Iterative reconstruction in prospective electrocardiogram-gated heart computed tomography combined with weight adjusting tube voltage and current:an experimental study-reducing radiation dose and controlling image quality

Objectives To evaluate the application of iterative reconstruction(iDose4) for reducing radiation dose and controlling image quality in prospective electrocardiogram(ECG)-gated computed tomography(CT) combined with weight adjusting tube voltage and current. Methods Ten pigs were included. All the pigs were scanned on a 256-slice prospective ECG-gated multilayer spiral CT system utilizing routine dose(group A) based on weight adjusting tube voltage and current and tube current reduced by 30%(group B), 50%(group C) and 70%(group D) respectively.Filtered back-projection(FBP) and iDose4were used for reconstruction respectively for all data. Radiation dose were calculated and noise, signal-to-noise ratio(SNR), contrast-to-noise rate(CNR) of ascending aortic root and left ventricle were measured, while general image quality and coronary artery image quality were graded(scale:1-5). All results reconstructed by FBP and iDose4were compared. Results The effective radiation doses for group A,B,C,D were(3.13 ±0.63) mSv,(2.26 ±0.51) mSv,(1.61 ±0.36) mSv,(1.01 ±0.23) mSv. The image noise increased as well as SNR, CNR and image quality decreased with the X-ray dose decreased. Image noise significantly decreased, while SNR and CNR obviously increased with iDose4reconstruction in each group(all P=0.000). For FBP / iDose4reconstruction,there were evident differences of image quality in group A(3.80±0.42 vs. 4.60±0.52, P0.05), group B(3.60±0.52vs. 4.40±0.52, P0.05), group C(3.00±0.67 vs. 3.80±0.42, P0.05) and group D(2.00±0.67 vs. 3.40±0.52, P 0.05). The diagnosed rates of proximal, distal coronary artery in group A, B, C, D with FBP reconstruction were100%, 95%, 70%, 20% and 92%, 72%, 36%, 0 respectively, while the diagnosed rates of proximal, distal coronary artery in group A, B, C with iDose4were not lower than those in group A with FBP(P0.05), whereas the diagnosed rates in group D with iDose4were significantly lower than those in group A with FBP(P0.05). Conclusions IDose4can sharply reduce image noise, improve SNR,CNR and image quality compared with FBP in prospective ECG-gated coronary CT combined with weight adjusting tube voltage and current. It's workable with a 50% reduction in radiation dose, while the image quality remains the same.