title: Dual-time point FDG PET imaging in the evaluation of pulmonary nodules with minimally increased metabolic activity.
abstract: OBJECTIVE
  FDG PET has high accuracy in the evaluation of lung nodules. A standardized uptake value (SUV) > or =2.5 is frequently used as a criterion for malignancy in this setting. However, some malignant nodules have only mild FDG activity with a SUV less than 2.5. Assessment of the etiology of lung nodules with only mild metabolic activity remains difficult. This study was undertaken to compare the accuracy of dual-time point and standard single-time FDG PET imaging in the evaluation of such lung nodules.
  
  
  METHODS
  Four hundred fifty-seven dual-time FDG PET scans for lung nodules were retrospectively analyzed. Among them, 46 met the selection criteria and were included for the final analysis. Five methods of interpreting FDG PET results were compared. These methods included visual analysis for both initial and delayed images; SUV analysis for both initial and delayed images in which a SUV of 2.5 is regarded as criteria for malignancy; and finally, the retention index analysis in which a 10% increase in SUV on the delayed images was regarded as an indication of malignancy.
  
  
  RESULTS
  The lowest accuracies came from the visual and single SUV analysis on the initial images. The visual and single SUV analyses on the delayed images produced increased accuracy. The highest accuracy (84.8%) was obtained when a retention index of more than 10% was used as criteria for malignancy.
  
  
  CONCLUSIONS
  Dual-time FDG PET imaging has the potential for improving accuracy of a test in the evaluation of lung nodules with only borderline levels of increased metabolic activity.
authors.affiliation: Department of Radiology, University of Pennsylvania School of Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiu
authors.forename: Chirdeep
authors.initials: C
authors.lastname: Bhutani
authors.forename: Thiruvenkatasamy
authors.initials: T
authors.lastname: Dhurairaj
authors.forename: Jian Q
authors.initials: JQ
authors.lastname: Yu
authors.forename: Simin
authors.initials: S
authors.lastname: Dadparvar
authors.forename: Swapna
authors.initials: S
authors.lastname: Reddy
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: Abass
authors.initials: A
authors.lastname: Alavi
authors.forename: Hongming
authors.initials: H
authors.lastname: Zhuang
mesh_terms: D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011859:Radiography; D019275:Radiopharmaceuticals; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging* / Q000378:metabolism*; D013997:Time Factors
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18