This is a model I made using a CT scan of an x-ray skull phantom ( eg a real skull embedded in a block of resin ). There are two versions of the skull there is a very hires version which might contain to much data for your computer to handle, or there is a lower res version containing 50000 polygons. After getting permission at work I used a GE ct scanner to acquire a very hires CT data set of the skull. I then used invesalius to extract and build the initial 3D model. There were too many polygons in the original model for practical purposes so I used Meshlab to create a model containing 50000 polygons which prints just fine. I have printed a lot of the skull models in ABS and one in PETG successfully. I printed the skull on a raft with supports every where using CURA as my slicer. The slicer software will complain that the model contains holes as it is a hollow model, you can just ignore the warnings and it should print fine. This skull model also looks great sprayed in gold paint.