title: Is there any additional benefit of contrast-enhanced CT as part of routine PET/CT protocols for the differentiation of suspicious incidental gastrointestinal 2-deoxy-(18)F-FDG uptake?
abstract: OBJECTIVE
  Suspicious incidental gastrointestinal FDG uptake during positron-emission tomography/computed tomography (PET/CT) examinations can be caused by different diseases, including malignancies. However, differentiation with PET alone is difficult. The aim of this study was to investigate the potential of PET alone, contrast-enhanced CT (ceCT), and low-dose CT (ldCT) in routine PET/CT protocols for differentiation of incidental gastrointestinal lesions.
  
  
  METHODS
  Sixty patients with incidental gastrointestinal lesions who underwent a routine PET/CT protocol with ldCT and ceCT were retrospectively analysed. The PET lesions were evaluated regarding their FDG uptake patterns and the standard uptake value. The anatomical correlates in both CT protocols were compared in regard to the correct lesion classification with the reference standard endoscopy.
  
  
  RESULTS
  Sixty-two lesions were found in 60 patients (17 malignant, 10 premalignant, 5 benign, 13 inflammatory, 17 physiological). The differentiation of the FDG uptake patterns did not enable reliable lesion classification. The positive predictive value for pathology was 0.81 for ceCT in PET/CT and 0.70 for ldCT. Malignancies were detected in 100% of the patients by ceCT vs. 29.4% by ldCT. The false negative rate of ceCT for all pathologies was 31.1%, vs. 68.9% for ldCT. False positive results (17/62) could not be excluded sufficiently by either CT protocol.
  
  
  CONCLUSIONS
  PET/ceCT protocols provide additional benefit especially in detecting gastrointestinal malignancies as a cause of suspicious incidental gastrointestinal FDG uptake. However, since follow-up endoscopy cannot be forgone due to the considerable false negative rate even with ceCT, the addition of ceCT to a routine PET/ldCT protocol cannot be recommended for this purpose.
authors.affiliation: Department of Radiology, Diagnostic and Interventional Radiology, University Hospital Tuebingen, Hoppe-Seyler-Straße 3, 72076 Tuebingen, Germany.
authors.forename: Cornelia Bettina
authors.initials: CB
authors.lastname: Brendle
authors.forename: Philip
authors.initials: P
authors.lastname: Aschoff
authors.forename: Thomas
authors.initials: T
authors.lastname: Kratt
authors.forename: Christina
authors.initials: C
authors.lastname: Schraml
authors.forename: Matthias
authors.initials: M
authors.lastname: Reimold
authors.forename: Claus Detlef
authors.initials: CD
authors.lastname: Claussen
authors.forename: Christina Anna
authors.initials: CA
authors.lastname: Pfannenberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000493:pharmacokinetics; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D005500:Follow-Up Studies; D005767:Gastrointestinal Diseases / Q000175:diagnosis* / Q000378:metabolism; D041981:Gastrointestinal Tract / Q000000981:diagnostic imaging / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D019788:Fluorodeoxyglucose F18
keywords: CT; Gastrointestinal lesions; Incidental FDG uptake; PET; PET/CT