  Stereotactic targeting is a commonly used technique for performing injections
in the brains of mice and other animals. The most common method for targeting
stereoscopic injections uses the skull indentations bregma and lambda as
reference points and is limited in its precision by factors such as skull
curvature and individual variation, as well as an incomplete correspondence
between skull landmarks and brain locations. In this software tool, a 3D laser
scan of the mouse skull is taken in vitro and registered onto a reference skull
using a point cloud matching algorithm, and the parameters of the
transformation are used to position a glass pipette to place tracer injections.
The software was capable of registering sample skulls with less than 100 micron
error, and was able to target an injection in a mouse with error of roughly 500
microns. These results indicate that using skull scan registration has the
potential to be widely applicable in automating stereotactic targeting of
tracer injections.
