Exploring High-Precision Non-Assembly Mechanisms: Design of a Vitrectome Mechanism for Eye Surgery.

A vitrectome is a commonly used instrument in eye surgery, which is used to cut and aspirate the vitreous body out of the eye. The mechanism of the vitrectome consists of miniature components that need to be assembled by hand due to their size. Non-assembly 3D printing, in which fully functional mechanisms can be produced in a single production step, can help create a more streamlined production process. We propose a vitrectome design based on a dual-diaphragm mechanism, which can be produced with minimal assembly steps using PolyJet printing. Two different diaphragm designs were tested to fulfill the requirements of the mechanism: a homogenous design based on 'digital' materials and a design using an ortho-planar spring. Both designs were able to fulfill the required displacement for the mechanism of 0.8 mm, as well as cutting forces of at least 8 N. The requirements for the cutting speed of the mechanism of 8000 RPM were not fulfilled by both designs, since the viscoelastic nature of the PolyJet materials resulted in a slow response time. The proposed mechanism does show promise to be used in vitrectomy; however, we suggest that more research into different design directions is required.

Additive Manufacturing of a Miniature Functional Trocar for Eye Surgery.

Stereolithography is emerging as a promising additive manufacturing technology for a range of applications in the medical domain. However, for miniature, medical devices such as those used in ophthalmic surgery, a number of production challenges arise due to the small size of the components. In this work, we investigate the challenges of creating sub-millimeter features for a miniature, functional trocar using Stereolithography. The trocar cannula system is used in eye surgery to facilitate a passage for other instruments. A standard trocar consists of a hollow cannula and a flexible check valve. The research was performed in two stages: in the first stage we investigated the effect of different materials and print settings on the current design of the cannula and the valve separately, and in the second stage we used these findings to optimize the design and production process. After the first investigation, it became apparent that even though the dimensions of the trocar are within the feature size range of Stereolithography, all hollow features tended to fuse shut during printing. This effect appeared regardless of the materials or print settings, and can be attributed to refraction of the laser source. In order to circumvent this, we identified two potential strategies: (1) increasing the negative space surrounding features; and (2) decreasing the surface area per layer. By applying these strategies, we tested a new design for the cannula and valve and managed to 3D print a functional trocar, which was tested in an artificial eye. The design of the 3D printed trocar allows for further personalization depending on the specific requirements of both patient and surgeon. The proposed strategies can be applied to different applications to create miniature features using Stereolithography.

Development of a Novel Wasp-Inspired Friction-Based Tissue Transportation Device.

Currently existing tubular transportation systems for the extraction of large tissue masses during Minimal Invasive Surgery (MIS) are subjected to a large amount of operating limitations. In this study, a novel transportation mechanism (patented) was developed inspired by the egg-laying structure of wasps. The developed mechanism consists of an outer tube within which six reciprocating semi-cylindrical blades are present and tissue is transported using a friction differential between the blades. Two motion sequences were developed: (1) 1-5 motion sequence, in which one blade moves forward, while the remaining five blades move backward and (2) 2-4 motion sequence, in which four blades move backward while two blades move forward. A proof-of-principle experiment was performed to investigate the effects of tissue elasticity, tissue heterogeneity, and the motion sequence on the transportation rate [mg/s], transportation efficiency [%], and transportation reliability [%]. The mean transportation rate and reliability was highest for the 9 wt% gelatine phantoms at 4.21 ± 0.74 mg/s and the 1-5 sequence at 100%, respectively. The prototype has shown that the friction-based transportation principle has the potential of becoming a viable and reliable alternative to aspiration as a transportation method within MIS.

Design of an ultra-thin steerable probe for percutaneous interventions and preliminary evaluation in a gelatine phantom.

Needles with diameter under 1 mm are used in various medical applications to limit the risk of complication and patient discomfort during the procedure. Next to a small diameter, needle steerability is an important property for reaching targets located deep inside the body accurately and precisely. In this paper, we present a 0.5-mm prototype probe which is able to steer in three dimensions (3D) without the need of axial rotation. The prototype consists of three Nitinol wires (each with a diameter of 0.125 mm) with a pre-curved tip. The wires are kept together by a stainless steel tube. Each wire is clamped to a block which translates along a leadscrew, the rotation of the latter being controlled by a wheel connected at the distal end of the leadscrew. The tip bends upon retraction of one or two wires. When pushed through a soft solid structure (e.g., a soft tissue or soft tissue phantom), the probe deflects due to off-axis forces acting on its tip by the surrounding structure. We tested the performance of the prototype into a 10% wt gelatine phantom, in terms of the predictability of the steering direction and the controllability of the final position after steering inside the substrate. The results showed that the probe steered in the direction of the retracted wire and that the final position varied from small deflections from the straight path when the wires were slightly retracted, to sharp curvatures for large wire retraction. The probe could be used in various applications, from cases where only a small correction of the path in one direction is needed to cases where the path to be followed includes obstacles and curves in multiple directions.

