IMAX^® DCPs typically have a resolution of 4K (3D) and a picture bit rate of up to 500 Mbps.

To create an IMAX^® DCP, tick on the checkbox "Enable Higher Bit Rates" (HBR) in the "Package Options" dialog and set the slider "Maximum Picture Bit Rate" to 500 Mbps (see screenshot):

The naming convention for IMAX^® DCPs is described here:
http://isdcf.com/dcnc/home/appendix-10-imax.html

Please note: 3D, HFR and HBR are only available in easyDCP Creator+.