Finite Transducer Size Compensation in Two-Dimensional Photoacoustic Computed Tomography

In circular photoacoustic computed tomography, for data acquisition, a single-element transducer rotates around the region of interest (ROI). Due to the limited acceptance angle of the finite size transducer, the reconstructed image becomes blurred, and tangential resolution/contrast degrades in off-center locations in the ROI. In this paper, we propose a compensation method in which in addition to the circular scanning, the transducer rotates around its center (with specific angles) at each detection point. The superposition of these central rotations and non-rotated transducer mimics a virtual detector with a wide acceptance angle. The angles are calculated based on the central frequency and diameter of the transducer and the radius of the region-of-interest. Three types of numerical phantom (point-like, vasculature and Derenzo) were used to evaluate the performance of our method. Features of Olympus NDT, V326-SU transducer were used to assemble the numerical data. The results show that the proposed method provides better structural information by lowering the image blurring, improves the tangential resolution by 90% and increases peak signal-to-noise ratio by 14%.