Clinical theranostics applications of photo-acoustic imaging as a future prospect for cancer.

Photoacoustic imaging (PAI) of biological tissue has been a fast developing biomedical multi-wave imaging modality, after its introduction in the mid90s. PAI couples laser excitation to acoustic detection. Especially, in recent years its significant advantages in onco-surgery has attracted much attention due to its ability to detect malignant tissues. Monitoring cancer angiogenesis, assessment of blood oxygen saturation, functional brain imaging, evaluation of cortical blood volume, detection of skin/conjunctival melanoma depth, assessment of met-hemoglobin, investigating tumor hypoxia andcancer lymph node metastases are some of its promising applications. Moreover, as a real-time monitoring strategy, PAI allows intraoperative imaging of micro-metastases and residual islands in onco-surgery. Herein, we provide a brief introduction to biophysics and fundamentals of PAI, potential novel endogenous and exogenous contrast agents, and novel techniques to develop engineered and targeted contrast agents with theranostic applications. We also summarize the clinical trial pipelines for PAI. Furthermore, we discuss the potential obstacles and limitation of PAI theranostic agents for further clinical applications and strategies to overcome these hurdles.