Ultrasound Imaging - James F. Greenleaf

Ultrasound Study of the Mechanical Properties of the Arterial Wall

Miguel Bernal Restrepo, Ph.D. November 2010

Abstract

Arterial elasticity has become an important predictor of cardiovascular diseases and mortality in the past few decades. Several in vivo and ex vivo techniques have been developed to characterize the elastic properties of vessels.

In vivo approaches, even though have shown correlation of diseases and mortality with arterial elasticity in population studies, are not widely used as a clinical tool for the diagnosis and follow up of patients. Ex vivo techniques have focused their efforts on studying the mechanical properties of the arterial tissue in different axes.

These techniques are usually destructive testing methods, which cannot be applied in an in vivo setting. In this work we present two different approaches to the characterization of the mechanical properties of arterial wall. One of the methodologies presented here uses piezoelectric elements attached to the arterial wall to measure the strain and the stresses in two directions (circumferential and longitudinal) as the arteries are pressurized.

The second part of this works focuses on a technique that uses ultrasound radiation force to generate mechanical waves in the arterial wall. These waves are measured and analyzed in the frequency domain to determine the different modes of propagation and from there, estimate the material properties of the wall tissue. This technique has a high temporal resolution which will allow the dynamic study of the elastic and viscous properties throughout the heart cycle. At the same time the method posses a high spatial resolution allowing the characterization of different vascular segments within the arterial tree.

We are currently working on the implementation of this methodology in a clinical system for the translation into a clinical setting.