Ultrasound-based Shear Wave Elastography Research Articles

Hamstring Muscle Stiffness in Athletes with and without Anterior Cruciate Ligament Reconstruction History: A Retrospective Study.

Introduction: Sports requiring sprinting, jumping, and kicking tasks frequently lead to hamstring strain injuries (HSI). One of the structural risk factors of HSI is the increased passive stiffness of the hamstrings. Anterior cruciate ligament (ACL) injury history is associated with a 70% increase in the incidence of HSI, according to a recent meta-analysis. The same report recommended that future research should concentrate on the relationships between the HSI risk factors. Hence, the present study aimed to retrospectively compare changes in the passive stiffness of the hamstrings in athletes with and without ACL reconstruction history. Methods: Using ultrasound-based shear-wave elastography, the mid-belly passive muscle stiffness values of the biceps femoris long head, semimembranosus, and semitendinosus muscles were assessed and compared amongst athletes with and without a history of ACL reconstruction. Results: There were no significant differences in the biceps femoris long head (injured leg (IL): 26.19 ± 5.28 KPa, uninjured contralateral (UL): 26.16 ± 7.41 KPa, control legs (CL): 27.64 ± 5.58 KPa; IL vs. UL: p = 1; IL vs. CL: p = 1; UL vs. CL: p = 1), semimembranosus (IL: 24.35 ± 5.58 KPa, UL: 24.65 ± 8.35 KPa, CL: 22.83 ± 5.67 KPa; IL vs. UL: p = 1; IL vs. CL: p = 1; UL vs. CL, p = 1), or semitendinosus (IL: 22.45 ± 7 KPa, UL: 25.52 ± 7 KPa, CL: 22.54 ± 4.4 KPa; IL vs. UL: p = 0.487; IL vs. CL: p = 1; UL vs. CL, p = 0.291) muscle stiffness values between groups. Conclusions: The passive mid-muscle belly stiffness values of the biceps femoris long head, semitendinosus, and semimembranosus muscles did not significantly differ between previously injured and uninjured athletes; therefore, further assessment for other muscle regions of hamstrings may be necessary. To collect more comprehensive data related to the structural changes that may occur following ACL reconstructions in athletes, a future study should examine the passive stiffness of wider muscle regions from origin to insertion.

Research on the mean maximum Young’s modulus value as a new diagnostic parameter for prostate cancer

Ultrasound-based shear wave elastography (SWE) can non-invasively assess prostate tissue stiffness for the diagnosis of prostate cancer (PCa). So far, there is no widely recognized standard for the detection process and calculation method of Young’s modulus value in transrectal SWE ultrasound imaging (TSWEUI). In our study, the mean maximum Young’s modulus value (m-Emax) of the maximum cross-section of prostate is obtained by calculating the mean of 12 measured Emax in the four quadrants. This retrospective study included 209 suspected malignant prostate disease patients with pathological results in our hospital. Among the 209 patients, 75 patients completed TSWEUI, and 63 of the 75 patients completed magnetic resonance imaging (MRI). The area under the receiver operating characteristic (ROC) curve (AUC) of 75 patients for m-Emax was 0.754. The prostate volume, prostate-specific antigen, and m-Emax were used to develop a nomogram (AUC = 0.868). The nomogram could effectively predict the probability of PCa, thereby reducing the needle biopsy rate for diagnosing PCa. The AUC of 63 patients was not statistically different between m-Emax (AUC = 0.717) and MRI (AUC = 0.787) (P = 0.361). These indicate that m-Emax can be used as an innovative parameter in TSWEUI to diagnosis PCa. TSWEUI is more cost-effective than MRI in diagnosing PCa.

Endoscopic Ultrasound-based Shear Wave Elastography for Detection of Advanced Liver Disease.

