Abstract：Objective To explore the feasibility of dual-layer spectral detector CT (SDCT) in rescuing intracranial CT angiography
(CTA) failure by using 50 keV images. Methods The clinical and imaging data of 31 patients with failed intracranial CTA
scanning by SDCT in our hospital were retrospectively analyzed. CT values of intracranial arteries, the contrast to noise ratio
(CNR) relative to the corpus callosum, diagnosability score, and difficulty of volume rendering (VR) for the intracranial artery
were compared between the low-energy virtual monoenergetic (50 keV) images and the conventional images. Wilcoxon test was
used for statistical analysis.Results CT values of the intracranial arteries in 50 keV images [e.g., the C7 segment of internal
carotid artery was (388.39±131.08) HU, basilar artery was (376.34±114.57) HU were much higher than those in conventional
images [e.g., the C7 segment of internal carotid artery was (202.61±53.60) HU, basilar artery was (196.18±50.22) HU], and the
difference was statistically significant (P<0.05). CNR of the intracranial arteries in 50 keV images (e.g., the C7 segment of internal
carotid artery was 43.15±23.07, basilar artery was 24.22±14.17) were much higher than those in conventional images (e.g., the C7
segment of internal carotid artery was 19.45±9.37, basilar artery was 15.90±6.98), and the difference was statistically significant (P<0.05).
The diagnostic value was improved in 50 keV images, and the cases with diagnosability score ≥2 were more in the 50 keV images
than those in the conventional images. VR for the intracranial artery branches was significantly easier in 50 keV images than in
conventional images. Conclusion Partially unsuccessful intracranial CTA scans can be rescued by taking advantage of low-energy
virtual monoenergetic images at 50 keV in dual-layer SDCT.
