Gonzalo Rojas 1, Jorge Fuentes 2, Carlos Montoya 2, Marcelo Gálvez 2
1Laboratory of Medical Image Processing, Clinica las Condes, Santiago, Chile, 2 Department of Radiology, Clinica las Condes, Santiago, Chile
Visualization of the human brain using complex images (tractography, functional connectivity, and functional imaging) is a formidable challenge, and combining that type of images produces an, even more, complex problem.
Different visualization solutions have been proposed. For example, Margulies et al. (2013), describe 2-D as well as 3-D neuroimaging visualization methods for anatomical, tractography, and functional connectivity data. Rojas et al. (2014), described a stereoscopic-related method to view neuroradiological 3-D images.
Virtual reality (VR) is an environment of scenes or real-life like objects, generated by computer technology, which create the feeling of being immersed in it. The environment is viewed by the user via a device usually known as glasses or virtual reality helmet.
Google Cardboard is a VR platform created by Google Inc. It is a low-cost device built using a piece of cardboard, 45 mm focal length lenses, magnets, VelcroTM, and optionally a near field communication tag (NFC), that uses a smartphone to generate VR stereoscopic 3D scenes with a broad field of view.
Here we describe an Android based mobile VR application that shows in 3D the seven standard functional connectivity networks with immersive characteristics (Yeo, 2011).
Using MNI152 2mm standard-space T1-weighted average structural template image we created a mesh using 3D Slicer 3.6.3 Grayscale Model Maker module (marching cubes; threshold: 5800, smooth: 50, decimate: 0.25). A seven Yeo Network Liberal Mask (surfer.nmr.mgh.harvard.edu/fswiki/CorticalParcellation_Yeo2011) was used to create the mesh model of the seven standard Yeo functional networks (using 3D Slicer Model Maker module, smooth: 10, filter type: Sinc, decimate: 0.25, split normals, point normals, pad). HC Laplacian smooth algorithm (MeshLab v 1.2.2) was used to smooth brain mesh model and the mesh of each 7 Yeo networks. The hippocampus and corpus callosum mesh were created with 3D Slicer using MNI152 mm standard-space T1 image segmented using Freesurfer v 5.3
The Android applications were created using C# language and software tools: Unity 5, (graphic engine; www.unity3d.com), 3DsMax (mesh and materials; www.autodesk.com), Gimp (textures; www.gimp.org).
We created an Android-based VR application for smartphones that use Google-Cardboard (VRiBraiN).
VRiBraiN (Virtual Reality intrinsic Brain Networks): The user views a 3D transparent brain fused with a functional connectivity network selected by the user among the seven standard networks (Yeo, 2011. See Fig 2). The network may be chosen in the Cardboard app scrolling menu by rotating the head of the user. The brain rotate continuously, and it could be zoom-in or zoom-out selecting the left buttons by viewing it, and the corpus callosum and hippocampus could be added to the visualization by selecting the corresponding buttons (Fig. 2).
The application also shows the functional and anatomical description of each functional connectivity network (see Fig. 3). The loading screen of the application is shown in Fig. 4.
VRiBraiN is an example of the use of low-cost VR devices (such as Google Cardboard) to visualize complex neuroimages such as functional connectivity data. Also, it might be possible to adapt further this application to show other neuroimages techniques such as tractography.
VRiBraiN has potential for use as an academic tool because it shows the position in the cortex in a stereoscopic 3D environment of different regions of each functional network with immersive experience (depth and breadth of the brain).
Margulies, D.S., Böttger, J., Watanabe A., Gorgolewski, K.J., (2013). Visualizing the human connectome, NeuroImage 80 (2013): 445-461.
Rojas, G.M., Gálvez, M., Vega Potler, N., et al., (2014). Stereoscopic three-dimensional visualization applied to multimodal brain images: clinical applications and a functional connectivity atlas, Front Neurosci 8: 328. doi: 10.3389/fnins.2014.00328.
Yeo, B.T., Krienen, F.M., Sepulcre, J., et al., (2011). The organization of the human cerebral cortex estimated by intrinsic functional connectivity, J Neurophysiol 106(3):1125-65.