MRI Cardiac Images Research Articles

Novel Self-Calibrated Threshold-Free Probabilistic Fibrosis Signature Technique for 3D Late Gadolinium Enhancement MRI.

Myocardial fibrosis, marked by excessive collagen buildup in the heart, is a crucial severity marker of heart muscle injury in several heart diseases, such as myocardial infarction, cardiomyopathies, and atrial fibrillation (AF). It is also vital for evaluating the efficacy of induced scarring (dense fibrosis) post-interventions, such as catheter ablation for AF. Cardiac MRI emerged as the gold standard for evaluating myocardial fibrosis and scarring for diagnosis and intervention planning. However, existing 3D cardiac MRI (CMR) fibrosis analysis methods are unreliable as they rely on variable thresholding and suffer from a lack of standardization and high sensitivity to typical MRI uncertainties. Importantly, these methods quantify severity based on fibrosis volume alone while ignoring the unique MRI characteristics of fibrosis distribution, which could better inform on disease severity. To address these limitations, we propose a novel thresholdfree and self-calibrating probabilistic method named "Fibrosis Signatures" for a comprehensive and reliable fibrosis analysis of 3D MRI cardiac images. Through a novel efficient (linear complexity) probabilistic encoding of 'multibillion' MRI intensity disparities into standardized probability density function, our method derives the patient's unique fibrosis signature profile and index (FSI). Our approach goes beyond mere measuring of fibrosis volume; it encodes both the extent and the unique MRI characteristics of fibrosis distribution beyond mere entropy for a more detailed evaluation of fibrosis burden/severity. Our self-calibrating design effectively adjusts for MRI uncertainties like noise, low spatial resolution, and segmentation errors to ensure robust and reproducible fibrosis evaluation pre- and post-intervention. Validated in numerical phantom and 143 in vivo MRI scans of AF patients and compared to five baseline methods, our method showed strong correlations with traditional volume measures of pre-intervention fibrosis and post-intervention scar and was up to 9- times more reliable and reproducible, highlighting its potential to enhance cardiac MRI's utility.

PO-02-226 NON-INVASIVE ELECTROCARDIOGRAPHIC IMAGING FOR THE CHARACTERIZATION OF COMPLEX ATRIAL TACHYARRHYTHMIAS

Non-invasive characterization of complex atrial tachyarrhythmias, regarding atrial flutter (AFL) and focal atrial tachycardia (AT) is challenging. Conventional electrocardiogram (ECG) faces several limitations. Planning a preprocedural strategy before AFL-AT catheter ablation (CA) is needed. To evaluate the diagnostic capacity of a novel non-invasive electrocardiographic imaging (ECGI) system that does not require previous CT or MRI cardiac imaging. 42 patients (27 males, CHA2DS2-VASc score 2±1, LVEF 54.5 ± 11.0 %, and LA area 31.3 ± 7.0 cm2) undergoing CA for AT-AFL were prospectively included in the study. Before the procedure, the ECGI system estimated the patient atria geometry using a 3D torso reconstruction and an artificial intelligence-based algorithm. Multiple electrocardiograms were recorded using a 64-electrodes vest during the CA procedure. The different diagnostic capacities of the periprocedural ECG and ECGI were assessed compared with endocavitary electroanatomical mapping (EAM) regarding three endpoints: (1) the involved atrial cavity, (2) the mechanism (focal or macro-reentry), and (3) the ablation target site defined as the area where the earliest activation was located for focal arrhythmias, and the precise anatomical pathway for macro re-entrant tachyarrhythmias. Regarding the ECG, endpoints were assessed based on validated algorithms by 2 different observers blinded from the diagnosis. 48 atrial tachyarrhythmias were evaluated and its characterization using this novel ECGI system was possible in 94% of the cases: directly for 36 arrhythmias and after decreasing ventricular response using vagal maneuvers for 9. ECGI obtained global accuracy to identify the involved atrial cavity of 92%, the mechanism of 90%, and the ablation target of 83% (Table). In challenging cases, such as in patients with a history of CA for atrial fibrillation and in patients without a final diagnosis of typical counterclockwise AFL, the accuracy of ECGI was consistent compared to the whole study population (Table). The ECGI diagnostic capacity significantly outclassed the ECG regarding the identification of the involved cavity (p<0.001), the mechanism (p<0.05), and the ablation target (p<0.001). ECGI could have prevented all unnecessary transseptal punctures (n=7), representing 28% of the overall punctures. This novel non-invasive ECGI system accurately characterizes complex atrial tachyarrhythmias (Figure) without needing previous CT or MRI cardiac imaging.

CT and MRI Cardiac Imaging in Singapore: A Historical Context

CT and MRI Cardiac Imaging in Singapore: A Historical Context

Scimitar syndrome with bicuspid aortic valve. A case report of cross-sectional non- invasive imaging allowing a complete anatomical and functional assessment

Scimitar syndrome is a variant of partial anomalous pulmonary venous return with an aberrant vein, the Scimitar vein, draining the right lung to the inferior vena cava instead of the left atrium, resulting in a left-to-right shunt. The classic frontal radiographic finding, designated as “the scimitar sign”, is of a scimitar (a Turkish sword) shaped density along the right cardiac border. The diagnosis can be made by echocardiography, and cardiac catheterisation remains the gold standard to assess the left-to-right shunt. However, the place of multimodal cardiac imaging by computed tomography and magnetic resonance imaging is increasing. We report the case of a 26 year-old man presenting with chest pain during a brief panic attack, in whom scimitar syndrome was associated with a bicuspid aortic valve, a clinical association rarely reported in the literature. CT and MRI cardiac imaging was as accurate as echocardiography and hemodynamics, particularly for shunt quantification.

