Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Q24: Novel Instrumentation and Measurements for Biomedical Research |
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Sponsoring Units: GIMS Chair: Larry Nagahara, Office of Physical Scinences - Oncology, National Cancer Institute Room: 504 |
Wednesday, March 5, 2014 2:30PM - 2:42PM |
Q24.00001: Numerical dosimetry of transcranial magnetic stimulation coils Lawrence Crowther, Ravi Hadimani, David Jiles Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique capable of stimulating neurons by means of electromagnetic induction. TMS can be used to map brain function and shows promise for the diagnosis and treatment of neurological and psychiatric disorders. Calculation of fields induced in the brain are necessary to accurately identify stimulated neural tissue during TMS. This allows the development of novel TMS coil designs capable of stimulating deeper brain regions and increasing the localization of stimulation that can be achieved. We have performed numerical calculations of magnetic and electric field with high-resolution anatomically realistic human head models to find these stimulated brain regions for a variety of proposed TMS coil designs. The realistic head models contain heterogeneous tissue structures and electrical conductivities, yielding superior results to those obtained from the simplified homogeneous head models that are commonly employed. The attenuation of electric field as a function of depth in the brain and the localization of stimulating field have been methodically investigated. In addition to providing a quantitative comparison of different TMS coil designs the variation of induced field between subjects has been investigated. We also show the differences in induced fields between adult, adolescent and child head models to preemptively identify potential safety issues in the application of pediatric TMS. [Preview Abstract] |
Wednesday, March 5, 2014 2:42PM - 2:54PM |
Q24.00002: Novel transcranial magnetic stimulation coil for mice Stephen March, Spencer Stark, Lawrence Crowther, Ravi Hadimani, David Jiles Transcranial magnetic stimulation (TMS) shows potential for non-invasive treatment of various neurological disorders. Significant work has been performed on the design of coils used for TMS on human subjects but few reports have been made on the design of coils for use on the brains of animals such as mice. This work is needed as TMS studies utilizing mice can allow rapid preclinical development of TMS for human disorders but the coil designs developed for use on humans are inadequate for optimal stimulation of the much smaller mouse brain. A novel TMS coil has been developed with the goal of inducing strong and focused electric fields for the stimulation of small animals such as mice. Calculations of induced electric fields were performed utilizing an MRI derived inhomogeneous model of an adult male mouse. Mechanical and thermal analysis of this new TMS helmet-coil design have also been performed at anticipated TMS operating conditions to ensure mechanical stability of the new coil and establish expected linear attraction and rotational force values. Calculated temperature increases for typical stimulation periods indicate the helmet-coil system is capable of operating within established medical standards. A prototype of the coil has been fabricated and characterization results are presented. [Preview Abstract] |
Wednesday, March 5, 2014 2:54PM - 3:06PM |
Q24.00003: A Label-Free, Redox Biosensor for Detection of Disease Biomarkers Michelle M. Archibald, Binod Rizal, Timothy Connolly, Michael J. Burns, Michael J. Naughton, Thomas C. Chiles Technologies to detect early stage cancer would provide significant benefit to cancer disease patients. Clinical measurement of biomarkers offers the promise of a noninvasive and cost effective screening for early stage detection. We have developed a novel 3-dimensional ``nanocavity'' array for the detection of human cancer biomarkers in serum and other fluids. This all-electronic diagnostic sensor is based on a nanoscale coaxial array architecture that we have modified to enable molecular-level detection and identification. Each individual sensor in the array is a vertically-oriented coaxial capacitor, whose dielectric impedance is measurably changed when target molecules enter the coax annulus. We are designing a nanocoaxial biosensor based on electronic response to antibody recognition of a specific disease biomarker ($e.g.$ CA-125 for early-stage ovarian cancer) on biofunctionalized metal surfaces within the nanocoax structure, thereby providing an all-electronic, ambient temperature, rapid-response, label-free redox biosensor. Our results demonstrate the feasibility of using this nanocoaxial array as an ultrasensitive device to detect a wide range of target proteins, including disease biomarkers. [Preview Abstract] |
Wednesday, March 5, 2014 3:06PM - 3:18PM |
Q24.00004: Nanocoax neurointerface array recordings of \textit{Hirudo medicinalis} neurons Jeffrey R. Naughton, Binod Rizal, Margaret H. Aasen, Michael J. Burns, Thomas C. Chiles, Michael J. Naughton We report results for a nanocoax-based neuroelectronic array. The device was used in real time to noninvasively couple to a ganglion sac located along the main nerve cord of the leech \textit{Hirudo medicinalis}. This allowed for extracellular recording of synaptic activity in the form of spontaneous synapse firing in pre- and post-synaptic somata. In addition, we show the ability to actuate localized stimulation (Faradaic regime) which, in some circumstances, appears to facilitate electroporation, which itself enables intracellular measurements. In conjunction with this latter recording with one subarray, we measured changes in the local field potential (extracellular) with another array at a second site, allowing us to calculate the action potential propagation or conduction speed. [Preview Abstract] |
