Brain death is the irreversible loss of all activity in the brain, brainstem, and cerebellum, the part of the central nervous system that remains inside the skull [1]. The clinical diagnosis of brain death should be supported by ancillary tests that provide information about cerebral blood flow or electrical activity in the brain. Some of the ancillary tests that evaluate cerebral blood flow include transcranial Doppler ultrasonography (TDUS), computed tomography (CT) angiography (CTA), and catheter-based cerebral angiography [2]. Among the ancillary tests that evaluate cerebral blood flow, cerebral angiography is the gold standard for diagnosis [3]. Cerebral angiography or other ancillary tests to assess cerebral blood flow (CT and MR angiography, etc.) have limitations such as patient transfer, use of contrast media, and the need for experienced medical staff. In addition, CT angiography's examination protocols and limited data compared with other blood flow detection tests limit its use as an adjunctive test, and its use is recommended for research purposes. However, given the widespread availability of CT angiography and differences in country conditions, the frequency of its use as an adjunctive test has increased [3], [4].

TDUS is a non-invasive, bedside method that can detect the absence of cerebral blood flow, which can be used to diagnose brain death and identify intracranial pathology [3]. The limitation of TDUS is that, in some cases, the area of interest may be partially covered due to bony structures. Orbital doppler ultrasonography (ODUS) can detect blood flow changes in the ophthalmic artery and central retinal artery as a component of TDUS or to identify various diseases glaucoma, diabetic retinopathy, etc.) [5], [6].

This study hypothesized that ODUS alone is more effective than TDUS in detecting intracranial blood flow in diagnosing brain death. To this end, we examined the results of ODUS in patients diagnosed as brain dead who underwent CT angiography.