Loading indicator?

This works great, thank you! My only issue is that there is no indicator that an image is loading. These are huge files (I’m getting 15-20 MB per xray) so they take awhile even on a fast connection. I’ve had people think the page that will eventually display the image is broken because there is no indication that it is loading something. I’ve tried to add this functionality myself with preloader style plugins, but they can’t seem to tell that the DICOM file is still loading and terminate the loading animation prematurely.