Accurate and precise control of catheters inside a vasculature is a difficult yet important task. Current manual approaches require significant surgical skill. Over the years, surgeons build up a sort of mental kinematic map telling them how to handle the catheter in order to steer the catheter tip safely through the vessel system. The input-output behaviour of the catheter is complex and depends heavily on its configuration within and contacts with the vasculature. This paper introduces an alternative approach to control robotic catheters. The input-output behaviour or so-called differential kinematics are derived from a patient-specific vasculature model, following a minimum-energy argumentation. The validity of the proposed approach is demonstrated experimentally. Whereas the performance of model-based approaches is obviously greatly influenced by the correctness of estimated parameters, within this work we show experimentally how reasonable performance can already be achieved within the setup that was constructed. We expect that there is still ample room for improvement by, e.g., putting more sophisticated identification, modeling and collision detection schemes into place.

Advances in miniature surgical instrumentation are key to less invasive and safer medical interventions. In cardiovascular procedures interventionalists turn towards catheter-based interventions, treating patients considered unfit for classical more invasive approaches. Improvements in design and steerability of catheters could further reduce the invasiveness of these interventions. For example, by improving controllability and interaction forces with the vessels, tissue damage could be limited. Through improved steerability and coordinated control, operation times and exposure to radiation might also be reduced. Latter argument formed the original motivation for the development of teleoperated robotic catheters. Despite the large kinematic dissimilarity and thus non-trivial mapping between joystick input and catheter output motion, few investigations have been conducted to find intuitive mappings that allow straightforward catheter steering. This paper presents some recent work in this direction. Three promising mappings are proposed. The mappings were implemented and validated upon a robotic catheter moving inside an artificial aorta model. Experimental results show good steerability of the robotic catheter for all the mappings. Although superiority of one mapping with respect to the others was observed, further investigation and validation is planned. In the future, additional visual cues that increase the situational awareness of the user are expected to further simplify the steering.

This paper introduces a framework for constraint-based force/position control of robots that exhibit large nonlinear structural compliance and that undergo large deformations. Controller synthesis follows hereto the principles of the Task Frame and instantaneous Task Specification using Constraints (iTaSC) formalisms. iTaSC is found particularly suitable due to its ability to express and combine control tasks in a natural way. Control tasks can be formulated as combinations of target positions, velocities, or forces expressed in an arbitrary number and type of coordinate frames. The proposed framework is applied to a mixed mechatronic system composed of a traditional rigid-link robot whose end-effector is a continuum (flexible) link. A selection of different position/force control tasks is prepared to demonstrate the validity and general nature of the proposed framework.

This paper presents a mathematical formulation for calculation of the compliance of continuum type of robots. The mathematical model of the continuum robot is built following the Cosserat rod theory and focuses on a single section Cosserat rod under arbitrary loading. The compliance of the robot is described as a set of ordinary differential equations with split boundary conditions. This new set of compliance equations is directly coupled to the solution of the forward kinematics of the robot. After solving the forward kinematics problem, these solutions can be directly used to compute the compliance. A particular class of continuum robots in which the compliance of the robot can be formulated as an initial value problem and solved in a single numerical integration is discussed. The paper provides experimental validation of the proposed method.

Polysomnography (PSG) is considered the gold standard to assess sleep accurately, but it can be expensive, time-consuming, and uncomfortable, specifically in long-term sleep studies. Actigraphy, on the other hand, is both cheap and userfriendly, but depending on the application lacks detail and accuracy. Our aim was to evaluate cardiorespiratory and movement signals in discriminating between wake, rapid-eye-movement (REM), light (N1N2), and deep (N3) sleep. The dataset comprised 85 nights of PSG from a healthy population. Starting from a total of 750 characteristic variables (features), problem-specific subsets of 40 features were forwardly selected using the combination of a wrapper method (Cohen's kappa statistic on radial basis function (RBF)-kernel support vector machine (SVM) classifier) and filter method (minimum redundancy maximum relevance criterion on mutual information). Final classification was performed using an RBF-kernel SVM. Non-subject-specific wake versus sleep classification resulted in a Cohen’s kappa value of 0.695, while REM versus NREM resulted in 0.558 and N3 versus N1N2 in 0.553. The broad pool of initial features gave insight in which features discriminated best between the different classes. The classification results demonstrate the possibility of making long-term sleep monitoring more widely available.

