High signal on T1-weighted MR images of the head: A pictorial essay

T1-weighted magnetic resonance images (T1WI) of the head may manifest high signal in many normal and pathologic situations. Normally, it may be seen i n fatty tissues, certain artifacts, and in areas without a blood-brain barr ier after gadolinium administration. It is also seen in the posterior pitui tary gland and in certain instances in the anterior pituitary gland. Pathol ogically, it may occur in many lesions after gadolinium. enhancement, in fa tty and cystic lesions, and in lesions with paramagnetic content. Occasiona lly, it may be seen in calcium deposition. Many of these are described and illustrated. (C) 2001 Elsevier Science Inc. All rights reserved.