Contributing Editor: Ray Ryan, Vice President of Sales, East Coast Metrology

East Coast Metrology (ECM) has a client who requires a special rectangular X-Ray fixture to be placed at the center of their imaging room to calibrate the position of the X-Rays relative to the treatment beam. Originally, each time the client wanted the X-Ray system checked for alignment, the fixture would need to be measured and moved accordingly until it was centered accurately. This required the measurement of 3 planes, construction of intersecting geometry, building a reference frame from the geometry and finally computing the corrections.  The process was iterative and very time consuming since the positioning tolerance was very tight (+/- 0.1 mm).