PosterPDF Available

A VR-based surgical simulation system using patient-specific physical computing model

Authors:
  • University Hospital Essen (AöR)

Abstract

Apart from the applications in surgical navigations, virtual surgery has become a new feasible method for training young surgeons. Since 2006 virtual simulation has been performed in selected patient cases affected by complex craniomaxillofacialdisorders (n = 8) in addition to standard surgical planning based on patient specific 3d-models. Although for training, standard models are enough for young surgeons to practice, we still need to build an accurate and personalized model to simulate a surgery better. Patients’ CT images are considered appropriate references for this procedure. CT images are taken along the axis of the body, and each of them represents the structure of a plane that is perpendicular to the body axis. Information like the gray scale levels of each pixel, which can be used in building a volume model, are also contained. During an operation, the model should be able to give some haptic feedback as well as to update the changes on the models in real time. In this project, we realize these functions with CHAI3D library. Omega 6 is the device we use for applying forces and receiving feedbacks.
A VR-based surgical simulation system using patient- specific
physical computing model
Yining Chen1, Denghong Liao2, Xiaojun Chen2,*, Jan Egger3,4
1 School of Electronic and Electrical Engineering , Shanghai Jiao Tong University, China
2 School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, China
3 Graz University of Technology, Department of Computer Graphics and Vision, Graz, Austria
4 Computer Algorithms for Médicine (Café) Laboratory, Graz, Austria
Hardware and Software implement
[1] Adolphs, Nicolai, et al. "Virtual planning for craniomaxillofacial
surgery7 Years of experience." Journal of Cranio-Maxillofacial
Surgery 42.5 (2014): e289-e295.
[2] http://www.chai3d.org/concept/about
[3] http://www.forcedimension.com/products/omega-6/overview
This work was supported by Natural Science Foundation of
China (Grant No.: 81511130089), Foundation of Science and
Technology Commission of Shanghai Municipality (Grant No.:
14441901002, 15510722200, and 16441908400).
References and Acknowledgement
In particular, we use the voxel data to determine the shape of the
model and then create it in the CHAI3D world. CHAI3D allows users
to load a stack of CT images into a multi-image pointer and analyze
them. After creating a CHAI3D world and allocating the voxel data
for them, we set an isosurface level to the object, and those voxels
which gray level values exceed the isosurface level will represent
unit points and form the model.
Collision detections and haptic feedback are also added to the
model. CHAI3D uses a virtual "finger-proxy" algorithm to compute
forces. When a tool object hit the surface of a model, the tool we
can see will stop moving directly into its goal. However, the proxy of
the tool is actually able to stick into the object, which is shown in the
figure below. In this case, forces are computed between the actual
tool and its proxy, assuming a string in the middle trying to drag
them back together. Users can define the stiffness of the model
according to the materials.
When users click on the switch on Omega 6 while the virtual tool hit
the object, the drilling operation is started. CHAI3D will read the
collision event, and the determine the point which is contact with the
tool. Then, the property of the point is changed, and it is no longer
visible and able to give any haptic feedback. Graphic rendering will
occur at the same time, and users can know about the result of their
operation immediately.
Methods
At present, some core functions such as loading image files,
creating volume objects, and modify objects are completed. Right
now, users can drill on models at random directions, and models
can update its data and graphics in real time. Simple textures and
haptic feedback are also applied on the models. Furthermore, for
better simulations, we will calibrate the haptic feedback, restrict the
drilling directions, and improve rendering through using colormap in
the model. We expect this virtual surgery program can simulate
cutting, grinding and even more complicated operations. Therefore,
surgical training can be feasible and thus save time and cost in
surgery practicing.
Results and ConclusionsPurpose
Apart from the applications in surgical navigations, virtual surgery
has become a new feasible method for training young surgeons.
Since 2006 virtual simulation has been performed in selected
patient cases affected by complex craniomaxillofacial disorders (n =
8) in addition to standard surgical planning based on patient specific
3d-models. [1] Although for training, standard models are enough for
young surgeons to practice, we still need to build an accurate and
personalized model to simulate a surgery better.
Patients' CT images are considered appropriate references for this
procedure. CT images are taken along the axis of the body, and
each of them represents the structure of a plane that is
perpendicular to the body axis. Information like the gray scale levels
of each pixel, which can be used in building a volume model, are
also contained. During an operation, the model should be able to
give some haptic feedback as well as to update the changes on the
models in real time.
In this project, we realize these functions with CHAI3D library.
Omega 6 is the device we use for applying forces and receiving
feedbacks.
* Contact
Xiaojun Chen, Ph.D
Email: xiaojunchen@163.com
SMIT 2017
29th Conference of the international Society
for Medical Innovation and Technology
Designed as a platform agnostic framework for computer haptics,
visualization, and interactive real- time simulation, CHAI3D is an
open source framework that supports a variety of commercially-
available three-, six- and seven-degree-of-freedom haptic devices,
and makes it simple to support new custom force feedback devices.
[2]
The omega.6 is the most advanced pen-shaped force- feedback
device available. The combination of full gravity compensation and
driftless calibration contributes to greater accuracy. [3]
Fig. 2 Program interface and Omega 6 Fig. 3 Motion of the virtual proxy
in Finger-proxy algorithm
Fig. 1 Construction of the surgical simulation program
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