Examinando por Autor "Yotti, R"

Mostrando 1 - 13 de 13

A New Method for Single-Step Robust Post-Processing of Flow Color Doppler M-Mode Images Using Support Vector Machines
(2009-06-15T10:08:10Z) Conde Pardo, P; Guerrero Curieses, A; Rojo-Álvarez, José Luis; Yotti, R; Requena Carrión, J; Antoranz, José Carlos; Bermejo, Javier
Intra-cardiac pressure gradients (ICPG) are usually es timated by post-processing of flow Color Doppler M-mode images (CDMMI) by using a sequence of processing steps. We propose a novel image processing method which gives a single-step approximation of the ICPG image, based on a simple, yet specifically developed, Support Vector Machine (SVM) algorithm. Our method only requires the SVM estimation of the blood velocity from the CDMMI. Given that ICPG images are obtained by deterministic operators (Euler's momentum equation) on the blood velocity, the ICPG estimation is a simple model that consists of the same coefficients and the operator applied to the Mercer's kernel. A diverse-width Mercer's kernel is proposed, as an alternative to conventional Radial Basis Function kernel. Simulations on a synthetic model and approximations of a real example image, trained with up to 10% of the pixels, show the possibilities of this new single-step postprocessing method.
A Noninvasive Method for Assessing Impaired Diastolic Suction in Patients With Dilated Cardiomyopathy
(2009-07-14T11:31:16Z) Yotti, R; Bermejo, Javier; Antoranz, José Carlos; Desco, Mar; Cortina, Cristina; Rojo-Álvarez, José Luis; Allué, Carmen; Martín, Laura; Moreno, Mar; Serrano, JA; Muñoz, Roberto; García Fernández, MA
Caracterización no invasiva de la contractilidad miocárdica mediante el análisis de los gradientes de presión intraventricular derivados de imágenes de Doppler-color
(2009-07-28T10:11:23Z) Yotti, R; Bermejo, Javier; Desco, Mar; Cortina, Cristina; Antoranz, José Carlos; Rojo-Álvarez, José Luis; Moreno, Mar; García Fernández, MA
Characterization of Aortic Input Impedance in the Supplemental Domain
(2005-09-01) Martínez Cruz, CE; Rojo-Álvarez, José Luis; Vallejo Ramos, FJ; Yotti, R; Antoranz, JC
Dependencia de la precarga y postcarga de los gradientes de presión intraventricular sistólicos medidos mediante ecocardiografía Doppler
(2009-07-28T10:20:30Z) Yotti, R; Bermejo, Javier; Desco, Mar; Antoranz, José Carlos; Rojo-Álvarez, José Luis; Cortina, Cristina; Rodríguez Abella, Hugo; García Fernández, MA
Doppler-Derived Ejection Intraventricular Pressure Gradients Provide a Reliable Assessment of Left Ventricular Systolic Chamber Function
(2009-07-23T10:19:06Z) Yotti, R; Bermejo, Javier; Desco, Mar; Antoranz, José Carlos; Rojo-Álvarez, José Luis; Cortina, Cristina; Allué, Carmen; Rodríguez Abella, Hugo; Moreno, Mar; García Fernández, Miguel Ángel
Effect of Spatial, Temporal, and Velocity Resolution on Doppler Tissue Image Derived Indices
(2009-06-15T09:59:02Z) Rojo-Álvarez, José Luis; Bermejo, Javier; Rodríguez González, AB; Yotti, R; Martínez Fernández, A; García Fernández, MA; Antoranz, José Carlos
Many indices derived from color Roppler Tissue Imaging (UTI) are computed mathematically from the velociy fields provided by the ultrasound scanner We developed a procedure for assessing the uncertainty that temporal, spatial, and velociry resolution causes on cardiovascular parameter5 derived from myocardial velociry. A first-order Taylor's series for the functional relationship between velocity and the cardiac index under study is proposed, and analytically solved by using the chain rule. Pedormance on myocardial acceleration, strain, and strain rate, was tested both on a simulation model (symbolic calculations) and on a clinical image example. Velociry and temporal resolutions were the most determinant on DTI-derived parameters, and increasing color-Doppler bit-depth from 5 to 7 bils reduced to less than 10% the uncertainty of all the analyzed indices. Taylor-based error bounds are a useful tool tu assess the effect of resolution on quantitative cardiovascular indices derived from tissue velocity measurements.
