she repeats it over and over, in her heavily accented voice: “once you in position, you cannot move.  you cannot move.  very important you do not move, okay?”

“okay,” i say from under the blanket.  she presses a little button and my gurney and i slide underneath the machine, until just my head sticks out.

“i will be in the other room,” she says, adjusting my covers and plugging some things in.  “i come on the intercom and tell you how long is left, but i cannot come on when it’s knocking.”

“okay,” i say again, and she walks out and closes the door behind her.  it’s quiet.  i can feel the padded shell she’s snapped around my right knee, locking it in place.  the bulge it makes in the blanket looks like a large cylindrical tumor, or an enormous, grossly misplaced erection.  it feels awkward, and it hurts a little.  i want to move my right heel a bit to relieve some of the pressure, but she said not to move, so i don’t.

“we start now,” she says over the intercom.  “this first one takes eight minutes.  you are in good position.  do not move.”

the machine begins to knock intermittently.  i don’t know why she calls it knocking, it’s more like a series of low, sustained booming noises.  there’s no way i can try to nap through this.  the noises are loud and they make my gurney shake a little, plus i’m uncomfortable and i might move in my sleep.  i think about playing the movie game with myself, but it won’t be fun winning every time, so i decide against it.  what should i do?  should i plan out the rest of my week?  sing songs?  count the spots on the acoustic ceiling tiles?  what?

the buttons she was pressing are just above my head, so i look at those for awhile.  next to the buttons is an LCD screen, which tells me that my POSITION is 000.  the light labeled HEIGHT is on, the LEFT/RIGHT light is off, and the SCAN light comes on whenever there’s knocking.  only now it’s not knocking.  now it’s a lot of really prolonged rumblings that i can feel coming from different parts of the machine.  after listening for awhile, i find a subtle pattern to the noises, like breathing.  it reminds me, for some reason, of flight of the navigator, or the panicked breath of some sort of possessed john deere tractor.

“you are doing good,” her voice says.  “the next three take seven minutes each.  you are in good position.  do not move.”

i’m only a foot below the underside of the machine.  what if i were claustrophobic?  would i be able to handle being under here for an hour?  what if i had to have an mri on my head, and they put me all the way in?  would i be able to hold still?  would i be allowed to blink?  i think i could do it if they let me lay on my stomach, with my head turned to the side.  that way i could relax and look at the side of the machine and pretend i wasn’t inside it.  perhaps i’d even fall asleep.

the noises are louder now, and even more like breathing.  maybe this isn’t a machine at all.  maybe it’s just a tan plastic shell housing a giant serpent that slithers around inside and looks at my knee with its x-ray vision.  that would explain the noises coming from different places.  that would explain the vibrations.  the serpent i imagine is bluish-purple, with curly eyebrows and tail.  it’s smiling at me.  hey, wait a minute.  i’m pretty thin, and the machine’s only a foot above me.  how would they fit a really fat guy in here?  a fat guy in a little coat?  fat guy in a little coat…

“okay, alison, we are all done.”  i think i must have fallen asleep, because her voice over the intercom startles me, and i can’t remember what i was thinking about before i heard it.  she comes in, presses another button, and i slide out from underneath the machine.  she takes off my covers and unsnaps my knee shell, and i get up from the gurney.  “you did a good job.  you did not move.  good.”  it’s cold in there without my blanket, so i put my shoes on quickly, grab my backpack, and run out to the car.

on my way home, an eighteen-wheeler blows a tire just in front of me on the freeway.  i slam on the brakes as strips of rubber and bits of machinery spew out all over the road.