This project focuses on the development of a unique sub-surface chemical imaging technique (i.e., multiphoton photoacoustic  spectroscopy) for the minimally invasive, sub-surface chemical imaging of tissues.  This technique is capable of providing high resolution tumor diagnosis and margining for primary brain tumors.  In addition to developing and demonstrating the technique for tumor imaging, this work also includes the development of a miniature fiber optic probe for potential clinical evaluation as well as automated diagnostic algorithms.