No abstract

Surgeons need to be able to measure angles and distances in three dimensions in the planning and assessment of knee replacement. Computed tomography (CT) offers the accuracy needed but involves greater radiation exposure to patients than traditional long-leg standing radiographs, which give very little information outside the plane of the image. There is considerable variation in CT radiation doses between research centres, scanning protocols and individual scanners, and ethics committees are rightly demanding more consistency in this area. By refining the CT scanning protocol we have reduced the effective radiation dose received by the patient down to the equivalent of one long-leg standing radiograph. Because of this, it will be more acceptable to obtain the three-dimensional data set produced by CT scanning. Surgeons will be able to document the impact of implant position on outcome with greater precision.

Abstract-Percutaneous intervention has attracted significant interest in recent years, but many of today's needles and catheters can only provide limited control of the trajectory between an entry site and soft tissue target. In order to address this fundamental shortcoming in minimally invasive surgery, we describe the first prototype of a bio-inspired multi-part probe able to steer along planar trajectories within a compliant medium by means of a novel "programmable bevel", where the steering angle becomes a function of the offset between interlocked probe segments. A kinematic model of the flexible probe and programmable bevel arrangement is derived. Several parameters of the kinematic model are then calibrated experimentally with a fully functional scaled-up prototype, which is 12 mm in diameter. A closed-loop control strategy with feed-forward and feedback components is then derived and implemented in vitro using an approximate linearization strategy first developed for car-like robots. Experimental results demonstrate satisfactory twodimensional trajectory following of the prototype (0.68 mm tracking error, with 1.45 mm STD) using an electromagnetic position sensor embedded at the tip of the probe.Index Terms-Biologically inspired robots, closed-loop control, medical robots and systems, needle steering, nonholonomic motion planning I. INTRODUCTIONERCUTANEOUS intervention has always attracted significant interest because it is performed through the skin and, as such, it has several advantages for the patient [1]. Tumor biopsy, brachytherapy, deep brain stimulation and localized drug delivery, for instance, benefit from this operative technique to reduce tissue trauma and hospitalization time.In order to localize a lesion, preoperative planning using Computer Tomography (CT) or Magnetic Resonance (MR) Manuscript received May 14, 2010. This work was supported by the EU-FP7 Project ROBOCAST (FP7-ICT-215190) and has also received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007(FP7/ -2013 / ERC grant agreement n° [258642-STING].S. Y. Ko and L. Frasson are with Department of Mechanical Engineering, Imperial College London, SW7 2AZ, UK (e-mail: s.ko@imperial.ac.uk, luca.frasson07@imperial.ac.uk).F. Rodriguez y Baena is with Department of Mechanical Engineering and the Institute of Biomedical Engineering, Imperial College London, SW7 2AZ, UK (corresponding author to provide phone: +44-(0)20-7594-7046; fax: +44-(0)20-7594-1472; e-mail: f.rodriguez@imperial.ac.uk).images is often necessary. If the lesion is reachable through a straight path, a straight rigid needle can be used. For a safe operation, the location of the needle tip can be monitored by means of external markers mounted on the proximal end of the needle by relying on the fixed geometrical relationship between the base and needle point.Recently, there have been efforts to introduce steerable needles in percutaneous interventions where a straight path does not seem possible or is not safe. Steerab...

This paper provides an overview of recent trends and developments in medical robotics for minimally invasive soft tissue surgery, with a view to highlight some of the issues posed and solutions proposed in the literature. The paper includes a thorough review of the literature, which focuses on soft tissue surgical robots developed and published in the last five years (between 2004 and 2008) in indexed journals and conference proceedings. Only surgical systems were considered; imaging and diagnostic devices were excluded from the review. The systems included in this paper are classified according to the following surgical specialties: neurosurgery; eye surgery and ear, nose, and throat (ENT); general, thoracic, and cardiac surgery; gastrointestinal and colorectal surgery; and urologic surgery. The systems are also cross-classified according to their engineering design and robotics technology, which is included in tabular form at the end of the paper. The review concludes with an overview of the field, along with some statistical considerations about the size, geographical spread, and impact of medical robotics for soft tissue surgery today.

Synthetic phantoms are valuable tools for training, research and development in traditional and computer aided surgery, but complex organs, such as the brain, are difficult to replicate. Here, we present the development of a new composite hydrogel capable of mimicking the mechanical response of brain tissue under loading. Our results demonstrate how the combination of two different hydrogels, whose synergistic interaction results in a highly tunable blend, produces a hybrid material that closely matches the strongly dynamic and non-linear response of brain tissue. The new synthetic material is inexpensive, simple to prepare, and its constitutive components are both widely available and biocompatible. Our investigation of the properties of this engineered tissue, using both small scale testing and life-sized brain phantoms, shows that it is suitable for reproducing the brain shift phenomenon and brain tissue response to indentation and palpation