Before the advent of diagnostic imaging, palpation was one of the main methods of clinical investigation for the evaluation of tumours. Malignant tumours feel harder that benign ones and this physical property is related to their coefficient of elasticity. Direct comparison of tissue images before and after application of a force is too crude a measure of elasticity except at extremes of differences in elasticity. Analysis of the raw imaging data, which contains very much more information than can be displayed for visual perception, can detect very much smaller differences in elasticity.
The radio frequency data of returning ultrasound echoes contain much more data than appears in an ultrasound image. Comparison, of the datasets of uncompressed tissue with compressed tissue, of a region of interest allows production of a strain (elasticity) image of that same region of interest. Change in tissue which is not visible on B-mode (greyscale) imaging can now be detected with real time strain imaging which is beginning to be developed on commercial ultrasound equipment. The information obtained with strain/elasticity imaging is now showing potential in influencing management of patients with breast problems.