Pancreatic adenocarcinoma: MRI conspicuity and pathologic correlations.

Abstract

To identify the MRI sequences producing the greatest pancreatic adenocarcinoma conspicuity and to assess correlations linking MRI signal intensity and apparent diffusion coefficient to histopathological findings. We retrospectively included 22 patients with pancreatic adenocarcinoma who underwent MRI (1.5 or 3T) before surgical resection. Fat-suppressed (FS) T1- and T2-weighted sequences; 3D FS dynamic T1-weighted gadolinium-enhanced gradient-echo (GRE) imaging at the arterial, portal, and delayed phases; and diffusion-weighted imaging (DWI) with b values of 600-800s/mm(2) were reviewed. On each sequence, we assessed tumor conspicuity both qualitatively (3-point scale) and quantitatively (tumor-to-proximal and -distal pancreas contrast ratios), and we performed paired Wilcoxon tests to compare these data across sequences. We evaluated correlations between histopathological characteristics and MRI features. 21/22 (95%) tumors were hypointense by 3D FS T1 GRE arterial phase imaging, which produced the greatest tumor conspicuity (p≤0.02). By DWI, 5/20 (25%) of tumors were isointense. The correlation between size by histology and MRI was strongest with DWI. A progressive enhancement pattern was associated with extensive and dense fibrous stroma (p≤0.03). 3D FS T1 GRE arterial phase imaging produces greater pancreatic adenocarcinoma conspicuity compared to DWI but underestimates tumor size. DWI provides the best size evaluation but fails to delineate the tumor in one-fourth of cases.