title: Noise reduction to decrease radiation dose and improve conspicuity of hepatic lesions at contrast-enhanced 80-kV hepatic CT using projection space denoising.
abstract: OBJECTIVE
  The purpose of this study was to investigate the combined potential of 80-kV CT and noise reduction using a projection space denoising algorithm to reduce radiation dose reduction or to improve the image quality of hepatic CT.
  
  
  METHODS
  Twenty patients with 56 liver lesions underwent dual-energy (80 and 140 kV) contrast-enhanced hepatic CT. Low-dose 80-kV-only images (comprising 26-54% of the total radiation dose), low-dose 80-kV projection space denoising images (routine and sharper reconstruction kernel), and full-dose mixed-kilovoltage with projection space denoising images were evaluated by three radiologists for lesion conspicuity, image noise, and sharpness. Lesions were compared with full-dose images using 5-point scales (0 = no change, +2 = markedly better, and -2 = markedly worse). Quantitative conspicuity in the form of lesion-to-liver contrast-to-noise ratio (CNR), image noise, and image sharpness were measured.
  
  
  RESULTS
  For all readers, the mean conspicuity rating of low-dose 80-kV projection space denoising images was better than that for full-dose images (mean conspicuity, 0.36-0.57; p < 0.001), with only 1.2% of lesions less conspicuous on 80-kV projection space denoising images. Eighty-kilovolt projection space denoising images reconstructed with a sharper kernel were subjectively similar to full-dose mixed-kilovoltage images comparing image noise (-0.054 to 0.018; p < 0.001 to p = 0.058) and sharpness (-0.64 to -0.09; p < 0.001 to p = 0.057). For 80-kV projection space denoising images with a sharper kernel, lesion-to-liver CNR was slightly higher than that for full-dose mixed-kilovoltage images (p < 0.001), whereas image sharpness and noise were unchanged (p = 0.74 and p = 0.02).
  
  
  CONCLUSIONS
  Eighty-kilovolt imaging with noise reduction can simultaneously increase lesion conspicuity and facilitate radiation dose reduction and image quality improvement at contrast-enhanced hepatic CT.
authors.affiliation: Mayo Medical School, Rochester, MN, USA.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Ehman
authors.forename: Luís S
authors.initials: LS
authors.lastname: Guimarães
authors.forename: Jeff L
authors.initials: JL
authors.lastname: Fidler
authors.forename: Naoki
authors.initials: N
authors.lastname: Takahashi
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Ramirez-Giraldo
authors.forename: Lifeng
authors.initials: L
authors.lastname: Yu
authors.forename: Armando
authors.initials: A
authors.lastname: Manduca
authors.forename: James E
authors.initials: JE
authors.lastname: Huprich
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
authors.forename: David
authors.initials: D
authors.lastname: Holmes
authors.forename: W Scott
authors.initials: WS
authors.lastname: Harmsen
authors.forename: Joel G
authors.initials: JG
authors.lastname: Fletcher
mesh_terms: D000368:Aged; D000465:Algorithms; D003287:Contrast Media; D005260:Female; D006801:Humans; D008107:Liver Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media