Intraoperative Tissue Youngs Modulus Identification During Needle Insertion Using A Laterally Actuated Needle

Needle insertion is a common minimally invasive medical procedure used for therapy and diagnosis. Among the therapeutic procedures is prostate brachytherapy, during which needle insertion is applied to implant radioactive seeds within the prostate. During insertion, the needle tends to deflect from a desired straight path thus causing misplacement of the seeds. While currently the needle is steered manually to correct for needle deflection, robotic assistance can be used towards this goal. A requirement for accurate robotic needle steering is needle deflection estimation or prediction obtained from needle deflection modeling. Various mechanics-based deflection models based on needle-tissue interactions have been introduced in the literature. Many models require the tissue Young’s modulus as parameter input that can be measured or quantified using methods of varying limitations with regard to complexity or access in the operating room. This work proposes an intraoperative method for the identification of tissue Young’s modulus using lateral actuation of the needle. The needle-tissue system’s response in terms of needle deflection and thus tissue displacement is observed during lateral needle displacement. The tissue Young’s modulus is then identified based on the energy stored in the needle-tissue system. Using this method, the actuated needle itself is the tool used to obtain the tissue Young’s modulus, facilitating clinical implementation. Experimental studies are presented to confirm a high accuracy of the identified tissue Young’s modulus when compared to an independent measurement. Moreover, the prediction accuracy of a deflection model that is calibrated with the proposed method is verified experimentally.