Marina Huguet

Morphologic pattern of late gadolinium enhancement in Takotsubo cardiomyopathy detected by early cardiovascular magnetic resonance

Takotsubo cardiomyopathy (TTC) presents clinically as an acute coronary syndrome. It is characterized by transient left ventricular wall dyskinesis‐akinesis, without significant epicardial coronary lesions. Late gadolinium enhancement (LGE) sequences on cardiac magnetic resonance (CMR) allow to clarify the pathophysiology in patients with chest pain, elevated troponin, and normal epicardial coronary arteries; in patients with TTC, previous studies have shown absence of LGE.

Cardiac motion estimation by joint alignment of tagged MRI sequences.

Image registration has been proposed as an automatic method for recovering cardiac displacement fields from tagged Magnetic Resonance Imaging (tMRI) sequences. Initially performed as a set of pairwise registrations, these techniques have evolved to the use of 3D+t deformation models, requiring metrics of joint image alignment (JA). However, only linear combinations of cost functions defined with respect to the first frame have been used. In this paper, we have applied k-Nearest Neighbors Graphs (kNNG) estimators of the α-entropy (H(α)) to measure the joint similarity between frames, and to combine the information provided by different cardiac views in an unified metric. Experiments performed on six subjects showed a significantly higher accuracy (p<0.05) with respect to a standard pairwise alignment (PA) approach in terms of mean positional error and variance with respect to manually placed landmarks. The developed method was used to study strains in patients with myocardial infarction, showing a consistency between strain, infarction location, and coronary occlusion. This paper also presents an interesting clinical application of graph-based metric estimators, showing their value for solving practical problems found in medical imaging.

Realistic simulation of cardiac magnetic resonance studies modeling anatomical variability, trabeculae, and papillary muscles

Simulated magnetic resonance imaging brain studies have been generated for over a decade. Despite their useful potential, simulated cardiac studies are only emerging. This article focuses on the realistic simulation of cardiac magnetic resonance imaging datasets. The methodology is based on the XCAT phantom, which is modified to increase realism of the simulated images. Modifications include the modeling of trabeculae and papillary muscles based on clinical measurements and published data. To develop and evaluate our approach, the clinical database included 40 patients for anatomical measurements, 10 patients for papillary muscle modeling, and 10 patients for local gray value statistics. The virtual database consisted of 40 digital voxel phantoms. Histograms from different tissues were obtained from the real datasets and compared with histograms of the simulated datasets with the Chi‐square dissimilarity metric (χ2) and Kullback‐Leibler divergence. For the original phantom, χ2 values averaged 0.65 ± 0.06 and Kullboek‐Leibler values averaged 0.69 ± 0.38. For the modified phantom, χ2 values averaged 0.34 ± 0.12 and Kullboek‐Leibler values averaged 0.32 ± 0.15. The proposed approach demonstrated a noticeable improvement of the local appearance of the simulated images with respect to the ones obtained originally. Magn Reson Med, 2010.

Characterizing Myocardial Deformation in Patients With Left Ventricular Hypertrophy of Different Etiologies Using the Strain Distribution Obtained by Magnetic Resonance Imaging

