18F-FDG PET/CT is a highly useful method for characterizing suspicious pancreatic cystic lesions particularly in patients who have inconclusive findings after undergoing multidetector row CT and/or MRI exams according to a study from Finland published online in the Journal of Nuclear Medicine. The imaging capabilities of CT and MRI are enabling radiologists to identify a dramatically increasing number of incidental cystic findings in the pancreas. In fact, one 2011 study determined that incidentally found pancreatic cysts were found in 45% of abdominal MRI examinations.1 However, preoperative diagnoses are difficult, and surgical resections are associated with high risks of co-morbidities.
The study’s lead author, Saila Kauhanen, M.D., of the Turku University Hospital’s Division of Digestive Surgery and Urology, and colleagues conducted a study to evaluate which imaging technique is best suited for the assessment of a pancreatic cystic lesion and to assess the impact of 18F-FDG PET/CT on the clinical management of patients identified as having pancreatic cysts. They hypothesized that 18F-FDG PET combined with contrast-enhanced CT is a more accurate imaging method than contrast-enhanced CT or MRI alone. Their study compared the results of conventional imaging methods with those of 18F-FDG PET/CT in a series of 31 consecutive patients with a pancreatic cystic lesion.
Each patient had undergone a CT, MRI, and contrast-enhanced 18F-FDG PET/CT within a six week period between June 2011 and November 2013. Of the 31 patients, six had malignant lesions; the remainder were benign. Surgical resection was performed for all main duct type intraductal papillary mucinous neoplasia and for branch-duct type lesions greater than 3 cm at follow-up, symptomatic, septal thickening, or with mural nodules at imaging. Diagnosis was based on histopathology and operative findings.
After analysis, the accuracy of contrast-enhanced 18F-FDG PET/CT was 94%, compared to 87% for MRI and 77% for CT. PET/CT had a sensitivity of 100% and a positive predictive value (PPV) of 75% in the differential diagnosis of malignant and benign pancreatic cystic lesions. The authors noted that its major limitations are false-negative results for borderline and in-situ tumors, and false positive uptakes in areas of lesion-associated pancreatitis. However, they recommend its use in the evaluation of diagnostically challenging pancreatic cysts.
Pancreatic cyst diagnosis: PET/CT outperforms CT and MRI. Appl Radiol.