Study on the combined application of selected virtual monoenergetic imaging, virtual non-contrast imaging, and adaptive statistical iterative reconstruction-V in head and neck CT angiography using 256-slice wide-body CT.

OBJECTIVE: To evaluate the value of combining spectral CT-derived virtual monoenergetic imaging, adaptive statistical iterative reconstruction-V (ASIR-V), and virtual non-contrast imaging in head and neck CT angiography (CTA) for patients with cerebrovascular disease (CVD). METHODS: 150 patients undergoing head and neck CTA for suspected or known CVD were randomly assigned 1:1:1 to the conventional-dose, spectral low-dose, and spectral ultra-low-dose groups. The conventional-dose group underwent a true non-contrast scan followed by 100-kVp polychromatic CTA with filtered back projection (FBP) reconstruction and received 0.90 mL/kg contrast at 5.0 mL/s, whereas the two spectral groups underwent a single GSI CTA acquisition generating virtual non-contrast images. Reported conventional-group DLP and ED included both acquisitions. The spectral low-dose group used 65-keV, 50% ASIR-V reconstruction and received 0.55 mL/kg at 4.5 mL/s, whereas the ultra-low-dose group used 60-keV, 70% ASIR-V reconstruction and received 0.50 mL/kg at 4.0 mL/s. Vascular CT attenuation, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), subjective image quality, dose-length product (DLP), effective dose (ED), total contrast agent volume, and total iodine load were compared among groups. RESULTS: CT values of the aortic arch, common carotid artery, internal carotid artery, and M1 segment, and cervical and cerebral vascular SNR and CNR, were lower in both spectral groups than in the conventional-dose group (p < 0.05). No significant differences were observed between the spectral low-dose and spectral ultra-low-dose groups (p > 0.05). Image-quality scores were higher in both spectral groups than in the conventional-dose group, despite their lower vascular attenuation, SNR, and CNR (p < 0.05). The DLP, ED, actual total contrast agent volume, and total iodine load were significantly lower in both spectral groups than in the conventional-dose group (p < 0.05). The spectral ultra-low-dose group showed a statistically significant further reduction in actual total contrast agent volume and the derived total iodine load. CONCLUSION: The integrated spectral CT protocols incorporating selected virtual monoenergetic imaging, ASIR-V reconstruction, and virtual non-contrast imaging were associated with lower radiation exposure and contrast agent use while maintaining diagnostically acceptable image quality, supporting the preliminary feasibility of the evaluated dose-reduction protocols in head and neck CTA.