Portable X-ray Units
Service Manual
SM-1076R2
37
3. Open the Collimator blades to set a Field Size of 24 x 30 cm for SID 1m.
4. Turn on Collimator light and center the Collimator in relation to the
Cassette Film. Horizontal and transverse position of the light axes
projected by the Collimator Light must be in line with the film axes or film
size edges.
5. Load the Cassette Film with a Film of 35 x 43 cm centered.
6. Make an exposure at 60kVp, 1mAs.
7. Process film and check the following measurements known (refer to
Illustration 4-3):
a. Measure the length of the X-ray Field on the Processed Film
(identified as L)
b. Measure the width of the X-ray Field on the Processed Film
(Identified as W)
Illustration 4-3
X-ray Field Size
X-RAY FIELD SIZE ON THE FILM
FILM 35x43 cm
PROCESSED FILM
LENTH DIMENSION (L)
WIDTH DIMENSION (W)
8. With the measurements obtained and according to the field size
indication selected, the results should be:
G Length dimension (L) = 300 mm
G Width dimension (W) = 240 mm
9. The difference between the indicated Field Size and the obtained Field
Size may not exceed 1.5 % (rejection limit) of the SID in either direction.
Therefore the deviation in any direction should not be higher than 15 mm
(rejection limit) for SID at 1 meter.
10. If the deviation of Field Size Indication is out acceptance limits, it is
necessary to readjust the index of Collimator Blades Control Knobs. For
that, loosen each Collimator Control Knob and position it according to
deviation. Repeat the complete tests until the X-Ray Field Size selected
(24 x 30 cm) is obtained.
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