Flow examination in abdominal aortic aneurysms: Reduced-order models driven by in vitro data and spectral proper orthogonal decomposition

Abstract

Although flow characteristics in abdominal aortic aneurysms (AAAs) have been extensively studied, they have not found their way into the clinical evaluation of the disease. We, therefore, present experimental AAA flow models, optimized using spectral proper orthogonal decomposition, to aid in gauging AAA severity based on the underlying flow. The resulting reduced-order AAA flow models capture pertinent pathological flow features. With progressive aneurysm expansion, the flow becomes increasingly complex, accompanied by larger vortical structures and elevated particle residence time. The presented models can lead to a more comprehensive clinical evaluation that includes patient-specific flow information.

Aneurysmal Growth in Type-B Aortic Dissection: Assessing the Impact of Patient-Specific Inlet Conditions on Key Haemodynamic Indices

“…The energy-based ranking of modes is performed such that the flow can be accurately reconstructed using a discrete quantity of these modes 2 , thus reducing the order of the system. The flow is said to be accurately represented by the ensemble of modes containing 98% of the total KE which, in cardiovascular flows, has been widely reported to occur within the first 1-10 modes 17,29,8,48 .…”

“…Due to the energy-based nature of this analysis, modes may not retain physical inter-pretability due to frequency mixing 2 . Nevertheless, POD analysis offers a means of examining how the fluid KE is distributed amongst coherent flow structures and how this energy changes over time, facilitating a decoupling of spatial and temporal behaviour which can provide valuable insights into the behaviour of the flow 29 . For example, POD analysis of the flow in ruptured and unruptured aneurysms showed that rupture was more strongly associated with spatial flow complexity, rather than temporal stability 8 ; similar insights may be available in the context of aneurysmal TBAD.…”

“…To further examine the impact of inlet conditions on the velocity field, we employ Proper Orthogonal Decomposition (POD), a reduced order modelling (ROM) technique that is becoming more widely used to analyse cardiovascular flows 29,47 . POD is typically used to identify coherent flow structures which optimally capture the fluctuating energy of the velocity field, facilitating a deeper understanding of complex flow fields 2 .…”

“…POD is typically used to identify coherent flow structures which optimally capture the fluctuating energy of the velocity field, facilitating a deeper understanding of complex flow fields 2 . POD has been applied to characterise turbulence in cerebral arteries 15,19 , examine the impact of inflow strength and angle in cerebral and abdominal aortic aneurysms and identify differences between healthy and pathological flow conditions within them 29,8 . It has also been used to enhance the resolution of 4DMR data in coronary and cerebral arteries 3,27 .…”

Aneurysmal growth in type-B aortic dissection: assessing the impact of patient-specific inlet conditions on key haemodynamic indices

“…The energy-based ranking of modes is performed such that the flow can be accurately reconstructed using a reduced number of these modes [17], thus reducing the order of the system. The flow is said to be accurately represented by the ensemble of modes containing 98% of the total KE which, in cardiovascular flows, has been widely reported to occur within the first 1-10 modes [16,19,33].…”