Max Schäfer

Abstract

Modern day biomedical research requires analysis of a considerable number of cell populations. Frequent observation of each sample is essential to determine e.g. growth characteristics of the cells. Automated high-throughput microscopes offer the ability to scan large numbers of samples in short periods of time. In order to get in-focus images of the sample, precise and fast positioning along the z-axis is needed. The availability of such automated microscopes, however, is limited due to high acquisition costs, resulting in tightly scheduled utilization. In this paper, a compact and inexpensive High-Throughput Microscope, using a monolithic lever mechanism for precise z-positioning, is presented. Multiple microscope elements are positioned along the z-axis in open loop control with a step-width of 10 μm and an overall displacement of 2 mm. Providing a reasonable trade-off between cost and positioning accuracy, the presented z-positioning unit is an inexpensive and compact approach for the use in the field of low-cost microscopy. However, further improvements in order to increase accuracy and enhance linear movement with little to no backlash must be considered.

Abstract

In developing countries airborne micro-organisms are one of the most common causes of surgical wound infection. In the operating room low-turbulence displacement-flow has been shown to reduce the influence of airborne bacteria. However, due to complexity and cost, current systems are not accessible to all potential users. In this paper a low-cost ventilation system is presented that provides low-turbulence displacement-flow over a surgical operating environment. A stand-alone, simple to assemble, mobile airflow system was developed using the principle of speed compensation for laminar airflow. From visual inspection and measurements, the system was seen to generate a continuous downwards displacement of air over the protected area around the situs. The entire system can be assembled quickly with minimal standard tools, making it very suitable for mobile use, such as in disaster areas. Future work is required to achieve the vertical dimension of a laminar flow field required by the DIN 1946-4. Overall, the low-cost and simple system could provide many potential users access to the technology and thus improving hygiene conditions in their operating environment.

Abstract

Robotic assistance in surgical interventions has been shown to improve both the surgical outcome and the surgeon’s performance. However, cost-efficient implementation of such systems in an operating room workflow is not yet resolved. Most of the current approaches use highly specialized and purpose-built robotic components, resulting in large costs. This paper presents an investigation into the usage of off-the-shelf robots as cost-efficient basis for teleoperated surgery. In addition, the modifications required of the robot and/or operating environment to make it suitable for the medical setting are assessed. The considered systems are found via a literature search and the MERODA-database, specifically focusing on systems designed for teleoperated surgery which use industrial robots. Among the 126 telemanipulated systems found, only 10 use industrial robots for surgical procedures. Overall, due to the better availability, reduced costs, and increased performance, current industrial robots should be further considered for new and versatile low cost approaches to teleoperated surgery.

Abstract

A twisted string actuator (TSA) is a small, strong, lightweight, and low-cost gear, transforming rotation into a linear pulling movement. The TSA consists of two or more strings that are twisted along their common longitudinal axis. The helix formed in this process becomes shorter the further the bundle is twisted. A possible application is a tendon-based endoscopic robot. To control the movement of the endoscope, a precise contraction of the tendon is necessary. Since the strings of the TSA show an elastic behaviour, position feedback is needed to determine the exact movement of the TSA. In this paper, a TSA with a closed-loop position control by a low-cost displacement sensor is presented.

Abstract

Minimally invasive surgery has been indispensable in the healthcare sector for many years due to crucial advantages compared to open surgery. Subse-quently, there has been a strong emergence of robot-assisted surgery to overcome remaining difficulties of conventional minimally invasive surgery, such as poor ergonomics and limited dexterity. However, the financial hurdle impedes a wide-spread use of systems for robot-assisted interventions and shows an apparent need for cost efficient solutions. The use of standard components for robot-assisted sur-gery, such as conventional minimally invasive instruments, can help to address this issue. In this paper, a modular interface is presented which enables the usage of conventional minimally invasive instruments in a robotic telemanipulation set-up. The interface allows to mount and actuate conventional instruments and thus enables the access to existing clinical processes, such as reprocessing and steriliza-tion. The evaluation of the interface demonstrates the feasibility of the concept, however, further effort is required to enable the use of instruments with extended dexterity due to wrist articulation.

