Breast elastography: the technical process and its applications.

Breast elastography is being increasingly used to better characterize breast lesions. Published studies have shown that it improved specificity of B mode ultrasound. Two elastography modes are available: free-hand elastography and shear wave elastography. Free-hand elastography is obtained by a mechanic wave induced by the ultrasound probe, deforming the target, either by small movements induced by breathe. An elastogram is obtained and displayed either as a colour map or a size ratio or elasticity ratio measurement. The second mode is shear wave elastography; two methods are available: Shear Wave Elastography (SWE) and ARFI mode (Acoustic Radiation Force Impulse). Shear wave elastography is less operator-dependent than free-hand elastography mode and provides a quantitative approach. A value of over 80kPa (SWE) or velocity results of over 2m/s (ARFI) are considered as suspicious. False negatives may occur in soft breast cancers (mucinous carcinoma, carcinoma with an inflammatory stroma, etc.) and false positives may be seen with poorly deformable benign lesions such as old fibrous adenomas. In practical use, elastography is a useful complementary tool for undetermined breast lesions categorized as BI-RADS 4a or BI-RADS 3, or for cystic lesions but cannot avoid fine needle aspiration or core biopsy if ultrasound features are clearly suspicious.