Reading slice # from volumetric data

Hi,

Thanks for this tool.  Very helpful!

It would be great if, in addition to the ROI data, this method would also return the slice # that the ROI was taken from in an image stack.  Here is an example [matlab function](https://www.mathworks.com/matlabcentral/fileexchange/32479-readimagejroi-cstrfilenames-) that accomplishes this.

Thanks!
Dave