Shear-Wave Elastography: Basic Physics and Musculoskeletal Applications

Muscle shear wave elastography, conventional B mode and power doppler ultrasonography in healthy adults and patients with autoimmune inflammatory myopathies: a pilot cross-sectional study

Background

Before the role of shear wave elastography (SWE) and B mode ultrasound (US) in the diagnosis of different forms of idiopathic inflammatory myopathies (IIM) can be investigated, normative data is required. This study aimed to describe and then compare normative SWE and B mode ultrasound metrics of muscles in healthy controls and patients with IIM.

Methods

Twenty nine healthy adult controls and 10 IIM patients (5 with inclusion body myositis and 5 with necrotising autoimmune myopathy) underwent a full clinical examination, laboratory investigations, SWE and US measurements of selected proximal and distal limb muscles. Shear wave speed (SWS) and multiple US domains [echogenicity, fascial thickness, muscle bulk and power Doppler (PD)] were measured in both groups.

Results

In healthy controls (n = 29; mean age 46.60 ± 16.10; 44.8 % female), age was inversely correlated with SWS at the deltoid (stretch) (Rs. -0.40, p = 0.030) and PD score at the deltoid (rest) (Rs. -0.40, P = 0.032). Those ≥ 50 years old had a lower SWS at the deltoid (stretch) compared to the < 50 year group (2.92 m/s vs. 2.40 m/s, P = 0.032). Age correlated with increased echogenicity in the flexor digitorum profundus (Rs. 0.38, P = 0.045). Females had a smaller muscle bulk in the deltoid (P = 0.022). Body mass index (BMI) was inversely associated with SWS in the deltoid (stretch) (Rs – 0.45, P = 0.026), and positively correlated with echogenicity in the deltoid (Rs. 0.69, P = 0.026). In patients ≥50 years of age, patients with IIM (mean age 61.00 ± 8.18; females 20.0 %) had a higher proportion of abnormal echogenicity scores at the flexor digitorum profundus (FDP) (40.00 % vs. 14.30 %, P = 0.022) and tibialis anterior (TA) (80.00 % vs. 28.60 %, P = 0.004). Fascial thickness was lower in the FDP (0.63mm vs. 0.50mm, p = 0.012) and TA (0.58mm vs. 0.45mm, P = 0.001).

Conclusions

Our findings suggest there is scope for US techniques to be useful for diagnostic screening of affected muscles in patients with IIM, especially in those with suspected inclusion body myositis or necrotising autoimmune myopathy. We provide normative data for future studies into SWE and US techniques in skeletal muscle. The differences between IIM patients and controls warrant further study in a broader IIM patient cohort.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04424-0.

Young's Modulus of Bilateral Infraspinatus Tendon Measured in Different Postures by Shear Wave Elastography Before and After Exercise

Objective

To investigate the Young's modulus value of infraspinatus tendons using shear wave elastography (SWE) technique in normal adults, and to analyze the influence of gender, postures, exercise, and dominant side on Young's modulus of infraspinatus tendons.

Methods

This is a prospective cross‐sectional study. From January 2019 to July 2020, 14 healthy subjects were identified, including seven males and seven females aged between 24 to 34, with a mean age of 27.67 ± 3.08 years. The Young's modulus of their infraspinatus tendons was measured by two operators using SWE in neutral and maximum external rotation positions of both sides before exercise and the dominant side after exercise. The Young's modulus values in different sexes, different postures, before vs after exercise, and dominant vs non‐dominant side were statistically analyzed.

Results

All 14 subjects completed the data collection process. The mean Young's modulus values of infraspinatus tendon for dominant sides in neutral position were 33.04 ± 3.01 kPa for males and 28.76 ± 3.09 kPa for females. And for non‐dominant sides in the neutral position, the values were 33.02 ± 2.38 kPa for males and 28.86 ± 2.47 kPa for females. In the maximum external rotation position, the values for dominant sides were 50.19 ± 4.86 kPa for males and 42.79 ± 4.44 kPa for females, and for non‐dominant sides were 50.95 ± 3.24 kPa for males and 42.42 ± 3.66 kPa for females. After exercise, the mean Young's modulus values of infraspinatus tendon for dominant sides in neutral position were 54.56 ± 3.76 kPa for males and 46.66 ± 5.99 kPa for females. And for the maximum external rotation position, the values were 59.13 ± 3.78 kPa for males and 54.49 ± 5.67 kPa for females. The Young's modulus of infraspinatus tendon in the neutral and maximum external rotation positions showed statistically significant differences in males and females, as well as before and after exercise (P < 0.05). However, the difference in Young's modulus between the dominant and non‐dominant sides was not statistically significant (P > 0.05). Intergroup reliability between both operators was excellent (ICC > 0.85).

Conclusion

There are gender‐related differences and post‐exercise increase in Young's modulus, yet such a difference cannot be witnessed between the dominant and non‐dominant sides.

Shoulder ultrasound: current concepts and future perspectives

Ultrasonography is an established and effective imaging technique that can be used to evaluate articular and periarticular structures around the shoulder. It has been shown to be useful in a wide range of rotator cuff diseases (e.g. tendon tears, rotator cuff calcific tendinopathy and bursitis) as well as non-rotator cuff abnormalities (instability, synovial joint diseases and nerve entrapment syndrome). A scanning protocol is highly recommended to reduce the rate of operators’ errors by following a standardized scheme including a list of main structures. Shoulder ultrasound has several advantages: it is a relatively cheap and widely available technique, free from ionizing radiation, that can reach excellent diagnostic accuracy even compared to magnetic resonance imaging. Moreover, it is the only imaging technique that allows dynamic evaluation of musculoskeletal structures, which is important for the evaluation of impingement. Also, due to the shoulder’s superficial anatomical position, ultrasound can also be helpful in guiding interventional percutaneous procedures, both for diagnostic (e.g. magnetic resonance arthrography) and therapeutic purposes (e.g. percutaneous treatment of calcific tendonitis). Contrast-enhanced ultrasound and speckle tracking offer complimentary evaluations of shoulder anatomy and biomechanics. Moreover, the advent of ultra-high-frequency US, with probes up to 70 MHz allowing for a resolution as low as 30 μm, is a promising tool for further evaluation of the shoulder anatomy, and diagnostic and therapeutic strategies.

