Ignacio Rodríguez

Boehringer Ingelheim Veterinary Research Center Gmbh & Co. Kg, Hanover, Lower Saxony, Germany

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Publications (33)78.23 Total impact

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    ABSTRACT: La obtención de imágenes dinámicas de resonancia magnética (MRI) en un sistema en línea, orientado su uso en líneas de clasificación, requiere secuencias rápidas con corrección de artefactos de movimiento. En este estudio se han utilizado dos tipos de secuencias (FLASH y UFLARE), con corrección de movimiento implementado en tiempo real, basadas en T2* y T2 respectivamente. La elección de una secuencia u otra viene dada por la naturaleza del desorden fisiológico a detectar y, por tanto, el contraste que genera en la imagen de resonancia. En el caso del tejido vitrescente, existe mayor intensidad de señal T2* al haber zonas con mayor movilidad de agua, mientras que en desórdenes relacionados con roturas internas y degradación del tejido hay una intensidad de la señal T2* menor por la desintegración de la textura. Para el estudio de vitrescencia se utilizaron cinco variedades de manzanas (Normanda-18-, Fuji-35-, Helada-36-, Verde Doncella-54-, Esperiega-71-) durante dos campañas (2011 y 2012). En total se midieron 218 frutos, en primer lugar en estático (20 cortes por fruto) y después en dinámico (3 repeticiones sin selección de corte). Para el problema de podredumbre interna se empleó la variedad Braeburn (en total 106 frutos) también bajo condiciones estáticas (20 cortes por fruto) y dinámicas (3 repeticiones con selección de corte). En este trabajo se quiere resaltar la repetibilidad de imágenes dinámicas y la estabilidad de la forma del histograma, lo cual resulta de gran interés para las aplicaciones industriales. También se analiza la capacidad de segregación de frutos con distinto grado de daño, empleando como referencia imágenes estáticas con 20 cortes por fruto, su segmentación 3D y la clasificación visual realizada por tres expertos.
    VII Contreso Ibérico de Agroingeniería; 08/2013
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    ABSTRACT: On-line dynamic MRI requires high-speed sequences with motion correction artifacts. In this study, two alternative motion corrected sequences are proposed and implemented in real-time (FLASH and UFLARE), based on T2* or T2 respectively. Sequence selection is related to the expected contrast effect of the disorder: while watercore enhances bright areas due to higher fluid mobility, internal breakdown potentiates low signal due to texture degradation. Metrological aspects such as repeatability of dynamic images and subsequent histogram feature stability become of major interest for further industrial application. Segregation ability among varyin degrees of disorder is also analyzed.
    InsideFood Symposium; 04/2013
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    ABSTRACT: The apparent diffusion coefficient (ADC) of hyperpolarized (HP) gases is a parameter that reflects changes in lung microstructure. However, ADC is dependent on many physiological and experimental variables that need to be controlled or specified in order to ensure the reliability and reproducibility of this parameter. A single breath-hold experiment is desirable in order to reduce the amount of consumed HP gas. The application of a positive end-expiratory pressure (PEEP) causes an increase in the residual gas volume. Depending on the applied PEEP, the ratio between the incoming and residual gas volumes will change and the ADC will vary, as long as both gases do not have the same diffusion coefficient. The most standard method for human applications uses air for breathing and a bolus of pure HP (3)He for MRI data acquisition. By applying this method in rats, we have demonstrated that ADC values are strongly dependent on the applied PEEP, and therefore on the residual gas volume in the lung. This outcome will play an important role in studies concerning certain diseases, such as emphysema, which is characterized by an increase in the residual volume. Ventilation with an oxygen-helium mixture (VOHeM) is a proposed single breath-hold method that uses two different gas mixtures (O(2)-(4)He for ventilation and HP (3)He-N(2) for imaging). The concentration of each gas in its respective mixture was calculated in order to obtain the same diffusion coefficient in both mixtures. ADCs obtained from VOHeM are independent of PEEP, thus minimizing the effect of the different residual volumes.
