Evaluation of healthy muscle tissue by strain and shear wave elastography - Dependency on depth and ROI position in relation to underlying bone

3D Ultrasound Shear Wave Elastography for Musculoskeletal Tissue Assessment Under Compressive Load: A Feasibility Study

Given its real-time capability to quantify mechanical tissue properties, ultrasound shear wave elastography holds significant promise in clinical musculoskeletal imaging. However, existing shear wave elastography methods fall short in enabling full-limb analysis of 3D anatomical structures under diverse loading conditions, and may introduce measurement bias due to sonographer-applied force on the transducer. These limitations pose numerous challenges, particularly for 3D computational biomechanical tissue modeling in areas like prosthetic socket design. In this feasibility study, a clinical linear ultrasound transducer system with integrated shear wave elastography capabilities was utilized to scan both a calibrated phantom and human limbs in a water tank imaging setup. By conducting 2D and 3D scans under varying compressive loads, this study demonstrates the feasibility of volumetric ultrasound shear wave elastography of human limbs. Our preliminary results showcase a potential method for evaluating 3D spatially varying tissue properties, offering future extensions to computational biomechanical modeling of tissue for various clinical scenarios.

Establishment and Validation of a Predictive Model for Sarcopenia Based on 2-D Ultrasound and Shear Wave Elastography in the Medial Gastrocnemius Muscle

OBJECTIVE

To develop and validate a predictive model for sarcopenia.

METHODS

A total of 240 subjects who visited our hospital between August 2021 and May 2023 were randomly divided by time of entry into a training set containing 2/3 of patients and a validation set containing 1/3 of patients. The muscle thickness (MT), echo intensity (EI), and shear wave velocity (SWV) of the medial gastrocnemius muscle were measured. Indicators that were meaningful in the univariate analysis in the training set were included in a binary logistic regression to derive a regression model, and the model was evaluated using a consistency index, calibration plot, and clinical validity curve. Diagnostic efficacy and clinical applicability were compared between the model and unifactorial indicators.

RESULTS

Four meaningful variables, age, body mass index (BMI), MT, and SWV, were screened into the predictive model. The model was Logit Y = 21.292 + 0.065 × Age - 0.411 × BMI - 0.524 × MT - 3.072 × SWV. The model was well differentiated with an internally validated C-index of 0.924 and an external validation C-index of 0.914. The calibration plot predicted probabilities against actual probabilities showed excellent agreement. The specificity, sensitivity, and Youden's index of the model were 73.80%, 97.40%, and 71.20%, respectively, when using the diagnostic cut-off value of >0.279 for sarcopenia. The logistic model had higher diagnostic efficacy (p < 0.001) and higher net clinical benefit (p < 0.001) over the same threshold range compared to indicators.

CONCLUSION

The logistic model of sarcopenia has been justified to have good discriminatory, calibrated, and clinical validity, and has higher diagnostic value than indicators.

Ultrasonographic Assessment of Tissue Stiffness: Recent Progress in Transient Elastography and Shear Wave Elastography in the Liver and Various Organs

Ultrasonography is a noninvasive and widely accessible modality in clinical practice. Recently, ultrasonography has been used to evaluate tissue stiffness; the two representative techniques are transient elastography (FibroScan®) and shear wave elastography. These modalities are now generally used for the assessment of liver fibrosis, the prediction of hepatocarcinogenesis, and determining prognosis. In addition, shear wave elastography is available, not only for the liver but also for various other organs, including the breast and brain. In the breast and brain, shear wave elastography distinguishes malignant lesions from benign ones. Moreover, shear wave elastography can be useful for differentiating between ischemic and hemorrhagic strokes. This review summarizes the recent progress in transient elastography and shear wave elastography of the liver and introduces the advantages of ultrasonographic assessment of tissue stiffness in various organs, including the breast, brain, kidney, heart, thyroid, pancreas, muscle, and bone.

Is musculoskeletal pain associated with increased muscle stiffness? Evidence map and critical appraisal of muscle measurements using shear wave elastography

INTRODUCTION AND AIMS

Approximately 21% of the world's population suffers from musculoskeletal conditions, often associated with sensations of stiff muscles. Targeted therapy requires knowing whether typically involved muscles are objectively stiffer compared to asymptomatic individuals. Muscle stiffness is quantified using ultrasound shear wave elastography (SWE). Publications on SWE-based comparisons of muscle stiffness between individuals with and without musculoskeletal pain are increasing rapidly. This work reviewed and mapped the existing evidence regarding objectively measured muscle stiffness in musculoskeletal pain conditions and surveyed current methods of applying SWE to measure muscle stiffness.

METHODS

A systematic search was conducted in PubMed and CINAHL using the keywords "muscle stiffness", "shear wave elastography", "pain", "asymptomatic controls" and synonyms. The search was supplemented by a hand search using Google Scholar. Included articles were critically appraised with the AXIS tool, supplemented by items related to SWE methods. Results were visually mapped and narratively described.

RESULTS

Thirty of 137 identified articles were included. High-quality evidence was missing. The results comprise studies reporting lower stiffness in symptomatic participants, no differences between groups and higher stiffness in symptomatic individuals. Results differed between pain conditions and muscles, and also between studies that examined the same muscle(s) and pathology. The methods of the application of SWE were inconsistent and the reporting was often incomplete.

CONCLUSIONS

Existing evidence regarding the objective stiffness of muscles in musculoskeletal pain conditions is conflicting. Methodological differences may explain most of the inconsistencies between findings. Methodological standards for SWE measurements of muscles are urgently required.

Ultrasonic shear wave elastography predicts the quality of the residual tendon before the rotator cuff repair

BACKGROUND AND PURPOSE

Effective evaluation of rotator cuff tear residual tendon quality is the key to surgical repair. However, until now, the evaluation of rotator cuff tissue by ultrasonic shear wave elasticity (SWE) has been controversial. This prospective study analyzed the association between preoperative SWE and arthroscopic residual tendon quality scores.

METHODS

The shear wave velocity (SWV) of the deltoid muscle, the supraspinatus tendon, and the supraspinatus muscle were measured in full-thickness rotator cuff tear patients. Tendon quality was scored according to tear size, tendon margin, tendon thickness, and footprint coverage during arthroscopy. The arthroscopic scores were used as the gold standard, and the SWV ratio of tendon and muscle (supraspinatus tendon/deltoid and supraspinatus muscle/deltoid) were calculated and correlated with the arthroscopic scores.

RESULT

Eighty-nine patients (129 shoulders) were enrolled, including 89 operation shoulders and 40 control shoulders. In the group of operation shoulders, both the SWV ratios of tendon (SWV-RT) and the SWV ratio of muscle (SWV-RM) were negatively correlated with arthroscopic scores (The correlation coefficient (R) ranged from -0.722 to -0.884 and -0.569 to -0.689). The SWV-RT and SWV-RM of the operation shoulders were significantly lower than that of the control shoulders (p < 0.05).

CONCLUSION

SWE could be used to predict the quality of the residual tendon before the rotator cuff repair. SWV of the supraspinatus tendon and muscle was a useful parameter to predict the quality of the residual tendon.

CRITICAL RELEVANCE STATEMENT

Measuring the shear wave velocity of the supraspinatus tendon and muscle with SWE is useful for predicting the quality of the residual tendon which is one of the key factors for a successful rotator cuff repair.

KEY POINTS

• Evaluating the quality of the residual tendon is important before surgery. • Elasticity measurements were negatively correlated with the arthroscopic score. • SWE is useful for predicting the quality of the residual tendon.

Evaluation of skeletal muscle elasticity using color Doppler shear wave imaging

PURPOSE

This study aimed to (1) assess the precision and reproducibility of color Doppler shear wave imaging (CD SWI) by comparing it with shear wave elastography (SWE) via elasticity phantom measurements, and (2) investigate the potential clinical applications of CD SWI in the upper limb muscles by assessing the reproducibility of skeletal muscle elasticity evaluations.

METHODS

Four elastography phantoms of different stiffness (6.0-7.5 wt%) were used to assess the precision and reproducibility of CD SWI (compared with SWE) at depths. Typical upper limb muscles of 24 men were also assessed for this comparison.

RESULTS

At superficial depths (0-2 cm), the phantom measurements obtained using CD SWI and SWE were similar at all levels of stiffness. Furthermore, both methods were highly reliable, with almost perfect intra- and inter-operator reliabilities. At greater depths (2-4 cm), measurements obtained using both methods were similar at all stiffness levels. Although standard deviations (SDs) of the phantom measurements obtained using both methods at lower stiffness were similar, those at higher stiffness were different. The SD of the CD SWI measurements was < 50% of that of the SWE measurements. However, both methods were highly reliable in the phantom test, with almost perfect intra- and inter-operator reliabilities. The intra- and inter-operator reliabilities of the shear wave velocity measurements for typical muscles of the upper limbs were also substantial in clinical settings.

CONCLUSION

CD SWI is a valid method for measuring elasticity, with precision and reliability as high as those of SWE.

