Aimée Sakes

Buckling prevention strategies in nature as inspiration for improving percutaneous instruments: a review

A typical mechanical failure mode observed in slender percutaneous instruments, such as needles and guidewires, is buckling. Buckling is observed when the axial compressive force that is required to penetrate certain tissue types exceeds the critical load of the instrument and manifests itself by sudden lateral deflection of the instrument. In nature, several organisms are able to penetrate substrates without buckling while using apparatuses with diameters smaller than those of off-the-shelf available percutaneous needles and guidewires. In this study we reviewed the apparatuses and buckling prevention strategies employed by biological organisms to penetrate substrates such as wood and skin. A subdivision is made between buckling prevention strategies that focus on increasing the critical load of the penetration tool and strategies that focus on decreasing the penetration load of the substrate. In total, 28 buckling prevention strategies were identified and categorized. Most organisms appear to be using a combination of buckling prevention strategies simultaneously. Integration and combination of these biological buckling prevention strategies in percutaneous instruments may contribute to increasing the success rate of percutaneous interventions.

Shooting Mechanisms in Nature: A Systematic Review

Background In nature, shooting mechanisms are used for a variety of purposes, including prey capture, defense, and reproduction. This review offers insight into the working principles of shooting mechanisms in fungi, plants, and animals in the light of the specific functional demands that these mechanisms fulfill. Methods We systematically searched the literature using Scopus and Web of Knowledge to retrieve articles about solid projectiles that either are produced in the body of the organism or belong to the body and undergo a ballistic phase. The shooting mechanisms were categorized based on the energy management prior to and during shooting. Results Shooting mechanisms were identified with projectile masses ranging from 1·10−9 mg in spores of the fungal phyla Ascomycota and Zygomycota to approximately 10,300 mg for the ballistic tongue of the toad Bufo alvarius. The energy for shooting is generated through osmosis in fungi, plants, and animals or muscle contraction in animals. Osmosis can be induced by water condensation on the system (in fungi), or water absorption in the system (reaching critical pressures up to 15.4 atmospheres; observed in fungi, plants, and animals), or water evaporation from the system (reaching up to −197 atmospheres; observed in plants and fungi). The generated energy is stored as elastic (potential) energy in cell walls in fungi and plants and in elastic structures in animals, with two exceptions: (1) in the momentum catapult of Basidiomycota the energy is stored in a stalk (hilum) by compression of the spore and droplets and (2) in Sphagnum energy is mainly stored in compressed air. Finally, the stored energy is transformed into kinetic energy of the projectile using a catapult mechanism delivering up to 4,137 J/kg in the osmotic shooting mechanism in cnidarians and 1,269 J/kg in the muscle-powered appendage strike of the mantis shrimp Odontodactylus scyllarus. The launch accelerations range from 6.6g in the frog Rana pipiens to 5,413,000g in cnidarians, the launch velocities from 0.1 m/s in the fungal phylum Basidiomycota to 237 m/s in the mulberry Morus alba, and the launch distances from a few thousands of a millimeter in Basidiomycota to 60 m in the rainforest tree Tetraberlinia moreliana. The mass-specific power outputs range from 0.28 W/kg in the water evaporation mechanism in Basidiomycota to 1.97·109 W/kg in cnidarians using water absorption as energy source. Discussion and conclusions The magnitude of accelerations involved in shooting is generally scale-dependent with the smaller the systems, discharging the microscale projectiles, generating the highest accelerations. The mass-specific power output is also scale dependent, with smaller mechanisms being able to release the energy for shooting faster than larger mechanisms, whereas the mass-specific work delivered by the shooting mechanism is mostly independent of the scale of the shooting mechanism. Higher mass-specific work-values are observed in osmosis-powered shooting mechanisms (≤ 4,137 J/kg) when compared to muscle-powered mechanisms (≤ 1,269 J/kg). The achieved launch parameters acceleration, velocity, and distance, as well as the associated delivered power output and work, thus depend on the working principle and scale of the shooting mechanism.

