Computed tomography angiography scoring systems and the role of skull defects in the confirmation of brain death oleh Petros Zampakis, Vasilios Panagiotopoulos, Christina Kalogeropoulou, Maria Karachaliou, Diamanto Aretha, Nektarios Sioulas, Sofia Dimoulia, Dimitrios Karnabatidis, Fotini Fligou