Endoscopic ultrasound shear wave elastography (EUS-SWE) is a novel modality for liver stiffness measurement. The aims of this study are to evaluate the performance and reliability of EUS-SWE for detecting advanced liver disease in a prospective cohort. EUS-SWE measurements were prospectively obtained from patients undergoing EUS between August 2020 and March 2023. Liver stiffness measurements were compared between patients with and without advanced liver disease (ALD), defined as stage ≥3, to determine diagnostic accuracy for advanced fibrosis and portal hypertension. Logistic regression was performed to identify variables that impact the reliability of EUS-SWE readings. Select patients underwent paired magnetic resonance elastography (MRE) for liver fibrosis correlation. Patients with ALD demonstrated higher liver stiffness compared to healthy controls (left lobe: 17.6 vs. 12.7 kPa, P<0.001; median right lobe: 24.8 vs. 11.0 kPa, P<0.001). The area under the receiver operator characteristic (AUROC) for the detection of ALD was 0.73 and 0.80 for left and right lobe measurements, respectively. General anesthesia was associated with reliable EUS-SWE liver readings (odds ratio: 2.73, 95% CI: 1.07-7.39, P=0.040). Left lobe measurements correlated significantly with MRE with an increase of 0.11 kPa (95% CI: 0.05-0.17 kPA) for every 1 kPa increase on EUS-SWE. D. SWE is a promising technology that can readily be incorporated into standard EUS examinations for the assessment of ALD.

Influence of toe flexor muscle fatigue on stiffness of the intrinsic foot muscles

BACKGROUND: Assessing intrinsic foot muscles (IFM) is important for understanding their role in loading movements. Additionally, knowledge of the impact of IFM following toe flexor muscle fatigue may aid the teaching of IFM exercises. OBJECTIVE: To examine the influence of toe flexor muscle fatigue on IFM stiffness using ultrasound shear-wave elastography. METHODS: This study included 19 college students. IFM stiffness at 10%, 50%, and 90% body weight was measured using ultrasound-based shear-wave elastography. IFM including the abductor hallucis (AbH), flexor hallucis brevis (FHB), flexor digitorum brevis (FDB), and quadratus plantae (QP) were assessed. The fatigue induction protocol comprised a series of toe flexions at a controlled pace of 40 beats per minute and an amplitude of 75% of the maximum toe flexor strength for a duration of 5 minutes. RESULTS: Muscle stiffness significantly increased with increasing load. Toe flexor muscle fatigue significantly increased the stiffness of the FDB. CONCLUSIONS: IFM stiffness significantly increased with increasing load, and the stiffness of FDB significantly increased in the toe flexor muscle fatigue condition at DLS and SLS loads. The findings of this study will contribute to the study and clinical setting of IFM exercises.

Investigating the role of ultrasound-based shear wave elastography in kidney transplanted patients: correlation between non-invasive fibrosis detection, kidney dysfunction and biopsy results-a systematic review and meta-analysis.

Interstitial fibrosis and tubular atrophy are leading causes of renal allograft failure. Shear wave elastography could be a promising noninvasive method for providing information on the state of the kidney, with specificregard to fibrosisbut currentlyavailable data in the literature are controversial. Our study aimed to analyze the correlation between shear wave elastography and various kidney dysfunction measures. This review was registered on PROSPERO (CRD42021283152). We systematically searched three major databases (MEDLINE, Embase, and CENTRAL) for articles concerning renal transplant recipients, shear wave elastography, fibrosis, and kidney dysfunction. Meta-analytical calculations for pooled Pearson and Spearman correlation coefficients (r) were interpreted with 95% confidence intervals (CIs). Heterogeneity was tested with Cochran's Q test. I2 statistic and 95% CI were reported as a measurement of between-study heterogeneity. Study quality was assessed with the QUADAS2 tool. In total, 16 studies were included in our meta-analysis. Results showed a moderate correlation between kidney stiffness and interstitial fibrosis and tubular atrophy, graded according to BANFF classification, on biopsy findings for pooled Pearson (r = 0.48; CI: 0.20, 0.69; I2 = 84%) and Spearman correlations (r = 0.57; CI: 0.35, 0.72; I2 = 74%). When compared to kidney dysfunction parameters, we found a moderate correlation between shear wave elastography and resistive index (r = 0.34 CI: 0.13, 0.51; I2 = 67%) and between shear wave elastography and estimated Glomerular Filtration Rate (eGFR) (r = -0.65; CI: -0.81, -0.40; I2 = 73%). All our outcomes had marked heterogeneity. Our results showed a moderate correlation between kidney stiffness measured by shear wave elastography and biopsy results. While noninvasive assessment of kidney fibrosis after transplantation is an important clinical goal,there is insufficient evidence to support the use ofelastography overthe performance of a kidney biopsy.

