Corrección de atenuación de imágenes PET usando datos de TAC en el escáner para animales pequeños Argus PET/CT

Actas de: XXVIII Congreso Anual de la Sociedad Española de Ingeniería Biomédica (CASEIB 2010). Madrid, 24-26 de noviembre de 2010.Existen diversos efectos físicos que degradan la calidad de la imagen PET, como por ejemplo la atenuación que sufren los fotones al atravesar el cuerpo en estudio. Este efecto reduce el número de fotones detectados, pero puede corregirse si se dispone de información anatómica del objeto. En este trabajo se describe la corrección de atenuación basada en una imagen TAC para el escáner de animales pequeños Argus PET/CT con imágenes PET reconstruidas con el algoritmo iterativo 3DOSEM.Este trabajo ha sido financiado en parte por el MEC (FPA2007-62216), la UCM (Grupos UCM, 910059), el CPAN (Consolider-Ingenio 2010, CSPD-2007-00042), la red RECAVA-RETIC el proyecto ARTEMIS (S2009/DPI-1802, Fondo Europeo de Desarrollo Regional), el proyecto ENTEPRASE (PSE-300000-2009-5, MICINN. España), por los proyectos del Ministerio de Ciencia e Innovación, TEC2007-64731, TEC 2008-06715-C02-1, la RETIC-RECAVA del Ministerio de Sanidad y Consumo, y el proyecto EU FP7 FMT-XCT-201792.Publicad

Restauración fluvial aplicando Algoritmos Genéticos Multiobjetivo

Analizando los procesos de gestión de los recursos ambientales, es evidente el aumento de la preocupación por el medio ambiente, configurándolo como un factor más (conjuntamente con criterios económicos, tecnológicos, etc.) a tener en cuenta en los procesos de toma de decisiones. Esta combinación de factores de diversa naturaleza complica el análisis cuantitativo de las alternativas a las que se ha de enfrentar el decisor, más aún si se tiene en cuenta que típicamente los factores ambientales, por su propia naturaleza, suelen ser de difícil comparación y cuantificación.La utilización de un sistema de ayuda a la decisión multicriterio que integran como motor de optimización un algoritmo genético multiobjetivo resulta idónea para la aplicación

Upscaling 3D coupled hydro mechanical properties of fractured porous rocks

A methodology for upscaling 3D coupled Hydro-Mechanical (HM) properties of fractured porous rocks is developed theoretically, tested on synthetic fractured rock samples, and applied to a real site. The upscaled HM equations take into account the HM coupling in the dual matrix/fracture medium, comprising the cracks system as well as the intact porous matrix, yielding the equivalent stiffness tensor and two different sets of equivalent tensorial Biot coefficients Bij (I) and Bij (II) and moduli M(I) and M(II) for the upscaled system (I and II become identical only under certain hypotheses). We provide detailed theoretical expressions in the general tensorial case,and in the particular case of statistically homogeneous and isotropic cracks. The real site application is performed in a damaged and fractured claystone around the GMR gallery (Meuse/Haute-Marne Underground Research Laboratory). The geometric structure of the fracture set around the "Excavation Damage Zone" of the GMR gallery is described by a hybrid model comprising: (i) a set of 10 000 fissures with radially inhomogeneous statistics (size, thickness and density increasing towards the wall) and; (ii) a deterministic set of large curved fractures, periodically spaced along the axis of the gallery according to a 3D chevron pattern. Both "3D" and "2D transverse" distributions of the upscaled coefficients are calculated, and displayed using spheres or ellipsoids. Global tensorial coefficients are also obtained by upscaling the entire annular fractured zone. Equivalent isotropic coefficients are extracted from these tensors: Young modulus E, bulk modulus K, Lamé shear modulus μ, Poisson ratio ν, and HM coupling coefficients: the Biot coefficient B and the Biot modulus M. In all cases considered, we discuss the impact of the degree of fissuring and fracturing on the upscaled stiffness and hydromechanical coefficients

