Usefulness of PET/CT for the differentiation and characterization of periampullary lesions.

Purpose: At present, there is no ideal imaging modality for the diagnosis of periampullary lesions. We prospectively evaluated the preoperative diagnostic usefulness of PET/CT for differentiating malignant from benign periampullary lesions. Methods: A total of 62 patients aged 27-86 years with periampullary lesions scheduled for surgical resection were consecutively recruited. Dual-phase F-18-FDG PET/CT was performed in all patients. An additional 3'-deoxy-3'-[F-18]fluorothymidine (FLT) scan was performed in 21 patients (33.9%). The relationship of visual interpretation, SUV, and lesion to background ratio (LBR) with surgical histopathology diagnosis was evaluated. Results: There were 36 patients with malignancies, 15 with benign neoplasms, and 11 with benign non-neoplasms. Using visual analysis, FDG PET/CT had good sensitivity (86.1%; 31/36), lower specificity (57.7%; 15/26), and fair accuracy (74.2%; 46/62). Regional lymph node metastases were identified in 7 of 11 patients by FDG PET/CT and only in 1 patient by abdominal CT. On the other hand, hepatic metastasis was detected in 1 patient by FDG PET/CT. Dual-phase FDG (P < 0.001) and FLT (P < 0.05) SUVmax and LBR were significantly higher in malignant than in benign lesions, and in malignant neoplasms than in benign neoplasms. Although average FLT SUVmax was significantly lower than the average FDG SUVmax (P < 0.001), the specificity and accuracy of the former were significantly better. Conclusion: FDG PET/CT may help identify patients with periampullary malignancy. FDG SUVmax and LBR appear to aid in the differential diagnosis and add diagnostic confidence. In addition, higher specificity and diagnostic accuracy may be achieved by additional FLT PET/CT.