Magnetic resonance imaging of brain tumors.

Since MR is a new imaging modality, a major question to answer is, "What is the role of MRI in relation to older, more traditional diagnostic techniques?" Several studies comparing CT and MRI for brain evaluation have shown MRI to be more sensitive, although not more specific. The advantages of MRI center around its ability to reveal abnormalities that may not be detectable or only poorly seen on CT. In cases in which only a nonspecific mass effect may be depicted on CT, the MR may define the precise extent and location of a tumor. Furthermore, MRI with its increased contrast discrimination and its ability to obtain images in many planes can better define the precise location of a lesion relative to key neuroanatomic structures. This is extremely important for optimal surgical and radiotherapy planning. The disadvantages of MRI include the fact that small calcifications cannot be seen and one cannot yet evaluate the presence of an altered blood-brain barrier. Despite these disadvantages, we feel that MRI should be the primary study for diagnosis of brain abnormalities. When an abnormality is detected and further information is desired, a complementary CT study should be performed in order to evaluate areas of blood-brain barrier alteration and the presence of abnormal calcification.