Browsing by Author "Irarrázaval Mena, Pablo"

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    3D multiple sound source localization by proposed cuboids nested microphone array in combination with adaptive wavelet-based subband GEVD
    (2020) Firoozabadi, A. D.; Irarrázaval Mena, Pablo; Adasme, P.; Zabala Blanco, D.; Palacios Jativa, P.; Azurdia Meza, C.
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    3D quantification of hemodynamics parameters of pulmonary artery and aorta using finite-element interpolations in 4D flow MR data
    (2015) Sotelo Parraguez, Julio Andrés; Urbina, Jesus.; Valverde, Israel.; Tejos Núñez, Cristián Andrés; Irarrázaval Mena, Pablo; Hurtado Sepúlveda, Daniel; Uribe Arancibia, Sergio A.
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    3D Quantification of Wall Shear Stress and Oscillatory Shear Index Using a Finite-Element Method in 3D CINE PC-MRI Data of the Thoracic Aorta
    (2016) Sotelo Parraguez, Julio Andrés; Urbina, Jesus; Valverde, Israel; Tejos Nunez, Cristian Andres; Irarrázaval Mena, Pablo; Andia Kohnenkampf, Marcelo Edgardo; Uribe Arancibia, Sergio A.; Hurtado Sepúlveda, Daniel
    Several 2D methods have been proposed to estimate WSS and OSI from PC-MRI, neglecting the longitudinal velocity gradients that typically arise in cardiovascular flow, particularly on vessel geometries whose cross section and centerline orientation strongly vary in the axial direction. Thus, the contribution of longitudinal velocity gradients remains understudied. In this work, we propose a 3D finite-element method for the quantification of WSS and OSI from 3D-CINE PC-MRI that accounts for both in-plane and longitudinal velocity gradients. We demonstrate the convergence and robustness of the method on cylindrical geometries using a synthetic phantom based on the Poiseuille flow equation. We also show that, in the presence of noise, the method is both stable and accurate. Using computational fluid dynamics simulations, we show that the proposed 3D method results in more accurate WSS estimates than those obtained from a 2D analysis not considering out-of-plane velocity gradients. Further, we conclude that for irregular geometries the accurate prediction of WSS requires the consideration of longitudinal gradients in the velocity field. Additionally, we compute 3D maps of WSS and OSI for 3D-CINE PC-MRI data sets from an aortic phantom and sixteen healthy volunteers and two patients. The OSI values show a greater dispersion than WSS, which is strongly dependent on the PC-MRI resolution. We envision that the proposed 3D method will improve the estimation of WSS and OSI from 3D-CINE PC-MRI images, allowing for more accurate estimates in vessels with pathologies that induce high longitudinal velocity gradients, such as coarctations and aneurisms.
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    4D FLOW: Una nueva herramienta de diagnóstico para cardiopatías congénitas
    (2011) Pinochet, N.; Bächler, P.; Tejos, C.; Crelier, G.; Parra Rojas, Rodrigo Orlando; Allendes, J. M.; Irarrázaval Mena, Pablo; Uribe, S.
    Purpose. To demonstrate the utility of 4D flow MR imaging for analyzing blood flow patterns and flow distribution in patients with congenital heart diseases. Methods: Six patients with congenital heart diseases were scanned using a standard cardiac MRI protocol, according to their condition. Additionally, 2D flow sequences of the great vessels, and a 4D flow sequence covering the entire heart were acquired. Flow patterns were visualized by using vector fields, streamlines and particle traces. Results: 4D flow technique depicted vortices and helical flow in the pulmonary artery of most patients, as well as in the aorta and superior vena cava of one patient with corrected aortic coarctation and a levoatrial cardinal vein. Conclusion: 4D flow MR imaging enables the identification of flow patterns difficult to detect with other diagnostic modalities. Comprehensive evaluation of flow patterns might help to understand the hemodynamic consequences of congenital heart diseases and their surgical procedures.
