title: Effect of radiation dose reduction and iterative reconstruction on computer-aided detection of pulmonary nodules: Intra-individual comparison.
abstract: OBJECTIVE
  To evaluate the effect of radiation dose reduction and iterative reconstruction (IR) on the performance of computer-aided detection (CAD) for pulmonary nodules.
  
  
  METHODS
  In this prospective study twenty-five patients were included who were scanned for pulmonary nodule follow-up. Image acquisition was performed at routine dose and three reduced dose levels in a single session by decreasing mAs-values with 45%, 60% and 75%. Tube voltage was fixed at 120 kVp for patients ≥ 80 kg and 100 kVp for patients < 80 kg. Data were reconstructed with filtered back projection (FBP), iDose(4) (levels 1,4,6) and IMR (levels 1-3). All noncalcified solid pulmonary nodules ≥ 4 mm identified by two radiologists in consensus served as the reference standard. Subsequently, nodule volume was measured with CAD software and compared to the reference consensus. The numbers of true-positives, false-positives and missed pulmonary nodules were evaluated as well as the sensitivity.
  
  
  RESULTS
  Median effective radiation dose was 2.2 mSv at routine dose and 1.2, 0.9 and 0.6 mSv at respectively 45%, 60% and 75% reduced dose. A total of 28 pulmonary nodules were included. With FBP at routine dose, 89% (25/28) of the nodules were correctly identified by CAD. This was similar at reduced dose levels with FBP, iDose(4) and IMR. CAD resulted in a median number of false-positives findings of 11 per scan with FBP at routine dose (93% of the CAD marks) increasing to 15 per scan with iDose(4) (95% of the CAD marks) and 26 per scan (96% of the CAD marks) with IMR at the lowest dose level.
  
  
  CONCLUSIONS
  CAD can identify pulmonary nodules at submillisievert dose levels with FBP, hybrid and model-based IR. However, the number of false-positive findings increased using hybrid and especially model-based IR at submillisievert dose while dose reduction did not affect the number of false-positives with FBP.
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands. Electronic address: a.m.denharder@umcutrecht.nl.
authors.forename: Annemarie M
authors.initials: AM
authors.lastname: Den Harder
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Willemink
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands.
authors.forename: Robbert W
authors.initials: RW
authors.lastname: van Hamersvelt
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands.
authors.forename: Evert-Jan P A
authors.initials: EJ
authors.lastname: Vonken
authors.affiliation: Philips Healthcare, Best, The Netherlands.
authors.forename: Julien
authors.initials: J
authors.lastname: Milles
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands.
authors.forename: Arnold M R
authors.initials: AM
authors.lastname: Schilham
authors.affiliation: Department of Respiratory Medicine, University Medical Center, Utrecht, The Netherlands.
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Lammers
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands.
authors.forename: Pim A
authors.initials: PA
authors.lastname: de Jong
authors.affiliation: Department of Radiology, University Medical Center, Utrecht, The Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Leiner
authors.affiliation: Department of Radiology, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Ricardo P J
authors.initials: RP
authors.lastname: Budde
mesh_terms: D000368:Aged; D000465:Algorithms; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012680:Sensitivity and Specificity; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Chest CT; Computer-aided detection; Iterative reconstruction; Pulmonary nodules