Abstract

In this paper the model-based assessment of the workspace of a planar Cable-Driven Haptic Device for telemanipulation in the field of Robot-Assisted Surgery is presented. The Cable-Driven Haptic Device is intended to be used for the control of a flexible robot for colonoscopy. It consists of four cables and provides, depending on the endeffector design, two or three Degrees of Freedom. Different endeffector geometries and sizes were investigated and evaluated using three quantitative assessment indices regarding the resulting workspaces. In addition, a set of external wrenches is used to examine the workspace with a haptic feedback force of 5 N which can be displayed to the user at each pose. For the intended application, a point-shaped and a line-shaped endeffector design showed to be a suitable solution based on the assessment indices. This work provides a basis for further research into telemanipulation with haptic user interfaces based on Cable-Driven Parallel Robots, enabling high fidelity haptic feedback.

Abstract

One of the major disadvantages of robot-assisted surgery is the absence of haptic feedback. A haptic user interface (HUI), which is part of a telemanipulation system addressing this issue, is described. To generate high-quality haptic feedback using the HUI, it is necessary to have a precise understanding of the system's behavior. The capstan drive of the HUI is modeled as a rotational two-mass system. The mechanical parameters are determined by minimizing the error between the mechanical transfer function, defined by motor torque as input and velocity as output, and measured frequency responses. The relationship between motor current and torque is approximated as Fourier series depending on the motor angle. Friction is modeled as Coulomb and viscous friction, Stribeck curve, and continuous approximation of the Stribeck curve. The model is utilized to enhance the precision of the generated feedback force. The described system enables the generation of haptic feedback with a maximum force of 6 N, a force resolution of 0.05 N, and a usable frequency bandwidth of 31 Hz.

Abstract

Recently, there has been a strong emergence of teleoperated minimally invasive surgery due to the potential benefits for both, the surgeon's performance and outcomes for the patient. However, due to high acquisition costs, no widespread use has been achieved so far. The use of low-cost components can help to address this issue. In this paper, a commercial handheld virtual reality controller as an unconventional and versatile approach for the input device, is presented and investigated. Assessment of the input device is done by performing an experimental study with 24 participants on two different fine motoric tasks. Additionally, motion scaling is investigated by using different transmission ratios for the user's movements. The large and unrestricted range of motion of the presented input device showed to be a promising alternative to conventional input devices. However, the tasks showed room for improvement regarding the controller's ergonomics and usability. For further comparative investigations, conventional input devices and mimetic input devices need to be considered.

Abstract

Microscopy is an essential tool in research and science. However, it is relatively resource consuming regarding cost, time of usage, and consumable supplies. Current low-cost approaches provide good imaging quality but struggle in terms of versatility or applicability to varying setups. In this paper, a Compact Microscope Module for versatile application in custom-made setups or research projects is presented. As a first application and proof of concept, the use of the module in a High-Throughput Microscope for screening of samples in microtiter plates is shown. The Compact Microscope Module allows for simple and resource-efficient microscopy in various applications while still enabling relatively good imaging qualities.

Abstract

Minimally invasive surgery (MIS) has been an essential tool in the surgical sector for many years due to its crucial advantages compared to open surgery. To overcome remaining limitations, teleoperated MIS experienced a strong emergence. However, the widespread usage of such systems is hindered by the enormous financial hurdle. The use of standard components and conventional tools for teleoperated MIS can facilitate integration into existing hospital workflows and can be a cost-efficient and versatile approach for research purposes. To compensate for the lack of haptic feedback, some teleoperation setups inherit a sensor system allowing them to record interaction forces and display them at the user interface. In research and in commercially available systems, different positions for the sensor can be found. In this paper, mechanical interfaces for the guidance and actuation of non-wristed and wristed standard instruments are presented. Furthermore, a method for the extracorporeal measurement of interaction forces is presented, characterized, and discussed. The overall mean relative error of the magnitude of the interaction force is 9.4%, while the overall mean absolute error of the force vector is 14.4 $^$ , both below the respective human differential perception threshold. The presented measurement method is a simple, yet sufficiently accurate approach to measure interaction forces in surgical telemanipulation.

Abstract

During laparoscopic procedures, the surgeon's view of the situs, and thus her or his performance, is dependent on the skills of the camera assistant. The surgeon lacks control over his own field of view and there is a high potential for reducing mental load and workflow issues. In this paper, a research setup of a 360° laparoscopic imaging system is presented and evaluated. The system consists of a 360° camera and a head-mounted display, through which the surgeon can inspect the situs. In a user test, the system showed advantages over a conventional laparoscope regarding orientation in thesitus, intuitiveness of operation, and faster task completion.

