title: Lung nodules: dual-kilovolt peak analysis with CT--multicenter study.
abstract: OBJECTIVE
  To test the following hypothesis: The greater the increase in the mean computed tomographic (CT) number of a radiologically indeterminate lung nodule from the CT number on a 140-kVp CT image to that on an 80-kVp CT image, the more likely the nodule is benign (ie, contains calcium).
  
  
  METHODS
  Two hundred forty indeterminate lung nodules were prospectively studied at four institutions: Mayo Clinic Scottsdale, Ariz (n = 160); Mayo Clinic Rochester, Minn (n = 50); Shiga Health Insurance Hospital, Otsu, Japan (n = 25); and Duke University Medical Center, Durham, NC (n = 5). Of the 240 nodules, 157 met the entrance criteria for this study and had a diagnosis. All nodules included were solid, 5-40-mm diameter, relatively spherical, homogeneous, and without visible evidence of calcification or fat. Each nodule was evaluated by using 3-mm-collimation, nonenhanced CT scans with both 140- and 80-kVp x-ray beams.
  
  
  RESULTS
  There were 86 (55%) benign and 71 (45%) malignant nodules. The median increase in the nodule mean CT number from the CT number on 140-kVp images to that on 80-kVp images was 2 HU for benign nodules and 3 HU for malignant nodules. This difference was not statistically significant. The area under the receiver operating characteristic curve was 0.505.
  
  
  CONCLUSIONS
  Dual-kilovolt peak analysis with current CT technology does not appear to be helpful in the identification of benign lung nodules.
authors.affiliation: Department of Diagnostic Radiology, Mayo Clinic, Rochester, MN 55905, USA. swensen.stephen@mayo.edu
authors.forename: S J
authors.initials: SJ
authors.lastname: Swensen
authors.forename: K
authors.initials: K
authors.lastname: Yamashita
authors.forename: C H
authors.initials: CH
authors.lastname: McCollough
authors.forename: R W
authors.initials: RW
authors.lastname: Viggiano
authors.forename: D E
authors.initials: DE
authors.lastname: Midthun
authors.forename: E F
authors.initials: EF
authors.lastname: Patz
authors.forename: J R
authors.initials: JR
authors.lastname: Muhm
authors.forename: A L
authors.initials: AL
authors.lastname: Weaver
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002114:Calcinosis / Q000000981:diagnostic imaging; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011856:Radiographic Image Enhancement; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed