Check if *ANY PART* of a UI reticle overlaps a gameobject?

I know I can raycast from the camera to tell if the very center of a reticle is overlapping a world gameobject, but that doesn't tell me about whether the rest of the reticle shape overlaps anything.

I also know I can world->screen the vertices from the gameobject's bounds, and then check that rectangle for overlap, but that gives false positives in the 'gaps' between parts of the gameobject that stick out (as the bounds encompass the entire shape, empty space and all).

Is there a way to check whether any part of a large UI reticle image is overlapping any part of a specified gameobject, without false positives?

 

Is it a perspective camera or orthographic? If it's orthographic you can do a physics.SphereCast.

 

Perspective, so that won't work (but thank you for the suggestion!)