Changes of trunk muscle stiffness in individuals with low back pain: a systematic review with meta-analysis

BACKGROUND

Low back pain (LBP) is one of the most common musculoskeletal conditions. People with LBP often display changes of neuromuscular control and trunk mechanical properties, including trunk stiffness. Although a few individual studies have examined back muscle stiffness in individuals with LBP, a synthesis of the evidence appears to be lacking. Therefore, the aim of this systematic review with meta-analysis was to synthesize and evaluate the available literature investigating back muscle stiffness in association with LBP.

METHODS

We conducted a systematic review of the literature according to the PRISMA guidelines. We searched Pubmed, Scopus, Web of Science and ScienceDirect for studies, that compared back muscle stiffness, measured either by ultrasound-based elastography or myotonometry, between individuals with and without LBP. Pooled data of the included studies were presented descriptively. Additionally, we performed two meta-analyses to calculate the standardized mean difference between the two groups for resting stiffness of the multifidus and erector spinae muscle. For both meta-analyses, the random effect model was used and the weight of individual studies was calculated using the inverse-variance method. The quality of the included studies was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional studies. Furthermore, the certainty of evidence was evaluated using the GRADE approach.

RESULTS

Nine studies were included in our systematic review. Our results suggest that individuals with LBP have higher stiffness of the multifidus (SMD = 0.48, 95% CI: 0.15 - 0.81, p < 0.01; I2 = 48 %, p = 0.11) and erector spinae at rest (SMD = 0.37, 95% CI: 0.11 - 0.62, p < 0.01; I2 = 39 %, p = 0.14) compared to asymptomatic controls. On the other hand, the evidence regarding muscle stiffness during submaximal contractions is somewhat contradictory.

CONCLUSIONS

Based on the findings of this systematic review we conclude that people with LBP may have higher back muscle stiffness compared to asymptomatic controls. Addressing muscle stiffness might represent an important goal of LBP treatment. Nevertheless, our findings should be interpreted with extreme caution due to a limited quality of evidence, small number of included studies and differences in measurement methodology.

Chinese Ultrasound Doctors Association Guideline on Operational Standards for 2-D Shear Wave Elastography Examination of Musculoskeletal Tissues

The Ultrasound Physician Branch of the Chinese Medical Doctor Association sought to develop evidence-based recommendations on the operational standards for 2-D shear wave elastography examination of musculoskeletal tissues. A consensus panel of 22 Chinese musculoskeletal ultrasound experts reviewed current scientific evidence and proposed a set of 12 recommendations for 13 key issues, including instruments, operating methods, influencing factors and image interpretation. A final consensus was reached through discussion and voting. On the basis of research evidence and expert opinions, the strength of recommendation for each proposition was assessed using a visual analog scale, while further emphasizing the best available evidence during the question-and-answer session. These expert consensus guidelines encourage facilitation of the standardization of clinical practices for collecting and reporting shear wave elastography data.

Sonographic methods to predict type 2 diabetes patients with sarcopenia: B mode ultrasound and shear wave elastography

BACKGROUND

Type 2 diabetes accelerates the loss of muscle mass and strength. Sarcopenia is also one of the chronic complications of diabetes.

OBJECTIVE

To investigate the clinical value of B mode ultrasound (BMUS) and shear wave elastography (SWE) for predicting type 2 diabetic sarcopenia.

METHODS

We recorded Skeletal Muscle Mass Index (ASMI), grip strength, muscle thickness (MT), pinna angle (PA), fascicle length (FL), and the difference of Young's modulus in the relaxed states and tense states (ΔSWE). The correlations between clinical indicators and ultrasound characteristics were compared. A diagnostic model of sarcopenia was developed to assess the independent correlates and evaluate the diagnostic efficacy of sarcopenia.

RESULTS

ASMI was significantly and positively correlated with MT and ΔSWE (r = 0.826, 0.765, P < 0.01), and grip strength was significantly and positively correlated with MT and ΔSWE (r = 0.797, 0.818, P < 0.01). MT was the most significant predictor of sarcopenia (OR = 4.576, P < 0.001), and the cut-off value of MT was 11.4 mm (AUC: 0.952).

CONCLUSION

BMUS and SWE can quantitatively assess muscle mass and strength, and are effective methods to predict the occurrence of sarcopenia in elderly patients with type 2 diabetes.

The Use of Shear-Wave Ultrasound Elastography in the Diagnosis and Monitoring of Musculoskeletal Injuries

Ultrasound elastography is a valuable method employed to evaluate tissue stiffness, with shear-wave elastography (SWE) recently gaining significance in various settings. This literature review aims to explore the potential of SWE as a diagnostic and monitoring tool for musculoskeletal injuries. In total, 15 studies were found and included in the review. The outcomes of these studies demonstrate the effectiveness of SWE in detecting stiffness changes in individuals diagnosed with Achilles tendinopathy, Achilles tendon rupture, rotator cuff rupture, tendinosis of the long head of the biceps tendon, injury of the supraspinatus muscle, medial tibial stress syndrome, and patellar tendinopathy. Moreover, SWE proves its efficacy in distinguishing variations in tissue stiffness before the commencement and after the completion of rehabilitation in cases of Achilles tendon rupture and patellar tendinopathy. In summary, the findings from this review suggest that SWE holds promise as a viable tool for diagnosing and monitoring specific musculoskeletal injuries. However, while the field of ultrasound elastography for assessing musculoskeletal injuries has made considerable progress, further research is imperative to corroborate these findings in the future.

The value of ultrasound measurement of muscle thickness at different sites and shear wave elastography in Parkinson's disease with sarcopenia: a pilot study

Background

Patients with Parkinson's disease (PD) and sarcopenia often exhibit resilience, frailty, disability, and depression, highlighting the complex and interrelated nature of these conditions.

Objective

Despite the presence of clinical manifestations of muscle atrophy in both PD and sarcopenia, accurately discerning the coexistence of sarcopenia in PD patients remains a challenging task with significant implications for treatment strategies and prognostic assessments. This study aims to elucidate the specific ultrasonic diagnostic parameters associated with PD accompanied by sarcopenia through a comparative analysis of muscle ultrasound parameters in patients with PD, thereby presenting a novel approach for rapid identification of this condition.

Methods

A total of 110 participants were enrolled in this study, including patients with PD and control subjects. Demographic data, clinical characteristics, physical performance tests, appendicular skeletal muscle mass index (ASMI), bioelectrical impedance analysis and muscle ultrasound measurements were collected from all participants. The muscle ultrasound measurements encompassed assessments of muscle thickness, pennation angle and shear wave elastography at various anatomical sites.

Results

Parkinson's disease patients exhibited decreased muscle strength and physical performance, and increased shear wave elastography value. In PD patients with sarcopenia, body circumference, including calf circumference, mid-arm circumference, Waist-to-Hip Ratio and body mass index (BMI) were all significantly decreased. Biceps brachii muscle thickness (MT) and gastrocnemius MT decreased in PD patients with sarcopenia and low ASMI. Binary logistic regression analysis revealed that male PD patients, BMI and gastrocnemius MT were predictive factors for ASMI in PD patients.

Conclusion

Biceps brachii MT and gastrocnemius MT are important indicators for distinguishing whether PD patients have sarcopenia. Male patients, low BMI and gastrocnemius MT were identified as valid predictors of low ASMI in PD patients. The findings of this study provide important insights into the use of muscle ultrasound in the diagnosis of PD with sarcopenia.

Shear wave imaging the active constitutive parameters of living muscles

Shear wave elastography (SWE) of human skeletal muscles allows for measurement of muscle elastic properties in vivo and has important applications in sports medicine and for the diagnosis and treatment of muscle-related diseases. Existing methods of SWE for skeletal muscles rely on the passive constitutive theory and have so far been unable to provide constitutive parameters describing muscle active behavior. In the present paper, we overcome this limitation by proposing a SWE method for quantitative inference of active constitutive parameters of skeletal muscles in vivo. To this end, we investigate the wave motion in a skeletal muscle described by a constitutive model in which muscle active behavior has been defined by an active parameter. An analytical solution relating shear wave velocities to both passive and active material parameters of muscles is derived, based upon which an inverse approach has been developed to evaluate these parameters. To demonstrate the usefulness of the reported method, in vivo experiments were carried out on 10 volunteers to obtain constitutive parameters, particularly those describing active deformation behaviors of living muscles. The results reveal that the active material parameter of skeletal muscles varies with warm-up, fatigue and rest. STATEMENT OF SIGNIFICANCE: Existing shear wave elastography methods are limited to imaging the passive parameters of muscles. This limitation is addressed in the present paper by developing a method to image the active constitutive parameter of living muscles using shear waves. We derived an analytical solution demonstrating the relationship between constitutive parameters of living muscles and shear waves. Relying on the analytical solution, we proposed an inverse method to infer active parameter of skeletal muscles. We performed in vivo experiments to demonstrate the usefulness of the theory and method; the quantitative variation of the active parameter with muscle states such as warm-up, fatigue and rest has been reported for the first time.

