Skeletal Muscle Assessment Using Quantitative Ultrasound: A Narrative Review

Abstract

Ultrasound (US) is an important imaging tool for skeletal muscle analysis. The advantages of US include point-of-care access, real-time imaging, cost-effectiveness, and absence of ionizing radiation. However, US can be highly dependent on the operator and/or US system, and a portion of the potentially useful information carried by raw sonographic data is discarded in image formation for routine qualitative US. Quantitative ultrasound (QUS) methods provide analysis of the raw or post-processed data, revealing additional information about normal tissue structure and disease status. There are four QUS categories that can be used on muscle and are important to review. First, quantitative data derived from B-mode images can help determine the macrostructural anatomy and microstructural morphology of muscle tissues. Second, US elastography can provide information about muscle elasticity or stiffness through strain elastography or shear wave elastography (SWE). Strain elastography measures the induced tissue strain caused either by internal or external compression by tracking tissue displacement with detectable speckle in B-mode images of the examined tissue. SWE measures the speed of induced shear waves traveling through the tissue to estimate the tissue elasticity. These shear waves may be produced using external mechanical vibrations or internal “push pulse” ultrasound stimuli. Third, raw radiofrequency signal analyses provide estimates of fundamental tissue parameters, such as the speed of sound, attenuation coefficient, and backscatter coefficient, which correspond to information about muscle tissue microstructure and composition. Lastly, envelope statistical analyses apply various probability distributions to estimate the number density of scatterers and quantify coherent to incoherent signals, thus providing information about microstructural properties of muscle tissue. This review will examine these QUS techniques, published results on QUS evaluation of skeletal muscles, and the strengths and limitations of QUS in skeletal muscle analysis.

Development of an Artificial Soft Solid Gel Using Gelatin Material for High-Quality Ultrasound Diagnosis

“…For therapeutic ultrasound, as depicted in Figure 13, the reflectance should be close to 0 (R = 0). However, in diagnostic ultrasound, where monitoring is through reflected images, higher reflectance, ideally above 0.5 (R > 0.5) as per Equation ( 11), indicates better performance [40]. Here, cg and d represent the acoustic velocity of a probe and the thickness of a gelatin layer, given as 3453 m/s and 1.0 cm, respectively [39].…”

“…It is crucial to use the proposed soft solid gel to avoid the temperature impact on the ultrasound probe. Traditional gels tend to dry out after approximately 15 min, leading to a degradation in image quality during diagnostic evaluations [36][37][38][39][40][41][42][43][44], although there are existing research results that indicate images come out better in obese patients [45]. The experimental results, as shown in Table 2, indicate that the gel began to dry out around 15 min.…”

Ultrasonographic Features of Muscular Weakness and Muscle Wasting in Critically Ill Patients

“…Normal ultrasonographic features of muscle show an organized structure allowing the transmission of sound waves [ 42 ]. Ultrasonographic evaluation can discriminate structures such as subcutaneous fat, bone, nerves, and blood vessels [ 43 ].…”

“…When US waves meet a tissue characterized by varying acoustic impedance, part of the acoustic waves is reflected; the amplitude of the reflected acoustic signal determines the brightness of the displayed image. Indeed, fibrous tissue presents a different acoustic impedance in comparison to muscle fibers, with high absorption and attenuation, resulting in a brighter image [ 42 ]. Discontinuity in muscle density results in a reflection and scattering phenomenon.…”

In Vivo Effects of Joint Movement on Nerve Mechanical Properties Assessed with Shear-Wave Elastography: A Systematic Review and Meta-Analysis

“…In the last years, shear-wave elastography (SWE) has been consolidating in the evaluation of tissues' mechanical properties as an adjunctive technique to conventional ultrasound [13][14][15][16][17][18][19]. SWE is a non-invasive ultrasound imaging technique that uses an acoustic pulse to generate a shear wave in the tissue [13][14][15].…”