title: Evaluation of delayed additional FDG PET imaging in patients with pancreatic tumour.
abstract: OBJECTIVE
  To evaluate whether delayed fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging is more helpful in differentiating between malignant and benign lesions and whether delayed FDG PET imaging can identify more lesions in patients in whom pancreatic cancer is suspected.
  
  
  METHODS
  The study evaluated 86 patients who were suspected of having pancreatic tumours. FDG PET imaging (whole body) was performed at 1 h (early) post-injection and repeated 2 h (delayed) after injection only in the abdominal region. Qualitative and semi-quantitative evaluation was performed. The semi-quantitative analysis was performed using the standardized uptake value (SUV), obtained from early and delayed images (SUVearly and SUVdelayed, respectively). Retention index (RI) was calculated according to the equation: (SUVdelayed-SUVearly)x100/SUVearly.
  
  
  RESULTS
  The final diagnosis was pancreatic cancer in 55 and benign disease in 31 patients. On visual and semi-quantitative analysis, the diagnostic accuracy of RI was the highest (88%). The differences between the SUVearly, SUVdelayed and RI value in both pancreatic cancer and benign disease were significant (P<0.01). The mean value of SUVdelayed was significantly higher than that of SUVearly (P<0.01) in pancreatic cancer. Furthermore, new foci of metastasis were seen in the liver in two patients and in the lymph node in one patient only on delayed images.
  
  
  CONCLUSIONS
  The RI values obtained using early and delayed FDG PET may help in evaluating pancreatic cancer. Furthermore, addition of delayed FDG PET imaging is helpful to identify more lesions in patients with pancreatic cancer.
authors.affiliation: Department of Radiology, Faculty of Medicine, Kagawa University, Japan. nisiyosi@kms.ac.jp
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Yuka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Toshihide
authors.initials: T
authors.lastname: Monden
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Sasakawa
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tsutsui
authors.forename: Hisao
authors.initials: H
authors.lastname: Wakabayashi
authors.forename: Motoomi
authors.initials: M
authors.lastname: Ohkawa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18