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