement are presented. They are applicable to arbitrary sizes of segments, well suited for numerical computations
Molecular Underpinnings of Fe(III Oxide Reduction by Shewanella oneidensis MR-1
Directory of Open Access Journals (Sweden)
Liang eShi
2012-02-01
Full Text Available In the absence of O2 and other electron acceptors, the Gram-negative bacterium Shewanella oneidensis MR-1 can use ferric [Fe(III] (oxy(hydroxide minerals as the terminal electron acceptors for anaerobic respiration. At circumneutral pH and in the absence of strong complexing ligands, Fe(III oxides are relatively insoluble and thus are external to the bacterial cells. S. oneidensis MR-1 has evolved the machinery (i.e., metal-reducing or Mtr pathway for transferring electrons across the entire cell envelope to the surface of extracellular Fe(III oxides. The protein components identified to date for the Mtr pathway include CymA, MtrA, MtrB, MtrC and OmcA. CymA is an inner-membrane tetraheme c-type cytochrome (c-Cyt that is proposed to oxidize the quinol in the inner-membrane and transfers the released electrons to redox proteins in the periplasm. Although the periplasmic proteins receiving electrons from CymA during Fe(III oxidation have not been identified, they are believed to relay the electrons to MtrA. A decaheme c-Cyt, MtrA is thought to be embedded in the trans outer-membrane and porin-like protein MtrB. Together, MtrAB deliver the electrons across the outer-membrane to the MtrC and OmcA on the outmost bacterial surface. Functioning as terminal reductases, the outer membrane and decaheme c-Cyts MtrC and OmcA can bind the surface of Fe(III oxides and transfer electrons directly to these minerals. To increase their reaction rates, MtrC and OmcA can use the flavins secreted by S. oneidensis MR-1 cells as diffusible co-factors for reduction of Fe(III oxides. MtrC and OmcA can also serve as the terminal reductases for soluble forms of Fe(III. Although our understanding of the Mtr pathway is still far from complete, it is the best characterized microbial pathway used for extracellular electron exchange. Characterizations of the Mtr pathway have made significant contributions to the molecular understanding of microbial reduction of Fe(III oxides.
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Goshima, Satoshi [Department of Radiology, Gifu University Hospital, 1-1 Yanagido, Gifu 501-1194 (Japan)], E-mail: gossy@par.odn.ne.jp; Kanematsu, Masayuki [Department of Radiology, Gifu University Hospital, 1-1 Yanagido, Gifu 501-1194 (Japan); Department of Radiology Services, Gifu University Hospital, 1-1 Yanagido, Gifu 501-1194 (Japan); Kondo, Hiroshi [Department of Radiology, Gifu University Hospital, 1-1 Yanagido, Gifu 501-1194 (Japan); Yokoyama, Ryujiro; Kajita, Kimihiro [Department of Radiology Services, Gifu University Hospital, 1-1 Yanagido, Gifu 501-1194 (Japan); Tsuge, Yusuke [Department of Radiology, Gifu University Hospital, 1-1 Yanagido, Gifu 501-1194 (Japan); Shiratori, Yoshimune [Department of Medical Informatics, Gifu University School of Medicine, Gifu (Japan); Onozuka, Minoru [Department of Physiology and Neuroscience, Kanagawa Dental College, Yokosuka (Japan); Moriyama, Noriyuki [Research Center for Cancer Prevention and Screening, National Cancer Center Hospital, Tsukiji (Japan)
2009-05-15
Purpose: To correlate hepatic hemangioma enhancement types in gadolinium-enhanced magnetic resonance (MR) images with diffusion-weighted MR findings and apparent diffusion coefficients (ADCs). Materials and methods: Respiratory-triggered diffusion-weighted MR images (TR/TE, 2422/46 ms; parallel imaging factor, 2; b factor, 500 s/mm{sup 2}; number of averaging, 6) obtained in 35 patients with 44 hepatic hemangiomas diagnosed by gadolinium-enhanced MR and by follow-up imaging were retrospectively evaluated. Hemangiomas were classified into three enhancement types based on gadolinium-enhanced MR imaging findings: type I, early-enhancement type; type II, peripheral nodular enhancement type; type III, delayed enhancement type. Two blinded readers qualitatively assessed lesion sizes and signal intensities on T2-weighted turbo spin-echo and diffusion-weighted images. The ADCs of hemangiomas were also measured. Results: No significant difference was observed between the three enhancement types in terms of signal intensities on T2-weighted images. Signal intensities on diffusion-weighted images were lower in the order type I to III (P < .01), and mean ADCs were 2.18 x 10{sup -3}, 1.86 x 10{sup -3}, and 1.71 x 10{sup -3} mm{sup 2}/s for types I, II, and III, respectively (P < .01). No correlation was found between lesion sizes and ADCs. Conclusion: Hepatic hemangiomas were found to have enhancement type dependent signal intensities and ADCs on diffusion-weighted MR images. Further studies will have to substantiate that these diffusion patterns might reflect intratumoral blood flow or perfusion.
Retrospective 5-year analysis of MR-guided biopsies in a low-field MR system
International Nuclear Information System (INIS)
Zangos, Stephan; Mueller, C.; Mayer, F.; Naguib, N.N.; Nour-Eldin, N.E.A.; Herzog, C.; Hammerstingl, R.M.; Thalhammer, A.; Mack, M.G.; Vogl, T.J.; Eichler, K.; Hansmann, M.L.
2009-01-01
Purpose: The purpose of this study was to evaluate the safety and clinical value of MR-guided biopsies in an open 0.2 T low-field system. Materials and methods: A total of 322 patients with suspicious lesions of different body regions were biopsied in a low-field MRI system (0.2 T, Concerto, Siemens). The procedures were guided using T1-weighted Flash sequences (TR/TE = 100/9; 70 ). The lesions were repeatedly biopsied using the coaxial technique with a 15-gauge (diameter 2 mm) puncture needle. Complications and biopsy findings were analyzed retrospectively. Results: In all cases the biopsy procedures were successfully performed with MR guidance. In 298 patients diagnosis was able to be confirmed on the basis of the probes. The clinical follow-up showed that in 24 patients the lesions were missed by MR-guided biopsy. From this a sensitivity of 86%, a specificity of 87% and an accuracy of 93% were calculated. In two patients major complications were observed (morbidity rate 0.6%). Conclusion: MR-guided biopsy can be performed safely and precisely in a low-field MR system and are a supplement to US or CT-guided biopsies. (orig.)
Knowledge brokerage context factors – What matters in knowledge exchange in impact assessment?
International Nuclear Information System (INIS)
Saarela, Sanna-Riikka; Söderman, Tarja; Lyytimäki, Jari
2015-01-01
Highlights: • Different knowledge brokerage strategies can be applied in impact assessment. • A conceptual framework for knowledge brokering is introduced. • Six test cases from different areas and jurisdictions are reviewed. • Various context factors affect the success of knowledge brokering in IA. - Abstract: The success of an impact assessment (IA) can mean both instrumental success of applying IA results directly in decision-making, and conceptual success linked to learning about policy problems more generally. Both instrumental and conceptual success can be claimed to be reliant on the knowledge exchange context of the IA, shaped by factors such as the complexity of the policy problem, type of policy area, organisational norms, actor constellations and continuance and openness of information sharing. Even though such context factors may be pre-set, they are nevertheless contested and reformulated during each IA process. This paper ties together lessons from six different IA processes that were performed between 2011 and 2013. The cases include agricultural policy at the EU and regional level in Greece, national-level climate change and energy policy in Finland and Estonia, resource efficiency policy at the German national level, and sustainable land use policy in Inner Mongolia, China. The paper introduces and applies a typology of knowledge brokerage context factors. The paper asks how knowledge brokerage is shaped by different contexts and what determines the consequent application (or non-application) of IA tools and the use of IA results. The paper concludes by highlighting the significance of identification and acknowledgement of different knowledge exchange contexts in IA
High-resolution MR imaging of urethra for incontinence by means of intracavitary surface coils
International Nuclear Information System (INIS)
Yang, A.; Mostwin, J.L.; Genadry, R.; Yang, S.S.
1991-01-01
Urinary incontinence is a major medical problem affecting millions of older women. This paper demonstrates the use of dynamic MR imaging in noninvasive quantification of prolapse in all three pelvic compartments. In this exhibit we use high-resolution MR imaging with intracavity (intravaginal, intrarectal) and surface/intracavitary coils to diagnose intrinsic urethral pathology that prevents opening (dysuria) or coaptation (incontinence). Normal anatomy, congenital anatomy (pelvic floor defects, hypoplasia), acquired anatomy (periurethral cyst/divertivulum, tumor, hypertrophy), and operative failure as causes of incontinence (postoperative scarring, misplacement/dehiscence of sutures and flaps) are shown. We demonstrate a novel method for MR cine voiding cystourethrography. Technical factors and applications are discussed
International Nuclear Information System (INIS)
Boesen, Mari E.; Eswaradass, Prasanna Venkatesan; Singh, Dilip; Mitha, Alim P.; Menon, Bijoy K.; Goyal, Mayank; Frayne, Richard
2017-01-01
We propose a magnetic resonance (MR) imaging protocol for the characterization of carotid web morphology, composition, and vessel wall dynamics. The purpose of this case series was to determine the feasibility of imaging carotid webs with MR imaging. Five patients diagnosed with carotid web on CT angiography were recruited to undergo a 30-min MR imaging session. MR angiography (MRA) images of the carotid artery bifurcation were acquired. Multi-contrast fast spin echo (FSE) images were acquired axially about the level of the carotid web. Two types of cardiac phase resolved sequences (cineFSE and cine phase contrast) were acquired to visualize the elasticity of the vessel wall affected by the web. Carotid webs were identified on MRA in 5/5 (100%) patients. Multi-contrast FSE revealed vessel wall thickening and cineFSE demonstrated regional changes in distensibility surrounding the webs in these patients. Our MR imaging protocol enables an in-depth evaluation of patients with carotid webs: morphology (by MRA), composition (by multi-contrast FSE), and wall dynamics (by cineFSE). (orig.)
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Boesen, Mari E. [University of Calgary, Department of Biomedical Engineering, Calgary (Canada); Foothills Medical Centre, Seaman Family MR Research Centre, Calgary (Canada); Eswaradass, Prasanna Venkatesan; Singh, Dilip; Mitha, Alim P.; Menon, Bijoy K. [University of Calgary, Department of Clinical Neurosciences, Calgary (Canada); Foothills Medical Centre, Calgary Stroke Program, Calgary (Canada); Goyal, Mayank [Foothills Medical Centre, Calgary Stroke Program, Calgary (Canada); University of Calgary, Department of Radiology, Calgary (Canada); Frayne, Richard [Foothills Medical Centre, Seaman Family MR Research Centre, Calgary (Canada); University of Calgary, Hotchkiss Brain Institute, Calgary (Canada)
2017-04-15
We propose a magnetic resonance (MR) imaging protocol for the characterization of carotid web morphology, composition, and vessel wall dynamics. The purpose of this case series was to determine the feasibility of imaging carotid webs with MR imaging. Five patients diagnosed with carotid web on CT angiography were recruited to undergo a 30-min MR imaging session. MR angiography (MRA) images of the carotid artery bifurcation were acquired. Multi-contrast fast spin echo (FSE) images were acquired axially about the level of the carotid web. Two types of cardiac phase resolved sequences (cineFSE and cine phase contrast) were acquired to visualize the elasticity of the vessel wall affected by the web. Carotid webs were identified on MRA in 5/5 (100%) patients. Multi-contrast FSE revealed vessel wall thickening and cineFSE demonstrated regional changes in distensibility surrounding the webs in these patients. Our MR imaging protocol enables an in-depth evaluation of patients with carotid webs: morphology (by MRA), composition (by multi-contrast FSE), and wall dynamics (by cineFSE). (orig.)
International Nuclear Information System (INIS)
Yamamoto, Yutaka; Kurebayashi, Junichi; Sonoo, Hiroshi
2002-01-01
Dynamic contrast-enhanced MR images were obtained between September 1998 and May 2000 from 44 primary breast cancer patients who were scheduled to undergo breast-conserving surgery. The MR images and clinico-pathological findings were analyzed to investigate the risk factors for histologically positive margins and histologically positive lymph node metastases. We elucidated the relationship between MR images and the biological background of breast cancer. The following interesting findings were made from these analyses. An irregular shape and unclear border of the tumor mass and the coexistence of daughter nodule(s) were significant risk factors for positive-surgical margins; an irregularly shaped tumor mass and spiculated tumor mass were significant risk factors for positive lymph node metastases; breast tumors with a strand-like appearance had a significantly lower histological grade; breast tumors with high contrast enhancement ratios had a significantly higher nuclear grade and progesterone receptor negativity; and breast tumors showing a ring-like enhancement expressed a low level of VEGF. These findings suggest that preoperative MR images of primary breast cancer provide not only useful information on the extent of breast tumors and the possibility of lymph node metastasis but also on the malignant potency and hormone responsiveness of breast tumors. (author)
International Nuclear Information System (INIS)
Le Blanche, Alain-Ferdinand; Rossert, Jerome; Wassef, Michel; Levy, Bernard; Bigot, Jean-Michel; Boudghene, Frank
2000-01-01
Purpose: To assess in vivo 1) MR-guided percutaneous transluminal renal angioplasty (PTRA) in experimental bilateral rabbit renal artery stenosis (RAS); 2) postprocedural follow-up by gadolinium-enhanced MR angiography versus histomorphometry.Methods: Fifteen male NZW rabbits of mean weight 4.0 kg (range 3.5-4.2 kg) underwent bilateral RAS induction by combined overdilation-deendothelialization with a gadolinium-filled balloon, passively MR-guided by the artifact of a 0.014-inch guidewire. After 4 weeks the rabbits were randomized into two groups: group A (n = 8) underwent right-sided PTRA for treatment of RAS, group B (n = 7) underwent left-sided PTRA. After another 4 weeks the rabbits were killed to assess by histomorphometry recurrent stenosis and contralateral induction injury stenosis lesions. Each step was preceded by gadolinium-enhanced three-dimensional MR angiography, and the cortex-to-aorta (C/A) signal intensity ratio was calculated.Results: RAS induction was successful in all cases. Fourteen arteries developed restenosis and 13 only initial stenosis. MR-guided PTRAs were feasible in 22 arteries (73%). For a successful catheterization of the ostium (20 arteries, 66% success rate), 10-25 steps were required. Five to eight steps were required for balloon localization and inflation for each PTRA. The restenosis effect was reflected by a 16% (12%-27%) decrease in C/A values on MR angiograms (p < 0.05).Conclusion: MR guidance and MR angiography represent a feasible, less invasive alternative for performing and assessing experimental PTRA in RAS
CT and MR imaging of craniopharyngioma
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Tsuda, M. [Tohoku Univ. School of Medicine, Sendai (Japan). Dept. of Radiology; Takahashi, S. [Tohoku Univ. School of Medicine, Sendai (Japan). Dept. of Radiology; Higano, S. [Tohoku Univ. School of Medicine, Sendai (Japan). Dept. of Radiology; Kurihara, N. [Tohoku Univ. School of Medicine, Sendai (Japan). Dept. of Radiology; Ikeda, H. [Tohoku Univ. School of Medicine, Sendai (Japan). Dept. of Neurosurgery; Sakamoto, K. [Tohoku Univ. School of Medicine, Sendai (Japan). Dept. of Radiology
1997-05-01
We reviewed imaging findings of CT and MR imaging in 20 cases of surgically confirmed craniopharyngioma in an attempt to determine their relation to patterns of tumor extent. The relationship between these patterns and the frequency of preoperative CT diagnosis and MR imaging diagnosis according to the surgical diagnosis were determined. The CT technique was superior to MR imaging in the detection of calcification. The MR imaging technique was superior to CT for determining tumor extent and provided valuable information about the relationships of the tumor to surrounding structures. Thus, CT and MR imaging have complementary roles in the diagnosis of craniopharyngiomas. In cases of possible craniopharyngioma, noncontrast sagittal T1-weighted images may enable the identification of the normal pituitary, possibly leading to the correct diagnosis. (orig.)
CT and MR imaging of craniopharyngioma
International Nuclear Information System (INIS)
Tsuda, M.; Takahashi, S.; Higano, S.; Kurihara, N.; Ikeda, H.; Sakamoto, K.
1997-01-01
We reviewed imaging findings of CT and MR imaging in 20 cases of surgically confirmed craniopharyngioma in an attempt to determine their relation to patterns of tumor extent. The relationship between these patterns and the frequency of preoperative CT diagnosis and MR imaging diagnosis according to the surgical diagnosis were determined. The CT technique was superior to MR imaging in the detection of calcification. The MR imaging technique was superior to CT for determining tumor extent and provided valuable information about the relationships of the tumor to surrounding structures. Thus, CT and MR imaging have complementary roles in the diagnosis of craniopharyngiomas. In cases of possible craniopharyngioma, noncontrast sagittal T1-weighted images may enable the identification of the normal pituitary, possibly leading to the correct diagnosis. (orig.)
MR imaging of acute subarachnoid hemorrhage
International Nuclear Information System (INIS)
Spickler, E.; Lufkin, R.B.; Frazee, J.; Lylyk, P.; Vinuela, F.; Bentson, J.R.; Dion, J.E.
1987-01-01
Subarachnoid hemorrhage was produced in four Macaca nemestrina monkeys using the technique of Frazee. CT and MR imaging were performed immediately after the procedure and at frequent intervals up to 2 weeks after hemorrhage. The imaging studies were compared with clinical evaluations and pathologic specimens of all animals. Additional human clinical CT/MR studies of subarachnoid hemorrhage were also studied. Acute hemorrhage was recognized on MR as an increase in signal in the region of clot compared with surrounding cerebrospinal fluid. This most likely reflects T1 shortening due to proton binding rather than a pure paramagnetic effect. While CT is sensitive to the hemoglobin protein in acute hemorrhage, the superior resolution of the basal cisterns on MR images results in equal or better definition of acute subarachnoid hemorrhage on MR in many cases
Fibrolipomatous hamartoma: MR imaging findings
International Nuclear Information System (INIS)
De Maeseneer, M.; Jaovisidha, S.; Lenchik, L.; Witte, D.; Schweitzer, M.E.; Sartoris, D.J.; Resnick, D.
1997-01-01
Objective. To analyze the MR imaging features of fibrolipomatous hamartoma (FLH) of nerves. Design and patients. MR imaging studies from six patients (three men and three women) were retrospectively reviewed by three musculoskeletal radiologists. In four patients, a biopsy of the nerve lesion was performed. In two patients, biopsy data were unavailable and the diagnosis was based on the clinical history combined with the MR imaging findings. Results and conclusion. MR imaging demonstrated fusiform nerve enlargement that was caused by fatty proliferation and thickening of nerve bundles. Nerve bundles appeared as serpentine tubular structures, hypointense on both T1- and T2-weighted images. The degree of fatty proliferation varied among patients. In addition, significant variation in the distribution of fat along the course of the nerves was noted. In three patients, FLH followed the branching pattern of the nerves, a characteristic pathologic finding. In two patients, intramuscular fat deposition (biceps and tibialis posterior muscles) was present. MR imaging findings of FLH are typical, allowing a confident diagnosis. The variation of fatty proliferation among patients and involved nerves as well as the tendency of the abnormalities to follow the branching pattern of the nerves is well demonstrated with MR imaging. FLH may present as an isolated nerve lesion, may be associated with intramuscular fat deposition, or may occur as a feature of macrodystrophia lipomatosa (MDL). (orig.). With 5 figs., 2 tabs
Meniscal tear. Diagnostic errors in MR imaging
International Nuclear Information System (INIS)
Barrera, M. C.; Recondo, J. A.; Gervas, C.; Fernandez, E.; Villanua, J. A.M.; Salvador, E.
2003-01-01
To analyze diagnostic discrepancies found between magnetic resonance (MR) and arthroscopy, and the determine the reasons that they occur. Two-hundred and forty-eight MR knee explorations were retrospectively checked. Forty of these showed diagnostic discrepancies between MR and arthroscopy. Two radiologists independently re-analyzed the images from 29 of the 40 studies without knowing which diagnosis had resulted from which of the two techniques. Their interpretations were correlated with the initial MR diagnosis, MR images and arthroscopic results. Initial errors in MR imaging were classified as either unavoidable, interpretive, or secondary to equivocal findings. Eleven MR examinations could not be checked since their corresponding imaging results could not be located. Of 34 errors found in the original diagnoses, 12 (35.5%)were classified as unavoidable, 14 (41.2%) as interpretative and 8 (23.5%) as secondary to equivocal findings. 41.2% of the errors were avoided in the retrospective study probably due to our department having greater experience in interpreting MR images, 25.5% were unavailable even in the retrospective study. A small percentage of diagnostic errors were due to the presence of subtle equivocal findings. (Author) 15 refs
Deller, Timothy W; Khalighi, Mohammad Mehdi; Jansen, Floris P; Glover, Gary H
2018-01-01
The recent introduction of simultaneous whole-body PET/MR scanners has enabled new research taking advantage of the complementary information obtainable with PET and MRI. One such application is kinetic modeling, which requires high levels of PET quantitative stability. To accomplish the required PET stability levels, the PET subsystem must be sufficiently isolated from the effects of MR activity. Performance measurements have previously been published, demonstrating sufficient PET stability in the presence of MR pulsing for typical clinical use; however, PET stability during radiofrequency (RF)-intensive and gradient-intensive sequences has not previously been evaluated for a clinical whole-body scanner. In this work, PET stability of the GE SIGNA PET/MR was examined during simultaneous scanning of aggressive MR pulse sequences. Methods: PET performance tests were acquired with MR idle and during simultaneous MR pulsing. Recent system improvements mitigating RF interference and gain variation were used. A fast recovery fast spin echo MR sequence was selected for high RF power, and an echo planar imaging sequence was selected for its high heat-inducing gradients. Measurements were performed to determine PET stability under varying MR conditions using the following metrics: sensitivity, scatter fraction, contrast recovery, uniformity, count rate performance, and image quantitation. A final PET quantitative stability assessment for simultaneous PET scanning during functional MRI studies was performed with a spiral in-and-out gradient echo sequence. Results: Quantitation stability of a 68 Ge flood phantom was demonstrated within 0.34%. Normalized sensitivity was stable during simultaneous scanning within 0.3%. Scatter fraction measured with a 68 Ge line source in the scatter phantom was stable within the range of 40.4%-40.6%. Contrast recovery and uniformity were comparable for PET images acquired simultaneously with multiple MR conditions. Peak noise equivalent count
Contribution of meson exchange currents to magnetic form factor of a few complex nuclei
International Nuclear Information System (INIS)
Mathiot, J.F.
1981-12-01
We were interested in the contribution of meson exchange currents (MEC) to the magnetic form factor (MFF) of 49 Ti, 51 V, 87 Sr, 93 Nb at high momentum transfer (1.8 fm -1 to 3.2 fm -1 ). We found that the contribution of tensor correlations to the 1 S 0 - 3 S 1 transition of MEC (adding the 3 D 1 tensor part to the 3 S 1 relative state) multiply the previous calculations by a factor of 2.5 to 4. The sensitivity of MEC to the hadronic form factor is also estimated. It remains of discrepancy of a factor 2 for the MFF at 3 fm -1 for the first three nuclei [fr
Actinomycotic brain infection: registered diffusion, perfusion MR imaging and MR spectroscopy
International Nuclear Information System (INIS)
Wang, Sumei; Wolf, Ronald L.; Woo, John H.; Melhem, Elias R.; Poptani, Harish; Wang, Jiongjiong; O'Rourke, Donald M.; Roy, Subhojit
2006-01-01
Introduction: Actinomycotic brain infection is caused by an organism of the Actinomyces genus. We report here one such case. Methods: The methods used included coregistered diffusion, perfusion and spectroscopic magnetic resonance (MR) imaging. Decreased apparent diffusion coefficient, markedly elevated fractional anisotropy (FA) and reduced cerebral blood flow were observed. MR spectroscopy demonstrated elevated amino acids, acetate and succinate. Elevated FA values may be due to the microstructure of this special brain infection. (orig.)
Haller, John W.; Botteron, K.; Brunsden, Barry S.; Sheline, Yvette I.; Walkup, Ronald K.; Black, Kevin J.; Gado, Mokhtar; Vannier, Michael W.
