ABSTRACT
This chapter describes a general model-based inversion scheme for recovering the concentrations of tissue chromophores from multiwavelength photoacoustic images. A diffusion-based finite element (FE) forward model of light transport is used to generate images of absorbed optical energy at different wavelengths as a function of chromophore concentrations. By iteratively adjusting the latter until the model output matches the measured multiwavelength images, a set of quantitative concentration maps that reveal the abundance of each chromophore can be obtained. The technique can be used to quantify physiologically important endogenous chromophores such as oxy (HbO2) and deoxyhemoglobin (HHb), or exogenous chromophores such as those used in molecular imaging. The chapter also describes a simplified implementation in which the concentrations of multiple chromophores are recovered from experimental measurements of multi-wavelength time-resolved photoacoustic signals detected at a single spatial point in a tissue-mimicking phantom. It explains measurements of the concentrations of the extravascular chromophores.