Shear Wave Elastography of the Plantar Fascia: Comparison between Patients with Plantar Fasciitis and Healthy Control Subjects

Background: The purpose of this study was to evaluate plantar fasciae of healthy subjects and patients with plantar fasciitis by shear wave velocity (SWV) and stiffness with correlation to B-Mode and color Doppler ultrasonography (CDUS) and to establish cut-off values. Methods: This observational study was conducted with the approval of the Institutional Review Boards (IRBs) of our institution. 108 unilateral plantar fasciae were evaluated by including 87 consecutive patients (mean age 51.7; range: 29–82) (66 women and 21 men) with plantar fasciitis and 21 asymptomatic age matched healthy volunteers (mean age 47.3; range: 32–58) (15 women and 6 men). All patients were prospectively imaged between July 2018 and March 2019. B-mode US was used to measure thickness and CDUS to grade vascularity. SWE measurements were repeated 3 times and mean was used for statistical analysis. Results: Mean SWV value in healthy subjects was 6.94 m/s and in patients 4.98 m/s with a mean stiffness value of 152.88 kPa and 93.54 kPa respectively (p < 0.001). For SWV a cut-off value of 6.16 m/s had a specificity of 80.95% and sensitivity of 79.31%. For stiffness a cut-off value of 125.57 kPa had a specificity of 80.95% and sensitivity of 80.46%. No correlation to CDUS was found. The mean thickness of healthy fascias was 3.3 mm (range 2.4–3.9) compared to 6.1 mm (range 2.0–22.0) in plantar fasciitis (p < 0.001) with no correlation to SWV or to stiffness (r² = 0.02, p = 0.06). Conclusion: SWE allows quantitative assessment of plantar fascia stiffness, which decreases in patients with plantar fasciitis. No correlation to the thickness of the plantar fascia was found, therefore it represents an independent factor for the diagnosis of plantar fasciitis and could be helpful in addition to thickness measurement in unclear cases.

Previous hamstring muscle strain injury alters passive tissue stiffness and vibration sense

BACKGROUND

Hamstring strain is one of the most common among sports injuries. A previous history of this injury is considered a strong predictor of recurrent hamstring strain injury. It has been suggested that fascial tissue alters after muscle strain injury. However, the association between previous hamstring strain injury and tissue stiffness and vibration sense detection has not been investigated.

OBJECTIVES

We aimed to determine whether a previous history of hamstring strain injury affects tissue stiffness and vibration sense in professional soccer players.

METHOD

The stiffness (MyotonPRO®) and vibration disappearance threshold (tuning fork) were measured in eight professional soccer players with previous history of hamstring strain and eight uninjured players. The differences between two groups' means were analyzed. Side-to-side differences between injured and uninjured legs were also analyzed.

RESULTS

The tissue stiffness was higher, and the vibration disappearance threshold was lower, in previously injured players when compared to uninjured players. Similar differences were found between injured and uninjured legs. No significant relationship was detected between the age or body mass index (BMI) for both tissue stiffness and vibration disappearance threshold (all P < 0.05).

CONCLUSIONS

Soccer players with a previous history of hamstring strain injury exhibited higher tissue stiffness and lower vibration sensitivity in the injured leg, regardless of the age and BMI. The results that players who have a previous hamstring strain injury with altered tissue stiffness and vibration sense will be useful and feasible evaluation for chronic muscle strain condition.

Measuring viscoelastic parameters in Magnetic Resonance Elastography: a comparison at high and low magnetic field intensity

Magnetic Resonance Elastography (MRE) is a non-invasive imaging technique which involves motion-encoding MRI for the estimation of the shear viscoelastic properties of soft tissues through the study of shear wave propagation. The technique has been found informative for disease diagnosis, as well as for monitoring of the effects of therapies. The development of MRE and its validation have been supported by the use of tissue-mimicking phantoms. In this paper we present our new MRE protocol using a low magnetic field tabletop MRI device at 0.5 T and sinusoidal uniaxial excitation in a geometrical focusing condition. Results obtained for gelatin are compared to those previously obtained using high magnetic field MRE at 11.7 T. A multi-frequency investigation is also provided via a comparison of commonly used rheological models: Maxwell, Springpot, Voigt, Zener, Jeffrey, fractional Voigt and fractional Zener. Complex shear modulus values were comparable when processed from images acquired with the tabletop low field scanner and the high field scanner. This study serves as a validation of the presented tabletop MRE protocol and paves the way for MRE experiments on ex-vivo tissue samples in both normal and pathological conditions.

Shear wave elastography of the knee menisci

OBJECTIVE

To determine the ability of shear wave elastography to measure the stiffness of the knee menisci in healthy adults.

METHODS

This observational cross-sectional study evaluated knee joints in healthy adults. Shear wave elastography was used to evaluate the anterior horn of the medial menisci bilaterally. The correlations between the mean elasticity bilaterally and age, weight, height and body mass index (BMI) were calculated using Pearson's correlation coefficient test.

RESULTS

A total of 34 knee joints in 17 healthy subjects were evaluated. The mean ± SD shear elastic modulus of the anterior horn of the right medial meniscus was 24.86 ± 6.35 kPa and of the anterior horn of the left medial meniscus was 23.86 ± 4.49 kPa. A significant inverse correlation was observed between the right medial meniscus elasticity and height. Other demographic factors showed no significant relationship to the anterior horn of the right medial meniscus elasticity. A significant inverse correlation was observed between the anterior horn of the left medial meniscus elasticity and age, while a significant positive correlation was observed between left medial meniscus elasticity and BMI.

CONCLUSION

These preliminary results suggest that shear wave elastography could be a potential tool to aid in studying the stiffness of the knee menisci.

Shear wave elastography of the radial nerve in healthy subjects

Objective

This study was performed to examine the sonoelastographic features of the radial nerve in healthy subjects.

Methods

In this observational cross-sectional study, shear wave elastography was used to evaluate the radial nerve. The cross-sectional area and stiffness were measured.

Results

The study included 37 nerves in 20 healthy adult subjects. The mean cross-sectional area of the radial nerve at the arm was 6.1 mm². The mean stiffness of the radial nerve in the short axis was 30.3 kPa, and that in the long axis was 34.9 kPa. The elasticity measurements were significantly different between the long axis and short axis.

Conclusion

The elastic modulus of the radial nerve was studied in healthy subjects and can serve as a reference for future assessment of different radial nerve pathologies.

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.

Feasibility of Harmonic Motion Imaging Using a Single Transducer: In Vivo Imaging of Breast Cancer in a Mouse Model and Human Subjects

Harmonic motion imaging (HMI) interrogates the mechanical properties of tissues by simultaneously generating and tracking harmonic oscillation using focused ultrasound and imaging transducers, respectively. Instead of using two transducers, the objective of this work is to develop a single transducer HMI (ST-HMI) to both generate and track harmonic motion at "on-axis" to the force for facilitating data acquisition. In ST-HMI, the amplitude-modulated force was generated by modulating excitation pulse duration and tracking of motion was performed by transmitting tracking pulses interleaved between excitation pulses. The feasibility of ST-HMI was performed by imaging two elastic phantoms with three inclusions (N = 6) and comparing it with acoustic radiation force impulse (ARFI) imaging, in vivo longitudinal monitoring of 4T1, orthotropic breast cancer mice (N = 4), and patients (N = 3) with breast masses in vivo. Six inclusions with Young's moduli of 8, 10, 15, 20, 40, and 60 kPa were embedded in a 5 kPa background. The ST-HMI-derived peak-to-peak displacement (P2PD) successfully detected all inclusions with [Formula: see text] of the linear regression between the P2PD ratio of background to inclusion versus Young's moduli ratio of inclusion to background. The contrasts of 10 and 15 kPa inclusions were higher in ST-HMI than ARFI-derived images. In the mouse study, the median P2PD ratio of tumor to non-cancerous tissues was 3.0, 5.1, 6.1, and 7.7 at 1, 2, 3, and 4 weeks post-injection of the tumor cells, respectively. In the clinical study, ST-HMI detected breast masses including fibroadenoma, pseudo angiomatous stromal hyperplasia, and invasive ductal carcinoma with a P2PD ratio of 1.37, 1.61, and 1.78, respectively. These results indicate that ST-HMI can assess the mechanical properties of tissues via generation and tracking of harmonic motion "on-axis" to the ARF. This study is the first step towards translating ST-HMI in clinics.