1994-09-01
Goal: To estimate hippocampal volumes from in vivo 3D magnetic resonance (MR) brain images and determine inter-rater and intra- rater repeatability. Objective: The precision and repeatability of hippocampal volume estimates using stereologic measurement methods is sought. Design: Five normal control and five schizophrenic subjects were MR scanned using a MPRAGE protocol. Fixed grid stereologic methods were used to estimate hippocampal volumes on a graphics workstation. The images were preprocessed using histogram analysis to standardize 3D MR image scaling from 16 to 8 bits and image volumes were interpolated to 0.5 mm3 isotropic voxels. The following variables were constant for the repeated stereologic measures: grid size, inter-slice distance (1.5 mm), voxel dimensions (0.5 mm3), number of hippocampi measured (10), total number of measurements per rater (40), and number of raters (5). Two grid sizes were tested to determine the coefficient of error associated with the number of sampled 'hits' (approximately 140 and 280) on the hippocampus. Starting slice and grid position were randomly varied to assure unbiased volume estimates. Raters were blind to subject identity, diagnosis, and side of the brain from which the image volumes were extracted and the order of subject presentation was randomized for each of the raters. Inter- and intra-rater intraclass correlation coefficients (ICC) were determined. Results: The data indicate excellent repeatability of fixed grid stereologic hippocampal volume measures when using an inter-slice distance of 1.5 mm and a 6.25 mm2 grid (inter-rater ICCs equals 0.86 - 0.97, intra- rater ICCs equals 0.85 - 0.97). One major advantage of the current study was the use of 3D MR data which significantly improved visualization of hippocampal boundaries by providing the ability to access simultaneous orthogonal views while counting stereological marks within the hippocampus. Conclusion: Stereological estimates of 3D volumes from 2D MR
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Jang, Seung Won; Kim, Sang Joon; Kim, Sun Mi; Lee, Jeong Hyun; Choi, Choong Gon; Lee, Deok Hee; Lee, Jung Kyo [University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of); Kim, Eun Ju [Philips Healthcare, Seoul (Korea, Republic of)
2010-06-15
We report a case of intracranial foreign body granuloma that showed features of a high grade tumor on magnetic resonance (MR) imaging. However, the relative cerebral blood volume was not increased in the enhancing mass on perfusion MRI and the choline/creatine ratio only slightly increased on MR spectroscopy. The results suggest that the lesion is benign in nature. Perfusion MRI and MR spectroscopy may be helpful to differentiate a foreign body granuloma from a neoplastic condition
Effect of MR contrast agents on quantitative accuracy of PET in combined whole-body PET/MR imaging
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Lois, Cristina [University of Santiago de Compostela, Department of Particle Physics, Santiago de Compostela (Spain); Health Research Institute of Santiago de Compostela (IDIS), Santiago de Compostela (Spain); Imaging Science Institute, Tuebingen (Germany); Bezrukov, Ilja [Eberhard Karls University, Laboratory for Preclinical Imaging and Imaging Technology of the Werner Siemens Foundation, Department of Preclinical Imaging and Radiopharmacy, Tuebingen (Germany); Max Plank Institute for Intelligent Systems, Department of Empirical Inference, Tuebingen (Germany); Schmidt, Holger [Eberhard Karls University, Laboratory for Preclinical Imaging and Imaging Technology of the Werner Siemens Foundation, Department of Preclinical Imaging and Radiopharmacy, Tuebingen (Germany); Eberhard Karls University, Diagnostic and Interventional Radiology, Department of Radiology, Tuebingen (Germany); Schwenzer, Nina; Werner, Matthias K. [Eberhard Karls University, Diagnostic and Interventional Radiology, Department of Radiology, Tuebingen (Germany); Kupferschlaeger, Juergen [Eberhard Karls University, Nuclear Medicine, Department of Radiology, Tuebingen (Germany); Beyer, Thomas [Imaging Science Institute, Tuebingen (Germany); cmi-experts GmbH, Zuerich (Switzerland)
2012-11-15
Clinical PET/MR acquisition protocols entail the use of MR contrast agents (MRCA) that could potentially affect PET quantification following MR-based attenuation correction (AC). We assessed the effect of oral and intravenous (IV) MRCA on PET quantification in PET/MR imaging. We employed two MRCA: Lumirem {sup registered} (oral) and Gadovist {sup registered} (IV). First, we determined their reference PET attenuation values using a PET transmission scan (ECAT-EXACT HR+, Siemens) and a CT scan (PET/CT Biograph 16 HI-REZ, Siemens). Second, we evaluated the attenuation of PET signals in the presence of MRCA. Phantoms were filled with clinically relevant concentrations of MRCA in a background of water and {sup 18}F-fluoride, and imaged using a PET/CT scanner (Biograph 16 HI-REZ, Siemens) and a PET/MR scanner (Biograph mMR, Siemens). Third, we investigated the effect of clinically relevant volumes of MRCA on MR-based AC using human pilot data: a patient study employing Gadovist {sup registered} (IV) and a volunteer study employing two different oral MRCA (Lumirem {sup registered} and pineapple juice). MR-based attenuation maps were calculated following Dixon-based fat-water segmentation and an external atlas-based and pattern recognition (AT and PR) algorithm. IV and oral MRCA in clinically relevant concentrations were found to have PET attenuation values similar to those of water. The phantom experiments showed that under clinical conditions IV and oral MRCA did not yield additional attenuation of PET emission signals. Patient scans showed that PET attenuation maps are not biased after the administration of IV MRCA but may be biased, however, after ingestion of iron oxide-based oral MRCA when segmentation-based AC algorithms are used. Alternative AC algorithms, such as AT and PR, or alternative oral contrast agents, such as pineapple juice, can yield unbiased attenuation maps. In clinical PET/MR scenarios MRCA are not expected to lead to markedly increased attenuation
DEFF Research Database (Denmark)
Rand, Kasper D; Andersen, Mette D; Olsen, Ole H
2008-01-01
Factor VIIa (FVIIa) circulates in the blood in a zymogen-like state. Only upon association with membrane-bound tissue factor (TF) at the site of vascular injury does FVIIa become active and able to initiate blood coagulation. Here we used hydrogen exchange monitored by mass spectrometry to invest......Factor VIIa (FVIIa) circulates in the blood in a zymogen-like state. Only upon association with membrane-bound tissue factor (TF) at the site of vascular injury does FVIIa become active and able to initiate blood coagulation. Here we used hydrogen exchange monitored by mass spectrometry...... to investigate the conformational effects of site-directed mutagenesis at key positions in FVIIa and the origins of enhanced intrinsic activity of FVIIa analogs. The differences in hydrogen exchange of two highly active variants, FVIIa(DVQ) and FVIIa(VEAY), imply that enhanced catalytic efficiency was attained...
Maspero, Matteo; van den Berg, Cornelis A. T.; Zijlstra, Frank; Sikkes, Gonda G.; de Boer, Hans C. J.; Meijer, Gert J.; Kerkmeijer, Linda G. W.; Viergever, Max A.; Lagendijk, Jan J. W.; Seevinck, Peter R.
2017-10-01
An MR-only radiotherapy planning (RTP) workflow would reduce the cost, radiation exposure and uncertainties introduced by CT-MRI registrations. In the case of prostate treatment, one of the remaining challenges currently holding back the implementation of an RTP workflow is the MR-based localisation of intraprostatic gold fiducial markers (FMs), which is crucial for accurate patient positioning. Currently, MR-based FM localisation is clinically performed manually. This is sub-optimal, as manual interaction increases the workload. Attempts to perform automatic FM detection often rely on being able to detect signal voids induced by the FMs in magnitude images. However, signal voids may not always be sufficiently specific, hampering accurate and robust automatic FM localisation. Here, we present an approach that aims at automatic MR-based FM localisation. This method is based on template matching using a library of simulated complex-valued templates, and exploiting the behaviour of the complex MR signal in the vicinity of the FM. Clinical evaluation was performed on seventeen prostate cancer patients undergoing external beam radiotherapy treatment. Automatic MR-based FM localisation was compared to manual MR-based and semi-automatic CT-based localisation (the current gold standard) in terms of detection rate and the spatial accuracy and precision of localisation. The proposed method correctly detected all three FMs in 15/17 patients. The spatial accuracy (mean) and precision (STD) were 0.9 mm and 0.5 mm respectively, which is below the voxel size of 1.1 × 1.1 × 1.2 mm3 and comparable to MR-based manual localisation. FM localisation failed (3/51 FMs) in the presence of bleeding or calcifications in the direct vicinity of the FM. The method was found to be spatially accurate and precise, which is essential for clinical use. To overcome any missed detection, we envision the use of the proposed method along with verification by an observer. This will result in a
Maspero, Matteo; van den Berg, Cornelis A T; Zijlstra, Frank; Sikkes, Gonda G; de Boer, Hans C J; Meijer, Gert J; Kerkmeijer, Linda G W; Viergever, Max A; Lagendijk, Jan J W; Seevinck, Peter R
2017-10-03
An MR-only radiotherapy planning (RTP) workflow would reduce the cost, radiation exposure and uncertainties introduced by CT-MRI registrations. In the case of prostate treatment, one of the remaining challenges currently holding back the implementation of an RTP workflow is the MR-based localisation of intraprostatic gold fiducial markers (FMs), which is crucial for accurate patient positioning. Currently, MR-based FM localisation is clinically performed manually. This is sub-optimal, as manual interaction increases the workload. Attempts to perform automatic FM detection often rely on being able to detect signal voids induced by the FMs in magnitude images. However, signal voids may not always be sufficiently specific, hampering accurate and robust automatic FM localisation. Here, we present an approach that aims at automatic MR-based FM localisation. This method is based on template matching using a library of simulated complex-valued templates, and exploiting the behaviour of the complex MR signal in the vicinity of the FM. Clinical evaluation was performed on seventeen prostate cancer patients undergoing external beam radiotherapy treatment. Automatic MR-based FM localisation was compared to manual MR-based and semi-automatic CT-based localisation (the current gold standard) in terms of detection rate and the spatial accuracy and precision of localisation. The proposed method correctly detected all three FMs in 15/17 patients. The spatial accuracy (mean) and precision (STD) were 0.9 mm and 0.5 mm respectively, which is below the voxel size of [Formula: see text] mm 3 and comparable to MR-based manual localisation. FM localisation failed (3/51 FMs) in the presence of bleeding or calcifications in the direct vicinity of the FM. The method was found to be spatially accurate and precise, which is essential for clinical use. To overcome any missed detection, we envision the use of the proposed method along with verification by an observer. This will result in a
Fast generation of 4D PET-MR data from real dynamic MR acquisitions
International Nuclear Information System (INIS)
Tsoumpas, C; Buerger, C; King, A P; Schleyer, P; Schaeffter, T; Marsden, P K; Mollet, P; Keereman, V; Vandenberghe, S; Schulz, V
2011-01-01
We have implemented and evaluated a framework for simulating simultaneous dynamic PET-MR data using the anatomic and dynamic information from real MR acquisitions. PET radiotracer distribution is simulated by assigning typical FDG uptake values to segmented MR images with manually inserted additional virtual lesions. PET projection data and images are simulated using analytic forward projections (including attenuation and Poisson statistics) implemented within the image reconstruction package STIR. PET image reconstructions are also performed with STIR. The simulation is validated with numerical simulation based on Monte Carlo (GATE) which uses more accurate physical modelling, but has 150x slower computation time compared to the analytic method for ten respiratory positions and is 7000x slower when performing multiple realizations. Results are validated in terms of region of interest mean values and coefficients of variation for 65 million coincidences including scattered events. Although some discrepancy is observed, agreement between the two different simulation methods is good given the statistical noise in the data. In particular, the percentage difference of the mean values is 3.1% for tissue, 17% for the lungs and 18% for a small lesion. The utility of the procedure is demonstrated by simulating realistic PET-MR datasets from multiple volunteers with different breathing patterns. The usefulness of the toolkit will be shown for performance investigations of the reconstruction, motion correction and attenuation correction algorithms for dynamic PET-MR data.
Davidson, Anthony C; Humphreys, Daniel; Brooks, Andrew B E; Hume, Peter J; Koronakis, Vassilis
2015-02-10
To establish intracellular infections, Salmonella bacteria trigger host cell membrane ruffling and invasion by subverting cellular Arf guanine nucleotide exchange factors (GEFs) that activate Arf1 and Arf6 GTPases by promoting GTP binding. A family of cellular Arf GTPase-activating proteins (GAPs) can downregulate Arf signaling by stimulating GTP hydrolysis, but whether they do this during infection is unknown. Here, we uncovered a remarkable role for distinct Arf GAP family members in Salmonella invasion. The Arf6 GAPs ACAP1 and ADAP1 and the Arf1 GAP ASAP1 localized at Salmonella-induced ruffles, which was not the case for the plasma membrane-localized Arf6 GAPs ARAP3 and GIT1 or the Golgi-associated Arf1 GAP1. Surprisingly, we found that loss of ACAP1, ADAP1, or ASAP1 impaired Salmonella invasion, revealing that GAPs cannot be considered mere terminators of cytoskeleton remodeling. Salmonella invasion was restored in Arf GAP-depleted cells by expressing fast-cycling Arf derivatives, demonstrating that Arf GTP/GDP cycles facilitate Salmonella invasion. Consistent with this view, both constitutively active and dominant-negative Arf derivatives that cannot undergo GTP/GDP cycles inhibited invasion. Furthermore, we demonstrated that Arf GEFs and GAPs colocalize at invading Salmonella and collaborate to drive Arf1-dependent pathogen invasion. This study revealed that Salmonella bacteria exploit a remarkable interplay between Arf GEFs and GAPs to direct cycles of Arf GTPase activation and inactivation. These cycles drive Salmonella cytoskeleton remodeling and enable intracellular infections. To initiate infections, the Salmonella bacterial pathogen remodels the mammalian actin cytoskeleton and invades host cells by subverting host Arf GEFs that activate Arf1 and Arf6 GTPases. Cellular Arf GAPs deactivate Arf GTPases and negatively regulate cell processes, but whether they target Arfs during infection is unknown. Here, we uncovered an important role for the Arf GAP
Modepalli, Vijayakumar; Jin, Mi-Jin; Park, Jungmin; Jo, Junhyeon; Kim, Ji-Hyun; Baik, Jeong Min; Seo, Changwon; Kim, Jeongyong; Yoo, Jung-Woo
2016-04-26
Electrical control of ferromagnetism in semiconductor nanostructures offers the promise of nonvolatile functionality in future semiconductor spintronics. Here, we demonstrate a dramatic gate-induced change of ferromagnetism in ZnO nanowire (NW) field-effect transistors (FETs). Ferromagnetism in our ZnO NWs arose from oxygen vacancies, which constitute deep levels hosting unpaired electron spins. The magnetic transition temperature of the studied ZnO NWs was estimated to be well above room temperature. The in situ UV confocal photoluminescence (PL) study confirmed oxygen vacancy mediated ferromagnetism in the studied ZnO NW FET devices. Both the estimated carrier concentration and temperature-dependent conductivity reveal the studied ZnO NWs are at the crossover of the metal-insulator transition. In particular, gate-induced modulation of the carrier concentration in the ZnO NW FET significantly alters carrier-mediated exchange interactions, which causes even inversion of magnetoresistance (MR) from negative to positive values. Upon sweeping the gate bias from -40 to +50 V, the MRs estimated at 2 K and 2 T were changed from -11.3% to +4.1%. Detailed analysis on the gate-dependent MR behavior clearly showed enhanced spin splitting energy with increasing carrier concentration. Gate-voltage-dependent PL spectra of an individual NW device confirmed the localization of oxygen vacancy-induced spins, indicating that gate-tunable indirect exchange coupling between localized magnetic moments played an important role in the remarkable change of the MR.
Contributions of chemical and diffusive exchange to T1ρ dispersion.
Cobb, Jared Guthrie; Xie, Jingping; Gore, John C
2013-05-01
Variations in local magnetic susceptibility may induce magnetic field gradients that affect the signals acquired for MR imaging. Under appropriate diffusion conditions, such fields produce effects similar to slow chemical exchange. These effects may also be found in combination with other chemical exchange processes at multiple time scales. We investigate these effects with simulations and measurements to determine their contributions to rotating frame (R1ρ ) relaxation in model systems. Simulations of diffusive and chemical exchange effects on R1ρ dispersion were performed using the Bloch equations. Additionally, R1ρ dispersion was measured in suspensions of Sephadex and latex beads with varying spin locking fields at 9.4 T. A novel analysis method was used to iteratively fit for apparent chemical and diffusive exchange rates with a model by Chopra et al. Single- and double-inflection points in R1ρ dispersion profiles were observed, respectively, in simulations of slow diffusive exchange alone and when combined with rapid chemical exchange. These simulations were consistent with measurements of R1ρ in latex bead suspensions and small-diameter Sephadex beads that showed single- and double-inflection points, respectively. These observations, along with measurements following changes in temperature and pH, are consistent with the combined effects of slow diffusion and rapid -OH exchange processes. Copyright © 2012 Wiley Periodicals, Inc.
MR of head and neck hemangiomas
International Nuclear Information System (INIS)
Bilaniuk, L.T.; Zimmerman, R.A.; Gusnard, D.A.
1990-01-01
This paper defines the MR characteristics of head and neck hemangiomas and to evaluate the role of MR in their diagnosis and management. Eighteen pediatric and young adult patients with head and neck hemangiomas (six neck, six face, three eyelid, two scalp, and one parotid) underwent high-field-strength 1.5-T MR imaging. Conventional spin-echo sequences with T1 and T2 weighting were performed. In addition, one-third of patients underwent MR angiography and gadolinium enhancement. The hemangiomas were isointense to muscle on T1-weighted images and hyperintense on proton-density and T2-weighted images
Brain MR imaging in child abuse
International Nuclear Information System (INIS)
Sato, Y.; Ellerbroek, C.J.; Alexander, R.; Kao, S.C.S.; Yuh, W.T.C.; Smith, W.L.
1988-01-01
Intracranial injuries represent the most severe manifestation of child abuse. CT of the brain is the current standard for evaluation of these infants; however, MR imaging offers several potential advantages. MR imaging and CT were performed in ten infants who suffered intracranial trauma owing to child abuse. CT was slightly better at demonstrating subarachnoid hemorrhage and had definite advantages for defining fractures. MR imaging was superior in the demonstration of subacute extraaxial hemorrhage, deep brain injuries owing to shearing effects from shaking, and anoxic injuries. MR imaging has a definite complementary role in the evaluation of acute intracranial trauma in child abuse victims
Energy Technology Data Exchange (ETDEWEB)
Ha, Hong Il [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology and Research Institute of Radiology, Seoul (Korea, Republic of); Hallym University Medical Center, Hallym University Sacred Heart Hospital, Department of Radiology, Anyang-si, Gyeonggi-do (Korea, Republic of); Kim, Ah Young; Park, Seong Ho; Ha, Hyun Kwon [University of Ulsan College of Medicine, Asan Medical Center, Department of Radiology and Research Institute of Radiology, Seoul (Korea, Republic of); Yu, Chang Sik [University of Ulsan College of Medicine, Asan Medical Center, Department of Colon and Rectal Surgery, Seoul (Korea, Republic of)
2013-12-15
To evaluate DW MR tumour volumetry and post-CRT ADC in rectal cancer as predicting factors of CR using high b values to eliminate perfusion effects. One hundred rectal cancer patients who underwent 1.5-T rectal MR and DW imaging using three b factors (0, 150, and 1,000 s/mm{sup 2}) were enrolled. The tumour volumes of T2-weighted MR and DW images and pre- and post-CRT ADC{sub 150-1000} were measured. The diagnostic accuracy of post-CRT ADC, T2-weighted MR, and DW tumour volumetry was compared using ROC analysis. DW MR tumour volumetry was superior to T2-weighted MR volumetry comparing the CR and non-CR groups (P < 0.001). Post-CRT ADC showed a significant difference between the CR and non-CR groups (P = 0.001). The accuracy of DW tumour volumetry (A{sub z} = 0.910) was superior to that of T2-weighed MR tumour volumetry (A{sub z} = 0.792) and post-CRT ADC (A{sub z} = 0.705) in determining CR (P = 0.015). Using a cutoff value for the tumour volume reduction rate of more than 86.8 % on DW MR images, the sensitivity and specificity for predicting CR were 91.4 % and 80 %, respectively. DW MR tumour volumetry after CRT showed significant superiority in predicting CR compared with T2-weighted MR images and post-CRT ADC. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Yilmaz, U. [Universitaetsklinikum des Saarlandes, Klinik fuer Diagnostische und Interventionelle Neuroradiologie, Homburg/Saar (Germany)
2017-06-15
Metabolic disorders of the brain often present a particular challenge for the neuroradiologist, since the disorders are rare, changes on conventional MR are often non-specific and there are numerous differential diagnoses for the white substance lesions. As a complementary method to conventional brain MRI, MR spectroscopy may help to reduce the scope of the differential diagnosis. Entities with specific MR spectroscopy patterns are Canavan disease, maple syrup urine disease, nonketotic hyperglycinemia and creatine deficiency. (orig.) [German] Die Diagnostik metabolischer Erkrankungen des Gehirns stellt eine besondere Herausforderung in der Neuroradiologie dar, da die Erkrankungen insgesamt selten, die bildmorphologischen Befunde haeufig unspezifisch sind und es eine Vielzahl von Differenzialdiagnosen fuer die Veraenderungen der weissen Substanz gibt. Als zusaetzliche Technik kann die MR-Spektroskopie bei Stoffwechselerkrankungen helfen, die Diagnose einzugrenzen. Krankheitsentitaeten, die spezifische Veraenderungen in der Spektroskopie aufweisen, sind der Morbus Canavan, die Ahornsirupkrankheit, die nichtketotische Hyperglyzinaemie und Kreatinmangelsyndrome. (orig.)
International Nuclear Information System (INIS)
Sokolov, V.V.; Smirnov, N.N.
1982-01-01
An investigation of the joint influence of hydrodynamic and concentration factors in sorption of iodine by AV-17-8 and anion exchange resins on the mass-transfer coefficient is the subject of this report. The method of central composite rotatable experimental design was used for quantitative assessment and derivation of the appropriate equations. The investigation yielded the necessary regression equations satisfactorily describing the influence of all the factors in the mass-transfer coefficient. the optimal mass-transfer conditions were determined. On the basis of the values obtained, recommendations are made on the optimal hydrodynamic conditions of operation of equipment with pneumatic circulation of the ion-exchanger
MR imaging evaluation of diabetic foot
International Nuclear Information System (INIS)
Beltran, J.; Campanini, D.S.; McCalla, M.; Knight, C.T.
1988-01-01
Fourteen diabetic patients with suspected foot infection and/or neuropathic joint were evaluated with MR imaging to identify the presence and extent of infection and also to exclude coexistent infection in the neuropathic joint. Osteomyelitis (n = 8), abscess (n = 7), septic arthritis (n = 4), tenosynovitis (n = 4), and neuropathic joint (n = 5) were diagnosed with MR imaging. Osteomyelitis and/or abscess were excluded by MR findings in 13 instances. Most patients with infection had one more than one site of involvement. Clinical or surgical confirmation of the MR diagnoses was obtained in all but nine of the infection sites or cases of neuropathic joint. Only one false-negative diagnosis of osteomyelitis was made in this series. It is concluded that MR imaging provided accurate information regarding the presence and extent of infection and that this information was decisive in patient management
MR diagnosis of dural sinus thrombosis
International Nuclear Information System (INIS)
Rovira Canellas, A.; Turon Estrada, A.; Alvarez Sabin, J.; Lozano Sanchez, M.; Castano Duque, Ch.; Grive Isern, E.; Sumalla Sune, J.
1994-01-01
Four adult patients were diagnosed as having dural sinus thrombosis (DST) by means of magnetic resonance (MR). In the three cases of acute thrombosis, MR disclosed diffuse or segmental hyperintensity in the sinuses involved, which persisted regardless of the sequence and orientation of the plane selected. MR angiography (MRA) provided diagnostic information that proved useful in the chronic case, as well as in the two cases in which follow-up was carried out to determine the degree to which permeability was restored to the sinuses involved. MR diagnosis of DST can produce false positives and negatives, the causes of which should be known, as well as the ways to avoid them, in order to prevent diagnostic errors. MR, when applied and interpreted correctly, can be considered the first, and in many cases the only, choice as a diagnostic method in DST. (Author)
International Nuclear Information System (INIS)
Kannan, K.; Vinod, V.; Padmakumar, G.; Rudramoorthy, R.; Rajan, K.K.
2015-01-01
Highlights: • A heat exchanger analysis (HE) before scale up reduces excess heat transfer area. • Representative Elementary Volume analysis of a HE speeds up the solution. • The error in air temperature rise prediction by numerical across HE is within 5%. • When both pitches are reduced, the maximum increase in heat flux is experienced. • The experience has resulted in better design of next level heat exchangers. - Abstract: Prototype fast breeder reactor (PFBR) has a safety grade decay heat removal system whose performance depends on the effective functioning of natural convection heat exchangers called sodium to air heat exchangers. The development of Representative Elementary Volume (REV) model for the sodium to air heat exchanger is necessary to envisage its design and to study the effect of various factors for continuous improvement in design. With a Representative Elementary Volume, the hydrodynamic and heat transfer characteristics of the heat exchanger was studied and the results agree well with experimental data. The effect of longitudinal pitch and transverse pitch on the heat exchanger performance has been studied and an improvement of 22% in heat transfer is predicted
Semiautomated spleen volumetry with diffusion-weighted MR imaging.
Lee, Jeongjin; Kim, Kyoung Won; Lee, Ho; Lee, So Jung; Choi, Sanghyun; Jeong, Woo Kyoung; Kye, Heewon; Song, Gi-Won; Hwang, Shin; Lee, Sung-Gyu
2012-07-01
In this article, we determined the relative accuracy of semiautomated spleen volumetry with diffusion-weighted (DW) MR images compared to standard manual volumetry with DW-MR or CT images. Semiautomated spleen volumetry using simple thresholding followed by 3D and 2D connected component analysis was performed with DW-MR images. Manual spleen volumetry was performed on DW-MR and CT images. In this study, 35 potential live liver donor candidates were included. Semiautomated volumetry results were highly correlated with manual volumetry results using DW-MR (r = 0.99; P volumetry was significantly shorter compared to that of manual volumetry with DW-MR (P volumetry with DW-MR images can be performed rapidly and accurately when compared with standard manual volumetry. Copyright © 2011 Wiley Periodicals, Inc.
