Robotic Framework for Small Animal Stereotaxy

This contribution presents the design of a robot-assisted neuronavigation framework for small animal stereotaxy. The aim is to improve brain research by providing a tool for accurate and repeatable insertion of microprobes. The frame consists of two major modules: a robotic, stereotactic assistant part and a software package allowing interactive planning and control (navigation). Small animal stereotaxy is a common procedure in brain research, e. g. research on the effect of deep brain stimulation for the treatment of Parkinson’s disease. Herein, microelectrodes and/or microdialysis probes are placed in predefined brain target areas. The major difficulty of current probe implantation is the manual handling of the stereotactic frame which causes positioning inaccuracies. Especially as the target areas in the rodent model are of small size, the allocation of the measured signal to the spatial position is unreliable. Following the known center-of-arc principle used in human stereotactic applications, a robotized spherical assistant for stereotactic surgery (SASSU) is designed. It provides 5 degrees of freedom (DOF) for the tool placement, three translational DOF and two rotational DOF. Thus, a tool can be placed at a desired position and with a preferred insertion angle with a positioning accuracy less than 0.045 mm. The SASSU is controlled by a navigation software and integrated into the surgical workflow. Preoperative planning is based on labeled coronal slices of the rat brain. It allows the specification of the target point (A/P, DV, and Lateral position) and of a preferred entry path. Registration to the rat skull is done using anatomical landmarks on the rat skull (Lambda and Bregma points). For the final insertion of the probe, parameters such as step size and velocity can be specified. To summarize, the presented framework provides improved accuracy and repeatability of tool placement in small animal brain research.