Pulse laser integrated photodynamic therapy and photoacoustic imaging

A unique photoacoustic system was developed for neovascular imaging during tumor photodynamic therapy (PDT). In this system, a single pulse laser beam is used as the light source for both PDT treatment and for concurrently generating ultrasound signals for photoacoustic imaging. To demonstrate its feasibility, this system was used to observe vascular changes during PDT treatment of chicken chorioallantoic membrane (CAM) tumors. The photosensitizer used in this study was protoporphyrin IX (PpIX) and the laser wavelength was 532 nm. Damage of the vascular structures by PDT was imaged before, during and after treatment. Rapid, real-time determination of the size of targeted tumor blood vessels was achieved, using time difference of positive and negative ultrasound peaks during PDT treatment. The experimental results show that a pulse laser can be conveniently used to hybridize PDT treatment and photoacoustic imaging and that this integrated system is capable of quantitatively monitoring the structural change of blood vessels during PDT. This method could be potentially used to guide PDT and other phototherapies using vascular changes during treatment to optimize treatment protocols, by choosing appropriate types and doses of photosensitizers, and doses of light.