Quantitative Photoacoustic Imaging

Abstract

Tumor angiogenesis is the cancer-induced chaotic proliferation of blood vessel structure penetrating into surrounding cancerous tissue. Effective micro-vasculature imaging method is urgently desired for both fundamental biological and clinical studies. However, this is a challenging task, as existing standard imaging techniques are limited by factors such as poor resolution, high cost, necessity of using imaging contrast agent and invasiveness. Photoacoustic (PA) imaging, as a non-ionizing modality, has drawn significant interest due to the promise it holds for high-resolution, noninvasiveness and its capability to reveal functional information based on intrinsic optical contrast. The ultimate goal of this dissertation is to further previous work on quantitative photoacoustic imaging, specifically, to contribute to quantitative imaging of tumor angiogenesis and anti-angiogenetic therapy. The work presented in this dissertation can be divided into three parts. In the first part, we focus on quantitative photoacoutic tomography (qPAT) for deep tissue imaging. We developed a series of algorithms that are able to quantify deep tissue photoacoustic imaging. We demonstrated by simulations that spatial distributions of optical properties, namely optical absorption and scattering, as well as the Grüneisen parameter can be faithfully reconstructed with our reconstruction algorithms. In the second part, we focused on developing new imaging platforms for quantitative photoacoustic microscopy (PAM) imaging for superficial imaging depths. We successfully included fluorescently-labeled molecular context in optical-resolution PAM (OR-PAM) imaging by our integrated micro-endoscopy system that is able to simultaneously accomplish fluorescence and OR-PAM imaging. With our fast, wide field-of-view OR-PAM imaging technique, we significantly reduced the data acquisition time of conventional OR-PAM systems to a clinically realistic level. In the third part, experimental work is presented for quantitative imaging of vasculature variations and oxygen depletions due to photodynamic therapy with an acoustic-resolution PAM (AR-PAM) system we developed.