Browsing by Author "Irarrazabal, P"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Measurement of the glaucomatous cup using sequentially acquired stereoscopic images
    (ELSEVIER SCI LTD, 2003) Guesalaga, A; Irarrazabal, P; Guarini, M; Alvarez, R
    This paper describes a new method for recovering the three-dimensional surface of the optic disc based on stereoscopic techniques. The images that form the stereo pair are obtained sequentially from standard ophthalmoscopes. The method is based on calibration algorithms for an optical set-up and uses a novel algorithm for the search of correspondences in the stereo pair that is unique for this kind of applications. It is proposed as a quantitative tool in the diagnosis of the primary open angle glaucoma. The technique shows a robust performance, is simple to embed in an clinical ophthalmoscope, and is a low-cost solution to diagnose and control the glaucoma pathology. (C) 2003 Elsevier Ltd. All rights reserved.
  • Thumbnail Image
    Item
    Volumetric spectroscopic imaging with spiral-based k-space trajectories
    (LIPPINCOTT WILLIAMS & WILKINS, 1998) Adalsteinsson, E; Irarrazabal, P; Topp, S; Meyer, C; Macovski, A; Spielman, DM
    Spiral-based k-space trajectories were applied in a spectroscopic imaging sequence with time-varying readout gradients to collect volumetric chemical shift information, In addition to spectroscopic imaging of low signal-to-noise ratio (SNR) brain metabolites, the spiral trajectories were used to rapidly collect reference signals from the high SNR water signal to automatically phase the spectra and to aid the reconstruction of metabolite maps. Spectral-spatial pulses were used for excitation and water suppression. The pulses were designed to achieve stable phase profiles in the presence of up to 20% variation in the radiofrequency field. A gridding algorithm was used to resample the data onto a rectilinear grid before fast Fourier transforms. This method was demonstrated by in vivo imaging of brain metabolites at 1.5 T with 10 slices of 18 x 18 pixels each. Nominal voxel size was 1.1 cc, spectral bandwidth was 400 Hz, scan time was 18 min for the metabolite scan and 3 min for the reference scan.