Review multiple scans or experiments simultaneously

[curtislisle]

Hans mentioned looking at more than one subject at the same time.
The annotation clinicians asked about looking at multiple scans within an experiment at the same time.

We discussed the concept of how to extend the MIQA UI so each vtkViewer has more controls (selecting the experiment and scan). MIQA could initialize its usual way, but then individual controls on the Viewer panels could allow the panels to change which scan (and/or experiment) they are looking at.

This might be too much work to undertake, but two different users have asked for something like this.