MR imaging of rotator cuff tears
International Nuclear Information System (INIS)
Kumagai, Hideo
1992-01-01
A total of 115 patients with clinical symptoms and signs suggesting rotator cuff tears underwent MR imaging with a 1.5-Tesla system. The body coil was used as the receiver coil in 24 patients and a single 10 cm surface coil in 91. Arthrography or MR imaging with intra-articular Gd-DTPA (MR arthrography) was performed in 95 of the 115. T2-weighted images with the body coil showed high signal intensity lesions in rotator cuffs in only seven of the 10 patients who had tears demonstrated by arthrography or MR arthrography. On the other hand, T2-weighted images with the surface coil demonstrated high signal intensity lesions in cuffs in all 27 patients who were diagnosed to have tears by arthrography or MR arthrography. In 12 patietns, T2-wighted images with the surface coil showed high signal intensity lesions in cuffs, while arthrography and MR arthrography did not show tears. Surgery was performed in four of the 12 patients and partial tears were confirmed. A single 10 cm surface coil, 3 mm slice thickness and 2.5 second repetition time seem to account for the fine visualization of cuff tears by the T2-weighted images. These results suggest that T2-weighted images obtained with the surface coil are superior to arthrography and MR arthrography. (author)
Energy Technology Data Exchange (ETDEWEB)
Muehlenweg, M. [Krankenhaus Martha-Maria Halle-Doelau, Institut fuer Radiologie, Halle (Saale) (Germany); Schaefers, G. [MR:comp GmbH, Gelsenkirchen (Germany)
2015-08-15
Before a magnetic resonance imaging (MRI) examination, implants in patients must be cleared for MR safety in order to exclude the risk of possible severe injuries and implant malfunction in an MR environment. The general contraindication for measurements of patients with implants still applies; however, in the recent past a way has been found to legally circumvent this contraindication. For this purpose special conditions are required: explicit implant identification and the original manufacturer's labelling are necessary, the required conditions for conditionally MR safe implants must be assured and a risk-benefit analysis with appropriate explanation to the patient has to be performed. This process can be very complex as the implants are often poorly documented and detailed information on the implant MR labelling is also often outdated or not easy to interpret. This article provides information about legal and normative principles of MR measurement of patients with implants. The possible physical interactions with implants will be briefly dealt with as well as possible strategies for better identification and investigation of implants and MR labelling. General approaches for minimizing the risk will be discussed using some examples. The second part deals with the content of MR implant labelling and the current test standards. Furthermore, the additional information from the operating instructions of the MR scanner that are necessary for the interpretation of the MR implant labelling, will be explained. The article concludes with an explanation of the current pattern for MR labelling of implants from the U.S. Food and Drug Administration (FDA) and an exemplary application. (orig.) [German] Implantate in Patienten muessen vor einer MR-Untersuchung auf MR-Sicherheit abgeklaert werden, um moegliche z. T. schwere Verletzungen und Implantatfehlfunktionen in einer MR-Umgebung weitestgehend auszuschliessen. Es gilt unveraendert die generelle Kontraindikation von
DEFF Research Database (Denmark)
Rist, Wolfgang; Jørgensen, Thomas J D; Roepstorff, Peter
2003-01-01
Stress conditions such as heat shock alter the transcriptional profile in all organisms. In Escherichia coli the heat shock transcription factor, sigma 32, out-competes upon temperature up-shift the housekeeping sigma-factor, sigma 70, for binding to core RNA polymerase and initiates heat shock...... gene transcription. To investigate possible heat-induced conformational changes in sigma 32 we performed amide hydrogen (H/D) exchange experiments under optimal growth and heat shock conditions combined with mass spectrometry. We found a rapid exchange of around 220 of the 294 amide hydrogens at 37...... degrees C, indicating that sigma 32 adopts a highly flexible structure. At 42 degrees C we observed a slow correlated exchange of 30 additional amide hydrogens and localized it to a helix-loop-helix motif within domain sigma 2 that is responsible for the recognition of the -10 region in heat shock...
Directory of Open Access Journals (Sweden)
Mark A Lum
Full Text Available To evaluate the ability of IA MR perfusion to characterize meningioma blood supply.Studies were performed in a suite comprised of an x-ray angiography unit and 1.5T MR scanner that permitted intraprocedural patient movement between the imaging modalities. Patients underwent intra-arterial (IA and intravenous (IV T2* dynamic susceptibility MR perfusion immediately prior to meningioma embolization. Regional tumor arterial supply was characterized by digital subtraction angiography and classified as external carotid artery (ECA dural, internal carotid artery (ICA dural, or pial. MR perfusion data regions of interest (ROIs were analyzed in regions with different vascular supply to extract peak height, full-width at half-maximum (FWHM, relative cerebral blood flow (rCBF, relative cerebral blood volume (rCBV, and mean transit time (MTT. Linear mixed modeling was used to identify perfusion curve parameter differences for each ROI for IA and IV MR imaging techniques. IA vs. IV perfusion parameters were also directly compared for each ROI using linear mixed modeling.18 ROIs were analyzed in 12 patients. Arterial supply was identified as ECA dural (n = 11, ICA dural (n = 4, or pial (n = 3. FWHM, rCBV, and rCBF showed statistically significant differences between ROIs for IA MR perfusion. Peak Height and FWHM showed statistically significant differences between ROIs for IV MR perfusion. RCBV and MTT were significantly lower for IA perfusion in the Dural ECA compared to IV perfusion. Relative CBF in IA MR was found to be significantly higher in the Dural ICA region and MTT significantly lower compared to IV perfusion.
CT and MR imaging of the kidney and adrenal glands: MR imaging of the kidney and adrenal glands
International Nuclear Information System (INIS)
Lee, J.K.T.
1987-01-01
The normal anatomy of the kidney is clearly demonstrated with MR imaging. The renal cortex can be differentiated from the renal medulla; renal vessels can also be identified. MR imaging can differentiate cystic from solid lesions. The signal intensity of a renal cell carcinoma varies and overlaps with the signal intensities of renal neoplasms of other etiologies. MR imaging is superior to CT in distinguishing vascular from nonvascular structures. It can distinguish collateral vessels from lymph nodes and can disclose tumoral thrombi. MR imaging can also aid in the differentiation of acute rejection from acute tubular necrosis in renal transplant recipients. Both normal and abnormal adrenal glands can be seen on MR imaging. A normal adrenal gland has a signal intensity higher than or equal to that of muscle but lower than that of fat. T1-weighted images offer excellent antomic resolution; T2-weighted images provide additional information about internal characteristics of adrenal neoplasms. Preliminary data indicate that MR imaging is useful in distinguishing nonfunctioning adenomas from adrenal metastases. The role of MR imaging of the kidney and adrenal gland is discussed
Normal anatomy of the fetus at MR imaging.
Amin, R S; Nikolaidis, P; Kawashima, A; Kramer, L A; Ernst, R D
1999-10-01
Owing to recent advances in magnetic resonance (MR) imaging, the role of obstetric MR imaging has increased in cases in which the results of ultrasonography are equivocal. Fast MR imaging sequences, such as T2-weighted fast spin-echo (SE), half-Fourier single-shot fast SE, 0.5-signal-acquired single-shot fast SE, and echo-planar imaging, have virtually eliminated the need for fetal premedication, with a concomitant improvement in image resolution and diminished blurring. Artifacts related to maternal respiratory motion and fetal motion no longer limit the anatomic detail that can be demonstrated with MR imaging. With such advances in obstetric MR imaging, knowledge of normal fetal anatomy at MR imaging is essential to detect disease in utero. MR imaging can demonstrate fetal anatomy in detail, especially the brain, thorax, abdomen, pelvis, and vasculature. Major developmental structures of the fetus, particularly the cranial nervous system, naso- and oropharynx, lungs, and major abdominal viscera, can be adequately evaluated with targeted fast MR imaging as early as the beginning of the second trimester. However, MR imaging of the heart remains limited. Fetal MR imaging during the first trimester remains controversial secondary to biosafety issues and is limited due to diminutive fetal size.
MR imaging of acute cervical spine injuries
Energy Technology Data Exchange (ETDEWEB)
Kim, Kyu Hwa; Lee, Jung Hyung; Joo, Yang Goo [School of Medicine, Keimyung University, Daegu (Korea, Republic of)
1995-01-15
To describe magnetic resonance (MR) findings of the patients with acute cervical spinal injury and to assess the usefulness of the MR imagings. We retrospectively reviewed the MR images of 32 patients with acute cervical spinal injury. MR images were obtained with a 2.0 T superconductive MR imaging units (Spectro-20000, Gold-Star, Seoul), using spin-echo and gradient-echo technique. Most of patients were in their 3rd-4th decades and motor vehicle accident was the most frequent cause of acute cervical trauma. We assessed the MR findings with respect to the spinal cord, ligaments, paravertebral soft tissues, intervertebral disk, and bony spine. Spinal cord injury was the most common (65%), where cord swelling, edema, and/or hematoma were demonstrated most frequently at C5-6 level. Traumatic intervertebral disk herniations were the second most common (62.5%) and frequently occurred at the lower cervical levels, mostly at C5-6. Paravertebral soft tissue injury, vertebral body fracture, bone marrow edema and displacement were also well shown on MR images. MR imaging appears to be essential for the evaluation of traumatic disk herniations, spinal cord abnormalities, and injury of paravertebral soft tissue in the acute injury of the cervical spine.
MR imaging of acute cervical spine injuries
International Nuclear Information System (INIS)
Kim, Kyu Hwa; Lee, Jung Hyung; Joo, Yang Goo
1995-01-01
To describe magnetic resonance (MR) findings of the patients with acute cervical spinal injury and to assess the usefulness of the MR imagings. We retrospectively reviewed the MR images of 32 patients with acute cervical spinal injury. MR images were obtained with a 2.0 T superconductive MR imaging units (Spectro-20000, Gold-Star, Seoul), using spin-echo and gradient-echo technique. Most of patients were in their 3rd-4th decades and motor vehicle accident was the most frequent cause of acute cervical trauma. We assessed the MR findings with respect to the spinal cord, ligaments, paravertebral soft tissues, intervertebral disk, and bony spine. Spinal cord injury was the most common (65%), where cord swelling, edema, and/or hematoma were demonstrated most frequently at C5-6 level. Traumatic intervertebral disk herniations were the second most common (62.5%) and frequently occurred at the lower cervical levels, mostly at C5-6. Paravertebral soft tissue injury, vertebral body fracture, bone marrow edema and displacement were also well shown on MR images. MR imaging appears to be essential for the evaluation of traumatic disk herniations, spinal cord abnormalities, and injury of paravertebral soft tissue in the acute injury of the cervical spine
Daly, Amanda; Barker, Michelle
2010-01-01
International student exchange programmes are acknowledged as one aspect of a broader suite of internationalisation strategies aimed at enhancing students' intercultural understanding and competence. The decision to participate in an exchange programme is dependent on both individual and contextual factors such as student exchange policies and…
International Nuclear Information System (INIS)
Gaffke, Gunnar; Nagel, Stefan; Hegemann, Olaf; Speck, Ulrich; Grosse-Siestrup, Christian; Jungnickel, Kerstin; Stroszczynski, Christian
2009-01-01
Purpose:To represent a MRI-compatible perfusion-system for extracorporeal perfusion of vital organs which permits the realisation of realistic experiments in a MR scanner. Material and methods: We performed MR examinations of explanted porcine livers and MR-guided interventions in porcine livers. Explanted organs were hemo-perfused under physiological conditions during the experiments. MR-sequences for diagnostic and interventional examinations were used. Results:The evaluated system was MRI-compatible. The achieved image quality of the used sequences showed excellent anatomical resolution. Planned experiments can be carried out with relatively low expenditure. Diagnostic as well as interventional investigations can be carried out. The used organs showed a stable function within physiological parameters up to 4 hours. Conclusion:It is possible to perform ex vivo experiments under in vivo conditions with this system. With the used MR-compatible system MR-guided experimental interventions and thermal ablations can be carried out in explanted organs under in vivo conditions. (orig.)
Deep MR to CT synthesis using unpaired data
Wolterink, Jelmer M.; Dinkla, Anna M.; Savenije, Mark H.F.; Seevinck, Peter R.; van den Berg, Cornelis A.T.; Išgum, Ivana
2017-01-01
MR-only radiotherapy treatment planning requires accurate MR-to-CT synthesis. Current deep learning methods for MR-to-CT synthesis depend on pairwise aligned MR and CT training images of the same patient. However, misalignment between paired images could lead to errors in synthesized CT images. To
Serial MR imaging in Creutzfeldt-Jakob disease
Energy Technology Data Exchange (ETDEWEB)
Uchino, A.; Hata, H.; Ohno, M. (Kyushu Rosai Hospital, Kitakyushu (Japan). Dept. of Radiology); Yoshinaga, M.; Shiokawa, O. (Kyushu Rosai Hospital, Kitakyushu (Japan). Stroke Care Unit)
1991-08-01
Serial magnetic resonance (MR) imagings of two autopsied patients with Creutzfeldt-Jakob disease (CJD) are presented. Both patients showed a dramatic progression of brain atrophy. The initial MR imagings were, however, interpreted as normal except for localized mild cortical atrophy in one patient. When a normal MR image is obtained in a demented middle-aged or aged patient, CJD may still need to be ruled out: follow up MR imaging may be useful. (orig.).
Serial MR imaging in Creutzfeldt-Jakob disease
International Nuclear Information System (INIS)
Uchino, A.; Hata, H.; Ohno, M.; Yoshinaga, M.; Shiokawa, O.
1991-01-01
Serial magnetic resonance (MR) imagings of two autopsied patients with Creutzfeldt-Jakob disease (CJD) are presented. Both patients showed a dramatic progression of brain atrophy. The initial MR imagings were, however, interpreted as normal except for localized mild cortical atrophy in one patient. When a normal MR image is obtained in a demented middle-aged or aged patient, CJD may still need to be ruled out: follow up MR imaging may be useful. (orig.)
MR findings of brainstem injury
Energy Technology Data Exchange (ETDEWEB)
Park, Man Soo; Hwang, Woo Cheol; Park, Choong Ki [Hallym University College of Medicine, Seoul (Korea, Republic of); Suh, Dae Chul [University of Ulsan College of Medicine, Seoul (Korea, Republic of); Kim, Sang Joon [Dankook University of College of Medicine, Cheonan (Korea, Republic of)
1995-02-15
To analyze the characteristics of traumatic brainstem injury by CT and MR. CT and MR studies of 10 patients with traumatic brainstem lesion in MR were retrospectively reviewed, particularly attended to location, signal intensity and associated lesions. CT failed to depict 8 of 10 brainstem lesions. All lesions were detected in MR images with T2-weighted images showing higher detection rate (n = 10) (100%) than T1-weighted images (n = 3) (30%) or CT (n = 2) (20%). The brainstem lesions located in the dorsolateral aspects of the rostral brainstem (mid brain and upper pons) in 7 (70%) cases, in ventral aspects of rostral brain in 2 (20%) cases and in median portion of pons in 1 (10%) case. Corpus callosal (n = 5), lobar white matter (n = 5) diffuse axonal injury, and 2 hemorrhagic lesions in basal ganglia were the associated findings. MR imaging is more helpful than CT in the detection of brainstem injury, especially T2 weighted images. Primary brainstem lesions were typically located in the dorsolateral aspect of rostral brainstem (midbrain and upper pons). Corpus callosum and white matter lesions were frequently associated.
International Nuclear Information System (INIS)
Victoria, Teresa; Chauvin, Nancy Anne; Johnson, Ann M.; Kramer, Sandra Sue; Epelman, Monica; Capilla, Elena
2011-01-01
Fetal demise is an uncommon event encountered at MR imaging. When it occurs, recognition by the interpreting radiologist is important to initiate appropriate patient management. To identify MR findings of fetal demise. Following IRB approval, a retrospective search of the radiology fetal MR database was conducted searching the words ''fetal demise'' and ''fetal death.'' Fetuses with obvious maceration or no sonographic confirmation of death were excluded. Eleven cases formed the study group. These were matched randomly to live fetuses of similar gestational age. Images were reviewed independently by three pediatric radiologists. The deceased fetus demonstrates decreased MR soft-tissue contrast and definition of tissue planes, including loss of gray-white matter differentiation in the brain. The signal within the cardiac chambers, when visible, is bright on HASTE sequences from the stagnant blood; the heart is small. Pleural effusions and decreased lung volumes may be seen. Interestingly, the fetal orbits lose their anatomical round shape and become smaller and more elliptical; a dark, irregular rim resembling a mask may be seen. Although fetal demise is uncommonly encountered at MR imaging, radiologists should be aware of such imaging findings so prompt management can be instituted. (orig.)
Unusual MR manifestations of neurocysticercosis
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Suh, D.C. (Seoul National Univ. (Republic of Korea). Dept. of Radiology; Woolsan Medical Coll., Seoul (Republic of Korea). Dept. of Radiology); Chang, K.H.; Han, M.H.; Han, M.C.; Kim, C.W. (Seoul National Univ. (Republic of Korea). Dept. of Radiology); Lee, S.R. (Hanyang Univ., Seoul (Republic of Korea). Dept. of Radiology)
1989-11-01
MR and CT features of neurocysticercosis are variable and depend fundamentally on the stage in evolution of the infection, location, number and size of the worm. The authors retrospectively evaluated MR images obtained on a 2.0T superconducting unit in 22 neurocysticercosis patients and observed various MR features including some new findings. A variety of MR findings are presented with special reference to six case reports. The features include: (1) A large simple cyst containing both internal septations and a scolex; (2) suprasellar racemose cysts mimicking other cysts, (3) a fourth ventricular cyst readily depicted by aid of CSF flow-void in the sagittal plane; (4) degenerating cysts showing 'white target' appearance; (5) granulomatous lesions having a 'black target' appearance; and (6) a meningitic form showing Gd-DTPA enhancement of basal cisterns and of a subacute infarct. (orig.).
Investigating the effects of liquidity and exchange rate on Tehran Stock Exchange
Directory of Open Access Journals (Sweden)
Younos Vakil Alroaia
2014-08-01
Full Text Available This paper presents an empirical investigation to study the effects of two macroeconomic factors; namely exchange rate and liquidity on stock index. The proposed study was applied in Iran and on major index of Tehran Stock Exchange over the period 2001-2011. They reported that the currency exchange maintained negative impact on stock exchange for the period of investigation. This is due to the fact that when currency devalued, working capital decreases and firms did not enough money to purchase raw materials, pay wages, etc. In addition, liquidity marinated a direct and positive relationship with exchange index. However, the impact of liquidity seems to be bigger than currency exchange.
International Nuclear Information System (INIS)
Kang, Heung Sik; Chung, Sung Hoon; KIm, Cheol Woo; Kim, Seong Moon; Im, Jung Gi; Han, Man Chung
1993-01-01
To evaluate the reliability of MR imaging in tissue characterization and depiction of tumor boundaries, we performed MR pathologic correlation using parosteally implanted VX-2 carcinoma in 17 rabbit thighs. T1-weighted, T2-weighted and Gd-DTPA enhanced T1-weighted axial images were obtained 10-30 days after tumor implantation. After the animals were killed, frozen and sectioned along the MR imaging planes, and histopathologic examination were done. For accurate MR pathologic correlation, rabbit were fixed on the cardboard plate to minimize position change during the procedure. Tumor boundaries depicted on MR images were larger than those depicted on the specimen. Small tumors were surrounded by capsule-like loose connective tissue. Loose connective tissue became compact with tumor growth. This connective tissue showed high signal intensity on both T2-weighted and Gd-DTPA enhanced T1-weighted images. Muscle atrophy with fatty tissue accumulation around the tumor also contributed to the high signal intensity on MR images. Peritumoral edema and inflammatory reaction were not remarkable. Six of 8 cases with bone marrow fibrosis were detected on MR images. We concluded that peritumoral loose connective tissue and muscle atrophy exaggerated the size of experimentally induced malignant musculoskeletal tumors on MR images
Questionnaire responses concerning safety issues in MR examination
International Nuclear Information System (INIS)
Yamaguchi-Sekino, Sachiko; Nakai, Toshiharu; Muranaka, Hiroyuki
2011-01-01
Recently, the rising numbers of medical implants and scanners with higher static magnetic field have increased safety concerns for magnetic resonance (MR) examination. To determine future safety focus, we distributed anonymous questionnaires to 3250 members of the Japanese Society for Magnetic Resonance in Medicine (JSMRM) and received 978 responses. Safety issues on the questionnaire concentrated on the handling of patients with implants (Q7-18, appendix), acoustic trauma due to scanning (Q19-21, appendix), and MR compatibility within the scanner room (Q22-25, appendix). Ninety-three percent of respondents indicated they had encountered cases with implants or medical materials of unknown MR compatibility; 21.7% reported heating problems and 15.0%, nerve stimulation problems, in patients with implants during MR examination. Although 88.7% of respondents recognized the term ''MR compatibility'', 68.2% indicated limited detailed understanding of the term. Eleven percent had had cases with suspected acoustic injury from MR scanner noise. Scanner noise levels were not clarified in any way in 37.4% cases, but 69.5% applied ear protection to patients. Labeling of ''MR compatibility'' of equipment brought into the MR scanner room was reported by 71.9%. More than 50% experienced MR compatibility issues related to equipment brought into the MR scanner room. With regard to safety issues on metallic objects which are implanted in MR workers, 88.1% indicated they would continue current operations even the implant is inside the body. Respondents identified lectures and seminars by professional societies, safety training by manufacturers, and information from the Internet and literature as the 3 main sources for up-dating safety information for MR examination. (author)
Craniofacial duplication (diprosopus): CT, MR imaging, and MR angiography findings case report.
Hähnel, Stefan; Schramm, Peter; Hassfeld, Stefan; Steiner, Hans H; Seitz, Angelika
2003-01-01
Diprosopus is one of the rarest malformations in humans. In addition to the facial structures, the cerebral frontal lobes were duplicated in this case. Three pairs of anterior cerebral arteries were detected, and the rostral parts of the superior sagittal sinus were duplicated. Computed tomography, magnetic resonance (MR) imaging, and MR angiography allowed study of the degree of duplicative changes in diprosopus, especially for planning cosmetic correction. Copyright RSNA, 2002
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Fukukura, Yoshihiko, E-mail: fukukura@m.kufm.kagoshima-u.ac.jp [Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City 890-8544 (Japan); Takumi, Koji [Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City 890-8544 (Japan); Higashi, Michiyo [Department of Human Pathology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City 890-8544 (Japan); Shinchi, Hiroyuki [Department of Surgical Oncology and Digestive Surgery, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City 890-8544 (Japan); Kamimura, Kiyohisa; Yoneyama, Tomohide; Tateyama, Akihiro [Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima City 890-8544 (Japan)
2014-04-15
Objective: To determine whether contrast enhancement of CT and apparent diffusion coefficient on diffusion-weighted MR imaging are important parameters that can predict outcomes for patients with pancreatic ductal adenocarcinoma. Materials and methods: Ninety-two patients with histologically confirmed pancreatic ductal adenocarcinoma who underwent quadriphasic CT (including unenhanced, pancreatic parenchymal, portal venous and delayed phases) and fat-suppressed single-shot echo-planar diffusion-weighted MR imaging at 3.0 T were retrospectively analyzed to investigate prognostic factors. Overall survival curves were drawn using the Kaplan–Meier method. Effects on survival of variables including age, sex, tumor location, tumor size, TNM stage, carbohydrate antigen 19-9, carcinoembryonic antigen, treatment, tumor contrast enhancement and apparent diffusion coefficient values were analyzed in univariate analysis using the log-rank test. Variables were analyzed in multivariate analyses using the Cox proportional hazards regression model. Results: Median survival for the entire patient population was 18.2 months. Higher contrast enhancement during all phases was associated with significantly longer overall survival (P < 0.001 for all phases). The difference in overall survival between groups divided by median apparent diffusion coefficient value was not significant (P = 0.672). TNM stage (P = 0.026) and tumor contrast enhancement on CT (P = 0.027) were significantly related to survival in multivariate analysis. Conclusions: Poor enhancement of pancreatic adenocarcinomas on enhanced CT is associated with reduced patient survival.
International Nuclear Information System (INIS)
Fukukura, Yoshihiko; Takumi, Koji; Higashi, Michiyo; Shinchi, Hiroyuki; Kamimura, Kiyohisa; Yoneyama, Tomohide; Tateyama, Akihiro
2014-01-01
Objective: To determine whether contrast enhancement of CT and apparent diffusion coefficient on diffusion-weighted MR imaging are important parameters that can predict outcomes for patients with pancreatic ductal adenocarcinoma. Materials and methods: Ninety-two patients with histologically confirmed pancreatic ductal adenocarcinoma who underwent quadriphasic CT (including unenhanced, pancreatic parenchymal, portal venous and delayed phases) and fat-suppressed single-shot echo-planar diffusion-weighted MR imaging at 3.0 T were retrospectively analyzed to investigate prognostic factors. Overall survival curves were drawn using the Kaplan–Meier method. Effects on survival of variables including age, sex, tumor location, tumor size, TNM stage, carbohydrate antigen 19-9, carcinoembryonic antigen, treatment, tumor contrast enhancement and apparent diffusion coefficient values were analyzed in univariate analysis using the log-rank test. Variables were analyzed in multivariate analyses using the Cox proportional hazards regression model. Results: Median survival for the entire patient population was 18.2 months. Higher contrast enhancement during all phases was associated with significantly longer overall survival (P < 0.001 for all phases). The difference in overall survival between groups divided by median apparent diffusion coefficient value was not significant (P = 0.672). TNM stage (P = 0.026) and tumor contrast enhancement on CT (P = 0.027) were significantly related to survival in multivariate analysis. Conclusions: Poor enhancement of pancreatic adenocarcinomas on enhanced CT is associated with reduced patient survival
MR imaging of the spine in children
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Duthoy, M.J.; Lund, G.
1988-08-01
MR imaging was reviewed in 66 pediatric spinal cord patients with diagnoses of posterior fossa tumor, primary spinal cord tumor, metastatic disease, neuroectodermal disorder, congenital malformation, trauma, and demyelinating, neurodegenerative, or metabolic disorders. MR proved to be useful in delineating the extent of posterior fossa and cord tumor including metastasis to the cord. MR was of limited value in demyelinating and metabolic disorders. Arnold Chiari malformations, syringomyelia, tethered cord and meningoceles were all easily evaluated using MR.
