WorldWideScience

Sample records for mri signal amplification

  1. An enzymatic signal amplification system for calorimetric studies of cellobiohydrolases

    DEFF Research Database (Denmark)

    Murphy, Leigh; Baumann, Martin Johannes; Borch, Kim

    2010-01-01

    amplification method has been developed to measure even slow hydrolytically active enzymes such as cellobiohydrolases. This method is explained in detail for the amplification of the heat signal by more than 130 times by using glucose oxidase and catalase. The kinetics of this complex coupled reaction system...

  2. Photoacoustic signal amplification through plasmonic nanoparticle aggregation

    OpenAIRE

    Bayer, Carolyn L.; Nam, Seung Yun; Chen, Yun-Sheng; Emelianov, Stanislav Y.

    2013-01-01

    Photoacoustic imaging, using targeted plasmonic metallic nanoparticles, is a promising noninvasive molecular imaging method. Analysis of the photoacoustic signal generated by plasmonic metallic nanoparticles is complex because of the dependence upon physical properties of both the nanoparticle and the surrounding environment. We studied the effect of the aggregation of gold nanoparticles on the photoacoustic signal amplitude. We found that the photoacoustic signal from aggregated silica-coate...

  3. Development of an electronic system for signals amplification

    International Nuclear Information System (INIS)

    Santos, Italo S.; Tobias, Carmen C.B.

    2009-01-01

    This paper presents the obtained results with a spectrometer for electromagnetic radiation whose detector, a Si PIN type diode, was directly coupled to a signal amplification system developed in this project for scientific initiation. The linearity conditions and the gain operational limits, constituted of two stages of amplification based on the employment of devices from AMTEK A225 and A206, were determined using a precision pulse generator. The obtained results shown that the developed system is stable and linear in the gain range of 50-150. The spectrometric response of the electronic system coupled to the Siemens SFH-00206 type diode, were studied in view of the register of the 59.5 keV gamma ray spectra proceeding from 241 Am as function of the reversal polarization voltage. The influence pf the voltage and the electronic contribution in the energy resolution of the registered spectra under room temperature (22 degree Celsius) had also investigated considering the more adequate value of the coupling capacitance of the amplification system diode. Up to the present. the best energy resolution (FWHM = 4.85 keV) of the 59.5 keV line was obtained for the condition of the detector polarization at 16 V. This result proves that the signal amplification system developed coupled to the SFH00206 diode, besides the low cost, excellent operational condition for the detection and spectrometry or low energy electromagnetic radiation

  4. Electrochemical DNA biosensor based on MNAzyme-mediated signal amplification

    International Nuclear Information System (INIS)

    Diao, Wei; Tang, Min; Ding, Xiaojuan; Zhang, Ye; Yang, Jianru; Cheng, Wenbin; Mo, Fei; Wen, Bo; Xu, Lulu; Yan, Yurong

    2016-01-01

    The authors describe an electrochemical sensing strategy for highly sensitive and specific detection of target (analyte) DNA based on an amplification scheme mediated by a multicomponent nucleic acid enzyme (MNAzyme). MNAzymes were formed by multicomponent complexes which produce amplified “output” signals in response to specific “input” signal. In the presence of target nucleic acid, multiple partial enzymes (partzymes) oligonucleotides are assembled to form active MNAzymes. These can cleave H0 substrate into two pieces, thereby releasing the activated MNAzyme to undergo an additional cycle of amplification. Here, the two pieces contain a biotin-tagged sequence and a byproduct. The biotin-tagged sequences are specifically captured by the detection probes immobilized on the gold electrode. By employing streptavidinylated alkaline phosphatase as an enzyme label, an electrochemical signal is obtained. The electrode, if operated at a working potential of 0.25 V (vs. Ag/AgCl) in solution of pH 7.5, covers the 100 pM to 0.25 μM DNA concentration range, with a 79 pM detection limit. In our perception, the strategy introduced here has a wider potential in that it may be applied to molecular diagnostics and pathogen detection. (author)

  5. Signal amplification for impedimetric genosensing using gold-streptavidin nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Bonanni, A.; Esplandiu, M.J. [Sensors and Biosensors Group, Department of Chemistry, Universitat Autonoma de Barcelona, Edifici Cn, 08193 Bellaterra, Barcelona (Spain); Valle, M. del [Sensors and Biosensors Group, Department of Chemistry, Universitat Autonoma de Barcelona, Edifici Cn, 08193 Bellaterra, Barcelona (Spain)], E-mail: manel.delvalle@uab.es

    2008-04-20

    Streptavidin-coated gold nanoparticles (strept-AuNPs) were used in this work to amplify the impedimetric signal generated in a biosensor detecting the DNA hybridization event. Probe oligomer was adsorbed onto a graphite epoxy composite (GEC) electrode surface and the impedance measurement was performed in a solution containing the redox marker ferrocyanide/ferricyanide. The biotinylated complementary oligomer was used as target. The change of interfacial charge transfer resistance (R{sub ct}), experimented by the redox marker, was recorded to confirm the hybrid formation. The addition of strept-AuNPs, binding to the target due to the strong streptavidin-biotin interaction, led to a further increment of R{sub ct} thus obtaining significant signal amplification. Strept-AuNPs on the electrode surface were observed by scanning electron microscopy (SEM) after silver enhancement treatment. A competitive binding assay was also performed using unlabelled DNA target to demonstrate its applicability to real sample analysis.

  6. Current Technologies of Electrochemical Immunosensors: Perspective on Signal Amplification

    Directory of Open Access Journals (Sweden)

    Il-Hoon Cho

    2018-01-01

    Full Text Available An electrochemical immunosensor employs antibodies as capture and detection means to produce electrical charges for the quantitative analysis of target molecules. This sensor type can be utilized as a miniaturized device for the detection of point-of-care testing (POCT. Achieving high-performance analysis regarding sensitivity has been one of the key issues with developing this type of biosensor system. Many modern nanotechnology efforts allowed for the development of innovative electrochemical biosensors with high sensitivity by employing various nanomaterials that facilitate the electron transfer and carrying capacity of signal tracers in combination with surface modification and bioconjugation techniques. In this review, we introduce novel nanomaterials (e.g., carbon nanotube, graphene, indium tin oxide, nanowire and metallic nanoparticles in order to construct a high-performance electrode. Also, we describe how to increase the number of signal tracers by employing nanomaterials as carriers and making the polymeric enzyme complex associated with redox cycling for signal amplification. The pros and cons of each method are considered throughout this review. We expect that these reviewed strategies for signal enhancement will be applied to the next versions of lateral-flow paper chromatography and microfluidic immunosensor, which are considered the most practical POCT biosensor platforms.

  7. Signal amplification and Pierce's instability in convergent particle beams

    International Nuclear Information System (INIS)

    Gnavi, G.; Gratton, F.T.

    1988-01-01

    Relativistic electron beams flowing between cylindrical and spherical electrodes (or solid angles sections of electrodes with these geometries) are studied. The beams are focused through the axis in the cylindrical case or through the center when spherical electrodes are considered. It is assumed that the external electrode is part of a device which accelerates the particles, the inner electrode is passive and removes the beams from the system. Electrons move by inertia in the interelectrode space, neutralized by an ion background. Properties of radial, small amplitude, perturbations are analyzed theoretically. Previous analyses of counterstreaming beams indicated that convergence modifies considerably the oscillations spectrum. Here, results on the amplification of signals when a beam is modulated at the external electrode are reported. Then, conditions for the instability of a beam when it flows through grounded electrodes (Pierce's instability of only one beam) are examined

  8. An ultrasensitive colorimeter assay strategy for p53 mutation assisted by nicking endonuclease signal amplification.

    Science.gov (United States)

    Lin, Zhenyu; Yang, Weiqiang; Zhang, Guiyun; Liu, Qida; Qiu, Bin; Cai, Zongwei; Chen, Guonan

    2011-08-28

    A novel catalytic colorimetric assay assisted by nicking endonuclease signal amplification (NESA) was developed. With the signal amplification, the detection limit of the p53 target gene can be as low as 1 pM, which is nearly 5 orders of magnitude lower than that of other previously reported colorimetric DNA detection strategies based on catalytic DNAzyme.

  9. PARAMETRIC AMPLIFICATION OF THE SIGNALS IN THE ELECTROSTATIC GRAVIINERTIAL SENSOR

    Directory of Open Access Journals (Sweden)

    I. Z. Gilavdary

    2017-01-01

    Full Text Available The challenges of designing simple, reliable, and high sensitivity graviinertial sensors are investigated. The sensor comprises a proof mass (PM and is fixed with the housing by the elastic torsion suspension. PM makes small rotations under the action of gravitational forces or inertial forces.The distinctive features of the sensor are that the differential electrostatic system provides simultaneous reading of the desired signal and a control the torsional rigidity of suspension. In addition, the PM's rotational angular velocity transforms in the alternating current flowing through the capacitors. The presence of аlternating current (AC voltage sources allows to get the parametric amplification of AC and significantly to improve the sensitivity of the sensor. In the simplest case, the sensor does not contain any feedback circuits.As an example, calculations of the micromechanical linear accelerations confirm that the periodic modulation of the coefficient of elastic stiffness of the suspension can significantly increase the sensitivity in the low frequency range, even in the absence of parametric resonance.Conditions for suppressions of background current participating in the output signal from a parametric pumping due to the asymmetry of the differential circuits are set. The frequency characteristics calculations of the sensor were carried out. It is expected, that the proposed sensor design ensures minimum noise level, which can be achievable in the graviinertial sensors. This design and the constructed theory can serve as a basis for creating a wide range of graviinertial devices operating on a movable base, for example, linear and angular accelerometer, gravity gradiometer, gravimeters, and inclinometers, which can be realized in the hybrid and in the micromechanical versions.

  10. Signal amplification of microRNAs with modified strand displacement-based cycling probe technology.

    Science.gov (United States)

    Jia, Huning; Bu, Ying; Zou, Bingjie; Wang, Jianping; Kumar, Shalen; Pitman, Janet L; Zhou, Guohua; Song, Qinxin

    2016-10-24

    Micro ribose nucleic acids (miRNAs) play an important role in biological processes such as cell differentiation, proliferation and apoptosis. Therefore, miRNAs are potentially a powerful marker for monitoring cancer and diagnosis. Here, we present sensitive signal amplification for miRNAs based on modified cycling probe technology with strand displacement amplification. miRNA was captured by the template coupled with beads, and then the first cycle based on SDA was repeatedly extended to the nicking end, which was produced by the extension reaction of miRNA. The products generated by SDA are captured by a molecular beacon (MB), which is designed to initiate the second amplification cycle, with a similar principle to the cycling probe technology (CPT), which is based on repeated digestion of the DNA-RNA hybrid by the RNase H. After one sample enrichment and two steps of signal amplification, 0.1 pM of let-7a can be detected. The miRNA assay exhibits a great dynamic range of over 100 orders of magnitude and high specificity to clearly discriminate a single base difference in miRNA sequences. This isothermal amplification does not require any special temperature control instrument. The assay is also about signal amplification rather than template amplification, therefore minimising contamination issues. In addition, there is no need for the reverse transcription (RT) process. Thus the amplification is suitable for miRNA detection.

  11. Simultaneous electrical and mechanical resonance drive for large signal amplification of micro resonators

    KAUST Repository

    Hasan, M. H.

    2018-01-12

    Achieving large signal-noise ratio using low levels of excitation signal is key requirement for practical applications of micro and nano electromechanical resonators. In this work, we introduce the double electromechanical resonance drive concept to achieve an order-of-magnitude dynamic signal amplification in micro resonators. The concept relies on simultaneously activating the micro-resonator mechanical and electrical resonance frequencies. We report an input voltage amplification up to 15 times for a micro-resonator when its electrical resonance is tuned to match the mechanical resonance that leads to dynamic signal amplification in air (Quality factor enhancement). Furthermore, using a multi-frequency excitation technique, input voltage and vibrational amplification of up to 30 times were shown for the same micro-resonator while relaxing the need to match its mechanical and electrical resonances.

  12. Simultaneous electrical and mechanical resonance drive for large signal amplification of micro resonators

    KAUST Repository

    Hasan, M. H.; Alsaleem, F. M.; Jaber, Nizar; Hafiz, Md Abdullah Al; Younis, Mohammad I.

    2018-01-01

    Achieving large signal-noise ratio using low levels of excitation signal is key requirement for practical applications of micro and nano electromechanical resonators. In this work, we introduce the double electromechanical resonance drive concept to achieve an order-of-magnitude dynamic signal amplification in micro resonators. The concept relies on simultaneously activating the micro-resonator mechanical and electrical resonance frequencies. We report an input voltage amplification up to 15 times for a micro-resonator when its electrical resonance is tuned to match the mechanical resonance that leads to dynamic signal amplification in air (Quality factor enhancement). Furthermore, using a multi-frequency excitation technique, input voltage and vibrational amplification of up to 30 times were shown for the same micro-resonator while relaxing the need to match its mechanical and electrical resonances.

  13. All-optical WDM Regeneration of DPSK Signals using Optical Fourier Transformation and Phase Sensitive Amplification

    DEFF Research Database (Denmark)

    Guan, Pengyu; Røge, Kasper Meldgaard; Kjøller, Niels-Kristian

    2015-01-01

    We propose a novel all-optical WDM regeneration scheme for DPSK signals based on optical Fourier transformation and phase sensitive amplification. Phase regeneration of a WDM signal consisting of 4x10-Gbit/s phase noise degraded DPSK channels is demonstrated for the first time.......We propose a novel all-optical WDM regeneration scheme for DPSK signals based on optical Fourier transformation and phase sensitive amplification. Phase regeneration of a WDM signal consisting of 4x10-Gbit/s phase noise degraded DPSK channels is demonstrated for the first time....

  14. Tiny Grains Give Huge Gains: Nanocrystal–Based Signal Amplification for Biomolecule Detection

    Science.gov (United States)

    Tong, Sheng; Ren, Binbin; Zheng, Zhilan; Shen, Han; Bao, Gang

    2013-01-01

    Nanocrystals, despite their tiny sizes, contain thousands to millions of atoms. Here we show that the large number of atoms packed in each metallic nanocrystal can provide a huge gain in signal amplification for biomolecule detection. We have devised a highly sensitive, linear amplification scheme by integrating the dissolution of bound nanocrystals and metal-induced stoichiometric chromogenesis, and demonstrated that signal amplification is fully defined by the size and atom density of nanocrystals, which can be optimized through well-controlled nanocrystal synthesis. Further, the rich library of chromogenic reactions allows implementation of this scheme in various assay formats, as demonstrated by the iron oxide nanoparticle linked immunosorbent assay (ILISA) and blotting assay developed in this study. Our results indicate that, owing to the inherent simplicity, high sensitivity and repeatability, the nanocrystal based amplification scheme can significantly improve biomolecule quantification in both laboratory research and clinical diagnostics. This novel method adds a new dimension to current nanoparticle-based bioassays. PMID:23659350

  15. Method for signal conditioning and data acquisition system, based on variable amplification and feedback technique

    Energy Technology Data Exchange (ETDEWEB)

    Conti, Livio, E-mail: livio.conti@uninettunouniversity.net [Facoltà di Ingegneria, Università Telematica Internazionale Uninettuno, Corso Vittorio Emanuele II 39, 00186 Rome, Italy INFN Sezione Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Sgrigna, Vittorio [Dipartimento di Matematica e Fisica, Università Roma Tre, 84 Via della Vasca Navale, I-00146 Rome (Italy); Zilpimiani, David [National Institute of Geophysics, Georgian Academy of Sciences, 1 M. Alexidze St., 009 Tbilisi, Georgia (United States); Assante, Dario [Facoltà di Ingegneria, Università Telematica Internazionale Uninettuno, Corso Vittorio Emanuele II 39, 00186 Rome, Italy INFN Sezione Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy)

    2014-08-21

    An original method of signal conditioning and adaptive amplification is proposed for data acquisition systems of analog signals, conceived to obtain a high resolution spectrum of any input signal. The procedure is based on a feedback scheme of the signal amplification with aim at maximizing the dynamic range and resolution of the data acquisition system. The paper describes the signal conditioning, digitization, and data processing procedures applied to an a priori unknown signal in order to enucleate its amplitude and frequency content for applications in different environments: on the ground, in space, or in the laboratory. An electronic board of the conditioning module has also been constructed and described. In the paper are also discussed the main fields of application and advantages of the method with respect to those known today.

  16. Method for signal conditioning and data acquisition system, based on variable amplification and feedback technique

    International Nuclear Information System (INIS)

    Conti, Livio; Sgrigna, Vittorio; Zilpimiani, David; Assante, Dario

    2014-01-01

    An original method of signal conditioning and adaptive amplification is proposed for data acquisition systems of analog signals, conceived to obtain a high resolution spectrum of any input signal. The procedure is based on a feedback scheme of the signal amplification with aim at maximizing the dynamic range and resolution of the data acquisition system. The paper describes the signal conditioning, digitization, and data processing procedures applied to an a priori unknown signal in order to enucleate its amplitude and frequency content for applications in different environments: on the ground, in space, or in the laboratory. An electronic board of the conditioning module has also been constructed and described. In the paper are also discussed the main fields of application and advantages of the method with respect to those known today

  17. A new ultrasonic signal amplification method for detection of bacteria

    Science.gov (United States)

    Kant Shukla, Shiva; Resa López, Pablo; Sierra Sánchez, Carlos; Urréjola, José; Segura, Luis Elvira

    2012-10-01

    A new method is presented that increases the sensitivity of ultrasound-based techniques for detection of bacteria. The technique was developed for the detection of catalase-positive microorganisms. It uses a bubble trapping medium containing hydrogen peroxide that is mixed with the sample for microbiological evaluation. The enzyme catalase is present in catalase-positive bacteria, which induces a rapid hydrolysis of hydrogen peroxide, forming bubbles which remain in the medium. This reaction results in the amplification of the mechanical changes that the microorganisms produce in the medium. The effect can be detected by means of ultrasonic wave amplitude continuous measurement since the bubbles increase the ultrasonic attenuation significantly. It is shown that microorganism concentrations of the order of 105 cells ml-1 can be detected using this method. This allows an improvement of three orders of magnitude in the ultrasonic detection threshold of microorganisms in conventional culture media, and is competitive with modern rapid microbiological methods. It can also be used for the characterization of the enzymatic activity.

  18. A new ultrasonic signal amplification method for detection of bacteria

    International Nuclear Information System (INIS)

    Shukla, Shiva Kant; López, Pablo Resa; Sánchez, Carlos Sierra; Segura, Luis Elvira; Urréjola, José

    2012-01-01

    A new method is presented that increases the sensitivity of ultrasound-based techniques for detection of bacteria. The technique was developed for the detection of catalase-positive microorganisms. It uses a bubble trapping medium containing hydrogen peroxide that is mixed with the sample for microbiological evaluation. The enzyme catalase is present in catalase-positive bacteria, which induces a rapid hydrolysis of hydrogen peroxide, forming bubbles which remain in the medium. This reaction results in the amplification of the mechanical changes that the microorganisms produce in the medium. The effect can be detected by means of ultrasonic wave amplitude continuous measurement since the bubbles increase the ultrasonic attenuation significantly. It is shown that microorganism concentrations of the order of 10 5 cells ml −1 can be detected using this method. This allows an improvement of three orders of magnitude in the ultrasonic detection threshold of microorganisms in conventional culture media, and is competitive with modern rapid microbiological methods. It can also be used for the characterization of the enzymatic activity. (paper)

  19. Amplification and discrimination of signals from proportional multiwire chambers

    International Nuclear Information System (INIS)

    Papadopoulos, L.; Bosio, C.; Cordelli, M.

    1976-03-01

    A circuit is described which detects signals from proportional multiwire chambers. The threshold is about 3μ A and the time jitter of the pulse obtained is better than 2.5 ns. The circuit has one negative input and two complementary outputs. The realized module includes 8 channels with common trigger level control and was built as NIM standard unit

  20. Dual-signal heterodyne lock-in amplification with lasers

    NARCIS (Netherlands)

    Witteman, W.J.

    2006-01-01

    High-sensitivity heterodyne detection with lasers applied to radar and satellite communication is seriously hampered by the large electronic bandwidth due to Doppler shift and frequency instability. These drawbacks can be circumvented by dual-signal heterodyne detection. The system consists of

  1. New frontiers of molecular beacons: signal amplification and nanomachines

    DEFF Research Database (Denmark)

    Della Vedova, Paolo

    2013-01-01

    by two complementary strands (stem), conjugated respectively with a fluorophore and a quencher. Upon hybridization with complementary target, the stem bonds break, parting the fluorophore from the quencher and resulting in a detectable signal. This thesis is divided in two major sections. The first...

  2. Thousand-fold fluorescent signal amplification for mHealth diagnostics

    Science.gov (United States)

    The low sensitivity of Mobile Health (mHealth) optical detectors, such as those found on mobile phones, is a limiting factor for many mHealth clinical applications. To improve sensitivity, we have combined two approaches for optical signal amplification: (1) a computational approach based on an imag...

  3. Homogeneous electrochemical aptamer-based ATP assay with signal amplification by exonuclease III assisted target recycling.

    Science.gov (United States)

    Liu, Shufeng; Wang, Ying; Zhang, Chengxin; Lin, Ying; Li, Feng

    2013-03-21

    A novel and homogeneous electrochemical aptamer-based adenosine triphosphate (ATP) assay was demonstrated with signal amplification by exonuclease III-assisted target recycling. A superior detection limit of 1 nM toward ATP with an excellent selectivity could be achieved.

  4. The importance of correcting for signal drift in diffusion MRI

    OpenAIRE

    Vos, Sjoerd B; Tax, Chantal M W; Luijten, Peter R; Ourselin, Sebastien; Leemans, Alexander; Froeling, Martijn

    2017-01-01

    PURPOSE: To investigate previously unreported effects of signal drift as a result of temporal scanner instability on diffusion MRI data analysis and to propose a method to correct this signal drift. METHODS: We investigated the signal magnitude of non-diffusion-weighted EPI volumes in a series of diffusion-weighted imaging experiments to determine whether signal magnitude changes over time. Different scan protocols and scanners from multiple vendors were used to verify this on phantom data, a...

  5. Differential diagnosis of the signal-compromised lunate in MRI

    International Nuclear Information System (INIS)

    Schmitt, R.; Christopoulos, G.; Coblenz, G.; Froehner, S.; Brunner, H.; Kalb, K.; Krimmer, H.; Lanz, U.

    2005-01-01

    Purpose: To define both the underlying pathology and diagnostic criteria in lunates presenting with conspicuous signal pattern in MRI. Materials and Methods: The retrospective evaluation of 2940 MRI examinations revealed 203 patients with signal alterations of the lunate. All MRI examinations were performed on 1.5-Tesla platforms using dedicated surface coils and an intravenous contrast agent. To establish a definitive diagnosis, a total of 252 MRI examinations (49 follow-ups), 22 CT examinations and 4 arthroscopic studies were obtained in addition to the obligatory conventional radiographs. Results: Incorporating all clinical data, radiographs and MRI examinations succeeded in assigning a diagnosis in 136 signal-compromised lunates (67.0%), whereas additional diagnostic procedures or follow-up examinations were required for the definitive diagnosis in 57 cases (33.0%). The most frequent entities were 51 cases of Kienboeck's disease (25.1%), 47 cases of ulnolunate-(triquetral) impaction syndromes (23.2%) and 44 cases of intra-osseous ganglion cysts (21.7%). Other pathologies included 23 degenerative, 19 traumatic and 10 inflammatory changes as well as 9 congenital conditions. For MRI assessment of the altered lunate, the most important parameters were location and morphology as well as involvement of the articular and osseous structures of the carpus. Conclusion: The lunate may be affected by different pathological states of the wrist. In total, only one quarter of the signal-compromised lunate represented Kienboeck's disease. (orig.)

  6. Simulations of signal amplification and oscillations using a SNS junction

    International Nuclear Information System (INIS)

    Luiz, A.M.; Soares, V.; Nicolsky, R.

    1998-01-01

    A superconducting - normal metal - superconducting junction (SNS junction) may exhibit a low voltage negative differential resistance (LVNDR) effect over part of its current voltage characteristic (CVC). As the LVNDR effect is stable against a bias voltage at this CVC range, it should be possible to combine a SNS junction with conventional electronic circuits to obtain electronic devices such as mixers, amplifiers and oscillators. Making use of this remarkable effect, we show that an amplifier may be feasible by assembling a simple voltage divider made up of a SNS junction in series with a resistor. The amplifier circuit includes an adjustable DC voltage supply (the bias voltage) and an AC signal source with a given voltage. The SNS junction is connected in series with a resistor R. Choosing values of the load resistance R approximately equal to the module of the negative differential resistance (dV/dI), at the bias voltage, we may obtain large gains in this amplifier device. In order to get an oscillator, the SNS junction should be connected to a RLC tank circuit with a bias voltage adjusted in the range of the LVNDR region of its CVC. A power output of the order of one microwatt may be easily obtained. (orig.)

  7. Directionality and signal amplification in cryogenic dark matter detection

    International Nuclear Information System (INIS)

    More, T.

    1996-05-01

    A mounting body of evidence suggests that most of the mass in our universe is not contained in stars, but rather exists in some non- luminous form. The evidence comes independently from astronomical observation, cosmological theory, and particle physics. All of this missing mass is collectively referred to as dark matter. In this thesis we discuss two ways to improve the performance of dark matter detectors based on the measurement of ballistic phonons. First, we address the issue of signal identification through solitons. Secondly, we discuss a method for lowering the detection threshold and improving the energy sensitivity: amplifying phonons through the evaporation of helium atoms from a superfluid film coating the target and the adsorption of the evaporated atoms onto a helium-free substrate. A phonon amplifier would also be of use in many other applications in which a few phonons are to be measured at low temperatures. Factors contributing to the low amplifier gains achieved thus far are described and proposals for avoiding them are analyzed and discussed. 101 refs., 30 figs., 2 tabs

  8. Oligomerization of Paramagnetic Substrates Result in Signal Amplification and Can be Used for MR Imaging of Molecular Targets

    Directory of Open Access Journals (Sweden)

    Alexei Bogdanov

    2002-01-01

    Full Text Available Magnetic resonance imaging (MRI has evolved into a sophisticated, noninvasive imaging modality capable of high-resolution anatomical and functional characterization of transgenic animals. To expand the capabilities MRI, we have developed a novel MR signal amplification (MRamp strategy based on enzyme-mediated polymerization of paramagnetic substrates into oligomers of higher magnetic relaxivity. The substrates consist of chelated gadolinium covalently bound to phenols, which then serve as electron donors during enzymatic hydrogen peroxide reduction by peroxidase. The converted monomers undergo rapid condensation into paramagnetic oligomers leading to a threefold increase in atomic relaxivity (R1/Gd. The observed relaxivity changes are largely due to an increase in the rotational correlation time τr of the lanthanide. Three applications of the developed system are demonstrated: (1 imaging of nanomolar amounts of an oxidoreductase (peroxidase; (2 detection of a model ligand using an enzyme-linked immunoadsorbent assay format; and (3 imaging of E-selectin on the surface of endothelial cells probed for with an anti-E-selectin – peroxidase conjugate. The development of “enzyme sensing” probes is expected to have utility for a number of applications including in vivo detection of specific molecular targets. One particular advantage of the MRamp technique is that the same paramagnetic substrate can be potentially used to identify different molecular targets by attaching enzymes to various antibodies or other target-seeking molecules.

  9. Comparison of calculated, simulated and measured signal amplification in variable pressure SEM

    Czech Academy of Sciences Publication Activity Database

    Neděla, Vilém; Konvalina, Ivo; Lencová, Bohumila; Zlámal, J.

    2011-01-01

    Roč. 645, č. 1 (2011), s. 79-83 ISSN 0168-9002 R&D Projects: GA ČR GAP102/10/1410; GA MPO FR-TI1/118; GA MPO FR-TI1/305 Institutional research plan: CEZ:AV0Z20650511 Keywords : electron-gas interactions * Monte Carlo simulation s * signal amplification * analytical models Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.207, year: 2011

  10. Two-phase xenon detector with gas amplification and electroluminescent signal detection

    International Nuclear Information System (INIS)

    Akimov, D.Yu.; Burenkov, A.A.; Grishkin, Yu.L.; Kovalenko, A.G.; Lebedenko, V.N.; Stekhanov, V.N.

    2008-01-01

    An optical technique for detecting ionization electrons produced during ionization of the liquid phase has been experimentally tested in two-phase (liquid-gas) xenon. The effects of gas and electroluminescent amplifications at the wire anode are simultaneously used for detection. This method allows construction of a supersensitive detector of small ionization signals-down to those corresponding to the detection of single electrons [ru

  11. Signal Amplification Technique (SAT): an approach for improving resolution and reducing image noise in computed tomography

    International Nuclear Information System (INIS)

    Phelps, M.E.; Huang, S.C.; Hoffman, E.J.; Plummer, D.; Carson, R.

    1981-01-01

    Spatial resolution improvements in computed tomography (CT) have been limited by the large and unique error propagation properties of this technique. The desire to provide maximum image resolution has resulted in the use of reconstruction filter functions designed to produce tomographic images with resolution as close as possible to the intrinsic detector resolution. Thus, many CT systems produce images with excessive noise with the system resolution determined by the detector resolution rather than the reconstruction algorithm. CT is a rigorous mathematical technique which applies an increasing amplification to increasing spatial frequencies in the measured data. This mathematical approach to spatial frequency amplification cannot distinguish between signal and noise and therefore both are amplified equally. We report here a method in which tomographic resolution is improved by using very small detectors to selectively amplify the signal and not noise. Thus, this approach is referred to as the signal amplification technique (SAT). SAT can provide dramatic improvements in image resolution without increases in statistical noise or dose because increases in the cutoff frequency of the reconstruction algorithm are not required to improve image resolution. Alternatively, in cases where image counts are low, such as in rapid dynamic or receptor studies, statistical noise can be reduced by lowering the cutoff frequency while still maintaining the best possible image resolution. A possible system design for a positron CT system with SAT is described

  12. Irreversible Catalyst Activation Enables Hyperpolarization and Water Solubility for NMR Signal Amplification by Reversible Exchange

    Science.gov (United States)

    2016-09-12

    G. R.; Duckett, S. B.; Spiess , H. W.; Schreiber, L. M.; Münnemann, K. Continuous Proton Hyperpolarization Via SABRE and Hollow Fibre Membranes. Proc...M.; Kindervater, P.; Raich, H.-P.; Bargon, J.; Spiess , H. W.; Muennemann, K. Continuous H-1 and C-13 Signal Enhancement in NMR Spectroscopy and MRI

  13. Three different signal amplification strategies for the impedimetric sandwich detection of thrombin

    Energy Technology Data Exchange (ETDEWEB)

    Ocaña, Cristina; Valle, Manel del, E-mail: manel.delvalle@uab.cat

    2016-03-17

    In this work, we report a comparative study on three highly specific amplification strategies for the ultrasensitive detection of thrombin with the use of aptamer sandwich protocol. The protocol consisted on the use of a first thrombin aptamer immobilized on the electrode surface, the recognition of thrombin protein, and the reaction with a second biotinylated thrombin aptamer forming the sandwich. Through the exposed biotin end, three variants have been tested to amplify the electrochemical impedance signal. The strategies included (a) silver enhancement treatment, (b) gold enhancement treatment and (c) insoluble product produced by the combination of the enzyme horseradish peroxidase (HRP) and 3-amino-9-ethylcarbazole (AEC). The properties of the sensing surface were probed by electrochemical impedance measurements in the presence of the ferrocyanide/ferricyanide redox marker. Insoluble product strategy and silver enhancement treatment resulted in the lowest detection limit (0.3 pM), while gold enhancement method resulted in the highest reproducibility, 8.8% RSD at the pM thrombin concentration levels. Results of silver and gold enhancement treatment also permitted direct inspection by scanning electron microscopy (SEM). - Highlights: • Aptasensor to detect thrombin reaching the femtomolar level. • Biosensing protocol employs two thrombin aptamers in a sandwich capture scheme. • Use of second biotinylated aptamer allows many amplification and detection variants. • Precipitation reaction provides the highest signal amplification of ca. 3 times. • Double recognition event improves remarkably selectivity for thrombin detection.

  14. Three different signal amplification strategies for the impedimetric sandwich detection of thrombin

    International Nuclear Information System (INIS)

    Ocaña, Cristina; Valle, Manel del

    2016-01-01

    In this work, we report a comparative study on three highly specific amplification strategies for the ultrasensitive detection of thrombin with the use of aptamer sandwich protocol. The protocol consisted on the use of a first thrombin aptamer immobilized on the electrode surface, the recognition of thrombin protein, and the reaction with a second biotinylated thrombin aptamer forming the sandwich. Through the exposed biotin end, three variants have been tested to amplify the electrochemical impedance signal. The strategies included (a) silver enhancement treatment, (b) gold enhancement treatment and (c) insoluble product produced by the combination of the enzyme horseradish peroxidase (HRP) and 3-amino-9-ethylcarbazole (AEC). The properties of the sensing surface were probed by electrochemical impedance measurements in the presence of the ferrocyanide/ferricyanide redox marker. Insoluble product strategy and silver enhancement treatment resulted in the lowest detection limit (0.3 pM), while gold enhancement method resulted in the highest reproducibility, 8.8% RSD at the pM thrombin concentration levels. Results of silver and gold enhancement treatment also permitted direct inspection by scanning electron microscopy (SEM). - Highlights: • Aptasensor to detect thrombin reaching the femtomolar level. • Biosensing protocol employs two thrombin aptamers in a sandwich capture scheme. • Use of second biotinylated aptamer allows many amplification and detection variants. • Precipitation reaction provides the highest signal amplification of ca. 3 times. • Double recognition event improves remarkably selectivity for thrombin detection.

  15. Light-Triggered Soft Artificial Muscles: Molecular-Level Amplification of Actuation Control Signals.

    Science.gov (United States)

    Dicker, Michael P M; Baker, Anna B; Iredale, Robert J; Naficy, Sina; Bond, Ian P; Faul, Charl F J; Rossiter, Jonathan M; Spinks, Geoffrey M; Weaver, Paul M

    2017-08-23

    The principle of control signal amplification is found in all actuation systems, from engineered devices through to the operation of biological muscles. However, current engineering approaches require the use of hard and bulky external switches or valves, incompatible with both the properties of emerging soft artificial muscle technology and those of the bioinspired robotic systems they enable. To address this deficiency a biomimetic molecular-level approach is developed that employs light, with its excellent spatial and temporal control properties, to actuate soft, pH-responsive hydrogel artificial muscles. Although this actuation is triggered by light, it is largely powered by the resulting excitation and runaway chemical reaction of a light-sensitive acid autocatalytic solution in which the actuator is immersed. This process produces actuation strains of up to 45% and a three-fold chemical amplification of the controlling light-trigger, realising a new strategy for the creation of highly functional soft actuating systems.

  16. Evolution and Design Governing Signal Precision and Amplification in a Bacterial Chemosensory Pathway.

    Directory of Open Access Journals (Sweden)

    Mathilde Guzzo

    2015-08-01

    Full Text Available Understanding the principles underlying the plasticity of signal transduction networks is fundamental to decipher the functioning of living cells. In Myxococcus xanthus, a particular chemosensory system (Frz coordinates the activity of two separate motility systems (the A- and S-motility systems, promoting multicellular development. This unusual structure asks how signal is transduced in a branched signal transduction pathway. Using combined evolution-guided and single cell approaches, we successfully uncoupled the regulations and showed that the A-motility regulation system branched-off an existing signaling system that initially only controlled S-motility. Pathway branching emerged in part following a gene duplication event and changes in the circuit structure increasing the signaling efficiency. In the evolved pathway, the Frz histidine kinase generates a steep biphasic response to increasing external stimulations, which is essential for signal partitioning to the motility systems. We further show that this behavior results from the action of two accessory response regulator proteins that act independently to filter and amplify signals from the upstream kinase. Thus, signal amplification loops may underlie the emergence of new connectivity in signal transduction pathways.

  17. Persistent Amplification of DNA Damage Signal Involved in Replicative Senescence of Normal Human Diploid Fibroblasts

    Directory of Open Access Journals (Sweden)

    Masatoshi Suzuki

    2012-01-01

    Full Text Available Foci of phosphorylated histone H2AX and ATM are the surrogate markers of DNA double strand breaks. We previously reported that the residual foci increased their size after irradiation, which amplifies DNA damage signals. Here, we addressed whether amplification of DNA damage signal is involved in replicative senescence of normal human diploid fibroblasts. Large phosphorylated H2AX foci (>1.5 μm diameter were specifically detected in presenescent cells. The frequency of cells with large foci was well correlated with that of cells positive for senescence-associated β-galactosidase staining. Hypoxic cell culture condition extended replicative life span of normal human fibroblast, and we found that the formation of large foci delayed in those cells. Our immuno-FISH analysis revealed that large foci partially localized at telomeres in senescent cells. Importantly, large foci of phosphorylated H2AX were always colocalized with phosphorylated ATM foci. Furthermore, Ser15-phosphorylated p53 showed colocalization with the large foci. Since the treatment of senescent cells with phosphoinositide 3-kinase inhibitor, wortmannin, suppressed p53 phosphorylation, it is suggested that amplification of DNA damage signaling sustains persistent activation of ATM-p53 pathway, which is essential for replicative senescence.

  18. Parametric Amplification Protocol for Frequency-Modulated Magnetic Resonance Force Microscopy Signals

    Science.gov (United States)

    Harrell, Lee; Moore, Eric; Lee, Sanggap; Hickman, Steven; Marohn, John

    2011-03-01

    We present data and theoretical signal and noise calculations for a protocol using parametric amplification to evade the inherent tradeoff between signal and detector frequency noise in force-gradient magnetic resonance force microscopy signals, which are manifested as a modulated frequency shift of a high- Q microcantilever. Substrate-induced frequency noise has a 1 / f frequency dependence, while detector noise exhibits an f2 dependence on modulation frequency f . Modulation of sample spins at a frequency that minimizes these two contributions typically results in a surface frequency noise power an order of magnitude or more above the thermal limit and may prove incompatible with sample spin relaxation times as well. We show that the frequency modulated force-gradient signal can be used to excite the fundamental resonant mode of the cantilever, resulting in an audio frequency amplitude signal that is readily detected with a low-noise fiber optic interferometer. This technique allows us to modulate the force-gradient signal at a sufficiently high frequency so that substrate-induced frequency noise is evaded without subjecting the signal to the normal f2 detector noise of conventional demodulation.

  19. Experimental study of MRI signal changes of calcification

    International Nuclear Information System (INIS)

    Gong Xiangyang; Li Senhua; Li Rongfen; Hong Xiang; Gong Xiaoya; Xu Fengfeng

    1999-01-01

    Objective: To evaluate MRI signal changes according to different calcium compound, concentration and proportion, and try to give an reasonable explanation. Methods: Sixty samples composed of different calcium powders, various concentration and proportion of calcium were examined with CT and MRI. Five different calcium particles were evaluated with scanning electron microscopy. Results: (1) CT value of calcium gradually increased as the concentration increased; (2) CaSO 4 ·H 2 O was similar to CaCO 3 in terms of MRI T 1 WI signal intensity (P > 0.05); (3) Ca 3 (PO 4 ) 2 and Ca(OH) 2 showed hyperintensity in T 1 WI and was higher than other calcium salts (P 1 WI signal intensity of Ca 3 (PO 4 ) 2 / and Ca(OH) 2 showed biphasic curves with their peaks at 0.3 g/ml; (5) T 2 WI signal intensity of all series of calcium decreased as the concentration increased; (6) Signal intensity of mixed Ca 3 (PO 4 ) 2 /CaCO 3 was higher than CaHPO 4 ·2H 2 O/CaCO 3 on T 1 WI and lower on T 2 WI (P 3 , CaHPO 4 ·2H 2 O and CaSO 4 ·2H 2 O showed regular crystal shapes and smooth surface under scanning electron microscopy, but Ca 3 (PO 4 ) 2 and Ca(OH) 2 displayed their irregular figures and rough surface. Conclusions: Calcifications show variable MR signal due to difference of calcium compounds, various concentration and proportion of calcium. Understanding of these finding will help interpretation of MR images more precisely

  20. Ternary Surface Monolayers for Ultrasensitive (Zeptomole) Amperometric Detection of Nucleic-Acid Hybridization without Signal Amplification

    Science.gov (United States)

    Wu, Jie; Campuzano, Susana; Halford, Colin; Haake, David A.; Wang, Joseph

    2010-01-01

    A ternary surface monolayer, consisting of co-assembled thiolated capture probe (SHCP) mercaptohexanol (MCH) and dithiothreitol (DTT), is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers (SAMs). Remarkably low detection limits down to 40 zmole (in 4 μL samples) as well as only 1 CFU E. coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3′,5,5′-tetramethylbenzidine (HRP/TMB) system. Such dramatic improvements in the detection limits (compared to common binary alkanethiol interfaces and to most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to non-specific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration ‘backfillers’ that leads to a remarkably low background noise even in the presence of complex sample matrices. A wide range of surface compositions have been investigated and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety and forensic analysis. PMID:20883023

  1. Ternary surface monolayers for ultrasensitive (zeptomole) amperometric detection of nucleic acid hybridization without signal amplification.

    Science.gov (United States)

    Wu, Jie; Campuzano, Susana; Halford, Colin; Haake, David A; Wang, Joseph

    2010-11-01

    A ternary surface monolayer, consisting of coassembled thiolated capture probe, mercaptohexanol and dithiothreitol, is shown to offer dramatic improvements in the signal-to-noise characteristics of electrochemical DNA hybridization biosensors based on common self-assembled monolayers. Remarkably low detection limits down to 40 zmol (in 4 μL samples) as well as only 1 CFU Escherichia coli per sensor are thus obtained without any additional amplification step in connection to the commonly used horseradish peroxidase/3,3',5,5'-tetramethylbenzidine system. Such dramatic improvements in the detection limits (compared to those of common binary alkanethiol interfaces and to those of most electrochemical DNA sensing strategies without target or signal amplification) are attributed primarily to the remarkably higher resistance to nonspecific adsorption. This reflects the highly compact layer (with lower pinhole density) produced by the coupling of the cyclic- and linear-configuration "backfillers" that leads to a remarkably low background noise even in the presence of complex sample matrixes. A wide range of surface compositions have been investigated, and the ternary mixed monolayer has been systematically optimized. Detailed impedance spectroscopy and cyclic voltammetric studies shed useful insights into the surface coverage. The impressive sensitivity and high specificity of the simple developed methodology indicate great promise for a wide range of nucleic acid testing, including clinical diagnostics, biothreat detection, food safety, and forensic analysis.

  2. Quantitative measurement of intervertebral disc signal using MRI

    International Nuclear Information System (INIS)

    Niemelaeinen, R.; Videman, T.; Dhillon, S.S.; Battie, M.C.

    2008-01-01

    Aim: To investigate the spinal cord as an alternative intra-body reference to cerebrospinal fluid (CSF) in evaluating thoracic disc signal intensity. Materials and methods: T2-weighted magnetic resonance imaging (MRI) images of T6-T12 were obtained using 1.5 T machines for a population-based sample of 523 men aged 35-70 years. Quantitative data on the signal intensities were acquired using an image analysis program (SpEx (copy right) ). A random sample of 30 subjects and intraclass correlation coeffcients (ICC) were used to examine the repeatability of the spinal cord measurements. The validity of using the spinal cord as a reference was examined by correlating cord and CSF samples. Finally, thoracic disc signal was validated by correlating it with age without adjustment and adjusting for either cord or CSF. Pearson's r was used for correlational analyses. Results: The repeatability of the spinal cord signal measurements was extremely high (≥0.99). The correlations between the signals of spinal cord and CSF by level were all above 0.9. The spinal cord-adjusted disc signal and age correlated similarly with CSF-adjusted disc signal and age (r = -0.30 to -0.40 versus r = -0.26 to -0.36). Conclusion: Adjacent spinal cord is a good alternative reference to the current reference standard, CSF, for quantitative measurements of disc signal intensity. Clearly fewer levels were excluded when using spinal cord as compared to CSF due to missing reference samples

  3. Biosensors for breast cancer diagnosis: A review of bioreceptors, biotransducers and signal amplification strategies.

    Science.gov (United States)

    Mittal, Sunil; Kaur, Hardeep; Gautam, Nandini; Mantha, Anil K

    2017-02-15

    Breast cancer is highly prevalent in females and accounts for second highest number of deaths, worldwide. Cumbersome, expensive and time consuming detection techniques presently available for detection of breast cancer potentiates the need for development of novel, specific and ultrasensitive devices. Biosensors are the promising and selective detection devices which hold immense potential as point of care (POC) tools. Present review comprehensively scrutinizes various breast cancer biosensors developed so far and their technical evaluation with respect to efficiency and potency of selected bioreceptors and biotransducers. Use of glycoproteins, DNA biomarkers, micro-RNA, circulatory tumor cells (CTC) and some potential biomarkers are introduced briefly. The review also discusses various strategies used in signal amplification such as nanomaterials, redox mediators, p19 protein, duplex specific nucleases (DSN) and redox cycling. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Quantitative measurement of intervertebral disc signal using MRI

    Energy Technology Data Exchange (ETDEWEB)

    Niemelaeinen, R. [Faculty of Rehabilitation Medicine, University of Alberta, Edmonton (Canada)], E-mail: riikka.niemelainen@ualberta.ca; Videman, T. [Faculty of Rehabilitation Medicine, University of Alberta, Edmonton (Canada); Dhillon, S.S. [Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton (Canada); Battie, M.C. [Faculty of Rehabilitation Medicine, University of Alberta, Edmonton (Canada)

    2008-03-15

    Aim: To investigate the spinal cord as an alternative intra-body reference to cerebrospinal fluid (CSF) in evaluating thoracic disc signal intensity. Materials and methods: T2-weighted magnetic resonance imaging (MRI) images of T6-T12 were obtained using 1.5 T machines for a population-based sample of 523 men aged 35-70 years. Quantitative data on the signal intensities were acquired using an image analysis program (SpEx (copy right) ). A random sample of 30 subjects and intraclass correlation coeffcients (ICC) were used to examine the repeatability of the spinal cord measurements. The validity of using the spinal cord as a reference was examined by correlating cord and CSF samples. Finally, thoracic disc signal was validated by correlating it with age without adjustment and adjusting for either cord or CSF. Pearson's r was used for correlational analyses. Results: The repeatability of the spinal cord signal measurements was extremely high ({>=}0.99). The correlations between the signals of spinal cord and CSF by level were all above 0.9. The spinal cord-adjusted disc signal and age correlated similarly with CSF-adjusted disc signal and age (r = -0.30 to -0.40 versus r = -0.26 to -0.36). Conclusion: Adjacent spinal cord is a good alternative reference to the current reference standard, CSF, for quantitative measurements of disc signal intensity. Clearly fewer levels were excluded when using spinal cord as compared to CSF due to missing reference samples.

  5. A sensitive detection assay based on signal amplification technology for Alzheimer's disease's early biomarker in exosome.

    Science.gov (United States)

    Zhou, Jie; Meng, Lingchang; Ye, Weiran; Wang, Qiaolei; Geng, Shizhen; Sun, Chong

    2018-08-31

    Alzheimer's disease (AD) considered as the third health "killer" has seriously threatened the health of the elderly. However, the modern diagnostic strategies of AD present several disadvantages: the low accuracy and specificity resulting in some false-negative diagnoses, and the poor sensitivity leading to a delayed treatment. In view of this situation, a enzyme-free and target-triggered signal amplification strategy, based on graphene oxide (GO) and entropy-driven strand displacement reaction (ESDR) principle, was proposed. In this strategy, when the hairpin structure probes (H)specially binds with beta-amyloid-(1-42) oligomers (Aβ42 oligomers), it's structure will be opened, causing the bases complementary to FAM-labeled replacement probes R (R1 and R2) exposed. At this time, R1 and R2 will hybridize with H, resulting in the bound Aβ42 oligomers released. The released Aβ42 oligomers would participate in the next cycle reaction, making the signal amplified. As a quencher, GO could absorb the free single-stranded DNA R1 and R2 and quench their fluorescence; however, the DNA duplex still exists free and keeps its signal-on. Through the detection of Aβ42 oligomers in exosomes, this ultrasensitive detection method with the advantages of low limit of detection (LOD, 20 pM), great accuracy, excellent precision and convenience provides an excellent prospect for AD's early diagnosis. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. Parametric Amplification, Wavelength Conversion, and Phase Conjugation of a 2.048-Tbit/s WDM PDM 16-QAM Signal

    DEFF Research Database (Denmark)

    Hu, Hao; Jopson, R. M.; Gnauck, A. H.

    2015-01-01

    We demonstrate polarization-independent parametric amplification of a 2.048-Tbit/s 8-WDM PDM 16-QAM signal and simultaneous wavelength conversion and phase conjugation in a highly nonlinear fiber. Two high-power continuous-wave pumps with orthogonal polarizations and counter-phase modulation are ...

  7. Parametric amplification and wavelength conversion of a 2.048-Tbit/s WDM PDM 16-QAM signal

    DEFF Research Database (Denmark)

    Hu, Hao; Jopson, R. M.; Gnauck, A. H.

    2014-01-01

    We demonstrate polarisation-insensitive parametric amplification in highly nonlinear fibre of a 2.048-Tbit/s dense WDM PDM 16-QAM signal with ∼10 dB on-off gain and simultaneous wavelength conversion and phase conjugation, with mean Q2 penalties of only 0.6 dB and 0.4 dB....

  8. An experimental study on MRI signal intensity of albumin solution

    International Nuclear Information System (INIS)

    Ahn, In Oak; Chang, Kee Hyun; Han, Moon Hee; Song, Chi Sung; Yeon, Kyung Mo

    1990-01-01

    This in vitro study attempted to correlate magnetic resonance (MR) signal intensity with concentration of albumin solution in magnetic field strength of 2.0 Tesla (T) and 0.5T. MR imaging of bovine serum albumin solutions of various concentrations ranging from 0 to 40 g/dl was performed on both 2.0T and 0.5T MR units. The relative (with respect to normal saline) signal intensities of each albumin solution were measured in T1-weighted, proton density-weighted and T2-weighted MR images, correlated with albumin concentration on each pulse sequence, and compared between 2.0T and 0.5T. Additionally, the albumin concentrations showing signal intensities identical to those of white matter, cortical gray matter and cerebrospinal fluid (CSF) of normal brain MRI were determined by visual comparison of those images. 1. On T1-weighted (SE 400-500 msec/30 msec) images under 2.0T and 0.5T field strength, the signal intensity increased with increasing albumin concentrations up to about 30-35 g/dl and the decreased. For the solutions ranging from 0 to about 5 g/dl concentration, the signal intensities appeared isointense to normal saline on visual inspection. 2. On proton density-weighted (SE 2000-2500 msec/30 msec) images under 2.0T and 0.5T field strength, the signal intensity slightly increased with increasing albumin concentrations up to about 7.5-10 g/dl, and then gradually decreased. 3. On T2-weighted (SE 2000-2500 msec/80-100 msec) images under 2.0T and 0.5T field strength, the signal intensity slightly increased with increasing albumin concentrations up to about 7.5-10 g/dl, and then gradually decreased. Above the concentration of about 25-30 g/dl, the signal intensity appeared lower than that of normal saline on visual inspection. 4. Compared with the signal intensities of normal brain structures on T1-weighted images under 2.0T and 0.5T field strength, the signal intensities of the albumin solution below 2.5-5 g/dl concentration were similar to that of CSF, and those of

  9. Stochastic amplification and signaling in enzymatic futile cycles through noise-induced bistability with oscillations

    Science.gov (United States)

    Samoilov, Michael; Plyasunov, Sergey; Arkin, Adam P.

    2005-02-01

    Stochastic effects in biomolecular systems have now been recognized as a major physiologically and evolutionarily important factor in the development and function of many living organisms. Nevertheless, they are often thought of as providing only moderate refinements to the behaviors otherwise predicted by the classical deterministic system description. In this work we show by using both analytical and numerical investigation that at least in one ubiquitous class of (bio)chemical-reaction mechanisms, enzymatic futile cycles, the external noise may induce a bistable oscillatory (dynamic switching) behavior that is both quantitatively and qualitatively different from what is predicted or possible deterministically. We further demonstrate that the noise required to produce these distinct properties can itself be caused by a set of auxiliary chemical reactions, making it feasible for biological systems of sufficient complexity to generate such behavior internally. This new stochastic dynamics then serves to confer additional functional modalities on the enzymatic futile cycle mechanism that include stochastic amplification and signaling, the characteristics of which could be controlled by both the type and parameters of the driving noise. Hence, such noise-induced phenomena may, among other roles, potentially offer a novel type of control mechanism in pathways that contain these cycles and the like units. In particular, observations of endogenous or externally driven noise-induced dynamics in regulatory networks may thus provide additional insight into their topology, structure, and kinetics. network motif | signal transduction | chemical reaction | synthetic biology | systems biology

  10. Modified beacon probe assisted dual signal amplification for visual detection of microRNA.

    Science.gov (United States)

    Sun, Xiuwei; Ying, Na; Ju, Chuanjing; Li, Zhongyi; Xu, Na; Qu, Guijuan; Liu, Wensen; Wan, Jiayu

    2018-04-21

    In a recent study, we reported a novel assay for the detection of microRNA-21 based on duplex-specific nuclease (DSN)-assisted isothermal cleavage and hybridization chain reaction (HCR) dual signal amplification. The Fam modified double-stranded DNA products were generated after the HCR, another biotin modified probe was digested by DSN and released from the magnetic beads after the addition of the target miRNA. The released sequence was then combined with HCR products to form a double-tagging dsDNA, which can be recognized by the lateral flow strips. In this study, we introduced a 2-OMethyl-RNA modified beacon probe (2-OMe-MB) to make some improvements based on the previous study. Firstly, the substitution of modified probe combined on magnetic beads avoids the fussy washing steps for the separation of un-reacted probes. Furthermore, the modification of 2-OMe on the stem of the probe avoided the unnecessary cleavage by DSN, which greatly reduce the background signal. Compared to the previous work, these improvements save us a lot of steps but possess the comparable sensitivity and selectivity. Copyright © 2018 Elsevier Inc. All rights reserved.

  11. Dual-signal amplification strategy for ultrasensitive chemiluminescence detection of PDGF-BB in capillary electrophoresis.

    Science.gov (United States)

    Cao, Jun-Tao; Wang, Hui; Ren, Shu-Wei; Chen, Yong-Hong; Liu, Yan-Ming

    2015-12-01

    Many efforts have been made toward the achievement of high sensitivity in capillary electrophoresis coupled with chemiluminescence detection (CE-CL). This work describes a novel dual-signal amplification strategy for highly specific and ultrasensitive CL detection of human platelet-derived growth factor-BB (PDGF-BB) using both aptamer and horseradish peroxidase (HRP) modified gold nanoparticles (HRP-AuNPs-aptamer) as nanoprobes in CE. Both AuNPs and HRP in the nanoprobes could amplify the CL signals in the luminol-H2 O2 CL system, owing to the excellent catalytic behavior of AuNPs and HRP in the CL system. Meanwhile, the high affinity of aptamer modified on the AuNPs allows detection with high specificity. As proof-of-concept, the proposed method was employed to quantify the concentration of PDGF-BB from 0.50 to 250 fm with a detection limit of 0.21 fm. The applicability of the assay was further demonstrated in the analysis of PDGF-BB in human serum samples with acceptable accuracy and reliability. The result of this study exhibits distinct advantages, such as high sensitivity, good specificity, simplicity, and very small sample consumption. The good performances of the proposed strategy provide a powerful avenue for ultrasensitive detection of rare proteins in biological sample, showing great promise in biochemical analysis. Copyright © 2015 John Wiley & Sons, Ltd.

  12. Performance evaluation of radiation sensors with internal signal amplification based on the BJT effect

    International Nuclear Information System (INIS)

    Bosisio, Luciano; Batignani, Giovanni; Bettarini, Stefano; Boscardin, Maurizio; Dalla Betta, Gian-Franco; Giacomini, Gabriele; Piemonte, Claudio; Verzellesi, Giovanni; Zorzi, Nicola

    2006-01-01

    Prototypes of ionizing radiation detectors with internal signal amplification based on the bipolar transistor effect have been fabricated at ITC-irst (Trento, Italy). Results from the electrical characterization and preliminary functional tests of the devices have been previously reported. Here, we present a more detailed investigation of the performance of this type of detector, with particular attention to their noise and rate limits. Measurements of the signal waveform and of the gain versus frequency dependence are performed by illuminating the devices with, respectively, pulsed or sinusoidally modulated IR light. Pulse height spectra of X-rays from an Am241 source have been taken with very simple front-end electronics (an LF351 operational amplifier) or by directly reading with an oscilloscope the voltage drop across a load resistor connected to the emitter. An equivalent noise charge (referred to input) of 380 electrons r.m.s. has been obtained with the first setup for a small device, with an active area of 0.5x0.5mm 2 and a depleted thickness of 0.6mm. The corresponding power dissipation in the BJT was 17μW. The performance limitations of the devices are discussed

  13. A sensitive electrochemical aptasensor for ATP detection based on exonuclease III-assisted signal amplification strategy.

    Science.gov (United States)

    Bao, Ting; Shu, Huawei; Wen, Wei; Zhang, Xiuhua; Wang, Shengfu

    2015-03-03

    A target-induced structure-switching electrochemical aptasensor for sensitive detection of ATP was successfully constructed which was based on exonuclease III-catalyzed target recycling for signal amplification. With the existence of ATP, methylene blue (MB) labeled hairpin DNA formed G-quadruplex with ATP, which led to conformational changes of the hairpin DNA and created catalytic cleavage sites for exonuclease III (Exo III). Then the structure-switching DNA hybridized with capture DNA which made MB close to electrode surface. Meanwhile, Exo III selectively digested aptamer from its 3'-end, thus G-quadruplex structure was destroyed and ATP was released for target recycling. The Exo III-assisted target recycling amplified electrochemical signal significantly. Fluorescence experiment was performed to confirm the structure-switching process of the hairpin DNA. In fluorescence experiment, AuNPs-aptamer conjugates were synthesized, AuNPs quenched fluorescence of MB, the target-induced structure-switching made Exo III digested aptamer, which restored fluorescence. Under optimized conditions, the proposed aptasensor showed a linear range of 0.1-20 nM with a detection limit of 34 pM. In addition, the proposed aptasensor had good stability and selectivity, offered promising choice for the detection of other small molecules. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Development and significance of a fetal electrocardiogram recorded by signal-averaged high-amplification electrocardiography.

    Science.gov (United States)

    Hayashi, Risa; Nakai, Kenji; Fukushima, Akimune; Itoh, Manabu; Sugiyama, Toru

    2009-03-01

    Although ultrasonic diagnostic imaging and fetal heart monitors have undergone great technological improvements, the development and use of fetal electrocardiograms to evaluate fetal arrhythmias and autonomic nervous activity have not been fully established. We verified the clinical significance of the novel signal-averaged vector-projected high amplification ECG (SAVP-ECG) method in fetuses from 48 gravidas at 32-41 weeks of gestation and in 34 neonates. SAVP-ECGs from fetuses and newborns were recorded using a modified XYZ-leads system. Once noise and maternal QRS waves were removed, the P, QRS, and T wave intervals were measured from the signal-averaged fetal ECGs. We also compared fetal and neonatal heart rates (HRs), coefficients of variation of heart rate variability (CV) as a parasympathetic nervous activity, and the ratio of low to high frequency (LF/HF ratio) as a sympathetic nervous activity. The rate of detection of a fetal ECG by SAVP-ECG was 72.9%, and the fetal and neonatal QRS and QTc intervals were not significantly different. The neonatal CVs and LF/HF ratios were significantly increased compared with those in the fetus. In conclusion, we have developed a fetal ECG recording method using the SAVP-ECG system, which we used to evaluate autonomic nervous system development.

  15. Efficient Sub-Bandgap Light Absorption and Signal Amplification in Silicon Photodetectors

    Science.gov (United States)

    Liu, Yu-Hsin

    This thesis focuses on two areas in silicon photodetectors, the first being enhancing the sub-bandgap light absorption of IR wavelenghts in silicon, and the second being intrinsic signal amplification in silicon photodetectors. Both of these are achieved using heavily doped p-n junction devices which create localized states that relax the k-selection rule of indirect bandgap material. The probability of transitions between impurity band and the conduction/valence band would be much more efficient than the one between band-to-band transition. The waveguide-coupled epitaxial p-n photodetector was demonstrated for 1310 nm wavelength detection. Incorporated with the Franz-Keldysh effect and the quasi-confined epitaxial layer design, an absorption coefficient around 10 cm-1 has been measured and internal quantum efficiency nearly 100% at -2.5V. The absorption coefficient is calculated from the wave function of the electron and hole in p-n diode. The heavily doped impurity wave function can be formulated as a delta function, and the quasi-confined conduction band energy states, and the wave function on each level can be obtained from the Silvaco software. The calculated theoretical absorption coefficient increases with the increasing applied bias and the doping concentration, which matches the experimental results. To solve the issues of large excess noise and high operation bias for avalanche photodiodes based on impact ionization, I presented a detector using the Cycling Excitation Process (CEP) for signal amplification. This can be realized in a heavily doped and highly compensated Si p-n junction, showing ultra high gain about 3000 at very low bias (<4 V), and possessing an intrinsic, phonon-mediated regulation process to keep the device stable without any quenching device required in today's Geiger-mode avalanche detectors. The CEP can be formulated with the rate equations in conduction bands and impurity states. The gain expression, which is a function of the

  16. Signal processing for high granularity calorimeter: amplification, filtering, memorization and digitalization

    Energy Technology Data Exchange (ETDEWEB)

    Royer, L; Manen, S; Gay, P, E-mail: royer@clermont.in2p3.f [Clermont Universite, Universite Blaise Pascal, CNRS/IN2P3, LPC, BP 10448, F-63000 Clermont-Ferrand (France)

    2010-12-15

    A very-front-end electronics dedicated to high granularity calorimeters has been designed and its performance measured. This electronics performs the amplification of the charge delivered by the detector thanks to a low-noise Charge Sensitive Amplifier. The dynamic range is improved using a bandpass filter based on a Gated Integrator. Studying its weighting function, we show that this filter is more efficient than standard CRRC shaper, thanks to the integration time which can be expand near the bunch interval time, whereas the peaking time of the CRRC shaper is limited to pile-up consideration. Moreover, the Gated Integrator performs intrinsically the analog memorization of the signal before its delayed digital conversion. The analog-to-digital conversion is performed through a 12-bit cyclic ADC specifically developed for this application. The very-front-end channel has been fabricated using a 0.35 {mu}m CMOS technology. Measurements show a global non-linearity better than 0.1%. The Equivalent Noise Charge at the input of the channel is evaluated to 1.8 fC, compare to the maximum input charge of 10 pC. The power consumption of the complete channel is limited to 6.5 mW.

  17. Amplification factor variable amplifier

    NARCIS (Netherlands)

    Akitsugu, Oshita; Nauta, Bram

    2007-01-01

    PROBLEM TO BE SOLVED: To provide an amplification factor variable amplifier capable of achieving temperature compensation of an amplification factor over a wide variable amplification factor range. ; SOLUTION: A Gilbert type amplification factor variable amplifier 11 amplifies an input signal and

  18. Amplification factor variable amplifier

    NARCIS (Netherlands)

    Akitsugu, Oshita; Nauta, Bram

    2010-01-01

    PROBLEM TO BE SOLVED: To provide an amplification factor variable amplifier capable of achieving temperature compensation of an amplification factor over a wide variable amplification factor range. ;SOLUTION: A Gilbert type amplification factor variable amplifier 11 amplifies an input signal and can

  19. Laser-enhanced ionization of mercury atoms in an inert atmosphere with avalanche amplification of the signal.

    Science.gov (United States)

    Clevenger, W L; Matveev, O I; Cabredo, S; Omenetto, N; Smith, B W; Winefordner, J D

    1997-07-01

    A new method for laser-enhanced ionization detection of mercury atoms in an inert gas atmosphere is described. The method, which is based on the avalanche amplification of the signal resulting from the ionization from a selected Rydberg level reached by a three-step laser excitation of mercury vapor in a simple quartz cell, can be applied to the determination of this element in various matrices by the use of conventional cold atomization techniques. The overall (collisional + photo) ionization efficiency is investigated at different temperatures, and the avalanche amplification effect is reported for Ar and P-10 gases at atmospheric pressure. It is shown that the amplified signal is related to the number of charges produced in the laser-irradiated volume. Under amplifier noise-limited conditions, a detection limit of ∼15 Hg atoms/laser pulse in the interaction region is estimated.

  20. Chemiluminescence immunoassay based on dual signal amplification strategy of Au/mesoporous silica and multienzyme functionalized mesoporous silica

    Energy Technology Data Exchange (ETDEWEB)

    Lin Jiehua, E-mail: linjiehua@qust.edu.cn [Key Laboratory of Eco-chemical Engineering, Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Zhao Yue; Wei Zhijing; Wang Wei [Key Laboratory of Eco-chemical Engineering, Ministry of Education, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China)

    2011-11-15

    Highlights: > The increased amount of monoclonal antibody in Au/SiO{sub 2} led to a wider linear range. > Due to the increased HRP tags in HRP-Ab{sub 2}/SiO{sub 2}, signal amplification achieved. > A simple dual amplification immunoassay achieved with flow injection analysis. - Abstract: A chemiluminescent dual signal amplification strategy for the determination of {alpha}-fetoprotein (AFP) was proposed based on a sandwich immunoassay format. Monoclonal antibody of AFP immobilized on the gold nanoparticles doped mesoporous SiO{sub 2} (Au/SiO{sub 2}) were prepared and used as a primary antibody. Horseradish peroxidase (HRP) and HRP-labeled secondary antibody (Ab{sub 2}) co-immobilized into the mesoporous SiO{sub 2} nanoparticles (HRP-Ab{sub 2}/SiO{sub 2}) were used as the labeled immunological probe. Due to the high ratio surface areas and pore volumes of the mesoporous SiO{sub 2}, not only the amount of AFP monoclonal antibody but also the amount of the modified HRP and Ab{sub 2} in HRP-Ab{sub 2}/SiO{sub 2} were largely increased. Thus the chemiluminescent signal was amplified by using the system of luminol and H{sub 2}O{sub 2} under the catalysis of HRP. Under the optimal conditions, two linear ranges for AFP were obtained from 0.01 to 0.5 ng mL{sup -1} and 0.5 to 100 ng mL{sup -1} with a detection limit of 0.005 ng mL{sup -1} (3{sigma}). The fabricated signal amplification strategy showed an excellent promise for sensitive detection of AFP and other tumor markers.

  1. Amplification of ABA biosynthesis and signaling through a positive feedback mechanism in seeds.

    Science.gov (United States)

    Nonogaki, Mariko; Sall, Khadidiatou; Nambara, Eiji; Nonogaki, Hiroyuki

    2014-05-01

    Abscisic acid is an essential hormone for seed dormancy. Our previous study using the plant gene switch system, a chemically induced gene expression system, demonstrated that induction of 9-cis-epoxycarotenoid dioxygenase (NCED), a rate-limiting ABA biosynthesis gene, was sufficient to suppress germination in imbibed Arabidopsis seeds. Here, we report development of an efficient experimental system that causes amplification of NCED expression during seed maturation. The system was created with a Triticum aestivum promoter containing ABA responsive elements (ABREs) and a Sorghum bicolor NCED to cause ABA-stimulated ABA biosynthesis and signaling, through a positive feedback mechanism. The chimeric gene pABRE:NCED enhanced NCED and ABF (ABRE-binding factor) expression in Arabidopsis Columbia-0 seeds, which caused 9- to 73-fold increases in ABA levels. The pABRE:NCED seeds exhibited unusually deep dormancy which lasted for more than 3 months. Interestingly, the amplified ABA pathways also caused enhanced expression of Arabidopsis NCED5, revealing the presence of positive feedback in the native system. These results demonstrated the robustness of positive feedback mechanisms and the significance of NCED expression, or single metabolic change, during seed maturation. The pABRE:NCED system provides an excellent experimental system producing dormant and non-dormant seeds of the same maternal origin, which differ only in zygotic ABA. The pABRE:NCED seeds contain a GFP marker which enables seed sorting between transgenic and null segregants and are ideal for comparative analysis. In addition to its utility in basic research, the system can also be applied to prevention of pre-harvest sprouting during crop production, and therefore contributes to translational biology. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

  2. Iron accumulation in deep cortical layers accounts for MRI signal abnormalities in ALS: correlating 7 tesla MRI and pathology.

    Directory of Open Access Journals (Sweden)

    Justin Y Kwan

    Full Text Available Amyotrophic lateral sclerosis (ALS is a progressive neurodegenerative disorder characterized by cortical and spinal motor neuron dysfunction. Routine magnetic resonance imaging (MRI studies have previously shown hypointense signal in the motor cortex on T(2-weighted images in some ALS patients, however, the cause of this finding is unknown. To investigate the utility of this MR signal change as a marker of cortical motor neuron degeneration, signal abnormalities on 3T and 7T MR images of the brain were compared, and pathology was obtained in two ALS patients to determine the origin of the motor cortex hypointensity. Nineteen patients with clinically probable or definite ALS by El Escorial criteria and 19 healthy controls underwent 3T MRI. A 7T MRI scan was carried out on five ALS patients who had motor cortex hypointensity on the 3T FLAIR sequence and on three healthy controls. Postmortem 7T MRI of the brain was performed in one ALS patient and histological studies of the brains and spinal cords were obtained post-mortem in two patients. The motor cortex hypointensity on 3T FLAIR images was present in greater frequency in ALS patients. Increased hypointensity correlated with greater severity of upper motor neuron impairment. Analysis of 7T T(2(*-weighted gradient echo imaging localized the signal alteration to the deeper layers of the motor cortex in both ALS patients. Pathological studies showed increased iron accumulation in microglial cells in areas corresponding to the location of the signal changes on the 3T and 7T MRI of the motor cortex. These findings indicate that the motor cortex hypointensity on 3T MRI FLAIR images in ALS is due to increased iron accumulation by microglia.

  3. Analysis of MRI signal changes in the adjacent pedicle of adolescent patients with fresh lumbar spondylolysis.

    Science.gov (United States)

    Goda, Yuichiro; Sakai, Toshinori; Sakamaki, Tadanori; Takata, Yoichiro; Higashino, Kosaku; Sairyo, Koichi

    2014-09-01

    The purpose of this study is to investigate a discrepancy between MRI and computed tomography (CT) findings in the spinal level distribution of spondylolysis. Recent advances in MRI have led to the early diagnosis of spondylolysis. Therefore, bony healing can be expected before the condition has a chance to worsen. In this study, we used MRI to examine the changes in spinal level signals in the pedicles adjacent to the pars interarticularis in adolescents with fresh lumbar spondylolysis. We then compared spinal level distribution of spondylolysis with that of previous results obtained by multidetector CT. The study included 98 adolescent patients (31 women and 67 men; mean age, 13.6 years; age range, 9-18 years) with fresh lumbar spondylolysis who showed MRI signal changes in the adjacent pedicle. An MRI signal change was defined as a high signal change on fat-suppressed imaging. MRI signal changes were detected in 150 adjacent pedicles of 101 vertebrae. Of these vertebrae, MRI signal changes in only 67 (66.3%) corresponded to L5, while changes in 34 (33.7%) corresponded to L3 or L4. In our follow-up study, the bone-healing rate with no vertebral defect was 100% at L3, 97.1% at L4, and 84.4% at L5. In addition, 11 of 34 (32.4%) vertebrae with signal changes at L3 or L4 occurred with L5 terminal-stage spondylolysis (no MRI signal change). MRI revealed a higher prevalence of L3 or L4 spondylolysis than observed with CT.

  4. Signal amplification in electrochemical detection of buckwheat allergenic protein using field effect transistor biosensor by introduction of anionic surfactant

    Directory of Open Access Journals (Sweden)

    Sho Hideshima

    2016-03-01

    Full Text Available Food allergens, especially buckwheat proteins, sometimes induce anaphylactic shock in patients after ingestion. Development of a simple and rapid screening method based on a field effect transistor (FET biosensor for food allergens in food facilities or products is in demand. In this study, we achieved the FET detection of a buckwheat allergenic protein (BWp16, which is not charged enough to be electrically detected by FET biosensors, by introducing additional negative charges from anionic surfactants to the target proteins. A change in the FET characteristics reflecting surface potential caused by the adsorption of target charged proteins was observed when the target sample was coupled with the anionic surfactant (sodium dodecyl sulfate; SDS, while no significant response was detected without any surfactant treatment. It was suggested that the surfactant conjugated with the protein could be useful for the charge amplification of the target proteins. The surface plasmon resonance analysis revealed that the SDS-coupled proteins were successfully captured by the receptors immobilized on the sensing surface. Additionally, we obtained the FET responses at various concentrations of BWp16 ranging from 1 ng/mL to 10 μg/mL. These results suggest that a signal amplification method for FET biosensing is useful for allergen detection in the food industry. Keywords: Field effect transistor biosensor, Food allergen, Signal amplification, Ionic surfactant, Intrinsic charge

  5. Signal-off Electrochemiluminescence Biosensor Based on Phi29 DNA Polymerase Mediated Strand Displacement Amplification for MicroRNA Detection.

