The paper describes a method able to perform an ultrasonic study of a single UCA bubble immersed in a tank filled with a liquid (water) by means of ultrasonic equipment able to insonify and acquire RF echo signals coming from an isolated bubble with a high frame rate. The work was focused on the study of subharmonic emission from an isolated bubble of SonoVue. In particular, the acoustic pressure threshold for a subharmonic stable emission was evaluated for a subset of 50 microbubbles at 3.3 MHz and at 5 MHz of insonation frequencies. An unexpected second pressure threshold, which caused the standstill of the subharmonic emission, was detected at 3.3 MHz and 5 MHz. A transient subharmonic emission, which is hypothesized as being related to the formation of new free gas bubbles, was detected during the ultrasound-induced destruction of microbubbles. Specific bubble behaviors concerning the stable subharmonic emission, the inhibition of subharmonic generation, and the transient subharmonic emission were investigated over a set of 400 isolated microbubbles and experimental results are reported and discussed in this paper.
Ultrasound Contrast Agent Microbubbles: Stable and Transient Subharmonic Emissions / L. Masotti; E. Biagi; L. Breschi; E. Vannacci. - STAMPA. - 122-n°5:(2007), pp. 3051-3052. (Intervento presentato al convegno Acoustical Society of America Meeting tenutosi a New Orleans, Louisiana).