1,721,040 research outputs found
Evaluating sleep-stage classification: how age and early-late sleep affects classification performance
No full textSleep stage classification is a common method used by experts to monitor the quantity and quality of sleep in humans, but it is a time-consuming and labour-intensive task with high inter- and intra-observer variability. Using wavelets for feature extraction and random forest for classification, an automatic sleep-stage classification method was sought and assessed. The age of the subjects, as well as the moment of sleep (early-night and late-night), were confronted to the performance of the classifier. From this study, we observed that these variables do affect the automatic model performance, improving the classification of some sleep stages and worsening others.Fil: Moris, Eugenia. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Larrabide, Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentin
Tratamiento virtual de aneurismas cerebrales
No full textLos stents desviadores de flujo son habitualmente usados para tratar aneurismas cerebrales debido a su capacidad de modificar los factores hemodinámicos locales. Una dificultad de este tratamiento es poder predecir su impacto. Para ello se puede utilizar la simulación computacional, que provee el valor de cada variable en cada punto e instante. Pero una de sus dificultades es el costo de modelar de forma eficiente las mallas de alambres. Una técnica para reducir el costo computacional de las simulaciones es modelando las mallas de alambres como medios porosos. Existen distintos de estos modelos en la literatura pero faltaba una comparación entre ellos en cuanto a dificultad de implementación y rendimiento. Algunos modelos representativos son relevados en este trabajo y presentados con una simbología unificada. Luego, son comparados en geometrías idealizadas contra modelos de alambres trenzados y simplificados. También se implementa una aplicación capaz de simular medios heterogéneos y se comparan modelos tanto homogéneos como heterogéneos en geometrías anatómicamente precisas obtenidas de distintos pacientes. Los modelos de medios porosos mostraron ser más rápidos que los de alambres de forma explícita con márgenes de error variados. Entre las variantes heterogéneas uno de los modelos mejora respecto a su homologo homogéneo mientras que el otro empeora. Finalmente, se aplica uno de los modelos de medios porosos a los aneurismas con dispositivos intrasaculares. Estos dispositivos están constituidos de una malla de alambre, al igual que los stents. Se comparan dispositivos de distintos tamaños en diferentes geometrías anatómicamente precisas. Los resultados muestran que los valores hemodinámicos globales no varían, pero existen diferencias locales respecto a la velocidad y tensión en las paredes.Fil: Dazeo, Nicolás. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas; Argentina.Fil: Boroni, Gustavo Adolfo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas; Argentina.Fil: Larrabide, Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas; Argentina
Modelos de simulación de dispositivos intrasaculares para el tratamiento de aneurismas intracraneales
No full textLos aneurismas intracraneales son dilataciones patológicas de las arterias cerebrales que surgen por el debilitamiento de la pared arterial. La constante interacción de esta pared debilitada con el flujo sanguíneo provoca su abultamiento y posterior crecimiento. El mayor peligro de este progresivo crecimiento del aneurisma es su ruptura, la cual genera una hemorragia con altas tasas de mortalidad y morbilidad.
El alto riesgo que implica la rotura de un aneurisma hace, que al ser detectados, sean tratados para evitar la ruptura. El tratamiento endovascular permite
ocluir el aneurisma desde el interior de la arteria mediante procedimientos mínimamente invasivos. Coils, stents, desviadores de flujo y dispositivos intrasaculares
son dispositivos desarrollados para este tipo de tratamiento.
La selección adecuada del dispositivo es una dificultad a la que pueden enfrentarse los intervencionistas. Las técnicas computacionales para simular la implantación de estos dispositivos se desarrollaron para dar respuesta a este problema, ofreciendo herramientas predictivas del resultado de tratamientos específicos.
En esta tesis se presenta el desarrollo de un método computacional para la
simulación de dispositivos intrasaculares, que a diferencia del resto no ha sido
ampliamente estudiada. Orientada a facilitar la selección de tamaño apropiado
para cada aneurisma, la técnica permite la simulación de diferentes tamaños de
dispositivos para analizar cuál ofrecería el mejor resultado.Intracranial aneurysms are pathological dilations of the cerebral arteries that
arise from weakening the arterial wall. The constant interaction of this weakened
wall with blood flow causes its bulging and subsequent growth. The greatest danger of this progressive growth of the aneurysm is its rupture, which generates a
haemorrhage with high mortality and morbidity rates.
