In the article we present pathological intracranial substances and lesions, which produce high signal intensity on T1-weighted MR images. Six groups of substances are discussed: 1. Gadolinium - based contrast agents, 2.hemoglobin degradation products (intra- and extra-cellular methemoglobin), 3. lipid-containing lesions (lipoma, dermoid cyst, implanted fatty materials, laminar cortical necrosis), 4. substances with high concentration of proteins (colloid cyst, craniopharyngioma, Rathke's cleft cyst, ectopic posterior pituitary gland), 5. melanin (metastatic melanoma), 6. lesions containing mineral substances such as: calcium (calcifications, Fahr's disease), copper (Wilson's disease) and manganese (hepatic encephalopathy, manganese intoxication in intravenous drug abusers). Appropriate interpretation of signal intensity as well as analysis of location of lesions and clinical symptoms enables planning of further diagnostics and, in many cases, establishing the final diagnosis based on MR examination.
Keywords: MRI; T1-weighted pictures; hyperintense.