Abstract
Concentric tube robots are catheter-sized continuum robots that are well suited for minimally invasive surgery inside confined body cavities. These robots are constructed from sets of pre-curved superelastic tubes and are capable of assuming complex 3D curves. The family of 3D curves that the robot can assume depends on the number, curvatures, lengths and stiffnesses of the tubes in its tube set. The robot design problem involves solving for a tube set that will produce the family of curves necessary to perform a surgical procedure. At a minimum, these curves must enable the robot to smoothly extend into the body and to manipulate tools over the desired surgical workspace while respecting anatomical constraints. This paper introduces an optimization framework that utilizes procedureor patient-specific image-based anatomical models along with surgical workspace requirements to generate robot tube set designs. The algorithm searches for designs that minimize robot length and curvature and for which all paths required for the procedure consist of stable robot configurations. Two mechanics-based kinematic models are used. Initial designs are sought using a model assuming torsional rigidity. These designs are then refined using a torsionally-compliant model. The approach is illustrated with clinically relevant examples from neurosurgery and intracardiac surgery.
Highlights
While in a few important cases, anatomical constraints can be obviated, e.g., by insufflation of the abdominal cavity, there are many sites within the body for which reducing procedural invasiveness requires inserting instruments along tortuous paths in a follow-the-leader fashion and manipulating tip-mounted tools inside small body cavities
The design problem is to solve for a telescoping arrangement of fixed- and variable-curvature robot sections in which the proximal sections are predominantly used for follow-the-leader navigation to the interventional site and the distal sections are used to perform the intervention
All of these frames and regions must be defined with respect to an anatomical model that is derived from images generated, e.g., using Magnetic Resonance Imaging (MRI), Computed Tomography (CT) or 3D ultrasound, together with software tools that enable user-guided organ segmentation and rendering, e.g. ITK-Snap
Summary
While in a few important cases, anatomical constraints can be obviated, e.g., by insufflation of the abdominal cavity, there are many sites within the body for which reducing procedural invasiveness requires inserting instruments along tortuous paths in a follow-the-leader fashion and manipulating tip-mounted tools inside small body cavities Such situations, involving coordinated control of an instrument’s many degrees of freedom to navigate in complex 3D geometries, are well suited to robotic solutions using continuum-type (continuous curve) architectures [2]–[6]. This leads to counterintuitive results crucial for understanding the robot design problem.
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