A decision support tool (R-SWAT-DS) for integrated watershed management

Best management practices (BMPs) can be used effectively to reduce nutrient and sediment loads generated from point sources or non-point sources to receiving water bodies. Methodologies for optimal, cost effective BMP selection and placement are needed to assist watershed management planners and stakeholders. We developed a modeling-optimization framework that can be used to find cost-effective solutions of BMP placement to attain nutrient load reduction targets. The framework integrates the Soil and Water Assessment Tool (SWAT) watershed model, spatial representation of BMPs, an economic component, and multi-objective optimization routines in the R environment. The framework can be used to launch individual or iterative BMPs simulations, or search for optimal strategies. Advanced plotting, mapping and statistical analysis functionalities that facilitate the interpretation and assessment of the results are included

Initial results of the explore vista small-animal positron emission tomography/computed tomography

[Abstract] The second International conference of the European Society for Molecular Imaging in Naples, Italy June 14-15, 2007Publicad

Assessment of a new CT system for small animals

Proceeding of: 2006 IEEE Nuclear Science Symposium Conference Record, San Diego, CA, Oct. 29 - Nov. 1, 2006We have developed an X-ray cone beam tomograph for in vivo small-animal imaging using a flat panel detector (CMOS technology with a columnar CsI scintillator plate) and a microfocus X-ray source in a geometric configuration with 1.6 magnification and 7.5 cm2 field of view. This work presents an initial characterization of this new system. We measured the detector modulation transfer function (MTF), detector stability, system resolution, the quality of the reconstructed tomographic images and radiated dose. The system resolution was measured following the standard test method ASTM E1696-95. For image quality evaluation, we assessed signal to noise ratio (SNR) and contrast to noise ratio (CNR) with respect to radiated dose. Measurements have been performed on Hounsfield-calibrated images of quantitative phantoms. Effective dose studies have been performed introducing TLD dosimeters in representative organs (ICRU criteria) of euthanized laboratory rats for different imaging protocols. Noise measurements indicate that 50 HU can be achieved at a dose of 10 cGy. Effective dose in standard research methods is below 200 mSv, confirming that the system is appropriate for in vivo imaging. Maximum spatial resolution achieved is better than 50 microns. Experimental results on image quality phantoms as well as on in-vivo studies show that the use of CMOS flat panel is a good choice in terms of quality with respect to radiated dose.This work was supported in part by the Spanish Ministerio de Educación y Ciencia under Grant No. TEC2004-07052-C02, la Comunidad de Madrid Grant No. GR/SAL/024104 CD Team,and the CENIT program of the Spanish Ministerio de Industria

Design and development of a high performance micro-CT system for small-animal imaging

Proceeding of: 2006 IEEE Nuclear Science Symposium Conference Record, San Diego, CA, Oct. 29 - Nov. 1, 2006The goal of this work was the development of a lowcost micro-CT scanner, which could be used as an add-on in our previously developed PET systems for small-animals. The scanner design consists of a single-processor computer controlling a micro-focus X-ray tube and a flat panel detector, assembled in a common rotating gantry. The geometrical configuration was selected to achieve a spatial resolution of about 12 lp/mm with a field of view appropriate for small animals such as mice and rats. The radiated dose is controlled during the acquisition by two different elements: an aluminium filter and a tungsten shutter, attached to the X-ray source. The shutter is controlled by the computer in synchronism with the gantry rotation and the detector image integration. In order to achieve high performance with regards to per-animal screening time and cost, the acquisition protocol is able to take advantage from the highest frame rate of the detector also performing onthe-fly corrections for the detector raw data. These corrections include geometrical misalignments, sensor non-uniformities and defective elements, as well as conversion to attenuation images. An FDK reconstruction algorithm adapted to the specific conebeam geometry has been implemented. Symmetries are exploited to accelerate the algorithm and fast back-projection techniques have been developed for those protocols where high resolution is not a requirement.This work was supported in part by the Spanish Ministerio de Educación y Ciencia under Grant No. TEC2004-07052-C02, la Comunidad de Madrid Grant No. GR/SAL/024104 CD Team, and the CENIT program of the Spanish Ministerio de Industria

Software architecture for multi-bed FDK-based reconstruction in X-ray CT scanners

