Image quality and radiation dose of ultra-low current CT colonography with adaptive iterative dose reduction three-dimensional in pig model

Objective: To investigate image quality and radiation dose of ultra-low current CT colonography with adaptive iterative dose reduction three-dimensional (AIDR3D) in pig model. Methods: Ten segments of porcine colon models were established, of which thirty pedunculated polyps with diameters ranging from 1 mm to 15 mm were implanted. All colon models were scanned using 640-slice CT scanner with tube voltage of 120 kVp, and current of 10, 20, 30, 40, 50 mAs, respectively. CT colonography images were reconstructed using filtered back projection (FBP) and AIDR3D. Ten groups data were obtained with 5 current doses and 2 reconstruction algorithms: Group A (10 mAs, FBP), group B (10 mAs, AIDR3D), group C (20 mAs, FBP), group D (20 mAs, AIDR3D), group E (30 mAs, FBP), group F (30 mAs, AIDR3D), group G (40 mAs, FBP), group H (40 mAs, AIDR3D), group I (50 mAs, FBP), group J (50 mAs, AIDR3D). Quantitative image quality evaluation was preformed, included image noise, SNR, and contrast-to-noise ratio (CNR). Qualitative image quality was also evaluated. Radiation dose was compared with the index of effective radiation dose. Results: At the same level of current, image noise with AIDR3D was lower than that with FBP, while SNR and CNR with AIDR3D were higher than those with FBP (all P<0.05). There was no statistically significant difference in image noise (P=0.052), SNR (P=0.129) and CNR (P=0.053) between groups D and I. Image noise of group B was higher than that of group I (P=0.002), while SNR and CNR were all lower than group I (both P<0.001). Qualitative image quality scores with AIDR3D were higher than that with FBP at the same level of current doses (all P<0.05). No significant difference of qualitative image quality scores between groups D and I was found (P=0.121). Qualitative image quality score of group B was lower than that of group I (P<0.001). Compared with group I, effective radiation dose of group D decreased by 59.90% (P<0.05). Conclusion: Image quality of ultra-low current of 20 mAs CT colonography with AIDR3D is comparable to currently standard low current dose of 50 mAs with FBP, and can decrease radiation dose effectively.