ChoRe: A device for trans-catheter chordae tendineae repair.

This work focuses on the design of a new device (called ChoRe) to place artificial chords in the mitral valve structure during a trans-catheter procedure. The aim of the device is to restore the correct functionality of the valve and solve mitral valve regurgitation, that is, a common consequence of chordae tendineae rupture. An analysis of the requirements was carried out and used to design and develop a first functional prototype. The resulting device was able to connect artificial chords at the posterior leaflet of the mitral valve and at the apex of the left ventricle, also allowing the control of the artificial chord length. The ChoRe was tested ex-vivo in bovine hearts. The qualitative assessment of the ChoRe focused on the performance of the device and preliminary evaluation of the procedure time. Results demonstrated that the device is able to create a top and bottom fixation in an average time of 3.45 ± 1.44 min. Future improvements will focus on enhancing the connection at the leaflet, as well as the overall functionality, in order to guarantee better control of the artificial chord length. This work shows future potentials for more patient-specific treatments in trans-catheter scenarios for mitral valve repair.

Surgical drilling of curved holes in bone - a patent review.

INTRODUCTION: Conventional surgical drills are rigid straight instruments used to make holes in bones. They lack the ability to follow a curved pathway, making them impractical for several surgical procedures. For this reason, there is a continuous need for improved devices for surgical drilling of curved holes. AREAS COVERED: This review provides a comprehensive overview and classification of the patent literature of surgical drills able to produce a curved hole. The goal is to identify the fundamental mechanical designs of the drills. The medical section of the Web of Science Derwent Innovation Index was scanned combining keywords for both steering and drilling. Overall, 41 unique patents were reviewed and categorized. EXPERT OPINION: Drills were subdivided in four groups based on the capability of either drilling a single curved path or a multi-curved path and on their ability to adjust the path after insertion of the drill into the bone. We found patents describing instrument designs for all these four groups. The insight in the drilling capabilities and in the mechanical designs described in the patents may serve as a source of inspiration for the design of novel surgical drills and the development of new surgical procedures.

[Electromagnetic interference in the current era of cardiac implantable electronic devices designed for magnetic resonance environment]. / Le interferenze elettromagnetiche nell'era dei dispositivi elettronici cardiaci impiantabili compatibili con la risonanza magnetica.

In the last decades we are observing a continuous increase in the number of patients wearing cardiac implantable electronic devices (CIEDs). At the same time, we face daily with a domestic and public environment featured more and more by the presence and the utilization of new emitters and finally, more medical procedures are based on electromagnetic fields as well. Therefore, the topic of the interaction of devices with electromagnetic interference (EMI) is increasingly a real and actual problem.In the medical environment most attention is paid to magnetic resonance, nevertheless the risk of interaction is present also with ionizing radiation, electrical nerve stimulation and electrosurgery. In the non-medical environment, most studies reported in the literature focused on mobile phones, metal detectors, as well as on headphones or digital players as potential EMI sources, but many other instruments and tools may be intentional or non-intentional sources of electromagnetic fields.CIED manufacturers are more and more focusing on new technological features in order to make implantable devices less susceptible to EMI. However, patients and emitter manufacturers should be aware that limitations exist and that there is not complete immunity to EMI.

Needle-like instruments for steering through solid organs: A review of the scientific and patent literature.

High accuracy and precision in reaching target locations inside the human body is necessary for the success of percutaneous procedures, such as tissue sample removal (biopsy), brachytherapy, and localized drug delivery. Flexible steerable needles may allow the surgeon to reach targets deep inside solid organs while avoiding sensitive structures (e.g. blood vessels). This article provides a systematic classification of possible mechanical solutions for three-dimensional steering through solid organs. A scientific and patent literature search of steerable instrument designs was conducted using Scopus and Web of Science Derwent Innovations Index patent database, respectively. First, we distinguished between mechanisms in which deflection is induced by the pre-defined shape of the instrument versus mechanisms in which an actuator changes the deflection angle of the instrument on demand. Second, we distinguished between mechanisms deflecting in one versus two planes. The combination of deflection method and number of deflection planes led to eight logically derived mechanical solutions for three-dimensional steering, of which one was dismissed because it was considered meaningless. Next, we classified the instrument designs retrieved from the scientific and patent literature into the identified solutions. We found papers and patents describing instrument designs for six of the seven solutions. We did not find papers or patents describing instruments that steer in one-plane on-demand via an actuator and in a perpendicular plane with a pre-defined deflection angle via a bevel tip or a pre-curved configuration.

