TARGETED ULTRASOUND CONTRAST ASSISTED IMAGING OF BACTERIAL ENDOCARDITIS

University Of Hawaii At Manoa, Honolulu HI

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Endocarditis is often accompanied by the formation of a biofilm known as a vegetation on a cardiac valve. The mortality rate for endocarditis can be upward of 70% as the treatment is typically limited to intravenous antibotics or surgery. Prolonged antibiotic treatment may be required. Furthermore, valve removal and replacement for endocarditis is a difficult and expensive procedure. A noninvasive diagnostic method which provides molecular information about this bacterial biofilm would foster significant improvements in endocarditis detection and treatment. Ultrasound imaging has unique advantages in terms of availability, cost and portability and in addition provides molecular imaging capabilities in conjunction with targeted ultrasound contrast agents. These agents are encapsulated gas which selectively bind to specific diseased tissue with unique scattering characteristics as they oscillate nonlinearly in an acoustic field, faciltiating the detection and imaging of the targets. We seek to develop a targeted molecular imaging method for the bacterial biofilms associated with endocarditis;however, some preliminary, exploratory investigations are needed to advance this novel area of ultrasound contrast aided imaging. We seek to investigate in a stationary, ambient fluid a) attachment to biofilms of antibodies-targeted ultrasound contrast agents, b) the acoustic scattering as a function of the binding and acoustic parameters, and c) the effect of bacteria viability on the acoustic scattering signatures. Future clinical success depends on the robustness of the binding on the valves and the acoustic scattering signals subject to blood flow. Therefore, we will also investigate the binding and acoustic scattering for physiologically relevant situations and anatomy (continuous flow, different binding surfaces) having similarity to heart valves.