title: Low-dose CT pulmonary angiography on a 15-year-old CT scanner: a feasibility study.
abstract: BACKGROUND
  Computed tomography (CT) low-dose (LD) imaging is used to lower radiation exposure, especially in vascular imaging; in current literature, this is mostly on latest generation high-end CT systems.
  
  
  OBJECTIVE
  To evaluate the effects of reduced tube current on objective and subjective image quality of a 15-year-old 16-slice CT system for pulmonary angiography (CTPA).
  
  
  METHODS
  CTPA scans from 60 prospectively randomized patients (28 men, 32 women) were examined in this study on a 15-year-old 16-slice CT scanner system. Standard CT (SD) settings were 100 kV and 150 mAs, LD settings were 100 kV and 50 mAs. Attenuation of the pulmonary trunk, various anatomic landmarks, and image noise were quantitatively measured; contrast-to-noise ratios (CNR) and signal-to-noise ratios (SNR) were calculated. Three independent blinded radiologists subjectively rated each image series using a 5-point grading scale.
  
  
  RESULTS
  CT dose index (CTDI) in the LD series was 66.46% lower compared to the SD settings (2.49 ± 0.55 mGy versus 7.42 ± 1.17 mGy). Attenuation of the pulmonary trunk showed similar results for both series (SD 409.55 ± 91.04 HU; LD 380.43 HU ± 93.11 HU;P= 0.768). Subjective image analysis showed no significant differences between SD and LD settings regarding the suitability for detection of central and peripheral PE (central SD/LD, 4.88; intra-class correlation coefficients [ICC], 0.894/4.83; ICC, 0.745; peripheral SD/LD, 4.70; ICC, 0.943/4.57; ICC, 0.919; allP> 0.4).
  
  
  CONCLUSIONS
  The LD protocol, on a 15-year-old CT scanner system without current high-end hardware or post-processing tools, led to a dose reduction of approximately 67% with similar subjective image quality and delineation of central and peripheral pulmonary arteries.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Kaup
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Gruber-Rouh
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Jan E
authors.initials: JE
authors.lastname: Scholtz
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Moritz H
authors.initials: MH
authors.lastname: Albrecht
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bucher
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Frellesen
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
authors.affiliation: Department of Diagnostic and Interventional Radiology, Clinic of the Goethe University, Frankfurt, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Beeres
keywords: Computed tomography pulmonary angiography (CTPA); low-dose imaging; CT pulmonary angiography; CT radiation exposure