Analysis of motion during the breast clamping phase of mammography

Objective: To measure paddle motion during the clamping phase of a breast phantom for a range of machine/ paddle combinations. Methods: A deformable breast phantom was used to simulate a female breast. 12 mammography machines from three manufacturers with 22 flexible and 20 fixed paddles were evaluated. Verticalmotion at the paddlewas measured using two calibrated linear potentiometers. For each paddle, the motion in millimetres was recorded every 0.5 s for 40s, while the phantom was compressed with 80N. Independent t-tests were used to determine differences in paddle motion between flexible and fixed, small and large, GE Senographe Essential (General Electric Medical Systems, Milwaukee, WI) and Hologic Selenia Dimensions paddles (Hologic, Bedford, MA). Paddle tilt in the medial-lateral plane for each machine/paddle combination was calculated. Results: All machine/paddle combinations demonstrate highest levels of motion during the first 10 s of the clamping phase. The least motion is 0.1760.05mm/10 s (n520) and the most motion is 0.5160.15mm/10 s (n580). There is a statistical difference in paddle motion between fixed and flexible (p,0.001), GE Senographe Essential and Hologic Selenia Dimensions paddles (p,0.001). Paddle tilt in the medial-lateral plane is independent of time and varied from 0.04 to 0.69. Conclusion: All machine/paddle combinations exhibited motion and tilting, and the extent varied with machine and paddle sizes and types.