    Science.gov (United States)

    Chen, Anyi; Gui, Guo-Feng; Zhuo, Ying; Chai, Ya-Qin; Xiang, Yun; Yuan, Ruo

    2015-06-16

    A target induced cycling strand displacement amplification (SDA) mediated by phi29 DNA polymerase (phi29) was first investigated and applied in a signal-off electrochemiluminescence (ECL) biosensor for microRNA (miRNA) detection. Herein, the target miRNA triggered the phi29-mediated SDA which could produce amounts of single-stranded DNA (assistant probe) with accurate and comprehensive nucleotide sequence. Then, the assistant probe hybridized with the capture probe and the ferrocene-labeled probe (Fc-probe) to form a ternary "Y" structure for ECL signal quenching by ferrocene. Therefore, the ECL intensity would decrease with increasing concentration of the target miRNA, and the sensitivity of biosensor would be promoted on account of the efficient signal amplification of the target induced cycling reaction. Besides, a self-enhanced Ru(II) ECL system was designed to obtain a stable and strong initial signal to further improve the sensitivity. The ECL assay for miRNA-21 detection is developed with excellent sensitivity of a concentration variation from 10 aM to 1.0 pM and limit of detection down to 3.3 aM.

  6. MRI of the sacroiliac joints in spondyloarthritis: the added value of intra-articular signal changes for a 'positive MRI'.

    Science.gov (United States)

    Laloo, Frederiek; Herregods, N; Jaremko, J L; Verstraete, K; Jans, L

    2018-05-01

    To determine if intra-articular signal changes at the sacroiliac joint space on MRI have added diagnostic value for spondyloarthritis, when compared to bone marrow edema (BME). A retrospective study was performed on the MRIs of sacroiliac joints of 363 patients, aged 16-45 years, clinically suspected of sacroiliitis. BME of the sacroiliac joints was correlated to intra-articular sacroiliac joint MR signal changes: high T1 signal, fluid signal, ankylosis and vacuum phenomenon (VP). These MRI findings were correlated with final clinical diagnosis. Sensitivity (SN), specificity (SP), likelihood ratios (LR), predictive values and post-test probabilities were calculated. BME had SN of 68.9%, SP of 74.0% and LR+ of 2.6 for diagnosis of spondyloarthritis. BME in absence of intra-articular signal changes had a lower SN and LR+ for spondyloarthritis (SN = 20.5%, LR+ 1.4). Concomitant BME and high T1 signal (SP = 97.2%, LR + = 10.5), BME and fluid signal (SP = 98.6%, LR + = 10.3) or BME and ankylosis (SP = 100%) had higher SP and LR+ for spondyloarthritis. Concomitant BME and VP had low LR+ for spondyloarthritis (SP = 91%, LR + =0.9). When BME was absent, intra-articular signal changes were less prevalent, but remained highly specific for spondyloarthritis. Our results suggest that both periarticular and intra-articular MR signal of the sacroiliac joint should be examined to determine whether an MRI is 'positive' or 'not positive' for sacroiliitis associated with spondyloarthritis.

  7. Muscle MRI STIR signal intensity and atrophy are correlated to focal lower limb neuropathy severity.

    Science.gov (United States)

    Deroide, N; Bousson, V; Mambre, L; Vicaut, E; Laredo, J D; Kubis, Nathalie

    2015-03-01

    The objective is to determine if muscle MRI is useful for assessing neuropathy severity. Clinical, MRI and electromyography (EMG) examinations were performed in 17 patients with focal lower limb neuropathies. MRI Short Tau Inversion Recovery (STIR) signal intensity, amyotrophy, and muscle fatty infiltration measured after T1-weighted image acquisition, EMG spontaneous activity (SA), and maximal voluntary contraction (MVC) were graded using semiquantitative scores and quantitative scores for STIR signal intensity and were correlated to the Medical Research Council (MRC) score for testing muscle strength. Within this population, subgroups were selected according to severity (mild versus severe), duration (subacute versus chronic), and topography (distal versus proximal) of the neuropathy. EMG SA and MVC MRI amyotrophy and quantitative scoring of muscle STIR intensity were correlated with the MRC score. Moreover, MRI amyotrophy was significantly increased in severe, chronic, and proximal neuropathies along with fatty infiltration in chronic lesions. Muscle MRI atrophy and quantitative evaluation of signal intensity were correlated to MRC score in our study. Semiquantitative evaluation of muscle STIR signal was sensitive enough for detection of topography of the nerve lesion but was not suitable to assess severity. Muscle MRI could support EMG in chronic and proximal neuropathy, which showed poor sensitivity in these patients.

  8. Muscle MRI STIR signal intensity and atrophy are correlated to focal lower limb neuropathy severity

    Energy Technology Data Exchange (ETDEWEB)

    Deroide, N.; Mambre, L.; Kubis, Nathalie [Service de Physiologie Clinique-Explorations Fonctionnelles, AP-HP, Hopital Lariboisiere, Paris (France); Universite Paris Diderot, Sorbonne Paris Cite France, Paris (France); Bousson, V.; Laredo, J.D. [Universite Paris Diderot, Sorbonne Paris Cite France, Paris (France); Radiologie Osteo-articulaire, AP-HP, Hopital Lariboisiere, Paris (France); Vicaut, E. [Universite Paris Diderot, Sorbonne Paris Cite France, Paris (France); URC, AP-HP, Hopital Lariboisiere, Paris (France)

    2014-09-26

    The objective is to determine if muscle MRI is useful for assessing neuropathy severity. Clinical, MRI and electromyography (EMG) examinations were performed in 17 patients with focal lower limb neuropathies. MRI Short Tau Inversion Recovery (STIR) signal intensity, amyotrophy, and muscle fatty infiltration measured after T1-weighted image acquisition, EMG spontaneous activity (SA), and maximal voluntary contraction (MVC) were graded using semiquantitative scores and quantitative scores for STIR signal intensity and were correlated to the Medical Research Council (MRC) score for testing muscle strength. Within this population, subgroups were selected according to severity (mild versus severe), duration (subacute versus chronic), and topography (distal versus proximal) of the neuropathy. EMG SA and MVC MRI amyotrophy and quantitative scoring of muscle STIR intensity were correlated with the MRC score. Moreover, MRI amyotrophy was significantly increased in severe, chronic, and proximal neuropathies along with fatty infiltration in chronic lesions. Muscle MRI atrophy and quantitative evaluation of signal intensity were correlated to MRC score in our study. Semiquantitative evaluation of muscle STIR signal was sensitive enough for detection of topography of the nerve lesion but was not suitable to assess severity. Muscle MRI could support EMG in chronic and proximal neuropathy, which showed poor sensitivity in these patients. (orig.)

  9. Signal-to-Noise Enhancement of a Nanospring Redox-Based Sensor by Lock-in Amplification

    Directory of Open Access Journals (Sweden)

    Pavel V. Bakharev

    2015-06-01

    Full Text Available A significant improvement of the response characteristics of a redox chemical gas sensor (chemiresistor constructed with a single ZnO coated silica nanospring has been achieved with the technique of lock-in signal amplification. The comparison of DC and analog lock-in amplifier (LIA AC measurements of the electrical sensor response to toluene vapor, at the ppm level, has been conducted. When operated in the DC detection mode, the sensor exhibits a relatively high sensitivity to the analyte vapor, as well as a low detection limit at the 10 ppm level. However, at 10 ppm the signal-to-noise ratio is 5 dB, which is less than desirable. When operated in the analog LIA mode, the signal-to-noise ratio at 10 ppm increases by 30 dB and extends the detection limit to the ppb range.

  10. Parametric amplification and phase preserving amplitude regeneration of a 640 Gbit/s RZ-DPSK signal

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Galili, Michael; Mulvad, Hans Christian Hansen

    2013-01-01

    We report the first experimental demonstration of parametric amplification and all-optical phase-preserving amplitude regeneration for a 640 Gbit/s return-to-zero (RZ) differential phase-shift keying (DPSK) optical time division multiplexed (OTDM) signal. In the designed gain-flattened single......-pump fiber optical parametric amplifier (FOPA), 620 fs short optical pulses are successfully amplified with 15 dB gain with error-free performance and less than 1 dB power penalty. Phase-preserving amplitude regeneration based on gain saturation in the FOPA is carried out for optical signals with degraded...... optical signal-to-noise ratio. An improvement of 2.2 dB in receiver sensitivity at a bit-error-ratio of 10−9 has been successfully achieved after regeneration, together with 13.3 dB net gain....

  11. Continuous diffusion signal, EAP and ODF estimation via Compressive Sensing in diffusion MRI.

    Science.gov (United States)

    Merlet, Sylvain L; Deriche, Rachid

    2013-07-01

    In this paper, we exploit the ability of Compressed Sensing (CS) to recover the whole 3D Diffusion MRI (dMRI) signal from a limited number of samples while efficiently recovering important diffusion features such as the Ensemble Average Propagator (EAP) and the Orientation Distribution Function (ODF). Some attempts to use CS in estimating diffusion signals have been done recently. However, this was mainly an experimental insight of CS capabilities in dMRI and the CS theory has not been fully exploited. In this work, we also propose to study the impact of the sparsity, the incoherence and the RIP property on the reconstruction of diffusion signals. We show that an efficient use of the CS theory enables to drastically reduce the number of measurements commonly used in dMRI acquisitions. Only 20-30 measurements, optimally spread on several b-value shells, are shown to be necessary, which is less than previous attempts to recover the diffusion signal using CS. This opens an attractive perspective to measure the diffusion signals in white matter within a reduced acquisition time and shows that CS holds great promise and opens new and exciting perspectives in diffusion MRI (dMRI). Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Electrophysiological correlates of the BOLD signal for EEG-informed fMRI

    Science.gov (United States)

    Murta, Teresa; Leite, Marco; Carmichael, David W; Figueiredo, Patrícia; Lemieux, Louis

    2015-01-01

    Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are important tools in cognitive and clinical neuroscience. Combined EEG–fMRI has been shown to help to characterise brain networks involved in epileptic activity, as well as in different sensory, motor and cognitive functions. A good understanding of the electrophysiological correlates of the blood oxygen level-dependent (BOLD) signal is necessary to interpret fMRI maps, particularly when obtained in combination with EEG. We review the current understanding of electrophysiological–haemodynamic correlates, during different types of brain activity. We start by describing the basic mechanisms underlying EEG and BOLD signals and proceed by reviewing EEG-informed fMRI studies using fMRI to map specific EEG phenomena over the entire brain (EEG–fMRI mapping), or exploring a range of EEG-derived quantities to determine which best explain colocalised BOLD fluctuations (local EEG–fMRI coupling). While reviewing studies of different forms of brain activity (epileptic and nonepileptic spontaneous activity; cognitive, sensory and motor functions), a significant attention is given to epilepsy because the investigation of its haemodynamic correlates is the most common application of EEG-informed fMRI. Our review is focused on EEG-informed fMRI, an asymmetric approach of data integration. We give special attention to the invasiveness of electrophysiological measurements and the simultaneity of multimodal acquisitions because these methodological aspects determine the nature of the conclusions that can be drawn from EEG-informed fMRI studies. We emphasise the advantages of, and need for, simultaneous intracranial EEG–fMRI studies in humans, which recently became available and hold great potential to improve our understanding of the electrophysiological correlates of BOLD fluctuations. PMID:25277370

  13. Close relationship between fMRI signals and transient heart rate changes accompanying K-complex. Simultaneous EEG/fMRI study

    International Nuclear Information System (INIS)

    Kan, Shigeyuki; Koike, Takahiko; Miyauchi, Satoru; Misaki, Masaya

    2009-01-01

    Combining functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) allows the investigation of spontaneous activities in the human brain. Recently, by using this technique, increases in fMRI signal accompanying transient EEG activities such as sleep spindles and slow waves were reported. Although these fMRI signal increases appear to arise as a result of the neural activities being reflected in the EEG, when the influence of physiological activities upon fMRI signals are taken into consideration, it is highly controversial that fMRI signal increases accompanying transient EEG activities reflect actual neural activities. In the present study, we conducted simultaneous fMRI and polysomnograph recording of 18 normal adults, to study the effect of transient heart rate changes after a K-complex on fMRI signals. Significant fMRI signal increase was observed in the cerebellum, the ventral thalamus, the dorsal part of the brainstem, the periventricular white matter and the ventricle (quadrigeminal cistern). On the other hand, significant fMRI signal decrease was observed only in the right insula. Moreover, intensities of fMRI signal increase that was accompanied by a K-complex correlated positively with the magnitude of heart rate changes after a K-complex. Previous studies have reported that K-complex is closely related with sympathetic nervous activity and that the attributes of perfusion regulation in the brain differ during wakefulness and sleep. By taking these findings into consideration, our present results indicate that a close relationship exists between a K-complex and the changes in cardio- and neurovascular regulations that are mediated by the autonomic nervous system during sleep; further, these results indicate that transient heart rate changes after a K-complex can affect the fMRI signal generated in certain brain regions. (author)

  14. Exploring fMRI Data for Periodic Signal Components

    DEFF Research Database (Denmark)

    Hansen, Lars Kai; Nielsen, Finn Årup; Larsen, Jan

    2002-01-01

    We use a Bayesian framework to detect periodic components in fMRI data. The resulting detector is sensitive to periodic components with a flexible number of harmonics and with arbitrary amplitude and phases of the harmonics. It is possible to detect the correct number of harmonics in periodic sig...

  15. MRI signal intensity as a maker of impairment in incomplete cervical spinal cord injuries

    International Nuclear Information System (INIS)

    Chiba, Hidefumi; Aoki, Haruhito; Hamabe, Masaki; Sasao, Yutaka; Miura, Takehiko

    1998-01-01

    Incomplete cervical spinal cord injuries such as central cord syndrome may result in prolonged spasticity of the limbs, especially disabilities of the upper extremities, even if the patient is able to walk. In this study, relationship between cord impairment and clinical outcome was investigated using MRI. Results showed that small foci of low signal intensity in T 1 -weighted imaging combined with foci of high signal intensity in T 2 -weighted imaging in follow-up MRI are closely related to the severity of sequelae. Small foci of low signal intensity in T 1 -weighted imaging are considered in the literature to indicate myelomalacia or cyst formation with gliosis. (author)

  16. Towards the use of protein A-tagged gold nanoparticles for signal amplification of electrochemical immunosensors in virus detection

    International Nuclear Information System (INIS)

    Huy Tran, Quang; Thuy Nguyen, Thanh; Chung Pham, Van; Hong Hanh Nguyen, Thi; Tuan Mai, Anh

    2012-01-01

    In this paper we represent a study on the potential use of protein A-tagged gold nanoparticles applied for signal amplification of electrochemical immunosensors. Gold nanoparticles (GNPs) were synthesized by the chemical reduction of tetrachloroauric (III) acid trihydrate using sodium ascorbate, and then tagged with protein A (PrA) via ultracentrifugation. UV-Vis spectroscopy and transmission electron microscopy were used to verify the characteristics of formed GNPs/PrA complex. The analyzed results indicate that GNPs were found spherically, homogeneously, and with an average diameter of about 10 nm. Immunoelectron microscopy was then used to investigate the bioactivity of the GNPs/PrA complex in solution by the effective binding of GNPs to viral particles. Scanning electron and fluorescence microscopies were also used to investigate the distribution and the bioactivity of the GNPs/PrA complex on the surface of the interdigitated sensor. Consequently, this study provided some assumptions of the potential application of protein A-tagged gold nanoparticles for signal amplification of electrochemical immunosensors in virus detection from clinical samples

  17. [Oligonucleotide derivatives in the nucleic acid hybridization analysis. II. Isothermal signal amplification in process of DNA analysis by minisequencing].

    Science.gov (United States)

    Dmitrienko, E V; Khomiakova, E A; Pyshnaia; Bragin, A G; Vedernikov, V E; Pyshnyĭ, D V

    2010-01-01

    The isothermal amplification of reporter signal via limited probe extension (minisequencing) upon hybridization of nucleic acids has been studied. The intensity of reporter signal has been shown to increase due to enzymatic labeling of multiple probes upon consecutive hybridization with one DNA template both in homophase and heterophase assays using various kinds of detection signal: radioisotope label, fluorescent label, and enzyme-linked assay. The kinetic scheme of the process has been proposed and kinetic parameters for each step have been determined. The signal intensity has been shown to correlate with physicochemical characteristics of both complexes: probe/DNA and product/DNA. The maximum intensity has been observed at minimal difference between the thermodynamic stability of these complexes, provided the reaction temperature has been adjusted near their melting temperature values; rising or lowering the reaction temperature reduces the amount of reporting product. The signal intensity has been shown to decrease significantly upon hybridization with the DNA template containing single-nucleotide mismatches. Limited probe extension assay is useful not only for detection of DNA template but also for its quantitative characterization.

  18. Broadband Electrophysiological Dynamics Contribute to Global Resting-State fMRI Signal.

    Science.gov (United States)

    Wen, Haiguang; Liu, Zhongming

    2016-06-01

    Spontaneous activity observed with resting-state fMRI is used widely to uncover the brain's intrinsic functional networks in health and disease. Although many networks appear modular and specific, global and nonspecific fMRI fluctuations also exist and both pose a challenge and present an opportunity for characterizing and understanding brain networks. Here, we used a multimodal approach to investigate the neural correlates to the global fMRI signal in the resting state. Like fMRI, resting-state power fluctuations of broadband and arrhythmic, or scale-free, macaque electrocorticography and human magnetoencephalography activity were correlated globally. The power fluctuations of scale-free human electroencephalography (EEG) were coupled with the global component of simultaneously acquired resting-state fMRI, with the global hemodynamic change lagging the broadband spectral change of EEG by ∼5 s. The levels of global and nonspecific fluctuation and synchronization in scale-free population activity also varied across and depended on arousal states. Together, these results suggest that the neural origin of global resting-state fMRI activity is the broadband power fluctuation in scale-free population activity observable with macroscopic electrical or magnetic recordings. Moreover, the global fluctuation in neurophysiological and hemodynamic activity is likely modulated through diffuse neuromodulation pathways that govern arousal states and vigilance levels. This study provides new insights into the neural origin of resting-state fMRI. Results demonstrate that the broadband power fluctuation of scale-free electrophysiology is globally synchronized and directly coupled with the global component of spontaneous fMRI signals, in contrast to modularly synchronized fluctuations in oscillatory neural activity. These findings lead to a new hypothesis that scale-free and oscillatory neural processes account for global and modular patterns of functional connectivity observed

  19. Imaging resolution signal-to-noise ratio in transverse phase amplification from classical information theory

    International Nuclear Information System (INIS)

    French, Doug; Huang Zun; Pao, H.-Y.; Jovanovic, Igor

    2009-01-01

    A quantum phase amplifier operated in the spatial domain can improve the signal-to-noise ratio in imaging beyond the classical limit. The scaling of the signal-to-noise ratio with the gain of the quantum phase amplifier is derived from classical information theory

  20. Visual detection and microplate assay for Staphylococcus aureus based on aptamer recognition coupled to tyramine signal amplification

    International Nuclear Information System (INIS)

    Yuan, Jinglei; Li, Can; Ma, Xiaoyuan; Xia, Yu; Chen, Jie; Wang, Zhouping; Yu, Ye

    2014-01-01

    We have developed a specific method for the visual detection of Staphylococcus aureus based on aptamer recognition coupled to tyramine signal amplification technology. A biotinylated aptamer specific for S. aureus was immobilized on the surface of the wells of a microplate via biotin-avidin binding. Then, the target bacteria (S. aureus), the biotinylated-aptamer-streptavidin-HRP conjugates, biotinylated tyramine, hydrogen peroxide and streptavidin-HRP were successively placed in the wells of the microplate. After adding TMB reagent and stop solution, the intensity of the yellow reaction product can be visually inspected or measured with a plate reader. Under optimized conditions, there is a linear relationship between absorbance at 450 nm and the concentration of S. aureus in the 10 to 107 cfu mL −1 concentration range (with an R 2 of 0.9976). The limit of detection is 8 cfu mL −1 . (author)

  1. Can the MRI signal of aggressive fibromatosis be used to predict its behavior?

    International Nuclear Information System (INIS)

    Castellazzi, G.; Vanel, D.; Le Cesne, A.; Le Pechoux, C.; Caillet, H.; Perona, F.; Bonvalot, S.

    2009-01-01

    Purpose: Aggressive fibromatosis is an invasive non-metastasizing soft-tissue tumor. Until recently, the standard treatment combined surgery and radiation therapy, but new studies reported that conservative strategies with or without medical treatment could be the best management. The aim of this study was to analyze and correlate the size and MR imaging signal features of aggressive fibromatosis with its behavior in order to choose the best treatment. Materials and methods: Between March 1985 and December 2005, 27 patients with at least 2 consecutive MRI examinations and no surgery or radiation therapy in between were recorded. There were 9 men and 18 women, and median age was 31 years. They underwent 107 MRI examinations of 47 lesions, 29 of which were medically treated, while the remaining 18 did not receive any drug administration. The size and signal changes of each lesion were studied over time on T2- and/or T1-weighted sequences after injection of contrast medium. RECIST criteria were used for size: only a 30% decrease or a 20% increase in the size of the main dimension was considered significant. We classified the appearance of the signal into six categories in order of increasing intensity and then we established the related variations over time. Results: The size of 79% of the lesions in the treated group and 82% in the untreated group remained stable. The initial signal of stable lesions or those exhibiting an increase in size was most frequently high. There was a high rate of signal stability over time, whatever the initial signal and size changes. Changes in size were not correlated with the initial MR signal. A decrease in size associated with a decreased signal was observed in three cases exclusively in the treated group. Conclusion: Fibromatoses are a group of soft-tissue tumors with variable characteristics on MRI, but it is not possible to predict their behavior based on the MRI signal

  2. Detection of lead(II) ions with a DNAzyme and isothermal strand displacement signal amplification.

    Science.gov (United States)

    Li, Wenying; Yang, Yue; Chen, Jian; Zhang, Qingfeng; Wang, Yan; Wang, Fangyuan; Yu, Cong

    2014-03-15

    A DNAzyme based method for the sensitive and selective quantification of lead(II) ions has been developed. A DNAzyme that requires Pb(2+) for activation was selected. An RNA containing DNA substrate was cleaved by the DNAzyme in the presence of Pb(2+). The 2',3'-cyclic phosphate of the cleaved 5'-part of the substrate was efficiently removed by Exonuclease III. The remaining part of the single stranded DNA (9 or 13 base long) was subsequently used as the primer for the strand displacement amplification reaction (SDAR). The method is highly sensitive, 200 pM lead(II) could be easily detected. A number of interference ions were tested, and the sensor showed good selectivity. Underground water samples were also tested, which demonstrated the feasibility of the current approach for real sample applications. It is feasible that our method could be used for DNAzyme or aptazyme based new sensing method developments for the quantification of other target analytes with high sensitivity and selectivity. © 2013 Elsevier B.V. All rights reserved.

  3. Electrochemical immunosensor with nanocellulose-Au composite assisted multiple signal amplification for detection of avian leukosis virus subgroup J.

    Science.gov (United States)

    Liu, Chao; Dong, Jing; Waterhouse, Geoffrey I N; Cheng, Ziqiang; Ai, Shiyun

    2018-03-15

    A sensitive sandwich-type electrochemical immunosensor was developed for the detection of avian leukosis virus subgroup J (ALV-J), which benefitted from multiple signal amplification involving graphene-perylene-3,4,9,10-tetracarboxylic acid nanocomposites (GR-PTCA), nanocellulose-Au NP composites (NC-Au) and the alkaline phosphatase (ALP) catalytic reaction. GR-PTCA nanocomposites on glassy carbon electrodes served as the immunosensor platform. Due to their excellent electrical conductivity and abundant polycarboxylic sites, the GR-PTCA nanocomposites allowed fast electron transfer and good immobilization of primary antibodies, thereby affording a strong immunosensor signal in the presence of ALV-J. The detected signal could be further amplified by the introduction of NC-Au composites as a carrier of secondary antibodies (Ab 2 ) and by harnessing the catalytic properties of Au and ALP. Under optimized testing conditions, the electrochemical immunosensor displayed excellent analytical performance for the detection of ALV-J, showing a linear current response from 10 2.08 to 10 4.0 TCID 50 /mL (TCID 50 : 50% tissue culture infective dose) with a low detection limit of 10 1.98 TCID 50 /mL (S/N = 3). In addition to high sensitivity, the immunosensor showed very good selectivity, reproducibility and operational stability, demonstrating potential application for the quantitative detection of ALV-J in clinical diagnosis. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Branched-DNA signal amplification combined with paper chromatography hybridization assay and used in hepatitis B virus DNA detection

    International Nuclear Information System (INIS)

    Fu, F.Z.; Liu, L.X.; Wang, W.Q.; Sun, S. H.; Liu, L.B.

    2002-01-01

    Nucleic acids detection method is vital to the clinical pathogen diagnosis. The established method can be classified into target direct amplification and signal amplification format according to the target DNA or RNA being directly amplified or not. Those methods have advantages and disadvantages respectively in the clinical application. In the United States of American, branched-DNA as a strong signal amplifier is broadly used in the quantification of the nucleic acids. To gain satisfied sensitivity, some expensive label molecular and instruments should be adopted. Personnel should be special trained to perform. Hence, those can't be widely carried out in the Third World. To avoid those disadvantages, we used the branched-DNA amplifier in the paper chromatography hybridization assay. Methods: Branched DNA signal amplifier and series of probes complementary to the nucleic acid sequence of hepatitis B virus (HBV) have been synthesized. HBV-DNA or it's capture probe were immobilized on the high flow nitrocellulose strip. Having loaded at one end of the strip in turn, probes or HBV-DNA in the hybridization solution migrate to the opposite end of the strip by capillary forces and hybridizes to the immobilized DNA. The branched-DNA signal amplifier and probe labeled with biotin or 32P were then loaded. Through streptavidin-alkaline phosphatase (SA-AP) conjugate and NBT/BCIP ( the specific chromogenic substrate of AP) or autoradiography, the result can be visualized by color reaction or image production on the X-ray film. Results: The sensitivity of this HBV-DNA detection method used probe labeled with biotin and 32P are 1ng and 10pg. The method using the probe labeled with biotin is simple and rapid (2h) without depending on special instruments, it also avoids the pollution of EtBr which can lead to tumor. And the method using the probe labeled with 32P is simple and sensitive, with the exception of long time autoradiography and the inconvenient isotopic disposal

  5. PULSE REFERENCED CONTROL METHOD FOR ENHANCED POWER AMPLIFICATION OF A PULSE MODULATED SIGNAL

    DEFF Research Database (Denmark)

    1998-01-01

    , by introducing continuous delays on the individual pulse edges on the basis of error information provided by an error processing block. One preferred embodiment of the invention comprises: a Correction Unit with means to control the delays of the individual pulse edges as a function of a control input signal $i...

  6. Ultrasensitive electrochemical immunoassay of staphylococcal enterotoxin B in food using enzyme-nanosilica-doped carbon nanotubes for signal amplification.

    Science.gov (United States)

    Tang, Dianping; Tang, Juan; Su, Biling; Chen, Guonan

    2010-10-27

    A new sandwich-type electrochemical immunoassay for ultrasensitive detection of staphylococcal enterotoxin B (SEB) in food was developed using horseradish peroxidase-nanosilica-doped multiwalled carbon nanotubes (HRPSiCNTs) for signal amplification. Rabbit polyclonal anti-SEB antibodies immobilized on the screen-printed carbon electrode (SPCE) and covalently bound to the HRPSiCNTs were used as capture antibodies and detection antibodies, respectively. In the presence of SEB analyte, the sandwich-type immunocomplex could be formed between the immobilized anti-SEB on the SPCE and anti-SEB-labeled HRPSiCNTs, and the carried HRP could catalyze the electrochemical reduction of H2O2 with the help of thionine. The high content of HRP in the HRPSiCNTs could greatly amplify the electrochemical signal. Under optimal conditions, the reduction current increased with the increase of SEB in the sample, and exhibited a dynamic range of 0.05-15 ng/mL with a low detection limit (LOD) of 10 pg/mL SEB (at 3σ). Intra- and interassay coefficients of variation were below 10%. In addition, the assay was evaluated with SEB spiked samples including watermelon juice, soymilk, apple juice, and pork food, receiving excellent correlation with results from commercially available enzyme-linked immunosorbent assay (ELISA).

  7. Persistence and dynamics of DNA damage signal amplification determined by microcolony formation and live-cell imaging

    International Nuclear Information System (INIS)

    Oka, Yasuyoshi; Yamauchi, Motohiro; Suzuki, Masatoshi; Yamashita, Shunichi; Suzuki, Keiji

    2011-01-01

    Cell cycle checkpoints are essential cellular process protecting the integrity of the genome from DNA damaging agents. In the present study, we developed a microcolony assay, in which normal human diploid fibroblast-like cells exposed to ionizing radiation, were plated onto coverslips at very low density (3 cells/cm 2 ). Cells were grown for up to 3 days, and phosphorylated ataxia-telangiectasia mutated (ATM) at Ser1981 and 53BP1 foci were analyzed as the markers for an amplified DNA damage signal. We observed a dose-dependent increase in the fraction of non-dividing cells, whose increase was compromised by knocking down p53 expression. While large persistent foci were predominantly formed in non-dividing cells, we observed some growing colonies that contained cells with large foci. As each microcolony was derived from a single cell, it appeared that some cells could proliferate with large foci. A live-imaging analysis using hTERT-immortalized normal human diploid cells transfected with the EGFP-tagged 53BP1 gene revealed that the formation of persistent large foci was highly dynamic. Delayed appearance and disappearance of large foci were frequently observed in exposed cells visualized 12-72 hours after X-irradiation. Thus, our results indicate that amplified DNA damage signal could be ignored, which may be explained in part by the dynamic nature of the amplification process. (author)

  8. Collective Signal Processing in Cluster Chemotaxis: Roles of Adaptation, Amplification, and Co-attraction in Collective Guidance

    Science.gov (United States)

    Camley, Brian A.; Zimmermann, Juliane; Levine, Herbert; Rappel, Wouter-Jan

    2016-01-01

    Single eukaryotic cells commonly sense and follow chemical gradients, performing chemotaxis. Recent experiments and theories, however, show that even when single cells do not chemotax, clusters of cells may, if their interactions are regulated by the chemoattractant. We study this general mechanism of “collective guidance” computationally with models that integrate stochastic dynamics for individual cells with biochemical reactions within the cells, and diffusion of chemical signals between the cells. We show that if clusters of cells use the well-known local excitation, global inhibition (LEGI) mechanism to sense chemoattractant gradients, the speed of the cell cluster becomes non-monotonic in the cluster’s size—clusters either larger or smaller than an optimal size will have lower speed. We argue that the cell cluster speed is a crucial readout of how the cluster processes chemotactic signals; both amplification and adaptation will alter the behavior of cluster speed as a function of size. We also show that, contrary to the assumptions of earlier theories, collective guidance does not require persistent cell-cell contacts and strong short range adhesion. If cell-cell adhesion is absent, and the cluster cohesion is instead provided by a co-attraction mechanism, e.g. chemotaxis toward a secreted molecule, collective guidance may still function. However, new behaviors, such as cluster rotation, may also appear in this case. Co-attraction and adaptation allow for collective guidance that is robust to varying chemoattractant concentrations while not requiring strong cell-cell adhesion. PMID:27367541

  9. Peri-ictal signal changes in seven patients with status epilepticus: interesting MRI observations

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, Manoj K; Sinha, Sanjib [National Institute of Mental Health and Neurosciences (NIMHANS), Department of Neurology, Bangalore, Karnataka (India); Ravishankar, Shivshankar; Shivshankar, Jai Jai [National Institute of Mental Health and Neurosciences (NIMHANS), Department of Neuroimaging and Interventional Radiology, Bangalore (India)

    2009-03-15

    Transient peri-ictal changes on imaging had been described following status epilepticus (SE), but its cause is not very well understood. We analyzed the magnetic resonance imaging (MRI) findings in SE patients in order to elucidate such changes including peri-ictal signal. This prospective study involved 34 patients (M/F 23:11, mean age 25.8 {+-} 17.2 years) who experienced SE. MRI was performed during or within 96 h of cessation of seizures. Twenty-five patients had generalized convulsive status epilectus (GCSE; ten secondary GCSE and 15 primary GCSE). Seven patients had epilepsia partialis continua and two patients non-convulsive SE. Eight patients had a history of seizures and three patients previous SE. The mean duration of SE prior to MRI was 89.2 {+-} 105.3 h (range 2-360 h). MRI provided diagnosis in 17 patients, and in 13 patients, no structural cause was identified. Peri-ictal focal signal changes with restricted diffusion on apparent diffusion coefficient maps were present in seven (20.6%) patients with SE (generalized convulsive, three; partial, three; non-convulsive, one). The changes were observed when MRI was performed during SE in 3/10 (30%) patients, or within 24 h in 1/7 (14.3%), 48 h in 1/5 (20%), 72 h in 1/6 (16.7%), or 96 h in 1/6 (16.7%) patients after cessation of seizures. Repeat MRI revealed disappearance of signal changes in two patients. Peri-ictal MR changes with restricted diffusion appear to be an effect rather than the cause of SE. (orig.)

  10. Peri-ictal signal changes in seven patients with status epilepticus: interesting MRI observations

    International Nuclear Information System (INIS)

    Goyal, Manoj K.; Sinha, Sanjib; Ravishankar, Shivshankar; Shivshankar, Jai Jai

    2009-01-01

    Transient peri-ictal changes on imaging had been described following status epilepticus (SE), but its cause is not very well understood. We analyzed the magnetic resonance imaging (MRI) findings in SE patients in order to elucidate such changes including peri-ictal signal. This prospective study involved 34 patients (M/F 23:11, mean age 25.8 ± 17.2 years) who experienced SE. MRI was performed during or within 96 h of cessation of seizures. Twenty-five patients had generalized convulsive status epilectus (GCSE; ten secondary GCSE and 15 primary GCSE). Seven patients had epilepsia partialis continua and two patients non-convulsive SE. Eight patients had a history of seizures and three patients previous SE. The mean duration of SE prior to MRI was 89.2 ± 105.3 h (range 2-360 h). MRI provided diagnosis in 17 patients, and in 13 patients, no structural cause was identified. Peri-ictal focal signal changes with restricted diffusion on apparent diffusion coefficient maps were present in seven (20.6%) patients with SE (generalized convulsive, three; partial, three; non-convulsive, one). The changes were observed when MRI was performed during SE in 3/10 (30%) patients, or within 24 h in 1/7 (14.3%), 48 h in 1/5 (20%), 72 h in 1/6 (16.7%), or 96 h in 1/6 (16.7%) patients after cessation of seizures. Repeat MRI revealed disappearance of signal changes in two patients. Peri-ictal MR changes with restricted diffusion appear to be an effect rather than the cause of SE. (orig.)

  11. A basic characteristic of signal intensity in MRI

    International Nuclear Information System (INIS)

    Doi, Tsukasa

    2009-01-01

    For evaluation of the significance of signal intensity and contrast which determine the MR imaging quality, SNR (signal-to-noise ratio) and CNR (contrast-to-noise ratio) were studied as their respective measures on the cross-talk artifact (CTA), partial volume effect (PVE), intensity of the fast spin echo (SE) imaging and contrast in the 3T field area (Con). The machine used was 3.0T Signa HDx (GE). CTA, the SNR-reducing coherence between neighboring slices at multi-slice imaging, was studied with a series of phantoms of 0.75-4 mm diameter acrylic pins in cupric sulfate solution with various imaging modes and slice numbers to calculate CNR and contrast (C) involving SNR factor. PVE, the determinant of the intensity depending on the mixture of different tissues within a voxel (slice thickness), was studied with similar phantoms to above with 1-12 mm thick slices and different slice gaps to obtain CNR and C. The intensity of fast SE image was studied with phantoms in a brain-equivalent 0.125 mM Gd solution of sealed water, 0.25-0.5mM Gd, butter, salad oil and detergent on magnetization transfer, J-coupling and diffusion. Con in the 3T machine was studied with the same phantoms as above on the image contrasts at the central and peripheral imaging areas and the intensity/contrast changes by different coils. Presented data of above examinations revealed the effects of characteristic of each environmental factor, and of which recognition was concluded necessary to exactly read the obtained images. (K.T.)

  12. A signal amplification assay for HSV type 1 viral DNA detection using nanoparticles and direct acoustic profiling

    Directory of Open Access Journals (Sweden)

    Hammond Richard

    2010-02-01

    Full Text Available Abstract Background Nucleic acid based recognition of viral sequences can be used together with label-free biosensors to provide rapid, accurate confirmation of viral infection. To enhance detection sensitivity, gold nanoparticles can be employed with mass-sensitive acoustic biosensors (such as a quartz crystal microbalance by either hybridising nanoparticle-oligonucleotide conjugates to complimentary surface-immobilised ssDNA probes on the sensor, or by using biotin-tagged target oligonucleotides bound to avidin-modified nanoparticles on the sensor. We have evaluated and refined these signal amplification assays for the detection from specific DNA sequences of Herpes Simplex Virus (HSV type 1 and defined detection limits with a 16.5 MHz fundamental frequency thickness shear mode acoustic biosensor. Results In the study the performance of semi-homogeneous and homogeneous assay formats (suited to rapid, single step tests were evaluated utilising different diameter gold nanoparticles at varying DNA concentrations. Mathematical models were built to understand the effects of mass transport in the flow cell, the binding kinetics of targets to nanoparticles in solution, the packing geometries of targets on the nanoparticle, the packing of nanoparticles on the sensor surface and the effect of surface shear stiffness on the response of the acoustic sensor. This lead to the selection of optimised 15 nm nanoparticles that could be used with a 6 minute total assay time to achieve a limit of detection sensitivity of 5.2 × 10-12 M. Larger diameter nanoparticles gave poorer limits of detection than smaller particles. The limit of detection was three orders of magnitude lower than that observed using a hybridisation assay without nanoparticle signal amplification. Conclusions An analytical model was developed to determine optimal nanoparticle diameter, concentration and probe density, which allowed efficient and rapid optimisation of assay parameters

  13. Brain MRI findings of welders : high signal intensity in T1WI secondary to manganese exposure

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K. W.; Lim, M. A.; Shon, M. Y.; Lee, S. H.; Ha, D. G.; Kwon, K. R.; Kim, S. S.; Hong, Y. S.; Lee, Y. H. [Sunlin Presbyterian Hospital, Pohang (Korea, Republic of); Cheong, H. K. [Dongguk University, Seoul (Korea, Republic of)

    1998-03-01

    To evaluate the clinical and brain MRI findings of welders and to determine the utility of MRI in the assessment of occupational manganese exposure. All welders complained of fatigue, headache, anorexia, and decreased libido. The palmomental reflex was positive in five (28%), Myerson`s sign in four (22%), and intention tremor in three (17%). Mean blood Mn was 5.18 (range, 1.77-9.34) {mu}g/dl, mean urine Mn was 5.84 (range, 1.07 -22) {mu}g/l, serum Fe was elevated in one welder, and serum Cd in two. T1WI of brain MRI revealed high signal intensities in the globus pallidus, the putamen, the substantia nigra, the tectum, the caudate nucleus, the subthalamic nucleus, the hypothalamus and the pituitary gland. These intensities correlated closely with blood Mn levels, suggesting their potential role in estimating the accumulation of Mn in the brain. (author). 25 refs., 2 tabs., 5 figs.

  14. Correlation between MEG and BOLD fMRI signals induced by visual flicker stimuli

    Institute of Scientific and Technical Information of China (English)

    Chu Renxin; Holroyd Tom; Duyn Jeff

    2007-01-01

    The goal of this work was to investigate how the MEG signal amplitude correlates with that of BOLD fMRI.To investigate the correlation between fMRI and macroscopic electrical activity, BOLD fMRI and MEG was performed on the same subjects (n =5). A visual flicker stimulus of varying temporal frequency was used to elicit neural responses in early visual areas. A strong similarity was observed in frequency tuning curves between both modalities.Although, averaged over subjects, the BOLD tuning curve was somewhat broader than MEG, both BOLD and MEG had maxima at a flicker frequency of 10 Hz. Also, we measured the first and second harmonic components as the stimuli frequency by MEG. In the low stimuli frequency (less than 6 Hz), the second harmonic has comparable amplitude with the first harmonic, which implies that neural frequency response is nonlinear and has more nonlinear components in low frequency than in high frequency.

  15. On-chip signal amplification of magnetic bead-based immunoassay by aviating magnetic bead chains.

    Science.gov (United States)

    Jalal, Uddin M; Jin, Gyeong Jun; Eom, Kyu Shik; Kim, Min Ho; Shim, Joon S

    2017-11-06

    In this work, a Lab-on-a-Chip (LOC) platform is used to electromagnetically actuate magnetic bead chains for an enhanced immunoassay. Custom-made electromagnets generate a magnetic field to form, rotate, lift and lower the magnetic bead chains (MBCs). The cost-effective, disposable LOC platform was made with a polymer substrate and an on-chip electrochemical sensor patterned via the screen-printing process. The movement of the MBCs is controlled to improve the electrochemical signal up to 230% when detecting beta-type human chorionic gonadotropin (β-hCG). Thus, the proposed on-chip MBC-based immunoassay is applicable for rapid, qualitative electrochemical point-of-care (POC) analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Effect of pulse sequence parameter selection on signal strength in positive-contrast MRI markers for MRI-based prostate postimplant assessment

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Tze Yee [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, Texas 77030 (United States); Kudchadker, Rajat J., E-mail: rkudchad@mdanderson.org; Wang, Jihong; Ibbott, Geoffrey S. [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Stafford, R. Jason [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); MacLellan, Christopher [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, Texas 77030 (United States); Rao, Arvind [Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States); Frank, Steven J. [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)

    2016-07-15

    Purpose: For postimplant dosimetric assessment, computed tomography (CT) is commonly used to identify prostate brachytherapy seeds, at the expense of accurate anatomical contouring. Magnetic resonance imaging (MRI) is superior to CT for anatomical delineation, but identification of the negative-contrast seeds is challenging. Positive-contrast MRI markers were proposed to replace spacers to assist seed localization on MRI images. Visualization of these markers under varying scan parameters was investigated. Methods: To simulate a clinical scenario, a prostate phantom was implanted with 66 markers and 86 seeds, and imaged on a 3.0T MRI scanner using a 3D fast radiofrequency-spoiled gradient recalled echo acquisition with various combinations of scan parameters. Scan parameters, including flip angle, number of excitations, bandwidth, field-of-view, slice thickness, and encoding steps were systematically varied to study their effects on signal, noise, scan time, image resolution, and artifacts. Results: The effects of pulse sequence parameter selection on the marker signal strength and image noise were characterized. The authors also examined the tradeoff between signal-to-noise ratio, scan time, and image artifacts, such as the wraparound artifact, susceptibility artifact, chemical shift artifact, and partial volume averaging artifact. Given reasonable scan time and managable artifacts, the authors recommended scan parameter combinations that can provide robust visualization of the MRI markers. Conclusions: The recommended MRI pulse sequence protocol allows for consistent visualization of the markers to assist seed localization, potentially enabling MRI-only prostate postimplant dosimetry.

  17. Modeling fMRI signals can provide insights into neural processing in the cerebral cortex.

    Science.gov (United States)

    Vanni, Simo; Sharifian, Fariba; Heikkinen, Hanna; Vigário, Ricardo

    2015-08-01

    Every stimulus or task activates multiple areas in the mammalian cortex. These distributed activations can be measured with functional magnetic resonance imaging (fMRI), which has the best spatial resolution among the noninvasive brain imaging methods. Unfortunately, the relationship between the fMRI activations and distributed cortical processing has remained unclear, both because the coupling between neural and fMRI activations has remained poorly understood and because fMRI voxels are too large to directly sense the local neural events. To get an idea of the local processing given the macroscopic data, we need models to simulate the neural activity and to provide output that can be compared with fMRI data. Such models can describe neural mechanisms as mathematical functions between input and output in a specific system, with little correspondence to physiological mechanisms. Alternatively, models can be biomimetic, including biological details with straightforward correspondence to experimental data. After careful balancing between complexity, computational efficiency, and realism, a biomimetic simulation should be able to provide insight into how biological structures or functions contribute to actual data processing as well as to promote theory-driven neuroscience experiments. This review analyzes the requirements for validating system-level computational models with fMRI. In particular, we study mesoscopic biomimetic models, which include a limited set of details from real-life networks and enable system-level simulations of neural mass action. In addition, we discuss how recent developments in neurophysiology and biophysics may significantly advance the modelling of fMRI signals. Copyright © 2015 the American Physiological Society.

  18. Attenuation of artifacts in EEG signals measured inside an MRI scanner using constrained independent component analysis

    International Nuclear Information System (INIS)

    Rasheed, Tahir; Lee, Young-Koo; Lee, Soo Yeol; Kim, Tae-Seong

    2009-01-01

    Integration of electroencephalography (EEG) and functional magnetic imaging (fMRI) resonance will allow analysis of the brain activities at superior temporal and spatial resolution. However simultaneous acquisition of EEG and fMRI is hindered by the enhancement of artifacts in EEG, the most prominent of which are ballistocardiogram (BCG) and electro-oculogram (EOG) artifacts. The situation gets even worse if the evoked potentials are measured inside MRI for their minute responses in comparison to the spontaneous brain responses. In this study, we propose a new method of attenuating these artifacts from the spontaneous and evoked EEG data acquired inside an MRI scanner using constrained independent component analysis with a priori information about the artifacts as constraints. With the proposed techniques of reference function generation for the BCG and EOG artifacts as constraints, our new approach performs significantly better than the averaged artifact subtraction (AAS) method. The proposed method could be an alternative to the conventional ICA method for artifact attenuation, with some advantages. As a performance measure we have achieved much improved normalized power spectrum ratios (INPS) for continuous EEG and correlation coefficient (cc) values with outside MRI visual evoked potentials for visual evoked EEG, as compared to those obtained with the AAS method. The results show that our new approach is more effective than the conventional methods, almost fully automatic, and no extra ECG signal measurements are involved

  19. Multifunctional reduced graphene oxide trigged chemiluminescence resonance energy transfer: Novel signal amplification strategy for photoelectrochemical immunoassay of squamous cell carcinoma antigen.

    Science.gov (United States)

    Zhang, Yan; Sun, Guoqiang; Yang, Hongmei; Yu, Jinghua; Yan, Mei; Song, Xianrang

    2016-05-15

    Herein, a photoelectrochemical (PEC) immunoassay is constructed for squamous cell carcinoma antigen (SCCA) detection using zinc oxide nanoflower-bismuth sulfide (Bi2S3) composites as photoactive materials and reduced graphene oxide (rGO) as signal labels. Horseradish peroxidase is used to block sites against nonspecific binding, and then participated in luminol-based chemiluminescence (CL) system. The induced CL emission is acted as an inner light source to excite photoactive materials, simplifying the instrument. A novel signal amplification strategy is stem from rGO because of the rGO acts as an energy acceptor, while luminol serves as a donor to rGO, triggering the CL resonance energy transfer phenomenon between luminol and rGO. Thus, the efficient CL emission to photoactive materials decreases. Furthermore, the signal amplification caused by rGO labeled signal antibodies is related to photogenerated electron-hole pairs: perfect matching of energy levels between rGO and Bi2S3 makes rGO a sink to capture photogenerated electrons from Bi2S3; the increased steric hindrance hinders the electron donor to the surface of Bi2S3 for reaction with the photogenerated holes. On the basis of the novel signal amplification strategy, the proposed immunosensor exhibits excellent analytical performance for PEC detection of SCCA, ranging from 0.8 pg mL(-1) to 80 ng mL(-1) with a low detection limit of 0.21 pg mL(-1). Meanwhile, the designed signal amplification strategy provides a general format for future development of PEC assays. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. A theoretical signal processing framework for linear diffusion MRI: Implications for parameter estimation and experiment design.

    Science.gov (United States)

    Varadarajan, Divya; Haldar, Justin P

    2017-11-01

    The data measured in diffusion MRI can be modeled as the Fourier transform of the Ensemble Average Propagator (EAP), a probability distribution that summarizes the molecular diffusion behavior of the spins within each voxel. This Fourier relationship is potentially advantageous because of the extensive theory that has been developed to characterize the sampling requirements, accuracy, and stability of linear Fourier reconstruction methods. However, existing diffusion MRI data sampling and signal estimation methods have largely been developed and tuned without the benefit of such theory, instead relying on approximations, intuition, and extensive empirical evaluation. This paper aims to address this discrepancy by introducing a novel theoretical signal processing framework for diffusion MRI. The new framework can be used to characterize arbitrary linear diffusion estimation methods with arbitrary q-space sampling, and can be used to theoretically evaluate and compare the accuracy, resolution, and noise-resilience of different data acquisition and parameter estimation techniques. The framework is based on the EAP, and makes very limited modeling assumptions. As a result, the approach can even provide new insight into the behavior of model-based linear diffusion estimation methods in contexts where the modeling assumptions are inaccurate. The practical usefulness of the proposed framework is illustrated using both simulated and real diffusion MRI data in applications such as choosing between different parameter estimation methods and choosing between different q-space sampling schemes. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Electrochemical DNA probe for Hg(2+) detection based on a triple-helix DNA and Multistage Signal Amplification Strategy.

    Science.gov (United States)

    Wang, Huan; Zhang, Yihe; Ma, Hongmin; Ren, Xiang; Wang, Yaoguang; Zhang, Yong; Wei, Qin

    2016-12-15

    In this work, an ultrasensitive electrochemical sensor was developed for detection of Hg(2+). Gold nanoparticles decorated bovine serum albumin reduction of graphene oxide (AuNP-BSA-rGO) were used as subsurface material for the immobilization of triple-helix DNA. The triple-helix DNA containing a thiol labelled single-stranded DNA (sDNA) and a thymine-rich DNA (T-rich DNA), which could be unwinded in the present of Hg(2+) to form more stable thymine-Hg(2+)-thymine (T-Hg(2+)-T) complex. T-Hg(2+)-T complex was then removed and the sDNA was left on the electrode. At this time, gold nanoparticle carrying thiol labelled cytosine-rich complementary DNA (cDNA-AuNP) could bind with the free sDNA. Meanwhile, the other free cDNA on AuNP could bind with each other in the present of Ag(+) to form the stable cytosine-Ag(+)-cytosine (C-Ag(+)-C) complex and circle amplification. Plenty of C-Ag(+)-C could form silver nanoclusters by electrochemical reduction and the striping signal of Ag could be measured for purpose of the final electrochemical detection of Hg(2+). This sensor could detect Hg(2+) over a wide concentration range from 0.1 to 130nM with a detection limit of 0.03nM. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Signal amplification strategy for biomarkers: Structural origins of epitaxial-growth twinned nanocrystals and D-π-A type polymers.

    Science.gov (United States)

    Liu, He; Gu, Yue; Dong, Tao; Yan, Liuqing; Yan, Xiaoyi; Zhang, Tingting; Lu, Nannan; Xu, Zhiqian; Xu, Haixin; Zhang, Zhiquan; Bian, Ting

    2018-06-30

    The combination of nanoparticles and biomarkers yields functional nanostructured biointerface, which is playing a notable role in biotechnology development. Due to the 5-fold twined structure in the Au-Pt star-shaped decahedra not only allowed it to act as efficient scaffold for immobilization of antibody, but it also exhibits superior electrocatalytic activity toward H 2 O 2 reduction, the nanocrystal as the efficient signal transduction label is first employed to construct an electrochemical immunosensor. Donor-π-Acceptor (D-π-A) linking fashion generates a dipolar push-pull system and assures superior intramolecular charge transfer. It is considered as a suitable π-conjugated backbone for conducting polymer on biointerface application. Under a D-π-A architecture which imidazole as the π-bridge and amino phenyl/phenyl groups as peripheral electron-donating/withdrawing functional groups, 4-(2,4,5-triphenyl-1H-imidazol-1-yl) aniline (TPIDA) is designed and synthesized for good biocompatibility and high conductivity. In this proposal, we attempt to integrate the above-mentioned two features from nanobiotechnology and organic bioelectronics. Then, a novel nonenzymatic sandwich-type immunosensor is performed by Au-Pt core-shell with surface-engineered twinning as a label and π-conjugated D-π-A polymers as the signal amplification platform. Human IgG (HIgG) as the model target protein can be detected with a wide linear range from 0.1 pg mL -1 to 100 ng mL -1 . The detection limit is down to 0.06 pg mL -1 (S/N = 3). Moreover, as a practical application, the prepared biosensor is used to monitor HIgG level in human serum with desirable results obtained. Copyright © 2018 Elsevier B.V. All rights reserved.

  3. Signal to noise comparison of metabolic imaging methods on a clinical 3T MRI

    DEFF Research Database (Denmark)

    Müller, C. A.; Hansen, Rie Beck; Skinner, J. G.

    MRI with hyperpolarized tracers has enabled new diagnostic applications, e.g. metabolic imaging in cancer research. However, the acquisition of the transient, hyperpolarized signal with spatial and frequency resolution requires dedicated imaging methods. Here, we compare three promising candidate...... for 2D MR spectroscopic imaging (MRSI): (i) multi-echo balanced steady-state free precession (me-bSSFP), 1,2 (ii) echo planar spectroscopic imaging (EPSI) sequence and (iii) phase-encoded, pulseacquisition chemical-shift imaging (CSI)...

  4. Ischiofemoral space on MRI in an asymptomatic population: Normative width measurements and soft tissue signal variations

    International Nuclear Information System (INIS)

    Maras Oezdemir, Zeynep; Goermeli, Cemile Ayse; Sagir Kahraman, Ayseguel; Aydingoez, Uestuen

    2015-01-01

    To make normative width measurements of the ischiofemoral (IF) space in an asymptomatic population and to record soft tissue MRI signal variations within the IF space in order to determine whether such variations are associated with IF space dimensions. Normative width measurements of the IF space were prospectively made in 418 hips on 1.5 T MR images of 209 asymptomatic volunteers. Quantitative and qualitative assessments of the IF soft tissues including the quadratus femoris (QF) muscle were also made. The mean IF space width was 2.56 ± 0.75 cm (right, 2.60 ± 0.75 cm; left, 2.53 ± 0.75 cm). Soft tissue MRI signal abnormalities were present within the IF space in 19 (9.1 %) of 209 volunteers. Soft tissue abnormalities within the IF space included oedema (3/209, 1.4 %) of the QF and/or surrounding soft tissue, and only fatty infiltration (16/209, 7.7 %) of the QF. Bilateral IF spaces are asymmetrical in asymptomatic persons. There is ≥10 % of width difference between right and left IF spaces in approximately half of asymptomatic individuals. Fatty infiltration and oedema can be present at the IF space in a small portion of the asymptomatic population, who also have narrower IF spaces than those without soft tissue MRI signal abnormalities. (orig.)

  5. Development of an efficient signal amplification strategy for label-free enzyme immunoassay using two site-specific biotinylated recombinant proteins

    International Nuclear Information System (INIS)

    Tang, Jin-Bao; Tang, Ying; Yang, Hong-Ming

    2015-01-01

    Highlights: • An efficient signal amplification strategy for label-free EIA is proposed. • Divalent biotinylated AP and monovalent biotinylated ZZ were prepared via Avitag–BirA system. • The above site-specific biotinylated fusion proteins form complex via SA–biotin interaction. • The mechanism relies on the ZZ–Avi-B/SA/AP–(Avi-B) 2 complex. • The analytical signals are enhanced (32-fold) by the proposed strategy. - Abstract: Constructing a recombinant protein between a reporter enzyme and a detector protein to produce a homogeneous immunological reagent is advantageous over random chemical conjugation. However, the approach hardly recombines multiple enzymes in a difunctional fusion protein, which results in insufficient amplification of the enzymatic signal, thereby limiting its application in further enhancement of analytical signal. In this study, two site-specific biotinylated recombinant proteins, namely, divalent biotinylated alkaline phosphatase (AP) and monovalent biotinylated ZZ domain, were produced by employing the Avitag–BirA system. Through the high streptavidin (SA)–biotin interaction, the divalent biotinylated APs were clustered in the SA–biotin complex and then incorporated with the biotinylated ZZ. This incorporation results in the formation of a functional macromolecule that involves numerous APs, thereby enhancing the enzymatic signal, and in the production of several ZZ molecules for the interaction with immunoglobulin G (IgG) antibody. The advantage of this signal amplification strategy is demonstrated through ELISA, in which the analytical signal was substantially enhanced, with a 32-fold increase in the detection sensitivity compared with the ZZ–AP fusion protein approach. The proposed immunoassay without chemical modification can be an alternative strategy to enhance the analytical signals in various applications involving immunosensors and diagnostic chips, given that the label-free IgG antibody is suitable for

  6. Development of an efficient signal amplification strategy for label-free enzyme immunoassay using two site-specific biotinylated recombinant proteins

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Jin-Bao [School of Pharmacy, Weifang Medical University, Weifang 261053 (China); Tang, Ying [Affiliated Hospital of Weifang Medical University, Weifang 261041 (China); Yang, Hong-Ming, E-mail: yanghongming2006@sohu.com [School of Pharmacy, Weifang Medical University, Weifang 261053 (China)

    2015-02-15

    Highlights: • An efficient signal amplification strategy for label-free EIA is proposed. • Divalent biotinylated AP and monovalent biotinylated ZZ were prepared via Avitag–BirA system. • The above site-specific biotinylated fusion proteins form complex via SA–biotin interaction. • The mechanism relies on the ZZ–Avi-B/SA/AP–(Avi-B){sub 2} complex. • The analytical signals are enhanced (32-fold) by the proposed strategy. - Abstract: Constructing a recombinant protein between a reporter enzyme and a detector protein to produce a homogeneous immunological reagent is advantageous over random chemical conjugation. However, the approach hardly recombines multiple enzymes in a difunctional fusion protein, which results in insufficient amplification of the enzymatic signal, thereby limiting its application in further enhancement of analytical signal. In this study, two site-specific biotinylated recombinant proteins, namely, divalent biotinylated alkaline phosphatase (AP) and monovalent biotinylated ZZ domain, were produced by employing the Avitag–BirA system. Through the high streptavidin (SA)–biotin interaction, the divalent biotinylated APs were clustered in the SA–biotin complex and then incorporated with the biotinylated ZZ. This incorporation results in the formation of a functional macromolecule that involves numerous APs, thereby enhancing the enzymatic signal, and in the production of several ZZ molecules for the interaction with immunoglobulin G (IgG) antibody. The advantage of this signal amplification strategy is demonstrated through ELISA, in which the analytical signal was substantially enhanced, with a 32-fold increase in the detection sensitivity compared with the ZZ–AP fusion protein approach. The proposed immunoassay without chemical modification can be an alternative strategy to enhance the analytical signals in various applications involving immunosensors and diagnostic chips, given that the label-free IgG antibody is suitable

  7. Parameter Optimization for Quantitative Signal-Concentration Mapping Using Spoiled Gradient Echo MRI

    Directory of Open Access Journals (Sweden)

    Gasser Hathout

    2012-01-01

    Full Text Available Rationale and Objectives. Accurate signal to tracer concentration maps are critical to quantitative MRI. The purpose of this study was to evaluate and optimize spoiled gradient echo (SPGR MR sequences for the use of gadolinium (Gd-DTPA as a kinetic tracer. Methods. Water-gadolinium phantoms were constructed for a physiologic range of gadolinium concentrations. Observed and calculated SPGR signal to concentration curves were generated. Using a percentage error determination, optimal pulse parameters for signal to concentration mapping were obtained. Results. The accuracy of the SPGR equation is a function of the chosen MR pulse parameters, particularly the time to repetition (TR and the flip angle (FA. At all experimental values of TR, increasing FA decreases the ratio between observed and calculated signals. Conversely, for a constant FA, increasing TR increases this ratio. Using optimized pulse parameter sets, it is possible to achieve excellent accuracy (approximately 5% over a physiologic range of concentration tracer concentrations. Conclusion. Optimal pulse parameter sets exist and their use is essential for deriving accurate signal to concentration curves in quantitative MRI.

  8. A receptor-based model for dopamine-induced fMRI signal

    Science.gov (United States)

    Mandeville, Joseph. B.; Sander, Christin Y. M.; Jenkins, Bruce G.; Hooker, Jacob M.; Catana, Ciprian; Vanduffel, Wim; Alpert, Nathaniel M.; Rosen, Bruce R.; Normandin, Marc D.

    2013-01-01

    This report describes a multi-receptor physiological model of the fMRI temporal response and signal magnitude evoked by drugs that elevate synaptic dopamine in basal ganglia. The model is formulated as a summation of dopamine’s effects at D1-like and D2-like receptor families, which produce functional excitation and inhibition, respectively, as measured by molecular indicators like adenylate cyclase or neuroimaging techniques like fMRI. Functional effects within the model are described in terms of relative changes in receptor occupancies scaled by receptor densities and neuro-vascular coupling constants. Using literature parameters, the model reconciles many discrepant observations and interpretations of pre-clinical data. Additionally, we present data showing that amphetamine stimulation produces fMRI inhibition at low doses and a biphasic response at higher doses in the basal ganglia of non-human primates (NHP), in agreement with model predictions based upon the respective levels of evoked dopamine. Because information about dopamine release is required to inform the fMRI model, we simultaneously acquired PET 11C-raclopride data in several studies to evaluate the relationship between raclopride displacement and assumptions about dopamine release. At high levels of dopamine release, results suggest that refinements of the model will be required to consistently describe the PET and fMRI data. Overall, the remarkable success of the model in describing a wide range of preclinical fMRI data indicate that this approach will be useful for guiding the design and analysis of basic science and clinical investigations and for interpreting the functional consequences of dopaminergic stimulation in normal subjects and in populations with dopaminergic neuroadaptations. PMID:23466936

  9. MRI evaluation of cranial bone marrow signal intensity and thickness in chronic anemia

    International Nuclear Information System (INIS)

    Yildirim, Tulin; Agildere, A. Muhtesem; Oguzkurt, Levent; Barutcu, Ozlem; Kizilkilic, Osman; Kocak, Rikkat; Alp Niron, Emin

    2005-01-01

    Background and purpose: The aim is to assess the magnetic resonance imaging (MRI) findings for cranial bone marrow (CBM) signal intensity and thickness in patients with chronic anemia and compared these with findings in healthy subjects. We also investigated the relationships between CBM changes and age, type of anemia (hemolytic versus non-hemolytic), and severity of anemia. Methods: We quantitatively evaluated CBM signal intensity and thickness on images from 40 patients with chronic anemia (20 with congenital hemolytic anemia (HA) and 20 with acquired anemia) and compared these to findings in 28 healthy subjects. The intensity of CBM relative to scalp, white matter (WM), gray matter (GM), and muscle intensity was also investigated in patients and subjects in the control group. The sensitivity and specificity of CBM hypointense to GM and CBM hypointense to WM as markers of anemia were evaluated. Relationships between age and CBM thickness/intensity, and between anemia severity (hemoglobin (Hb) level) and CBM thickness/intensity were evaluated. Results: Cranial bone marrow signal intensity was lower in the chronic anemia patients than in the controls (P 0.05 for both). There were no correlations between age and CBM intensity or thickness, or between anemia severity and CBM intensity or thickness. Conclusion: Patients with chronic anemia exhibit lower CBM signal intensity on MRI than healthy subjects. Patients with hemolytic anemia have thicker CBM than patients with non-hemolytic anemia or healthy individuals. Decreased CBM intensity may indicate that the patient has anemia, and increased CBM thickness may specifically point to hemolytic anemia. These MRI findings may signal the need for further evaluation for the clinician

  10. MRI

    DEFF Research Database (Denmark)

    Schroeter, Aileen; Rudin, Markus; Gianolio, Eliana

    2017-01-01

    This chapter discusses principles of nuclear magnetic resonance (NMR) and MRI followed by a survey on the major classes of MRI contrast agents (CA), their modes of action, and some of the most significative applications. The two more established classes of MRI-CA are represented by paramagnetic...... been attained that markedly increase the number and typology of systems with CEST properties. Currently much attention is also devoted to hyperpolarized molecules that display a sensitivity enhancement sufficient for their direct exploitation for the formation of the MR image. A real breakthrough...

  11. Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

    Science.gov (United States)

    Chizhevsky, V. N.

    2018-01-01

    For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

  12. Kerr nonlinearity mitigation in 5 × 28-GBd PDM16-QAM signal transmission over a dispersion-uncompensated link with backward-pumpeddistributed Raman amplification

    DEFF Research Database (Denmark)

    Sackey, I.; Da Ros, Francesco; Jazayerifar, M.

    2014-01-01

    We present experimental and numerical investigations of Kerr nonlinearity compensation in a 400-km standard single-mode fiber link with distributed Raman amplification with backward pumping. A dual-pump polarization-independent fiber-based optical parametric amplifier is used for mid-link spectra...... to numerical simulations with good agreement. It is also shown with simulations that a maximum transmission reach of 2400 km enabled by the optical phase conjugator is possible for the WDM signal...

  13. Increased working memory related fMRI signal in children following Tick Borne Encephalitis.

    Science.gov (United States)

    Henrik, Ullman; Åsa, Fowler; Ronny, Wickström

    2016-01-01

    Tick Borne Encephalitis (TBE) is a viral infection in the central nervous system endemic in Europe and Asia. While pediatric infection may carry a lower risk for serious neurological sequelae compared to adults, a large proportion of children experience long term cognitive problems, most markedly decreased working memory capacity. We explored whether task related functional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) could reveal a biological correlate of status-post TBE in children. We examined 11 serologically verified pediatric TBE patients with central nervous system involvement with 55 healthy controls with working memory tests and MRI. The TBE patients showed a prominent deficit in working memory capacity and an increased task related functional MRI signal in working memory related cortical areas during a spatial working memory task performed without sedation. No diffusion differences could be found with DTI, in line with the reported paucity of anatomical abnormalities. This study is the first to demonstrate functional MRI abnormalities in TBE patients that bears similarity to other patient groups with diffuse neuronal damage. Copyright © 2015 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.

  14. Comparison of causality analysis on simultaneously measured fMRI and NIRS signals during motor tasks.

    Science.gov (United States)

    Anwar, Abdul Rauf; Muthalib, Makii; Perrey, Stephane; Galka, Andreas; Granert, Oliver; Wolff, Stephan; Deuschl, Guenther; Raethjen, Jan; Heute, Ulrich; Muthuraman, Muthuraman

    2013-01-01

    Brain activity can be measured using different modalities. Since most of the modalities tend to complement each other, it seems promising to measure them simultaneously. In to be presented research, the data recorded from Functional Magnetic Resonance Imaging (fMRI) and Near Infrared Spectroscopy (NIRS), simultaneously, are subjected to causality analysis using time-resolved partial directed coherence (tPDC). Time-resolved partial directed coherence uses the principle of state space modelling to estimate Multivariate Autoregressive (MVAR) coefficients. This method is useful to visualize both frequency and time dynamics of causality between the time series. Afterwards, causality results from different modalities are compared by estimating the Spearman correlation. In to be presented study, we used directionality vectors to analyze correlation, rather than actual signal vectors. Results show that causality analysis of the fMRI correlates more closely to causality results of oxy-NIRS as compared to deoxy-NIRS in case of a finger sequencing task. However, in case of simple finger tapping, no clear difference between oxy-fMRI and deoxy-fMRI correlation is identified.

  15. Enzyme-free and label-free ultrasensitive electrochemical detection of DNA and adenosine triphosphate by dendritic DNA concatamer-based signal amplification.

    Science.gov (United States)

    Liu, Shufeng; Lin, Ying; Liu, Tao; Cheng, Chuanbin; Wei, Wenji; Wang, Li; Li, Feng

    2014-06-15

    Hybridization chain reaction (HCR) strategy has been well developed for the fabrication of various biosensing platforms for signal amplification. Herein, a novel enzyme-free and label-free ultrasensitive electrochemical DNA biosensing platform for the detection of target DNA and adenosine triphosphate (ATP) was firstly proposed, in which three auxiliary DNA probes were ingeniously designed to construct the dendritic DNA concatamer via HCR strategy and used as hexaammineruthenium(III) chloride (RuHex) carrier for signal amplification. With the developed dendritic DNA concatamer-based signal amplification strategy, the DNA biosensor could achieve an ultrasensitive electrochemical detection of DNA and ATP with a superior detection limit as low as 5 aM and 20 fM, respectively, and also demonstrate a high selectivity for DNA and ATP detection. The currently proposed dendritic DNA concatamer opens a promising direction to construct ultrasensitive DNA biosensing platform for biomolecular detection in bioanalysis and clinical biomedicine, which offers the distinct advantages of simplicity and cost efficiency owing to no need of any kind of enzyme, chemical modification or labeling. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. MRI

    Science.gov (United States)

    ... the room. Pins, hairpins, metal zippers, and similar metallic items can distort the images. Removable dental work ... an MRI can cause heart pacemakers and other implants not to work as well. The magnets can ...

  17. Brain MRI signal abnormalities and right-to-left shunting in asymptomatic military divers.

    Science.gov (United States)

    Gempp, Emmanuel; Sbardella, Fabrice; Stephant, Eric; Constantin, Pascal; De Maistre, Sebastien; Louge, Pierre; Blatteau, Jean-Eric

    2010-11-01

    We conducted a controlled study to assess the prevalence of brain MRI hyperintense signals and their correlation with right-to-left shunting (RLS) in military divers. We prospectively enrolled 32 asymptomatic military divers under 41 yr of age and 32 non-diving healthy subjects matched with respect to age and vascular disease risk factors. We examined both groups with a 3-Tesla brain MRI; RLS was detected using transcranial pulsed Doppler in divers only. Hyperintense spots were observed in 43.7% of the divers and 21.8% of the control subjects. In particular, divers with significant shunting exhibited a higher prevalence of hyperintensities compared to those with slight or no RLS (75% vs. 25%, respectively). Linear trend analysis also revealed a positive correlation between focal white matter changes, determined using a validated visual rating scale and the RLS grade. Healthy military divers with a hemodynamically relevant RLS have an increased likelihood of cerebral hyperintense spots compared to age-matched normal subjects. The clinical relevance of these MRI signal abnormalities and their causal relationship with diving remain unclear.

  18. Aptamer based fluorescent cocaine assay based on the use of graphene oxide and exonuclease III-assisted signal amplification

    International Nuclear Information System (INIS)

    Zhang, Yulin; Zhang, Guo-Jun; Sun, Zhongyue; Tang, Lina; Zhang, Hong

    2016-01-01

    The article reports an aptamer based assay for cocaine by employing graphene oxide and exonuclease III-assisted signal amplification. It is based on the following scheme and experimental steps: (1) Exo III can digest dsDNA with blunt or recessed 3-terminus, but it has limited activity to ssDNA or dsDNA with protruding 3-terminus; (2) GO can absorb the FAM-labeled ssDNA probe and quench the fluorescence of probe, while the affinity between FAM-labeled mononucleotide and GO is negligible; (3) Cocaine aptamer can be split into two flexible ssDNA pieces (Probe 1 and Probe 2) without significant perturbation of cocaine-binding abilities; (4) The triple complex consisting of Probe 1, Probe 2 and cocaine can be digested by Exo III with the similar efficiency as normal dsDNA. Cocaine aptamer is split into two flexible ssDNA pieces (Probe 2 and 3′-FAM-labeled Probe 1). Cocaine can mediate the cocaine aptamer fragments forming a triplex. The triple complex has unique characteristic with 3′-FAM-labeled blunt end at the Probe 1 and 3′-overhang end at Probe 2. If exonuclease III is added, it will catalyze the stepwise removal of fluorescein (FAM) labeled mononucleotides from the 3-hydroxy termini of the special triplex complex, resulting in liberation of cocaine. The cocaine released in this step can produce a new cleavage cycle, thereby leading to target recycling. Through such a cyclic bound-hydrolysis process, small amounts of cocaine can induce the cleavage of a large number of FAM-labeled probe 1. The cleaved FAM-labeled mononucleotides are not adsorbed on the surface of graphene oxide (GO), so a strong fluorescence signal enhancement is observed as the cocaine triggers enzymatic digestion. Under optimized conditions, the assay allows cocaine to be detected in the 1 to 500 nM concentration range with a detection limit of 0.1 nM. The method was applied to the determination of cocaine in spiked human plasma, with recoveries ranging from 92.0 to 111.8 % and RSD of <12

  19. PARTICLE FILTERING WITH SEQUENTIAL PARAMETER LEARNING FOR NONLINEAR BOLD fMRI SIGNALS.

    Science.gov (United States)

    Xia, Jing; Wang, Michelle Yongmei

    Analyzing the blood oxygenation level dependent (BOLD) effect in the functional magnetic resonance imaging (fMRI) is typically based on recent ground-breaking time series analysis techniques. This work represents a significant improvement over existing approaches to system identification using nonlinear hemodynamic models. It is important for three reasons. First, instead of using linearized approximations of the dynamics, we present a nonlinear filtering based on the sequential Monte Carlo method to capture the inherent nonlinearities in the physiological system. Second, we simultaneously estimate the hidden physiological states and the system parameters through particle filtering with sequential parameter learning to fully take advantage of the dynamic information of the BOLD signals. Third, during the unknown static parameter learning, we employ the low-dimensional sufficient statistics for efficiency and avoiding potential degeneration of the parameters. The performance of the proposed method is validated using both the simulated data and real BOLD fMRI data.

  20. High signal of the striatum in sporadic Creutzfeldt-Jakob disease: sequential change on T2-weighted MRI

    International Nuclear Information System (INIS)

    Uemura, A.; O'uchi, T.; Sakamoto, T.; Yashiro, N.

    2002-01-01

    The object of this study is to describe the sequential change of high signal of the striatum on T2-weighted MRI in sporadic Creutzfeldt-Jakob disease (CJD). Three cases of autopsy-proven sporadic CJD and a total of 18 serial MR images are included in this study. The degree of high signal of the striatum on T2-weighted MRI was evaluated by two neuroradiologists and divided into four grades by mutual agreement. Initial MRI of all three cases showed a slightly high signal of the bilateral striatum, and the conspicuity of the high signal became more prominent as the disease progressed. In each case the pathological change of striatum and globus pallidus was compared with the high signal on the last MR image. (orig.)