Crossing Total Occlusions: Navigating Towards Recanalization

Chronic total occlusions (CTOs) represent the “last frontier” of percutaneous interventions. The main technical challenges lies in crossing the guidewire into the distal true lumen, which is primarily due to three problems: device buckling during initial puncture, inadequate visualization, and the inability to actively navigate through the CTO. To improve the success rate and to identify future research pathways, this study systematically reviews the state-of-the-art of all existing and invented devices for crossing occlusions. The literature search was executed in the databases of Scopus and Espacenet using medical and instrument-related keyword combinations. The search yielded over 840 patents and 69 articles. After scanning for relevancy, 45 patents and 16 articles were included. The identified crossing devices were subdivided based on the determinant for the crossing path through the occlusion, which is either the device (straight and angled crossing), the environment (least resistance, tissue selective, centerline, and subintimal crossing) or the user (directly steered and sensor enhanced crossing). It was found that each crossing path is characterized by specific advantages and disadvantages. For a future crossing device, a combination of crossing paths is suggested were the interventionist is able to exert high forces on the CTO (as seen in the device approach) and actively steer through the CTO (user: directly steered crossing) aided by intravascular imaging (user: sensor enhanced crossing) or an intrinsically safe device following the centerline or path of least resistance (environment: centerline crossing or least resistance crossing) to reach the distal true lumen.

Treating Total Occlusions: Applying Force for Recanalization

Goal: The aim of this review was to analyze and review the state of the art devices for the endovascular treatment of chronic and acute total occlusions in the different vascular beds (coronary, peripheral, carotid, and intracranial arteries) based on the forces exerted on the occlusion during treatment. Methods: The literature search was executed in the databases of Scopus and Espacenet. Overall, 120 patents and 49 articles have been reviewed and categorized. Results: The identified treatment tools were divided into three treatment modalities: compression, resection, and conversion. A further subdivision was made based on the force direction, i.e., axial, radial, tangential, or energy conversion process (dissolving or state change). Conclusion: The working principles of the identified treatment tools relate strongly to the (biomechanical) properties of the occlusion and environment. In order to increase procedural success, especially in chronic occlusions, the applied force should be increased by applying buckling prevention methods, the penetration force decreased by smart tip design or dynamic loading, and the energy dissipation to the environment minimized. Significance: Insight in the working principles of the treatment tools and their effect on the environment can in future aid designers to overcome current challenges and develop new, innovative treatment tools.

Design of an endovascular morcellator for the surgical treatment of equine Cushing's disease.

Background: A new paradigm of surgical treatment of equine Cushings disease has been developed using the vascular system combined with a flexible morcellation instrument to reach the pituitary gland. Objective: The goal was twofold: (1) to design, prototype, and test an instrument that can reach the pituitary gland using the vascular system unique to equids and (2) to test the feasibility of the endovascular approach. Animals and methods: The morcellator consists of a radial rotating cutting blade for tissue resection, a flexible shaft incorporating a cable drive for flexible actuation, and central morcellated tissue transportation lumen. The morcellator prototype was tested on a horses cadaver head for the validation of the cutting blade design, actuator design, and feasibility of the endovascular approach. Results: The overall assembled length of the morcellator tip was 13.9 mm, allowing for non-traumatic steering through the vascular system from the proximal end. The radially rotating cutting blade (barrel of Ø 4 and 4.4 mm width) incorporated multiple cutting edges to deliver the action force during resection and provides the necessary grasping force to draw the tissue towards the second cutting edge of the morcellator incorporated inside the blunted cuboidal static tip element (5 mm square and wall-thickness of 0.3 mm). In the tests, the morcellator was successfully guided towards the pituitary and managed to sample pituitary tissue. Conclusion and clinical importance: Continued development of the prototype and the endovascular approach may in time improve the outcome and quality of life of horses suffering from Cushings disease.

