In this paper, we describe the state of the art in continuum robot manipulators and systems intended for application to interventional medicine. Inspired by biological trunks, tentacles, and snakes, continuum robot designs can traverse confined spaces, manipulate objects in complex environments, and conform to curvilinear paths in space. In addition, many designs offer inherent structural compliance and ease of miniaturization. After decades of pioneering research, a host of designs have now been investigated and have demonstrated capabilities beyond the scope of conventional rigid-link robots. Recently, we have seen increasing efforts aimed at leveraging these qualities to improve the frontiers of minimally invasive surgical interventions. Several concepts have now been commercialized, which are inspiring and enabling a current paradigm shift in surgical approaches toward flexible access routes, e.g., through natural orifices such as the nose. In this paper, we provide an overview of the current state of this field from the perspectives of both robotics science and medical applications. We discuss relevant research in design, modeling, control, and sensing for continuum manipulators, and we highlight how this work is being used to build robotic systems for specific surgical procedures. We provide perspective for the future by discussing current limitations, open questions, and challenges.

Continuum Robots for Medical Applications: A Survey

Background: Although technology-enhanced simulation is increasingly used in health professions education, features of effective simulation-based instructional design remain uncertain. Aims: Evaluate the effectiveness of instructional design features through a systematic review of studies comparing different simulation-based interventions. Methods: We systematically searched MEDLINE, EMBASE, CINAHL, ERIC, PsycINFO, Scopus, key journals, and previous review bibliographies through May 2011. We included original research studies that compared one simulation intervention with another and involved health professions learners. Working in duplicate, we evaluated study quality and abstracted information on learners, outcomes, and instructional design features. We pooled results using random effects meta-analysis. Results: From a pool of 10 903 articles we identified 289 eligible studies enrolling 18 971 trainees, including 208 randomized trials. Inconsistency was usually large (I 2 4 50%). For skills outcomes, pooled effect sizes ( positive numbers favoring the instructional design feature) were 0.68 for range of difficulty (20 studies; p5 0.001), 0.68 for repetitive practice (7 studies; p ¼ 0.06), 0.66 for distributed practice (6 studies; p ¼ 0.03), 0.65 for interactivity (89 studies; p5 0.001), 0.62 for multiple learning strategies (70 studies; p5 0.001), 0.52 for individualized learning (59 studies; p5 0.001), 0.45 for mastery learning (3 studies; p ¼ 0.57), 0.44 for feedback (80 studies; p5 0.001), 0.34 for longer time (23 studies; p ¼ 0.005), 0.20 for clinical variation (16 studies; p ¼ 0.24), and � 0.22 for group training (8 studies; p ¼ 0.09). Conclusions: These results confirm quantitatively the effectiveness of several instructional design features in simulation-based education.

https://www.tandfonline.com/doi/pdf/10.3109/0142159X.2012.714886

Comparative effectiveness of instructional design features in simulation-based education: Systematic review and meta-analysis

On the other hand: dummy hands and peripersonal space.

Background
Virtual reality (VR) as surgical training tool has become a state-of-the-art technique in training and teaching skills for minimally invasive surgery (MIS). Although intuitively appealing, the true benefits of haptic (VR training) platforms are unknown. Many questions about haptic feedback in the different areas of surgical skills (training) need to be answered before adding costly haptic feedback in VR simulation for MIS training. This study was designed to review the current status and value of haptic feedback in conventional and robot-assisted MIS and training by using virtual reality simulation.

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The value of haptic feedback in conventional and robot-assisted minimal invasive surgery and virtual reality training: a current review

The origin of variability in goal-directed movements is not well understood. Variability can originate from several neural processes such as target localization, movement planning, and movement execution. Here we examine variability resulting from noise in movement execution. In several experiments, subjects moved their unseen hand to visual targets, under conditions which were designed to minimize the variability expected from localization and planning processes. We tested short movements in 32 directions in a center-out reaching task. The variability in the movement endpoints and in the initial movement direction varied systematically with the movement direction, with some directions having up to twice the variability of others. In a second experiment we tested four movements in the same direction but with different extents. Here, the longer movements were systematically curved, and the endpoint ellipses were not aligned with the straight line between starting and end position, but they were roughly aligned with the last part of the trajectory. We show that the variability observed in these experiments cannot be explained by planning noise but is well explained by noise in movement execution. A combination of both signal-dependent and signal-independent noise in the amplitude of the motor commands and temporal noise in their duration can explain the observed variability. Our results suggest that, in general, execution noise accounts for at least a large proportion of movement variability.