Influence of Measurement Depth and Acquisition Parameters on Shear Wave Speed and Shear Wave Dispersion in Certified Phantoms Using a Canon Aplio Clinical Ultrasound Scanner

OBJECTIVE

The aim of the work described here was to investigate the relative contribution of confounding factors on liver shear wave speed (SWS) and shear wave dispersion slope (SWDS) measurements in three certified phantoms using a Canon Aplio clinical ultrasound scanner.

METHODS

A Canon Aplio i800 i-series ultrasound system (Canon Medical Systems Corporation, Otawara, Tochigi, Japan) with i8CX1 convex array (center frequency = 4 MHz) was used to examine dependencies caused by the depth, width and height of the acquisition box (AQB), the depth and size of the region of interest (ROI), the AQB angle and the pressure of the ultrasound probe on the surface of the phantom.

RESULTS

Results revealed that depth is the most significant confounder in both SWS and SWDS measurements. AQB angle, height and width and ROI size exhibited minimal confounding effects on measurements. For SWS, the most consistent measurement depth is when the top of the AQB is placed between 2 and 4 cm, and the ROI is located between 3 and 7 cm deep. For SWDS, results indicate that measurement values significantly decrease with depth from the surface of the phantom until approximately 7 cm deep, and consequently no stable area of AQB placement or ROI depth exists.

CONCLUSION

In contrast to SWS, the same ideal acquisition depth range cannot necessarily be applied to SWDS measurements because of a significant depth dependency.

Measuring Shear Wave Velocity in Adult Skeletal Muscle with Ultrasound 2-D Shear Wave Elastography: A Scoping Review

Ultrasound 2-D shear wave elastography (US 2D-SWE) is a non-invasive, cost-effective tool for quantifying tissue stiffness. Amidst growing interest in US 2D-SWE for musculoskeletal research, it has been recommended that shear wave velocity (SWV) should be reported instead of elastic moduli to avoid introducing unwanted error into the data. This scoping review examined the evolving use of US 2D-SWE to measure SWV in skeletal muscle and identified strengths and weaknesses to guide future research. We searched electronic databases and key review reference lists to identify articles published between January 2000 and May 2021. Two reviewers assessed the eligibility of records during title/abstract and full-text screening, and one reviewer extracted and coded the data. Sixty-six studies met the eligibility criteria, of which 58 were published in 2017 or later. We found a striking lack of consensus regarding the effects of age and sex on skeletal muscle SWV, and widely variable reliability values. Substantial differences in methodology between studies suggest a pressing need for developing standardized, validated scanning protocols. This scoping review illustrates the breadth of application for US 2D-SWE in musculoskeletal research, and the data synthesis exposed several notable inconsistencies and gaps in current literature that warrant consideration in future studies.

Shear Wave Elastography for Detecting Calf Muscle Stiffness: An Effective Tool for Assessing Sarcopenia

OBJECTIVES

To explore the feasibility of shear wave elastography for evaluating sarcopenia.

METHODS

The shear wave velocities (SWV) of the tibialis anterior, medial gastrocnemius, and soleus were measured in 130 subjects in the Second Affiliated Hospital of Fujian Medical University from January 2021 to June 2022. Consistency was evaluated in 20 cases using the intraclass correlation coefficient. According to the 2019 Asian Working Group for Sarcopenia（AWGS） diagnostic criteria, the patients were divided into a healthy and a sarcopenia group. The differences in SWV between the two groups were compared, and their correlation between calf muscles and muscle mass, grip strength, and pace were analyzed. The diagnostic cutoff value of calf muscle SWV for sarcopenia was obtained using receiver operating characteristic (ROC) curves, and the diagnostic efficacy of different ROC curves was compared.

RESULTS

The SWV inter-group and intra-group correlation coefficients of the three lower limbs muscles were all greater than 0.85. Moreover, the corresponding SWV in the sarcopenia group were significantly smaller than those in the healthy control group (P < .05). Further, SWV were positively correlated with the appendicular skeletal muscle mass index (ASMI), grip strength, and gait speed. Finally, the SWV of the anterior tibialis and medial gastrocnemius muscles were 3.02 and 2.26 m/s, respectively, and their diagnostic efficacy for sarcopenia did not differ significantly (Z = 0.190, P = .8497).

CONCLUSION

SWE can be used to detect the hardness of the anterior tibialis and medial gastrocnemius, calculate their muscle mass as an effective tool to evaluate sarcopenia.

Preliminary investigation of the effects of sitting with and without short active breaks on muscle stiffness assessed with shear-wave elastography

Purpose

The purpose of this preliminary study was to compare the effects of 1-h sitting with and without short active breaks on muscle stiffness as measured by shear-wave elastography (SWE).

Methods

The participants (7 females, 3 males; age: 24.9 ± 1.2 years) completed two (with and without active breaks) 1-h sitting exposures on separate days. Active breaks (2–3 min) were performed at 20 min and 40 min time marks and comprised simple stretching and activation exercises. Before, during (30 min) and after (1 h) of sitting, shear modulus of upper trapezius, lumbar region of erector spinae and rectus femoris muscles was measured with SWE.

Results

Statistically significant effects of sitting exposure in erector spinae muscle stiffness were noted (p = 0.041; η2 = 0.38). There were no other statistically significant effects of sitting exposure or condition (with/without breaks).

Conclusions

Although few statistically significant effects were detected, the trends in this preliminary trial suggest that prolonged sitting increases muscle stiffness and warrants further investigation of short active breaks with larger sample sizes.

Assessment of ultrasound shear wave elastography: An animal ex-vivo study

OBJECTIVES

To explore the influence of the surrounding environment of the target tissue, lesion size, and rectangular sampling box size on shear wave speed (SWS).

METHODS

The tendon SWS was acquired ex-vivo. Then the tendons were dissected and buried in the couplant (gel) and evaluated by two-dimensional shear wave elastography (2D-SWE). Finally, the tendons were placed in the isolated muscles to simulate the intramuscular lesions, and their elasticity was tested under two rectangular sampling box conditions. The isolated complete liver SWS was acquired. Similarly, the large and small pieces of livers were cut out, placed in the muscles, and assessed by SWE under two rectangular sampling box conditions. The SWS acquired under different conditions was compared. Variability was evaluated using the coefficient of variation (CV). The intraclass correlation coefficient (ICC) was used to evaluate repeatability.

RESULTS

The SWS of the tendons ex-vivo, buried in the couplant and placed in the isolated muscles showed significant differences (p < 0.001). The ex-vivo condition produced the highest SWS and CV values. There were significant differences in SWS of livers with different sizes placed in muscles (p < 0.001). The highest SWS value was associated with small pieces of livers. No significant difference was found in SWS acquired under different rectangular box sizes (p > 0.05).

CONCLUSIONS

Under the present study conditions, the surrounding environment of the target tissue makes a big difference to lesion SWS values. The lesion size will affect the assessment of its inherent elasticity. The size of the sampling frame has no significant effect on the tissue SWS.

Relationship Between Muscle Quality or Stiffness Measured by Ultrasonography and Range of Motion in Hospitalized Older Adults

Older adults who require nursing care have joint contractures characterized by limited range of motion (ROM). The present study investigated age-related muscle changes using ultrasonography and the relationship between ROM and muscle changes in older adults. Twenty-two healthy young adults (mean age: 23.3 y) and 60 hospitalized older adults (mean age: 86.1 y) participated. ROM of hip abduction was measured using a goniometer. Echo intensity (EI), reflecting interstitial fibrous tissue or fat within adductor longus (ADDl) was measured using B-mode ultrasonography, and strain ratio (SR), reflecting ADDl stiffness, was measured by strain elastography. The Mann-Whitney U-test and Spearman's correlation test were used for analysis. The ROM and SR of older adults were significantly lower than those of young adults (both p values <0.001). The EI was significantly higher in older adults than in young adults (p < 0.001). In older adults, the SR was moderately correlated with ROM (ρ = 0.49, p < 0.001). In conclusion, limited ROM and increase in interstitial fibrous tissue or fat and stiffness occur with aging, and the SR measured by strain elastography is useful for investigating the effect of muscle stiffness on the ROM of hospitalized older adults.

