Development of novel magnetic resonance methods for advanced parametric mapping of the right ventricle

The detection of diffuse fibrosis is of particular interest in congenital heart disease patients, including repaired Tetralogy of Fallot (rTOF), as clinical outcome is linked to the accurate identification of diffuse fibrosis. In the Left Ventricular (LV) myocardium native T1 mapping and Diffusion Tensor Cardiac Magnetic Resonance (DT-CMR) are promising approaches for detection of diffuse fibrosis. In the Right Ventricle (RV) current techniques are limited due to the thinner, mobile and complex shaped compact myocardium. This thesis describes technical development of RV tissue characterisation methods. An interleaved variable density spiral DT-CMR method was implemented on a clinical 3T scanner allowing both ex and in vivo imaging. A range of artefact corrections were implemented and tested (gradient timing delays, off-resonance and T2* corrections). The off- resonance and T2* corrections were evaluated using computational simulation demonstrating that for in vivo acquisitions, off-resonance correction is essential. For the first-time high-resolution Stimulated Echo Acquisition Mode (STEAM) DT-CMR data was acquired in both healthy and rTOF ex-vivo hearts using an interleaved spiral trajectory and was shown to outperform single-shot EPI methods. In vivo the first DT-CMR data was shown from the RV using both an EPI and an interleaved spiral sequence. Both sequences provided were reproducible in healthy volunteers. Results suggest that the RV conformation of cardiomyocytes differs from the known structure in the LV. A novel STEAM-SAturation-recovery Single-sHot Acquisition (SASHA) sequence allowed the acquisition of native T1 data in the RV. The excellent blood and fat suppression provided by STEAM is leveraged to eliminate partial fat and blood signal more effectively than Modified Look-Locker Imaging (MOLLI) sequences. STEAM-SASHA T1 was validated in a phantom showing more accurate results in the native myocardial T1 range than MOLLI. STEAM-SASHA demonstrated good reproducibility in healthy volunteers and initial promising results in a single rTOF patient.Open Acces

Multimodality Imaging of the Tricuspid Valve and Right Heart Anatomy

The characterization of tricuspid valve and right-heart anatomy has been gaining significant interest in the setting of new percutaneous transcatheter interventions for tricuspid regurgitation. Multimodality cardiac imaging provides a wealth of information about the anatomy and function of the tricuspid valve apparatus, right ventricle, and right atrium, which is pivotal for diagnosis and prognosis and for planning of percutaneous interventions. The present review describes the role of echocardiography, cardiac magnetic resonance, and multidetector row cardiac computed tomography for right heart and tricuspid valve assessment

3D cine DENSE MRI: ventricular segmentation and myocardial stratin analysis

Includes abstract. Includes bibliographical references

Comparison of cardiac volumetry using real-time MRI during free-breathing with standard cine MRI during breath-hold in children

Background Cardiac real-time magnetic resonance imaging (RT-MRI) provides high-quality images even during free- breathing. Difficulties in post-processing impede its use in clinical routine. Objective To demonstrate the feasibility of quantitative analysis of cardiac free-breathing RT-MRI and to compare image quality and volumetry during free-breathing RT-MRI in pediatric patients to standard breath-hold cine MRI. Materials and methods Pediatric patients (n= 22) received cardiac RT-MRI volumetry during free breathing (1.5 T; short axis; 30 frames per s) in addition to standard breath-hold cine imaging in end-expiration. Real-time images were binned retrospec- tively based on electrocardiography and respiratory bellows. Image quality and volumetry were compared using the European Cardiovascular Magnetic Resonance registry score, structure visibility rating, linear regression and Bland–Altman analyses. Results Additional time for binning of real-time images was 2 min. For both techniques, image quality was rated good to excellent. RT-MRI was significantly more robust against artifacts (P< 0.01). Linear regression revealed good correlations for the ventricular volumes. Bland–Altman plots showed a good limit of agreement (LoA) for end-diastolic volume (left ventricle [LV]: LoA -0.1 ± 2.7 ml/m2, right ventricle [RV]: LoA -1.9 ± 3.4 ml/m2), end-systolic volume (LV: LoA 0.4 ± 1.9 ml/m2, RV: LoA 0.6 ± 2.0 ml/m2), stroke volume (LV: LoA -0.5± 2.3 ml/m2, RV: LoA -2.6± 3.3 ml/m2) and ejection fraction (LV: LoA -0.5 ± 1.6%, RV: LoA -2.1 ± 2.8%). Conclusion Compared to standard cine MRI with breath hold, RT-MRI during free breathing with retrospective respiratory binning offers good image quality, reduced image artifacts enabling fast quantitative evaluations of ventricular volumes in clinical practice under physiological conditions