The effect of breast positioning on breast compression in mammography: a pressure distribution perspective

Abstract

The standard procedure at mammography is to compress the breast in order to improve image quality, better separate tissue components and reduce absorbed dose to the breast. Traditionally, compression guidelines have been based on applied force, rather than actual thickness reduction. Structures such as the pectoral muscle are stiffer than breast tissue and if compressed along with it, as in the MLO-projection, might absorb much of the applied force. This study investigated the difference in compression of breasts before and after they were repositioned to exclude 1 cm of the juxtathoracic part. Twenty-one women were included in the study. The distribution of compression pressure was measured using thin FSR (Force Sensing Resistor) pressure sensors attached to the compression paddle. Breast thickness and compression force were measured by the mammographic device. Compared to standard positioning the repositioned breasts were thinner by 4.4±2.3 mm (P < 0.001) (from 50.3 mm to 45.9 mm) and had a 12.3±24.5 cm² (P = 0.032) larger area over which pressure was distributed (from 97.6 cm² to 109.9 cm²), despite less of the breast being included in the projection. This indicates that the inclusion of the pectoral muscle and other juxtathoracic structures in the MLOprojection substantially affects pressure distribution and prevents proper compression of the breast. The results suggest that the exact positioning of the MLO-projection should be carefully evaluated in order to find a balance between breast compression and tissue inclusion.