Fig. 9.

Photoacoustic images acquired with (a) Orientation 1, containing minimal acoustic clutter and (b) Orientation 4, containing acoustic clutter from the out-of-plane tool tip. The field-of-view was extended in the axial dimension of photoacoustic images from Orientation 4 in order for us to fully characterize and confirm the source of the extra signals. (c) Bar graph summarizing the mean $\pm$ one standard deviation of background SNR measured in all images from each tool orientation. Additional sample photoacoustic images from all orientations (including Orientations 2 and 3, which are not shown here) are shown in Fig. 7.