Experimental investigation of thermal response of the backscatter from untrasound contrast agent by means of a commercial clinical ultrasound equipment

ABSTRACT Extraordinary progresses have been made in the diagnostic potential of ultrasonography in recent years, due to the combination of ultrasound contrast agents and contrast specific imaging techniques. Dedicated ultrasonography using low acoustic energy emission (Mechanical Index <0,1) applied to contrast microbubbles, the so-called second generation, produces reduced intravascular microbubble destruction, allowing prolonged in vivo circulation time of the contrast agents and Real-Time continuous scanning. The object of this article is to measure the frequency response of SonoVueTM at various temperature, ranging from 37 to 43 °C. This range corresponds to the temperature variations imposed to tissues during hyperthermia treatments in oncological applications. The method is based on the spectral analysis in vitro of the backscattered Radio Frequency signals acquired from commercial ultrasound scanning equipment, modified ad hoc for this purpose, with a convex array transducer. This feature allowed us to analyze in the frequency domain the backscattered echoes coming from a region of interest (ROI) of relatively large size.