Browsing by Author "Guarini, Marcelo"

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    A 3D trajectory for undersampling k-space in MRSI applications
    (ELSEVIER SCIENCE INC, 2007) Uribe, Sergio; Guesalaga, Andres; Mir, Roberto; Guarini, Marcelo; Irarrazaval, Pablo
    Magnetic resonance spectroscopic imaging (MRSI) is a noninvasive technique for producing spatially localized spectra. MRSI presents the important challenge of reducing the scan time while maintaining the spatial resolution. The preferred approach for this is to use time-varying readout gradients to collect the spatial and chemical-shift information. Fast, three-dimensional (3D) spatial encoded methods also reduce the scan time. Despite the existence of several new and faster 3D encoded methods, or k-space trajectories, for magnetic resonance imaging (MRI), only stack of spirals and echo planar have been studied in 3D MRSI. A novel formulation for designing fast, 3D k-space trajectory applicable to 3D MRSI is presented. This approach is simple and consists of rays expanding from the origin of k-space into a revolving sphere, collecting spectral data of all 3D spatial k-space at different times in the same scan. This article describes this new method and presents some results of its application to 3D MRSI. This technique allows some degree of undersampling; hence, it is possible to reconstruct high-quality undersampled spectroscopic imaging in order to recognize different compounds in short scan times. Additionally, the method is tested in regular 3D MRI. This proposed method can also be used for dynamic undersampled imaging. (c) 2007 Elsevier Inc. All rights reserved.
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    Ultrasound based measurements of sugar and ethanol concentrations in hydroalcoholic solutions
    (ELSEVIER SCI LTD, 2008) Sint Jan, Michael Van; Guarini, Marcelo; Guesalaga, Andrs; Perez Correa, J. Ricardo; Vargas, Yolanda
    Industrial automation is useful to reduce production costs and improve product quality. The wine industry has been increasingly adopting industrial automation seeking these objectives. In Chile, wineries have been lagging behind in embracing new technologies to control the fermentation process. In most cases, enologists decide control actions (cooling, heating, pumping over) based on off line periodic measurements. In this work we explore the applicability of ultrasound to measure the sugar and alcohol concentrations of hydroalcoholic solutions mimicking fermenting musts. Additionally, implementation issues such as the attenuation effect of bubbles and tank curvature are analyzed. We show that working at two sufficiently distinct frequencies, we can measure sugar and alcohol content simultaneously. Measurement resolution achieved for the wave time of travel translates to a better than 0.02% for both concentrations, depending on the container size. (c) 2007 Elsevier Ltd. All rights reserved,