Multi-Stencil Streamline Fast Marching: a general 3D Framework to determine Myocardial Thickness and Transmurality in Late Enhancement Images

We propose a fully three-dimensional methodology for the computation of myocardial non-viable tissue transmurality in contrast enhanced magnetic resonance images. The outcome is a continuous map defined within the myocardium where not only current state-of-the-art measures of transmurality can be calculated, but also information on the location of non-viable tissue is preserved. The computation is done by means of a partial differential equation framework we have called Multi- Stencil Streamline Fast Marching (MSSFM). Using it, the myocardial and scarred tissue thickness is simultaneously computed. Experimental results show that the proposed 3D method allows for the computation of transmurality in myocardial regions where current 2D methods are not able to as conceived, and it also provides more robust and accurate results in situations where the assumptions on which current 2D methods are based —i.e., there is a visible endocardial contour and its corresponding epicardial points lie on the same slice—, are not met

Contribución a técnicas de procesado de imagen relacionadas con ecuaciones en derivadas parciales para la ayuda al diagnóstico de cardiopatías mediante resonancia magnética de realce tardío

La modalidad de resonancia magnética cardíaca de realce tardío con contraste de gadolinio (RMC-RTG) permite la identificación de tejido dañado (escara o fibrosis) presente en el miocardio gracias a la acumulación de contraste en el mismo. Es, por ello, una importante herramienta diagnóstica en patologías tales como la cardiopatía isquémica y la miocardiopatía hipertrófica. La contribución principal del presente trabajo es un método para calcular mapas densos del grosor del miocardio y de la transmuralidad de la escara basado en una ecuación en derivadas parciales e implementado numéricamente empleando un esquema multistencil. El método se ha probado empleando funciones analíticas y tres bancos de imágenes RMC-RTG reales diferentes. Proponemos también un método de segmentación multimodal cuando se dispone de las imágenes RMC-RTG y RMC-CINE y de una segmentación del miocardio en RMC-CINE, que permite pequeños desplazamientos de los contornos endocárdico y epicárdico. Se trata de una variante de un método variacional existente que utiliza un algoritmo de esperanza maximización novedoso para estimar los parámetros de las distribuciones de probabilidad empleando una función de log-verosimilitud que incorpora tanto las imágenes RMC-RTG y RMC-CINE como la segmentación del miocardio de RMC-CINE. Estudiamos también la influencia del conjunto de stencils escogido en los resultados del método Multi-Stencil Fast Marching. Se ha propuesto también una nueva versión utilizando un esquema en diferencias finitas centrado para las derivadas parciales.Departamento de Teoría de la Señal y Comunicaciones e Ingeniería TelemáticaDoctorado en Tecnologías de la Información y las Telecomunicacione

USER INTERFACES TO INTERACT WITH TENSOR FIELDS. A STATE-OF-THE-ART ANALYSIS

In this article we review the current situation of user interfaces for tensor fields. This is a very active research field nowadays, because the amount of information that tensors contain makes them difficult to design, and achieve an intuitive and easy to use interface. From a medical point of view, diffusion and strain tensors are the most widely used tensor images nowadays. The use of diffusion tensor magnetic resonance imaging (DTMRI) is being increasingly introduced in clinical practice. An important part of these interfaces is the visualization of the tensor field. Due to the high number of degrees of freedom, this is a difficult task, and many methods have been developed for it. We should also take into account that new hardware devices with a larger variety of functions could greatly help this kind of interfaces. However, most of these devices are being developed nowadays. As two examples, we study the DTMRI module of Slicer 3D and an immersive virtual environment for DTMRI visualization, as well as some of the feedback of their users. 1

Time-efficient three-dimensional transmural scar assessment provides relevant substrate characterization for ventricular tachycardia features and long-term recurrences in ischemic cardiomyopathy

Delayed gadolinium-enhanced cardiac magnetic resonance (LGE-CMR) imaging requires novel and time-efficient approaches to characterize the myocardial substrate associated with ventricular arrhythmia in patients with ischemic cardiomyopathy. Using a translational approach in pigs and patients with established myocardial infarction, we tested and validated a novel 3D methodology to assess ventricular scar using custom transmural criteria and a semiautomatic approach to obtain transmural scar maps in ventricular models reconstructed from both 3D-acquired and 3D-upsampled-2D-acquired LGE-CMR images. The results showed that 3D-upsampled models from 2D LGE-CMR images provided a time-efficient alternative to 3D-acquired sequences to assess the myocardial substrate associated with ischemic cardiomyopathy. Scar assessment from 2D-LGE-CMR sequences using 3D-upsampled models was superior to conventional 2D assessment to identify scar sizes associated with the cycle length of spontaneous ventricular tachycardia episodes and long-term ventricular tachycardia recurrences after catheter ablation. This novel methodology may represent an efficient approach in clinical practice after manual or automatic segmentation of myocardial borders in a small number of conventional 2D LGE-CMR slices and automatic scar detection.Depto. de MedicinaFac. de MedicinaTRUEpu

A Second Order Multi-Stencil Fast Marching Method with a Non-Constant Local Cost Model

International audienc