An accurate discretization for an inhomogeneous transport equation with arbitrary coefficients and source

A new way of obtaining the algebraic relation between the nodal values in a general one-dimensional transport equation is presented. The equation can contain an arbitrary source and both the convective flux and the diffusion coefficient may vary arbitrarily. Contrary to the usual approach of approximating the derivatives involved, the algebraic relation is based on the exact solution written in integral terms. The required integrals can be speedily evaluated by approximating the integrand with Hermite splines or applying Gauss quadrature rules. The startling point about the whole procedure is that a very high accuracy can be obtained with few nodes, and more surprisingly, it can be increased almost up to machine accuracy by augmenting the number of quadrature points or the Hermite spline degree with little extra cost

Comparison of the ENATE approach and discontinuous Galerkin spectral element method in 1D nonlinear transport equations

In this paper a comparison of the performance of two ways of discretizing the nonlinear convection-diffusion equation in a one-dimensional (1D) domain is performed. The two approaches can be considered within the class of high-order methods. The first one is the discontinuous Galerkin method, which has been profusely used to solve general transport equations, either coupled as the Navier-Stokes equations, or on their own. On the other hand, the ENATE procedure (Enhanced Numerical Approximation of a Transport Equation), uses the exact solution to obtain an exact algebraic equation with integral coefficients that link nodal values with a three-point stencil. This paper is the first of thorough assessments of ENATE by comparing it with well-established high-order methods. Several test cases of the steady Burgers' equation with and without source have been chosen for comparison

Preliminary results of the small animal rotational positron emisson tomography scanner

[Abstract] AMI Annual Conference 2004, March 27-31, Orlando, FloridaThis contribution reports preliminary results of a high-resolution small animal positron emission tomography (PET) based on pairs of opposed scintillation rotating detectors working in time coincidencePublicad

Exact positioning for OSEM reconstructions on the atlas depth-of-interaction small animal scanner

[Abstract] AMI Annual Conference 2002, October 23 - 27Publicad

Features of the NIH atlas small animal pet scanner and its use with a coaxial small animal volume CT scanner

Proceeding of: 2002 IEEE International Symposium On Biomedical Imaging, Washington, D.C., USA, July 7-10, 2002ATLAS (Advanced Technology Laboratory Animal Scanner), a small animal PET scanner designed to image animals the size of rats and mice, is about to enter service on the NIH campus in Bethesda, Maryland. This system is the first small animal PET scanner with a depth-ofinteraction capability and the first to use iterative resolution recovery algorithms, rather than conventional filtered back projection, for "production" image reconstruction. ATLAS is also proximate to, and co-axial with, a high resolution small animal CT scanner. When fully integrated, spatially registered PET and CT images of each animal will be used to correct the emission data for radiation attenuation and to aid in target identification. In this report we describe some of the technical and functional features of this system and illustrate how these features are used in an actual small animal imaging studyThis work was supported in part by projects FIS 00/0036 and 11I PRICIT Comunidad de Madrid, Spain

Imagen de alta resolución en pequeños animales de laboratorio

La posibilidad de visualizar y cuantificar la función de un determinado órgano en animales de laboratorio es una herramienta científica de gran importancia en el estudio de modelos de enfermedades humanas, en el descubrimiento y desarrollo de nuevos medicamentos y en la caracterización del fenotipo de animales transgénicos y noqueados. La tomografía por emisión de positrones (PET) y la imagen proyectiva de radiofármacos marcados con emisores de positrones proporcionan una herramienta genérica y no invasiva para la investigación científica en los casos anteriormente expuestos. En este trabajo se describe un sistema mutimodal PET/CT basado en cámaras de coincidencia y detectores de estado sólido para los rayos X, diseñado para adquirir tanto imágenes tomográficas como de proyección con alta resolución temporal, con capacidad para visualizar ratas y ratones, estos últimos en cuerpo completo en un solo campo de visión.Publicad

Estudio de la viabilidad de la integración de un Sistema de Posicionamiento Óptico en el entorno de la radioterapia intraoperatoria

Actas de: XXIX Congreso Anual de la Sociedad Espñaola de Ingeniería Biomédica (CASEIB 2011). Cáceres, 16-18 Noviembre 2011.La radioterapia intraoperatoria (RIO) es una técnica que combina cirugía y radioterapia, que se aplica en pacientes con tumores para los que se ha indicado su resección y con alto riesgo recidivante. El oncólogo radioterapeuta planifica esta intervención sobre una imagen TAC del paciente. Sin embargo, los datos del escenario real encontrado en la sala de tratamiento (posición y orientación del aplicador respecto del paciente y energía del haz) se deben recoger de forma manual para actualizar la planificación. Esta información es muy valiosa para la documentación y posterior seguimiento del procedimiento realizado. En este trabajo se evalúa la viabilidad de la integración de un sistema de posicionamiento óptico en el entorno RIO, y su precisión para localizar el aplicador sobre la imagen de planificación.Este trabajo ha sido financiado por el Minsiterio de Ciencia e Innovación (PI09/90568 IPT-3000000-2010-3, TEC2010-21619-C04-01), la Comunidad de Madrid (ARTEMIS S2009/DPI-1802) y fondos FEDER.Publicad

Intraoperative computed tomography imaging for dose calculation in intraoperative electron radiation therapy: Initial clinical observations

