I had to get some chest x-rays done at the hospital today on a
prescription from my doctor. When we got done, I asked the tech how much
radiation I had just received. She said, "Not much." I told her I wanted
to know the numbers. She quoted me 14 mA, 100 kV, and 0.20 s exposure
times. Actually, she gave me just the current and I had to ask for the
plate voltage and the exposure times. I asked how many sieverts or rems
of radiation I received and got a look of panic. I told her that it was
my right as a patient to be told the amount of my exposure and that
those numbers would help her use her charts to figure that out. She
dutifully went back into her office for a few minutes and came out to
tell me that each exposure gave me a dose of 0.02 mSv. I gave her a pat
on the back.
Now, I have no idea whether her calculations were correct or not. (They
seem low to me; I'm more inclined to believe 0.2 mSv.) But this was only
the second time in over 30 years that I have had a radiology tech give
me a value for my radiation exposure. The last time I got a value cited
was decades ago and that was in millirems, and for a different kind of
"shot".
This is a fun drill! I encourage all of you to ask what your exposure
was after getting x-rays taken. I'm sure that RTs are taught this in
their courses. Consider it a way to relieve the boredom in their workday
lives and a means to keep their training fresh.
Note that 0.14 mA at 100 kV for 0.20 s says that 2.8 J were delivered to
the plate by the impinging electron beam. IF all of that entered my
thoracic mass (say, 50 kg) and IF all of that were absorbed, that would
an exposure of 0.56 J/kg. That puts an "upper lid" on things.
Jim
--
James R. Frysinger
632 Stoney Point Mountain Road
Doyle TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
