The coordinates in the BrainSuite’s surface-space (which is same space as the curves’ space) are related to voxel-coordinates simply by scaling with voxel-dimension (and not by 3×3 inverse affine-matrix). For x-coordinates this would be:
voxel_coord_x = curve_coord_x/pixdim; and likewise for y and z — Note that this expression uses c-based indexing, i.e. array (and voxel) indexing start from 0.
Another similar question: https://forums.brainsuite.org/forums/topic/surface-mesh-space/