Closed-loop control of compression paddle motion to reduce blurring in mammograms.
Since the introduction of full field digital mammography (FFDM) a large number of UK breast cancer screening centers have reported blurred images, which can be caused by movement at the compression paddle during image acquisition. To propose and investigate the use of position feedback from the breast side of the compression paddle to reduce the settling time of breast side motion. Movement at the breast side of the paddle was measured using two calibrated linear potentiometers. A mathematical model for the compression paddle, machine drive, and breast was developed using the paddle movement data. Simulation software was used to optimize the position feedback controller parameters for different machine drive time constants and simulate the potential performance of the proposed system. The results obtained are based on simulation alone and indicate that closed-loop control of breast side paddle position dramatically reduced the settling time from over 90 s to less than 4 s. The effect of different machine drive time constants on the open-loop response is insignificant. With closed-loop control, the larger the time constant the longer the time required for the breast side motion to settle. Paddle motion induced blur could be significantly reduced by implementing the proposed closed-loop control.