Ultrasound in vascular pathologies

The choice of the optimal ultrasonic frequency for vascular studies is determined by the required resolution and penetration. Anatomical real-time two-dimensional imaging and blood flow studies provide complementary information. Intravascular scanning allows high-frequency ultrasound to be used, with correspondingly good spatial resolution. Contrast resolution is degraded by beam side lobes and the limited dynamic range of the ultrasonic pulse. The physics of ultrasonic scattering by blood, pulsed Doppler and duplex scanning and colour flow imaging performances determines the limits of clinical applications. Contrast agents enhance the echogenicity of blood, improving sensitivity and, through second harmonic detection, suppressing solid tissue echoes. Three-dimensional display, with segmentation by the presence of the flow signal, facilitates spatial perception. Clinical applications in vascular pathologies are summarised.