4th Dutch Bio-Medical Engineering Conference 2013
24-25 January 2013, Egmond aan Zee, The Netherlands

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10:40   Surgical Techniques - Needles
Chair: Jenny Dankelman
15 mins
Filip Jelinek, Rob Pessers, Paul Breedveld
Abstract: Background – Despite its success, e.g. in prostatectomy, da Vinci’s steerable grasper EndoWrist from Intuitive Surgical has a complex design prone to steel cable fatigue, potential sterilisation issues and associated high costs, all of which insinuate a need for an alternative. Aim – Design a structurally simple handheld steerable laparoscopic grasping forceps free from cable fatigue, while attaining sufficient bending stiffness for surgery and improving on EndoWrist’s manoeuvrability and dimensions. Description – Having equal functionality to EndoWrist, DragonFlex’s instrument tip contains only four parts, driven and bound by two steel cables mechanically fixed in the handle. Two orthogonal planar joints feature an innovative rolling link mechanism allowing the cables to follow circular arc profiles of a diameter 1.5 times larger than the width of the instrument shaft. Besides maximising the cable lifespan, the rolling link was designed to equalise the force requirements on both cables throughout joint rotation, making the handling fluid and effortless. The smart joint design and stacked instrument construction enable control of 7 degrees of freedom by only 7 structural instrument components. Results – Two DragonFlex prototypes were developed by means of rapid prototyping technology, allowing grasping and omnidirectional steering over +/-90°, exhibiting promisingly high bending stiffness and featuring extreme simplicity at 5 mm dimensions. The DragonFlex concept sheds new light on the possibilities of rapid prototyping manufacture of surgical instruments, allowing for a feature-packed design, simple assembly and suitability for disposable use. Acknowledgements – This research was supported by the Center for Translational Molecular Medicine (project MUSIS).
15 mins
Nick van de Berg, John van den Dobbelsteen
Abstract: During diagnosis and treatment of diseased tissue structures, needles form an increasingly popular and minimally invasive alternative to reach deep seated locations within the human body. One example of such procedures is radio frequency ablation (RFA) of tumorous structures. As the target depth increases, needle deflections, tissue deformations, and relative movement of the internal constellation can, however, lead to target errors. The development of a steerable needle tip was motivated by the desire to correct for these errors and ensure a successful and complete treatment. The presented work describes the design of a 3 degree of freedom (3 DOF) steerable needle actuator and control interface. A flexible needle (3 mm in diameter) is actuated by means of steering cables, running through the needle lumen. The cables are connected to a 2 DOF freely rotating disk that can be actuated independently by two servo motors. Opposing actuation cables are loosened and tightened by rotation of the disk, causing the tip element to steer. The third degree of freedom translates the entire setup forwards or backwards by means of a linear stage, simulating the needle insertion. All actuators are connected to a computer and controlled by either a keyboard or SpaceNavigator through MATLAB. The possibility to correct needle placement errors by means of a steerable instrument was demonstrated by a working prototype. Experiments to investigate placement accuracy are planned for the near future. As visual feedback on the needle location is lost in actual tissue (opposed to gel phantoms) and haptic feedback is lost in a robotic system, ongoing efforts aim to sensorize the steerable needle by means of fiber bragg gratings (FBG’s) in order to reconstruct the needle shape and measure interaction forces. This information can be fed back to the user, providing support on both a visual and haptic (e.g. shared control) level.
15 mins
Kirsten Henken, Jenny Dankelman, John van den Dobbelsteen
Abstract: Introduction Accurate positioning of the needle tip is essential in percutaneous therapies such as radiofrequency ablation of liver tumors. Navigating a steerable needle with a robotic system guided by MRI could improve the targeting accuracy in these procedures. Therefore, an MR-compatible steerable needle is developed, which is equipped with fiber Bragg gratings (FBGs) for shape sensing [1]. Approach The aim is to develop a flexible shaft that incorporates optical fibers and steering cables in its wall. The device, and consequently all components and materials, should MR-safe. In addition, devices currently used in percutaneous interventions in the liver should fit through the shaft, while the outer diameter of the shaft should be as small as possible. Results The needle consists of a 20cm tube with a steerable tip made of PEEK with an inner and outer diameter of 2 and 3.2mm, respectively. Each steering segment in the tip can be rotated up to 5° by pulling a cable. The Dyneema steering cables and the fibers with FBGs are integrated in the wall of the tube. A cutting stylet that runs through this channel enables penetration of the tissue during insertion and can be removed when the target has been reached. After this, any other flexible instrument can be inserted in the channel to execute the actual procedure. During needle insertion as well as during treatment, the shape of the needle is detected by the FBGs at high frequency (<20 kHz) with an accuracy of estimated tip position of 1 mm. The location of the target and the effect of the treatment can be monitored on MR images at lower refresh rate. Discussion This needle allows dexterous navigation of different instruments to targets within the liver with one single needle insertion. It supports targeting accuracy, but also allows difficult areas to be reached without damaging other important tissues such as the lungs. REFERENCES [1] K. Henken, D. van Gerwen, J. Dankelman, J. van den Dobbelsteen, “Accuracy of needle position measurements using fiber Bragg gratings”. Minim Invasive Ther Allied Technol, 2012 Mar 29 [Epub ahead of print].
