Comparison of elastic modulus inverse estimation and the pulse wave velocity estimation for monitoring abdominal aortic aneurysms

Abstract

The necessity of surgical intervention of abdominal aorta aneurysms is based on a risk-reduction paradigm primarily relying on trans-abdominal ultrasound (US) measurements of the maximum diameter of an AAA. However, the AAA diameter is only a rough estimate of rupture potential, and elastographic estimates of material property changes within aortic tissue may be a better predictor. This work compares an elastic imaging technique measuring aortic tissue stiffness in cross-section to a pulse wave velocity (PWV) estimate obtained from longitudinal images of the same geometry using a two-dimensional clinical US machine. The elastic imaging technique uses a linear elastic finite-element model to solve the elastic inverse problem and estimates the shear modulus. This technique uses a non-invasive pressure cuff to estimate the pressure in the aorta and normalizes the modulus values. The PWV technique uses geometric measurements and simplifies assumptions to create a direct relation between the wave speed and the modulus. Results of validation studies using aortic mimicking phantoms comparing modulus obtained from each of the techniques are presented. Initial clinical results will be also be presented.