Development of new broad-band ultrasound transducers as well as new, fully digitised, technology of image processing opened the way to harmonic imaging. In this new technology the transducer does not receive echoes of the basic emitted frequency, but it receives vibrations of the 2nd harmonic frequency which originates either from vibration of bubbles of echocontrast agents, introduced in the circulatory system (contrast harmonic imaging), or from vibration of tissue structures as a consequence of non-linear wave propagation in tissues (native harmonic imaging). By suppressing the basic frequency a significant improvement of the signal/noise ratio in the range of 2nd harmonic frequency takes place. This is followed by improvement of contrast and spatial resolution. Harmonic imaging is especially useful in patients where conventional ultrasound examination is difficult.

        Key words: broad-band transducers - digital ultrasound image processing - harmonic imaging