A retrospective comparison of the biceps femoris long head muscle structure in athletes with and without hamstring strain injury history.

Hamstring strain injuries (HSI) and re-injuries are endemic in high-speed running sports. The biceps femoris long head (BFlh) is the most frequently injured muscle among the hamstrings. Structural parameters of the hamstring muscle are stated to be susceptible to strain injuries at this location. This retrospective study targeted comparing the BFlh's structural parameters between previously injured and uninjured athletes. Nineteen male athletes with previous BFlh strain injury history and nineteen athletes without former lower extremity injury history were included in this study. Fascicle length, mid-muscle belly and distal musculotendinous (MTJ) passive stiffnesses of the biceps femoris long head (BFlh) were examined via b-mode panoramic ultrasound scanning and ultrasound-based shear-wave elastography. Parameter comparisons of both legs within and between athletes with and without injury history were performed. Comparison of the BFlh fascicle length between the injured leg of the injured group and the legs of the controls revealed a trend to shorter fascicle lengths in the injured leg (p = 0.067, d = -0.62). However, the mid-muscle belly passive stiffness of the BFlh was significantly higher in the injured legs (p = 0.009, d = 0.7) compared with the controls. Additionally, the distal MTJ stiffness was much higher in the previously injured legs compared with controls (p < 0.001, d = 1.6). Outcomes support the importance of BFlh properties related to stiffness, and fascicle length for injury susceptibility in athletes. Future prospective studies should determine whether the higher stiffness in the injured athletes is a cause or consequence of the HSI. Physical therapy and rehabilitation programmes after HSI should focus on BFlh muscle properties i.e., elasticity and fascicle length for reducing re-injury and increasing sports performance.

Hamstrings mechanical properties profiling in football players of different competitive levels and positions after a repeated sprint protocol.

Purpose: This study compares the average speed, knee flexor peak torque and shear modulus of the hamstrings after a repeated sprint task, in football players of different competitive levels and playing positions. Methods: Fifty-four football field players without hamstring strain injury history participated, 15 being categorized as professional (2nd league) and 39 as semi-professional (17 in 3rd and 22 in 4th league). Muscle shear modulus was assessed using ultrasound-based shear wave elastography at rest and at 20% of maximal voluntary isometric effort before and immediately after the repeated sprint protocol. Results: No significant differences were seen in average sprint speed between competitive levels (p = 0.07; η2p = 0.28) and positions (p = 0.052; η2p = 0.29). Moreover, the sprint fatigue index showed no significant differences between competitive levels (p = 0.14; η2p = 0.08) and playing positions (p = 0.89; η2p = 0.05). No significant differences were observed in hamstring shear modulus changes between competitive levels (p = 0.94; η2p = 0.03) and positions (p = 0.92; η2p = 0.03). Peak torque changes also showed non-significant association with competitive levels (p = 0.46; η2p = 0.03) and positions (p = 0.60; η2p = 0.02). Conclusion: The results of this study suggest that the average sprint speed performance parameter and mechanical parameters are not able to distinguish football players of different competitive levels and positions.

