3D photoacoustic imaging system for in vivo studies of small animal models

A 3D photoacoustic (PA) imaging system has been developed for the non-invasive, in vivo characterization of small animal models of human disease processes. The system utilizes a Fabry Perot polymer film sensing interferometer (FPI) for mapping the spatial-temporal distribution of the PA signals in 2D enabling a 3D PA image to be reconstructed. The mirrors of the sensing FPI are transparent between 590 and 1200nm and highly reflective between 1500 and 1600nm. This enables the transmission of excitation laser pulses from an OPO laser in the former wavelength range through the sensor into the tissue. The induced PA signals are then detected with a CW focused interrogating laser beam at 1550nm which is scanned across the surface of the sensor point by point. Hence, the system is capable of operating in backward mode. The operation of a two-channel interrogating scheme for the FPI sensor has been demonstrated, which will lead to multi-point simultaneous sampling of the PA signals and consequently significantly reduces the data acquisition time. Other measures for speeding up the imaging process and further enhancing image resolution are examined. The system was used to obtain 3D images of mouse tumours of various sizes and in vivo images of the superficial vasculature of the human palm illustrating the potential for characterising small animal cancer models.