Intensifying Screens with Poor Alignment
Intensifying screens which had been poorly aligned with the chest wall edge of the cassette during the manufacturing process may result in an image with a narrow low-density strip along the chest wall edge of the film (since there is no intensifying screen underlying this area). DMQS has confirmed that the industry allows manufacturers a "tolerance" in screen-cassette alignment that may result in such a strip on the edge of the film. This low-density strip may simulate the appearance of the compression paddle being visible on the film and could lead to the inspector inappropriately citing the facility for compression paddle misalignment.
The strip is most visible on your alignment test film but can also be seen below the phantom on the phantom image films, once its presence is recognized. Once you are aware of this poor screen-cassette alignment as a possible cause for a narrow low-density strip on the chest wall edge of an image, it will usually be clear to you that it is not a compression paddle misalignment problem. Please take care not to "misread" an image which was produced with a poor screen-cassette problem and then cite it as compression paddle misalignment.
There is not a question in the inspection procedures that addresses this issue. Since any tissue which is at the chest wall on a mammogram will not be imaged, many interpreting physicians will find this poor alignment undesirable. FDA suggests that if you observe a poor screen-cassette alignment, you note it in the Printable Remarks Section and discuss it with the facility. It will then be up to the facility to decide what action to take.