ABSTRACT
The combination of high optical contrast and low acoustic scattering has made photoacoustics (PA) a promising tool in several biomedical applications, including blood oxygenation monitoring and breast tumor detection. This chapter describes PA methods for quantitative blood flow estimation. It also describes the shape-dependent absorption spectrum and photo-induced shape transition properties of gold nanoparticles to facilitate flow measurements. In particular, gold nanoparticles are used as the contrast agent for signal enhancement and for time-intensity curve (TIC) measurements. For the dual-energy method, only the TIC in the replenishment step is used to estimate the flow velocity. The chapter presents the mathematical models and measurement results for wash-out TICs and wash-in TICs. It discusses potential clinical applications and performance issues. For in vivo applications, the TIC can also be measured using a sequence of two-dimensional (2D) images. As a demonstration, TIC measurements were conducted with a perfusion phantom, which was constructed from an optically and acoustically transparent material.
