Dynamic MRI has been used to improve the detection of tumors and to make differential diagnosis. Most malignant lesions show early enhancement and early washout of contrast media on dynamic MRI, but the characterization of the tumor remains unclear. Pharmacokinetic analysis of dynamic MRI can provide information about the permeability of contrast media in the tumor that may reflect the oxygen concentration of the tumor. This information may be useful in the prediction of a tumor's response to radiation therapy.