Role of Ultrasound Elastography in Evaluation of Breast Lesions

Abstract

Elasticity imaging is a relatively new technique for studying the stiffness of tissue. Elastography is performed in the same session of ultrasound taking about five minutes more than the conventional ultrasound examination. The information acquired with these techniques is similar to that obtained with manual palpation which states that malignant tissues are harder than benign ones. Thus by measuring tissue stiffness we can estimate the probability of malignancy, but elasticity imaging is more sensitive and less subjective than palpation. Further, the information is provided in an image format so that it can be compared with data from other image modalities and can more easily be documented and shared with others. The principle of elastography is that tissue compression produces strain (displacement) within the tissue and that the strain is smaller in harder tissue than in softer tissue. Therefore, by measuring the tissue strain induced by compression, we can estimate tissue hardness, which may be useful in diagnosing breast cancer. By means of light compression with the probe the image will be displayed either by the lesion size comparison method or the colour coding method. Colour coded images is the most applicable method. The colour code will range from red for the softest tissues to blue for the most hard. Usually the lesion gives a mixture of the different colour which by using a scoring system could be given of a degree of stiffness and thus determines the probability of malignancy. Recently colour coded images is the most applicable methodwhere images are displayed on the screen,superimposed on the normal B-mode ultrasound image. This is performed through an integrated software in the conventional ultrasound machine. The colour code will range from red for the softest tissues to blue for the most hard. Usually the lesion gives a mixture of the different colours which by using a scoring system could be given a degree of stiffness and thus determine the probability of malignancy. The idea of the scoring system is based on the relative ratio between soft and hard areas within the lesion. If all of the lesion is soft, it is given a score of 1. If all the lesion is hard together with the surrounding area it is given a score of 5.