Introduccion y objetivos. Se ha senalado que, en la miocardiopatia hipertrofica (MCH), la desorganizacion de las fibras regionales da lugar a segmentos en los que la deformacion es nula o esta gravemente reducida, y que estos segmentos tienen una distribucion no uniforme en el ventriculo izquierdo (VI). Esto contrasta con lo observado en otros tipos de hipertrofia como en el corazon de atleta o la hipertrofia ventricular izquierda hipertensiva (HVI-HT), en los que puede haber una deformacion cardiaca anormal, pero nunca tan reducida como para que se observe ausencia de deformacion. Asi pues, proponemos el empleo de la distribucion de los valores de strain para estudiar la deformacion en la MCH. Metodos. Con el empleo de resonancia magnetica marcada (tagged), reconstruimos la deformacion sistolica del VI de 12 sujetos de control, 10 atletas, 12 pacientes con MCH y 10 pacientes con HVI-HT. La deformacion se cuantifico con un algoritmo de registro no rigido y determinando los valores de strain sistolico maximo radial y circunferencial en 16 segmentos del VI. Resultados. Los pacientes con MCH presentaron unos valores medios de strain significativamente inferiores a los de los demas grupos. Sin embargo, aunque la deformacion observada en los individuos sanos y en los pacientes con HVI-HT se concentraba alrededor del valor medio, en la MCH coexistian segmentos con contraccion normal y segmentos con una deformacion nula o significativamente reducida, con lo que se producia una mayor heterogeneidad de los valores de strain. Se observaron tambien algunos segmentos sin deformacion incluso en ausencia de fibrosis o hipertrofia. Conclusiones. La distribucion de strain caracteriza los patrones especificos de deformacion miocardica en pacientes con diferentes etiologias de la HVI. Los pacientes con MCH presentaron un valor medio de strain significativamente inferior, asi como una mayor heterogeneidad de strain (en comparacion con los controles, los atletas y los pacientes con HVI-HT), y tenian regiones sin deformacion.INTRODUCTION AND OBJECTIVES In hypertrophic cardiomyopathy (HCM), it has been suggested that regional fiber disarray produces segments that exhibit no or severely reduced deformation, and that these segments are distributed nonuniformly within the left ventricle (LV). This contrasts with observations in other types of hypertrophy, such as in athletes heart or hypertensive left ventricular hypertrophy (HLVH), in which abnormal cardiac deformation may exist but the reduction is not so severe that some segments exhibit no deformation. Our aim was to use the strain distribution to study deformation in HCM. METHODS We used tagged magnetic resonance imaging to reconstruct LV systolic deformation in 12 controls, 10 athletes, 12 patients with HCM, and 10 patients with HLVH. Deformation was quantified using a fast nonrigid registration algorithm and peak radial and circumferential systolic strain values were determined in 16 LV segments. RESULTS Patients with HCM had significantly lower average strain values than individuals in other groups. However, while the deformation observed in healthy subjects and HLVH patients clustered around the mean, in HCM patients, segments with normal contraction coexisted with segments exhibiting no or significantly reduced deformation, which resulted in a greater heterogeneity of strain values. Moreover, some nondeforming segments were observed even when fibrosis and hypertrophy were absent. CONCLUSIONS The strain distribution characterized specific patterns of myocardial deformation in patients with LVH due to different etiologies. Patients with HCM had significantly lower mean strain values and a greater heterogeneity in strain values than controls, athletes and HLVH patients. In addition, they had nondeforming regions.

Cardiac injuries in blunt chest trauma

Blunt chest traumas are a clinical challenge, both for diagnosis and treatment. The use of Cardiovascular Magnetic Resonance can play a major role in this setting. We present two cases: a 12-year-old boy and 45-year-old man. Late gadolinium enhancement imaging enabled visualization of myocardial damage resulting from the trauma.

Caracterización de la deformación miocárdica en pacientes con hipertrofia ventricular izquierda de diferente etiología mediante el uso de distribuciones de strain obtenidas de imágenes de resonancia magnética

Introduccion y objetivos. Se ha senalado que, en la miocardiopatia hipertrofica (MCH), la desorganizacion de las fibras regionales da lugar a segmentos en los que la deformacion es nula o esta gravemente reducida, y que estos segmentos tienen una distribucion no uniforme en el ventriculo izquierdo (VI). Esto contrasta con lo observado en otros tipos de hipertrofia como en el corazon de atleta o la hipertrofia ventricular izquierda hipertensiva (HVI-HT), en los que puede haber una deformacion cardiaca anormal, pero nunca tan reducida como para que se observe ausencia de deformacion. Asi pues, proponemos el empleo de la distribucion de los valores de strain para estudiar la deformacion en la MCH. Metodos. Con el empleo de resonancia magnetica marcada (tagged), reconstruimos la deformacion sistolica del VI de 12 sujetos de control, 10 atletas, 12 pacientes con MCH y 10 pacientes con HVI-HT. La deformacion se cuantifico con un algoritmo de registro no rigido y determinando los valores de strain sistolico maximo radial y circunferencial en 16 segmentos del VI. Resultados. Los pacientes con MCH presentaron unos valores medios de strain significativamente inferiores a los de los demas grupos. Sin embargo, aunque la deformacion observada en los individuos sanos y en los pacientes con HVI-HT se concentraba alrededor del valor medio, en la MCH coexistian segmentos con contraccion normal y segmentos con una deformacion nula o significativamente reducida, con lo que se producia una mayor heterogeneidad de los valores de strain. Se observaron tambien algunos segmentos sin deformacion incluso en ausencia de fibrosis o hipertrofia. Conclusiones. La distribucion de strain caracteriza los patrones especificos de deformacion miocardica en pacientes con diferentes etiologias de la HVI. Los pacientes con MCH presentaron un valor medio de strain significativamente inferior, asi como una mayor heterogeneidad de strain (en comparacion con los controles, los atletas y los pacientes con HVI-HT), y tenian regiones sin deformacion.