Application of Multiparametric Intraoperative Ultrasound in Glioma Surgery

Gliomas are the most invasive and fatal primary malignancy of the central nervous system that have poor prognosis, with maximal safe resection representing the gold standard for surgical treatment. To achieve gross total resection (GTR), neurosurgery relies heavily on generating continuous, real-time, intraoperative glioma descriptions based on image guidance. Given the limitations of currently available equipment, developing a real-time image-guided resection technique that provides reliable functional and anatomical information during intraoperative settings is imperative. Nowadays, the application of intraoperative ultrasound (IOUS) has been shown to improve resection rates and maximize brain function preservation. IOUS, which presents an attractive option due to its low cost, minimal operational flow interruptions, and lack of radiation exposure, is able to provide real-time localization and accurate tumor size and shape descriptions while helping distinguish residual tumors and addressing brain shift. Moreover, the application of new advancements in ultrasound technology, such as contrast-enhanced ultrasound, three-dimensional ultrasound, navigable ultrasound, ultrasound elastography, and functional ultrasound, could help to achieve GTR during glioma surgery. The current review describes current advancements in ultrasound technology and evaluates the role and limitation of IOUS in glioma surgery.

An International Continence Society (ICS) report on the terminology for pelvic floor muscle assessment

INTRODUCTION

The terminology for female and male pelvic floor muscle (PFM) assessment has expanded considerably since the first PFM function and dysfunction standardization of terminology document in 2005. New terms have entered assessment reports, and new investigations to measure PFM function and dysfunction have been developed. An update of this terminology was required to comprehensively document the terms and their definitions, and to describe the assessment method and interpretation of the finding, to standardize assessment procedures and aid diagnostic decision making.

METHODS

This report combines the input of members of the Standardisation Committee of the International Continence Society (ICS) Working Group 16, with contributions from recognized experts in the field and external referees. A logical, sequential, clinically directed assessment framework was created against which the assessment process was mapped. Within categories and subclassifications, each term was assigned a numeric coding. A transparent process of 12 rounds of full working group and external review was undertaken to exhaustively examine each definition, plus additional extensive internal development, with decision making by collective opinion (consensus).

RESULTS

A Terminology Report for the symptoms, signs, investigations, and diagnoses associated with PFM function and dysfunction, encompassing 185 separate definitions/descriptors, has been developed. It is clinically based with the most common assessment processes defined. Clarity and user-friendliness have been key aims to make it interpretable by clinicians and researchers of different disciplines.

CONCLUSION

A consensus-based Terminology Report for assessment of PFM function and dysfunction has been produced to aid clinical practice and be a stimulus for research.

Region- and degeneration dependent stiffness distribution in intervertebral discs derived by shear wave elastography

Information on the local stiffness characteristics of the intervertebral disc (IVD) is crucial for the understanding of its structure-function properties in health and disease and may improve numerical modeling. Previous studies have attempted to map local tissue stiffness by sectioning the disc and performing mechanical testing on these discrete tissue units, which is technically challenging and may bias the results. Shear wave elastography (SWE) represents a nondestructive alternative that can provide spatially continuous elasticity estimates. We investigated the feasibility of SWE for human intervertebral disc elasticity mapping in a laboratory setting. To this end, global spinal segment mechanical behavior was determined in 6 loading directions and served as ground truth data for the validation of the approach. Subsequently, the cranial spinal vertebra was removed and shear wave elastographic scans of the IVD were acquired. SWE-measurements were reconstructed into three-dimensional elastographic maps, discretized into distinct IVD regions and correlated with global segment mechanical parameters. SWE-derived Young's modulus estimates were compared among different regions and as a function of their state of degeneration. We found annulus shear wave speed to be moderately correlated with segment mechanical behavior irrespective of the loading direction whereas shear wave speed in the nucleus pulposus showed a very weak association (mean (SD) absolute Pearson correlation coefficients: 0.51 (0.14) and 0.17 (0.12), respectively). Young's modulus mapping of the intervertebral disc revealed stiffness to be highest in the ventral annulus with a stiffness decrease both circumferentially towards the dorsal aspect as well as towards the center of the disc. SWE hence provides a valid alternative to disc sectioning and piecewise mechanical testing.

Use of vibrational optical coherence tomography to measure viscoelastic properties of muscle and tendon: A new method to follow musculoskeletal injury and pathology In vivo

The biomechanical properties of muscles and tendons in vivo are important parameters needed to understand musculoskeletal physiology and pathology. Values of the shear moduli reported for human musculoskeletal components using elastographic techniques range from several KPa to about 100 KPa and are much lower than the tensile moduli measured in vivo which are reported to be as high as several hundred MPa at high strains. In this paper we report the results of a pilot study to measure the mechanical properties of human muscles and tendons non-invasively and non-destructively in vivo using vibrational optical coherence tomography (VOCT). VOCT is a non-invasive technique that uses audible sound and reflected infrared light to measure the resonant frequency of each tissue component. Using VOCT we report that the moduli at the biceps muscle-tendon junction are about 24-30 MPa even though moduli in other anatomic locations of muscle and tendons can vary by as much as 10 MPa. It is concluded that the modulus and stress exerted by tendons and muscles at the muscle-tendon junction are similar and that deposition of fibrous tissue at the junction will lead to reduced values of the modulus leading to tissue pathology and muscle injury.

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.

Shearwave elastography of the Sartorius muscle

The aim of the study was to study sonoelastographic features of thesartorius muscle, and its relation to the demographic factors.The study included 70 muscles in 35 healthy subjects. High-resolution ultrasound and shearwave elastography were used to evaluate the sartorius muscle. Stiffness values were measured.The mean shear elastic modulus of the sartorius muscle was 21.96 ± 5.1 kPa. Demographic factors showed no relation to the elastic modulus of the left sartorius muscle. Positive statistical correlation was noted between the elastic modulus of the right sartorius muscle, weight, and body mass index.Our results could be a reference point for evaluating sartorius muscle stiffness in future research considering different pathologies.