The high risk involved in the aneurysm rupture means that they are treated to
avoid rupture when detected. Endovascular treatment allows the aneurysm to be
occluded from within the artery using minimally invasive procedures. Coils, stents,
flow diverters, and intrasacular devices are devices developed for this treatment
type.
One difficulty that interventionists often face is the appropriate selection of
the device to use. Computational techniques to simulate the implantation of these
devices were developed to respond to this problem, offering predictive tools for
the outcome of specific treatments.
In this thesis, the development of a computational method for the simulation
of intrasacular devices, which, unlike the rest, has not been widely studied, is
presented. Aimed at facilitating the selection of the appropriate size for each
aneurysm, the technique allows the simulation of different device sizes within the
aneurysm to analyze which one would offer the best fit of the device to the patient
anatomy.Fil: Muñoz, Romina Luciana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas; Argentina.Fil: Larrabide, Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas; Argentina
ID-Fit: Intra-Saccular Device Adjustment for Personalized Cerebral Aneurysm Treatment
No full textIntrasaccular devices, like Woven EndoBridge (WEB), are novel braided devices employed for the treatment of aneurysms with a complex shape and location, mostly terminal aneurysms. Such aneurysms are often challenging or impossible to treat with other endovascular techniques such as coils, stents, flow diverter stents. The selection of an appro- AQ1 priate endosaccular device size is crucial for a successful treatment and strongly depends of the final configuration that the device adopts when it adapts to the aneurysm sac morphology. This is frequently a problem during the intervention, leading to replacement of the device, reopening of the aneurysm or a need for re-treatment. A technique that allows predicting the released WEB configuration before intervention will provide a powerful computational tool to aid the interventionist during device selection. We propose a technique based on device design and aneurysm morphology that, by virtually deploying a WEB, will enable the assessment of different device sizes before the device implantation. This technique was tested on 6 MCA aneurysm cases and the simulation results were compared to the size of the deployed device on the patient, using post-treatment images.Fil: Muñoz, Romina Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Narata, Ana Paula. University Hospital of Southampton; Reino UnidoFil: Larrabide, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaMedical Image Computing and Computer Assisted InterventionLimaPerúMedical Image Computing and Computer Assisted Interventio
Change in aneurysmal flow pulsatility after flow diverter treatment
Get PDFMotivation: Treatment of intracranial aneurysms with flow diverters (FDs) has recently become an attractive alternative. Although considerable effort has been devoted to understand their effects on the time-averaged or peak systolic flow field, no previous study has analyzed the variability of FD-induced flow reduction along the cardiac cycle. Methods: Fourteen saccular aneurysms, candidates for FD treatment because of their morphology, located on the internal carotid artery were virtually treated with FDs and pre- and post-treatment blood flow was simulated with CFD techniques. Common hemodynamic variables were recorded at each time step of the cardiac cycle and differences between the untreated and treated models were assessed. Results: Flow pulsatility, expressed by the pulsatility index (PI) of the velocity, significantly increased (36.0%; range: 14.6–88.3%) after FD treatment. Peak systole velocity reduction was significantly smaller (30.5%; range: 19.6–51.0%) than time-averaged velocity reduction (43.0%; range: 29.1–69.8%). No changes were observed in the aneurysmal pressure. Conclusions: FD-induced flow reduction varies considerably during the cardiac cycle. FD treatment significantly increased the flow pulsatility in the aneurysm.Fil: Larrabide, Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Geers, Arjan J.. Universitat Pompeu Fabra; EspañaFil: Morales; Hernán G.. Medisys; FranciaFil: Bijlenga, Philippe. Universidad de Ginebra; SuizaFil: Rufenacht, Daniel A.. Hirslanden Clinic; Suiz
Lumen-intima and media-adventitia segmentation in IVUS images using supervised classifications of arterial layers and morphological structures
