CFD-Based Postprocessing of CT-MRI Data to Determine the Mechanics of Rupture in Abdominal Aortic Aneurysms

Abstract

Multimodality imaging techniques are becoming the norm in medical imaging. Using a combination of techniques, clinicians can make a more informed diagnosis. In the case of abdominal aortic aneurysms (AAA), a combination of CT and MRI imaging techniques is used to diagnose and subsequently decide on surgical intervention. Clinicians use a maximum transverse diameter metric of 55 mm to recommend surgery in AAA patients based on the images obtained. However, the clinical metric by itself is not sufficient to prognose rupture. Hence, a mechanics-based approach can be employed to extract biomechanical parameters such as wall shear stress and principal stresses to predict rupture well in advance. With the application of computational fluid dynamics (CFD), these parameters can be estimated from a fluid–structure interaction (FSI)-based analysis of the abnormal aorta. Patient-specific geometry and boundary conditions such as velocity, pressure, and material properties are used in these methods. In this chapter, an FSI-based approach to study the rupture mechanics of AAA is discussed in detail. Subsequently, the need of studying AAA in Asian population is outlined and a case study is presented on a patient-specific model to illustrate the mechanics-based approach in predicting rupture in AAA. Results from the case study reveal that the maximum transverse diameter is not the sole determinant of AAA rupture risk. Hence, mechanics-based method supplements the image-based techniques for better patient management.