The Measurement of Stiffness for Major Muscles with Shear Wave Elastography and Myoton: A Quantitative Analysis Study

The present study was performed to assess the relationship between hand-held myotonometer MyotonPRO and shear wave elastography (SWE) measurements of lower limb muscle stiffness during resting and active voluntary contraction. Forty healthy young adults, (20 males and 20 females) participated in the study. The stiffness of each subject’s rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) was measured repeatedly by MyotonPRO and SWE. Moderate to strong correlations between the two methods’ measurements were found for both resting and active voluntary contraction. (r = 0.416–0.669, p < 0.05; r = 0.398–0.594, p < 0.05, respectively). Muscle stiffness at rest was significantly lower compared contraction in all four muscles measured by both methods (p < 0.05). Intra-rater reliabilities were generally lower when measurements were taken during contraction. Additionally, when compared by gender, muscle stiffness measured by MyotonPRO was significantly higher at rest in men compared to women, except for the TA. However, a significant difference was found in TA muscle stiffness by gender when measured with SWE. When muscles were contracted, all muscles showed significantly higher stiffness in men compared to women. There were moderate to good correlations in muscle stiffness between measurements of SWE and MyotonPRO at rest and during active voluntary contraction. Additionally, both instruments showed good intra-rater reliability.

Preliminary study on the influencing factors of shear wave elastography for peripheral nerves in healthy population

This study took shear wave elastography (SWE) technology to measure the shear wave velocity (SWV) of peripheral nerve in healthy population, which represents the stiffness of the peripheral nerves, and research whether these parameters (location, age, sex, body mass index (BMI), the thickness and cross-sectional area(CSA) of the nerve) would affect the stiffness of the peripheral nerves. 105 healthy volunteers were enrolled in this study. We recorded the genders and ages of these volunteers, measured height and weight, calculated BMI, measured nerve thickness and CSA using high-frequency ultrasound (HFUS), and then, we measured and compared the SWV of the right median nerve at the middle of the forearm and at the proximal entrance of the carpal tunnel. The SWV of the median nerve of the left side was measured to explore whether there exist differences of SWV in bilateral median nerve. Additionally, we also measured the SWV of the right tibial nerve at the ankle canal to test whether there is any difference in shear wave velocity between different peripheral nerves. This study found that there existed significant differences of SWV between different sites in one nerve and between different peripheral nerves. No significant difference was found in SWV between bilateral median nerves. Additionally, the SWV of peripheral nerves was associated with gender, while not associated with age or BMI. The mean SWV of the studied male volunteers in median nerve were significantly higher than those of female (p < 0.05). Peripheral nerve SWE measurement in healthy people is affected by different sites, different nerves and genders, and not associated with age, BMI, nerve thickness or CSA.

Shear wave elastography detects novel imaging biomarkers of aromatase inhibitor-induced joint pain: a pilot study

Aim

To determine whether differences in joint and tendon stiffness as measured by ultrasound shear wave elastography are present in breast cancer patients with aromatase inhibitor-associated arthralgias compared to age-comparable healthy control women.

Methods

Postmenopausal women with stage I–III breast cancer who were taking adjuvant aromatase inhibitors and complained of joint pain were enrolled (n = 6). Postmenopausal women with no history of breast cancer, hormone treatment, or joint pain served as controls (n = 7). All subjects had bilateral hands and wrists evaluated by gray-scale and power Doppler ultrasound, and shear wave elastography ultrasound.

Results

Patients with AI-associated arthralgias had significantly stiffer tendons than controls in the 1^st extensor compartment (long axis; p = 0.001), 4^th extensor compartment (long axis; p = 0.014), 3^rd metacarpophalangeal joint (p = 0.002), the pooled values of the extensor compartments, both long (p = 0.044) and short axes (p = 0.035), and the pooled values for the metacarpophalangeal joints (p = 0.002). On ultrasound, the patients (but not controls) presented with hyperemia and increased tenosynovial fluid in the flexor and extensor tendon sheaths, and the median nerves were symptomatic and bifid; however, these differences were not statistically significant.

Conclusions

This is the first study to identify increased tendon stiffness as a putative physiological characteristic of aromatase inhibitor–associated arthralgias. Future studies should determine whether increased tendon stiffness is a risk factor for the development of aromatase inhibitor–associated arthralgias, or a result of aromatase inhibitor treatment.

Quantitative Ultrasound to Assess Skeletal Muscles in Post Stroke Spasticity

Quantitative ultrasound (QUS) techniques such as pixel intensity, ultrasound strain, and shear wave elastography have made it possible to identify the echogenicity (brightness) and mechanical properties (stiffness) of normal and pathological tissues. These techniques can be utilized as an alternative diagnosis tool to assess post stroke spasticity. Current clinical assessment methods include the Modified Ashworth Scale (MAS) and the Modified Tardieu Scale (MTS), which can result in inconsistencies due to their subjective nature. QUS provides robust approaches to assessing muscle stiffness associated with post stroke spasticity. Computer-aided pixel count quantifies tissue echogenicity in grayscale image. A strain ratio in ultrasound strain imaging compares the stiffness and movement (lengthening or shortening) of a spastic muscle with nonspecific muscle. In addition, shear wave elastography provides the shear wave velocity of an affected muscle that directly associated with the muscle stiffness before and after treatment for spasticity. This article reviews the theory behind these aforementioned concepts and discuss the relations between QUS and skeletal muscles in post stroke spasticity.

Intraoperative Ultrasound Shear-Wave Elastography in Focal Cortical Dysplasia Surgery

Previous studies reported interest in intraoperative shear-wave elastography (SWE) guidance for brain-tumor and epilepsy surgeries. Focal cortical dysplasia (FCD) surgery is one of the most appropriate indications for using SWE guidance. The aim of this study was to evaluate the efficacy of ultrasound SWE techniques for the intraoperative detection of FCDs. We retrospectively analyzed data from 18 adult patients with drug-resistant epilepsy associated with FCD who had undergone SWE-guided surgery. Conventional B-mode images detected FCD in 2 patients (11.1%), while SWE detected FCD in 14 patients (77.8%). The stiffness ratios between MRI-positive and -negative cases were significantly different (3.6 ± 0.4 vs. 2.2 ± 0.6, respectively; p < 0.001). FCDs were significantly more frequently detected by interoperative SWE in women (OR 4.7, 95% CI (1.7–12.7); p = 0.004) and in patients in whom FCD was visible on magnetic resonance imaging (MRI; OR 2.3, 95% CI (1.3–4.3); p = 0.04). At 1 year after surgery and at last follow-up (mean = 21 months), seizure outcome was good (International League Against Epilepsy (ILAE) Class 1 or 2) in 72.2% and 55.6% of patients, respectively. Despite some limitations, our study highlighted the potential of SWE as an intraoperative tool to detect FCD. Future technical developments should allow for optimizing intraoperative surgical-cavity evaluation from the perspective of complete FCD resection. Interobserver reliability of SWE measurements should also be assessed by further studies.

