Ultra-fast, low dose high-pitch (FLASH) versus prospectively-gated coronary computed tomography angiography: Comparison of image quality and patient radiation exposure

BACKGROUND: Coronary computed tomography angiography (CCTA) is increasingly being used for the evaluation of coronary artery disease; however, radiation exposure remains a major limitation of its use. OBJECTIVE: To compare image quality and radiation exposure in two groups of patients undergoing CCTA using a 256-slice dual-source helical computed tomography scanner with high-pitch (FLASH) or prospective [step-and-shoot (SAS)] gating protocols. METHODS: A prospective, single-center study was performed in our cardiac center. In total, 162 patients underwent CCTA with either FLASH or SAS scanning protocols. Subjective image quality was graded on the basis of a four-point grading system (1, non-diagnostic; 2, adequate; 3, good; 4, excellent). Objective image quality was assessed using image signal, noise, and signal-to-noise ratio (SNR). The effective radiation dose was also estimated. RESULTS: The clinical and demographic characteristics of the patients in both groups were similar. The median age of the patients in both groups was 48.43 years, and males accounted for 63% and 68.7% of the FLASH and SAS groups, respectively. We found that the subjective image quality obtained with the FLASH protocol was superior to that obtained with the SAS protocol (3.35 ± 0.6 mSv vs. 2.82 ± 0.61 mSv; p < 0.001). Image noise was higher in the FLASH group but was not statistically significant (25.0 ± 6.13 vs. 24.0 ± 6.8; p = 0.10), whereas the signal and SNR was significantly higher with the FLASH protocol than with the SAS protocol [(469 ± 116 vs. 397 ± 106; p > 0.001) and (21.6 ± 8.7 mSv vs. 16.6 ± 7.7 mSv; p < 0.001), respectively]. Radiation exposure was 62% lower in the FLASH protocol than in the SAS protocol, (1.9 ± 0.4 mSv vs. 5.12 ± 1.8 mSv; p < 0.001). CONCLUSION: The use of 256-slice CCTA performed with the FLASH protocol has a better objective and subjective image quality as well as lower radiation exposure when compared with the use of prospective electrocardiography gating.