Value of new MR techniques in MR-PET
International Nuclear Information System (INIS)
Attenberger, U.I.; Schoenberg, S.O.; Quick, H.H.; Guimaraes, A.; Catalano, O.; Morelli, J.N.
2013-01-01
The unparalleled soft tissue contrast of magnetic resonance imaging (MRI) and the functional information obtainable with 18-F fluorodeoxyglucose positron emission tomography (FDG-PET) render MR-PET well-suited for oncological and psychiatric imaging. The lack of ionizing radiation with MRI also makes MR-PET a promising modality for oncology patients requiring frequent follow-up and pediatric patients. Lessons learned with PET computed tomography (CT) over the last few years do not directly translate to MR-PET. For example, in PET-CT the Hounsfield units derived from CT are used for attenuation correction (AC). As 511 keV photons emitted in PET examinations are attenuated by the patient's body CT data are converted directly to linear attenuation coefficients (LAC); however, proton density measured by MRI is not directly related to the radiodensity or LACs of biological tissue. Thus, direct conversion to LAC data is not possible making AC more challenging in simultaneous MRI-PET scanning. In addition to these constraints simultaneous MRI-PET acquisitions also improve on some solutions to well-known challenges of hybrid imaging techniques, such as limitations in motion correction. This article reports on initial clinical experiences with simultaneously acquired MRI-PET data, focusing on the potential benefits and limitations of MRI with respect to motion correction as well as metal and attenuation correction artefacts. (orig.) [de
International Nuclear Information System (INIS)
Blumhagen, Jan O.; Ladebeck, Ralf; Fenchel, Matthias; Braun, Harald; Quick, Harald H.; Faul, David; Scheffler, Klaus
2014-01-01
Purpose: In quantitative PET imaging, it is critical to accurately measure and compensate for the attenuation of the photons absorbed in the tissue. While in PET/CT the linear attenuation coefficients can be easily determined from a low-dose CT-based transmission scan, in whole-body MR/PET the computation of the linear attenuation coefficients is based on the MR data. However, a constraint of the MR-based attenuation correction (AC) is the MR-inherent field-of-view (FoV) limitation due to static magnetic field (B 0 ) inhomogeneities and gradient nonlinearities. Therefore, the MR-based human AC map may be truncated or geometrically distorted toward the edges of the FoV and, consequently, the PET reconstruction with MR-based AC may be biased. This is especially of impact laterally where the patient arms rest beside the body and are not fully considered. Methods: A method is proposed to extend the MR FoV by determining an optimal readout gradient field which locally compensates B 0 inhomogeneities and gradient nonlinearities. This technique was used to reduce truncation in AC maps of 12 patients, and the impact on the PET quantification was analyzed and compared to truncated data without applying the FoV extension and additionally to an established approach of PET-based FoV extension. Results: The truncation artifacts in the MR-based AC maps were successfully reduced in all patients, and the mean body volume was thereby increased by 5.4%. In some cases large patient-dependent changes in SUV of up to 30% were observed in individual lesions when compared to the standard truncated attenuation map. Conclusions: The proposed technique successfully extends the MR FoV in MR-based attenuation correction and shows an improvement of PET quantification in whole-body MR/PET hybrid imaging. In comparison to the PET-based completion of the truncated body contour, the proposed method is also applicable to specialized PET tracers with little uptake in the arms and might reduce the
MR evaluation of brachial plexus injuries
International Nuclear Information System (INIS)
Gupta, R.K.; Jain, R.K.; Mehta, V.S.; Banerji, A.K.
1989-01-01
Ten cases of brachial plexus injury were subjected to magnetic resonance (MR) to demonstrate the roots, trunks, divisions or cord abnormalities. Both normal and abnormal brachial plexuses were imaged in sagittal, axial, coronal and axial oblique planes. Myelography, using water soluble contrast agents, was performed in seven cases. MR demonstrated one traumatic meningocele, one extradural cerebrospinal fluid (CSF) collection, trunk and/or root neuromas in four, focal root fibrosis in two and diffuse fibrosis in the remaining two cases. Results of MR were confirmed at surgery in four cases with neuromas, while myelography was normal in two and was not carried out in the remaining two. In two cases, where MR demonstrated diffuse fibrosis of the brachial plexus, myelography showed C7 and T1 traumatic meningocele in one and was normal in the other. Both these patients showed excellent clinical and electrophysiological correlation with MR findings and in one of them surgical confirmation was also obtained. In the other two cases with focal nerve root fibrosis, myelography was normal in one and showed a traumatic meningocele in another. Operative findings in these cases confirmed focal root fibrosis but no root avulsion was observed although seen on one myelogram. Focal fibrosis, however, was noted at operation in more roots than was observed with MR. Initial experience suggests that MR may be the diagnostic procedure of choice for complete evaluation of brachial plexus injuries. (orig.)
MR imaging of von Hippel-Lindau disease
International Nuclear Information System (INIS)
Sato, Y.; Waziri, M.H.; Smith, W.L.; Frey, E.E.; Franken, E.A.
1986-01-01
Sixteen patients with von Hippel-Lindau disease (VH-L) and 11 asymptomatic family members underwent a total of 29 central nervous system (CNS) and 23 body MR imaging evaluations during a 2-year study period. Nineteen CNS and spinal lesions and nine abdominal visceral lesions were identified on MR imaging and were confirmed at surgery or by other imaging modalities. MR imaging is superior to CT in the evaluation of intraocular vitreous abnormalities and cerebellar and spinal hemangioblastomas because of superior tissue characterization and lack of bone artifacts. MR imaging adequately demonstrated the abdominal visceral lesions. MR imaging is a sensitive and reliable imaging modality for the various lesions of VH-L
MR imaging of pleural and peritoneal effusion
International Nuclear Information System (INIS)
Shiono, Takahiro; Yoshikawa, Kohki; Takenaka, Eiichi; Hisamatsu, Katsuji
1993-01-01
The purpose of this study was to assess the efficacy of MR imaging in predicting the quality of ascites and pleural effusion. MR examinations of 20 patients with different benign or malignant diseases accompanied with ascites or pleural effusion were retrospectively studied. Results were compared with histopathological findings. On T 1 - and T 2 -weighted images, the MR intensity of the effusion depended mainly on the concentration of protein, whereas on gradient echo images, it depended mainly on the concentration of blood. MR examination was useful in non-invasively differentiating exudative or hemorrhagic effusion from serous effusion. Knowledge or inference of the quality of effusion can direct MR interpretation and may improve diagnostic accuracy. (author)
Trosiuk, Tetiana V; Shalak, Vyacheslav F; Szczepanowski, Roman H; Negrutskii, Boris S; El'skaya, Anna V
2016-02-01
Eukaryotic translation elongation factor 1Bα (eEF1Bα) is a functional homolog of the bacterial factor EF-Ts, and is a component of the macromolecular eEF1B complex. eEF1Bα functions as a catalyst of guanine nucleotide exchange on translation elongation factor 1A (eEF1A). The C-terminal domain of eEF1Bα is necessary and sufficient for its catalytic activity, whereas the N-terminal domain interacts with eukaryotic translation elongation factor 1Bγ (eEF1Bγ) to form a tight complex. However, eEF1Bγ has been shown to enhance the catalytic activity of eEF1Bα attributed to the C-terminal domain of eEF1Bα. This suggests that the N-terminal domain of eEF1Bα may in some way influence the guanine nucleotide exchange process. We have shown that full-length recombinant eEF1Bα and its truncated forms are non-globular proteins with elongated shapes. Truncation of the N-terminal domain of eEF1Bα, which is dispensable for catalytic activity, resulted in acceleration of the rate of guanine nucleotide exchange on eEF1A compared to full-length eEF1Bα. A similar effect on the catalytic activity of eEF1Bα was observed after its interaction with eEF1Bγ. We suggest that the non-catalytic N-terminal domain of eEF1Bα may interfere with eEF1A binding to the C-terminal catalytic domain, resulting in a decrease in the overall rate of the guanine nucleotide exchange reaction. Formation of a tight complex between the eEF1Bγ and eEF1Bα N-terminal domains abolishes this inhibitory effect. © 2015 FEBS.
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Abd Ellah, Mohamed, E-mail: dr_m_hamdy2006@hotmail.co [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria); Kremser, Christian, E-mail: christian.kremser@i-med.ac.a [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria); Pallwein, Leo, E-mail: leo.pallwein-prettner@uki.a [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria); Aigner, Friedrich, E-mail: friedrich.Aigner@uki.a [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria); Schocke, Michael, E-mail: michael.schocke@i-med.ac.a [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria); Peschel, Reinhard, E-mail: reinhard.peschel@uki.a [Innsbruck Medical University, Urology Dept., Anich St. 35, 6020 Innsbruck (Austria); Pedross, Florian, E-mail: florian.pedross@i-med.ac.a [Innsbruck Medical University, Medical Statistics Dept., Anich St. 35, 6020 Innsbruck (Austria); Pinggera, Germar-Michael, E-mail: germar.pinggera@uki.a [Innsbruck Medical University, Urology Dept., Anich St. 35, 6020 Innsbruck (Austria); Wolf, Christian, E-mail: christian.wolf@bkh-reutte.a [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria); Alsharkawy, Mostafa A.M., E-mail: drmostafamri@yahoo.co [Assiut University, Radiology Dept., Assiut (Egypt); Jaschke, Werner, E-mail: werner.jaschke@i-med.ac.a [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria); Frauscher, Ferdinand, E-mail: ferdinand.frauscher@uki.a [Innsbruck Medical University, Radiology Dept., Anich St. 35, 6020 Innsbruck (Austria)
2010-10-15
The annual incidence of stone formation is increased in the industrialised world. Extracorporeal shockwave lithotripsy is a non-invasive effective treatment of upper urinary tract stones. This study is aimed to evaluate changes of renal blood flow in patients undergoing extracorporeal shock wave lithotripsy (ESWL) by arterial spin labeling (ASL) MR imaging, contrast enhanced dynamic MR imaging, and renal resistive index (RI). Thirteen patients with nephrolithiasis were examined using MR imaging and Doppler ultrasound 12 h before and 12 h after ESWL. ASL sequence was done for both kidneys and followed by contrast enhanced MR imaging. In addition RI Doppler ultrasound measurements were performed. A significant increase in RI (p < 0.001) was found in both treated and untreated kidneys. ASL MR imaging also showed significant changes in both kidneys (p < 0.001). Contrast enhanced dynamic MR imaging did not show significant changes in the kidneys. ESWL causes changes in RI and ASL MR imaging, which seem to reflect changes in renal blood flow.
Functional analysis in MR urography - made simple
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Khrichenko, Dmitry; Darge, Kassa [Children' s Hospital of Philadelphia, Department of Radiology, Philadelphia, PA (United States)
2010-02-15
MR urography (MRU) has proved to be a most advantageous imaging modality of the urinary tract in children, providing one-stop comprehensive morphological and functional information, without the utilization of ionizing radiation. The functional analysis of the MRU scan still requires external post-processing using relatively complex software. This has proved to be a limiting factor in widespread routine implementation of MRU functional analysis and use of MRU functional parameters similar to nuclear medicine. We present software, developed in a pediatric radiology department, that not only enables comprehensive automated functional analysis, but is also very user-friendly, fast, easily operated by the average radiologist or MR technician and freely downloadable Virtual Machine is required for the installation, which is obtained at no charge. The analysis software, known as ''CHOP-fMRU,'' has the potential to help overcome the obstacles to widespread use of functional MRU in children. (orig.)
High-resolution MR imaging of wrist cartilage
International Nuclear Information System (INIS)
Rominger, M.B.; Bernreuter, W.K.; Listinsky, J.J.; Lee, D.H.; Kenney, P.J.; Colgin, S.L.
1991-01-01
This paper reports that cartilage is an important prognostic factor in arthritis. MR imaging can demonstrate both articular cartilage and subchondral bone. Our purpose was to compare various sequences, for wrist cartilage imaging and determine how extensive damage must be before it is detectable with MR imaging. Six cadaver wrists were imaged before and after arthroscopic cartilage injury (coronal and axial T1- and T2-weighted SE sequences, 3-mm sections; SPGR 45 degrees flip angle volume images with fat saturation. 1.2-mm sections; plus T1-weighted coronal images with fat saturation after injury; General Electric Signa, 1.5 T, with transmit-receive extremity coil). Twenty-two defects were created arthroscopically. Five normal volunteers were imaged for comparison. The greatest contrast among bone, cartilage, and synovial fluid was achieved with T1-weighted fat-suppressed SE image and SPGR. Gradient-recalled volume sequences generated very thin sections but were susceptible to artifact
MR imaging of the neonatal brain: Pathologic features
International Nuclear Information System (INIS)
McArdle, C.B.; Richardson, C.J.; Nicholas, D.A.; Hayden, C.K.; Amparo, E.G.
1986-01-01
Seventy-three neonates, aged 29-43 weeks since conception, were studied. US and/or CT correlations were obtained in most infants with pathology. In the first 4-5 days after hemorrhage, US and CT were superior to MR imaging, but after that time MR imaging was the single best modality for imaging blood. In early premature infants with very watery white matter, US detected infarction and brain edema that were poorly seen on both MR imaging and CT. However, in late premature and full-term infants, MR imaging was better than CT in distinguishing between normal white matter and infarction. Only MR imaging disclosed delayed myelination in 13 term infants with hydrocephalus and severe asphyxia. MR imaging with play an important role in imaging neonates once MR imaging-compatible monitors and neonatal head coils become widely available
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Min, Soo Hyun; Kim, Soo Youn; Lee, Ghi Jai; Shim, Jae Chan; Oh, Tae Kyung; Kim, Ho Kyun [College of Medicine, Jnje University, Seoul (Korea, Republic of)
2000-03-01
To compare the findings of fluid-attenuated inversion recovery (FLAIR) MR imaging in the detection of subarachnoid hemorrhage (SAH), with those of precontrast CT and T1-weighted MR imaging. In 13 patients (14 cases) with SAH, FLAIR MR images were retrospectively analyzed and compared with CT (10 patients, 11 cases) and T1-weighted MR images (9 cases). SAH was confirmed on the basis of high density along the subarachnoid space, as seen on precontrast CT, or lumbar puncture. MR imaging was performed on a 1.0T unit. FLAIR MR and CT images were obtained during the acute stage(less than 3 days after ictus) in 10 and 9 cases, respectively, during the subacute stage (4-14 days after ictus) in two cases and one, respectively, and during the chronic stage (more than 15 days after ictus) in two cases and one, respectively. CT was performed before FLAIR MR imaging, and the interval between CT and FLAIR ranged from 24 hours (6 cases) to 2-3 (2 cases) or 4-7 days (3 cases). In each study, the conspicuity of visualization of SAH was graded as excellent, good, fair, or negative at five locations (sylvian fissure, cortical sulci, anterior basal cistern, posterior basal cistern, and perimesencephalic cistern). In all cases, subarachnoid hemorrhages were demonstrated as high signal intensity areas on FLAIR images. The detection rates for SAH on CT and T1-weighted MR images were 100% (11/11) and 89% (8/9), respectively. FLAIR was superior to T1-weighted imaging in the detection of SAH at all sites except the anterior basal cistern (p less than 0.05) and superior to CT in the detection of SAH at the cortical sulci (p less than 0.05). On FLAIR MR images, subarachnoid hemorrhages at all stages are demonstrated as high signal intensity areas; the FLAIR MR sequence is thus considered useful in the detection of SAH. In particular FLAIR is more sensitive than CT for the detection of SAH in the cortical sulci. (author)
Directory of Open Access Journals (Sweden)
Farhad Heydarian
2010-12-01
Full Text Available Hyperbilirubinemia is common in neonates; it can have a serious rising course. Due to its critical morbidity called "kernicterus", severe neonatal hyperbilirubinemia causes which lead to exchange transfusion, should be clarified. This descriptive cross sectional study performed with reviewing of files of 118 neonates weighting 2kg and more who had exchange transfusion in pediatrics ward at Ghaem training hospital in Mashhad from April 2004 to March 2007. Among 118 patients, 75 (63.6% were male, and 43 patients (36.4% were female. The most common cause of exchange transfusion was ABO incompatibility (38.1%. In order of frequency, unknown etiology (25.4%, Rh incompatibility (16.1% with no immune hydrops, Sepsis(8.5%, urinary tract infection (5.1% and others (3.4% (Including Crigler-Najjar and cephalohematoma were next ones. Vaginal delivery and exclusive breast feeding were detected as associated factors. Mean serum bilirubin levels was 28.7 mg/dl (SD. 9.2 ABO incompatibility. ABO incompatibility was the main cause of exchange transfusion. Male gender, vaginal delivery and exclusive breast feeding were seen more among patients who need to be exchanged. So in case of ABO incompatibility especially when delivery route is vaginal, newborns should be visited soon again after early discharge from hospital.
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Sittek, H.; Perlet, C.; Kessler, M.; Reiser, M. [Institut fuer Radiologische Diagnostik, Klinikum Grossenhadern, Ludwig-Maximilians-Univ., Muenchen (Germany); Untch, M. [Klinik und Poliklinik fuer Frauenheilkunde und Geburtshilfe, Klinikum Grossenhadern, Ludwig-Maximilians-Univ., Muenchen (Germany)
1998-12-31
Material and Methods: We carried out 1505 MR mammographoes in 1357 patients. Biopsy was indicated in 413 cases. Among the malignancies, 23/214 (10%) were ILC. MR-M was performed with a 1.0 T whole body MRI system with a dynamic FLASH-3D sequence. Relative signal enhancement within lesions detected and morphologic pattern of contrast enhancement (mep) were determined. Three types of mep were distinguished: type 1 without contrast enhancement, type 2 with focal contrast enhancement, and type 3 with diffuse contrast enhancement of the glandular body. Results: Within MR-M alone, 19/23 (82.6%) of ILC were detected due to a mep type 2. Four ILC were false negative on MR-M (2 cases show mep type 1 or mep type 3). The sensitivity of Mx alone was 86.9% (20/23). When both Mx and MR-M were combined, all 23 ILC were detected. The addition of MR-M to Mx may increase sensitivity to about 100% in the detection of ILC. (orig.) [Deutsch] Material und Methode: Im Zeitraum 05/1993 bis 06/1996 fuehrten wir bei 1357 Patientinnen 1505 MR-Mammographien durch. In 413 Faellen wurde eine Probeexzision indiziert. Die histologische Untersuchung ergab in 214 Faellen einen malignen Tumor. Darunter befanden sich 23 ILC. Die MR-M wurden an einem 1,0 T MRT-System (Impact, Siemens, Erlangen) mit einer dynamischen FLASH 3D Sequenz durchgefuehrt. Neben dem prozentualen Anstieg der Signalintensitaet innerhalb einer Laesion haben wir fuer die Diagnostik folgende morphologische Befundmuster (BM) unterschieden: Typ 1: Keine Aufnahme, Typ 2: Fokale Aufnahme, Typ 3: Diffuse Aufnahme des Druesenkoerpers in der MR-M. Ergebnisse: Mit der MR-M konnten 19/23 (82,6%) der ILC anhand einer fokalen Zunahme der Signalintensitaet richtig positiv erkannt werden (BM Typ 2). Vier der ILC waren in der MR-M falsch negativ. In zwei Faellen (2/23) war keine Zunahme der Signalintensitaet zu verzeichnen (BM Typ 1). In zwei weiteren Faellen (2/23) maskierte eine diffuse Signalintensitaetszunahme des Druesenkoerpers (BM Typ 3
International Nuclear Information System (INIS)
Yu, Miao; Peng, Youxiang; Wang, Siqi; Fu, Jie; Choi, S B
2014-01-01
Under extreme service conditions in vehicle suspension systems, some defects exist in the hardening, bodying, and poor temperature stability of magnetorheological (MR) fluid. These defects can cause weak and even invalid performance in the MR fluid damper (MR damper for short). To ensure the effective validity of the practical applicability of the MR damper, one must implement an online state-monitoring sensor to monitor several performance factors, such as acceleration. In this empirical work, we propose a new energy-harvesting device system for the wireless sensor system of an MR damper. The monitoring sensor system consists of several components, such as an energy-harvesting device, energy-management circuit, and wireless sensor node. The electrical energy harvested from the kinetic energy of the MR fluid that flows within the MR damper can be automatically charged and discharged with the help of an energy-management circuit for the wireless sensor node. After verifying good performance from each component, an experimental apparatus is built to evaluate the feasibility of the proposed self-powered wireless sensor system. The measured results of pressure, temperature, and acceleration data within the MR damper clearly demonstrate the practical applicability of monitoring the operating work states of the MR damper when it is subjected to sinusoidal excitation. (technical note)
International Nuclear Information System (INIS)
Paetzel, C.; Zorger, N.; Bachthaler, M.; Voelk, M.; Seitz, J.; Herold, T.; Feuerbach, S.; Lenhart, M.; Nitz, W.R.
2004-01-01
Purpose: To show the feasibility of magnetic resonance (MR) for guided interventional therapy of femoral and popliteal artery stenoses with commercially available materials supported by MR real-time imaging and intraarterial MR angiography. Materials and Methods: Three patients (1 female, 2 male), suffering from symptomatic arterial occlusive disease with stenoses of the femoral (n=2) or popliteal (n=1) arteries were included. Intraarterial digital subtraction angiography was performed in each patient pre- and post-interventionally as standard of reference to quantify stenoses. The degree of the stenoses reached from 71-88%. The MR images were acquired on a 1.5 T MR scanner (Magnetom Sonata; Siemens, Erlangen, Germany). For MR-angiography, a Flash 3D sequence was utilized following injection of 5 mL diluted gadodiamide (Omniscan; Amersham Buchler, Braunschweig, Germany) via the arterial access. Two maximum intensity projections (MIP) were used as road maps and localizer for the interactive positioning of a continuously running 2D-FLASH sequence with a temporal solution of 2 images per second. During the intervention, an MR compatible monitor provided the image display inside the scanner room. Safety guidelines were followed during imaging in the presence of a conductive guidewire. The lesion was crossed by a commercially available balloon catheter (Wanda, Boston Scientific; Ratingen, Germany), which was mounted on a 0.035'' guidewire (Terumo; Leuven, Belgium). The visibility was provided by radiopaque markers embedded in the balloon and was improved by injection of 1 mL gadodiamide into the balloon. After dilation, the result was checked by intraarterial MR angiography and catheter angiography. Results: The stenoses could be correctly localized by intraarterial MR angiography. There was complete correlation between intraarterial MR angiography and digital subtraction angiography. The combination of guidewire and balloon was visible and the balloon was placed
Brain MR imaging in systemic lupus erythematous
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Park, Hyun Ae; Chang, Kee Hyun; Han, Moon Hee; Lee, Kyung Hwon; Kim, Sung Kwon; Lee, Jung Sang [Seoul National University College of Medicine, Seoul (Korea, Republic of); Cha, Sang Hoon [Chungbuk National University College of Medicine, Chungju (Korea, Republic of)
1992-09-15
To present MR imaging findings of intracranial lesions in systemic lupus erythematosus(SLE), a retrospective study was performed on MR images of 33 SLE patients with neurologic symptoms and signs. MR imaging was performed on either a 0.5 T (21 patients) or 2.0 T unit (12 patients), using T1-weighted, proton-density-weighted, and T2-weighted spin echo sequences in all patients. In seven patients, post-contrast T1-weighted images were also obtained after administration of gadopentetate dimeglumine. The main MR findings consisted of focal lesions suggesting ischemia/infarct (15 patients), diffuse brain atrophy (8), and findings associated with infection (4). The MR findings were normal in 11 patients (33%). The focal lesions suggesting ischemia/infarcts presumably secondary to vasculitis were distributed in the cortex or subcortical white matter (7 patients), deep periventricular white matter (3), or in both areas (5). Most of the focal lesions were multiple and small in size. The findings associated with infection were variable and included communicating hydrocephalus, meningeal enhancement, granuloma, etc. MR findings of SLE were non-specific and therefore clinical correlation is needed when evaluating SLE in MR.
Rosen's (M,R) system in process algebra.
Gatherer, Derek; Galpin, Vashti
2013-11-17
Robert Rosen's Metabolism-Replacement, or (M,R), system can be represented as a compact network structure with a single source and three products derived from that source in three consecutive reactions. (M,R) has been claimed to be non-reducible to its components and algorithmically non-computable, in the sense of not being evaluable as a function by a Turing machine. If (M,R)-like structures are present in real biological networks, this suggests that many biological networks will be non-computable, with implications for those branches of systems biology that rely on in silico modelling for predictive purposes. We instantiate (M,R) using the process algebra Bio-PEPA, and discuss the extent to which our model represents a true realization of (M,R). We observe that under some starting conditions and parameter values, stable states can be achieved. Although formal demonstration of algorithmic computability remains elusive for (M,R), we discuss the extent to which our Bio-PEPA representation of (M,R) allows us to sidestep Rosen's fundamental objections to computational systems biology. We argue that the behaviour of (M,R) in Bio-PEPA shows life-like properties.
Does MR imaging effectively replace diagnostic arthroscopy
International Nuclear Information System (INIS)
Ruwe, P.; McCarthy, S.; Wright, J.; Randall, L.; Lynch, K.; Jokyl, P.
