Insulinoma: correlation of short-TI inversion-recovery (STIR) imaging and histopathologic findings

We studied the value of short-TI inversion-recovery (STIR) imaging for the localization of pancreatic insulinoma. Four patients (three women and one man aged 35-65 years) with surgically proven insulinoma were included in this study. All patients were examined by MR imaging with spin echo (SE) and STIR sequences. The STIR images were compared with the histopathologic findings in each case. In two patients, the tumors were markedly hyperintense on STIR images, and a 5-mm insulinoma was depicted only by this imaging method in one of the two. In the other two patients, 10-mm insulinomas were only slightly hyperintense on STIR images. The latter tumors had a higher content of collagen fibers than the former, indicating that the amount of collagen influences the signal intensity of insulinoma. Despite some limitations, STIR imaging is a useful noninvasive method for the localization of pancreatic insulinoma.