Mammographic unit compression force: acceptance test and quality control protocols.
Firm compression of the breast in screen-film mammography procedures lowers the radiation dose to patients, enhances image contrast and definition, and improves visibility of pathologic conditions. Most mammography unit compression systems have no force-level indicator. Some systems show force variations with time and others, with angle and region of the compression device. Still other systems give poorly reproducible compression-force levels, and in one unit the force release mechanism jammed repeatedly. Detailed procedures for initial acceptance testing and continuing quality control checks are listed. Recommended measurements include levels of manual and automatic applied force, stability, reproducibility, and dependence on angulation and breast size and evaluation of operation of release mechanisms. Also necessary are observations of the condition and operation of the compression system. Test equipment is described and measurement frequency is specified, as well as suggested tolerance limits. Manufacturers of mammographic units are urged to build in compression-force gauges and to provide both a manual mode and a variable-force automatic mode.