title: Detection of urolithiasis: comparison of 100% tube exposure images reconstructed with filtered back projection and 50% tube exposure images reconstructed with sinogram-affirmed iterative reconstruction.
abstract: OBJECTIVE
  To compare images acquired with 50% tube exposure with a dual-source computed tomographic (CT) scanner and reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE) with 100% exposure images reconstructed with filtered back projection (FBP) for reader ability to detect stones, reader confidence, and findings outside the urinary tract.
  
  
  METHODS
  In this HIPAA-compliant, institutional review board-approved study, imaging examinations in 99 patients with urolithiasis were assessed. Data from both tubes were reconstructed with FBP; data from the primary tube only were reconstructed with SAFIRE. Seven readers evaluated randomized studies for calculi in nine regions. Reader confidence was scored by using a five-point scale. Ancillary findings were noted. Nonparametric methods for clustered data were used to estimate the area under the receiver operating characteristic curves with 95% confidence intervals to test for noninferiority of 50% exposure with SAFIRE.
  
  
  RESULTS
  Calculi were found in 113 locations (pyelocalyceal ureter, 86; proximal ureter, seven; midureter, four; distal ureter, 15; bladder, one) and not found in 752 locations. Mean area under the receiver operating characteristic curve for FBP was 0.879 (range, 0.607-0.967) and for SAFIRE, 0.883 (range, 0.646-0.971; 95% confidence interval: -0.025, 0.031). The SAFIRE images were not significantly inferior to FBP images (P = .001). Reader confidence levels for images with stones were similar with FBP and SAFIRE (P = .963). For the 52 patients who had extraurinary findings, readers reported them correctly in 74.4% (271 of 364) and 72.0% (262 of 364) of cases (P = .215) for FBP and SAFIRE, respectively. For the nine patients with potentially important findings per the reference standard, the detection rates were 44% (28 of 63) and 33% (21 of 63, P = .024), respectively. For the 43 patients with unimportant or likely unimportant findings, the false detection rates were 15% (44 of 301) and 14% (43 of 301, P = .756), respectively.
  
  
  CONCLUSIONS
  The 50% tube exposure CT images reconstructed with SAFIRE were not inferior to 100% exposure images reconstructed with FBP for diagnosis of urolithiasis, without decreases in reader confidence.
authors.affiliation: From the Imaging Institute (E.M.R., B.R.H., N.A.O., A.G., D.M.R., A.S.P., M.K.F., S.N.S., F.D., M.E.B.), Glickman Urological and Kidney Institute (E.M.R., B.R.H., S.D., M.M.), and Department of Quantitative Health Sciences (N.A.O.), Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195; and Siemens Medical Systems, Malvern, Pa (A.P.).
authors.forename: Erick M
authors.initials: EM
authors.lastname: Remer
authors.forename: Brian R
authors.initials: BR
authors.lastname: Herts
authors.forename: Andrew
authors.initials: A
authors.lastname: Primak
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Obuchowski
authors.forename: Alison
authors.initials: A
authors.lastname: Greiwe
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Roesel
authors.forename: Andrei S
authors.initials: AS
authors.lastname: Purysko
authors.forename: Myra K
authors.initials: MK
authors.lastname: Feldman
authors.forename: Shubha
authors.initials: S
authors.lastname: De
authors.forename: Shetal N
authors.initials: SN
authors.lastname: Shah
authors.forename: Frank
authors.initials: F
authors.lastname: Dong
authors.forename: Manoj
authors.initials: M
authors.lastname: Monga
authors.forename: Mark E
authors.initials: ME
authors.lastname: Baker
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006801:Humans; D016247:Information Storage and Retrieval / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D052878:Urolithiasis / Q000000981:diagnostic imaging*