In vitro characterization of a novel, tissue-targeted ultrasonic contrast system with acoustic microscopy

Targeted ultrasonic contrast systems are designed to enhance the reflectivi ty of selected tissues in vivo [Lanza et nl., Circulation 94, 3334 (1996)]. In particular, these agents hold promise for the minimally invasive diagno sis and treatment of a wide array of pathologies, most notably tumors, thro mboses, and inflamed tissues. In the present study, acoustic microscopy was used to assess the efficacy of a novel, perfluorocarbon based contrast age nt to enhance the inherent acoustic reflectivity of biological and syntheti c substrates. Data from these experiments were used to postulate a simple m odel describing the observed enhancements. Frequency averaged reflectivity (30-55 MHz) was shown to increase 7.0+/-1.1 dB for nitrocellulose membranes with targeted contrast. Enhancements of 36.0+/-2.3 dB and 8.5+/-0.9 dB for plasma and whole blood clots, respectively, were measured between 20 and 3 5 MHz. A proposed acoustic transmission Line model predicted the targeted c ontrast system would increase the acoustic reflectivity of the nitrocellulo se membrane, whole blood clot, and fibrin plasma clot by 2.6, 8.0, and 31.8 dB, respectively. These predictions were in reasonable agreement with the experimental results of this paper. In conclusion, acoustic microscopy prov ides a rapid and sensitive approach for in vitro characterization, developm ent, and testing of mathematical models of targeted contrast systems. Given the current demand for targeted contrast systems for medical diagnostic an d therapeutic use, the use of acoustic microscopy may provide a useful tool in the development of these agents. (C) 1998 Acoustical Society of America . [S0001-4966(98)01412-X].