Characterizing Musculoskeletal Tissue Mechanics Based on Shear Wave Propagation: A Systematic Review of Current Methods and Reported Measurements

Developing methods for the non-invasive characterization of the mechanics of musculoskeletal tissues is an ongoing research focus in biomechanics. Often, these methods use the speed of shear wave propagation to characterize tissue mechanics (e.g., shear wave elastography and shear wave tensiometry). The primary purpose of this systematic review was to identify, compare, and contrast current methods for exciting and measuring shear wave propagation in musculoskeletal tissues. We conducted searches in the Web of Science, PubMed, and Scopus databases for studies published from January 1, 1900, to May 1, 2020. These searches targeted both shear wave excitation using acoustic pushes and mechanical taps, and shear wave speed measurement using ultrasound, magnetic resonance imaging, accelerometers, and laser Doppler vibrometers. Two reviewers independently screened and reviewed the articles, identifying 524 articles that met our search criteria. Regarding shear wave excitation, we found that acoustic pushes are useful for exciting shear waves through the thickness of the tissue of interest, and mechanical taps are useful for exciting shear waves in wearable applications. Regarding shear wave speed measurement, we found that ultrasound is used most broadly to measure shear waves due to its ability to study regional differences and target specific tissues of interest. The strengths of magnetic resonance imaging, accelerometers, and laser Doppler vibrometers make them advantageous to measure shear wave speeds for high-resolution shear wave imaging, wearable measurements, and non-contact ex vivo measurements, respectively. The advantages that each method offers for exciting and measuring shear waves indicate that a variety of systems can be assembled using currently available technologies to determine musculoskeletal tissue material behavior across a range of innovative applications.

Muscle Shear Elastic Modulus Provides an Indication of the Protection Conferred by the Repeated Bout Effect

Background: The neuromuscular system is able to quickly adapt to exercise-induced muscle damage (EIMD), such that it is less affected by subsequent damaging exercise, a phenomenon known as the repeated bout effect (RBE). The objective was to determine whether the mechanical properties of the quadriceps, as evaluated by shear wave elastography (SWE), were less affected when a second bout of eccentric-biased exercise was performed 2 weeks later. It was hypothesized that the first bout would confer protection against extensive muscle damage through an adaptation of the muscle stiffness before the second bout (i.e., higher muscle stiffness).

Methods: Sixteen males performed two identical bouts of downhill walking separated by 2 weeks (45 min at 4.5 km.h−1; gradient: 25%; load: 30% of the body mass). Rectus femoris (RF) and vastus lateralis (VL) resting shear elastic modulus (µ) and EIMD symptoms were measured before and up to 7 days following the exercise bouts. Changes in neuromuscular function was evaluated by maximal voluntary contraction torque, voluntary activation level, evoked mechanical response to single and double (10 and 100 Hz doublets) electrical stimulation. An index of protection (IP) was calculated for EIMD symptoms to assess magnitude the RBE.

Results: EIMD symptoms were less affected after the second than the first exercise bout. RF and VL-µ increased (p &lt; 0.001) only after the first exercise. RF µ was elevated up to 2 weeks after the end of the first exercise (p &lt; 0.001) whereas VL µ was only increased up to 24 h. The increase in µ observed 2 weeks after the end of the first exercise was correlated with the IP; i.e., attenuation of alterations in muscle µ, 10 Hz-doublet amplitude and rate of torque development after the second exercise bout (p &lt; 0.05).

Conclusion: We showed that muscle µ assessed by SWE was sensitive to the RBE, with a differential effect between VL and RF. The persistent increase in µ was associated with the attenuation of neuromuscular impairments observed after the second bout, suggesting that the increased muscle stiffness could be a “protective” adaptation making muscles more resistant to the mechanical strain associated to eccentric contractions.

A scoping review of methods used in musculoskeletal soft tissue and nerve shear wave elastography studies

This scoping review of shear wave elastography (SWE) articles in musculoskeletal soft tissue and nerve research demonstrates methodological heterogeneity resulting from a lack of standardized data collection and reporting requirements. Seven literature databases were searched for original articles published in English from 2004-2020 that examine human skeletal muscles, tendons, and nerves in vivo. Although 5,868 records were initially identified, only 375 reports met inclusion criteria. Of the 375 articles, 260 examined 89 unique muscles, 94 examined 14 unique tendons, and 43 examined 8 unique nerves. Cohorts were often small (n = 11-20) and young (mean = 20-29 years), and participants were typically tested in the prone position. Regarding equipment, a variety of ultrasound systems (n = 11), ultrasound models (n = 18), and transducers (n = 19) were identified. Only 11% of articles contained information on the use of electromyography to confirm absence of muscle activity, and only 8% reported measurement depth. Since musculoskeletal soft tissue and nerve stiffness can vary significantly based on data collection methods, it is essential to standardize SWE collection and reporting procedures. This will allow SWE to serve as a valid and reproducible tool for assessing tissue pathology, disease progression, and response to intervention within a variety of musculoskeletal and nerve-related disorders.

Assessment of knee collateral ligament stiffness by strain ultrasound elastography

BACKGROUND: Knowledge of the biomechanics of the normal collateral ligaments is important to secure optimal stability of the knee following injury. Various in vitro methods have been described in evaluating the biomechanics of these ligaments. However, a method of direct evaluation has not been reported. OBJECTIVE: To determine the stiffness characteristics of the collateral ligaments of the knee using strain ultrasound elastography. METHODS: Strain ultrasound elastography was performed on different components of the collateral ligaments in various angles of knee flexion in 18 healthy males (36 ligaments). We measured relative stiffness of the ligaments using strain ratio (SR = target tissue strain/reference strain). A lower strain ratio indicates higher relative stiffness. RESULTS: There was moderate to excellent intra- and inter-rater agreement for strain ratio measurements in all ligament portions. Strain ratios were lowest at 0° in all three ligaments, indicating high relative stiffness. In the superficial and deep medial collateral ligaments, the strain ratio increased with increasing knee flexion, whereas in the lateral collateral ligament, stiffness showed a tendency to fluctuate. CONCLUSION: Strain ultrasound elastography is a reliable tool for monitoring relative stiffness of the collateral ligaments of the knee and is easily applied to the routine clinical setting.

Limitations of Muscle Ultrasound Shear Wave Elastography for Clinical Routine-Positioning and Muscle Selection

Shear wave elastography (SWE) is a clinical ultrasound imaging modality that enables non-invasive estimation of tissue elasticity. However, various methodological factors—such as vendor-specific implementations of SWE, mechanical anisotropy of tissue, varying anatomical position of muscle and changes in elasticity due to passive muscle stretch—can confound muscle SWE measurements and increase their variability. A measurement protocol with a low variability of reference measurements in healthy subjects is desirable to facilitate diagnostic conclusions on an individual-patient level. Here, we present data from 52 healthy volunteers in the areas of: (1) Characterizing different limb and truncal muscles in terms of inter-subject variability of SWE measurements. Superficial muscles with little pennation, such as biceps brachii, exhibit the lowest variability whereas paravertebral muscles show the highest. (2) Comparing two protocols with different limb positioning in a trade-off between examination convenience and SWE measurement variability. Repositioning to achieve low passive extension of each muscle results in the lowest SWE variability. (3) Providing SWE shear wave velocity (SWV) reference values for a specific ultrasound machine/transducer setup (Canon Aplio i800, 18 MHz probe) for a number of muscles and two positioning protocols. We argue that methodological issues limit the current clinical applicability of muscle SWE.

Sources of Variability in Shear Wave Speed and Dispersion Quantification with Ultrasound Elastography: A Phantom Study

There is a growing interest in quantifying shear-wave dispersion (SWD) with ultrasound shear-wave elastography (SWE). Recent studies suggest that SWD complements shear-wave speed (SWS) in diffuse liver disease diagnosis. To accurately interpret these metrics in clinical practice, we analyzed the impact of operator-dependent acquisition parameters on SWD and SWS measurements. Considered parameters were the acquisition depth, lateral position and size of the region of interest (ROI), as well as the size of the SWE acquisition box. Measurements were performed using the Canon Aplio i800 system (Canon Medical Systems, Otawara, Tochigi, Japan) and four homogeneous elasticity phantoms with certified stiffness values ranging from 3.7 to 44 kPa. In general, SWD exhibited two to three times greater variability than SWS. The acquisition depth was the main variance-contributing factor for both SWS and SWD, which decayed significantly with depth. The lateral ROI position contributed as much as the acquisition depth to the total variance in SWD. Locations close to the initial shear-wave excitation pulse were more robust to biases because of inaccurate probe-phantom coupling. The size of the ROI and acquisition box did not introduce significant variations. These results suggest that future guidelines on multiparametric elastography should account for the depth- and lateral-dependent variability of measurements.

Muscle Ultrasonographic Elastography in Children: Review of the Current Knowledge and Application

Ultrasonographic elastography is a relatively new imaging modality for the qualitative and quantitative assessments of tissue elasticity. While it has steadily gained use in adult clinical practice, including for liver diseases, breast cancer, thyroid pathologies, and muscle and tendon diseases, data on its paediatric application is still limited. Moreover, diagnosis of muscular diseases in children remains challenging. The gold standard methods, namely biopsy, electroneurography, and electromyography, are often limited owing to their invasive characteristics, possible contraindications, complications, and need for good cooperation, that is, a patient’s ability to perform certain tasks during the examination while withstanding discomfort, which is a significant problem especially in younger or uncooperative children. Genetic testing, which has broad diagnostic possibilities, often entails a high cost, which limits its application. Thus, a non-invasive, objective, repeatable, and accessible tool is needed to aid in both the diagnosis and monitoring of muscle pathologies. We believe that elastography may prove to be such a method. The aim of this review was to present the current knowledge on the use of muscle elastography in the paediatric population and information on the limitations of elastography in relation to examination protocols and factors for consideration in everyday practice and future studies.

