US shear-wave elastography technique
2D-SWV based US elastography was performed using Toshiba Aplio i800 (Canon Medical systems, Japan) ultrasound system with an ultra-wideband convex transducer (i8CX1). The images were obtained while the patients lying in the lateral decubitus position with breath-hold during data acquisition. The sample box was placed in the renal cortex of the upper, middle and lower portions of each kidney, respectively (Fig. 1). A fixed region-of-interest (ROI) size was chosen for each measurement. The 2D-SWV was measured 4-6 times for each renal portions and the mean of the measurements were recorded accordingly. The mean 2D-SWV values of the whole right and left kidneys were also calculated by averaging the values of three renal portions. A second radiologist repeated the right kidney average 2D-SWV measurements in randomly selected 10 healthy subjects on the same day.