Collimator Light Field Alignment Issue

Updated on April 6, 2020 in X-Ray Equipment Service Issues
0 on June 22, 2015

We recently got a call from a customer that said they had an alignment issue with their collimator light field.  When they did a tabletop x-ray the image clipped 1” of the image from the side closest to the front edge of the table.  If they swung the tube to the chest board, the vertical center line was shifted 1” off the center of the chest board.  This sounded to us like the tube arm was not in the center detent position.  After talking to the customer about this they assured us it was in the center detent and in fact they were taking it out of detent to line it up with the chest board to get images that weren’t clipped.  No service had been performed recently to the collimator or tube so it seemed unlikely that the x-ray / light field would be that far off for no good reason so we scheduled a service call. Upon arrival the service tech verified that the centerline to the chest board was off and all images were being clipped.  At this point he decided to adjust the x-ray / light field and took off the cover to proceed.  After the covers were removed he happened to take a close look at the collimator bulb and noticed that it was sitting in the socket cock eyed.  One of the prongs was almost out of the contacts while the other was seated down properly.  It turns out that the customer had recently replaced the bulb and didn’t get the new one pressed all the way into both contacts.  This caused the bulb to set at an angle which projected the light to the mirror at an angle which shifted the light field.  The tech simply pressed the bulb all the way into both contacts, problem solved.

The next time you have a light field alignment issue ask the customer if they have recently changed the bulb and take a moment to inspect the bulb and ensure it sits all the way into the socket.

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