Doppler color flow, harmonic imaging, and 3D stand as markers on the winding road to modern diagnostic ultrasound. Elastography may soon be recognized as the most recent milepost, if efforts by vendors both large and small pan out. At RSNA 2008, Siemens Healthcare, Toshiba America Medical Systems, and industry newcomer SuperSonic Imagine vetted this technology for its potential in breast imaging.
The technology for this next advance drew from the conventional and the sublime. With data gathered using its Aplio XG, Toshiba showed the results from ElastoQ, which displays differences in the relative elasticity of tumor and surrounding tissue. Operators examine breast tissue slightly compressed and then decompressed, assigning colors to a tomographic image or, alternatively, as a graph.
Cancerous tissue tends to have a significantly lower elasticity than healthy tissue, providing the diagnostic principle underlying the company's work-in-progress, which is being positioned as a possible future means to assess tumors. The underlying technology is already established, according to Gordon Parhar, director of the TAMS ultrasound business unit.
Toshiba's proprietary elastography method is based on tissue Doppler, a method vetted in peer reviewed research for its accuracy in elastrography and already in practice elsewhere in diagnostic ultrasound.
“Tissue Doppler is used a lot in [the] cardiac world,” Parhar said.
Siemens takes the concept of elastography a step further with its Acuson S2000 automated breast volume scanner, which, as the name implies, automates the mechanism for compressing breast tissue and gathering volumetric data. The experimental breast scanner, which works in concert with the high-end Acuson S2000 ultrasound system, is built around a blocklike transducer mounted on the end of an articulated arm. The transducer mechanically sweeps the breast, acquiring volumetric data on tissue as it compresses along the leading edge of the transducer and decompresses along the trailing edge.
The scan provides volumetric data about the breast, including its coronal plane, which is not seen with conventional ultrasound, according to Andy Milkowski, vice president of sales at Siemens Ultrasound. It also generates values indicating the relative stiffness of breast tissues, providing practitioners another metric for distinguishing tissues. The goal is to increase the reproducibility and accuracy of elastography exams as an adjunct to mammography.
“The ideal workflow is one in which a lot of indeterminate mammographies from dense-breasted women can be quickly assessed,” Milkowski said.
Unlike Toshiba's reliance on operator compression or Siemens' articulated arm, SuperSonic Imagine uses a proprietary technique called ShearWave Elastography to produce consistent results.
Aixplorer's ultrasound beams create shear waves in tissue. These waves, which travel through tissues at right angles from the ultrasound beam, slow down in proportion to the stiffness of the tissue through which they pass. Aixplorer records these changes in speed, turning the data into colorcoded maps of tissue elasticity.
