Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Monday, February 06, 2006

Murphy's Law of Medical Imaging

Sydney is such a nice city - to leave behind you.

I had a P.E.T. Scan today (Positron Emission Tomography - a radioactive trace is injected and then any accumulation of the trace in certain tissues, i.e., tumours, should be detected by the “reader” machine as a “hot spot” - a source of emissions). I have had this test twice before, and so it does not scare me (much). But I cannot say I like the thought of it, either.

However, there is a benefit. When it comes to the “ethical debate” as to whether or not to microwave one’s food, the P.E.T. scan makes that virtually irrelevant.

George (he of the Lyrebirds, in "Lower Ranelagh") drove me up and back to Liverpool today. George was very patient, as the P.E.T. Scanner system was delayed, and he had to wait for 5 1/2 hours until I finished. That is along time for George to wander around the commercial centre of Liverpool, while I was in a dark room, lying on an ironing-board sized hospital bench before I was transferred to the actual scanner. Also, when we did leave, it was very hot when we got back in the car, and headed out of town. I am glad that I was not driving, though. Thanks, George.


And then there is the other issue with all these “negative” scans. It is not like an X-Ray machine where it quickly exposes you to a burst of radiation. No, in this case, I become the “light bulb” - I have the radiation within me, (at low power, of course) and so the machine “senses” the emissions from my body. OK in theory, but it is like the early days of photography, with hugely slow “exposure times” - the subject has to stay absolutely still, so as to not blur the images.
(Photo of the "Richmond Grays" - an American Civil War image - coutesy of the Valentine Museum.) The Civil War is famous for the number of photographs taken, but they are unually very formally "posed" images, precisely because of the long exposure times required.

So, inside the P.E.T. Scanner, one is stretched out on a board, inside a circular framed machine, with one’s arms locked over one’s head, for 45 minutes or more. Inevitably the nose decides it is itchy, and needs to be scratched.

Murphy’s Law of Medical Imaging!

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