Tobias Ortmaier

Publications of Tobias Ortmaier

• Design and analysis of a head-mounted parallel kinematic device for skull surgery.

  Authors: Jan-Philipp Kobler, Jens Kotlarski, Julian Öltjen, Stephan Baron, Tobias Ortmaier

  Int. J. Computer Assisted Radiology and Surgery. 01/2012; 7:137-149.

• Rotationally acquired four-dimensional optical coherence tomography of embryonic chick hearts using retrospective gating on the common central A-scan.

  Authors: Christoph M Happel, Jan Thommes, Lars Thrane, Jrög Männer, Tobias Ortmaier, Bodo Heimann, Talat Mesud Yelbuz

  Journal of biomedical optics. 09/2011; 16(9):096007.

  We introduce a new method of rotational image acquisition for four-dimensional (4D) optical coherence tomography (OCT) of beating embryonic chick hearts. The rotational axis and the central A-scan ofWe introduce a new method of rotational image acquisition for four-dimensional (4D) optical coherence tomography (OCT) of beating embryonic chick hearts. The rotational axis and the central A-scan of the OCT are identical. An out-of-phase image sequence covering multiple heartbeats is acquired at every angle of an incremental rotation of the deflection mirrors of the OCT system. Image acquisition is accomplished after a rotation of 180°. Comparison of a displayed live M-mode of the central A-scan with a reference M-mode allows instant detection of translational movements of the embryo. For calculation of 4D data sets, we apply an image-based retrospective gating algorithm using the phase information of the common central A-scan present in all acquired images. This leads to cylindrical three-dimensional data sets for every time step of the cardiac cycle that can be used for 4D visualization. We demonstrate this approach and provide a video of a beating Hamburger and Hamilton stage 16 embryonic chick heart generated from a 4D OCT data set using rotational image acquisition.

• Design and analysis of a head-mounted parallel kinematic device for skull surgery.

  Authors: Jan-Philipp Kobler, Jens Kotlarski, Julian Oltjen, Stephan Baron, Tobias Ortmaier

  International journal of computer assisted radiology and surgery. 05/2011; 7(1):137-49.

  Precision skull surgery requires specialized instrumentation to satisfy demanding requirements in cochlear array implantation, deep brain stimulation electrode placement, and related applications. APrecision skull surgery requires specialized instrumentation to satisfy demanding requirements in cochlear array implantation, deep brain stimulation electrode placement, and related applications. A miniaturized reconfigurable parallel kinematic mechanism which can be directly mounted on a patient's skull was designed, built, and tested for precision skull surgery. A Stewart-Gough platform is attached to a patient's skull so no optical tracking affecting the overall accuracy in keyhole surgery is required. Six bone anchors comprising the mechanism base joints are implanted at positions with sufficient skull thickness. Since no fixation frame is required, intervention planning flexibility is increased. The centers of the spherical shaped bone anchors can be localized accurately in the image space. An implicit registration to the physical space is performed by assembling the kinematics. Registration error is minimized compared to common optical tracker-based approaches. Due to the reconfigurable mechanism, an optimization of the hexapod's configuration is needed to maximize accuracy and mechanical stability during the incision. Mathematical simulation was conducted to estimate system performance. Simulation results revealed significant improvement in accuracy and stability when exploiting the redundant degrees of freedom and the implemented reconfigurability. Inaccurate localization of base points in the image data set was identified as the main source of error. A first prototype with passive prismatic actuators, i.e. micrometer calipers, was successfully built. A head-mounted parallel kinematic device for high precision skull surgery was developed that provides submillimetric accuracy in straight-line incisions. The system offers enhanced flexibility due to the absence of a rigid fixation frame.

• Experimental validation of the influence of kinematic redundancy on the pose accuracy of parallel kinematic machines.

  Authors: Jens Kotlarski, Bodo Heimann, Tobias Ortmaier

  IEEE International Conference on Robotics and Automation, ICRA 2011, Shanghai, China, 9-13 May 2011; 01/2011

• Improving the Pose Accuracy of Planar Parallel Robots using Mechanisms of Variable Geometry

  Authors: Jens Kotlarski, Bodo Heimann, Tobias Ortmaier

  04/2010;

  ISBN: 978-953-307-070-4

• An automated insertion tool for cochlear implants: another step towards atraumatic cochlear implant surgery.

