The initial power drive on some mammography units (e.g., Siemens Mammomat) is designed with a built-in sensor that terminates the pressure applied to the paddle once the system’s software algorithm determines that additional force will not achieve further thickness reduction.
This design is intended to maximize patient comfort while achieving optimum compression. When such a device is pressed against a hard surface (such as a bathroom scale), the sensor, recognizing that very little or no compression has been achieved by the applied force up to that point, terminates the pressure before the maximum force can be achieved. When performing the compression test with such a device, the person conducting the test (i.e., radiologic technologist or medical physicist) may have to press the foot pedal more than once to accurately measure the maximum force.
Failure to do so may lead the person conducting the test to report an artificially low maximum compression force. This could lead to an inappropriate failure of the initial power drive compression device quality control test.