74
3.4 Beam Quality
4
Position the paddle as close to the tube as possible, all the way up.
5
Make the rst exposure and record the mGy.
6
Make the second exposure and record the mGy.
7
Calculate the average of the two mGy values and record it.
8
Add 0.3 mm of Al ltration between the tube and the detector of the dose meter and repeat the
process, from Step 5 through Step 7.
9
Keep on adding 0.1 mm of Al ltration and repeat the process, from Step 5 through Step 7, un-
til the average mGy value drops more than half of that without any Al ltration.