  Authors: Andreas Hussong, Thomas S Rau, Tobias Ortmaier, Bodo Heimann, Thomas Lenarz, Omid Majdani

  International journal of computer assisted radiology and surgery. 03/2010; 5(2):163-71.

  Atraumatic electrode insertion has been identified to be a crucial step for the preservation of residual hearing abilities, which allows hybrid electro-acoustic stimulation (EAS). The authors proposeAtraumatic electrode insertion has been identified to be a crucial step for the preservation of residual hearing abilities, which allows hybrid electro-acoustic stimulation (EAS). The authors propose a tool for automation of the insertion process to achieve this. General benefits as well as concept and design of an automated insertion tool are presented. Thirty insertions of Nucleus 24 Contour Advance Practice Electrodes in an artificial scala tympani model as well as 20 insertions in a human cochlea specimen were performed using the tool, implementing the AOS technique. For both studies, the achieved insertion depth angle was evaluated by photographic or X-ray documentation. The mean achieved insertion depth angle was 410 degrees for the lubricated model and 330 degrees for the human cochlea specimen. The automated insertion tool has proven its capability to perform electrode insertions with final insertion depth angles within the target range of a standard cochlear implant surgery. Additionally, to the knowledge of the authors, it represents the only possibility to automatically insert cochlear implant electrodes via minimally invasive approaches.

• Practical Model-based and Robust Control of Parallel Manipulators Using Passivity and Sliding Mode Theory

  Authors: Houssem Abdellatif, Jens Kotlarski, Tobias Ortmaier, Bodo Heimann

  02/2010;

  ISBN: 978-953-7619-78-7

• Optimization strategies for additional actuators of kinematically redundant parallel kinematic machines.

  Authors: Jens Kotlarski, Trung Do Thanh, Bodo Heimann, Tobias Ortmaier

  IEEE International Conference on Robotics and Automation, ICRA 2010, Anchorage, Alaska, USA, 3-7 May 2010; 01/2010

• A robot-guided minimally invasive approach for cochlear implant surgery: preliminary results of a temporal bone study.

  Authors: Omid Majdani, Thomas S Rau, Stephan Baron, Hubertus Eilers, Claas Baier, Bodo Heimann, Tobias Ortmaier, Sönke Bartling, Thomas Lenarz, Martin Leinung

  International journal of computer assisted radiology and surgery. 09/2009; 4(5):475-86.

  The aim of this study was to create an access canal to the inner ear, by drilling, and perform the cochleostomy for cochlear implant surgery using robot guidance. A robot, a surgical drill and anThe aim of this study was to create an access canal to the inner ear, by drilling, and perform the cochleostomy for cochlear implant surgery using robot guidance. A robot, a surgical drill and an Image-Guided Surgery (IGS) system were combined in a closed-loop setup. Ten temporal bones were scanned at the planning stages of the procedure. The robot guided the drill along the preplanned trajectory and created the approach. Postoperative scans were obtained. The cochleostomy was performed completely in nine out of ten cases. This did not prove possible for one of the specimens, the target site selected being in too superficial a location in relation to the round window. No violation of the facial nerve took place, although the chorda tympani nerve was violated in one case and the stapes in two. It was obvious during preoperative planning that these structures would be violated, but this was accepted in order to maintain a safety margin from the facial nerve. No other unforeseen damage occurred. This preliminary study suggests that robot-guided drilling of a minimally invasive approach to the cochlea might be feasible, but further improvements are necessary before any clinical application becomes possible. Where the width of the facial recess is less than 2.5 mm, the chorda tympani nerve and the ossicles are at risk.

• Bildbasierte Navigationsdatenkorrektur für endoskopische Augmented Reality Anwendungen.

  Authors: Andreas Hussong, Omid Majdani, Tobias Ortmaier

  Bildverarbeitung für die Medizin 2009: Algorithmen - Systeme - Anwendungen, Proceedings des Workshops vom 22. bis 25. März 2009 in Heidelberg; 01/2009

• Kinematic Design Optimization of an Actuated Carrier for the DLR Multi-Arm Surgical System.

  Authors: Rainer Konietschke, Tobias Ortmaier, Ulrich Hagn, Gerd Hirzinger, Silvia Frumento

  2006 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2006, October 9-15, 2006, Beijing, China; 01/2006

• Motion estimation in beating heart surgery.

