Tissue Doppler and strain imaging for evaluating tissue elasticity of breast lesions

Sonoelastography depicts the intrinsic elastic properties of a tissue which are characterized by the strain applied to achieve tissue deformation and the velocity at which tissue deformation occurs. The present study served to investigate whether the specificity of B-mode ultrasound (US) can be improved by combining B-mode imaging with tissue Doppler imaging (TDI) and offline analysis of tissue strain imaging (TSI).

Fifty women, 25 with malignant and 25 with benign focal breast lesions, were examined by US with a linear transducer (9 MHz, Aplio, Toshiba, Otawara, Japan). B-mode US views of the lesions were overlaid with color-coded TDI information and area quotients (AQ = area B-mode view/area TDI) were calculated. TSI views were reconstructed offline from the source data. This was done by placing a region of interest (ROI) in the target lesion and color-encoded display of the information. In addition, tissue elasticity was evaluated using a scale of 1-5 corresponding to the BI-RADS categories. Maximum strain (strain factor, SF) was determined in the ROI. All patients also underwent mammography. Sensitivities and specificities were calculated and statistical analysis was performed using Wilcoxon's test.

Sensitivity/specificity was 96%/68% for B-mode US, 100%/40% for combined B-mode US and mammography, and 96%/80% for TSI. The AQ of benign and malignant lesions was significantly different (p = .00008) as was the difference in SF (p = .0004). The readers considered TSI a feasible technique.

Evaluation of elasticity based on the quantification of strain factors improves characterization of focal breast lesions, especially the differentiation of BI-RADS 3 and 4 lesions. Surprisingly, significant results in characterizing breast lesions were obtained with the simple technique of TDI, showing a lower tissue displacement in malignant cases.