Most small-animal X-ray computed tomography (CT) scanners are based on cone-beam geometry with a flat-panel detector orbiting in a circular trajectory. Image reconstruction in these systems is usually performed by approximate methods based on the algorithm proposed by Feldkamp et al. (FDK). Besides the implementation of the reconstruction algorithm itself, in order to design a real system it is necessary to take into account numerous issues so as to obtain the best quality images from the acquired data. This work presents a comprehensive, novel software architecture for small-animal CT scanners based on cone-beam geometry with circular scanning trajectory. The proposed architecture covers all the steps from the system calibration to the volume reconstruction and conversion into Hounsfield units. It includes an efficient implementation of an FDK-based reconstruction algorithm that takes advantage of system symmetries and allows for parallel reconstruction using a multiprocessor computer. Strategies for calibration and artifact correction are discussed to justify the strategies adopted. New procedures for multi-bed misalignment, beam-hardening, and Housfield units calibration are proposed. Experiments with phantoms and real data showed the suitability of the proposed software architecture for an X-ray small animal CT based on cone-beam geometry.This work was partially funded by AMIT project from the CDTI CENIT program, TEC2007-64731, TEC2008-06715- C02-01, RD07/0014/2009, TRA2009 0175, RECAVA-RETIC, and RD09/0077/00087 (Ministerio de Ciencia e Inovación), and ARTEMIS S2009/DPI-1802 (Comunidad de Madrid).Publicad

VrPET/CT: development of a rotating multimodality scanner for small-animal imaging

Proceeding of: 2008 IEEE Nuclear Science Symposium Conference Record (NSS '08), Dresden, Germany, 19-25 Oct. 2008This work reports on the development and evaluation of the PET component of a PETtCT system for small-animal in-vivo imaging. The PET and CT subsystems are assembled in a rotary gantry in such a way that the center of rotation for both imaging modalities is mechanically aligned. The PET scanner configuration is based on 2 detector modules, each of which consist of 2 flat-panel type PS-PMTs (Hamamatsu, H8500) and 2 (30 x 30 elements) LYSO arrays. The dimension of the crystal matrix elements are 1.4 x 1.4 mm2 in cross section and 12 mm in depth. The VrPET detector modules are positioned in opposite sides of a 140 mm diameter ring, providing a transaxial field of view of 86.6 mm diameter and an axial field of view of 45.6 mm. The experimental results obtained in the performance tests are transaxial resolution of 1.5 mm FWHM in the CFOV, and the axial resolution of 2.3 mm FWHM. The absolute coincidence sensitivity is 2.22 % for a coincidence window of 6 ns (100-700 keY). The imaging capability of the PET unit is demonstrated on phantom and animal studies.This work is partially funded by the CD-TEAM project, CENIT Program, Spanish Ministerio de Industria and with grants from the Ministerio de Educaci6n y Ciencia, Projects TEC2007-6473I and TEC2008-06715-C02-01Publicad

Use of IBASPM atlas-based automatic segmentation toolbox in pathological brains: effect of template selection

Proceeding of: 2008 IEEE Nuclear Science Symposium Conference Record (NSS '08), Dresden, Germany, 19-25 Oct. 2008IBASPM software is an atlas-based method for automatic segmentation of brain structures, available as a freeware toolbox for the SPM package. To test the influence of the atlas when segmenting normal and pathologic brains, manual segmentation of the caudate nucleus head was compared to automatic segmentations using four different atlases: the default MNI AAL atlas; a customized atlas created from a combined sample of patients (n=20) and controls (n=18); and a customized atlas obtained separately for each group. Maximum average ratio of overlapping voxels (dice overlap) between manual and automatic segmentation was 71 o~ for controls and 52% for patients. In both groups, overlap ratios were better when using the customized atlases, instead of the standard MNI AAL atlas. Accuracy of the method was biased between left and right hemispheres, and also between groups, individual variability being higher in patients than in controls. Volumetric measurements using the customized atlases were also more accurate than using the MNI AAL atlas. Volume data were closer to manual segmentation values than dice overlap ratio (average differences ranging from 22.7°~ for MNI AAL atlas to 10.1 for customized atlas of patients and controls combined). Results suggests a low overaU performance of IBASPM as an automatic segmentation method for the head of the caudate nucleus. Because of the biases observed, the use of this method for analyzing caudate nucleus in patients presenting anatomical abnormalities should be cautiously carried out.This work is partially funded by the following projects: CD-TEAM Project, CENIT Program (Spanish Ministerio de Industria)~ FIS PI052271 (Spanish Ministerio de Sanidad y Consumo)~ and Fundación Mutua Madrilen