Magnetic resonance imaging of brain metastases of cholangiocarcinoma. (a) Multiple metastases of the cholangiocarcinoma were observed before radiotherapy in a T1 multiplanar reconstruction of magnetic resonance imaging sequences after intravenous injection of a gadolinium chelated contrast agent. Rounded lesions are present in the left frontal lobe and right cerebellum. The lesions show peripheral enhancement and are moderately thick and irregular. The lesion center is hypointense or nonenhancing (thick arrows). A perilesional hyposignal corresponding to perilesional edema (thin arrow) is also present. (b) Evolution of brain metastases 2 months after the end of radiotherapy, followed by chemotherapy. The lesion volume is reduced, but no changes are apparent in the enhancement features or in the perilesional edema.