The references for CT brain death diagnosis http://www.ajnr.org/content/30/8/1566 (2009):
4 point score: opacification of the cortical segments of the MCA (M4) and the ICVs.
7 point score: additionally the pericallosal arteries (A3) and the great cerebral vein.
10 point score: additionally the basilar artery and the P2 segments of the PCAs.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4463321/ (2015 comparison)
Non-opacification of the deep cerebral veins appears to be the most sensitive CT-sign for brain death.
Caveat! Thrombosis of the deep cerebral veins and other topics related to changes in intracranial pressure addressed in this letter to the editor: https://doi.org/10.3171/2017.6.JNS171335
Systematic review by the authors who wrote the letter to the editor above: 10.1016/j.neurad.2015.07.006