title: Prospective trial of the detection of urolithiasis on ultralow dose (sub mSv) noncontrast computerized tomography: direct comparison against routine low dose reference standard.
abstract: OBJECTIVE
  In this prospective trial we compared ultralow dose computerized tomography reconstruction algorithms and routine low dose computerized tomography for detecting urolithiasis.
  
  
  METHODS
  A total of 48 consenting adults prospectively underwent routine low dose noncontrast computerized tomography immediately followed by an ultralow dose series targeted at a 70% to 90% reduction from the routine low dose technique (sub mSv range). Ultralow dose series were reconstructed with filtered back projection, and adaptive statistical and model based iterative reconstruction techniques. Transverse (axial) and coronal images were sequentially reviewed by 3 relatively inexperienced trainees, including a radiology resident, a urology fellow and an abdominal imaging fellow. Three experienced abdominal radiologists independently reviewed the routine low dose filtered back projection images, which served as the reference standard.
  
  
  RESULTS
  The mean effective dose for the ultralow dose scans was 0.91 mSv (median 0.82), representing a mean ± SD 78% ± 5% decrease compared to the routine low dose. Overall sensitivity and positive predictive value per stone for ultralow dose computerized tomography at a 4 mm threshold was 0.91 and 0.98, respectively. Sensitivity, specificity, positive and negative predictive values, and accuracy per patient were 0.87, 1.00, 1.00, 0.94 and 0.96, respectively. At a 4 mm threshold the sensitivity and positive predictive value per stone of the ultralow dose series for filtered back projection, and adaptive statistical and model based iterative reconstruction was 0.89 and 0.96, 0.91 and 0.98, and 0.93 and 1.00, respectively. Sensitivity, specificity, positive and negative predictive values, and accuracy per patient at the 4 mm threshold were 0.82, 1.00, 1.00, 0.91 and 0.94 for filtered back projection, 0.85, 1.00, 1.00, 0.93 and 0.95 for adaptive statistical iterative reconstruction, and 0.94, 1.00, 1.00, 0.97 and 0.98 for model based iterative reconstruction, respectively. Sequential review of coronal images changed the final stone reading in 13% of cases and improved diagnostic confidence in 49%.
  
  
  CONCLUSIONS
  At a 4 mm renal calculus size threshold ultralow dose computerized tomography is accurate for detection when referenced against routine low dose series with dose reduction to below the level of a typical 2-view plain x-ray of the kidneys, ureters and bladder. Slight differences were seen among the reconstruction algorithms. There was mild improvement with model based iterative reconstruction over filtered back projection and adaptive statistical iterative reconstruction. Coronal images improved detection and diagnostic confidence over axial images alone.
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: B Dustin
authors.initials: BD
authors.lastname: Pooler
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Meghan G
authors.initials: MG
authors.lastname: Lubner
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: David H
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Ryckman
authors.affiliation: Department of Urology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Sri
authors.initials: S
authors.lastname: Sivalingam
authors.affiliation: Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Jie
authors.initials: J
authors.lastname: Tang
authors.affiliation: Department of Urology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Stephen Y
authors.initials: SY
authors.lastname: Nakada
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin; Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Guang-Hong
authors.initials: GH
authors.lastname: Chen
authors.affiliation: Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin. Electronic address: ppickhardt2@uwhealth.org.
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Pickhardt
mesh_terms: D000328:Adult; D000465:Algorithms; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000592:standards*; D011446:Prospective Studies; D012372:ROC Curve; D011857:Radiographic Image Interpretation, Computer-Assisted; D012015:Reference Standards; D015203:Reproducibility of Results; D052878:Urolithiasis / Q000000981:diagnostic imaging*
keywords: algorithms; emission-computed; kidney; radiation dosage; tomography; urolithiasis