Minimally invasive surgical instruments with an accessory channel capable of integrating fibre-optic cable for optical biopsy: a review of the state of the art.

This review article provides a comprehensive overview and classification of minimally invasive surgical instruments with an accessory channel incorporating fibreoptics or another auxiliary device for various purposes. More specifically, this review was performed with the focus on the newly emerging field of optical biopsy, its objective being to discuss primarily the instruments capable of carrying out the optical biopsy and subsequent tissue resection. Instruments housing the fibreoptics for other uses, as well as instruments with an accessory channel capable of housing the fibreoptics instead of their original auxiliary device after relevant design modifications, supplement the review. The entire Espacenet and Scopus databases were searched, yielding numerous patents and articles on conceptual and existing instruments satisfying the criteria. The instruments were categorised based on the function the fibreoptics or the auxiliary device serves. On the basis of their geometrical placement with respect to the tissue resector or manipulator, the subcategories were further defined. This subdivision was used to identify the feasibility of performing the optical biopsy and the tissue resection in an accurate and successive fashion. In general, the existing concepts or instruments are regarded as limited with regard to such a functionality, either due to the placement of their accessory channel with or without the fibreoptics or due to the operational restrictions of their tissue manipulators. A novel opto-mechanical biopsy harvester, currently under development at Delft University of Technology, is suggested as a promising alternative, ensuring a fast and accurate succession of the optical and the mechanical biopsies of a flat superficial tissue.

3D Imaging with a single-element forward-looking steerable IVUS catheter: initial testing

In the field of vascular interventions, forward-looking intravascular ultrasound transducers (FL-IVUS) are needed for better visualization of complex lesions, such as chronic total occlusions. In this work, we propose a strategy for 3D imaging using a single-element transducer and an optical shape sensing fiber (OSS) in a steerable catheter tip. We evaluate the performance of the integrated device by imaging a six-wire phantom submerged in water. While steering the catheter tip across the wires, ultrasound and OSS data are acquired continuously. We combine the distance information obtained from the ultrasound data with the tip position and direction obtained from the OSS data to reconstruct the wires in 3D space. We quantify the accuracy of the imaging technique by the distance between the wires, and find a mean relative error of 36%. We discuss how this estimate can be further improved by modifications of the probe. This proof-of-principle test demonstrates the feasibility of FL-IVUS imaging using a single-element transducer integrated in a steerable catheter together with an OSS fiber.

Novel Miniature Tip Design for Enhancing Dexterity in Minimally Invasive Surgery

Even though technological advances have increased the application area of minimally invasive surgery (MIS), there are still hurdles to allow for widespread adoption for more complex procedures. The development of steerable instruments, in which the surgeon can alter the tip orientation, has increased the application area of MIS, but they are bulky, which limits their ability to navigate through narrow environments, and complex, which complicates miniaturization. Furthermore, they do not allow for navigating through complex anatomies. In an effort to improve the dexterity of the MIS instruments, while minimizing the outer dimensions, the previously developed cable-ring mechanism was redesigned, resulting in the thinnest, O2mm (O 1mm lumen), eight degrees-of-freedom (DOF) multisteerable tip for MIS to date. The multisteerable tip consists of four steerable segments of 2DOF stackable elements allowing for ±90 deg articulation, as well the construction of complex shapes, actuated by 16 O0.2mm stainless steel cables. In a proof-of-principle experiment, an ultrasound transducer and optical shape sensing (OSS) fiber were inserted in the lumen, and the multisteerable tip was used to perform scanning motions in order to reconstruct a wire frame in three-dimensional (3D). This configuration could in future be used to safely navigate through delicate environments and allow for tissue characterization. Therefore, the multisteerable tip has the potential to increase the application area of MIS in future, as it allows for improved dexterity, the ability to guide several tip tools toward the operation area, and the ability to navigate through tight anatomies.