title: Combining automatic tube current modulation with adaptive statistical iterative reconstruction for low-dose chest CT screening.
abstract: OBJECTIVE
  To reduce radiation dose while maintaining image quality in low-dose chest computed tomography (CT) by combining adaptive statistical iterative reconstruction (ASIR) and automatic tube current modulation (ATCM).
  
  
  METHODS
  Patients undergoing cancer screening (n = 200) were subjected to 64-slice multidetector chest CT scanning with ASIR and ATCM. Patients were divided into groups 1, 2, 3, and 4 (n = 50 each), with a noise index (NI) of 15, 20, 30, and 40, respectively. Each image set was reconstructed with 4 ASIR levels (0% ASIR, 30% ASIR, 50% ASIR, and 80% ASIR) in each group. Two radiologists assessed subjective image noise, image artifacts, and visibility of the anatomical structures. Objective image noise and signal-to-noise ratio (SNR) were measured, and effective dose (ED) was recorded.
  
  
  RESULTS
  Increased NI was associated with increased subjective and objective image noise results (P<0.001), and SNR decreased with increasing NI (P<0.001). These values improved with increased ASIR levels (P<0.001). Images from all 4 groups were clinically diagnosable. Images with NI = 30 and 50% ASIR had average subjective image noise scores and nearly average anatomical structure visibility scores, with a mean objective image noise of 23.42 HU. The EDs for groups 1, 2, 3 and 4 were 2.79 ± 1.17, 1.69 ± 0.59, 0.74 ± 0.29, and 0.37 ± 0.22 mSv, respectively. Compared to group 1 (NI = 15), the ED reductions were 39.43%, 73.48%, and 86.74% for groups 2, 3, and 4, respectively.
  
  
  CONCLUSIONS
  Using NI = 30 with 50% ASIR in the chest CT protocol, we obtained average or above-average image quality but a reduced ED.
authors.affiliation: Department of Radiology, Beijing Friendship Hospital, Capital Medical University, XiCheng District, Beijing, China.
authors.forename: Jiang-Hong
authors.initials: JH
authors.lastname: Chen
authors.affiliation: Department of Radiology, Beijing Friendship Hospital, Capital Medical University, XiCheng District, Beijing, China.
authors.forename: Er-Hu
authors.initials: EH
authors.lastname: Jin
authors.affiliation: Department of Radiology, Beijing Friendship Hospital, Capital Medical University, XiCheng District, Beijing, China.
authors.forename: Wen
authors.initials: W
authors.lastname: He
authors.affiliation: Department of Radiology, Beijing Friendship Hospital, Capital Medical University, XiCheng District, Beijing, China.
authors.forename: Li-Qin
authors.initials: LQ
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001331:Automation; D001827:Body Height; D001835:Body Weight; D004560:Electricity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement; D011857:Radiographic Image Interpretation, Computer-Assisted; D013902:Radiography, Thoracic; D013223:Statistics as Topic; D014057:Tomography, X-Ray Computed / Q000379:methods*