title: CT for evaluation of urolithiasis: image quality of ultralow-dose (Sub mSv) CT with knowledge-based iterative reconstruction and diagnostic performance of low-dose CT with statistical iterative reconstruction.
abstract: OBJECTIVE
  To compare radiation dose and image quality in regular, low, and ultralow-dose CT protocols, and to evaluate diagnostic performance of low-dose CT for urolithiasis.
  
  
  METHODS
  Sixty-five patients with suspected urolithiasis underwent three different scans under the regular, low, and ultralow-dose protocols. The regular dose scans were reconstructed using filtered back projection and the low-dose scans were reconstructed using a statistical iterative reconstruction. The ultralow-dose scans were reconstructed using both techniques in addition to a knowledge-based IR. Effective radiation doses were compared. Objective image noise was assessed by measuring standard deviation of HU and subjective image assessment was performed with a 3- or 5-point scale. Diagnostic performance of the low-dose image was evaluated, using the regular dose image as a standard reference and the interobserver agreement between two reviewers with different levels of experience was calculated.
  
  
  RESULTS
  The effective radiation dose was significantly different in each protocol (p < 0.001) and estimated dose reduction of the low-dose and ultralow-dose protocols was 76.4% and 89.8%, respectively. The knowledge-based iterative reconstruction algorithm showed poorer subjective image quality than the regular and low-dose protocols, but it also had the least objective image noise. Overall, the low-dose image set showed a greater than 84% concordance rate and 100% in ureter stones larger than 3 mm. Interobserver agreement was substantial (kappa value = 0.61).
  
  
  CONCLUSIONS
  The knowledge-based IR can provide a better quality image while reducing radiation exposure under the same protocol. Furthermore, the diagnostic performance of the low-dose CT protocol is comparable to the regular dose scan.
authors.affiliation: Department of Radiology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea.
authors.forename: Joonho
authors.initials: J
authors.lastname: Hur
authors.affiliation: Department of Radiology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea. pksungbin@paran.com.
authors.forename: Sung Bin
authors.initials: SB
authors.lastname: Park
authors.affiliation: Department of Radiology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea.
authors.forename: Jong Beum
authors.initials: JB
authors.lastname: Lee
authors.affiliation: Department of Radiology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea.
authors.forename: Hyun Jeong
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Department of Urology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea.
authors.forename: In Ho
authors.initials: IH
authors.lastname: Chang
authors.affiliation: Department of Urology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea.|Department of Urology, Haeundae Paik Hospital, Inje University College of Medicine, 875, Haeundae-ro, Haeundae-gu, Busan, 612-896, Korea.
authors.forename: Jong Kyou
authors.initials: JK
authors.lastname: Kwon
authors.affiliation: Department of Radiology, Chung-Ang University College of Medicine, Chung-Ang University Hospital, 102, Heukseok-ro, Dongjak-gu, Seoul, 156-755, Korea.
authors.forename: Yang Soo
authors.initials: YS
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014567:Urography; D052878:Urolithiasis / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: Filtered back projection; Knowledge-based iterative reconstruction; Low-dose computed tomography; Model-based iterative reconstruction; Radiation dosage; Statistical iterative reconstruction; Urolithiasis