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The Role of Execution Noise in Movement Variability

We present a prototype of a flexible nitinol needle (φ 1.0 mm and length 172 mm) integrated with an array of 12 Fiber Bragg Grating (FBG) sensors. These sensors measure the axial strain, which enables the computation of the needle curvature. We reconstruct the three-dimensional (3-D) needle shape from the curvature. Experiments are performed where the needle is deflected in free space. The maximum errors between the experiments and beam theory-based model are 0.20 mm (in-plane deflection with single bend), 0.51 mm (in-plane deflection with double bend), and 1.66 mm (out-of-plane). We also describe kinematics-based and mechanics-based models for predicting the 3-D needle shape during insertion into soft tissue. We perform experiments where the needle is inserted into a soft-tissue simulant, and the 3-D needle shape is reconstructed using the FBG sensors. We compare the reconstructed needle shape to deflection obtained from camera images and our models. The maximum error between the experiments and the camera images is 0.74 mm. The maximum errors between the kinematics-based and mechanics-based models and the camera images are 3.77 mm and 2.20 mm, respectively. This study demonstrates that deflection models and needles integrated with FBG sensors have the potential to be used in combination with clinical imaging modalities in order to enable accurate needle steering.

Three-Dimensional Needle Shape Reconstruction Using an Array of Fiber Bragg Grating Sensors

One generally has the impression that one feels one's hand at the same location as one sees it. However, because our brain deals with possibly conflicting visual and proprioceptive information about hand position by combining it into an optimal estimate of the hand's location, mutual calibration is not necessary to achieve such a coherent percept. Does sensory integration nevertheless entail sensory calibration? We asked subjects to move their hand between visual targets. Blocks of trials without any visual feedback about their hand's position were alternated with blocks with veridical visual feedback. Whenever vision was removed, individual subjects' hands slowly drifted toward the same position to which they had drifted on previous blocks without visual feedback. The time course of the observed drift depended in a predictable manner (assuming optimal sensory combination) on the variable errors in the blocks with and without visual feedback. We conclude that the optimal use of unaligned sensory information, rather than changes within either of the senses or an accumulation of execution errors, is the cause of the frequently observed movement drift. The conclusion that seeing one's hand does not lead to an alignment between vision and proprioception has important consequences for the interpretation of previous work on visuomotor adaptation.

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Sensory integration does not lead to sensory calibration

Needle-tissue interaction forces--a survey of experimental data.

Alignment errors can arise during needle tip placement in deep-seated tissue structures. This can lead to undesired diagnostic and therapeutic outcomes. Path correction by means of needle steering has been investigated in scientific studies for the past decades. Several approaches exist, each of them with their own strengths and weaknesses. This paper describes the various needle-steering techniques, and discusses their applicability in terms of mechanical design choices in order to assess and guide on-going work in this research area. Included steering techniques apply needle base manipulations, bevel tips, precurved stylets, active cannulas, programmable bevels, and tendon actuated tips. Techniques are classified as either passive or active, based on how steering is achieved. Mechanical properties of developed needles differ largely. Flexural rigidity, for instance, was found to vary with a factor 106. Mechanical interactions, such as torsion and buckling, are described individually. Different research objectives have led to different steerable needle designs. Design criteria are typically based on these objectives, and not necessarily on clinical needs. However, the effectiveness of steering techniques depends heavily on this design, the navigation medium, and the intended task. In the proposed classification scheme, this dependence is quantified by the flexural rigidity.

Design Choices in Needle Steering—A Review

Background - Not much is known about the exact role offorce feedback in laparoscopy. This study aimed to determine whether force feedback influences movements of instruments during training in laparoscopic tasks and whether force feedback is required for training in basic laparoscopic force application tasks. Methods - A group of 19 gynecologic residents, randomly divided into two groups, performed three laparoscopic tasks in both the box trainer and the virtual reality (VR) trainer. The box-VR group began with the box trainer, whereas the VR-box group began with the VR trainer. The three selected tasks included different levels of force application. The box trainer provides natural force feedback, whereas the VR trainer does not provide force feedback. The performance of the two groups was compared with regard to time, path length, and depth perception. Results - For the tasks in which force plays hardly a role, no differences between box-VR group and the VR-box group were found. During a task in which force application (pulling and pushing forces) plays a role, the box-VR group outperformed VR-box group in the box trainer. Moreover, training with the box trainer had a positive effect on subsequent performance of the task with the VR trainer. This was not found the other way around. No differences were found between box-VR and the VR-box group in tasks not requiring force application. Conclusion - Force feedback influences basic laparoscopic skills during tasks in which pulling and pushing forces are applied. For these tasks, the switch from the trainer without force feedback to the one with natural force feedback has a detrimental effect on performance. Therefore, training for tasks in which forces play an important role (e.g., stretching, grasping) should be done using systems with natural force feedback, whereas eye–hand coordination can be trained without force feedback.

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John J. van den Dobbelsteen

Papers

Three-Dimensional Needle Shape Reconstruction Using an Array of Fiber Bragg Grating Sensors

Sensory integration does not lead to sensory calibration

Needle-tissue interaction forces--a survey of experimental data.

Design Choices in Needle Steering—A Review

Force feedback and basic laparoscopic skills.