15 mins
Guus Vrooijink, Momen Abayazid, Sachin Patil, Ron Alterovitz, Sarthak Misra
Abstract: One of the most commonly performed minimally invasive surgical procedures is needle insertion. Such needle insertions are often performed either for diagnosis (e.g., biopsies) or therapy (e.g., brachytherapy), both of which require accurate needle placement. These procedures are frequently performed under ultrasound image-guidance which provides visual feedback. Clinicians usually use rigid bevel-tipped needles that easily cut and penetrate the soft tissue. The use of rigid bevel-tipped needles offer limited steering capabilities. Steering allows for the compensation of target motion, and the initial misalignment between needle and target. Flexible bevel-tipped needles offer steering capabilities to compensate for target motion and initial misalignment. Further, flexible needles can be steered to avoid sensitive organs and obstacles. In order to provide accurate steering, the needle needs to be accurately controlled at its base. Steering a flexible needle in three-dimensional (3D) space is a demanding task, and requires needle visualization throughout the entire insertion. In this study, 3D needle tip pose is obtained by a novel technique which uses a two-dimensional (2D) ultrasound transducer [1]. The 2D transducer is placed perpendicular to the needle insertion direction (Fig. 1). Position measurement of the needle tip in the out-of-plane direction of the transducer cannot be obtained directly. Therefore, the transducer needs to be positioned at the needle tip during insertion, which is done by a positioning device. Relocation of the transducer is performed using a Kalman observer and compensator. The observer is used to minimize the influence of noise, and to estimate the needle tip position and velocity. The compensator uses the needle insertion velocity corrected by tip velocities to determine the required out-of-plane motion. Locating the transducer at the needle tip during insertion allows for the computation of the tip pose. Experiments show that maximum mean errors in needle tip positions are 0.64 mm, 0.25 mm and 0.27 mm along the x-, y- and z-axes, respectively, while the tip orientation errors are 2.68º and 2.83º about y- and z-axes, respectively. The tip pose is used to steer the flexible needle towards a target while avoiding obstacles. Steering of a flexible needle at its base such that it moves towards a target avoiding obstacles requires extensive training and experience. This study uses a customized Rapidly-exploring Random Trees (RRTs)-based path planner, to determine feasible trajectories [2]. These trajectories are computed online and consider the constant radius of curvature introduced by the asymmetric distributed forces acting on the bevel tip. The trajectory is determined by optimizing clinically motivated criteria such as minimizing the insertion length to minimize tissue damage, or maximizing the minimum clearance to obstacles to maximize safety. Control of the needle along such a trajectory is done by duty cycled spinning of the needle during insertion. Duty cycling relaxes the constraint on the constant-curvature of the needle trajectory, and allows any needle curvature between straight and the constant radius of curvature. Improved needle steering is achieved by combining visualization with path planning and duty cycling, which offers the clinician better targeting accuracy in minimally invasive procedures.
15 mins
Peter Krekel, Charl Botha, Maarten Röling, Rolf Bloem
Abstract: In femoroacetabular impingement (FAI), deformations of the femoral head or the acetabular rim lead to bony impingement, resulting in limited hip motion, pain and progressive damage to the labrum. Recent work suggests that FAI may lead to osteoarthritis (OA) [1]. Although the etiology of FAI is still unclear, a variety of possible causes are described, such as excessive sporting activities and posttraumatic deformities (e.g. acetabular dysplasia). No golden standard has yet been developed for the diagnostic pathway in FAI. Regular x-rays, marcainization, MRI scans and CT scan are widely used and might indicate for FAI. The alpha-angle, determined on an x-ray, is often used for indicating FAI, but does not have a high specificity. Our objective was to determine if 3D motion simulation [2] is an improvement in the analysis compared to regular diagnostic methods of FAI. We analyzed 20 patients with chronic groin pain with the 3D software from Clinical Graphics, Delft, for the presence of hip impingement (see Figure 1). This software analyses CT scans and creates a three-dimensional movement analysis of the joint. With this analysis, a precise localization of the impingement deformity (cam and pincer) as well as the range of motion can be obtained. Also, the amount of resection to create a free range of motion can be determined. These results are compared to the alpha angle, measured on an x-ray. Demography, preoperative complaints, postoperative pain relief and complications were analyzed in all patients. In total 20 patients, 12 male, were analyzed. The average age was 36.4 years (18-60). Patients experienced pain for an average of 4.0 years (1.0-14.0) and 55% were active athletes. The average alpha-angle was 65° (40-105). In 35% of all patients, the alpha-angle was not indicative for cam-deformity (<60°), but with the 3D CT movement analysis an impinging deformity was diagnosed in all patients. The impingement was confirmed during arthroscopy in all patients. 95% of the patients improved in pain relief after surgery, and no complications were registered. We conclude that three-dimensional CT movement analysis is a promising innovative technique in visualizing FAI and might be used for diagnosis. The technique is now used and evaluated in a prospective follow up cohort.