  Photoacoustic imaging (PAI), is a promising medical imaging technique that
provides the high contrast of the optical imaging and the resolution of
ultrasound (US) imaging. Among all the methods, Three-dimensional (3D) PAI
provides a high resolution and accuracy. One of the most common algorithms for
3D PA image reconstruction is delay-and-sum (DAS). However, the quality of the
reconstructed image obtained from this algorithm is not satisfying, having high
level of sidelobes and a wide mainlobe. In this paper, delay-multiply-and-sum
(DMAS) algorithm is suggested to overcome these limitations in 3D PAI. It is
shown that DMAS algorithm is an appropriate reconstruction technique for 3D PAI
and the reconstructed images using this algorithm are improved in the terms of
the width of mainlobe and sidelobes, compared to DAS. Also, the quantitative
results show that DMAS improves signal-to-noise ratio (SNR) and
full-width-half-maximum (FWHM) for about 25 dB and 0.2 mm, respectively,
compared to DAS.
