Magnetic Resonance Imaging Guidance of Histotripsy Therapy.

Histotripsy is a cavitation based surgical therapy that transmits high amplitude acoustic pulses into a tissue target to stimulate the formation of energetic clouds of microbubbles. These microbubble clouds then exert a mechanical load on the surrounding cellular and extracellular structure, and, eventually, render a precise volume of tissue into a liquid homogenate devoid of any visible cellular structure. This technology has many potential applications including the erosion of intracranial blood clots, deep vein thrombi, liver tumors, and kidney stones. Histotripsy is a non-invasive surgery and cannot ensure the accurate ablation of the target without an accompanying image-based guidance system. The objective of this dissertation is to explore and develop magnetic resonance imaging (MRI) based tools to 1) visualize and monitor the cavitation process within the ablation target and 2) assess the state of the target after ablation. To this end, this dissertation proposes and characterizes a novel cavitation imaging scheme to visualize the histotripsy process. The technique employs synchronized bipolar gradients as a simultaneous temporal and magnitude filter that selectively sensitizes the resulting image to incoherent water flow generated by the histotripsy bubble cloud. It is shown to be easily integrated into various image acquisition schemes. When used with single-shot, fast imaging schemes, the technique can simultaneously localize individual bubble clouds and provide feedback on the ablated state of the target. The dissertation then examines the response of several basic MR signal evolution processes as tissues are ablated by histotripsy. These processes are related to the diffusion and interaction of water molecules within a tissue and are characterized by the time constants T1, and T2, as well as a diffusion coefficient. The work presented here demonstrates that the magnitude of response of these processes is specific to both the tissue target and the treatment history. Further, the response of the process characterized by T2 is shown to depend the ability of the bubble cloud to erode and disperse aggregations of paramagnetic proteins such as hemoglobin and ferritin. Together, this dissertation provides useful magnetic resonance imaging tools for the visualization and assessment of histotripsy therapy.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133238/1/stevepa_1.pd

A brief history of the British Neuroscience Association

As the British Neuroscience Association commemorates 50 years of existence in 2018, this article recalls its founding as a discussion group, its establishment as the Brain Research Association, its transition to a professional society encompassing all aspects of neuroscience research, both clinical and non-clinical, and its re-branding as the British Neuroscience Association in the late 1990s. Neuroscience as a branch of life science has expanded hugely in the last 25 years and the British Neuroscience Association has adapted, frequently working with partner societies, to serve as an interdisciplinary hub for professionals working in this exciting and crucial field. The authors have attempted to highlight some key events in the Association’s history and acknowledge the contributions made by many people over half a century

Application of physical parameter identification to finite-element models

The time domain parameter identification method described previously is applied to TRW's Large Space Structure Truss Experiment. Only control sensors and actuators are employed in the test procedure. The fit of the linear structural model to the test data is improved by more than an order of magnitude using a physically reasonable parameter set. The electro-magnetic control actuators are found to contribute significant damping due to a combination of eddy current and back electro-motive force (EMF) effects. Uncertainties in both estimated physical parameters and modal behavior variables are given

Application of physical parameter identification to finite element models

A time domain technique for matching response predictions of a structural dynamic model to test measurements is developed. Significance is attached to prior estimates of physical model parameters and to experimental data. The Bayesian estimation procedure allows confidence levels in predicted physical and modal parameters to be obtained. Structural optimization procedures are employed to minimize an error functional with physical model parameters describing the finite element model as design variables. The number of complete FEM analyses are reduced using approximation concepts, including the recently developed convoluted Taylor series approach. The error function is represented in closed form by converting free decay test data to a time series model using Prony' method. The technique is demonstrated on simulated response of a simple truss structure

Ariel - Volume 2 Number 2

Editors Delvyn C. Case, Jr. Paul M. Fernhoff News Editors Richard Bonanno Daniel B. Gould Ronald A. Hoffman Lay-Out Editor Carol Dolinskas Sports Editor James J. Nocon Contributing Editors MichaeI J. Blecker Lin Sey Edwards Jack Guralnik W. Cherry Light Features Editor Donald A. Bergman Stephen P. Flynn Business Manager Nick Grego Public Relations Robin A. Edward

