• Topic ID: id_15460172
  • Version: 5.0
  • Date: Jan 20, 2020 8:34:36 PM

Alignment Lights Visual Checks

Prerequisites

Overview

This procedure defines the steps necessary to check the alignment light visibility.

1 Setup for Checks

Procedure

    • warning
    • Possible Eye Injury.
    • Laser beams can cause permanent eye damage.
    • When operating the alignment lights, do not stare at the laser beams.
  1. Press the alignment light button on the gantry control panel, to position the gantry with the alignment lights on.
  2. Remove the right side gantry cover.

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

  3. Stop the rotor of X-ray tube in case of Liquid Bearing Tube before HVDC off. Refer to Liquid Bearing Tube Rotor stop procedure for details.
  4. Turn OFF the axial drive enable and HVDC enable service switches. (Alignment lights will turn off but will be turned back on in the next step)
    note:

    For the procedures below, the axial alignment lights create the lines across the bore left to right and are positioned on the left and right sides of the bore. The coronal laser creates a horizontal line in and out of the bore along the center line of the table and is positioned at the top of the bore.

2 Internal Alignment Lights

Procedure

  1. 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. Perform this check for both axial and coronal alignment lights.
  2. Place the paper in the center of the Gantry opening, and use a level to verify that the coronal lines are horizontal.

    If alignment light adjustment is required for the above checks, reference Alignment Light Adjustment to perform the adjustment required.

    note:

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

3 External Axial to Internal Axial Alignment Light Distance

Procedure

  1. Raise the table to its highest elevation. Extend the cradle until both the internal and external laser lights shine on the cradle.
  2. 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 ±1.0 mm. Place the rule on the left edge of the cradle and measure again.
  3. Lower the table to the interference limit, leaving the table extended to show both internal and external lasers.
  4. Verify the 240.0 mm ±1.0 mm distance between the internal and external lights, on both edges of the cradle, as above.

    If any adjustment is required reference Alignment Light Adjustment to perform the adjustment required.

4 Alignment Light Visibility

Regulatory. requirements state that lights used to define the tomographic plane must be visible under ambient light conditions, up to 500 lux. To verify perform the following steps.

Procedure

  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.
  4. Repeat the procedure with the internal axial lights.
  5. If you cannot see the external or internal axial lights under the conditions described above, obtain a light meter (See Tool Depot tool listing for currently available part numbers) measure the ambient light intensity at the cradle surface at the external and internal alignment light locations.

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

    note:

    Foot-candles x 10.76 = lux.

5 Finalization

Perform any finalization required by the alignment light adjustment procedure if used.