Airway Segmentation and Centerline Extraction from Thoracic CT - Comparison of a New Method to State of the Art Commercialized Methods.

INTRODUCTION: Our motivation is increased bronchoscopic diagnostic yield and optimized preparation, for navigated bronchoscopy. In navigated bronchoscopy, virtual 3D airway visualization is often used to guide a bronchoscopic tool to peripheral lesions, synchronized with the real time video bronchoscopy. Visualization during navigated bronchoscopy, the segmentation time and methods, differs. Time consumption and logistics are two essential aspects that need to be optimized when integrating such technologies in the interventional room. We compared three different approaches to obtain airway centerlines and surface. METHOD: CT lung dataset of 17 patients were processed in Mimics (Materialize, Leuven, Belgium), which provides a Basic module and a Pulmonology module (beta version) (MPM), OsiriX (Pixmeo, Geneva, Switzerland) and our Tube Segmentation Framework (TSF) method. Both MPM and TSF were evaluated with reference segmentation. Automatic and manual settings allowed us to segment the airways and obtain 3D models as well as the centrelines in all datasets. We compared the different procedures by user interactions such as number of clicks needed to process the data and quantitative measures concerning the quality of the segmentation and centrelines such as total length of the branches, number of branches, number of generations, and volume of the 3D model. RESULTS: The TSF method was the most automatic, while the Mimics Pulmonology Module (MPM) and the Mimics Basic Module (MBM) resulted in the highest number of branches. MPM is the software which demands the least number of clicks to process the data. We found that the freely available OsiriX was less accurate compared to the other methods regarding segmentation results. However, the TSF method provided results fastest regarding number of clicks. The MPM was able to find the highest number of branches and generations. On the other hand, the TSF is fully automatic and it provides the user with both segmentation of the airways and the centerlines. Reference segmentation comparison averages and standard deviations for MPM and TSF correspond to literature. CONCLUSION: The TSF is able to segment the airways and extract the centerlines in one single step. The number of branches found is lower for the TSF method than in Mimics. OsiriX demands the highest number of clicks to process the data, the segmentation is often sparse and extracting the centerline requires the use of another software system. Two of the software systems performed satisfactory with respect to be used in preprocessing CT images for navigated bronchoscopy, i.e. the TSF method and the MPM. According to reference segmentation both TSF and MPM are comparable with other segmentation methods. The level of automaticity and the resulting high number of branches plus the fact that both centerline and the surface of the airways were extracted, are requirements we considered particularly important. The in house method has the advantage of being an integrated part of a navigation platform for bronchoscopy, whilst the other methods can be considered preprocessing tools to a navigation system.

Navigated bronchoscopy: a technical review.

BACKGROUND: Navigated bronchoscopy uses virtual 3-dimensional lung model visualizations created from preoperative computed tomography images often in synchronization with the video bronchoscope to guide a tool to peripheral lesions. Navigated bronchoscopy has developed fast since the introduction of virtual bronchoscopy with integrated electromagnetic sensors in the late 1990s. The purposes of the review are to give an overview and update of the technological components of navigated bronchoscopy, an assessment of its clinical usefulness, and a brief assessment of the commercial platforms for navigated bronchoscopy. METHODS: We performed a literature search with relevant keywords to navigation and bronchoscopy and iterated on the reference lists of relevant papers, with emphasis on the last 5 years. RESULTS: The paper presents an overview of the components necessary for performing navigated bronchoscopy, assessment of the diagnostic accuracy of different approaches, and an analysis of the commercial systems. We were able to identify 4 commercial platforms and 9 research and development groups with considerable activity in the field. Finally, on the basis of our findings and our own experience, we provide a discussion on navigated bronchoscopy with focus on the next steps of development. CONCLUSIONS: The literature review showed that the peripheral diagnostic accuracy has improved using navigated bronchoscopy compared with traditional bronchoscopy. We believe that there is room for improvement in the diagnostic success rate by further refinement of methods, approaches, and tools used in navigated bronchoscopy.