Aims: Viscosity is an important mechanical property directly linked to the shear wave dispersion within tissues. The purpose of this study was to establish the normal viscosity value of the parotid gland (PG) and submandibular gland (SMG) in a group of healthy subjects, using the novel Viscosity Plane-wave UltraSound (ViPLUS) technique, and to assess its potential dependence on gender and age.
Material and methods: The study group included a total of 49 healthy volunteers (median age 31, 65% females) prospectively examined between February 2021 and March 2021. The viscosity of both PG and SMG was measured using the new Aixplorer MACH 30 ultrasound system (SuperSonic Imagine, Aix-en-Provence, France) equipped with a curvilinear C6-1X transducer. The mean value of three valid measurements was considered (quantified in Pa.s).
Results: The mean viscosity value for the PG was 2.13±0.23 Pa.s, significantly lower than the mean viscosity value of the SMG 2.44±0.35 Pa.s (p<0.0001). A negative low correlation between SMG viscosity and age was found (rho=-0.38, p=0.006). Viscosity values of the SMG were significantly lower in the age group between 35-77 years (2.12±0.35 Pa.s) than in the age groups 25-34 years (2.52±0.36 Pa.s), and 20-24 years (2.53±0.24 Pa.s), respectively (p<0.05). Viscosity values of both salivary glands did not differ significantly between gender groups.
Conclusions: Supersonic ViPLUS represents an innovative and useful non-invasive method to assess the viscosity of the parotid and submandibular glands. Age is a potential confounding factor in the evaluation of normal SMG viscosity.