Initial experiences with dynamic, quality indicator-based multimodal tissue analysis (M-Ref) with parallel assessment of viscosity and shear wave elastography in liver parenchyma alterations1

Background and objective: Modern ultrasound technology enables detailed tissue morphology analysis. A novel approach involves measuring viscoelasticity or viscosity. This pilot study investigates the potential of a novel high-end ultrasound system with dynamic quality indicators and the M-Ref tool.

Methods: Using a novel premium high-end ultrasound system (Resona A20/Mindray), comparative investigations were conducted on 52 patients, evaluating B-mode morphology, shear wave tissue elastography (STE), and viscosity (STVi) of the liver parenchyma. The study utilized a cohort of 25 healthy volunteers as a control group. The examinations were performed intercostally using a multifrequency convex probe SC7-1U (1-7 MHz) and breath-hold technique, ensuring that at least the highest or second-highest score in the dynamic quality control (5 stars) was achieved. Measurements were made in a color-coded region with a maximum 2 cm diameter and a depth of no more than 2 cm, avoiding bile ducts or blood vessels, at a depth up 2 cm from the liver capsule.

Results: A minimum of 10 measurements were taken for each parameter: liver steatosis (based on acoustic attenuation coefficient, USAT), viscosity (STVi), and shear wave elastography (STE) with correlation to fibrosis grade. Reference values for the control group were <1.4 m/s and <5 kPa for STE, with cirrhosis criteria defined as values >2.6 m/s and >15 kPa. For steatosis, values up to 0.5 dB/cm/MHz were considered normal, while values >0.8 dB/cm/MHz indicated fatty liver. Viscosity values <1.7 Pa.s were deemed normal, with >3.6 Pa.s indicating significant abnormality. Major causes of increased viscosity included severe steatosis, active hepatitis, hepatic tumors, or post-ablative states. In all cases, a high-quality indicator score (>93%) was achieved with at least 4/5 top reference markers in green.

Conclusions: This pilot study confirms the comprehensive capabilities of multimodal imaging for tissue characterization using B-mode, elastography, and new techniques for assessing viscoelasticity. However, extensive multicenter evaluations will be needed to definitively establish reference values specific to the type of transducer and equipment used.