1990-01-01
This paper determines if MR imaging reduces the number of diagnostic arthroscopic procedures required in patients with knee complaints and if MR imaging is cost-effective compared with diagnostic arthroscopy. The cohort analysis consists of 100 patients seen in a sports medicine clinic by two orthopedic surgeons who agreed on well-defined criteria for performing MR imaging and arthroscopy. Each orthopedic surgeon referring a patient for MR imaging checked a form regarding the plans for arthroscopy. Outcome analysis was conducted at 6 months
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Yamaguchi, Takako; Lee, Jin; Takahashi, Nobukazu; Oka, Takashi; Shizukuishi, Kazuya; Inoue, Tomio [Yokohama City University School of Medicine, Department of Radiology, Yokohama (Japan); Uemura, Hiroji; Kubota, Yoshinobu [Yokohama City University School of Medicine, Department of Urology, Kanagawa (Japan); Sasaki, Takeshi [Yokohama City University School of Medicine, Department of Pathology, Kanagawa (Japan); Endou, Hisashi [Yokohama City University School of Medicine, Department of Pharmacy, Kanagawa (Japan)
2005-07-01
Prostate cancer is difficult to visualise in its early stages using current imaging technology. The present study aimed to clarify the utility of {sup 11}C-choline PET for localising and evaluating cancer lesions in patients with prostate cancer by conducting a prospective comparison with magnetic resonance (MR) imaging combined with proton MR spectroscopy. PET and MR imaging combined with proton MR spectroscopy were performed in 20 patients with prostate cancer. Correlations among the metabolite ratio of choline + creatine to citrate (Cho+Cr/Ci) on MR spectroscopy, serum PSA and maximum standardised uptake value (SUV{sub max}) of {sup 11}C-choline were assessed. The location of the primary lesion was assessed by the site of SUV{sub max} and the laterality of the highest Cho+Cr/Ci ratio and confirmed by examination of surgical pathology specimens (n=16). PET exhibited a diagnostic sensitivity of 100% (20/20) for primary lesions, while the sensitivities of MR imaging and MR spectroscopy were 60% (12/20) and 65% (13/20), respectively. Weak linear correlations were observed between SUV{sub max} and serum PSA (r=0.52, p<0.05), and between SUV{sub max} and Cho+Cr/Ci ratio (r=0.49, p<0.05). Regarding the localisation of main primary lesions, PET results agreed with pathological findings in 13 patients (81%) ({kappa}=0.59), while MR spectroscopy results were in accordance with pathological findings in eight patients (50%) ({kappa}=0.11). This preliminary study suggests that {sup 11}C-choline PET may provide more accurate information regarding the localisation of main primary prostate cancer lesions than MR imaging/MR spectroscopy. A further clinical study of {sup 11}C-choline PET in a large number of patients suspected of prostate cancer will be necessary to determine the clinical utility of {sup 11}C-choline PET in patients who clinically require biopsy. (orig.)
MR imaging features of craniodiaphyseal dysplasia
Energy Technology Data Exchange (ETDEWEB)
Marden, Franklin A. [Mallinckrodt Institute of Radiology, Washington University Medical Center, 510 South Kingshighway Blvd., MO 63110, St. Louis (United States); Department of Radiology, St. Louis Children' s Hospital, Children' s Place, MO 63110, St. Louis (United States); Wippold, Franz J. [Mallinckrodt Institute of Radiology, Washington University Medical Center, 510 South Kingshighway Blvd., MO 63110, St. Louis (United States); Department of Radiology, St. Louis Children' s Hospital, Children' s Place, MO 63110, St. Louis (United States); Department of Radiology/Nuclear Medicine, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences, MD 20814, Bethesda (United States)
2004-02-01
We report the magnetic resonance (MR) imaging findings in a 4-year-old girl with characteristic radiographic and computed tomography (CT) features of craniodiaphyseal dysplasia. MR imaging exquisitely depicted cranial nerve compression, small foramen magnum, hydrocephalus, and other intracranial complications of this syndrome. A syrinx of the cervical spinal cord was demonstrated. We suggest that MR imaging become a routine component of the evaluation of these patients. (orig.)
International Nuclear Information System (INIS)
Bankaoglu, M.
2012-01-01
Full text: Magnetic resonance imaging has to rely on improving new various sequences and techniques and to get the best imaging quality so magnetic resonance (MR) arthrography is one of the most important technique in the assessment of selected musculoskeletal disorders. It is now widely utilized and considered by most musculoskeletal radiologists and some orthopedists to be an integral part of their clinical practice. The technique include: desired degree of joint distension with contrast medium; markedly improved imaging quality of intra-articular structures with the direct delineation so improved detection of pathology with MRI. As appliance and technique of MR arthrography is completely based on traditional arthrography of X ray. In MR arthrography additional very little amount of Gadolinium based contrast agent is added to the desired mixture of contrast material injected to the joint. As in conventional radiography MR arthrography is used to get extra information for conventional MRI . Practically any joint that can be accessed by a needle can be imaged using MR arthrography but it has been applied to limited number of joints to compare with the traditional arthrography so shoulder, knee, wrist, elbow, ankle, and hip are mostly subjects to do in MR arthrography. The procedure is also less invasive and expensive rather than diagnostic arthroscopy and should carefully indicated because it is not completely noninvasive technique so previous imaging modalities and MRI of the patients should be completed and evaluated well. During or after the procedure there has been no major complication reported by so far but more than two third of patients are known to complain some degree of pain right after or several times later than the procedure. As it is more than twenty years now it has been widely accepted helpful for diagnosis and adds some extra sensitivity to conventional MRI . Up to this time MR arthrography has proven to increase sensitivity of conventional MRI in
International Nuclear Information System (INIS)
Jang, Jin Hee; Kim, Bum Soo; KIm, Bom Yi; Choi, Hyun Seok; Jung, So Lyung; Ahn, Kook Jin; Sung, Ji Kyeong
2015-01-01
To evaluate the image characteristics of subtraction magnetic resonance venography (SMRV) from time-resolved contrast-enhanced MR angiography (TRMRA) compared with phase-contrast MR venography (PCMRV) and single-phase contrast-enhanced MR venography (CEMRV). Twenty-one patients who underwent brain MR venography (MRV) using standard protocols (PCMRV, CEMRV, and TRMRA) were included. SMRV was made by subtracting the arterial phase data from the venous phase data in TRMRA. Co-registration and subtraction of the two volume data was done using commercially available software. Image quality and the degree of arterial contamination of the three MRVs were compared. In the three MRVs, 19 pre-defined venous structures (14 dural sinuses and 5 cerebral veins) were evaluated. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the three MRVs were also compared. Single-phase contrast-enhanced MR venography showed better image quality (median score 4 in both reviewers) than did the other two MRVs (p < 0.001), whereas SMRV (median score 3 in both reviewers) and PCMRV (median score 3 in both reviewers) had similar image quality (p ≥ 0.951). SMRV (median score 0 in both reviewers) suppressed arterial signal better than did the other MRVs (median score 1 in CEMRV, median score 2 in PCMRV, both reviewers) (p < 0.001). The dural sinus score of SMRV (median and interquartile range [IQR] 48, 43-50 for reviewer 1, 47, 43-49 for reviewer 2) was significantly higher than for PCMRV (median and IQR 31, 25-34 for reviewer 1, 30, 23-32 for reviewer 2) (p < 0.01) and did not differ from that of CEMRV (median and IQR 50, 47-52 for reviewer 1, 49, 45-51 for reviewer 2) (p = 0.146 in reviewer 1 and 0.123 in reviewer 2). The SNR and CNR of SMRV (median and IQR 104.5, 83.1-121.2 and 104.1, 74.9-120.5, respectively) were between those of CEMRV (median and IQR 150.3, 111-182.6 and 148.4, 108-178.2) and PCMRV (median and IQR 59.4, 49.2-74.9 and 53.6, 43.8-69.2). Subtraction magnetic
Directory of Open Access Journals (Sweden)
Chunmei eLi
2015-10-01
Full Text Available Parkinson’s disease (PD is a neurodegenerative disorder characterized by nigrostriatal cell loss. To date the diagnosis of PD is still based primarily on the clinical manifestations which may be typical and obvious only in advanced-stage PD. Thus, it is crucial to find a reliable marker for the diagnosis of PD. We conducted this study to assess the diagnostic efficiency of chemical-exchange-saturation-transfer (CEST imaging and diffusion-tensor imaging (DTI in PD at 3 Tesla by evaluating changes on substantia nigra and striatum. Twenty-three PD patients and twenty-three age-matched normal controls were recruited. All patients and controls were imaged on a 3 Tesla MR system, using an 8-channel head coil. CEST imaging was acquired in two transverse slices of the head, including substantia nigra and striatum. The magnetization-transfer-ratio asymmetry at 3.5 ppm, MTRasym(3.5ppm, and the total CEST signal intensity between 0 and 4 ppm were calculated. Multi-slice DTI was acquired for all the patients and normal controls. Quantitative analysis was performed on the substantia nigra, globus pallidus, putamen and caudate. The MTRasym(3.5ppm value, the total CEST signal intensity and fractional anisotropy (FA value of the substantia nigra were all significantly lower in PD patients than in normal controls (P = 0.003, P = 0.004 and P < 0.001, respectively. The MTRasym(3.5ppm values of the putamen and the caudate were significantly higher in PD patients than in normal controls (P = 0.010 and P = 0.009, respectively. There were no significant differences for the mean diffusivity (MD in these four regions between PD patients and normal controls. In conclusion, CEST MR imaging provided multiple CEST image contrasts in the substantia nigra and the striatum in PD and may be superior to DTI in the diagnosis of PD.
Multipurpose simulator ''MR TRIOS'' for reprocessing plant
International Nuclear Information System (INIS)
Mitsui, Takeshi; Uehara, Shigeru; Takata, Hideo; Kamishima, Naoyuki
1993-01-01
MHI (Mitsubishi Heavy Industries) has developed MR TRIOS (Mitsubishi Reprocessing plant TRansient simulation code for Integrated process for Operation Support), the realtime dynamic simulator, for multipurpose use to support the Reprocessing Plant operation in various aspects. MR TRIOS integrates the Simulation Models of the unit process in a Reprocessing Plant, including Shearing, Dissolution, NOx absorption, Accountability and Adjustment and Co-decontamination process, where each Simulation Model has two kinds of models: Process and Control System. MR TRIOS can simulate the process behavior of the unit process in an integrated manner as well as independently. It is supported by MR CONTROL, the simulator control program developed by MHI. From MR TRIOS one can obtain real-time process values, such as temperature, pressure, density, flow rate, and concentration of nuclides, enabling the evaluation of the process dynamic characteristics under various operating conditions. MR TRIOS has proved to be an effective tool for the comprehensive study of the process and system dynamics, for operation technique improvements and for training
High-field MR imaging of tethered cord
International Nuclear Information System (INIS)
Sigal, R.; Bicetre, L.; Blass, C.; Doyon, D.; Pariente, D.
1986-01-01
MR imaging examinations of 12 patients with tethered cord syndrome have been performed on a 1.5-T MR imaging unit. Patients ranged in age from 3 to 60 years. MR findings were compared with those of myelography and metrizamide CT in all cases. Five patients underwent surgical control and postoperative MR imaging. Sagittal and axial sections were obtained using a spin-echo multisection, multiecho technique. T1-axial weighted images (SE 600/25) were sufficient to locate the position of the tip of the conus. They also allowed identification of extraspinal and intraspinal lipomas and clear-cut demarcation form associated tethered cord. Drawbacks of MR imaging were lack of precise depiction of the bone structures and the fact that clear identification of abnormal roots was problematic. The craniovertebral junction was always checked; two asymptomatic Chiari malformations were visualized. This study leads the authors to conclude that MR imaging should be used as the examination of first choice in the management of tethered cord syndrome
MR imaging of posttraumatic spinal ligament injury
International Nuclear Information System (INIS)
Pathria, M.N.; Emery, S.; Masaryk, T.J.; Wilber, R.G.; Bohlman, H.
1988-01-01
The accuracy of MR imaging in the detection of ligamentous injury was evaluated in 29 patients (24 male, five female) with spinal injury resulting in fractures (n=27), evidence of instability (n=11), or neurologic deficit (n=2). MR examinations were performed acutely (average, 7.5 days posttrauma) with T1- and T2-weighted imaging and were blindly evaluated. Subsequently, plain films (n=27), tomograms (n=10), and CT scans (n=22) were evaluated. Eighteen patients underwent surgery. Fourteen patients had torn ligaments as indicated by clinical and surgical findings. MR imaging demonstrated ligament damage in 13. One case imaged 40 days following trauma was not detected. No patients with intact ligaments had evidence of ligamentous damage on MR images. MR imaging demonstrated retropulsed fractures in six patients in whom the posterior longitudinal ligament was intact but displaced from the vertebra. MR imaging was more reliable than radiography and CT for detection of ligamentous injury, and T2- weighted sequences are essential in such cases
Dynamic MR imaging of the musculoskeletal system
International Nuclear Information System (INIS)
Shah, A.S.; Hylton, H.; Hentz, V.R.; Schattner, P.
1991-01-01
This paper reports on dynamic MR imaging which is an MR technique that allows imaging of the musculoskeletal system in motion. Current methods for observing the articulation of muscles and joints are limited to acquisition of stationary images at different spatial orientations. These images are then replayed from computer memory to simulate motion. Unlike stationary acquisition, dynamic MR imaging allows the volume of interest to be subjected to motion and dynamic stress, which is important for detecting stress-induced pathology. To demonstrate the utility of dynamic MR imaging, a system for imaging a moving wrist has been developed. The system consists of apparatus capable of providing simultaneous radialulnar deviation and flexion-extension, and hardware for system control and acquisition gating. The apparatus is mounted on the patient bed and is transferable to a variety of standard clinical MR imaging systems. Images were obtained during motion, and the ability of dynamic MR imaging to accurately image the moving wrist with very little motion artifact was demonstrated
MR guided spatial normalization of SPECT scans
International Nuclear Information System (INIS)
Crouch, B.; Barnden, L.R.; Kwiatek, R.
2010-01-01
Full text: In SPECT population studies where magnetic resonance (MR) scans are also available, the higher resolution of the MR scans allows for an improved spatial normalization of the SPECT scans. In this approach, the SPECT images are first coregistered to their corresponding MR images by a linear (affine) transformation which is calculated using SPM's mutual information maximization algorithm. Non-linear spatial normalization maps are then computed either directly from the MR scans using SPM's built in spatial normalization algorithm, or, from segmented TI MR images using DARTEL, an advanced diffeomorphism based spatial normalization algorithm. We compare these MR based methods to standard SPECT based spatial normalization for a population of 27 fibromyalgia patients and 25 healthy controls with spin echo T 1 scans. We identify significant perfusion deficits in prefrontal white matter in FM patients, with the DARTEL based spatial normalization procedure yielding stronger statistics than the standard SPECT based spatial normalization. (author)
Meisamy, Sina; Hines, Catherine D G; Hamilton, Gavin; Sirlin, Claude B; McKenzie, Charles A; Yu, Huanzhou; Brittain, Jean H; Reeder, Scott B
2011-03-01
To prospectively compare an investigational version of a complex-based chemical shift-based fat fraction magnetic resonance (MR) imaging method with MR spectroscopy for the quantification of hepatic steatosis. This study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained before all studies. Fifty-five patients (31 women, 24 men; age range, 24-71 years) were prospectively imaged at 1.5 T with quantitative MR imaging and single-voxel MR spectroscopy, each within a single breath hold. The effects of T2 correction, spectral modeling of fat, and magnitude fitting for eddy current correction on fat quantification with MR imaging were investigated by reconstructing fat fraction images from the same source data with different combinations of error correction. Single-voxel T2-corrected MR spectroscopy was used to measure fat fraction and served as the reference standard. All MR spectroscopy data were postprocessed at a separate institution by an MR physicist who was blinded to MR imaging results. Fat fractions measured with MR imaging and MR spectroscopy were compared statistically to determine the correlation (r(2)), and the slope and intercept as measures of agreement between MR imaging and MR spectroscopy fat fraction measurements, to determine whether MR imaging can help quantify fat, and examine the importance of T2 correction, spectral modeling of fat, and eddy current correction. Two-sided t tests (significance level, P = .05) were used to determine whether estimated slopes and intercepts were significantly different from 1.0 and 0.0, respectively. Sensitivity and specificity for the classification of clinically significant steatosis were evaluated. Overall, there was excellent correlation between MR imaging and MR spectroscopy for all reconstruction combinations. However, agreement was only achieved when T2 correction, spectral modeling of fat, and magnitude fitting for eddy current correction were used (r(2
International Nuclear Information System (INIS)
Heuck, A.; Appel, M.; Kaiser, E.; Luttke, G.; Lukas, P.
1990-01-01
This paper evaluates the occurrence, frequency, and significance of increased signal intensity (SI) in the rotator cuff (RC) of normal volunteers suggestive of pathologic findings such as partial tears and tendinitis. Shoulders of 30 volunteers without evidence of prior shoulder disease or trauma were studied. MR imaging at 1.5 T included T1-weighted, proton-density, and T2-weighted spin-echo (SE) and T2*-weighted gradient-echo sequences in axial, oblique coronal, and sagittal planes. Shoulders of 30 cadavers were dissected and studied for correlation with MR findings, five of them after MR examination
Evaluation of Marfan syndrome: MR imaging versus CT
International Nuclear Information System (INIS)
Soulen, R.L.; Fishman, E.K.; Pyeritz, R.E.; Gott, V.L.; Zerhouni, E.A.
1986-01-01
Twenty-five patients with Marfan, syndrome underwent both CT and MR imaging. MR imaging were interpreted in blinded fashion and then compared with CT scans MR imaging was found to be equivalent to CT in the detection of aortic, dural, and hip abnormalities in patients not operated on. MR imaging was superior to CT in the evaluation of postoperative patients because the artifact produced by Bjork-Shirley or St. Jude valves precludes adequate evaluation of the aortic root on CT while producing only a small inferior field distortion (a ''pseudo-ventricular septal defect'') on MR imaging. The absence of radiation exposure is another major advantage of MR imaging in this relatively young population requiring serial studies. The authors conclude that MR imaging is the modality of choice for the evaluation and follow-up of patients with Marfan syndrome and offers an appropriate means of screening their kindred
How to perform and interpret cine MR enterography.
Wnorowski, Amelia M; Guglielmo, Flavius F; Mitchell, Donald G
2015-11-01
Magnetic resonance (MR) enterography has become a fundamental tool for small bowel evaluation. Multiphasic cine imaging is a useful component of MR enterography evaluation because it provides functional information about bowel motility. Cine MR enterography can be used to evaluate for strictures and adhesions. Bowel motility evaluation has been shown to increase pathologic lesion detection in Crohn's disease and has been incorporated into disease activity scoring systems. Currently, cine MR enterography remains underutilized. The purpose of this article is to outline how to perform and interpret cine MR enterography. The authors describe how to perform a multiphasic balanced steady state free precession sequence using different MR systems and give practical advice on how to display and interpret the cine sequence. Sample cases illustrate how the cine sequence complements standard MR enterography evaluation with T2 -weighted, contrast-enhanced T1 -weighted, and diffusion-weighted imaging. © 2015 Wiley Periodicals, Inc.
International Nuclear Information System (INIS)
Yoon, Sang Hum; Chang, Seung Kuk; Cho, Mee Young; Park, Dong Woo; Kim, Jong Deok; Eun, Choong Ki
1994-01-01
To evaluate the MR findings of brain damage in cerebral palised patients and to correlate it with gestational age and the time of damage. A retrospective analysis was performed in 40 patients who underwent MR scanning for evaluation of brain lesion in clinically diagnosed cerebral palsy. Authors classified the patients into two groups as premature and full-term and compared MR findings of the two groups. Abnormal MR findings were noted in 28 cases (70%). Five out of 6 patients who had been born prematurely showed isolate periventricular white matter lesions. Twenty-three out of 34 patients who had been born at full-term showed abnormal MR findings. Of these 23 patients, migration anomalies in 7 patients, isolate periventricular white matter lesions in 3 patients, and other combined periventricular subcortical white matter and deep gray matter lesions in 14 patients were seen. At least, 10 patients(43%) of full term group showed abnormal MRI findings reflecting intrauterine brain damage and all 5 patients of premature group showed isolate periventricular white matter lesions suggesting immaturity of brain. MRI is thought to be very useful in the assessment of brain damage for the patients with cerebral palsy by recognizing the location of the lesion and estimating the time of damage
Energy Technology Data Exchange (ETDEWEB)
Yoon, Sang Hum; Chang, Seung Kuk; Cho, Mee Young; Park, Dong Woo; Kim, Jong Deok; Eun, Choong Ki [Pusan Paik Hospital, Pusan (Korea, Republic of)
1994-11-15
To evaluate the MR findings of brain damage in cerebral palised patients and to correlate it with gestational age and the time of damage. A retrospective analysis was performed in 40 patients who underwent MR scanning for evaluation of brain lesion in clinically diagnosed cerebral palsy. Authors classified the patients into two groups as premature and full-term and compared MR findings of the two groups. Abnormal MR findings were noted in 28 cases (70%). Five out of 6 patients who had been born prematurely showed isolate periventricular white matter lesions. Twenty-three out of 34 patients who had been born at full-term showed abnormal MR findings. Of these 23 patients, migration anomalies in 7 patients, isolate periventricular white matter lesions in 3 patients, and other combined periventricular subcortical white matter and deep gray matter lesions in 14 patients were seen. At least, 10 patients(43%) of full term group showed abnormal MRI findings reflecting intrauterine brain damage and all 5 patients of premature group showed isolate periventricular white matter lesions suggesting immaturity of brain. MRI is thought to be very useful in the assessment of brain damage for the patients with cerebral palsy by recognizing the location of the lesion and estimating the time of damage.
International Nuclear Information System (INIS)
Buchberger, W.; Springer, P.; Birbamer, G.; Judmaier, W.; Kathrein, A.; Daniaux, H.
1995-01-01
To assess the value of MR imaging in the acute and chronic stages of spinal trauma. 126 MR examinations of 120 patients were evaluated retrospectively. In 15 cases of acute spinal cord injury, correlation of MR findings with the degree of neurological deficit and eventual recovery was undertaken. Cord anomalies in the acute stage were seen in 16 patients. Intramedullary haemorrhage (n=6) and cord transection (n=2) were associated with complete injuries and poor prognosis, whereas patients with cord oedema (n=7) had incomplete injuries and recovered significant neurological function. In the chronic stage, MR findings included persistent cord compression in 8 patients, syringomyelia or post-traumatic cyst in 12, myelomalacia in 6, cord atrophy in 9, and cord transection in 7 patients. In acute spinal trauma, MR proved useful in assessing spinal cord compression and instability. In addition, direct visualisation and characterisation of posttraumatic changes within the spinal cord may offer new possibilities in establishing the prognosis for neurological recovery. In the later stages, potentially remediable causes of persistent or progressive symptoms, such as chronic spinal cord compression or syringomyelia can be distinguished from other sequelae of spinal trauma, such as myelomalacia, cord transection or atrophy. (orig.) [de
Role of MR imaging in chronic wrist pain
Energy Technology Data Exchange (ETDEWEB)
Zanetti, Marco; Saupe, Nadja [University Hospital Balgrist, Department of Radiology, Zurich (Switzerland); Nagy, Ladislav [University Hospital Balgrist, Department of Orthopedic Surgery, Zurich (Switzerland)
2007-04-15
Magnetic resonance (MR) imaging for chronic wrist pain is challenging. Correct assessment of the triangular fibrocartilage, hyaline cartilage, ligaments, and tendons has become mandatory for comprehensive decision making in wrist surgery. The MR technique, potential and limits of MR imaging in patients with chronic wrist pain will be discussed. MR arthrography with injection of gadolinium-containing contrast material into the distal radioulnar joint is suggested for evaluation of the triangular fibrocartilage. The clinically meaningful ulnar-sided peripheral tears are otherwise hard to diagnose. The diagnostic performance of MR imaging for interosseous ligament tears varies considerably. The sensitivity for scapholunate ligament tears is consistently better than for lunotriquetral ligament tears. Gadolinium-enhanced MR imaging is considered to be the best technique for detecting established avascularity of bone, but the assessment of the MR results remains challenging. Most cases of ulnar impaction syndrome have characteristic focal signal intensity changes in the ulnar aspect of the lunate. Avascular necrosis of the lunate (Kienboeck's disease) is characterized by signal changes starting in the proximal radial aspect of the lunate. MR imaging is extremely sensitive for occult fractures. Questions arise if occult posttraumatic bone lesions seen on MR images only necessarily require the same treatment as fractures evident on plain films or computed tomography (CT) images. MR imaging and ultrasound are equally effective for detecting occult carpal ganglia. Carpe bossu (carpal boss) is a bony protuberance of a carpometacarpal joint II and III which may be associated with pain. (orig.)
Role of MR imaging in chronic wrist pain
International Nuclear Information System (INIS)
Zanetti, Marco; Saupe, Nadja; Nagy, Ladislav
2007-01-01
Magnetic resonance (MR) imaging for chronic wrist pain is challenging. Correct assessment of the triangular fibrocartilage, hyaline cartilage, ligaments, and tendons has become mandatory for comprehensive decision making in wrist surgery. The MR technique, potential and limits of MR imaging in patients with chronic wrist pain will be discussed. MR arthrography with injection of gadolinium-containing contrast material into the distal radioulnar joint is suggested for evaluation of the triangular fibrocartilage. The clinically meaningful ulnar-sided peripheral tears are otherwise hard to diagnose. The diagnostic performance of MR imaging for interosseous ligament tears varies considerably. The sensitivity for scapholunate ligament tears is consistently better than for lunotriquetral ligament tears. Gadolinium-enhanced MR imaging is considered to be the best technique for detecting established avascularity of bone, but the assessment of the MR results remains challenging. Most cases of ulnar impaction syndrome have characteristic focal signal intensity changes in the ulnar aspect of the lunate. Avascular necrosis of the lunate (Kienboeck's disease) is characterized by signal changes starting in the proximal radial aspect of the lunate. MR imaging is extremely sensitive for occult fractures. Questions arise if occult posttraumatic bone lesions seen on MR images only necessarily require the same treatment as fractures evident on plain films or computed tomography (CT) images. MR imaging and ultrasound are equally effective for detecting occult carpal ganglia. Carpe bossu (carpal boss) is a bony protuberance of a carpometacarpal joint II and III which may be associated with pain. (orig.)