Myocardial deformation from tagged MRI in hypertrophic cardiomyopathy using an efficient registration strategy

This paper combines different parallelization strategies for speeding up motion and deformation computation by non-rigid registration of a sequence of images. The registration is performed in a two-level acceleration approach: (1) parallelization of each registration process using MPI and/or threads, and (2) distribution of the sequential registrations over a cluster. On a 24-node double quad-core Intel Xeon (2.66 GHz CPU, 16 GB RAM) cluster, the method is demonstrated to efficiently compute the deformation of a cardiac sequence reducing the computation time from more than 3 hours to a couple of minutes (for low downsampled images). It is shown that the distribution of the sequential registrations over the cluster together with the parallelization of each pairwise registration by multithreading lowers the computation time towards values compatible with clinical requirements (a few minutes per patient). The combination of MPI and multithreading is only advantageous for large input data sizes. Performances are assessed for the specific scenario of aligning cardiac sequences of taggedMagnetic Resonance (tMR) images, with the aim of comparing strain in healthy subjects and hypertrophic cardiomyopathy (HCM) patients. In particular, we compared the distribution of systolic strain in both populations. On average, HCM patients showed lower average values of strain with larger deviation due to the coexistence of regions with impaired deformation and regions with normal deformation.

3D mesh based wall thickness measurement: Identification of left ventricular hypertrophy phenotypes

Left ventricular hypertrophy (LVH) is a complex cardiac condition mainly identified by the thickening of the myocardial wall. Although most of the contemporary cardiac imaging modalities provide high resolution 3D images, the wall thickness (WT) is still measured within the acquired planes. This way of measurement may introduce an error as cardiac wall is not necessarily orthogonal to the plane. In this study we analyze how different approaches to measure WT can affect an automatic identification of hypertrophy. The compared approaches are: WT measured along surface normal and the one provided by a medial surface. For both approaches we evaluated their ability to identify LVH phenotypes by testing with two classifiers: Transductive Confidence Machine-k Nearest Neighbor (TCM-kNN) and Linear Discriminant Analysis (LDA). Fifty three subjects were included in this study: 18 patients with hypertrophic cardiomyopathy (HCM), 13 patients with hypertensive heart disease (HDD) and 22 sedentary subjects (CG). Medial surface based approach allowed obtaining higher classification accuracy in HDD patients, while normal based approach allowed for higher classification accuracy in HCM patients.

Utility of Real Time 3D Echocardiography for the Assessment of Left Ventricular Mass in Patients with Hypertrophic Cardiomyopathy: Comparison with Cardiac Magnetic Resonance.

Patients with hypertrophic cardiomyopathy (HCM) have irregular ventricular shapes with small and sometimes obliterated cavities at end‐systole that affect the quantification of left ventricular mass (LVM) by conventional methods, such as M‐mode or two‐dimensional echocardiography. The goal of this study was to validate the use of real time three‐dimensional echocardiography (RT3DE) to quantify LVM using cardiac magnetic resonance imaging (CMR) as a reference, in a large population of patients with different types of HCM.

Simulation of late gadolinium enhancement cardiac magnetic resonance studies

In this study we propose a pipeline for simulation of late gadolinium enhancement images. We used a modified version of the XCAT phantom to improve simulation realism. Modifications included the modeling of trabeculae and papillary muscles, and the increase of sublabels to resemble tissue intensity variability. Magnetic properties for each body tissue were sampled in three settings: from Gaussian distributions, combining Rayleigh-Gaussian distributions, and from Rayleigh distributions. Thirty-two simulated datasets were compared with 32 clinical datasets from infarcted patients. Histograms were obtained for five tissues: lung, pericardium, myocardium, blood and hyper-enhanced area. Real and simulated histograms were compared with the Chi-square dissimilarity metric (χ2) and Kullback-Leibler divergence (KL). The generated simulated images look similar to real images according to both metrics. Rayleigh and the Rayleigh-Gaussian models obtained comparable average results (respectively: χ2= 0.16±0.12 and 0.18±0.11; KL=0.15±0.17 and 0.16±0.18).