Computational Design Optimization of Concentric Tube Robots for Patient-Specific Volumes and End Effector Tasks

Concentric Tube Robots (CTRs) show high potential as patient- and task-specific minimally invasive robots, as their workspace can be optimized for task completion in confined workspaces such as the human bladder. Ensuring high-quality task completion at regions of interest on the bladder wall, however, requires precise positioning and orienting of imaging devices or tooling relative to the bladder wall. To this end, we present an optimization framework for the design parameters of the CTR which not only considers position, but also orientation of the CTR End-Effector (EE) with respect to the task surface. This ensures that the EE-task can be performed under the set constraints at the desired task surface within a given workspace. Our results show the coverage of five EE-tasks over two task surfaces; a simplified model of the lower urinary tract (urethra and bladder) and an anatomically correct model based on MR-image segmentation. Optimization focused solely on positioning yields a notable 94.2 % reduction in task surface coverage when orientational considerations are incorporated into the EE-task. Moreover, the introduction of an alternative orientation for the EE-task results in an 18% decrease in coverage. Therefore, we conclude that task optimization should be performed based on both the position and orientation of the EE with respect to the task surface.