Abstract: Recently a new therapeutic approach for cancer has exhibited high promise termed adoptive cell therapy. This approach involves treating patients with immune cells such as T cells or Natural Killer (NK) cells instead of drug therapy. While some cell therapies have exhibited high promise for at least a subset of cancers, a major technological challenge in the development of this field is the lack of knowledge of where these cells reside in the body once they are infused. While it is readily easy to monitor the blood for the presence of the infused immune cells, there is no satisfactory method to monitor the cells that traffic into tissue (ex. colon tumors). In this proposal, we will develop a novel method to label immune cells using nanobubbles (NBs). These labelled cells then can be monitored non-invasively using an ultrasound. As NBs are a component of an already FDA approved product, we anticipate this approach will not only be safe but can be translated quickly to human testing. It is hoped that this work will lead to new technology that will enable us to monitor the trafficking of immune cell therapies so that we can optimally select which patients/tumor types would most benefit from a given cell therapy product.