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Other SOFTWARE EXHIBITS ESMRMB 2012 627 856 Images Preview with a Dynamic Acquisition Real-time System (DARTS) C. Meyer 1 , P. Vuissoz 2 , J. Felblinger 3 1 Iadi, Université de Lorraine, Nancy/FRANCE, 2 Iadi U947, INSERM, Nancy/ FRANCE, 3 Pôle Imagerie, CHU Nancy, Nancy/FRANCE Purpose of the soſtware: Magnetic Resonance Imaging is an intrinsically slow acquisition process. Sequences can take minutes to run and images are displayed only aſter the whole sequence is complete. e proposed soſtware displays partial images as soon as they are acquired using a real-time commu- nication framework with the scanner. us, adjustments to the scan parameters can be decided and the sequence aborted and restarted, if judged necessary, without having to wait for a useless sequence to complete. is new technique allows for a constant feedback of the acquisition process and reduces the machine to human feedback loop delay. Methods/Implementation: A 3T MRI scanner (Signa HDxt, General Electric, Milwaukee, WI) with an 8-channel cardiac coil and a 2D cartesian fast gradi- ent recalled echo sequence was used to acquire CINE data from a volunteer (scan time : 4 minutes). MR coils data are received as soon as they are acquired using the Raw Data Server soſtware version 15M4 offered by the vendor (subject to research agree- ment). Since only k-space raw data is transferred by this mean, the sequence was modified to send the trajectory (i.e. phase encoding step) at each TR. ose two separate signals were acquired with distinct threads and stored in two queues in memory. Only raw data that were associated with a phase encode step (and vice versa) were used to fill zero-initialized partial k-spaces. e latter were transformed into images using the FFTW3 library [1] and displayed (along with general user interface) using Qt4 [2]. e “views per transfer” parameter of the Raw Data Server was controlling the refresh rate of the images previewing. Our soſtware runs on a standard PC with a Linux operating system (kernel version 2.6.33.5) patched for reduced latency (rt-patch 22). An Ethernet con- nection with the MR cabinet permits bi-directional communication between the running sequence (EPIC environment) and our soſtware. Features illustrated at the exhibit: At the exhibit, the soſtware will illustrate (fig. 1) its two main features while an actual acquisition previously recorded will be simulated: (i) preview images will be displayed and (ii) the trajectory of acquisition in k-space will be shown, both in real-time. Figure 1: User interface showing preview of partial acquisition (leſt) and trajectory (right). About 3/4 of data were acquired at the time of screenshot. Segmented CINE acquisition is represented as a “serrated” trajectory (“View order” plot). References: [1] Frigo M., 2005, Proc. IEEE, 216-231 [2] Blanchette J., 2007, Prentice Hall, ISBN 0132354160 857 openEMS – A Free and Open Source FDTD Soſtware Package, Supporting Cartesian and Cylindrical Coordinates Ideally Suited for MRI Applications T. Liebig, A. Rennigs, D. Erni General And eoretical Electrical Engineering (ate), University of Duisburg- Essen, Duisburg/GERMANY Purpose of the soſtware: OpenEMS [1] is a fully-vectorial three-dimensional finite-difference time-domain (FDTD) simulation platform supporting Car- tesian as well as cylindrical coordinates. In bioelectromagnetics the FDTD method has already been established as one of the most powerful numerical tools for designing e.g. complex radio frequency (RF) systems for advanced MRI scanners. Although the relevant RF structures used in MRI systems are confined to a cylindrical shape, the pertinent commercial FDTD soſtware packages (e.g. SEMCAD X, XFdtd, EMPIRE XCcel, etc.) do not explicitly foster cylindrical meshing, whereas the cylindrical version of openEMS is ideally suited for handling e.g. thin conformal structures such as the resonant birdcage coil shown in Fig.1. e coil is discretized using a rather coarse mesh without displaying any stair-casing effects, rendering the numerical analysis highly efficient. In the context of a multi-channel traveling-wave MRI system we have recently demonstrated [2] that openEMS can handle multiple con- formal ring antennas where any Cartesian FDTD implementation is supposed to completely fail. Fig. 1: Low-pass birdcage coil being well resolved by the cylindrical version of openEMS. Methods/Implementation: e cylindrical (equivalent circuit-based [1]) FDTD scheme is mostly identical to the Cartesian counterpart and therefore apt for a generic highly optimized iteration engine as implemented in openEMS using C++ with multi-threading support. OpenEMS is memory and speed efficient and can be deployed on any personal computer running Linux or Windows – and with the support of MPI, openEMS is even ready to run on a Linux cluster (or a supercomputer). Features illustrated at the exhibit: OpenEMS relies on a user friendly Matlab/ Octave interface for scripting purposes and a graphical user interface as a struc- tural 2D/3D viewer (cf. Fig. 1). e interface and a couple of ready-made MRI examples (e.g. birdcage-coils) will be elucidated at the exhibit. Furthermore we will promote an integrated user interface between the well-known “Birdcage Builder” from the Penn State Center for NMR Research [3] and openEMS advancing a fast comprehensive full-wave coil design.
