Methods of masseter and temporal muscle thickness and elasticity measurements by ultrasound imagining: a literature review.

Background: The positive correlation between changes in morphology of masseter and temporal muscles, and some disorders, incline diagnosticians to search for an effective method of assessment muscle thickness and elasticity. Ultrasound imaging as a relatively simple and cheap method seems to be a useful diagnostic tool. Objective: The aim of this study was to present the existing ultrasound imaging methods in the assessment of the elasticity and thickness of the masseter and temporal muscles. Methods: The literature review has been done with a focus on the accurate description of the masseter and/or temporal muscle examination by ultrasonography imaging methods. Articles were categorized into two groups. First group included articles in which muscle thickness was assessed by ultrasound imaging. Second group concerned elasticity aspect of mentioned muscles. Results: It is difficult to achieve an objective protocol of masseter and temporal thickness assessment by ultrasonography and there is no method that has been fully verified in terms of reliability. The shear-wave sonoelastography revealed higher-level reliability of masseter muscle elasticity than strain sonoelastography. During the shear-wave sonoelastography the effect of scan plane in relation to masseter muscle pennation and the day-to-day variation were statistically significant. With regard to elasticity of temporal muscle further research is needed. Conclusion: This review has shown that there is a limited number of methods for masseter and temporal muscle thickness and elasticity measurements by ultrasonography. All procedures (methods) were not fully verified in terms of reliability and agreement. Thus, it is still necessary to develop standardize procures to assess thickness and elasticity of the masseter and temporal muscles with appropriate reliability and agreement.

Toward Accurate Quantitative Elasticity Mapping of Rigid Nanomaterials by Atomic Force Microscopy: Effect of Acquisition Frequency, Loading Force, and Tip Geometry

Atomic force microscopy (AFM) has emerged as a popular tool for the mechanical mapping of soft nanomaterials due to its high spatial and force resolution. Its applications in rigid nanomaterials, however, have been underexplored. In this work, we studied elasticity mapping of common rigid materials by AFM, with a focus on factors that affect the accuracy of elasticity measurements. We demonstrated the advantages in speed and noise level by using high frequency mechanical mapping compared to the classical force volume mapping. We studied loading force dependency, and observed a consistent pattern on all materials, where measured elasticity increased with loading force before stabilizing. Tip radius was found to have a major impact on the accuracy of measured elasticity. The blunt tip with 200 nm radius measured elasticity with deviation from nominal values up to 13% in different materials, in contrast to 122% by the sharp tip with 40 nm radius. Plastic deformation is believed to be the major reason for this difference. Sharp tips, however, still hold advantages in resolution and imaging capability for nanomaterials.

Interconversion of elasticity measurements between two-dimensional shear wave elastography and transient elastography

Aims: To enable comparison and interconversion of elasticity measurements between two-dimensional (2D) shear wave elastography (SWE) and transient elastography (TE).Materials and methods: Elasticities of three phantoms were measured by 2D SWE (supersonic shear imaging) using four probes and TE using two probes. We performed regression analyses to evaluate correlation between the measurements and phantom elasticities, and make converting equations. In pediatric biliary atresia patients who had stiffness measurements by both 2D SWE and TE within 1-year interval, TE measurements were retrospectively converted into correlating 2D SWE values. We compared the calculated values with 2D SWE measurements by intraclass correlation coefficient.Results: Measurements in phantoms varied according to elastography method and probe selection. However, the measurement by both 2D SWE (R2, 0.974-0.985; p<0.001) and TE (R2, 0.996-0.999; p<0.001) showedsignificant linear correlation with phantom elasticity in all probe settings. From 67 biliary atresia patients (age, 2 months-20 years), agreements between the measured and calculated values were excellent in all 88 examinations within 1-year interval(ρ=0.828; p<0.001) and in 63 examinations within 2-month interval (ρ=0.863, p<0.001). Conclusions: The equations enabledinterconversion of elasticity values among different probes of 2D SWE and TE and provided reliable estimation of elasticityvalues for different probe settings in biliary atresia patients.