Changes in passive and active hamstrings shear modulus are not related after a warmup protocol

This study aimed to determine whether changes in hamstrings passive and active shear modulus after a warmup protocol are correlated. Twenty males without a history of hamstring strain injury participated. Muscle shear modulus was assessed using ultrasound-based shear wave elastography at rest and during isometric contractions at 20% of maximal voluntary isometric effort before and immediately after a warmup protocol. Changes in passive shear modulus did not seem to be associated with changes in active shear modulus. The results of this study suggest that changes in passive and active hamstring shear modulus are not associated after a standardized warmup intervention.

Radiological Significance of Shear-Wave Elastography Technique for Evaluation of Solid Breast Masses with Histopathological Correlation

Background: Although various imaging modalities are available for evaluating suspicious breast lesions, ultrasound-based Shear-Wave Elastography (SWE) is an advanced, non-invasive technique complementary to grayscale sonography. This technique evaluates the elasticity of a specific tissue by applying sonic pressure to that tissue. Objective: The aim is to assess the role of SWE in evaluating solid breast masses in correlation to histopathological study results. Subjects and Methods: This prospective study was done in a tertiary care teaching hospital from September 2019 to August 2020. A study population of 50 women aged 18 years or above with an ultrasonographic (USG) diagnosis of solid breast masses was included. Results: A significantly higher value of SWE elasticity ratio (E-mean) was observed in malignant tumors than in benign tumors (p &lt;0.0001). The area-under-curve (AUC) for the BI-RADS 4 lesions was 0.522 (95% CI, 0.343-0.701) with an E-ratio cut-off score of 85.25, the sensitivity and specificity were 50% for diagnosing malignant tumors, whereas AUC for the HPE study was 1.000 (95% CI, 1.000-1.000) with an E-ratio cut-off score of 134.25; both the sensitivity and specificity were 100% for diagnosing malignant tumors. Conclusions: Carcinoma breast is one of the most prevalent cancers globally. The most common benign tumor of the breast is a fibroadenoma, whereas Invasive Ductal Carcinoma is the most common malignant breast mass. A well-defined SWE elasticity ratio range might help predict the aggressiveness of breast tumors. SWE's correlation with BI-RADS in suspicious lesions adds to histopathology's advantage in distinguishing malignant tumors from benign ones.

Morphological and mechanical characteristics of the intrinsic and extrinsic foot muscles under loading in individuals with flat feet

BackgroundThe intrinsic and extrinsic foot softtissue structures that apply force and support the medial longitudinal arch (MLA) have been implicated in the development of flat feet. However, the relationship between the changes in MLA height under increasing load and the morphological and mechanical properties of individual intrinsic and extrinsic foot soft tissue structures is not fully understood. Research questionTo examine the morphological and mechanical characteristics of the foot soft tissue structures in flat feet when subjected to loading. MethodsThis study consisted of two studies focusing on the extrinsic foot muscles (10 normal feet/11 flat feet) and intrinsic foot muscles (14 normal feet/13 flat feet). Images of the extrinsic and intrinsic foot muscles and plantar fascia (PF) under 10%, 50%, and 90% body weight conditions were obtained using ultrasound-based shear-wave elastography. ResultsThe cross-sectional area (CSA) of the peroneus brevis was larger in the flat-foot group than in the normal-foot group under all loading conditions. The CSAs of the intrinsic foot muscles (abductor hallucis, flexor digitorum brevis, and quadratus plantae) and thickness of the PF in the flat-foot group decreased significantly with increasing load. As for mechanical characteristics, the stiffness of the flexor digitorum longus and abductor hallucis was higher in the flat-foot group than in the normal group under high loading conditions. In addition, flat feet with greater flexibility tended to exhibit a greater decrease in PF thickness and smaller increase in stiffness. SignificanceExcessive stretching of the intrinsic foot muscles and PF occurs in flat feet, and excessive contraction of the flexor digitorum longus may counteract the excessive lowering of the foot arch. Therefore, it is necessary to promote the contraction of the intrinsic foot musculature in feet with greater flexibility of the MLA during loading.