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    A multi-channel speech enhancement method based on subband affine projection algorithm in combination with proposed circular nested microphone array
    (2021) Firoozabadi, A. D.; Irarrázaval Mena, Pablo; Adasme, P.; Durney, H.; Olave, M. S.; Zabala Blanco, D.; Azurdia Meza, C.
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    A novel method for estimating the number of speakers based on generalized eigenvalue-vector decomposition and adaptive wavelet transform by using K-means clustering
    (2020) Dehghan Firoozabadi, A.; Irarrázaval Mena, Pablo; Adasme, P.; Zabala Blanco, D.; Azurdia Meza, C.
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    A realistic MR compatible aortic phantom to validate hemodynamic parameters from MRI data: aortic coarctation patients comparison using catheterization
    (2015) Urbina, Jesus; Sotelo Parraguez, Julio Andrés; Tejos Núñez, Cristián Andrés; Irarrázaval Mena, Pablo; Andía Kohnenkampf, Marcelo Edgardo; Razavi, Reza; Valverde, Israel; Uribe Arancibia, Sergio A.
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    A technique for reconstruction using intensity order (TRIO) : an application to undersampled data
    (2008) Ramírez Mac-Lean, Leonardo Andrés; Irarrázaval Mena, Pablo; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    La naturaleza no invasiva de las Imágenes de Resonancia Magnética (MRI por sus siglas en inglés) junto con su flexibilidad las han convertido en una técnica de imágenes médicas muy usada. Sin embargo, los largos tiempos de adquisición han limitado su uso para imágenes dinámicas y 3D. Una forma de resolver este problema ha sido el submuestreo del espacio-k, permitiendo menores tiempos de adquisición, seguido por un algoritmo de reconstrucción que recupera la información que no fue adquirida usando algún tipo de información previa. La mayoría de los métodos de reconstrucción tales como keyhole, sliding window y k-t BLAST son susceptibles a introducir borrosidad espacial o temporal en las imágenes.
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    Accelerating the acquisition of the 3D Dual Cardiac Phase technique using RPE trajectories
    (2014) Letelier Farías, Karis del Pilar; Andía Kohnenkampf, Marcelo Edgardo; Tejos Núñez, Cristián Andrés; Irarrázaval Mena, Pablo; Prieto Vásquez, Claudia; Uribe Arancibia, Sergio A.
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    Adipose tissue MRI for quantitative measurement of central obesity
    (2013) Poonawalla, Aziz H.; Sjoberg, Brett P.; Rehm, Jennifer L.; Hernando, Diego; Hines, Catherine D.; Irarrázaval Mena, Pablo; Reeder, Scott B.
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    Application of the fractional Fourier transform to image reconstruction in MRI
    (2009) Parot Fernández, Vicente José; Irarrázaval Mena, Pablo; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Para obtener Imágenes de Resonancia Magnética (MRI) de buena calidad, es necesario tener una buena homogeneidad espacial en el campo B0 de la región a observar. La homogeneidad de campo es difícil de lograr, particularmente para imanes de núcleo corto y campos altos. Cuando el ajuste fino pasivo o activo no es suficiente, o cuando la inhomogeneidad viene de diferencias en la susceptibilidad entre regiones adyacentes dentro de un objeto, hay varias técnicas de post\2013procesamiento para corregir las distorsiones. ´Estas técnicas no tienen un fundamento teórico sólido con la excepción de las relativas a términos lineales. Proponemos usar la Transformada Fraccionaria de Fourier (FrFT) para reconstruir señales MRI obtenidas en campos con desviaciones cuadráticas. La FrFT provee un marco teórico preciso para esto.
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    Assessment of blood flow patterns in the pulmonary artery using 4D flow
    (2011) Bächler, Pablo.; Pinochet, Natalia.; Tejos Núñez, Cristián Andrés; Gerard, Crelier; Irarrázaval Mena, Pablo; Uribe Arancibia, Sergio A.
