Enhancing Depth of Penetration in PLD-Based Photoacoustic Imaging: Preliminary Results.

In most cases, high energy solid state lasers such as Nd:YAG are used as source of illumination for Photoacoustic Tomography (PAT). However the bulkiness, high cost and low pulse repetition frequency (PRF) poses a challenge in translating this technology to an affordable clinical imaging option at bed-side. Pulsed Laser Diodes (PLD) on the other hand is portable, inexpensive and offers high PRF. However, the achievable depth of penetration using PLD is much lower than the solid state lasers. In this work, we demonstrate the feasibility of using sub-pitch translation approach on the receive-side ultrasound transducer to increase the depth sensitivity in PAT imaging system while using PLD as a source of illumination. The preliminary results obtained from experiments suggest that the higher density data obtained by augmenting raw RF lines from λ/2 positions of a linear array transducer provides better signal strength from deeper located targets and thereby increasing the depth of penetration by about 15% that reaches up to a depth of 14.3 mm.