Triple-rule-out CT angiography using two axial scans with 16 cm wide-detector for radiation dose reduction

Objective: To explore the use of two consecutive axial scans in triple-rule-out (TRO) examination on a 16 cm wide-detector CT for radiation dose reduction.

Materials and methods: Sixty TRO patients were assigned to either study group (Group A, n = 30) or control group (Group B, n = 30). Group A used a two-phasic contrast injection: 25mgI/kg/s for 12 s in 1st and at 3.0 ml/s injection rate for 7 s in 2nd phase. The pulmonary artery, coronary artery and aorta were scanned in succession with two axial scans using smart-coverage technique. Group B used the conventional protocol of scanning pulmonary arteries first in helical, followed by coronary arteries in axial and aorta in helical mode with contrast injection of 25mgI/kg/s for 14 s. All images were reconstructed with 80% ASIR-V. The qualitative and quantitative image assessment and effective dose of the two groups were statistically compared.

Results: The demographic data and quantitative measurements and qualitative image scores between the two groups were statistically the same (p > 0.05). However, Group A reduced radiation dose by 52% (2.67 ± 0.98 mSv vs. 5.65 ± 1.37 mSv) (p < 0.001).

Conclusion: Using two consecutive axial scans in triple-rule-out on a 16 cm wide-detector CT reduces radiation dose while maintaining image quality compared with the conventional TRO protocol.

Key points: • Triple-rule-out can be performed with two-axial scans on a wide-detector CT system. • TRO with two-axial scans maintain image quality compared with conventional protocol. • TRO with two-axial scans reduces 52% radiation dose over conventional protocol.