In 1985 the Department of Mechanical Engineering at Imperial College began research into medical robotics for neurosurgery. Further research into a robot for prostatectomy, commencing in 1988 culminated, in 1991, in a "World First" with the demonstration of robotic prostate surgery. This robot was the first to actively remove tissue from a human patient in an operating theatre.

With the expansion of robotic surgery applications, the Mechatronics in Medicine Laboratory was set up in 1993, as part of the Computer Aided Systems Engineering Section, to research and develop mechatronic aids to surgery. The group has gained a world-wide reputation as a centre of excellence for medical robotic research.

The group has developed mechatronic applications in fields as diverse as neurosurgery, magnetic resonance imaging (MRI) compatible robotics, haptic training systems for surgeons, urological surgery and orthopaedics, high intensity focused ultrasound and blood sampling.

A proprietary haptic system was developed to give surgeons the sense of touch in a virtual reality simulation of knee arthroscopy surgery. During real diagnostic knee arthroscopy, the surgeon operates inside the knee with long tools (an endoscope and a hooked probe) that pass through keyholes in the skin. The surgeon uses visual and haptic (touch) feedback to diagnose problems in the knee.

In the virtual reality simulation, a haptic device is used to replace the real hooked probe. The virtual model of the hooked probe moves when the haptic device is moved. When the virtual model of the hooked probe contacts a virtual bone model, the haptic device physically generates a reaction force through motor torque. This system allows surgeons to practice diagnosis tasks on a realistic virtual patient before examining a real patient.

We developed our own haptic device, based on specifications observed and measured during real knee arthroscopy. Furthermore, we developed a special purpose haptic rendering algorithm, to faithfully recreate the touch sensations from contact anywhere along the virtual model of the hooked probe. This allows the user, for example, to hook and pull on virtual surfaces in the simulation.

Computer-assisted fracture reduction planning
Bone fractures may require surgical management. Specific types of fracture, particularly those of the acetabulum, present a technical challenge to the surgeon, owing to very limited access to the injured bone. We are investigating methods to perform the surgery minimally invasively, which has the advantages of reduced blood loss, decreased infection risk and shorter hospital stay.

We are currently focussing on the pre-operative planning of these operations. We are developing techniques to plan the reduction using statistical shape models.

MRI can produce high resolution 3D images of human anatomy, making it unrivalled for disease diagnosis. Robotic tools can target structures inside the body using MRI images as guidance.

Diagnosis Prostate Cancer
Prostate cancer kills over 10,000 men in the UK every year. The current diagnostic procedure involves a biopsy of the prostate using ultrasound (US) image guidance. US leads to 20% false negatives. MRI can solve this problem effectively.

The Prostate Biopsy Robot
Images from the MRI scanner allow the surgeon to track the needle and to guide the tip into a target in the prostate. By using our Prostate Biopsy Robot, the surgeon controls the robot “remotely”, thus improving safety and accuracy. The robot can extract cells from the prostate within 2mm.

Diagnosis Tendon Disease

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.

A proprietary haptic system was developed to give surgeons the sense of touch in a virtual reality simulation of knee arthroscopy surgery. This system allows surgeons to practice diagnosis tasks on a realistic virtual patient before examining a real patient.

We developed our own haptic device, based on specifications observed and measured during real knee arthroscopy. Furthermore, we developed a special purpose haptic rendering algorithm. This project was conducted in collaboration with Sheffield University and Warwick University.

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 processes.

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.

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.

The project dealt with the generic problem of training and monitoring minimally invasive endoscopic soft tissue surgery by tracking tools and tissue.

A training system for transurethral resection of the prostate (TURP) was developed as a particular concept demonstrator (hence the name TURP - Trainer/ Monitor).

The objectives of this project were:

• To identify generic criteria for in vitro and in vivo computer-based endoscopic surgery training aids #
• To provide a camera-based tracking system with fixed model prostate phantom as a computer-based in vitro prostatectomy training aid
• To provide a tracking system and ultrasound measurement facility as a computer-based in vivo prostatectomy training aid.

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.

In this study, a number of urological procedures are examined and their applicability for robotic implementation is considered. In previous robotic systems, robots have been developed specifically for a particular task. It is acknowledged that to cover the range of procedures typically performed by a urological department, such an approach will require a number of robots and great expense. In this study, commonalities between procedures will be investigated with the aim of providing a 'generic' robot onto which task specific intelligent tools may be attached.

Robotics may be considered for use for a number of reasons:

• Where extra accuracy is required.
• Where faster procedures are required.
• Where application of robotics results in improvements in safety or comfort for surgeon or patient.
• Where the result is a treatment that cannot be performed easily by any other method.

Brachytherapy and biopsy were chosen as appropriate tasks for such a system. This involves depositing a series of small radioactive seeds within the prostate using needles inserted into the prostate through the perineum. The robot manipulates the needles, inserting them under ultrasound guidance.

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.