title: One-mSv CT colonography: Effect of different iterative reconstruction algorithms on radiologists' performance.
abstract: OBJECTIVE
  To analyze the effect of different reconstruction algorithms on image noise and radiologists' performance at ultra-low dose CT colonography (CTC) in human subjects.
  
  
  METHODS
  This retrospective study had institutional review board approval, with waiver of the need to obtain informed consent. CTC and subsequent colonoscopy were performed at the same day in 28 patients. CTC was scanned at the supine/prone positions using 120/100kVp and fixed 10mAs, and reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based IR (Veo) algorithms. Size-specific dose estimates (SSDE) and effective radiation doses were recorded. Image noise was compared among the three datasets using repeated measures analysis of variance (ANOVA). Per-polyp sensitivity and figure-of-merits were compared among the datasets using the McNemar test and jackknife alternative free-response receiver operating characteristic (JAFROC) analysis, respectively, by one novice and one expert reviewer in CTC.
  
  
  RESULTS
  Mean SSDE and effective radiation dose of CTC were 1.732mGy and 1.002mSv, respectively. Mean image noise at supine/prone position datasets was significantly lowest with Veo (17.2/13.3), followed by ASIR (52.4/38.9) and FBP (69.9/50.8) (P<0.0001). Forty-two polyps in 25 patients were reference polyps. For both readers, per-polyp sensitivity of all 42 polyps was highest with Veo reconstruction (81.0%, 64.3%), followed by ASIR (73.8%, 54.8%) and FBP (57.1%, 50.0%) with statistical significance between Veo and FBP for reader 1 (P=0.002). JAFROC analysis revealed that the figure-of-merit for the detection of polyps was highest with Veo (0.917, 0.786), followed by ASIR (0.881, 0.750) and FBP (0.750, 0.746) with statistical significances between Veo or ASIR and FBP for reader 1 (P<0.05).
  
  
  CONCLUSIONS
  One-mSv CTC was not feasible using the standard FBP algorithm. However, diagnostic performance expressed as per-polyp sensitivity and figures-of-merit can be improved with the application of IR algorithms, particularly Veo.
authors: Department of Radiology, Seoul National University Hospital, Republic of Korea; Department of Radiology, Seoul National University College of Medicine, Republic of Korea.
authors: Cheong-Il
authors: CI
authors: Shin
authors: Department of Radiology, Seoul National University Hospital, Republic of Korea; Department of Radiology, Seoul National University College of Medicine, Republic of Korea. Electronic address: shkim7071@gmail.com.
authors: Se Hyung
authors: SH
authors: Kim
authors: Department of Radiology, Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, Republic of Korea.
authors: Jong Pil
authors: JP
authors: Im
authors: Department of Radiology, Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, Republic of Korea.
authors: Sang Gyun
authors: SG
authors: Kim
authors: Department of Radiology, KonKuk University Medical Center, Republic of Korea.
authors: Mi Hye
authors: MH
authors: Yu
authors: Department of Radiology, Chung-Ang University Hospital, Republic of Korea.
authors: Eun Sun
authors: ES
authors: Lee
authors: Department of Radiology, Seoul National University Hospital, Republic of Korea; Department of Radiology, Seoul National University College of Medicine, Republic of Korea; Department of Radiology, Institute of Radiation Medicine, Seoul National University Medical Research Center, Republic of Korea.
authors: Joon Koo
authors: JK
authors: Han
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D000704:Analysis of Variance; D002983:Clinical Competence / Q000706:statistics & numerical data*; D003111:Colonic Polyps / Q000000981:diagnostic imaging*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
keywords: Colonic polyps; Computed tomographic colonoscopy; Diagnostic performance; Iterative reconstruction; Low dose CT