Multidisciplinary Functional MR Imaging for Prostate Cancer
International Nuclear Information System (INIS)
Kim, Jeong Kon; Jang, Yun Jin; Cho, Gyung Goo
2009-01-01
Various functional magnetic resonance (MR) imaging techniques are used for evaluating prostate cancer including diffusion-weighted imaging, dynamic contrast- enhanced MR imaging, and MR spectroscopy. These techniques provide unique information that is helpful to differentiate prostate cancer from non-cancerous tissue and have been proven to improve the diagnostic performance of MRI not only for cancer detection, but also for staging, post-treatment monitoring, and guiding prostate biopsies. However, each functional MR imaging technique also has inherent challenges. Therefore, in order to make accurate diagnoses, it is important to comprehensively understand their advantages and limitations, histologic background related with image findings, and their clinical relevance for evaluating prostate cancer. This article will review the basic principles and clinical significance of functional MR imaging for evaluating prostate cancer
Visualization of the 3D shape of the articular cartilage of the femoral head from MR images
International Nuclear Information System (INIS)
Kubota, Tetsuya; Sato, Yoshinobu; Nakanishi, Katsuyuki
1999-01-01
This paper describes methods for visualizing the three-dimensional (3D) cartilage thickness distribution from MR images. Cartilage thickness is one of the most important factors in joint diseases. Although the evaluation of cartilage thickness has received considerable attention from orthopedic surgeons and radiologists, evaluation is usually performed based on visual analysis or measurements obtained using calipers on original MR images. Our aim is to employ computerized quantification of MR images for the evaluation of the cartilage thickness of the femoral head. First, we extract an ROI and interpolate all ROI images by sinc interpolation. Next, we extract cartilage regions from MR images using a 3D multiscale sheet filter. Finally, we reconstruct 3D shapes by summing the extracted cartilage regions. We investigate partial volume effects in this method using synthesized images, and show results for in vitro and in vivo MR images. (author)
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Park, Jeong Ha; Lee, Myung Jun; Lee, Chang Joon [National Medical Center, Seoul (Korea, Republic of)
2001-10-01
To determine the usefulness of MR urography technique for the evaluation of urinary systems in patients with obstructed urinary tract and normal volunteers with non-obstructed urinary tract after intravenous normal saline and diuretic injection. Three normal volunteers and 12 patients with urinary tract obstruction [ureteral calculi (n=8), extraurinary mass (n=1), ureteral tumor invasion (n=3)] underwent MR urography using a 1.0T scanner and a 2D non-breath-hold heavily T2-weighted fast spin-cho sequence. These acquisition were post-processed with a maximum intensity projection (MIP) algorithm. Two acquisitions were performed, the first prior to saline solution infusion following standard MR urography procedures, and the second, within 2-3 minutes of the infusion of 250 ml saline solution followed by 20 mg of Lasix administered intravenously. For this latter, drug-induced MR urography procedures were followed. In healthy volunteer (n=3) and those experiencing partial obstruction (n=4) by a urinary stone, drug-induced MR urography provided better images of the urinary tract than did standard MR urography. In those in whom a urinary stone or tumor had caused complete obstruction (n=8), standard MR urography provided good images, as did drug-induced MR urography. In patients with a partially or non-obstructed urinary tract, drug-induced MR urography provided better anatomic and functional details of the kidney and urinary tract than did standard MR urography. In those experiencing complete obstruction of the urinary tract, however, standard or drug-induced MR urography permitted very adequate evaluation of the tract, and drug-induced MR urography was unnecessary.
Evaluation of meniscal subluxation of the knee with MR imaging
International Nuclear Information System (INIS)
Kim, Hyun Chul; Park, Jin Gyoon; Kang, Heoung Keun; Kim, Jae Kyu; Seo, Jeong Jin; Kim, Yun Hyeon; Chung, Tae Woong
2000-01-01
The purpose of this study was to determine the normal meniscal position and meniscal subluxation by means of MR imaging. The normal position of the meniscus was determined by measuring the distance between the peripheral meniscal borders and the tibial plateau, as seen on coronal, sagittal and oblique MR images of 40 normal knees. For 33 abnormal knees in which outward subluxation of the meniscus from the tibial plateau was noted, the involved site, the predisposing factor, and the frequency of meniscus tearing were analyzed. In normal knees, the peripheral border of the meniscus extruded 3mm or less from the peripheral border of the tibial plateau. Among 33 abnormal knees, in which 5mm or more outward subluxation of the meniscus was seen, 19 menisci were medial and 14 were lateral. Among the 19, the body was involved in 12, the anterior horn in six, and the posterior horn in one. With regard to the 14 lateral subluxations, involvement of the posterior horn occurred in ten, of both the body and posterior horn in two, of the anterior horn in one, and of the body in one. The common predisposing factor in medial meniscus subluxation was osteoarthritis, seen in 89% of such cases, and in lateral subluxation, anterior cruciate ligament tear, which occurred in 79% of cases. Medial meniscus tear was noted in 89% of medial meniscus subluxations and lateral meniscus tear in 43% of lateral subluxations. Meniscal subluxation was easily detected by MR imaging of the knee. The common predisposing factor in medial meniscus subluxation was osteoarthritis, and in lateral meniscus subluxation, anterior cruciate ligament tear. A torn meniscus frequently co-occurred
Intravascular (catheter) MR imaging
International Nuclear Information System (INIS)
Cohen, A.M.; Hurst, G.C.; Katz, D.E.; Dverk, J.L.; Wiesen, E.J.; Czerski, L.W.; Malaya, R.; Bellon, E.M.
1989-01-01
Intravascular MR probes allow excellent spatial resolution and have the potential to detect arterial wall microstructure. Ultrasonic intravascular probes suggest that detailed morphologic information can assist clinical decision making. Catheter MR probes of 2--7 mm outside diameter (OD) were built of copper wire, Teflon, and parts from standard commercial catheters. The probes were connected to the surface coil receiver input of our Picker VISTA 2055HP 1.5-T imaging system. The extant (linear) body coil was used for transmit. Phantoms were constructed of coaxial glass MR tubes, filled with doped water. Watanabe rabbit aorta and human autopsy iliac artery specimens were examined within 4 hours of excision or stored by freezing. In vivo iliac arteries in dogs under general anesthesia were imaged, with percutaneous placement of the probe. Results are presented
MR imaging and clinical findings of spontaneous spinal epidural hematoma
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Kim, Sam Soo [Seoul City Boramae Hospital, Seoul (Korea, Republic of); Han, Moon Hee; Kim, Hyun Beom [College of Medicine, Seoul National University, Seoul (Korea, Republic of)] [and others
2000-01-01
To describe the MR imaging and clinical findings of spontaneous spinal epidural hematoma. The MR and clinical findings in six patients (M:F=3D4:2;adult:child=3D3:3) with spontaneous spinal epidural hematoma were reviewed. Five patients without any predisposing factor which might cause the condition and one with acute myelogenous leukemia were included. Emergency surgery was performed in two patients, and the other four were managed conservatively. The epidural lesion involved between three and seven vertebrae (mean:4.5), and relative to the spinal cord was located in the posterior-lateral (n=3D4), anterior (n=3D1), or right lateral (n=3D1) area. The hematoma was isointense (n=3D1) or hyperintense (n=3D5) with spinal cord on T1-weighted images, and hypointense (n=3D2) or hyperintense (n=3D4) on T2-weighted images. It was completely absorbed in four of five patients who underwent follow-up MR imaging, but not changed in one. The clinical outcome of these patients was complete recovery (n=3D4), spastic cerebral palsy (n=3D1), or unknown (n=3D1). Because of the lesion's characteristic signal intensity; MR imaging is very useful in the diagnosis and evaluation of spontaneous spinal epidural hematoma. (author)
Influence of obstetric complication severity on brain morphology in schizophrenia: an MR study
Energy Technology Data Exchange (ETDEWEB)
Bersani, G.; Quartini, A.; Manuali, G.; Iannitelli, A. [University of Rome, Polo Pontino, Department of Psychiatric Sciences and Psychological Medicine, Rome (Italy); Pucci, D. [University of Rome, Department of Public Health ' ' G. Sanarelli' ' , Rome (Italy); Conforti, F. [University of Rome, I Medical Clinic, Magnetic Resonance Imaging Unit, Rome (Italy); Di Biasi, C.; Gualdi, G.
2009-06-15
The purpose of this study was to determine if a causal relationship exists between obstetric complications (OCs) severity and linear magnetic resonance (MR) measurements of brain atrophy in patients with schizophrenia. Linear measurements of ventricular enlargement (bifrontal span, Evans ratio, and bicaudate ratio) and hippocampal atrophy (interuncal distance) were completed on MR images obtained in 47 patients with schizophrenia. Regression analysis was used to look at association with OCs severity, assessed by the ''Midwife protocol'' of Parnas and colleagues. The relationship between MR measurements and phenomenologic variables such as age at onset, illness duration, and exposure to antipsychotic medications was explored. The relationship between MR measurements, OCs severity, and symptom presentation was also investigated. OCs severity was significantly associated with MR measurements of ventricular enlargement (bifrontal span, Evans ratio). As the severity of OCs increased, bifrontal span and Evans ratio increased. This effect was independent of age at onset, illness duration, or even antipsychotic treatment. Interestingly, bifrontal span, Evans ratio, and OCs severity score all showed a significant positive correlation with hallucinatory symptomatology. Although confirmatory studies are needed, our findings would support the idea that environmental factors, in this case severe OCs, might partly contribute to ventricular abnormalities in schizophrenia. (orig.)
Influence of obstetric complication severity on brain morphology in schizophrenia: an MR study
International Nuclear Information System (INIS)
Bersani, G.; Quartini, A.; Manuali, G.; Iannitelli, A.; Pucci, D.; Conforti, F.; Di Biasi, C.; Gualdi, G.
2009-01-01
The purpose of this study was to determine if a causal relationship exists between obstetric complications (OCs) severity and linear magnetic resonance (MR) measurements of brain atrophy in patients with schizophrenia. Linear measurements of ventricular enlargement (bifrontal span, Evans ratio, and bicaudate ratio) and hippocampal atrophy (interuncal distance) were completed on MR images obtained in 47 patients with schizophrenia. Regression analysis was used to look at association with OCs severity, assessed by the ''Midwife protocol'' of Parnas and colleagues. The relationship between MR measurements and phenomenologic variables such as age at onset, illness duration, and exposure to antipsychotic medications was explored. The relationship between MR measurements, OCs severity, and symptom presentation was also investigated. OCs severity was significantly associated with MR measurements of ventricular enlargement (bifrontal span, Evans ratio). As the severity of OCs increased, bifrontal span and Evans ratio increased. This effect was independent of age at onset, illness duration, or even antipsychotic treatment. Interestingly, bifrontal span, Evans ratio, and OCs severity score all showed a significant positive correlation with hallucinatory symptomatology. Although confirmatory studies are needed, our findings would support the idea that environmental factors, in this case severe OCs, might partly contribute to ventricular abnormalities in schizophrenia. (orig.)
Cross-calibration of the Siemens mMR
DEFF Research Database (Denmark)
Keller, Sune H; Jakoby, Björn; Svalling, Susanne
2016-01-01
BACKGROUND: We present a quick and easy method to perform quantitatively accurate PET scans of typical water-filled PET plastic shell phantoms on the Siemens Biograph mMR PET/MR system. We perform regular cross-calibrations (Xcal) of our PET systems, including the PET/MR, using a Siemens mCT water...
Nuts and Bolts of CEST MR imaging
Liu, Guanshu; Song, Xiaolei; Chan, Kannie W.Y.
2013-01-01
Chemical Exchange Saturation Transfer (CEST) has emerged as a novel MRI contrast mechanism that is well suited for molecular imaging studies. This new mechanism can be used to detect small amounts of contrast agent through saturation of rapidly exchanging protons on these agents, allowing a wide range of applications. CEST technology has a number of indispensable features, such as the possibility of simultaneous detection of multiple “colors” of agents and detecting changes in their environment (e.g. pH, metabolites, etc) through MR contrast. Currently a large number of new imaging schemes and techniques have been developed to improve the temporal resolution and specificity and to correct the influence of B0 and B1 inhomogeneities. In this review, the techniques developed over the last decade have been summarized with the different imaging strategies and post-processing methods discussed from a practical point of view including describing their relative merits for detecting CEST agents. The goal of the present work is to provide the reader with a fundamental understanding of the techniques developed, and to provide guidance to help refine future applications of this technology. This review is organized into three main sections: Basics of CEST Contrast, Implementation, Post-Processing, and also includes a brief Introduction section and Summary. The Basics of CEST Contrast section contains a description of the relevant background theory for saturation transfer and frequency labeled transfer, and a brief discussion of methods to determine exchange rates. The Implementation section contains a description of the practical considerations in conducting CEST MRI studies, including choice of magnetic field, pulse sequence, saturation pulse, imaging scheme, and strategies to separate MT and CEST. The Post-Processing section contains a description of the typical image processing employed for B0/B1 correction, Z-spectral interpolation, frequency selective detection, and
MR staging of endometrial carcinoma
International Nuclear Information System (INIS)
Innocenti, P.; Agostini, S.; Erroi, C.; Ambrogetti, D.; Cellerini, A.; Nori, J.
1991-01-01
Biopsy is the technique of choice for the definitive diagnosis of endometrial carcinoma. Since lymphatic tumor spread has been demonstrated to depend on the degree of myometrial involvement, the definition of the latter with imaging techniques may significantly affect both pfognosis and therapy. We investigated, by means of MR imaging at 0.5 T, 14 patients with endometrial carcinoma, to assess both tumor stage and myometrial involvement. FIGO staging system was employed, and M parameter evaluated (M0= no myometrial involvement; M1involvement confined to the inner third; M2= Involvement confined to the middle third; M3= involvement of the whole myometrium). Another parameter was the characteristic high signal of the tumor on PD and T2W images. The patients were then operated and MR information was correlated with surgical findings. Overall diagnostic accuracy of MR imaging was 85.7% in tumor staging, and 92.2% in defining M parameter. Tumor spread into adnexa and into cervical canal was poorly demonstrated by MR imaging
Technical errors in MR arthrography
International Nuclear Information System (INIS)
Hodler, Juerg
2008-01-01
This article discusses potential technical problems of MR arthrography. It starts with contraindications, followed by problems relating to injection technique, contrast material and MR imaging technique. For some of the aspects discussed, there is only little published evidence. Therefore, the article is based on the personal experience of the author and on local standards of procedures. Such standards, as well as medico-legal considerations, may vary from country to country. Contraindications for MR arthrography include pre-existing infection, reflex sympathetic dystrophy and possibly bleeding disorders, avascular necrosis and known allergy to contrast media. Errors in injection technique may lead to extra-articular collection of contrast agent or to contrast agent leaking from the joint space, which may cause diagnostic difficulties. Incorrect concentrations of contrast material influence image quality and may also lead to non-diagnostic examinations. Errors relating to MR imaging include delays between injection and imaging and inadequate choice of sequences. Potential solutions to the various possible errors are presented. (orig.)
Technical errors in MR arthrography
Energy Technology Data Exchange (ETDEWEB)
Hodler, Juerg [Orthopaedic University Hospital of Balgrist, Radiology, Zurich (Switzerland)
2008-01-15
This article discusses potential technical problems of MR arthrography. It starts with contraindications, followed by problems relating to injection technique, contrast material and MR imaging technique. For some of the aspects discussed, there is only little published evidence. Therefore, the article is based on the personal experience of the author and on local standards of procedures. Such standards, as well as medico-legal considerations, may vary from country to country. Contraindications for MR arthrography include pre-existing infection, reflex sympathetic dystrophy and possibly bleeding disorders, avascular necrosis and known allergy to contrast media. Errors in injection technique may lead to extra-articular collection of contrast agent or to contrast agent leaking from the joint space, which may cause diagnostic difficulties. Incorrect concentrations of contrast material influence image quality and may also lead to non-diagnostic examinations. Errors relating to MR imaging include delays between injection and imaging and inadequate choice of sequences. Potential solutions to the various possible errors are presented. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Mehranian, Abolfazl; Zaidi, Habib [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211 Geneva (Switzerland)
2014-07-29
The maximum likelihood estimation of attenuation and activity (MLAA) algorithm has been proposed to jointly estimate activity and attenuation from emission data only. Salomon et al employed the MLAA to estimate activity and attenuation from time-of-flight PET data with spatial MR prior information on attenuation. Recently, we proposed a novel algorithm to impose both spatial and statistical constraints on attenuation estimation within the MLAA algorithm using Dixon MR images and a constrained Gaussian mixture model (GMM). In this study, we compare the proposed algorithm with MLAA and MLAA-Salomon in brain TOF-PET/MR imaging.
International Nuclear Information System (INIS)
Mehranian, Abolfazl; Zaidi, Habib
2014-01-01
The maximum likelihood estimation of attenuation and activity (MLAA) algorithm has been proposed to jointly estimate activity and attenuation from emission data only. Salomon et al employed the MLAA to estimate activity and attenuation from time-of-flight PET data with spatial MR prior information on attenuation. Recently, we proposed a novel algorithm to impose both spatial and statistical constraints on attenuation estimation within the MLAA algorithm using Dixon MR images and a constrained Gaussian mixture model (GMM). In this study, we compare the proposed algorithm with MLAA and MLAA_Salomon in brain TOF-PET/MR imaging.
Infantile and congenital hip dislocation: Assessment by MR imaging
International Nuclear Information System (INIS)
Johnson, N.D.; Wood, B.P.; Jackman, K.V.
1986-01-01
Dislocations of the infant hip, particularly those that responded poorly to standard treatment, were imaged using a 1.5-T MR imaging unit. Excellent detail of the cartilaginous structures of the femoral head, acetabulum, labrum, pulvinar, and capsular abnormalities was achieved. The most detailed images were obtained using a 3-inch surface coil. The shape and orientation of the acetabulum and femoral head cannot otherwise be as well evaluated, nor can their relationship be as clearly established. Technical factors and considerations of imaging with a 1.5-T magnet, the anatomy of the normal and dislocated hip, and observed variations in acetabular shape and orientation are discussed. MR imaging reliably demonstrates dislocation, and the prolonged T2 of synovial fluid produced an ''arthrogram'' effect, which is useful in the treatment of complicated hip dislocation
Energy Technology Data Exchange (ETDEWEB)
Obenauer, S.; Grabbe, E.; Knollmann, F. [Abt. Diagnostische Radiologie, Georg-August-Univ. Goettingen (Germany)
2006-05-15
Contrast-enhanced dynamic MR mammography can provide important additional diagnostic information when performed for certain indications. When suspicious lesions are identified on MR mammography and cannot be reproduced using other imaging modalities, a decision must be made as to its management, i.e. further diagnostic work-up. One possibility is the short-term follow-up of such findings, resulting in higher costs and a possible delay in the start of treatment of a malignant lesion. An alternative to a follow-up is an MR-guide intervention. MR-compatible equipment has been developed for this purpose. This includes equipment specialized for percutaneous biopsy and preoperative localization. The following is an overview of the diagnostic value of MR-guided biopsy and preoperative localization including the relevant literature. (orig.)
MR imaging of central nervous system birth injuries
International Nuclear Information System (INIS)
Heier, L.A.; Zimmerman, R.D.
1991-01-01
This paper reports on head injuries due to birth trauma that have been evaluated with plain radiography, US, and CT. In the past, patient monitoring and transportation difficulties for a neonate have limited the use of MR. Does MR provide more information that would assist the management and prognostic assessment of these patients? An MR examination was requested on all neonates born or transferred to our institution with a documented traumatic delivery. CT and MR studies were compared for seven patients, including three cases of difficult forceps delivery, one case of double footling breech with forceps head extraction, two cases of shoulder dystocias, and one case of vacuum extraction. CT caused underestimation of subdural hematomas and contusions in three of five patients with this injury. The appreciation of a large subdural hematoma at MR resulted in surgical intervention. Both unsuspected cervical cord contusion and complete cord transection were identified on sagittal head MR images. Four of four skull fractures identified at CT were not seen at MR
Contrast-enhanced MR angiography in Leriche's syndrome
International Nuclear Information System (INIS)
Link, J.; Steffens, J.C.; Brossmann, J.; Heller, M.; Loose, R.
1998-01-01
Purpose: To determine the usefulness of contrast-enhanced MR angiography for the diagnosis of Leriche's syndrome. Material and methods: Leriche's syndrome was seen in 7 patients via DSA. In [dition, contrast-enhanced MR angiography was performed (T R 7.8 ms/T E 2.1 ms, flip angle 30 , slab thickness 116 mm, slice thickness 1.82 mm, 64 partitions, FOV 500x438 mm, matrix 224x512). Results: Diagnosis of Leriche's syndrome was possible by contrast-enhanced MR angiography in each case. Visualisation of the femoral arteries was not possible in two patients by intraarterial DSA, in three other patients there was an insufficient contrast in the femoral arteries with DSA. Contrast-enhanced MR angiography revealed good visualisation of the femoral arteries in these patients. In [dition, contrast-enhanced MR angiography allowed complete visualisation of the patent lower limb arteries. In intraarterial DSA visualisation of the lower limb arteries was achieved reached in only one patient, but was incomplete. Conclusion: Contrast-enhanced MR angiography yielded the correct diagnosis of Leriche's syndrome in all 7 patients. Contrast-enhanced MR angiography was superior to DSA in the assessment of the distal run-off vessels in five of seven patients. (orig.) [de
Dimerization of DOCK2 is essential for DOCK2-mediated Rac activation and lymphocyte migration.
Directory of Open Access Journals (Sweden)
Masao Terasawa
Full Text Available The migratory properties of lymphocytes depend on DOCK2, an atypical Rac activator predominantly expressed in hematopoietic cells. Although DOCK2 does not contain the Dbl homology domain typically found in guanine nucleotide exchange factors (GEFs, DOCK2 mediates the GTP-GDP exchange reaction for Rac via its DOCK homology region (DHR-2 (also known as CZH2 or Docker domain. DOCK2 DHR-2 domain is composed of three lobes, and Rac binding site and catalytic center are generated entirely from lobes B and C. On the other hand, lobe A has been implicated in dimer formation, yet its physiological significance remains unknown. Here, we report that lobe A-mediated DOCK2 dimerization is crucial for Rac activation and lymphocyte migration. We found that unlike wild-type DOCK2, DOCK2 mutant lacking lobe A failed to restore motility and polarity when expressed in thymoma cells and primary T cells lacking endogenous expression of DOCK2. Similar results were obtained with the DOCK2 point mutant having a defect in dimerization. Deletion of lobe A from the DHR-2 domain did not affect Rac GEF activity in vitro. However, fluorescence resonance energy transfer analyses revealed that lobe A is required for DOCK2 to activate Rac effectively during cell migration. Our results thus indicate that DOCK2 dimerization is functionally important under the physiological condition where only limited amounts of DOCK2 and Rac are localized to the plasma membrane.
MR tomography of the elbow joint
Energy Technology Data Exchange (ETDEWEB)
Zwaan, M.; Rinast, E.; Weiss, H.D.; Pressler, M.; Vogel, H.
1989-03-01
MR examinations of the elbow joint of three healthy subjects and a comparison with corresponding sections of anatomical preparations show that MR tomography enables not only an excellent differentiation of muscles, tendons and of the articular capsule, but will also visualise vessels and nerve tracts. MR tomography proved superior to the conventional methods in demonstration of separate fragments and inflammatory changes in the bone on examining 11 pathological elbow joints: congenital malformation, osteochondritis dissecans, ostitis, ulnar and radial nerve lesions, completely healed radius fracture and epicondylitis of the radial and ulnar humerus. Epicondylitis could not be demonstrated by MR. Magnetic resonance tomography seems to be the only method that enables direct visualisation of the nerve paths at the elbow joint.
Rosen's (M,R) system in Unified Modelling Language.
Zhang, Ling; Williams, Richard A; Gatherer, Derek
2016-01-01
Robert Rosen's (M,R) system is an abstract biological network architecture that is allegedly non-computable on a Turing machine. If (M,R) is truly non-computable, there are serious implications for the modelling of large biological networks in computer software. A body of work has now accumulated addressing Rosen's claim concerning (M,R) by attempting to instantiate it in various software systems. However, a conclusive refutation has remained elusive, principally since none of the attempts to date have unambiguously avoided the critique that they have altered the properties of (M,R) in the coding process, producing merely approximate simulations of (M,R) rather than true computational models. In this paper, we use the Unified Modelling Language (UML), a diagrammatic notation standard, to express (M,R) as a system of objects having attributes, functions and relations. We believe that this instantiates (M,R) in such a way than none of the original properties of the system are corrupted in the process. Crucially, we demonstrate that (M,R) as classically represented in the relational biology literature is implicitly a UML communication diagram. Furthermore, since UML is formally compatible with object-oriented computing languages, instantiation of (M,R) in UML strongly implies its computability in object-oriented coding languages. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
MR Imaging of Articular Hyaline Cartilage
Uetani, Masataka
2005-01-01
MR imaging is still an evolving technique for the diagnosis of joint cartilage lesions. Early morphologic changes in the degenerative cartilage are not reliably diagnosed even with use of tailored MR imaging techniques. The detection of the biochemical changes of cartilage or high-resolution MRI will serve as an important tool for the early diagnosis of cartilage degeneration in near future. Further prospective studies are needed to establish the role of MR imaging in clinical use.
