Multifunctional theranostic nanoparticles hold promise for enabling non-invasive image guided cancer therapy such as photothermal therapy. Human breast tumor models in which response to image guided therapy can quickly and non-invasively be determined are needed to facilitate translation and application of these technologies. We hypothesize that a system utilizing a murine light-reporter mammary tumor cell line and near-infrared nanoparticles (NIR-NP) can be used to quantify response to therapy and determine fate of nanoparticles following photothermal ablation.