Sci‐PM Fri ‐ 04: A three‐dimensional micro‐ultrasound image‐guided and robotically assisted needle positioning system

Abstract

Biomedical research using small animals often requires interventional procedures such as biopsies and injections. When performed inaccurately, these procedures can produce poor results, jeopardizing the study. A needle‐positioning robot for three‐dimensional micro‐ultrasound guided interventions was developed to improve the accuracy of needle insertion. The robot has three degrees of freedom for positioning the needle in three dimensions. Two rotational joints are used to control orientation (roll and pitch), while another joint linearly translates the needle to perform insertion. The three axes intersect at a single point, producing a remote centre of motion (RCM) that acts as a fulcrum for the three‐dimensional orientation of the needle. The RCM corresponds to the insertion point of the needle into the animal. The robot was calibrated to ensure that the three axes intersected at a single point, and that the needle tip was positioned at the RCM. The calibration was performed using a high‐resolution digital camera to find the centre of rotation about the pitch and roll axes separately. The position of the needle was adjusted until it was aligned with the RCM. Calibration results indicate that the distance from the needle to the pitch and roll axes are 24±30 μm and 18±15 μm, respectively. The pitch and roll axes are separated by 11±3 μm. The calibration procedure allowed us to detect and correct manufacturing and design errors. The expected maximum needle positioning error computed from the calibration is 32 μm when the needle tip is moved to the boundary of the workspace.