  1. High signal of the striatum in sporadic Creutzfeldt-Jakob disease: sequential change on T2-weighted MRI

    Energy Technology Data Exchange (ETDEWEB)

    Uemura, A.; O' uchi, T.; Sakamoto, T.; Yashiro, N. [Department of Radiology, Kameda Medical Center, Kamogawa, Chiba (Japan)

    2002-04-01

    The object of this study is to describe the sequential change of high signal of the striatum on T2-weighted MRI in sporadic Creutzfeldt-Jakob disease (CJD). Three cases of autopsy-proven sporadic CJD and a total of 18 serial MR images are included in this study. The degree of high signal of the striatum on T2-weighted MRI was evaluated by two neuroradiologists and divided into four grades by mutual agreement. Initial MRI of all three cases showed a slightly high signal of the bilateral striatum, and the conspicuity of the high signal became more prominent as the disease progressed. In each case the pathological change of striatum and globus pallidus was compared with the high signal on the last MR image. (orig.)

  2. Temporal dependence of in vivo USPIO-enhanced MRI signal changes in human carotid atheromatous plaques

    Energy Technology Data Exchange (ETDEWEB)

    Tang, T.Y.; Sadat, U. [Cambridge University Hospitals NHS Foundation Trust, University Department of Radiology, Cambridge (United Kingdom); Cambridge University Hospitals NHS Foundation Trust, Cambridge Vascular Unit, Cambridge (United Kingdom); Patterson, A.J.; Graves, M.J.; Howarth, S.P.S.; U-King-Im, J.M.; Li, Z.Y.; Young, V.E.; Gillard, J.H. [Cambridge University Hospitals NHS Foundation Trust, University Department of Radiology, Cambridge (United Kingdom); Miller, S.R. [GlaxoSmithKline, Biostatistics and Data Sciences, Harlow (United Kingdom); Walsh, S.R.; Boyle, J.R.; Gaunt, M.E. [Cambridge University Hospitals NHS Foundation Trust, Cambridge Vascular Unit, Cambridge (United Kingdom)

    2009-07-15

    Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI has been shown to be a useful modality to image activated macrophages in vivo, which are principally responsible for plaque inflammation. This study determined the optimum imaging time-window to detect maximal signal change post-USPIO infusion using T{sub 1}-weighted (T{sub 1}w), T{sub 2}*-weighted (T{sub 2}*w) and quantitative T{sub 2}* (qT{sub 2}*) imaging. Six patients with an asymptomatic carotid stenosis underwent high resolution T{sub 1}w, T{sub 2}*w and qT{sub 2}* MR imaging of their carotid arteries at 1.5 T. Imaging was performed before and at 24, 36, 48, 72 and 96 h after USPIO (Sinerem trademark, Guerbet, France) infusion. Each slice showing atherosclerotic plaque was manually segmented into quadrants and signal changes in each quadrant were fitted to an exponential power function to model the optimum time for post-infusion imaging. The power function determining the mean time to convergence for all patients was 46, 41 and 39 h for the T{sub 1}w, T{sub 2}*w and qT{sub 2}* sequences, respectively. When modelling each patient individually, 90% of the maximum signal intensity change was observed at 36 h for three, four and six patients on T{sub 1}w, T{sub 2}*w and qT{sub 2}*, respectively. The rates of signal change decrease after this period but signal change was still evident up to 96 h. This study showed that a suitable imaging window for T{sub 1}w, T{sub 2}*w and qT{sub 2}* signal changes post-USPIO infusion was between 36 and 48 h. Logistically, this would be convenient in bringing patients back for one post-contrast MRI, but validation is required in a larger cohort of patients. (orig.)

  3. Temporal dependence of in vivo USPIO-enhanced MRI signal changes in human carotid atheromatous plaques

    International Nuclear Information System (INIS)

    Tang, T.Y.; Sadat, U.; Patterson, A.J.; Graves, M.J.; Howarth, S.P.S.; U-King-Im, J.M.; Li, Z.Y.; Young, V.E.; Gillard, J.H.; Miller, S.R.; Walsh, S.R.; Boyle, J.R.; Gaunt, M.E.

    2009-01-01

    Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI has been shown to be a useful modality to image activated macrophages in vivo, which are principally responsible for plaque inflammation. This study determined the optimum imaging time-window to detect maximal signal change post-USPIO infusion using T 1 -weighted (T 1 w), T 2 *-weighted (T 2 *w) and quantitative T 2 * (qT 2 *) imaging. Six patients with an asymptomatic carotid stenosis underwent high resolution T 1 w, T 2 *w and qT 2 * MR imaging of their carotid arteries at 1.5 T. Imaging was performed before and at 24, 36, 48, 72 and 96 h after USPIO (Sinerem trademark, Guerbet, France) infusion. Each slice showing atherosclerotic plaque was manually segmented into quadrants and signal changes in each quadrant were fitted to an exponential power function to model the optimum time for post-infusion imaging. The power function determining the mean time to convergence for all patients was 46, 41 and 39 h for the T 1 w, T 2 *w and qT 2 * sequences, respectively. When modelling each patient individually, 90% of the maximum signal intensity change was observed at 36 h for three, four and six patients on T 1 w, T 2 *w and qT 2 *, respectively. The rates of signal change decrease after this period but signal change was still evident up to 96 h. This study showed that a suitable imaging window for T 1 w, T 2 *w and qT 2 * signal changes post-USPIO infusion was between 36 and 48 h. Logistically, this would be convenient in bringing patients back for one post-contrast MRI, but validation is required in a larger cohort of patients. (orig.)

  4. Target-induced formation of gold amalgamation on DNA-based sensing platform for electrochemical monitoring of mercury ion coupling with cycling signal amplification strategy

    International Nuclear Information System (INIS)

    Chen, Jinfeng; Tang, Juan; Zhou, Jun; Zhang, Lan; Chen, Guonan; Tang, Dianping

    2014-01-01

    Graphical abstract: -- Highlights: •We report a new electrochemical sensing protocol for the detection of mercury ion. •Gold amalgamation on DNA-based sensing platform was used as nanocatalyst. •The signal was amplified by cycling signal amplification strategy. -- Abstract: Heavy metal ion pollution poses severe risks in human health and environmental pollutant, because of the likelihood of bioaccumulation and toxicity. Driven by the requirement to monitor trace-level mercury ion (Hg 2+ ), herein we construct a new DNA-based sensor for sensitive electrochemical monitoring of Hg 2+ by coupling target-induced formation of gold amalgamation on DNA-based sensing platform with gold amalgamation-catalyzed cycling signal amplification strategy. The sensor was simply prepared by covalent conjugation of aminated poly-T (25) oligonucleotide onto the glassy carbon electrode by typical carbodiimide coupling. Upon introduction of target analyte, Hg 2+ ion was intercalated into the DNA polyion complex membrane based on T–Hg 2+ –T coordination chemistry. The chelated Hg 2+ ion could induce the formation of gold amalgamation, which could catalyze the p-nitrophenol with the aid of NaBH 4 and Ru(NH 3 ) 6 3+ for cycling signal amplification. Experimental results indicated that the electronic signal of our system increased with the increasing Hg 2+ level in the sample, and has a detection limit of 0.02 nM with a dynamic range of up to 1000 nM Hg 2+ . The strategy afforded exquisite selectivity for Hg 2+ against other environmentally related metal ions. In addition, the methodology was evaluated for the analysis of Hg 2+ in spiked tap-water samples, and the recovery was 87.9–113.8%

  5. Target-induced formation of gold amalgamation on DNA-based sensing platform for electrochemical monitoring of mercury ion coupling with cycling signal amplification strategy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jinfeng; Tang, Juan; Zhou, Jun; Zhang, Lan; Chen, Guonan; Tang, Dianping, E-mail: dianping.tang@fzu.edu.cn

    2014-01-31

    Graphical abstract: -- Highlights: •We report a new electrochemical sensing protocol for the detection of mercury ion. •Gold amalgamation on DNA-based sensing platform was used as nanocatalyst. •The signal was amplified by cycling signal amplification strategy. -- Abstract: Heavy metal ion pollution poses severe risks in human health and environmental pollutant, because of the likelihood of bioaccumulation and toxicity. Driven by the requirement to monitor trace-level mercury ion (Hg{sup 2+}), herein we construct a new DNA-based sensor for sensitive electrochemical monitoring of Hg{sup 2+} by coupling target-induced formation of gold amalgamation on DNA-based sensing platform with gold amalgamation-catalyzed cycling signal amplification strategy. The sensor was simply prepared by covalent conjugation of aminated poly-T{sub (25)} oligonucleotide onto the glassy carbon electrode by typical carbodiimide coupling. Upon introduction of target analyte, Hg{sup 2+} ion was intercalated into the DNA polyion complex membrane based on T–Hg{sup 2+}–T coordination chemistry. The chelated Hg{sup 2+} ion could induce the formation of gold amalgamation, which could catalyze the p-nitrophenol with the aid of NaBH{sub 4} and Ru(NH{sub 3}){sub 6}{sup 3+} for cycling signal amplification. Experimental results indicated that the electronic signal of our system increased with the increasing Hg{sup 2+} level in the sample, and has a detection limit of 0.02 nM with a dynamic range of up to 1000 nM Hg{sup 2+}. The strategy afforded exquisite selectivity for Hg{sup 2+} against other environmentally related metal ions. In addition, the methodology was evaluated for the analysis of Hg{sup 2+} in spiked tap-water samples, and the recovery was 87.9–113.8%.

  6. Macrophage phagocytosis alters the MRI signal of ferumoxytol-labeled mesenchymal stromal cells in cartilage defects

    Science.gov (United States)

    Nejadnik, Hossein; Lenkov, Olga; Gassert, Florian; Fretwell, Deborah; Lam, Isaac; Daldrup-Link, Heike E.

    2016-05-01

    Human mesenchymal stem cells (hMSCs) are a promising tool for cartilage regeneration in arthritic joints. hMSC labeling with iron oxide nanoparticles enables non-invasive in vivo monitoring of transplanted cells in cartilage defects with MR imaging. Since graft failure leads to macrophage phagocytosis of apoptotic cells, we evaluated in vitro and in vivo whether nanoparticle-labeled hMSCs show distinct MR signal characteristics before and after phagocytosis by macrophages. We found that apoptotic nanoparticle-labeled hMSCs were phagocytosed by macrophages while viable nanoparticle-labeled hMSCs were not. Serial MRI scans of hMSC transplants in arthritic joints of recipient rats showed that the iron signal of apoptotic, nanoparticle-labeled hMSCs engulfed by macrophages disappeared faster compared to viable hMSCs. This corresponded to poor cartilage repair outcomes of the apoptotic hMSC transplants. Therefore, rapid decline of iron MRI signal at the transplant site can indicate cell death and predict incomplete defect repair weeks later. Currently, hMSC graft failure can be only diagnosed by lack of cartilage defect repair several months after cell transplantation. The described imaging signs can diagnose hMSC transplant failure more readily, which could enable timely re-interventions and avoid unnecessary follow up studies of lost transplants.

  7. A method to determine the necessity for global signal regression in resting-state fMRI studies.

    Science.gov (United States)

    Chen, Gang; Chen, Guangyu; Xie, Chunming; Ward, B Douglas; Li, Wenjun; Antuono, Piero; Li, Shi-Jiang

    2012-12-01

    In resting-state functional MRI studies, the global signal (operationally defined as the global average of resting-state functional MRI time courses) is often considered a nuisance effect and commonly removed in preprocessing. This global signal regression method can introduce artifacts, such as false anticorrelated resting-state networks in functional connectivity analyses. Therefore, the efficacy of this technique as a correction tool remains questionable. In this article, we establish that the accuracy of the estimated global signal is determined by the level of global noise (i.e., non-neural noise that has a global effect on the resting-state functional MRI signal). When the global noise level is low, the global signal resembles the resting-state functional MRI time courses of the largest cluster, but not those of the global noise. Using real data, we demonstrate that the global signal is strongly correlated with the default mode network components and has biological significance. These results call into question whether or not global signal regression should be applied. We introduce a method to quantify global noise levels. We show that a criteria for global signal regression can be found based on the method. By using the criteria, one can determine whether to include or exclude the global signal regression in minimizing errors in functional connectivity measures. Copyright © 2012 Wiley Periodicals, Inc.

  8. An experimental study on MRI signal intensity vs concentration of water-soluble contrast media

    International Nuclear Information System (INIS)

    Lee, Ghi Jai; Han, Chang Yul; Chang, Kee Hyun; Han, Moon Hee; Han, Man Chung

    1991-01-01

    There has been only one report that water-soluble contrast media containing iodine and used in conventional X -ray radiography reduce T1-and T2-relaxation times. We evaluated the relationship between signal intensity (relative signal intensity to normal saline) and T2-relaxation time of MRI and the concentration of 3 water-soluble contrast media [meglumine ioxithalamate (Telebrix 30), iopromide (Ultravist 300), iotrolan (Isovist 300)] through the phantom study, using both 2.0T and 0.5T MR units. We found that the signal intensity increased significantly on the T1-weighted images as the concentration of contrast media increased. The degree of the increase was larger on 0.5T MR than on 2.0T MR. The signal intensity on proton density image showed no significant difference at various concentrations. However, there were significant decreases of both signal intensity on the T2-weighted images and T2-relaxation time as the concentration of contrast media increased, which was more prominent on 2.0T MR than 0.5T MR. Between the contrast media of the same concentration, there was no significant difference in signal intensity and T2-relaxation time

  9. Aberrant paramagnetic signals outside the tumor volume on routine surveillance MRI of brain tumor patients.

    Science.gov (United States)

    Yust-Katz, Shlomit; Inbar, Edna; Michaeli, Natalia; Limon, Dror; Siegal, Tali

    2017-09-01

    Late complications of cerebral radiation therapy (RT) involve vascular injury with acquired cavernous malformation, telangiectasias and damage to vascular walls which are well recognized in children. Its incidence in adults is unknown. Blood products and iron deposition that accompany vascular injury create paramagnetic effects on MRI. This study retrospectively investigated the frequency of paramagnetic lesions on routine surveillance MRI of adult brain tumor patients. MRI studies of 115 brain tumor patients were reviewed. Only studies containing sequences of either susceptibility weighted images or gradient echo or blood oxygenation level dependent imaging were included. Lesions inside the tumor volume were not considered. 68 studies fulfilled the above criteria and included 48 patients with previous RT (35 followed for >2 years and 13 for 1 year) and 20 patients who were not treated with RT. The median age at time of irradiation was 47 years. Aberrant paramagnetic lesions were found in 23/35 (65%) patients followed for >2 years after RT and in only 1/13 (8%) patients followed for 1-year after radiation (p = 0.03). The 1-year follow-up group did not differ from the control group [2/20 (9%)]. Most lesions were within the radiation field and none of the patients had related symptomatology. The number and incidence of these lesions increased with time and amounted to 75% over 3 years post RT. MRI paramagnetic signal aberrations are common findings in adult brain tumor patients that evolve over time after RT. The clinical significance of these lesions needs further investigation.

  10. Hurst Exponent Analysis of Resting-State fMRI Signal Complexity across the Adult Lifespan

    Directory of Open Access Journals (Sweden)

    Jianxin Dong

    2018-02-01

    Full Text Available Exploring functional information among various brain regions across time enables understanding of healthy aging process and holds great promise for age-related brain disease diagnosis. This paper proposed a method to explore fractal complexity of the resting-state functional magnetic resonance imaging (rs-fMRI signal in the human brain across the adult lifespan using Hurst exponent (HE. We took advantage of the examined rs-fMRI data from 116 adults 19 to 85 years of age (44.3 ± 19.4 years, 49 females from NKI/Rockland sample. Region-wise and voxel-wise analyses were performed to investigate the effects of age, gender, and their interaction on complexity. In region-wise analysis, we found that the healthy aging is accompanied by a loss of complexity in frontal and parietal lobe and increased complexity in insula, limbic, and temporal lobe. Meanwhile, differences in HE between genders were found to be significant in parietal lobe (p = 0.04, corrected. However, there was no interaction between gender and age. In voxel-wise analysis, the significant complexity decrease with aging was found in frontal and parietal lobe, and complexity increase was found in insula, limbic lobe, occipital lobe, and temporal lobe with aging. Meanwhile, differences in HE between genders were found to be significant in frontal, parietal, and limbic lobe. Furthermore, we found age and sex interaction in right parahippocampal gyrus (p = 0.04, corrected. Our findings reveal HE variations of the rs-fMRI signal across the human adult lifespan and show that HE may serve as a new parameter to assess healthy aging process.

  11. Age dependence of spleen- and muscle-corrected hepatic signal enhancement on hepatobiliary phase gadoxetate MRI

    Energy Technology Data Exchange (ETDEWEB)

    Matoori, Simon [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Hirslanden Clinic St. Anna, Clinical Research Group, Lucerne (Switzerland); Froehlich, Johannes M. [Hirslanden Clinic St. Anna, Clinical Research Group, Lucerne (Switzerland); ETH Zurich, Department of Chemistry and Applied Biosciences, Institute of Pharmaceutical Sciences, Zurich (Switzerland); Cantonal Hospital Winterthur, Department of Radiology, Winterthur (Switzerland); Breitenstein, Stefan [Cantonal Hospital Winterthur, Department of Surgery, Clinic for Visceral and Thoracic Surgery, Winterthur (Switzerland); Doert, Aleksis [Cantonal Hospital Winterthur, Department of Radiology, Winterthur (Switzerland); Pozdniakova, Viktoria [Stavanger University Hospital, Department of Radiology, Stavanger (Norway); Koh, Dow-Mu [Royal Marsden Hospital, Department of Radiology, Surrey, England (United Kingdom); Gutzeit, Andreas [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Hirslanden Clinic St. Anna, Clinical Research Group, Lucerne (Switzerland); Cantonal Hospital Winterthur, Department of Radiology, Winterthur (Switzerland)

    2016-06-15

    To identify correlations of signal enhancements (SE) and SE normalized to reference tissues of the spleen, kidney, liver, musculus erector spinae (MES) and ductus hepatocholedochus (DHC) on hepatobiliary phase gadoxetate-enhanced MRI with patient age in non-cirrhotic patients. A heterogeneous cohort of 131 patients with different clinical backgrounds underwent a standardized 3.0-T gadoxetate-enhanced liver MRI between November 2008 and June 2013. After exclusion of cirrhotic patients, a cohort of 75 patients with no diagnosed diffuse liver disease was selected. The ratio of signal intensity 20 min post- to pre-contrast administration (SE) in the spleen, kidney, liver, MES and DHC, and the SE of the kidney, liver and DHC normalized to the reference tissues spleen or MES were compared to patient age. Patient age was inversely correlated with the liver SE normalized to the spleen and MES SE (both p < 0.001) and proportionally with the SE of the spleen (p = 0.043), the MES (p = 0.030) and the kidney (p = 0.022). No significant correlations were observed for the DHC (p = 0.347) and liver SE (p = 0.606). The age dependence of hepatic SE normalized to the enhancement in the spleen and MES calls for a cautious interpretation of these quantification methods. (orig.)

  12. Detecting Activation in fMRI Data: An Approach Based on Sparse Representation of BOLD Signal

    Directory of Open Access Journals (Sweden)

    Blanca Guillen

    2018-01-01

    Full Text Available This paper proposes a simple yet effective approach for detecting activated voxels in fMRI data by exploiting the inherent sparsity property of the BOLD signal in temporal and spatial domains. In the time domain, the approach combines the General Linear Model (GLM with a Least Absolute Deviation (LAD based regression method regularized by the pseudonorm l0 to promote sparsity in the parameter vector of the model. In the spatial domain, detection of activated regions is based on thresholding the spatial map of estimated parameters associated with a particular stimulus. The threshold is calculated by exploiting the sparseness of the BOLD signal in the spatial domain assuming a Laplacian distribution model. The proposed approach is validated using synthetic and real fMRI data. For synthetic data, results show that the proposed approach is able to detect most activated voxels without any false activation. For real data, the method is evaluated through comparison with the SPM software. Results indicate that this approach can effectively find activated regions that are similar to those found by SPM, but using a much simpler approach. This study may lead to the development of robust spatial approaches to further simplifying the complexity of classical schemes.

  13. Age dependence of spleen- and muscle-corrected hepatic signal enhancement on hepatobiliary phase gadoxetate MRI

    International Nuclear Information System (INIS)

    Matoori, Simon; Froehlich, Johannes M.; Breitenstein, Stefan; Doert, Aleksis; Pozdniakova, Viktoria; Koh, Dow-Mu; Gutzeit, Andreas

    2016-01-01

    To identify correlations of signal enhancements (SE) and SE normalized to reference tissues of the spleen, kidney, liver, musculus erector spinae (MES) and ductus hepatocholedochus (DHC) on hepatobiliary phase gadoxetate-enhanced MRI with patient age in non-cirrhotic patients. A heterogeneous cohort of 131 patients with different clinical backgrounds underwent a standardized 3.0-T gadoxetate-enhanced liver MRI between November 2008 and June 2013. After exclusion of cirrhotic patients, a cohort of 75 patients with no diagnosed diffuse liver disease was selected. The ratio of signal intensity 20 min post- to pre-contrast administration (SE) in the spleen, kidney, liver, MES and DHC, and the SE of the kidney, liver and DHC normalized to the reference tissues spleen or MES were compared to patient age. Patient age was inversely correlated with the liver SE normalized to the spleen and MES SE (both p < 0.001) and proportionally with the SE of the spleen (p = 0.043), the MES (p = 0.030) and the kidney (p = 0.022). No significant correlations were observed for the DHC (p = 0.347) and liver SE (p = 0.606). The age dependence of hepatic SE normalized to the enhancement in the spleen and MES calls for a cautious interpretation of these quantification methods. (orig.)

  14. Signal-inducing bone cements for MRI-guided spinal cementoplasty: evaluation of contrast-agent-based polymethylmethacrylate cements

    International Nuclear Information System (INIS)

    Bail, Hermann Josef; Tsitsilonis, Serafim; Wichlas, Florian; Sattig, Christoph; Papanikolaou, Ioannis; Teichgraeber, Ulf Karl Mart

    2012-01-01

    The purpose of this work is to evaluate two signal-inducing bone cements for MRI-guided spinal cementoplasty. The bone cements were made of polymethylmethacrylate (PMMA, 5 ml monomeric, 12 g polymeric) and gadoterate meglumine as a contrast agent (CA, 0-40 μl) with either saline solution (NaCl, 2-4 ml) or hydroxyapatite bone substitute (HA, 2-4 ml). The cement's signal was assessed in an open 1-Tesla MR scanner, with T1W TSE and fast interventional T1W TSE pulse sequences, and the ideal amount of each component was determined. The compressive and bending strength for different amounts of NaCl and HA were evaluated. The cement's MRI signal depended on the concentration of CA, the amount of NaCl or HA, and the pulse sequence. The signal peaks were recorded between 1 and 10 μl CA per ml NaCl or HA, and were higher in fast T1W TSE than in T1W TSE images. The NaCl-PMMA-CA cements had a greater MRI signal intensity and compressive strength; the HA-PMMA-CA cements had a superior bending strength. Concerning the MR signal and biomechanical properties, these cements would permit MRI-guided cementoplasty. Due to its higher signal and greater compressive strength, the NaCl-PMMA-CA compound appears to be superior to the HA-PMMA-CA compound. (orig.)

  15. Amplification of weak signals via the non-adiabatic regime of stochastic resonance in a bistable dynamical system with time delay

    International Nuclear Information System (INIS)

    Du Luchun; Mei Dongcheng

    2011-01-01

    The non-adiabatic regime of stochastic resonance (SR) in a bistable system with time delay, an additive white noise and a periodic signal was investigated. The signal power amplification η was employed to characterize the SR of the system. The simulation results indicate that (i) in the case of intermediate frequency Ω of the periodic signal, the typical behavior of SR is lowered monotonically by increasing the delay time τ; in the case of large Ω, τ weakens the SR behavior and then enhances it, with a non-monotonic behavior as a function of time delay; (ii) time delay induces SR when A is above the threshold, whereas no such resonance exists in the absence of time delay; (iii) time delay induces a transition from bimodal to unimodal configuration of η; (iv) varying the particular form of time delay results in different phenomena.

  16. Dual-cyclical nucleic acid strand-displacement polymerization based signal amplification system for highly sensitive determination of p53 gene.

    Science.gov (United States)

    Xu, Jianguo; Wu, Zai-Sheng; Li, Hongling; Wang, Zhenmeng; Le, Jingqing; Zheng, Tingting; Jia, Lee

    2016-12-15

    In the present study, we proposed a novel dual-cyclical nucleic acid strand-displacement polymerization (dual-CNDP) based signal amplification system for highly sensitive determination of tumor suppressor genes. The system primarily consisted of a signaling hairpin probe (SHP), a label-free hairpin probe (LHP) and an initiating primer (IP). The presence of target DNA was able to induce one CNDP through continuous process of ligation, polymerization and nicking, leading to extensively accumulation of two nicked triggers (NT1 and NT2). Intriguingly, the NT1 could directly hybridize SHP, while the NT2 could act as the target analog to induce another CNDP. The resulting dual-CNDP contributed the striking signal amplification, and only a very weak blank noise existed since the ligation template of target was not involved. In this case, the target could be detected in a wide linear range (5 orders of magnitude), and a low detection limit (78 fM) was obtained, which is superior to most of the existing fluorescent methods. Moreover, the dual-CNDP sensing system provided a high selectivity towards target DNA against mismatched target and was successfully applied to analysis of target gene extracted from cancer cells or in human serum-contained samples, indicating its great potential for practical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. A Dictionary Learning Approach for Signal Sampling in Task-Based fMRI for Reduction of Big Data.

    Science.gov (United States)

    Ge, Bao; Li, Xiang; Jiang, Xi; Sun, Yifei; Liu, Tianming

    2018-01-01

    The exponential growth of fMRI big data offers researchers an unprecedented opportunity to explore functional brain networks. However, this opportunity has not been fully explored yet due to the lack of effective and efficient tools for handling such fMRI big data. One major challenge is that computing capabilities still lag behind the growth of large-scale fMRI databases, e.g., it takes many days to perform dictionary learning and sparse coding of whole-brain fMRI data for an fMRI database of average size. Therefore, how to reduce the data size but without losing important information becomes a more and more pressing issue. To address this problem, we propose a signal sampling approach for significant fMRI data reduction before performing structurally-guided dictionary learning and sparse coding of whole brain's fMRI data. We compared the proposed structurally guided sampling method with no sampling, random sampling and uniform sampling schemes, and experiments on the Human Connectome Project (HCP) task fMRI data demonstrated that the proposed method can achieve more than 15 times speed-up without sacrificing the accuracy in identifying task-evoked functional brain networks.

  18. A Dictionary Learning Approach for Signal Sampling in Task-Based fMRI for Reduction of Big Data

    Science.gov (United States)

    Ge, Bao; Li, Xiang; Jiang, Xi; Sun, Yifei; Liu, Tianming

    2018-01-01

    The exponential growth of fMRI big data offers researchers an unprecedented opportunity to explore functional brain networks. However, this opportunity has not been fully explored yet due to the lack of effective and efficient tools for handling such fMRI big data. One major challenge is that computing capabilities still lag behind the growth of large-scale fMRI databases, e.g., it takes many days to perform dictionary learning and sparse coding of whole-brain fMRI data for an fMRI database of average size. Therefore, how to reduce the data size but without losing important information becomes a more and more pressing issue. To address this problem, we propose a signal sampling approach for significant fMRI data reduction before performing structurally-guided dictionary learning and sparse coding of whole brain's fMRI data. We compared the proposed structurally guided sampling method with no sampling, random sampling and uniform sampling schemes, and experiments on the Human Connectome Project (HCP) task fMRI data demonstrated that the proposed method can achieve more than 15 times speed-up without sacrificing the accuracy in identifying task-evoked functional brain networks. PMID:29706880

  19. Modelling cardiac signal as a confound in EEG-fMRI and its application in focal epilepsy studies

    DEFF Research Database (Denmark)

    Liston, A. D.; Ellegaard Lund, Torben; Salek-Haddadi, A

    2006-01-01

    effects to be modelled, as effects of no interest. Our model is based on an over-complete basis set covering a linear relationship between cardiac-related MR signal and the phase of the cardiac cycle or time after pulse (TAP). This method showed that, on average, 24.6 +/- 10.9% of grey matter voxels......Cardiac noise has been shown to reduce the sensitivity of functional Magnetic Resonance Imaging (fMRI) to an experimental effect due to its confounding presence in the blood oxygenation level-dependent (BOLD) signal. Its effect is most severe in particular regions of the brain and a method is yet...... to take it into account in routine fMRI analysis. This paper reports the development of a general and robust technique to improve the reliability of EEG-fMRI studies to BOLD signal correlated with interictal epileptiform discharges (IEDs). In these studies, ECG is routinely recorded, enabling cardiac...

  20. Time courses of MRI BOLD signals in prolonged visual stimulation. Comparison between colors and orders

    International Nuclear Information System (INIS)

    Kashikura, Kenichi; Fujita, Hideaki; Kershaw, J.B.; Matsuura, Tetsuya; Seki, Chie; Kashikura, Akemi; Ardekani, B.A.; Kanno, Iwao

    1998-01-01

    We investigated: the BOLD signal response during 270 second photic stimulation using an EPI pulse sequence; the BOLD signal response for two different color checkerboards; and the BOLD signal response during six consecutive stimulation series. Ten healthy human subjects (age 25±5.5 years) were studied with a 1.5 T MRI system (Siemens Vision, Erlangen, Germany). Black and white (BW) and red and white (RW) checkerboards alternating at 8 Hz were applied in turns for a total series of six. Stimulation timing was: 30 sec. off, 15 sec. on, 15 sec. off, 270 sec. on, 15 sec. off, 15 sec. on, 15 sec. off. Acquired data were analyzed according to color and/or order: color (without considering the order); color and order (1st BW vs. 1st RW, 2nd BW vs. 2nd RW, 3rd BW vs. 3rd RW); and order (without considering the color). A t-test (p<0.001) was used for obtaining the activated areas, and simple regression and two-way repeated-measures ANOVA were used for testing the statistical significance of the BOLD response. Results were: the BOLD signal responses during sustained photic stimulation maintained a constant level for the full duration and all series, suggesting stable levels of oxygen extraction and metabolism during cortical activation; the BOLD signal responses in two colors showed no significant difference in time response, suggesting that the neuronal populations perceiving black and red give a similar time response; and the effect of habituation or fatigue as observed by a signal decrease was not obtained, although the S.D. for each subject greatly increased with time and might be an indicator for evaluation fatigue or attention. (author)

  1. Parenchymal signal intensity in 3-T body MRI of dogs with hematopoietic neoplasia.

    Science.gov (United States)

    Feeney, Daniel A; Sharkey, Leslie C; Steward, Susan M; Bahr, Katherine L; Henson, Michael S; Ito, Daisuke; O'Brien, Timothy D; Jessen, Carl R; Husbands, Brian D; Borgatti, Antonella; Modiano, Jaime F

    2013-04-01

    We performed a preliminary study involving 10 dogs to assess the applicability of body MRI for staging of canine diffuse hematopoietic neoplasia. T1-weighted (before and after intravenous gadolinium), T2-weighted, in-phase, out-of-phase, and short tau inversion recovery pulse sequences were used. By using digital region of interest (ROI) and visual comparison techniques, relative parenchymal organ (medial iliac lymph nodes, liver, spleen, kidney cortex, and kidney medulla) signal intensity was quantified as less than, equal to, or greater than that of skeletal muscle in 2 clinically normal young adult dogs and 10 dogs affected with either B-cell lymphoma (n = 7) or myelodysplastic syndrome (n = 3). Falciform fat and urinary bladder were evaluated to provide additional perspective regarding signal intensity from the pulse sequences. Dogs with nonfocal disease could be distinguished from normal dogs according to both the visual and ROI signal-intensity relationships. In normal dogs, liver signal intensity on the T2-weighted sequence was greater than that of skeletal muscle by using either the visual or ROI approach. However in affected dogs, T2-weighted liver signal intensity was less than that of skeletal muscle by using either the ROI approach (10 of 10 dogs) or the visual approach (9 of 10 dogs). These findings suggest that the comparison of relative signal intensity among organs may have merit as a research model for infiltrative parenchymal disease (ROI approach) or metabolic effects of disease; this comparison may have practical clinical applicability (visual comparison approach) as well.

  2. Change in signal intensity on MRI of fat in the head of markedly emaciated patients

    International Nuclear Information System (INIS)

    Okamoto, K.; Ishikawa, K.; Sakai, K.

    2001-01-01

    The amount of fat in various parts of the body decreases in emaciated patients, but responds differently to disease processes. The order of disappearance of fat in various parts of the head has rarely been studied with MRI. We imaged ten patients with anorexia nervosa and one cachectic patient with a psychiatric disorder with a 1.5 T imager. Signal intensities of bone marrow of the skull, subcutaneous tissue, and orbits were assessed on T1- and T2-weighted images, and correlated with the body mass index (BMI) and haemoglobin concentration (Hb). On T1-weighted images, five patients (BMI 15.6-17.8 kg/m 2 , mean 16.6 kg/m 2 ; Hb 10.1-14.2 g/dl, mean 13.8 g/dl) showed the normal pattern of fat. One (BMI 13.6 kg/m 2 , Hb 10.4 g/dl) lost the high signal of bone marrow, but high signal of subcutaneous tissue and the orbits was preserved. High signal from bone marrow and subcutaneous tissue disappeared in three patients (BMI 11.5-13.5 kg/m 2 , mean 12.5 kg/m 2 ; Hb 7.9-9.7 g/dl, mean 8.7 g/dl), but orbital high signal was preserved. The remaining two patients (BMI 9.3 and 13.5 kg/m 2 , mean 11.5 kg/m 2 ; Hb 7.6 and 8.9 g/dl, mean 8.3 g/dl) showed complete loss of high signal from fat in the head. The order of disappearance of fat (bone marrow, subcutaneous fat, then orbits) correlated with both BMI and Hb. Atrophy of bone marrow was demonstrated on T2-weighted images in five patients with BMI 13.5 kg/m 2 or less, and Hb 9.7 g/dl or less. (orig.)

  3. Amygdala fMRI Signal as a Predictor of Reaction Time

    Directory of Open Access Journals (Sweden)

    Philipp Riedel

    2016-10-01

    Full Text Available Reaction times (RT are a valuable measure for assessing cognitive processes. However, RTs are susceptible to confounds and therefore variable. Exposure to threat, for example, speeds up or slows down responses. Distinct task types to some extent account for differential effects of threat on RTs. But also do inter-individual differences like trait anxiety. In this functional magnetic resonance imaging study, we investigated whether activation within the amygdala, a brain region closely linked to the processing of threat, may also function as a predictor of RTs, similar to trait anxiety scores. After threat conditioning by means of aversive electric shocks, 45 participants performed a choice RT task during alternating 30s blocks in the presence of the threat conditioned stimulus CS+ or of the safe control stimulus CS-. Trait anxiety was assessed with the State-Trait-Anxiety-Inventory and participants were median split into a high- and a low-anxiety subgroup. We tested three hypotheses: 1 RTs will be faster during the exposure to threat compared to the safe condition in individuals with high trait anxiety. 2 The amygdala fMRI signal will be higher in the threat condition compared to the safe condition. 3 Amygdala fMRI signal prior to a RT trial will be correlated with the corresponding RT. We found that, the high-anxious subgroup showed faster responses in the threat condition compared to the safe condition, while the low-anxious subgroup showed no significant difference in RTs in the threat condition compared to the safe condition. Though the fMRI analysis did not reveal an effect of condition on amygdala activity, we found a trial-by-trial correlation between blood-oxygen-level-dependent signal within the right amygdala prior to the CRT task and the subsequent RT. Taken together, the results of this study showed that: Exposure to threat modulates task performance. This modulation is influenced by personality trait. Additionally and most

  4. Free induction decay MR signal measurements toward ultra-low field MRI with an optically pumped atomic magnetometer.

    Science.gov (United States)

    Oida, Takenori; Kobayashi, Tetsuo

    2013-01-01

    Ultra-low field magnetic resonance imaging (ULF-MRI) has attracted attention because of its low running costs and minimum patient exposure. An optically pumped atomic magnetometer (OPAM) is a magnetic sensor with high sensitivity in the low frequency range, which does not require a cryogenic cooling system. In an effort to develop a ULF-MRI, we attempted to measure the free induction decay MR signals with an OPAM. We successfully detected the MR signals by combining an OPAM and a flux transformer, demonstrating the feasibility of the proposed system.

  5. Globus pallidus high-signal lesions: A predominant MRI finding in children with neurofibromatosis type 1

    Directory of Open Access Journals (Sweden)

    Arif Khan

    2013-01-01

    Full Text Available Introduction: Lesions of the brain, recognized as unidentified bright objects (UBOs, are commonly observed as areas of increased T2-weighted signal intensity on magnetic resonance imaging (MRI in children with neurofibromatosis type 1 (NF1. Identification of these lesions is not currently encompassed in the National Institute of Health (NIH diagnostic criteria for NF1. Objective: We aimed to determine the prevalence of UBOs in children with NF1 and identify areas of the brain that are commonly affected by these lesions, allowing us to evaluate whether UBOs should be included in the diagnostic criteria for the diagnosis of NF1. Materials and Methods: We reviewed the cranial MRI scans of 22 children who had been diagnosed with sporadic or familial NF1 in accordance with the criteria established by NIH. UBOs were present in 81% of the children with NF1. Results: These lesions have a predilection for specific areas of the brain, including the globus pallidus (72%, cerebellum (66%, brainstem (27% and cerebral hemispheres (16%. The prevalence of UBOs identified varied significantly with age and sex; they were infrequent in children less than 4 years of age but were common in those aged between 4 and 12 years of age. UBOs were more commonly seen in males (66.6% compared with females (33.3%. Repeat MRI scan on a subset of these patients with UBOs did not show any significant changes despite a worsening in clinical symptoms. Conclusion and Discussion: We have shown that UBOs are a common finding in children with NF1, and are most prevalent between the ages of 4 and 12 years. Many sites of the brain are affected by these lesions, most notably the globus pallidus and the cerebellum. Further research must be conducted to elucidate the significance of UBOs in patients with NF1 and whether these lesions have any utility in the clinical detection of NF1.

  6. Characteristics of seizure-induced signal changes on MRI in patients with first seizures.

    Science.gov (United States)

    Kim, Si Eun; Lee, Byung In; Shin, Kyong Jin; Ha, Sam Yeol; Park, JinSe; Park, Kang Min; Kim, Hyung Chan; Lee, Joonwon; Bae, Soo-Young; Lee, Dongah; Kim, Sung Eun

    2017-05-01

    The aim of this study was to investigate the predictive factors and identify the characteristics of the seizure-induced signal changes on MRI (SCM) in patients with first seizures. We conducted a retrospective study of patients with first seizures from March 2010 to August 2014. The inclusion criteria for this study were patients with 1) first seizures, and 2) MRI and EEG performed within 24h of the first seizures. The definition of SCM was hyper-intensities in the brain not applying to cerebral arterial territories. Multivariate logistic regression was performed with or without SCM as a dependent variable. Of 431 patients with seizures visiting the ER, 69 patients met the inclusion criteria. Of 69 patients, 11 patients (15.9%) had SCM. Epileptiform discharge on EEG (OR 29.7, 95% CI 1.79-493.37, p=0.018) was an independently significant variable predicting the presence of SCM in patients with first seizures. In addition, the topography of SCM was as follows; i) ipsilateral hippocampus, thalamus and cerebral cortex (5/11), ii) unilateral cortex (4/11), iii) ipsilateral thalamus and cerebral cortex (1/11), iv) bilateral hippocampus (1/11). Moreover, 6 out of 7 patients who underwent both perfusion CT and MRI exhibited unilateral cortical hyperperfusion with ipsilateral thalamic involvement reflecting unrestricted vascular territories. There is an association between epileptiform discharges and SCM. Additionally, the involvement of the unilateral cortex and ipsilateral thalamus in SCM and its hyperperfusion state could be helpful in differentiating the consequences of epileptic seizures from other pathologies. Copyright © 2017 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

  7. Exact algebraization of the signal equation of spoiled gradient echo MRI

    Energy Technology Data Exchange (ETDEWEB)

    Dathe, Henning [Department of Orthodontics, Biomechanics Group, University Medical Centre, Goettingen (Germany); Helms, Gunther, E-mail: ghelms@gwdg.d [MR-Research in Neurology and Psychiatry, University Medical Centre, Goettingen (Germany)

    2010-08-07

    The Ernst equation for Fourier transform nuclear magnetic resonance (MR) describes the spoiled steady-state signal created by periodic partial excitation. In MR imaging (MRI), it is commonly applied to spoiled gradient-echo acquisition in the steady state, created by a small flip angle {alpha} at a repetition time TR much shorter than the longitudinal relaxation time T{sub 1}. We describe two parameter transformations of {alpha} and TR/T{sub 1}, which render the Ernst equation as a low-order rational function. Computer algebra can be readily applied for analytically solving protocol optimization, as shown for the dual flip angle experiment. These transformations are based on the half-angle tangent substitution and its hyperbolic analogue. They are monotonic and approach identity for small {alpha} and small TR/T{sub 1} with a third-order error. Thus, the exact algebraization can be readily applied to fast gradient echo MRI to yield a rational approximation in {alpha} and TR/T{sub 1}. This reveals a fundamental relationship between the square of the flip angle and TR/T{sub 1} which characterizes the Ernst angle, constant degree of T{sub 1}-weighting and the influence of the local radio-frequency field.

  8. Nicking endonuclease-assisted signal amplification of a split molecular aptamer beacon for biomolecule detection using graphene oxide as a sensing platform.

    Science.gov (United States)

    Li, Xiang; Ding, Xuelian; Fan, Jing

    2015-12-07

    Sensitive and selective detection of ultralow concentrations of specific biomolecules is important in early clinical diagnoses and biomedical applications. Many types of aptasensors have been developed for the detection of various biomolecules, but usually suffer from false positive signals and high background signals. In this work, we have developed an amplified fluorescence aptasensor platform for ultrasensitive biomolecule detection based on enzyme-assisted target-recycling signal amplification and graphene oxide. By using a split molecular aptamer beacon and a nicking enzyme, the typical problem of false positive signals can be effectively resolved. Only in the presence of a target biomolecule, the sensor system is able to generate a positive signal, which significantly improves the selectivity of the aptasensor. Moreover, using graphene oxide as a super-quencher can effectively reduce the high background signal of a sensing platform. We select vascular endothelial growth factor (VEGF) and adenosine triphosphate (ATP) as model analytes in the current proof-of-concept experiments. It is shown that under optimized conditions, our strategy exhibits high sensitivity and selectivity for the quantification of VEGF and ATP with a low detection limit (1 pM and 4 nM, respectively). In addition, this biosensor has been successfully utilized in the analysis of real biological samples.

  9. Gold nanoparticles and the corresponding filter membrane as chemosensors and adsorbents for dual signal amplification detection and fast removal of mercury(ii).

    Science.gov (United States)

    Chen, Gaosong; Hai, Jun; Wang, Hao; Liu, Weisheng; Chen, Fengjuan; Wang, Baodui

    2017-03-02

    Nowadays, the development of a multifunction system for the simultaneous multiple signal amplification detection and fast removal of Hg 2+ remains a major challenge. Herein, we for the first time used gold nanoparticles (Au NPs) and the corresponding filter membrane as chemosensors and adsorbents for dual signal amplification detection and fast removal of Hg 2+ . Such a system was based on the formation of gold amalgam and a gold amalgam-based reaction between rhodamine B (RhB) and NaBH 4 with fluorescence and colorimetric sensing functions. When the gold amalgam catalyzes the reduction of RhB, the red color and orange fluorescence of RhB gradually changed to colorless by switching the amount of Hg 2+ deposited on 13 nm Au NPs. The detection limit of the fluorescence assay and colorimetric assay is 1.16 nM and 2.54 nM for Hg 2+ , respectively. Interestingly, the color and fluorescence of RhB could be recovered when the above colorless reaction solution was exposed to air for about 2 hours. Taking advantage of the above optical phenomenon, a recyclable paper-based sensor has been developed by immobilizing the Au NPs and RhB dye on filter paper and has been successfully used for detection of Hg 2+ in real water samples. In addition, the filter membrane immobilized Au NPs could allow fast removal of mercury ions in Yellow river water and tap water with the removal efficiency close to 99%.

  10. Correlation of BOLD Signal with Linear and Nonlinear Patterns of EEG in Resting State EEG-Informed fMRI

    Directory of Open Access Journals (Sweden)

    Galina V. Portnova

    2018-01-01

    Full Text Available Concurrent EEG and fMRI acquisitions in resting state showed a correlation between EEG power in various bands and spontaneous BOLD fluctuations. However, there is a lack of data on how changes in the complexity of brain dynamics derived from EEG reflect variations in the BOLD signal. The purpose of our study was to correlate both spectral patterns, as linear features of EEG rhythms, and nonlinear EEG dynamic complexity with neuronal activity obtained by fMRI. We examined the relationships between EEG patterns and brain activation obtained by simultaneous EEG-fMRI during the resting state condition in 25 healthy right-handed adult volunteers. Using EEG-derived regressors, we demonstrated a substantial correlation of BOLD signal changes with linear and nonlinear features of EEG. We found the most significant positive correlation of fMRI signal with delta spectral power. Beta and alpha spectral features had no reliable effect on BOLD fluctuation. However, dynamic changes of alpha peak frequency exhibited a significant association with BOLD signal increase in right-hemisphere areas. Additionally, EEG dynamic complexity as measured by the HFD of the 2–20 Hz EEG frequency range significantly correlated with the activation of cortical and subcortical limbic system areas. Our results indicate that both spectral features of EEG frequency bands and nonlinear dynamic properties of spontaneous EEG are strongly associated with fluctuations of the BOLD signal during the resting state condition.

  11. MRI signal changes of the bone marrow in HIV-infected patients with lipodystrophy: correlation with clinical parameters

    International Nuclear Information System (INIS)

    Garcia, Ana I.; Tomas, Xavier; Pomes, Jaume; Amo, Montserrat del; Milinkovic, Ana; Perez, Inaki; Mallolas, Josep; Rios, Jose; Vidal-Sicart, Sergi

    2011-01-01

    To assess the prevalence, imaging appearance, and clinical significance, of bone marrow MR signal changes in a group of human immunodeficiency virus (HIV)-infected patients with lipodystrophy syndrome. Twenty-eight HIV-infected patients with lipodystrophy syndrome treated with highly active antiretroviral therapy, and 12 HIV-negative controls underwent MRI of the legs. Whole-body MRI, SPECT/CT, and a complete radiographic skeletal survey were obtained in subjects with signal changes in bone marrow. MRI and clinical evaluations were reviewed 6 months after baseline to determine changes after switching from thymidine analogs (TA) to tenofovir-DF (TDF). MRI results correlated with clinical parameters. We observed foci of a serous-like pattern (low signal and no enhancement on T1-weighted, high signal on T2-weighted images) in 4 out of 28 patients (14.3%) and an intermediate signal on T1-weighted images in 4 out of 28 patients (14.3%). Serous-like lesions were located in the lower limbs and scattered in the talus, calcaneus, femurs, and humeral bones; they showed slight uptake on SPECT bone scans and were normal on CT and radiographs. Patients with serous-like lesions had significantly lower peripheral and total fat at baseline than other groups (P < 0.05). No changes at 6 months were observed on MRI, and the serous-like lesion group showed good peripheral fat recovery after changing drug treatment. A serous-like MRI pattern is observed in the peripheral skeletons of HIV-infected patients with lipodystrophy, which correlates with peripheral lipoatrophy, and should not be misdiagnosed as malignant or infectious diseases. Although the MR lesions did not improve after switching the treatment, there was evidence of lipoatrophy recovery. (orig.)

  12. WE-DE-206-01: MRI Signal in Biological Tissues - Proton, Spin, T1, T2, T2*

    Energy Technology Data Exchange (ETDEWEB)

    Gorny, K. [Mayo Clinic (United States)

    2016-06-15

    Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation. This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner, and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner. Learning Objectives: Understand the origin of the MR signal and contrast from the spin physics level. Understand the main hardware components of a MRI scanner and their purposes Understand steps for MR image formation including spatial encoding and image reconstruction Understand the main kinds of MR pulse sequences and their characteristics.

  13. Modelling Cardiac Signal as a Confound in EEG-fMRI and its Application in Focal Epilepsy

    DEFF Research Database (Denmark)

    Liston, Adam David; Salek-Haddadi, Afraim; Hamandi, Khalid

    2005-01-01

    Cardiac noise has been shown to reduce the sensitivity of functional Magnetic Resonance Imaging (fMRI) to an experimental effect due to its confounding presence in the blood oxygenation level-dependent (BOLD) signal. Its effect is most severe in particular regions of the brain and a method is yet...

  14. Space-dependent effects of motion on the standard deviation of fMRI signals : a simulation study.

    NARCIS (Netherlands)

    Renken, R; Muresan, L; Duifhuis, H; Roerdink, JBTM; Yaffe, MK; Antonuk, LE

    2003-01-01

    In fMRI, any fluctuation of signal intensity, not recognized as a result of a specific task, is treated as noise. One source for "noise" is subject motion. Normally, motion effects are reduced by applying realignment. We investigate how apt a realignment procedure is in removing motion-related

  15. Synthesis of Intrinsically Disordered Fluorinated Peptides for Modular Design of High-Signal 19 F MRI Agents.

    Science.gov (United States)

    Kirberger, Steven E; Maltseva, Sofia D; Manulik, Joseph C; Einstein, Samuel A; Weegman, Bradley P; Garwood, Michael; Pomerantz, William C K

    2017-06-01

    19 F MRI is valuable for in vivo imaging due to the only trace amounts of fluorine in biological systems. Because of the low sensitivity of MRI however, designing new fluorochemicals remains a significant challenge for achieving sufficient 19 F signal. Here, we describe a new class of high-signal, water-soluble fluorochemicals as 19 F MRI imaging agents. A polyamide backbone is used for tuning the proteolytic stability to avoid retention within the body, which is a limitation of current state-of-the-art perfluorochemicals. We show that unstructured peptides containing alternating N-ϵ-trifluoroacetyllysine and lysine provide a degenerate 19 F NMR signal. 19 F MRI phantom images provide sufficient contrast at micromolar concentrations, showing promise for eventual clinical applications. Finally, the degenerate high signal characteristics were retained when conjugated to a large protein, indicating potential for in vivo targeting applications, including molecular imaging and cell tracking. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. A sensitive electrochemical aptasensor based on palladium nanoparticles decorated graphene–molybdenum disulfide flower-like nanocomposites and enzymatic signal amplification

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Pei; Yi, Huayu; Xue, Shuyan; Chai, Yaqin; Yuan, Ruo; Xu, Wenju, E-mail: xwju@swu.edu.cn

    2015-01-01

    Highlights: • PDDA–G–MoS{sub 2} nanoflowers were firstly used for the fabrication of thrombin aptasensor. • MoS{sub 2} was adopted to enhance the surface area of graphene and accelerate the electron transfer. • GOD, PdNPs and hemin/G-quadruplex could amplify the electrochemical signal through synergetic catalysis. • The proposed aptasensor displayed an improved sensitivity. - Abstract: In the present study, with the aggregated advantages of graphene and molybdenum disulfide (MoS{sub 2}), we prepared poly(diallyldimethylammonium chloride)–graphene/molybdenum disulfide (PDDA–G–MoS{sub 2}) nanocomposites with flower-like structure, large surface area and excellent conductivity. Furthermore, an advanced sandwich-type electrochemical assay for sensitive detection of thrombin (TB) was fabricated using palladium nanoparticles decorated PDDA–G–MoS{sub 2} (PdNPs/PDDA–G–MoS{sub 2}) as nanocarriers, which were functionalized by hemin/G-quadruplex, glucose oxidase (GOD), and toluidine blue (Tb) as redox probes. The signal amplification strategy was achieved as follows: Firstly, the immobilized GOD could effectively catalyze the oxidation of glucose to gluconolactone, coupling with the reduction of the dissolved oxygen to H{sub 2}O{sub 2}. Then, both PdNPs and hemin/G-quadruplex acting as hydrogen peroxide (HRP)-mimicking enzyme could further catalyze the reduction of H{sub 2}O{sub 2}, resulting in significant electrochemical signal amplification. So the proposed aptasensor showed high sensitivity with a wide dynamic linear range of 0.0001 to 40 nM and a relatively low detection limit of 0.062 pM for TB determination. The strategy showed huge potential of application in protein detection and disease diagnosis.

  17. Target-induced formation of gold amalgamation on DNA-based sensing platform for electrochemical monitoring of mercury ion coupling with cycling signal amplification strategy.

    Science.gov (United States)

    Chen, Jinfeng; Tang, Juan; Zhou, Jun; Zhang, Lan; Chen, Guonan; Tang, Dianping

    2014-01-31

    Heavy metal ion pollution poses severe risks in human health and environmental pollutant, because of the likelihood of bioaccumulation and toxicity. Driven by the requirement to monitor trace-level mercury ion (Hg(2+)), herein we construct a new DNA-based sensor for sensitive electrochemical monitoring of Hg(2+) by coupling target-induced formation of gold amalgamation on DNA-based sensing platform with gold amalgamation-catalyzed cycling signal amplification strategy. The sensor was simply prepared by covalent conjugation of aminated poly-T(25) oligonucleotide onto the glassy carbon electrode by typical carbodiimide coupling. Upon introduction of target analyte, Hg(2+) ion was intercalated into the DNA polyion complex membrane based on T-Hg(2+)-T coordination chemistry. The chelated Hg(2+) ion could induce the formation of gold amalgamation, which could catalyze the p-nitrophenol with the aid of NaBH4 and Ru(NH3)6(3+) for cycling signal amplification. Experimental results indicated that the electronic signal of our system increased with the increasing Hg(2+) level in the sample, and has a detection limit of 0.02nM with a dynamic range of up to 1000nM Hg(2+). The strategy afforded exquisite selectivity for Hg(2+) against other environmentally related metal ions. In addition, the methodology was evaluated for the analysis of Hg(2+) in spiked tap-water samples, and the recovery was 87.9-113.8%. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Change in signal intensity on MRI of fat in the head of markedly emaciated patients

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, K.; Ishikawa, K.; Sakai, K. [Niigata Univ. (Japan). Dept. of Radiology; Ito, J.; Tokiguchi, S. [Dept. of Radiology, Niigata Univ. (Japan)

    2001-02-01

    The amount of fat in various parts of the body decreases in emaciated patients, but responds differently to disease processes. The order of disappearance of fat in various parts of the head has rarely been studied with MRI. We imaged ten patients with anorexia nervosa and one cachectic patient with a psychiatric disorder with a 1.5 T imager. Signal intensities of bone marrow of the skull, subcutaneous tissue, and orbits were assessed on T1- and T2-weighted images, and correlated with the body mass index (BMI) and haemoglobin concentration (Hb). On T1-weighted images, five patients (BMI 15.6-17.8 kg/m{sup 2}, mean 16.6 kg/m{sup 2}; Hb 10.1-14.2 g/dl, mean 13.8 g/dl) showed the normal pattern of fat. One (BMI 13.6 kg/m{sup 2}, Hb 10.4 g/dl) lost the high signal of bone marrow, but high signal of subcutaneous tissue and the orbits was preserved. High signal from bone marrow and subcutaneous tissue disappeared in three patients (BMI 11.5-13.5 kg/m{sup 2}, mean 12.5 kg/m{sup 2}; Hb 7.9-9.7 g/dl, mean 8.7 g/dl), but orbital high signal was preserved. The remaining two patients (BMI 9.3 and 13.5 kg/m{sup 2}, mean 11.5 kg/m{sup 2}; Hb 7.6 and 8.9 g/dl, mean 8.3 g/dl) showed complete loss of high signal from fat in the head. The order of disappearance of fat (bone marrow, subcutaneous fat, then orbits) correlated with both BMI and Hb. Atrophy of bone marrow was demonstrated on T2-weighted images in five patients with BMI 13.5 kg/m{sup 2} or less, and Hb 9.7 g/dl or less. (orig.)

  19. Broadband Amplification of Low-Terahertz Signals Using Axis-Encircling Electrons in a Helically Corrugated Interaction Region

    Science.gov (United States)

    He, W.; Donaldson, C. R.; Zhang, L.; Ronald, K.; Phelps, A. D. R.; Cross, A. W.

    2017-11-01

    Experimental results are presented of a broadband, high power, gyrotron traveling wave amplifier (gyro-TWA) operating in the (75-110)-GHz frequency band and based on a helically corrugated interaction region. The second harmonic cyclotron mode of a 55-keV, 1.5-A, axis-encircling electron beam is used to resonantly interact with a traveling TE21 -like eigenwave achieving broadband amplification. The gyro-TWA demonstrates a 3-dB gain bandwidth of at least 5.5 GHz in the experimental measurement with 9 GHz predicted for a wideband drive source with a measured unsaturated output power of 3.4 kW and gain of 36-38 dB. The approach may allow a gyro-TWA to operate at 1 THz.

  20. Porous platinum nanotubes labeled with hemin/G-quadruplex based electrochemical aptasensor for sensitive thrombin analysis via the cascade signal amplification.

    Science.gov (United States)

    Sun, Aili; Qi, Qingan; Wang, Xuannian; Bie, Ping

    2014-07-15

    For the first time, a sensitive electrochemical aptasensor for thrombin (TB) was developed by using porous platinum nanotubes (PtNTs) labeled with hemin/G-quadruplex and glucose dehydrogenase (GDH) as labels. Porous PtNTs with large surface area exhibited the peroxidase-like activity. Coupling with GDH and hemin/G-quadruplex as NADH oxidase and HRP-mimicking DNAzyme, the cascade signal amplification was achieved by the following ways: in the presence of glucose and NAD(+) in the working buffer, GDH electrocatalyzed the oxidation of glucose with the production of NADH. Then, hemin/G-quadruplex as NADH oxidase catalyzed the oxidation of NADH to in situ generate H2O2. Based on the corporate electrocatalysis of PtNTs and hemin/G-quadruplex toward H2O2, the electrochemical signal was significantly amplified, allowing the detection limit of TB down to 0.15 pM level. Moreover, the proposed strategy was simple because the intercalated hemin offered the readout signal, avoiding the adding of additional redox mediator as signal donator. Such an electrochemical aptasensor is highly promising for sensitive detection of other proteins in clinical diagnostics. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. T2 hyperintense signal in patients with temporal lobe epilepsy with MRI signs of hippocampal sclerosis and in patients with temporal lobe epilepsy with normal MRI.

    Science.gov (United States)

    Kubota, Bruno Yukio; Coan, Ana Carolina; Yasuda, Clarissa Lin; Cendes, Fernando

    2015-05-01

    Increased MRI T2 signal is commonly present not only in the hippocampus but also in other temporal structures of patients with temporal lobe epilepsy (TLE), and it is associated with histological abnormalities related to the epileptogenic lesion. This study aimed to verify the distribution of T2 increased signal in temporal lobe structures and its correlations with clinical characteristics of TLE patients with (TLE-HS) or without (TLE-NL) MRI signs of hippocampal sclerosis. We selected 203 consecutive patients: 124 with TLE-HS and 79 with TLE-NL. Healthy controls (N=59) were used as a comparison group/comparative group. T2 multiecho images obtained via a 3-T MRI were evaluated with in-house software. T2 signal decays were computed from five original echoes in regions of interest in the hippocampus, amygdala, and white matter of the anterior temporal lobe. Values higher than 2 standard deviations from the mean of controls were considered as abnormal. T2 signal increase was observed in the hippocampus in 78% of patients with TLE-HS and in 17% of patients with TLE-NL; in the amygdala in 13% of patients with TLE-HS and in 14% of patients with TLE-NL; and in the temporal lobe white matter in 22% of patients with TLE-HS and in 8% of patients with TLE-NL. Group analysis demonstrated a significant difference in the distribution of the T2 relaxation times of the hippocampus (ANOVA, ptemporal lobe white matter (ptemporal lobe white matter (ANOVA, p=0.025) for patients with TLE-NL compared with controls. The average signal from the hippocampus ipsilateral to the epileptogenic zone was significantly higher in patients with no family history of epilepsy (two-sample T-test, p=0.005). Increased T2 signal occurs in different temporal structures of patients with TLE-HS and in patients with TLE-NL. The hippocampal hyperintense signal is more pronounced in patients without family history of epilepsy and is influenced by earlier seizure onset. These changes in T2 signal may be

  2. Direct RNA detection without nucleic acid purification and PCR: Combining sandwich hybridization with signal amplification based on branched hybridization chain reaction.

    Science.gov (United States)

    Xu, Yao; Zheng, Zhi

    2016-05-15

    We have developed a convenient, robust and low-cost RNA detection system suitable for high-throughput applications. This system uses a highly specific sandwich hybridization to capture target RNA directly onto solid support, followed by on-site signal amplification via 2-dimensional, branched hybridizing chain polymerization through toehold-mediated strand displacement reaction. The assay uses SYBR Green to detect targets at concentrations as low as 1 pM, without involving nucleic acid purification or any enzymatic reaction, using ordinary oligonucleotides without modification or labeling. The system was demonstrated in the detection of malaria RNA in blood and GAPDH gene expression in cell lysate. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. KSHV cell attachment sites revealed by ultra sensitive tyramide signal amplification (TSA) localize to membrane microdomains that are up-regulated on mitotic cells.

    Science.gov (United States)

    Garrigues, H Jacques; Rubinchikova, Yelena E; Rose, Timothy M

    2014-03-01

    Cell surface structures initiating attachment of Kaposi's sarcoma-associated herpesvirus (KSHV) were characterized using purified hapten-labeled virions visualized by confocal microscopy with a sensitive fluorescent enhancement using tyramide signal amplification (TSA). KSHV attachment sites were present in specific cellular domains, including actin-based filopodia, lamellipodia, ruffled membranes, microvilli and intercellular junctions. Isolated microdomains were identified on the dorsal surface, which were heterogeneous in size with a variable distribution that depended on cellular confluence and cell cycle stage. KSHV binding domains ranged from scarce on interphase cells to dense and continuous on mitotic cells, and quantitation of bound virus revealed a significant increase on mitotic compared to interphase cells. KSHV also bound to a supranuclear domain that was distinct from microdomains in confluent and interphase cells. These results suggest that rearrangement of the cellular membrane during mitosis induces changes in cell surface receptors implicated in the initial attachment stage of KSHV entry. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Photoelectrochemical sensitive detection of insulin based on CdS/polydopamine co-sensitized WO3 nanorod and signal amplification of carbon nanotubes@polydopamine.

    Science.gov (United States)

    Wang, Rongyu; Ma, Hongmin; Zhang, Yong; Wang, Qi; Yang, Zhongping; Du, Bin; Wu, Dan; Wei, Qin

    2017-10-15

    An ultrasensitive photoelectrochemical sandwich immunosensor was designed for detection of insulin based on WO 3 /CdS/polydopamine (WO 3 /CdS/PDA) co-sensitized and PDA@carbon nanotubes (PDA@CNT) conjugates for signal amplification. The CdS nanoparticles were first deposited on the WO 3 nanorods via sequential chemical bath deposition to form the WO 3 /CdS structure to enhance photocurrent. Then equipped with PDA to form the WO 3 /CdS/PDA photosensitive structure. The PDA was used not only to reduce the toxicity of CdS but also adsorb insulin primary antibodies (Ab 1 ). Meanwhile, insulin secondary antibodies (Ab 2 ) were decorated by PDA@CNT conjugates for signal amplification and further enhance photocurrent. Different photocurrent intensities were obtained by the photoelectrochemical workstation at applied bias of 0V due to the different amount of the PDA@CNT conjugates introduced by the different concentrations of insulin. A good linear relationship was obtained between the increased photocurrent and insulin concentrations range from 0.01ngmL -1 to 50ngmL -1 . And a detection limit of 2.8pgmL -1 was obtained. The proposed sensor was applied to the determination of the insulin in human serum sample, and satisfactory results were obtained. The sensor presented good specificity, reproducibility and stability, thus it might find application in the clinical diagnosis of insulin or other biomarkers in the near future. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Sensitive and fast detection of fructose in complex media via symmetry breaking and signal amplification using surface-enhanced Raman spectroscopy.

    Science.gov (United States)

    Sun, Fang; Bai, Tao; Zhang, Lei; Ella-Menye, Jean-Rene; Liu, Sijun; Nowinski, Ann K; Jiang, Shaoyi; Yu, Qiuming

    2014-03-04

    A new strategy is proposed to sensitively and rapidly detect analytes with weak Raman signals in complex media using surface-enhanced Raman spectroscopy (SERS) via detecting the SERS signal changes of the immobilized probe molecules on SERS-active substrates upon binding of the analytes. In this work, 4-mercaptophenylboronic acid (4-MPBA) was selected as the probe molecule which was immobilized on the gold surface of a quasi-three-dimensional plasmonic nanostructure array (Q3D-PNA) SERS substrate to detect fructose. The molecule of 4-MPBA possesses three key functions: molecule recognition and reversible binding of the analyte via the boronic acid group, amplification of SERS signals by the phenyl group and thus shielding of the background noise of complex media, and immobilization on the surface of SERS-active substrates via the thiol group. Most importantly, the symmetry breaking of the 4-MPBA molecule upon fructose binding leads to the change of area ratio between totally symmetric 8a ring mode and nontotally symmetric 8b ring mode, which enables the detection. The detection curves were obtained in phosphate-buffered saline (PBS) and in undiluted artificial urine at clinically relevant concentrations, and the limit of detection of 0.05 mM was achieved.

  6. Recovering task fMRI signals from highly under-sampled data with low-rank and temporal subspace constraints.

    Science.gov (United States)

    Chiew, Mark; Graedel, Nadine N; Miller, Karla L

    2018-07-01

    Recent developments in highly accelerated fMRI data acquisition have employed low-rank and/or sparsity constraints for image reconstruction, as an alternative to conventional, time-independent parallel imaging. When under-sampling factors are high or the signals of interest are low-variance, however, functional data recovery can be poor or incomplete. We introduce a method for improving reconstruction fidelity using external constraints, like an experimental design matrix, to partially orient the estimated fMRI temporal subspace. Combining these external constraints with low-rank constraints introduces a new image reconstruction model that is analogous to using a mixture of subspace-decomposition (PCA/ICA) and regression (GLM) models in fMRI analysis. We show that this approach improves fMRI reconstruction quality in simulations and experimental data, focusing on the model problem of detecting subtle 1-s latency shifts between brain regions in a block-design task-fMRI experiment. Successful latency discrimination is shown at acceleration factors up to R = 16 in a radial-Cartesian acquisition. We show that this approach works with approximate, or not perfectly informative constraints, where the derived benefit is commensurate with the information content contained in the constraints. The proposed method extends low-rank approximation methods for under-sampled fMRI data acquisition by leveraging knowledge of expected task-based variance in the data, enabling improvements in the speed and efficiency of fMRI data acquisition without the loss of subtle features. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  7. Amplification of the Signal Intensity of Fluorescence-Based Fiber-Optic Biosensors Using a Fabry-Perot Resonator Structure

    Directory of Open Access Journals (Sweden)

    Meng-Chang Hsieh

    2015-02-01

    Full Text Available Fluorescent biosensors have been widely used in biomedical applications. To amplify the intensity of fluorescence signals, this study developed a novel structure for an evanescent wave fiber-optic biosensor by using a Fabry-Perot resonator structure. An excitation light was coupled into the optical fiber through a laser-drilled hole on the proximal end of the resonator. After entering the resonator, the excitation light was reflected back and forth inside the resonator, thereby amplifying the intensity of the light in the fiber. Subsequently, the light was used to excite the fluorescent molecules in the reactive region of the sensor. The experimental results showed that the biosensor signal was amplified eight-fold when the resonator reflector was formed using a 92% reflective coating. Furthermore, in a simulation, the biosensor signal could be amplified 20-fold by using a 99% reflector.

  8. The study of amplification circuit characteristics of photocurrent signal of high-energy industrial CT detection system

    International Nuclear Information System (INIS)

    Wang Jue; Tan Hui; Wang Xin; Chen Jiaoze

    2011-01-01

    According to characteristics of the Photocurrent signal from detection system of high energy industrial CT, sets up the integral amplifier circuit test platform based ACF2101, through the study of this amplifier circuit, a integral capacitor using air as dielectric is proposed in order to get high-gain. After experimental tests, results are good. (authors)

  9. Amplification of R-spondin1 signaling induces granulosa cell fate defects and cancers in mouse adult ovary

    NARCIS (Netherlands)

    De Cian, M-C; Pauper, E.; Bandiera, R.; Vidal, V. P. I.; Sacco, S.; Gregoire, E. P.; Chassot, A-A; Panzolini, C.; WILHELM, D; Pailhoux, E.; Youssef, Sameh A.; de Bruin, A.; Teerds, K.; Schedl, A.; Gillot, I.; Chaboissier, M-C

    2017-01-01

    R-spondin1 is a secreted regulator of WNT signaling, involved in both embryonic development and homeostasis of adult organs. It can have a dual role, acting either as a mitogen or as a tumor suppressor. During ovarian development, Rspo1 is a key factor required for sex determination and

  10. Phase-encoded MRI for geometrically undistorted imaging and signal characterization

    NARCIS (Netherlands)

    van Gorp, JS

    2016-01-01

    Magnetic resonance imaging (MRI) is a versatile diagnostic modality that has earned its place in clinical practice all over the world. MRI delivers excellent soft-tissue contrast that can be utilized to detect disease and measure physiological properties in a non-invasive manner. As long as the main

  11. A label-free electrochemical immunosensor based on the novel signal amplification system of AuPdCu ternary nanoparticles functionalized polymer nanospheres.

    Science.gov (United States)

    Yan, Qin; Yang, Yuying; Tan, Zhaoling; Liu, Qing; Liu, Hui; Wang, Ping; Chen, Lei; Zhang, Daopeng; Li, Yueyun; Dong, Yunhui

    2018-04-30

    A sensitive label-free electrochemical immunosensor was designed using a novel signal amplification system for quantitative detecting hepatitis B surface antigen (HBsAg). Nitrogen-doped graphene quantum dots (N-GQDs) supported surfactant-free AuPdCu ternary nanoparticles (AuPdCu/N-GQDs), which featured with good conductivity and excellent catalytic properties for the reduction of hydrogen peroxide (H 2 O 2 ), was synthesized by a simple and benign hydrothermal procedure. At the same time, the electroactive polymer nanospheres (PS) was synthesized by infinite coordination polymers of ferrocenedicarboxylic acid, which could play as carrier and electronic mediator to load AuPdCu/N-GQDs. The PS not only improved the ability to load antibodies because of the good biocompatibility, but also accelerated electron transport of the electrode interface attribute to plentiful ferrocene unit. Thus, the prepared AuPdCu/N-GQDs@PS has abilities of good biocompatibility, catalytic activity and electrical conductivity to be applied as transducing materials to amplify electrochemical signal in detection of HBsAg. Under optimal conditions, the fabricated immunosensor exhibited high sensitivity and stability in the detection of HBsAg. A linear relationship between current signals and the concentrations of HBsAg was obtained in the range from 10fg/mL to 50ng/mL and the detection limit of HBsAg was 3.3fg/mL (signal-to-noise ratio of 3). Moreover, the designed immunosensor with excellent selectivity, reproducibility and stability shows excellent performance in detection of human serum samples. Furthermore, this label-free electrochemical immunosensor has promising application in clinical diagnosis of HBsAg. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Magnetic Particle-Based Immunoassay of Phosphorylated p53 Using Protein-Cage Templated Lead Phosphate and Carbon Nanospheres for Signal Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Aiqiong; Bao, Yuanwu; Ge, Xiaoxiao; Shin, Yongsoon; Du, Dan; Lin, Yuehe

    2012-11-20

    Phosphorylated p53 at serin 15 (phospho-p53-15) is a potential biomarker of Gamma-radiation exposure. In this paper, we described a new magnetic particles (MPs)-based electrochemical immunoassay of human phospho-p53-15 using carbon nanospheres (CNS) and protein-cage templated lead phosphate nanoparticles for signal amplification. Greatly enhanced sensitivity was achieved by three aspects: 1) The protein-cage nanoparticle (PCN) and p53-15 signal antibody (p53-15 Ab2) are linked to CNS (PCNof each apoferritin; 3) MPs capture a large amount of primary antibodies. Using apoferritin templated metallic phosphate instead of enzyme as label has the advantage of eliminating the addition of mediator or immunoreagents and thus makes the immunoassay system simpler. The subsequent stripping voltammetric analysis of the released lead ions were detected on a disposable screen printed electrode. The response current was proportional to the phospho-p53-15 concentration in the range of 0.02 to 20 ng mL-1 with detection limit of 0.01 ng mL-1. This method shows a good stability, reproducibility and recovery.

  13. Gold nanoparticle labeling with tyramide signal amplification for highly sensitive detection of alpha fetoprotein in human serum by ICP-MS.

    Science.gov (United States)

    Li, Xiaoting; Chen, Beibei; He, Man; Xiao, Guangyang; Hu, Bin

    2018-01-01

    In this work, we developed an immunoassay based on tyramide signal amplification (TSA) and gold nanoparticles (Au NPs) labeling for highly sensitive detection of alpha fetoprotein (AFP) by inductively coupled plasma mass spectrometry (ICP-MS). AFP was captured by anti-AFP1 coating on the 96-well plate and labeled by anti-AFP2-horseradish peroxidase (HRP), in which the HRP can catalyze the deposition of biotinylated tyramine on the nearby protein. Then the streptavidin (SA)-Au NPs was labeled on the deposited biotinylated tyramine as the intensive signal probe for ICP-MS measurement. Under the optimal experimental conditions, the limit of detection of the developed method for AFP was 1.85pg/mL and the linear range was 0.005-2ng/mL. The relative standard deviation for seven replicate detections of 0.01ng/mL AFP was 5.2%. The proposed method was successfully applied to the detection of AFP in human serum with good recoveries. This strategy is highly sensitive and easy to operate, and can be extended to the sensitive detection of other biomolecules in human serum. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Amplification of a bi-phase shift-key modulated signal by a mm-wave FEL

    International Nuclear Information System (INIS)

    Prosnitz, D.; Scharlemann, E.T.; Sheaffer, M.K.