Continuous shear wave measurements for dynamic cardiac stiffness evaluation in pigs

Ultrasound-based shear wave elastography is a promising technique to non-invasively assess the dynamic stiffness variations of the heart. The technique is based on tracking the propagation of acoustically induced shear waves in the myocardium of which the propagation speed is linked to tissue stiffness. This measurement is repeated multiple times across the cardiac cycle to assess the natural variations in wave propagation speed. The interpretation of these measurements remains however complex, as factors such as loading and contractility affect wave propagation. We therefore applied transthoracic shear wave elastography in 13 pigs to investigate the dependencies of wave speed on pressure–volume derived indices of loading, myocardial stiffness, and contractility, while altering loading and inducing myocardial ischemia/reperfusion injury. Our results show that diastolic wave speed correlates to a pressure–volume derived index of operational myocardial stiffness (R = 0.75, p < 0.001), suggesting that both loading and intrinsic properties can affect diastolic wave speed. Additionally, the wave speed ratio, i.e. the ratio of systolic and diastolic speed, correlates to a pressure–volume derived index of contractility, i.e. preload-recruitable stroke work (R = 0.67, p < 0.001). Measuring wave speed ratio might thus provide a non-invasive index of contractility during ischemia/reperfusion injury.

Reliability of shear-wave elastography in assessing the stiffness of the nuchal fascia and the thickness of upper cervical muscles.

To determine the reliability of shear-wave elastography (SWE)in assessing the stiffness of the nuchal fascia and the thickness of upper cervical muscles in neutral head posture (NHP) or forward head posture (FHP). Sixteen healthy adults (mean age: 21.69±1.01years, 9 females) were included. SWE mode was chosen to measure the nuchal fascia shear modulus and muscle thickness was measured in B-mode. Measurements were collected by two independent investigators on two different days. The intraclass correlation coefficient (ICC) was used to measure the relative reliability, and the standard error of measurement (SEM) were used to measure the absolute reliability. Intra‑rater (ICC=0.63-0.89) and inter-rater (ICC=00.54-0.82) reliability for the nuchal fascia shear modulus were moderate to excellent. Intra‑rater (ICC=00.64-0.96) and inter-rater (ICC=00.48-0.86) reliability for upper cervical muscles thickness were moderate to excellent. The SEM percentage oscillated from 3.27% to 13.55%. There were significant differences(P<0.05) between NHP and FHP on nuchal fascia shear modulus, right side splenius capitis muscle thickness and left side semispinalis capitis muscle thickness, but no significant differences(P>0.05) were observed between the right and left sides. The upper cervical muscles thickness of males was significantly thicker(P<0.01) than females while no significant differences were observed (P>0.05) on the nuchal fascia shear modulus. Ultrasound-based SWE may be a reliable tool for assessing the stiffness of the nuchal fascia and the thickness of upper cervical muscles in clinical practice. ChiCTR2200055736.

Nondestructive ultrasound evaluation of microstructure-related material parameters of skeletal muscle: an in silico and in vitro study

