Unfortunately, contemporary US imaging is not sufficiently sensitive to delineate the lumpectomy bed for PBI. We propose to supplant B-mode imaging with a novel US elasticity imaging (USEI) method to delineate the subtle and complex boundaries of the lumpectomy cavity. Our preliminary studies suggest that USEI may be superior to B-mode imaging (see statistical section and Ref. 6-7). However our work was only done in ex-vivo tissue models. In the literature, there are many studies showing the superior sensitivity and specificity of strain imaging compared to regular B-mode imaging7.