Wednesday, March 5, 2014 3:18PM - 3:30PM |
Q24.00005: Unlocking the Full Potential of MR Imaging of Multi-Spin Solids Jared Rovny, Sean Barrett, Merideth Frey Advances in magnetic resonance pulse sequences have allowed dramatic increases in imaging resolution of single-spin solids by exploiting the internal dynamics of radio-frequency pulses. The ``Quadratic Echo" pulse sequence [1] used to accomplish this provides results about 1000-fold worse when applied to multi-spin solids primarily due to heteronuclear dipolar interactions. Our preliminary goal is to discover an effective decoupling scheme for Phosphorus and Hydrogen in wet bone samples and integrate it with the complicated Quadratic Echo pulse sequence by advancing our understanding of the Hamiltonian dynamics of these systems. Initial trials will focus on simple systems and naive decoupling schemes, the results of which will serve to improve our understanding of the internal spin dynamics and guide further trials. Results will be presented from a benchmark study of Ammonium Dihydrogen Phosphate crystal as a simple multi-spin system under continuous-wave decoupling. Implications of these results and further possibilities for more complicated decoupling schemes will be discussed. [1] Proc. Natl. Acad. Sci. USA \textbf{109}, 5190 (2012) [Preview Abstract] |
Wednesday, March 5, 2014 3:30PM - 3:42PM |
Q24.00006: Accelerating multidimensional NMR and MRI experiments using iterated maps Sean Barrett, Merideth Frey, Zachary Sethna, Gregory Manley, Suvrajit Sengupta, Kurt Zilm, J. Patrick Loria Techniques that accelerate data acquisition without sacrificing the advantages of fast Fourier transform (FFT) reconstruction could benefit a wide variety of magnetic resonance experiments. Here we discuss an approach for reconstructing multidimensional nuclear magnetic resonance (NMR) spectra and MR images from sparsely-sampled time domain data, by way of iterated maps [1]. This method exploits the computational speed of the FFT algorithm and is done in a deterministic way, by reformulating any \textit{a priori} knowledge or constraints into projections, and then iterating. In this paper we explain the motivation behind this approach, the formulation of the specific projections, the benefits of using a `QUasi-Even Sampling, plus jiTter' (QUEST) sampling schedule, and various methods for handling noise. Applying the iterated maps method to real 2D NMR and 3D MRI of solids data, we show that it is flexible and robust enough to handle large data sets with significant noise and artifacts. [1] M. A. Frey, Z. Sethna et al., Journal of Magnetic Resonance v237, 100 (2013). [Preview Abstract] |
Wednesday, March 5, 2014 3:42PM - 4:18PM |
Q24.00007: TBD Invited Speaker: Thomas Thundat |
Wednesday, March 5, 2014 4:18PM - 4:30PM |
Q24.00008: Feedback-driven tracking and trapping of a single fluorescent nanoparticle in a confocal microscope Lloyd Davis, James Germann, Jason King, Brian Canfield Improved techniques for recording the three-dimensional motion and spectroscopic dynamics of single fluorescent emitters with ever higher temporal and spatial resolution and for longer periods of observation will benefit future studies of molecular behavior and cellular mechanisms in biomedical research. Feedback-driven tracking and trapping, which relies on rapid determination of particle position followed by low latency application of motion to counteract Brownian diffusion, has been demonstrated by a number of techniques, each with their advantages and shortcommings. We have recently demonstrated a new method for tracking the motion of single emitters with diffusivities up to $\sim$ 12 square-microns/second by use of a confocal fluorescence microscope with four slightly spatially offset temporally modulated laser foci for position determination and a 3D-piezo stage to counteract diffusion. Here, the instrument achieves single-molecule sensitivity but the update rate of the piezo stage limits the response of the tracking. Also, we have recently shown trapping of a single nanoparticle by use of astigmatic imaging for position determination and a simple four-electrode microfluidic device for applying electrokinetic motion in three dimensions. Here, the frame rate of the imaging limits the response of the trap. We discuss combining the advantages of each these methods and the projected capabilities. [Preview Abstract] |
Wednesday, March 5, 2014 4:30PM - 4:42PM |
Q24.00009: Laser speckle visibility acoustic spectroscopy in soft turbid media Fr\'{e}d\'{e}ric Wintzenrieth, Sylvie Cohen-Addad, Marie Le Merrer, Reinhard H\"{o}hler We image the evolution in space and time of an acoustic wave propagating along the surface of turbid soft matter by shining coherent light on the sample. The wave locally modulates the speckle interference pattern of the backscattered light and the speckle visibility\footnote{P. K. Dixon et D. J. Durian, ``Speckle Visibility Spectroscopy and Variable Granular Fluidization,'' Phys. Rev. Lett., vol. 90, no 18, p. 184302, 2003.} is recorded using a camera. We show both experimentally and theoretically how the temporal and spatial correlations in this pattern can be analyzed to obtain the acoustic wavelength and attenuation length. The technique is validated using shear waves propagating in aqueous foam.\footnote{F. Wintzenrieth, S. Cohen-Addad, M. Le Merrer, et R. H\"{o}hler, ``Laser speckle visibility acoustic spectroscopy in soft turbid media,'' Phys. Rev. E, 2013. (Submitted)} It may be applied to other kinds of acoustic wave in different forms of turbid soft matter, such as biological tissues, pastes or concentrated emulsions. [Preview Abstract] |