    NMR in Biomedicine 01/2012; 25(9):1026-32. · 3.45 Impact Factor
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    ABSTRACT: Pulmonary diseases are known to be largely inhomogeneous. To evaluate such inhomogeneities, we are testing an image-based method to measure gas flow in the lung regionally. Dynamic, spin-density-weighted hyperpolarized (3)He MR images performed during slow inhalation of this gas were analyzed to quantify regional inflation rate. This parameter was measured in regions of interest (ROIs) that were defined by a rectangular grid that covered the entire rat lung and grew dynamically with it during its inflation. We used regional inflation rate to quantify elastase-induced emphysema and to differentiate healthy (n = 8) from elastase-treated (n = 9) rat lungs as well as healthy from elastase-treated areas of one rat unilaterally treated with elastase in the left lung. Emphysema was also assessed by gold standard morphological and well-established hyperpolarized (3)He MRI diffusion measurements. Mean values of regional inflation rates were significantly different for healthy and elastase-treated animals and correlated well with the apparent diffusion coefficient of (3)He and morphological measurements. The image-based biomarker inflation rate may be useful for the assessment of regional lung ventilation.
    IEEE transactions on bio-medical engineering 12/2011; 59(3):777-86. · 2.15 Impact Factor
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    Progress in Nuclear Magnetic Resonance Spectroscopy 10/2011; 59(3):263-70. · 6.02 Impact Factor
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    ABSTRACT: The combination of nanoparticles, gene therapy, and medical imaging has given rise to a new field known as gene theranostics, in which a nanobioconjugate is used to diagnose and treat the disease. The process generally involves binding between a vector carrying the genetic information and a nanoparticle, which provides the signal for imaging. The synthesis of this probe generates a synergic effect, enhancing the efficiency of gene transduction and imaging contrast. We discuss the latest approaches in the synthesis of nanoparticles for magnetic resonance imaging, gene therapy strategies, and their conjugation and in vivo application.
    Microscopy Research and Technique 07/2011; 74(7):577-91. · 1.59 Impact Factor
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    ABSTRACT: Brain magnetic resonance imaging studies performed in some patients with acute intermittent porphyria (AIP) showed reversible white-matter lesions, compatible with the hypothesis of vasospasm due to a diminution in the nitric oxide production in the brain. In this study we try to identify low perfusion areas in the brain of AIP mice. The cerebral blood flow (CBF) values were measured by functional magnetic resonance imaging (fMRI) in wild type and AIP female mice before and during an acute attack induced by phenobarbital. In order to verify relationship between CBF and glucose metabolism, specific regional brain fluoro-2-deoxy-D-glucose (18F-FDG) uptake was evaluated by autoradiography. All autoradiographic slices form each animal were digitalized and aligned to create an autoradiographic three-dimensional (3D) volume stack from each brain (PMOD software). Those 3D volumes were spatially normalized to a standard space in order to perform a voxel-based analysis using Statistical Parametric Mapping (SPM), resulting in statistical image that anatomically localize significant information. Finally, classical histological analysis was performed in another cohort of animals before and after phenobarbital administration. No histological differences were present between AIP and wild type mice groups with respect to mass and number of neural cell or to neural fibers structures. No structural changes were observed in the brain after repeated acute attacks induced by phenobarbital. MRI analysis showed major depression of cerebral blood flow in female AIP mice when compared with wild type animals (0.65 ±0.23 AU vs 1.5 ± 1.2 AU respectively, p=0.01). The phenobarbital administration reduced brain perfusion in wild type animals (to 1.04 AU, p=0.02) but did not modify blood flow in AIP mice. By regions, the cortex from females AIP mice showed attenuated perfusion when compared to control wild type (0.73±0.2 AU vs1.7± 0.12 AU respectively, p=0.02). No blood flow differences were observed after phenobarbital administration.3D autoradiography following SPM analysis confirm low 18F-FDG uptake in the brain of AIP mice when compared to wild type mice. Significant differences (p =0.01) were localized in primary somatosensorial cortex. In conclusion, primary somatosensorial cortex was identified as a region with attenuated perfusion and glucose hypometabolism in the brain of female AIP mice. Measurements of perfusion and/or glucose metabolism in the substructures of the brain cortex could provide a new tool for the future investigation of related central nervous system abnormalities observed in patients with AIP.