Evaporation of Lennard-Jones Fluids

Evaporation and condensation at a liquid/vapor interface are ubiquitous interphase mass and energy transfer phenomena that are still not well understood. We have carried out large scale molecular dynamics simulations of Lennard-Jones (LJ) fluids composed of monomers, dimers, or trimers to investigate these processes with molecular detail. For LJ monomers in contact with a vacuum, the evaporation rate is found to be very high with significant evaporative cooling and an accompanying density gradient in the liquid domain near the liquid/vapor interface. Increasing the chain length to just dimers significantly reduces the evaporation rate. We confirm that mechanical equilibrium plays a key role in determining the evaporation rate and the density and temperature profiles across the liquid/vapor interface. The velocity distributions of evaporated molecules and the evaporation and condensation coefficients are measured and compared to the predictions of an existing model based on kinetic theory of gases. Our results indicate that for both monatomic and polyatomic molecules, the evaporation and condensation coefficients are equal when systems are not far from equilibrium and smaller than one, and decrease with increasing temperature. For the same reduced temperature $T/T_c$, where $T_c$ is the critical temperature, these two coefficients are higher for LJ dimers and trimers than for monomers, in contrast to the traditional viewpoint that they are close to unity for monatomic molecules and decrease for polyatomic molecules. Furthermore, data for the two coefficients collapse onto a master curve when plotted against a translational length ratio between the liquid and vapor phase.Comment: revised version, 15 pages, 15 figures, to appear in J. Chem. Phy

Ariel - Volume 2 Number 7

Editors Richard J. Bonanno Robin A. Edwards Associate Editors Steven Ager Stephen Flynn Shep Dickman Tom Williams Lay-out Editor Eugenia Miller Contributing Editors Michael J. Blecker W. Cherry Light James J. Nocon Lynne Porter Editors Emeritus Delvyn C. Case, Jr. Paul M. Fernhof

Toward one-band superconductivity in MgB2

The two-gap model for superconductivity in MgB2 predicts that interband impurity scattering should be pair breaking, reducing the critical temperature. This is perhaps the only prediction of the model that has not been confirmed experimentally. It was previously shown theoretically that common substitutional impurities lead to negligible interband scattering - if the lattice is assumed not to distort. Here we report theoretical results showing that certain impurities can indeed produce lattice distortions sufficiently large to create measurable interband scattering. On this basis, we predict that isoelectronic codoping with Al and Na will provide a decisive test of the two-gap model.Comment: 4 pages, 2 figures, to appear in Phys. Rev.

Directions for 21st Century Lifelong Learning Institutes: Elucidating Questions from Osher Lifelong Learning Institute Studies

The literature regarding lifelong learning is robust, while the literature on lifelong learning institutions, centers, and programs remain under-researched in comparison. This article draws insights from a specific network of lifelong learning institutes with a rich history and high rapport in the United States: the Osher Lifelong Learning Institute (OLLI) network. Sixty articles regarding OLLIs are catalogued and highlighted to elucidate twelve thematic areas and twelve questions for future research and practice. In particular, these themes are related to adult education, healthy aging, and educational gerontology. The article concludes by reflecting on trends in and needs for institutional research and practice.Les publications portant sur l’éducation permanente sont nombreuses, contrairement à celles touchant les institutions, centres et programmes d’éducation permanente qui, en comparaison, demeurent généralement mal connus. Cet article recueille des idées d’un réseau d’instituts d’éducation permanente ayant un passé riche et de bons rapports aux États-Unis : le réseau Osher Lifelong Learning Institute (OLLI). Soixante articles portant sur OLLI ont été catalogués et analysés pour faire ressortir douze thèmes et douze questions pour la recherche et la pratique à l’avenir. Ces thèmes se rattachent à l’éducation des adultes, le vieillissement sain et la gérontologie éducative. L’article se termine par des réflexions sur des tendances et des besoins relatifs à la recherche et la pratique institutionnelles.Mots clés : recherche institutionnelle, éducation permanente, ainés, éducation des adultes, universités adaptées aux personnes âgée