Ben Ockert

Dr. med. Ben Ockert Post Doctoral Fellow Tissue Morphology AO Research Institute Clavadelerstrasse 8 CH-7270 Davos Platz, Switzerland m Tel.: 0041 81 4142343

Active research projects

MeTaTop A Multi Sensory Table Top System for Medical Procedures A tabletop system in medical environments can be used for interactive and collaborative analysis of patient data but also as a multimedia user interface within sterile space. For preoperative planning physicians in charge with a particular patient meet to discuss the medical case and plan further steps for therapy. For this reason, they could collaboratively view and browse through all kind of available medical imaging data with the tabletop system. Alternatively such a system could be a central interaction device for all kind of equippment within the OR requiring user input, however, can not be operated by the sterile surgeon. We believe that the projection of all kind of user and information interfaces on a sterile glass plane would facilitate the clinical workflow. This project is strongly related to the Tangible Interaction Surface for Collaboration between Humans project.

ARAV Augmented Reality Aided Vertebroplasty In today’s ORs more and more operations are performed employing minimally invasive procedures. Surgical instruments are inserted through a tiny cut on the patient’s skin, the port to the inside of the patient. In some cases endoscope cameras record video images of the operation site that are presented on a monitor. As a consequence of this technique, the surgeon’s field of view is divided into several work spaces, the monitor, the patient and information of medical imaging data presented on a third station. The missing direct view on the workspace complicates intuitive control of surgical tools. In contrast to open surgery the physician has to collect information from several fields of view at the same time and fuse information mentally to create a complete model of his working space, the operation site. The minimally invasive intervention vertebroplasty was determined as a suitable medical application to bring an Head Mounted Display (HMD) into the OR for augmentation of surgical instruments and medical imaging data. In-situ visualization with an HMD presents all available imaging data and navigational information in one field of view. The objective of vertebroplasty is the insertion of cement into weak and brittle vertebrae through a trocar for stabilization. In this case the view on the inside of the patient is not provided by an endoscope camera. However, since the operation is performed under a CT scanner, imaging data is permanently updated to check position of the trocar and amount of inserted cement. Imaging data is presented on a monitor and has to be mapped mentally by the surgeon on the real operation site.

Virtual Mirror: Interaction Paradigm for Augmented Reality Applications Augmented Reality offers a higher degree of freedom for the programmer than classical visualization of volume data on a screen. The existing paradigms for interaction with 3D objects are not satisfactory for particular applications since the majority of them rotate and move the object of interest. The classic manipulation of virtual objects cannot be used while keeping real and virtual spaces in alignment within an AR environment. This project introduces a simple and efficient interaction paradigm allowing the users to interact with 3D objects and visualize them from arbitrary viewpoints without disturbing the in-situ visualization, or requiring the user to change the viewpoint. We present a virtual, tangible mirror as a new paradigm for interaction with 3D models. The concept borrows its visualization paradigm in some sense from methodology used by dentists to examine the oral cavity without constantly changing their own viewpoint or moving the patients head. The virtual mirror improves the understanding of complex structures, enables completely new concepts to support navigational aid for different tasks and provides the user with intuitive views on physically restricted areas.

Improving Depth Perception and Perception of Layout for In-Situ Visualization in Medical Augmented Reality In-situ visualization in medical augmented reality (AR) using for instance a video see-through head mounted display (HMD) and an optical tracking system enables the stereoscopic view on visualized CT data registered with the real anatomy of a patient. Data can aligned with the required accuracy and the surgeons do not have to analyze data on an external monitor or images attached to the wall somewhere in the operating room. Thanks to a medical AR system like mentioned before, surgeons get a direct view onto and also ”into” the patient. Mental registration of medical imagery with the operation site is not necessary anymore. In addition surgical instruments can be augmented inside the human body. Bringing medical imagery and surgical instruments in the same field of action provides the most intuitive way to understand the patient’s anatomy within the region of interest and allows for the development of completely new generations of surgical navigation systems. Unfortunately, this method of presenting medical data suffers from a serious lack. Virtual imagery, such as a volume rendered spinal column, can only be displayed superimposed on real objects. If virtual entities of the scene are expected behind real ones, like the virtual spinal column beneath the real skin surface, this problem implicates incorrect perception of the viewed objects respective their distance to the observer. The strong visual depth cue interposition is responsible for misleading depth perception. This project aims at the development and evaluation of methods to improve depth perception for in-situ visualization in medical AR. Its intention is to provide an extended view onto the human body that allows an intuitive localization of visualized bones and tissue.

Publications with CAMP

	C. Bichlmeier, B. Ockert, S.M. Heining, A. Ahmadi, N. Navab Stepping into the Operating Theater: ARAV - Augmented Reality Aided Vertebroplasty The 7th IEEE and ACM International Symposium on Mixed and Augmented Reality, Cambridge, UK, Sept. 15 - 18, 2008. (bib)
	O. Kutter, A. Aichert, C. Bichlmeier, J. Traub, S.M. Heining, B. Ockert, E. Euler, N. Navab Real-time Volume Rendering for High Quality Visualization in Augmented Reality International Workshop on Augmented environments for Medical Imaging including Augmented Reality in Computer-aided Surgery (AMI-ARCS 2008), USA, New York, September 2008 (bib)
	C. Bichlmeier, B. Ockert, O. Kutter, M. Rustaee, S.M. Heining, N. Navab The Visible Korean Human Phantom: Realistic Test & Development Environments for Medical Augmented Reality International Workshop on Augmented environments for Medical Imaging including Augmented Reality in Computer-aided Surgery (AMI-ARCS 2008), USA, New York, September 2008 (bib)

Teaching with CAMP

• Recent Advances in Computer Assisted Surgery: Hauptseminar (2008WiSe)
• Recent Advances in Computer Assisted Surgery: Hauptseminar (2008SoSe)