LAUSR

Needle insertion is a minimally invasive procedure finding applications in biopsy, ablation, drug delivery, and cancer therapy. Prostate brachytherapy is a therapeutic procedure where radioactive agents are implanted within the prostate using long needles for the purpose of cancer irradiation. During insertion, each inserted needle needs to remain on a straight path due to dosage distribution requirements. This is difficult to achieve as the beveled needle tip causes needle deflection. A common method for the surgeon to steer beveled-tip needles manually is intermittent axial rotation. Over the last decade, substantial advancements have been made in robotic assistance during needle steering. The most common steering input has, however, been axial needle rotation. A novel needle steering input proposed and investigated recently by our research group is lateral needle actuation near the needle's entry point into tissue. The investigations have yielded promising results with respect to the overall steering potential and improving the steerability of the needle. In this letter, a model-based control algorithm is presented that uses only lateral needle actuation to minimize needle deflection at the final insertion depth. The algorithm consists of two stages: an off-line trajectory planning stage and an on-line trajectory adjustment stage. Insertion experiments into phantom tissue were carried out to validate the proposed control algorithm. The results show that the algorithm is able to steer the needle toward the desired target whereas only using lateral needle actuation as steering input.