Optimal Contrast Enhancement of the Anastomotic Site in Brain CTA Following STA-MCA Bypass

This study aimed to determine the optimal scan delay time for obtaining maximum contrast enhancement at the anastomosis site during Brain CTA in patients who underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis for moyamoya disease. Forty patients who underwent Brain CTA at our hospital from January 2023 to December 2024 were included. The control group (n=10) had an ROI set at the C5 level of the carotid artery bifurcation, and scanning was performed with a 6-second delay immediately after the contrast medium reached 100 HU in the common carotid artery (CCA). The experimental group was scanned using the same method as the control, with scan delay times of 8, 10, and 12 seconds for groups A, B, and C, respectively. Contrast enhancement (Mean HU) was measured at the CCA, superficial temporal artery, middle cerebral artery, and anastomosis site to calculate the HU ratio. Statistical analysis was performed using SPSS for quantitative evaluation. The analysis showed that the anastomosis-to-CCA HU ratio increased with a longer scan delay time, peaking at 10 seconds.(p<0.001) Pearson correlation analysis revealed that the correlation coefficient between the middle cerebral artery and anastomosis enhancement was highest at 8 seconds, (r=0.69) while the correlation between the superficial temporal artery and anastomosis enhancement was highest at 10 seconds.(r=0.74) Notably, blood supply via the superficial temporal artery was the most significant factor affecting anastomosis enhancement. Effect size analysis also showed the largest effect size when the scan delay time was changed from 6 seconds to 10 seconds. Comparing Brain CTA scans of patients with STA-MCA anastomosis across control and experimental groups, a scan delay time of 10 seconds was found to be the most optimal for achieving superior contrast enhancement at the anastomosis site. This method is considered clinically useful.