Quantitative analysis on in vivo tumor-microvascular images from optical-resolution photoacoustic microscopy

Optical-resolution photoacoustic microscopy (OR-PAM) has been shown to be an excellent imaging modality for monitoring and study of tumor microvasculature. However, previous studies focused mainly on the normal tissues and did not quantify the tumor microvasculature. In this study, we present an in vivo OR-PAM imaging of the melanomas and hepatoma implanted in the mouse ear. We quantify the vessel growth by extracting the skeletons of both dense and thin branches of the tumor microvasculature obtained by Hessian matrix enhancement followed by improved two-step multistencils fast marching method. Compared with the previous methods of using OR-PAM for normal tissues, our method was more effective in extracting the binary vascular network in the tumor images and in obtaining the complete and continuous microvascular skeleton maps. Our demonstration of using OR-PAM in improving microvasculature of tumors and quantification of tumor growth would push deep this technology for the early diagnosis and treatment of cancers.