Get PDFBackground: Intravascular ultrasound (IVUS) provides axial grey-scale images of blood vessels. The large number of images require automatic analysis, specifically to identify the lumen and outer vessel wall. However, the high amount of noise, the presence of artifacts and anatomical structures, such as bifurcations, calcifications and fibrotic plaques, usually hinder the proper automatic segmentation of the vessel wall. Methods: Lumen, media, adventitia and surrounding tissues are automatically detected using Support Vector Machines (SVMs). The classification performance of the SVMs vary according to the kind of structure present within each region of the image. Random Forest (RF) is used to detect different morphological structures and to modify the initial layer classification depending on the detected structure. The resulting classification maps are fed into a segmentation method based on deformable contours to detect lumen-intima (LI) and media-adventitia (MA) interfaces. Results: The modifications in the layer classifications according to the presence of structures proved to be effective improving LI and MA segmentations. The proposed method reaches a Jaccard Measure (JM) of 0.88 ± 0.08 for LI segmentation, compared with 0.88 ± 0.05 of a semiautomatic method. When looking at MA, our method reaches a JM of 0.84 ± 0.09, and outperforms previous automatic methods in terms of HD, with 0.51mm ± 0.30. Conclusions: A simple modification to the arterial layer classification produces results that match and improve state-of-the-art fully-automatic segmentation methods for LI and MA in 20MHz IVUS images. For LI segmentation, the proposed automatic method performs accurately as semi-automatic methods. For MA segmentation, our method matched the quality of state-of-the-art automatic methods described in the literature. Furthermore, our implementation is modular and open-source, allowing for future extensions and improvements.Fil: Lo Vercio, Lucas. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: del Fresno, Mirta Mariana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Larrabide, Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentin
Improving realism in patient-specific abdominal ultrasound simulation using CycleGANs
No full textPurpose: In this paper, we propose to apply generative adversarial neural networks trained with a cycle consistency loss, or CycleGANs, to improve realism in ultrasound (US) simulation from computed tomography (CT) scans. Methods: A ray-casting US simulation approach is used to generate intermediate synthetic images from abdominal CT scans. Then, an unpaired set of these synthetic and real US images is used to train CycleGANs with two alternative architectures for the generator, a U-Net and a ResNet. These networks are finally used to translate ray-casting based simulations into more realistic synthetic US images. Results: Our approach was evaluated both qualitatively and quantitatively. A user study performed by 21 experts in US imaging shows that both networks significantly improve realism with respect to the original ray-casting algorithm (p≪ 0.0001), with the ResNet model performing better than the U-Net (p≪ 0.0001). Conclusion: Applying CycleGANs allows to obtain better synthetic US images of the abdomen. These results can contribute to reduce the gap between artificially generated and real US scans, which might positively impact in applications such as semi-supervised training of machine learning algorithms and low-cost training of medical doctors and radiologists in US image interpretation.Fil: Vitale, Santiago. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Orlando, José Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Iarussi, Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional; ArgentinaFil: Larrabide, Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentin
Software-based simulation for preprocedural assessment of braided stent sizing: A validation study
Get PDFOBJECTIVE The authors sought to validate the use of a software-based simulation for preassessment of braided self-expanding stents in the treatment of wide-necked intracranial aneurysms. METHODS This was a retrospective, observational, single-center study of 13 unruptured and ruptured intracranial aneurysms treated with braided self-expanding stents. Pre- and postprocedural angiographic studies were analyzed. ANKYRAS software was used to compare the following 3 variables: the manufacturer-given nominal length (NL), software-calculated simulated length (SL), and the actual measured length (ML) of the stent. Appropriate statistical methods were used to draw correlations among the 3 lengths. RESULTS In this study, data obtained in 13 patients treated with braided self-expanding stents were analyzed. Data for the 3 lengths were collected for all patients. Error discrepancy was calculated by mean squared error (NL to ML -22.2; SL to ML -6.14, p < 0.05), mean absolute error (NL to ML 3.88; SL to ML -1.84, p < 0.05), and mean error (NL to ML -3.81; SL to ML -1.22, p < 0.05). CONCLUSIONS The ML was usually less than the NL given by the manufacturer, indicating significant change in length in most cases. Computational software-based simulation for preassessment of the braided self-expanding stents is a safe and effective way for accurately calculating the change in length to aid in choosing the right-sized stent for optimal placement in complex intracranial vasculature.Fil: Joshi, Krishna Chaitanya. Rush Medical Center; Estados UnidosFil: Larrabide, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; ArgentinaFil: Saied, Ahmed. Mansoura University; EgiptoFil: Elsaid, Nada. Rush Medical Center; Estados UnidosFil: Fernandez, Hector. Galgo Medical SL; EspañaFil: Lopes, Demetrius K.. Rush Medical Center; Estados Unido
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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