Ultrasound contrast agents (UCAs- also known as "microbubbles") are small gas particles that volumetrically expand and contract in an ultrasound field, creating a backscattered signal. Their application in imaging and therapy is rapidly growing, requiring continuous optimization to meet the demands of emerging applications. We have recently developed and published a new class of lipid-based UCAs that called chemically cross-linked microbubbles clusters (CCMCs). Unlike individual UCAs, CCMCs are uniquely able to undergo ultrasound-induced bubble fusion using low-intensity pulsed ultrasound. In this study, we continue to optimize or formulation process to develop a rapid and facile means of generating usable and stable clusters for in vivo delivery. Our overall hypothesis is that the unique fusion response of CCMCs in an ultrasound field can generate novel acoustic responses and will eventually enable new methods of contrast agent imaging which cannot be accomplished with traditional UCAs.