Hines, Catherine D. G.; Hamilton, Gavin; Sirlin, Claude B.; McKenzie, Charles A.; Yu, Huanzhou; Brittain, Jean H.; Reeder, Scott B.
2011-01-01
Purpose: To prospectively compare an investigational version of a complex-based chemical shift–based fat fraction magnetic resonance (MR) imaging method with MR spectroscopy for the quantification of hepatic steatosis. Materials and Methods: This study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained before all studies. Fifty-five patients (31 women, 24 men; age range, 24–71 years) were prospectively imaged at 1.5 T with quantitative MR imaging and single-voxel MR spectroscopy, each within a single breath hold. The effects of T2* correction, spectral modeling of fat, and magnitude fitting for eddy current correction on fat quantification with MR imaging were investigated by reconstructing fat fraction images from the same source data with different combinations of error correction. Single-voxel T2-corrected MR spectroscopy was used to measure fat fraction and served as the reference standard. All MR spectroscopy data were postprocessed at a separate institution by an MR physicist who was blinded to MR imaging results. Fat fractions measured with MR imaging and MR spectroscopy were compared statistically to determine the correlation (r2), and the slope and intercept as measures of agreement between MR imaging and MR spectroscopy fat fraction measurements, to determine whether MR imaging can help quantify fat, and examine the importance of T2* correction, spectral modeling of fat, and eddy current correction. Two-sided t tests (significance level, P = .05) were used to determine whether estimated slopes and intercepts were significantly different from 1.0 and 0.0, respectively. Sensitivity and specificity for the classification of clinically significant steatosis were evaluated. Results: Overall, there was excellent correlation between MR imaging and MR spectroscopy for all reconstruction combinations. However, agreement was only achieved when T2* correction, spectral modeling of fat, and magnitude
MR guided percutaneous laser lumbar disk hernia ablation
Energy Technology Data Exchange (ETDEWEB)
Hashimoto, Takuo; Terao, Tohru; Ishibashi, Toshihiro; Yuhki, Ichiro; Harada, Junta; Tashima, Michiko [Jikei Univ., Chiba (Japan). Kashiwa Hospital; Abe, Toshiaki
1998-03-01
An MRI unit for interventional procedure is very useful for minimally invasive surgery of the brain and spine. Percutaneous laser disc decompression (PLDD) utilizing X-ray fluoroscopy is a relatively new less invasive procedure for treatment of lumbar disc herniation. MR guided laser surgery is applied to patients with disc herniation at our department. Approaching the target of the disc protrusion was easily conducted and vaporizing the disc hernia directly using a laser was possible under MR fluoroscopy. The purpose of the present study is to evaluate the usefulness of MR guided percutaneous laser disc hernia ablation (MR-guided PLDHA). As subjects, 36 patients with lumbar disc herniation, including 23 cases with L4/5 involvement and 13 cases with L5/S1 involvement were studied. Among these, 26 were males and 10 were females, age ranging from 24 to 62. We used an open type MR system (Hitachi, Airis 0.3T), a permanent, open configuration MR system. A YAG laser (LaserScope, USA) was used for PLDHA. An MR compatible 18G titanium needle 15 cm in length was used to puncture the herniated discs. The MR compatible needle was clearly visualized, and used to safely and accurately puncture the target herniated disc in each case with multidimensional guidance. Application of the laser was performed with MR guidance. The energy dose from the laser ranged from 800 to 2100 joules. In most cases, signs and symptoms improved in the patients immediately after disc vaporization. The overall success rate was 88.9%. The complication rate was 2.8%, including one case of discitis after PLDHA. MR fluoroscopy sequence permits near real time imaging and provides an easy approach to the therapeutic target of disc herniation. MR guided PLDHA is a minimally invasive procedure and is very useful for the treatment of lumbar disc protrusion. (author)
MR guided percutaneous laser lumbar disk hernia ablation
International Nuclear Information System (INIS)
Hashimoto, Takuo; Terao, Tohru; Ishibashi, Toshihiro; Yuhki, Ichiro; Harada, Junta; Tashima, Michiko; Abe, Toshiaki.
1998-01-01
An MRI unit for interventional procedure is very useful for minimally invasive surgery of the brain and spine. Percutaneous laser disc decompression (PLDD) utilizing X-ray fluoroscopy is a relatively new less invasive procedure for treatment of lumbar disc herniation. MR guided laser surgery is applied to patients with disc herniation at our department. Approaching the target of the disc protrusion was easily conducted and vaporizing the disc hernia directly using a laser was possible under MR fluoroscopy. The purpose of the present study is to evaluate the usefulness of MR guided percutaneous laser disc hernia ablation (MR-guided PLDHA). As subjects, 36 patients with lumbar disc herniation, including 23 cases with L4/5 involvement and 13 cases with L5/S1 involvement were studied. Among these, 26 were males and 10 were females, age ranging from 24 to 62. We used an open type MR system (Hitachi, Airis 0.3T), a permanent, open configuration MR system. A YAG laser (LaserScope, USA) was used for PLDHA. An MR compatible 18G titanium needle 15 cm in length was used to puncture the herniated discs. The MR compatible needle was clearly visualized, and used to safely and accurately puncture the target herniated disc in each case with multidimensional guidance. Application of the laser was performed with MR guidance. The energy dose from the laser ranged from 800 to 2100 joules. In most cases, signs and symptoms improved in the patients immediately after disc vaporization. The overall success rate was 88.9%. The complication rate was 2.8%, including one case of discitis after PLDHA. MR fluoroscopy sequence permits near real time imaging and provides an easy approach to the therapeutic target of disc herniation. MR guided PLDHA is a minimally invasive procedure and is very useful for the treatment of lumbar disc protrusion. (author)
MR urography: examination techniques and clinical applications
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Nolte-Ernsting, C.C.A.; Adam, G.B.; Guenther, R.W. [Technische Hochschule Aachen (Germany). Klinik fuer Radiologische Diagnostik
2001-03-01
Modern MR urography is performed on the basis of two different imaging strategies, which can be used complementarily to cover almost all aspects in the diagnosis of upper urinary tract diseases. The first technique utilizes unenhanced, heavily T2-weighted pulse sequences to obtain static-fluid images of the urinary tract. T2-weighted MR urograms have proved to be excellent in the visualization of the markedly dilated urinary tract, even if the renal excretory function is quiescent. Static-fluid MR urography is less suitable for imaging of disorders that occur in the nondilated collecting system. The second MR urography technique is analogous to the methodology of conventional intravenous pyelography and is, therefore, designated as excretory MR urography. For this purpose, a non-nephrotoxic gadolinium chelate is intravenously administered and after its renal excretion, the gadolinium-enhanced urine is visualized using fast T1-weighted gradient-echo sequences. The combination of gadolinium and low-dose furosemide (5-10 mg) is the key for achieving a uniform distribution of the contrast material inside the entire urinary tract and, secondly, to avoid high endoluminal gadolinium concentrations, which cause signal loss of the urine due to T2{sup *} effects. Gadolinium excretory MR urography allows to obtain high-quality images of both nondilated and obstructed urinary tracts in patients with normal or moderately impaired renal function. This article reviews the principles of T2- and T1-weighted MR urography in detail and informs how to use these techniques safely in potential clinical applications such as chronic urolithiasis, intrinsic and extrinsic tumor diseases, and congenital anomalies. Magnetic resonance urography performed in combination with standard MR imaging offers a potential to reduce the need for invasive retrograde pyelography. Although the economic aspect is still problematic, it is obvious that MR urography will continue to increase its role in
International Nuclear Information System (INIS)
Zhang, Chenghu; Li, Yaping
2017-01-01
Concept of reversible heat exchange process as the theoretical model of the cycle combined heat exchanger could be useful to determine thermodynamics characteristics and the limitation values in the isolated heat exchange system. In this study, the classification of the reversible heat exchange processes is presented, and with the numerical method, medium temperature variation tendency and the useful work production and usage in the whole process are investigated by the construction and solution of the mathematical descriptions. Various values of medium inlet temperatures and heat capacity ratio are considered to analyze the effects of process parameters on the outlet temperature lift/drop. The maximum process work transferred from the Carnot cycle region to the reverse cycle region is also researched. Moreover, influence of the separating point between different sub-processes on temperature variation profile and the process work production are analyzed. In addition, the heat-exchange-enhancement-factor is defined to study the enhancement effect of the application of the idealized process in the isolated heat exchange system, and the variation degree of this factor with process parameters change is obtained. The research results of this paper can be a theoretical guidance to construct the cycle combined heat exchange process in the practical system. - Highlights: • A theoretical model of Cycle combined heat exchange process is proposed. • The classification of reversible heat exchange process are presented. • Effects of Inlet temperatures and heat capacity ratio on process are analyzed. • Process work transmission through the whole process is studied. • Heat-exchange-enhancement-factor can be a criteria to express the application effect of the idealized process.
Lim, Young-Min; Pyun, So Young; Kang, Bong-Hui; Kim, Jimin; Kim, Kwang-Kuk
2013-08-01
To identify factors associated with plasma exchange response in neuromyelitis optica (NMO) spectrum disorders, the clinical and magnetic resonance imaging (MRI) features of 31 NMO-IgG-positive patients receiving plasma exchange for steroid-resistant exacerbations were analyzed. Functional improvement was observed in 65% of the patients. A lower baseline Expanded Disability Status Scale score was associated with favorable response (p = 0.040). Patients without cord atrophy had a higher success rate than patients with atrophy (p = 0.016). Levels of NMO-IgG did not differ between responders and non-responders before and after plasma exchange. In conclusion, a minimal pre-existing disability is the primary determinant of the effectiveness of plasma exchange.
MR imaging of chondramalacia patella
International Nuclear Information System (INIS)
Yulish, B.S.; Montanez, J.; Mulopulos, G.P.; Goodfellow, D.; Dollinger, B.; Bryan, P.J.; Modic, M.T.
1986-01-01
Because of its inherent soft-tissue contrast, MR imaging can distinguish hyaline articular cartilage, fibrocartilage, and cortical and medullary bone, and thus seems a method ideally suited to examine the posterior patellar hyaline articular cartilage. The authors studied the knees of people with suspected chondromalacia patella using MR imagine and compared our findings to normal knees and, where available, results of surgery. They find that we can distinguish swollen cartilage, irregular cartilage, absent cartilage, and bony patellar defects. Joint fluid and meniscal injuries could also be identified. MR imaging is a useful method for evaluation of chondromalacia patella and may reduce the need for arthroscopy and arthrography for diagnosis
International Nuclear Information System (INIS)
Mink, J.H.
1987-01-01
There is increasing evidence that MR imaging of the knee can accurately evaluate the menisci and the cruciate and collateral ligaments with an accuracy equal to that of conventional anthrography. MR imaging can, as a simple test, definitively assess a wide spectrum of the causes of knee pain, including osteonecrosis/osteochondritis dissecans, chondral and bony fractures, abnormal plicae, and chondromalacia. The presentation focuses on the optimal imaging parameters that will ensure accuracy and maximize patient throughput. The etiology and significance of meniscal signal is discussed, and the criteria for an MR imaging-based diagnosis of meniscal tears, cruciate and collateral ligament and extensor mechanism abnormalities, osteonecrosis, and stress fractures are presented
The use of MR in cardiological diagnostics
International Nuclear Information System (INIS)
Smith, Hans-Joergen
2004-01-01
Image diagnostics is playing an important role in cardiology, and magnetic resonance tomography (MR) is one of many methods used in examinations of the heart. Based on studies of the literature and his own experience the author surveys the potential of MR in today's and tomorrow's diagnostics of heart diseases. Among the image diagnostic methods MR is the one that can give the most extensive information about the heart's anatomy and function. In a non-invasive way and without the use of ionizing radiation, MR can represent the anatomy in selectable planes, visualize and quantify the heart's pumping function and functioning of the cardiac valves, and give detailed information about the regional contractility, blood flow and viability of myocard. MR is capable of giving important and to some extent unique contributions to heart diseases, both congenital and contracted heart disease. Because of failing availability and competence MR is still little used in cardiological diagnostics, but the method undoubtedly has the potential to play a very important role in the future
MR angiography of the TMJ in asymptomatic volunteers
International Nuclear Information System (INIS)
Takagi, Ritsuo; Ohashi, Yasushi; Westesson, P.L.; Togashi, Hirosuke
1998-01-01
To evaluate the vascular anatomy of the temporomandibular joint (TMJ) and surrounding soft tissue non-invasively, we applied magnetic resonance (MR) angiography for delineating the arterial architecture around the TMJ. MR angiograms of the left and right TMJs in asymptomatic volunteers were obtained using 3D/Time-of-flight (TOF) (First Field Echo, TR/TE/FLIP=46 ms/6.8 ms/17 deg) with intravenous contrast. These MR angiograms were compared with experimental angiograms of human TMJ autopsy specimens in order to identify each of the branches of the arteries on the MR angiograms. This study enabled the depiction by MR angiography of arterial vessels around the TMJ region to some degree. In conclusion, MR angiography appears promising as a non-invasive tool to evaluate the vascular anatomy of the TMJ. (author)
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Rand, T. [Einrichtung fuer Magnetresonanz, Ludwig Boltzmann-Inst. fuer Radiologische Tumordiagnostik, Univ. Wien (Austria); Trattnig, S. [Einrichtung fuer Magnetresonanz, Ludwig Boltzmann-Inst. fuer Radiologische Tumordiagnostik, Univ. Wien (Austria); Breitenseher, M. [Einrichtung fuer Magnetresonanz, Ludwig Boltzmann-Inst. fuer Radiologische Tumordiagnostik, Univ. Wien (Austria); Freilinger, W. [Orthopaedisches Krankenhaus Speising (Austria); Cochole, M. [Orthopaedische Abt., Allgemein Oeffentliches Krankenhaus Amstetten (Austria); Imhof, H. [Einrichtung fuer Magnetresonanz, Ludwig Boltzmann-Inst. fuer Radiologische Tumordiagnostik, Univ. Wien (Austria)
1996-12-01
Indications of MR arthrography were analyzed in this prospective study. The aim was to evaluate possible advantages over conventional MRI, establish diagnostic criteria and to analyze its meaning further for the therapeutic management of postoperative patients. MR arthrography was performed in eight patients who had undergone surgical repair of rotator cuff lesions (modified Neer acromioplasty) and in six patients who had undergone arthroscopic therapy of recurrent unidirectional dislocation of the shoulder by combined arthroscopic intra- and extracapsular repair. MR investigations were performed before and after application of a contrast solution (2 mmol Gd-DTPA). All patients suffered from chronic postoperative pain. In patients with rotator cuff lesions, a partial tear could be verified in one patient and excluded in all others. In patients after arthroscopic therapy by combined intra- and extracapsular repair, a radiologically patulous-appearing capsule correlated with clinically recurrent dislocations. In all other patients diagnostic criteria, such as distribution of the intra-articular contrast solution, proliferation of scar tissue, nodular appearance of the glenohumeral ligaments and capsule thickness, correlated with a regular postoperative status. MR arthrography of the shoulder represents a promising method in the evaluation of the postoperative shoulder. It might further improve the evaluation of reactive capsule alterations, scar tissue proliferation, and the labroligamentous complex, as well as the ability to differentiate partial and complete rerupture from degenerative changes of the rotator cuff. (orig.) [Deutsch] In einer prospektiven Studie sollten die Einsatzmoeglichkeiten der MR-Arthrographie am operierten Schultergelenk erfasst werden. Ziel der Studie war einerseits eine gegenueber der konventionellen MR-Untersuchung verbesserten Diagnosestellung und andererseits die Erstellung von fuer die Rezidivdiagnostik relevanten Diagnosekriterien
Park, In-Hee; Venable, John D.; Steckler, Caitlin; Cellitti, Susan E.; Lesley, Scott A.; Spraggon, Glen; Brock, Ansgar
2015-01-01
Hydrogen exchange (HX) studies have provided critical insight into our understanding of protein folding, structure and dynamics. More recently, Hydrogen Exchange Mass Spectrometry (HX-MS) has become a widely applicable tool for HX studies. The interpretation of the wealth of data generated by HX-MS experiments as well as other HX methods would greatly benefit from the availability of exchange predictions derived from structures or models for comparison with experiment. Most reported computational HX modeling studies have employed solvent-accessible-surface-area based metrics in attempts to interpret HX data on the basis of structures or models. In this study, a computational HX-MS prediction method based on classification of the amide hydrogen bonding modes mimicking the local unfolding model is demonstrated. Analysis of the NH bonding configurations from Molecular Dynamics (MD) simulation snapshots is used to determine partitioning over bonded and non-bonded NH states and is directly mapped into a protection factor (PF) using a logistics growth function. Predicted PFs are then used for calculating deuteration values of peptides and compared with experimental data. Hydrogen exchange MS data for Fatty acid synthase thioesterase (FAS-TE) collected for a range of pHs and temperatures was used for detailed evaluation of the approach. High correlation between prediction and experiment for observable fragment peptides is observed in the FAS-TE and additional benchmarking systems that included various apo/holo proteins for which literature data were available. In addition, it is shown that HX modeling can improve experimental resolution through decomposition of in-exchange curves into rate classes, which correlate with prediction from MD. Successful rate class decompositions provide further evidence that the presented approach captures the underlying physical processes correctly at the single residue level. This assessment is further strengthened in a comparison of
MR cisternography after intrathecal Gd-DTPA application
International Nuclear Information System (INIS)
Reiche, Werner; Komenda, Yvonne; Steudel, Wolf-Ingo; Schick, Bernhard; Grunwald, Iris; Reith, Wolfgang
2002-01-01
The purpose of this study was to establish and to evaluate MR cisternography after intrathecal Gd-DTPA administration to detect rhinobasal cerebrospinal fluid (CSF) fistulae in patients with suspected CSF rhinorrhoea. Ten patients with suspected CSF rhinorrhoea were examined. The MR cisternography included the following investigation steps: acquisition of nonenhanced fat-suppressed T1-weighted spin-echo (SE) scans of the skull base and the paranasal sinuses, lumbar puncture with administration of 1 ml Gd-DTPA solute with 4 ml NaCl and performance of MR cisternography with the same fat-suppressed T1-weighted sequences as used initially. In 10 patients with suspected CSF rhinorrhoea Gd-DTPA enhanced MR cisternography detected 5 CSF fistulae. In 3 of 5 CSF leaks were located in the cribriform plate and in 2 of 5 sphenoidal. Whereas 4 of these depicted leaks were confirmed surgically, in 1 case the CSF fistula closed spontaneously. In another case, CSF leakage after severe head injury was clinically highly suspected but ceased prior to MR cisternography with inability to detect the temporary fistula. In the remaining 4 patients with serous rhinorrhoea MR cisternography did not provide any evidences for CSF fistulae. Intrathecal Gd-DTPA injection was tolerated excellently. Clinical and EEG examinations showed no gross behavioural or neurological disturbances and no seizure activity, respectively. The MR cisternography after intrathecal administration of Gd-DTPA represents a safe, promising and minimally invasive method for detection of CSF fistulae. This MR investigation provides excellent depiction of CSF spaces and pinpoints CSF fistulae. (orig.)
An MR-compatible neonatal incubator.
Paley, M N J; Hart, A R; Lait, M; Griffiths, P D
2012-07-01
To develop a neonatal MR-compatible incubator for transporting babies between a neonatal intensive care unit and an MRI unit that is within the same hospital but geographically separate. The system was strapped to a standard MR-compatible patient trolley, which provides space for resuscitation outside the incubator. A constant-temperature exothermic heat pad was used to maintain temperature together with a logging fluoro-optic temperature monitor and alarm system. The system has been designed to accommodate standard knee-sized coils from the major MR manufacturers. The original incubator was constructed from carbon fibre, but this required modification to prevent radiofrequency shading artefacts due to the conducting properties of the carbon fibre. A high-tensile polyester material was used, which combined light weight with high impact strength. The system could be moved onto the patient bed with the coils and infant in place by one technologist. Studies in eight neonatal patients produced high quality 1.5 T MR images with low motion artefacts. The incubator should also be compatible with imaging in 3 T MR systems, although further work is required to establish this. Images were acquired using both rapid and high-resolution sequences, including three-dimensional volumes, proton spectra and diffusion weighting. The incubator provides a safe, quiet environment for neonates during transport and imaging, at low cost.
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Sommer, T. [German Red Cross Hospital Neuwied (Germany). Dept. of Diagnostic and Interventional Radiology; Luechinger, R. [Zuerich Univ. (Switzerland). Inst. for Biomedical Engineering; Barkhausen, J. [University Hospital Luebeck (Germany). Dept. of Radiology and Nuclear Medicine; Gutberlet, M. [Univ. Leipzig - German Heart Center Leipzig (Germany). Dept. of Diagnostic and Interventional Radiology; Quick, H.H. [University Hospital Essen (Germany). Erwin L. Hahn Inst. for MR Imaging, High Field and Hybrid MR Imaging; Fischbach, K. [University Hospital Magdeburg (Germany). Dept. of Radiology and Nuclear Medicine
2015-09-15
The aim of this paper is to inform physicians, especially radiologists and cardiologists, about the technical and electrophysiological background of MR imaging of patients with implanted cardiac pacemakers (PM) and to provide dedicated clinical practice guidelines how to perform MR exams in this patient group. The presence of a conventional PM system is not any more considered an absolute contraindication for MR imaging. The prerequisites for MR imaging on pacemaker patients include the assessment of the individual risk/benefit ratio as well as to obtain full informed consent about the off label character of the procedure and all associated risks. Furthermore the use of special PM-related (e.g. re-programming of the PM) and MRI-related (e.g. limitation of whole body SAR to 2 W/kg) precautions is required and needs to be combined with adequate monitoring during MR imaging using continuous pulsoximetry. MR conditional PM devices are tested and approved for the use in the MR environment under certain conditions, including the field strength and gradient slew rate of the MR system, the maximum whole body SAR value and the presence of MR imaging exclusion zones. Safe MR imaging of patients with MR conditional PM requires the knowledge of the specific conditions of each PM system. If MR imaging within these specific conditions cannot be guaranteed in a given patient, the procedure guidelines for conventional PM should be used. The complexity of MR imaging of PM patients requires close cooperation of radiologists and cardiologists.
Chen, Peng-Chieh; Wakimoto, Hiroko; Conner, David; Araki, Toshiyuki; Yuan, Tao; Roberts, Amy; Seidman, Christine E.; Bronson, Roderick; Neel, Benjamin G.; Seidman, Jonathan G.; Kucherlapati, Raju
2010-01-01
Noonan syndrome (NS) is an autosomal dominant genetic disorder characterized by short stature, unique facial features, and congenital heart disease. About 10%–15% of individuals with NS have mutations in son of sevenless 1 (SOS1), which encodes a RAS and RAC guanine nucleotide exchange factor (GEF). To understand the role of SOS1 in the pathogenesis of NS, we generated mice with the NS-associated Sos1E846K gain-of-function mutation. Both heterozygous and homozygous mutant mice showed many NS-associated phenotypes, including growth delay, distinctive facial dysmorphia, hematologic abnormalities, and cardiac defects. We found that the Ras/MAPK pathway as well as Rac and Stat3 were activated in the mutant hearts. These data provide in vivo molecular and cellular evidence that Sos1 is a GEF for Rac under physiological conditions and suggest that Rac and Stat3 activation might contribute to NS phenotypes. Furthermore, prenatal administration of a MEK inhibitor ameliorated the embryonic lethality, cardiac defects, and NS features of the homozygous mutant mice, demonstrating that this signaling pathway might represent a promising therapeutic target for NS. PMID:21041952
MR imaging of sacral and perisacral lesions
International Nuclear Information System (INIS)
Wetzel, L.H.; Levine, E.; Murphey, M.D.
1987-01-01
This exhibit demonstrates the utility of MR imaging in evaluating sacral and perisacral lesions. Thirty-two lesions were studied using a superconducting 1.0-T MR imager. Eleven primary and 13 metastatic tumors, four congenital lesions, and four arachnoid cysts were evaluated. MR did not usually enable a more specific histologic diagnosis than other imaging techniques. However, extraosseous and proximal spinal extent of tumors was well defined without use of oral or intravenous contrast material. MR imaging is an excellent noninvasive technique for evaluating most sacral and perisacral lesions and is particularly helpful when precise tumor extent must be determined for treatment planning
Energy Technology Data Exchange (ETDEWEB)
Kozioł-Rachwał, A. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków (Poland); National Institute of Advanced Industrial Science and Technology, Spintronics Research Center, Tsukuba, Ibaraki 305-8568 (Japan); Skowroński, W.; Frankowski, M. [AGH University of Science and Technology, Department of Electronics, al. Mickiewicza 30, 30-059 Kraków (Poland); Chęciński, J. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków (Poland); AGH University of Science and Technology, Department of Electronics, al. Mickiewicza 30, 30-059 Kraków (Poland); Ziętek, S.; Rzeszut, P. [AGH University of Science and Technology, Department of Electronics, al. Mickiewicza 30, 30-059 Kraków (Poland); Ślęzak, M.; Matlak, K.; Ślęzak, T. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków (Poland); Stobiecki, T. [AGH University of Science and Technology, Department of Electronics, al. Mickiewicza 30, 30-059 Kraków (Poland); Korecki, J. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków (Poland); Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Kraków (Poland)
2017-02-15
Fe/MgO/Fe trilayers with a subnanometer MgO tunnel barrier were grown by molecular beam epitaxy. Longitudinal magnetooptic Kerr effect measurements confirmed the existence of the antiferromagnetic interlayer exchange coupling (IEC) between the Fe layers for 2 Å
Fujiwara, Sachiko; Ohashi, Kazumasa; Mashiko, Toshiya; Kondo, Hiroshi; Mizuno, Kensaku
2016-03-15
Mechanical force-induced cytoskeletal reorganization is essential for cell and tissue remodeling and homeostasis; however, the underlying cellular mechanisms remain elusive. Solo (ARHGEF40) is a RhoA-targeting guanine nucleotide exchange factor (GEF) involved in cyclical stretch-induced human endothelial cell reorientation and convergent extension cell movement in zebrafish gastrula. In this study, we show that Solo binds to keratin-8/keratin-18 (K8/K18) intermediate filaments through multiple sites. Solo overexpression promotes the formation of thick actin stress fibers and keratin bundles, whereas knockdown of Solo, expression of a GEF-inactive mutant of Solo, or inhibition of ROCK suppresses stress fiber formation and leads to disorganized keratin networks, indicating that the Solo-RhoA-ROCK pathway serves to precisely organize keratin networks, as well as to promote stress fibers. Of importance, knockdown of Solo or K18 or overexpression of GEF-inactive or deletion mutants of Solo suppresses tensile force-induced stress fiber reinforcement. Furthermore, knockdown of Solo or K18 suppresses tensile force-induced RhoA activation. These results strongly suggest that the interplay between Solo and K8/K18 filaments plays a crucial role in tensile force-induced RhoA activation and consequent actin cytoskeletal reinforcement. © 2016 Fujiwara et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).
