The reconstruction of a slice image from the inverse Radon transform of the Abel-transformed signals still, however, contains artifacts, which can be classified in in-plane distortion and out-of-plane cross-talk. The former is due to the aperture of the cylindrical lens detector, which leads to a limited depth of field. During a full rotation, objects lying in the focus plane at some distance from the rotation axis move in and out of focus, whereas objects near the rotation axis always stay in focus. This description assumes that the rotation axis is located at or near the focal distance, which was the case in our experiments. If a PA source lies at an out-of-focus position, signals from waves emanating at a point in the source are spread over time, leading to a radial blurring in the final image. Cross-talk between sections is due to signals from positions outside the focus plane, which are nevertheless recorded with sufficient strength to create ghost images in the observed section. The two kinds of artifacts are linked because both become worse with distance from the focus. It is not possible to reduce these artifacts by modifications of the imaging hardware. The temporal spreading of signals recorded from out-of-focus sources, which causes the radial blurring, could be reduced by using a smaller NA of the lens, leading to a larger depth of field. However, at the same time, this would enhance cross-talk artifacts owing to the weaker focusing capability of the low-NA lens. For a reduction of cross-talk, the excitation light pulses could be focused into the imaged section, which is usually not possible in strongly light scattering biological tissues. Finally, a large NA means a tight acoustic focus and seems to be able to avoid cross-talk, but only in the narrow region within the focal depth, preventing imaging of extended objects.