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Purpose To assess radiation dose and image quality of CT colonography(CTC)with iterative model reconstruction algorithm(IMR)at 10 mAs/100 kVp compared with filtered back projection(FBP)at 50 mAs/120 kVp in polyp detection in pig colon model.Methods and Materials Ten segments of pig colon phantoms with average length of 100cm of porcine colon phantom and 150 polyps(ranging from 1 mm to 15 mm)were collected.Image data were acquired with two tube peak voltage(100 and 120)KVp and five current dose(10 mAs to 50 mAs).Images were reconstructed using FBP and IMR.Two radiologists independently evaluated image quality.Qualitative image quality was assessed with a five-score scale.Image noise,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR),and effective radiation dose were recorded and calculated.Qualitative and quatitative values were analysed by using Wilcoxon signed rank test and the paired t test,respectively.