Sonoelastography in the Diagnosis of Carpal Tunnel Syndrome: A Systematic Review of Diagnostic Values Compared With the Normative Population

BACKGROUND

Sonoelastography (SEL) is widely used for assessing tissue stiffness and pathophysiology. It has also been used to diagnose carpal tunnel syndrome (CTS). However, the current criteria to diagnose CTS in SEL are diverse. The aim of this study was to systematically review the literature and assess the diagnostic value of SEL for CTS.

METHODS

A literature review was performed using MEDLINE (PubMed), EMBASE, and the Cochrane Collaboration Library for primary research articles using the keywords sonoelastography and carpal tunnel syndrome. Data related to diagnostic and cutoff value were extracted. Bias assessment was performed.

RESULTS

A total of 121 publications were reviewed. Nineteen primary case series met the inclusion criteria and were selected for full analysis. Different diagnostic approaches were identified, with units/expressions including kilopascals, conduct velocity, and strain ratio. The kilopascals and conduct velocity were measured using shear wave elastography, whereas strain ratio was calculated by relative compression quantification. A mean shear modulus cutoff value from 38.25 to 86 kPa and an acoustic radiation force impulse cutoff value of 3.0 to 3.23 m/s were used to diagnose CTS. Eight articles reported strain ratio between the median nerve and nearby tissues with diverse results due to different reference points. The other 3 additional diagnostic values were reported.

CONCLUSIONS

Sonoelastography is a useful noninvasive and promising modality to diagnose CTS. It may reflect both the condition of soft tissue scarring and quantitative values for CTS and median nerve stiffness. A diversity of examination values was found in different modalities. A high level of evidence was absent.

Sonographic and radiographic evaluation of the extensor tendons in early postoperative period after total knee arthroplasty

OBJECTIVE

To prospectively assess the early changes in the quadriceps and patellar tendons before and after total knee arthroplasty using ultrasound, shear wave elastography, and X-rays.

MATERIALS AND METHODS

Radiographs, ultrasound, and shear wave elastography were performed on 23 patients (16 women; aged 51-85, mean 66 ± 9 years) before and after surgery at 6 weeks and on 11 patients at 3 months. Patellar position and patellar tendon lengths were evaluated by radiography; joint effusion or synovitis, quadriceps and patellar tendon lengths, and thicknesses, echogenicity, vascularity, and stiffness were assessed with ultrasound and shear wave elastography.

RESULTS

In the early postoperative period, 87% of the patients had joint effusion, and 43% had signs of synovitis. There was a significant thickening of the quadriceps tendon in 51.5% (p < .0001) and of the patellar tendon in 93.8% (p < .0001) of patients with a significant shortening of the patellar tendon in 7.8% (p < .0001). A hypoechoic defect on the medial aspect of the quadriceps tendon was found in 87% of the patients. There was a significant increase in Young's modulus in the quadriceps tendon (p = .0006) but not in the patellar tendon.

CONCLUSION

The following should not be considered to be pathological findings at early postoperative imaging: joint effusion, synovitis, increasing of stiffness and thickening of quadriceps tendons by more than 50%, thickening of patellar tendon by more than 90%, focal defect through the medial aspect of the quadriceps tendon, and shortening of the patellar tendon by 8%.

Influence of transducer orientation on shear wave velocity measurements of the iliotibial band

Tissue anisotropy influences estimation of mechanical properties of connective tissues, such as the iliotibial band (ITB). This study investigated the influence of ultrasound transducer rotation and tilt on shear wave velocity (SWV, an index of stiffness) measurements of the ITB and the intra-rater repeatability of SWV measurements in the longitudinal direction. SWV was measured unilaterally (dominant limb) using ultrasound shear wave elastography in the middle region of the ITB in supine at rest (20-25° knee flexion) in ten healthy volunteers (4 females). A 3-dimensional video system provided real-time feedback of probe orientation with respect to the thigh. Measurements were made at 10° increments of probe rotation, from longitudinal to transverse alignment relative to the approximate direction of ITB fibres, and 5-10° tilts about the longitudinal and sideways axes of the transducer. One-way repeated measures ANOVA compared SWV between angles and tilts. Intraclass correlation coefficients (ICCs) and standard error of measurement (SEM) were used to calculate repeatability for two to five (longitudinal only) repetitions. SWV was greatest when the transducer was aligned to ITB fibres (longitudinal: 10.5 ± 1.7 m/s) and lowest when perpendicular (transverse: 5.8 ± 2.4 m/s). Compared to longitudinal alignment, SWV decreased significantly (p < 0.01) when the transducer was rotated 20° or more. Tilted measurements did not differ between angles. Intra-rater repeatability was excellent with the average of two measurements (ICC = 0.99, 95% CI 0.95, 0.99; SEM = 0.31 m/s). These findings show that SWV changes with orientation relative to fibre direction. Transducer orientation requires careful control to ensure comparable measures.

Electronic Point Spread Function Rotation Using a Three-Row Transducer for ARFI-Based Elastic Anisotropy Assessment: In Silico and Experimental Demonstration

Degree of anisotropy (DoA) of mechanical properties has been assessed as the ratio of acoustic radiation force impulse (ARFI)-induced peak displacements (PDs) achieved using spatially asymmetric point spread functions (PSFs) that are rotated 90° to each other. Such PSF rotation has been achieved by manually rotating a linear array transducer, but manual rotation is cumbersome and prone to misalignment errors and higher variability in measurements. The purpose of this work is to evaluate the feasibility of electronic PSF rotation using a three-row transducer, which will reduce variability in DoA assessment. A Siemens 9L4, with 3×192 elements, was simulated in Field II to generate spatially asymmetric ARFI PSFs that were electronically rotated 63° from each other. Then, using the finite element method (FEM), PD due to the ARFI excitation PSFs in 42 elastic, incompressible, transversely isotropic (TI) materials with shear moduli ratios of 1.0-6.0 were modeled. Finally, the ratio of PDs achieved using the two rotated PSFs was evaluated to assess elastic DoA. DoA increased with increasing shear moduli ratios and distinguished materials with 17% or greater difference in shear moduli ratios (Wilcoxon, ). Experimentally, the ratio of PDs achieved using ARFI PSF rotated 63° from each other distinguished the biceps femoris muscle from two pigs, which had median shear moduli ratios of 4.25 and 3.15 as assessed by shear wave elasticity imaging (SWEI). These results suggest that ARFI-based DoA assessment can be achieved without manual transducer rotation using a three-row transducer capable of electronically rotating PSFs by 63°. It is expected that electronic PSF rotation will facilitate data acquisitions and improve the reproducibility of elastic anisotropy assessments.

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.

Clinical applicability of shear wave elastography for the evaluation of medial epicondylitis

OBJECTIVES

To evaluate the ability of shear wave elastography (SWE) in diagnosing medial epicondylitis and to compare the diagnostic performance of SWE with that of grey-scale ultrasound (GSU) and strain elastography (SE).