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    Assessment of normal flow patterns in the pulmonary circulation by using 4D magnetic resonance velocity mapping
    (2013) Bächler, Pablo; Pinochet, Natalia; Sotelo Parraguez, Julio Andrés; Crelier, Gérard; Irarrázaval Mena, Pablo; Tejos Núñez, Cristián Andrés; Uribe Arancibia, Sergio A.
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    Attenuation of atherogenic apo B-48-dependent hyperlipidemia and high density lipoprotein remodeling induced by vitamin C and E combination and their beneficial effect on lethal ischemic heart disease in mice
    (2018) Contreras-Duarte, Susana; Chen, P.; Andía Kohnenkampf, Marcelo Edgardo; Uribe Arancibia, Sergio A.; Irarrázaval Mena, Pablo; Kopp, S.; Kern, S.; Marsche, G.; Busso, Dolores; Rigotti Rivera, Attilio
    Abstract Background and aims Atherosclerotic cardiovascular disease is highly prevalent and its underlying pathogenesis involves dyslipidemia including pro-atherogenic high density lipoprotein (HDL) remodeling. Vitamins C and E have been proposed as atheroprotective agents for cardiovascular disease management. However, their effects and benefits on high density lipoprotein function and remodeling are unknown. In this study, we evaluated the role of vitamin C and E on non HDL lipoproteins as well as HDL function and remodeling, along with their effects on inflammation/oxidation biomarkers and atherosclerosis in atherogenic diet-fed SR-B1 KO/ApoER61h/h mice. Methods and results: Mice were pre-treated for 5 weeks before and during atherogenic diet feeding with vitamin C and E added to water and diet, respectively. Compared to a control group, combined vitamin C and E administration reduced serum total cholesterol and triglyceride levels by decreasing apo B-48-containing lipoproteins, remodeled HDL particles by reducing phospholipid as well as increasing PON1 and apo D content, and diminished PLTP activity and levels. Vitamin supplementation improved HDL antioxidant function and lowered serum TNF-α levels. Vitamin C and E combination attenuated atherogenesis and increased lifespan in atherogenic diet-fed SR-B1 KO/ApoER61h/h mice. Conclusions Vitamin C and E administration showed significant lipid metabolism regulating effects, including HDL remodeling and decreased levels of apoB-containing lipoproteins, in mice. In addition, this vitamin supplementation generated a cardioprotective effect in a murine model of severe and lethal atherosclerotic ischemic heart disease.
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    Calcium (Ca2+) waves data calibration and analysis using image processing techniques
    (2013) Milovic Fabregat, Carlos Andrés; Oses, Carolina; Villalón, Manuel J.; Uribe Arancibia, Sergio A.; Prieto Vásquez, Claudia; Andía Kohnenkampf, Marcelo Edgardo; Irarrázaval Mena, Pablo; Tejos Núñez, Cristián Andrés; Lizama, Carlos
    Abstract Background Calcium (Ca2+) propagates within tissues serving as an important information carrier. In particular, cilia beat frequency in oviduct cells is partially regulated by Ca2+ changes. Thus, measuring the calcium density and characterizing the traveling wave plays a key role in understanding biological phenomena. However, current methods to measure propagation velocities and other wave characteristics involve several manual or time-consuming procedures. This limits the amount of information that can be extracted, and the statistical quality of the analysis. Results Our work provides a framework based on image processing procedures that enables a fast, automatic and robust characterization of data from two-filter fluorescence Ca2+ experiments. We calculate the mean velocity of the wave-front, and use theoretical models to extract meaningful parameters like wave amplitude, decay rate and time of excitation. Conclusions Measurements done by different operators showed a high degree of reproducibility. This framework is also extended to a single filter fluorescence experiments, allowing higher sampling rates, and thus an increased accuracy in velocity measurements.
