Real Time Estimator to Perform Targeted Biopsies With a Free-Wrist Robot Despite Large Deformations of the Insertion Orifice.

Rémi Chalard,Afshin Fazel,Marie-Aude Vitrani

doi:10.3389/frobt.2021.780505

Abstract

In the context of keyhole surgery, and more particularly of uterine biopsy, the fine automatic movements of a surgical instrument held by a robot with 3 active DOF’s require an exact knowledge of the point of rotation of the instrument. However, this center of rotation is not fixed and moves during an examination. This paper deals with a new method of detecting and updating the interaction matrix linking the movements of the robot with the surgical instrument. This is based on the method of updating the Jacobian matrix which is named the “Broyden method”. It is able to take into account body tissue deformations in real time in order to improve the pointing task for automatic movements of a surgical instrument in an unknown environment.

Highlights

During minimally invasive surgery (MIS), instruments and imaging devices are inserted into a patient through small orifices
Test protocol: it needs sufficient data that represent the dynamics of the system
This paper focuses on the definition of the interaction matrix J and its importance for the realization of a precise control in minimally invasive robotic surgery and more for uterus biopsy

Summary

Introduction

During minimally invasive surgery (MIS), instruments and imaging devices are inserted into a patient through small orifices. The orifice can be artificial, e.g., during laparoscopy where cannulas are placed through the abdominal wall It can be natural, e.g., during a vaginal manipulation where a manipulator (and/or an ultrasound probe) is inserted through the patient’s vagina. Inserting an instrument through an orifice is equivalent to rigidly constrains the movements of the instrument along 4 degrees of freedom (DOFs): one translation along the axis of the penetration and three rotations around a given point R. This kinematic constraint come from the assumption that the body stiffness in an orifice is maximal at an anatomical point A located a few millimeters under the body surface. To minimize the forces at the insertion area it is necessary to achieve R A

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