On the Use of Patient-specific Tissue Mechanics for Abdominal Aortic Aneurysm Wall Stress Assessment




Thirugnanasambandam, Mirunalini

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Abdominal aortic aneurysms (AAA) are characterized by the expansion of the infrarenal region of the abdominal aorta by more than 50% of its physiological diameter. Current clinical markers for rupture risk prediction are based on maximum diameter of the AAA. The efficacy of this traditional marker is being challenged by biomechanical markers such as peak wall stress (PWS) and 99th percentile wall stress (99th-WS). However, the processes involved in biomechanical evaluation of wall stress are particularly laborious and non-patient-specific due to the unavailability of mechanical properties and thickness of the AAA wall. Thus, there is a critical need to simplify the procedure by reducing computational time and resources and to circumvent the need for material model description. In this study, we developed a novel technique called image-based Vascular Mechanical Characterization (iV-MeCh), which has the ability to bypass the use of finite element analysis and generalized material models while computing wall stress distribution. An in-vitro benchtop flow-loop was designed and constructed to replicate physiological behavior. iV-MeCh was implemented on a patient-specific AAA phantom geometry which was reconstructed from time-resolved MR images of the flow-loop. Wall stress based biomechanical markers evaluated using iV-MeCh were compared with those from FEA as a validation step. iV-MeCh was further used in a patient-specific AAA dataset to verify feasibility of the implementation in human AAAs. In summary, we developed, validated and tested a new membrane-based algorithm for evaluation of AAA rupture risk indices, while avoiding the use of FEA and material model specification.


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Abdominal aortic aneurysm, benchtop model, membrane analysis, patient-specific, peak wall stress, Windkessel



Biomedical Engineering