DEVELOPMENTS IN CARDIOVASCULAR ULTRASOUND - PART 2 - ARTERIAL APPLICATIONS

Many of the changes resulting from arterial disease can be measured, u sing Doppler ultrasound for measurement of blood velocity and B-scan i maging for measurement of tissue structure and composition. Wall thick ness, the degree of arterial narrowing and plaque volume can be measur ed using B-scan imaging, and 3D ultrasound can be used to improve the accuracy of measurements of plaque volume and for improved visualisati on of complex arterial geometries. Measurement of the dynamic properti es of the arterial wall permits estimation of wall elasticity and plaq ue motion. From the Doppler signal, measurements of blood velocity are used to estimate the degree of arterial narrowing and volumetric flow , although measurement errors can be large. Wall shear stress can be e stimated by measuring the velocity gradient at the vessel wall. The pr oblems of inadequate spatial resolution and interference from overlyin g tissue are largely removed when intravascular systems are used, and these have superior capability in the assessment of arterial structure and tissue composition. However, measurement of quantities relating t o blood flow is more difficult using the intravascular approach, as th e indwelling cather disturbs the blood flow pattern, and currently, as sessment of flow and vessel cross-section are not performed at the sam e site.