【正文】 On the left a craniopharyngioma with an enhancing rim surrounding the cystic ponent. In the middle a neuroenteric cyst with the contents of which have the same signal intensity as CSF. On the right a glioblastoma multiforme (GBM) with a central cystic ponent. The enhancement in GBM is usually more irregular. Most tumors have a low or intermediate signal intensity on T1WI. Exceptions to this rule can indicate a specific type of tumor. Calcifications are mostly dark on T1WI, but depending on the matrix of the calcifications they can sometimes be bright on T1. Especially on gradient echo images slow flow can be seen as bright signal on T1WI and should not be confused with enhancement. If you only do an enhanced scan, remember that high signal is not always enhancement. High on T1 Some tumors with high signal intensities on T1WI. On the far left images of a patient who presented with apoplexy. The high signal is due to hemorrhage in a pituitary macroadenoma. The patient in the middle has a glioblastoma multiforme, which caused a hemorrhage in the splenium of the corpus callosum. On the right is a patient with a metastasis of a melanoma. The high signal intensity is due to the melanin content. Most tumors will be bright on T2WI due to a high water content. When tumors have a low water content they are very dense and hypercellular and the cells have a high nuclearcytoplasmasmic tumors will be dark on T2WI. The classic examples are CNS lymphoma and PNET (also hyperdense on CT). Calcifications are mostly dark on T2WI. Paramagic effects cause a signal drop and are seen in tumors that contain hemosiderin. Proteinaceous material can be dark on T2 depending on the content of the protein itself. A classic example of this is the colloid cyst. Flow voids are also dark on T2 and indicate the presence of vessels or flow within a lesion. This is seen in tumors that contain a lot of vessels like hemangioblastomas, but also in nontumorous lesions like vascular malformations. Low on T2 Melanoma with melanin. GBM sometimes with a high nuclearcytoplasmic ratio. Most GBM39。Brain Tumor Systematic Approach by Robin Smithuis and Walter Montanera 河南省人民醫(yī)院放射科 高明 譯講 Introduction Incidence of CNS tumors Age distribution Tumor spread Intra versus Extraaxial Midline crossing Multifocal disease Cortical based tumors CT and MR Characteristics Fat Calcification Cyst High on T1 Low on T2 Diffusion weighted imaging Perfusion Imaging Enhancement Differential diagnosis for specific anatomic area Skull base Sella/suprasellar Cerebellopontine angle Pineal region Intraventricular 4th ventricle Tumor Mimics Schwannoma located in the cerebellopontine angle (CPA) with typical signs of an extraaxial tumor Meningioma with a broad dural base and a dural tail ， hyperostosis in the adjacent bone ， enhances homogeneously ， no bloodbrainbarrier Melanoma metastasis with gray matter on the anteromedial side of the lesion (red arrow) ， intraaxial. Ependymoma with extension to the cerebellopontine angle (blue arrow) and into the foramen magnum (red arrow) or to the cisterna magna To assess the extent of a tumor. An extraaxial tumor in the region of the left cavernous sinus with homogeneous enhancement and a broad dural tail. This is typical for a meningioma. Actual extent of this tumor is greater than expected. The tumor is situated in the pterygopalatine fossa and extends into the orbit. It also spreads anteriorly into the middle cranial fossa. Consideration for the effect on the surrounding structures . Primary