Free Philip Glass Concert!

      Okay, maybe it's not exactly his style, but if you're not claustrophobic -- and I most definitely am not -- and you put in the earplugs and remember to ask for a blanket -- which I certainly did -- there's something restful about relaxing cozily inside an MRI in a loose-fitting hospital gown and scrub pants with your eyes shut while the machine does its thing:

     CLACK! Tick, Tick, Tick, Tick, Tock.
     Brzzt-brzzt-brzzt-brzzt-brzzt (pause)
      Brzzt-brzzt-brzzt-brzzt-brzzt (pause)
       Brzzt-brzzt-brzzt-brzzt-brzzt (pause)
        Brzzt-brzzt-brzzt-brzzt-brzzt (pause)

     CLACK. Tic-tic-tic-tic-tic-tic, clunk.
     Braaap!   Braaap!   Braaap!   Braaap!   Braaap!   Braaap!   Braaap!  
     Braaap!   Braaap!   Braaap!   Braaap!  Braaap!    Braaap!   Braaap!  

     And so on, for nearly half an hour, while I drifted, toasty and half-asleep, trying to work out plot developments in a short story and counting repetitions.  This was all lower back, and while I did feel strangely warm from time to time, I didn't experience the thing that sometimes happens when they're looking at your skull: spinning rings of white light, apparently when the scanning RF beam intersects some part of the eye or optic nerve.  Anyway, I have been plenty magnetized to last me for awhile.

     MRI machines use a series of clever tricks to take a look at your innards, including the parts too soft and squishy to register in any detail on an X-ray, and while an MRI is generally louder and larger than an X-ray machine, the part that's actually scanning you is a little less intense.  The dodge is, the huge electromagnet you're inside has lined up each and every tiny proton in each tiny atom, and the detector is just looking to see how much they wiggle when the scanning beam zips by.  Each pass of the beam results in a series of data points, ${\displaystyle \rho }$ (rho) much amplitude at an angle of ${\displaystyle \phi }$ (phi) over and over and over, and they slowly build an image in the form of a series of  "slices."  Smart processing software can turn that into a 3-D model or show flat projections at various angles, but it takes a lot of samples -- which is why it takes so long and you're not supposed to move while it's happening.

     If you're not much minded to panic, it's a good time to relax, half-dozing.  Might as well; you're not going anywhere until it is over.

     Despite my very best intentions, I walked to the room with a couple of metal clips in my hair.  The techs give you the once-over, twice, before you cross the threshold, and spotted them.  "Don't feel too bad about it," one of them told me, "I confiscated two lighters from a guy just last week.  I still can't figure out why he brought them."

     What they found out about my back, I don't know yet.  Maybe some time next week.