CT collimator damage: detection by testing scan beam and laser-light alignment.
A test for CT scanner laser-light alignment is described. Ready-pack film is taped around a cylindrical phantom, and laser-light position relative to x-ray beam track is indicated by an arrangement of pin pricks through the film jacket. Performance of this test after x-ray tube replacement showed a band of stray radiation running parallel to the scan beam. The errant beam was caused by a failure to interlock the prepatient collimator and scatter shield correctly.
D007834:Lasers; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*