METHODS

GSU, SE, and SWE were performed on 61 elbows of 54 patients from March 2018 to April 2019. An experienced radiologist evaluated the GSU findings (swelling, cortical irregularity, hypoechogenicity, calcification, and tear), colour Doppler findings (hyperaemia), SE findings (strain ratio [SR]), and SWE findings (stiffness and shear wave velocity [SWV]). Participants were divided in two groups: patients with clinically diagnosed medial epicondylitis and patients without medial elbow pain. Findings from the two groups were compared, and the receiver operating characteristic (ROC) curves were calculated for significant features.

RESULTS

Of the 54 patients, 25 patients with 28 imaged elbows were clinically diagnosed with medial epicondylitis and 29 patients with 33 imaged elbows had no medial elbow pain. Cortical irregularity, hypoechogenicity, calcification, hyperaemia, SR, stiffness, and SWV were significantly different between the two groups. The areas under the ROC curves were 0.838 for hypoechogenicity, 0.948 for SR, 0.999 for stiffness, and 0.999 for SWV. The diagnostic performances of SR, stiffness, and SWV were significantly superior compared to that of hypoechogenicity. However, there were no significant differences among SR, stiffness, and SWV.

CONCLUSIONS

SWE can obtain both stiffness and SWV, which are valuable diagnostic tools in the diagnosis of medial epicondylitis. The diagnostic performance of SWE and SE is similar in detecting medial epicondylitis.

KEY POINTS

• Shear wave elastography providing stiffness and shear wave velocity showed excellent performance in the diagnosis of medial epicondylitis. • There was no significant difference in the ability of SE and SWE for diagnosing medial epicondylitis.

Ultrasound Elastographic Measurement of Rigor Mortis in an Animal Model: A Feasibility Study for Improved Time-of-Death Estimates in Forensic Investigations

OBJECTIVE. The purpose of our study was to assess the feasibility of 2D shear wave ultrasound elastography to quantitatively measure changes of rigor mortis. SUBJECTS AND METHODS. Muscle stiffness of two live pigs and nine sacrificed pigs was measured in kilopascals using ultrasound elastography. The nine sacrificed pigs were divided into three groups of three pigs each and placed in one of three environments at 90°F (32°C), 70°F (21°C), or 34°F (1°C). Ultrasound elastography of five muscles was performed at 1- to 2-hour intervals for up to 50 hours postmortem. For each pig and muscle location, the time to start, peak intensity, duration of peak, and time to decline of rigor mortis were identified from the graphs of muscle stiffness values over time. These outcome variables were then compared across ambient temperature, body weight, and age groups using the Wilcoxon rank sum test. RESULTS. Postmortem measurements show a rise, peak, and decline of muscle stiffness after death. Rigor mortis was highly significantly affected by ambient temperature (p < .001), was significantly affected by body weight (p = .04), and was not significantly affected by animal age or muscle location (facial vs truncal vs limb) (p > .50). Peak intensity of rigor mortis developed more quickly but attained lower levels of muscle stiffness at 90°F (80-100 kPa) compared with 70°F and 34°F (280-300 kPa) (p < .001). The duration of peak rigor mortis and the time to decline of rigor mortis were significantly longer for the lower temperatures (p < .001). CONCLUSION. Two-dimensional shear wave ultrasound elastography can quantifi-ably measure the trajectory of rigor mortis in an animal model. This new approach may have direct implications for human forensic investigations.

Greater Muscle Stiffness during Contraction at Menstruation as Measured by Shear-Wave Elastography

It is important to measure mechanical properties of muscle, since muscle stiffness is an important component of stabilizing or controlling joint stability. The levels of sex hormones especially estrogen vary over the phase of the menstrual cycle and impact the mechanical properties of soft tissue such as muscle, tendon, and ligaments due to the presence of 17-β estradiol receptor in human connective tissues. Recently, shear-wave elastography (SWE), based on ultrasound imaging, has been used as an accurate technique for visualizing and assessing tissue stiffness. The purpose of this study was to compare the muscle stiffness at rest and during contraction condition between the early follicular phase (menstruation) and ovulation in young women, measured using SWE. Thirty-seven young women with regular menstrual cycles completed this study throughout one full menstrual cycle. Stiffness of lower limb muscles such as the rectus femoris, biceps femoris, tibialis anterior, and medial gastrocnemius was measured at resting and during contraction conditions using SWE during menstruation and ovulation. All muscles showed significantly greater stiffness during the menstruation than ovulation when muscles were actively contracted (P < 0.05), whereas no significant differences in muscle stiffness at rest were noted across phase of the menstrual cycle. These significant findings suggest that muscular factors are changed with estradiol fluctuations; muscles are less stiff during ovulation where the levels of estradiol peak when muscles in a contraction condition. As muscle stiffness is an important part of joint stability, these differences should be recognized to prevent the risk of musculoskeletal injuries.

Material Properties of the Medial Elbow During Passive Valgus and Self-Initiated Varus Torques

Shear wave elastography imaging of the ulnar collateral ligament (UCL) is used to help understand changes in material properties of the ligament. Ensuring that the wrist flexors are relaxed is essential as muscle contractions can alter the alignment of the medial elbow. The purpose of this study was to determine how the structural and material properties of the medial elbow respond to various elbow torques. The medial elbows of 20 healthy adults, free from upper extremity disorders, were imaged in 3 of the following torque conditions: (1) neutral relaxed, (2) passive valgus, and (3) active varus. Structural properties (ulnohumeral gap and UCL length) using B-mode and material properties (UCL and flexor muscle stiffness) using shear wave were measured. Passive valgus torque opened the ulnohumeral gap (P < .001), and increased UCL (P < .001) and wrist flexor stiffness (P = .001), compared with the neutral condition. Under an active varus contraction, the gap returned back to the neutral position, but UCL (P < .008) and wrist flexor stiffness (P < .004) remained elevated compared with neutral, meaning low-intensity torques can influence structural and material properties of the medial elbow. Therefore, effort should be taken to minimize muscle activation during imaging in order to accurately measure medial elbow properties.

Sonographic measures and sensory threshold of the normal sciatic nerve and hamstring muscles

PURPOSE

The sciatic nerve innervates the hamstring muscles. Occasionally, the sciatic nerve is injured along with a hamstring muscle. Detailed biomechanical and sensory thresholds of these structures are not well-characterized. Therefore, we designed a prospective study that explored high-resolution ultrasound (US) at multiple sites to evaluate properties of the sciatic nerve, including cross-sectional area (CSA) and shear-wave elastography (SWE). We also assessed SWE of each hamstring muscle at multiple sites. Mechanical algometry was obtained from the sciatic nerve and hamstring muscles to assess multi-site pressure pain threshold (PPT).

METHODS

Seventy-nine asymptomatic sciatic nerves and 147 hamstring muscles (25 males, 24 females) aged 18-50 years were evaluated. One chiropractic radiologist with 4.5 years of US experience performed the evaluations. Sciatic nerves were sampled along the posterior thigh at four sites obtaining CSA, SWE, and algometry. All three hamstring muscles were sampled at two sites utilizing SWE and algometry. Descriptive statistics, two-way ANOVA, and rater reliability were assessed for data analysis with p ≤ 0.05.

