Tuesday, April 7, 2015

Pituitary MRI -Review

I was PM'd today on Facebook by someone asking questions about the MRI's.  So, I figured I'd revisit some pituitary MRI info in today's post since I've pretty much already typed it all up!

Pituitary MRI's (Magnetic Resonance Imaging) for Cushing's Disease are almost universally ordered as 3T Dynamic MRI's now.  They are basically super-finely sliced pictures of your pituitary (and brain, etc), quite different from a standard brain MRI.  The 3T is the strength of the MRI machine (It's magnet -3 Teslas).  Dynamic refers to the protocol's contrast dye timing.  They will do the full MRI scan, then inject dye through an IV and scan AS it is going into your body, then a bit more after the dye is fully injected.  This is usually accomplished by either an infusion machine that can be triggered or set to inject while the technician starts the MRI scan, or it can be done with a second technician helping briefly and a countdown between the person pushing the injection and the person starting the MRI scan to be sure they time it just right.     

As these are often tiny tumors, roughly half the size of a pencil eraser, and usually only visible (or more obvious) during the dynamic portion of the scan, when the dye is being absorbed by the pituitary tissues, reading these MRI's is usually more of an art than a science.  The tumor tissues do absorb the dye,  they just don't absorb the dye as quickly as the rest of the pituitary.  So, if the MRI tech injects the medication, walks to the other room, sits down, then starts the scan, it might never show a tumor even if one is present.  It takes someone with a lot of pituitary-specific experience to be able to see them.  Most radiologists miss these tiny slightly-darker dots, but some well-Cushing's-experienced Endocrinologists and Neurosurgeons can see them readily.   

The longest part is the beginning, before the dye is injected.  It takes maybe 45-60 minutes, depending.  It is a good idea to get yourself as comfortable as possible before you start (back/leg support if needed) because you won't be able to move for a decent amount of time.  Make sure you also get copies of your MRI disc for your records and if you are traveling to the neurosurgeon of your choice, they'll want a copy for their records too. 

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