    International Meeting on Porphyrins and Porphyrias - Cardiff, April 10th–14th 2011; 05/2011
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    ABSTRACT: This work was carried out in the frame of the European project InsideFood (Integrated sensing and imaging devices for designing, monitoring and controlling microstructure of foods). The aim of this project is to provide technological solutions for exploring the microstructure of foods, by the development, combination and application of different non destructive techniques: X-ray CT, OCT, MRI, NMR, TRS and SRS aimed at on-line sensing food microstructure, water status, texture and optical properties. Nuclear magnetic resonance (NMR) was used in order to detect watercore in three different varieties of apples: Ascara2, Rebellón and Tempera. These three varieties were chosen due to their susceptibility to develop watercore and were grown under favorable conditions to enhance such disorder. Magnetic resonance imaging (MRI) was used under several sequences: 2D T2 weighed sequences, and 3D sequences, proton density and T2 weighed, such as Fast Low Angle SHot (FLASH) and COMSPIRA 3D, all of them with varying acquisition times. The study aims at defining the optimal conditions for on-line segregation. Also, a methabonomic study was made to some of these apples, to obtain a metabolic profile of apples affected by watercore, as an indication of the metabolic pathway involved in the disorder.
    International Conference on Agricultural Engineering (AgEng 2010), Clemont-Ferrand, France; 09/2010
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    ABSTRACT: We have developed over the past years an experimental magnetic resonance imaging (MRI) and polarized gases compatible mechanical respirator for the study of the small experimental animal. The respirator has been successfully used for experiments both in the MRI setting for polarized (3)He, (19)F, and proton imaging as well as for functional measurements of the lungs. The new main pneumatic valve with the two integrated sensors for simultaneous lung pressure and volume measurements and the proportional valve to set the tidal volume of the respiration are described. It is shown how the device measures and controls the tidal volume of the lungs.
    IEEE transactions on bio-medical engineering 02/2010; 57(7):1745-9. · 2.15 Impact Factor
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    ABSTRACT: Apparent diffusion coefficient (ADC) measurement in the lung using gas magnetic resonance imaging is a promising technique with potential for reflecting changes in lung microstructure. Despite some recent impressive human applications, full interpretation of ADC measures remains an elusive goal, due to a lack of detailed knowledge about the structure dependency of ADC. In an attempt to fill this gap we have performed random walk simulations in a three-dimensional geometrical model of the lung acinus, the distal alveolated sections of the lung tree accounting for approximately 90% of the total lung volume. Simulations were carried out adjusting model parameters after published morphological data for the rat peripheral airway system, which predict an ADC behavior as microstructure changes with lung inflation in partial agreement with measured ADCs at different airway pressures. The approach used to relate experimental ADCs to lung microstructural changes does not make any assumption about the cause of the changes, so it could be applied to other scenarios such as chronic obstructive pulmonary disease, lung development, etc. The work presented here predicts numerically for the first time ADC values measured in the lung from independent morphological measures of lung microstructure taken at different inflation stages during the breath cycle.
    Biophysical Journal 08/2009; 97(2):656-64. · 3.67 Impact Factor
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    ABSTRACT: Based on a stimulated-echo technique, a method to construct an apparent diffusion coefficient (ADC) map of hyperpolarized (3)He in a long-range diffusion scale is presented with a phase-cycle alternative to remove all unwanted echoes. The approach was successfully applied to determine in vivo diffusion constants in rat lungs. The ADC values in healthy rats show a good agreement with reported values for diffusion times of approximately. These long diffusivity measurements may be sensitive to detect emphysema progression or tissue remodeling and thus have enormous potential for the diagnosis and tracking of disease progression and for drug evaluation.
    Magnetic Resonance in Medicine 01/2009; 61(1):54-8. · 3.27 Impact Factor
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    ABSTRACT: Analysis of the plethora of metabolites found in the NMR spectra of biological fluids or tissues requires data complexity to be simplified. We present a graphical user interface (GUI) for NMR-based metabonomic analysis. The "Metabonomic Package" has been developed for metabonomics research as open-source software and uses the R statistical libraries. The package offers the following options: Raw 1-dimensional spectra processing: phase, baseline correction and normalization. Importing processed spectra. Including/excluding spectral ranges, optional binning and bucketing, detection and alignment of peaks. Sorting of metabolites based on their ability to discriminate, metabolite selection, and outlier identification. Multivariate unsupervised analysis: principal components analysis (PCA). Multivariate supervised analysis: partial least squares (PLS), linear discriminant analysis (LDA), k-nearest neighbor classification. Neural networks.Visualization and overlapping of spectra. Plot values of the chemical shift position for different samples. Furthermore, the "Metabonomic" GUI includes a console to enable other kinds of analyses and to take advantage of all R statistical tools. We made complex multivariate analysis user-friendly for both experienced and novice users, which could help to expand the use of NMR-based metabonomics.
