The intent of this regulation is to prevent the use of paddles with a significant concave shape to the central portion of the chest wall edge of the paddle. These types of paddles have been found to provide inadequate imaging of chest wall breast tissue.
The edge of the straight paddle does not have to be perfectly straight, but rather, it is required that the manufacturer intended it to be straight and that it be made as straight as manufacturing processes allow. For example, if an original or third party manufacturer offers a paddle with a curved chest wall edge in addition to their straight edge paddle, then the curved paddle would not meet the requirement. As an aid in determining the adequacy of a particular design, the user may consult the manufacturer.
For each x-ray unit, the facility must have at least one standard full-sized compression paddle for both required image receptor sizes. These paddles must have a straight chest wall edge. Special purpose paddles may be provided as needed. Under the regulations, compression paddles that are designed for special purposes are exempt from the requirement that the chest wall edge of the paddle be straight and parallel to the edge of the image receptor. Special purpose paddles are those not routinely used to produce the standard MLO and CC mammographic views.