Model Based Back-Projection Method In Photoacoustic Tomography For Improved Tangential Resolution

The back-projection method is mostly used in the circular or spherical scanning based photoacoustic tomography for its computational efficiency and robustness. However, it models the transducer as a point detector, which leads to the "finite aperture" problem. To solve this, here we for the first time propose to calculate the time delay and weighting factor in the back-projection method with a forward linear model. Compared with the conventional back-projection method, our proposed method can almost completely resolve the "finite aperture effect", which was validated with simulation and experimental results. Results also show that by improving the tangential resolution in the off-center regions, our proposed new method can provide clearer details when imaging complicated targets. However, results also imply that it's still important to try making all the targets effectively detected at each position when scanning the transducers.