Feasibility of superficial temporal artery as the input artery for cerebral perfusion CT.

OBJECTIVE: The purpose of this study was to determine whether the superficial temporal artery as a surrogate arterial input function, compared with the anterior cerebral artery as the arterial input function, generates accurate perfusion CT maps with significant correlates for cerebral blood flow, cerebral blood volume, and mean transit time.
MATERIALS AND METHODS: One hundred perfusion CT examinations performed on 90 patients (51 women and girls, 39 men and boys) were retrospectively reviewed and postprocessed by one investigator using CT perfusion software at a workstation. Color-coded cerebral blood flow, cerebral blood volume, and mean transit time maps were constructed with the superficial temporal artery as a surrogate arterial input function and the anterior cerebral artery as the arterial input function. The effect of input artery choice on mean cerebral blood flow, cerebral blood volume, and mean transit time values in six regions of interest (one region of interest in each anterior cerebral artery, middle cerebral artery, and posterior cerebral artery territory) was assessed.
RESULTS: All graphs of correlation between the anterior cerebral artery as the arterial input function and the superficial temporal artery as a surrogate arterial input function produced significant results (p < 0.0001). Excellent correlation existed between the cerebral blood flow (r = 0.96 [Pearson correlation coefficient]; rho(c) = 0.96 [concordance correlation coefficient]), cerebral blood volume (r = 0.97; rho(c) = 0.97), and mean transit time (r = 0.97; rho(c) = 0.97) values obtained with the anterior cerebral artery and the values obtained with the superficial temporal artery. Linear regression lines produced strong agreement between use of the anterior cerebral artery and use of the superficial temporal artery (cerebral blood flow, y = 1.03x + 0.65; cerebral blood volume, y = 1.05x - 0.09; mean transit time, y = 0.92x + 0.21).
CONCLUSION: The preliminary results show that using an extracranial vessel such as the superficial temporal artery as a surrogate input artery can generate perfusion maps comparable with those generated with an intracranial vessel such as the anterior cerebral artery. This knowledge can be useful if the proximal intracranial vessels typically used for arterial input are not visible owing to diffuse disease, such as diffuse vasospasm and atherosclerosis, or are not included in the field of view of perfusion CT.