Abstract

In robotic telemanipulation for minimally-invasive surgery, lack of haptic sensation and non-congruent movement of input device and manipulator are major drawbacks. Input devices based on cable-driven parallel mechanisms have the potential to be a stiff alternative to input devices based on rigid parallel or serial kinematics by offering low inertia and a scalable workspace. In this paper, the haptic user interface of a cable-driven input device and its technical specifications are presented and assessed. The haptic user interface allows to intuitively control the gripping movement of the manipulator’s end effector by providing a two-finger precision grasp. By design, the interface allows to command input angles between 0° and 45°. Furthermore, interaction forces from the manipulator’s end effector can be displayed to the user’s two-finger grasp in a range from 0 N to 6 N with a frequency bandwidth of 17 Hz.

Abstract

Access to systems for robot-assisted surgery is limited due to high costs. To enable widespread use, numerous issues have to be addressed to improve and/or simplify their components. Current systems commonly use universal linkage-based input devices, and only a few application-oriented and specialized designs are used. A versatile virtual reality controller is proposed as an alternative input device for the control of a seven degree of freedom articulated robotic arm. The real-time capabilities of the setup, replicating a system for robot-assisted teleoperated surgery, are investigated to assess suitability. Image-based assessment showed a considerable system latency of 81.7 ± 27.7 ms. However, due to its versatility, the virtual reality controller is a promising alternative to current input devices for research around medical telemanipulation systems.

Abstract

When manipulating tissue during medical interventions, high-accuracy movements are important to avoid injuries. However, feedback is limited and it is hard to establish control loops to ensure correct movements. We propose the use of a novel highly compact 6-axis force / torque sensor (Ø 10.5 mm x 11.0 mm) within a hand piece to determine low forces and torques during various small-scale procedures including gentle tool-tissue interaction. For a first validation of the system, different venepuncture cannulas were connected to the sensor top and driven into skinned fruits (toma-toes and grapes) as well as into a silicone block. During insertion of the needle tips, maximum forces of 74 – 158 mN (tomato) and 51 - 161 mN (grape) were recorded, and steadily increasing forces in the range of 0 – 250 mN when insert-ing needles 7.5 mm into silicone. For a 0.99 g screw nut (9.73 mN), the measured gravitational force was 10.6 ± 1.5 mN during ten measurement sets. During the insertion, needle torques of up to 9.5 mNm were observed. Different cutting phases were seen similar to the phases during needle penetration testing. We conclude that the compact measurement setup used is suitable to measure the low forces and torques occurring when cutting soft, aqueous human tissues with or without skin-like layers.

Abstract

In conventional laparoscopy, the field of view of the surgeon is limited. Angled laparoscopes enable the observation of surrounding structures, however, to change the viewing perspective on a specific object, permanent repositioning and rotation of the shaft is required. In this paper, a demonstrator of a steerable flexible laparoscope is presented, enabling the user to intuitively adjust the perspective onto an object by means of a single control element. The laparoscope provides a viewing angle of ± 50° at 50 mm working distance. In first tests, the presented laparoscope showed advantages regarding intuitiveness of the control, easier handling, and improved depth perception.

Abstract

Microscopy enables fast and effective diagnostics. However, its functionality is not accessible to everyone. Smartphone-based low-cost microscopes could be a powerful tool for diagnostics and educational purposes. Current smartphone-based microscopy approaches struggle with high cost, poor image quality and/or insufficient smartphone compatibility. In this paper, a very feasible and effective lowcost microscope is presented which addresses these issues. To minimize cost, a monolithic foldable structure is designed for production by injection molding. The design has a high order of functional integration, minimizing the number of components, while still enabling a micrometer focusing accuracy.

Abstract

Microscopy enables fast and effective diagnostics. However, in resource-limited regions microscopy is not accessible to everyone. Smartphone-based low-cost microscopes could be a powerful tool for diagnostic and educational purposes. In this paper, the imaging quality of a smartphone-based microscope with four different optical parameters is presented and a systematic overview of the resulting diagnostic applications is given. With the chosen configuration, aiming for a reasonable trade-off, an average resolution of 1.23 μm and a field of view of 1.12 mm2 was achieved. This enables a wide range of diagnostic applications such as the diagnosis of Malaria and other parasitic diseases.

Abstract

Accurate measurement of interaction forces during robot-assisted surgery requires compact force sensing modalities in the surgical tools, thus might add considerable cost to the setup. Measuring the motor current to estimate gripping forces, is an advantageous approach since no expensive force sensor is needed. In this paper, a mechanical interface is presented, which allows actuating conventional articulated instruments for robot-assisted surgery. The interface features the estimation of static gripping forces at the instrument’s tip based on the motor current. The evaluation shows reproducible results, and the current-based approach seems to be a cost-efficient way to estimate gripping forces.