The best way to look at tumors or other abnormalities of the pituitary gland and nearby area is magnetic resonance imaging (MRI). An MRI scan gives a much better image of the gland and surrounding structures than other types of scans.
A specialized pituitary MRI is critical to an evaluation of a patient's condition. The pituitary gland is small and some tumors and growths and brain structures within and around it are even smaller.
A pituitary gland MRI is different than a regular MRI of the brain. It creates high resolution images that allow doctors to see the pituitary region better. It needs to be ordered specially by the doctor.A closed MRI is preferred over an open MRI because the resolution is better. Most commercial MRI scanners have a strength of 1.5 Tesla. Newer, 3.0 Tesla scanners create even better images.
When a pituitary MRI is done, scans are made, then a contrast dye is injected. A second set of scans are then made. The dye (usually gadolinium) makes it easier to tell the difference between normal pituitary gland tissue and tumors, infection or other abnormalities.
Unlike the iodine-based contrast dyes used in other tests, even a person allergic to iodine or shellfish can take gadolinium.
A normal pituitary gland will usually look very white on a MRI after the dye has been used. The tumors will appear darker. This pattern is different than it is for other tumors. It is important to have a radiologist who specializes in reviewing pituitary MRIs to interpret the scans.
When a very small tumor is being searched for, a dynamic MRI will sometimes be done. In this type of imaging, a series of MRI images are taken quickly over several minutes after the gadolinium has been injected. This type of scan is based on the idea that pituitary tumors and normal gland tissue absorb the dye at different speeds. The contrast between the normal tissue and tumor may be easier to see in the earlier images when compared to the later ones.
Dynamic MRIs may be especially important when a small tumor of the type that causes acromegaly or Cushing's disease is suspected.