The beam alignment of a panoramic X-ray unit and its influence on image quality

Abstract

The objectives of this project was to develop a more accurate, faster and less expensive procedure for aligning the beam of a dental panoramic X-ray unit than the existing procedure and to investigate mathematically how different errors in beam alignment affect the shape, position and thickness of the panoramic focal trough and ultimately the image quality. The errors in beam alignment can be due to errors in the position of the axes, along which the different mechanical assemblies move, and/or errors in the position of components through which the X-ray beam passes.The new beam alignment procedure is carried out using a laser, and new alignment tools and programs. This new procedure saves a considerably amount of time and money because it eliminates much of the film exposure and processing that the old beam alignment procedure required. In addition, the accuracy was increased because it was easier to see errors using a thin narrow laser beam than thick X-ray exposure lines on a radiograph. Accuracy was improved still further by using thinner pins in the pin phantom and by designing an alignment validation program that would make it easier to see the errors on the checking exposure.The new alignment procedure proved to be so successful that is now in use in the final test department where the Cranex Tome units are checked and aligned.