Yeah I know about CT, but that doesn't look like a CT scanner - those are big donut shaped devices with an x-ray camera on the inside spinning around. The patient needs be as still as possible so its usually done lying down, with support.

Regarding the color count you could definitely texture the alien nicer with your skills.

CT (xray in general) is for dense material like bone, MRI's show soft tissue like brain and other organs great, and PET combined with CT can give nice 3D images of both (http://www.radiationatpmh.com/i/imgmgr/elpet%202_1.jpg).

Here's some ref's you might find helpful;

CT - with contrast to highlight vessels - http://www.montclairradiology.com/deploy/content/services/CT/angio/Cerebral-Angiogram.jpg

CT and MRI - A + B are CT, C + D are MRI - http://img.medscape.com/fullsize/migrated/554/258/nf554258.fig1.gif

MRI (your image looks like one of these but it doesn't use x-rays) - http://medexpert.com.ua/images/news/mri-brain.jpg

Thanks for the tips. CT Scanning shows you the brain (a combination of Xray + sophisticated computers)

You can't see brain through skull in an x-ray :P, looks cool but it's pretty flat, if you still wanna work on this try and give the brain, inside of skull and skin some depth.