Ultrasound in vascular pathologies

Abstract

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.

A comprehensive approach to visual and functional assessment of experimental vascular lesions in vivo

“…Because flow alterations determine clinical relevance of vascular lesions, duplex sonography gives the advantage to directly monitor in-lesion flow velocity combined with geographic lesion assessment. The importance of hemo- dynamic measurements in addition to geographic lesion assessment are 1) hemodynamic measurements are more stable in conditions with impaired signal quality than geometric measurements because they usually require a lower signal-to-noise ratio (11); 2) since hemodynamic and geometric lesion assessment provide complementary information (24), both together strengthen the observation; and 3) hemodynamic lesion assessment is critical for determination of the hemodynamic relevance of a particular lesion. Duplex-based assessment of vascular lesions in the rat carotid injury model may additionally enable the characterization of the importance of particular genes or gene clusters on both time-dependent lesion development and alterations of flow, which cannot be determined by histomorphometry, although this method can substantially add valuable information to duplex-acquired parameters.…”

Interpretation of Doppler signals

“…Secondly, frequency shifts and velocities may vary with blood pressure [13]. Thirdly, the use of short pulse duration and/or wide Doppler aperture with linear array probes may induce a so-called intrinsic spectral broadening responsible for inaccurate calculations [4,14]; therefore, care and prudence are required in clinical practice [4].…”

“…Good knowledge of the Doppler technique and specific training is required to generate a high level of practice with accurate and reproducible acquisitions and accurate interpretations. Principles of the Doppler effect and of the various Doppler techniques, as continuous, pulsed, or bi-dimensional sampling, are beyond the scope of this review and are well described elsewhere [1,2,3,4].…”

Duplex Ultrasonography of the Aorto‐Iliac and Leg Arteries

“…This paper will address the applications and limitations of DS in the investigation of aorto‐iliac and leg arteries. For the more technical aspects and physical principles of DS in peripheral arterial disease, the reader is referred to other publications (4, 5).…”