Geometric Surrogates for Clinical Management of Abdominal Aortic Aneurysms

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 DESCRIPTION (provided by applicant): This proposal will investigate the following hypothesis: that the quantification of geometric surrogates, which predict the ensuing peak wall rupture risk index (PWRRI), will provide an improved estimate of aneurysm rupture risk compared to the clinical standard of maximum aneurysm diameter. We thus propose the highly innovative use of both radiological and non-radiological clinical imaging to develop a computational tool that can assess AAA risk of rupture with greater accuracy than the current clinical standard. Such a tool will allow the accurate quantification of individual AAA geometry to achieve the main goal of the study, which is to identify the patient-specific AAA geometry characteristics that are surrogates for patient-specific PWRRI. In the proposed approach, we will first compute a truly individualized PWRRI based on an innovative method called image-based Vascular Mechanical Characterization technology (iV-MeCh). The geometry characteristics highly correlated with PWRRI will be considered the surrogates of this biomechanics-based index. A second phase of the study will be the validation of the surrogates with actual clinical outcomes, which will yield the accurate predictors of rupture. This approach, devoid of complex finite element modeling and based on a fast, nearly automated computational tool for geometry quantification, would provide an exceptional rationale for the need for surgical intervention and be of major clinical significance. Therefore, the following specific aims are to be completed during the project period to address the aforementioned hypothesis: (1) Validate iV-MeCh for estimating patient-specific spatio-temporal AAA wall stress; (2) Calculate individual PWRRI using iV-MeCh for high and low risk of rupture AAA; (3) Identify the individual geometry characteristics that are surrogates of PWRRI; and (4) Assess the clinical significance of geometric surrogates for the prediction of AAA rupture risk. The primary outcome of this research will be the ability to disambiguate or demystify rupture risk in AAA for which the standard of care (maximum diameter) is not an accurate metric for assessing their at-risk condition. The geometric surrogates of PWRRI are hypothesized to reduce false positives and false negatives compared to the conventional maximum diameter cut-off for recommending elective repair. In addition, PWRRI is predicted by means of a new, novel technique (iV-MeCh), which estimates wall stress in aneurysms by means of non-radiological clinical imaging and without the use of constitutive soft tissue mechanics.