4 research outputs found
Aortic haemodynamics and wall stress analysis following arch aneurysm repair using a single-branched endograft
IntroductionThoracic endovascular aortic repair (TEVAR) of the arch is challenging given its complex geometry and the involvement of supra-aortic arteries. Different branched endografts have been designed for use in this region, but their haemodynamic performance and the risk for post-intervention complications are not yet clear. This study aims to examine aortic haemodynamics and biomechanical conditions following TVAR treatment of an aortic arch aneurysm with a two-component single-branched endograft.MethodsComputational fluid dynamics and finite element analysis were applied to a patient-specific case at different stages: pre-intervention, post-intervention and follow-up. Physiologically accurate boundary conditions were used based on available clinical information.ResultsComputational results obtained from the post-intervention model confirmed technical success of the procedure in restoring normal flow to the arch. Simulations of the follow-up model, where boundary conditions were modified to reflect change in supra-aortic vessel perfusion observed on the follow-up scan, predicted normal flow patterns but high levels of wall stress (up to 1.3M MPa) and increased displacement forces in regions at risk of compromising device stability. This might have contributed to the suspected endoleaks or device migration identified at the final follow up.DiscussionOur study demonstrated that detailed haemodynamic and biomechanical analysis can help identify possible causes for post-TEVAR complications in a patient-specific setting. Further refinement and validation of the computational workflow will allow personalised assessment to aid in surgical planning and clinical decision making
Data-driven generation of 4D velocity profiles in the aneurysmal ascending aorta
Numerical simulations of blood flow are a valuable tool to investigate the
pathophysiology of ascending thoracic aortic aneurysms (ATAA). To accurately
reproduce hemodynamics, computational fluid dynamics (CFD) models must employ
realistic inflow boundary conditions (BCs). However, the limited availability
of in vivo velocity measurements still makes researchers resort to idealized
BCs. In this study we generated and thoroughly characterized a large dataset of
synthetic 4D aortic velocity profiles suitable to be used as BCs for CFD
simulations. 4D flow MRI scans of 30 subjects with ATAA were processed to
extract cross-sectional planes along the ascending aorta, ensuring spatial
alignment among all planes and interpolating all velocity fields to a reference
configuration. Velocity profiles of the clinical cohort were extensively
characterized by computing flow morphology descriptors of both spatial and
temporal features. By exploiting principal component analysis (PCA), a
statistical shape model (SSM) of 4D aortic velocity profiles was built and a
dataset of 437 synthetic cases with realistic properties was generated.
Comparison between clinical and synthetic datasets showed that the synthetic
data presented similar characteristics as the clinical population in terms of
key morphological parameters. The average velocity profile qualitatively
resembled a parabolic-shaped profile, but was quantitatively characterized by
more complex flow patterns which an idealized profile would not replicate.
Statistically significant correlations were found between PCA principal modes
of variation and flow descriptors. We built a data-driven generative model of
4D aortic velocity profiles, suitable to be used in computational studies of
blood flow. The proposed software system also allows to map any of the
generated velocity profiles to the inlet plane of any virtual subject given its
coordinate set.Comment: 21 pages, 5 figures, 2 tables To be submitted to "Computer methods
and programs in biomedicine" Scripts: https://github.com/saitta-s/flow4D
Synthetic velocity profiles: //doi.org/10.5281/zenodo.725198
2-(Alkyl/aryl)amino-6-benzylpyrimidin-4(3H)-ones as inhibitors of wild-type and mutant HIV-1: enantioselectivity studies.
The single enantiomers of two pyrimidine-based HIV-1 non-nucleoside reverse transcriptase inhibitors, 1 (MC1501) and 2 (MC2082), were tested in both cellular and enzyme assays. In general, the R forms were more potent than their S counterparts and racemates and (R)-2 was more efficient than (R)-1 and the reference compounds, with some exceptions. Interestingly, (R)-2 displayed a faster binding to K103N RT with respect to WT RT, while (R)-1 showed the opposite behavior. © 2012 American Chemical Societ
2-(Alkyl/Aryl)Amino-6-Benzylpyrimidin-4(3<i>H</i>)-ones as Inhibitors of Wild-Type and Mutant HIV-1: Enantioselectivity Studies
The single enantiomers of two pyrimidine-based HIV-1
non-nucleoside
reverse transcriptase inhibitors, <b>1</b> (MC1501) and <b>2</b> (MC2082), were tested in both cellular and enzyme assays.
In general, the <i>R</i> forms were more potent than their <i>S</i> counterparts and racemates and (<i>R</i>)-<b>2</b> was more efficient than (<i>R</i>)-<b>1</b> and the reference compounds, with some exceptions. Interestingly,
(<i>R</i>)-<b>2</b> displayed a faster binding to
K103N RT with respect to WT RT, while (<i>R</i>)-<b>1</b> showed the opposite behavior