2.2. Data acquisition

Figure ​Figure22 explains how to proceed with our research. Three breast radiologists who had 15 to 25 years of experience in breast US and 5 years in elastography, examined 8 targets in the elasticity phantom: 11 mm and 4 mm size of targets with 4 different levels of stiffness. The phantom was imaged by 2 different SWE systems: SuperSonic Imagine (SSI) (SSI, Aix en Provence, France) and ShearScan (RS-80A, Samsung Medison, Seoul, Korea) using 50-mm 15 to 4 MHz linear array transducer. The B-mode image, color elstography image, and measurement of elasticity of 8 targets were obtained twice by each radiologist over a one-week interval. After scanning of the target with B-mode with 4 cm imaging depth, SWE was obtained. For measurement of elasticity, a region of interest (ROI) was placed at the stiffest area within or just around the target on a semitransparent color map of the tissue, ranging from blue (indicating the lowest stiffness) to red (indicating the highest stiffness) (0–100 kPa). Mean, minimum, and maximum values of elasticity were measured automatically following placing the ROI, and mean value was used to analyze the accuracy and compare the agreement. The elasticity ratio between the lesion and background was automatically calculated by placing another ROI at the representative area of the background (Fig. ​(Fig.3A).3A). Color elastography and measurement of elasticity were separated in ShearScan (Fig. ​(Fig.3B).3B). After measuring the elasticity, the elastic score was calibrated to 0 to 100 kPa scale based on the color of stiffness in the color elastography. To compare the reproducibility of the measurement, the same procedure was repeated with a week interval and results were compared to evaluate the conformity between 2 data sets.

A flowchart explaining the process of study. Three radiologists (R1-3) measured elasticity of the phantom lesions using equipment 1 and repeated the same measurement using equipment 2 with 1 week interval.

Measurement of elasticity by placing a region of interest (ROI) at the stiffest area within or just around the target using SuperSonic Imagine (A) and ShearScan (B).