Most breast neoplasms are tougher than the adjacent normal tissues.
In recent decades many ultrasound techniques or MRI for estimating mechanical response of tissues to external excitation have been proposed. The principle that underlies sonoelastography is the slower movement in hard tissues which undergo a slight compression compared to that in a soft structure. Thus, by measuring tissue displacement induced by an applied compression we can estimate the structures hardness. The maximum displacement of the tissue during elastography is produced in the direction of the ultrasounds, in a longitudinal direction. Today, thanks to technical progress sonoelastography can be done in real time, with the same transduction that is performed in classic ultrasound.
Sonoelastography reveals information difficult or impossible to obtain by conventional ultrasound, being an useful imaging method in differentiating breast masses in combination with mammography, gray scale ultrasound and Doppler. Applying Sonoelastography in breast pathology is easy due to the possibility of performing a light compression at this level. Elastography image is obtained by comparing data before and after the light compression on the area of interest. Elastography image is encoded in color or gray scale depending on the device used.
Elastography sample image of a cyst
Hard, incompressible areas deform harder and can be traced on the elastography image in shades of blue or dark gray, while the soft, elastic areas are rendered in shades of red, bright colors or bright gray. Malignant tumors typically appear darker and larger than the classic ultrasound image. Elastography is a fast and simple method that can improve the specificity of conventional ultrasound examination (morphology) in nodular lesions scoring BIRADS 3 and IV A, with fewer biopsies and unnecessary re-examination.Elastography limit is the impossibility of conducting an adequate compression in case of hematomas, breast implants or fibrous breast parenchyma. Elastography is not indicated in the evaluation of postoperative changes of diffuse lesions or those that exceed the size of the scan field.