Magnetic susceptibility artifact in spin-echo MR imaging of the pituitary gland.

PURPOSE To evaluate the magnetic susceptibility effect on spin-echo MR images of the pituitary gland. METHODS Air-in-water phantom experiments and studies in normal volunteers were performed using various sampling bandwidth (8.3-33.3 kHz) spin-echo sequences with the polarity of the readout gradient normal or reversed. RESULTS Attachment of a sphenoid septum to the sellar floor was the major factor in the appearance of the inferior surface of the pituitary gland. Patterns of distortion and/or artifactual signal intensities, related to the presence or absence of the attachment, were accentuated on the images with narrower bandwidth. A "spearhead shape" deformity of the sphenoid sinus was observed both in the air-in-water phantom experiment, and when no sphenoid septum was present. When a sphenoid septum was present, two spearhead shapes side by side were present. High-intensity artifacts were seen where the sellar floor was misplaced into the pituitary gland. CONCLUSION Knowledge of the patterns of distortion and high-intensity artifact is important in the diagnosis of pituitary lesions.