Experimental Evaluation of Novel Two-Dimensional Endoscopic Ultrasound Shear Wave Elastography: A Phantom-Based Study

Point shear wave elastography (SWE) can indicate tissue elasticity using absolute values, but it remains difficult to determine which areas are suitable for measurement. Recently, two-dimensional endoscopic ultrasound SWE (2D-EUS-SWE), which allows visual assessment of appropriate measurement locations, has become possible. However, it remains unclear how to set the measurement and color regions of interest (ROIs) appropriately. This study aimed to evaluate the optimal ROI settings for 2D-EUS-SWE under various measurement conditions with phantom. Two types of commercially available elasticity phantoms were used to evaluate 2D-EUS-SWE. The conditions were set for five parameters: measurement ROI size, color ROI size, color ROI depth, degree of probe pressure, and color ROI angle. Measurements were performed 10 times for each setting. In a tumor model, the color ROI was set over or within the tumor. Reproducibility and reliability were then evaluated for each setting. Setting the color ROI at a depth range of 1-3 cm was found to be appropriate. The measurements were possible regardless of the color and measurement ROI sizes. When the color ROI was positioned directly below (0°), tilting it up to 45° had no effect on the measurement. In the tumor model, measurements were possible regardless of the color ROI size. In addition to clarifying the optimal condition settings, the present findings indicate that 2D-EUS-SWE is an accurate and reliable method for performing measurements using EUS. However, this was conducted under phantom conditions, and future clinical evaluation is necessary.