title: Virtual monoenergetic dual-energy computed tomography: optimization of kiloelectron volt settings in head and neck cancer.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effects on objective and subjective image quality of virtual monoenergetic reconstructions at various energy levels of dual-energy computed tomography (DECT) in patients with head and neck cancer.
  
  
  METHODS
  We included 71 (53 men, 18 women; age, 59.3 ± 12.0 years; range, 33-90 years) patients with biopsy-proven untreated primary (n = 55) or recurrent (n = 16) squamous cell carcinoma who underwent head and neck DECT. Images were reconstructed with a linear blending setting emulating 120 kV acquisition (M_0.3; 30% of 80 kV, 70% of 140 kV spectrum) and as virtual monoenergetic images with photon energies of 40, 60, 80, and 100 keV. Attenuation of lesion, various anatomic landmarks, and image noise were objectively measured, and lesion contrast-to-noise ratio (CNR) was calculated. Two independent blinded radiologists subjectively rated each image series using a 5-point grading scale regarding overall image quality, lesion delineation, image sharpness, and image noise.
  
  
  RESULTS
  Tumor attenuation peaked at 40 keV (140.2 ± 42.6 HU) followed by the 60 keV (121.7 ± 25.5 HU) and M_0.3 series (102.7 ± 22.3; all P < 0.001). However, the calculated lesion CNR was highest in the 60 keV reconstructions (12.45 ± 7.17), 80 keV reconstructions (8.66 ± 6.58), and M_0.3 series (5.21 ± 3.15; all P < 0.001) and superior to the other monoenergetic series (all P < 0.001). Subjective image analysis was highest for the 60 keV series regarding overall image quality (4.22; κ = 0.411) and lesion delineation (4.35; κ = 0.459) followed by the M_0.3 series (3.81; κ = 0.394; 3.77; κ = 0.451; all P < 0.001). Image sharpness showed no significant difference between both series (3.81 vs 3.79; P = 0.78). Image noise was rated superior in the 80 and 100 keV series (4.31 vs 4.34; P = 0.522).
  
  
  CONCLUSIONS
  Compared with linearly blended images, virtual monoenergetic reconstructions of DECT data at 60 keV significantly improve lesion enhancement and CNR, subjective overall image quality, and tumor delineation of head and neck squamous cell carcinoma.
authors.affiliation: From the Departments of *Diagnostic and Interventional Radiology and †Otolaryngology, Head and Neck Surgery, University Hospital Frankfurt, Frankfurt, Germany.
authors.forename: Julian L
authors.initials: JL
authors.lastname: Wichmann
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Nöske
authors.forename: Johannes
authors.initials: J
authors.lastname: Kraft
authors.forename: Iris
authors.initials: I
authors.lastname: Burck
authors.forename: Jens
authors.initials: J
authors.lastname: Wagenblast
authors.forename: Anne
authors.initials: A
authors.lastname: Eckardt
authors.forename: Claudia
authors.initials: C
authors.lastname: Frellesen
authors.forename: J Matthias
authors.initials: JM
authors.lastname: Kerl
authors.forename: Ralf W
authors.initials: RW
authors.lastname: Bauer
authors.forename: Boris
authors.initials: B
authors.lastname: Bodelle
authors.forename: Thomas
authors.initials: T
authors.lastname: Lehnert
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
authors.forename: Boris
authors.initials: B
authors.lastname: Schulz
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging*; D003287:Contrast Media; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007479:Iopamidol; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014584:User-Computer Interface
chemical_list: D003287:Contrast Media; D007479:Iopamidol