We had an interesting lab in our Radiographic Imaging class on Tuesday. We talked about the scientific method and we’ll probably be using that to write up lab reports for each set of experiments we do this semester.
In Tuesday’s lab, our objective was to solve this problem:
What is the relationship between mAs and radiation intensity (quantity)?
We knew from previous classes that, with a given kVp and SID setting, doubling the mAs would also double the intensity of the radiation. Our objective was to demonstrate and document this hypothesis.
Our instructor sent us on a bit of a wild goose chase before we got started on this experiment though. We had no idea how we were going to measure the radiation output from the x-ray tube. We were trying to figure out how we were going to demonstrate this idea by exposing film. Any increase in density that we would be able to measure would not demonstrate a linear relationship between mAs and radiation output.
After we spent about 30 minutes trying to figure out how we would measure the radiation output, our instructor popped back into the lab carrying an electronic dosimeter that would read radiation intensity in milliroentgens. He had a nice chuckle as he watched us wipe the sweat from our brows…
After we got the proper equipment, we set up a little experiment. We set the dosimeter on the x-ray table and colimated the beam over the top of it. We set the SID to 40″, set the kVp to 80, and shot our first exposure with a mAs of 2.0. This exposure gave a reading of 21 milliroentgens of radiation. On our next exposure, we increased the mAs to 4.2 (our controller would not let us set to 4.0) and got a dose reading of 21 milliroentgens. We did five more exposures, approximately doubling the mAs each time, and our dose readings approximately doubled each time also. With this data, we were able to establish a linear relationship between mAs and radiation intensity.
I know you are really wondering why there is no picture today :)
I got my positioning videos started and posted to YouTube…
Cervical and Thoracic Spine Routines
I’ll be posting more videos as I collect them.
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Tags: 2nd Semester, RAD-121 by John Setzler
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