    1991-10-01

    Bi-phase shift keying (BPSK) is a modulation scheme used in communications and radar in which the phase of a transmitted rf signal is switched in a coded pattern between discrete values differing by π radians. The transmitted information rate (in communications) or resolution (in imaging radar) depends on the rate at which the transmitted signal can be modulated. Modulation rates of greater than 1 GHz are generally desired. Although the instantaneous gain bandwidth of a mm-wave FEL amplifier can be much greater than 10 GHz, slippage may limit the BPSK modulation rate that can be amplified. Qualitative slippage arguments would limit the modulation rate to relatively low values; nevertheless, simulations with a time-dependent FEL code (GINGER) indicate that rates of 2 GHz or more are amplified without much loss in modulation integrity. In this paper we describe the effects of slippage in the simulations and discuss the limits of simple arguments

  15. Cine MRI of the ascending aorta in the elderly with respect to the flow signal void and aortic valve morphology

    International Nuclear Information System (INIS)

    Nakayama, Masafumi; Kyomasu, Yoshinori; Suzuki, Yasuko; Mashima, Yasuoki; Tanno, Munehiko; Endo, Kazuo; Yamada, Hideo

    1990-01-01

    Cine flow MRI was performed on a 1.5 Tesla system to observe signal intensity of blood flow within the ascending aorta in the elderly who had no aortic stenosis and to determine frequency of the flow signal void. Coronal and sagittal imaging planes of the ascending aorta were obtained in 27 aged patients with no known cardiac diseases (14 men and 13 women, mean age of 76) and 7 young volunteers (7 men, mean age of 24), utilizing ECG-gating, GRASS (gradient-recalled acquisition in steady state), and a flow compensation sequence. The young volunteers presented little or no signal void within the ascending aorta. In 26 (96%) of the 27 aged patients, on the other hand, signal void was demonstrated in the blood flow distal to the aortic valve during systole. The maximum length of the signal void that was measured at 318∼632 msec after the R wave of ECG ranged from 33 to 97 mm. Conventional and Doppler echocardiography was used to evaluate motion and morphology of the aortic valve in 19 of the 27 aged patients. Eighteen of these 19 subjects had aortic signal void on cine MRI. Echocardiography showed sclerotic changes of the aortic valve (i.e., increased echogenicity of the cusps and/or commissure fusion) in 10 (53%) of the 19 subjects. The mean maximum length of the signal void in the 10 patients with aortic valve sclerosis was significantly greater than that in the 9 patients with echocardiographically normal valve (68 vs.45 mm, p<0.01). These results suggest that signal void of blood flow in the ascending aorta, which is recognized as one of the characteristic findings in patients with aortic stenosis, is not a specific feature for this disease but rather a commom one in the elderly particularly those with sclerotic changes of the aortic valve. However, the length of the signal void may distinguish between nonstenotic and stenotic aortic valves. (author)

  16. Suitability of cerebrospinal fluid as a signal-intensity reference on MRI: evaluation of signal-intensity variations in the lumbosacral dural sac

    International Nuclear Information System (INIS)

    Luoma, E.K.; Luukkonen, R.; Riihimaeki, H.A.; Raininko, R.; Manninen, H.I.; Nummi, P.J.

    1997-01-01

    The suitability of the cerebrospinal fluid (CSF) in the lumbosacral dural sac as an internal signal-intensity reference was studied on magnetic resonance imaging (MRI) of the lumbar spine using a surface coil and motion artefact suppression technique. A signal-intensity reference is needed when signal is compared between images, studies or subjects. Homogeneity of the CSF was estimated visually on T2-weighted images of 60 subjects at 1.5 T and of another 60 subjects at 0.1 T. Spines with a severely narrowed dural sac or marked scoliosis were excluded from the study to avoid partial volume effect. CSF was homogeneous in 82% and 73% of the examinations at 1.5 T and 0.1 T, respectively. The type and location of the local inhomogeneities did not relate to local narrowings of the dural sac. The signal intensity of CSF was measured in 108 examinations at 0.1 T after correcting the spatially-dependent signal-intensity nonuniformities with a phantom-based method. The signal-intensity difference between the CSF in the upper and lower lumbar dural sac was less than 10% in 73% of the examinations. The CSF in the lumbosacral dural sac can be a useful signal-intensity reference for estimation of the signal of the adjacent structures in patients without severe narrowing of the dural sac or marked scoliosis. It may contribute to assessing spinal disease processes. (orig.). With 1 fig., 3 tabs

  17. Non-enzymolytic adenosine barcode-mediated dual signal amplification strategy for ultrasensitive protein detection using LC-MS/MS.

    Science.gov (United States)

    Yang, Wen; Li, Tengfei; Shu, Chang; Ji, Shunli; Wang, Lei; Wang, Yan; Li, Duo; Mtalimanja, Michael; Sun, Luning; Ding, Li

    2018-05-10

    A method is described for the determination of proteins with LC-MS/MS enabled by a small molecule (adenosine) barcode and based on a double-recognition sandwich structure. The coagulation protein thrombin was chosen as the model analyte. Magnetic nanoparticles were functionalized with aptamer29 (MNP/apt29) and used to capture thrombin from the samples. MNP/apt29 forms a sandwich with functionalized gold nanoparticles modified with (a) aptamer15 acting as thrombin-recognizing element and (b) a large number of adenosine as mass barcodes. The sandwich formed (MNP/apt29-thrombin-apt15/AuNP/adenosine) can ben magnetically separated from the sample. Mass barcodes are subsequently released from the sandwiched structure for further analysis by adding 11-mercaptoundecanoic acid. Adenosine is then detected by LC-MS/MS as it reflects the level of thrombin with impressively amplified signal. Numerous adenosines introduced into the sandwich proportional to the target concentration further amplify the signal. Under optimized conditions, the response is linearly proportional to the thrombin concentration in the range of 0.02 nM to 10 nM, with a detection limit of 9 fM. The application of this method to the determination of thrombin in spiked plasma samples gave recoveries that ranged from 92.3% to 104.7%. Graphical abstract Schematic representation of a method for the determination of thrombin with LC-MS/MS. The method is based on a double-recognition sandwiched structure. With LC-MS/MS, mass barcodes (adenosine) are detected to quantify thrombin, which amplifies the detection signal impressively.

  18. A Carbon Nanotube-based NEMS Parametric Amplifier for Enhanced Radio Wave Detection and Electronic Signal Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Aleman, B J; Sussman, A; Zettl, A [Physics Department, University of California, Berkeley, CA 94720 (United States); Mickelson, W, E-mail: azettl@berkeley.edu [Center of Integrated Nanomechanical Systems, University of California, Berkeley, CA 94720 (United States)

    2011-07-20

    We propose a scheme for a parametric amplifier based on a single suspended carbon nanotube field-emitter. This novel electromechanical nanotube device acts as a phase-sensitive, variable-gain, band-pass-filtering amplifier for electronic signal processing and, at the same time, can operate as a variable-sensitivity, tuneable detector and transducer of radio frequency electromagnetic waves. The amplifier can exhibit infinite gain at pumping voltages much less than 10 Volts. Additionally, the amplifier's low overhead power consumption (10-1000 nW) make it exceptionally attractive for ultra-low-power applications.

  19. A Carbon Nanotube-based NEMS Parametric Amplifier for Enhanced Radio Wave Detection and Electronic Signal Amplification

    International Nuclear Information System (INIS)

    Aleman, B J; Sussman, A; Zettl, A; Mickelson, W

    2011-01-01

    We propose a scheme for a parametric amplifier based on a single suspended carbon nanotube field-emitter. This novel electromechanical nanotube device acts as a phase-sensitive, variable-gain, band-pass-filtering amplifier for electronic signal processing and, at the same time, can operate as a variable-sensitivity, tuneable detector and transducer of radio frequency electromagnetic waves. The amplifier can exhibit infinite gain at pumping voltages much less than 10 Volts. Additionally, the amplifier's low overhead power consumption (10-1000 nW) make it exceptionally attractive for ultra-low-power applications.

  20. Conflict anticipation in alcohol dependence - A model-based fMRI study of stop signal task.

    Science.gov (United States)

    Hu, Sien; Ide, Jaime S; Zhang, Sheng; Sinha, Rajita; Li, Chiang-Shan R

    2015-01-01

    Our previous work characterized altered cerebral activations during cognitive control in individuals with alcohol dependence (AD). A hallmark of cognitive control is the ability to anticipate changes and adjust behavior accordingly. Here, we employed a Bayesian model to describe trial-by-trial anticipation of the stop signal and modeled fMRI signals of conflict anticipation in a stop signal task. Our goal is to characterize the neural correlates of conflict anticipation and its relationship to response inhibition and alcohol consumption in AD. Twenty-four AD and 70 age and gender matched healthy control individuals (HC) participated in the study. fMRI data were pre-processed and modeled with SPM8. We modeled fMRI signals at trial onset with individual events parametrically modulated by estimated probability of the stop signal, p(Stop), and compared regional responses to conflict anticipation between AD and HC. To address the link to response inhibition, we regressed whole-brain responses to conflict anticipation against the stop signal reaction time (SSRT). Compared to HC (54/70), fewer AD (11/24) showed a significant sequential effect - a correlation between p(Stop) and RT during go trials - and the magnitude of sequential effect is diminished, suggesting a deficit in proactive control. Parametric analyses showed decreased learning rate and over-estimated prior mean of the stop signal in AD. In fMRI, both HC and AD responded to p(Stop) in bilateral inferior parietal cortex and anterior pre-supplementary motor area, although the magnitude of response increased in AD. In contrast, HC but not AD showed deactivation of the perigenual anterior cingulate cortex (pgACC). Furthermore, deactivation of the pgACC to increasing p(Stop) is positively correlated with the SSRT in HC but not AD. Recent alcohol consumption is correlated with increased activation of the thalamus and cerebellum in AD during conflict anticipation. The current results highlight altered proactive

  1. Signal amplification and leakage current suppression in amorphous silicon p-i-n diodes by field profile tailoring

    International Nuclear Information System (INIS)

    Hong, W.S.; Zhong, F.; Mireshghi, A.; Perez-Mendez, V.

    1999-01-01

    The performance of amorphous silicon p-i-n diodes as radiation detectors in terms of signal amplitude can be greatly improved when there is a built-in signal gain mechanism. The authors describe an avalanche gain mechanism which is achieved by introducing stacked intrinsic, p-type, and n-type layers into the diode structure. They replaced the intrinsic layer of the conventional p-i-n diode with i 1 -p-i 2 -n-i 3 multilayers. The i 2 layer (typically 1 ∼ 3 microm) achieves an electric field > 10 6 V/cm, while maintaining the p-i interfaces to the metallic contact at electric fields 4 V/cm, when the diode is fully depleted. For use in photo-diode applications the whole structure is less than 10 microm thick. Avalanche gains of 10 ∼ 50 can be obtained when the diode is biased to ∼ 500 V. Also, dividing the electrodes to strips of 2 microm width and 20 microm pitch reduced the leakage current up to an order of magnitude, and increased light transmission without creating inactive regions

  2. Mixed-Signal Architectures for High-Efficiency and Low-Distortion Digital Audio Processing and Power Amplification

    Directory of Open Access Journals (Sweden)

    Pierangelo Terreni

    2010-01-01

    Full Text Available The paper addresses the algorithmic and architectural design of digital input power audio amplifiers. A modelling platform, based on a meet-in-the-middle approach between top-down and bottom-up design strategies, allows a fast but still accurate exploration of the mixed-signal design space. Different amplifier architectures are configured and compared to find optimal trade-offs among different cost-functions: low distortion, high efficiency, low circuit complexity and low sensitivity to parameter changes. A novel amplifier architecture is derived; its prototype implements digital processing IP macrocells (oversampler, interpolating filter, PWM cross-point deriver, noise shaper, multilevel PWM modulator, dead time compensator on a single low-complexity FPGA while off-chip components are used only for the power output stage (LC filter and power MOS bridge; no heatsink is required. The resulting digital input amplifier features a power efficiency higher than 90% and a total harmonic distortion down to 0.13% at power levels of tens of Watts. Discussions towards the full-silicon integration of the mixed-signal amplifier in embedded devices, using BCD technology and targeting power levels of few Watts, are also reported.

  3. Sensing miRNA: Signal Amplification by Cognate RISC for Intracellular Detection of miRNA in Live Cells.

    Science.gov (United States)

    Kavishwar, Amol; Medarova, Zdravka

    2016-01-01

    The ability to detect miRNA expression in live cells would leave these cells available for further manipulation or culture. Here, we describe the design of a miRNA sensor oligonucleotide whose sequence mimics the target mRNA. The sensor has a fluorescent label on one end of the oligo and a quencher on the other. When inside the cell, the sensor is recognized by its cognate miRNA-RISC and gets cleaved, setting the fluorophore free from its quencher. This results in fluorescence "turn on." Since cleavage by the RISC complex is an enzymatic process, the described approach has a very high level of sensitivity (nM). The rate of nonspecific cleavage of the sensor is very slow permitting the collection of meaningful signal over a long period of time.

  4. Thoughts turned into high-level commands: Proof-of-concept study of a vision-guided robot arm driven by functional MRI (fMRI) signals.

    Science.gov (United States)

    Minati, Ludovico; Nigri, Anna; Rosazza, Cristina; Bruzzone, Maria Grazia

    2012-06-01

    Previous studies have demonstrated the possibility of using functional MRI to control a robot arm through a brain-machine interface by directly coupling haemodynamic activity in the sensory-motor cortex to the position of two axes. Here, we extend this work by implementing interaction at a more abstract level, whereby imagined actions deliver structured commands to a robot arm guided by a machine vision system. Rather than extracting signals from a small number of pre-selected regions, the proposed system adaptively determines at individual level how to map representative brain areas to the input nodes of a classifier network. In this initial study, a median action recognition accuracy of 90% was attained on five volunteers performing a game consisting of collecting randomly positioned coloured pawns and placing them into cups. The "pawn" and "cup" instructions were imparted through four mental imaginery tasks, linked to robot arm actions by a state machine. With the current implementation in MatLab language the median action recognition time was 24.3s and the robot execution time was 17.7s. We demonstrate the notion of combining haemodynamic brain-machine interfacing with computer vision to implement interaction at the level of high-level commands rather than individual movements, which may find application in future fMRI approaches relevant to brain-lesioned patients, and provide source code supporting further work on larger command sets and real-time processing. Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

  5. Molecular beacon based biosensor for the sequence-specific detection of DNA using DNA-capped gold nanoparticles-streptavidin conjugates for signal amplification

    International Nuclear Information System (INIS)

    Fang, Xian; Jiang, Wei; Han, Xiaowei; Zhang, Yuzhong

    2013-01-01

    We describe a highly sensitive and selective molecular beacon-based electrochemical impedance biosensor for the sequence-specific detection of DNA. DNA-capped conjugates between gold nanoparticles (Au-NPs) and streptavidin are used for signal amplification. The molecular beacon was labeled with a thiol at its 5′ end and with biotin at its 3′ end, and then immobilized on the surface of a bare gold electrode through the formation of Au-S bonds. Initially, the molecular beacon is present in the “closed” state, and this shields the biotin from being approached by streptavidin due to steric hindrance. In the presence of the target DNA, the target DNA molecules hybridize with the loop and cause a conformational change that moves the biotin away from the surface of the electrode. The biotin thereby becomes accessible for the reporter (the DNA-streptavidin capped Au-NPs), and this results in a distinct increase in electron transfer resistance. Under optimal conditions, the increase in resistance is linearly related to the logarithm of the concentration of complementary target DNA in the range from 1.0 fM to 0.1 μM, with a detection limit of 0.35 fM (at an S/N of 3). This biosensor exhibits good selectivity, and acceptable stability and reproducibility. (author)

  6. Pitfalls using tyramide signal amplification (TSA) in the mouse gastrointestinal tract: endogenous streptavidin-binding sites lead to false positive staining.

    Science.gov (United States)

    Horling, L; Neuhuber, W L; Raab, M

    2012-02-15

    Highly sensitive immunohistochemical detection systems such as tyramide signal amplification (TSA) are widely used, since they allow using two primary antibodies raised in the same species. Most of them are based on the streptavidin-biotin-peroxidase system and include streptavidin-coupled secondary antibodies. Using TSA in cryostat-sectioned tissues of mouse esophagus, we were puzzled by negative controls with unexpected staining mostly in the ganglionic areas. This prompted us to search for the causing agent and to include also other parts of the mouse gastrointestinal tract for comparison. Streptavidin-coupled antibodies bound to endogenous binding sites yet to be characterized, which are present throughout the mouse intestines. Staining was mainly localized around neuronal cell bodies of enteric ganglia. Thus, caution is warranted when applying streptavidin-coupled antibodies in the mouse gastrointestinal tract. The use of endogenous biotin-blocking kits combined with a prolonged post-fixation time could significantly reduce unintentional staining. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Ultrasensitive electrochemical biosensor for detection of DNA from Bacillus subtilis by coupling target-induced strand displacement and nicking endonuclease signal amplification.

    Science.gov (United States)

    Hu, Yuhua; Xu, Xueqin; Liu, Qionghua; Wang, Ling; Lin, Zhenyu; Chen, Guonan

    2014-09-02

    A simple, ultrasensitive, and specific electrochemical biosensor was designed to determine the given DNA sequence of Bacillus subtilis by coupling target-induced strand displacement and nicking endonuclease signal amplification. The target DNA (TD, the DNA sequence from the hypervarient region of 16S rDNA of Bacillus subtilis) could be detected by the differential pulse voltammetry (DPV) in a range from 0.1 fM to 20 fM with the detection limit down to 0.08 fM at the 3s(blank) level. This electrochemical biosensor exhibits high distinction ability to single-base mismatch, double-bases mismatch, and noncomplementary DNA sequence, which may be expected to detect single-base mismatch and single nucleotide polymorphisms (SNPs). Moreover, the applicability of the designed biosensor for detecting the given DNA sequence from Bacillus subtilis was investigated. The result obtained by electrochemical method is approximately consistent with that by a real-time quantitative polymerase chain reaction detecting system (QPCR) with SYBR Green.

  8. Parallel feedback active noise control of MRI acoustic noise with signal decomposition using hybrid RLS-NLMS adaptive algorithms.

    Science.gov (United States)

    Ganguly, Anshuman; Krishna Vemuri, Sri Hari; Panahi, Issa

    2014-01-01

    This paper presents a cost-effective adaptive feedback Active Noise Control (FANC) method for controlling functional Magnetic Resonance Imaging (fMRI) acoustic noise by decomposing it into dominant periodic components and residual random components. Periodicity of fMRI acoustic noise is exploited by using linear prediction (LP) filtering to achieve signal decomposition. A hybrid combination of adaptive filters-Recursive Least Squares (RLS) and Normalized Least Mean Squares (NLMS) are then used to effectively control each component separately. Performance of the proposed FANC system is analyzed and Noise attenuation levels (NAL) up to 32.27 dB obtained by simulation are presented which confirm the effectiveness of the proposed FANC method.

  9. A study of MRI gradient echo signals from discrete magnetic particles with considerations of several parameters in simulations.

    Science.gov (United States)

    Kokeny, Paul; Cheng, Yu-Chung N; Xie, He

    2018-05-01

    Modeling MRI signal behaviors in the presence of discrete magnetic particles is important, as magnetic particles appear in nanoparticle labeled cells, contrast agents, and other biological forms of iron. Currently, many models that take into account the discrete particle nature in a system have been used to predict magnitude signal decays in the form of R2* or R2' from one single voxel. Little work has been done for predicting phase signals. In addition, most calculations of phase signals rely on the assumption that a system containing discrete particles behaves as a continuous medium. In this work, numerical simulations are used to investigate MRI magnitude and phase signals from discrete particles, without diffusion effects. Factors such as particle size, number density, susceptibility, volume fraction, particle arrangements for their randomness, and field of view have been considered in simulations. The results are compared to either a ground truth model, theoretical work based on continuous mediums, or previous literature. Suitable parameters used to model particles in several voxels that lead to acceptable magnetic field distributions around particle surfaces and accurate MR signals are identified. The phase values as a function of echo time from a central voxel filled by particles can be significantly different from those of a continuous cubic medium. However, a completely random distribution of particles can lead to an R2' value which agrees with the prediction from the static dephasing theory. A sphere with a radius of at least 4 grid points used in simulations is found to be acceptable to generate MR signals equivalent from a larger sphere. Increasing number of particles with a fixed volume fraction in simulations reduces the resulting variance in the phase behavior, and converges to almost the same phase value for different particle numbers at each echo time. The variance of phase values is also reduced when increasing the number of particles in a fixed

  10. Identification of Voxels Confounded by Venous Signals Using Resting-State fMRI Functional Connectivity Graph Clustering

    Directory of Open Access Journals (Sweden)

    Klaudius eKalcher

    2015-12-01

    Full Text Available Identifying venous voxels in fMRI datasets is important to increase the specificity of fMRI analyses to microvasculature in the vicinity of the neural processes triggering the BOLD response. This is, however, difficult to achieve in particular in typical studies where magnitude images of BOLD EPI are the only data available. In this study, voxelwise functional connectivity graphs were computed on minimally preprocessed low TR (333 ms multiband resting-state fMRI data, using both high positive and negative correlations to define edges between nodes (voxels. A high correlation threshold for binarization ensures that most edges in the resulting sparse graph reflect the high coherence of signals in medium to large veins. Graph clustering based on the optimization of modularity was then employed to identify clusters of coherent voxels in this graph, and all clusters of 50 or more voxels were then interpreted as corresponding to medium to large veins. Indeed, a comparison with SWI reveals that 75.6 ± 5.9% of voxels within these large clusters overlap with veins visible in the SWI image or lie outside the brain parenchyma. Some of the remainingdifferences between the two modalities can be explained by imperfect alignment or geometric distortions between the two images. Overall, the graph clustering based method for identifying venous voxels has a high specificity as well as the additional advantages of being computed in the same voxel grid as the fMRI dataset itself and not needingany additional data beyond what is usually acquired (and exported in standard fMRI experiments.

  11. A sensitive biosensor using double-layer capillary based immunomagnetic separation and invertase-nanocluster based signal amplification for rapid detection of foodborne pathogen.

    Science.gov (United States)

    Huang, Fengchun; Zhang, Huilin; Wang, Lei; Lai, Weihua; Lin, Jianhan

    2018-02-15

    Combining double-layer capillary based high gradient immunomagnetic separation, invertase-nanocluster based signal amplification and glucose meter based signal detection, a novel biosensor was developed for sensitive and rapid detection of E. coli O157:H7 in this study. The streptavidin modified magnetic nanobeads (MNBs) were conjugated with the biotinylated polyclonal antibodies against E. coli O157:H7 to form the immune MNBs, which were captured by the high gradient magnetic field in the double-layer capillary to specifically separate and efficiently concentrate the target bacteria. Calcium chloride was used with the monoclonal antibodies against E. coli O157:H7 and the invertase to form the immune invertase-nanoclusters (INCs), which were used to react with the target bacteria to form the MNB-bacteria-INC complexes in the capillary. The sucrose was then injected into the capillary and catalyzed by the invertase on the complexes into the glucose, which was detected using the glucose meter to obtain the concentration of the glucose for final determination of the E. coli O157:H7 cells in the sample. A linear relationship between the readout of the glucose meter and the concentration of the E. coli O157:H7 cells (from 10 2 to 10 7 CFU/mL) was found and the lower detection limit of this biosensor was 79 CFU/mL. This biosensor might be extended for the detection of other foodborne pathogens by changing the antibodies and has shown the potential for the detection of foodborne pathogens in a large volume of sample to further increase the sensitivity. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Miniaturized isothermal nucleic acid amplification, a review.

    Science.gov (United States)

    Asiello, Peter J; Baeumner, Antje J

    2011-04-21

    Micro-Total Analysis Systems (µTAS) for use in on-site rapid detection of DNA or RNA are increasingly being developed. Here, amplification of the target sequence is key to increasing sensitivity, enabling single-cell and few-copy nucleic acid detection. The several advantages to miniaturizing amplification reactions and coupling them with sample preparation and detection on the same chip are well known and include fewer manual steps, preventing contamination, and significantly reducing the volume of expensive reagents. To-date, the majority of miniaturized systems for nucleic acid analysis have used the polymerase chain reaction (PCR) for amplification and those systems are covered in previous reviews. This review provides a thorough overview of miniaturized analysis systems using alternatives to PCR, specifically isothermal amplification reactions. With no need for thermal cycling, isothermal microsystems can be designed to be simple and low-energy consuming and therefore may outperform PCR in portable, battery-operated detection systems in the future. The main isothermal methods as miniaturized systems reviewed here include nucleic acid sequence-based amplification (NASBA), loop-mediated isothermal amplification (LAMP), helicase-dependent amplification (HDA), rolling circle amplification (RCA), and strand displacement amplification (SDA). Also, important design criteria for the miniaturized devices are discussed. Finally, the potential of miniaturization of some new isothermal methods such as the exponential amplification reaction (EXPAR), isothermal and chimeric primer-initiated amplification of nucleic acids (ICANs), signal-mediated amplification of RNA technology (SMART) and others is presented.

  13. Are MRI high-signal changes of alar and transverse ligaments in acute whiplash injury related to outcome?

    Directory of Open Access Journals (Sweden)

    Eide Geir E

    2010-11-01

    Full Text Available Abstract Background Upper neck ligament high-signal changes on magnetic resonance imaging (MRI have been found in patients with whiplash-associated disorders (WAD but also in non-injured controls. The clinical relevance of such changes is controversial. Their prognostic role has never been evaluated. The purpose of this study was to examine if alar and transverse ligament high-signal changes on MRI immediately following the car accident are related to outcome after 12 months for patients with acute WAD grades 1-2. Methods Within 13 days after a car accident, 114 consecutive acute WAD1-2 patients without prior neck injury or prior neck problems underwent upper neck high-resolution proton-weighted MRI. High-signal changes of the alar and transverse ligaments were graded 0-3. A questionnaire including the impact of event scale for measuring posttraumatic stress response and questions on patients' expectations of recovery provided clinical data at injury. At 12 months follow-up, 111 (97.4% patients completed the Neck Disability Index (NDI and an 11-point numeric rating scale (NRS-11 on last week neck pain intensity. Factors potentially related to these outcomes were assessed using multiple logistic regression analyses. Results Among the 111 responders (median age 29.8 years; 63 women, 38 (34.2% had grades 2-3 alar ligament changes and 25 (22.5% had grades 2-3 transverse ligament changes at injury. At 12 months follow-up, 49 (44.1% reported disability (NDI > 8 and 23 (20.7% neck pain (NRS-11 > 4. Grades 2-3 ligament changes in the acute phase were not related to disability or neck pain at 12 months. More severe posttraumatic stress response increased the odds for disability (odds ratio 1.46 per 10 points on the impact of event scale, p = 0.007 and so did low expectations of recovery (odds ratio 4.66, p = 0.005. Conclusions High-signal changes of the alar and transverse ligaments close after injury did not affect outcome for acute WAD1-2 patients

  14. Ridding fMRI data of motion-related influences: Removal of signals with distinct spatial and physical bases in multiecho data.

    Science.gov (United States)

    Power, Jonathan D; Plitt, Mark; Gotts, Stephen J; Kundu, Prantik; Voon, Valerie; Bandettini, Peter A; Martin, Alex

    2018-02-27

    "Functional connectivity" techniques are commonplace tools for studying brain organization. A critical element of these analyses is to distinguish variance due to neurobiological signals from variance due to nonneurobiological signals. Multiecho fMRI techniques are a promising means for making such distinctions based on signal decay properties. Here, we report that multiecho fMRI techniques enable excellent removal of certain kinds of artifactual variance, namely, spatially focal artifacts due to motion. By removing these artifacts, multiecho techniques reveal frequent, large-amplitude blood oxygen level-dependent (BOLD) signal changes present across all gray matter that are also linked to motion. These whole-brain BOLD signals could reflect widespread neural processes or other processes, such as alterations in blood partial pressure of carbon dioxide (pCO 2 ) due to ventilation changes. By acquiring multiecho data while monitoring breathing, we demonstrate that whole-brain BOLD signals in the resting state are often caused by changes in breathing that co-occur with head motion. These widespread respiratory fMRI signals cannot be isolated from neurobiological signals by multiecho techniques because they occur via the same BOLD mechanism. Respiratory signals must therefore be removed by some other technique to isolate neurobiological covariance in fMRI time series. Several methods for removing global artifacts are demonstrated and compared, and were found to yield fMRI time series essentially free of motion-related influences. These results identify two kinds of motion-associated fMRI variance, with different physical mechanisms and spatial profiles, each of which strongly and differentially influences functional connectivity patterns. Distance-dependent patterns in covariance are nearly entirely attributable to non-BOLD artifacts.

  15. MEG and fMRI fusion for nonlinear estimation of neural and BOLD signal changes

    Directory of Open Access Journals (Sweden)

    Sergey M Plis

    2010-11-01

    Full Text Available The combined analysis of MEG/EEG and functional MRI measurements can lead to improvement in the description of the dynamical and spatial properties of brain activity. In this paper we empirically demonstrate this improvement using simulated and recorded task related MEG and fMRI activity. Neural activity estimates were derived using a dynamic Bayesian network with continuous real valued parameters by means of a sequential Monte Carlo technique. In synthetic data, we show that MEG and fMRI fusion improves estimation of the indirectly observed neural activity and smooths tracking of the BOLD response. In recordings of task related neural activity the combination of MEG and fMRI produces a result with greater SNR, that confirms the expectation arising from the nature of the experiment. The highly nonlinear model of the BOLD response poses a difficult inference problem for neural activity estimation; computational requirements are also high due to the time and space complexity. We show that joint analysis of the data improves the system's behavior by stabilizing the differential equations system and by requiring fewer computational resources.

  16. Clinical Implications of Diffuse Excessive High Signal Intensity (DEHSI on Neonatal MRI in School Age Children Born Extremely Preterm.

    Directory of Open Access Journals (Sweden)

    Lina Broström

    Full Text Available Magnetic resonance imaging (MRI of the brain carried out during the neonatal period shows that 55-80% of extremely preterm infants display white matter diffuse excessive high signal intensity (DEHSI. Our aim was to study differences in developmental outcome at the age of 6.5 years in children born extremely preterm with and without DEHSI.This was a prospective cohort study of 83 children who were born in Stockholm, Sweden, between 2004 and 2007, born at gestational age of < 27 weeks + 0 days and who underwent an MRI scan of their brain at term equivalent age. The outcome measures at 6.5 years included testing 66 children with the modified Touwen neurology examination, the Movement Assessment Battery for Children 2, the Wechsler Intelligence Scale for Children-Fourth Edition, Beery Visual-motor Integration test-Sixth Edition, and the Strengths and Difficulties Questionnaire. Group-wise comparisons were done between children with and without DEHSI using Student t-test, Mann Whitney U test, Chi square test and regression analysis.DEHSI was detected in 39 (59% of the 66 children who were assessed at 6.5 years. The presence of DEHSI was not associated with mild neurological dysfunction, scores on M-ABC assessment, cognition, visual-motor integration, or behavior at 6.5 years.The presence of qualitatively defined DEHSI on neonatal MRI did not prove to be a useful predictor of long-term impairment in children born extremely preterm.

  17. Predicting local recurrence following breast-conserving treatment: parenchymal signal enhancement ratio (SER) around the tumor on preoperative MRI

    International Nuclear Information System (INIS)

    Kim, Mi Young; Cho, Nariya; Koo, Hye Ryoung; Yun, Bo La; Bae, Min Sun; Moon, Woo Kyung; Chie, Eui Kyu

    2013-01-01

    Background: The level of background parenchymal enhancement around tumor is known to be associated with breast cancer risk. However, there is no study investigating predictive power of parenchymal signal enhancement ratio (SER) around tumor for ipsilateral breast tumor recurrence (IBTR). Purpose: To investigate whether the breast parenchymal SER around the tumor on preoperative dynamic contrast-enhanced magnetic resonance imaging (MRI) is associated with subsequent IBTR in breast cancer patients who had undergone breast-conserving treatment. Material and Methods: Nineteen consecutive women (mean age, 44 years; range, 34-63 years) with breast cancer who developed IBTR following breast-conserving treatment and 114 control women matched for age, as well as T and N stages were included. We compared the clinicopathologic features of the two groups including nuclear grade, histologic grade, hormonal receptor status, human epidermal growth factor receptor-2 (HER-2) status, lymphovascular invasion, negative margin width, use of adjuvant therapy, and parenchymal SER around the tumor on preoperative DCE-MRI. The SER was measured on a slice showing the largest dimension of the tumor. Multivariate conditional logistic regression analysis was used to identify independent factors associated with IBTR. Results: In univariate analysis, ER negativity (odds ratio [OR] = 4.7; P = 0.040), PR negativity (OR = 4.0; P = 0.013), HER-2 positivity (OR = 3.6; P = 0.026), and a parenchymal SER greater than 0.53 (OR = 23.3; P = 0.011) were associated with IBTR. In multivariate analysis, ER negativity (OR = 3.8; P = 0.015) and a parenchymal SER greater than 0.53 (OR = 13.2; P = 0.040) on preoperative MRI were independent factors associated with IBTR. Conclusion: In addition to ER negativity, a higher parenchymal SER on preoperative MRI was an independent factor associated with subsequent IBTR in patients with breast cancer who had undergone breast-conserving treatment

  18. Prussian blue mediated amplification combined with signal enhancement of ordered mesoporous carbon for ultrasensitive and specific quantification of metolcarb by a three-dimensional molecularly imprinted electrochemical sensor.

    Science.gov (United States)

    Yang, Yukun; Cao, Yaoyu; Wang, Xiaomin; Fang, Guozhen; Wang, Shuo

    2015-02-15

    In this work, we presented a three-dimensional (3D) molecularly imprinted electrochemical sensor (MIECS) with novel strategy for ultrasensitive and specific quantification of metolcarb based on prussian blue (PB) mediated amplification combined with signal enhancement of ordered mesoporous carbon. The molecularly imprinted polymers were synthesized by electrochemically induced redox polymerization of para aminobenzoic acid (p-ABA) in the presence of template metolcarb. Ordered mesoporous carbon material (CMK-3) was introduced to enhance the electrochemical response by improving the structure of the modified electrodes and facilitating charge transfer processes of PB which was used as an inherent electrochemical active probe. The modification process for the working electrodes of the MIECS was characterized by scanning electron microscope (SEM) and cyclic voltammetry (CV), and several important parameters controlling the performance of the MIECS were investigated and optimized in detail. The MIECS with 3D structure had the advantages of ease of preparation, high porous surface structure, speedy response, ultrasensitivity, selectivity, reliable stability, good reproducibility and repeatability. Under the optimal conditions, the MIECS offered an excellent current response for metolcarb in the linear response range of 5.0 × 10(-10)-1.0 × 10(-4) mol L(-1) and the limit of detection (LOD) was calculated to be 9.3 × 10 (-11)mol L(-1) (S/N = 3). The proposed MIECS has been successfully applied for the determination of metolcarb in real samples with satisfactory recoveries. Furthermore, the construction route of this ultrasensitive 3D MIECS may provide a guideline for the determination of non-electroactive analytes in environmental control and food safety. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Amplified amperometric aptasensor for selective detection of protein using catalase-functional DNA-PtNPs dendrimer as a synergetic signal amplification label.

    Science.gov (United States)

    Zhang, Juan; Yuan, Yali; biXie, Shun; Chai, Yaqin; Yuan, Ruo

    2014-10-15

    In this work, we present a new strategy to construct an electrochemical aptasensor for sensitive detection of platelet-derived growth factor BB (PDGF-BB) based on the synergetic amplification of a three-dimensional (3D) nanoscale catalase (CAT) enzyme-functional DNA-platinum nanoparticles (PtNPs) dendrimer through autonomous layer-by-layer assembly. Firstly, polyamidoaminedendrimer (PAMAM) with a hyper-branched and three-dimensional structure was served as nanocarriers to coimmobilize a large number of PDGF-BB binding aptamer (PBA II) and ssDNA 1 (S1) to form PBA II-PAMAM-S1 bioconjugate. In the presence of PDGF-BB, the bioconjugate was self-assembled on the electrode by sandwich assay. Following that, the carried S1 propagated a chain reaction of hybridization events between CAT-PtNPs-S1 and CAT-PtNPs-ssDNA 2 (S2) to form a 3D nanoscale CAT-functional PtNPs-DNA dendrimer, which successfully immobilized substantial CAT enzyme and PtNPs with superior catalysis activity. In this process, the formed negatively charged double-helix DNA could cause the intercalation of hexaammineruthenium(III) chloride (RuHex) into the groove via electrostatic interactions. Thus, numerous RuHex redox probes and CAT were decorated inside/outside of the dendrimer. In the presence of H2O2 in electrolytic cell, the synergistic reaction of CAT and PtNPs towards electrocatalysis could further amplify electrochemical signal. Under optimal condition, the CAT-PtNPs-DNA dendrimer-based sensing system presented a linear dependence between the reduction peak currents and logarithm of PDGF-BB concentrations in the range of 0.00005-35 nM with a relatively low detection limit of 0.02 pM. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Highly sensitive and label-free electrochemical detection of microRNAs based on triple signal amplification of multifunctional gold nanoparticles, enzymes and redox-cycling reaction.

    Science.gov (United States)

    Liu, Lin; Xia, Ning; Liu, Huiping; Kang, Xiaojing; Liu, Xiaoshuan; Xue, Chan; He, Xiaoling

    2014-03-15

    MicroRNAs (miRNAs) are believed to be important for cancer diagnosis and prognosis, serving as reliable molecular biomarkers. In this work, we presented a label-free and highly sensitive electrochemical genosensor for miRNAs detection with the triple signal amplification of gold nanoparticles (AuNPs), alkaline phosphatase (ALP) and p-aminophenol (p-AP) redox cycling. The label-free strategy is based on the difference in the structures of RNA and DNA. Specifically, miRNAs were first captured by the pre-immobilized DNA probes on a gold electrode. Next, the cis-diol group of ribose sugar at the end of the miRNAs chain allowed 3-aminophenylboronic acid (APBA)/biotin-modified multifunctional AuNPs (denoted as APBA-biotin-AuNPs) to be attached through the formation of a boronate ester covalent bond, which facilitated the capture of streptavidin-conjugated alkaline phosphatase (SA-ALP) via the biotin-streptavidin interaction. After the addition of the 4-aminophenylphosphate (p-APP) substrate, the enzymatic conversion from p-APP to p-AP occurred. The resulting p-AP could be cycled by a chemical reducing reagent after its electro-oxidization on the electrode (known as p-AP redox cycling), thus enabling an increase in the anodic current. As a result, the current increased linearly with the miRNAs concentration over a range of 10 fM-5 pM, and a detection limit of 3 fM was achieved. We believe that this work will be valuable for the design of new types of label-free and sensitive electrochemical biosensors. © 2013 Published by Elsevier B.V.

  1. Highly sensitive photoelectrochemical biosensor for kinase activity detection and inhibition based on the surface defect recognition and multiple signal amplification of metal-organic frameworks.

    Science.gov (United States)

    Wang, Zonghua; Yan, Zhiyong; Wang, Feng; Cai, Jibao; Guo, Lei; Su, Jiakun; Liu, Yang

    2017-11-15

    A turn-on photoelectrochemical (PEC) biosensor based on the surface defect recognition and multiple signal amplification of metal-organic frameworks (MOFs) was proposed for highly sensitive protein kinase activity analysis and inhibitor evaluation. In this strategy, based on the phosphorylation reaction in the presence of protein kinase A (PKA), the Zr-based metal-organic frameworks (UiO-66) accommodated with [Ru(bpy) 3 ] 2+ photoactive dyes in the pores were linked to the phosphorylated kemptide modified TiO 2 /ITO electrode through the chelation between the Zr 4+ defects on the surface of UiO-66 and the phosphate groups in kemptide. Under visible light irradiation, the excited electrons from [Ru(bpy) 3 ] 2+ adsorbed in the pores of UiO-66 injected into the TiO 2 conduction band to generate photocurrent, which could be utilized for protein kinase activities detection. The large surface area and high porosities of UiO-66 facilitated a large number of [Ru(bpy) 3 ] 2+ that increased the photocurrent significantly, and afforded a highly sensitive PEC analysis of kinase activity. The detection limit of the as-proposed PEC biosensor was 0.0049UmL -1 (S/N!=!3). The biosensor was also applied for quantitative kinase inhibitor evaluation and PKA activities detection in MCF-7 cell lysates. The developed visible-light PEC biosensor provides a simple detection procedure and a cost-effective manner for PKA activity assays, and shows great potential in clinical diagnosis and drug discoveries. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Test-retest reliability of evoked BOLD signals from a cognitive-emotive fMRI test battery.

    Science.gov (United States)

    Plichta, Michael M; Schwarz, Adam J; Grimm, Oliver; Morgen, Katrin; Mier, Daniela; Haddad, Leila; Gerdes, Antje B M; Sauer, Carina; Tost, Heike; Esslinger, Christine; Colman, Peter; Wilson, Frederick; Kirsch, Peter; Meyer-Lindenberg, Andreas

    2012-04-15

    Even more than in cognitive research applications, moving fMRI to the clinic and the drug development process requires the generation of stable and reliable signal changes. The performance characteristics of the fMRI paradigm constrain experimental power and may require different study designs (e.g., crossover vs. parallel groups), yet fMRI reliability characteristics can be strongly dependent on the nature of the fMRI task. The present study investigated both within-subject and group-level reliability of a combined three-task fMRI battery targeting three systems of wide applicability in clinical and cognitive neuroscience: an emotional (face matching), a motivational (monetary reward anticipation) and a cognitive (n-back working memory) task. A group of 25 young, healthy volunteers were scanned twice on a 3T MRI scanner with a mean test-retest interval of 14.6 days. FMRI reliability was quantified using the intraclass correlation coefficient (ICC) applied at three different levels ranging from a global to a localized and fine spatial scale: (1) reliability of group-level activation maps over the whole brain and within targeted regions of interest (ROIs); (2) within-subject reliability of ROI-mean amplitudes and (3) within-subject reliability of individual voxels in the target ROIs. Results showed robust evoked activation of all three tasks in their respective target regions (emotional task=amygdala; motivational task=ventral striatum; cognitive task=right dorsolateral prefrontal cortex and parietal cortices) with high effect sizes (ES) of ROI-mean summary values (ES=1.11-1.44 for the faces task, 0.96-1.43 for the reward task, 0.83-2.58 for the n-back task). Reliability of group level activation was excellent for all three tasks with ICCs of 0.89-0.98 at the whole brain level and 0.66-0.97 within target ROIs. Within-subject reliability of ROI-mean amplitudes across sessions was fair to good for the reward task (ICCs=0.56-0.62) and, dependent on the particular ROI

  3. Effects of glyceryl trinitrate and calcitonin-gene-related peptide on BOLD signal and arterial diameter –methodological studies by fMRI and MRA

    DEFF Research Database (Denmark)

    Asghar, Mohammed Sohail; Ashina, Messoud

    2013-01-01

    Over the last decades MRI has proved to be very useful in the field of drug development and discovery. Pharmacological MRI (phMRI) explores the interaction between brain physiology, neuronal activity and drugs[1]. The BOLD-signal is an indirect method to investigate brain activity by way...... of measuring task-related hemodynamic changes. Pharmacological substances that induce hemodynamic changes can therefore potentially alter the BOLD-signal that in turn falsely can be interpreted as changes in neuronal activity. It is therefore important to characterize possible effects of a pharmacological...... substance on the BOLD-response per see before that substance can be used in an fMRI experiment. Furthermore MR-angiography is useful in determining the vascular site-of-action of vasoactive substances....

  4. Improving the arterial input function in dynamic contrast enhanced MRI by fitting the signal in the complex plane.

    Science.gov (United States)

    Simonis, Frank F J; Sbrizzi, Alessandro; Beld, Ellis; Lagendijk, Jan J W; van den Berg, Cornelis A T

    2016-10-01

    Dynamic contrast enhanced (DCE) imaging is a widely used technique in oncologic imaging. An essential prerequisite for obtaining quantitative values from DCE-MRI is the determination of the arterial input function (AIF). However, it is very challenging to accurately estimate the AIF using MR. A comprehensive model, which uses complex data instead of either magnitude or phase, was developed to improve AIF estimation. The model was first applied to simulated data. Subsequently, the accuracy of the estimated contrast agent concentration was validated in a phantom. Finally the method was applied to existing DCE scans of 13 prostate cancer patients. The complex signal method combines the complementary strengths of the magnitude and phase method, increasing the precision and accuracy of concentration estimation in simulated and phantom data. The in vivo AIFs show a good agreement between arterial voxels (standard deviation in the peak and tail equal 0.4 mM and 0.12 mM, respectively). Furthermore, the dynamic behavior closely followed the AIF obtained with DCE-CT in the same patients (mean correlation coefficient: 0.92). By using the complex signal, the AIF estimation becomes more accurate and precise. This might enable patient specific AIFs, thereby improving the quantitative values obtained from DCE-MRI. Magn Reson Med 76:1236-1245, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  5. In contrast to BOLD: signal enhancement by extravascular water protons as an alternative mechanism of endogenous fMRI signal change.

    Science.gov (United States)

    Figley, Chase R; Leitch, Jordan K; Stroman, Patrick W

    2010-10-01

    Despite the popularity and widespread application of functional magnetic resonance imaging (fMRI) in recent years, the physiological bases of signal change are not yet fully understood. Blood oxygen level-dependant (BOLD) contrast - attributed to local changes in blood flow and oxygenation, and therefore magnetic susceptibility - has become the most prevalent means of functional neuroimaging. However, at short echo times, spin-echo sequences show considerable deviations from the BOLD model, implying a second, non-BOLD component of signal change. This has been dubbed "signal enhancement by extravascular water protons" (SEEP) and is proposed to result from proton-density changes associated with cellular swelling. Given that such changes are independent of magnetic susceptibility, SEEP may offer new and improved opportunities for carrying out fMRI in regions with close proximity to air-tissue and/or bone-tissue interfaces (e.g., the prefrontal cortex and spinal cord), as well as regions close to large blood vessels, which may not be ideally suited for BOLD imaging. However, because of the interdisciplinary nature of the literature, there has yet to be a thorough synthesis, tying together the various and sometimes disparate aspects of SEEP theory. As such, we aim to provide a concise yet comprehensive overview of SEEP, including recent and compelling evidence for its validity, its current applications and its future relevance to the rapidly expanding field of functional neuroimaging. Before presenting the evidence for a non-BOLD component of endogenous functional contrast, and to enable a more critical review for the nonexpert reader, we begin by reviewing the fundamental principles underlying BOLD theory. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. Persistency of priors-induced bias in decision behavior and the fMRI signal

    Directory of Open Access Journals (Sweden)

    Kathleen eHansen

    2011-03-01

    Full Text Available It is well known that people take advantage of prior knowledge to bias decisions. To investigate this phenomenon behaviorally and in the brain, we acquired fMRI data while human subjects viewed ambiguous abstract shapes and decided whether a shape was of Category A (smoother or B (bumpier. The decision was made in the context of one of two prior knowledge cues, 80/20 and 50/50. The 80/20 cue indicated that upcoming shapes had an 80% probability of being of one category, e.g. B, and a 20% probability of being of the other. The 50/50 cue indicated that upcoming shapes had an equal probability of being of either category. The ideal observer would bias decisions in favor of the indicated alternative at 80/20 and show zero bias at 50/50. We found that subjects did bias their decisions in the predicted direction at 80/20 but did not show zero bias at 50/50. Instead, at 50/50 the subjects retained biases of the same sign as their 80/20 biases, though of diminished magnitude. The signature of a persistent though diminished bias at 50/50 was also evident in fMRI data from frontal and parietal regions previously implicated in decision-making. As a control, we acquired fMRI data from naïve subjects who experienced only the 50/50 stimulus distributions during both the prescan training and the fMRI experiment. The behavioral and fMRI data from the naïve subjects reflected decision biases closer to those of the ideal observer than those of the prior knowledge subjects at 50/50. The results indicate that practice making decisions in the context of non-equal prior probabilities biases decisions made later when prior probabilities are equal. This finding may be related to the anchoring and adjustment strategy described in the psychology, economics and marketing literatures, in which subjects adjust a first approximation response – the anchor – based on additional information, typically applying insufficient adjustment relative to the ideal observer.

  7. Spatial attention related SEP amplitude modulations covary with BOLD signal in S1--a simultaneous EEG--fMRI study.

    Science.gov (United States)

    Schubert, Ruth; Ritter, Petra; Wüstenberg, Torsten; Preuschhof, Claudia; Curio, Gabriel; Sommer, Werner; Villringer, Arno

    2008-11-01

    Recent studies investigating the influence of spatial-selective attention on primary somatosensory processing have produced inconsistent results. The aim of this study was to explore the influence of tactile spatial-selective attention on spatiotemporal aspects of evoked neuronal activity in the primary somatosensory cortex (S1). We employed simultaneous electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) in 14 right-handed subjects during bilateral index finger Braille stimulation to investigate the relationship between attentional effects on somatosensory evoked potential (SEP) components and the blood oxygenation level-dependent (BOLD) signal. The 1st reliable EEG response following left tactile stimulation (P50) was significantly enhanced by spatial-selective attention, which has not been reported before. FMRI analysis revealed increased activity in contralateral S1. Remarkably, the effect of attention on the P50 component as well as long-latency SEP components starting at 190 ms for left stimuli correlated with attentional effects on the BOLD signal in contralateral S1. The implications are 2-fold: First, the correlation between early and long-latency SEP components and the BOLD effect suggest that spatial-selective attention enhances processing in S1 at 2 time points: During an early passage of the signal and during a later passage, probably via re-entrant feedback from higher cortical areas. Second, attentional modulations of the fast electrophysiological signals and the slow hemodynamic response are linearly related in S1.

  8. Restoring susceptibility induced MRI signal loss in rat brain at 9.4 T: A step towards whole brain functional connectivity imaging.

    Directory of Open Access Journals (Sweden)

    Rupeng Li

    Full Text Available The aural cavity magnetic susceptibility artifact leads to significant echo planar imaging (EPI signal dropout in rat deep brain that limits acquisition of functional connectivity fcMRI data. In this study, we provide a method that recovers much of the EPI signal in deep brain. Needle puncture introduction of a liquid-phase fluorocarbon into the middle ear allows acquisition of rat fcMRI data without signal dropout. We demonstrate that with seeds chosen from previously unavailable areas, including the amygdala and the insular cortex, we are able to acquire large scale networks, including the limbic system. This tool allows EPI-based neuroscience and pharmaceutical research in rat brain using fcMRI that was previously not feasible.

  9. Differentiating BOLD and non-BOLD signals in fMRI time series using multi-echo EPI.

    Science.gov (United States)

    Kundu, Prantik; Inati, Souheil J; Evans, Jennifer W; Luh, Wen-Ming; Bandettini, Peter A

    2012-04-15

    A central challenge in the fMRI based study of functional connectivity is distinguishing neuronally related signal fluctuations from the effects of motion, physiology, and other nuisance sources. Conventional techniques for removing nuisance effects include modeling of noise time courses based on external measurements followed by temporal filtering. These techniques have limited effectiveness. Previous studies have shown using multi-echo fMRI that neuronally related fluctuations are Blood Oxygen Level Dependent (BOLD) signals that can be characterized in terms of changes in R(2)* and initial signal intensity (S(0)) based on the analysis of echo-time (TE) dependence. We hypothesized that if TE-dependence could be used to differentiate BOLD and non-BOLD signals, non-BOLD signal could be removed to denoise data without conventional noise modeling. To test this hypothesis, whole brain multi-echo data were acquired at 3 TEs and decomposed with Independent Components Analysis (ICA) after spatially concatenating data across space and TE. Components were analyzed for the degree to which their signal changes fit models for R(2)* and S(0) change, and summary scores were developed to characterize each component as BOLD-like or not BOLD-like. These scores clearly differentiated BOLD-like "functional network" components from non BOLD-like components related to motion, pulsatility, and other nuisance effects. Using non BOLD-like component time courses as noise regressors dramatically improved seed-based correlation mapping by reducing the effects of high and low frequency non-BOLD fluctuations. A comparison with seed-based correlation mapping using conventional noise regressors demonstrated the superiority of the proposed technique for both individual and group level seed-based connectivity analysis, especially in mapping subcortical-cortical connectivity. The differentiation of BOLD and non-BOLD components based on TE-dependence was highly robust, which allowed for the

  10. Reversible brain atrophy and subcortical high signal on MRI in a patient with anorexia nervosa

    International Nuclear Information System (INIS)

    Drevelengas, A.; Chourmouzi, D.; Boulogianni, G.; Pitsavas, G.; Charitandi, A.

    2001-01-01

    Anorexia nervosa (AN), usually seen in young girls, is characterised by severe emaciation induced by self-imposed starvation. Enlargement of the ventricular system and sulci has been reported, as has high signal on T2-weighted images. We present a case with atrophic changes and high signal on T2-weighted images, which resolved completely following weight gain. (orig.)

  11. Reversible brain atrophy and subcortical high signal on MRI in a patient with anorexia nervosa

    Energy Technology Data Exchange (ETDEWEB)

    Drevelengas, A. [Asklipios-Aristotelio Diagnostic Centre, Thessaloniki (Greece); Dept. of Radiology, AHEPA University Hospital, Thessaloniki (Greece); Chourmouzi, D.; Boulogianni, G. [Asklipios-Aristotelio Diagnostic Centre, Thessaloniki (Greece); Pitsavas, G. [Paediatric Clinic, AHEPA University Hospital, Thessaloniki (Greece); Charitandi, A. [Dept. of Radiology, AHEPA University Hospital, Thessaloniki (Greece)

    2001-10-01

    Anorexia nervosa (AN), usually seen in young girls, is characterised by severe emaciation induced by self-imposed starvation. Enlargement of the ventricular system and sulci has been reported, as has high signal on T2-weighted images. We present a case with atrophic changes and high signal on T2-weighted images, which resolved completely following weight gain. (orig.)

  12. A novel method, digital genome scanning detects KRAS gene amplification in gastric cancers: involvement of overexpressed wild-type KRAS in downstream signaling and cancer cell growth

    Directory of Open Access Journals (Sweden)

    Yanagihara Kazuyoshi

    2009-06-01

    Full Text Available Abstract Background Gastric cancer is the third most common malignancy affecting the general population worldwide. Aberrant activation of KRAS is a key factor in the development of many types of tumor, however, oncogenic mutations of KRAS are infrequent in gastric cancer. We have developed a novel quantitative method of analysis of DNA copy number, termed digital genome scanning (DGS, which is based on the enumeration of short restriction fragments, and does not involve PCR or hybridization. In the current study, we used DGS to survey copy-number alterations in gastric cancer cells. Methods DGS of gastric cancer cell lines was performed using the sequences of 5000 to 15000 restriction fragments. We screened 20 gastric cancer cell lines and 86 primary gastric tumors for KRAS amplification by quantitative PCR, and investigated KRAS amplification at the DNA, mRNA and protein levels by mutational analysis, real-time PCR, immunoblot analysis, GTP-RAS pull-down assay and immunohistochemical analysis. The effect of KRAS knock-down on the activation of p44/42 MAP kinase and AKT and on cell growth were examined by immunoblot and colorimetric assay, respectively. Results DGS analysis of the HSC45 gastric cancer cell line revealed the amplification of a 500-kb region on chromosome 12p12.1, which contains the KRAS gene locus. Amplification of the KRAS locus was detected in 15% (3/20 of gastric cancer cell lines (8–18-fold amplification and 4.7% (4/86 of primary gastric tumors (8–50-fold amplification. KRAS mutations were identified in two of the three cell lines in which KRAS was amplified, but were not detected in any of the primary tumors. Overexpression of KRAS protein correlated directly with increased KRAS copy number. The level of GTP-bound KRAS was elevated following serum stimulation in cells with amplified wild-type KRAS, but not in cells with amplified mutant KRAS. Knock-down of KRAS in gastric cancer cells that carried amplified wild

  13. A novel method, digital genome scanning detects KRAS gene amplification in gastric cancers: involvement of overexpressed wild-type KRAS in downstream signaling and cancer cell growth

    International Nuclear Information System (INIS)

    Mita, Hiroaki; Yanagihara, Kazuyoshi; Fujita, Masahiro; Hosokawa, Masao; Kusano, Masanobu; Sabau, Sorin Vasile; Tatsumi, Haruyuki; Imai, Kohzoh; Shinomura, Yasuhisa; Tokino, Takashi; Toyota, Minoru; Aoki, Fumio; Akashi, Hirofumi; Maruyama, Reo; Sasaki, Yasushi; Suzuki, Hiromu; Idogawa, Masashi; Kashima, Lisa

    2009-01-01

    Gastric cancer is the third most common malignancy affecting the general population worldwide. Aberrant activation of KRAS is a key factor in the development of many types of tumor, however, oncogenic mutations of KRAS are infrequent in gastric cancer. We have developed a novel quantitative method of analysis of DNA copy number, termed digital genome scanning (DGS), which is based on the enumeration of short restriction fragments, and does not involve PCR or hybridization. In the current study, we used DGS to survey copy-number alterations in gastric cancer cells. DGS of gastric cancer cell lines was performed using the sequences of 5000 to 15000 restriction fragments. We screened 20 gastric cancer cell lines and 86 primary gastric tumors for KRAS amplification by quantitative PCR, and investigated KRAS amplification at the DNA, mRNA and protein levels by mutational analysis, real-time PCR, immunoblot analysis, GTP-RAS pull-down assay and immunohistochemical analysis. The effect of KRAS knock-down on the activation of p44/42 MAP kinase and AKT and on cell growth were examined by immunoblot and colorimetric assay, respectively. DGS analysis of the HSC45 gastric cancer cell line revealed the amplification of a 500-kb region on chromosome 12p12.1, which contains the KRAS gene locus. Amplification of the KRAS locus was detected in 15% (3/20) of gastric cancer cell lines (8–18-fold amplification) and 4.7% (4/86) of primary gastric tumors (8–50-fold amplification). KRAS mutations were identified in two of the three cell lines in which KRAS was amplified, but were not detected in any of the primary tumors. Overexpression of KRAS protein correlated directly with increased KRAS copy number. The level of GTP-bound KRAS was elevated following serum stimulation in cells with amplified wild-type KRAS, but not in cells with amplified mutant KRAS. Knock-down of KRAS in gastric cancer cells that carried amplified wild-type KRAS resulted in the inhibition of cell growth and

  14. Interventional MRI

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Junta; Dohi, Michiko; Yoshihiro, Akiko; Mogami, Takuji; Kuwada, Tomoko; Nakata, Norio [Jikei Univ., Chiba (Japan). Kashiwa Hospital

    2000-06-01

    Open type MR system and fast sequence is now available and MRI becomes a new modality for interventional Radiology, including biopsy, drainage operation, and monitoring for minimally invasive therapy. Experimental studies of temperature monitoring were performed under hot and cold status. Signal changes of porcine disc and meat under microwave and laser ablation were observed as low signal area by signal intensity method. Using proton chemical shift method, signal change by laser ablation was displaced color imaging and correlated with thermometric temperature measurement. The very T2 relaxation time of ice affords excellent contrast between ice and surrounding gelatin tissue allowing acute depiction of the extent of the iceball under MRI. (author)

  15. Optimizing signal intensity correction during evaluation of hepatic parenchymal enhancement on gadoxetate disodium-enhanced MRI: Comparison of three methods

    International Nuclear Information System (INIS)

    Onoda, Minori; Hyodo, Tomoko; Murakami, Takamichi; Okada, Masahiro; Uto, Tatsuro; Hori, Masatoshi; Miyati, Tosiaki

    2015-01-01

    Highlights: •Signal intensity is often used to evaluate hepatic enhancement with Gd-EOB-DTPA in the hepatobiliary phase. •Comparison of uncorrected signal intensity with T 1 value revealed signal intensity instability. •Measurement of uncorrected liver SI or SNR often yields erroneous results on late-phase gadoxetate MRI due to shimming and other optimization techniques. •Signal intensity corrected by scale and rescale slope from DICOM data gave comparable results. -- Abstract: Objective: To compare signal intensity (SI) correction using scale and rescale slopes with SI correction using SIs of spleen and muscle for quantifying multiphase hepatic contrast enhancement with Gd-EOB-DTPA by assessing their correlation with T 1 values generated from Look-Locker turbo-field-echo (LL-TFE) sequence data (ER-T 1 ). Materials and methods: Thirty patients underwent Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) in this prospective clinical study. For each patient, breath-hold T 1 -weighted fat-suppressed three-dimensional (3D) gradient echo sequences (e-THRIVE) were acquired before and 2 (first phase), 10 (second phase), and 20 min (third phase) after intravenous Gd-EOB-DTPA. Look-Locker turbo-field-echo (LL-TFE) sequences were acquired before and 1.5 (first phase), 8 (second phase), and 18 min (third phase) postcontrast. The liver parenchyma enhancement ratios (ER) of each phase were calculated using the SI from e-THRIVE sequences (ER-SI) and the T 1 values generated from LL-TFE sequence data (ER-T 1 ) respectively. ER-SIs were calculated in three ways: (1) comparing with splenic SI (ER-SI-s), (2) comparing with muscle SI (ER-SI-m), (3) using scale and rescale slopes obtained from DICOM headers (ER-SI-c), to eliminate the effects of receiver gain and scaling. For each of the first, second and third phases, correlation and agreement were assessed between each ER-SI and ER-T 1 . Results: In the first phase, all ER-SIs correlated weakly with ER-T 1 . In the second

  16. Bell's palsy: what is the prognostic value of measurements of signal intensity increases with contrast enhancement on MRI?

    International Nuclear Information System (INIS)

    Kress, B.P.J.; Efinger, K.; Solbach, T.; Gottschalk, A.; Baehren, W.; Griesbeck, F.; Kornhuber, A.W.

    2002-01-01

    Our objective was to assess the prognostic value of measurements of the degree of contrast enhancement of the intratemporal segments of the facial nerve. We prospectively obtained MRI, slice thickness <1 mm of 20 patients with a facial palsy on the first day of inpatient treatment, and measured contrast enhancement of the nerve. The data were compared with compound muscle action potential (CMAP) measurements and the clinical course. Analysis of the initial enabled differentiation of three patients whose palsy was to show no improvement from 17 whose palsy was to resolve as expected. No patient with a poor outcome showed lesser increase in signal in the internal auditory canal, pars tympanica and pars mastoidea than patients who fully recovered. In no patient who had been diagnosed on the basis of the initial MRI as having a ''normal'' palsy was the amplitude of the (CMAP) reduced to less than 20% that of the normal side. Measurement of contrast enhancement was thus shown to be a prognostic indicator and may provide a basis for a differential treatment of facial palsy. (orig.)

  17. Neural Substrates of Social Emotion Regulation: A fMRI Study on Imitation and Expressive Suppression to Dynamic Facial Signals

    Directory of Open Access Journals (Sweden)

    Pascal eVrticka

    2013-02-01

    Full Text Available Emotion regulation is crucial for successfully engaging in social interactions. Yet, little is known about the neural mechanisms controlling behavioral responses to emotional expressions perceived in the face of other people, which constitute a key element of interpersonal communication. Here, we investigated brain systems involved in social emotion perception and regulation, using functional magnetic resonance imaging (fMRI in 20 healthy participants who saw dynamic facial expressions of either happiness or sadness, and were asked to either imitate the expression or to suppress any expression on their own face (in addition to a gender judgment control task. fMRI results revealed higher activity in regions associated with emotion (e.g., the insula, motor function (e.g., motor cortex, and theory of mind during imitation. Activity in dorsal cingulate cortex was also increased during imitation, possibly reflecting greater action monitoring or conflict with own feeling states. In addition, premotor regions were more strongly activated during both imitation and suppression, suggesting a recruitment of motor control for both the production and inhibition of emotion expressions. Expressive suppression produced increases in dorsolateral and lateral prefrontal cortex typically related to cognitive control. These results suggest that voluntary imitation and expressive suppression modulate brain responses to emotional signals perceived from faces, by up- and down-regulating activity in distributed subcortical and cortical networks that are particularly involved in emotion, action monitoring, and cognitive control.

  18. Concurrent fNIRS-fMRI measurement to validate a method for separating deep and shallow fNIRS signals by using multidistance optodes

    Science.gov (United States)

    Funane, Tsukasa; Sato, Hiroki; Yahata, Noriaki; Takizawa, Ryu; Nishimura, Yukika; Kinoshita, Akihide; Katura, Takusige; Atsumori, Hirokazu; Fukuda, Masato; Kasai, Kiyoto; Koizumi, Hideaki; Kiguchi, Masashi

    2015-01-01

    Abstract. It has been reported that a functional near-infrared spectroscopy (fNIRS) signal can be contaminated by extracerebral contributions. Many algorithms using multidistance separations to address this issue have been proposed, but their spatial separation performance has rarely been validated with simultaneous measurements of fNIRS and functional magnetic resonance imaging (fMRI). We previously proposed a method for discriminating between deep and shallow contributions in fNIRS signals, referred to as the multidistance independent component analysis (MD-ICA) method. In this study, to validate the MD-ICA method from the spatial aspect, multidistance fNIRS, fMRI, and laser-Doppler-flowmetry signals were simultaneously obtained for 12 healthy adult males during three tasks. The fNIRS signal was separated into deep and shallow signals by using the MD-ICA method, and the correlation between the waveforms of the separated fNIRS signals and the gray matter blood oxygenation level–dependent signals was analyzed. A three-way analysis of variance (signal depth×Hb kind×task) indicated that the main effect of fNIRS signal depth on the correlation is significant [F(1,1286)=5.34, pdeep and shallow signals, and the accuracy and reliability of the fNIRS signal will be improved with the method. PMID:26157983

  19. Bone signal abnormality, as seen on knee joint MRI : relationship between its location and associated injury

    International Nuclear Information System (INIS)

    Kim, Young Nam; Kim, Baek Hyun; Jung, Hoe Seok; Na, Eui Sung; Seol, Hye Young; Cha, In Ho; Lim, Hong Chul

    1998-01-01

    The purpose of the study was to evaluate the relationship between the location of bone signal abnormality and associated injury, as seen on MR, in patients with acute knee joint injury. Materials and Methods: Thirty-six patients with acute knee injury and bone signal abnormalities on MR were included in this study. The femur and tibia were each divided into six compartments, namely the anteromedial, medial, posteromedial,anterolateral, lateral, and posterolateral ; these were obtained in each knee joint. We evaluated the location of bone signal abnormality and the corresponding arthroscopic or operative findings of injury to ligaments and menisci. Cases with signal abnormalities involving more than three compartments were excluded. Results : Bone signal abnormalities were demonstrated in 51 compartments. Most(84%, 43/51) were noted in the lateral half of the knee joint, the most common location being the tibio- posterolateral compartment(13/51). The femoro-lateral(11/51) and tibio- anterolateral compartment(8/51) were the next most common locations. All cases(13/13)with bone signal abnormality in the tibio- posterolateral compartment had tears at the anterior cruciate ligament,while 9 of 11 cases(81%) with abnormality in the femoro- lateral compartment had tears at the anterior cruciate ligament. Six of eight cases(75%) with signal abnormality in the tibio- anterolateral compartment had tears at the posterior cruciate ligament ; 31 of 43 cases (72%) with abnormality in the lateral half of the knee joint had tears at the medial collateral ligament. Six of eight cases(75%) with signal abnormality in the medial half of the knee joint had tears at the medial meniscus, but no lateral meniscal tear was found. Among patients with signal abnormality in the lateral half of the knee joint, the tear was lateral meniscal in nine of 43 cases(21%) and medial meniscal in six of 43(14%). Conclusion : The location of bone signal abnormality, as seen on knee MR, inpatients with

  20. Quality assurance in MRI breast screening: comparing signal-to-noise ratio in dynamic contrast-enhanced imaging protocols

    Science.gov (United States)

    Kousi, Evanthia; Borri, Marco; Dean, Jamie; Panek, Rafal; Scurr, Erica; Leach, Martin O.; Schmidt, Maria A.

    2016-01-01

    MRI has been extensively used in breast cancer staging, management and high risk screening. Detection sensitivity is paramount in breast screening, but variations of signal-to-noise ratio (SNR) as a function of position are often overlooked. We propose and demonstrate practical methods to assess spatial SNR variations in dynamic contrast-enhanced (DCE) breast examinations and apply those methods to different protocols and systems. Four different protocols in three different MRI systems (1.5 and 3.0 T) with receiver coils of different design were employed on oil-filled test objects with and without uniformity filters. Twenty 3D datasets were acquired with each protocol; each dataset was acquired in under 60 s, thus complying with current breast DCE guidelines. In addition to the standard SNR calculated on a pixel-by-pixel basis, we propose other regional indices considering the mean and standard deviation of the signal over a small sub-region centred on each pixel. These regional indices include effects of the spatial variation of coil sensitivity and other structured artefacts. The proposed regional SNR indices demonstrate spatial variations in SNR as well as the presence of artefacts and sensitivity variations, which are otherwise difficult to quantify and might be overlooked in a clinical setting. Spatial variations in SNR depend on protocol choice and hardware characteristics. The use of uniformity filters was shown to lead to a rise of SNR values, altering the noise distribution. Correlation between noise in adjacent pixels was associated with data truncation along the phase encoding direction. Methods to characterise spatial SNR variations using regional information were demonstrated, with implications for quality assurance in breast screening and multi-centre trials.

  1. Low-intensity pulsed ultrasound is effective for progressive-stage lumbar spondylolysis with MRI high-signal change.

    Science.gov (United States)

    Arima, Hideyuki; Suzuki, Yoshiji; Togawa, Daisuke; Mihara, Yuki; Murata, Hideyuki; Matsuyama, Yukihiro

    2017-12-01

    This study aimed to investigate the treatment effects of low-intensity pulsed ultrasound (LIPUS) on progressive-stage spondylolysis. Spondylolysis is a stress fracture of the pars interarticularis. Based on the results of computed tomography, spondylolysis was classified into three categories: early, progressive, and terminal. Bone healing was prolonged or not obtained in progressive-stage spondylolysis. The progression of spondylolysis to nonunion has been associated with an increased incidence of spondylolisthesis. To prevent these clinical conditions, achieving bony healing of the spondylolysis site should be the goal of treatment. 15 consecutive pediatric patients with progressive-stage spondylolysis (defects) with MRI high-signal change were analyzed. Nine patients were treated conservative treatment including avoidance of any sport activity and the use of a brace during treatment (conventional). Six patients were treated using LIPUS everyday during treatment in addition to conservative treatment. Approximately every 1.5 months, bone healing was evaluated via CT. Cases that retained defects after 4.5 months were defined as nonunion. Two patients dropped out during the study period. A total of 13 patients (mean 14.6 ± 2.5 years) from the database met with 19 interarticularis defects. The bone union rate in LIPUS group was significantly higher than that in conventional group (66.7 vs. 10.0%, p = 0.020). The treatment period to bone union was 3.8 months and 2.7 ± 0.3 months in conventional and LIPUS groups. This study revealed that LIPUS treatment might be effective for bone union in patients with progressive-stage spondylolysis with MRI high-signal change. 4.

  2. Indirect MRI of 17 o-labeled water using steady-state sequences: Signal simulation and preclinical experiment.

    Science.gov (United States)

    Kudo, Kohsuke; Harada, Taisuke; Kameda, Hiroyuki; Uwano, Ikuko; Yamashita, Fumio; Higuchi, Satomi; Yoshioka, Kunihiro; Sasaki, Makoto

    2018-05-01

    Few studies have been reported for T 2 -weighted indirect 17 O imaging. To evaluate the feasibility of steady-state sequences for indirect 17 O brain imaging. Signal simulation, phantom measurements, and prospective animal experiments were performed in accordance with the institutional guidelines for animal experiments. Signal simulations of balanced steady-state free precession (bSSFP) were performed for concentrations of 17 O ranging from 0.037-1.600%. Phantom measurements with concentrations of 17 O water ranging from 0.037-1.566% were also conducted. Six healthy beagle dogs were scanned with intravenous administration of 20% 17 O-labeled water (1 mL/kg). Dynamic 3D-bSSFP scans were performed at 3T MRI. 17 O-labeled water was injected 60 seconds after the scan start, and the total scan duration was 5 minutes. Based on the result of signal simulation and phantom measurement, signal changes in the beagle dogs were measured and converted into 17 O concentrations. The 17 O concentrations were averaged for every 15 seconds, and compared to the baseline (30-45 sec) with Dunnett's multiple comparison tests. Signal simulation revealed that the relationships between 17 O concentration and the natural logarithm of relative signals were linear. The intraclass correlation coefficient between relative signals in phantom measurement and signal simulations was 0.974. In the animal experiments, significant increases in 17 O concentration (P O. At the end of scanning, mean respective 17 O concentrations of 0.084 ± 0.026%, 0.117 ± 0.038, 0.082 ± 0.037%, and 0.049 ± 0.004% were noted for the cerebral cortex, cerebellar cortex, cerebral white matter, and ventricle. Dynamic steady-state sequences were feasible for indirect 17 O imaging, and absolute quantification was possible. This method can be applied for the measurement of permeability and blood flow in the brain, and for kinetic analysis of cerebrospinal fluid. 2 Technical Efficacy: Stage 1 J. Magn. Reson

  3. Visualization of mcr mRNA in a methanogen by fluorescence in situ hybridization with an oligonucleotide probe and two-pass tyramide signal amplification (two-pass TSA-FISH).

