Figure 5.

“Virtual surgery” used to estimate potential treatment-induced vision loss. (A) T1-weighted anatomical image with superimposed fMRI vision mapping. Visually active voxels (squares) are color coded (inset shows key) to indicate the eccentricity of the stimulus ring that maximally activated each voxel. The thin white outline shows the planned resection zone containing an obviously eloquent portion of the visual cortex. (B) FFMap constructed from the fMRI activation of A plus a complementary mapping of visual field angular preference (not shown) based on the rotating wedge stimulus. Circle symbols are pseudocolored using the same color code shown by the inset to figure A to emphasize the correspondence of the FFMap symbols with the fMRI activation in the brain. (C) The same FFMap but after all active voxels within the planned resection zone have been removed by computational “virtual surgery.” The dashed white outline surrounds the portion of the patient's visual field that might be impaired (reduced symbol density) by the planned resection. Though many factors (eg, collateral tissue damage at a distance from the resection) might compromise the accuracy of this estimate, this case illustrates the potential to provide surgical guidance at a level of sophistication that was not previously possible. (Color version of figure is available online.)