Feasibility of MR urography in patients with urinary diversion
International Nuclear Information System (INIS)
Battal, Bilal; Kocaoglu, Murat; Ilica, Turan; Akgun, Veysel; Aydur, Emin; Dayanc, Murat
2011-01-01
The aims of this study were to determine the diagnostic value of MR urography and to compare the T2- and T1-weighted MR urography techniques in patients with urinary diversion. We retrospectively reviewed 19 MR urograms in 14 patients (13 male and one female, 8–77 years old, mean age: 54.2) with urinary diversion. Magnetic resonance urography examinations were performed with 1.5-T MR scanners. In addition to T2- and T1-weighted MR urography techniques, conventional T1- and T2-weighted axial and coronal sequences were also obtained. Collecting systems were evaluated in five segments (right proximal and distal collecting system, left proximal and distal collecting system and conduit or reservoir). Imaging features of the urinary collecting systems were evaluated with T2- and T1-weighted MR urography images. The clinical, laboratory data and follow-up imaging findings were regarded as standard. A cross table was formed to determine sensitivity, specificity and accuracy of MR urography techniques. T2-weighted MR urography, T1-weighted MR urography and combination of these two techniques could demonstrate 89.01, 87.65 and 93.83% of all collecting system segments, respectively. For the detection of the pathologic urinary segments, sensitivity, specificity and accuracy were 100, 95.29 and 95.6% in T2-weighted MR urography and 100, 93.42 and 93.82% in T1-weighted MR urography, respectively. Sensitivity, specificity and accuracy were 100% in combined T2- and T1-weighted MR urography technique. Magnetic resonance urography is an effective imaging method for the evaluation of the urinary system in patients with urinary diversion. T2-weighted MR urography alone has high sensitivity, specificity and accuracy, does not require intravenous contrast medium and can be obtained in 3–5 min. However, T1-weighted MR urography may provide additional information in some cases.
Epstein-Barr virus encephalitis and encephalomyelitis: MR findings
International Nuclear Information System (INIS)
Shian, W.J.; Chi, C.S.
1996-01-01
The purpose of this project is to investigate the clinical and brain MR characteristics of Epstein-Barr virus (EBV) encephalitis and encephalomyelitis. Clinical and 30 MR findings of 29 patients with EBV encephalitis or encephalomyelitis were retrospectively reviewed. Patients included 24 with encephalitis, 3 with encephalomyelitis, and 2 with brain-stem encephalitis. Altered consciousness, seizures, visual hallucination, and acute psychotic reaction were the common presentations. Eight patients had positive MR findings. These included T2 prolongation over gray and white matter, periventricular leukomalacia, and brain atrophy. Transient T2 prolongation over gray and white matter was found in one patient. Our results indicate that EBV encephalitis and encephalomyelitis have a wide range of both clinical and MR findings. The MR lesions may disappear in a short period, so the timing for the MR scan may be critical. (orig.). With 5 figs., 2 tabs
Epstein-Barr virus encephalitis and encephalomyelitis: MR findings
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Shian, W.J. [Department of Pediatrics, Tao-Yuan Veterans Hospital, No. 100, Sec 3, Cheng-Kung Rd, City of Tao-Yuan, Taiwan (Taiwan, Province of China); Chi, C.S. [Department of Pediatrics, Taichung Veterans General Hospital, Taichung, Taiwan (Taiwan, Province of China)
1996-09-01
The purpose of this project is to investigate the clinical and brain MR characteristics of Epstein-Barr virus (EBV) encephalitis and encephalomyelitis. Clinical and 30 MR findings of 29 patients with EBV encephalitis or encephalomyelitis were retrospectively reviewed. Patients included 24 with encephalitis, 3 with encephalomyelitis, and 2 with brain-stem encephalitis. Altered consciousness, seizures, visual hallucination, and acute psychotic reaction were the common presentations. Eight patients had positive MR findings. These included T2 prolongation over gray and white matter, periventricular leukomalacia, and brain atrophy. Transient T2 prolongation over gray and white matter was found in one patient. Our results indicate that EBV encephalitis and encephalomyelitis have a wide range of both clinical and MR findings. The MR lesions may disappear in a short period, so the timing for the MR scan may be critical. (orig.). With 5 figs., 2 tabs.
MR pancreatography (MRP) for mucin-producing pancreatic tumors
International Nuclear Information System (INIS)
Usuki, Noriaki; Nishimoto, Masaoki; Shima, Tomoko; Hirokawa, Keiko; Tashiro, Takahiko; Saiwai, Shigeo; Miyamoto, Takeshi; Okabe, Sumihiro
1997-01-01
MR pancreatography was performed in 11 patients with mucin-producing pancreatic tumor (main duct type: four and branch duct type: seven) using HASTE with a body phased array coil on a 1.5-T unit. The results of MR pancreatography were compared with imaging of endoscopic retrograde pancreatography (ERP). In all cases, MR pancreatography demonstrated all dilated pancreatic ducts and cysts. ERP did not completely demonstrate dilated ducts and cysts because of mucinous materials. Conspicuity of an intraductal tumor was more excellent by ER pancreatography than MR pancreatography. Therefore MR pancreatography and ER pancreatography are complementary methods in diagnosis for mucin-producing pancreatic tumors. (author)
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Izquierdo-Garcia, David [Mount Sinai School of Medicine, Translational and Molecular Imaging Institute, New York, NY (United States); Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA (United States); Sawiak, Stephen J. [University of Cambridge, Wolfson Brain Imaging Centre, Cambridge (United Kingdom); Knesaurek, Karin; Machac, Joseph [Mount Sinai School of Medicine, Division of Nuclear Medicine, Department of Radiology, New York, NY (United States); Narula, Jagat [Mount Sinai School of Medicine, Department of Cardiology, Zena and Michael A. Weiner Cardiovascular Institute and Marie-Josee and Henry R. Kravis Cardiovascular Health Center, New York, NY (United States); Fuster, Valentin [Mount Sinai School of Medicine, Department of Cardiology, Zena and Michael A. Weiner Cardiovascular Institute and Marie-Josee and Henry R. Kravis Cardiovascular Health Center, New York, NY (United States); The Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid (Spain); Fayad, Zahi A. [Mount Sinai School of Medicine, Translational and Molecular Imaging Institute, New York, NY (United States); Mount Sinai School of Medicine, Department of Cardiology, Zena and Michael A. Weiner Cardiovascular Institute and Marie-Josee and Henry R. Kravis Cardiovascular Health Center, New York, NY (United States); Mount Sinai School of Medicine, Department of Radiology, New York, NY (United States)
2014-08-15
The objective of this study was to evaluate the performance of the built-in MR-based attenuation correction (MRAC) included in the combined whole-body Ingenuity TF PET/MR scanner and compare it to the performance of CT-based attenuation correction (CTAC) as the gold standard. Included in the study were 26 patients who underwent clinical whole-body FDG PET/CT imaging and subsequently PET/MR imaging (mean delay 100 min). Patients were separated into two groups: the alpha group (14 patients) without MR coils during PET/MR imaging and the beta group (12 patients) with MR coils present (neurovascular, spine, cardiac and torso coils). All images were coregistered to the same space (PET/MR). The two PET images from PET/MR reconstructed using MRAC and CTAC were compared by voxel-based and region-based methods (with ten regions of interest, ROIs). Lesions were also compared by an experienced clinician. Body mass index and lung density showed significant differences between the alpha and beta groups. Right and left lung densities were also significantly different within each group. The percentage differences in uptake values using MRAC in relation to those using CTAC were greater in the beta group than in the alpha group (alpha group -0.2 ± 33.6 %, R{sup 2} = 0.98, p < 0.001; beta group 10.31 ± 69.86 %, R{sup 2} = 0.97, p < 0.001). In comparison to CTAC, MRAC led to underestimation of the PET values by less than 10 % on average, although some ROIs and lesions did differ by more (including the spine, lung and heart). The beta group (imaged with coils present) showed increased overall PET quantification as well as increased variability compared to the alpha group (imaged without coils). PET data reconstructed with MRAC and CTAC showed some differences, mostly in relation to air pockets, metallic implants and attenuation differences in large bone areas (such as the pelvis and spine) due to the segmentation limitation of the MRAC method. (orig.)
International Nuclear Information System (INIS)
Izquierdo-Garcia, David; Sawiak, Stephen J.; Knesaurek, Karin; Machac, Joseph; Narula, Jagat; Fuster, Valentin; Fayad, Zahi A.
2014-01-01
The objective of this study was to evaluate the performance of the built-in MR-based attenuation correction (MRAC) included in the combined whole-body Ingenuity TF PET/MR scanner and compare it to the performance of CT-based attenuation correction (CTAC) as the gold standard. Included in the study were 26 patients who underwent clinical whole-body FDG PET/CT imaging and subsequently PET/MR imaging (mean delay 100 min). Patients were separated into two groups: the alpha group (14 patients) without MR coils during PET/MR imaging and the beta group (12 patients) with MR coils present (neurovascular, spine, cardiac and torso coils). All images were coregistered to the same space (PET/MR). The two PET images from PET/MR reconstructed using MRAC and CTAC were compared by voxel-based and region-based methods (with ten regions of interest, ROIs). Lesions were also compared by an experienced clinician. Body mass index and lung density showed significant differences between the alpha and beta groups. Right and left lung densities were also significantly different within each group. The percentage differences in uptake values using MRAC in relation to those using CTAC were greater in the beta group than in the alpha group (alpha group -0.2 ± 33.6 %, R 2 = 0.98, p 2 = 0.97, p < 0.001). In comparison to CTAC, MRAC led to underestimation of the PET values by less than 10 % on average, although some ROIs and lesions did differ by more (including the spine, lung and heart). The beta group (imaged with coils present) showed increased overall PET quantification as well as increased variability compared to the alpha group (imaged without coils). PET data reconstructed with MRAC and CTAC showed some differences, mostly in relation to air pockets, metallic implants and attenuation differences in large bone areas (such as the pelvis and spine) due to the segmentation limitation of the MRAC method. (orig.)
International Nuclear Information System (INIS)
Ahn, Yong Sik; Yu, Hyeon; Kim, Wan Tae; Bae, Jin Woo; Moon, Hee Jung; Shin, Hyun Ja
1999-01-01
To evaluate the incidence and characteristic findings of pineal cyst incidentally detected on magnetic resonance (MR) imaging. Brain MR images obtained in 2432 patients were retrospectively reviewed to determine the incidence and MR findings of pineal cysts, which were evaluated according to their size, shape, location, signal intensity, interval change, contrast enhancement and mass effect on adjacent structures. Cysts were encountered in 107(4.4 %) of 2432 patients evaluated. their size ranged from 1 X 1 X 1 to 15 X 8 X 9 (mean, 5.97 X 3.82 X 4.82)mm. All were spherical (n=53) or oval (n=54) in shape. Their margin was smooth and they were homogeneous in nature. On T1-weighted images, the cysts were seen to be hyperintense (n=57) or isointense (n=50) to cerebrospinal fluid, but less so than brain parenchyma. T2-weighted images showed them to be isointense (n=51)or hyperintense (n=56) to cerebrospinal fluid. The cysts were centrally located in 65 cases and eccentrically in 42. Compression of the superior colliculi of the tectum was demonstrated in 17 cases (15.9 %). NO patients presented clinical symptoms or signs related to either pineal or tectal lesions. Peripheral enhancement around the cyst after Gd-DTPA injection was demonstrated in 51 cases(100 %). Follow-up examinations in 19 cases demonstrated no interval change. The incidence of pineal cysts was 4.4 %. The MR characteristics of simple pineal cysts include: (1) an oval or spherical shape, (2) a smooth outer margin and homogeneous nature, (3) isosignal or slightly high signal intensity to cerebrospinal fluid on whole pulse sequences, (4) ring enhancement after contrast injection, (5) an absence of interval change, as seen during follow up MR study. These MR appearances of pineal cysts might be helpful for differentiating them from pineal tumors
Choice of exchange rate regimes for African countries: Fixed or Flexible Exchange rate regimes?
Simwaka, Kisu
2010-01-01
The choice of an appropriate exchange rate regime has been a subject of ongoing debate in international economics. The majority of African countries are small open economies and thus where the choice of the exchange rate regime is an important policy issue. Aside from factors such as interest rates and inflation, the exchange rate is one of the most important determinants of a country’s relative level of economic health. For this reason, exchange rates are among the most watched analyzed and ...
MR findings of cerebral arteriovenous malformations associated with hemorrhage
Energy Technology Data Exchange (ETDEWEB)
Tsuchiya, Kazuhiro (National Defence Medical Coll., Tokorozawa, Saitama (Japan))
1990-10-01
This study was developed to assess the role of magnetic resonance (MR) imaging in the diagnosis of cerebral arteriovenous malformations (AVMs) associated with hemorrhage. MR images were retrospectively reviewed in 10 patients (age 8 to 60 years) who had an AVM with intracerebral or intraventricular hemorrhage. MR imaging was performed at 1.5 T obtaining T{sub 1}- and T{sub 2}-weighted spin-echo images with a slice thickness of 5 mm, and a slice interval of 0-5 mm. The AVM was detected on MR in seven patients (70%), while enhanced CT was positive in six of eight patients (75%). In six patients in whom both the AVM and intracerebral hematoma (ICH) were depicted on MR, the nidi were located not inside but adjacent to the ICH. In three patients, MR disclosed a thin subdural hematoma (SDH) which was not noted on CT. There is little difference in the detectability of AVMs by MR and enhanced CT. However, MR clearly demonstrates the anatomic relationship to associated ICH. A non-traumatic SDH with an ICH demonstrated on MR may indicate the presence of an AVM even when the AVM itself is not apparent. (author).
Utility of MR imaging in pediatric spinal cord injury
International Nuclear Information System (INIS)
Felsberg, G.J.; Tien, R.D.; Osumi, A.K.; Cardenas, C.A.
1995-01-01
We evaluated the utility of MR imaging in pediatric patients with acute and subacute spinal cord injuries. MR imaging of 22 pediatric patients with suspected traumatic spinal cord injuries was reviewed. MR findings were correlated with physical examination and compared to available radiographs and CT examinations performed at time of presentation. Twelve patients had abnormalities on MR imaging. Seven had spinal cord contusions; five contusions were hemorrhagic. Five of seven patients with cord contusion had normal radiographs and CT exams. Six patients with normal radiographs and CT examinations had abnormal MR studies revealing cord contusion, ligamentous injury, disc herniation, and epidural hematoma. MR is useful in initial evaluation of pediatric patients with spinal cord injuries and in prognosis of future neurologic function. In the setting of spinal cord symptomatology and negative radiographic studies, MR imaging should be performed. Surgically correctable causes of cord compression demonstrated by MR imaging include disc herniation, epidural hematoma, and retropulsed fracture fragments. The entity of spinal cord injury without radiographic abnormality is a diagnosis of exclusion which should only be made after radiologic investigation with radiographs, high-resolution thin-section CT, and MR imaging. (orig.)
Lifescience Database Archive (English)
Full Text Available factor RasGEF Q (gefQ) gene, complete cds. 597 0.0 3 AB022770 |AB022770.1 Human rotavirus mRNA for NSP2, com...ne, complete cds. 50 0.024 1 X57944 |X57944.1 Human rotavirus segment 7 gp33 gene. 50 0.024 1 AC092543 |AC09
Interventional and intravascular MR angiography
International Nuclear Information System (INIS)
Ladd, M.E.; Debatin, J.F.
2000-01-01
Magnetic resonance imaging (MRI) has a number of characteristics which make it attractive for guidance of intravascular therapeutic procedures, including high soft tissue contrast, imaging in any arbitrary oblique plane, lack of ionizing radiation, and the ability to provide functional information, such as flow velocity and volume per unit time. For MR guidance of vascular interventions to be safe, catheters and guidewires must be visualized relative to the vascular system and surrounding tissues. A number of approaches for making instruments visible in an MR environment are presented, including both passive and active techniques. Passive techniques depend on contrast agents or susceptibility artifacts, whereas active techniques, including MR tracking, MR profiling, and active field inhomogeneity, use some form of electrical coil built into the instrument. The potential for obtaining high-resolution images of the vessel wall using coils built into a catheter is also discussed. These images provide the capability to distinguish and identify various plaque components. The additional capabilities of MRI could potentially open up new applications beyond those currently performed under X-ray fluoroscopic guidance. (orig.) [de
MR diagnosis of temporomandibular arthrosis
Energy Technology Data Exchange (ETDEWEB)
Suenaga, Shigeaki [Kagoshima Univ. (Japan). Faculty of Dentistry
1996-09-01
This review described lesions of articular disk and its surrounding tissues revealed by MR examination in temporomandibular arthrosis, and problems and limits of the examination. Apparatus and imaging methods: Spin echo method was generally used and gradient echo method was alternatively used. Author`s apparatus was 1.5 tesla Signa, Advantage type, equipped with surface coil for temporomandibular joint. Imaging conditions were T1-weighted spin echo method, T2-weighted fast spin echo method, spoiled GRASS (gradient recalled acquisition in the steady state) method and GRASS method. MR findings of articular disk: MR images of normal and abnormal temporomandibular joint were presented together with computed radiographic findings. The role of dynamic imaging was described for evaluation and analysis of the joint functioning. MR findings of surrounding tissues of the disk: Dynamic MRI of the tissues was found useful to see whether the cause of pain was present inside or outside of the articular capsule. Joint effusion could not be fully imaged in T2-weighted conditions. (K.H.)
MR diagnosis of temporomandibular arthrosis
International Nuclear Information System (INIS)
Suenaga, Shigeaki
1996-01-01
This review described lesions of articular disk and its surrounding tissues revealed by MR examination in temporomandibular arthrosis, and problems and limits of the examination. Apparatus and imaging methods: Spin echo method was generally used and gradient echo method was alternatively used. Author's apparatus was 1.5 tesla Signa, Advantage type, equipped with surface coil for temporomandibular joint. Imaging conditions were T1-weighted spin echo method, T2-weighted fast spin echo method, spoiled GRASS (gradient recalled acquisition in the steady state) method and GRASS method. MR findings of articular disk: MR images of normal and abnormal temporomandibular joint were presented together with computed radiographic findings. The role of dynamic imaging was described for evaluation and analysis of the joint functioning. MR findings of surrounding tissues of the disk: Dynamic MRI of the tissues was found useful to see whether the cause of pain was present inside or outside of the articular capsule. Joint effusion could not be fully imaged in T2-weighted conditions. (K.H.)
Cardiac and vascular imaging with snapshot FLASH MR imaging
International Nuclear Information System (INIS)
Matthaei, D.; Haase, A.; Norris, D.; Leibfritz, D.; Henrich, D.; Duhmke, E.
1989-01-01
Acceleration of fast low-angle-shot (FLASH) MR imaging to about 200 msec measuring time on dedicated MR systems is called snapshot FLASH MR imaging. It snaps real-time series of MR images of the MR relaxation and of physiologic motions with nearly absent motion and susceptibility artifacts. Results in animals (4.7T) and human volunteers (2.0T) show plain vascular and cardiac snapshot FLASH MR images obtained as single shot, triggered reconstructed motion, or real-time films. The reduction of artifacts and the high resolution (triggered, three-dimensional moving heart images are possible) result in favorable applications in myocardial and great vascular disease
Catana, Ciprian; Wu, Yibao; Judenhofer, Martin S; Qi, Jinyi; Pichler, Bernd J; Cherry, Simon R
2006-12-01
PET and MRI are powerful imaging techniques that are largely complementary in the information they provide. We have designed and built a MR-compatible PET scanner based on avalanche photodiode technology that allows simultaneous acquisition of PET and MR images in small animals. The PET scanner insert uses magnetic field-insensitive, position-sensitive avalanche photodiode (PSAPD) detectors coupled, via short lengths of optical fibers, to arrays of lutetium oxyorthosilicate (LSO) scintillator crystals. The optical fibers are used to minimize electromagnetic interference between the radiofrequency and gradient coils and the PET detector system. The PET detector module components and the complete PET insert assembly are described. PET data were acquired with and without MR sequences running, and detector flood histograms were compared with the ones generated from the data acquired outside the magnet. A uniform MR phantom was also imaged to assess the effect of the PET detector on the MR data acquisition. Simultaneous PET and MRI studies of a mouse were performed ex vivo. PSAPDs can be successfully used to read out large numbers of scintillator crystals coupled through optical fibers with acceptable performance in terms of energy and timing resolution and crystal identification. The PSAPD-LSO detector performs well in the 7-T magnet, and no visible artifacts are detected in the MR images using standard pulse sequences. The first images from the complete system have been successfully acquired and reconstructed, demonstrating that simultaneous PET and MRI studies are feasible and opening up interesting possibilities for dual-modality molecular imaging studies.
MR imaging in hemophilic arthropathy
International Nuclear Information System (INIS)
Baunin, C.; Railhac, J.J.; Younes, I.; Gaubert, J.; DuBoullay, C.; Dirat, G.; Robert, A.
1990-01-01
This paper reports on twenty children with hemophilia examined to determine if MR imaging could be used to assess hemophilic arthropathy. Twenty-eight joints were imaged (17 knees, 10 ankles, 1 elbow) with plain radiography, US, CT, and MR imaging. The results were compared with the surgical view and histologic study of the articular components when synovectomy was done. These results show the usefulness of MR imaging: fluid collections in the joint space were evaluated, and it was possible to distinguish blood from inflammatory fluid. Synovial hypertrophy was appreciated, and findings correlated well with histologic study. Anomalies of articular cartilage, joint-space narrowing, and bone lesions were demonstrated early, when plain radiography findings were still normal
Retroperitoneal fibrosis: findings with MR
International Nuclear Information System (INIS)
Martinez Rodrigo, J.; Marti-Bonnati, L.; Diago, T.; Ferrer, M.D.; Aleixandre, A.; Morote, V.
1993-01-01
Retroperitoneal fibrosis (RF) is an uncommon disease characterized by the presence of a chronic inflammatory reaction, with the formation of fibrous tissue that replaces the normal retroperitoneal tissue, trapping vessels and/or ureters. We present a retrospective review of 3 cases of idiopathic RF studied by means of ultrasound, CT scan and MR imaging, and we assess the features of the MR image, as well as its capacity for characterizing the lesion. We compare the findings obtained with 3 imaging techniques, describing the utility of each one, and their advantages and disadvantages in the assessment of this pathology. In MR, idiopathic RF appears as a hypodense mass in SET1, SE-T2 and STIR sequences. (Author) 9 ref
Valuation of dynamic MR imaging for diagnosis of pituitary microadenomas
International Nuclear Information System (INIS)
Lu Wu; Zhou Shengli; Liu Yusheng
2003-01-01
Objective: To evaluate the use of keyhole dynamic magnetic resonance (MR) imaging in evaluation of pituitary microadenomas. Methods: Fifty-three patients with pituitary microadenomas proved by operation or clinical findings such as headache, amenorrhea, lactating, fat or acromegaly were retrospectively studied on dynamic MR, conventional contrast enhanced MR, and unenhanced MR. Then the image data were analyzed by two experienced doctors who didn't know the details and three degrees were made as follows: grade 0, no evidence of the tumor; grade I, asymmetry signals in the pituitary; and grade II, nodulated or sheets signals in the pituitary. The grading data were compared with statistical methods. Results: In dynamic MR grading system: grade 0 was revealed in 1 patient, grade I in 29 patients and grade II in 23 patients. In conventional enhanced MR: grade 0 in 26 patients, grade I in 17 patients and grade II in 10 patients. In conventional unenhanced MR: grade 0 in 39 patients, grade I in 10 patients and grade II in 4 patients. The diagnostic rate of dynamic MR, conventional enhanced MR, and unenhanced MR was 98.1%, 51.9%, and 26.4%, respectively. (P < 0.005). Dynamic MR can increase the grade of tumor compared to the other two, which is significant statistically. Conclusion: Keyhole dynamic MR can increase the diagnostic accuracy of pituitary microadenomas while decreasing the uncertainty. So dynamic MR should become a routine examination for pituitary microadenoma when suspected by clinical findings but negative in conventional MR