Direct and nondestructive assessment of material properties of skeletal muscle in vivo shall advance our understanding of intact muscle mechanics and facilitate personalized interventions. However, this is challenged by intricate hierarchical microstructure of the skeletal muscle. We have previously regarded the skeletal muscle as a composite of myofibers and extracellular matrix (ECM), formulated shear wave propagation in the undeformed muscle using the acoustoelastic theory, and preliminarily demonstrated that ultrasound-based shear wave elastography (SWE) could estimate microstructure-related material parameters (MRMPs): myofiber stiffness μf, ECM stiffness μm, and myofiber volume ratio Vf. The proposed method warrants further validation but is hampered by the lack of ground truth values of MRMPs. In this study, we presented analytical and experimental validations of the proposed method using finite-element (FE) simulations and 3D-printed hydrogel phantoms, respectively. Three combinations of different physiologically relevant MRMPs were used in the FE simulations where shear wave propagations in the corresponding composite media were simulated. Two 3D-printed hydrogel phantoms with the MRMPs close to those of a real skeletal muscle (i.e., μf=2.02kPa, μm=52.42kPa, and Vf=0.675,0.832) for ultrasound imaging were fabricated by an alginate-based hydrogel printing protocol that we modified and optimized from the freeform reversible embedding of suspended hydrogels (FRESH) method in literature. Average percent errors of (μf,μm,Vf) estimates were found to be (2.7%,7.3%,2.4%)in silico and (3.0%,8.0%,9.9%)in vitro. This quantitative study corroborated the potential of our proposed theoretical model along with ultrasound SWE for uncovering microstructural characteristics of the skeletal muscle in an entirely nondestructive way.

Tibialis posterior muscle stiffness assessment in flat foot subjects by ultrasound based Shear-Wave Elastography

BackgroundFew methodologies are used to assess Tibialis Posterior muscle stiffness. Those present limitations leading to a lack of evidence. Muscle stiffness assessment can help in the injuries risk factors identification while coupling with Ultrasound based Shear-Wave Elastography for its management. However, a precise and reliable methodology needs to be utilized to increase stiffness accuracy among the entire Tibialis Posterior muscle. Therefore, this study aims to investigate the stiffness association between Tibialis posterior deep and superficial layer and between flat and neutral footed subjects. MethodsThe sample consisted of 18 participants, where 9 subjects represent the flatfoot group and 9 the neutral foot group. Only the subjects who presented a Navicular Drop Test value of > 9 mm were included in the flatfooted group. All participants were submitted to the Tibialis posterior stiffness assessment with the help of Ultrasound base Shear-Wave Elastography in a lying supine position. Association between Tibialis Posterior deep and superficial layers were determined by Pearson's correlation analysis and group differences were assessed using the U-Mann Whitney test in the comparison between flat foot and neutral foot group (p < 0.05). ResultsNo significant correlations between Tibialis Posterior layers stiffness were found (p = 0.194), nor in the comparison between both neutral and flat foot groups (p = 0.424/p = 0.258). ConclusionAmong participants, no associations between tibialis posterior layers stiffness were found. Also, we did not find any differences in the stiffness between flat and neutral foot groups. In this study, the stiffness did not differentiate flat-footed subjects from neutral subjects.

Effects of Hip Joint Angle on Quadriceps Recruitment Pattern During Knee Extension in Healthy Individuals: Analysis by Ultrasound-Based Shear-Wave Elastography.

Purposes: To detect the effects of hip joint position on the quadriceps recruitment pattern of different resistance levels of rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL), and vastus medialis obliquus (VMO) in healthy people during knee extension. Methods: Twenty healthy females performed isometric knee extension contractions at 0, 10, 20, and 30% of maximal voluntary isometric contraction (MVIC) with a 90° and 0° hip angle. Ultrasound shear-wave elastography was used to evaluate the shear elastic modulus of RF, VI, VL, and VMO during resting and contraction states. Results: At resting state, stiffness of RF was about 50% higher at 0° compared with at 90° of the hip (p < 0.01). There were significant differences in comparisons between 0 and 10% MVIC, 10 and 20% MVIC, and 20 and 30% MVIC in the four muscles, except that there was no significant difference between 20 and 30% MVIC for RF. There was a significant positive correlation between muscle stiffness and resistance level (r = 0.78–0.94, p < 0.001). Conclusions: Hip joint position had effects on the quadriceps recruitment pattern of different resistance levels in healthy people during knee extension.

Longitudinal stability of a multimodal visco-elastic polyacrylamide gel phantom for magnetic resonance and ultrasound shear-wave elastography.

