Fig 1.
Physical vs. virtual tissue registration.
(A) Bisected kidney on a dissecting board. Pink outlines indicate where the tissue block highlighted pink (shown in top right) will be extracted. (B) RUI with reference kidney of about the same size in x-y view. (C) RUI in z-y view with user interface that supports entry of tissue block size in mm, review of x, y, z position values, and change of tissue block rotation in 3D.
Fig 2.
The task setup in our user study.
Reference organ with target block indicated (purple) and tissue block (white) to be registered into the target block. The light blue arrow indicates block centroid (mid-point) distance. Task difficulty increases as the tissue blocks get smaller, block rotation increases, and distance between the blocks increases. (A) 2D Desktop setup. (B) The two VR setups.
Fig 3.
Setup, screen, and actions for 2D Desktop, VR Tabletop, and VR Standup.
(A-C) Three RUI setups with a human subject. (D-I) screenshots of the user interface. (J) Required actions. The tissue block is outlined in blue, the target block in green, and the kidney—providing context and domain relevance—in pink. Tasks are submitted by selecting the purple NEXT/red button. The user could reset the position or rotation of the tissue block by pressing the corresponding yellow-brown virtual (2D Desktop) and physical buttons (VR).
Fig 4.
Task setup and levels of difficulty used in this study.
Distance, angular difference, size difference, number of tasks, and prompt type for the one Tutorial, 14 Ramp-Up, and 30 Plateau tasks. The offset (computed via Eq 1) is a value that is added to gradually increase the distance and angular difference between the two blocks, and that is used to gradually decrease the size of the two blocks. Note that due to the layout of this figure, only 13 out of the 14 Ramp-Up tasks are illustrated on the left.
Fig 5.
Graphs for position and rotation accuracy.
(A-I) Scatter graphs showing the error for position accuracy (in mm), normalized by kidney height, during the Plateau phase. Each dot represents one of the 30 tissue block placements. The blue cross at the origin of each scatter graph shows the location of the target block. The blue dot shows the average of all centroids (bias). (J-L) Line graphs with rotation accuracy for each axis (x, y, z).
Fig 6.
Completion time for both phases and all three setups.
(A-C) During the Ramp-Up phase. (D-F) During the Plateau phase. The vertical dash-dot line (black arrow) indicates after what task the plateau was reached, on average.
Fig 7.
Position accuracy vs. completion time dependent on task number, i.e., tissue block size, with a log-log scale.
Fig 8.
Position accuracy vs. completion time dependent on instructions.
The blue circles and blue crosses mark the average completion time and position accuracy for speed and accuracy prompts, respectively.
Fig 9.
Grouped bar graph of overall user satisfaction.