Imaging instrumentation for ultrasound contrast agents

The past decade has seen dramatic improvements in ultrasound imaging system performance. The introduction of color Doppler imaging has added a new dimension to blood flow measurement, displaying blood flow as a real-time map over a two-dimensional image rather than as a spectrum from the single point of pulsed Doppler or the single line of continuous wave Doppler. The more recent refinement of power Doppler (also known as Color Power AngiographyTM) has increased the imaging sensitivity of color Doppler to the point where images such as that shown in Figure 1 have become common place. If the function of a contrast agent is to enhance the echo from blood, is such help needed with state of the art ultrasound instruments? We believe that it is. First, not all patients yield images like that shown in Figure 1, nor can such images be obtained in all anatomical locations. Contrast agents can extend the anatomical scope, and hence the clinical utility, of conventional ultrasound imaging. Second, as we shall see, contrast agents allow renegotiation of some of the fundamental compromises inherent in a blood flow image and allow system design changes which result in improvements that go far beyond Doppler signal enhancement.