Human Brain Model-Importing into HFSS

Hi,

I want to Export a <256x256x128 double> matrix ( It's a multilayer image; it's human brain model) to a .DXF file, is there any way to do this?
I need it to work on it in HFSS. So I am thinking of exporting a .DXF ,and then using AutoCAD export another one so at the end I am able to open the image in HFSS.
is there any other suggestion?

Thanks.