    BMC Bioinformatics 01/2009; 10:363. · 3.02 Impact Factor
  • BIOSIGNALS 2009 - Proceedings of the International Conference on Bio-inspired Systems and Signal Processing, Porto, Portugal, January 14-17, 2009; 01/2009
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    ABSTRACT: This review presents an overview of some recent magnetic resonance (MR) techniques for pharmaceutical research. MR is noninvasive, and does not expose subjects to ionizing radiation. Some methods that have been used in pharmaceutical research MR include magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) methods, among them, diffusion-weighted MRI, perfusion-weighted MRI, functional MRI, molecular imaging and contrast-enhance MRI. Some applications of MR in pharmaceutical research include MR in metabonomics, in vivo MRS, studies in cerebral ischemia and infarction, degenerative joint diseases, oncology, cardiovascular disorders, respiratory diseases and skin diseases. Some of these techniques, such as cardiac and joint imaging, or brain fMRI are standard, and are providing relevant data routinely. Skin MR and hyperpolarized gas lung MRI are still experimental. In conclusion, considering the importance of finding and characterizing biomarkers for improved drug evaluation, it can be expected that the use of MR techniques in pharmaceutical research is going to increase in the near future. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:3637–3665, 2008
    Journal of Pharmaceutical Sciences 01/2008; 97(9):3637 - 3665. · 3.13 Impact Factor
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    ABSTRACT: Carbon encapsulated iron/iron-oxide nanoparticles were obtained using laser pyrolysis method. The powders were processed to produce stable and biocompatible colloidal aqueous dispersions. The synthesis method consisted in the laser decomposition of an aerosol of ferrocene solution in toluene. This process generated, in a continuous way and in a single step, a nanocomposite formed by amorphous carbon nanoparticles of 50-100 nm size in which isolated iron based nanoparticles of 3-10 nm size are located. The effect of using different carriers and additives was explored in order to improve the efficiency of the process. The samples after purification by solid-liquid extraction with toluene, were oxidised in concentrated nitric acid solution of sodium chlorate, washed and finally ultrasonically dispersed in 1 mM tri-sodium citrate solutions. The dispersions obtained have hydrodynamic particle size less than 150 nm and are stable in the pH range of 2-11. Finally the shortening of the transversal relaxation time of water protons produced by the dispersed particles was studied in order to test the feasibility of these systems to be traced by magnetic resonance imaging techniques.
    Journal of Colloid and Interface Science 10/2007; 313(2):511-8. · 3.55 Impact Factor
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    ABSTRACT: Magnetic composites of Fe-based nanoparticles encapsulated in carbon/silica (C/SiO2@Fe) or carbon (C@Fe) matrices were prepared by laser-induced pyrolysis of aerosols. The powders were dispersed in aqueous solutions at pH 7 resulting in biocompatible colloidal dispersions with a high resistance to biodegradation. Structural and magnetic properties and the suitability of aqueous dispersions as contrast agent for MRI were analyzed. The results of these characterizations and the NMR relaxivity data are very encouraging for application of laser pyrolysis products in the field of living tissues.
    MRS Online Proceeding Library 01/2007;
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    ABSTRACT: A combined approach to 3D radial and spiral MRI is presented. Although radial and spiral MRI have some similarities from the viewpoint of their mathematical properties, sequence design, and reconstruction procedures, they are usually implemented in separate pulse sequences. In this article, a common mathematical foundation for both sampling methods is used. The COMSPIRA3D (COMbined SPIral and RAdial 3D) pulse sequence permits one to choose between spiral and radial center-out k-space trajectories in two and three dimensions. Several numerical simulations to study possible artifacts and images resulting from the actual implementation of COMSPIRA3D in a 4.7 T system are shown. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson 29B: 115–124, 2006.
