Current Research by Rupert Paget

Hysteroscopy Simulator

Participants:Matthias Harders, Raimundo Sierra, Janos Zatonyi, Rupert Paget, Dominik Szczerba, Gabor Székely

Partner:	Computer Graphics Laboratory, ETH Zürich
	Institute of Biomechanical Engineering, ETH Zürich Institute for Mechanical Systems, ETH Zürich Institute of Computational Science, ETH Zürich Micromachines and Precision Instrumentation Lab, EPFL Lausanne Clinic of Gynecology, Dept. OB/GYN, University Hospital Zürich

Objective: Hysteroscopy is the second most often performed endoscopic procedure in gynaecology and is mostly part of any specialization program for gynaecology. It is to be expected that training on a reasonably realistic simulator could substantially contribute to reduce the rate of complications. The simulator will allow realistic real-time visualization of the intervention scene including changes due to surgical actions and the control of the hydrometra by manipulating the liquid influx and efflux as well as realistic tactile sensation.

The following components provided by all partners will be integrated into the simulator:

Mechanical modeling module based on basic components for tissue deformation calculation and real-time cutting
Specialized force-feedback instrument emulating the hysteroscope
Visualization algorithms for reasonably realistic presentation of the interventional field
Generation of anatomical models for the simulation, covering a possibly large range of pathologies

Clinical evaluation will be carried out in order to gain insight into which level of realism is needed to actually reach the goals of efficient surgical training on VR-based trainer, with special emphasis on visual fidelity and the presence and quality of force feedback.

Please also have a look at a former surgery simulation project in our lab.

Surgical scene visualization - Realistic Texturing for Hysteroscopy Simulator

Participants:Rupert Paget, Gabor Székely

Partner:	Computer Graphics Laboratory, ETH Zürich
	Clinic of Gynecology, Dept. OB/GYN, University Hospital Zürich

Objective: A basic requirement in the complete texturing solution for the hysteroscopic simulator is the ability to texture the surfaces and under surfaces of the uterus and pathologies. As the texture can vary substantial over the life cycle of the uterus and with different pathologies, a texturing approach that allows for easy user interaction has been developed. This makes it possible for a novice user to design their own surgical scenarios with an evolving library of textures.

The interactive 3D surface texturing performs automatic mesh cutting and parameterisation. This technique provides a viable mapping between a 2D texture and a 3D surface, with the aim of reducing distortion. This technique also allows arbitrary textures of any size to be placed over a 3D surface. As it is the mesh parameterisation that defines the mapping, a texture can be scaled, rotated and translated over the surface interactively. With this kind of approach what has to managed are the cuts, as they disrupt the surface texture.

Surgical scene visualization - Bleeding Synthesis for Hysteroscopy Simulator

Participants:Janos Zatonyi, Rupert Paget, Gabor Székely

Extended Information: Project Homepage

Objective: In a realistic hysteroscopic simulator special interest has to be devoted to the simulation of intra-uterine bleeding, influencing the visibility of the surgical scene, until the correct adjustment of the inflow and outflow valves on the instrument are performed by the surgeon.

The aim of this project is to develop a computer model that can produce a visually appealing reconstruction of bleeding for hysteroscopic simulator. Therefore, our task incorporates the needs for real-time synthesis and responsiveness of the model to any actions introduced by the surgeon to the dynamic virtual reality environment.

Texture Reconstruction

Participants:Rupert Paget, Alexey Zalesny, Luc Van Gool

Extended Information: Project Homepage

Objective: One of the neat applications of Paget and Longstaff's texture synthesis algorithm is in texture reconstruction. This technique was used as part of some collaboration work within 3D Murale: 3D Measurement & Virtual Reconstruction of Ancient Lost Worlds of Europe. The results of which were published in IEEE/CVPR Workshop on Applications of Computer Vision in Archaeolog ACVA'03.

nymphaeum__texture-test-2.avi (2.7mb, divx 5.05 encoded avi)

nymphaeum__texture-test-3.avi (5.2mb, divx 5.05 encoded avi)

The problem that was presented, was that they required realistic texture maps for their 3D model. They had sample textures of particular types of marble that they wanted to use, but unfortunately due to circumstances, these were not ideal textures from which to synthesis texture maps. Most had unwanted reflections from not using diffuse lighting during photography. But in the most extreme cases, the marble had suffered a great deal of weathering, resulting in a high density of cracks and fractures over the sample texture. These flaws in the sample texture needed to be absent in the synthetic texture.

The solution to the problem was to use the fast version of Paget and Longstaff's texture synthesis algorithm. Because Paget and Longstaff's algorithm is pixel based, not patch based, it was easy to incorporate an arbitrary mask over the input sample texture. This mask did not affect the sampling procedure, nor did it effect the multi-resolution modelling, as that was done via quad-tree decimation. This meant that the flaws in the input sample texture could be masked out while still preserving the long and short range texture characteristics.