title: [The best noise index combined with ASIR weighting selection in low-dose chest scanning].
abstract: OBJECTIVE
  To discuss the best noise index combined with ASIR weighting selection in low-dose chest scanning based on BMI.
  
  
  METHODS
  200 patients collected from May to December 2014 underwent non-contrast chest CT examinations, they were randomly assigned into standard dose group (Group A, NI15 combined with 30% ASIR) and low-dose groups (Group B, NI25 combined with 40% ASIR, Group C, NI30 combined with 50% ASIR, Group D, NI35 combined with 60% ASIR), 50 cases in each group; the patients were assigned into three groups based on BMI (kg/m2): BMI<18.5; 18.5≤BMI≤25; BMI>25. Signal-to-nosie ratio (SNR), contrast-to noise ratio (CNR), CT dose index volume (CTDIvol), dose-length product (DLP), effective dose (ED) and subjective scoring between the standard and low-dose groups were compared and analyzed statistically. Differences of SNR, CNR, CTDIvol, DLP and ED among groups were determined with ANOVA analysis and the consistency of diagnosis with Kappa test.
  
  
  RESULTS
  SNR, CTDIvol, DLP and ED reduced with the increase of nosie index, the differences among the groups were statistically significant (P<0.05). Kappa value of the two reviewers were 0.888. Subjective scoring of four groups were all above 3 points in BMI<18.5 kg/m2 group; subjective scoring of ABC groups were all above 3 points in 18.5 kg/m2≤BMI≤25 kg/m2 group and subjective scoring of AB groups were all above 3 points in BMI>25 kg/m2 group.
  
  
  CONCLUSIONS
  NI35 combined with 60% ASIR in BMI<18.5 kg/m2 group; NI30 combined with 50% ASIR in 18.5 kg/m2≤BMI≤25 kg/m2 group; NI25 combined with 40% ASIR in 18.5 kg/m2≤BMI≤25 kg/m2 group were the best parameters combination which both can significantly reduce the radiation dose and ensure the image quality.
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Henan 450052, China.
authors.forename: Huijuan
authors.initials: H
authors.lastname: Xiao
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Henan 450052, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Hou
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Henan 450052, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Henan 450052, China; Email: cjr.gaojianbo@vip.163.com.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Gao
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Henan 450052, China.
authors.forename: Hongna
authors.initials: H
authors.lastname: Tan
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Henan 450052, China.
authors.forename: Pan
authors.initials: P
authors.lastname: Liang
authors.affiliation: Department of Radiology, the First Affiliated Hospital of Zhengzhou University, Henan 450052, China.
authors.forename: Shi
authors.initials: S
authors.lastname: Pu
mesh_terms: D001835:Body Weight; D054893:Cone-Beam Computed Tomography; D006801:Humans; D009622:Noise; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed