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| The feasibility study of ATCM combined with ASiR-V technique to detect the pulmonary GGO nodules with a diameter around 10 mm using ultra-low dose CT |
| Wang Naiwu1, Han Wenjuan2, Li Qingguo1, Li Ying1, Yang Chenxiao1, Jia Shouqiang1, Wang Junxin1 |
1. department of radiology, Laiwu Affiliated Hospital of Taishan Medical University, Laiwu 271100 China;
2. Scientific education section, Laiwu Affiliated Hospital of Taishan Medical University |
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Abstract Objective To investigate the feasibility of ATCM combined with ASiR-V technique for ultra-low-dose CT examination and to determine the optimal level of ASiR-V for displaying pulmonary ground-glass-opacity nodules (GGO) with a diameter around 10mm.Methods Three GGO of diameter 12 mm, 10 mm and 8mm were randomly placed in a chest phantom. The chest phantom was scanned on a Revolution CT and ATCM at a high noise index(NI=35 Hu), with different levels of ASiR-V (0%、20%、40%、60%、80%、100%). Scanning parameters included:tube voltage 120 kVp,Helical scan,GP:0.5s,SPR:0.992:1. Images were reconstructed by standard algorithm with slice thickness of 5mm. The background image noise of the three nodules was measured as the average of the standard deviations of ROIs (≧1.0 cm2) placed in the heart as the same slice. CT dose index (CTDIvol) and dose length product (DLP) were measured and effective radiation dose (ED) was calculated. Objective analysis and subjective evaluation was done with image quality and radiation dose. Image noise with different nodules at different weighted levels was compared with Single factor ANOVA and correlation analysis by using SPSS 20.0 statistical software. Subjective evaluation was performed by two radiologists using a 5-point scale, and Kappa test was used to examine the agreement of the two readers.Results NI=35Hu.With the increase of prescribed ASiR-V weight, the tube current decreased(16~34 mA,11~24 mA,9~15 mA,9~10 mA,9 mA,9 mA),and ED decreased (0.62 mSv,0.44 mSv,0.30 mSv,0.25 mSv,0.24 mSv,0.24 mSv). The image background noises (SD) at the slice of the three nodules (12mm,10mm,8mm) were (0% ASiR-V,21.33±1.88;20%ASiR-V,21.27±1.43;40% ASiR-V,19.30±1.90;60%ASiR-V,13.73±1.36;80%ASiR-V,10.63±0.45;100%ASiR-V,9.70±0.82),the SD decreased(P<0.05). Two physicians had good agreement on subjective scores (K=0.75). The subjective scores with the increase of ASiR-V were 4.50、4.50、4.67、5.00、4.16、3.50. The highest subjective score was with 60% ASiR-V.Conclusion Radiation dose and image noise can be significantly reduced by using ATCM combined with ASiR-V technique on Revolution CT, and Image quality meets the requirement of clinic diagnosis. Ultra-low-dose scanning using NI=35 combined with 60% ASiR-V is the optimal scanning parameters for the GGO nodules with a diameter around 10 mm.
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Received: 13 July 2018
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