Echocolor Doppler Physics: Basic Principles

Are defined "ultrasound" (sounds inaudible to the human ear) the waves with frequencies above 20 kHz. In diagnostics, ultrasound are generated and received by transducers (piezoelectric materials), which convert electric energy into mechanical energy and vice versa: the most frequencies used are comprised from 2 and 10 MHz.

The propagation of the signal and its tissue penetration depends on the frequency of transmission of the crystal: a transducer frequency of 7-10 MHz is useful for the study of the superficial vessels (depth up to 3-4 cm.) while a transducer frequency of 2-3 MHz can be employed in the study of deep vessels, such as the abdominal vessels (it is able to get up to 20-25 cm depth).

The echocolor Doppler is the integration of information: 1) B-mode: gray scale image of the anatomical structures; 2) color: to the B-mode images are superimposed those with blood flow (color code); 3) Doppler: to obtain hemodynamic information is selected, with the pulsed Doppler, the position and the size of the area to explore.

This information allows to explore reliably and noninvasively all the vascular districts.

In this lesson the basic principles of the echocolor Doppler physics are presented.

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