Biology subjects

Renzi, F.

Publications and source records attributed to Renzi, F..

3 recordsLinked to original sources

bioRxiv2023

Accurate and Efficient 3D Reconstruction of Right Heart Shape and Motion from Multi-Series Cine-MRI

The accurate reconstruction of the right heart geometry and motion from time-resolved medical images enhances diagnostic tools based on image visualization as well as the analysis of cardiac blood dynamics through computational methods. Due to the peculiarity of the right heart morphology and motion, commonly used segmentation and/or reconstruction techniques, which only employ Short-Axis cine-MRI, lack accuracy in relevant regions of the right heart, like the ventricular base and the outflow tract. Moreover, the reconstruction procedure is time-consuming and, in the case of the generation of computational domains, requires a lot of manual intervention. This paper presents a new method for the accurate and efficient reconstruction of the right heart geometry and motion from time-resolved MRI. In particular, the proposed method makes use of surface morphing to merge information coming from multi-series cine-MRI (such as Short/Long-Axis and 2/3/4 Chambers acquisitions) and to reconstruct important cardiac features. It also automatically provides the complete cardiac contraction and relaxation motion by exploiting a suitable image registration technique. The method is applied both to a healthy and a pathological (tetralogy of Fallot) case, and yelds more accurate results than standard procedures. The proposed method is also employed to provide significant input for computational fluid dynamics. The corresponding numerical results demonstrate the reliability of our approach in the computation of clinically relevant blood dynamics quantities.

bioengineering↗

bioRxiv2023

Turbulence and blood washout in presence of mitral regurgitation: a computational fluid-dynamics study in the complete left heart

In this work we performed a computational image-based study of blood dynamics in the whole left heart, both in a healthy subject and in a patient with mitral valve regurgitation (MVR). We elaborated dynamic cine-MRI images with the aim of reconstructing the geometry and the corresponding motion of left ventricle, left atrium, mitral and aortic valves, and aortic root of the subjects. This allowed us to prescribe such motion to computational blood dynamics simulations where, for the first time, the whole left heart motion of the subject is considered, allowing us to obtain reliable subject-specific information. The final aim is to investigate and compare between the subjects the occurrence of turbulence and the risk of hemolysis and of thrombi formation. In particular, we modeled blood with the Navier-Stokes equations in the Arbitrary Lagrangian-Eulerian framework, with a Large Eddy Simulation model to describe the transition to turbulence and a resistive method to manage the valve dynamics, and we used a Finite Elements discretization implemented in an in-house code for the numerical solution. Our results highlighted that the regurgitant jet in the MVR case gave rise to a large amount of transition to turbulence in the left atrium resulting in a higher risk of formation of hemolysis. Moreover, MVR promoted a more complete washout of stagnant fiows in the left atrium during the systolic phase and in the left ventricle apex during diastole. NEW & NOTEWORTHYReconstruction from cine-MRI images of geometries and motion of the left heart (left atrium and ventricle, aortic root, aortic and mitral valve) of a healthy and mitral regurgitant patient. Prescription of such motion to a complete subject-specific computational fluid-dynamic simulation of the left heart. Investigation of turbulence in a regurgitant scenario. Study of the mechanisms of prevention from stagnant flows and hemolysis formation in the atrium.

bioengineering↗

bioRxiv2020

ACE2 fragment as a decoy for novel SARS-Cov-2 virus

Novel SARS-Cov-2 enters human cells via interaction between the surface spike (S) glycoprotein and the cellular membrane receptor angiotensin-converting enzyme 2 (ACE2). Using a combination of comparative structural analyses of the binding surface of the S protein to ACE2, docking experiments, and molecular dynamics simulations we computationally identified a minimal, stable fragment of ACE2. This fragment binds to the S protein, is soluble, and appears not to bind to the physiological ligand angiotensinII. These results suggest a possible use of the ACE2 fragment as a decoy that could interfere with viral binding by competition.

bioinformatics↗