ABSTRACT
This chapter analyzes the modulation characteristic and describes an algorithm for estimating the local distribution of acoustic parameters such as the acoustic attenuation coefficient. Acoustic propagation properties such as acoustic attenuation and sound velocity in biological soft tissue have been found to be temperature dependent. If the change in the acoustic parameter can be measured precisely and simply, with ultrasound diagnostic equipment, non-invasive ultrasound thermometry could be a useful technique for use in hyperthermic therapy. A new ultrasound method using acoustic nonlinearity in the pulse reflection mode has been developed to measure the change related to the acoustic nonlinearity parameter and the acoustic attenuation coefficient in soft tissues. In contrast, the modulated probe pulse wave caused by pump pulse wave distortion through the propagation is shifted to a higher frequency range (solid line) or lower frequency range (broken line) according to the sign of particle acceleration.