We evaluated the long-term stability of a newly developed viscoelastic phantom made of polyacrylamide (PAAm) gel for magnetic resonance elastography (MRE) and ultrasound-based shear-wave elastography (US SWE). The stiffness of the cylindrical phantom was measured at 0, 13 and 18 months. Storage and loss moduli were measured with MRE, and shear-wave speed (SWS) was measured with US SWE. Long-term stability was evaluated in accordance with the Quantitative Imaging Biomarker Alliance (QIBA) profiles for each modality. The initial storage and loss moduli of the phantom were 5.01±0.22 and 1.11±0.15 respectively, and SWS was 2.57±0.04 m/s. The weight of the phantom decreased by 0.6% over the 18 months. When measured with MRE, the stiffness of the phantom decreased and changes to the storage and loss moduli were -3.0% and -4.6% between 0 and 13 months, and -4.3% and 0.0% between 0 and 18 months. The US measurements found that SWS decreased by 2.4% over the first 13 months and 3.6% at 18 months. These changes were smaller than the tolerances specified in the QIBA profiles, so the viscoelastic PAAm gel phantom fulfilled the condition for long-term stability. This new phantom has the potential to be used as a quality assurance and quality control phantom for MRE and US SWE.

Semitendinosus and biceps femoris long head active stiffness response until failure in professional footballers with vs. without previous hamstring injury

ABSTRACT This study sought to examine the active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh) during a knee flexor isometric contraction at 20% of maximal voluntary isometric contraction until failure in elite footballers (n = 50, age: 22.3 ± 5.3 years; height: 1.82 ± 0.08 m; body mass: 74.7 ± 9.0 kg). Active stiffness was assessed using ultrasound-based shear wave elastography by means of shear modulus quantification. Comparisons were performed between limbs with (n = 11) vs. without (n = 89) previous hamstring injury. A similar time until failure in the knee flexor fatigue task was observed between groups (p = .401). At the start of the task, lower limbs with previous hamstring injury showed a lower BFlh active stiffness (31.0.1 ± 10.4 kPa, p = .023) and BFlh/ST active stiffness ratio (0.50 ± 0.29), and no differences for ST (72.8 ± 26.8 kPa, p = .221) compared to lower limbs without previous hamstring injuries (BFlh: 38.0 ± 9.6 kPa; ST: 64.0 ± 18.4 kPa; BFlh/ST: 0.65 ± 0.27). During the task, the ST active stiffness in both groups decreased from 80% of task time (p = .032), in the absence of changes in BFlh active stiffness (p = .534), resulting in an increase in BFlh/ST active stiffness from 80% of task time (p = .029). No differences between limbs were observed during the fatigue task for all parameters (p > .099). Future research is warranted to verify if the differences found represent an increased risk of hamstring injury. Highlights The hamstring's active stiffness response to a fatigue protocol in soccer athletes with a history of injury is unknown. Athletes with previous injury showed less active stiffness in the biceps femoris long head. Similar response to fatigue was observed between athletes with and without hamstring injury history.

Elastography—A Bona Fide Non-Invasive Method for Assessing Non-Alcoholic Fatty Liver Disease in Children

