• Topic ID: id_11038964
  • Version: 2.0
  • Date: Jan 30, 2019 9:43:11 PM

Alignment Lights Visual Checks

  • danger
  • Possible Physical Injury
  • Gantry may rotate when alignment lights are turned on.
  • Verify that all personnel are clear of the system, and the Gantry rotates freely to 180 degrees.

  1. Press the alignment light button on the gantry-mounted table controls, to position the gantry.

  2. Remove gantry covers as required.

    Refer to Parts Replacement > Gantry > Enclosure > (Cover Removal Procedure).

  3. Turn OFF the axial drive enable and HVDC enable service switches.

  • warning
  • Possible Eye Injury.
  • Laser beams can cause permanent eye damage.
  • When operating the alignment lights, do not stare at the laser beams.

1 Internal Axial Lights

Place a sheet of plain white paper over the output port of each light and verify that the two lines of laser light coincide with each other.

Do not try to adjust the internal axial lasers on the CT system to shine “down” on the collimator.

2 External Axial to Internal Axial Distance

Raise the table to its highest elevation. Extend the cradle until both the internal and external laser lights shine on the cradle. Place a metric rule on the right edge of the cradle, and measure the distance from the internal axial laser line to the external axial line generated by each laser. Verify this distance equals 240.0 mm ±1.0mm. Place the rule on the left edge of the cradle and measure again.

Extend the cradle until both internal and external laser lines shine on it. Lower the table to the interference limit. Verify the 240.0 mm ±1.0mm distance between the internal and external lights, on both edges of the cradle, as above.

3 Coronal Lights

Place a sheet of plain white paper at the left side of the patient opening, in front of the coronal laser light. Verify that the two coronal lines coincide with each other. Check the right side in the same way.

Place the paper in the center of the Gantry opening, and use a level to verify that the coronal lines are horizontal.

4 Alignment Light Visibility

H.H.S. requirements state that lights used to define the tomographic plane must be visible under ambient light conditions, up to 500 lux. To verify:

  1. Turn the scan room lights on to their brightest normal level. Do not add localized spot lights to increase the brightness level.

  2. Raise the table to its highest position, advance the cradle into the gantry, and turn on the alignment lights.

  3. Center the back of your hand over the cradle, and hold it in the alignment light. Make sure you can see the external axial alignment lights on your hand. You only have to see the axial lights, not the sagittal or coronal lights.

    If you cannot see the external or axial lights under the conditions described above, obtain a DIGAPHOT model #3300 or 3303 light meter; measure the ambient light intensity at the cradle surface at the external and internal alignment light locations.

    note:

    Foot-candles x 10.76 = lux.

    If the light reading(s) exceeds 500 lux, reduce the room lighting to the 500 lux level, and repeat steps 3. If the light meter readings equal 500 lux or less, replace the laser light(s) and/or their power supplies.