    Science.gov (United States)

    Kubota, Kengo; Ohashi, Akiyoshi; Imachi, Hiroyuki; Harada, Hideki

    2006-09-01

    Two-pass tyramide signal amplification-fluorescence in situ hybridization (two-pass TSA-FISH) with a horseradish peroxidase (HRP)-labeled oligonucleotide probe was applied to detect prokaryotic mRNA. In this study, mRNA of a key enzyme for methanogenesis, methyl coenzyme M reductase (mcr), in Methanococcus vannielii was targeted. Applicability of mRNA-targeted probes to in situ hybridization was verified by Clone-FISH. It was observed that sensitivity of two-pass TSA-FISH was significantly higher than that of TSA-FISH, which was further increased by the addition of dextran sulphate in TSA working solution. Signals from two-pass TSA-FISH were more reliable compared to the weak, spotty signals yielded by TSA-FISH.

  4. High spatial correspondence at a columnar level between activation and resting state fMRI signals and local field potentials.

    Science.gov (United States)

    Shi, Zhaoyue; Wu, Ruiqi; Yang, Pai-Feng; Wang, Feng; Wu, Tung-Lin; Mishra, Arabinda; Chen, Li Min; Gore, John C

    2017-05-16

    Although blood oxygenation level-dependent (BOLD) fMRI has been widely used to map brain responses to external stimuli and to delineate functional circuits at rest, the extent to which BOLD signals correlate spatially with underlying neuronal activity, the spatial relationships between stimulus-evoked BOLD activations and local correlations of BOLD signals in a resting state, and whether these spatial relationships vary across functionally distinct cortical areas are not known. To address these critical questions, we directly compared the spatial extents of stimulated activations and the local profiles of intervoxel resting state correlations for both high-resolution BOLD at 9.4 T and local field potentials (LFPs), using 98-channel microelectrode arrays, in functionally distinct primary somatosensory areas 3b and 1 in nonhuman primates. Anatomic images of LFP and BOLD were coregistered within 0.10 mm accuracy. We found that the point spread functions (PSFs) of BOLD and LFP responses were comparable in the stimulus condition, and both estimates of activations were slightly more spatially constrained than local correlations at rest. The magnitudes of stimulus responses in area 3b were stronger than those in area 1 and extended in a medial to lateral direction. In addition, the reproducibility and stability of stimulus-evoked activation locations within and across both modalities were robust. Our work suggests that the intrinsic resolution of BOLD is not a limiting feature in practice and approaches the intrinsic precision achievable by multielectrode electrophysiology.

  5. Increased signal intensities in the dentate nucleus and globus pallidus on unenhanced T1-weighted images: evidence in children undergoing multiple gadolinium MRI exams

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Houchun H.; Pokorney, Amber; Towbin, Richard B.; Miller, Jeffrey H. [Phoenix Children' s Hospital, Department of Medical Imaging and Radiology, Phoenix, AZ (United States)

    2016-10-15

    Recent reports have suggested residual gadolinium deposition in the brain in subjects undergoing multiple contrast-enhanced MRI exams. These findings have raised some concerns regarding gadolinium-based contrast agent (GBCA) usage and retention in brain tissues. To summarize findings of hyperintense brain structures on precontrast T1-weighted images in 21 children undergoing multiple GBCA MRI exams. This retrospective study involved 21 patients, each of whom received multiple MRI examinations (range: 5-37 exams) with GBCA over the course of their medical treatment (duration from first to most recent exam: 1.2-12.9 years). The patients were between 0.9 and 14.4 years of age at the time of their first GBCA exam. Regions of interest were drawn in the dentate nucleus and the globus pallidus on 2-D fast spin echo images acquired at 1.5 T. The signal intensities of these two structures were normalized by that of the corpus callosum genu. Signal intensity ratios from these patients were compared to control patients of similar ages who have never received GBCA. Signal intensity ratios increased between the first and the most recent MRI exam in all 21 patients receiving GBCA, with an increase of 18.6%±12.7% (range: 0.5% to 47.5%) for the dentate nucleus and 12.4%±7.4% (range: -1.2% to 33.7%) for the globus pallidus (P<0.0001). Signal intensity ratios were also higher in GBCA patients than in controls (P<0.01). The degree of signal intensity enhancement did not correlate with statistical significance to the cumulative number or volume of GBCA administrations each patient received, the patient's age or the elapsed time between the first and most recent GBCA MRI exams. These results in children are consistent with recent findings in adults, suggesting possible gadolinium deposition in the brain. (orig.)

  6. Relationship of signal-to-noise ratio with acquisition parameters in MRI for a given contrast

    International Nuclear Information System (INIS)

    Bittoun, J.; Leroy-Willig, A.; Idy, I.; Halimi, P.; Syrota, A.; Desgrez, A.; Saint-Jalmes, H.

    1987-01-01

    The signal-to-noise ratio (SNR) is certainly the most important characteristic of medical images, since the spatial resolution and the visualization of contrast are dependent on its value. On the other hand, modifying an acquisition variable in magnetic resonance imaging, in order to improve spatial resolution for example, may induce a SNR loss and finally alter the image quality. We have studied a theoretical relation between SNR and 2DFT method acquisition variables with the exception of parameters such as TR, TE and TI; these parameters are determined by the desired contrast in order to confirm a diagnosis. According to this relation SNR is proportional to each dimension of the slice, and to the square root of the number of averaged signals; it is inversely proportional to the number of frequency points and to the square root of the number of phase points. This relation was experimentally verified with phantoms and on an MR system at 1.5 T. It was then plotted as a multiple-entry graph on which operators at the console can read the number of averaged signals necessary to compensate SNR loss induced by a modification of other parameters [fr

  7. Signal-to-noise ratio measurement in parallel MRI with subtraction mapping and consecutive methods

    International Nuclear Information System (INIS)

    Imai, Hiroshi; Miyati, Tosiaki; Ogura, Akio; Doi, Tsukasa; Tsuchihashi, Toshio; Machida, Yoshio; Kobayashi, Masato; Shimizu, Kouzou; Kitou, Yoshihiro

    2008-01-01

    When measuring the signal-to-noise ratio (SNR) of an image the used parallel magnetic resonance imaging, it was confirmed that there was a problem in the application of past SNR measurement. With the method of measuring the noise from the background signal, SNR with parallel imaging was higher than that without parallel imaging. In the subtraction method (NEMA standard), which sets a wide region of interest, the white noise was not evaluated correctly although SNR was close to the theoretical value. We proposed two techniques because SNR in parallel imaging was not uniform according to inhomogeneity of the coil sensitivity distribution and geometry factor. Using the first method (subtraction mapping), two images were scanned with identical parameters. The SNR in each pixel divided the running mean (7 by 7 pixels in neighborhood) by standard deviation/√2 in the same region of interest. Using the second (consecutive) method, more than fifty consecutive scans of the uniform phantom were obtained with identical scan parameters. Then the SNR was calculated from the ratio of mean signal intensity to the standard deviation in each pixel on a series of images. Moreover, geometry factors were calculated from SNRs with and without parallel imaging. The SNR and geometry factor using parallel imaging in the subtraction mapping method agreed with those of the consecutive method. Both methods make it possible to obtain a more detailed determination of SNR in parallel imaging and to calculate the geometry factor. (author)

  8. Phase-synchronization-based parcellation of resting state fMRI signals reveals topographically organized clusters in early visual cortex

    NARCIS (Netherlands)

    Gravel, Nicolás G; Harvey, Ben M; Renken, Remco K; Dumoulin, Serge O; Cornelissen, Frans W

    2018-01-01

    Resting-state fMRI is widely used to study brain function and connectivity. However, interpreting patterns of resting state (RS) fMRI activity remains challenging as they may arise from different neuronal mechanisms than those triggered by exogenous events. Currently, this limits the use of RS-fMRI

  9. Dissecting the pathobiology of altered MRI signal in amyotrophic lateral sclerosis: A post mortem whole brain sampling strategy for the integration of ultra-high-field MRI and quantitative neuropathology.

    Science.gov (United States)

    Pallebage-Gamarallage, Menuka; Foxley, Sean; Menke, Ricarda A L; Huszar, Istvan N; Jenkinson, Mark; Tendler, Benjamin C; Wang, Chaoyue; Jbabdi, Saad; Turner, Martin R; Miller, Karla L; Ansorge, Olaf

    2018-03-13

    Amyotrophic lateral sclerosis (ALS) is a clinically and histopathologically heterogeneous neurodegenerative disorder, in which therapy is hindered by the rapid progression of disease and lack of biomarkers. Magnetic resonance imaging (MRI) has demonstrated its potential for detecting the pathological signature and tracking disease progression in ALS. However, the microstructural and molecular pathological substrate is poorly understood and generally defined histologically. One route to understanding and validating the pathophysiological correlates of MRI signal changes in ALS is to directly compare MRI to histology in post mortem human brains. The article delineates a universal whole brain sampling strategy of pathologically relevant grey matter (cortical and subcortical) and white matter tracts of interest suitable for histological evaluation and direct correlation with MRI. A standardised systematic sampling strategy that was compatible with co-registration of images across modalities was established for regions representing phosphorylated 43-kDa TAR DNA-binding protein (pTDP-43) patterns that were topographically recognisable with defined neuroanatomical landmarks. Moreover, tractography-guided sampling facilitated accurate delineation of white matter tracts of interest. A digital photography pipeline at various stages of sampling and histological processing was established to account for structural deformations that might impact alignment and registration of histological images to MRI volumes. Combined with quantitative digital histology image analysis, the proposed sampling strategy is suitable for routine implementation in a high-throughput manner for acquisition of large-scale histology datasets. Proof of concept was determined in the spinal cord of an ALS patient where multiple MRI modalities (T1, T2, FA and MD) demonstrated sensitivity to axonal degeneration and associated heightened inflammatory changes in the lateral corticospinal tract. Furthermore

  10. Dietary pattern associated with selenoprotein P and MRI-derived body fat volumes, liver signal intensity, and metabolic disorders.

    Science.gov (United States)

    di Giuseppe, Romina; Plachta-Danielzik, Sandra; Koch, Manja; Nöthlings, Ute; Schlesinger, Sabrina; Borggrefe, Jan; Both, Marcus; Müller, Hans-Peter; Kassubek, Jan; Jacobs, Gunnar; Lieb, Wolfgang

    2018-02-14

    The association of complex dietary patterns with circulating selenoprotein P (SELENOP) levels in humans is unknown. In a general population sample, we aimed to identify a dietary pattern explaining inter-individual variation in circulating SELENOP concentrations and to study this pattern in relation to prevalent diabetes, metabolic syndrome (MetS), MRI-determined total volumes of visceral (VAT) and subcutaneous (SAT) abdominal adipose tissue, and liver signal intensity/fatty liver disease. In this cross-sectional study, serum SELENOP levels were measured in 853 individuals. In a subsample of 553 participants, whole-body MRI was performed to assess body fat distribution and liver fat. Dietary intake was assessed by a self-administered food frequency questionnaire and the dietary pattern identified using reduced-rank regression (RRR). Multivariable linear and logistic regressions were used to investigate associations between dietary pattern score and metabolic traits. Characterized by high intake of fruit, vegetables and antioxidant beverages, the RRR-derived dietary pattern displayed inverse associations with VAT, SAT, MetS, and prevalent diabetes in multivariable-adjusted restricted cubic splines. Each unit increase in dietary pattern score was associated with 31% higher SELENOP levels, 12% lower VAT (95% CI: - 19%; - 5%), 13% (95% CI: - 20%; - 6%) lower SAT values and 46% (95% CI: 27%; 60%) and 53% (95% CI: 22%; 72%) lower odds of having MetS or diabetes, respectively. No meaningful relations were observed between the dietary pattern and liver traits. Our observations propose diet-related regulation in SELENOP levels and that the identified dietary pattern is inversely related to VAT, SAT, MetS, and prevalent diabetes.

  11. Comparison of facet joint activity on 99mTc-MDP SPECT/CT with facet joint signal change on MRI with fat suppression.

    Science.gov (United States)

    Lehman, Vance T; Murphy, Robert C; Schenck, Louis A; Carter, Rickey E; Johnson, Geoffrey B; Kotsenas, Amy L; Morris, Jonathan M; Nathan, Mark A; Wald, John T; Maus, Timothy P

    2016-01-01

    We compared signal change on magnetic resonance imaging (MRI) with fat suppression and bone scan activity of lumbar facet joints to determine if these two imaging findings are correlated. We retrospectively identified all patients who underwent imaging of the lumbar spine for pain evaluation using both technetium-99m methylene disphosphonate single-photon emission computed tomography/computed tomography (99mTc-MDP SPECT/CT) and MRI with at least one fat-suppressed T2- or T1-weighted sequence with gadolinium enhancement within a 180-day interval, at our institution between 1 January 2008 and 19 February 2013. Facet joint activity on 99mTc-MDP SPECT/CT and peri-facet signal change on MRI were rated as normal or increased. Agreement between the two examination types were determined with the κ and prevalence-adjusted bias-adjusted κ (PABAK) statistics. This study included 60 patients (28 male, 47%), with a mean age of 49±19.7 years (range, 12-93 years). The κ value indicated no agreement between 99mTc-MDP SPECT/CT and MRI (κ=-0.026; 95% confidence interval: -0.051, 0.000). The PABAK values were fair to high at each spinal level, which suggests that relatively low disease prevalence lowered the κ values. Together, the κ and PABAK values indicate that there is some degree of intermodality agreement, but that it is not consistent. Overall, facet joint signal change on fat-suppressed MRI did not always correlate with increased 99mTc-MDP SPECT/CT activity. MRI and 99mTc-MDP SPECT/CT for facet joint evaluation should not be considered interchangeable examinations in clinical practice or research.

  12. High signals in the uterine cervix on T2-weighted MRI sequences

    International Nuclear Information System (INIS)

    Graef, De M.; Karam, R.; Daclin, P.Y.; Rouanet, J.P.; Juhan, V.; Maubon, A.J.

    2003-01-01

    The aim of this pictorial review was to illustrate the normal cervix appearance on T2-weighted images, and give a review of common or less common disorders of the uterine cervix that appear as high signal intensity lesions on T2-weighted sequences. Numerous aetiologies dominated by cervical cancer are reviewed and discussed. This gamut is obviously incomplete; however, radiologists who perform MR women's imaging should perform T2-weighted sequences in the sagittal plane regardless of the indication for pelvic MR. Those sequences will diagnose some previously unknown cervical cancers as well as many other unknown cervical or uterine lesions. (orig.)

  13. Optimizing signal intensity correction during evaluation of hepatic parenchymal enhancement on gadoxetate disodium-enhanced MRI: Comparison of three methods

    Energy Technology Data Exchange (ETDEWEB)

    Onoda, Minori, E-mail: onoda@radt.med.kindai.ac.jp [Department of Radiological Technology, Kinki University Hospital, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942 (Japan); Hyodo, Tomoko, E-mail: neneth@m.ehime-u.ac.jp [Department of Radiology, Kinki University Faculty of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Murakami, Takamichi, E-mail: murakami@med.kindai.ac.jp [Department of Radiology, Kinki University Faculty of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Okada, Masahiro, E-mail: okada777@med.u-ryukyu.ac.jp [Department of Radiology, Kinki University Faculty of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Uto, Tatsuro, E-mail: chuho@med.kindai.ac.jp [Department of Radiological Technology, Kinki University Hospital, 377-2 Ohno-Higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Hori, Masatoshi, E-mail: mhori@radiol.med.osaka-u.ac.jp [Department of Radiology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871 (Japan); Miyati, Tosiaki, E-mail: ramiyati@mhs.mp.kanazawa-u.ac.jp [Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942 (Japan)

    2015-03-15

    Highlights: •Signal intensity is often used to evaluate hepatic enhancement with Gd-EOB-DTPA in the hepatobiliary phase. •Comparison of uncorrected signal intensity with T{sub 1} value revealed signal intensity instability. •Measurement of uncorrected liver SI or SNR often yields erroneous results on late-phase gadoxetate MRI due to shimming and other optimization techniques. •Signal intensity corrected by scale and rescale slope from DICOM data gave comparable results. -- Abstract: Objective: To compare signal intensity (SI) correction using scale and rescale slopes with SI correction using SIs of spleen and muscle for quantifying multiphase hepatic contrast enhancement with Gd-EOB-DTPA by assessing their correlation with T{sub 1} values generated from Look-Locker turbo-field-echo (LL-TFE) sequence data (ER-T{sub 1}). Materials and methods: Thirty patients underwent Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) in this prospective clinical study. For each patient, breath-hold T{sub 1}-weighted fat-suppressed three-dimensional (3D) gradient echo sequences (e-THRIVE) were acquired before and 2 (first phase), 10 (second phase), and 20 min (third phase) after intravenous Gd-EOB-DTPA. Look-Locker turbo-field-echo (LL-TFE) sequences were acquired before and 1.5 (first phase), 8 (second phase), and 18 min (third phase) postcontrast. The liver parenchyma enhancement ratios (ER) of each phase were calculated using the SI from e-THRIVE sequences (ER-SI) and the T{sub 1} values generated from LL-TFE sequence data (ER-T{sub 1}) respectively. ER-SIs were calculated in three ways: (1) comparing with splenic SI (ER-SI-s), (2) comparing with muscle SI (ER-SI-m), (3) using scale and rescale slopes obtained from DICOM headers (ER-SI-c), to eliminate the effects of receiver gain and scaling. For each of the first, second and third phases, correlation and agreement were assessed between each ER-SI and ER-T{sub 1}. Results: In the first phase, all ER-SIs correlated

  14. MRI of ventilated neonates and infants: respiratory pressure as trigger signal

    International Nuclear Information System (INIS)

    Lotz, J.; Reiffen, H.P.

    2004-01-01

    Introduction: motivated by the difficulties often encountered in the setup of respiratory trigger in MR imaging of mechanical ventilated pediatric patients, a simplified approach in terms of time and reliability was sought. Method: with the help of a male-to-male Luer-Lock adapter in combination with a 3-way adapter the tube of the respiratory compensation bellow was fixed to the output channel for capnography of the airway filter. Ten patients (age 4 months to 6 years) were tested with spin echo imaging and either respiration compensation (T1-weighted imaging) or respiratory triggered (T2-weighted imaging). Results: a clear trigger signal was achieved in all cases. No negative influence on the quality or security of the mechanical ventilation of the patients was observed. Summary: the proposed adapter is safe, efficient and fast to install in patients undergoing MR imaging in general anaesthesia. (orig.) [de

  15. Appearance of low signal intensity lines in MRI of silicone breast implants.

    Science.gov (United States)

    Stroman, P W; Rolland, C; Dufour, M; Grondin, P; Guidoin, R G

    1996-05-01

    Magnetic resonance (MR) images of five explanted mammary prostheses were obtained with a 1.5 T GE Signa system using a conventional spin-echo pulse sequence, in order to investigate the low-intensity curvilinear lines which may be observed in MR images of silicone gel-filled breast implants under pressure from fibrous capsules. MR images showed ellipsoid prostheses, often containing multiple low-intensity curvilinear lines which in some cases presented an appearance very similar to that of the linguine sign. Upon opening the fibrous capsules, however, all of the prostheses were found to be completely intact demonstrating that the appearance of multiple low signal intensity curvilinear lines in MR images of silicone gel-filled prostheses is not necessarily a sign of prosthesis rupture. The MR image features which are specific to the linguine sign must be more precisely defined.

  16. MRI signal-based quantification of subchondral bone at the tibial plateau: a population study

    Energy Technology Data Exchange (ETDEWEB)

    MacKay, James W. [Norfolk and Norwich University Hospital, Department of Radiology, Norwich (United Kingdom); Norfolk and Norwich University Hospital, Radiology Academy, Cotman Centre, Norwich (United Kingdom); Godley, Keith C.; Toms, Andoni P. [Norfolk and Norwich University Hospital, Department of Radiology, Norwich (United Kingdom)

    2014-11-15

    To determine whether differences in subchondral sclerosis at the tibial plateau could be detected with magnetic resonance (MR) imaging in two different age groups. This was a retrospective hypothesis-testing study. Thirty-two knees in group A (25-30 year olds) and 32 knees in group B (45-50 years old) were included. Participants had no MR features of osteoarthritis (OA). On coronal images, tibial articular cartilage thickness was measured, and regions of interest were created in the medial and lateral tibial plateau subchondral bone and in the tibial metaphysis. The measure of heterogeneity at the tibial plateaux was the ratio of the standard deviation of the signal in the medial/lateral compartment to the standard deviation of the signal in the metaphysis (ratio of standard deviations - RSS{sub medial}/RSS{sub lateral}). Differences between groups were assessed using unpaired Student's t-tests. Mean RSS{sub medial} was 2.61 (standard deviation, SD = 0.77) in group A and 2.97 (SD = 0.59) in group B. Mean RSS{sub lateral} in group A was 1.86 (SD = 0.63) and 1.89 (SD = 0.43) in group B. Mean total cartilage thickness (in mm) in group A was 3.38 (SD = 0.90) for the medial and 3.90 (SD = 1.09) for the lateral compartment and 3.44 (SD = 0.74) for the medial and 3.96 (SD = 0.96) for the lateral compartment in group B. The only parameter to show a statistically significant difference between groups was RSS{sub medial} (p = 0.04). A difference in medial subchondral bone sclerosis between two age groups was demonstrated in the absence of MR features of OA. This may represent the earliest OA change detectable on MR imaging. (orig.)

  17. The sandwich-type electrochemiluminescence immunosensor for {alpha}-fetoprotein based on enrichment by Fe{sub 3}O{sub 4}-Au magnetic nano probes and signal amplification by CdS-Au composite nanoparticles labeled anti-AFP

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Hankun [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China); Gan Ning, E-mail: ganning@nbu.edu.cn [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China); Li Tianhua; Cao Yuting; Zeng Saolin [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China); Zheng Lei, E-mail: nfyyzl@163.com [Department of Laboratory Medicine, Nanfang Hospital, Southern Medical University, Guangzhou 510515 (China); Guo Zhiyong [State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211 (China)

    2012-10-09

    Highlights: Black-Right-Pointing-Pointer Sandwich immunoreaction, testing a large number of samples simultaneously. Black-Right-Pointing-Pointer The magnetic separation and enrichment by Fe{sub 3}O{sub 4}-Au magnetic nano probes. Black-Right-Pointing-Pointer The amplification of detection signal by CdS-Au composite nanoparticles labeled anti-AFP. Black-Right-Pointing-Pointer Almost no background signal, which greatly improve the sensitivity of detection. - Abstract: A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated on a glassy carbon electrode (GCE) for ultra trace levels of {alpha}-fetoprotein (AFP) based on sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantum dots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared by immobilizing the primary antibody of AFP (Ab1) on the core/shell Fe{sub 3}O{sub 4}-Au nanoparticles, which was first employed to capture AFP antigens to form Fe{sub 3}O{sub 4}-Au/Ab1/AFP complex from the serum after incubation. The product can be separated from the background solution through the magnetic separation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) was conjugated successfully with Fe{sub 3}O{sub 4}-Au/Ab1/AFP complex to form a sandwich-type immunocomplex (Fe{sub 3}O{sub 4}-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by an external magnetic field and produce ECL signals at a fixed voltage. The signal was proportional to a certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor with magnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at a level of high sensitivity and a broad concentration range for AFP between 0.0005 and 5.0 ng mL{sup -1} with a detection limit of 0.2 pg mL{sup -1}. The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to the

  18. MRI investigation of normal fetal lung maturation using signal intensities on different imaging sequences

    International Nuclear Information System (INIS)

    Balassy, Csilla; Kasprian, Gregor; Weber, Michael; Hoermann, Marcus; Prayer, Daniela; Brugger, Peter C.; Csapo, Bence; Mittermayer, Christoph

    2007-01-01

    To purpose of this paper is to study the relation between normal lung maturation signal and changes in intensity ratios (SIR) and to determine which magnetic resonance imaging sequence provides the strongest correlation of normal lung SIs with gestational age. 126 normal singleton pregnancies (20-37 weeks) were examined with a 1.5 Tesla unit. Mean SIs for lungs, liver, and gastric fluid were assessed on six different sequences, and SIRs of lung/liver (LLSIR) and lung/gastric fluid (LGSIR) were correlated with gestational age for each sequence. To evaluate the feasibility of SIRs in the prediction of the state of the lung maturity, accuracy of the predicted SIRs (D*) was measured by calculating relative residuals (D*-D)/D for each sequence. LLSIRs showed significant changes in every sequence (p<0.05), while LGSIRs only on two sequences. Significant differences were shown for the mean of absolute residuals for both LLSIRs (p<0.001) and for LGSIRs (p=0.003). Relative residuals of LLSIRs were significantly smaller on T1-weighted sequence, whereas they were significantly higher for LGSIRs on FLAIR sequence. Fetal liver seems to be adequate reference for the investigation of lung maturation. T1-weighted sequence was the most accurate for the measurement of the lung SIs; thus, we propose to determine LLSIR on T1-weighted sequence when evaluating lung development. (orig.)

  19. Widespread correlation patterns of fMRI signal across visual cortex reflect eccentricity organization

    Science.gov (United States)

    Arcaro, Michael J; Honey, Christopher J; Mruczek, Ryan EB; Kastner, Sabine; Hasson, Uri

    2015-01-01

    The human visual system can be divided into over two-dozen distinct areas, each of which contains a topographic map of the visual field. A fundamental question in vision neuroscience is how the visual system integrates information from the environment across different areas. Using neuroimaging, we investigated the spatial pattern of correlated BOLD signal across eight visual areas on data collected during rest conditions and during naturalistic movie viewing. The correlation pattern between areas reflected the underlying receptive field organization with higher correlations between cortical sites containing overlapping representations of visual space. In addition, the correlation pattern reflected the underlying widespread eccentricity organization of visual cortex, in which the highest correlations were observed for cortical sites with iso-eccentricity representations including regions with non-overlapping representations of visual space. This eccentricity-based correlation pattern appears to be part of an intrinsic functional architecture that supports the integration of information across functionally specialized visual areas. DOI: http://dx.doi.org/10.7554/eLife.03952.001 PMID:25695154

  20. MRI investigation of normal fetal lung maturation using signal intensities on different imaging sequences

    Energy Technology Data Exchange (ETDEWEB)

    Balassy, Csilla; Kasprian, Gregor; Weber, Michael; Hoermann, Marcus; Prayer, Daniela [Medical University of Vienna, Department of Radiology, Vienna (Austria); Brugger, Peter C. [Medical University of Vienna, Center of Anatomy and Cell Biology, Vienna (Austria); Csapo, Bence [Medical University of Vienna, Department of Obstetrics and Gyneocology, Vienna (Austria); Mittermayer, Christoph [Medical University of Vienna, Department of Pediatrics, Vienna (Austria)

    2007-03-15

    To purpose of this paper is to study the relation between normal lung maturation signal and changes in intensity ratios (SIR) and to determine which magnetic resonance imaging sequence provides the strongest correlation of normal lung SIs with gestational age. 126 normal singleton pregnancies (20-37 weeks) were examined with a 1.5 Tesla unit. Mean SIs for lungs, liver, and gastric fluid were assessed on six different sequences, and SIRs of lung/liver (LLSIR) and lung/gastric fluid (LGSIR) were correlated with gestational age for each sequence. To evaluate the feasibility of SIRs in the prediction of the state of the lung maturity, accuracy of the predicted SIRs (D*) was measured by calculating relative residuals (D*-D)/D for each sequence. LLSIRs showed significant changes in every sequence (p<0.05), while LGSIRs only on two sequences. Significant differences were shown for the mean of absolute residuals for both LLSIRs (p<0.001) and for LGSIRs (p=0.003). Relative residuals of LLSIRs were significantly smaller on T1-weighted sequence, whereas they were significantly higher for LGSIRs on FLAIR sequence. Fetal liver seems to be adequate reference for the investigation of lung maturation. T1-weighted sequence was the most accurate for the measurement of the lung SIs; thus, we propose to determine LLSIR on T1-weighted sequence when evaluating lung development. (orig.)

  1. EEG-informed fMRI analysis during a hand grip task: estimating the relationship between EEG rhythms and the BOLD signal

    Directory of Open Access Journals (Sweden)

    Roberta eSclocco

    2014-04-01

    Full Text Available In the last decade, an increasing interest has arisen in investigating the relationship between the electrophysiological and hemodynamic measurements of brain activity, such as EEG and (BOLD fMRI. In particular, changes in BOLD have been shown to be associated with changes in the spectral profile of neural activity, rather than with absolute power. Concurrently, recent findings showed that different EEG rhythms are independently related to changes in the BOLD signal: therefore, it would be important to distinguish between the contributions of the different EEG rhythms to BOLD fluctuations when modeling the relationship between the two signals. Here we propose a method to perform EEG-informed fMRI analysis, in which the EEG regressors take into account both the changes in the spectral profile and the rhythms distinction. We applied it to EEG-fMRI data during a hand grip task in healthy subjects, and compared the results with those obtained by two existing models found in literature. Our results showed that the proposed method better captures the correlations between BOLD signal and EEG rhythms modulations, identifying task-related, well localized activated volumes. Furthermore, we showed that including among the regressors also EEG rhythms not primarily involved in the task enhances the performance of the analysis, even when only correlations with BOLD signal and specific EEG rhythms are explored.

  2. Incidentally detected enhancing lesions found in breast MRI: analysis of apparent diffusion coefficient and T2 signal intensity significantly improves specificity

    Energy Technology Data Exchange (ETDEWEB)

    Arponen, Otso; Masarwah, Amro; Taina, Mikko [Kuopio University Hospital, Kuopio University Hospital, Diagnostic Imaging Centre, Department of Clinical Radiology, PO Box 1777, Kuopio (Finland); Kuopio University Hospital, University of Eastern Finland, Institute of Clinical Medicine, School of Medicine, Department of Clinical Radiology, PO Box 1777, Kuopio (Finland); Sutela, Anna; Koenoenen, Mervi; Hakumaeki, Juhana; Sudah, Mazen [Kuopio University Hospital, Kuopio University Hospital, Diagnostic Imaging Centre, Department of Clinical Radiology, PO Box 1777, Kuopio (Finland); Sironen, Reijo [Kuopio University Hospital, Kuopio University Hospital, Department of Pathology, PO Box 1777, Kuopio (Finland); Kuopio University Hospital, University of Eastern Finland, Institute of Clinical Medicine, School of Medicine, Clinical Pathology and Forensic Medicine, PO Box 1777, Kuopio (Finland); University of Eastern Finland, Cancer Center of Eastern Finland, Kuopio (Finland); Vanninen, Ritva [Kuopio University Hospital, Kuopio University Hospital, Diagnostic Imaging Centre, Department of Clinical Radiology, PO Box 1777, Kuopio (Finland); Kuopio University Hospital, University of Eastern Finland, Institute of Clinical Medicine, School of Medicine, Department of Clinical Radiology, PO Box 1777, Kuopio (Finland); University of Eastern Finland, Cancer Center of Eastern Finland, Kuopio (Finland)

    2016-12-15

    To evaluate the value of adding T2- and diffusion-weighted imaging (DWI) to the BI-RADS registered classification in MRI-detected lesions. This retrospective study included 112 consecutive patients who underwent 3.0T structural breast MRI with T2- and DWI on the basis of EUSOMA recommendations. Morphological and kinetic features, T2 signal intensity (T2 SI) and apparent diffusion coefficient (ADC) findings were assessed. Thirty-three (29.5 %) patients (mean age 57.0 ± 12.7 years) had 36 primarily MRI-detected incidental lesions of which 16 (44.4 %) proved to be malignant. No single morphological or kinetic feature was associated with malignancy. Both low T2 SI (P = 0.009) and low ADC values (≤0.87 x 10{sup -3} mm{sup 2}s{sup -1}, P < 0.001) yielded high specificity (80.0 %/80.0 %). The BI-RADS classification supplemented with information from DWI and T2-WI improved the diagnostic performance of the BI-RADS classification as sensitivity remained 100 % and specificity improved from 30 % to 65.0 %. The numbers of false positive lesions declined from 39 % (N = 14) to 19 % (N = 7). MRI-detected incidental lesions may be challenging to characterize as they have few specific malignancy indicating features. The specificity of MRI can be improved by incorporating T2 SI and ADC values into the BI-RADS assessment. (orig.)

  3. Statistical approach of measurement of signal to noise ratio in according to change pulse sequence on brain MRI meningioma and cyst images

    International Nuclear Information System (INIS)

    Lee, Eul Kyu; Choi, Kwan Woo; Jeong, Hoi Woun; Jang, Seo Goo; Kim, Ki Won; Son, Soon Yong; Min, Jung Whan; Son, Jin Hyun

    2016-01-01

    The purpose of this study was to needed basis of measure MRI CAD development for signal to noise ratio (SNR) by pulse sequence analysis from region of interest (ROI) in brain magnetic resonance imaging (MRI) contrast. We examined images of brain MRI contrast enhancement of 117 patients, from January 2005 to December 2015 in a University-affiliated hospital, Seoul, Korea. Diagnosed as one of two brain diseases such as meningioma and cysts SNR for each patient's image of brain MRI were calculated by using Image J. Differences of SNR among two brain diseases were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p < 0.05). We have analysis socio-demographical variables, SNR according to sequence disease, 95% confidence according to SNR of sequence and difference in a mean of SNR. Meningioma results, with the quality of distributions in the order of T1CE, T2 and T1, FLAIR. Cysts results, with the quality of distributions in the order of T2 and T1, T1CE and FLAIR. SNR of MRI sequences of the brain would be useful to classify disease. Therefore, this study will contribute to evaluate brain diseases, and be a fundamental to enhancing the accuracy of CAD development

  4. Statistical approach of measurement of signal to noise ratio in according to change pulse sequence on brain MRI meningioma and cyst images

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Eul Kyu [Inje Paik University Hospital Jeo-dong, Seoul (Korea, Republic of); Choi, Kwan Woo [Asan Medical Center, Seoul (Korea, Republic of); Jeong, Hoi Woun [The Baekseok Culture University, Cheonan (Korea, Republic of); Jang, Seo Goo [The Soonchunhyang University, Asan (Korea, Republic of); Kim, Ki Won [Kyung Hee University Hospital at Gang-dong, Seoul (Korea, Republic of); Son, Soon Yong [The Wonkwang Health Science University, Iksan (Korea, Republic of); Min, Jung Whan; Son, Jin Hyun [The Shingu University, Sungnam (Korea, Republic of)

    2016-09-15

    The purpose of this study was to needed basis of measure MRI CAD development for signal to noise ratio (SNR) by pulse sequence analysis from region of interest (ROI) in brain magnetic resonance imaging (MRI) contrast. We examined images of brain MRI contrast enhancement of 117 patients, from January 2005 to December 2015 in a University-affiliated hospital, Seoul, Korea. Diagnosed as one of two brain diseases such as meningioma and cysts SNR for each patient's image of brain MRI were calculated by using Image J. Differences of SNR among two brain diseases were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p < 0.05). We have analysis socio-demographical variables, SNR according to sequence disease, 95% confidence according to SNR of sequence and difference in a mean of SNR. Meningioma results, with the quality of distributions in the order of T1CE, T2 and T1, FLAIR. Cysts results, with the quality of distributions in the order of T2 and T1, T1CE and FLAIR. SNR of MRI sequences of the brain would be useful to classify disease. Therefore, this study will contribute to evaluate brain diseases, and be a fundamental to enhancing the accuracy of CAD development.

  5. Single-trial EEG-informed fMRI reveals spatial dependency of BOLD signal on early and late IC-ERP amplitudes during face recognition.

    Science.gov (United States)

    Wirsich, Jonathan; Bénar, Christian; Ranjeva, Jean-Philippe; Descoins, Médéric; Soulier, Elisabeth; Le Troter, Arnaud; Confort-Gouny, Sylviane; Liégeois-Chauvel, Catherine; Guye, Maxime

    2014-10-15

    Simultaneous EEG-fMRI has opened up new avenues for improving the spatio-temporal resolution of functional brain studies. However, this method usually suffers from poor EEG quality, especially for evoked potentials (ERPs), due to specific artifacts. As such, the use of EEG-informed fMRI analysis in the context of cognitive studies has particularly focused on optimizing narrow ERP time windows of interest, which ignores the rich diverse temporal information of the EEG signal. Here, we propose to use simultaneous EEG-fMRI to investigate the neural cascade occurring during face recognition in 14 healthy volunteers by using the successive ERP peaks recorded during the cognitive part of this process. N170, N400 and P600 peaks, commonly associated with face recognition, were successfully and reproducibly identified for each trial and each subject by using a group independent component analysis (ICA). For the first time we use this group ICA to extract several independent components (IC) corresponding to the sequence of activation and used single-trial peaks as modulation parameters in a general linear model (GLM) of fMRI data. We obtained an occipital-temporal-frontal stream of BOLD signal modulation, in accordance with the three successive IC-ERPs providing an unprecedented spatio-temporal characterization of the whole cognitive process as defined by BOLD signal modulation. By using this approach, the pattern of EEG-informed BOLD modulation provided improved characterization of the network involved than the fMRI-only analysis or the source reconstruction of the three ERPs; the latter techniques showing only two regions in common localized in the occipital lobe. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. The Standardized Histogram Shift of T2 Magnetic Resonance Image (MRI) Signal Intensities of Nephroblastoma Does Not Predict Histopathological Diagnostic Information

    OpenAIRE

    M?ller, Sabine; David, Ruslan; Marias, Kostas; Graf, Norbert

    2015-01-01

    The objective of this study is to assess standardized histograms of signal intensities of T2-weighted magnetic resonance image (MRI) modality before and after preoperative chemotherapy for nephroblastoma (Wilms? tumor). All analyzed patients are enrolled in the International Society of Paediatric Oncology (SIOP) 2001/GPOH trial.1 The question to be answered is whether the comparison of the histograms can add new knowledge by comparing them with the histology of the tumor after preoperative ch...

  7. The relationship between prevalent medial meniscal intrasubstance signal changes and incident medial meniscal tears in women over a 1-year period assessed with 3.0 T MRI

    International Nuclear Information System (INIS)

    Crema, Michel D.; Hunter, David J.; Roemer, Frank W.; Li, Ling; Marra, Monica D.; Nogueira-Barbosa, Marcello H.; Hellio Le Graverand, Marie-Pierre; Wyman, Bradley T.; Guermazi, Ali

    2011-01-01

    Intrasubstance meniscal signal changes not reaching the articular surface on fast spin echo (FSE) sequences are considered to represent mucoid degeneration on MRI. The aim of this study was to evaluate the association of prevalent intrasubstance signal changes with incident tears of the medial meniscus detected on 3.0 T MRI over a 1-year period. A total of 161 women aged ≥40 years participated in a longitudinal 1-year observational study of knee osteoarthritis. MRI (3.0 T) was performed at baseline and 12-month follow-up. The anterior horn, body, and posterior horn of the medial meniscus were scored by two experienced musculoskeletal radiologists using the Boston-Leeds Osteoarthritis Knee Score (BLOKS) system. Four grades were used to describe the meniscal morphology: grade 0 (normal), grade 1 (intrasubstance signal changes not reaching the articular surface), grade 2 (single tears), and grade 3 (complex tears and maceration). Fisher's exact test and the Cochran-Armitage trend test were performed to evaluate whether baseline intrasubstance signal changes (grade 1) predict incident meniscal tears/maceration (grades 2 and/or 3) in the same subregion of the medial meniscus, when compared to subregions without pathology as the reference group (grade 0). Medial meniscal intrasubstance signal changes at baseline did not predict tears at follow-up when evaluating the anterior and posterior horns (left-sided p-values 0.06 and 0.59, respectively). No incident tears were detected in the body. We could not demonstrate an association between prevalent medial meniscal intrasubstance signal changes with incident tears over a 1-year period. (orig.)

  8. The relationship between prevalent medial meniscal intrasubstance signal changes and incident medial meniscal tears in women over a 1-year period assessed with 3.0 T MRI

    Energy Technology Data Exchange (ETDEWEB)

    Crema, Michel D. [Boston University School of Medicine, Department of Radiology, Quantitative Imaging Center, Boston, MA (United States); Ribeirao Preto School of Medicine, University of Sao Paulo (USP), Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus, and Department of Internal Medicine, Radiology Division, Ribeirao Preto (Brazil); Institute of Diagnostic Imaging (IDI), Ribeirao Preto (Brazil); Hunter, David J. [The University of Sydney, Sydney School of Medicine, Sydney (Australia); Roemer, Frank W. [Boston University School of Medicine, Department of Radiology, Quantitative Imaging Center, Boston, MA (United States); Klinikum Augsburg, Department of Radiology, Augsburg (Germany); Li, Ling [New England Baptist Hospital, Division of Research, Boston, MA (United States); Marra, Monica D. [Boston University School of Medicine, Department of Radiology, Quantitative Imaging Center, Boston, MA (United States); Institute of Diagnostic Imaging (IDI), Ribeirao Preto (Brazil); Nogueira-Barbosa, Marcello H. [Ribeirao Preto School of Medicine, University of Sao Paulo (USP), Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus, and Department of Internal Medicine, Radiology Division, Ribeirao Preto (Brazil); Hellio Le Graverand, Marie-Pierre; Wyman, Bradley T. [Pfizer Global Research and Development, New London, CT (United States); Guermazi, Ali [Boston University School of Medicine, Department of Radiology, Quantitative Imaging Center, Boston, MA (United States)

    2011-08-15

    Intrasubstance meniscal signal changes not reaching the articular surface on fast spin echo (FSE) sequences are considered to represent mucoid degeneration on MRI. The aim of this study was to evaluate the association of prevalent intrasubstance signal changes with incident tears of the medial meniscus detected on 3.0 T MRI over a 1-year period. A total of 161 women aged {>=}40 years participated in a longitudinal 1-year observational study of knee osteoarthritis. MRI (3.0 T) was performed at baseline and 12-month follow-up. The anterior horn, body, and posterior horn of the medial meniscus were scored by two experienced musculoskeletal radiologists using the Boston-Leeds Osteoarthritis Knee Score (BLOKS) system. Four grades were used to describe the meniscal morphology: grade 0 (normal), grade 1 (intrasubstance signal changes not reaching the articular surface), grade 2 (single tears), and grade 3 (complex tears and maceration). Fisher's exact test and the Cochran-Armitage trend test were performed to evaluate whether baseline intrasubstance signal changes (grade 1) predict incident meniscal tears/maceration (grades 2 and/or 3) in the same subregion of the medial meniscus, when compared to subregions without pathology as the reference group (grade 0). Medial meniscal intrasubstance signal changes at baseline did not predict tears at follow-up when evaluating the anterior and posterior horns (left-sided p-values 0.06 and 0.59, respectively). No incident tears were detected in the body. We could not demonstrate an association between prevalent medial meniscal intrasubstance signal changes with incident tears over a 1-year period. (orig.)

  9. Cortical activities evoked by the signals ascending through unmyelinated C fibers in humans. A fMRI study

    International Nuclear Information System (INIS)

    Kakigi, Ryusuke; Qiu, Yunhai; Noguchi, Yasuki

    2006-01-01

    Acute pain is classified as first and second pain associated with rapidly conducting Aδ fibers and slowly conducting unmyelinated C fibers, respectively. First pain aims at achieving relative safety from the source of injury, whereas second pain, with its strong affective component, attracts longer-lasting attention and initiates behavioral responses in order to limit further injury and optimize recovery. Accordingly, the distinct brain representations for first and second pain should reflect distinct biological functions of both sensations. In this study, therefore, an event-related functional magnetic resonance imaging (fMRI) was used to investigate brain processing of the signals ascending from peripheral C and Aδ fibers evoked by phasic laser stimuli on the right hand in humans. The stimulation of both C and Aδ nociceptors activated the bilateral thalamus, bilateral secondary somatosensory cortex (SII), right (ipsilateral) middle insula, and bilateral Brodmann's area (BA) 24/32, with the majority of activity found in the posterior portion of the anterior cingulate cortex (pACC). However, magnitude of activity in the right (ipsilateral) BA32/8/6, including dorsal parts in the anterior portion of the ACC (aACC) and pre-supplementary motor area (pre-SMA), and the bilateral anterior insula was significantly stronger following the stimulation of C nociceptors than Aδ nociceptors. It was concluded that the activation of C nociceptors, related to second pain, evokes different brain processing from that of Aδ nociceptors, related to first pain, probably due to the differences in the emotional and motivational aspects of either pain, which are mainly related to the aACC, pre-SMA and anterior insula. (author)

  10. Effect of Phase-Encoding Reduction on Geometric Distortion and BOLD Signal Changes in fMRI

    Directory of Open Access Journals (Sweden)

    Golestan karami

    2013-03-01

    Full Text Available Introduction Echo-planar imaging (EPI is a group of fast data acquisition methods commonly used in fMRI studies. It acquires multiple image lines in k-space after a single excitation, which leads to a very short scan time. A well-known problem with EPI is that it is more sensitive to distortions due to the used encoding scheme. Source of distortion is inhomogeneity in the static B0 field that causes more geometric distortion in phase encoding direction. This inhomogeneity is induced mainly by the magnetic susceptibility differences between various structures within the object placed inside the scanner, often at air-tissue or bone-tissue interfaces. Methods of reducing EPI distortion are mainly based on decreasing steps of the phase encoding. Reducing steps of phase encoding can be applied by reducing field of view, slice thickness, and/or the use of parallel acquisition technique. Materials and Methods We obtained three data acquisitions with different FOVs including: conventional low resolution, conventional high resolution, and zoomed high resolution EPIs. Moreover we used SENSE technique for phase encoding reduction. All experiments were carried out on three Tesla scanners (Siemens, TIM, and Germany equipped with 12 channel head coil. Ten subjects participated in the experiments. Results The data were processed by FSL software and were evaluated by ANOVA. Distortion was assessed by obtaining low displacement voxels map, and calculated from a field map image. Conclusion We showed that image distortion can be reduced by decreasing slice thickness and phase encoding steps. Distortion reduction in zoomed technique resulted the lowest level, but at the cost of signal-to-noise loss. Moreover, the SENSE technique was shown to decrease the amount of image distortion, efficiently.

  11. The sandwich-type electrochemiluminescence immunosensor for α-fetoprotein based on enrichment by Fe3O4-Au magnetic nano probes and signal amplification by CdS-Au composite nanoparticles labeled anti-AFP.

    Science.gov (United States)

    Zhou, Hankun; Gan, Ning; Li, Tianhua; Cao, Yuting; Zeng, Saolin; Zheng, Lei; Guo, Zhiyong

    2012-10-09

    A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated on a glassy carbon electrode (GCE) for ultra trace levels of α-fetoprotein (AFP) based on sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantum dots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared by immobilizing the primary antibody of AFP (Ab1) on the core/shell Fe(3)O(4)-Au nanoparticles, which was first employed to capture AFP antigens to form Fe(3)O(4)-Au/Ab1/AFP complex from the serum after incubation. The product can be separated from the background solution through the magnetic separation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) was conjugated successfully with Fe(3)O(4)-Au/Ab1/AFP complex to form a sandwich-type immunocomplex (Fe(3)O(4)-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by an external magnetic field and produce ECL signals at a fixed voltage. The signal was proportional to a certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor with magnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at a level of high sensitivity and a broad concentration range for AFP between 0.0005 and 5.0 ng mL(-1) with a detection limit of 0.2 pg mL(-1). The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to the amplification of the signal tag, the immunosensor is highly sensitive, which can offer great promise for rapid, simple, selective and cost-effective detection of effective biomonitoring for clinical application. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Correcting for Blood Arrival Time in Global Mean Regression Enhances Functional Connectivity Analysis of Resting State fMRI-BOLD Signals.

    Science.gov (United States)

    Erdoğan, Sinem B; Tong, Yunjie; Hocke, Lia M; Lindsey, Kimberly P; deB Frederick, Blaise

    2016-01-01

    Resting state functional connectivity analysis is a widely used method for mapping intrinsic functional organization of the brain. Global signal regression (GSR) is commonly employed for removing systemic global variance from resting state BOLD-fMRI data; however, recent studies have demonstrated that GSR may introduce spurious negative correlations within and between functional networks, calling into question the meaning of anticorrelations reported between some networks. In the present study, we propose that global signal from resting state fMRI is composed primarily of systemic low frequency oscillations (sLFOs) that propagate with cerebral blood circulation throughout the brain. We introduce a novel systemic noise removal strategy for resting state fMRI data, "dynamic global signal regression" (dGSR), which applies a voxel-specific optimal time delay to the global signal prior to regression from voxel-wise time series. We test our hypothesis on two functional systems that are suggested to be intrinsically organized into anticorrelated networks: the default mode network (DMN) and task positive network (TPN). We evaluate the efficacy of dGSR and compare its performance with the conventional "static" global regression (sGSR) method in terms of (i) explaining systemic variance in the data and (ii) enhancing specificity and sensitivity of functional connectivity measures. dGSR increases the amount of BOLD signal variance being modeled and removed relative to sGSR while reducing spurious negative correlations introduced in reference regions by sGSR, and attenuating inflated positive connectivity measures. We conclude that incorporating time delay information for sLFOs into global noise removal strategies is of crucial importance for optimal noise removal from resting state functional connectivity maps.

  13. Heart MRI

    Science.gov (United States)

    Magnetic resonance imaging - cardiac; Magnetic resonance imaging - heart; Nuclear magnetic resonance - cardiac; NMR - cardiac; MRI of the heart; Cardiomyopathy - MRI; Heart failure - MRI; Congenital heart disease - MRI

  14. MRI angiography

    International Nuclear Information System (INIS)

    Poncelet, B.; Baleriiaux, D.; struyven, J.; Segebarth, C.

    1989-01-01

    In MRI angiography two basis images are measured which only differ by the signal intensity of the flowing blood in the vessels. Subtraction of these two images produces a high contrast-to-noise representation of the vessels. Contrast between stationary tissues and flowing blood is changed, for one image compared to the second one, using a selective modification of the phase of the signal from the flowing blood, and/or using a selective modification of its longitudinal magnetization: The macroscopic spin motions along the selection and the measurement gradient directions affect the phase of the nuclear signal; assuming constant velocity, the phase is proportional to the velocity and to the first moment of the gradient waveforms applied. This work concentrates on the generarion of MRI angiograms, following a phase-based approach, of the carotid bifurcation and of different intracranical regions including the carotid syphon and the circle of Willis. (author). 21 refs.; 3 figs

  15. Amplification of the angiogenic signal through the activation of the TSC/mTOR/HIF axis by the KSHV vGPCR in Kaposi's sarcoma.

    Directory of Open Access Journals (Sweden)

    Bruno C Jham

    2011-04-01

    Full Text Available Kaposi's sarcoma (KS is a vascular neoplasm characterized by the dysregulated expression of angiogenic and inflammatory cytokines. The driving force of the KS lesion, the KSHV-infected spindle cell, secretes elevated levels of vascular endothelial growth factor (VEGF, essential for KS development. However, the origin of VEGF in this tumor remains unclear.Here we report that the KSHV G protein-coupled receptor (vGPCR upregulates VEGF in KS through an intricate paracrine mechanism. The cytokines secreted by the few vGPCR-expressing tumor cells activate in neighboring cells multiple pathways (including AKT, ERK, p38 and IKKβ that, in turn, converge on TSC1/2, promoting mTOR activation, HIF upregulation, and VEGF secretion. Conditioned media from vGPCR-expressing cells lead to an mTOR-dependent increase in HIF-1α and HIF-2α protein levels and VEGF upregulation. In a mouse allograft model for KS, specific inhibition of the paracrine activation of mTOR in non-vGPCR-expressing cells was sufficient to inhibit HIF upregulation in these cells, and abolished the ability of the vGPCR-expressing cells to promote tumor formation in vivo. Similarly, pharmacologic inhibition of HIF in this model blocked VEGF secretion and also lead to tumor regression.Our findings provide a compelling explanation for how the few tumor cells expressing vGPCR can contribute to the dramatic amplification of VEGF secretion in KS, and further provide a molecular mechanism for how cytokine dysregulation in KS fuels angiogenesis and tumor development. These data further suggest that activation of HIF by vGPCR may be a vulnerable target for the treatment of patients with KS.

  16. Music reduces pain and increases resting state fMRI BOLD signal amplitude in the left angular gyrus in fibromyalgia patients

    DEFF Research Database (Denmark)

    Garza-Villarreal, Eduardo A; Jiang, Zhiguo; Vuust, Peter

    2015-01-01

    , correlated to the analgesia reports. The post-hoc seed-based functional connectivity analysis of the lAnG showed found higher connectivity after listening to music with right dorsolateral prefrontal cortex (rdlPFC), the left caudate (lCau), and decreased connectivity with right anterior cingulate cortex (r......Music reduces pain in fibromyalgia (FM), a chronic pain disease, but the functional neural correlates of music-induced analgesia (MIA) are still largely unknown. We recruited FM patients (n = 22) who listened to their preferred relaxing music and an auditory control (pink noise) for 5 min without...... external noise from fMRI image acquisition. Resting state fMRI was then acquired before and after the music and control conditions. A significant increase in the amplitude of low frequency fluctuations of the BOLD signal was evident in the left angular gyrus (lAnG) after listening to music, which in turn...

  17. "Smart" gold nanoparticles for photoacoustic imaging: an imaging contrast agent responsive to the cancer microenvironment and signal amplification via pH-induced aggregation.

    Science.gov (United States)

    Song, Jaejung; Kim, Jeesu; Hwang, Sekyu; Jeon, Mansik; Jeong, Sanghwa; Kim, Chulhong; Kim, Sungjee

    2016-07-07

    'Smart' gold nanoparticles can respond to mild acidic environments, rapidly form aggregates, and shift the absorption to red and near-infrared. They were used as a photoacoustic imaging agent responsive to the cancer microenvironment, and have demonstrated the cancer-specific accumulation at the cellular level and an amplified signal which is twice higher than the control in vivo.

  18. Hyperintense signal alteration in the suprapatellar fat pad on MRI is associated with degeneration of the patellofemoral joint over 48 months. Data from the Osteoarthritis Initiative

    International Nuclear Information System (INIS)

    Schwaiger, Benedikt J.; Gersing, Alexandra S.; Mbapte Wamba, John; Facchetti, Luca; Link, Thomas M.; Nevitt, Michael C.; McCulloch, Charles E.

    2018-01-01

    To analyze associations of suprapatellar fat pad (SPFP) hyperintense signal alterations and mass effect with progression of patellofemoral osteoarthritis (OA) and clinical symptoms over 48 months. Subjects from the Osteoarthritis Initiative (n = 426; 51.8 ± 3.8 years; 49.8% women) without radiographic tibiofemoral OA underwent 3T-MRI of their right knees and clinical evaluation using the Knee Injury and Osteoarthritis Outcome Score at baseline and at 48 months. Elevated SPFP signal was assessed on intermediate-weighted, fat-saturated turbo spin-echo (TSE) images. Mass effect was defined as a convex posterior contour. Patellofemoral cartilage, bone marrow lesions (BML), and subchondral cysts were assessed using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Associations of SPFP imaging findings with MRI and clinical progression were assessed using general linear models and logistic regressions. Baseline SPFP signal alterations were found in 51% of the subjects (n = 217), of whom 11% (n = 23) additionally had a mass effect. Progression of cartilage lesions was significantly higher in subjects with signal alteration versus without (adjusted mean increases, 95% CI; patella: 0.29, -0.07 to 0.64 vs -0.04, -0.40 to 0.31; p < 0.001; trochlea: 0.47, 0.16 to 0.77 vs 0.31, 0.01 to 0.61; p = 0.007). BML progression was also more likely in subjects with signal alteration (OR 1.75, 95% CI 1.09 to 2.82; p = 0.021). Mass effect was not associated with joint degeneration and SPFP findings were not associated with clinical worsening (p > 0.18 for all). Patellofemoral joint degeneration over 48 months was significantly increased in subjects with SPFP signal alteration, suggesting an association between SPFP abnormalities and the progression of patellofemoral OA. (orig.)

  19. Hyperintense signal alteration in the suprapatellar fat pad on MRI is associated with degeneration of the patellofemoral joint over 48 months. Data from the Osteoarthritis Initiative

    Energy Technology Data Exchange (ETDEWEB)

    Schwaiger, Benedikt J.; Gersing, Alexandra S. [University of California, San Francisco, Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); Technical University of Munich, Department of Radiology, Klinikum Rechts der Isar, Munich (Germany); Mbapte Wamba, John; Facchetti, Luca; Link, Thomas M. [University of California, San Francisco, Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); Nevitt, Michael C.; McCulloch, Charles E. [University of California, Department of Epidemiology and Biostatistics, San Francisco, CA (United States)

    2018-03-15

    To analyze associations of suprapatellar fat pad (SPFP) hyperintense signal alterations and mass effect with progression of patellofemoral osteoarthritis (OA) and clinical symptoms over 48 months. Subjects from the Osteoarthritis Initiative (n = 426; 51.8 ± 3.8 years; 49.8% women) without radiographic tibiofemoral OA underwent 3T-MRI of their right knees and clinical evaluation using the Knee Injury and Osteoarthritis Outcome Score at baseline and at 48 months. Elevated SPFP signal was assessed on intermediate-weighted, fat-saturated turbo spin-echo (TSE) images. Mass effect was defined as a convex posterior contour. Patellofemoral cartilage, bone marrow lesions (BML), and subchondral cysts were assessed using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Associations of SPFP imaging findings with MRI and clinical progression were assessed using general linear models and logistic regressions. Baseline SPFP signal alterations were found in 51% of the subjects (n = 217), of whom 11% (n = 23) additionally had a mass effect. Progression of cartilage lesions was significantly higher in subjects with signal alteration versus without (adjusted mean increases, 95% CI; patella: 0.29, -0.07 to 0.64 vs -0.04, -0.40 to 0.31; p < 0.001; trochlea: 0.47, 0.16 to 0.77 vs 0.31, 0.01 to 0.61; p = 0.007). BML progression was also more likely in subjects with signal alteration (OR 1.75, 95% CI 1.09 to 2.82; p = 0.021). Mass effect was not associated with joint degeneration and SPFP findings were not associated with clinical worsening (p > 0.18 for all). Patellofemoral joint degeneration over 48 months was significantly increased in subjects with SPFP signal alteration, suggesting an association between SPFP abnormalities and the progression of patellofemoral OA. (orig.)

  20. A novel non-invasive detection method for the FGFR3 gene mutation in maternal plasma for a fetal achondroplasia diagnosis based on signal amplification by hemin-MOFs/PtNPs.

    Science.gov (United States)

    Chen, Jun; Yu, Chao; Zhao, Yilin; Niu, Yazhen; Zhang, Lei; Yu, Yujie; Wu, Jing; He, Junlin

    2017-05-15

    The small amount of cell-free fetal DNA (cffDNA) can be a useful biomarker for early non-invasive prenatal diagnosis (NIPD) of achondroplasia. In this study, a novel non-invasive electrochemical DNA sensor for ultrasensitive detecting FGFR3 mutation gene, a pathogenic gene of achondroplasia, based on biocatalytic signal materials and the biotin-streptavidin system are presented. Notably encapsulation of hemin in metal-organic frameworks-based materials (hemin-MOFs) and platinum nanoparticles (PtNPs) were used to prepare hemin-MOFs/PtNPs composites via a one-beaker-one-step reduction. We utilized hemin-MOFs/PtNPs for signal amplification because the promising hemin-MOFs/PtNPs nanomaterial has remarkable ability of catalyze H 2 O 2 as well as excellent conductivity. To further amplify the electrochemical signal, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA), gold nanoparticles and streptavidin were selected for modification of the electrode to enhance the conductivity and immobilize more biotin-modified capture probe (Bio-CP) through the high specificity and superior affinity between streptavidin and biotin. The electrochemical signal was primarily derived from the synergistic catalysis of H 2 O 2 by hemin and PtNPs and recorded by Chronoamperometry. Under the optimal conditions, this newly designed biosensor exhibited sensitive detection of FGFR3 from 0.1fM to 1nM with a low detection limit of 0.033fM (S/N=3). We proposed that this ultrasensitive biosensor is useful for the early non-invasive prenatal diagnosis of achondroplasia. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Aptamer-based electrochemical assay of 17β-estradiol using a glassy carbon electrode modified with copper sulfide nanosheets and gold nanoparticles, and applying enzyme-based signal amplification

    International Nuclear Information System (INIS)

    Huang, Ke-Jing; Liu, Yu-Jie; Zhang, Ji-Zong

    2015-01-01

    We have developed an electrochemical method for the determination of 17β-estradiol. A glassy carbon electrode was modified with a composite made from copper sulfide nanosheets, gold nanoparticles, and glucose oxidase. The copper sulfide nanosheet was prepared by a single-step hydrothermal process, and its properties were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Finally, an estradiol-specific aptamer was assembled on the electrode. The copper sulfide nanosheet on the electrode surface acts as a relatively good electrical conductor. Glucose oxidase acts as an indicator, and the dual modification of glucose oxidase and gold nanoparticles for signal amplification. The determination of 17β-estradiol was performed by differential pulse voltammetry of glucose oxidase because the signal measured at typically −0.43 V depends on the concentration of 17β-estradiol because addition of 17β-estradiol at electrode hinders electron transfer. A linear relationship exists between the peak current and the logarithm of concentration of 17β-estradiol in the 0.5 pM to 5 nM range, with a 60 f. detection limit (at 3σ/S). The method displays good selectivity over bisphenol A, 1-aminoanthraquinone and naphthalene even if present in 100-fold concentrations. (author)

  2. Electrochemical immunoassay for the carcinoembryonic antigen based on the use of a glassy carbon electrode modified with an octahedral Cu2O-gold nanocomposite and staphylococcal protein for signal amplification.

    Science.gov (United States)

    Qin, Zhen; Xu, Wei; Chen, Shuai; Chen, Jun; Qiu, Jing Fu; Li, Chao Rui

    2018-04-24

    The authors describe an electrochemical immunoassay for ultrasensitive direct determination of the carcinoembryonic antigen (CEA). A nanocomposite consisting of octahedral Cu2O nanocrystals covered with gold nanoparticles was utilized to modify a glassy carbon electrode which gives a strongly enhanced chronoamperometric signal for H 2 O 2 which is used as an electrochemical probe. The morphology and elemental composition of the the nanocomposite was studied by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. In addition, staphylococcal protein A was placed on the electrode for efficient capture of antibody to further enhance the sensitivity of the assay. Under optimal conditions and at a typical working voltage of -0.4 V (vs. Ag/AgCl), the response covers the 2 pg·mL -1 to 20 ng·mL -1 CEA concentration range with a 200 fg·mL -1 lower detection limit. The method was successfully applied to the determination of CEA in (spiked) human serum. Graphical abstract Schematic of the fabrication of an electrochemical immunosensor for ultrasensitive detection the carcinoembryonic antigen. The sensor is based on the use of a glassy carbon electrode modified with an octahedral Cu 2 O-gold nanocomposite and staphylococcal protein A for signal amplification.

  3. Estimating achievable signal-to-noise ratios of MRI transmit-receive coils from radiofrequency power measurements: applications in quality control

    International Nuclear Information System (INIS)

    Redpath, T.W.

    2000-01-01

    The inverse relationship between the radiofrequency (RF) power needed to transmit a 90 deg. RF pulse, and the signal-to-noise ratio (SNR) available from a transmit-receive RF coil is well known. The theory is restated and a formula given for the signal-to-noise ratio from water, achievable from a single-shot MRI experiment, in terms of the net forward RF power needed for a rectangular 90 deg. RF pulse of known shape and duration. The result is normalized to a signal bandwidth of 1 Hz and a sample mass of 1 g. The RF power information needed is available on most commercial scanners, as it is used to calculate specific absorption rates for RF tissue heating. The achievable SNR figure will normally be larger that that actually observed, mainly because of receiver noise, but also because of inaccuracies in setting RF pulse angles, and relaxation effects. Phantom experiments were performed on the transmit-receive RF head coil of a commercial MRI system at 0.95 T using a projection method. The measured SNR agreed with that expected from the formula for achievable SNR once a correction was made for the noise figure of the receiving chain. Comparisons of measured SNR figures with those calculated from RF power measurements are expected to be of value in acceptance testing and quality control. (author)

  4. Electrochemical gene sensor for Mycoplasma pneumoniae DNA using dual signal amplification via a Pt-Pd nanowire and horse radish peroxidase

    International Nuclear Information System (INIS)

    Liu, Linlin; Xiang, Guiming; Jiang, Dongneng; Du, Chunlan; Liu, Chang; Huang, Weiwei; Pu, Xiaoyun

    2016-01-01

    A dually amplified DNA biosensor was constructed for the determination of the DNA of Mycoplasma pneumoniae (M. pneu). A gold electrode was modified with 3,4,9,10-perylenetetracarboxylic acid dianhydride (PTCDA; a π-stacking perylene semiconductor dye with outstanding electronic and optical properties), a layer of gold nanoparticles (nano-Au), and capture DNA. Pt-Pd nanowires served as carriers for the co immobilization of complementary probe (CP2) and the mediator thionine (Thi). Horseradish peroxidase (HRP) acted as a blocking reagent and signal enhancer. Following base pairing, the modified Pt-Pd nanowires were captured on the surface of the gold electrode. After addition of H 2 O 2 , the Pt-Pd nanowires and HRP both catalyzed the reduction of H 2 O 2 and promoted the electron transfer via the mediator Thi, resulting in an amplified electrochemical signal. The electrical signal, best measured at a working voltage of −200 mV (vs a SCE), is logarithmically related to the concentration of the M. pneu DNA in the 0.1 pM to 20 nM concentration range, and the detection limit (at an S/N ratio of 3) is 0.03 pM. The assay is robust, sensitive and specific. Conceivably, it is a cost-effective alternative to the established PCR method for the detection of M. pneu in clinical samples. (author)

  5. GH signaling in human adipose and muscle tissue during 'feast and famine': amplification of exercise stimulation following fasting compared to glucose administration.

    Science.gov (United States)

    Vendelbo, Mikkel H; Christensen, Britt; Grønbæk, Solbritt B; Høgild, Morten; Madsen, Michael; Pedersen, Steen B; Jørgensen, Jens O L; Jessen, Niels; Møller, Niels

    2015-09-01

    Fasting and exercise stimulates, whereas glucose suppresses GH secretion, but it is uncertain how these conditions impact GH signaling in peripheral tissues. To test the original 'feast and famine hypothesis' by Rabinowitz and Zierler, according to which the metabolic effects of GH are predominant during fasting, we specifically hypothesized that fasting and exercise act in synergy to increase STAT-5b target gene expression. Eight healthy men were studied on two occasions in relation to a 1 h exercise bout: i) with a concomitant i.v. glucose infusion ('feast') and ii) after a 36 h fast ('famine'). Muscle and fat biopsy specimens were obtained before, immediately after, and 30 min after exercise. GH increased during exercise on both examination days and this effect was amplified by fasting, and free fatty acid (FFA) levels increased after fasting. STAT-5b phosphorylation increased similarly following exercise on both occasions. In adipose tissue, suppressors of cytokine signaling 1 (SOCS1) and SOCS2 were increased after exercise on the fasting day and both fasting and exercise increased cytokine inducible SH2-containing protein (CISH). In muscle, SOCS2 and CISH mRNA were persistently increased after fasting. Muscle SOCS1, SOCS3, and CISH mRNA expression increased, whereas SOCS2 decreased after exercise on both examination days. This study demonstrates that fasting and exercise act in tandem to amplify STAT-5b target gene expression (SOCS and CISH) in adipose and muscle tissue in accordance with the 'feast and famine hypothesis'; the adipose tissue signaling responses, which hitherto have not been scrutinized, may play a particular role in promoting FFA mobilization. © 2015 European Society of Endocrinology.

  6. Significance of high-intensity signals on cranial MRI T2 weighted image in diagnosis of age-associated dementia. From a viewpoint of reversibility of brain function

    International Nuclear Information System (INIS)

    Kishiro, Masaki

    1994-01-01

    This study was undertaken to determine whether changes of EEG band profile in patients showing high-intensity signal (HIS) on cranial magnetic resonance images (MRI), who had however no vascular lesions on cranial CT, were similar to those in multi-infarct dementia (MID) or senile dementia of Alzheimer type (SDAT) patients and to determine the significance of HIS in the diagnosis of SDAT. Forty-two patients with dementia diagnosed according to DSM-III-R were divided into HIS (n=21), MID (n=13), and SDAT (n=8) based on CT and MRI findings. Multi-infarcted lesions were seen on cranial CT and HIS was seen on cranial MRI in MID patients. There were no abnormal lesions except brain atrophy on cranial CT and MRI in SDAT patients. Appearance rates (%) of the 2-18 c/s frequency bands using computerized quantitative EEG before and after administration of protirelin tartrate (TRH-T) were analyzed in the frontal, central, parietal and occipital areas of the brain. There were no significant differences in appearance rates of EEG frequency bands before administration of TRH-T in HIS, MID, and SDAT patients. A significant decrease in appearance rates of slow waves and a significant increase in appearance rates of α waves were observed after administration of TRH-T in the four areas in MID patients compared with those before administration. No significant differences in appearance rates of EEG frequency bands were observed after administration of TRH-T in the four areas in HIS and SDAT patients compared with those before administration. Changes of the EEG band profile in HIS patients were similar to those in SDAT patients. In the presence of appearance of HSI on cranial MRI T 2 weighted images, the possibility of SDAT patients cannot be excluded. Therefore, SDAT should be diagnosed based on both clinical data and the absence of brain vascular lesions on cranial CT. Also, HIS on MRI T 2 -weighted images is considered to reflect non-vascular lesions. (J.N.P.)

  7. Highly sensitive aptasensor based on synergetic catalysis activity of MoS2-Au-HE composite using cDNA-Au-GOD for signal amplification.

    Science.gov (United States)

    Song, Hai-Yan; Kang, Tian-Fang; Lu, Li-Ping; Cheng, Shui-Yuan

    2017-03-01

    Single or few-layer nanosheets of MoS 2 (MoS 2 nanosheets) and a composite composed of MoS 2 nanosheets, Au nanoparticles (AuNPs) and hemin (HE) (denoted as MoS 2 -Au-HE) were prepared. The composites possessed high synergetic catalysis activity towards the electroreduction of hydrogen peroxide. Furthermore, glucose oxidase (GOD) and AuNPs were used as marker of the complementary DNA (cDNA) strand of kanamycin aptamer to prepare a conjugate (reffered as cDNA-Au-GOD) that was designed as the signal probe. Both cDNA-Au-GOD and MoS 2 -Au-HE were applied to fabricate aptasensor for kanamycin. MoS 2 -Au-HE acted as solid platform for kanamycin aptamer and signal transmitters. AuNPs were employed as the supporter of cDNA and GOD which catalyze dissolved oxygen to produce hydrogen peroxide in the presence of glucose. Then cathodic peak current of H 2 O 2 was recorded by differential pulse voltammetry (DPV). The electrochemical reduction of H 2 O 2 was catalyzed by MoS 2 -Au-HE that was modified onto the surface of a glassy carbon electrode (GCE). The cathodic peak current of H 2 O 2 was highly linearly decreased with an increase of kanamycin concentrations from 1.0ng/L to 1.0×10 5 ng/L, with a detection limit of 0.8ng/L. This aptasensor can be used to detect kanamycin in milk with high specificity, sensitivity and selectivity. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. MRI of the normal brain from early childhood to middle age. Pt. 2. Age dependence of signal intensity changes on T2-weighted images

    International Nuclear Information System (INIS)

    Autti, T.; Raininko, R.; Vanhanen, S.L.; Kallio, M.; Santavuori, P.

    1994-01-01

    We examined 66 healthy volunteers aged 4 to 50 years by magnetic resonance imaging (MRI) and the signal intensity was measured on T2-weighted images in numerous sites and correlated with age and sex. Using distilled water and cerebrospinal fluid (CSF) as references on each slice, we calculated the signal intensities of the brain structures. Calculated ratios between structures did not change with age, except for those of the globus pallidus and thalamus, in which the signal intensities decreased more rapidly. The signal intensities of other brain structures changed equally but this could not be discerned visually and quantitative measurements were required. The signal intensities in the white and deep grey matter decreased rapidly in the first decade and then gradually to reach a plateau after the age of 18 years. Maturation of the brain thus seems to continue until near the end of the second decade of life. No sex differences were found. Quantitative analysis requires intensity references. The CSF in the tips of the frontal horns seems to be as reliable as an external fluid reference for intensity, and can be used in routine examinations provided the frontal horns are large enough to avoid partial volume effect. (orig.)

  9. Camera-based ratiometric fluorescence transduction of nucleic acid hybridization with reagentless signal amplification on a paper-based platform using immobilized quantum dots as donors.

    Science.gov (United States)

    Noor, M Omair; Krull, Ulrich J

    2014-10-21

    Paper-based diagnostic assays are gaining increasing popularity for their potential application in resource-limited settings and for point-of-care screening. Achievement of high sensitivity with precision and accuracy can be challenging when using paper substrates. Herein, we implement the red-green-blue color palette of a digital camera for quantitative ratiometric transduction of nucleic acid hybridization on a paper-based platform using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). A nonenzymatic and reagentless means of signal enhancement for QD-FRET assays on paper substrates is based on the use of dry paper substrates for data acquisition. This approach offered at least a 10-fold higher assay sensitivity and at least a 10-fold lower limit of detection (LOD) as compared to hydrated paper substrates. The surface of paper was modified with imidazole groups to assemble a transduction interface that consisted of immobilized QD-probe oligonucleotide conjugates. Green-emitting QDs (gQDs) served as donors with Cy3 as an acceptor. A hybridization event that brought the Cy3 acceptor dye in close proximity to the surface of immobilized gQDs was responsible for a FRET-sensitized emission from the acceptor dye, which served as an analytical signal. A hand-held UV lamp was used as an excitation source and ratiometric analysis using an iPad camera was possible by a relative intensity analysis of the red (Cy3 photoluminescence (PL)) and green (gQD PL) color channels of the digital camera. For digital imaging using an iPad camera, the LOD of the assay in a sandwich format was 450 fmol with a dynamic range spanning 2 orders of magnitude, while an epifluorescence microscope detection platform offered a LOD of 30 fmol and a dynamic range spanning 3 orders of magnitude. The selectivity of the hybridization assay was demonstrated by detection of a single nucleotide polymorphism at a contrast ratio of 60:1. This work provides an

  10. Signal to noise ratio (SNR) and image uniformity: an estimate of performance of magnetic resonance imaging (MRI) system

    International Nuclear Information System (INIS)

    Narayan, P.; Suri, S.; Choudhary, S.R.