Pediatric obesity has become a major public health problem worldwide, resulting in a wide spectrum of systemic complications. Liver disease associated with obesity, also known as nonalcoholic fatty liver disease (NAFLD), is currently the most common chronic liver condition in children. Therefore, its timely and proper diagnosis is essential for preventing further development of cirrhosis. Multiple studies focused on identifying the most accurate non-invasive diagnostic method for liver fibrosis or cirrhosis. Although liver biopsy remains the gold-standard in terms of this hepatopathy, elastography methods emerged as a relatively reliable alternative to liver biopsy. Thus, recent studies revealed the great importance of these non-invasive methods not only in diagnosing pediatric NAFLD, but also in its staging. MRE is commonly considered to have a greater accuracy than ultrasound-based elastography methods, but with lower availability and higher costs. Ultrasound-based elastography methods (transient elastography (TE), p-SWE, and 2-dimensional shear wave elastography (2D-SWE)) were proved to have similar accuracy in NAFLD staging. Nevertheless, multiple confounding factors account for potential challenges when using elastography for liver stiffness measurement, such as age, obesity itself (i.e., BMI), transaminase levels, or portal flow. A potential solution for facing these challenges might be represented by a complex approach based on the combination between elastography, clinical and laboratory findings. Although the studies that assessed the role of elastography in pediatric NAFLD staging are scarce, the current knowledge underlines a crucial role of these techniques taking into account their ability to distinguish between fibrosis degrees, their non-invasive patterns, lower costs and side effects when compared to liver biopsy. Therefore, elastography might become a cornerstone in staging pediatric NAFLD.

Three-Dimensional Mapping of Shear Wave Velocity in Human Tendon: A Proof of Concept Study.

Ultrasound-based shear wave elastography (SWE) provides the means to quantify tissue mechanical properties in vivo and has proven valuable in detecting degenerative processes in tendons. Its current mode of use is for two-dimensional rendering measurements, which are highly position-dependent. We therefore propose an approach to create a volumetric reconstruction of the mechano-acoustic properties of a structure of interest based on optically tracking the ultrasound probe during free-hand measurement sweeps. In the current work, we aimed (1) to assess the technical feasibility of the three-dimensional mapping of unidirectional shear wave velocity (SWV), (2) to evaluate the possible artefacts associated with hand-held image acquisition, (3) to investigate the reproducibility of the proposed technique, and (4) to study the potential of this method in detecting local adaptations in a longitudinal study setting. Operative and technical feasibility as well as potential artefacts associated with hand-held image acquisition were studied on a synthetic phantom containing discrete targets of known mechanical properties. Measurement reproducibility was assessed based on inter-day and inter-reader scans of the patellar, Achilles, and supraspinatus tendon of ten healthy volunteers and was compared to traditional two-dimensional image acquisition. The potential of this method in detecting local adaptations was studied by testing the effect of short-term voluntary isometric loading history on SWV along the tendon long axis. The suggested approach was technically feasible and reproducible, with a moderate to very good reliability and a standard error of measurement in the range of 0.300–0.591 m/s for the three assessed tendons at the two test-retest modalities. We found a consistent variation in SWV along the longitudinal axis of each tendon, and isometric loading resulted in regional increases in SWV in the patellar and Achilles tendons. The proposed method outperforms traditional two-dimensional measurement with regards to reproducibility and may prove valuable in the objective assessment of pathological tendon changes.

Regional Differences in Biceps Femoris Long Head Stiffness during Isometric Knee Flexion.

This study sought to investigate whether the stiffness of the biceps femoris long head differs between proximal and distal regions during isometric knee flexion at different contraction intensities and muscle lengths. Twelve healthy individuals performed knee flexion isometric contractions at 20% and 60% of maximum voluntary isometric contraction, with the knee flexed at 15 and 45 degrees. Muscle stiffness assessment was performed using ultrasound-based shear wave elastography. Proximal and distal regions of the biceps femoris long head were assessed. Biceps femoris long head muscle showed a greater stiffness (i) in the distal region, (ii) at higher contraction intensity, and (iii) at longer muscle length. The proximal-to-distal stiffness ratio was significantly lower than 1 (i.e., heterogenous) at lower contraction intensity regardless of the muscle length. However, this was not observed at higher contraction intensity. This study is the first to show heterogeneity in the active stiffness of the biceps femoris long head. Given the greater incidence of injury at the proximal region of biceps femoris long head, this study opens new directions for future research. Additionally, the present study results indicate that studies assessing muscle stiffness at one single muscle region should be interpreted with caution.