Appendix E Maintenance and Inspection
Mobile DaRt Installation Manual
E-xiv
E.6 Centering the Collimator and X-Ray
Focus
There are following two kinds of discrepancy between the collimator illumination
field and X-ray irradiation field. When installing the apparatus, make sure which
discrepancy is occurring and adjust the discrepancy:
1. Discrepancy between the collimator illumination field center and X-ray
irradiation field center.
2. Discrepancy between the collimator illumination field size and X-ray
irradiation field size.
Discrepancy between the collimator illumination field center and X-ray
irradiation field center.
How to adjust the collimator illumination field center and X-ray
irradiation field center.
If the center axis of the collimator blades and the axis of conical X-ray beam are
discrepant when the collimator is mounted on the X-ray tube, the collimator
illumination field center shifts from the X-ray irradiation field center.
In this case, align the center axis of the collimator blades with the axis of conical
X-ray beam by moving the collimator itself without displacing the lamp mounting
board as follows:
1. Show the illumination field on a cassette placed on the exposure top panel
(10-cm square).
2. Put a piece of line solder along the four sides of the illumination field and
operate exposure.
3. Then, widen the illumination field further (15-cm square), leaving the line
solder as it is.
4. Operate another exposure (double exposure).
5. After developing the radiograph, compare the illumination field center
(center of the image of the line solder) with the X-ray irradiation center, and
measure the discrepancy between them.
6. As shown in the illustration on the next page, loosen the screw a little, and
correct the above discrepancy in no. 5. by adjusting the position where the
screw is to be tightened. After making sure that the discrepancy is
eliminated, firmly tighten the screw, and then replace the screw or leave it a
loosened.
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