Muscle elasticity is different in individuals with diastasis recti abdominis than healthy volunteers

Objective

To determine the value of shear wave elastography (SWE) in assessing abdominal wall muscles, including rectus abdominis (RA), external oblique muscle (EO), internal oblique muscle, and transversus abdominis (TrA) in patients with diastasis recti abdominis (DRA) and healthy controls.

Methods

From October 2018 to December 2019, 36 postpartum DRA patients and 24 nulliparous healthy women were identified. Inter-rectus distance (IRD) measurements were taken by B-mode ultrasound. Shear wave speed (SWS) values were acquired by one operator at ten specific locations. Clinical and ultrasound variables, including demographics, IRD, muscle thickness, and muscle SWS, were compared between the two groups using Student’s t test or Fisher's exact test. Pearson correlation analyses were conducted for the variables of IRD, muscle thickness, and SWS in the 36 DRA patients.

Results

The maximum diameter of recti abdominus separation was located at the umbilicus in DRA patients (4.59 ± 1.14 cm). The SWS value was significantly lower in the RA (p = 0.003) and higher in the TrA muscle (p < 0.001) in DRA patients compared with the age-matched controls. However, SWS in both muscles (RA and TrA) showed a statistically positive correlation with IRD (p < 0.05). In addition, the SWS value in EO statistically decreased in DRA patients compared with the healthy controls (1.65 ± 0.15 vs. 1.79 ± 0.14, p = 0.001).

Conclusions

The application of SWE to abdominal wall muscles in DRA patients is feasible. The correlation between SWS value and IRD in RA should be interpreted with caution.

Objective Assessment of Regional Stiffness in Vastus Lateralis with Different Measurement Methods: A Reliability Study

The objective of this study was to evaluate the reliability of four methods of assessing vastus lateralis (VL) stiffness, and to describe the influence of structural characteristics on them. The stiffness of the dominant lower-limb’s VL was evaluated in 53 healthy participants (28.4 ± 9.1 years) with shear wave elastography (SWE), strain elastography (SE), myotonometry and tensiomyography (TMG). The SWE, SE and myotonometry were performed at 50%, and TMG was assessed at 30%, of the length from the upper pole of the patella to the greater trochanter. The thickness of the VL, adipose tissue and superficial connective tissue was also measured with ultrasound. Three repeated measurements were acquired to assess reliability, using intraclass correlation coefficients (ICC). Pearson’s correlation coefficients were calculated to determine the relationships between methodologic assessments and between structural characteristics and stiffness assessments of the VL. Myotonometry (ICC = 0.93; 95%-CI = 0.89,0.96) and TMG (ICC = 0.89; 95%-CI = 0.82,0.94) showed excellent inter-day reliability whereas with SWE (ICC = 0.62; 95%-CI = 0.41,0.77) and SE (ICC = 0.71; 95%-CI = 0.57,0.81) reliability was moderate. Significant correlations were found between myotonometry and VL thickness (r = 0.361; p = 0.008), adipose tissue thickness (r = −0.459; p = 0.001) and superficial connective tissue thickness (r = 0.340; p = 0.013). Myotonometry and TMG showed the best reliability values, although myotonometry stiffness values were influenced by the structural variables of the supra-adjacent tissue.

Hamstring strains in professional rugby players result in increased fascial stiffness without muscle quality changes as assessed using shear wave elastography

INTRODUCTION

Hamstring strain injury is common among sports injuries. A previous history of this injury is considered a strong predictor of recurrent hamstring strain injury. Fascial tissue reportedly becomes stiffer after hamstring strain injury. However, the association between fascial stiffness and previous hamstring strain injury has not been investigated in clinical studies. We aimed to determine whether a previous history of hamstring strain injury affects fascial tissue and muscle tissues using shear wave elastography.

METHOD

In eleven male professional rugby players, the stiffness as a shear modulus (kPa) of fascial tissue and muscle was measured on the specific injured area measured by magnetic resonance imaging (MRI) at resting position by using shear wave elastography. The side-to-side differences between the injured and the uninjured side were analyzed. The length and area of the muscle scar tissue were evaluated by MRI in relation to fascial stiffness.

RESULTS

The shear elastic modulus of fascia was stiffer in the injured vs. the uninjured side; however, no difference was observed in the muscle. No significant relationship was detected between the length and area of the muscle scar tissue (all P > 0.05).

DISCUSSION

Rugby players with a previous history of hamstring strain injury exhibited passive stiffness of fascial tissues in the injured leg, regardless of the length or area of the muscle scar tissue. However, the passive stiffness of muscles was same between the injured and the uninjured leg.

CONCLUSION

The results can be beneficial to consider future risk for hamstring strain injuries.

Reliability and Validity of Ultrasound Elastography for Evaluating Muscle Stiffness in Neurological Populations: A Systematic Review and Meta-Analysis

OBJECTIVE

Ultrasound elastography is an emerging diagnostic technology used to investigate the biomechanical properties of the musculoskeletal system. The purpose of this study was to systematically review the psychometric properties of ultrasound elastography techniques for evaluating muscle stiffness in people with neurological conditions.

METHODS

A systematic search of MEDLINE, EMBASE, CINAHL, and Cochrane Library databases was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Using software, reviewers independently screened citations for inclusion. Peer-reviewed studies that evaluated in vivo muscle stiffness in people with neurological conditions and reported relevant psychometric properties were considered for inclusion. Twenty-one articles were included for final review. Data relevant to measurement technique, site, and neurological condition were extracted. The Consensus-Based Standards for the Selection of Health Measurement Instruments checklist was used to rate the methodological quality of included studies. The level of evidence for specific measurement outcomes was determined using a best-evidence synthesis approach.

RESULTS

Reliability varied across populations, ultrasound systems, and assessment conditions (ie, joint/body positions, active/passive muscle conditions, probe orientation), with most studies indicating moderate to good reliability (ICC = 0.5-0.9, n = 13). Meta-analysis results showed a good overall correlation across studies (r = 0.78, 95% confidence interval = 0.64-0.86), with no between-group difference based on population (Q1 = 0.00). Convergent validity was demonstrated by strong correlations between stiffness values and measures of spasticity (n = 5), functional motor recovery or impairment (n = 5), and grayscale or color histogram pixel intensities (n = 3). Discriminant or known-groups validity was also established for multiple studies and indicated either significant between-group differences in stiffness values (n = 12) or within-group differences between more and less affected limbs (n = 6). Responsiveness was observed in all intervention studies reporting posttreatment stiffness changes (n = 6).

CONCLUSIONS

Overall, ultrasound elastography techniques showed moderate reliability in evaluating in vivo muscle stiffness, good convergent validity with relevant clinical assessments, and good divergent validity in discriminating tissue changes within and between groups.

IMPACT

Ultrasound elastography has clinical utility in assessing muscle stiffness, monitoring its temporal changes, and measuring the response to intervention in people with neurological conditions.

Shear modulus of multifidus and longissimus muscles measured using shear wave elastography correlates with muscle activity, but depends on image quality

Shear wave elastography (SWE) estimates shear modulus in muscle. This is interpreted as an index of muscle stiffness, but depends on muscle characteristics. This study evaluated relationship between shear modulus and myoelectric activity of lumbar multifidus and longissimus muscles to assess its validity. Intramuscular electromyography (EMG) of multifidus (deep [DM], superficial [SM] fibres) at L4/5, longissimus [LG] at L2, were recorded in nine healthy participants. Participants performed isometric trunk extension in side-lying from 0 to 30% maximal voluntary contraction (MVC) with EMG amplitude feedback. Using SWE, two regions of interest (ROI) were investigated in each muscle. Generally, shear modulus was moderately correlated with root mean squared (RMS) EMG (r = 0.50-0.78). Univariate and multiple regression analyses showed ultrasound/SWE features of 'B-mode quality' (24.5%), '%Void pixels' (17.9%) and 'Connective tissue' (16.2%) explained most variation in the shear modulus/EMG relationship. Regression prediction scores generated using imaging features were correlated with r-coefficients of shear modulus/EMG relationship. When analysis was restricted to high quality data (i.e., regression prediction score above an a priori defined threshold), the shear modulus/EMG relationship increased to r = 0.70-0.96. Although a linear relationship between shear modulus/EMG was confirmed, supporting validity of SWE measures in anatomically distinct back muscles, this depends on image quality.

