1-7
7. Expose film.
D 60 kVp, 2 mAs.
D Do not disturb the cassette and pattern because a second exposure is to be
made.
8. Open collimator blades wide enough to include test pattern.
9. Expose film a second time and develop the film.
D 60 kVp, 2 mAs.
D This exposure should include the 810 inch rectangle. Refer to Illustration
1-4. If the rectangle does not show, reload the cassette and repeat steps 1
through 8 but open the collimator blades in step 7 wider than last time.
10. Measure and record the horizontalA&Bdistances, in inches, between the x-
ray field and the light field. See Illustration 1-5.
11. Measure and record the verticalC&Ddistances, in inches, between the x-ray
field and the light field. See Illustration 1-5.
12. The total of the horizontal differences as well as the total of the vertical differĆ
ences must each be less than 1.8% of the SID:
D A+B<1.8% SID=A+B<0.018 40 inches=A+B<0.72 inches
D C+D<1.8% SID=C+D<0.018 40 inches=C+D<0.72 inches
If the above requirements are met, go to step 18. If they are not met, proceed with
the following steps.
Ideally, the x-ray field and the light field should coincide but this is rarely the
case. The best compromise is to move the light field so the x-ray field is cenĆ
tered within it. Usually the light field area will be larger than the x-ray area.
The size and location of the light field can be adjusted by moving the bulb.
13. To place the two fields as close to coincidence as possible, only the light field area
is moved. The light field area adjustment is made by repositioning the field lamp
housing.
14. Loosen the two Phillips head adjustment screws located in the back of the colliĆ
mator. See Illustration 1-6.
To Next Page
Loading...
Need help?
General
