Measurement of the acoustic scatterers distribution within the imaged sample in an optoacoustic tomographic setup

We present in this work a method to estimate the distribution of acoustic scatterers within the imaged sample in an optoacoustic tomographic setup and, subsequently, to reduce the artefacts in the tomographic reconstructions due to reflection or scattering events. The procedure to determine the position of the scatterers consists of measuring the scattered waves generated at a point light absorber located in between the transducer and the imaged sample. Such absorber is positioned in a way that the acoustic waves generated at this absorber and scattered within the sample arrive at the position of the transducer after the waves generated within the sample that propagate directly until the measuring point. Then, the signals captured by the acoustic transducer can be used to reconstruct the distribution of acoustic scatterers and to perform the optoacoustic reconstruction itself. Also, the information retrived on the distribution of acoustic scatterers can be used to improve the optoacoustic tomographic reconstructions. For this, we use a modification of the filtered back-projection algorithm based on weighting the signals with the probability that they are not affected by scattered or reflected waves, so that the artefacts in the images due to these acoustic phenomena are reduced. The experimental results obtained with a tissue-mimicking phantom in which a straw filled with air was included in order to cause scattering of the acoustic waves indicate a good performance of the method proposed.