title: Impact of a 4th generation iterative reconstruction technique on image quality in low-dose computed tomography of the chest in immunocompromised patients.
abstract: OBJECTIVE
  To determine the image quality of an iterative reconstruction (IR) technique in low-dose MDCT (LDCT) of the chest of immunocompromised patients in an intraindividual comparison to filtered back projection (FBP) and to evaluate the dose reduction capability.
  
  
  METHODS
  30 chest LDCT scans were performed in immunocompromised patients (Brilliance iCT; 20-40 mAs; mean CTDIvol: 1.7 mGy). The raw data were reconstructed using FBP and the IR technique (iDose4™, Philips, Best, The Netherlands) set to seven iteration levels. 30 routine-dose MDCT (RDCT) reconstructed with FBP served as controls (mean exposure: 116 mAs; mean CDTIvol: 7.6 mGy). Three blinded radiologists scored subjective image quality and lesion conspicuity. Quantitative parameters including CT attenuation and objective image noise (OIN) were determined.
  
  
  RESULTS
  In LDCT high iDose4™ levels lead to a significant decrease in OIN (FBP vs. iDose7: subscapular muscle 139.4 vs. 40.6 HU). The high iDose4™ levels provided significant improvements in image quality and artifact and noise reduction compared to LDCT FBP images. The conspicuity of subtle lesions was limited in LDCT FBP images. It significantly improved with high iDose4™ levels (> iDose4). LDCT with iDose4™ level 6 was determined to be of equivalent image quality as RDCT with FBP.
  
  
  CONCLUSIONS
  iDose4™ substantially improves image quality and lesion conspicuity and reduces noise in low-dose chest CT. Compared to RDCT, high iDose4™ levels provide equivalent image quality in LDCT, hence suggesting a potential dose reduction of almost 80%.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. a.laqmani@uke.de
authors.forename: A
authors.initials: A
authors.lastname: Laqmani
authors.forename: J H
authors.initials: JH
authors.lastname: Buhk
authors.forename: F O
authors.initials: FO
authors.lastname: Henes
authors.forename: T
authors.initials: T
authors.lastname: Klink
authors.forename: S
authors.initials: S
authors.lastname: Sehner
authors.forename: H C
authors.initials: HC
authors.lastname: von Schultzendorff
authors.forename: D
authors.initials: D
authors.lastname: Hammerle
authors.forename: H D
authors.initials: HD
authors.lastname: Nagel
authors.forename: G
authors.initials: G
authors.lastname: Adam
authors.forename: M
authors.initials: M
authors.lastname: Regier
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000886:Anthropometry; D016477:Artifacts; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods* / Q000592:standards; D007091:Image Processing, Computer-Assisted / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D015588:Observer Variation; D009894:Opportunistic Infections / Q000000981:diagnostic imaging*; D011014:Pneumonia / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D055815:Young Adult