Lung nodules: Dual-kilovolt peak analysis with CT - Multicenter study

PURPOSE: To test the following hypothesis: The greater the increase in the mean computed tomographic (CT) number of a radiologically indeterminate lun g nodule from the CT number on a 140-kVp CT image to that on an 80-kVp CT i mage, the more likely the nodule is benign (ie, contains calcium). MATERIALS AND METHODS: Two hundred forty indeterminate lung nodules were pr ospectively studied at four institutions: Mayo Clinic Scottsdale, Ariz (n = 160); Mayo Clinic Rochester, Minn (n = 50); Shiga Health insurance Hospita l, 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, relativ ely spherical, homogeneous, and without visible evidence of calcification o r 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 med ian increase in the nodule mean CT number from the CT number on 140-kVp ima ges to that on 80-kVp images was 2 HU for benign nodules and 3 HU for malig nant nodules. This difference was not statistically significant. The area u nder the receiver operating characteristic curve was 0.505. CONCLUSION: Dual-kilovolt peak analysis with current CT technology does not appear to be helpful in the identification of benign lung nodules.