Quantitative three-dimensional photoacoustic tomography of the finger joints: phantom studies in a spherical scanning geometry

In this paper, we present a series of phantom experiments that aim to systematically evaluate the possibility of quantitative three-dimensional (3D) photoacoustic imaging of the finger joints in a spherical scanning geometry. The 3D absorption coefficient images of the joint-mimicking phantoms are obtained using our finite-element-based photoacoustic image reconstruction algorithm coupled with the photon diffusion equation. The results show that a 1 mm thick 'cartilage' can be accurately differentiated from the 'bones' with a 1 MHz transducer. In addition, the absorption coefficient of the 'cartilage' can be effectively recovered when this optical property is varied from 0.015 to 0.04 mm-1. The phantom images shown in this paper suggest that 3D photoacoustic tomography in a spherical scanning geometry has the potential to image a realistic human joint.