- J.B. Marshall Laboratory for Neurovascular Therapeutics, NH, USA
- Section of Neurosurgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
- Department of Neurosurgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
Correspondence Address:
Robert J. Singer
J.B. Marshall Laboratory for Neurovascular Therapeutics, NH, USA
Section of Neurosurgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
DOI:10.4103/2152-7806.125858
Copyright: © 2014 Khan IS. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.How to cite this article: Khan IS, Kelly PD, Singer RJ. Prototyping of cerebral vasculature physical models. Surg Neurol Int 27-Jan-2014;5:11
How to cite this URL: Khan IS, Kelly PD, Singer RJ. Prototyping of cerebral vasculature physical models. Surg Neurol Int 27-Jan-2014;5:11. Available from: http://sni.wpengine.com/surgicalint_articles/prototyping-of-cerebral-vasculature-physical-models/
Abstract
Background:Prototyping of cerebral vasculature models through stereolithographic methods have the ability to accurately depict the 3D structures of complicated aneurysms with high accuracy. We describe the method to manufacture such a model and review some of its uses in the context of treatment planning, research, and surgical training.
Methods:We prospectively used the data from the rotational angiography of a 40-year-old female who presented with an unruptured right paraclinoid aneurysm. The 3D virtual model was then converted to a physical life-sized model.
Results:The model constructed was shown to be a very accurate depiction of the aneurysm and its associated vasculature. It was found to be useful, among other things, for surgical training and as a patient education tool.
Conclusion:With improving and more widespread printing options, these models have the potential to become an important part of research and training modalities.
Keywords: Cerebral aneurysm, physical model, rapid prototyping, stereolithographic methods, training tool, 3D modeling
INTRODUCTION
The treatment of complicated cerebral vascular lesions, such as aneurysms, poses a challenge due their intricate anatomy. Over the past few decades, improving diagnostic imaging techniques have made it easier to determine the 3D structure of the aneurysm with its associated microvascular anatomy. While these virtual 3D depictions of the cerebral vasculature allow a good visualization of the aneurysm, there remain concerns regarding the interpretation of the actual image and the underlying anatomical structures.[
Historically, various milling methods have been used to carve out 3D models but these methods lack accuracy when faced with very fine structures and overhanging features.[
TECHNIQUE
For the purpose of a 3D aneurysm model production, we prospectively used the data of a 40-year-old female who presented new-onset headache. Angiography revealed a 4 mm right paraclinoid aneurysm [
On the nonworkstation computer, the VRML file was imported into MeshLab, a free, open-source program for displaying and editing mesh-based graphics. Gaps in the rendered surface model were then filled by applying an existing editing function in MeshLab, and the file was converted to the SL format (file extension: *.stl).
To review the model before printing, the SL file was imported into STLView, a free program distributed by ModuleWorks, GmbH. The SL file was then sent to a local rapid prototyping business, and physical models were printed on a Stratasys Objet 500 Connex (Stratasys Ltd, Minnesota USA). This machine can print two materials at one time allowing someone to print a rigid model with a rubber over mold at the same time. The parts were printed with an encapsulation of support material that was washed away, and then dyed red to mimic tissue. The material used to construct the blood vessels and aneurysm is called Tango+ - a clear rubber material with a shore value of 27. The resolution of the printer was set at 30-micron (0.03 mm) layer levels for the model.
Images from each stage of the prototyping process are shown in
Figure 2
(a) Virtual Reality Modeling Language (VRML) file displayed in MeshLab. Note that areas of gray discoloration are gaps in the mesh rendering of the model. These gaps were filled using built-in functionality of MeshLab. (b) Stereolithography file created from the VRML file after filling mesh gaps. (c) Stereolithography file as rendered in STLView prior to printing. (d) Physical model printed in Tango+
DISCUSSION
The term “stereolithography” was coined in 1986 by Charles Hull, who patented it as a method and apparatus for making solid objects by successively “printing” thin layers of an ultraviolet curable material one on top of the other to form a 3D structure.[
D’Urso and colleagues were the first to use this technology to model cerebral aneurysms by using 3D computed tomography (CT) and/or magnetic resonance (MR) angiograms.[
One of the major advantages of having a physical model of the aneurysm is the opportunity to plan a surgical procedure.[
Complicated aneurysm clipping is a challenging procedure that can only be mastered under the guidance of a seasoned surgeon. However, the number of clipped aneurysms has been steadily decreasing with only the most complicated aneurysms being selected for surgical management.[
While the model can be used to plan the surgery, the act of clipping the model aneurysm itself may not be representative of actual clipping of the aneurysm if the resin used is very rigid.[
Another limitation of these models lies in the fact that their surface represents the intraluminal surface of the aneurysm and its surrounding vessels rather than the outside surfaces that are seen during microsurgical exposures. The exclusion of the arterial wall can potentially mislead regarding of the true origins and courses of the adjacent arteries on relation to the aneurysm neck and dome in terms of proper placement of clip(s). The concomitant reconstruction of the bony anatomy in the region of the diseased vasculature can further help in surgical planning with regards to head positioning during the surgery.
SL aneurysm modeling can also be used for coiling considerations. Wetzel and colleagues used the lost-wax technique to form a tubular model from the original wax SL aneurysm model.[
These models can also be used for patient education and counseling. According to an informal survey by Wurm and colleagues, patient and family understanding of the complex disease condition was increased with the use of these models.[
While there are multiple advantages of accurate physical prototypes of aneurysms, there remain a few limitations and challenges for the future. Due to the imaging processing techniques, the model does not have the ability to demonstrate the presence or extent of an intraarterial thrombus and the aneurysm wall thickness. The other disadvantage is the time it takes to manufacture and ship such a model (in the magnitude of days), making it impractical for patients presenting with ruptured aneurysms. With the increasing availability of desktop 3D printers, however, it is possible to manufacture these models much quicker (in the magnitude of hours). Improving techniques and printing technology will make manufacturing these models even quicker and, in the future, viable for the management of patients who require urgent intervention.
CONCLUSION
We described the technical details behind the production of 3D physical SL aneurysm models. These models can be used to help in various aspects of treatment planning, biomedical research, patient education, and training. With improving and more widespread printing options, these models have the potential to become an important part of research and training modalities.
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