A deformable model based system for 3D analysis and visualization of left ventricle in MRI cardiac images

Nous avons developpd un systeme pour etudier la fonction du ventricule gauche et obtenir la visualisation 3D de la cavite cardiaque en utilisant les images d'IRM cardiaque. L'algorithme propose est base sur trois techniques differentes: 1) un algorithme d'extraction d'objet flou, 2) contour actif et 3) un algorithme de propagation de contour. Nous utilisons l'extraction d'objet flou comme une etape de pretraitement qui nous premet d'eliminer les points de bruit a l'interieur de la cavite ventriculaire sans modifier les valeurs des voxels representant le muscle cardiaque sur les coupes d'images d'IRM. Afin d'automatiser l'analyse, nous avons utilise des modeles deformables. Le systeme est initialise en tracant une courbe fermee a l'interieur du ventricule gauche. Nous avons applique une methode de propagation de contour pour rendre la detection fiable contre le bruit, les artefacts et la resolution faible temporelle. Les contours du volume ventriculaire extraits au cours du cycle cardiaque ont ete utilises pour determiner les informations quantitatives de la fonction cardiaque, et pour visualiser les deformations de la cavite ventriculaire avec le mouvement. Vue la taille des donnees a traiter, le cout de calcul des algorithmes appliques est acceptable avec un temps de traitement raisonnable sur une station de travail classique.

Diagnostic considerations in patients with suspected coronary artery anomalies

The diagnosis of coronary artery anomalies requires a high index of suspicion during the history and physical examination. Nonspecific presentations are common, although dramatic presentations such as myocardial infarction or aborted sudden death will occur. Typically the results of the physical examination and ECG and the chest x-ray film are normal except with ALCAPA or coronary-artery fistulas. Screening studies such as exercise stress testing have low sensitivity, and a negative evaluation does not rule out the presence of a significant anomaly. These important limitations must be considered. Echocardiography is a practical and frequently diagnostic test if specific attention is paid to the coronary arteries. This examination should be performed in most patients with suspect symptoms. Other noninvasive techniques such as nuclear and cine MRI cardiac imaging may become increasingly important, but their current use is anecdotal. Cardiac catheterization remains the gold standard; however, recognition of important clues and specific angiographic views are required to fully delineate many anomalies.

Measurement of left ventricular mass in hypertrophic cardiomyopathy using MRI: Comparison with echocardiography

Left ventricular mass (LVM) is an important consideration in the management of cardiac hypertrophy associated with hypertrophic cardiomyopathy (HCM), systemic hypertension, and other diseases. A brief MRI cardiac imaging procedure used to monitor regression of LVM during treatment would be beneficial in management of these patients, since echocardiograms cannot be obtained in all patients and since the volume of a hypertrophic heart can straightforwardly be assessed from a series of tomographic slices. The present study was designed to evaluate a brief cardiac MRI procedure for measurement of LVM in HCM and compare it to echocardiography. MRI images acquired in a simulated transverse body plane were used to evaluate the mass of the left ventricle in 6 ex vivo human hearts obtained at autopsy. The estimates of LVM by MRI in the ex-vivo hearts were within 8% of the actual LVM. MRI images were acquired to evaluate LVM in 5 normal subjects and 12 patients diagnosed with HCM. Echocardiography was accomplished on 4 of the normal subjects and 10 of the patients having HCM. There were no significant differences in LVM by MRI and echocardiographic techniques in normal subjects. Transverse MRI images acquired on normal subjects demonstrated that estimates of LVM are reproducible when repeated over 3-w to 3-mo intervals. Images selected for analysis represented the heart in an early diastolic phase. MRI and echocardiographic techniques demonstrated significant differences in LVM in HCM patients. Estimates of LVM in normal subjects and patients diagnosed with HCM were normalized for body weight. The LVM estimates for HCM patients were very significantly different than normal subjects. A short (20 min) in vivo cardiac MRI exam acquired in the transverse body plane can be used to accurately measure LVM. Normalized estimates of LVM may be a useful index for monitoring the progression or regression of LVM in HCM and hypertension and following aortic valve replacement for aortic stenosis.

Three-Dimensional Magnetic Resonance Cardiac Imaging Shows Initial Promise

THREE-DIMENSIONAL magnetic resonance imaging (3-D MRI) of the heart is already receiving encouraging reviews from heart surgeons, says Michael Vannier, MD, an associate professor of radiology at Washington University School of Medicine, St Louis. In fact, the demand for his group's 3-D images is becoming overwhelming, Vannier says. Vannier says his group is the only one of which he is aware that is doing the 3-D MRI cardiac imaging. He credits its development to a cardiothoracic surgery fellow, John Laschinger, MD, who wondered if Washington's Mallinckrodt Institute of Radiology's 3-D imaging capabilities could be adapted to the heart. So far, the group has used 3-D MRI to evaluate congenital heart disease. The advantage of the 3-D system is that, even to an untrained eye, anomalies are apparent and the images can even be animated, Vannier says. Perhaps even more important, he says, is the fact that MRI is noninvasive.