Assessment of Bi-Ventricular and Bi-Atrial Areas Using Four-Chamber Cine Cardiovascular Magnetic Resonance Imaging: Fully Automated Segmentation with a U-Net Convolutional Neural Network

Four-chamber (4CH) cine cardiovascular magnetic resonance imaging (CMR) facilitates simultaneous evaluation of cardiac chambers; however, manual segmentation is time-consuming and subjective in practice. We evaluated deep learning based on a U-Net convolutional neural network (CNN) for fully automated segmentation of the four cardiac chambers using 4CH cine CMR. Cine CMR datasets from patients were randomly assigned for training (1400 images from 70 patients), validation (600 images from 30 patients), and testing (1000 images from 50 patients). We validated manual and automated segmentation based on the U-Net CNN using the dice similarity coefficient (DSC) and Spearman’s rank correlation coefficient (ρ); p < 0.05 was statistically significant. The overall median DSC showed high similarity (0.89). Automated segmentation correlated strongly with manual segmentation in all chambers—the left and right ventricles, and the left and right atria (end-diastolic area: ρ = 0.88, 0.76, 0.92, and 0.87; end-systolic area: ρ = 0.81, 0.81, 0.92, and 0.83, respectively; p < 0.01). The area under the curve for the left ventricle, left atrium, right ventricle, and right atrium showed high scores (0.96, 0.99, 0.88, and 0.96, respectively). Fully automated segmentation could facilitate simultaneous evaluation and detection of enlargement of the four cardiac chambers without any time-consuming analysis

Differentiation between mild and severe myocarditis using multiparametric cardiac magnetic resonance

The pathophysiology of myocarditis is associated with mild inflammation and may progress silently, or in severe cases such as fulminant myocarditis, may lead to sudden hemodynamic compromise. An invasive myocardial biopsy is generally required for a definitive myocarditis diagnosis. Alternatively, cardiac magnetic resonance (CMR), which evaluates myocardial characteristics and cardiac function, can be used as a noninvasive tool for diagnosing myocarditis. We describe the cases of a 49-year-old woman with mild acute eosinophilic myocarditis and a 48-year-old man with severe acute lymphocytic myocarditis. CMR was performed during the acute and convalescent phases in both cases. Compared with mild myocarditis, CMR in severe myocarditis showed higher T2 values and decreased left ventricular and atrial volumes and strains; however, the right ventricular strain was preserved. Late gadolinium enhancement showed faint contrast enhancement in the whole and strong enhancement in the local myocardium. Follow-up CMR showed recovery from myocardial inflammation and cardiac function. Some late gadolinium enhancement persisted whereas acute inflammation-associated enhancement disappeared. This case report highlights the differences between the cardiac parameters of patients with mild and severe myocarditis. Severe myocardial inflammation can be caused by severe heart failure owing to the concurrent reduction of cardiac function and compliance. Additionally, preserved right ventricular strain may predict cardiac function recovery in acute myocarditis. Noninvasive and repeatable CMR provides information on myocardial characteristics, cardiac function, and hemodynamics in a single scan at that time, which is useful not only for diagnosis but also for severity assessment and patient management in acute myocarditis

Assessing myocardial circumferential strain using cardiovascular magnetic resonance after magnetic resonance-conditional cardiac resynchronization therapy

Nondrug therapy for arrhythmia patients had been developed dramatically until recent years. Cardiac resynchronization therapy (CRT), a nondrug therapy for arrhythmia, is especially utilized for the treatment of left ventricular (LV) severe heart failure caused by cardiac dyssynchrony. Prolonged QRS duration (≧130 ms) is strongly used as a CRT indication criterion, but QRS is not the direct clinical index of mechanical contraction delay of the LV myocardium. Therefore, identifying the presence of dyssynchrony by diagnostic imaging is necessary. Echocardiography is widely used for the assessment of dyssynchrony as a standard diagnostic imaging. Several studies have addressed the efficacy of cardiovascular magnetic resonance feature tracking (CMR-FT) in the diagnosis of dyssynchrony for arrythmia patients. In addition, cardiac implantable electronic devices (CIEDs) were not available to examine CMR until recent years; however, new MR-conditional CIEDs have become available for use before and after CRT. Recently, diagnostic imaging using CMR-FT has been attracting attention for the assessment of dyssynchrony. However, a strong metal artifact caused by CIEDs may make the analysis difficult after CRT implantation. Strain analysis using short-axis (SA) cine CMR overcame this issue of artifact by enabling slice selection by avoiding artifact. Moreover, circumferential strain has superiority over other strain methods with respect to sensitivity, and we focused on these advantages. This case illustrates that circumferential strain with CMR-FT using SA cine CMR is useful in the assessment of improvement of myocardial motion after CRT and can provide useful additional information with imaging to determine the responders of CRT

Differentiation between mild and severe myocarditis using multiparametric cardiac magnetic resonance

The pathophysiology of myocarditis is associated with mild inflammation and may progress silently, or in severe cases such as fulminant myocarditis, may lead to sudden hemodynamic compromise. An invasive myocardial biopsy is generally required for a definitive myocarditis diagnosis. Alternatively, cardiac magnetic resonance (CMR), which evaluates myocardial characteristics and cardiac function, can be used as a noninvasive tool for diagnosing myocarditis. We describe the cases of a 49-year-old woman with mild acute eosinophilic myocarditis and a 48-year-old man with severe acute lymphocytic myocarditis. CMR was performed during the acute and convalescent phases in both cases. Compared with mild myocarditis, CMR in severe myocarditis showed higher T2 values and decreased left ventricular and atrial volumes and strains; however, the right ventricular strain was preserved. Late gadolinium enhancement showed faint contrast enhancement in the whole and strong enhancement in the local myocardium. Follow-up CMR showed recovery from myocardial inflammation and cardiac function. Some late gadolinium enhancement persisted whereas acute inflammation-associated enhancement disappeared. This case report highlights the differences between the cardiac parameters of patients with mild and severe myocarditis. Severe myocardial inflammation can be caused by severe heart failure owing to the concurrent reduction of cardiac function and compliance. Additionally, preserved right ventricular strain may predict cardiac function recovery in acute myocarditis. Noninvasive and repeatable CMR provides information on myocardial characteristics, cardiac function, and hemodynamics in a single scan at that time, which is useful not only for diagnosis but also for severity assessment and patient management in acute myocarditis