    2001-01-01

    In most general definition, noise in an image, is any variation that represents a deviation from truth. Noise sources in MRI can be systematic or random and statistical in nature. Data processing algorithms that smooth and enhance the edges by non-linear intensity assignments among other factors can affect the distribution of statistical noise. The SNR and image uniformity depends on the various parameters of NMR imaging system (viz. General system calibration, Gain coil tuning, AF shielding, coil loading, image processing and scan parameters like TE, TR, interslice distance, slice thickness, pixel size and matrix size). A study on SNR and image uniformity have been performed using standard head AF coil with different TR and the estimates of their variation are presented. A comparison between different techniques has also been evaluated using standard protocol of the Siemens Magnetom Vision Plus MRI system

  11. Identification of a c-Jun N-terminal kinase-2-dependent signal amplification cascade that regulates c-Myc levels in ras transformation

    DEFF Research Database (Denmark)

    Mathiasen, D.P.; Egebjerg, C.; Andersen, S.H.

    2012-01-01

    are essential for ras transformation. Previous studies show that ERK-mediated serine 62 phosphorylation protects c-Myc from proteasomal degradation. ERK is, however, not alone sufficient to stabilize c-Myc but requires the cooperation of cancerous inhibitor of protein phosphatase 2A (CIP2A), an oncogene...... that counteracts protein phosphatase 2A-mediated dephosphorylation of c-Myc. Here we show that JNK2 regulates Cip2a transcription via ATF2. ATF2 and c-Myc cooperate to activate the transcription of ATF3. Remarkably, not only ectopic JNK2, but also ectopic ATF2, CIP2A, c-Myc and ATF3 are sufficient to rescue...... the defective ras transformation of JNK2-deficient cells. Thus, these data identify the key signal converging point of JNK2 and ERK pathways and underline the central role of CIP2A in ras transformation.Oncogene advance online publication, 27 June 2011; doi:10.1038/onc.2011.230....

  12. Static and Dynamic Amplification Using Strong Mechanical Coupling

    KAUST Repository

    Ilyas, Saad; Jaber, Nizar; Younis, Mohammad I.

    2016-01-01

    Amplifying the signal-to-noise ratio of resonant sensors is vital toward the effort to miniaturize devices into the sub-micro and nano regimes. In this paper, we demonstrate theoretically and experimentally, amplification through mechanically

  13. Detection of biological molecules using chemical amplification and optical sensors

    Science.gov (United States)

    Van Antwerp, William Peter; Mastrototaro, John Joseph

    2000-01-01

    Methods are provided for the determination of the concentration of biological levels of polyhydroxylated compounds, particularly glucose. The methods utilize an amplification system that is an analyte transducer immobilized in a polymeric matrix, where the system is implantable and biocompatible. Upon interrogation by an optical system, the amplification system produces a signal capable of detection external to the skin of the patient. Quantitation of the analyte of interest is achieved by measurement of the emitted signal.

  14. Diffusion, confusion and functional MRI

    International Nuclear Information System (INIS)

    Le Bihan, Denis

    2012-01-01

    Diffusion MRI has been introduced in 1985 and has had a very successful life on its own. While it has become a standard for imaging stroke and white matter disorders, the borders between diffusion MRI and the general field of fMRI have always remained fuzzy. First, diffusion MRI has been used to obtain images of brain function, based on the idea that diffusion MRI could also be made sensitive to blood flow, through the intra-voxel incoherent motion (IVIM) concept. Second, the IVIM concept helped better understand the contribution from different vasculature components to the BOLD fMRI signal. Third, it has been shown recently that a genuine fMRI signal can be obtained with diffusion MRI. This 'DfMRI' signal is notably different from the BOLD fMRI signal, especially for its much faster response to brain activation both at onset and offset, which points out to structural changes in the neural tissues, perhaps such as cell swelling, occurring in activated neural tissue. This short article reviews the major steps which have paved the way for this exciting development, underlying how technical progress with MRI equipment has each time been instrumental to expand the horizon of diffusion MRI toward the field of fMRI. (authors)

  15. Gene amplification in carcinogenesis

    Directory of Open Access Journals (Sweden)

    Lucimari Bizari

    2006-01-01

    Full Text Available Gene amplification increases the number of genes in a genome and can give rise to karyotype abnormalities called double minutes (DM and homogeneously staining regions (HSR, both of which have been widely observed in human tumors but are also known to play a major role during embryonic development due to the fact that they are responsible for the programmed increase of gene expression. The etiology of gene amplification during carcinogenesis is not yet completely understood but can be considered a result of genetic instability. Gene amplification leads to an increase in protein expression and provides a selective advantage during cell growth. Oncogenes such as CCND1, c-MET, c-MYC, ERBB2, EGFR and MDM2 are amplified in human tumors and can be associated with increased expression of their respective proteins or not. In general, gene amplification is associated with more aggressive tumors, metastases, resistance to chemotherapy and a decrease in the period during which the patient stays free of the disease. This review discusses the major role of gene amplification in the progression of carcinomas, formation of genetic markers and as possible therapeutic targets for the development of drugs for the treatment of some types of tumors.

  16. Social amplification of risk

    International Nuclear Information System (INIS)

    Kasperson, R.E.; Renn, O.; Slovic, P.; Kasperson, J.X.; Emani, S.

    1989-01-01

    The risks associated with radioactive and other hazardous waste disposal may be expected to interact with societal processes to enlarge or attenuate the consequences of risks and risk events. This article summarizes a conceptual framework that depicts the social amplification of risk. Using a data base of 128 hazard events that have occurred largely over the past ten years, the authors examine the role of physical consequences, media coverage, and public perceptions of risk in generating social and economic impacts. The analysis concludes that social amplification processes substantially shape the nature and magnitude of those impacts but also that such social amplification appears to be systematically related to characteristics of the risks and risk events

  17. Bell's palsy: what is the prognostic value of measurements of signal intensity increases with contrast enhancement on MRI?

    Energy Technology Data Exchange (ETDEWEB)

    Kress, B.P.J.; Efinger, K.; Solbach, T.; Gottschalk, A.; Baehren, W. [Department of Radiology, Armed Forces Hospital, Deutsche Bundeswehr, Ulm (Germany); Griesbeck, F.; Kornhuber, A.W. [Department of Neurology/Psychiatry, Armed Forces Hospital, Deutsche Bundeswehr, Ulm (Germany)

    2002-05-01

    Our objective was to assess the prognostic value of measurements of the degree of contrast enhancement of the intratemporal segments of the facial nerve. We prospectively obtained MRI, slice thickness <1 mm of 20 patients with a facial palsy on the first day of inpatient treatment, and measured contrast enhancement of the nerve. The data were compared with compound muscle action potential (CMAP) measurements and the clinical course. Analysis of the initial enabled differentiation of three patients whose palsy was to show no improvement from 17 whose palsy was to resolve as expected. No patient with a poor outcome showed lesser increase in signal in the internal auditory canal, pars tympanica and pars mastoidea than patients who fully recovered. In no patient who had been diagnosed on the basis of the initial MRI as having a ''normal'' palsy was the amplitude of the (CMAP) reduced to less than 20% that of the normal side. Measurement of contrast enhancement was thus shown to be a prognostic indicator and may provide a basis for a differential treatment of facial palsy. (orig.)

  18. Music reduces pain and increases resting state fMRI BOLD signal amplitude in the left angular gyrus in fibromyalgia patients

    Directory of Open Access Journals (Sweden)

    Eduardo A. Garza-Villarreal

    2015-07-01

    Full Text Available Music reduces pain in fibromyalgia (FM, a chronic pain disease, but the functional neural correlates of music-induced analgesia are still largely unknown. We recruited FM patients (n = 22 who listened to their preferred relaxing music and an auditory control (pink noise for 5 minutes without external noise from fMRI image acquisition. Resting state fMRI was then acquired before and after the music and control conditions. A significant increase in the amplitude of low frequency fluctuations of the BOLD signal was evident in the left angular gyrus after listening to music, which in turn, correlated to the analgesia reports. The post-hoc seed-based functional connectivity analysis of the left angular gyrus showed found higher connectivity after listening to music with right dorsolateral prefrontal cortex, the left caudate, and decreased connectivity with right anterior cingulate cortex, right supplementary motor area, precuneus and right precentral gyrus. Pain intensity analgesia was correlated (r = .61 to the connectivity of the left angular gyrus with the right precentral gyrus. Our results show that music-induced analgesia in FM is related to top-down regulation of the pain modulatory network by the default-mode network.

  19. Cluster analysis of signal-intensity time course in dynamic breast MRI: does unsupervised vector quantization help to evaluate small mammographic lesions?

    Energy Technology Data Exchange (ETDEWEB)

    Leinsinger, Gerda; Schlossbauer, Thomas; Scherr, Michael; Lange, Oliver; Reiser, Maximilian; Wismueller, Axel [Institute for Clinical Radiology University of Munich, Munich (Germany)

    2006-05-15

    We examined whether neural network clustering could support the characterization of diagnostically challenging breast lesions in dynamic magnetic resonance imaging (MRI). We examined 88 patients with 92 breast lesions (51 malignant, 41 benign). Lesions were detected by mammography and classified Breast Imaging and Reporting Data System (BIRADS) III (median diameter 14 mm). MRI was performed with a dynamic T1-weighted gradient echo sequence (one precontrast and five postcontrast series). Lesions with an initial contrast enhancement {>=}50% were selected with semiautomatic segmentation. For conventional analysis, we calculated the mean initial signal increase and postinitial course of all voxels included in a lesion. Secondly, all voxels within the lesions were divided into four clusters using minimal-free-energy vector quantization (VQ). With conventional analysis, maximum accuracy in detecting breast cancer was 71%. With VQ, a maximum accuracy of 75% was observed. The slight improvement using VQ was mainly achieved by an increase of sensitivity, especially in invasive lobular carcinoma and ductal carcinoma in situ (DCIS). For lesion size, a high correlation between different observers was found (R{sup 2} = 0.98). VQ slightly improved the discrimination between malignant and benign indeterminate lesions (BIRADS III) in comparison with a standard evaluation method. (orig.)

  20. MRI of the Chest

    Medline Plus

    Full Text Available ... The magnetic field is produced by passing an electric current through wire coils in most MRI units. ... signals that are detected by the coils. The electric current does not come in contact with the ...

  1. Towards MRI microarrays.

    Science.gov (United States)

    Hall, Andrew; Mundell, Victoria J; Blanco-Andujar, Cristina; Bencsik, Martin; McHale, Glen; Newton, Michael I; Cave, Gareth W V

    2010-04-14

    Superparamagnetic iron oxide nanometre scale particles have been utilised as contrast agents to image staked target binding oligonucleotide arrays using MRI to correlate the signal intensity and T(2)* relaxation times in different NMR fluids.

  2. New MRI findings in Creutzfeldt-Jakob disease: high signal in the globus pallidus on T 1-weighted images

    International Nuclear Information System (INIS)

    Priester, J.A. de; Wilmink, J.T.; Jansen, G.H.; Kruijk, J.R. de

    1999-01-01

    We report a 49-year-old woman with Creutzfeldt-Jakob disease (CJD). In addition to typical high-signal lesions on proton-density and T 2-weighted images there was high signal in the globus pallidus bilaterally on T 1-weighted images. The latter feature has not been described previously and probably due to deposition of prion protein, as found at autopsy. (orig.)

  3. New MRI findings in Creutzfeldt-Jakob disease: high signal in the globus pallidus on T 1-weighted images

    Energy Technology Data Exchange (ETDEWEB)

    Priester, J.A. de; Wilmink, J.T. [Dept. of Radiology, University Hospital Maastricht (Netherlands); Jansen, G.H. [Department of Neuropathology, University Hospital Utrecht (Netherlands); Kruijk, J.R. de [Department of Neurology, University Hospital Maastricht (Netherlands)

    1999-04-01

    We report a 49-year-old woman with Creutzfeldt-Jakob disease (CJD). In addition to typical high-signal lesions on proton-density and T 2-weighted images there was high signal in the globus pallidus bilaterally on T 1-weighted images. The latter feature has not been described previously and probably due to deposition of prion protein, as found at autopsy. (orig.) With 3 figs., 11 refs.

  4. Relations between the distribution of signal strength on dynamic MRI imaging and the effect of primary systemic chemotherapy on breast cancer

    International Nuclear Information System (INIS)

    Ohta, Koji; Endo, Naoki; Miyanaga, Tamon; Hosokawa, Osamu; Takeda, Takayuki; Kaizaki, Yasuharu

    2009-01-01

    The subjects were 24 patients in whom MRI was performed before and after primary system chemotherapy (PSC). We investigated the pattern of contrast enhancement with respect to treatment responses. We prepared the time-signal intensity in each region of interest (ROI) (small ROI), established by dividing the maximum cut surface of each tumor into 9, and then subdividing them, and examined the distribution of enhancement. We counted small ROIs showing early enhancement and late washout per lesion. Counts were plotted on the longitudinal axis, and the tumor reduction rate on the transverse axis based on data for all tumors. These were also evaluated with respect to subtypes. The complete response (CR) group showed early enhancement and late washout. In addition, the small ROI count was correlated with the tumor reduction rate only in the luminal group. In this group, treatment responses may have more strongly depended on the intra-tumoral vascular density and permeability, because anticancer agent sensitivity was low. (author)

  5. Closed-form expressions for flip angle variation that maximize total signal in T1-weighted rapid gradient echo MRI.

    Science.gov (United States)

    Drobnitzky, Matthias; Klose, Uwe

    2017-03-01

    Magnetization-prepared rapid gradient-echo (MPRAGE) sequences are commonly employed for T1-weighted structural brain imaging. Following a contrast preparation radiofrequency (RF) pulse, the data acquisition proceeds under nonequilibrium conditions of the relaxing longitudinal magnetization. Variation of the flip angle can be used to maximize total available signal. Simulated annealing or greedy algorithms have so far been published to numerically solve this problem, with signal-to-noise ratios optimized for clinical imaging scenarios by adhering to a predefined shape of the signal evolution. We propose an unconstrained optimization of the MPRAGE experiment that employs techniques from resource allocation theory. A new dynamic programming solution is introduced that yields closed-form expressions for optimal flip angle variation. Flip angle series are proposed that maximize total transverse magnetization (Mxy) for a range of physiologic T1 values. A 3D MPRAGE sequence is modified to allow for a controlled variation of the excitation angle. Experiments employing a T1 contrast phantom are performed at 3T. 1D acquisitions without phase encoding permit measurement of the temporal development of Mxy. Image mean signal and standard deviation for reference flip angle trains are compared in 2D measurements. Signal profiles at sharp phantom edges are acquired to access image blurring related to nonuniform Mxy development. A novel closed-form expression for flip angle variation is found that constitutes the optimal policy to reach maximum total signal. It numerically equals previously published results of other authors when evaluated under their simplifying assumptions. Longitudinal magnetization (Mz) is exhaustively used without causing abrupt changes in the measured MR signal, which is a prerequisite for artifact free images. Phantom experiments at 3T verify the expected benefit for total accumulated k-space signal when compared with published flip angle series. Describing

  6. Modulation of 7 T fMRI Signal in the Cerebellar Cortex and Nuclei During Acquisition, Extinction, and Reacquisition of Conditioned Eyeblink Responses.

    Science.gov (United States)

    Ernst, Thomas M; Thürling, Markus; Müller, Sarah; Kahl, Fabian; Maderwald, Stefan; Schlamann, Marc; Boele, Henk-Jan; Koekkoek, Sebastiaan K E; Diedrichsen, Jörn; De Zeeuw, Chris I; Ladd, Mark E; Timmann, Dagmar

    2017-08-01

    Classical delay eyeblink conditioning is likely the most commonly used paradigm to study cerebellar learning. As yet, few studies have focused on extinction and savings of conditioned eyeblink responses (CRs). Saving effects, which are reflected in a reacquisition after extinction that is faster than the initial acquisition, suggest that learned associations are at least partly preserved during extinction. In this study, we tested the hypothesis that acquisition-related plasticity is nihilated during extinction in the cerebellar cortex, but retained in the cerebellar nuclei, allowing for faster reacquisition. Changes of 7 T functional magnetic resonance imaging (fMRI) signals were investigated in the cerebellar cortex and nuclei of young and healthy human subjects. Main effects of acquisition, extinction, and reacquisition against rest were calculated in conditioned stimulus-only trials. First-level β values were determined for a spherical region of interest (ROI) around the acquisition peak voxel in lobule VI, and dentate and interposed nuclei ipsilateral to the unconditioned stimulus. In the cerebellar cortex and nuclei, fMRI signals were significantly lower in extinction compared to acquisition and reacquisition, but not significantly different between acquisition and reacquisition. These findings are consistent with the theory of bidirectional learning in both the cerebellar cortex and nuclei. It cannot explain, however, why conditioned responses reappear almost immediately in reacquisition following extinction. Although the present data do not exclude that part of the initial memory remains in the cerebellum in extinction, future studies should also explore changes in extracerebellar regions as a potential substrate of saving effects. Hum Brain Mapp 38:3957-3974, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  7. Biomaterials in light amplification

    Science.gov (United States)

    Mysliwiec, Jaroslaw; Cyprych, Konrad; Sznitko, Lech; Miniewicz, Andrzej

    2017-03-01

    Biologically produced or inspired materials can serve as optical gain media, i.e. they can exhibit the phenomenon of light amplification. Some of these materials, under suitable dye-doping and optical pumping conditions, show lasing phenomena. The emerging branch of research focused on obtaining lasing action in highly disordered and highly light scattering materials, i.e. research on random lasing, is perfectly suited for biological materials. The use of biomaterials in light amplification has been extensively reported in the literature. In this review we attempt to report on progress in the development of biologically derived systems able to show the phenomena of light amplification and random lasing together with the contribution of our group to this field. The rich world of biopolymers modified with molecular aggregates and nanocrystals, and self-organized at the nanoscale, offers a multitude of possibilities for tailoring luminescent and light scattering properties that are not easily replicated in conventional organic or inorganic materials. Of particular importance and interest are light amplification and lasing, or random lasing studies in biological cells and tissues. In this review we will describe nucleic acids and their complexes employed as gain media due to their favorable optical properties and ease of manipulation. We will report on research conducted on various biomaterials showing structural analogy to nucleic acids such as fluorescent proteins, gelatins in which the first distributed feedback laser was realized, and also amyloids or silks, which, due to their dye-doped fiber-like structure, allow for light amplification. Other materials that were investigated in that respect include polysaccharides, like starch exhibiting favorable photostability in comparison to other biomaterials, and chitosan, which forms photonic crystals or cellulose. Light amplification and random lasing was not only observed in processed biomaterials but also in living

  8. Signal amplification of dopamine using lanthanum hexacyanoferrate ...

    Indian Academy of Sciences (India)

    rare earth metal hexacyanoferrates, for e.g., lanthanum ... to facilitate the electrochemical reactions of biological molecules.9,10 In general ... bic acid and potassium hexacyanoferrate (Merck) were ... were prepared using doubly distilled water.

  9. Anti-correlated networks, global signal regression, and the effects of caffeine in resting-state functional MRI.

    Science.gov (United States)

    Wong, Chi Wah; Olafsson, Valur; Tal, Omer; Liu, Thomas T

    2012-10-15

    Resting-state functional connectivity magnetic resonance imaging is proving to be an essential tool for the characterization of functional networks in the brain. Two of the major networks that have been identified are the default mode network (DMN) and the task positive network (TPN). Although prior work indicates that these two networks are anti-correlated, the findings are controversial because the anti-correlations are often found only after the application of a pre-processing step, known as global signal regression, that can produce artifactual anti-correlations. In this paper, we show that, for subjects studied in an eyes-closed rest state, caffeine can significantly enhance the detection of anti-correlations between the DMN and TPN without the need for global signal regression. In line with these findings, we find that caffeine also leads to widespread decreases in connectivity and global signal amplitude. Using a recently introduced geometric model of global signal effects, we demonstrate that these decreases are consistent with the removal of an additive global signal confound. In contrast to the effects observed in the eyes-closed rest state, caffeine did not lead to significant changes in global functional connectivity in the eyes-open rest state. Copyright © 2012 Elsevier Inc. All rights reserved.

  10. MO-F-CAMPUS-J-03: Sorting 2D Dynamic MR Images Using Internal Respiratory Signal for 4D MRI

    International Nuclear Information System (INIS)

    Wen, Z; Hui, C; Beddar, S; Stemkens, B; Tijssen, R; Berg, C van den

    2015-01-01

    Purpose: To develop a novel algorithm to extract internal respiratory signal (IRS) for sorting dynamic magnetic resonance (MR) images in order to achieve four-dimensional (4D) MR imaging. Methods: Dynamic MR images were obtained with the balanced steady state free precession by acquiring each two-dimensional sagittal slice repeatedly for more than one breathing cycle. To generate a robust IRS, we used 5 different representative internal respiratory surrogates in both the image space (body area) and the Fourier space (the first two low-frequency phase components in the anterior-posterior direction, and the first two low-frequency phase components in the superior-inferior direction). A clustering algorithm was then used to search for a group of similar individual internal signals, which was then used to formulate the final IRS. A phantom study and a volunteer study were performed to demonstrate the effectiveness of this algorithm. The IRS was compared to the signal from the respiratory bellows. Results: The IRS computed by our algorithm matched well with the bellows signal in both the phantom and the volunteer studies. On average, the normalized cross correlation between the IRS and the bellows signal was 0.97 in the phantom study and 0.87 in the volunteer study, respectively. The average difference between the end inspiration times in the IRS and bellows signal was 0.18 s in the phantom study and 0.14 s in the volunteer study, respectively. 4D images sorted based on the IRS showed minimal mismatched artifacts, and the motion of the anatomy was coherent with the respiratory phases. Conclusion: A novel algorithm was developed to generate IRS from dynamic MR images to achieve 4D MR imaging. The performance of the IRS was comparable to that of the bellows signal. It can be easily implemented into the clinic and potentially could replace the use of external respiratory surrogates. This research was partially funded by the the Center for Radiation Oncology Research from

  11. Parametric nanomechanical amplification at very high frequency.

    Science.gov (United States)

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  12. MRI features of chondroblastoma

    International Nuclear Information System (INIS)

    Cheng Xiaoguang; Liu Xia; Cheng Kebin; Liu Wei

    2009-01-01

    Objective: To evaluate the MR imaging features of chondroblastoma. Methods: MRI examinations of 20 patients with histological proven chondmblastoma were reviewed retrospectively. The MRI findings of chondroblastoma including the signal intensity, the shape, the growth patterns, and the surrounding bone marrow edema and the adjacent soft tissue edema, the periosteal reaction, the adjacent joint effusion were analyzed. Results: All 20 cases demonstrated heterogeneous MR signal intensity on T 1 WI and T 2 WI images and showed lobular margins. Sixteen cases demonstrated expansive growth patterns. Surrounding bone marrow edema was found in 18 cases and adjacent soft tissue edema in 14 cases. Periosteal reaction was identified in 6 cases. In 7 cases the tumor extended to adjacent soft tissue. Adjacent joint effusion was visible on MRI in 6 cases. Conclusion: Heterogeneous signal intensity, lobular margins and expansive growth pattern, adjacent bone marrow and soft tissue edema were the common features of chondroblastoma on MRI. (authors)

  13. Correction of inhomogeneous RF field using multiple SPGR signals for high-field spin-echo MRI

    International Nuclear Information System (INIS)

    Ishimori, Yoshiyuki; Monma, Masahiko; Yamada, Kazuhiro; Kimura, Hirohiko; Uematsu, Hidemasa; Fujiwara, Yasuhiro; Yamaguchi, Isao

    2007-01-01

    The purpose of this study was to propose a simple and useful method for correcting nonuniformity of high-field (3 Tesla) T 1 -weighted spin-echo (SE) images based on a B1 field map estimated from gradient recalled echo (GRE) signals. The method of this study was to estimate B1 inhomogeneity, spoiled gradient recalled echo (SPGR) images were collected using a fixed repetition time of 70 ms, flip angles of 45 and 90 degrees, and echo times of 4.8 and 10.4 ms. Selection of flip angles was based on the observation that the relative intensity changes in SPGR signals were very similar among different tissues at larger flip angles than the Ernst angle. Accordingly, spatial irregularity that was observed on a signal ratio map of the SPGR images acquired with these 2 flip angles was ascribed to inhomogeneity of the B1 field. Dual echo time was used to eliminate T 2 * effects. The ratio map that was acquired was scaled to provide an intensity correction map for SE images. Both phantom and volunteer studies were performed using a 3T magnetic resonance scanner to validate the method. In the phantom study, the uniformity of the T 1 -weighted SE image improved by 23%. Images of human heads also showed practically sufficient improvement in the image uniformity. The present method improves the image uniformity of high-field T 1 -weighted SE images. (author)

  14. Clinical-Radiological Parameters Improve the Prediction of the Thrombolysis Time Window by Both MRI Signal Intensities and DWI-FLAIR Mismatch.

    Science.gov (United States)

    Madai, Vince Istvan; Wood, Carla N; Galinovic, Ivana; Grittner, Ulrike; Piper, Sophie K; Revankar, Gajanan S; Martin, Steve Z; Zaro-Weber, Olivier; Moeller-Hartmann, Walter; von Samson-Himmelstjerna, Federico C; Heiss, Wolf-Dieter; Ebinger, Martin; Fiebach, Jochen B; Sobesky, Jan

    2016-01-01

    With regard to acute stroke, patients with unknown time from stroke onset are not eligible for thrombolysis. Quantitative diffusion weighted imaging (DWI) and fluid attenuated inversion recovery (FLAIR) MRI relative signal intensity (rSI) biomarkers have been introduced to predict eligibility for thrombolysis, but have shown heterogeneous results in the past. In the present work, we investigated whether the inclusion of easily obtainable clinical-radiological parameters would improve the prediction of the thrombolysis time window by rSIs and compared their performance to the visual DWI-FLAIR mismatch. In a retrospective study, patients from 2 centers with proven stroke with onset value/mean value of the unaffected hemisphere). Additionally, the visual DWI-FLAIR mismatch was evaluated. Prediction of the thrombolysis time window was evaluated by the area-under-the-curve (AUC) derived from receiver operating characteristic (ROC) curve analysis. Factors such as the association of age, National Institutes of Health Stroke Scale, MRI field strength, lesion size, vessel occlusion and Wahlund-Score with rSI were investigated and the models were adjusted and stratified accordingly. In 82 patients, the unadjusted rSI measures DWI-mean and -SD showed the highest AUCs (AUC 0.86-0.87). Adjustment for clinical-radiological covariates significantly improved the performance of FLAIR-mean (0.91) and DWI-SD (0.91). The best prediction results based on the AUC were found for the final stratified and adjusted models of DWI-SD (0.94) and FLAIR-mean (0.96) and a multivariable DWI-FLAIR model (0.95). The adjusted visual DWI-FLAIR mismatch did not perform in a significantly worse manner (0.89). ADC-rSIs showed fair performance in all models. Quantitative DWI and FLAIR MRI biomarkers as well as the visual DWI-FLAIR mismatch provide excellent prediction of eligibility for thrombolysis in acute stroke, when easily obtainable clinical-radiological parameters are included in the prediction

  15. Social amplification of risk: a conceptual framework

    International Nuclear Information System (INIS)

    Kasperson, R.E.; Renn, O.; Slovic, P.; Brown, H.S.; Emel, J.; Goble, R.; Kasperson, J.X.; Ratick, S.

    1988-01-01

    One of the most perplexing problems in risk analysis is why some relatively minor risks or risk events, as assessed by technical experts, often elicit strong public concerns and result in substantial impacts upon society and economy. This article sets forth a conceptual framework that seeks to link systematically the technical assessment of risk with psychological, sociological, and cultural perspectives of risk perception and risk-related behavior. The main thesis is that hazards interact with psychological, social, institutional, and cultural processes in ways that may amplify or attenuate public responses to the risk or risk event. A structural description of the social amplification of risk is now possible. Amplification occurs at two stages: in the transfer of information about the risk, and in the response mechanisms of society. Signals about risk are processed by individual and social amplification stations, including the scientist who communicates the risk assessment, the news media, cultural groups, interpersonal networks, and others. Key steps of amplifications can be identified at each stage. The amplified risk leads to behavioral responses, which, in turn, result in secondary impacts. Models are presented that portray the elements and linkages in the proposed conceptual framework

  16. Two Methods of Automatic Evaluation of Speech Signal Enhancement Recorded in the Open-Air MRI Environment

    Science.gov (United States)

    Přibil, Jiří; Přibilová, Anna; Frollo, Ivan

    2017-12-01

    The paper focuses on two methods of evaluation of successfulness of speech signal enhancement recorded in the open-air magnetic resonance imager during phonation for the 3D human vocal tract modeling. The first approach enables to obtain a comparison based on statistical analysis by ANOVA and hypothesis tests. The second method is based on classification by Gaussian mixture models (GMM). The performed experiments have confirmed that the proposed ANOVA and GMM classifiers for automatic evaluation of the speech quality are functional and produce fully comparable results with the standard evaluation based on the listening test method.

  17. A decade of decoding reward-related fMRI signals and where we go from here.

    Science.gov (United States)

    Kahnt, Thorsten

    2017-06-04

    Information about potential rewards in the environment is essential for guiding adaptive behavior, and understanding neural reward processes may provide insights into neuropsychiatric dysfunctions. Over the past 10 years, multivoxel pattern analysis (MVPA) techniques have been used to study brain areas encoding information about expected and experienced outcomes. These studies have identified reward signals throughout the brain, including the striatum, medial prefrontal cortex, orbitofrontal cortex, dorsolateral prefrontal cortex, and parietal cortex. This review article discusses some of the assumptions and models that are used to interpret results from these studies, and how they relate to findings from animal electrophysiology. The article reviews and summarizes some of the key findings from MVPA studies on reward. In particular, it first focuses on studies that, in addition to mapping out the brain areas that process rewards, have provided novel insights into the coding mechanisms of value and reward. Then, it discusses examples of how multivariate imaging approaches are being used more recently to decode features of expected rewards that go beyond value, such as the identity of an expected outcome or the action required to obtain it. The study of such complex and multifaceted reward representations highlights the key advantage of using representational methods, which are uniquely able to reveal these signals and may narrow the gap between animal and human research. Applied in a clinical context, MVPA may advance our understanding of neuropsychiatric disorders and the development of novel treatment strategies. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Sequential MRI Study of Graft Integrity and Signal Following Pediatric All-epiphyseal ACL Reconstruction: Does the “Sharp Turn” at the Socket of the Distal Femoral Aperture Matter?

    Science.gov (United States)

    Tuca, Maria; Greditzer, Harry Gus; Gausden, Elizabeth Bishop; Uppstrom, Tyler J.; Potter, Hollis G.; Cordasco, Frank A.; Green, Daniel W.

    2017-01-01

    Objectives: To analyze graft structure and signal with particular emphasis on the distal femoral socket aperture following all-epiphyseal ACLR using hamstring autografts with sequential MRI in skeletally immature athletes. Methods: Retrospective cohort study of 23 skeletally immature patients who underwent ACLR by the same surgical team at a tertiary center during 2011-2013. Athletes had at least two follow-up MRIs, the first MRI 6-12 months after surgery and the second MRI >18 months, were included. Exclusion criteria included those athletes with inMRI follow-up (6) or with a failure of their reconstructions (1). All athletes were treated with an arthroscopic all-inside, all-epiphyseal ACLR, using hamstring autograft, secured with adjustable loop cortical buttons on both tibia and femur. MRI images were analyzed independently and blinded by an orthopaedic surgery fellow and a musculoskeletal radiology fellow. Using a GE Functional Analysis Software, the signal intensity (SI) of the graft was measured in 5 different locations: 1) femoral tunnel, 2) intra-articular proximal turn, 3) midsubstance, 4) intra-articular distal turn, and 5) tibial tunnel. Values were normalized to cortical bone density. The amount of perigraft scarring and synovitis was analyzed. An intraclass correlation coefficient was used to quantify inter-rater reliability, non-parametric Wilcoxon test for perigraft scarring and synovitis, one-way ANOVA to test if significant differences of SI were seen between the different graft locations, and a 2-tailed student t-test for SI changes from 1st to 2nd MRI. Results: The study included 16 patients (5 girls and 11 boys), with an average age at surgery of 11.9 years (range 10-15). The first follow-up MRI was on average at 8.4 months (range 6-12 months), while the 2nd MRI was on average 30.7 months (range 18-40) after surgery. Intra-class correlation coefficients were above 0.7 for all measurements, indicating an excellent concordance between observers

  19. MRI in gout

    International Nuclear Information System (INIS)

    Seidl, G.; Ullrich, R.; Trattnig, S.; Dominkus, M.; Morscher, M.; Aringer, M.; Imhof, H.

    1996-01-01

    The appearance of gouty tophus in magnetic resonance imaging (MRI) is characteristic. On T1- and T2-weighted SE images, the signal intensity of tophaceous lesions is similar to that of muscles. According to the histology, T2-weighted SE images demonstrate extremely hyperintense signals, which reflect the high protein content in the amorpheous center of the tophus. The microscopic urate crystals deposited there have no MRI signal and are of no further diagnostic impact. Vascularized granulation tissue surrounding the tophus center enhance after intervenous application of contrast agents (Gadolinium). The inflammed tophus is associated with local edema, causing high signal intensity. MRI is superior to plain radiography for early detection of intraosseous tophi. Involvement of anatomical structures such as ligaments and tendons can be evaluated sufficiently. For peripheral joints, axial slice orientation is most helpful. (orig.) [de

  20. Sensitivity enhancement of remotely coupled NMR detectors using wirelessly powered parametric amplification.

    Science.gov (United States)

    Qian, Chunqi; Murphy-Boesch, Joseph; Dodd, Stephen; Koretsky, Alan

    2012-09-01

    A completely wireless detection coil with an integrated parametric amplifier has been constructed to provide local amplification and transmission of MR signals. The sample coil is one element of a parametric amplifier using a zero-bias diode that mixes the weak MR signal with a strong pump signal that is obtained from an inductively coupled external loop. The NMR sample coil develops current gain via reduction in the effective coil resistance. Higher gain can be obtained by adjusting the level of the pumping power closer to the oscillation threshold, but the gain is ultimately constrained by the bandwidth requirement of MRI experiments. A feasibility study here shows that on a NaCl/D(2) O phantom, (23) Na signals with 20 dB of gain can be readily obtained with a concomitant bandwidth of 144 kHz. This gain is high enough that the integrated coil with parametric amplifier, which is coupled inductively to external loops, can provide sensitivity approaching that of direct wire connection. Copyright © 2012 Wiley Periodicals, Inc.

  1. Marrow signal changes observed in follow-up whole-body MRI studies in children and young adults with neurofibromatosis type 1 treated with imatinib mesylate (Gleevec) for plexiform neurofibromas

    Energy Technology Data Exchange (ETDEWEB)

    Karmazyn, Boaz; Cohen, Mervyn D. [Riley Hospital for Children, Indiana University Health, Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, IN (United States); Jennings, Samuel Gregory [Indiana University School of Medicine, Department of Radiology and Imaging Sciences, Indianapolis, IN (United States); Robertson, Kent A. [Riley Hospital for Children, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN (United States)

    2012-10-15

    We observed bone marrow signal changes (BMSC) in patients with plexiform neurofibromas after treatment with imatinib mesylate (Gleevec). To evaluate the pattern and natural history of BMSC. The data were obtained from a pilot study of imatinib mesylate in patients with plexiform neurofibromas. All patients underwent baseline and sequential whole-body STIR 1.5-T MRI after treatment. The bone marrow signal on MRI was evaluated for abnormalities, location and pattern, and any change on follow-up studies. The study group included 16 patients (8 males) with a median age of 14 years (range 4 to 25 years). The mean whole-body MRI follow-up duration was 1.9 years. Of the 16 patients, 14 (88%) developed BMSC. The signal change was asymmetrical in 9 of the 14 patients (64%). The appendicular skeleton was involved in all 14 patients and the axial skeleton in 3 patients (21%). BMSC was followed in 13 patients and decreased signal was seen in 9 patients (69%) after a mean duration of 1.3 years of treatment (range 0.6 to 2.9 years); no complications were observed. BMSC appeared in most patients with neurofibromatosis type 1 following treatment with imatinib mesylate. BMSC was unusually asymmetrical and involved the lower extremities. On follow-up, BMSC often showed a decrease without complications. (orig.)

  2. Evidence of high-elevation amplification versus Arctic amplification.

    Science.gov (United States)

    Wang, Qixiang; Fan, Xiaohui; Wang, Mengben

    2016-01-12

    Elevation-dependent warming in high-elevation regions and Arctic amplification are of tremendous interest to many scientists who are engaged in studies in climate change. Here, using annual mean temperatures from 2781 global stations for the 1961-2010 period, we find that the warming for the world's high-elevation stations (>500 m above sea level) is clearly stronger than their low-elevation counterparts; and the high-elevation amplification consists of not only an altitudinal amplification but also a latitudinal amplification. The warming for the high-elevation stations is linearly proportional to the temperature lapse rates along altitudinal and latitudinal gradients, as a result of the functional shape of Stefan-Boltzmann law in both vertical and latitudinal directions. In contrast, neither altitudinal amplification nor latitudinal amplification is found within the Arctic region despite its greater warming than lower latitudes. Further analysis shows that the Arctic amplification is an integrated part of the latitudinal amplification trend for the low-elevation stations (≤500 m above sea level) across the entire low- to high-latitude Northern Hemisphere, also a result of the mathematical shape of Stefan-Boltzmann law but only in latitudinal direction.

  3. Non-Cartesian MRI scan time reduction through sparse sampling

    NARCIS (Netherlands)

    Wajer, F.T.A.W.

    2001-01-01

    Non-Cartesian MRI Scan-Time Reduction through Sparse Sampling Magnetic resonance imaging (MRI) signals are measured in the Fourier domain, also called k-space. Samples of the MRI signal can not be taken at will, but lie along k-space trajectories determined by the magnetic field gradients. MRI

  4. Realization of the conceptual ideal for x-ray amplification

    Energy Technology Data Exchange (ETDEWEB)

    Borisov, Alex B; Racz, Ervin; Zhang Ping; McCorkindale, John C; Khan, Shahab F; Poopalasingam, Sankar; Zhao Ji; Rhodes, Charles K [Laboratory for X-Ray Microimaging and Bioinformatics, Department of Physics, University of Illinois at Chicago, Chicago, IL 60607-7059 (United States)

    2008-05-28

    The Xe(L) system is an amplifier with fundamentally different dynamic characteristics from all previously developed laser amplifiers; it represents the conceptual ideal through full utilization of the Kramers-Kronig relations that fundamentally couple the dispersive and absorptive components. The dispersive response of the system, through optimal governance of the power compression, rules the amplification and establishes a minimum gain for the amplifier. Accordingly, the amplification requires a minimum value of the dispersion to be surpassed; the corresponding gain follows automatically. As a leading consequence, since this minimum gain is sufficiently high, the key experimental observation is the uniform presence of saturated amplification signaled by strong spectral hole burning on all transitions exhibiting amplification, including double-vacancy lines. This cardinal signature demonstrates that the amplification is legislated by the saturated gain g{sub s}, not the corresponding small signal value g{sub 0}. The chief outcome is that explosive dispersion yields perforce explosive amplification and the efficient generation of maximally bright coherent power.

  5. Targeting MET Amplification as a New Oncogenic Driver

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami, Hisato [Department of Medical Oncology, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Okamoto, Isamu, E-mail: okamotoi@kokyu.med.kyushu-u.ac.jp [Department of Medical Oncology, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Center for Clinical and Translational Research, Kyushu University Hospital, 3-1-1 Maidashi, Higashiku, Fukuoka 812-8582 (Japan); Okamoto, Wataru [Department of Medical Oncology, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Division of Transrlational Research, Exploratory Oncology Research & Clinical Trial Center, National Cancer Center, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577 (Japan); Tanizaki, Junko [Department of Medical Oncology, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Lowe Center for Thoracic Oncology, Dana-Farber Cancer Institute, HIM223, 450 Brookline Avenue, Boston, MA 02215 (United States); Nakagawa, Kazuhiko [Department of Medical Oncology, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Osaka 589-8511 (Japan); Nishio, Kazuto [Department of Genome Biology, Kinki University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Osaka 589-8511 (Japan)

    2014-07-22

    Certain genetically defined cancers are dependent on a single overactive oncogene for their proliferation and survival, a phenomenon known as “oncogene addiction”. A new generation of drugs that selectively target such “driver oncogenes” manifests a clinical efficacy greater than that of conventional chemotherapy in appropriate genetically defined patients. MET is a proto-oncogene that encodes a receptor tyrosine kinase, and aberrant activation of MET signaling occurs in a subset of advanced cancers as result of various genetic alterations including gene amplification, polysomy, and gene mutation. Our preclinical studies have shown that inhibition of MET signaling either with the small-molecule MET inhibitor crizotinib or by RNA interference targeted to MET mRNA resulted in marked antitumor effects in cancer cell lines with MET amplification both in vitro and in vivo. Furthermore, patients with non-small cell lung cancer or gastric cancer positive for MET amplification have shown a pronounced clinical response to crizotinib. Accumulating preclinical and clinical evidence thus suggests that MET amplification is an “oncogenic driver” and therefore a valid target for treatment. However, the prevalence of MET amplification has not been fully determined, possibly in part because of the difficulty in evaluating gene amplification. In this review, we provide a rationale for targeting this genetic alteration in cancer therapy.

  6. Targeting MET Amplification as a New Oncogenic Driver

    International Nuclear Information System (INIS)

    Kawakami, Hisato; Okamoto, Isamu; Okamoto, Wataru; Tanizaki, Junko; Nakagawa, Kazuhiko; Nishio, Kazuto

    2014-01-01

    Certain genetically defined cancers are dependent on a single overactive oncogene for their proliferation and survival, a phenomenon known as “oncogene addiction”. A new generation of drugs that selectively target such “driver oncogenes” manifests a clinical efficacy greater than that of conventional chemotherapy in appropriate genetically defined patients. MET is a proto-oncogene that encodes a receptor tyrosine kinase, and aberrant activation of MET signaling occurs in a subset of advanced cancers as result of various genetic alterations including gene amplification, polysomy, and gene mutation. Our preclinical studies have shown that inhibition of MET signaling either with the small-molecule MET inhibitor crizotinib or by RNA interference targeted to MET mRNA resulted in marked antitumor effects in cancer cell lines with MET amplification both in vitro and in vivo. Furthermore, patients with non-small cell lung cancer or gastric cancer positive for MET amplification have shown a pronounced clinical response to crizotinib. Accumulating preclinical and clinical evidence thus suggests that MET amplification is an “oncogenic driver” and therefore a valid target for treatment. However, the prevalence of MET amplification has not been fully determined, possibly in part because of the difficulty in evaluating gene amplification. In this review, we provide a rationale for targeting this genetic alteration in cancer therapy

  7. Efficient Audio Power Amplification - Challenges

    DEFF Research Database (Denmark)

    Andersen, Michael Andreas E.

    2005-01-01

    For more than a decade efficient audio power amplification has evolved and today switch-mode audio power amplification in various forms are the state-of-the-art. The technical steps that lead to this evolution are described and in addition many of the challenges still to be faced and where...

  8. Efficient audio power amplification - challenges

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Michael A.E.

    2005-07-01

    For more than a decade efficient audio power amplification has evolved and today switch-mode audio power amplification in various forms are the state-of-the-art. The technical steps that lead to this evolution are described and in addition many of the challenges still to be faced and where extensive research and development are needed is covered. (au)

  9. MRI appearance of muscle denervation

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, S. [University Hospital of Wales, Department of Radiology, Cardiff (United Kingdom); Venkatanarasimha, N.; Walsh, M.A.; Hughes, P.M. [Derriford Hospital, Department of Radiology, Plymouth (United Kingdom)

    2008-05-15

    Muscle denervation results from a variety of causes including trauma, neoplasia, neuropathies, infections, autoimmune processes and vasculitis. Traditionally, the diagnosis of muscle denervation was based on clinical examination and electromyography. Magnetic resonance imaging (MRI) offers a distinct advantage over electromyography, not only in diagnosing muscle denervation, but also in determining its aetiology. MRI demonstrates characteristic signal intensity patterns depending on the stage of muscle denervation. The acute and subacutely denervated muscle shows a high signal intensity pattern on fluid sensitive sequences and normal signal intensity on T1-weighted MRI images. In chronic denervation, muscle atrophy and fatty infiltration demonstrate high signal changes on T1-weighted sequences in association with volume loss. The purpose of this review is to summarise the MRI appearance of denervated muscle, with special emphasis on the signal intensity patterns in acute and subacute muscle denervation. (orig.)

  10. Optical parametric amplification and oscillation assisted by low-frequency stimulated emission

    OpenAIRE

    Longhi, Stefano

    2016-01-01

    Optical parametric amplification/oscillation provide a powerful tool for coherent light generation in spectral regions inaccessible to lasers. Parametric gain is based on a frequency {\\it down-conversion} process, and thus it can not be realized for signal waves at a frequency $\\omega_3$ {\\it higher} than the frequency of the pump wave $\\omega_1$. In this work we suggest a route toward the realization of {\\it up-conversion} optical parametric amplification and oscillation, i.e. amplification ...

  11. Signal-to-noise ratio, T2 , and T2* for hyperpolarized helium-3 MRI of the human lung at three magnetic field strengths.

    Science.gov (United States)

    Komlosi, Peter; Altes, Talissa A; Qing, Kun; Mooney, Karen E; Miller, G Wilson; Mata, Jaime F; de Lange, Eduard E; Tobias, William A; Cates, Gordon D; Mugler, John P

    2017-10-01

    To evaluate T 2 , T2*, and signal-to-noise ratio (SNR) for hyperpolarized helium-3 ( 3 He) MRI of the human lung at three magnetic field strengths ranging from 0.43T to 1.5T. Sixteen healthy volunteers were imaged using a commercial whole body scanner at 0.43T, 0.79T, and 1.5T. Whole-lung T 2 values were calculated from a Carr-Purcell-Meiboom-Gill spin-echo-train acquisition. T2* maps and SNR were determined from dual-echo and single-echo gradient-echo images, respectively. Mean whole-lung SNR values were normalized by ventilated lung volume and administered 3 He dose. As expected, T 2 and T2* values demonstrated a significant inverse relationship to field strength. Hyperpolarized 3 He images acquired at all three field strengths had comparable SNR values and thus appeared visually very similar. Nonetheless, the relatively small SNR differences among field strengths were statistically significant. Hyperpolarized 3 He images of the human lung with similar image quality were obtained at three field strengths ranging from 0.43T and 1.5T. The decrease in susceptibility effects at lower fields that are reflected in longer T 2 and T2* values may be advantageous for optimizing pulse sequences inherently sensitive to such effects. The three-fold increase in T2* at lower field strength would allow lower receiver bandwidths, providing a concomitant decrease in noise and relative increase in SNR. Magn Reson Med 78:1458-1463, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  12. An aptasensor for staphylococcus aureus based on nicking enzyme amplification reaction and rolling circle amplification.

    Science.gov (United States)

    Xu, Jingguo; Guo, Jia; Maina, Sarah Wanjiku; Yang, Yumeng; Hu, Yimin; Li, Xuanxuan; Qiu, Jiarong; Xin, Zhihong

    2018-05-15

    An ultra-sensitive aptamer-based biosensor for the detection of staphylococcus aureus was established by adopting the nicking enzyme amplification reaction (NEAR) and the rolling circle amplification (RCA) technologies. Aptamer-probe (AP), containing an aptamer and a probe sequence, was developed to act as the recognition unit of the biosensor, which was specifically bound to S. aureus. The probe was released from AP and initiated into the subsequent DNA amplification reactions where S. aureus was present, converting the detection of S. aureus to the investigation of probe oligonucleotide. The RCA amplification products contained a G-quadruplex motif and formed a three dimensional structure in presence of hemin. The G4/hemin complex showed horseradish peroxidase (HRP)-mimic activity and catalyzed the chemiluminescence reaction of luminol mediated by H 2 O 2 . The results showed that the established biosensor could detect S. aureus specifically with a good linear correlation at 5-10 4  CFU/mL. The signal values based on NEAR-RCA two-step cycle were boosted acutely, much higher than that relied on one-cycle magnification. The limit of detection (LoD) was determined to be as low as 5 CFU/mL. The established aptasensor exhibited a good discrimination of living against dead S. aureus, and can be applied to detect S. aureus in the food industry. Copyright © 2018 Elsevier Inc. All rights reserved.

  13. Chest MRI

    Science.gov (United States)

    ... resonance imaging - chest; NMR - chest; MRI of the thorax; Thoracic MRI Patient Instructions ... Gotway MB, Panse PM, Gruden JF, Elicker BM. Thoracic radiology. In: Broaddus VC, Mason RJ, Ernst JD, et ...

  14. Studying neuroanatomy using MRI.

    Science.gov (United States)

    Lerch, Jason P; van der Kouwe, André J W; Raznahan, Armin; Paus, Tomáš; Johansen-Berg, Heidi; Miller, Karla L; Smith, Stephen M; Fischl, Bruce; Sotiropoulos, Stamatios N

    2017-02-23

    The study of neuroanatomy using imaging enables key insights into how our brains function, are shaped by genes and environment, and change with development, aging and disease. Developments in MRI acquisition, image processing and data modeling have been key to these advances. However, MRI provides an indirect measurement of the biological signals we aim to investigate. Thus, artifacts and key questions of correct interpretation can confound the readouts provided by anatomical MRI. In this review we provide an overview of the methods for measuring macro- and mesoscopic structure and for inferring microstructural properties; we also describe key artifacts and confounds that can lead to incorrect conclusions. Ultimately, we believe that, although methods need to improve and caution is required in interpretation, structural MRI continues to have great promise in furthering our understanding of how the brain works.

  15. MRI diagnosis of eyeball diseases

    International Nuclear Information System (INIS)

    Tao Xiaofeng; Shi Zengru; Xiao Xiangsheng; Yu Hong; Wei Ruili

    2003-01-01

    Objective: To review the MR imaging of eyeball mass in 75 patients with the intention to enhance the acknowledgement to eyeball diseases. Methods: Seventy-five patients, 45 males and 30 females, were examined with MRI before treatment. Most MRI studies were performed with head coil and a few with orbit surface coil. Sagittal, coronal, and axial images were attained. Enhanced MRI studies were performed in 37 cases. High magnetic field MRI studies were performed with additional fat saturation technique. Results: Retinoblastoma (20 cases) showed isointensity in 11 and low signal intensity in 9 on T 1 WI, and isointensity in 5 and slight high signal in 15 on T 2 WI. Coats' disease (5 cases) involved single eyeball in all cases without calcification or eyeball enlargement, and presented as slight high signal on T 1 WI and high signal on T 2 WI. Choroidal angioma (3 cases) showed slight high signal on T 1 WI and high signal on T 2 WI. Metastasis (20 cases) was located in the posterior wall of the eyeball. Extra-global invasion occurred in 8 cases and intra-global invasion in 20. Marked thickening of the global wall with isointensity (8 cases) or low signal intensity (12 cases) was detected on T 1 WI, and isointensity (6 cases) or slight high signal intensity (14 cases) was demonstrated on T 2 WI. Marked enhancement was revealed in all 15 cases. Melanoma (7 cases) showed high signal intensity (5) and isointensity (2) on T 1 WI, and low signal (7) on T 2 WI. Retinal detachment (19 cases) showed high signal on both T 1 and T 2 WI, etc. In the diagnosis of eyeball diseases with MRI, the total sensitivity was 100% and specificity was 86.7%. Conclusions: MRI imaging is an important examination method to eyeball diseases, and most diagnosis and differential diagnosis of eyeball diseases can be made correctly with MRI

  16. Optimization of an Optical Parametric Chirped Pulse Amplification System for the OMEGA EP Laser System

    International Nuclear Information System (INIS)

    Begishev, I.; Bagnoud, V.; Guardalben, M.; Waxer, L.; Puth, J.; Zuegel, J.

    2003-01-01

    OAK B204 We report on the experimental achievements of the optical parametric chirped-pulse amplification (OPCPA) system, including 29% pump-to-signal conversion efficiency and 107 gain using two LBO crystals configured as a single amplification stage. Temporal and spatial shaping of the pump laser pulse is required to achieve both high-gain and high-conversion efficiency

  17. DNAzyme Feedback Amplification: Relaying Molecular Recognition to Exponential DNA Amplification.

    Science.gov (United States)

    Liu, Meng; Yin, Qingxin; McConnell, Erin M; Chang, Yangyang; Brennan, John D; Li, Yingfu

    2018-03-26

    Technologies capable of linking DNA amplification to molecular recognition are very desirable for ultrasensitive biosensing applications. We have developed a simple but powerful isothermal DNA amplification method, termed DNAzyme feedback amplification (DFA), that is capable of relaying molecular recognition to exponential DNA amplification. The method incorporates both an RNA-cleaving DNAzyme (RCD) and rolling circle amplification (RCA) carried out by a special DNA polymerase using a circular DNA template. DFA begins with a stimulus-dependent RCA reaction, producing tandemly linked RCDs in long-chain DNA products. These RCDs cleave an RNA-containing DNA sequence to form additional primers that hybridize to the circular DNA molecule, giving rise to DNA assemblies that act as the new inputs for RCA. The RCA reaction and the cleavage event keep on feeding each other autonomously, resulting in exponential growth of repetitive DNA sequences that can be easily detected. This method can be used for the detection of both nucleic acid based targets and non-nucleic acid analytes. In this article, we discuss the conceptual framework of the feedback amplification approach, the essential features of this method as well as remaining challenges and possible solutions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... The magnetic field is produced by passing an electric current through wire coils in most MRI units. ... signals that are detected by the coils. The electric current does not come in contact with the ...

  19. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... MRI. For more information, consult your radiologist. The computer workstation that processes the imaging information is located ... not come in contact with the patient. A computer then processes the signals and generates a series ...

  20. Intranodular signal intensity analysis of hypovascular high-risk borderline lesions of HCC that illustrate multi-step hepatocarcinogenesis within the nodule on Gd–EOB–DTPA-enhanced MRI

    International Nuclear Information System (INIS)

    Kobayashi, Satoshi; Matsui, Osamu; Gabata, Toshifumi; Koda, Wataru; Minami, Tetsuya; Ryu, Yasuji; Kozaka, Kazuto; Kitao, Azusa

    2012-01-01

    Objectives: To analyze intranodular signal intensity pattern of hypovascular high-risk borderline lesions of HCC that illustrate multi-step hepatocarcinogenesis within the nodule on Gd–EOB–DTPA-enhanced MRI. Methods: A total of 73 nodules showing hypervascular foci in hypovascular high-risk borderline lesions identified by angiography-assisted CT were included in this study. The intranodular signal intensities of both the hypervascular foci and the hypovascular high-risk borderline lesions were evaluated on hepatobiliary-phase EOB-enhanced MRI obtained 20 min after intravenous injection of contrast media. Results: Among 59 hypervascular foci within hypointense hypovascular high-risk borderline lesions, 6 showed more hypointensity, 32 isointensity, and 21 hyperintensity compared to the surrounding hypointense, hypovascular portion of the nodules. Among 14 hypervascular foci within isointense hypovascular high-risk borderline lesions, 5 showed isointensity, and 9 hypointensity compared to the surrounding isointense hypovascular high-risk borderline lesions. No hypervascular foci showed hyperintensity compared to the surrounding isointense hypovascular high-risk borderline lesions. Conclusions: In most of the hypovascular high-risk borderline lesions containing hypervascular foci within the nodule, the signal intensity was decreased in hypervascular foci as compared with hypovascular high-risk borderline lesions and the surrounding background liver parenchyma. This supports the concept of signal intensity decrease during the dedifferentiation process in multistep hepatocarcinogenesis. However, around 30% of the nodules did not follow this rule, and hypervascular foci showed hyperintensity relative to the hypovascular high-risk borderline lesions.

  1. Next generation Chirped Pulse Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Nees, J; Biswal, S; Mourou, G [Univ. Michigan, Center for Ultrafast Optical Science, Ann Arbor, MI (United States); Nishimura, Akihiko; Takuma, Hiroshi

    1998-03-01

    The limiting factors of Chirped Pulse Amplification (CPA) are discussed and experimental results of CPA in Yb:glass regenerative amplifier are given. Scaling of Yb:glass to the petawatt level is briefly discussed. (author)

  2. Differential transimpedance amplifier circuit for correlated differential amplification

    Science.gov (United States)

    Gresham, Christopher A [Albuquerque, NM; Denton, M Bonner [Tucson, AZ; Sperline, Roger P [Tucson, AZ

    2008-07-22

    A differential transimpedance amplifier circuit for correlated differential amplification. The amplifier circuit increase electronic signal-to-noise ratios in charge detection circuits designed for the detection of very small quantities of electrical charge and/or very weak electromagnetic waves. A differential, integrating capacitive transimpedance amplifier integrated circuit comprising capacitor feedback loops performs time-correlated subtraction of noise.

  3. MRI of 'brain death'

    International Nuclear Information System (INIS)

    Nishino, Shigeki; Itoh, Takahiko; Tuchida, Shohei; Kinugasa, Kazushi; Asari, Shoji; Nishimoto, Akira; Sanou, Kazuo.

    1990-01-01

    Magnetic resonance imaging (MRI) was undertaken for two patients who suffered from severe cerebrovascular diseases and were clinically brain dead. The MRI system we used was Resona (Yokogawa Medical Systems, superconductive system 0.5 T) and the CT apparatus was Toshiba TCT-300. Initial CT and MRI were undertaken as soon as possible after admission, and repeated sequentially. After diagnosis of brain death, we performed angiography to determine cerebral circulatory arrest, and MRI obtained at the same time was compared with the angiogram and CT. Case 1 was a 77-year-old man who was admitted in an unconscious state. CT and MRI on the second day after hospitalization revealed cerebellar infarction. He was diagnosed as brain dead on day 4. Case 2 was a 35-year-old man. When he was transferred to our hospital, he was in cardiorespiratory arrested. Cardiac resuscitation was successful but no spontaneous respiration appeared. CT and MRI on admission revealed right intracerebral hemorrhage. Angiography revealed cessation of contrast medium in intracranial vessels in both of the patients. We found no 'flow signal void sign' in the bilateral internal carotid and basilar arteries on MRI images in both cases after brain death. MRI, showing us the anatomical changes of the brain, clearly revealed brain herniations, even though only nuclear findings of 'brain tamponade' were seen on CT. But in Case 1, we could not see the infarct lesions in the cerebellum on MR images obtained after brain death. This phenomenon was caused by the whole brain ischemia masking the initial ischemic lesions. We concluded that MRI was useful not only the anatomical display of lesions and brain herniation with high contrast resolution but for obtaining information on cerebral circulation of brain death. (author)

  4. MRI of the alar and transverse ligaments in whiplash-associated disorders (WAD) grades 1-2: high-signal changes by age, gender, event and time since trauma

    Energy Technology Data Exchange (ETDEWEB)

    Vetti, Nils; Kraakenes, Jostein; Roervik, Jarle; Espeland, Ansgar [Haukeland University Hospital, Department of Radiology, Bergen (Norway); University of Bergen, Section for Radiology, Department of Surgical Sciences, Bergen (Norway); Eide, Geir Egil [Haukeland University Hospital, Centre for Clinical Research, Bergen (Norway); University of Bergen, Department of Public Health and Primary Health Care, Bergen (Norway); Gilhus, Nils Erik [Haukeland University Hospital, Department of Neurology, Bergen (Norway); University of Bergen, Section for Neurology, Department of Clinical Medicine, Bergen (Norway)

    2009-04-15

    This study describes the prevalence of high-signal changes at magnetic resonance imaging (MRI) of the alar and transverse ligaments in whiplash-associated disorders (WAD) grades 1-2 in relation to age, gender, spinal degeneration, type of trauma event and time since trauma. In 1,266 consecutive WAD1-2 patients (779 women, 487 men; mean age 42 years) referred from clinicians, high-signal changes in the alar and transverse ligaments at high-resolution proton-weighted MRI were prospectively graded 0-3 based on a previously reported, reliable grading system. Type of event according to The International Statistical Classification of Diseases and Related Health Problems and time of trauma were obtained from referral letters. MRI showed grades 2-3 alar ligament changes in 449 (35.5%; 95% confidence interval (CI), 32.8 to 38.1%) and grades 2-3 transverse ligament changes in 311 (24.6%; 95% CI, 22.2% to 26.9%) of the 1,266 patients. Grades 2-3 changes were more common in men than women, odds ratio 1.9 (95% CI, 1.5 to 2.5) for alar and 1.5 (95% CI, 1.1 to 2.0) for transverse ligament changes. High-signal changes were not related to age, spinal degeneration, type of trauma event or time since trauma (median 5 years). Unilateral changes were more often left- than right-sided. High-signal changes of the alar and transverse ligaments are common in WAD1-2 and unlikely to represent age-dependent degeneration. Their male and left-side preponderance cannot be explained by variation in ligament stretching or image artefacts. Further studies are needed to clarify whether such changes are caused by trauma. (orig.)

  5. MRI of the alar and transverse ligaments in whiplash-associated disorders (WAD) grades 1-2: high-signal changes by age, gender, event and time since trauma

    International Nuclear Information System (INIS)

    Vetti, Nils; Kraakenes, Jostein; Roervik, Jarle; Espeland, Ansgar; Eide, Geir Egil; Gilhus, Nils Erik

    2009-01-01

    This study describes the prevalence of high-signal changes at magnetic resonance imaging (MRI) of the alar and transverse ligaments in whiplash-associated disorders (WAD) grades 1-2 in relation to age, gender, spinal degeneration, type of trauma event and time since trauma. In 1,266 consecutive WAD1-2 patients (779 women, 487 men; mean age 42 years) referred from clinicians, high-signal changes in the alar and transverse ligaments at high-resolution proton-weighted MRI were prospectively graded 0-3 based on a previously reported, reliable grading system. Type of event according to The International Statistical Classification of Diseases and Related Health Problems and time of trauma were obtained from referral letters. MRI showed grades 2-3 alar ligament changes in 449 (35.5%; 95% confidence interval (CI), 32.8 to 38.1%) and grades 2-3 transverse ligament changes in 311 (24.6%; 95% CI, 22.2% to 26.9%) of the 1,266 patients. Grades 2-3 changes were more common in men than women, odds ratio 1.9 (95% CI, 1.5 to 2.5) for alar and 1.5 (95% CI, 1.1 to 2.0) for transverse ligament changes. High-signal changes were not related to age, spinal degeneration, type of trauma event or time since trauma (median 5 years). Unilateral changes were more often left- than right-sided. High-signal changes of the alar and transverse ligaments are common in WAD1-2 and unlikely to represent age-dependent degeneration. Their male and left-side preponderance cannot be explained by variation in ligament stretching or image artefacts. Further studies are needed to clarify whether such changes are caused by trauma. (orig.)

  6. Molecular MRI in the Earth's Magnetic Field Using Continuous Hyperpolarization of a Biomolecule in Water.

    Science.gov (United States)

    Rovedo, Philipp; Knecht, Stephan; Bäumlisberger, Tim; Cremer, Anna Lena; Duckett, Simon B; Mewis, Ryan E; Green, Gary G R; Burns, Michael; Rayner, Peter J; Leibfritz, Dieter; Korvink, Jan G; Hennig, Jürgen; Pütz, Gerhard; von Elverfeldt, Dominik; Hövener, Jan-Bernd

    2016-06-30

    In this work, we illustrate a method to continuously hyperpolarize a biomolecule, nicotinamide, in water using parahydrogen and signal amplification by reversible exchange (SABRE). Building on the preparation procedure described recently by Truong et al. [ J. Phys. Chem. B , 2014 , 118 , 13882 - 13889 ], aqueous solutions of nicotinamide and an Ir-IMes catalyst were prepared for low-field NMR and MRI. The (1)H-polarization was continuously renewed and monitored by NMR experiments at 5.9 mT for more than 1000 s. The polarization achieved corresponds to that induced by a 46 T magnet (P = 1.6 × 10(-4)) or an enhancement of 10(4). The polarization persisted, although reduced, if cell culture medium (DPBS with Ca(2+) and Mg(2+)) or human cells (HL-60) were added, but was no longer observable after the addition of human blood. Using a portable MRI unit, fast (1)H-MRI was enabled by cycling the magnetic field between 5 mT and the Earth's field for hyperpolarization and imaging, respectively. A model describing the underlying spin physics was developed that revealed a polarization pattern depending on both contact time and magnetic field. Furthermore, the model predicts an opposite phase of the dihydrogen and substrate signal after one exchange, which is likely to result in the cancelation of some signal at low field.

  7. Spin noise amplification and giant noise in optical microcavity

    Energy Technology Data Exchange (ETDEWEB)

    Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S. [Spin-Optics Laboratory, St. Petersburg State University, 198504 St. Petersburg (Russian Federation); Kavokin, A. V. [Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Spin-Optics Laboratory, St. Petersburg State University, 198504 St. Petersburg (Russian Federation); Lagoudakis, P. V. [Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-06-14

    When studying the spin-noise-induced fluctuations of Kerr rotation in a quantum-well microcavity, we have found a dramatic increase of the noise signal (by more than two orders of magnitude) in the vicinity of anti-crossing of the polariton branches. The effect is explained by nonlinear optical instability of the microcavity giving rise to the light-power-controlled amplification of the polarization noise signal. In the framework of the developed model of built-in amplifier, we also interpret the nontrivial spectral and intensity-related properties of the observed noise signal below the region of anti-crossing of polariton branches. The discovered effect of optically controllable amplification of broadband polarization signals in microcavities in the regime of optical instability may be of interest for detecting weak oscillations of optical anisotropy in fundamental research and for other applications in optical information processing.

  8. A large ungated TPC with GEM amplification

    Science.gov (United States)

    Berger, M.; Ball, M.; Fabbietti, L.; Ketzer, B.; Arora, R.; Beck, R.; Böhmer, F. V.; Chen, J.-C.; Cusanno, F.; Dørheim, S.; García, F.; Hehner, J.; Herrmann, N.; Höppner, C.; Kaiser, D.; Kis̆, M.; Kleipa, V.; Konorov, I.; Kunkel, J.; Kurz, N.; Leifels, Y.; Müllner, P.; Münzer, R.; Neubert, S.; Rauch, J.; Schmidt, C. J.; Schmitz, R.; Soyk, D.; Vandenbroucke, M.; Voss, B.; Walther, D.; Zmeskal, J.

    2017-10-01

    A Time Projection Chamber (TPC) is an ideal device for the detection of charged particle tracks in a large volume covering a solid angle of almost 4 π. The high density of hits on a given particle track facilitates the task of pattern recognition in a high-occupancy environment and in addition provides particle identification by measuring the specific energy loss for each track. For these reasons, TPCs with Multiwire Proportional Chamber (MWPC) amplification have been and are widely used in experiments recording heavy-ion collisions. A significant drawback, however, is the large dead time of the order of 1 ms per event generated by the use of a gating grid, which is mandatory to prevent ions created in the amplification region from drifting back into the drift volume, where they would severely distort the drift path of subsequent tracks. For experiments with higher event rates this concept of a conventional TPC operating with a triggered gating grid can therefore not be applied without a significant loss of data. A continuous readout of the signals is the more appropriate way of operation. This, however, constitutes a change of paradigm with considerable challenges to be met concerning the amplification region, the design and bandwidth of the readout electronics, and the data handling. A mandatory prerequisite for such an operation is a sufficiently good suppression of the ion backflow from the avalanche region, which otherwise limits the tracking and particle identification capabilities of such a detector. Gas Electron Multipliers (GEM) are a promising candidate to combine excellent spatial resolution with an intrinsic suppression of ions. In this paper we describe the design, construction and the commissioning of a large TPC with GEM amplification and without gating grid (GEM-TPC). The design requirements have driven innovations in the construction of a light-weight field-cage, a supporting media flange, the GEM amplification and the readout system, which are

  9. Scintillation light detectors with Neganov Luke amplification

    Science.gov (United States)

    Isaila, C.; Boslau, O.; Coppi, C.; Feilitzsch, F. v.; Goldstraß, P.; Jagemann, T.; Jochum, J.; Kemmer, J.; Lachenmaier, T.; Lanfranchi, J.-C.; Pahlke, A.; Potzel, W.; Rau, W.; Stark, M.; Wernicke, D.; Westphal, W.

    2006-04-01

    For an active suppression of the gamma and electron background in the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) dark matter experiment both phonons and scintillation light generated in a CaWO 4 crystal are detected simultaneously. The phonon signal is read out by a transition edge sensor (TES) on the CaWO 4 crystal. For light detection a silicon absorber equipped with a TES is employed. An efficient background discrimination requires very sensitive light detectors. The threshold can be improved by applying an electric field to the silicon crystal leading to an amplification of the thermal signal due to the Neganov-Luke effect. Measurements showing the improved sensitivity of the light detectors as well as future steps for reducing the observed extra noise will be presented.

  10. MRI diagnosis of meningovascular neurosyphilis

    International Nuclear Information System (INIS)

    Chen Shuang; Qian Jianguo; Feng Xiaoyuan

    2005-01-01

    Objective: To evaluate the value and limitation of MRI in the diagnosis of meningovascular neurosyphilis. Methods: Five cases of neurosyphilis confirmed by clinical history/laboratory were examined with MRI (3 plain MRI, 2 enhanced MRI). The results of blood and CSF TPPA/RPR were positive and HIV was negative. Results: Abnormal signals were demonstrated in the temporal lobe in 3 cases, and infarction was revealed in the basal ganglion and periventricular white matter in another 2 cases. There was no marked contrast enhancement in the 2 cases. Conclusion: Meningovascular neurosyphilis has no characteristic features on MRI, but MRI is an effective method in delineating the size, range, and characters of neurosyphilis, and it is also an useful modality to follow-up after antibiotic therapy. (authors)

  11. Parametric amplifications in the nonlinear transmission line

    Energy Technology Data Exchange (ETDEWEB)

    Kawata, T; Sakai, J; Inoue, H [Toyama Univ., Takaoka (Japan). Faculty of Engineering

    1980-03-01

    The parametric amplification in a transmission line with nonlinear capacitors is analysed theoretically using the equations of three wave interactions. Since this line has two modes, high frequency and low frequency modes, there may occur some mode coupling phenomena through the resonant interactions. We consider three waves with wave number k sub(j) and frequency ..omega..sub(j) in resonance with each other, that is, ..omega../sub 1/ + ..omega../sub 2/ = ..omega../sub 3/ and k/sub 1/ + k/sub 2/ = k/sub 3/, where 0 <= ..omega../sub 1/ <= ..omega../sub 2/ <= ..omega../sub 3/ and k/sub 3/ >= 0. Such conditions are realized in our network and there exist two states: ''forward state'' (each group velocity is positive) and ''backward state'' (one of the group velocities is negative). The coupled equations of three waves has two constant pumps: high frequency (HF) pump and low frequency (LF) pump. Using linear approximations, we examine the possible types of parametric amplification and obtain the power gains depending on the frequency deviation. For only the case of HF pump we get the gain between signals with seme frequency and also get the gain from the low frequency signal to the high frequency signal (''up-conversion'') for the LF pump. The nonlinear analysis gives the exact relation between input and output signals. For the forward state the gain is absolutely suppressed by the ratio of pumping power to input power, while the gain of backward state has no finite maximum and there may appear an ''oscillating state'' if the pumping power is comparatively small.

  12. Weak value amplification via second-order correlated technique

    International Nuclear Information System (INIS)

    Cui Ting; Huang Jing-Zheng; Zeng Gui-Hua; Liu Xiang

    2016-01-01

    We propose a new framework combining weak measurement and second-order correlated technique. The theoretical analysis shows that weak value amplification (WVA) experiment can also be implemented by a second-order correlated system. We then build two-dimensional second-order correlated function patterns for achieving higher amplification factor and discuss the signal-to-noise ratio influence. Several advantages can be obtained by our proposal. For instance, detectors with high resolution are not necessary. Moreover, detectors with low saturation intensity are available in WVA setup. Finally, type-one technical noise can be effectively suppressed. (paper)

  13. Isothermal amplification detection of nucleic acids by a double-nicked beacon.

    Science.gov (United States)

    Shi, Chao; Zhou, Meiling; Pan, Mei; Zhong, Guilin; Ma, Cuiping

    2016-03-01

    Isothermal and rapid amplification detection of nucleic acids is an important technology in environmental monitoring, foodborne pathogen detection, and point-of-care clinical diagnostics. Here we have developed a novel method of isothermal signal amplification for single-stranded DNA (ssDNA) detection. The ssDNA target could be used as an initiator, coupled with a double-nicked molecular beacon, to originate amplification cycles, achieving cascade signal amplification. In addition, the method showed good specificity and strong anti-jamming capability. Overall, it is a one-pot and isothermal strand displacement amplification method without the requirement of a stepwise procedure, which greatly simplifies the experimental procedure and decreases the probability of contamination of samples. With its advantages, the method would be very useful to detect nucleic acids in point-of-care or field use. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Signal detection

    International Nuclear Information System (INIS)

    Tholomier, M.