In intraoperative electron radiation therapy (IOERT) the energy of the electron beam is selected under the conventional assumption of water-equivalent tissues at the applicator end. However, the treatment field can deviate from the theoretic flat irradiation surface, thus altering dose profiles. This patient-based study explored the feasibility of acquiring intraoperative computed tomography (CT) studies for calculating three-dimensional dose distributions with two factors not included in the conventional assumption, namely the air gap from the applicator end to the irradiation surface and tissue heterogeneity. In addition, dose distributions under the conventional assumption and from preoperative CT studies (both also updated with intraoperative data) were calculated to explore whether there are other alternatives to intraoperative CT studies that can provide similar dose distributions. The IOERT protocol was modified to incorporate the acquisition of intraoperative CT studies before radiation delivery in six patients.This study was supported by Ministerio de Ciencia, Innovación y Universidades (http://www.ciencia.gob.es) [grant number TEC2013–48251-C2 to JP, VG-V and MJL-C], co-funded by European Regional Development Fund (ERDF), “A way of making Europe” (https://ec.europa.eu/regional_policy/en/funding/erdf); by Ministerio de Ciencia, Innovación y Universidades (http://www.ciencia.gob.es), Instituto de Salud Carlos III (https://www.isciii.es) [grant numbers DTS14/00192 to JP, VG-V and FAC; PI15/02121 to FAC and JC-H; PI18/01625 to JP], co-funded by European Regional Development Fund (ERDF), “A way of making Europe” (https://ec.europa.eu/regional_policy/en/funding/erdf); and by Comunidad de Madrid (http://www.comunidad.madrid) [grant number TOPUS-CM S2013/MIT3024 to JP], co-funded by European Structural and Investment Fund (https://ec.europa.eu/info/funding-tenders/funding-opportunities/funding-programmes/overview-funding-programmes_en). The CNIC is supported by the Ministerio de Ciencia, Innovación y Universidades (http://www.ciencia.gob.es) and the Pro CNIC Foundation (https://www.fundacionprocnic.es) [to MD], and is a Severo Ochoa Center of Excellence (SEV-2015-0505). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Small-animal PET registration method with intrinsic validation designed for large datasets

Proceeding of: 2007 IEEE Nuclear Science Symposium Conference Record (NSS'07), Honolulu, Hawaii, USA, Oct. 27 - Nov. 3, 2007We present a procedure to validate the results of small animal Positron Emission Tomography (PET) image registration by means of consistency measures. Small animal 2-Deoxy-2-[F-18]fluoro-D-glucose (FDG) PET studies do not show the same intensity distribution even for images acquired in similar conditions, as the resulting image is influenced by several variables which are not always completely under control. Because of these difficulties, the results from automatic registration methods have to be visually inspected to detect failures. We propose a method to automate this validation process. Two reference images from the dataset are selected by an expert user avoiding images with poor contrast, animal movement or low quality, and both are co-registered using anatomical landmarks. All the remaining images in the dataset are then registered to every reference with an automatic two-step algorithm based on Mutual Information. The known transformation relating both references allows measuring the registration consistency, which is a good estimator of the accuracy of the alignment process, for every image in the dataset. This value can be used to assess the quality of the registration and therefore detect the incorrect results. We have applied this validation process on a large dataset of 120 FDG-PET rat brain images obtained with a rotating PET scanner. The registration consistency was calculated for every image in the dataset and values below 1.65 mm (PET image resolution) were considered as successful registrations. 116 images were correctly registered with an average error of 0.839 mm, while in four images the proposed method detected a registration failure. Two of these failures were due to very low image quality and these studies were discarded from the study, while the other two were correctly aligned after applying a manual pre-alignment step. Our approach requires minimal user interaction and provides automatic assessment of the registration error, making it unnecessary to visually inspect and check every registration result.This work was supported by projects CIBER CB06/01/0079 (Ministerio de Sanidad y Consumo) and CDTEAM (CENIT program, Ministerio de Industria)

The knee prosthesis constraint dilemma: Biomechanical comparison between varus-valgus constrained implants and rotating hinge prosthesis. A cadaver study

The real degree of constriction of rotating hinge knee (RHK) and condylar constrained prostheses (CCK) is a matter of discussion in revision knee arthroplasty. The objectives of this study are to compare the tibial rotation of both implants and validate the use of inertial sensors with optical tracking system as movement measurement tools. A total of 16 cadaver knees were used. Eight knees were replaced using a RHK (Endomodel LINK), and the remaining eight received a CCK prosthesis (LCCK, Zimmer). Tibial rotation range of motion was measured in full extension and at 30°, 60°, and 90° of flexion, with four continuous waveforms for each measurement. Measurements were made using two inertial sensors with specific software and compared with measurements obtained using the gold standard technique - the motion capture camera. The comparison of the accuracy of both measurement methods showed no statistically significant differences between inertial sensors and motion capture cameras, with p > .1; the mean error for tibial rotation was 0.21°. Tibial rotation in the RHK was significantly greater than in the CCK (5.25° vs. 2.28°, respectively), p < .05. We have shown that RHK permit greater tibial rotation, being closer to physiological values than CCKs. Inertial sensors have been validated as an effective and accurate method of measuring knee movement. The clinical significance: RHK appears to represent a lower constriction degree than CCK systems.This study wassupported by Ministerio de Ciencia, Innovación y Universidades, Instituto de Salud Carlos III and European Regional Development Fund "Una manera de hacer Europa" (grant number PI18/01625