Saturday, September 18, 2010

Because I do things like this ...

I have been practicing what it is like to be in an MRI machine by laying on the couch with pillows around my upper body and pillows only six inches above my face. Although I looked up the specs on the type of MRI they have at Polyclinic and it's "bore" is two feet, so I'll have at least a foot above my face, which is quite a bit actually.

My husband just left with our daughter to go ride bikes around Greenlake and said he's hoping I'll come back with super powers. Alas, there are no gamma rays involved. Last night when I said I just needed to remember I was not going to get stuck and the machine would not collapse in on me he said, "Yes, but if it sucked you in and you became a giant, super-magnet robot I would still love you - in fact I might love you even more!" To which I reminded him, "This is why my mother is going with me and not you."

So, the first MRI was done in 1977, which seems like a long time ago to a lot of people but is not that long ago to me because I was actually alive and a whopping ten years old in 1977, which makes it not seem so long ago. Obviously magnets are the main component (thus the name) and an example of how powerful and MRI magnet is would be to compare it to the magnetic force of the Earth. The Earth has a .5 gauss magenetic field. It takes 10,000 gauss to create 1 tesla and the MRI I'm getting today is 1.5 tesla (or 15,000 gauss). Wasn't there a video game called Tesla? Or am I thinking of Tetra?

So my big question is - how do magnets create an image of the inside of the body? The answer is that of all the many different types of atoms in the body, the hydrogen atom has a single proton in its nuclei and has a large magnetic moment - meaning it has a tendency to line up with a magnetic field. Inside the MRI machine, when all the hydrogen atoms are all lined up the MRI machine sends out a radio frequency pulse specific only to hydrogen. The pulse causes the protons to absorb the energy and spin in a different direction - thus the "resonance" part of "magenetic resonance imaging". When the radio frequency pulse is turned off, the protons release an energy which is picked up by the coils of the machine and and sent to the computer in the pattern it was received in order to create the image on the computer. Well, that least sentence is kind of an "in short". Actually it receives mathmatical data that is then converted through a Fourier transform into a picture of what's inside my head (or whatever is getting the MRI). I'm not quite ready to try and explain what Fourier transformation is - something about translating the frequency representation of the original form. Ok, keep in mind I've had a stomach ache for days and haven't really eaten much of anything and I'm nervous about this actual MRI experience so I'm not at my peak intellectual functioning right now.

EDIT: Well, laying down and having a cage put over my head and being backed into a small tube was much scarier than I thought it would be. Initially when the guy got me hooked in and had the bed slide back into the tube I felt really panicked and tried calming myself down but I felt so incredibly helpless and trapped that I couldn't get my body to calm down. So, I pressed the "emergency button" and told the tech. I didn't think I could do it. He said to sit and breathe for a moment because he knew that my doctor wanted the MRI for my diagnosis and he believed I could do it. So, I asked if my mom could come in and sit next to me and that helped more than valium probably would have. She sat next to the machine with her hand on my lower leg and that was all I needed to remind me that I wasn't totally helpless and alone and then I was fine. I even relaxed a little. After I figured out what my "happy place" was. And of course, it was riding horses - riding Girlfriend, riding Clyde at Mt St Helens and I tried to remember what it felt like to jump and how it would feel again to jump. I also remembered how good it felt to climb up to the top of the wall at Stone Gardens and how I had to stop part way up and take a deep breath and remind myself I was safe and fine and that helped too.

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