Speckle-based off-axis holographic detection for non-contact photoacoustic tomography

Abstract

A very fast innovative holographic off-axis non-contact detection method for Photoacoustic Tomography (PAT) is introduced. It overcomes the main problems of most state-of-the-art photoacoustic imaging approaches that are long acquisition times and the requirement of acoustic contact. In order to increase the acquisition speed significantly, the surface displacements of the object, caused by the photoacoustic pressure waves, are measured interferometrically in two dimensions. Phase alterations in the observed speckle field are used to identify changes in the object's topography. A sampling rate of up to 80 MHz is feasible, which reduces the occurrence of motion artefacts. This approach was validated with a silicone phantom with cylindrical absorbers that are similar to the shape of blood vessels. A tomographic reconstruction leads to the three dimensional location of the absorbers. A reliable reconstruction proves the ability of the method.