Multimodal simultaneous photoacoustic tomography, optical resolution microscopy, and OCT system

Abstract

A novel combined photoacoustic tomography (PAT), optical resolution photoacoustic microscopy (ORPAM) and optical coherence tomography (OCT) instrument has been developed for imaging biological tissues. The system is based on the use of a Fabry-Perot (FP) polymer film ultrasound sensor. This is designed to be transparent to wavelengths between 590nm and 1200nm so that photoacoustic excitation laser pulses in this spectral range can be transmitted through the sensor into the underlying tissue to allow backward mode operation. The dual PAT-ORPAM capability of the system was demonstrated by imaging a tissue phantom composed of 7μm diameter carbon fibres immersed in an optically scattering liquid. The lateral and vertical spatial resolutions in ORPAM mode are approximately 7μm and 10μm respectively for sub-mm depths. In PAT mode, the lateral spatial resolution is less than 50μm for depths up to 5mm and the vertical resolution is approximately 10μm. The transparent nature of the FP polymer film ultrasound sensor offers a convenient platform for combining other optical imaging modalities with PAT and ORPAM. To illustrate this, a frequency-domain OCT system operating at 1060nm was integrated into the system and combined PAT/OCT images of the skin of a mouse were obtained in vivo.