Purpose: To investigate capabilities of an open-source-based VR tool for interactive multi-volume data presentation and medical physics education on a commercially available computer.
Methods: VR headset and controller system (Samsung Odyssey+) was set-up with 3D-Slicer (v4.10.2) on a PC with modern graphics card (NVIDIA RTX 2080). Six VR scenes were constructed within 3D Slicer based on anonymized radiation therapy (RT) cases, including lung stereotactic body radiotherapy and head and neck proton therapy. Position and 6D motion data from headset and controllers were inputted into 3D-Slicer’s volume renderer to visualize multi-volumetric information in real-time. User could navigate freely within the VR scene using natural head and body movement. Stability and frame-rate (frames-per-second, or fps) of VR displays were qualitatively tested under various stressing conditions (e.g. multiple volume visualization, real-time re-slicing), and subjective experience such as motion sickness was tested on volunteers.
Results: VR cases with less than 4 volumes simultaneously rendered in real-time had minimal perceptible loss in VR display fps~60. Performance suffered minimally with 4D-CT visualization involving 8 breathing phases (fps>50). Interaction with a single volumetric image decreased performance slightly while interaction with two simultaneously decreased performance significantly (fps<50 vs. <30), especially when real-time volume re-slicing was involved (fps<20). Performance increased significantly when images were rendered only on VR headset and not on the computer (50 vs. 35fps). Turning off shading also improved volume quality and performance substantially, while minimally impacting data visualization. Overall volunteers reported minimal motion sickness, except when frame-rate dropped below 20fps.
Conclusion: VR scenes based on radiotherapy patient cases were created using open-source software. The ability to navigate and visualize complex 3D multi-volume information with intuitive body movements makes this a valuable tool for medical physics education. Various frame-rate optimization strategies can be employed to improved usability and reduce motion sickness of VR on this platform.