Magnetic resonance can image the brain in coronal, axial or sagittal planes. Different sequences are used to demonstrate and characterise lesions.
This has now taken over from computed tomography in several areas
Sequences are chosen for each patient but in general, images are obtained in coronal an sagittal planes, in T1 and T2 sequences. They may need to be repeated following injection of Gadolinium
Glioma is the commonest primary tumour and on computed tomography shows as a dark area (low attenuation) usually in the
white matter. It causes mass effect and is usually heterogenous. There is surrounding oedema showing as a darker area around it. The tumour enhances (appears brighter) to some extent after intravenous contrast. This tumour may contain calcifications which appear very bright on scanning (similar attenuation to the skull vault).
On magnetic resonance it appears dark on T1 and bright on T2..
Metastases: may be single or multiple. If single it is not possible to differentiate from a primary lesion. They commonly present in cases of carcinoma of the breast or bronchus. They show ring enhancement and are often much smaller than the size of the abnormality suggests because of surrounding oedema. They may also appear haemorrhagic or cystic.