RESULTS

A significant decrease in sciatic CSA from proximal to distal was correlated with increasing BMI (p < 0.001). Intra-rater and inter-rater reliability for CSA was moderate and poor, respectively. Elastographic values significantly increased from proximal to distal with significant differences in gender and BMI (p = 0.002). Sciatic PPT significantly decreased between sites 1 and 2, 1 and 3, and 1 and 4. Significant correlation between gender and PPT was noted as well as BMI (p < 0.001). Hamstring muscle elastographic values significantly differed between biceps femoris and semitendinosus (p < 0.001) and biceps femoris and semimembranosus (p < 0.001). All three hamstring muscles demonstrated increased PPT in males compared to females (p < 0.001). In addition, PPT of the biceps femoris correlated with BMI (p = 0.02).

CONCLUSION

High-resolution US provided useful metrics of sciatic nerve size and biomechanical properties. PPT for the normal sciatic nerve and hamstring muscles was obtained for future clinical application.

Shear wave elastography of the tibial nerve in healthy subjects

The purpose of this study is to investigate sonoelastographic features of the tibial nerve.The study included 72 tibial nerves in 36 healthy subjects. High resolution ultrasound and Shear wave elastography were used to evaluate the tibial nerve. Cross sectional area and stiffness were measured.The mean cross sectional area of the tibial nerve was 13.4 mm2. The mean shear elastic modulus of the tibial nerve in the short axis was 23.3 kPa. The mean shear elastic modulus of the tibial nerve in long axis was 26.1 kPa. The tibial nerve elastic modulus also showed no correlation with cross sectional area neither in the long axis nor short axis. Age, height, weight, and body mass index showed no correlation with tibial nerve elastic modulus in short or long axes.The elastic modulus of the tibial nerve has been determined in healthy subjects and can serve as a reference for future assessment of polyneuropathy.

Medical imaging of tissue engineering and regenerative medicine constructs

Advancement of tissue engineering and regenerative medicine (TERM) strategies to replicate tissue structure and function has led to the need for noninvasive assessment of key outcome measures of a construct's state, biocompatibility, and function. Histology based approaches are traditionally used in pre-clinical animal experiments, but are not always feasible or practical if a TERM construct is going to be tested for human use. In order to transition these therapies from benchtop to bedside, rigorously validated imaging techniques must be utilized that are sensitive to key outcome measures that fulfill the FDA standards for TERM construct evaluation. This review discusses key outcome measures for TERM constructs and various clinical- and research-based imaging techniques that can be used to assess them. Potential applications and limitations of these techniques are discussed, as well as resources for the processing, analysis, and interpretation of biomedical images.

Shear wave elastography of the ulnar nerve at the forearm

The study included 38 ulnar nerves in 20 healthy subjects. High-resolution ultrasound and Shear wave elastography were used to evaluate the ulnar nerve at the mid forearm. The mean cross-sectional area of the ulnar nerve was 7.1 mm2. The mean shear elastic modulus of the nerve in the short axis was 27.4 kPa. The mean shear elastic modulus of the nerve in long axis was 24.7 kPa. No statistical relation could be noted between elasticity measurements in long and short axes. The ulnar nerve elastic modulus also showed no correlation with CSA neither in the long axis nor short axis. Age, height, weight, and body mass index showed no correlation with the ulnar elastic modulus in short or long axes. The elastic modulus of the ulnar nerve has been determined in healthy subjects and can serve as a reference for future assessment of compressive neuropathies of the ulnar nerve.

A comparison of visual analog scale and shear-wave ultrasound elastography data in fibromyalgia patients and the normal population

[Purpose] The aim of this study was to compare Visual Analog Scale (VAS) values with the Shear Wave Elastography (SWE) values of rhomboid major muscles in fibromyalgia (FM) patients with those of a normal healthy population. [Participants and Methods] Evaluation was made of 53 female patients diagnosed with FM according to the American Collage of Rheumatology criteria, and a control group of 47 healthy volunteers with a VAS score of 0. All the patients were applied with ultrasonography. The severity of pain was measured using a VAS. [Results] Mean age was calculated as 39 years (range, 23–60 years) in the patient group and 37 years (range, 21–58 years) in the control group. The mean SWE value of the rhomboid major muscle of the patients was 4.74 m/sn and 70.21 kPa on the right side and 4.46 m/sn and 58.78 kPa on the left side. In the control group, these values were 4.18m/sn and 55.03 kPa on the right side and 3.78 m/sn and 44.21 kPa on the left side. The mean VAS score of the patients was 7.3. [Conclusion] The use of SWE values could be more objective than the subjective parameter of the VAS score in the evaluation of the severity of pain in fibromyalgia.

Application of virtual touch tissue imaging quantification in diagnosis of supraspinatus tendon injury

OBJECTIVE

To explore the value of virtual touch imaging and quantification (VTIQ) shear wave elastography (SWE) in diagnosis of supraspinatus tendon tear.

METHODS

Eighty patients with unilateral supraspinatus tendon tear underwent shoulder arthroscopy were prospective studied. Tendinopathy, partial-thickness tear or full-thickness tear of supraspinatus tendon were diagnosed according 2D ultrasound examination. Sensitivity, specificity and accuracy of ultrasonic diagnosis of supraspinatus tendon tear were calculated by arthroscopy as the gold standard. VTIQ was applied to measure the shear-wave velocity (SWV) of both normal and affected supraspinatus tendon. The differences of SWV in three types of supraspinatus tendon tear and receiver operating characteristic (ROC) curves were analyzed.

RESULTS

Among 80 patients, there were 20 tendinopathy, 31 partial tears and 29 full-thickness tears diagnosed by shoulder arthroscopy. Sensitivity, specificity and accuracy of 2D ultrasound in diagnosis of tendinopathy, partial tear and full-thickness tear groups were 78%, 90%and 83%; 71%, 86%and 73%; 86%, 88%and 88%, respectively. SWV of 80 supraspinatus tendon tears was 4.59±1.00 m/s, which was lower than that of normal supraspinatus tendon (4.59±1.00 m/s vs. 6.68±1.05 m/s, P < 0.01). SWV of supraspinatus tendon in tendinopathy, partial tear and full-thickness tear groups respectively were 5.66±0.97, 4.66±1.00, and 3.78±0.55 m/s, all lower than that of the contralateral normal supraspinatus tendon (all P < 0.05). In addition, the analysis of variance and pairwise comparison showed that SWV of supraspinatus tendon among three different degree of injury was statistically significant (all P < 0.001). The cutoff thresholds of SWV was 4.83 m/s to identify tendinopathy tear from partial tear and was 4.08 m/s to identify full-thickness tear from partial-thickness tear.

CONCLUSION

VTIQ SWE with SWV might identify degree of supraspinatus tendon tear and improve the value of ultrasonography, which should be further evaluated in large multicenter studies.

