Browsing by Author "Fernandez, MP"

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    Computer reconstruction of pine growth rings using MRI
    (ELSEVIER SCIENCE INC, 2004) Morales, S; Guesalaga, A; Fernandez, MP; Guarini, M; Irarrazaval, P
    This work explores the use of magnetic resonance imaging (MRI) for nondestructive determination of wood characteristics and for 3D wood modeling. In this context, one of the applications under development is the automatic recognition and reconstruction of rings from transversal images obtained from MRI scanners. The algorithm analyzes a set of transversal MRI images, detecting and reconstructing growth ring edges. The information generated is then interpolated in order to obtain an accurate 3D picture of the log and its fundamental constituents (individual rings, knots, defects, etc). Results also show that the technique has potential for defect recognition, providing a powerful tool for future developments in wood analysis. The results are encouraging and further research is needed to develop automatic detection not only of rings, but also of different types of defects that are of paramount importance in the sawmill and plywood industries. (C) 2004 Elsevier Inc. All rights reserved.
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    MRI fast tree log scanning with helical undersampled projection acquisitions
    (ELSEVIER SCIENCE INC, 2002) Contreras, I; Guesalga, A; Fernandez, MP; Guarini, M; Irarrazaval, P
    Magnetic Resonance Imaging opens an alternative way to analyze wood structures using a non-destructive technology. It provides high resolution, compound-based contrast manipulation and increased data acquisition flexibility. The technique is particularly useful for tree logs, since they present several characteristics that can be used to reduce the long scan time. This study proposes a method that takes advantage of the log cylindrical symmetry, acquiring transverse 1-D projections with a helical and undersampled pattern. Linear interpolation is used to estimate the skipped data and slice images are reconstructed by filtered backprojection. The sequence is improved using selective multi-pass scanning, without major variations of the scan time. Computer simulations and experimental results show that the proposed technique can increase the scan speed by a factor of 6, while maintaining the ability to identify typical tree log characteristics. (C) 2002 Elsevier Science Inc. All rights reserved.