Cerebral computed tomography angiography using a 70 kVp protocol: improved vascular enhancement with a reduced volume of contrast medium and radiation dose.

OBJECTIVES: To determine the feasibility of using a 70-kVp protocol compared with a 120-kVp protocol for cerebral CT angiography. An additional target was to investigate a possible reduction in the volume of contrast medium (CM) using the 70-kVp protocol. METHODS: Attenuation value and CNR for iodine were determined at various tube voltage settings using a phantom. Sixty-nine volunteers were randomly assigned to one of three protocols: group A (120-kVp and CM 64 mL), group B (70-kVp and CM 64 mL), or group C (70-kVp and CM 40 mL). The attenuation value, SNR, and CNR of cerebral arteries, subjective image quality, and radiation dose were compared among the groups. RESULTS: The vascular attenuation, SNR, and CNR of group B were significantly higher than those of group A. Group C had a significantly higher vascular attenuation than group A. Groups B and C were significantly better than group A with respect to subjective image quality. An effective dose of 70-kVp was 10 % lower than that of 120-kVp. CONCLUSIONS: Using 70-kVp improved arterial enhancement, SNR, and CNR, and provided better subjective image quality, using a 10 % lower effective dose. Furthermore, the 70-kVp protocol may both reduce volume of CM by 37.5 % and improve arterial enhancement. KEY POINTS: • Cerebral CT angiography at 70-kVp substantially improved vascular enhancement • Subjective image quality was better at 70-kVp, with lower radiation dose • The volume of contrast media can be substantially reduced at 70-kVp.