Compensation of acoustic attenuation for high resolution photoacoustic imaging with line detectors

Photoacoustic imaging is based on the generation of acoustic waves in a semitransparent sample after illumination with short pulses of light or radio waves. The goal is to recover the spatial distribution of absorbed energy density inside the sample from acoustic pressure signals measured outside the sample (photoacoustic inverse problem). We have proposed a numerical method to calculate directly the time reversed field by retransmitting the measured pressure on the detection surface in reversed temporal order. This model-based time reversal method can solve the photoacoustic inverse problem exactly for an arbitrary closed detection surface. Recently we presented a set up which requires a single rotation axis and line detectors perpendicular to the rotation axis. Using a two-dimensional reconstruction method, such as time reversal in two dimensions, and applying the inverse two-dimensional radon transform afterwards gives an exact reconstruction of a three-dimensional sample with this set up. The resolution in photoacoustic imaging is limited by the acoustic bandwidth and therefore by acoustic attenuation, which can be substantial for high frequencies. This effect is usually ignored in reconstruction algorithms but has a strong impact on the resolution of small structures. It is demonstrated that the model based time reversal method allows to partly compensate this effect.