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    Cardiovascular magnetic resonance findings in a pediatric population with isolated left ventricular non-compaction
    (2012) Uribe Arancibia, Sergio A.; Cadavid, Lina; Parra Rojas, Rodrigo Orlando; Urcelay Montecinos, Gonzalo; Heusser Risopatron, Felipe; Andía Kohnenkampf, Marcelo Edgardo; Tejos Núñez, Cristián Andrés; Irarrázaval Mena, Pablo; Hussain, Tarique
    Abstract Background Isolated Left Ventricular Non-compaction (LVNC) is an uncommon disorder characterized by the presence of increased trabeculations and deep intertrabecular recesses. In adults, it has been found that Ejection Fraction (EF) decreases significantly as non-compaction severity increases. In children however, there are a few data describing the relation between anatomical characteristics of LVNC and ventricular function. We aimed to find correlations between morphological features and ventricular performance in children and young adolescents with LVNC using Cardiovascular Magnetic Resonance (CMR). Methods 15 children with LVNC (10 males, mean age 9.7 y.o., range 0.6 - 17 y.o.), underwent a CMR scan. Different morphological measures such as the Compacted Myocardial Mass (CMM), Non-Compaction (NC) to the Compaction (C) distance ratio, Compacted Myocardial Area (CMA) and Non-Compacted Myocardial Area (NCMA), distribution of NC, and the assessment of ventricular wall motion abnormalities were performed to investigate correlations with ventricular performance. EF was considered normal over 53%. Results The distribution of non-compaction in children was similar to published adult data with a predilection for apical, mid-inferior and mid-lateral segments. Five patients had systolic dysfunction with decreased EF. The number of affected segments was the strongest predictor of systolic dysfunction, all five patients had greater than 9 affected segments. Basal segments were less commonly affected but they were affected only in these five severe cases. Conclusion The segmental pattern of involvement of non-compaction in children is similar to that seen in adults. Systolic dysfunction in children is closely related to the number of affected segments.
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    Caval Blood Flow Distribution in Patients with Fontan Circulation : Quantification by Using Particle Traces from 4D Flow MR Imaging
    (2013) Bächler, Pablo; Valverde, Israel; Pinochet, Natalia; Nordmeyer, Sarah; Kuehne, Titus; Crelier, Gérard; Tejos Núñez, Cristián Andrés; Irarrázaval Mena, Pablo; Beerbaum, P.; Uribe Arancibia, Sergio A.
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    Chemical species separation in MRI with simultaneous estimation of field map and T2* using a k - space formulation
    (2011) Honorato Lira, José Luis; Irarrázaval Mena, Pablo; Pontificia Universidad Católica de Chile. Escuela de Ingeniería
    Separar diferentes especies químicas en imágenes de resonancia magnética (MRI) es relevante en el diagnóstico de pacientes, ya que permite identificar estructuras que típicamente resultan opacadas en imágenes comunes. Se han logrado buenos resultados con algoritmos en el espacio de la imagen, incluyendo en el modelo de señal parámetros de decaimiento transversal (R*2) y modelo multipico del espectro de la grasa. Sin embargo, separar especies en el espacio de la imagen, es decir, asumiendo un tiempo de adquisición instantáneo, causa artefactos en las imágenes resultantes. Algunos esfuerzos se han hecho para separar considerando un tiempo de adquisición no instantáneo, pero la corrección del mapa de campo y de R*2 aún se realiza en el espacio de la imagen, donde el objeto no se encuentra en las posiciones correctas. En este trabajo presentamos un nuevo método para separar especies químicas en MRI.
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    Comparison of basis functions and q-space sampling schemes for robust compressed sensing reconstruction accelerating diffusion spectrum imaging
    (2019) Tobisch, Alexandra; Schultz, Thomas; Stirnberg, Rudiger; Varela Mattatall, Gabriel Enrique; Knutsson, Hans; Irarrázaval Mena, Pablo; Stocker, Tony
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    Comparison of parameter optimization methods for quantitative susceptibility mapping
    (2020) Milovic Fabregat, Carlos Andrés; Prieto Vásquez, Claudia; Bilgic, B.; Uribe Arancibia, Sergio A.; Acosta Cabronero, J.; Irarrázaval Mena, Pablo; Tejos Núñez, Cristián Andrés