    1985-01-01

    In a scanning electron microscope, whatever is the measured signal, the same set is found: incident beam, sample, signal detection, signal amplification. The resulting signal is used to control the spot luminosity with the observer cathodoscope. This is synchronized with the beam scanning on the sample; on the cathodoscope, the image in secondary electrons, backscattered electrons,... of the sample surface is reconstituted. The best compromise must be found between a register time low enough to remove eventual variations (under the incident beam) of the nature of the observed phenomenon, and a good spatial resolution of the image and a signal-to-noise ratio high enough. The noise is one of the basic limitations of the scanning electron microscope performance. The whose measurement line must be optimized to reduce it [fr

  15. Detection of biological molecules using boronate-based chemical amplification and optical sensors

    Science.gov (United States)

    Van Antwerp, William Peter; Mastrototaro, John Joseph; Lane, Stephen M.; Satcher, Jr., Joe H.; Darrow, Christopher B.; Peyser, Thomas A.; Harder, Jennifer

    1999-01-01

    Methods are provided for the determination of the concentration of biological levels of polyhydroxylated compounds, particularly glucose. The methods utilize an amplification system that is an analyte transducer immobilized in a polymeric matrix, where the system is implantable and biocompatible. Upon interrogation by an optical system, the amplification system produces a signal capable of detection external to the skin of the patient. Quantitation of the analyte of interest is achieved by measurement of the emitted signal.

  16. Fiber Optical Parametric Chirped Pulse Amplification of Sub-Picosecond Pulses

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Da Ros, Francesco

    2013-01-01

    We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs.......We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs....

  17. Contrast agents for MRI

    International Nuclear Information System (INIS)

    Bonnemain, B.

    1994-01-01

    Contrast agents MRI (Magnetic Resonance Imaging) have been developed to improve the diagnostic information obtained by this technic. They mainly interact on T1 and T2 parameters and increase consequently normal to abnormal tissues contrast. The paramagnetic agents which mainly act on longitudinal relaxation rate (T1) are gadolinium complexes for which stability is the main parameter to avoid any release of free gadolinium. The superparamagnetic agents that decrease signal intensity by an effect on transversal relaxation rate (T2) are developed for liver, digestive and lymph node imaging. Many area of research are now opened for optimal use of present and future contrast agents in MRI. (author). 28 refs., 4 tabs

  18. Alternative Chemical Amplification Methods for Peroxy Radical Detection

    Science.gov (United States)

    Wood, E. C. D.

    2014-12-01

    Peroxy radicals (HO2, CH3O2, etc.) are commonly detected by the chemical amplification technique, in which ambient air is mixed with high concentrations of CO and NO, initiating a chain reaction that produces 30 - 200 NO2 molecules per sampled peroxy radical. The NO2 is then measured by one of several techniques. With the exception of CIMS-based techniques, the chemical amplification method has undergone only incremental improvements since it was first introduced in 1982. The disadvantages of the technique include the need to use high concentrations of CO and the greatly reduced sensitivity of the amplification chain length in the presence of water vapor. We present a new chemical amplification scheme in which either ethane or acetaldehyde is used in place of CO, with the NO2 product detected using Cavity Attenuated Phase Shift spectroscopy (CAPS). Under dry conditions, the amplification factor of the alternative amplifiers are approximately six times lower than the CO-based amplifier. The relative humidity "penalty" is not as severe, however, such that at typical ambient relative humidity (RH) values the amplification factor is within a factor of three of the CO-based amplifier. Combined with the NO2 sensitivity of CAPS and a dual-channel design, the detection limit of the ethane amplifier is less than 2 ppt (1 minute average, signal-to-noise ratio 2). The advantages of these alternative chemical amplification schemes are improved safety, a reduced RH correction, and increased sensitivity to organic peroxy radicals relative to HO2.

  19. Significance of high-intensity signals on cranial MRI T{sub 2} weighted image in diagnosis of age-associated dementia. From a viewpoint of reversibility of brain function

    Energy Technology Data Exchange (ETDEWEB)

    Kishiro, Masaki [St. Marianna Univ., Kawasaki, Kanagawa (Japan). School of Medicine

    1994-08-01

    This study was undertaken to determine whether changes of EEG band profile in patients showing high-intensity signal (HIS) on cranial magnetic resonance images (MRI), who had however no vascular lesions on cranial CT, were similar to those in multi-infarct dementia (MID) or senile dementia of Alzheimer type (SDAT) patients and to determine the significance of HIS in the diagnosis of SDAT. Forty-two patients with dementia diagnosed according to DSM-III-R were divided into HIS (n=21), MID (n=13), and SDAT (n=8) based on CT and MRI findings. Multi-infarcted lesions were seen on cranial CT and HIS was seen on cranial MRI in MID patients. There were no abnormal lesions except brain atrophy on cranial CT and MRI in SDAT patients. Appearance rates (%) of the 2-18 c/s frequency bands using computerized quantitative EEG before and after administration of protirelin tartrate (TRH-T) were analyzed in the frontal, central, parietal and occipital areas of the brain. There were no significant differences in appearance rates of EEG frequency bands before administration of TRH-T in HIS, MID, and SDAT patients. A significant decrease in appearance rates of slow waves and a significant increase in appearance rates of {alpha} waves were observed after administration of TRH-T in the four areas in MID patients compared with those before administration. No significant differences in appearance rates of EEG frequency bands were observed after administration of TRH-T in the four areas in HIS and SDAT patients compared with those before administration. Changes of the EEG band profile in HIS patients were similar to those in SDAT patients. In the presence of appearance of HSI on cranial MRI T{sub 2} weighted images, the possibility of SDAT patients cannot be excluded. Therefore, SDAT should be diagnosed based on both clinical data and the absence of brain vascular lesions on cranial CT. Also, HIS on MRI T{sub 2}-weighted images is considered to reflect non-vascular lesions. (J.N.P.).

  20. Genome position and gene amplification

    Czech Academy of Sciences Publication Activity Database

    Jirsová, Pavla; Snijders, A.M.; Kwek, S.; Roydasgupta, R.; Fridlyand, J.; Tokuyasu, T.; Pinkel, D.; Albertson, D. G.

    2007-01-01

    Roč. 8, č. 6 (2007), r120 ISSN 1474-760X Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : gene amplification * array comparative genomic hybridization * oncogene Subject RIV: BO - Biophysics Impact factor: 6.589, year: 2007

  1. MRI Primer

    International Nuclear Information System (INIS)

    Oldendorf, W.; Oldendorf, W. Jr.

    1991-01-01

    Designed for studies, radiologists, and clinicians at all levels of training, this book provides a basic introduction to the principles, physics, and instrumentation of magnetic resonance imaging. The fundamental concepts that are essential for the optimal clinical use of MRI are thoroughly explained in easily accessible terms. To facilitate the reader's comprehension, the material is presented nonmathematically, using no equations and a minimum of symbols and abbreviations. MRI Primer presents a clear account of the phenomenon of nuclear magnetic resonance and the use of gradient magnetic fields to create clinically useful images of cross-sectional slices. Close attention is given to the magnetization vector as a means of expressing nuclear behavior, the role of T 1 and T 2 weighing in imaging, the use of contrast agents, and the pulse sequences most often used in clinical practice, as well as to the relative capabilities and limitations of MRI and CT. The basic hardware components of an MRI scanner are described in detail. Sample MRI scans illustrate how MRI characterizes tissue. An appendix provides a brief introduction to quantum processes in MRI

  2. Rare case of acute dengue encephalitis with correlated MRI findings

    International Nuclear Information System (INIS)

    Mathew, Rishi Philip; Basti, Ram Shenoy; Hegde, Pavan; Devdas, Jaidev M.; Khan, Habeeb Ullah; Bukelo, Mario Joseph

    2014-01-01

    Dengue encephalitis is extremely rare, with most patients showing no significant abnormality on neuroimaging (CT/MRI). We report one of the very few documented cases of dengue encephalitis, with abnormal signal intensities on all major sequences on brain MRI.

  3. Comparison of diffusion-weighted fMRI and BOLD fMRI responses in a verbal working memory task

    International Nuclear Information System (INIS)

    Aso, Toshihiko; Urayama, Shin-ichi; Fukuyama, Hidenao; Le Bihan, Denis

    2013-01-01

    Diffusion-weighted functional MRI (DfMRI) has been reported to have a different response pattern in the visual cortex than that of BOLD-fMRI. Especially, the DfMRI signal shows a constantly faster response at both onset and offset of the stimulus, suggesting that the DfMRI signal might be more directly linked to neuronal events than the hemodynamic response. However, because the DfMRI response also contains a residual sensitivity to BOLD this hypothesis has been challenged. Using a verbal working memory task we show that the DfMRI time-course features are preserved outside visual cortices, but also less liable to between-subject/between-regional variation than the BOLD response. The overall findings not only support the feasibility of DfMRI as an approach for functional brain imaging, but also strengthen the uniqueness of the DfMRI signal origin. (authors)

  4. Metformin inhibits age-related centrosome amplification in Drosophila midgut stem cells through AKT/TOR pathway.

    Science.gov (United States)

    Na, Hyun-Jin; Park, Joung-Sun; Pyo, Jung-Hoon; Jeon, Ho-Jun; Kim, Young-Shin; Arking, Robert; Yoo, Mi-Ae

    2015-07-01

    We delineated the mechanism regulating the inhibition of centrosome amplification by metformin in Drosophila intestinal stem cells (ISCs). Age-related changes in tissue-resident stem cells may be closely associated with tissue aging and age-related diseases, such as cancer. Centrosome amplification is a hallmark of cancers. Our recent work showed that Drosophila ISCs are an excellent model for stem cell studies evaluating age-related increase in centrosome amplification. Here, we showed that metformin, a recognized anti-cancer drug, inhibits age- and oxidative stress-induced centrosome amplification in ISCs. Furthermore, we revealed that this effect is mediated via down-regulation of AKT/target of rapamycin (TOR) activity, suggesting that metformin prevents centrosome amplification by inhibiting the TOR signaling pathway. Additionally, AKT/TOR signaling hyperactivation and metformin treatment indicated a strong correlation between DNA damage accumulation and centrosome amplification in ISCs, suggesting that DNA damage might mediate centrosome amplification. Our study reveals the beneficial and protective effects of metformin on centrosome amplification via AKT/TOR signaling modulation. We identified a new target for the inhibition of age- and oxidative stress-induced centrosome amplification. We propose that the Drosophila ISCs may be an excellent model system for in vivo studies evaluating the effects of anti-cancer drugs on tissue-resident stem cell aging. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

  5. MRI and intraocular tamponade media

    International Nuclear Information System (INIS)

    Manfre, I.; Fabbri, G.; Avitabile, T.; Biondi, P.; Reibaldi, A.; Pero, G.

    1993-01-01

    Thirteen patients who underwent surgery for retinal detachment and injection of intraocular tamponade media (silicone oil, flurosilicone oil, or perfluoro-carbon liquid) underwent magnetic resonance imaging (MRI), using spin-echo T1- and T2-weighted images. The ophthalmic tamponade media showed different signal intensity, according to their chemical structure. Unlike ophthalmoscopy or ultrasonography, MRI showed no oil-related artefact, making possible recognition of recurrent retinal detachment. (orig.)

  6. MRI and intraocular tamponade media

    Energy Technology Data Exchange (ETDEWEB)

    Manfre, I. (Dept. of Neuroradiology, Inst. of Neurosurgery, Univ. of Catania (Italy)); Fabbri, G. (Dept. of Neuroradiology, Inst. of Neurosurgery, Univ. of Catania (Italy)); Avitabile, T. (Inst. of Ophthalmology, Univ. of Catania (Italy)); Biondi, P. (Inst. of Ophthalmology, Univ. of Catania (Italy)); Reibaldi, A. (Inst. of Ophthalmology, Univ. of Catania (Italy)); Pero, G. (Dept. of Neuroradiology, Inst. of Neurosurgery, Univ. of Catania (Italy))

    1993-05-01

    Thirteen patients who underwent surgery for retinal detachment and injection of intraocular tamponade media (silicone oil, flurosilicone oil, or perfluoro-carbon liquid) underwent magnetic resonance imaging (MRI), using spin-echo T1- and T2-weighted images. The ophthalmic tamponade media showed different signal intensity, according to their chemical structure. Unlike ophthalmoscopy or ultrasonography, MRI showed no oil-related artefact, making possible recognition of recurrent retinal detachment. (orig.)

  7. MRI: Imaging of stomach

    International Nuclear Information System (INIS)

    Lam, W. W. M; Lee, J. S. W.; Ho, G.

    2007-01-01

    Full text: The study is to determine the optimal MRI bowel preparation regime for visualization of the stomach anatomy, Eight healthy volunteers were asked to take water, 75% barium and blueberry juice. The image quality and tolerance of different stomach distension regime were evaluated. Blueberry juice gave the best distension, but the signal intensity was not very homogeneous. Taking into account the image quality, tolerability and adverse effects, it is concluded that water is the most desirable oral contrast for MR stomach imaging

  8. Head MRI

    Science.gov (United States)

    ... hearing aids Pins, hairpins, metal zippers, and similar metallic items Removable dental work How the Test will ... an MRI can make heart pacemakers and other implants not work as well. It can also cause ...

  9. Pediatric MRI

    Data.gov (United States)

    U.S. Department of Health & Human Services — The NIH Study of Normal Brain Development is a longitudinal study using anatomical MRI, diffusion tensor imaging (DTI), and MR spectroscopy (MRS) to map pediatric...

  10. Circulation and Directional Amplification in the Josephson Parametric Converter

    Science.gov (United States)

    Hatridge, Michael

    Nonreciprocal transport and directional amplification of weak microwave signals are fundamental ingredients in performing efficient measurements of quantum states of flying microwave light. This challenge has been partly met, as quantum-limited amplification is now regularly achieved with parametrically-driven, Josephson-junction based superconducting circuits. However, these devices are typically non-directional, requiring external circulators to separate incoming and outgoing signals. Recently this limitation has been overcome by several proposals and experimental realizations of both directional amplifiers and circulators based on interference between several parametric processes in a single device. This new class of multi-parametrically driven devices holds the promise of achieving a variety of desirable characteristics simultaneously- directionality, reduced gain-bandwidth constraints and quantum-limited added noise, and are good candidates for on-chip integration with other superconducting circuits such as qubits.

  11. Abnormal diffusion-weighted MRI in medulloblastoma: does it reflect small cell histology?

    International Nuclear Information System (INIS)

    Kotsenas, A.L.; Roth, T.C.; Manness, W.K.; Faerber, E.N.

    1999-01-01

    A 12-year-old boy presented with the classic CT and MRI findings of medulloblastoma and the unusual finding of increased signal on diffusion MRI. The small-cell histology of medulloblastoma may account for the increased signal seen on diffusion MRI. Diffusion MRI with echoplanar technique may be useful in evaluation of these tumors and metastatic disease. (orig.)

  12. Laser amplification in excited dielectrics

    Science.gov (United States)

    Winkler, Thomas; Haahr-Lillevang, Lasse; Sarpe, Cristian; Zielinski, Bastian; Götte, Nadine; Senftleben, Arne; Balling, Peter; Baumert, Thomas

    2018-01-01

    Wide-bandgap dielectrics such as glasses or water are transparent at visible and infrared wavelengths. This changes when they are exposed to ultrashort and highly intense laser pulses. Different interaction mechanisms lead to the appearance of various transient nonlinear optical phenomena. Using these, the optical properties of dielectrics can be controlled from the transparent to the metal-like state. Here we expand this range by a yet unexplored mechanism in excited dielectrics: amplification. In a two-colour pump-probe experiment, we show that a 400 nm femtosecond laser pulse is coherently amplified inside an excited sapphire sample on a scale of a few micrometres. Simulations strongly support the proposed two-photon stimulated emission process, which is temporally and spatially controllable. Consequently, we expect applications in all fields that demand strongly localized amplification.

  13. MRI of the cardiomyopathies

    International Nuclear Information System (INIS)

    Di Cesare, Ernesto

    2001-01-01

    We examined the potentialities of Magnetic resonance imaging (MRI) in the evaluation of the main cardiomyopathies: hypertrophic, dilated, restrictive and arrhythmogenic right ventricular. The hypertrophic cardiomyopathy is generally adequately investigated by echocardiography, that well defines the myocardial thickening and the obstruction of the left ventricular output. However, by echocardiography we still have difficulties in the evaluation of the apex of the left ventricle and the right ventricle involvement. MRI provides a complete evaluation of the heart with a clear evidence also of the echocardiographic dark zones by means of a clear evidence of the apex of the right ventricle. The dilated form is also well investigated by MRI that provides a clear evaluation of the volumes, mass and ejection fraction by means of the 3D analysis including conditions of the ventricular remodelling. Moreover, this technique helps in the differential diagnosis of acute myocarditis. In the acute phase of myocarditis (first 2 weeks), in fact, the myocardium produces high signal intensity on the T2 weighted sequences due to the presence of oedema. The third form of cardiomyopathy is the restrictive one, characterised by reduced diastolic filling and diastolic volume, normality of the systolic function and parietal thickness, interstitial fibrosis and enlargement of both atria. The mean potentiality of MRI is related to the differential diagnosis with constrictive pericarditis. Only in the former, the pericardium appears irregularly thickened with areas exceeding 4 mm of pericardial thickness. Finally, the right ventricular arrhythmogenic cardiomyopathy represents the main indication to MRI evaluation. With this imaging modality we are can obtain a clear morpho-functional evaluation of the right ventricle and distinguish the intramyocardial adipose substitution characterised by areas of high signal in the myocardium

  14. Influence of the position of the foot on MRI signal in the deep digital flexor tendon and collateral ligaments of the distal interphalangeal joint in the standing horse.

    Science.gov (United States)

    Spriet, M; Zwingenberger, A

    2009-05-01

    Hyperintense signal is sometimes observed in ligaments and tendons of the equine foot on standing magnetic resonance examination without associated changes in size and shape. In such cases, the presence of a true lesion or an artifact should be considered. A change in position of a ligament or tendon relative to the magnetic field can induce increased signal intensity due to the magic angle effect. To assess if positional rotation of the foot in the solar plane could be responsible for artifactual changes in signal intensity in the collateral ligaments of the distal interphalangeal joint and in the deep digital flexor tendon. Six isolated equine feet were imaged with a standing equine magnetic resonance system in 9 different positions with different degrees of rotation in the solar plane. Rotation of the limb induced a linear hyperintense signal on all feet at the palmar aspect of one of the lobes of the deep digital flexor tendon and at the dorsal aspect of the other lobe. Changes in signal intensity in the collateral ligaments of the distal interphalangeal joint occurred with rotation of the limb only in those feet where mediolateral hoof imbalance was present. The position and conformation of the foot influence the signal intensity in the deep digital flexor tendon and in the collateral ligaments of the distal interphalangeal joint. The significance of increased signal intensity in the deep digital flexor tendon and in the collateral ligaments of the distal interphalangeal joint should be interpreted with regard to the position and the conformation of the foot.

  15. Measuring the amplification of attention

    OpenAIRE

    Blaser, Erik; Sperling, George; Lu, Zhong-Lin

    1999-01-01

    An ambiguous motion paradigm, in which the direction of apparent motion is determined by salience (i.e., the extent to which an area is perceived as figure versus ground), is used to assay the amplification of color by attention to color. In the red–green colored gratings used in these experiments, without attention instructions, salience depends on the chromaticity difference between colored stripes embedded in the motion sequence and the yellow background. Selective attention to red (or to ...

  16. An ultrasensitive sandwich-type electrochemical immunosensor based on the signal amplification system of double-deck gold film and thionine unite with platinum nanowire inlaid globular SBA-15 microsphere.

    Science.gov (United States)

    Wang, Ping; Li, Mingdang; Pei, Fubin; Li, Yueyun; Liu, Qing; Dong, Yunhui; Chu, Qingyan; Zhu, Hongjun

    2017-05-15

    A novel thionine unites with platinum nanowire inlaid globular SBA-15 (Pt NWs@g-SBA-15/Thi) not only utilizes as an efficient electrical signal probe but also constitutes an amplifying system with double-deck gold film (D-Au film) have been applied to the fabrication of sandwich-type immunosensor for detecting hepatitis B surface antigen (HBs Ag). The D-Au film can accelerate the electron transfer on the electrode interface due to the tunneling effect between the two Au films and can improve the load capacity of primary antibodies (Ab 1 ) because of the good biocompatibility. The Pt NWs@g-SBA-15/Thi with uniform globular morphology not only can effectively reduce the spatial limitation for loading the secondary antibodies (Ab 2 ) but also can provide outstanding pore accessibility of guest species from outside and offer catalytically active sites in a large scale. Besides, the presence of Thi can well enhance the electrical conductivity of Pt NWs@g-SBA-15/Thi. With the good cooperation between D-Au film and Pt NWs@g-SBA-15/Thi, a linear relationship between current signals and the concentrations of HBs Ag was obtained in the wide range from 10 fg/mL to 100ng/mL and the detection limit of HBs Ag was 3.3 fg/mL (signal-to-noise ratio of 3). Furthermore, the designed immunosensor with excellent selectivity, reproducibility and stability shows excellent performance in detection of human serum samples and provides a promising capacity for detecting a wide range of other tumor markers in clinical application. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Spheromak Impedance and Current Amplification

    International Nuclear Information System (INIS)

    Fowler, T K; Hua, D D; Stallard, B W

    2002-01-01

    It is shown that high current amplification can be achieved only by injecting helicity on the timescale for reconnection, τ REC , which determines the effective impedance of the spheromak. An approximate equation for current amplification is: dI TOR 2 /dt ∼ I 2 /τ REC - I TOR 2 /τ closed where I is the gun current, I TOR is the spheromak toroidal current and τ CLOSED is the ohmic decay time of the spheromak. Achieving high current amplification, I TOR >> I, requires τ REC CLOSED . For resistive reconnection, this requires reconnection in a cold zone feeding helicity into a hot zone. Here we propose an impedance model based on these ideas in a form that can be implemented in the Corsica-based helicity transport code. The most important feature of the model is the possibility that τ REC actually increases as the spheromak temperature increases, perhaps accounting for the ''voltage sag'' observed in some experiments, and a tendency toward a constant ratio of field to current, B ∝ I, or I TOR ∼ I. Program implications are discussed

  18. Designing a compact MRI motion phantom

    Directory of Open Access Journals (Sweden)

    Schmiedel Max

    2016-09-01

    Full Text Available Even today, dealing with motion artifacts in magnetic resonance imaging (MRI is a challenging task. Image corruption due to spontaneous body motion complicates diagnosis. In this work, an MRI phantom for rigid motion is presented. It is used to generate motion-corrupted data, which can serve for evaluation of blind motion compensation algorithms. In contrast to commercially available MRI motion phantoms, the presented setup works on small animal MRI systems. Furthermore, retrospective gating is performed on the data, which can be used as a reference for novel motion compensation approaches. The motion of the signal source can be reconstructed using motor trigger signals and be utilized as the ground truth for motion estimation. The proposed setup results in motion corrected images. Moreover, the importance of preprocessing the MRI raw data, e.g. phase-drift correction, is demonstrated. The gained knowledge can be used to design an MRI phantom for elastic motion.

  19. [Prognostic significance of MYCN amplification in children neuroblastic tumors].

    Science.gov (United States)

    Niu, Huilin; Xu, Tao; Wang, Fenghua; Chen, Zhengrong; Gao, Qiu; Yi, Peng; Xia, Jianqing

    2015-02-01

    To summarize the clinicopathologic features of neuroblastic tumors (NT), and to explore the prognostic significance of MYCN amplification in NT. The clinicopathologic data of 267 NT were reviewed. MYCN gene amplification was detected by fluorescence in situ hybridization (FISH) in 119 cases and the relationship with pathological characteristics and prognostic significance were analyzed. The study included 267 cases of children NT from patients aged from 1 day to 13 years (median 27 months). The male to female ratio was 1.43. There were 38 cases (14.2%), 43 cases (16.1%), 71 cases (26.6%), and 115 cases (43.1%) of INSS stages I, II, III and IV respectively.Favorable histology group had 157 cases (59.9%); unfavorable histology group had 110 cases (40.1%).Of the 119 NT cases with MYCN FISH performed, 18 cases (15.1%) showed amplification and the signal ratio of MYCN to CEP2 was 4.08-43.29. One hundred and one cases of non-amplified MYCN included MYCN gain in 79 cases (66.3%) and MYCN negative in 22 cases (18.5%). MYCN expression showed significant difference (P = 0.000) between ages, gender, NT type and MKI, but not INPC and clinical stage (P > 0.05).Of the 18 cases with MYCN amplification, 3 were undifferentiated, and 15 poorly differentiated; 17 had high MKI and one moderate MKI. All 18 cases were in unfavorable histology group; the overall survival rate was 3/18, with an average survival time of (17.9 ± 2.4) months.Of the 101 MYCN non-amplification cases, the overall survival rate was 68.3% (69/101), with an average survival time of (29.8 ± 1.3) months. Survival analysis showed the cases with MYCN amplification had worse prognosis (P < 0.05). NT were commonly diagnosed in early ages and easily to metastasize. Most of cases with favorable histology. The cases of MYCN amplification showed unfavorable histology, and the majority cases with high MKI; The patients with MYCN gene amplification had poor prognosis.

  20. MRI of focal cortical dysplasia

    International Nuclear Information System (INIS)

    Lee, B.C.P.; Hatfield, G.A.; Bourgeois, B.; Park, T.S.

    1998-01-01

    We studied nine cases of focal cortical dysplasia (FCD) by MRI, with surface-rendered 3D reconstructions. One case was also examined using single-voxel proton MR spectroscopy (MRS). The histological features were reviewed and correlated with the MRI findings. The gyri affected by FCD were enlarged and the signal of the cortex was slightly increased on T1-weighted images. The gray-white junction was indistinct. Signal from the subcortical white matter was decreased on T1- and increased on T2-weighted images in most cases. Contrast enhancement was seen in two cases. Proton MRS showed a spectrum identical to that of normal brain. (orig.) (orig.)

  1. MRI-based liver iron content determination at 3 T in regularly transfused patients by signal intensity ratio using an alternative analysis approach based on R{sub 2}* theory

    Energy Technology Data Exchange (ETDEWEB)

    Wunderlich, A.P. [Universitaetsklinikum Ulm (Germany). Section for Experimental Radiology; Cario, H. [Universitaetsklinik Ulm (Germany). Children' s Hospital; Bommer, M. [Alb-Fils-Clinics, Goeppingen (Germany). Hematology and Oncology Dept.; Beer, M.; Schmidt, S.A. [Universitaetsklinikum Ulm (Germany). Dept. for Diagnostic and Interventional Radiology; Juchems, M.S. [Klinikum Konstanz (Germany). Diagnostic and Interventional Radiology

    2016-09-15

    To evaluate the feasibility of addressing liver iron content (LIC) in regularly transfused patients by MR imaging at 3 T based on the signal intensity ratio (SIR). An innovative data analysis approach was developed for this purpose. 47 consecutive examinations of regularly transfused patients were included. In all cases, we expected high LIC levels. Patients were scanned with MRI at 3 T with multi-echo gradient echo sequences (GRE) at four different flip angles between 20 and 90 with echo times (TE) ranging from 0.9 to 9.8 ms. Spin-echo protocols were acquired to determine the LIC with a reference MRI method working at 1.5 T. 3 T GRE data were analyzed using the liver-to-muscle SIR. Since the method known for 1.5 T was not expected to be applicable for analyzing 3 T data, theoretic dependence of the SIR on the LIC was derived from the equation describing R{sub 2}* signal decay. Obtained SIR values were correlated to reference LIC to get a relation for calculating LIC from SIR quantities. LIC values and their uncertainties were determined from GRE data and correlated to LIC reference values. For two LIC thresholds, the diagnostic accuracy was determined. LIC was reliably determined from SIR in our patient cohort even for large LIC values. Median of LIC uncertainties was 10%, and the diagnostic accuracy was 0.92 and 0.91, respectively. Determination of even high LIC, resulting in small SIR values, is feasible at 3 T using appropriate SIR analysis.

  2. Hippocampal malrotation: MRI findings

    International Nuclear Information System (INIS)

    Yanez, Paulina; Martinez, Adriana; Romero, Carlos; Lopez, Miriam; Zaffaroni, Alejandra; Lopez, Adriana

    2001-01-01

    Purpose: To demonstrate the common features of hippocampus malrotation in patients with epilepsy by volumetric and high-resolution MRI. Material and methods: MRI study was performed in 5 patients (2 females and 3 males) ages ranged between 6-41 years (average: 25 years), all of them with epilepsy diagnosis. MRI was performed with a 1.5 T (GE Signa). The epilepsy protocol include sagittal T1, axial T1 and T2, coronal FLAIR, coronal T2 (high-resolution) and volumetric 3D SPGR IR 1.5 mm thick sequences. Results: The common features found in all patients were: a) Incomplete inversion and round configuration of the hippocampus; b) Unilateral affectation; c) Variable affectation of the hippocampus; d) Normal signal intensity; e) Modification of the inner structure of the hippocampus; f) Abnormal angularity of the collateral sulcus; g) Abnormal position and size of the fornix; h) Normal size of the temporal lobe; and i) Enlargement of the temporal horn with particular configuration. Conclusion: Hippocampus malrotation is a malformation that should be included in the differential diagnosis of the epilepsy patients. MRI provides accurate information for the diagnosis. (author)

  3. Markovian Dynamics of Josephson Parametric Amplification

    Directory of Open Access Journals (Sweden)

    W. Kaiser

    2017-09-01

    Full Text Available In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA. The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

  4. Markovian Dynamics of Josephson Parametric Amplification

    Science.gov (United States)

    Kaiser, Waldemar; Haider, Michael; Russer, Johannes A.; Russer, Peter; Jirauschek, Christian

    2017-09-01

    In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA). The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

  5. Cascade DNA nanomachine and exponential amplification biosensing.

    Science.gov (United States)

    Xu, Jianguo; Wu, Zai-Sheng; Shen, Weiyu; Xu, Huo; Li, Hongling; Jia, Lee

    2015-11-15

    DNA is a versatile scaffold for the assembly of multifunctional nanostructures, and potential applications of various DNA nanodevices have been recently demonstrated for disease diagnosis and treatment. In the current study, a powerful cascade DNA nanomachine was developed that can execute the exponential amplification of p53 tumor suppressor gene. During the operation of the newly-proposed DNA nanomachine, dual-cyclical nucleic acid strand-displacement polymerization (dual-CNDP) was ingeniously introduced, where the target trigger is repeatedly used as the fuel molecule and the nicked fragments are dramatically accumulated. Moreover, each displaced nicked fragment is able to activate the another type of cyclical strand-displacement amplification, increasing exponentially the value of fluorescence intensity. Essentially, one target binding event can induce considerable number of subsequent reactions, and the nanodevice was called cascade DNA nanomachine. It can implement several functions, including recognition element, signaling probe, polymerization primer and template. Using the developed autonomous operation of DNA nanomachine, the p53 gene can be quantified in the wide concentration range from 0.05 to 150 nM with the detection limit of 50 pM. If taking into account the final volume of mixture, the detection limit is calculated as lower as 6.2 pM, achieving an desirable assay ability. More strikingly, the mutant gene can be easily distinguished from the wild-type one. The proof-of-concept demonstrations reported herein is expected to promote the development and application of DNA nanomachine, showing great potential value in basic biology and medical diagnosis. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Processes of synchronization, chaotization and amplification in a germanium oscillistor

    Energy Technology Data Exchange (ETDEWEB)

    Abakarova, N.S.; Aliev, K.M.; Ibragimov, Kh.O.; Kamilov, I.K. [Institute of Physics, Dagestan Science Centre, RAS, Makhachkala (Russian Federation)

    2001-12-03

    The effect of an external harmonic signal on the screw instability of the current in the electron-hole plasma has been studied experimentally in Ge at 77 K and 300 K. The influence exerted by external signals with various amplitudes and frequencies, applied to a sample both additively and multiplicatively, on the synchronization, amplification and stability of the system in absolute and convective modes of instability excitation has been investigated at points of bifurcation in a wide region of the parametric space. (author)

  7. Portable MRI

    Energy Technology Data Exchange (ETDEWEB)

    Espy, Michelle A. [Los Alamos National Laboratory

    2012-06-29

    This project proposes to: (1) provide the power of MRI to situations where it presently isn't available; (2) perform the engineering required to move from lab to a functional prototype; and (3) leverage significant existing infrastructure and capability in ultra-low field MRI. The reasons for doing this: (1) MRI is the most powerful tool for imaging soft-tissue (e.g. brain); (2) Billions don't have access due to cost or safety issues; (3) metal will heat/move in high magnetic fields; (4) Millions of cases of traumatic brain injury in US alone; (5) even more of non-traumatic brain injury; (6) (e.g. stroke, infection, chemical exposure); (7) Need for early diagnostic; (8) 'Signature' wound of recent conflicts; (9) 22% of injuries; (10) Implications for post-traumatic stress disorder; and (11) chronic traumatic encephalopathy.

  8. Portable MRI

    International Nuclear Information System (INIS)

    Espy, Michelle A.

    2012-01-01

    This project proposes to: (1) provide the power of MRI to situations where it presently isn't available; (2) perform the engineering required to move from lab to a functional prototype; and (3) leverage significant existing infrastructure and capability in ultra-low field MRI. The reasons for doing this: (1) MRI is the most powerful tool for imaging soft-tissue (e.g. brain); (2) Billions don't have access due to cost or safety issues; (3) metal will heat/move in high magnetic fields; (4) Millions of cases of traumatic brain injury in US alone; (5) even more of non-traumatic brain injury; (6) (e.g. stroke, infection, chemical exposure); (7) Need for early diagnostic; (8) 'Signature' wound of recent conflicts; (9) 22% of injuries; (10) Implications for post-traumatic stress disorder; and (11) chronic traumatic encephalopathy.

  9. Fetal MRI

    International Nuclear Information System (INIS)

    Prayer, D.; Brugger, P.C.

    2004-01-01

    New, ultrafast sequences have made it possible to obtain MR images of the fetus without maternal sedation or immobilization of the fetus itself. While fetal MRI began as an adjunct to ultrasound, it has now been shown that MRI can provide additional information that may change prognosis, the management of pregnancy, or the treatment of the newborn child. It is of particular value in the assessment of malformations of the central nervous system. The steady development and adaptation of MR-sequences to the needs of fetal imaging has led to new indications that can support prognostic and therapeutic decisions. (orig.)

  10. Fetal MRI

    Energy Technology Data Exchange (ETDEWEB)

    Prayer, D.; Brugger, P.C. [University Hospital of Vienna (Austria). Division of Neuroradiology

    2004-07-01

    New, ultrafast sequences have made it possible to obtain MR images of the fetus without maternal sedation or immobilization of the fetus itself. While fetal MRI began as an adjunct to ultrasound, it has now been shown that MRI can provide additional information that may change prognosis, the management of pregnancy, or the treatment of the newborn child. It is of particular value in the assessment of malformations of the central nervous system. The steady development and adaptation of MR-sequences to the needs of fetal imaging has led to new indications that can support prognostic and therapeutic decisions. (orig.)

  11. MRI of plants and foods

    Science.gov (United States)

    Van As, Henk; van Duynhoven, John

    2013-04-01

    The importance and prospects for MRI as applied to intact plants and to foods are presented in view of one of humanity's most pressing concerns, the sustainable and healthy feeding of a worldwide increasing population. Intact plants and foods have in common that their functionality is determined by complex multiple length scale architectures. Intact plants have an additional level of complexity since they are living systems which critically depend on transport and signalling processes between and within tissues and organs. The combination of recent cutting-edge technical advances and integration of MRI accessible parameters has the perspective to contribute to breakthroughs in understanding complex regulatory plant performance mechanisms. In food science and technology MRI allows for quantitative multi-length scale structural assessment of food systems, non-invasive monitoring of heat and mass transport during shelf-life and processing, and for a unique view on food properties under shear. These MRI applications are powerful enablers of rationally (re)designed food formulations and processes. Limitations and bottlenecks of the present plant and food MRI methods are mainly related to short T2 values and susceptibility artefacts originating from small air spaces in tissues/materials. We envisage cross-fertilisation of solutions to overcome these hurdles in MRI applications in plants and foods. For both application areas we witness a development where MRI is moving from highly specialised equipment to mobile and downscaled versions to be used by a broad user base in the field, greenhouse, food laboratory or factory.

  12. MRI findings in bipartite patella

    International Nuclear Information System (INIS)

    Kavanagh, Eoin C.; Zoga, Adam; Omar, Imran; Ford, Stephanie; Eustace, Stephen; Schweitzer, Mark

    2007-01-01

    Bipartite patella is a known cause of anterior knee pain. Our purpose was to detail the magnetic resonance imaging (MRI) features of bipartite patella in a retrospective cohort of patients imaged at our institution. MRI exams from 53 patients with findings of bipartite patella were evaluated to assess for the presence of bone marrow edema within the bipartite fragment and for the presence of abnormal signal across the synchondrosis or pseudarthrosis. Any other significant knee pathology seen at MRI was also recorded. We also reviewed 400 consecutive knee MRI studies to determine the MRI prevalence of bipartite patella. Of the 53 patients with bipartite patella 40 (75%) were male; 35 (66%) had edema within the bipartite fragment. Of the 18 with no edema an alternative explanation for knee pain was found in 13 (72%). Edema within the bipartite fragment was the sole finding in 26 of 53 (49%) patients. Bipartite patella was seen in 3 (0.7%) of 400 patients. In patients with bipartite patella at knee MRI, bone marrow edema within the bipartite fragment was the sole finding on knee MRI in almost half of the patients in our series. (orig.)

  13. Superparamagnetic iron oxides for MRI

    International Nuclear Information System (INIS)

    Weissleder, R.; Reimer, P.

    1993-01-01

    Pharmaceutical iron oxide preparations have been used as MRI contrast agents for a variety of purposes. These agents predominantly decrease T2 relaxation times and therefore cause a decrease in signal intensity of tissues that contain the agent. After intravenous administration, dextran-coated iron oxides typically accumulate in phagocytic cells in liver and spleen. Clinical trials have shown that iron oxide increases lesion/liver and lesion/spleen contrast, that more lesions can be depicted than on plain MRI or CT, and that the size threshold for lesion detection decreases. Decreased uptake of iron oxides in liver has been observed in hepatitis and cirrhosis, potentially allowing the assessment of organ function. More recently a variety of novel, target-specific monocrystalline iron oxides compounds have been used for receptor and immunospecific images. Future development of targeted MRI contrast agents is critical for organ- or tissue-specific quantitative and functional MRI. (orig.)

  14. Superparamagnetic iron oxides for MRI

    Energy Technology Data Exchange (ETDEWEB)

    Weissleder, R [MGH-NMR Center, Dept. of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA (United States); Reimer, P [MGH-NMR Center, Dept. of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA (United States); [Inst. fuer Klinische Radiologie, Zentrale Roentgendiagnostik, Westfaelische-Wilhelms-Univ., Muenster (Germany)

    1993-06-01

    Pharmaceutical iron oxide preparations have been used as MRI contrast agents for a variety of purposes. These agents predominantly decrease T2 relaxation times and therefore cause a decrease in signal intensity of tissues that contain the agent. After intravenous administration, dextran-coated iron oxides typically accumulate in phagocytic cells in liver and spleen. Clinical trials have shown that iron oxide increases lesion/liver and lesion/spleen contrast, that more lesions can be depicted than on plain MRI or CT, and that the size threshold for lesion detection decreases. Decreased uptake of iron oxides in liver has been observed in hepatitis and cirrhosis, potentially allowing the assessment of organ function. More recently a variety of novel, target-specific monocrystalline iron oxides compounds have been used for receptor and immunospecific images. Future development of targeted MRI contrast agents is critical for organ- or tissue-specific quantitative and functional MRI. (orig.)

  15. Laser amplification in excited dielectrics

    DEFF Research Database (Denmark)

    Winkler, Thomas; Haahr-Lillevang, Lasse; Sarpe, Cristian

    2018-01-01

    Wide-bandgap dielectrics such as glasses or water are transparent at visible and infrared wavelengths. This changes when they are exposed to ultrashort and highly intense laser pulses. Different interaction mechanisms lead to the appearance of various transient nonlinear optical phenomena. Using...... these, the optical properties of dielectrics can be controlled from the transparent to the metal-like state. Here we expand this range by a yet unexplored mechanism in excited dielectrics: amplification. In a two-colour pump-probe experiment, we show that a 400nm femtosecond laser pulse is coherently...

  16. Telomerase Repeated Amplification Protocol (TRAP).

    Science.gov (United States)

    Mender, Ilgen; Shay, Jerry W

    2015-11-20

    Telomeres are found at the end of eukaryotic linear chromosomes, and proteins that bind to telomeres protect DNA from being recognized as double-strand breaks thus preventing end-to-end fusions (Griffith et al. , 1999). However, due to the end replication problem and other factors such as oxidative damage, the limited life span of cultured cells (Hayflick limit) results in progressive shortening of these protective structures (Hayflick and Moorhead, 1961; Olovnikov, 1973). The ribonucleoprotein enzyme complex telomerase-consisting of a protein catalytic component hTERT and a functional RNA component hTR or hTERC - counteracts telomere shortening by adding telomeric repeats to the end of chromosomes in ~90% of primary human tumors and in some transiently proliferating stem-like cells (Shay and Wright, 1996; Shay and Wright, 2001). This results in continuous proliferation of cells which is a hallmark of cancer. Therefore, telomere biology has a central role in aging, cancer progression/metastasis as well as targeted cancer therapies. There are commonly used methods in telomere biology such as Telomere Restriction Fragment (TRF) (Mender and Shay, 2015b), Telomere Repeat Amplification Protocol (TRAP) and Telomere dysfunction Induced Foci (TIF) analysis (Mender and Shay, 2015a). In this detailed protocol we describe Telomere Repeat Amplification Protocol (TRAP). The TRAP assay is a popular method to determine telomerase activity in mammalian cells and tissue samples (Kim et al. , 1994). The TRAP assay includes three steps: extension, amplification, and detection of telomerase products. In the extension step, telomeric repeats are added to the telomerase substrate (which is actually a non telomeric oligonucleotide, TS) by telomerase. In the amplification step, the extension products are amplified by the polymerase chain reaction (PCR) using specific primers (TS upstream primer and ACX downstream primer) and in the detection step, the presence or absence of telomerase is

  17. Resonant primordial gravitational waves amplification

    Directory of Open Access Journals (Sweden)

    Chunshan Lin

    2016-01-01

    Full Text Available We propose a mechanism to evade the Lyth bound in models of inflation. We minimally extend the conventional single-field inflation model in general relativity (GR to a theory with non-vanishing graviton mass in the very early universe. The modification primarily affects the tensor perturbation, while the scalar and vector perturbations are the same as the ones in GR with a single scalar field at least at the level of linear perturbation theory. During the reheating stage, the graviton mass oscillates coherently and leads to resonant amplification of the primordial tensor perturbation. After reheating the graviton mass vanishes and we recover GR.

  18. MET amplification, expression, and exon 14 mutations in colorectal adenocarcinoma.

    Science.gov (United States)

    Zhang, Meng; Li, Guichao; Sun, Xiangjie; Ni, Shujuan; Tan, Cong; Xu, Midie; Huang, Dan; Ren, Fei; Li, Dawei; Wei, Ping; Du, Xiang

    2018-04-08

    MET amplification, expression, and splice mutations at exon 14 result in dysregulation of the MET signaling pathway. The aim of this study was to identify the relationship between MET amplification, protein or mRNA expression, and mutations in colorectal cancer (CRC). MET immunohistochemistry (IHC) was used for MET protein expression analysis and fluorescence in situ hybridization (FISH) was used for MET amplification detection. Both analyses were performed in tissue microarrays (TMA) containing 294 of colorectal adenocarcinoma tissue samples and 131 samples of adjacent normal epithelial tissue. MET mRNA expression was examined by real-time quantitative polymerase chain reaction (qRT-PCR) in 72 fresh colorectal adenocarcinoma tissue samples and adjacent normal colon tissue. PCR sequencing was performed to screen for MET exon 14 splice mutations in 59 fresh CRC tissue samples. Our results showed that MET protein expression was higher in colorectal tumor tissue than in adjacent normal intestinal epithelium. Positive MET protein expression was associated with significantly poorer overall survival (OS) and disease-free survival (DFS). Multivariate analysis revealed that positive MET protein expression was an independent risk factor for DFS, but not for OS. MET mRNA expression was upregulated in tumor tissues compared with the adjacent normal tissues. The incidence of MET amplification was 4.4%. None of the patients was positive for MET mutation. Collectively, MET was overexpressed in colorectal adenocarcinoma, and its positive protein expression predicted a poorer outcome in CRC patients. Furthermore, according to our results, MET amplification and 14 exon mutation are extremely rare events in colorectal adenocarcinoma. Copyright © 2018. Published by Elsevier Inc.

  19. 85 km Long Reach PON System Using a Reflective SOA-EA Modulator and Distributed Raman Fiber Amplification

    DEFF Research Database (Denmark)

    Tafur Monroy, Idelfonso; Öhman, Filip; Yvind, Kresten

    2006-01-01

    We report on a bidirectional 85 km long reach PON system supported by distributed fiber Raman amplification with a record 7.5 Gb/s remote carrier modulated upstream signal by employing a reflective SOA-EA monolithically integrated circuit......We report on a bidirectional 85 km long reach PON system supported by distributed fiber Raman amplification with a record 7.5 Gb/s remote carrier modulated upstream signal by employing a reflective SOA-EA monolithically integrated circuit...

  20. Amplification biases: possible differences among deviating gene expressions

    Directory of Open Access Journals (Sweden)

    Piumi Francois

    2008-01-01

    Full Text Available Abstract Background Gene expression profiling has become a tool of choice to study pathological or developmental questions but in most cases the material is scarce and requires sample amplification. Two main procedures have been used: in vitro transcription (IVT and polymerase chain reaction (PCR, the former known as linear and the latter as exponential. Previous reports identified enzymatic pitfalls in PCR and IVT protocols; however the possible differences between the sequences affected by these amplification defaults were only rarely explored. Results Screening a bovine cDNA array dedicated to embryonic stages with embryonic (n = 3 and somatic tissues (n = 2, we proceeded to moderate amplifications starting from 1 μg of total RNA (global PCR or IVT one round. Whatever the tissue, 16% of the probes were involved in deviating gene expressions due to amplification defaults. These distortions were likely due to the molecular features of the affected sequences (position within a gene, GC content, hairpin number but also to the relative abundance of these transcripts within the tissues. These deviating genes mainly encoded housekeeping genes from physiological or cellular processes (70% and constituted 2 subsets which did not overlap (molecular features, signal intensities, gene ID. However, the differential expressions identified between embryonic stages were both reliable (minor intersect with biased expressions and relevant (biologically validated. In addition, the relative expression levels of those genes were biologically similar between amplified and unamplified samples. Conclusion Conversely to the most recent reports which challenged the use of intense amplification procedures on minute amounts of RNA, we chose moderate PCR and IVT amplifications for our gene profiling study. Conclusively, it appeared that systematic biases arose even with moderate amplification procedures, independently of (i the sample used: brain, ovary or embryos, (ii

  1. MRI diagnosis of tongue tumors

    International Nuclear Information System (INIS)

    Minowa, Kazuyuki; Abe, Satoru; Ohmori, Keiichi; Hosokawa, Yoichirou; Yamasaki, Michio; Hirano, Masayasu.

    1992-01-01

    MRI studies were performed on 29 patients with tongue tumors. Twenty-six cases were fresh, others were recurrent. Signal intensity of tongue tumor was not characteristic and specific, and it was a low∼iso signal on T1 weighted image (WI), heterogeneously iso∼high signal intensity on T2 WI, heterogeneous enhancement on gadolinium-DTPA enhanced image compared to muscle signal intensity. In 3 of 29 patients, the tongue tumor invaded to the mandible. With regard to the grasping tumor invasion to the mandible, the STIR method was superior to T1, T2 WI of the spin echo method. Dynamic enhanced MR images were performed in 6 of 29 patients. Dynamic change of signal intensity after gadolinium-DTPA administration were assessed with fast low angle shot imaging. On dynamic study at about 20 seconds after gadolinium-DTPA injection, the first signal intensity in the periphery of the tumor gradually began to increase. Maximum signal intensity of the tumor showed at about 70 seconds after gadolinium-DTPA injection. In search from 0 to 5 minutes, after the tongue tumor showed maximum signal intensity, its signal maintain the maximum. Necrotic and peritumorous edema showed a significantly lower and more gradual increase in signal intensity than adjacent neoplastic tissue on dynamic enhanced MRI. (author)

  2. Functional MRI experiments : acquisition, analysis and interpretation of data

    NARCIS (Netherlands)

    Ramsey, NF; Hoogduin, H; Jansma, JM

    2002-01-01

    Functional MRI is widely used to address basic and clinical neuroscience questions. In the key domains of fMRI experiments, i.e. acquisition, processing and analysis, and interpretation of data, developments are ongoing. The main issues are sensitivity for changes in fMRI signal that are associated

  3. Risk Perception and Social Amplification

    International Nuclear Information System (INIS)

    Smith, R.E.

    2001-01-01

    This paper seeks to consider social amplification as it applies to risk perception. Perceptions of the magnitude of a risk are conditioned by issues such as the degree of uncertainty in probability and consequences, the nature of the consequences and the relative weightings placed on probability and consequences. Risk perceptions are also influenced by factors such as confidence in the operator of an industrial process, trust in the regulator and the perceived fairness of regulatory decision-making. Different people may hold different views about these issues and there may also be difficulties in communication. The paper identifies and discusses self-reinforcing mechanisms, which will be labelled 'lock-in' here. They appear to apply in many situations where social amplification is observed. Historically, the term 'lock-in' has been applied mainly in the technological context but, in this paper, four types of lock-in are identified, namely scientific/technological, economic, social and institutional lock-in. One type of lock-in tends to lead to the next and all are buttressed by people's general acceptance of the familiar, fear of the unknown and resistance to change. The regulator seeks to make decisions which achieve the common good rather than supporting or perpetuating any set of vested interests. In this regard the locked-in positions of stakeholders, whether organisations, interest groups, or individual members of the public, are obstacles and challenges. Existing methods of consultation are unsatisfactory in terms of achieving a proper and productive level of dialogue with stakeholders

  4. CT and MRI of vertebral haemangiomas

    International Nuclear Information System (INIS)

    Braitinger, S.; Weigert, F.; Held, P.; Obletter, N.; Breit, A.

    1989-01-01

    A retrospective comparative study of CT and MRI was carried out involving 38 vertebral haemangiomas; this revealed a typical signal pattern on MRI from benign lesions. It consists of a hyper-intense signal from the bone marrow affecting the T 1 /T 2 sequences; this may be focal or involve the entire vertebral body. These characteristic signals were compared with CT images of the spine. The areas of bone that produce the high intensity signals on MRI appear on CT as spongey patterns with hypertrophic trabeculae surrounding mostly areas with negative absorption values. An analysis of the changes in the spongiosa has revealed three clearly defined types. The signals derived from haemangiomas extending beyond the bone have an intensity of normal spongiosa; this corresponds with an absence of fat, as demonstrated by CT. Extra-osseous components have low intensity T 1 signals that increase in T 2 sequences. (orig.) [de

  5. Vertebral involvement in SAPHO syndrome: MRI findings

    Energy Technology Data Exchange (ETDEWEB)

    Nachtigal, A.; Cardinal, E.; Bureau, N.J. [Dept. of Radiology, Univ. de Montreal, QC (Canada); Sainte-Marie, L.G. [Dept. of Internal Medicine, Univ. de Montreal, QC (Canada); Milette, F. [Department of Pathology, Univ. de Montreal, QC (Canada)

    1999-03-01

    We report on the MRI findings in the vertebrae and surrounding soft tissues in two patients with the SAPHO syndrome (Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis). The MRI findings include abnormal bone marrow signal, either focal or diffuse, of the vertebral bodies and posterior elements; hyperintense paravertebral soft tissue swelling and abnormal signal of the intervertebral discs. These changes are consistent with discitis and osteitis. (orig.) With 6 figs., 17 refs.

  6. Catechol-chitosan redox capacitor for added amplification in electrochemical immunoanalysis.

    Science.gov (United States)

    Yan, Kun; Liu, Yi; Guan, Yongguang; Bhokisham, Narendranath; Tsao, Chen-Yu; Kim, Eunkyoung; Shi, Xiao-Wen; Wang, Qin; Bentley, William E; Payne, Gregory F

    2018-05-22

    Antibodies are common recognition elements for molecular detection but often the signals generated by their stoichiometric binding must be amplified to enhance sensitivity. Here, we report that an electrode coated with a catechol-chitosan redox capacitor can amplify the electrochemical signal generated from an alkaline phosphatase (AP) linked immunoassay. Specifically, the AP product p-aminophenol (PAP) undergoes redox-cycling in the redox capacitor to generate amplified oxidation currents. We estimate an 8-fold amplification associated with this redox-cycling in the capacitor (compared to detection by a bare electrode). Importantly, this capacitor-based amplification is generic and can be coupled to existing amplification approaches based on enzyme-linked catalysis or magnetic nanoparticle-based collection/concentration. Thus, the capacitor should enhance sensitivities in conventional immunoassays and also provide chemical to electrical signal transduction for emerging applications in molecular communication. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Optical parametric amplification and oscillation assisted by low-frequency stimulated emission.

    Science.gov (United States)

    Longhi, Stefano

    2016-04-15

    Optical parametric amplification and oscillation provide powerful tools for coherent light generation in spectral regions inaccessible to lasers. Parametric gain is based on a frequency down-conversion process and, thus, it cannot be realized for signal waves at a frequency ω3 higher than the frequency of the pump wave ω1. In this Letter, we suggest a route toward the realization of upconversion optical parametric amplification and oscillation, i.e., amplification of the signal wave by a coherent pump wave of lower frequency, assisted by stimulated emission of the auxiliary idler wave. When the signal field is resonated in an optical cavity, parametric oscillation is obtained. Design parameters for the observation of upconversion optical parametric oscillation at λ3=465 nm are given for a periodically poled lithium-niobate (PPLN) crystal doped with Nd(3+) ions.

  8. Patterns of cortical oscillations organize neural activity into whole-brain functional networks evident in the fMRI BOLD signal

    Directory of Open Access Journals (Sweden)

    Jennifer C Whitman

    2013-03-01

    Full Text Available Recent findings from electrophysiology and multimodal neuroimaging have elucidated the relationship between patterns of cortical oscillations evident in EEG / MEG and the functional brain networks evident in the BOLD signal. Much of the existing literature emphasized how high-frequency cortical oscillations are thought to coordinate neural activity locally, while low-frequency oscillations play a role in coordinating activity between more distant brain regions. However, the assignment of different frequencies to different spatial scales is an oversimplification. A more informative approach is to explore the arrangements by which these low- and high-frequency oscillations work in concert, coordinating neural activity into whole-brain functional networks. When relating such networks to the BOLD signal, we must consider how the patterns of cortical oscillations change at the same speed as cognitive states, which often last less than a second. Consequently, the slower BOLD signal may often reflect the summed neural activity of several transient network configurations. This temporal mismatch can be circumvented if we use spatial maps to assess correspondence between oscillatory networks and BOLD networks.

  9. A Label-Free and Sensitive Fluorescent Qualitative Assay for Bisphenol A Based on Rolling Circle Amplification/Exonuclease III-Combined Cascade Amplification.

    Science.gov (United States)

    Li, Xia; Song, Juan; Xue, Qing-Wang; You, Fu-Heng; Lu, Xia; Kong, Yan-Cong; Ma, Shu-Yi; Jiang, Wei; Li, Chen-Zhong

    2016-10-21

    Bisphenol A (BPA) detection in drinking water and food packaging materials has attracted much attention since the discovery that BPA can interfere with normal physiological processes and cause adverse health effects. Here, we constructed a label-free aptamer fluorescent assay for selective and sensitive detection of BPA based on the rolling circle amplification (RCA)/Exonuclease III (Exo III)-combined cascade amplification strategy. First, the duplex DNA probe (RP) with anti-BPA aptamer and trigger sequence was designed for BPA recognition and signal amplification. Next, under the action of BPA, the trigger probe was liberated from RP to initiate RCA reaction as primary amplification. Subsequently, the RCA products were used to trigger Exo III assisted secondary amplification with the help of hairpin probes, producing plenty of "G-quadruplex" in lantern-like structures. Finally, the continuously enriched "G-quadruplex lanterns" were lightened by zinc(II)-protoporphyrin IX (ZnPPIX) generating enhanced fluorescence signals. By integrating the primary RCA and secondary Exo III mediated cascade amplification strategy, this method displayed an excellent sensitivity with the detection limits of 5.4 × 10 -17 M. In addition, the anti-BPA aptamer exhibits high recognition ability with BPA, guaranteeing the specificity of detection. The reporter signal probe (G-quadruplex with ZnPPIX) provides a label-free fluorescence signals readout without complicated labeling procedures, making the method simple in design and cost-effective in operation. Moreover, environmental samples analysis was also performed, suggesting that our strategy was reliable and had a great potential application in environmental monitoring.

  10. A Label-Free and Sensitive Fluorescent Qualitative Assay for Bisphenol A Based on Rolling Circle Amplification/Exonuclease III-Combined Cascade Amplification

    Directory of Open Access Journals (Sweden)

    Xia Li

    2016-10-01

    Full Text Available Bisphenol A (BPA detection in drinking water and food packaging materials has attracted much attention since the discovery that BPA can interfere with normal physiological processes and cause adverse health effects. Here, we constructed a label-free aptamer fluorescent assay for selective and sensitive detection of BPA based on the rolling circle amplification (RCA/Exonuclease III (Exo III-combined cascade amplification strategy. First, the duplex DNA probe (RP with anti-BPA aptamer and trigger sequence was designed for BPA recognition and signal amplification. Next, under the action of BPA, the trigger probe was liberated from RP to initiate RCA reaction as primary amplification. Subsequently, the RCA products were used to trigger Exo III assisted secondary amplification with the help of hairpin probes, producing plenty of “G-quadruplex” in lantern-like structures. Finally, the continuously enriched “G-quadruplex lanterns” were lightened by zinc(II-protoporphyrin IX (ZnPPIX generating enhanced fluorescence signals. By integrating the primary RCA and secondary Exo III mediated cascade amplification strategy, this method displayed an excellent sensitivity with the detection limits of 5.4 × 10−17 M. In addition, the anti-BPA aptamer exhibits high recognition ability with BPA, guaranteeing the specificity of detection. The reporter signal probe (G-quadruplex with ZnPPIX provides a label-free fluorescence signals readout without complicated labeling procedures, making the method simple in design and cost-effective in operation. Moreover, environmental samples analysis was also performed, suggesting that our strategy was reliable and had a great potential application in environmental monitoring.

  11. Theoretical considerations in measurement of time discrepancies between input and myocardial time-signal intensity curves in estimates of regional myocardial perfusion with first-pass contrast-enhanced MRI.

    Science.gov (United States)

    Natsume, Takahiro; Ishida, Masaki; Kitagawa, Kakuya; Nagata, Motonori; Sakuma, Hajime; Ichihara, Takashi

    2015-11-01

    The purpose of this study was to develop a method to determine time discrepancies between input and myocardial time-signal intensity (TSI) curves for accurate estimation of myocardial perfusion with first-pass contrast-enhanced MRI. Estimation of myocardial perfusion with contrast-enhanced MRI using kinetic models requires faithful recording of contrast content in the blood and myocardium. Typically, the arterial input function (AIF) is obtained by setting a region of interest in the left ventricular cavity. However, there is a small delay between the AIF and the myocardial curves, and such time discrepancies can lead to errors in flow estimation using Patlak plot analysis. In this study, the time discrepancies between the arterial TSI curve and the myocardial tissue TSI curve were estimated based on the compartment model. In the early phase after the arrival of the contrast agent in the myocardium, the relationship between rate constant K1 and the concentrations of Gd-DTPA contrast agent in the myocardium and arterial blood (LV blood) can be described by the equation K1={dCmyo(tpeak)/dt}/Ca(tpeak), where Cmyo(t) and Ca(t) are the relative concentrations of Gd-DTPA contrast agent in the myocardium and in the LV blood, respectively, and tpeak is the time corresponding to the peak of Ca(t). In the ideal case, the time corresponding to the maximum upslope of Cmyo(t), tmax, is equal to tpeak. In practice, however, there is a small difference in the arrival times of the contrast agent into the LV and into the myocardium. This difference was estimated to correspond to the difference between tpeak and tmax. The magnitudes of such time discrepancies and the effectiveness of the correction for these time discrepancies were measured in 18 subjects who underwent myocardial perfusion MRI under rest and stress conditions. The effects of the time discrepancies could be corrected effectively in the myocardial perfusion estimates. Copyright © 2015 Elsevier Inc. All rights

  12. Ultrashort pulse shaping by optical parametric chirped amplification

    International Nuclear Information System (INIS)

    Nelet, Ambre

    2007-01-01

    The aim of this work is to propose new laser architectures based on optical parametric chirped pulse amplification (OPCPA). Common goals of OPCPA pre-amplifiers are to reach high energy level while maintaining the spectrum width and to adapt geometry of the amplified beam to the high power laser chain optics. We consider OPCPA as a way to control and to sculpt ultrashort pulses. Our first set-up aims at thwarting possible time recovery default between pump and signal pulses, which lower the energy extraction. A regenerative OPCPA, idler resonant, is a way to produce a high-intensity and high-repetition rate train of amplified signal replicas. Our second laser system pre-compensates the spectral gain narrowing by sculpting pulses directly within the OPCPA section, where a temporal shaping of the pump beam permits a spectro-spectral shaping of the amplified signal. Finally, we propose an OPCPA based on spatial coding and uniform amplification of spectral signal components by using a fan-out periodically poled crystal and a zero dispersion line. (author) [fr

  13. PET/MRI. Challenges, solutions and perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Herzog, Hans [Forschungszentrum Juelich (Germany). Inst. of Neuroscience and Medicine - 4

    2012-07-01

    Already from the start of PET/CT integrating positron emission tomography (PET) and computed tomography (CT) in one instrument, there have been considerations how to combine PET and magnetic resonance imaging (MRI) so that their complementary abilities can be utilized in a single investigation. Since classical PET electronics fail in an even weak magnetic field and PET signal processing might disturb high-frequency signals of MRI, it soon became clear that new solutions had to be found to avoid mutual interferences. During the last fifteen years a number of different approaches towards PET/MRI for small animal imaging have been developed by research groups which together with their specific features are summarized in this review. Recently, PET/MRI for human imaging became available as well - this time by industrial initiatives. First some prototypes of BrainPET/MRI were developed followed by commercial products for simultaneous and non-simultaneous whole-body PET/MRI. Although only PET/MRI integrated in one scanner offers the full diversity of complementary multiparametric imaging, there are also promising applications of non-simultaneous sequential PET/MRI. While describing the present instrumentation for human PET/MRI, this review discusses the challenges and promises related to this new imaging technology. (orig.)

  14. MRI in Optic Neuritis: Structure, Function, Interactions

    DEFF Research Database (Denmark)

    Fuglø, Dan

    2011-01-01

    resonance imaging (MRI), and the visual evoked potential (VEP) continues to show a delayed P100 indicating persistent demyelination. The explanation for this apparent discrepancy between structure and function could be due to either a redundancy in the visual pathways so that some degree of signal loss...... will have very few or no clinical symptoms, or it could be due to compensatory mechanisms in the visual pathway or the visual cortex. In order to understand the pathophysiology and recovery processes in ON it is essential to have sensitive methods to asses both structure and function. These methods...... are low. Functional MRI (fMRI) is a non-invasive technique that can measure brain activity with a high spatial resolution. Recently, technical and methodological advancements have made it feasible to record VEPs and fMRI simultaneously and the relationship between averaged VEPs and averaged fMRI signals...

  15. Reye's syndrome with cortical laminar necrosis: MRI

    International Nuclear Information System (INIS)

    Kinoshita, T.; Takahashi, S.; Ishii, K.; Higano, S.; Matsumoto, K.; Sakamoto, K.; Haginoya, K.; Iinuma, K.

    1996-01-01

    Serial MRI findings are described in two patients with Reye's syndrome, demonstrating diffuse cortical and white matter changes. In the acute stage, T2-weighted images showed subtle but definite laminar high signal and contrast-enhanced T1-weighted images laminar enhancement, along the entire cerebral cortex bilaterally. In the chronic stage, unenhanced T1-weighted images showed diffuse cortical laminar high signal. These characteristic MRI features seemed very similar to those of laminar cortical necrosis in hypoxic brain damage. MRI also displayed delayed white matter changes with cerebral atrophy. (orig.)

  16. Complex Wavelet transform for MRI

    International Nuclear Information System (INIS)

    Junor, P.; Janney, P.

    2004-01-01

    Full text: There is a perpetual compromise encountered in magnetic resonance (MRl) image reconstruction, between the traditional elements of image quality (noise, spatial resolution and contrast). Additional factors exacerbating this trade-off include various artifacts, computational (and hence time-dependent) overhead, and financial expense. This paper outlines a new approach to the problem of minimizing MRI image acquisition and reconstruction time without compromising resolution and noise reduction. The standard approaches for reconstructing magnetic resonance (MRI) images from raw data (which rely on relatively conventional signal processing) have matured but there are a number of challenges which limit their use. A major one is the 'intrinsic' signal-to-noise ratio (SNR) of the reconstructed image that depends on the strength of the main field. A typical clinical MRI almost invariably uses a super-cooled magnet in order to achieve a high field strength. The ongoing running cost of these super-cooled magnets prompts consideration of alternative magnet systems for use in MRIs for developing countries and in some remote regional installations. The decrease in image quality from using lower field strength magnets can be addressed by improvements in signal processing strategies. Conversely, improved signal processing will obviously benefit the current conventional field strength MRI machines. Moreover, the 'waiting time' experienced in many MR sequences (due to the relaxation time delays) can be exploited by more rigorous processing of the MR signals. Acquisition often needs to be repeated so that coherent averaging may partially redress the shortfall in SNR, at the expense of further delay. Wavelet transforms have been used in MRI as an alternative for encoding and denoising for over a decade. These have not supplanted the traditional Fourier transform methods that have long been the mainstay of MRI reconstruction, but have some inflexibility. The dual

  17. MRI zoo

    DEFF Research Database (Denmark)

    Laustsen, Christoffer

    The basic idea was to use MRI to produce a sequence of 3D gray scale image slices of various animals, subsequentlyimaged with a clinical CT system. For this purpose, these animals were used: toad, lungfish, python snake and a horseshoe crab. Each animal was sacrificed according to standard...... visually inspected, both in 2D and 3D, and compared with photographs and anatomy atlases found at library and on the internet....

  18. Multiscale image contrast amplification (MUSICA)

    Science.gov (United States)

    Vuylsteke, Pieter; Schoeters, Emile P.

    1994-05-01

    This article presents a novel approach to the problem of detail contrast enhancement, based on multiresolution representation of the original image. The image is decomposed into a weighted sum of smooth, localized, 2D basis functions at multiple scales. Each transform coefficient represents the amount of local detail at some specific scale and at a specific position in the image. Detail contrast is enhanced by non-linear amplification of the transform coefficients. An inverse transform is then applied to the modified coefficients. This yields a uniformly contrast- enhanced image without artefacts. The MUSICA-algorithm is being applied routinely to computed radiography images of chest, skull, spine, shoulder, pelvis, extremities, and abdomen examinations, with excellent acceptance. It is useful for a wide range of applications in the medical, graphical, and industrial area.

  19. Measuring the amplification of attention.

    Science.gov (United States)

    Blaser, E; Sperling, G; Lu, Z L

    1999-09-28

    An ambiguous motion paradigm, in which the direction of apparent motion is determined by salience (i.e., the extent to which an area is perceived as figure versus ground), is used to assay the amplification of color by attention to color. In the red-green colored gratings used in these experiments, without attention instructions, salience depends on the chromaticity difference between colored stripes embedded in the motion sequence and the yellow background. Selective attention to red (or to green) alters the perceived direction of motion and is found to be equivalent to increasing the physical redness (or greenness) by 25-117%, depending on the observer and color. Whereas attention to a color drastically alters the salience of that color, it leaves color appearance unchanged. A computational model, which embodies separate, parallel pathways for object perception and for salience, accounts for 99% of the variance of the experimental data.

  20. MRI diagnosis of meniscal tears

    International Nuclear Information System (INIS)

    Kuga, Naoyuki; Oh, Toshihiro

    1996-01-01

    We studied the accuracy of magnetic resonance imaging (MRI) of the knee in fifty-six patients who were also examined arthroscopically. The accuracy, sensitivity, and specificity were 96%, 100%, and 95% for medial meniscal tears, and 91%, 67%, and 100% for lateral meniscal tears respectively. Two MRIs of the medial meniscus were false-positives. These MRI findings were both meniscocapsular separation of the medial meniscus, but the arthroscopic findings were normal. One case was an ACL injury and the other PCL and MCL injury. Hemorrhage and edema of the medial capsule caused by valgus stress at injury may look like a meniscal pseudo-tear on MRI. Five MRIs of the lateral meniscus were false-negatives. All menisci showed normal signal and shape on MRI but traumatic and stable tears of the lateral meniscus were identified arthroscopically. All were associated with ACL tears and lateral condylar bone bruise. The traumatic and stable tear of the meniscus tended to be overlooked on MRI because a meniscus without degeneration shows a normal signal. (author)

  1. Risk Perception and Social Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Smith, R.E. [Environment Agency (United Kingdom)

    2001-07-01

    This paper seeks to consider social amplification as it applies to risk perception. Perceptions of the magnitude of a risk are conditioned by issues such as the degree of uncertainty in probability and consequences, the nature of the consequences and the relative weightings placed on probability and consequences. Risk perceptions are also influenced by factors such as confidence in the operator of an industrial process, trust in the regulator and the perceived fairness of regulatory decision-making. Different people may hold different views about these issues and there may also be difficulties in communication. The paper identifies and discusses self-reinforcing mechanisms, which will be labelled 'lock-in' here. They appear to apply in many situations where social amplification is observed. Historically, the term 'lock-in' has been applied mainly in the technological context but, in this paper, four types of lock-in are identified, namely scientific/technological, economic, social and institutional lock-in. One type of lock-in tends to lead to the next and all are buttressed by people's general acceptance of the familiar, fear of the unknown and resistance to change. The regulator seeks to make decisions which achieve the common good rather than supporting or perpetuating any set of vested interests. In this regard the locked-in positions of stakeholders, whether organisations, interest groups, or individual members of the public, are obstacles and challenges. Existing methods of consultation are unsatisfactory in terms of achieving a proper and productive level of dialogue with stakeholders.

  2. MRI of menisci repaired with bioabsorbable arrows

    International Nuclear Information System (INIS)

    Mustonen, Antti O.T.; Kiuru, Martti; Koskinen, Seppo K.; Tielinen, Laura; Lindahl, Jan; Hirvensalo, Eero

    2006-01-01

    To analyze with conventional magnetic resonance imaging (MRI) the signal appearance of menisci repaired with bioabsorbable arrows. Forty-four patients with 47 meniscal tears treated with bioabsorbable arrows underwent follow-up conventional MRI examination. The time interval between the surgery and MRI varied from 5 to 67 months (mean 26 months). Twenty-six patients also had concurrent repair of torn anterior cruciate ligament. The following grades were used to classify meniscal signal intensity: (a) G0; low signal intensity on all sequences and regular configuration in every plane, (b) G1; increased signal intensity within the meniscus, not extending to the meniscal surface, (c) G2; increased signal intensity linear in shape, which may or may not communicate with the capsular margin of the meniscus, without extending to the meniscal surface, and (d) G3; increased signal intensity extending to the meniscal surface. Thirteen menisci (27.5%) had normal signal intensity, 13 menisci (27.5%) Grade 1 signal intensity, 9 menisci (19%) Grade 2 signal intensity and 12 menisci (26%) Grade 3 signal intensity. The time difference between operation and MRI was statistically significant between the G0 (36 months) and G3 groups (14 months; P=0.0288). There was no statistical significance in different grades between medial and lateral meniscus or between patients with operated or intact ACL. On physical examination sixteen patients reported slight symptoms, seen evenly in each group. (orig.)

  3. MRI of symptomatic shoulders

    International Nuclear Information System (INIS)

    Kikukawa, Kenshi; Segata, Tateki; Kunitake, Katsuhiko; Morisawa, Keizo; Harada, Masataka; Hirano, Mako

    2004-01-01

    The purpose of this study was to determine the prevalence of cuff tear and acromioclavicular joint (ACJ) osteoarthrosis by magnetic resonance imaging (MRI) evaluation in symptomatic shoulders. MRI was performed on 124 shoulders in 115 patients whose age ranged from 16 to 83 years (average: 58.0 years). There were 74 men (79 shoulders) and 41 women (45 shoulders). The patients were divided into three groups according to age; A group (10 shoulders: 16-29 years), B group (43 shoulders: 30-59 years), and C group (71 shoulders: 60-83 years). Rotator cuff tears and ACJ osteoarthrosis were graded on scales 0 to 3 (normal, increased signal intensity, incomplete, complete), and 1 to 4 (none, mild, moderate, severe), respectively. There was a significant difference in the severity of the cuff tears and the ACJ osteoarthrosis with respect to age. Twenty percent of the shoulders were graded incomplete or complete cuff tears in group A, 88% in group B, and 93% in group C. No shoulders were graded moderate or severe ACJ changes in group A, 63% in group B, and 93% in group C. There was a definite correlation between the cuff tears and ACJ osteoarthrosis. MRI of the symptomatic shoulders indicated well correlation between the rotator cuff tears and ACJ osteoarthrosis. (author)

  4. Impact of tissue atrophy on high-pass filtered MRI signal phase-based assessment in large-scale group-comparison studies: A simulation study

    Science.gov (United States)

    Schweser, Ferdinand; Dwyer, Michael G.; Deistung, Andreas; Reichenbach, Jürgen R.; Zivadinov, Robert

    2013-10-01

    The assessment of abnormal accumulation of tissue iron in the basal ganglia nuclei and in white matter plaques using the gradient echo magnetic resonance signal phase has become a research focus in many neurodegenerative diseases such as multiple sclerosis or Parkinson’s disease. A common and natural approach is to calculate the mean high-pass-filtered phase of previously delineated brain structures. Unfortunately, the interpretation of such an analysis requires caution: in this paper we demonstrate that regional gray matter atrophy, which is concomitant with many neurodegenerative diseases, may itself directly result in a phase shift seemingly indicative of increased iron concentration even without any real change in the tissue iron concentration. Although this effect is relatively small results of large-scale group comparisons may be driven by anatomical changes rather than by changes of the iron concentration.

