Speckle-based holographic detection for non-contact Photoacoustic Tomography

The main problems of most state-of-the-art Photoacoustic Imaging approaches are long acquisition times and the requirement of acoustic contact. We introduce a very fast innovative holographic-optical full field non-contact detection method to overcome these problems. In order to increase the acquisition speed significantly, the surface displacements of the object, caused by the photoacoustic pressure waves, are interferometrically measured by a high speed camera in two dimensions. Phase alterations in the observed speckle field determined by Electronic Speckle Pattern Interferometry (ESPI) are used to identify changes in the object’s topography. The total acquisition time can be reduced to 100 ms. This approach was validated with a silicone phantom with an embedded spherical absorber. After recording the topography of the object over time, a tomographic reconstruction leads to the three dimensional location of the different absorbers. A reliable reconstruction proves the ability of the method.