Optimal scan timing for artery-vein separation at whole-brain CT angiography using a 320-row MDCT volume scanner.

OBJECTIVE: A 320-row multidetector CT (MDCT) is expected for a good artery-vein separation in terms of temporal resolution. However, a shortened scan duration may lead to insufficient vascular enhancement. We assessed the optimal scan timing for the artery-vein separation at whole-brain CT angiography (CTA) when bolus tracking was used at 320-row MDCT.

METHODS: We analyzed 60 patients, who underwent whole-brain four-dimensional CTA. Difference in CT attenuation between the internal carotid artery (ICA) and the superior sagittal sinus (Datt ) was calculated in each phase. Using a visual evaluation score for the depiction of arteries and veins, we calculated the difference between the mean score for the intracranial arteries and the mean score for the veins (Dscore ). We assessed the time at which the maximum Datt and Dscore were simultaneously observed.

RESULTS: The maximum Datt was observed at 6.0 s and 8.0 s in the arterial-dominant phase and at 16.0 s and 18.0 s in the venous-dominant phase after the contrast media arrival time at the ICA (Taa ). The maximum Dscore was observed at 6.0 s and 8.0 s in the arterial-dominant phase and at 16.0 s in the venous-dominant phase after the Taa . There were no statistically significant differences in Datt (p = 0.375) or Dscore (p = 0.139) between these scan timings.

CONCLUSION: The optimal scan timing for artery-vein separation at whole-brain CTA was 6.0 s or 8.0 s for the arteries and 16.0 s for the veins after the Taa . Advances in knowledge: Optimal scan timing allowed us to visualize intracranial arteries or veins with minimal superimposition.