Biceps brachii muscle hardness assessed by a push-in meter in comparison to ultrasound strain elastography

This study investigated the relationship between push-in meter (PM) and ultrasound strain elastography (USE) for biceps brachii (BB) muscle hardness. BB hardness of 21 young men was assessed by PM and USE during rest and isometric contractions of six different intensities (15, 30, 45, 60, 75, 90% of maximal voluntary contraction: MVC) at 30°, 60° and 90° elbow flexion. Muscle hardness (E) was calculated from the force-displacement relationship in PM, and strain ratio (SR) between an acoustic coupler (elastic modulus: 22.6 kPa) and different regions of interest (ROIs) in BB was calculated and converted to Young's modulus (YM) in USE. In resting muscle, E was 26.1 ± 6.4 kPa, and SR and YM for the whole BB was 0.88 ± 0.4 and 30.8 ± 12.8 kPa, respectively. A significant (p < 0.01) correlation was evident between E and logarithmical transformed SR (LTSR) for the ROI of whole BB (r = - 0.626), and E and converted YM (r = 0.615). E increased approximately ninefold from resting to 90% MVC, and E and LTSR (r = - 0.732 to - 0.880), and E and converted YM for the SR above 0.1 were correlated (r = 0.599-0.768, p < 0.01). These results suggest that muscle hardness values obtained by PM and USE are comparable.

Usability and Pitfalls of Shear-Wave Elastography for Evaluation of Muscle Quality and Its Potential in Assessing Sarcopenia: A Review

Sarcopenia is age-related progressive and generalized loss of skeletal muscle mass and strength. Its prevalence is rising, which poses a burden for society because it increases disability and dependency and therefore raises health care costs. Muscle mass quality, however-an essential part of sarcopenia-is not easily diagnosable yet. Recent interest has risen for ultrasonographic evaluation of muscle. This review introduces muscle elastography as a possible, easy and cheap tool to evaluate qualitative muscle parameters. Basic principles of muscle elastography are described, as well as different elastography techniques and some technical considerations. Furthermore, a proposal for practical guidelines is offered and factors influencing muscle stiffness are highlighted.

Site dependent elastic property of human iliotibial band and the effect of hip and knee joint angle configuration

The iliotibial band (ITB) is the lateral thickening of the fascia lata. The ITB has been extensively studied for its relevance to injury, but not much is known about its elastic properties. We aimed to investigate the site- and joint angle-dependence of ITB elasticity. We tested twelve healthy males (22-30 years; in vivo) and twelve male cadavers (69-93 years; cadaver). The Young's modulus of the ITB was measured in the longitudinal direction at five sites (over the proximal, middle, and distal bellies of the vastus lateralis (VL), superior border of the patella, and between femur and tibia) of the right limb, by ultrasound shear wave elastography (in vivo) and the tensile test (cadaver). Joint angle-dependence was also studied for nine different positions (knee angles at 0, 25, 90˚ x hip angles at 0, 40, 90˚) (in vivo). Over VL, the ITB was more compliant at the distal (17.6-190.1 kPa; in vivo, 219.4 ± 68.8 MPa; cadaver, mean ± SD) than other sites (24.2-221.4 kPa, 337.9-362.7 MPa). The ITB at the superior border of the patella and between femur and tibia was stiffer in vivo (31.8-271.8 and 50.9-208.8 kPa), while it was more compliant in cadavers (113.4 ± 63.7 and 130.4 ± 73.7 MPa), compared to other sites. The ITB became stiffer associated with increasing hip extension angle and knee flexion angle, and the hip remarkably affecting the values regardless of site (in vivo). Our findings have clinical significance with respect to the site- and joint angle-dependence of ITB-related overuse injury.

Use of Shear Wave Elastography to Quantify Abdominal Wall Muscular Properties in Patients With Incisional Hernia

Shear wave elastography (SWE) is a potential modality that quantitatively measures the elasticity (shear wave speed [SWS]) of musculoskeletal structure. This SWS was bilaterally measured in the rectus abdominis (RA), external oblique (EO) muscle, internal oblique (IO) muscle and transversus abdominis (TrA) using SWE in 28 patients with incisional hernia and 14 healthy controls. The differences in muscle thickness for IO and TrA were significant between the two groups (p < 0.05). The SWS of RA, EO, IO and TrA was significantly higher in the incisional hernia patient group than in the healthy controls (p < 0.05). Significant differences were also observed between the upper and lower points in both groups (p < 0.05). The measurements of SWS help in evaluating the elastic properties of abdominal wall muscles, which could further aid in preparing treatment plans to improve muscle strength.

Shear-Wave and Strain Ultrasound Elastography of the Supraspinatus and Infraspinatus Tendons in Patients with Idiopathic Adhesive Capsulitis of the Shoulder: A Prospective Case-Control Study

Objective

To compare the elasticity of the supraspinatus tendon (SST) and infraspinatus tendon (IST) in patients with idiopathic adhesive capsulitis of the shoulder (ACS) with those in the control groups and to evaluate the relationship between age and tendon elasticity.

Materials and Methods

The Institutional Review Board approved this prospective, case-control study, which was conducted between November 2017 and March 2018, and informed consent was obtained from all participants. Control groups comprised healthy individuals or those with asymptomatic contralateral shoulders. Twenty-five shoulders in 20 participants in the ACS group (14 women; 53.5 ± 7.9 years) and 24 shoulders in 18 participants in the control group (6 women; 52.6 ± 10.5 years) were included. Elastography was performed in the oblique coronal plane at the neutral shoulder position. Mean/maximum/minimum velocity and stiffness from the shear-wave ultrasound elastography (SWE) and strain ratio (subcutaneous fat/target-tendon) from the strain ultrasound elastography (SE) of the SST and IST were evaluated. Statistical analyses were performed using the Mann-Whitney U test, receiver operating characteristic (ROC) curve, and Spearman correlation.

Results

Both velocity and stiffness in SWE were higher, and the strain ratio in SE was lower in participants with symptomatic shoulders than in those with normal shoulders (p < 0.001). SST- and IST-mean velocity, mean stiffness, and strain ratios showed excellent area under the ROC curve (> 0.970). The elastic modulus was little correlated with age (ρ = −0.340–0.239).

Conclusion

SWE and SE indicated that SST and IST were stiffer in patients with ACS than in those with normal shoulders regardless of aging.

Influence of Load and Transducer Bandwidth on the Repeatability of In Vivo Tendon Stiffness Evaluation Using Shear Wave Elastography

Objective:

To determine how different examination protocols with the use of transducers, of different bandwidths, and applied with varied tension to tendons would influence the sonographic study results.

Methods:

Thirty-one participants were divided into two groups, with one subject used for theoretical investigation (A) and the remaining participants (B = 30) forming the study cohort. Both sets of participants were examined with three different transducers (SL10–3, SL15–4, and SL18–7) as well as with variable loading on the Achilles tendon (relaxed, tensed, and loaded). The resulting coverage of the color map provided qualitative tendon stiffness and quantitative tendon stiffness values.

Results:

The estimated mean coverage extent, using elastographic color maps, produced by the three transducers was 98%, 98%, and 99%, respectively, in the relaxed state. Likewise, in the tensed state, mean coverage was 85%, 82%, and 77% in group A and 91%, 78%, and 71% in group B, respectively. Examining tendons that were loaded, the mean coverage was 68%, 42%, and 41%, respectively. The quantitative relaxed mean tendon elasticity values were 323, 366, and 393 kPa, respectively, in group A. Likewise, the relaxed mean values were 329, 341, and 358 kPa, respectively, in group B. The quantitative tensed mean tendon elasticity values were 413, 460, and 426 kPa, respectively, in group A. Likewise the tensed mean values were 412, 440, and 436 kPa, respectively, in group B.

Conclusions:

Varying the tendon loading significantly influenced the color map coverage, which governs the most reliable quantitative measurements on relaxed tendons. The best color map coverage was achieved using the transducer with the lowest frequency, regardless of the tension applied.

Can Strain Elastography Predict Malignancy of Soft Tissue Tumors in a Tertiary Sarcoma Center?

This study aims to investigate the ability of ultrasound strain elastography as an adjunct to predict malignancy in soft tissue tumors suspect of sarcoma or metastasis in a tertiary reference center for sarcoma. A total of 137 patients were included prospectively. Patients were referred on the basis of clinical or radiological suspicion of malignant soft tissue tumor. All patients had previously undergone diagnostic imaging (MRI, CT or PET-CT). After recording strain elastography cine loops, ultrasound guided biopsy was performed. Three investigators, who were blinded to final diagnosis, reviewed all elastograms retrospectively. For each elastogram, a qualitative, visual 5-point score was decided in consensus and a strain ratio was calculated. Final pathology obtained from biopsy or tumor resection served as gold standard. Eighty-one tumors were benign, and 56 were malignant. t-tests showed a significant difference in mean visual score between benign and malignant tumors. There was no significant difference in mean strain ratio between the two groups. Strain elastography may be a valuable adjunct to conventional B-mode ultrasound, perhaps primarily in primary care, when considering whether to refer to a sarcoma center or to biopsy, although biopsies cannot reliably be ruled out based on the current data.

Effect of acquisition depth and precompression from probe and couplant on shear wave elastography in soft tissue: an in vitro and in vivo study

Background

Shear wave elastography is a promising method to diagnose early musculoskeletal lesions. We aimed to explore the feasible depth and acceptable precompression applied by probe and couplant for soft tissues in the present system.