    Concepts in Magnetic Resonance Part B Magnetic Resonance Engineering 07/2006; 29B(3):115 - 124. · 0.71 Impact Factor
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    ABSTRACT: Diffusion weighted 19F images of rat lung in vivo using SF6 are presented. Projection-reconstruction images were acquired by filling the rat lung with a mixture of SF6 and air, during 64 successive apneas. Each apnea lasted for 6 s, the time required to perform 100 accumulations of each k-space radial phase step for the five values of the diffusion gradient (TR = 10 ms). After diffusion images were acquired, an apparent diffusion coefficient (ADC) map was generated, yielding an average value for the ADC of 2.22 x 10(-6) m2/s and SD for ADC values of 1.27 x 10(-6) m2/s. To the best of our knowledge, this is the first in vivo diffusion weighting imaging application and the first ADC map obtained using 19F MRI.
    Magnetic Resonance in Medicine 09/2005; 54(2):460-3. · 3.27 Impact Factor
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    ABSTRACT: Lung functional magnetic resonance imaging (MRI) has become a reality using different inert hyperpolarized gases, such as 3He and 129Xe, which have provided an extraordinary boost in lung imaging and has also attracted interest to other chemically inert gaseous contrast agents. In this context, we have recently demonstrated the first diffusion-weighted images using thermally polarized inhaled sulfur hexafluoride (SF6) in small animals. The aim of this study was to evaluate whether or not the diffusion coefficient of this fluorinated gas is sensitive to pulmonary structure, gas concentration and air pressure in the airways. Diffusion coefficients of SF6 (both pure and in air mixtures) measured in vitro at different pressures and 20 degrees C showed an excellent agreement with theoretical values. Measurements of diffusion coefficients were also performed in vivo and post-mortem on healthy rats, achieving satisfactory signal-to-noise ratios (SNRs), and SF6 gas was found to be in an almost completely restricted diffusion regime in the lung, i.e., the transport by molecular diffusion is delayed by collisions with barriers such as the alveolar septa. This observed low diffusivity means that this gas will be less sensitive to structural changes in the lungs than other magnetic resonance sensitive gas such as 3He, particularly at human scale. However, it is still possible that SF6 plays a role since it opens a new structural window. Thus, the interest of researchers in delimiting the important limiting technical factors that makes this process very challenging is obvious. Among them, T2 relaxation is very fast, so gradient systems with very fast switching rate and probably large radiofrequency (RF) power and high field systems will be needed for hexafluoride to be used in human studies.
    Respiratory Physiology & Neurobiology 09/2005; 148(1-2):43-56. · 2.05 Impact Factor
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    ABSTRACT: An approach for an animal MRI-compatible ventilator is described, which might be useful for some applications, such as those dependent on gas flow. The ventilator has been optimized for small rodents, although the instrument may easily be conveyed to human scale. Its essential features are a real-time module that also prevents lung overpressure, control from a personal computer through a versatile parallel port, small dead volume (0.24 ± 0.02 cm3 and about 0.8 cm3, including the endotracheal tube volume), and a specifically designed pneumatic breathing module compatible with hyperpolarized gases. One distinguishing characteristic from previously published approaches is a fast-acting open/close pneumatic valve arrangement (delays are lower than 5 ms after software postcorrection) that allows the system to reproduce animal breathing rates and to generate different breathing patterns and gas mixtures. The gas mixing compositions quantified from valve opening times agree (error lower than 3 %) with the experimental values measured by mass spectrometry. The inspiratory and expiratory transit time delays (opening and closing pneumatic ports) are short and highly reproducible. The ventilator has been evaluated in vivo for different breathing patterns with rats using MRI techniques, as it includes an additional stage to acquire NMR data or locate excitation pulses in synchronism with a specific point in the respiratory cycle. Finally, it has been made using locally available low-cost materials, and no system faults or errors have been reported during 1 year of operation. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson 26B: 93–103, 2005.
    Concepts in Magnetic Resonance Part B Magnetic Resonance Engineering 07/2005; 26B(1):93 - 103. · 0.71 Impact Factor