"EUS-Guided Attenuation Imaging and Shear Wave Elastography in Individuals With Normal FibroScan: Establishing Preliminary Reference Values in a Pilot Feasibility Study".

Vibration-controlled transient elastography (FibroScan) with Liver Stiffness Measurement (LSM) and Controlled Attenuation Parameter (CAP) is widely used for the non-invasive assessment of liver fibrosis and steatosis. Although these techniques have demonstrated good diagnostic performance, they have several limitations, including technical failure in obese individuals, reduced accuracy in the presence of ascites or narrow intercostal spaces, and the inability to obtain real-time image-guided measurements from specific areas of the liver.

Endoscopic ultrasound (EUS) provides high-resolution imaging of both hepatic lobes through the stomach and duodenum, allowing quantitative assessment of liver tissue under direct visualization. Recent advances have enabled the integration of Attenuation Imaging (ATI), which quantifies hepatic steatosis, and Shear Wave Elastography (SWE), which measures liver stiffness by estimating tissue elasticity and shear wave velocity, into EUS platforms. These techniques may overcome several limitations of conventional transabdominal elastography and have the potential to provide more reliable liver tissue characterization.

Before EUS-guided ATI and SWE can be evaluated as diagnostic tools for liver disease, normal reference values in individuals without liver disease must be established. Currently, there are limited data regarding normal EUS-guided ATI and SWE measurements, particularly in healthy adults with normal FibroScan findings. Establishing these reference ranges is essential for interpreting future studies involving patients with hepatic steatosis and chronic liver disease.

This prospective, single-center, observational pilot feasibility study aims to establish preliminary reference values for EUS-guided ATI and SWE in adults undergoing diagnostic EUS for non-hepatobiliary indications who have normal FibroScan examinations. A total of 100 participants will be enrolled after confirming normal liver stiffness (LSM <7.5 kPa) and steatosis (CAP <238 dB/m), along with adequate FibroScan quality criteria.

During the clinically indicated EUS examination, quantitative liver assessment will be performed without introducing additional invasive procedures beyond standard EUS. Attenuation Imaging will be obtained from both the right and left hepatic lobes, with five valid measurements acquired per lobe. Shear Wave Elastography will also be performed in both lobes, with ten valid measurements obtained per lobe. Measurements will be accepted only if predefined quality criteria are met, including acceptable correlation coefficients, propagation maps, and reliability indices. Acquisition time, technical success, and measurement reproducibility will also be recorded.