Mucin-producing tumor of the pancreas: Diagnostic value of diffusion-weighted echo-planar MR imaging

PURPOSE: To determine whether diffusion-weighted echo-planar magnetic resonance (MR) imaging can help differentiate mucin-producing tumors of the pancreas from other cystic lesions. MATERIALS AND METHODS: Diffusion-weighted echo-planar 1.5-T MR imaging was performed in patients with mucin-producing tumor (n = 15), pseudocyst (n = 15), or serous microcystic tumor (n = 2). Images were obtained with diffusion-sensitizing gradients of 30 and 300 sec/mm(2). the apparent diffusion coefficient (ADC) was calculated. RESULTS: At 30 sec/mm(2), all cystic lesions had very high signal intensity. The dilated main pancreatic duct was depicted in eight patients with mucin-producing tumor and in six with pseudocyst. The mean (+/- standard deviation) ADCs of mucin-producing tumor (2.7 x 10(-3) mm(2)/sec +/- x 10(-3)) and pseudocysts (3.2 x 10(-3) mm(2)/sec +/- 1.0 x 10(-3)) were significantly lower (P < .01) than those of serous cysts of cerebrospinal fluid (5.8 x 10(-3) mm(2)/sec +/- 2.0 x 10(-3)). At 300 sec/mm(2), cysts and the main pancreatic ducts had high signal intensity in cases of mucin-producing tumor, indicative of the presence of mucinous products in both the cystic cavity and the main pancreatic duct. The signal intensity of cystic fluid in pseudocysts was high on diffusion-weighted images, but that of the pancreatic duct was decreased (ADC = 5.1 x 10(-3) mm(2)/sec +/- 1.7 x 10(-3)). CONCLUSION: Diffusion-weighted MR imaging can help characterize cystic lesions of the pancreas. Findings suggestive of viscous fluid in mucin-producing tumors are present on such images.