MR imaging of metastatic GI adenocarcinoma in brain.

PURPOSE To investigate an observed preferential T2-shortening effect seen in patients with intracerebral metastases from adenocarcinoma of the GI tract. METHODS Ten patients with intracerebral metastases from adenocarcinoma of the GI tract were evaluated with MR imaging with CT and histopathologic correlation. RESULTS Nine of 10 patients demonstrated intracranial masses with decreased signal intensity on T2-weighted images. T1-weighted images showed decreased or isointense signal in all cases. Special histologic staining was performed in four of 10 cases, all of which were positive for increased protein (mucin) with no evidence of blood products or calcium. CONCLUSION We propose that the observed preferential T2-shortening effect is secondary to slowing of rotational and translational proton motion caused by increased protein concentration in the form of mucin.