Diffusion-weighted MRI in the characterization of cystic pancreatic lesions: usefulness of ADC values.

PURPOSE: To evaluate the usefulness of diffusion-weighted magnetic resonance imaging (DW-MRI) in the differentiation of cystic pancreatic lesions. MATERIALS AND METHODS: Institutional review board approval was obtained, and written informed consent was taken from all enrolled subjects. Fifty-four patients with cystic pancreatic lesions of at least 1 cm in diameter (range:10-96 mm) at ultrasonography and/or computed tomography and 10 normal subjects underwent MRI at 1.5 T. These subjects included thirty-four patients with intraductal papillary mucinous tumors (IPMTs), 10 with pseudocysts, 5 with serous cystoadenoma and 5 with mucinous cystoadenoma. The MR protocol included axial T1w and T2w sequences and coronal MR cholangiopancreatography images. DW-MRI was performed using a breath-hold single-shot echo-planar sequence with a b gradient factor value of 500 s/mm(2) in the three orthogonal axes. Apparent diffusion coefficient (ADC) was calculated for cerebrospinal fluid, normal pancreatic parenchyma, and for each focal pancreatic lesion. Imaging results were correlated with endoscopic retrograde cholangiopancreatography, endoscopic ultrasound-guided fine needle aspiration, surgery and/or imaging follow-up. RESULTS: Mean ADC value was 4.1×10(-3) mm(2)/s for cerebrospinal fluid, 1.73×10(-3) mm(2)/s for normal pancreatic parenchyma, 4.09×10(-3) mm(2)/s for IPMT, 3.89×10(-3) mm(2)/s for mucinous cystoadenoma, 3.65×10(-3) mm(2)/s for serous cystoadenoma and 2.83×10(-3) mm(2)/s for pseudocyst. Mean ADC values of each of the different types of pancreatic lesions were statistically different (P<.05). CONCLUSION: DW-MRI may be helpful in the differential diagnosis of cystic pancreatic lesions.