title: The evolution of radiation dose over time: Measurement of a patient cohort undergoing whole-body examinations on three computer tomography generations.
abstract: OBJECTIVE
  To evaluate and compare the radiation dose and image quality of whole-body-CT (WBCT) performed on the 3rd-generation dual-source-CT (DSCT) with 2nd-generation DSCT and 64-slices-Single-Source-CT (SSCT) in a large patient cohort.
  
  
  METHODS
  Using a monitoring and tracking software 1451, 747 and 1861 patients scanned with a one-spiral-thorax-abdomen-pelvis-CT-examination on a 3rd-, 2nd-generation DSCT and SSCT, respectively, were extracted from the PACS server. For the intra-individual analysis, 203 patients on the 3rd-generation DSCT were identified. Out of those 203 patients, 155 had the same examination on the 2nd-generation DSCT, 91 patients had the same examination on the SSCT and 43 patients had an examination on all three CT-generations. Automatic tube current modulation was active on all three CT-generations, whereas automatic tube voltage selection was only available on both DSCT-generations. Dose was recorded by the size-specific-dose-estimate-method (SSDE); signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR) were calculated placing a ROI on the ascending aorta/liver and the subcutaneous adipose tissue at comparable level. Image quality of axillary and mediastinal lymph nodes and adrenal glands was assessed by two experienced radiologists.
  
  
  RESULTS
  Subjective image quality was excellent throughout all three CT-generations (p=0.38-0.98). Quantitative image quality in both DSCT generations was superior to SSCT (p<0.001). SNR and CNR in the liver parenchyma were superior in the 3rd-generation DSCT compared to the 2nd generation DSCT (p<0.001), whereas there was no difference in the aorta. In the inter-individual analysis, CTDIvolwas lower by 26.9% and 44.3% in the 3rd-generation DSCT, when compared to the 2nd-generation DSCT and SSCT, respectively; SSDE was lower by 31.5% and 51% in the 3rd-generation DSCT, when compared to the 2nd-generation DSCT and SSCT, respectively. In the intra-individual comparison CTDIVolin the 3rd-generation DSCT was lower by 33% and 45%, when compared to the 2nd-gneration DSCT and the SSCT, respectively. Consequently, SSDE in the 3rd-generation DSCT was lower by 29% and by 43% when compared to the 2nd-generation DSCT and SSCT, respectively.
  
  
  CONCLUSIONS
  State-of-the-art CT-equipment substantially reduce radiation dose without affecting image quality.
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Eberhard-Karls-Universität, Tübingen, Germany; Department of Radiology, Mayo Clinic, Rochester, MN, United States. Electronic address: roy.marcus@med.uni-tuebingen.de.
authors.forename: Roy P
authors.initials: RP
authors.lastname: Marcus
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Eberhard-Karls-Universität, Tübingen, Germany.
authors.forename: Elise
authors.initials: E
authors.lastname: Koerner
authors.affiliation: Institute for Computational Mechanics, Technische Universität München, Garching, Germany.
authors.forename: Roland C
authors.initials: RC
authors.lastname: Aydin
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Eberhard-Karls-Universität, Tübingen, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Zinsser
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Eberhard-Karls-Universität, Tübingen, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Finke
authors.affiliation: Institute for Computational Mechanics, Technische Universität München, Garching, Germany.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Cyron
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Eberhard-Karls-Universität, Tübingen, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Bamberg
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Eberhard-Karls-Universität, Tübingen, Germany.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
authors.affiliation: Institute of Diagnostic and Interventional Radiology, Eberhard-Karls-Universität, Tübingen, Germany.
authors.forename: Mike
authors.initials: M
authors.lastname: Notohamiprodjo
mesh_terms: D001013:Aorta, Thoracic / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008099:Liver / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D010808:Physical Examination; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D012189:Retrospective Studies; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: CTDI; Computed tomography; Dose saving technique; Dual-Source-CT; SSDE