The risk-related brain structure is developed by considering, for the specified area, both the neural function in healthy subjects and the severity of dysfunctions related to the potential local damage. The brain “zones” are sorted into 6 groups according to the neurological prognosis that would be caused following damage during insertion, from “accessible” to “avoid” through “common”, “careful”, “warning” and “dangerous”.
The Biological Inspiration
Nature is often a good inspiration for demanding engineering tasks and, particularly, a novel smart actuator has being inspired by the penetration strategy developed by ovipositing wasps: these insects can penetrate different kind of tissues (wood, leaves, host larvae) to lay their eggs. The ovipositor of the wood wasp, Sirex noctilio, for example, has the main function of delivering eggs through a hollow tube along its length. Its tip is about 0.2~0.3mm in diameter and can drill to a depth of up to 20mm into the sapwood of a tree. The applicability of the wood wasp’s anatomy resides in the mechanism of drilling, which does not require rotary motion or impaction.
The ovipositor is made of two interlocked halves, or “valves,” rather like the zip on a “zip-lock” polyethylene bag, which slide relative to each other. Backward pointing teeth (numbered in Fig. 1b) hold on to the substrate, resisting pulling forces. The pull on one of the valves provides stabilization along the length of the ovipositor to prevent buckling so that the other valve can be pushed with an equal and opposite force, to produce a net force near zero. The reciprocating motion of the two valves drives the ovipositor’s penetration, as one valve is pushed deeper into the wood stabilized by tension generated in the other valve. Since there is no net force in the ovipositor assembly, there are no stability problems and there is no theoretical limit on its length.
J. F. V. Vincent and M. J. King. The mechanism of drilling by wood wasp ovipositors. Biomimetics, 3(4):187–201, 1995.
A biomimetic flexible steerable probe is currently being developed at Imperial College London: the aim is the access of deep brain areas with minimum damage in order to accurately place minimally invasive instrumentation (catheters, electrodes for deep brain stimulation), to perform clinical analysis and diagnosis (biopsy, sampling), localized drug delivery and micro neurosurgery.
FP7 ROBOCAST, Eurpean project
ROBOCAST is a 3 year European project (Framework 7 funding) to develop an integrated neurosurgical suite. Robotic assistance, smart sensors, augmented reality and an intelligent user interface are among the deliverables of the project. Imperial’s involvement in ROBOCAST pertains to the development of the biologically inspired flexible probe for brain interventions, described above. Visit www.robocast.eu for more information.
Politecnico di Milano (Italy, coordinator), Azienda Ospedaliera di Verona (Italy), UniversitÃ di Siena(Italy), Imperial College (UK), Prosurgics Ltd. (UK), The Hebrew University of Jerusalem (Israel), Technion – Israel Institute of Technology (Israel), Mazor Surgical Technologies Ltd (Israel), Technische UniversitÃ¤t MÃ¼nchen (Germany), UniversitÃ¤t Karlsruhe (TH) (Germany), CF consulting S.r.l. (Italy)
Knee replacement surgery requires good accuracy to replace bone at the knee
with a prosthesis as each part of the prosthesis has to mate well with the
bone and with each other. The Acrobot provides the surgeon with this
accuracy. While normal robots take over from the surgeon, the Acrobot works
with him by allowing him to move a cutter under force control. The robot
also constrains the surgeon to cut within safe regions and prevents damage
to surrounding tissue.
This project resulted in the formation of The Acrobot Company Limited, a spinout company to commercialise the research.
Intense ultrasound can be used to treat tumours deep within the body (for
example, deep seated brain tumours). The effect of ultrasound is to head
tissue to a temperature at which it is killed, after which the dead tissue
is gradually re-absorbed into the human body and removed via natually
To perform tumour treatment effectively, ultrasound from a transducer must be focused to a small region within the tumour. This requires that the transducer is carefully designed to produce the appropriate beam profile leading to a tight focal point, and that the transducer is correctly positioned and aligned to put the focal point within the tumour.
To achieve alignment of transducers, a robotic approach is being adopted, mounting transducers on a robot, with a variable dimension interface matching bag between transducer and brain to allow the focal depth within the brain to be adjusted, and to provide impedance matching, allowing good transfer of energy into the brain. A project to assess the feasibilty of a robot was undertaken - the following animation shows the robot design in three positions. A more surgically applicable robot is now under development by Selvan Pather.
This project was aimed at investigating how force information gained during a medical procedure may be used by a mechatronic device. The particular procedure chosen was that of taking blood samples from the forearm, as this procedure is reliant on feeling the prescence of veins and feeling the moment of breakthrough of the needle into the vein. One of the problems when taking samples manually is needle overshoot resulting in the needle piercing both sides of the vein resulting in bruising. The robot can find the vein by touch, and when inserting the needle monitors the insertion force and reacts to the elastic properties of the vessel to prevent overshoot.
A robot for transurethral resection of the prostate (TURP). The PROBOT is an active robot for prostate resection. It is designed to allow a surgeon to specify a volume within the prostate to be cut, and then automatically cut this without further intervention from the surgeon. Ultrasound images are used to plan the procedure.
The removal of deep-seated brain tumours requires endoscopic surgery and high precision. As part of a multi-national European project, a robot is being developed that holds an endoscope and allows a surgeon to manipulate it within the brain. The robot constrains motions to a specific region using the Active Constraint principle. This project is multi-disciplinary and involves MRI processing, ultrasound guidance, robotics and visualisation.