New Developments in Mammography/Elastography

Elastography is a new technique that uses ultrasound to assess the relative stiffness of different tissues. Adding a fourth dimension—time—to ultrasounds allows the movement and elasticity of normal tissue to be compared to the movement of lesions within the tissue. Because malignancies tend to be harder than normal tissue, stiffness is a promising diagnostic indicator.
Recent studies have found this technique to be valuable for distinguishing between malignant and benign lesions in breast tissue.

Elastography is accomplished through a three-step process: First, stress is generated in the tissue to be examined. The resulting strain is measured throughout the tissue. Finally, stiffness is assessed as well.

There are two primary methods for generating stress in the tissue. In strain elastography, the breast tissue is manually compressed and decompressed to generate stress. In shear wave elastography, stress is generated through mechanical vibration, allowing for a greater degree of standardization.

In a recent study, ultrasound elastography was found to be better than sonography and as good as mammography in distinguishing between benign lesions and malignant ones. Combining elastography and sonography yielded best results. Increased accuracy can reduce the number of biopsies that are performed on lesions that are benign, reducing patient anxiety and distress as well as costs.

A number of medical equipment manufacturers offer elastography options on their ultrasound systems. Elastography generally utilizes existing ultrasound consoles and transducers and as such, can be added via software packages. A number of ultrasound equipment producers have developed proprietary elastography technologies for generating stress and/or for displaying results.

Hitachi Medical System’s Real-time Tissue Elastography (HI-RTE) is a strain ratio tool that integrates with the company’s Hi Vision ultrasound systems and measures tissue elasticity. Data is presented clearly on the system’s real-time color display. Color transparencies allow B-mode ultrasound and elastography images to be correlated. Philips Healthcare also offers a strain-based elastography analysis tool in a number of its ultrasound transducers.

The Ultrasonix elastography module is compatible with all of the company’s ultrasound systems. It uses shear waves and extremely fast algorithms to generate elastograms in real-time, at a rate of two frames per second. Siemens' ultrasound tissue strain analytics applications use Acoustic Radiation Force Impulse (ARFI) technology to compress deep tissue.