Minimally invasive endovascular procedures including robotically assisted intervention require effective intraoperative guidance. This is mainly achieved through intraoperative imaging such as fluoroscopy. Concerns over excessive x-ray radiation and nephrotoxicity due to repeated injection of contrast agents have motivated the development of effective catheter navigation schemes based on limited imaging data. This paper presents a catheter navigation technique based on probabilistic fusion of in situ real-time electromagnetic tracking with physically-based simulation of the mechanical characteristics of the catheter. A catheter with multiple electromagnetic sensors placed along its length has been developed. The sensor data and the catheter insertion-length are used as the boundary condition for determining the shape and position of the catheter within the vasculature. A probabilistic framework based on a Kalman Filter is used to combine the information from the catheter motion algorithm and the electromagnetic tracking data. This provides continuous visualization of the catheter within the lumen without the need of continuous fluoroscopy and contrast injection. The proposed approach has been validated with detailed in vitro experiments demonstrating the potential clinical application of the technique.

This study investigates how integrated bed measurements can be used to assess motor patterns (movements and postures) during sleep. An algorithm has been developed that detects movements based on the time derivate of mattress surface indentation. After each movement, the algorithm recognizes the adopted sleep posture based on an image feature vector and an optimal separating hyperplane constructed with the theory of support vector machines. The developed algorithm has been tested on a dataset of 30 fully recorded nights in a sleep laboratory. Movement detection has been compared to actigraphy, whereas posture recognition has been validated with a manual posture scoring based on video frames and chest orientation. Results show a high sensitivity for movement detection (91.2%) and posture recognition (between 83.6% and 95.9%), indicating that mattress indentation provides an accurate and unobtrusive measure to assess motor patterns during sleep.

Recently developed atrophic non-union models are a good representation of the clinical situation in which many non-unions develop. Based on previous experimental studies with these atrophic non-union models, it was hypothesized that in order to obtain successful fracture healing, blood vessels, growth factors, and (proliferative) precursor cells all need to be present in the callus at the same time. This study uses a combined in vivo-in silico approach to investigate these different aspects (vasculature, growth factors, cell proliferation). The mathematical model, initially developed for the study of normal fracture healing, is able to capture essential aspects of the in vivo atrophic non-union model despite a number of deviations that are mainly due to simplifications in the in silico model. The mathematical model is subsequently used to test possible treatment strategies for atrophic non-unions (i.e. cell transplant at post-osteotomy, week 3). Preliminary in vivo experiments corroborate the numerical predictions. Finally, the mathematical model is applied to explain experimental observations and identify potentially crucial steps in the treatments and can thereby be used to optimize experimental and clinical studies in this area. This study demonstrates the potential of the combined in silico-in vivo approach and its clinical implications for the early treatment of patients with problematic fractures.

Visual servoing refers to the closed-loop position control of the robot end-effector (Hutchinson et al., 1996) using visual feedback and should be distinguished from vision-based expert systems (Corke and Good, 1996). In this work, we focus our interest on high performance visual servoing. Our goal is to maximize the bandwidth of the visual loop. This means usually, considering the average dynamics of robots, that the use of a high speed camera is necessary. To achieve this goal, the model of the visual loop must be known with a good accuracy. This includes the dynamics of the robot and the dynamics of the vision system. The main objective of this work is to propose a new dynamic model for the vision sensor. The proposed model is validated by experiments. Ultrasonic motors are used in the experiments since they exhibit a very short response time and can be modeled by a simple transfer function, thus simplifying the decoupling between vision and actuation.

The aim of this research is to apply a laparoscopic robot to improve and facilitate the procedures of laser laparoscopy performed by gynecological surgeons. We took advantages of the existing laparoscopic robot and made digitizer tablet and wireless pen as intuitive interface for this particular purpose. The What-You-Draw-is-What-You-Cut (WYDIWYC) control scheme provide surgeons a natural interface to perform laser ablation as he is sketching by pen. The auto-focus functionality helps surgeons to focus the laser automatically by an laparoscopic distance sensor. Some safety measures are installed in DSP controller. The accuracy of the robot is examined by a sinusoidal test and is more than the demand in laser laparoscopy. The simplicity of usage of the intuitive writing interface is demonstrated by a volunteer and shows the excellent results by cutting on an apple. Some considerations for safety issues are discussed in this paper.