Estimación Paramétrica de la Impedancia de Entrada Arterial: Alcance y Limitaciones
(2009-07-28T09:47:27Z) Arenas García, J.; Rojo-Álvarez, José Luis; Yotti, R; Antoranz, José Carlos; García Fernández, MA; Bermejo, Javier
El estudio de la función ventricular a través de la impedancia de entrada arterial se ha realizado habitualmente mediante el desarrollo en Series de Fourier de la presión aórtica y del flujo de salida valvular. Aunque el modelado paramétrico ha sido propuesto como un método alternativo de estimación de la impedancia, no ha sido utilizado en la práctica. En este trabajo se estudia el valor y las limitaciones de los métodos de modelado paramétrico utilizando señales de presión y flujo obtenidas in vivo. Se concluye que la estimación de la admitancia, el inverso de la impedancia, es un problema clínicamente equivalente pero numéricamente mejor condicionado para la estimación paramétrica.
Estimation of the End of Ejection in aortic Stenosis. An Unreported Source of Error in the Invasive Assessment of Severity
(2009-07-23T10:11:51Z) Bermejo, Javier; Rojo-Álvarez, José Luis; Antoranz, José Carlos; Abel, Mónica; G. Burwash, Ian; Yotti, R; Moreno, Mar; García Fernández, Miguel Ángel; G. Lehmann, Kenneth; M. Otto, Catherine
Impact of Image Spatial, Temporal, and Velocity Resolutions on Cardiovascular Indices Derived from Color-Doppler Echocardiography
(2009-07-23T09:04:29Z) Rojo-Álvarez, José Luis; Bermejo, Javier; Rodríguez González, Ana Belén; Martínez Fernández, A; Yotti, R; García Fernández, Miguel Ángel; Antoranz, José Carlos
Quantitative processing of color-Doppler echocardiographic images has substantially improved noninvasive assessment of cardiac physiology. Many indices are computed from the velocity fields derived either from color-Doppler tissue imaging (DTI), such as acceleration, strain and strain-rate, or from blood-flow color-Doppler, such as intracardiac pressure gradients (ICPG). All of these indices are dependent on the finite resolution of the ultrasound scanner. Therefore, we developed an image-dependent method for assessing the influence of temporal, spatial, and velocity resolutions, on cardiovascular parameters derived from velocity images. In order to focus our study on the spatial, temporal, and velocity resolutions of the digital image, we did not consider the effect of other sources of noise such as the interaction between ultrasound and tissue. A simple first-order Taylor's expansion was used to establish the functional relationship between the acquired image velocity and the calculated cardiac index. Resolutions were studied on: (a) myocardial acceleration, strain, and strain-rate from DTI, and (b) ICPG from blood-flow color-Doppler. The performance of Taylor's-based error bounds (TBEB) was demonstrated on simulated models and illustrated on clinical images. Velocity and temporal resolution were highly relevant for the accuracy of DTI-derived parameters and ICPGs. TBEB allow to assess the effects of ideal digital image resolution on quantitative cardiovascular indices derived from velocity measurements obtained by cardiac imaging techniques.
Noninvasive Assessment of Ejection Intraventricular Pressure Gradients
(2009-07-23T10:26:02Z) Yotti, R; Bermejo, Javier; Antoranz, José Carlos; Rojo-Álvarez, José Luis; Allué, Carmen; Silva, Jacobo; Desco, Mar; Moreno, Mar; García Fernández, Miguel Ángel
Noninvasive Assessment of the Right Ventricular Filling Pressure Gradient
(2009-07-23T10:33:36Z) Cortina, Cristina; Bermejo, Javier; Yotti, R; Desco, Mar; Rodríguez Pérez, Daniel; Antoranz, José Carlos; Rojo-Álvarez, José Luis; García, Damien; García Fernández, Miguel Ángel; Fernández Avilés, F.
Noninvasive Estimation of Maximum Elastance from Color-Doppler M-Mode Echocardiograms Using Support Vector Machines
(2009-06-15T09:52:52Z) Rojo-Álvarez, José Luis; Bermejo, Javier; Juarez Caballero, VM; Yotti, R; García Fernández, MA; Antoranz, José Carlos