Pancreatic tumors: role of imaging in the diagnosis, staging, and treatment.

Because most patients with pancreatic cancer present with biliary obstruction, percutaneous transhepatic cholangiopancreatography (PTC) or endoscopic retrograde cholangiopancreatography (ERCP) is often performed first to relieve obstruction. Fine needle biopsy (FNA) provides a tissue diagnosis, but is often nondiagnostic due to sampling error. Computed tomography (CT) is the workhorse of oncology, but is poor at defining the nature of pancreatic lesions. Small primary tumors are often not visualized. Fast magnetic resonance imaging (MRI) techniques allowing dynamic imaging after IV gadolinium and new contrast agents allow better characterization of the lesions for patients having contraindications for IV CT contrast agents. Magnetic resonance cholangiopancreatography (MRCP) allows noninvasive visualization of the biliary tree. Endoscopic ultrasonography (EUS) allows evaluation of the detailed regional anatomy with the possibility of FNA. 18F-Fluorodeoxyglucose (FDG) is the most common tracer used in positron emission tomography (PET), and most malignant tumors, including pancreatic carcinoma, have increased FDG uptake compared with normal cells. This functional imaging does not replace but is complementary to morphological imaging. FDG PET is particularly helpful: (1) for the diagnosis in patients with suspected pancreatic cancer in whom CT fails to identify a mass, or those in whom FNAs are nondiagnostic; (2) for staging by detecting CT-occult metastases; (3) for detecting recurrence; and (4) for monitoring therapy. Limitations include false-positive inflammatory processes and false-negative carcinoma in patients with diabetes and hyperglycemia, and islet cell tumors.