title: CT patterns of fungal pulmonary infections of the lung: comparison of standard-dose and simulated low-dose CT.
abstract: OBJECTIVE
  To assess the effect of radiation dose reduction on the appearance and visual quantification of specific CT patterns of fungal infection in immuno-compromised patients.
  
  
  METHODS
  Raw data of thoracic CT scans (64 × 0.75 mm, 120 kVp, 300 reference mAs) from 41 consecutive patients with clinical suspicion of pulmonary fungal infection were collected. In 32 patients fungal infection could be proven (median age of 55.5 years, range 35-83). A total of 267 cuboids showing CT patterns of fungal infection and 27 cubes having no disease were reconstructed at the original and 6 simulated tube currents of 100, 40, 30, 20, 10, and 5 reference mAs. Eight specific fungal CT patterns were analyzed by three radiologists: 76 ground glass opacities, 42 ground glass nodules, 51 mixed, part solid, part ground glass nodules, 36 solid nodules, 5 lobulated nodules, 6 spiculated nodules, 14 cavitary nodules, and 37 foci of air-space disease. The standard of reference was a consensus subjective interpretation by experts whom were not readers in the study.
  
  
  RESULTS
  The mean sensitivity and standard deviation for detecting pathological cuboids/disease using standard dose CT was 0.91 ± 0.07. Decreasing dose did not affect sensitivity significantly until the lowest dose level of 5 mAs (0.87 ± 0.10, p=0.012). Nodular pattern discrimination was impaired below the dose level of 30 reference mAs: specificity for fungal 'mixed nodules' decreased significantly at 20, 10 and 5 reference mAs (p<0.05). At lower dose levels, classification drifted from 'solid' to 'mixed nodule', although no lesion was missed.
  
  
  CONCLUSIONS
  Our simulation data suggest that tube current levels can be reduced from 300 to 30 reference mAs without impairing the diagnostic information of specific CT patterns of pulmonary fungal infections.
authors.affiliation: Department of Radiology, Stanford University Medical Center, 300 Pasteur Drive, Stanford, CA 94305, USA. andreas.christe@insel.ch
authors.forename: Andreas
authors.initials: A
authors.lastname: Christe
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Lin
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Yen
authors.forename: Rich L
authors.initials: RL
authors.lastname: Hallett
authors.forename: Kingshuk
authors.initials: K
authors.lastname: Roychoudhury
authors.forename: Florian
authors.initials: F
authors.lastname: Schmitzberger
authors.forename: Dominik
authors.initials: D
authors.lastname: Fleischmann
authors.forename: Ann N
authors.initials: AN
authors.lastname: Leung
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Rubin
authors.forename: Geoffry D
authors.initials: GD
authors.lastname: Rubin
authors.forename: Peter
authors.initials: P
authors.lastname: Vock
authors.forename: Justus E
authors.initials: JE
authors.lastname: Roos
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001822:Body Burden; D005260:Female; D006801:Humans; D008172:Lung Diseases, Fungal / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D013902:Radiography, Thoracic / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*