  Authors: Tobias Ortmaier, Martin Gröger, Dieter H Boehm, Volkmar Falk, Gerd Hirzinger

  IEEE transactions on bio-medical engineering. 11/2005; 52(10):1729-40.

  Minimally invasive beating-heart surgery offers substantial benefits for the patient, compared to conventional open surgery. Nevertheless, the motion of the heart poses increased requirements to theMinimally invasive beating-heart surgery offers substantial benefits for the patient, compared to conventional open surgery. Nevertheless, the motion of the heart poses increased requirements to the surgeon. To support the surgeon, algorithms for an advanced robotic surgery system are proposed, which offer motion compensation of the beating heart. This implies the measurement of heart motion, which can be achieved by tracking natural landmarks. In most cases, the investigated affine tracking scheme can be reduced to an efficient block matching algorithm allowing for realtime tracking of multiple landmarks. Fourier analysis of the motion parameters shows two dominant peaks, which correspond to the heart and respiration rates of the patient. The robustness in case of disturbance or occlusion can be improved by specially developed prediction schemes. Local prediction is well suited for the detection of single tracking outliers. A global prediction scheme takes several landmarks into account simultaneously and is able to bridge longer disturbances. As the heart motion is strongly correlated with the patient's electrocardiogram and respiration pressure signal, this information is included in a novel robust multisensor prediction scheme. Prediction results are compared to those of an artificial neural network and of a linear prediction approach, which shows the superior performance of the proposed algorithms.

• Structure Tensor Based Substitution of Specular Reflections for Improved Heart Surface Tracking.

  Authors: Martin Gröger, Tobias Ortmaier, Gerd Hirzinger

  Bildverarbeitung für die Medizin 2005, Algorithmen - Systeme - Anwendungen, Proceedings des Workshops vom 13.-15. März 2005 in Heidelberg; 01/2005

• Toward High-Fidelity Telepresence in Space and Surgery Robotics.

  Authors: Detlef Reintsema, Carsten Preusche, Tobias Ortmaier, Gerd Hirzinger

  Presence. 01/2004; 13:77-98.

• A virtual-reality-based haptic surgical training system.

  Authors: Holger Weiss, Tobias Ortmaier, Heiko Maass, Gerd Hirzinger, Uwe Kuehnapfel

  Computer aided surgery : official journal of the International Society for Computer Aided Surgery. 02/2003; 8(5):269-72.

  To improve training facilities for surgeons, a surgical training system based on virtual reality techniques has been developed. The goal of the developed system is to improve education of surgeons byTo improve training facilities for surgeons, a surgical training system based on virtual reality techniques has been developed. The goal of the developed system is to improve education of surgeons by making the knowledge of expert surgeons directly available to trainees. The system realizes two different approaches: the library and the driving school paradigm. In its current form, the system consists of two modules. The main module combines the virtual reality kernel KISMET, a visual and haptic display, and a database of different operations and/or techniques. The master station is a copy of the input and output facilities of the main module. Both modules communicate by a TCP/ IP-based connection. Initial tests demonstrated the feasibility of the chosen framework. Further developments include the gathering of data not only from virtual reality but also from real operations. Robotic-assisted surgery provides an attractive way of accomplishing this.

• Link length optimisation of a medical robot in minimally invasive surgery.

  Authors: Rainer Konietschke, Tobias Ortmaier, Holger Weiss, Robert Engelke, Gerd Hirzinger

  CARS 2003. Computer Assisted Radiology and Surgery. Proceedings of the 17th International Congress and Exhibition, London, June 25-28, 2003; 01/2003

• Reconstruction of Image Structure in Presence of Specular Reflections.

  Authors: Martin Gröger, Wolfgang Sepp, Tobias Ortmaier, Gerd Hirzinger

  Pattern Recognition, 23rd DAGM-Symposium, Munich, Germany, September 12-14, 2001, Proceedings; 01/2001

• A Co-Robotic Positioning Device for Carrying Surgical End-Effectors

  Authors: Silvia Frumento, R. Michelini, Rainer Konietschke, Ulrich Hagn, Tobias Ortmaier, Gerd Hirzinger

  ESDA 2006;

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• Image Guided Robotic Surgery - Towards Less Invasive Therapy

  Authors: Tobias Ortmaier, Rainer Konietschke

  ICRA;

  -

• Structure tensor based substitution of specular reflections for improved heart surface tracking

  Authors: Martin Groeger, Tobias Ortmaier, Gerd Hirzinger

  BVM;