Wednesday, March 5, 2014 4:42PM - 4:54PM |
Q24.00010: Graphene-based platform for nano-scale infrared near-field spectroscopy of biological materials Omar Khatib, Joshua D. Wood, Gregory P. Doidge, Gregory L. Damhorst, Aniruddh Rangarajan, Rashid Bashir, Eric Pop, Joseph W. Lyding, Dimitri N. Basov In biological and life sciences, Fourier Transform Infrared (FTIR) spectroscopy serves as a noninvasive probe of vibrational fingerprints used to identify chemical and molecular species. Near-field spectroscopy, based on the illumination of an atomic force microscope (AFM) tip with an infrared laser, allows for determination of IR properties of a material at nanometer length scales. However, application of near-field IR spectroscopy to most biological systems has thus far been elusive. Physiological conditions required for experimentation are incompatible with typical implementations of nano-FTIR. Recently it became possible to trap water and small biomolecules underneath large-area graphene sheets grown by chemical vapor deposition (CVD). The graphene layer serves as an IR-transparent cover that allows for a near-field interrogation of the underlying layers. We discuss the applicability of near-field IR nano-imaging and spectroscopy to trapped biomolecules in aqueous environments. [Preview Abstract] |
Wednesday, March 5, 2014 4:54PM - 5:06PM |
Q24.00011: Biological Applications of Extraordinary Electroconductance (EEC) L.C. Tran, F.M. Werner, S.A. Solin Rapid detection of biomolecular concentration is a fundamental goal for lab on a chip diagnostic systems. The Extraordinary Electroconductance (EEC) sensor, a stacked, AuTi-GaAs metal semiconductor hybrid structure (MSH), has been previously demonstrated to have an electric field sensitivity of 3.05V/cm[1] in a mesoscopic-scale structure fabricated at the center of a parallel plate capacitor. In this work, we demonstrate the first successful application of EEC sensors as electrochemical detectors of molecular binding to the sensor surface. The negatively charged avidin derivative, captavidin, was applied with varying captavidin concentrations in phosphate buffered saline (PBS). The four-point measured resistance of bare EEC sensors was shown to increase by a factor of four due to captavidin binding at the sensor surface, as compared to a baseline binding assay in which the captavidin binding sites were blocked. Calculations for approximate electric field strengths introduced by a bound captavidin molecule will also presented. EEC sensors' four point measurements showed robustness and stability in spite of variations in the functional, linking layer. Ref [1] A.K.M. Newaz, et al, Phys Rev B. 79, 195308 (2009). [Preview Abstract] |
Wednesday, March 5, 2014 5:06PM - 5:18PM |
Q24.00012: Ultra-low field SQUID magnetic resonance for biomedical research P. Bhupathi, I. Hahn We are developing a SQUID (Superconducting QUantum Interference Device)-magnetometer system operating at 4K, for electron paramagnetic resonance (EPR) detection from room temperature samples in magnetic fields of the order of a Gauss. The magnetometer consists of a home-built, a second order gradiometer pick-up coil inductively coupled to the input of a commercially available two-stage dc SQUID amplifier with high bandwidth suitable for EPR, as well as NMR detection at wide range of frequencies up to a few MHz. Preliminary tests were done on samples of Pt powder at 4K and NMR signals have been detected in fields of few tens of gauss, with a minimum system sensitivity for spin concentration of $\sim $10$^{\mathrm{17}}$. We are currently developing an optimal SQUID gradiometer and a low temperature dewar for the EPR measurements. We plan to operate at low EPR excitation frequencies of a few MHz with the advantages of negligible sample heating and high penetration depth in biological systems. We discuss the prospects for \textit{in vivo} biomedical EPR imaging. [Preview Abstract] |
Wednesday, March 5, 2014 5:18PM - 5:30PM |
Q24.00013: Single Cell Magnetic Measurements with a Superconducting Quantum Interference Device Johanna C. Palmstrom, Jennifer Arps, Bo Dwyer, Beena Kalisky, John R. Kirtley, Kathryn A. Moler, Lisa C. Qian, Aaron J. Rosenberg, Brian Rutt, Sui Seng Tee, Eric Theis, Elana Urbach, Yihua Wang Magnetic nanoparticles play an important role in numerous biomedical applications such as magnetic resonance imaging and targeted drug delivery. There is a need for tools to characterize individual magnetic nanoparticles and the magnetic properties of individual cells. We use a scanning superconducting quantum interference device (SQUID) to observe the magnetic fields from single mammalian cells loaded with superparamagnetic iron oxide nanoparticles. We show that the SQUID is a useful tool for imaging biological magnetism and is capable of resolving cell to cell variations in magnetic dipole moments. We hope to correlate these magnetic images with real space imaging techniques such as optical and scanning electron microscopy. The visualization of single cell magnetism can be used to optimize biological magnetic imaging techniques, such as MRI, by quantifying the strength of magnetic dipole moments of in vitro magnetic labeling. [Preview Abstract] |
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