ABSTRACT
Ultrasound imaging is a noninvasive approach to in vivo visualization of exogenously delivered stem cells, which may have unique advantages for clinical application. Therapeutically administered stem cells are acoustically indistinguishable from surrounding tissue and cannot be uniquely identi-‹ed using standard ultrasound imaging. An ultrasound approach to imaging stem cells is based on the premise that stem cell attachment to, or internalization of, ultrasound contrast agents renders the cells detectable by clinical ultrasound imaging systems. An acoustic approach to imaging stem cells has two fundamental requirements: an ultrasound contrast agent that links to the stem cell and a detection strategy that senses a unique acoustic signature from the contrast agent-stem cell construct, which can thus be anatomically coregistered on a two-dimensional ultrasound image. This chapter outlines the current work in achieving these requirements. A brief review of ultrasound contrast agent technology and detection is provided in the context of de‹ning the ideal stem cell contrast agent. This is followed by a description of labeling strategies that have been thus far developed, their strengths and limitations, and requirements for moving forward with this technology.
