Integrated photoacoustic and diffuse optical tomography system for imaging of human finger joints in vivo

In this study, we developed a dual-modality tomographic system that integrated photoacoustic imaging (PAI) and diffuse optical tomography (DOT) into a single platform for imaging human finger joints with fine structures and associated optical properties. In PAI, spherical focused transducers were utilized to collect acoustic signals, and the concept of virtual detector was applied in a conventional back-projection algorithm to improve the image quality. A finite-element based reconstruction algorithm was employed to quantitatively recover optical property distribution in the objects for DOT. The phantom results indicate that PAI has a maximum lateral resolution of 70 µm in resolving structures of targets. DOT was able to recover both optical absorption and reduced scattering coefficients of targets accurately. To validate the potential of this system in clinical diagnosis of joint diseases, the distal interphalangeal (DIP) joints of 4 healthy female volunteers were imaged. We successfully obtained high-resolution images of the phalanx and the surrounding soft tissue via PAI, and recovered both optical absorption and reduced scattering coefficients of phalanx using DOT. The in vivo results suggest that this dual-modality system has the potential for the early diagnosis of joint diseases such as osteoarthritis (OA) and rheumatoid arthritis (RA). Integrated PAI/DOT imaging interface (top) and typical reconstruction of structures and associated optical properties of a female finger joint via PAI and DOT (bottom).