Highly resolved strain imaging during needle insertion: Results with a novel biologically inspired device.

Percutaneous needle insertions are a common part of minimally invasive surgery. However, the insertion process is necessarily disruptive to the substrate. Negative side effects are migration of deep-seated targets and trauma to the surrounding material. Mitigation of these effects is highly desirable, but relies on a detailed understanding of the needle-tissue interactions, which are difficult to capture at a sufficiently high resolution. Here, an adapted Digital Image Correlation (DIC) technique is used to quantify mechanical behaviour at the sliding interface, with resolution of measurement points which is better than 0.5mm, representing a marked improvement over the state of the art. A method for converting the Eulerian description of DIC output to Lagrangian displacements and strains is presented and the method is validated during the simple insertion of a symmetrical needle into a gelatine tissue phantom. The needle is comprised of four axially interlocked quadrants, each with a bevel tip. Tests are performed where the segments are inserted into the phantom simultaneously, or in a cyclic sequence taking inspiration from the unique insertion strategy associated to the ovipositor of certain wasps. Data from around the needle-tissue interface includes local strain variations, material dragged along the needle surface and relaxation of the phantom, which show that the cyclic actuation of individual needle segments is potentially able to mitigate tissue strain and could be used to reduce target migration.

Insertion experiments of a biologically inspired microtextured and multi-part probe based on reciprocal motion.

While there have been significant advances in minimally invasive surgical instrumentation, the majority of tools still rely on a push from the back to aid insertion into the tissue, whether the process is manual or servo assisted. In this work, a novel approach to tool insertion is proposed which is based on the concept of a multi-part probe with at least three interlocking segments. By means of a sequential insertion process, where each segment is pushed further into the tissue while stabilized by the remaining stationary parts, the multi-part probe concept is shown to successfully "insinuate itself" within a synthetic soft tissue specimen without the need for an overall forward push. The presence of an anisotropic microtextured outer probe surface is also shown to affect the overall speed of insertion and can thus be used to optimize the interaction forces at the probe-tissue interface. A measured reduction in the force transferred to the back of the specimen also suggests that this approach to tool insertion may result in reduced tissue disruption, a result which could lead to less tissue damage and a reduction in target displacement.

STING: a soft-tissue intervention and neurosurgical guide to access deep brain lesions through curved trajectories.

Current trends in surgical intervention favour a minimally invasive approach, in which complex procedures are performed through very small incisions. Specifically, in neurosurgery there is a need for minimally invasive keyhole access, which conflicts with the lack of manoeuvrability of conventional rigid instruments. In an attempt to address this shortcoming, the current state of progress is reported on a soft-tissue intervention and neurosurgical guide (STING) to access deep brain lesions through curved trajectories. The underlying mechanism of motion, based on the reciprocal movement of interlocked probe segments, is biologically inspired and was designed around the unique features of the ovipositor of certain parasitic wasps. Work to date has focused on probe development, low- and high-level control, and trajectory planning. These aspects are described, together with results on each aspect of the work, including biomimetic microtexturing of the probe surface. Progress is very encouraging and demonstrates that forward motion into soft tissue through a reciprocating mechanism is indeed viable and can be achieved through a suitable combination of microtexturing and microfabrication techniques.

Biologically inspired microtexturing: investigation into the surface topography of next-generation neurosurgical probes.

Minimally Invasive (MI) surgery represents the future of many types of medical intervention (keyhole neurosurgery, natural orifice trans-luminal endoscopic surgery, etc.). However, the shortcomings of today's surgical tools fuel the need for the development of next-generation 'smart instrumentation', which will be more accurate and safer for the patient. This paper presents the preliminary results of a biologically inspired microtexturing method, based on UV-lithography, and its application to MI neurosurgery. These results suggest that the size and geometry of the texture 'printed' on the outer surface of a neurosurgical probe clearly affect the insertion and extraction forces generated at the brain-probe interface. Thus, by carefully choosing an appropriate microtexture, unique insertion characteristics can be obtained, which can improve the performance of existing instruments (e.g. reducing slippage in permanent electrodes such as those used in deep brain stimulation) or enable the development of novel designs altogether.