Fluence Compensation for Linear Array-Based Photoacoustic Imaging System Using Geometrical Depth Mapping

Linear array-based photoacoustic (PA) imaging has been applied in tissue imaging. Due to optical attenuation, deep tissue receives less optical energy compared to surface tissue and thus generates weaker acoustic signals. To compensate for fluence change along light penetration direction, methods have been proposed based on optical transport model or statistical learning. However, these methods either require knowledge about optical properties of the tissue or involve extensive computation. In this work, we propose a fluence compensation method based on geometrical depth mapping derived from outer contour of the tissue. Our method requires no information on optical properties and does not involve extensive computation. Validations were carried out in simulation and ex vivo experiment. Results show that image intensities in deep tissue are enhanced, and image intensity distribution is more homogenous along the light penetration depth after fluence compensation. The proposed method proved effective for fluence compensation in imaging ex vivo tissue with homogeneous optical properties.