- G Rizzatto1
© BioMed Central Ltd 2008
Published: 7 July 2008
Real-time elastography (RTE) of the breast is accurate and reproducible, and may easily and quickly integrate conventional ultrasound and other breast imaging.
We use a new five-step score that modifies the original Tsukuba classification. In fact, this last score is related only to solid lesions while the BI-RADS Breast Imaging Reporting and Data System considers also nonsolid lesions; in our practice we observed that the cysts always show a typical three-layered pattern.
This pattern is due to an artifact. With RTE scanning, many elasticity images are obtained by comparing two adjacent frames to evaluate the displacement generated by the probe with continuous compression and relaxation movements. The displacement of these two adjacent frames is usually small (<0.5 mm). The echo intensity inside the cyst is extremely low. The displacement at the center is erroneously estimated as almost 0 and is represented as a green band. The two areas near the cystic wall have a different displacement value, with a strain that is lower in the front (blue) and higher in the back (red).
RTE shows a very high specificity in benign lesions, including BI-RADS category 3 lesions. With the best cutoff point between elasticity scores 3 and 4, the negative predictive value is around 98%. RTE works better with small lesions. RTE is insensitive to the thickness and the echogenicity of the breast, and to the depth and the size of the lesion.
RTE scores are well reproducible. Indexes of intra-observer (κ = 0.93) and inter-observer (κ = 0.90) agreement are very good.