  5. Combination of signal intensity measurements of lesions in the peripheral zone of prostate with MRI and serum PSA level for differentiating benign disease from prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Engelhard, K.; Kreckel, M. [Department of Radiology, Martha-Maria Hospital Nuernberg (Germany); Hollenbach, H.P.; Deimling, M. [Siemens Medical Engineering Group, Erlangen (Germany); Riedl, C. [Dept. of Urology, University of Erlangen-Nuernberg, Erlangen (Germany)

    2000-12-01

    The aim of this study was to predict the benign or malignant nature of a prostatic lesion by defining a threshold value of signal intensity ratio and a limiting value of serum prostate-specific antigen (PSA) in patients with elevated PSA level. Twenty-six patients with elevated PSA level and no hypoechogenic lesions at endosonography underwent MR imaging using an endorectal body phased-array coil at 1.5 T (Siemens Magnetom Symphony). A T2-weighted turbo-spin-echo (TSE) pulse sequence was applied in a transverse orientation. Two radiologists evaluated the images. In the presence of a pathological finding they defined regions of interest (ROI) in the suspicious pathological area of the peripheral zone and in muscle for reference. The quotient of the two ROIs was calculated and then correlated with the actual PSA level. Diagnosis was confirmed by prostate biopsy. Ten of 12 patients with quotients smaller than 4 showed cancer at histology. Nine of 12 men with cancer proven by biopsy had PSA levels higher than 10 ng/ml. A significant difference (p < 0.001) was found between the quotients of cancer and quotients of chronic prostatitis, fibrosis, or glandular atrophy. The accuracy of tumor differentiation of the method was 77 %. Measurement of signal intensity quotients in the peripheral zone of the prostate in combination with knowledge of defined limits of PSA levels the technique could be helpful in detecting additional cancer areas for prostate biopsy. False-negative tumor results of standard sextant biopsy can be reduced. In men with high PSA values the method has a role in differentiating between patients who require prostate biopsy and those of clinical observation. (orig.)

  6. FGFR-1 amplification in metastatic lymph-nodal and haematogenous lobular breast carcinoma

    Directory of Open Access Journals (Sweden)

    Brunello Eleonora

    2012-12-01

    Full Text Available Abstract Background Lobular breast carcinoma usually shows poor responsiveness to chemotherapies and often lacks targeted therapies. Since FGFR1 expression has been shown to play pivotal roles in primary breast cancer tumorigenesis, we sought to analyze the status of FGFR1 gene in a metastatic setting of lobular breast carcinoma, since promising FGFR1 inhibitors has been recently developed. Methods Fifteen tissue metastases from lobular breast carcinomas with matched primary infiltrative lobular breast carcinoma were recruited. Eleven cases showed loco-regional lymph-nodal and four haematogenous metastases. FGFR-1 gene (8p12 amplification was evaluated by chromogenic in situ hybridization (CISH analysis. Her-2/neu and topoisomerase-IIα gene status was assessed. E-cadherin and Hercept Test were also performed. We distinguished amplification (>6 or cluster of signals versus gains (3–6 signals of the locus specific FGFR-1 gene. Results Three (20% primary lobular breast carcinomas showed >6 or cluster of FGFR1 signals (amplification, six cases (40% had a mean of three (range 3–6 chromogenic signals (gains whereas in 6 (40% was not observed any abnormality. Three of 15 metastasis (20% were amplified, 2/15 (13,4% did not. The ten remaining cases (66,6% showed three chromogenic signals. The three cases with FGFR-1 amplification matched with those primary breast carcinomas showing FGFR-1 amplification. The six cases showing FGFR-1 gains in the primary tumour again showed FGFR-1 gains in the metastases. Four cases showed gains of FGFR-1 gene signals in the metastases and not in the primary tumours. Her-2/neu gene amplification was not observed in all cases but one (6% case. Topoisomerase-IIα was not amplified in all cases. Conclusions 1 a subset of metastatic lobular breast carcinoma harbors FGFR-1 gene amplification or gains of chromogenic signals; 2 a minor heterogeneity has been observed after matching primary and metastatic carcinomas; 3 in the

  7. MRI in recurrent nasopharyngeal carcinoma

    International Nuclear Information System (INIS)

    Ng, S.H.; Ko, S.F.; Wan, Y.L.; Chang, J.T.C.; Chen, W.C.; Tang, L.M.

    1999-01-01

    In this study, we retrospectively reviewed the MRI features of recurrent nasopharyngeal carcinoma (NPC) in 72 patients who underwent MRI before and after gadolinium injection. Recurrent NPC exhibited a high degree of regional spread and a variety of signal intensities and contours. MRI showed a nasopharyngeal mass in 50 patients (69.4 %); other sites of involvement included the parapharyngeal space (44.4 %), nasal cavity (12.5 %), paranasal sinuses (27.8 %), oropharynx (4.2 %), orbit (8.3 %), infratemporal fossa (18.1 %), skull base (59.8 %), intracranial area (51.4 %) and regional lymph nodes (15.3 %). On T2-weighted images, the nasopharyngeal mass gave high signal in 9 of 50 cases (18 %), intermediate in 27 (54 %), mixed in 8 (16 %) and low signal in 6 (12 %). Contrast enhancement was strong in 12 cases (24 %), moderate in 29 (58 %) and heterogeneous in 9 (18 %). The lesion was convex in 31 cases (62 %) and concave or straight in 19 (38 %). Recognition of the distribution and the appearance of recurrent NPC on MRI is essential for timely diagnosis and appropriate treatment. (orig.)

  8. Phase Sensitive Amplification using Parametric Processes in Optical Fibers

    DEFF Research Database (Denmark)

    Kang, Ning

    . Further, phase sensitive parametric processes in a nano-engineered silicon waveguide have been measured experimentally for the first time. Numerical optimizations show that with reduced waveguide propagation loss and reduced carrier life time, larger signal phase sensitive extinction ratio is achievable......Phase sensitive amplification using the parametric processes in fiber has the potential of delivering high gain and broadband operation with ultralow noise. It is able to regenerate both amplitude and phase modulated signals, simultaneously, with the appropriate design. This thesis concerns...... types. The regeneration capability of PSAs on phase encoded signal in an optical link has been optimized. Flat-top phase sensitive profile has been synthesized. It is able to provide simultaneous amplitude and phase noise squeezing, with enhanced phase noise margin compared to conventional designs...

  9. MRI finding of hemangioblastomas

    International Nuclear Information System (INIS)

    Park, Seung Cheol; Oh, Min Cheol; Chung, Hwan Hoon; Seol, Hye Young; Lee, Nam Joon; Kim, Jung Hyuk

    1994-01-01

    The purpose of this study is to evaluate the findings of magnetic resonance imaging (MRI) of posterior fossa hemanangioblastoma and usefulness of contrast enhancement with Gd-DTPA. Seven patients with posterior fossa hemangioblastoma were studied with both pre- and post-enhanced MRI. The MR images were reviewed regarding the location, size, signal intensities of cysts and mural nodules, and their contrast enhancement pattern. Five tumors were located in cerebellar hemisphere, one in vermis, and one in posterior part of medulla. One patient with von Hippel-Lindau disease had a medullary hemangioblastoma with multiple pancreatic cysts. In 6 cases, the major portion of the tumor was cysts and had small mulkal nodules. The solid portion was relatively lange in one cases, cemprising half of the tumor cysts were oval shaped and their sized were 3-6.7 cm in diameter. In five cases(71%), septations were noted within the cysts. Cysts were isointense or slightly hyperintense on T1-weighted image and hyperintense on T2- weighted image compared with cerebrospinal fluid. Mural nodules were oval or rounded radiotherapy had better prognosis than those treated with radiotherapy alwas 0.5-2.5 cm in diameter. Mural nodules were isointense to gray matter. They were detected in five cases on T1-weighted images and one case on T2-weighted images. In two cases, vascular signal void area was noted in mural nodules. On contrast-enhanced T1-weighted images, all mural nodules were intensely enhanced. MRI provide to be a good diagnostic method to detect and characterize posterior fossa hemangioblastoma. The most common finding is Cystic posterior fossa lesion with enhancing mural nodule. Contrast enhancement is essential for specific diagnosis

  10. Precision phase estimation based on weak-value amplification

    Science.gov (United States)

    Qiu, Xiaodong; Xie, Linguo; Liu, Xiong; Luo, Lan; Li, Zhaoxue; Zhang, Zhiyou; Du, Jinglei

    2017-02-01

    In this letter, we propose a precision method for phase estimation based on the weak-value amplification (WVA) technique using a monochromatic light source. The anomalous WVA significantly suppresses the technical noise with respect to the intensity difference signal induced by the phase delay when the post-selection procedure comes into play. The phase measured precision of this method is proportional to the weak-value of a polarization operator in the experimental range. Our results compete well with the wide spectrum light phase weak measurements and outperform the standard homodyne phase detection technique.

  11. Is there any correlation between model-based perfusion parameters and model-free parameters of time-signal intensity curve on dynamic contrast enhanced MRI in breast cancer patients?

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Boram; Kang, Doo Kyoung; Kim, Tae Hee [Ajou University School of Medicine, Department of Radiology, Suwon, Gyeonggi-do (Korea, Republic of); Yoon, Dukyong [Ajou University School of Medicine, Department of Biomedical Informatics, Suwon (Korea, Republic of); Jung, Yong Sik; Kim, Ku Sang [Ajou University School of Medicine, Department of Surgery, Suwon (Korea, Republic of); Yim, Hyunee [Ajou University School of Medicine, Department of Pathology, Suwon (Korea, Republic of)

    2014-05-15

    To find out any correlation between dynamic contrast-enhanced (DCE) model-based parameters and model-free parameters, and evaluate correlations between perfusion parameters with histologic prognostic factors. Model-based parameters (Ktrans, Kep and Ve) of 102 invasive ductal carcinomas were obtained using DCE-MRI and post-processing software. Correlations between model-based and model-free parameters and between perfusion parameters and histologic prognostic factors were analysed. Mean Kep was significantly higher in cancers showing initial rapid enhancement (P = 0.002) and a delayed washout pattern (P = 0.001). Ve was significantly lower in cancers showing a delayed washout pattern (P = 0.015). Kep significantly correlated with time to peak enhancement (TTP) (ρ = -0.33, P < 0.001) and washout slope (ρ = 0.39, P = 0.002). Ve was significantly correlated with TTP (ρ = 0.33, P = 0.002). Mean Kep was higher in tumours with high nuclear grade (P = 0.017). Mean Ve was lower in tumours with high histologic grade (P = 0.005) and in tumours with negative oestrogen receptor status (P = 0.047). TTP was shorter in tumours with negative oestrogen receptor status (P = 0.037). We could acquire general information about the tumour vascular physiology, interstitial space volume and pathologic prognostic factors by analyzing time-signal intensity curve without a complicated acquisition process for the model-based parameters. (orig.)

  12. Assessment of ameloblastomas using MRI and dynamic contrast-enhanced MRI

    International Nuclear Information System (INIS)

    Asaumi, Jun-ichi; Hisatomi, Miki; Yanagi, Yoshinobu; Matsuzaki, Hidenobu; Choi, Yong Suk; Kawai, Noriko; Konouchi, Hironobu; Kishi, Kanji

    2005-01-01

    We retrospectively evaluated magnetic resonance images (MRI) and dynamic contrast-enhanced MRI (DCE-MRI) of ameloblastomas. MRI and DCE-MRI were performed for 10 ameloblastomas. We obtained the following results from the MRI and DCE-MRI. (a) Ameloblastomas can be divided into solid and cystic portions on the basis of MR signal intensities. (b) Ameloblastomas show a predilection for intermediate signal intensity on T1WI, high signal intensity on T2WI, and well enhancement in the solid portion; they also show a homogeneous intermediate signal intensity on T1WI and homogeneous high signal intensity on T2WI, and no enhancement in the cystic portion. (c) The mural nodule or thick wall can be detected in ameloblastomas lesions. (d) CI curves of ameloblastomas show two patterns: the first pattern increases, reaches a plateau at 100-300 s, then sustains the plateau or decreases gradually to 600-900 s, while the other increases relatively rapidly, reaches a plateau at 90-120 s, then decreases relatively rapidly to 300 s, and decreases gradually thereafter. There was no difference in the CI curve patterns among primary and recurrent cases, a case with glandular odontogenic tumor in ameloblastoma or among histopathological types such as plexiform, follicular, mixed, desmoplastic, and unicystic type

  13. MRI of the Chest

    Medline Plus

    Full Text Available ... affecting the MRI images, these objects can become projectiles within the MRI scanner room and may cause ... MRI has proven valuable in diagnosing a broad range of conditions, including cancer, heart and vascular disease, ...

  14. MRI of the Chest

    Medline Plus

    Full Text Available ... or patients with claustrophobia. Other MRI machines are open on the sides (open MRI). Open units are especially helpful for examining larger patients or those with claustrophobia. Newer open MRI units provide very high quality images for ...

  15. MRI (Magnetic Resonance Imaging)

    Science.gov (United States)

    ... Procedures Medical Imaging MRI (Magnetic Resonance Imaging) MRI (Magnetic Resonance Imaging) Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Magnetic Resonance Imaging (MRI) is a medical imaging procedure for ...

  16. MRI of the Chest

    Medline Plus

    Full Text Available ... does not completely surround you. Some newer MRI machines have a larger diameter bore which can be ... size patients or patients with claustrophobia. Other MRI machines are open on the sides (open MRI). Open ...

  17. MRI of the Chest

    Medline Plus

    Full Text Available ... in the first three to four months of pregnancy unless the potential benefit from the MRI exam ... the MRI Safety page for more information about pregnancy and MRI. If you have claustrophobia (fear of ...

  18. MRI of the Chest

    Medline Plus

    Full Text Available ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) - Chest Magnetic resonance imaging (MRI) ... clearer and more detailed than with other imaging methods. This detail makes MRI an invaluable tool in ...

  19. Play the MRI Game

    Science.gov (United States)

    ... Teachers' Questionnaire MRI Play MRI the Magnetic Miracle Game About the game In the MRI imaging technique, strong magnets and ... last will in Paris. Play the Blood Typing Game Try to save some patients and learn about ...

  20. Four-Wave Optical Parametric Amplification in a Raman-Active Gas

    Directory of Open Access Journals (Sweden)

    Yuichiro Kida

    2015-08-01

    Full Text Available Four-wave optical parametric amplification (FWOPA in a Raman-active medium is experimentally investigated by use of an air-filled hollow fiber. A femtosecond pump pulse shorter than the period of molecular motion excites the coherent molecular motion of the Raman-active molecules during the parametric amplification of a signal pulse. The excited coherent motion modulates the frequency of the signal pulse during the parametric amplification, and shifts it to lower frequencies. The magnitude of the frequency redshift depends on the pump intensity, resulting in intensity-dependent spectral characteristics that are different from those in the FWOPA induced in a noble-gas-filled hollow fiber.

  1. A cascade amplification strategy based on rolling circle amplification and hydroxylamine amplified gold nanoparticles enables chemiluminescence detection of adenosine triphosphate.

    Science.gov (United States)

    Wang, Ping; Zhang, Tonghuan; Yang, Taoyi; Jin, Nan; Zhao, Yanjun; Fan, Aiping

    2014-08-07

    A highly sensitive and selective chemiluminescent (CL) biosensor for adenosine triphosphate (ATP) was developed by taking advantage of the ATP-dependent enzymatic reaction (ATP-DER), the powerful signal amplification capability of rolling circle amplification (RCA), and hydroxylamine-amplified gold nanoparticles (Au NPs). The strategy relies on the ability of ATP, a cofactor of T4 DNA ligase, to trigger the ligation-RCA reaction. In the presence of ATP, the T4 DNA ligase catalyzes the ligation reaction between the two ends of the padlock probe, producing a closed circular DNA template that initiates the RCA reaction with phi29 DNA polymerase and dNTP. Therein, many complementary copies of the circular template can be generated. The ATP-DER is eventually converted into a detectable CL signal after a series of processes, including gold probe hybridization, hydroxylamine amplification, and oxidative gold metal dissolution coupled with a simple and sensitive luminol CL reaction. The CL signal is directly proportional to the ATP level. The results showed that the detection limit of the assay is 100 pM of ATP, which compares favorably with those of other ATP detection techniques. In addition, by taking advantage of ATP-DER, the proposed CL sensing system exhibits extraordinary specificity towards ATP and could distinguish the target molecule ATP from its analogues. The proposed method provides a new and versatile platform for the design of novel DNA ligation reaction-based CL sensing systems for other cofactors. This novel ATP-DER based CL sensing system may find wide applications in clinical diagnosis as well as in environmental and biomedical fields.

  2. Distribution of MRI signal alterations of the cartilage endplate in pre-operated patients with special focus on recurrent lumbar disc herniation

    International Nuclear Information System (INIS)

    Becker, G.T.; Liphofer, J.; Koester, O.; Willburger, R.E.; Schmid, G.

    2006-01-01

    Purpose: To study the location of (Modic) MR signal alterations (SA) of the cartilage endplate (CEP) in pre- and non-operated segments L3-S1 with special focus on the presence of recurrent lumbar disc herniation (RLDH). Materials and Methods: In a retrospective study the MR images of vertebrae L3-S1 of 65 consecutive patients with a history of microdiscectomy were evaluated. Of the 190 segments studied, 67 were pre-operated. These were divided into a group with recurrent lumbar disc herniation (RLDH) (n=19) and a group without evidence of RLDH (n=48). Non-operated segments (n=123) were also considered as a separate group. In these three groups the prevalence of different Modic types was determined using the sag. T1- and T2-weighted images, and, in particular, the distribution of SA at the upper and lower CEP was examined by evaluating the sag. T2-weighted images. In order to achieve this, each CEP was divided into nine regions. Results: Pre-operated segments showed significantly more frequent (p<0.001) and more expansive (p<0.001) SA than non-operated segments. Non-operated segments showed SA less frequently in the central region of both upper and lower CEP (p=0.056 and p=0.015, respectively). In operated segments without RLDH, the upper CEP had significantly more SA on the operation side than in the mid-sagittal and contra-lateral regions (p=0.016, p=0.037) and significantly more on the operation side of the lower CEP than in the contra-lateral region (p=0.027). Operated segments with RLDH did not show an emphasis of SA on the operation side. In this group SA occurred significantly more often in the central and ventral mid-sagittal regions of the upper CEP than in the preoperated segments without RLDH. (orig.)

  3. Diagnostic Devices for Isothermal Nucleic Acid Amplification

    Directory of Open Access Journals (Sweden)

    Chia-Chen Chang

    2012-06-01

    Full Text Available Since the development of the polymerase chain reaction (PCR technique, genomic information has been retrievable from lesser amounts of DNA than previously possible. PCR-based amplifications require high-precision instruments to perform temperature cycling reactions; further, they are cumbersome for routine clinical use. However, the use of isothermal approaches can eliminate many complications associated with thermocycling. The application of diagnostic devices for isothermal DNA amplification has recently been studied extensively. In this paper, we describe the basic concepts of several isothermal amplification approaches and review recent progress in diagnostic device development.

  4. Diagnostic devices for isothermal nucleic acid amplification.

    Science.gov (United States)

    Chang, Chia-Chen; Chen, Chien-Cheng; Wei, Shih-Chung; Lu, Hui-Hsin; Liang, Yang-Hung; Lin, Chii-Wann

    2012-01-01

    Since the development of the polymerase chain reaction (PCR) technique, genomic information has been retrievable from lesser amounts of DNA than previously possible. PCR-based amplifications require high-precision instruments to perform temperature cycling reactions; further, they are cumbersome for routine clinical use. However, the use of isothermal approaches can eliminate many complications associated with thermocycling. The application of diagnostic devices for isothermal DNA amplification has recently been studied extensively. In this paper, we describe the basic concepts of several isothermal amplification approaches and review recent progress in diagnostic device development.

  5. Computational Diffusion MRI : MICCAI Workshop

    CERN Document Server

    Grussu, Francesco; Ning, Lipeng; Tax, Chantal; Veraart, Jelle

    2018-01-01

    This volume presents the latest developments in the highly active and rapidly growing field of diffusion MRI. The reader will find numerous contributions covering a broad range of topics, from the mathematical foundations of the diffusion process and signal generation, to new computational methods and estimation techniques for the in-vivo recovery of microstructural and connectivity features, as well as frontline applications in neuroscience research and clinical practice. These proceedings contain the papers presented at the 2017 MICCAI Workshop on Computational Diffusion MRI (CDMRI’17) held in Québec, Canada on September 10, 2017, sharing new perspectives on the most recent research challenges for those currently working in the field, but also offering a valuable starting point for anyone interested in learning computational techniques in diffusion MRI. This book includes rigorous mathematical derivations, a large number of rich, full-colour visualisations and clinically relevant results. As such, it wil...

  6. Animal MRI Core

    Data.gov (United States)

    Federal Laboratory Consortium — The Animal Magnetic Resonance Imaging (MRI) Core develops and optimizes MRI methods for cardiovascular imaging of mice and rats. The Core provides imaging expertise,...

  7. Signal flow analysis

    CERN Document Server

    Abrahams, J R; Hiller, N

    1965-01-01

    Signal Flow Analysis provides information pertinent to the fundamental aspects of signal flow analysis. This book discusses the basic theory of signal flow graphs and shows their relation to the usual algebraic equations.Organized into seven chapters, this book begins with an overview of properties of a flow graph. This text then demonstrates how flow graphs can be applied to a wide range of electrical circuits that do not involve amplification. Other chapters deal with the parameters as well as circuit applications of transistors. This book discusses as well the variety of circuits using ther

  8. Privacy amplification for quantum key distribution

    International Nuclear Information System (INIS)

    Watanabe, Yodai

    2007-01-01

    This paper examines classical privacy amplification using a universal family of hash functions. In quantum key distribution, the adversary's measurement can wait until the choice of hash functions is announced, and so the adversary's information may depend on the choice. Therefore the existing result on classical privacy amplification, which assumes the independence of the choice from the other random variables, is not applicable to this case. This paper provides a security proof of privacy amplification which is valid even when the adversary's information may depend on the choice of hash functions. The compression rate of the proposed privacy amplification can be taken to be the same as that of the existing one with an exponentially small loss in secrecy of a final key. (fast track communication)

  9. Dynamic characterization and amplification of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Rishøj, Lars Søgaard

    2013-01-01

    We show a first-time demonstration of amplification of 400 fs pulses in a fiber optical parametric amplifier. The 400 fs signal is stretched in time, amplified by 26 dB and compressed back to 500 fs. A significant broadening of the pulses is experimentally shown due to dispersion and limited gain...

  10. MOSFET-Only Mixer/IIR Filter with Gain using Parametric Amplification

    DEFF Research Database (Denmark)

    Custódio, José R.; Oliveira, J.; Oliveira, L. B.

    2010-01-01

    This paper describes the design of a discrete-time passive Mixer/IIR filter. The use of an improved MOS Parametric Amplification leads to a moderate gain in the signal path and improved noise performance, instead of the conversion loss inherent to passive mixers. Simulation results demonstrate th...

  11. Rolling circle amplification of metazoan mitochondrialgenomes

    Energy Technology Data Exchange (ETDEWEB)

    Simison, W. Brian; Lindberg, D.R.; Boore, J.L.

    2005-07-31

    Here we report the successful use of rolling circle amplification (RCA) for the amplification of complete metazoan mt genomes to make a product that is amenable to high-throughput genome sequencing techniques. The benefits of RCA over PCR are many and with further development and refinement of RCA, the sequencing of organellar genomics will require far less time and effort than current long PCR approaches.

  12. MRI of medulloblastoma in adults

    International Nuclear Information System (INIS)

    Malheiros, S.M.F.; Santos, A.J.; Borges, L.R.R.; Guimaraes, I.F.; Franco, C.M.R.; Gabbai, A.A.; Carrete, H.; Stavale, J.N.; Pelaez, M.P.

    2003-01-01

    Medulloblastoma has variable appearances on MRI in both children and adults. Adults are more likely to have heterogeneous cerebellar hemisphere tumours, and this is thought to be related to the greater prevalence of desmoplastic tumours in adulthood. Few studies have addressed the MRI features of adult medulloblastoma and the specific characteristics of desmoplastic and classic tumours have not been analysed. Our aim was to analyse the imaging characteristics of desmoplastic (DM) and classic (CM) medulloblastomas in adult. We retrospectively studied preoperative MRI of six men and three women, median age 33 years, range 23-53 years, with pathologically proved medulloblastomas. There were six (67%) with DM. The tumour was in the cerebellar hemisphere in eight patients (89%), including the three with CM, one of which was bilateral. All tumours were heterogeneous, giving predominantly low or isointense signal on T1- and isointense signal on T2-weighted images. Cystic or necrotic areas in all patients were particularly visible on T2-weighted images. Contrast enhancement was absent in one DM and varied from slight to intense in eight (three CM), homogeneous in one DM and patchy in seven. All tumours extended to the surface of the cerebellum and two had well-defined margins. MRI does not allow a clear distinction between DM and CM in adults. (orig.)

  13. MRI findings of achilles tendon rupture

    International Nuclear Information System (INIS)

    Zhang Xuezhe

    2009-01-01

    Objective: To evaluate the MRI findings of achilles tendon rupture. Methods: The MRI data of 7 patients with achilles tendon rupture were retrospectively analysed. All 7 patients were male with the age ranging from 34 to 71 years. Routine MR scanning was performed in axial and sagittal planes, including T 1 WI, T 2 WI and a fat suppression MRI (SPIR). Results: Among 7 patients, complete achilles tendon rupture was seen in 6 cases, partial achilles tendon rupture 1 case. The site of tendon disruption were 2.6-11.0 cm( mean 5.4 cm) proximal to the insertion in the calcaneus. The MRI findings of a partial or complete rupture of the achilles tendon included enlarged and thickened achilles tendon (7 cases), wavy lax achilles tendon (2 cases), discontinuity of some or all of its fibers and intratendinous regions of increased signal intensity (7 cases). In the cases of complete tendon rupture, the size of the tendinous gap varied from 3.0-8.0 mm, which was filled with blood and appeared as edema of increase signal intensity on T 2 WI and SPIR. In all 7 patients, MR scanning showed medium signal intensity (7 cases) on T 1 WI, or medium signal intensity (1 cases), medium-high signal intensity (3 cases ), high signal intensity (3 cases) on T 2 WI, and medium-high signal intensity (2 cases), high signal intensity (5 cases) on fat suppression MRI. The preachilles fat pad showed obscure in 6 cases of complete achilles tendon rupture. Conclusion: MRI is an excellent method for revealing achilles tendon rupture and confirming the diagnosis. (authors)

  14. MRI findings in 100 epileptic children

    Energy Technology Data Exchange (ETDEWEB)

    Suzukawa, Junko; Sugimoto, Tateo; Araki, Atsushi (Kansai Medical School, Moriguchi, Osaka (Japan)) (and others)

    1993-02-01

    Findings of magnetic resonance imaging (MRI) of the brain were retrospectively reviewed in 100 consecutive pediatric patients with epilepsy in relation to the type of epilepsy and prognosis. There were 65 boys and 35 girls, ranging in age from 3 months to 25 years. Among 100 patients, 67 (a total of 102 lesions) showed abnormal findings on MRI. Morphological abnormalities, including ventricular enlargement, atrophy and malformation, were seen in 54 patients. Periventricular (n=14), frontal (n=3), temporal (n=8) and occipital (n=7) areas were of high signal intensity on T2-weighted images. According to the type of epilepsy, MRI abnormality was seen in 34 (61%) of 56 patients with partial seizures and 33 (76%) of 44 patients with generalized seizures. When associated with cerebral palsy and mental retardation, the incidence of MRI abnormality was high. There was no sigificant correlation between MRI findings and prognosis. (N.K.).

  15. PET/MRI for neurologic applications.

    Science.gov (United States)

    Catana, Ciprian; Drzezga, Alexander; Heiss, Wolf-Dieter; Rosen, Bruce R

    2012-12-01

    PET and MRI provide complementary information in the study of the human brain. Simultaneous PET/MRI data acquisition allows the spatial and temporal correlation of the measured signals, creating opportunities impossible to realize using stand-alone instruments. This paper reviews the methodologic improvements and potential neurologic and psychiatric applications of this novel technology. We first present methods for improving the performance and information content of each modality by using the information provided by the other technique. On the PET side, we discuss methods that use the simultaneously acquired MRI data to improve the PET data quantification. On the MRI side, we present how improved PET quantification can be used to validate several MRI techniques. Finally, we describe promising research, translational, and clinical applications that can benefit from these advanced tools.

  16. fMRI. Basics and clinical applications

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, Stephan; Jansen, Olav (eds.) [University Hospital of Schleswig-Holstein, Kiel (Germany). Inst. of Neuroradiology, Neurocenter

    2010-07-01

    Functional MRI (fMRI) and the basic method of BOLD imaging were introduced in 1993 by Seiji Ogawa. From very basic experiments, fMRI has evolved into a clinical application for daily routine brain imaging. There have been various improvements in both the imaging technique as such as well as in the statistical analysis. In this volume, experts in the field share their knowledge and point out possible technical barriers and problems explaining how to solve them. Starting from the very basics on the origin of the BOLD signal, the book covers technical issues, anatomical landmarks, presurgical applications, and special issues in various clinical fields. Other modalities for brain mapping such as PET, TMS, and MEG are also compared with fMRI. This book is intended to give a state-of-the-art overview and to serve as a reference and guide for clinical applications of fMRI. (orig.)

  17. MRI findings in 100 epileptic children

    International Nuclear Information System (INIS)

    Suzukawa, Junko; Sugimoto, Tateo; Araki, Atsushi

    1993-01-01

    Findings of magnetic resonance imaging (MRI) of the brain were retrospectively reviewed in 100 consecutive pediatric patients with epilepsy in relation to the type of epilepsy and prognosis. There were 65 boys and 35 girls, ranging in age from 3 months to 25 years. Among 100 patients, 67 (a total of 102 lesions) showed abnormal findings on MRI. Morphological abnormalities, including ventricular enlargement, atrophy and malformation, were seen in 54 patients. Periventricular (n=14), frontal (n=3), temporal (n=8) and occipital (n=7) areas were of high signal intensity on T2-weighted images. According to the type of epilepsy, MRI abnormality was seen in 34 (61%) of 56 patients with partial seizures and 33 (76%) of 44 patients with generalized seizures. When associated with cerebral palsy and mental retardation, the incidence of MRI abnormality was high. There was no sigificant correlation between MRI findings and prognosis. (N.K.)

  18. Virtual phantom magnetic resonance imaging (ViP MRI) on a clinical MRI platform.

    Science.gov (United States)

    Saint-Jalmes, Hervé; Bordelois, Alejandro; Gambarota, Giulio

    2018-01-01

    The purpose of this study was to implement Virtual Phantom Magnetic Resonance Imaging (ViP MRI), a technique that allows for generating reference signals in MR images using radiofrequency (RF) signals, on a clinical MR system and to test newly designed virtual phantoms. MRI experiments were conducted on a 1.5 T MRI scanner. Electromagnetic modelling of the ViP system was done using the principle of reciprocity. The ViP RF signals were generated using a compact waveform generator (dimensions of 26 cm × 18 cm × 16 cm), connected to a homebuilt 25 mm-diameter RF coil. The ViP RF signals were transmitted to the MRI scanner bore, simultaneously with the acquisition of the signal from the object of interest. Different types of MRI data acquisition (2D and 3D gradient-echo) as well as different phantoms, including the Shepp-Logan phantom, were tested. Furthermore, a uniquely designed virtual phantom - in the shape of a grid - was generated; this newly proposed phantom allows for the investigations of the vendor distortion correction field. High quality MR images of virtual phantoms were obtained. An excellent agreement was found between the experimental data and the inverse cube law, which was the expected functional dependence obtained from the electromagnetic modelling of the ViP system. Short-term time stability measurements yielded a coefficient of variation in the signal intensity over time equal to 0.23% and 0.13% for virtual and physical phantom, respectively. MR images of the virtual grid-shaped phantom were reconstructed with the vendor distortion correction; this allowed for a direct visualization of the vendor distortion correction field. Furthermore, as expected from the electromagnetic modelling of the ViP system, a very compact coil (diameter ~ cm) and very small currents (intensity ~ mA) were sufficient to generate a signal comparable to that of physical phantoms in MRI experiments. The ViP MRI technique was successfully implemented on a clinical MR

  19. Static and Dynamic Amplification Using Strong Mechanical Coupling

    KAUST Repository

    Ilyas, Saad

    2016-07-28

    Amplifying the signal-to-noise ratio of resonant sensors is vital toward the effort to miniaturize devices into the sub-micro and nano regimes. In this paper, we demonstrate theoretically and experimentally, amplification through mechanically coupled microbeams. The device is composed of two identical clamped-clamped beams, made of polyimide, connected at their middle through a third beam, which acts as a mechanical coupler. Each of the clamped-clamped microbeams and the coupler are designed to be actuated separately, hence providing various possibilities of actuation and sensing. The coupled resonator is driven into resonance near its first resonance mode and its dynamic behavior is explored via frequency sweeps. The results show significant amplification in the resonator amplitude when the signal is measured at the midpoint of the coupler compared with the response of the individual uncoupled beams. The static pull-in characteristics of the resonator are also studied. It is shown that the compliant mechanical coupler can serve as a low-power radio frequency switch actuated at low voltage loads. [2016-0100

  20. MRI of Wolfram syndrome (DIDMOAD)

    Energy Technology Data Exchange (ETDEWEB)

    Galluzzi, P.; Filosomi, G.; Vallone, I.M.; Venturi, C. [Dept. of Neuroradiology, Policlinico ' ' Le Scotte' ' , Siena (Italy); Bardelli, A.M. [Dept. of Ophthalmological Sciences, Unit of Paediatric Ophthalmology, University of Siena (Italy)

    1999-10-01

    Wolfram syndrome (DIDMOAD) is a rare diffuse neurodegenerative disorder characterised by diabetes insipidus, diabetes mellitus, optic atrophy, deafness, and a wide variety of abnormalities of the central nervous system, urinary tract and endocrine glands. It may be familial or sporadic. Reported features on MRI of the brain are absence of the physiological high signal of the posterior lobe of the pituitary, shrinkage of optic nerves, chiasm and tracts, atrophy of the hypothalamic region, brain stem, cerebellum, and cerebral cortex. We report a 12-year-old girl with a 5-year history without brain stem, cerebellar or cerebral atrophy. MRI showed an unusual feature: a focus of high signal on PD- and T2-weighted images in the right substantia nigra. This is consistent with previously reported neuropathological post-mortem studies, but has never been reported in vivo. (orig.)

  1. MRI of Wolfram syndrome (DIDMOAD)

    International Nuclear Information System (INIS)

    Galluzzi, P.; Filosomi, G.; Vallone, I.M.; Venturi, C.; Bardelli, A.M.

    1999-01-01

    Wolfram syndrome (DIDMOAD) is a rare diffuse neurodegenerative disorder characterised by diabetes insipidus, diabetes mellitus, optic atrophy, deafness, and a wide variety of abnormalities of the central nervous system, urinary tract and endocrine glands. It may be familial or sporadic. Reported features on MRI of the brain are absence of the physiological high signal of the posterior lobe of the pituitary, shrinkage of optic nerves, chiasm and tracts, atrophy of the hypothalamic region, brain stem, cerebellum, and cerebral cortex. We report a 12-year-old girl with a 5-year history without brain stem, cerebellar or cerebral atrophy. MRI showed an unusual feature: a focus of high signal on PD- and T2-weighted images in the right substantia nigra. This is consistent with previously reported neuropathological post-mortem studies, but has never been reported in vivo. (orig.)

  2. Hedgehog signaling pathway in neuroblastoma differentiation.

    Science.gov (United States)

    Souzaki, Ryota; Tajiri, Tatsuro; Souzaki, Masae; Kinoshita, Yoshiaki; Tanaka, Sakura; Kohashi, Kenichi; Oda, Yoshinao; Katano, Mitsuo; Taguchi, Tomoaki

    2010-12-01

    The hedgehog (Hh) signaling pathway is activated in some adult cancers. On the other hand, the Hh signaling pathway plays an important role in the development of the neural crest in embryos. The aim of this study is to show the activation of Hh signaling pathway in neuroblastoma (NB), a pediatric malignancy arising from neural crest cells, and to reveal the meaning of the Hh signaling pathway in NB development. This study analyzed the expression of Sonic hedgehog (Shh), GLI1, and Patched 1 (Ptch1), transactivators of Hh signaling pathway, by immunohistochemistry in 82 NB and 10 ganglioneuroblastoma cases. All 92 cases were evaluated for the status of MYCN amplification. Of the 92 cases, 67 (73%) were positive for Shh, 62 cases (67%) were positive for GLI1, and 73 cases (79%) were positive for Ptch1. Only 2 (10%) of the 20 cases with MYCN amplification were positive for Shh and GLI1, and 4 cases (20%) were positive for Ptch1 (MYCN amplification vs no MYCN amplification, P ≦ .01). The percentage of GLI1-positive cells in the cases with INSS stage 1 without MYCN amplification was significantly higher than that with INSS stage 4. Of 72 cases without MYCN amplification, 60 were GLI1-positive. Twelve cases were GLI1-negative, and the prognosis of the GLI1-positive cases was significantly better than that of the GLI1-negative cases (P = .015). Most of NBs without MYCN amplification were positive for Shh, GLI1, and Ptch1. In the cases without MYCN amplification, the high expression of GLI1 was significantly associated with early clinical stage and a good prognosis of the patients. In contrast to adult cancers, the activation of the Hh signaling pathway in NB may be associated with the differentiation of the NB. Copyright © 2010 Elsevier Inc. All rights reserved.

  3. Scintillation light detectors with Neganov-Luke amplification

    Energy Technology Data Exchange (ETDEWEB)

    Isaila, C. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany)]. E-mail: cisaila@ph.tum.de; Boslau, O. [Ketek GmbH, Gustav Heinemann Ring 125, 81739 Munich (Germany); Coppi, C. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); Feilitzsch, F. von [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); Goldstrass, P. [Ketek GmbH, Gustav Heinemann Ring 125, 81739 Munich (Germany); Jagemann, T. [Eberhard Karls Universitaet Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen (Germany); Jochum, J. [Eberhard Karls Universitaet Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen (Germany); Kemmer, J. [Ketek GmbH, Gustav Heinemann Ring 125, 81739 Munich (Germany); Lachenmaier, T. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); Lanfranchi, J.-C. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); Pahlke, A. [Ketek GmbH, Gustav Heinemann Ring 125, 81739 Munich (Germany); Potzel, W. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); Rau, W. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); Stark, M. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); Wernicke, D. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany); VeriCold Technologies GmbH, Bahnhofstrasse 21, 85737 Ismaning (Germany); Westphal, W. [Physik Department E15, Technische Universitaet Muenchen, James Franck Strasse, 85748 Garching (Germany)

    2006-04-15

    For an active suppression of the gamma and electron background in the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) dark matter experiment both phonons and scintillation light generated in a CaWO{sub 4} crystal are detected simultaneously. The phonon signal is read out by a transition edge sensor (TES) on the CaWO{sub 4} crystal. For light detection a silicon absorber equipped with a TES is employed. An efficient background discrimination requires very sensitive light detectors. The threshold can be improved by applying an electric field to the silicon crystal leading to an amplification of the thermal signal due to the Neganov-Luke effect. Measurements showing the improved sensitivity of the light detectors as well as future steps for reducing the observed extra noise will be presented.

  4. Scintillation light detectors with Neganov-Luke amplification

    International Nuclear Information System (INIS)

    Isaila, C.; Boslau, O.; Coppi, C.; Feilitzsch, F. von; Goldstrass, P.; Jagemann, T.; Jochum, J.; Kemmer, J.; Lachenmaier, T.; Lanfranchi, J.-C.; Pahlke, A.; Potzel, W.; Rau, W.; Stark, M.; Wernicke, D.; Westphal, W.

    2006-01-01

    For an active suppression of the gamma and electron background in the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) dark matter experiment both phonons and scintillation light generated in a CaWO 4 crystal are detected simultaneously. The phonon signal is read out by a transition edge sensor (TES) on the CaWO 4 crystal. For light detection a silicon absorber equipped with a TES is employed. An efficient background discrimination requires very sensitive light detectors. The threshold can be improved by applying an electric field to the silicon crystal leading to an amplification of the thermal signal due to the Neganov-Luke effect. Measurements showing the improved sensitivity of the light detectors as well as future steps for reducing the observed extra noise will be presented

  5. Shoulder MRI after surgical treatment of instability

    Energy Technology Data Exchange (ETDEWEB)

    Vahlensieck, Martin [University of Bonn, Department of Radiology, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Lang, Philipp [University of California San Francisco, Department of Radiology, 505 Pamassus Avenue, San Francisco, CA 94143 (United States); Wagner, Ulli [University of Bonn, Department of Orthopedic Surgery, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Moeller, Frank [University of Bonn, Department of Orthopedic Surgery, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Deimling, Urs van [University of Bonn, Department of Orthopedic Surgery, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany); Genant, H K [University of California San Francisco, Department of Radiology, 505 Pamassus Avenue, San Francisco, CA 94143 (United States); Schild, Hans H [University of Bonn, Department of Radiology, Sigmund-Freud-Strasse 25, 53105 Bonn (Germany)

    1999-04-01

    Objective: To analyze magnetic resonance imaging (MRI) findings of the shoulder after an instability operation. Materials and methods: Physical examinations, radiographs and MRI of 10 patients after anterior glenoid bone block insertion for ventral instability were compared. MRI included T{sub 1}-weighted spin-echo (TR=600, TE=20 ms) and T{sub 2}*-weighted gradient-echo sequences (TE=600, TE=18, Flip=30 deg.) in the axial, oblique-coronal and oblique-sagittal planes. Results: No patient suffered from recurrent subluxation. We found fusion of the bone block with the anterior glenoid in seven cases, dislocation of the bone block without contact to the glenoid in one case, and no visible bone block in two cases. On MRI, the bone block showed either signal intensity equivalent to fatty bone marrow (n=4) or was devoid of signal consistent with cortical bone or bone sclerosis (n=4). In all patients, a low signal intensity mass, 2-4 cm in diameter, was visible next to the glenoid insertion site. Conclusion: Insertion of a bone block onto the anterior glenoid induces formation of scar tissue, increasing the stability of the shoulder joint. This scar is well visible on MRI and forms independently of the behavior of the bone block itself. MRI is ideally suited for evaluating postoperative shoulder joints after bone-grafting procedures.

  6. Shoulder MRI after surgical treatment of instability

    International Nuclear Information System (INIS)

    Vahlensieck, Martin; Lang, Philipp; Wagner, Ulli; Moeller, Frank; Deimling, Urs van; Genant, H.K.; Schild, Hans H.

    1999-01-01

    Objective: To analyze magnetic resonance imaging (MRI) findings of the shoulder after an instability operation. Materials and methods: Physical examinations, radiographs and MRI of 10 patients after anterior glenoid bone block insertion for ventral instability were compared. MRI included T 1 -weighted spin-echo (TR=600, TE=20 ms) and T 2 *-weighted gradient-echo sequences (TE=600, TE=18, Flip=30 deg.) in the axial, oblique-coronal and oblique-sagittal planes. Results: No patient suffered from recurrent subluxation. We found fusion of the bone block with the anterior glenoid in seven cases, dislocation of the bone block without contact to the glenoid in one case, and no visible bone block in two cases. On MRI, the bone block showed either signal intensity equivalent to fatty bone marrow (n=4) or was devoid of signal consistent with cortical bone or bone sclerosis (n=4). In all patients, a low signal intensity mass, 2-4 cm in diameter, was visible next to the glenoid insertion site. Conclusion: Insertion of a bone block onto the anterior glenoid induces formation of scar tissue, increasing the stability of the shoulder joint. This scar is well visible on MRI and forms independently of the behavior of the bone block itself. MRI is ideally suited for evaluating postoperative shoulder joints after bone-grafting procedures

  7. [Investigation of RNA viral genome amplification by multiple displacement amplification technique].

    Science.gov (United States)

    Pang, Zheng; Li, Jian-Dong; Li, Chuan; Liang, Mi-Fang; Li, De-Xin

    2013-06-01

    In order to facilitate the detection of newly emerging or rare viral infectious diseases, a negative-strand RNA virus-severe fever with thrombocytopenia syndrome bunyavirus, and a positive-strand RNA virus-dengue virus, were used to investigate RNA viral genome unspecific amplification by multiple displacement amplification technique from clinical samples. Series of 10-fold diluted purified viral RNA were utilized as analog samples with different pathogen loads, after a series of reactions were sequentially processed, single-strand cDNA, double-strand cDNA, double-strand cDNA treated with ligation without or with supplemental RNA were generated, then a Phi29 DNA polymerase depended isothermal amplification was employed, and finally the target gene copies were detected by real time PCR assays to evaluate the amplification efficiencies of various methods. The results showed that multiple displacement amplification effects of single-strand or double-strand cDNA templates were limited, while the fold increases of double-strand cDNA templates treated with ligation could be up to 6 X 10(3), even 2 X 10(5) when supplemental RNA existed, and better results were obtained when viral RNA loads were lower. A RNA viral genome amplification system using multiple displacement amplification technique was established in this study and effective amplification of RNA viral genome with low load was achieved, which could provide a tool to synthesize adequate viral genome for multiplex pathogens detection.

  8. MRI findings of uveal metastases

    International Nuclear Information System (INIS)

    Chen Qinghua; Wang Zhenchang; Xian Junfang; Yan Fei; He Liyan; Tian Qichang; Yang Bentao; Liu Zhonglin

    2007-01-01

    Objective: To evaluate MR imaging findings of uveal metastases. Methods: MR imaging findings of 20 cases with uveal metastases comfirmed by pathology or follow-up were retrospectively analyzed. MR imaging was performed in 20 patients, of which postcontrast T 1 -weighted imaging was performed in 19 patients including dynamic contrast enhancement scanning in four cases. Results: Metastatic tumor was found in the iris and ciliary body in two cases, and in choroid in 18 cases. The tumor demonstrated slightly hypointense signal on T 1 -weighted imaging and isointense signal on T 2 -weighted imaging in two cases, isointense signal on T 1 -weighted imaging and isointense signal on T 2 -weighted imaging in nine cases, isointense signal on T 1 -weighted imaging and slightly hyperintense signal on T 2 -weighted imaging in three cases, isointense signal on T 1 -weighted imaging and slightly hypointense signal on T 2 - weighted imaging in three cases, slightly hyperintense signal on T 1 -weighted imaging and slightly hypointense signal on T 2 -weighted imaging in two cases, and slightly hyperintense signal on T 1 -weighted imaging and slightly hyperintense signal on T 2 -weighted imaging in one case. The tumor appeared as mild thickness of the wall of the globe in eight cases, a crescent mass in three cases, a fusiform mass in seven cases, and a nodule in two cases. Nineteen patients showed moderate or marked enhancement on postcontrast T 1 -weighted imaging. The time-intensity curve of dynamic contrast enhancement in four patients suggested a rapid enhancement and slow washout pattern. Retinal detachment was observed in 11 patients and abnormal signal intensity within the vitreous body was seen in two cases. Conclusion: MRI can display the location, shape, signal characteristics, and enhancement pattern of uveal metastases, contributing to diagnosis and differential diagnosis. (authors)

  9. Helicase-dependent amplification of nucleic acids.

    Science.gov (United States)

    Cao, Yun; Kim, Hyun-Jin; Li, Ying; Kong, Huimin; Lemieux, Bertrand

    2013-10-11

    Helicase-dependent amplification (HDA) is a novel method for the isothermal in vitro amplification of nucleic acids. The HDA reaction selectively amplifies a target sequence by extension of two oligonucleotide primers. Unlike the polymerase chain reaction (PCR), HDA uses a helicase enzyme to separate the deoxyribonucleic acid (DNA) strands, rather than heat denaturation. This allows DNA amplification without the need for thermal cycling. The helicase used in HDA is a helicase super family II protein obtained from a thermophilic organism, Thermoanaerobacter tengcongensis (TteUvrD). This thermostable helicase is capable of unwinding blunt-end nucleic acid substrates at elevated temperatures (60° to 65°C). The HDA reaction can also be coupled with reverse transcription for ribonucleic acid (RNA) amplification. The products of this reaction can be detected during the reaction using fluorescent probes when incubations are conducted in a fluorimeter. Alternatively, products can be detected after amplification using a disposable amplicon containment device that contains an embedded lateral flow strip. Copyright © 2013 John Wiley & Sons, Inc.

  10. MRI manifestations of severe SSPE in infants

    International Nuclear Information System (INIS)

    Liu Hui; Xiao Enhua; Tan Lihua; Wu Xiaochuan; Fan Songqing

    2006-01-01

    Objective: To improve the understanding of MRI findings in severe SSPE. Methods: The MRI features in 2 cases of severe SSPE confirmed by pathology were reported, and related literature was reviewed. Results: In one case, various degrees of asymmetrical cerebral swelling were seen in bilateral gray matter and white matter under the cortex, and without clear dividing line between gray and white matter, especially in temporal lobe. Abnormal signals were revealed on T 1 and T 2 WI. In another case, lesions in the brain stem, temporal lobe, globus pallidus, putamen, thalamus, and radiate coronet showed hypointense signal on T 1 WI and hyperintense signal on T 2 WI with cerebral swelling, and no obviouse cerebral atrophy was found. The local abnormal lesions had occupying effects and enhancement in both cases. Conclusion: Lasting of various degrees of cerebral swelling may be the characteristic sign on MRI in severe SSPE, differing from cerebral atrophy that might be seen in common SSPE. (authors)

  11. Amplification through chaotic synchronization in spatially extended beam-plasma systems

    Science.gov (United States)

    Moskalenko, Olga I.; Frolov, Nikita S.; Koronovskii, Alexey A.; Hramov, Alexander E.

    2017-12-01

    In this paper, we have studied the relationship between chaotic synchronization and microwave signal amplification in coupled beam-plasma systems. We have considered a 1D particle-in-cell numerical model of unidirectionally coupled beam-plasma oscillatory media being in the regime of electron pattern formation. We have shown the significant gain of microwave oscillation power in coupled beam-plasma media being in the different regimes of generation. The discovered effect has a close connection with the chaotic synchronization phenomenon, so we have observed that amplification appears after the onset of the complete time scale synchronization regime in the analyzed coupled spatially extended systems. We have also provided the numerical study of physical processes in the chain of beam-plasma systems leading to the chaotic synchronization and the amplification of microwave oscillations power, respectively.

  12. Highly sensitive chemiluminescent point mutation detection by circular strand-displacement amplification reaction.

    Science.gov (United States)

    Shi, Chao; Ge, Yujie; Gu, Hongxi; Ma, Cuiping

    2011-08-15

    Single nucleotide polymorphism (SNP) genotyping is attracting extensive attentions owing to its direct connections with human diseases including cancers. Here, we have developed a highly sensitive chemiluminescence biosensor based on circular strand-displacement amplification and the separation by magnetic beads reducing the background signal for point mutation detection at room temperature. This method took advantage of both the T4 DNA ligase recognizing single-base mismatch with high selectivity and the strand-displacement reaction of polymerase to perform signal amplification. The detection limit of this method was 1.3 × 10(-16)M, which showed better sensitivity than that of most of those reported detection methods of SNP. Additionally, the magnetic beads as carrier of immobility was not only to reduce the background signal, but also may have potential apply in high through-put screening of SNP detection in human genome. Copyright © 2011 Elsevier B.V. All rights reserved.

  13. ESTIMATION OF AMPLIFICATION FACTOR IN EARTHQUAKE ENGINEERING

    Directory of Open Access Journals (Sweden)

    Nazarov Yuriy Pavlovich

    2015-03-01

    Full Text Available The authors are the developers of Odyssey Software (Eurosoft Co. for the analysis of seismological data and computing of seismic loads and their parameters. While communicating with the users of the software, the authors have revealed some uncertainty about both understanding of the term "amplification factor (AF" and calculation of the amplification factor using various methods. In this article, a simple example shows that the determination of the amplification factor as the ratio of the acceleration’s spectrum to the maximal acceleration is derived from the classical definition of AF in the form of the ratio of maximal dynamic displacement to the displacement by the action of static load. Deterministic and probabilistic ap-proaches for the calculating of the AF were discussed. There was an example of AFs calculation and their envelopes for translational and rotational components of seismic impact by using Odyssey Software.

  14. Amplification of hofmeister effect by alcohols.

    Science.gov (United States)

    Xu, Yun; Liu, Guangming

    2014-07-03

    We have demonstrated that Hofmeister effect can be amplified by adding alcohols to aqueous solutions. The lower critical solution temperature behavior of poly(N-isopropylacrylamide) has been employed as the model system to study the amplification of Hofmeister effect. The alcohols can more effectively amplify the Hofmeister effect following the series methanol alcohols and following the series d-sorbitol ≈ xylitol ≈ meso-erythritol alcohols. Our study reveals that the relative extent of amplification of Hofmeister effect is determined by the stability of the water/alcohol complex, which is strongly dependent on the chemical structure of alcohols. The more stable solvent complex formed via stronger hydrogen bonds can more effectively differentiate the anions through the anion-solvent complex interactions, resulting in a stronger amplification of Hofmeister effect. This study provides an alternative method to tune the relative strength of Hofmeister effect besides salt concentration.

  15. Lidar using the backscatter amplification effect

    Science.gov (United States)

    Razenkov, Igor A.; Banakh, Victor A.

    2018-04-01

    Experimental data proving the possibility of lidar measurement of the refractive turbulence strength based on the effect of backscatter amplification (BSA) are reported. It is shown that the values of the amplification factor correlate with the variance of random jitter of optical image of an incoherent light source depending on the value of the structure constant of the air refractive index turbulent fluctuations averaged over the probing path. This paper presents the results of measurements of the BSA factor in comparison with the simultaneous measurements of the BSA peak, which is very narrow and only occurs on the laser beam axis. It is constructed the range-time images of the derivative of the amplification factor gives a comprehensive picture of the location of turbulent zones and their temporal dynamics.

  16. MRI features of placenta accreta

    International Nuclear Information System (INIS)

    Cao Manrui; Du Mu; Huang Yi; Liu Bingguang; Zhang Fangjing; Guo Jimin; Zhu Zhijun

    2012-01-01

    Objective: To investigate the MRI features of placenta accreta. Methods: From Apr 2009 to Jun 2011, 15 patients with placenta accrete received MRI examination. In them, placenta accreta was diagnosed based on clinical manifestations or postoperative histopathology. The MR features of placenta accreta in them (study group) were retrospectively analyzed and compared with those in 15 pregnant women without placenta accreta (control group) with Fisher exact test. Results: In the 15 patients with placenta accreta,uterine bulging and (or) a focal outward contour bulge was detected in 14 patients; heterogeneous signal intensity in the placenta was detected in 15 patients; dark intraplacental bands on T 2 -weighted images was detected in 15 patients; and increased subplacental vascularity was detected in 11 patients on T 1 - weighted images. In the study group, 14 patients showed at least three of the above four features, and in all of them uterine bulging and (or) a focal outward contour bulge, heterogeneous signal intensity in the placenta and dark intraplacental bands on T 2 -weighted images were detected; one patient showed heterogeneous signal intensity in the placenta, dark intraplacental bands on T 2 -weighted images and increased subplacental vascularity. In the control group,none patient had three of the above features.Uterine bulging and (or) a focal outward contour bulge, heterogeneous signal intensity in the placenta, dark intraplacental bands on T 2 -weighted images and increased subplacental vascularity were detected in 3, 6, 3 and 4 patients (P=0.000, 0.001, 0.000 and 0.027), respectively. Conclusions: The main MRI features of placenta accreta are uterine bulging and (or) a focal outward contour bulge, heterogeneous signal intensity in the placenta and dark intraplacental bands on T 2 -weighted images Besides, increased subplacental vascularity also could provide useful information for the diagnosis of placenta accreta. (authors)

  17. Optical nano-biosensing interface via nucleic acid amplification strategy: construction and application.

    Science.gov (United States)

    Zhou, Hong; Liu, Jing; Xu, Jing-Juan; Zhang, Shu-Sheng; Chen, Hong-Yuan

    2018-03-21

    Modern optical detection technology plays a critical role in current clinical detection due to its high sensitivity and accuracy. However, higher requirements such as extremely high detection sensitivity have been put forward due to the clinical needs for the early finding and diagnosing of malignant tumors which are significant for tumor therapy. The technology of isothermal amplification with nucleic acids opens up avenues for meeting this requirement. Recent reports have shown that a nucleic acid amplification-assisted modern optical sensing interface has achieved satisfactory sensitivity and accuracy, high speed and specificity. Compared with isothermal amplification technology designed to work completely in a solution system, solid biosensing interfaces demonstrated better performances in stability and sensitivity due to their ease of separation from the reaction mixture and the better signal transduction on these optical nano-biosensing interfaces. Also the flexibility and designability during the construction of these nano-biosensing interfaces provided a promising research topic for the ultrasensitive detection of cancer diseases. In this review, we describe the construction of the burgeoning number of optical nano-biosensing interfaces assisted by a nucleic acid amplification strategy, and provide insightful views on: (1) approaches to the smart fabrication of an optical nano-biosensing interface, (2) biosensing mechanisms via the nucleic acid amplification method, (3) the newest strategies and future perspectives.

  18. NAIMA: target amplification strategy allowing quantitative on-chip detection of GMOs.

    Science.gov (United States)

    Morisset, Dany; Dobnik, David; Hamels, Sandrine; Zel, Jana; Gruden, Kristina

    2008-10-01

    We have developed a novel multiplex quantitative DNA-based target amplification method suitable for sensitive, specific and quantitative detection on microarray. This new method named NASBA Implemented Microarray Analysis (NAIMA) was applied to GMO detection in food and feed, but its application can be extended to all fields of biology requiring simultaneous detection of low copy number DNA targets. In a first step, the use of tailed primers allows the multiplex synthesis of template DNAs in a primer extension reaction. A second step of the procedure consists of transcription-based amplification using universal primers. The cRNA product is further on directly ligated to fluorescent dyes labelled 3DNA dendrimers allowing signal amplification and hybridized without further purification on an oligonucleotide probe-based microarray for multiplex detection. Two triplex systems have been applied to test maize samples containing several transgenic lines, and NAIMA has shown to be sensitive down to two target copies and to provide quantitative data on the transgenic contents in a range of 0.1-25%. Performances of NAIMA are comparable to singleplex quantitative real-time PCR. In addition, NAIMA amplification is faster since 20 min are sufficient to achieve full amplification.

  19. Optic nerve injury demonstrated by MRI with STIR sequences

    International Nuclear Information System (INIS)

    Takehara, S.; Tanaka, T.; Uemura, K.; Shinohara, Y.; Yamamoto, T.; Tokuyama, T.; Satoh, A.

    1994-01-01

    We studied nine patients with optic nerve injury associated with closed head trauma by magnetic resonance imaging (MRI) with short inversion time inversion recovery (STIR) sequences on 11 occasions from 4 days to 14 years after the injury: three studies were within 17 days and eight over 4 months to 14 years. MRI revealed abnormal high signal in 10 of the 11 injured nerves. MRI 4 days after the injury showed no abnormality. (orig.)

  20. MRI Compatibility of Robot Actuation Techniques – A Comparative Study

    OpenAIRE

    Fischer, Gregory S.; Krieger, Axel; Iordachita, Iulian; Csoma, Csaba; Whitcomb, Louis L.; Fichtinger, Gabor

    2008-01-01

    This paper reports an experimental evaluation of the following three different MRI-compatible actuators: a Shinsei ultrasonic motor, a Nanomotion ultrasonic motor and a pneumatic cylinder actuator. We report the results of a study comparing the effect of these actuators on the signal to noise ratio (SNR) of MRI images under a variety of experimental conditions. Evaluation was performed with the controller inside and outside the scanner room and with both 1.5T and 3T MRI scanners. Pneumatic cy...

  1. Beyond Words: Amplification of Cancer Risk Communication on Social Media.

    Science.gov (United States)

    Strekalova, Yulia A; Krieger, Janice L

    2017-10-01

    Social media provide a unique channel for disseminating evidence-based information to diverse audiences and organizational and private stakeholders, thus facilitating a dialog about health and health risks. Guided by the social amplification of risk framework, the goal of this study was to assess the level of audience engagement with messages posted on the National Cancer Institute (NCI) Facebook page and evaluate the differences in the audience information behavior toward risk-related and non-risk posts. Data included 1,975 posts published on the NCI Facebook page as well as the corresponding 4,537 comments, 77,298 shares, and 145,462 likes. Links and images were the top two most frequent types of content for both risk-related and non-risk posts, but risk-related messages were more amplified through comments, shares, and likes. Comparing the modality of risk-related messages, videos, contrary to the prediction, were not more effective in attracting audience engagement than images. Finally, comments to risk-related posts did not repeat risk-related language suggesting that future studies should examine risk signal recognition and dissemination as separate behaviors. This study's findings emphasize the importance of focused investigation of message design strategies and message effects on the dissemination and amplification of communication related to health risks.

  2. Mutually incoherent beam combining through optical parametric amplification

    International Nuclear Information System (INIS)

    Tropheme, B.

    2012-01-01

    This work deals with a technique of combination of coherent beams: Optical Parametric Amplification (OPA) with Multiple Pumps. This technique is used to instantly transfer the energy of several pumps on one beam, without energy storage and thus avoiding thermal effects in the amplifying media. It can be useful to combine energy of numerous fiber lasers and to amplify with a high repetition rate very high energy lasers or broadband pulses. With a numerical and experimental study using BBO and LBO as nonlinear crystal, we determine how to dispose the pumps around the signal and the corresponding angular tolerances of such set up. Then we focus our attention on recombining mechanisms between a pump and a non-corresponding idler. We demonstrate experimentally that these cascading effects may decrease the spatial and spectral quality of the amplified signal, and that these phenomena can be avoided with a minimum angle between the different pumps. A novel modelling of multi-pumps OPA links these cascading effects to the gratings generated by the interaction between the pumps. The last part presents a 5 pump OPA experiment. We achieve a pump-to-signal efficiency of 27% and so that a signal more powerful than each pump is obtained. (author) [fr

  3. Comparison of different cardiac MRI sequences at 1.5T/3.0T with respect to signal-to-noise and contrast-to-noise ratios - initial experience

    International Nuclear Information System (INIS)

    Gutberlet, M.; Spors, B.; Grothoff, M.; Freyhardt, P.; Schwinge, K.; Plotkin, M.; Amthauer, H.; Felix, R.

    2004-01-01

    Purpose: To compare image quality, signal-to-noise (SNR) and contrast-to-noise ratios (CNR) of different MRI sequences for cardiac imaging at 1.5 T and 3.0 T in volunteers. Material and Methods: 10 volunteers (5 male, 5 female) with a mean age of 33 years (±8) without any history of cardiac diseases were examined on a GE Signa 3.0 T and a GE Signa 1.5 T TwinSpeed Excite (GE Medical Systems, Milwaukee, WI, USA) scanner using a 4-element phased array surface coil (same design) on the same day. For tissue characterization ECG gated Fast Spinecho (FSE) T 1 - (Double IR), T 1 -STIR (Triple IR) and T 2 -weighted sequences in transverse orientation were used. For functional analysis a steady state free precession (SSFP-FIESTA) sequence was performed in the 4-chamber, 2-chamber long axis and short axis view. The flip angle used for the SSFP sequence at 3.0 T was reduced from 45 to 30 to keep short TR times while staying within the pre-defined SAR limitations. All other sequence parameters were kept constant. Results: All acquisitions could successfully be completed for the 10 volunteers. The mean SNR 3.0 T compared to 1.5 T was remarkably increased (p 2 - (160% SNR increase), the STIR-T 1 - (123%) and the T 1 - (91%) weighted FSE. Similar results were found comparing CNR at 3.0 T and 1.5 T. The mean SNR achieved using the SSFP sequences was more than doubled by 3.0 T (150%), but did not have any significant effect on the CNR. The image quality at 3.0 T did not appear to be improved, and was considered to be significantly worse when using SSFP sequences. Artefacts like shading in the area of the right ventricle (RV) were found to be more present at 3.0 T using FSE sequences. After a localized shim had been performed in 5/10 volunteers at the infero-lateral wall of the left ventricle (LV) with the SSFP sequences at 3.0 T no significant increase in artefacts could be detected. (orig.) [de

  4. Magnetic Resonance Imaging (MRI) Safety

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Magnetic Resonance Imaging (MRI) Safety What is MRI and how ... What is MRI and how does it work? Magnetic resonance imaging, or MRI, is a way of obtaining ...

  5. MRI diagnosis of pigmented villonodular synovitis

    International Nuclear Information System (INIS)

    Shang Zhongpu; Sui Zhengyan; Xue Jianrong; Song Cuizhi; Liu Yuekui; Li Jinwang

    2007-01-01

    Objective: To explore the MRI characteristics of pigmented villonodular synovitis. Methods: MRI and clinic data of 14 patients with pigmented villonodular synovitis proved by pathology were reviewed retrospectively. Results: MRI showed diffusible lesions in all 14 cases. 12 cases were located in knee joint, 2 in hip. MRI revealed nodules and masses formed by villis hyperplasia in the joints. MRI demonstrated the nodules with slightly low signal intensity on both T 1 WI and T 2 WI in 13 cases, the destruction of the cartilage in 8 cases, the destruction of the ligament in 5 cases, and the hydropsy in joint cavity in 10 cases, the destruction of the meniscus in 2 cases. Conclusion: The typical features of pigmented villonodular synovitis on MRI revealed the nodules formed by villis hyperplasia in the joint. Hemosiderin in the nodules demonstrated slightly low signal intensity on both T 1 WI and T 2 WI, with the presence of typical features like 'foam rubber cushion' sign and 'lichen' sign. (authors)

  6. MRI of the Chest

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    Full Text Available ... examination poses almost no risk to the average patient when appropriate safety guidelines are followed. If sedation is used, there ... patient story here Images × ... Imaging (MRI) Safety Contrast Materials MRI Safety During Pregnancy Images related ...

  7. MRI of the Chest

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    Full Text Available ... to a CD or uploaded to a digital cloud server. MRI of the chest gives detailed pictures ... over time. top of page What are the benefits vs. risks? Benefits MRI is a noninvasive imaging ...

  8. MRI of the Chest

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    Full Text Available ... images and send a signed report to your primary care or referring physician, who will share the ... This detail makes MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has ...

  9. MRI of the Chest

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    Full Text Available ... metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In most cases, an MRI exam is safe for patients with metal implants, except for a few types. ...

  10. MRI of the Chest

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    Full Text Available ... interfere with the magnetic field of the MRI unit, metal and electronic items are not allowed in ... does the equipment look like? The traditional MRI unit is a large cylinder-shaped tube surrounded by ...

  11. MRI of the Chest

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    Full Text Available ... items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings In most cases, an MRI exam is safe for patients with metal implants, except for a ...

  12. MRI of the Chest

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    Full Text Available ... metallic items, which can distort MRI images removable dental work pens, pocket knives and eyeglasses body piercings ... tomography (CT) scans, MRI does not utilize ionizing radiation. Instead, radiofrequency pulses re-align hydrogen atoms that ...

  13. MRI of the Chest

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    Full Text Available ... women should not have this exam in the first three to four months of pregnancy unless the ... not to have an MRI exam during the first trimester unless medically necessary. MRI may not always ...

  14. MRI of the Chest

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    Full Text Available ... important to assess the health and function of these structures (heart, valves, great vessels, etc.). top of ... room. In addition to affecting the MRI images, these objects can become projectiles within the MRI scanner ...

  15. MRI of the Chest

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    Full Text Available ... conditions. MRI uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures ... may follow your regular daily routine and take food and medications as usual. Some MRI examinations may ...

  16. MRI of the Chest

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    Full Text Available ... are the limitations of MRI of the Chest? What is MRI of the Chest? Magnetic resonance imaging ( ... heart, valves, great vessels, etc.). top of page What are some common uses of the procedure? MR ...

  17. MRI of the Chest

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    Full Text Available ... is done because a potential abnormality needs further evaluation with additional views or a special imaging technique. ... MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has proven valuable in ...

  18. MRI of the Chest

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    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... used in MRI exams is less likely to produce an allergic reaction than the iodine-based contrast ...

  19. MRI of the Chest

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    Full Text Available ... or headphones during the exam. MRI scanners are air-conditioned and well-lit. Music may be played ... the limitations of MRI of the Chest? High-quality images are assured only if you are able ...

  20. MRI of the Chest

    Science.gov (United States)

    ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... tissue and fluid, known as edema . MRI typically costs more and may take more time to perform ...

  1. MRI of the Chest

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    Full Text Available ... MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help ... tissue and fluid, known as edema . MRI typically costs more and may take more time to perform ...

  2. MRI of the Chest

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    Full Text Available ... clearer and more detailed than with other imaging methods. This detail makes MRI an invaluable tool in ... might be obscured by bone with other imaging methods. The contrast material used in MRI exams is ...

  3. MRI of the Chest

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    Full Text Available ... top of page What are the benefits vs. risks? Benefits MRI is a noninvasive imaging technique that ... risking the side effects of conventional (catheter) angiography . Risks The MRI examination poses almost no risk to ...

  4. MRI of the Chest

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    Full Text Available ... MRI examination poses almost no risk to the average patient when appropriate safety guidelines are followed. If ... tissue and fluid, known as edema . MRI typically costs more and may take more time to perform ...

  5. MRI of the Chest

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    Full Text Available ... other internal body structures. MRI does not use ionizing radiation (x-rays). Detailed MR images allow physicians ... computed tomography (CT) scans, MRI does not utilize ionizing radiation. Instead, radiofrequency pulses re-align hydrogen atoms ...

  6. MRI of the Chest

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    Full Text Available ... This detail makes MRI an invaluable tool in early diagnosis and evaluation of cardiovascular conditions. MRI has ... have special pediatric considerations. The teddy bear denotes child-specific content. Related Articles and Media MR Angiography ( ...

  7. Canalis basilaris medianus: MRI

    International Nuclear Information System (INIS)

    Jacquemin, C.; Bosley, T.M.; Al Saleh, M.; Mullaney, P.

    2000-01-01

    We report the MRI appearances of an developmental anatomical variant of the basiocciput, with neuroimaging findings (CT and MRI). Such variants are commonly asymptomatic, but may be associated with episodes of meningitis. (orig.)

  8. 7 T renal MRI : challenges and promises

    NARCIS (Netherlands)

    de Boer, A.; Hoogduin, J.M.; Blankestijn, P.J.; Li, X.; Luijten, P.R.; Metzger, G.J.; Raaijmakers, A.J.E.; Umutlu, L.; Visser, F.; Leiner, T.

    The progression to 7 Tesla (7 T) magnetic resonance imaging (MRI) yields promises of substantial increase in signal-to-noise (SNR) ratio. This increase can be traded off to increase image spatial resolution or to decrease acquisition time. However, renal 7 T MRI remains challenging due to

  9. MRI of Neurosyphilis Presenting as Mesiotemporal Abnormalities: a Case Report

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Yu Mi; Hwang, Hee Young; Kim, Hyung Sik [Gachon University, Gil Medical Center, Incheon (Korea, Republic of)

    2009-06-15

    The high signal intensities in bilateral mesiotemporal lobes on T2-weighted images are typical findings of herpes encephalitis or paraneoplastic limbic encephalitis. We report a case of neurosyphilis with mesiotemporal involvement on MRI. Positive antibodies in the cerebrospinal fluid confirmed the diagnosis. The results suggest that neurosyphilis should be considered when MRI results indicate mesiotemporal abnormalities.

  10. Amplification in Technical Manuals: Theory and Practice.

    Science.gov (United States)

    Killingsworth, M. Jimmie; And Others

    1989-01-01

    Examines how amplification (rhetorical techniques by which discourse is extended to enhance its appeal and information value) tends to increase and improve the coverage, rationale, warnings, behavioral alternatives, examples, previews, and general emphasis of technical manuals. Shows how classical and modern rhetorical theories can be applied to…

  11. Intelligence amplification framework for enhancing scheduling processes

    NARCIS (Netherlands)

    Dobrkovic, Andrej; Liu, Luyao; Iacob, Maria Eugenia; van Hillegersberg, Jos

    2016-01-01

    The scheduling process in a typical business environment consists of predominantly repetitive tasks that have to be completed in limited time and often containing some form of uncertainty. The intelligence amplification is a symbiotic relationship between a human and an intelligent agent. This

  12. Noise amplification of plant gravisensing

    Science.gov (United States)

    Ma, Zhong; Hasenstein, Karl H.

    A common problem in sensory physiology is the detection of