Methods

Ex-vivo muscles were evaluated at depths of 0.5-6 cm by 3 operators, using 1-5 mm couplant thickness and 0-3.0 kPa probe pressure. We compared the shear wave speed (SWS) and used intraclass correlation coefficients to assess reproducibility. In vivo skin and subcutaneous superficial fascia from volunteers were tested at depths ranging from 0.1-0.5 cm with 1-20 mm couplant thickness.

Results

The SWS of ex-vivo muscles varied and increased with depth, and could not be acquired at 6 cm because the shear wave failed to be detected. Furthermore, while the SWS of ex-vivo muscles were not affected by the couplant thickness, it was affected by probe pressure. Most cases demonstrated a satisfactory agreement degree of the intraoperator reproducibility (ICC, 0.81-0.95) and a substantial interoperator reproducibility (ICC >0.60). Inter- and intra-operator reproducibility was better at a depth of 0.5-4 cm than at 5 cm. In the in vivo study, when tissues within a 0.2 cm depth were evaluated, the SWS that was acquired using a couplant thickness of >10 mm was different from that acquired using other thicknesses.

Conclusions

The SWS acquired at a depth of ≤3 cm with a suitable amount of couplant is recommended.

Changes in the Linear Relationship between Muscle Contraction Intensity and Muscle Hardness after Rectus Femoris Muscle Strain

Objective

Joint torque differences between healthy and rehabilitated legs are often measured as a clinical index of recovery from muscle strain injury. Unfortunately, it should be noted that this is a questionable evaluation measure of the muscle after injury because it is a composite value including related cooperating muscles. Meanwhile, the use of ultrasound elastography for the measurement of individual muscle mechanical properties (i.e., muscle hardness) has recently expanded. The purpose of this study was to examine, using ultrasound elastography, the differences in the linear relationship between muscle contraction intensity and muscle hardness during knee extension in athletes who had recovered from grade II rectus femoris muscle strain injury through comparison of the healthy and rehabilitated legs.

Methods

Six athletes participated. Rectus femoris muscle hardness, determined during isometric contraction at 10%, 20%, 30%, and 40% of maximum voluntary contraction, was evaluated using ultrasound strain elastography.

Results and Conclusion

The results indicated that for the healthy legs, the strain ratios, as indicated by muscle hardness, decreased linearly (became harder) with contraction intensity, but the strain ratios for the rehabilitated legs decreased nonlinearly. These results show the danger of judging the recovery period using only the difference between healthy and rehabilitated muscle strengths and the importance of evaluating individual muscles.

Which Confounders Have the Largest Impact in Shear Wave Elastography of Muscle and How Can They be Minimized? An Elasticity Phantom, Ex Vivo Porcine Muscle and Volunteer Study Using a Commercially Available System

The goal of the study was to investigate the quantitative impact of region of interest (ROI), software choice, muscle fiber orientation and preload tension on shear wave velocity (SWV). First, SWV was assessed in an isotropic elasticity phantom and ex vivo porcine muscle using a commercially available clinical ultrasound system. Secondly, SWV was acquired in relaxed and stretched calf muscles of healthy volunteers (dorsal extension of the talocrural joint), for both parallel and transverse probe direction to the fibers, as well as for different ROIs and software versions. The effect of intermediate probe-fiber alignments was also analyzed. Finally, the impact of confounding factors on SWV reproducibility was minimized with a second force-controlled volunteer study, in which the calf was isometrically loaded, and fiber orientation and ROI were well-defined. 2046 in vivoSWE images were acquired to analyze SWV reproducibility with different confounder settings. In healthy volunteers, the main variance-contributing factors were in order of importance muscle tension, fiber orientation, horizontal ROI size and insertion depth. Regression analysis showed significantly reduced SWV with increasing insertion depth for each study material. Parallel probe-fiber orientation, muscle stretch and increasing horizontal ROI size led to significantly higher SWV. Based on the results of the study, we provide recommendations to minimize the impact of confounders in musculoskeletal elastography and discuss the main confounding mechanisms and trade-offs between confounding variables. Coefficients of variation can be significantly reduced with a controlled protocol, if the confounders are clinically taken into account.

Using shear-wave elastography in skeletal muscle: A repeatability and reproducibility study on biceps femoris muscle

Shear-wave electrography (SWE) is a method used to assess tissue elasticity. Recently, it has been used to assess muscle stiffness, but the reliability of SWE for this purpose has not been thoroughly investigated. The purpose of this study was to evaluate the repeatability and reproducibility of SWE on porcine meat specimens and the human biceps femoris muscle. Measurements on meat specimens (n = 20) were performed by three raters and with a custom-built device that allowed constant application force. Measurements on human participants (n = 20) were performed by two raters in relaxed and stretched muscle positions on two visits. Most aspects of repeatability and reproducibility were good or high, with intra-class correlation coefficient (ICC) values above 0.70. Minimal detectable changes were lower in a relaxed (6–10%) than stretched (15-16%) muscle position. In conclusion, SWE is a reliable tool for assessing muscle stiffness if the muscle is examined in relaxed condition, while changing the force applied with the probe for as little as 1.5 N results in significantly lower repeatability.

Quantifying cervical and axioscapular muscle stiffness using shear wave elastography

This study aimed to assess intra-rater (intra-session and inter-day) reliability and influence of side dominance and the scapular resting position on the shear modulus (an index of stiffness) of resting cervical and axioscapular muscles. Sixteen healthy participants were recruited. On day one, ultrasound shear wave elastography was used to measure the shear modulus of superficial and deep cervical extensor and axioscapular muscles bilaterally. Clinical assessments of scapular resting position were performed bilaterally. On day two, testing was repeated on the dominant side. Both intra-session and inter-day reliability were good to excellent for shear modulus of superficial muscles, and poor to excellent for deep muscles. Side differences of shear modulus for posterior upper trapezius were statistically significant but clinically irrelevant. The shear modulus of posterior upper trapezius and middle trapezius were significantly correlated with scapular depression. Ultrasound shear wave elastography is a reliable tool for quantitatively assessing stiffness of superficial cervical and axioscapular muscles. The influence of scapular position should be considered in future comparative studies of healthy controls and patients with neck/shoulder pain. This study provides the necessary first step for future studies on assessing and interpreting the stiffness of cervical and axioscapular muscles for neck and shoulder musculoskeletal disorders.

Posture-related stiffness mapping of paraspinal muscles

The paraspinal compartment acts as a bone-muscle composite beam of the spine. The elastic properties of the paraspinal muscles play a critical role in spine stabilization. These properties depend on the subjects' posture, and they may be drastically altered by low back pain. Supersonic shear wave elastography can be used to provide quantitative stiffness maps (elastograms), which characterize the elastic properties of the probed tissue. The aim of this study was to challenge shear wave elastography sensitivity to postural stiffness changes in healthy paraspinal muscles. The stiffness of the main paraspinal muscles (longissimus, iliocostalis, multifidus) was measured by shear wave elastography at the lumbosacral level (L3 and S1) for six static postures performed by volunteers. Passive postures (rest, passive flexion, passive extension) were performed in a first shear wave elastography session, and active postures (upright, bending forward, bending backward) with rest posture for reference were performed in a second session. Measurements were repeated three times for each posture. Sixteen healthy young adults were enrolled in the study. Non-parametric paired tests, multiple analyses of covariance, and intra-class correlations were implemented for analysis. Shear wave elastography showed good to excellent reliability, except in the multifidus at S1, during bending forward, and in the multifidus at L3, during bending backward. Yet, during bending forward, only poor quality was recorded for nine volunteers in the longissimus. Significant intra- and inter-muscular changes were observed with posture. Stiffness significantly increased for the upright position and bending forward with respect to the reference values recorded in passive postures. In conclusion, shear wave elastography allows reliable assessment of the stiffness of the paraspinal muscles except in the multifidus at S1 and longissimus, during bending forward, and in the multifidus at L3, during bending backward. It reveals a different biomechanical behaviour for the multifidus, the longissimus, and the iliocostalis.

Diaphragm shear modulus reflects transdiaphragmatic pressure during isovolumetric inspiratory efforts and ventilation against inspiratory loading

The reference method for the assessment of diaphragm function relies on the measurement of transdiaphragmatic pressure (Pdi). Local muscle stiffness measured using ultrafast shear wave elastography (SWE) provides reliable estimates of muscle force in locomotor muscles. This study aimed at investigating whether SWE could be used as a surrogate of Pdi to evaluate diaphragm function. Fifteen healthy volunteers underwent a randomized stepwise inspiratory loading protocol of 0–60% of maximal isovolumetric inspiratory pressure during closed-airways maneuvers and 0–50% during ventilation against an external inspiratory threshold load. During all tasks, Pdi was measured and SWE was used to assess shear modulus of the right hemidiaphragm (SMdi) at the zone of apposition. Pearson correlation coefficients ( r) and repeated-measures correlation coefficients ( R) were computed to determine within-individual and overall relationships between Pdi and SMdi, respectively. During closed-airways maneuvers, mean Pdi correlated to mean SMdi in all participants [ r ranged from 0.77 to 0.96, all P < 0.01; R = 0.82, 95% confidence intervals (0.76, 0.86), P < 0.01]. During ventilation against inspiratory threshold loading, Pdi swing correlated to maximal SMdi in all participants [ r ranged from 0.40 to 0.90, all P < 0.01; R = 0.70, 95% confidence intervals (0.66, 0.73), P < 0.001]. Changes in diaphragm stiffness as assessed by SWE reflect changes in transdiaphragmatic pressure. SWE provides a new opportunity for direct and noninvasive assessment of diaphragm function.

