What is the role of imaging studies in the diagnosis of pituitary macroadenomas?

Updated: Mar 23, 2018
  • Author: James R Mulinda, MD, FACP; Chief Editor: George T Griffing, MD  more...
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Answer

Pituitary imaging is important in confirming the diagnosis of pituitary macroadenoma and also for determining the differential diagnoses of other sellar lesions. Plain skull radiographs are poor at delineating soft tissues and so have been replaced by CT scanning and MRI.

CT scanning is better at depicting bony structures and calcifications within soft tissues than either plain radiography or MRI. Differential diagnoses of tumors with calcification, such as germinomas, craniopharyngiomas, and meningiomas, are better determined with CT scanning. CT scans are valuable when MRI is contraindicated, such as in patients with pacemakers or metallic implants in the brain or eyes. Drawbacks include less optimal soft tissue imaging compared to MRI, use of intravenous contrast media that is needed to enhance images, and exposure to radiation. This makes MRI the modality of choice for pituitary imaging.

MRI is more expensive than CT scans but is the preferred imaging study for the pituitary because it provides better visualization of soft tissues and vascular structures. No exposure to ionizing radiation occurs. Images are generated based upon the magnetic properties of the hydrogen atoms. With spin-echo, T1-weighted images, fat produces high–signal intensity images. Structures such as fatty marrow and orbital fat show up as bright images. T2-weighted images of structures with high water content, such as cerebrospinal fluid and cystic lesions, produce high-intensity signals, while structures with high fat content present with low-intensity signals. At least a 1.5-T magnet should be used for MRI of the pituitary. [3, 4]


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