NEW & NOTEWORTHY Accurate and specific estimation of diaphragm effort is critical for evaluating and monitoring diaphragm dysfunction. The measurement of transdiaphragmatic pressure requires the use of invasive gastric and esophageal probes. In the present work, we demonstrate that changes in diaphragm stiffness assessed with ultrasound shear wave elastography reflect changes in transdiaphragmatic pressure, therefore offering a new noninvasive method for gauging diaphragm effort.

Effects of physical therapy agents on pain, disability, quality of life, and lumbar paravertebral muscle stiffness via elastography in patients with chronic low back pain

Objectives

This study aims to evaluate early effects of combined hot pack (HP) and transcutaneous electrical nerve stimulation (TENS) treatment and therapeutic ultrasound (US) on pain, quality of life, disability, and the multifidus muscle stiffness.

Patients and methods

Between December 2016 and March 2017, a total of 69 patients (36 females, 33 males; mean age 48.9±10.9; range, 27 to 73 years) were included in this randomized-controlled study. The patients were divided into three groups as HT + TENS (Group H+T, n=23), HP + TENS + US (Group H+T+U, n=23), and controls (control group, n=23). All patients filled out the Numeric Rating Scale (NRS), Oswestry Disability Index (ODI), and Short Form-36 (SF-36) questionnaire at baseline and at the end of treatment. The left multifidus muscle strain ratio at fourth lumbar spinal level was obtained from the upper, middle, and lower parts of the muscle along the longitudinal axis on the first and last days of treatment.

Results

There was a significant improvement in the NRS, ODI, and SF-36 physical function, physical role function, pain, and general health perceptions in the H+T and H+T+U groups, compared to the control group (p<0.05). However, there was no significant difference between the H+T and H+T+U groups. The H+T+U group showed an improvement in the SF-36 social role function and emotional role function. There was no significant difference in the multifidus muscle strain ratios among the groups.

Conclusion

Our study results suggest that H+T treatment has a beneficial effect on pain, disability, and certain subscales of the quality of life. However, US seems not to have an additional benefit.

Shear Wave and Strain Elastographic Features of the Brachial Plexus in Healthy Adults: Reliability of the Findings-a Pilot Study

OBJECTIVES

To determine the sonoelastographic findings for the normal brachial plexus via shear wave elastography (SWE) and strain elastography (SE) and the reliability of the measurements.

METHODS

Thirty-nine healthy adult volunteers were included in the study. The brachial plexus was evaluated with SWE and SE at the interscalene region by 2 observers separately, and the observers were unaware of each other's outcomes. The elastic modulus (kilopascals), shear wave velocity (SWV, meters per second), and strain ratio were obtained. Elasticity patterns on SE were assessed as hard, intermediate, and soft. An intraclass correlation coefficient analysis was performed for determining the reliability of sonoelastographic findings. The correlation of sonoelastographic features with age and sex was investigated.

RESULTS

The volunteers included 13 men and 26 women. The mean age of the participants ± SD was 36.2 ± 7.8 (range, 25-56) years. The mean elasticity modulus values of the brachial plexus for observers 1 and 2 were 17.03 (95% confidence interval [CI], 15.03, 19.03) and 13.83 (95% CI, 12.23, 15.43) kPa, respectively; the SWVs were 2.24 (95% CI, 2.12, 2.36) and 2.04 (95% CI, 1.93, 2.15) m/s; and the strain ratios were 1.20 (95% CI, 1.18, 1.25) 1.38 (95% CI, 1.22, 1.54). The elasticity pattern was mostly intermediate stiffness for both observers (n = 72 [92.3%]; n = 75 [96.1%]). The intraclass correlation coefficient was poor to moderate and statistically significant for the elastic modulus, SWV, and elasticity pattern (P < .05 for all parameters). The sonoelastographic characteristics of the brachial plexus had no correlation with age or sex.

CONCLUSIONS

The reliability and reproducibility of sonoelastography of the brachial plexus are low, and the appropriateness of this technique in this manner is controversial.

Reference Values for Shear Wave Elastography of Neck and Shoulder Muscles in Healthy Individuals

Purpose

to establish reference values for ultrasound shear-wave elastography for pericranial muscles in healthy individuals (m. trapezius, m. splenius capitis, m. semispinalis capitis, m. sternocleidomastoideus and m. masseter). Also to evaluate day-to-day variations in the shear-wave speeds and evaluate the effect of the pennation of the muscle fibers, ie scanning parallel or perpendicularly to the fibers.

Materials and Methods

10 healthy individuals (5 males and 5 females) had their pericranial muscles examined with shear-wave elastography in two orthogonal planes on two different days for their dominant and non-dominant side. Mean shear wave speeds from 5 ROI’s in each muscle, for each scan plane for the dominant and non-dominant side for the two days were calculated. The effect of the different parameters – muscle pennation, gender, dominant vs non-dominant side and day was evaluated.

Results

The effect of scan plane in relation to muscle pennation was statistically significant (p<0.0001). The mean shear-wave speed when scanning parallel to the muscle fibers was significantly higher than the mean shear-wave speed when scanning perpendicularly to the fibers. The day-to-day variation was statistically significant (p=0.0258), but not clinically relevant. Shear-wave speeds differed significantly between muscles. Mean shear wave speeds (m/s) for the muscles in the parallel plane were: for masseter 2.45 (SD:+/−0.25), semispinal 3.36 (SD:+/−0.75), splenius 3.04 (SD:+/−0.65), sternocleidomastoid 2.75 (SD:+/−0.23), trapezius 3.20 (SD:+/−0.27) and trapezius lateral 3.87 (SD:+/−3.87).

Conclusion

The shear wave speed variation depended on the direction of scanning. Shear wave elastography may be a method to evaluate muscle stiffness in patients suffering from chronic neck pain.

Influencing Factors of 2D Shear Wave Elastography of the Muscle - An Ex Vivo Animal Study

OBJECTIVE

To evaluate measurement confounders on 2D shear wave elastography (2D-SWE) elastography of muscle.

MATERIALS AND METHODS

Ex vivo , porcine muscle was examined with a GE LOGIQ E9 ultrasound machine with a 9 L linear (9 MHz) and C1-6 convex probe (operating at 2.5 or 6 MHz). The influence of different confounders on mean shear wave velocity (SWVmean) was analyzed: probes, pressure applied by probe, muscle orientation, together with the impact of different machine settings such as frequency, placement depth and size of region of interest (ROI). The mean of twelve repeated SWVmean measurements (m/s) and coefficient of variation (CV; standard deviation/mean in %) were assessed for each test configuration.

RESULTS

Reproducibility (CV) and maximum possible tissue depth of the linear probe were inferior to the convex probe. With the linear probe, there was a linear decrease of SWVmean with placement depth from 4.56 m/s to 1.81 m/s. A significant increase of SWVmean (p<0.001) was observed for larger ROI widths (range 3.96 m/s to 6.8 m/s). A change in the machine operation mode ('penetration' instead of 'general') led to a significant increase of SWVmean (p=0.04). SWVmean in the longitudinal direction of muscle was significantly higher than in cross section (p<0.001) (e. g. 4.56 m/s versus 3.42 m/s). An increase of linear probe pressure significantly increased muscle SWVmean from 5.29 m/s to 7.21 m/s (p<0.001).

CONCLUSIONS

2D-SWE of muscle is influenced by a wealth of parameters. Therefore, standardization of measurement is advisable before application in clinical research studies and routine patient assessment.

Shear wave sonoelastography of skeletal muscle: basic principles, biomechanical concepts, clinical applications, and future perspectives

Imaging plays an important role in the diagnosis and therapeutic response evaluation of muscular diseases. However, one important limitation is its incapacity to assess the in vivo biomechanical properties of the muscles. The emerging shear wave sonoelastography technique offers a quantifiable spatial representation of the viscoelastic characteristics of skeletal muscle. Elastography is a non-invasive tool used to analyze the physiologic and biomechanical properties of muscles in healthy and pathologic conditions. However, radiologists need to familiarize themselves with the muscular biomechanical concepts and technical challenges of shear wave elastography. This review introduces the basic principles of muscle shear wave elastography, analyzes the factors that can influence measurements and provides an overview of its potential clinical applications in the field of muscular diseases.