Synthetic Elastography Using B-Mode Ultrasound Through a Deep Fully Convolutional Neural Network

Shear-wave elastography (SWE) permits local estimation of tissue elasticity, an important imaging marker in biomedicine. This recently developed, advanced technique assesses the speed of a laterally traveling shear wave after an acoustic radiation force "push" to estimate local Young's moduli in an operator-independent fashion. In this work, we show how synthetic SWE (sSWE) images can be generated based on conventional B-mode imaging through deep learning. Using side-by-side-view B-mode/SWE images collected in 50 patients with prostate cancer, we show that sSWE images with a pixel-wise mean absolute error of 4.5 ± 0.96 kPa with regard to the original SWE can be generated. Visualization of high-level feature levels through t -distributed stochastic neighbor embedding reveals substantial overlap between data from two different scanners. Qualitatively, we examined the use of the sSWE methodology for B-mode images obtained with a scanner without SWE functionality. We also examined the use of this type of network in elasticity imaging in the thyroid. Limitations of the technique reside in the fact that networks have to be retrained for different organs, and that the method requires standardization of the imaging settings and procedure. Future research will be aimed at the development of sSWE as an elasticity-related tissue typing strategy that is solely based on B-mode ultrasound acquisition, and the examination of its clinical utility.

Association of Clinical Assessments of Hand Function and Quantitative Ultrasound Metrics in First Carpometacarpal Osteoarthritis

BACKGROUND

Thumb carpometacarpal (CMC) osteoarthritis (OA), a degenerative condition affecting hand use, is typically evaluated through radiographs and clinical examination. Although this can determine treatment, it is difficult to evaluate functional limitations. Shear wave elastography (SWE) is a quantitative ultrasound technique that characterizes tissue stiffness.

QUESTIONS/PURPOSES

This pilot study aimed to establish data of the SWE findings in the thenar eminence muscles in patients with first CMC OA and correlate these findings with the clinical tests of hand function.

METHODS

This cross-sectional study correlated the SWE stiffness of thenar eminence muscles to clinical tests of hand function in patients with first CMC OA and in asymptomatic control subjects, using Spearman's correlation coefficient. Mean SWE values of the thenar eminence muscles in patients were compared with those in control subjects. The study was performed in a non-profit tertiary care hospital setting. Patients and control subjects were recruited on a volunteer basis.

RESULTS

SWE values in the abductor pollicis brevis and flexor pollicis brevis muscles showed moderate to very strong correlation with multiple measures of hand function. Mean SWE values of the thenar eminence muscles in first CMC OA patients were lower than those in asymptomatic control subjects.

CONCLUSIONS

Correlations between mean SWE values in the thenar eminence muscles and clinical measures of hand function suggest decreased function in subjects with less stiff thenar eminence muscles.

Changes in Muscle Mass in Patients With Renal Transplants Based on Ultrasound: A Prospective Study

OBJECTIVES

This original research aimed to investigate the value of ultrasound (US), including grayscale US and shear wave elastography (SWE), in quantitatively evaluating muscle mass after kidney transplantation.

METHODS

A total of 52 patients and 54 healthy control participants were recruited. High-frequency US was used to evaluate the echo intensity and muscle morphologic features. Muscle stiffness in the rectus femoris was assessed with SWE. Interclass and intraclass correlation coefficients were used for evaluating measurement reliability. The diagnostic performance of SWE was determined by a receiver operating characteristic curve analysis.

RESULTS

The intraobserver and interobserver repeatability was excellent (all correlation coefficients >0.940; P < .05). The best evaluation point after right iliac fossa transplantation was at the lower third of the right leg. In patients, the skin (0.154 versus 0.192 cm) and rectus femoris (0.700 versus 0.905 cm) were thinner, and the pinnate angle (6.500° versus 8.000°) and area (0.965 versus 1.270 cm² ) were smaller (all P < .05). The US results showed that, compared with the controls, all patients' rectus femoris echo intensity (P < .001 in the transverse section) and elastic modulus (P < .001 in the Young modulus and shear wave speed) increased significantly. The cutoff values were 10.05 and 10.37, and the areas under the receiver operating characteristic curves were 0.843 and 0.845 for predicting kidney transplant and sarcopenia, respectively.

CONCLUSIONS

This noninvasive and convenient technique might be effective for objectively evaluating the muscle mass of patients after kidney transplantation.

Conventional ultrasound and elastography as imaging outcome tools in autoimmune myositis: A systematic review by the OMERACT ultrasound group

AIMS

To analyze whether there is sufficient data from published literature to demonstrate that ultrasound, including elastography, present good metric properties (truth, discrimination and feasibility) in autoimmune myositis (AIM).

METHODS

A population, intervention, comparator and outcome-structured (PICO) search was performed in Medline, Cochrane Library and Embase database from 01/01/1973 to 08/05/2019. The inclusion criteria required original research involving adult humans, reported in English, assessing ultrasound and elastography in patients with an AIM. Conference abstracts and computer-assisted diagnostics that focused on technique and not ultrasound domains were excluded.

RESULTS

Approximately 2670 articles were identified. Forty-one full-text articles were included in the final analysis. There were 551 AIM patients studied. Eighteen studies (43.9%) had a control group, of which 15 (63.3%) were healthy controls. The age of participants (including controls) varied from 18 to 86 years, and most were females (59%). Diagnosis of AIM was largely biopsy-proven, although some were derived through clinical presentation, positive clinical imaging (ultrasound or otherwise) and/or electromyography and steroid responsiveness. The features examined with ultrasound in the 41 included articles consisted of: muscle echogenicity, bulk, atrophy, architecture, power Doppler, perfusion characteristics, shear wave modulus, shear wave velocity, elasticity index and fasciculations. Twelve studies (29.2%) used quantitative methods to assess these characteristics, whilst others used semi-quantitative, dichotomous/binary and descriptive scoring systems. Criterion validity was met in 14 studies (12/14, 85.7%) and construct validity in 22 studies (22/25, 88.0%). Most published articles reported Level 3b to Level 5 evidence with varying degrees of bias. There was only one longitudinal study examining discrimination. Reliability and feasibility were under-reported.

CONCLUSION

This is the first systematic review studying the utility of ultrasound, including elastography, in AIM. There is some evidence for criterion and construct validity, suggesting that ultrasound may be a promising outcome measurement instrument in AIM. Agreement on the standardization of acquisition, and the definitions of target domains, is required. Additionally, further validation studies are required to determine discrimination, reliability and feasibility.

Ultrasound-guided platelet-rich plasma injection and multimodality ultrasound examination of peripheral nerve crush injury

Ultrasound-guided platelet-rich plasma (PRP) injection is able to make up for the limitations of applying a single growth factor. The goal of this study was to investigate the effects of serial ultrasound-guided PRP injections of the appropriate concentration on the treatment of sciatic nerve crush injury, and explore the value of multimodality ultrasound techniques in evaluating the prognosis of crushed peripheral nerve. In vitro, optimal concentration of PRP (from 150%, 250%, 450%, and 650%) was screened due for its maximal effect on proliferation and neurotrophic function of Schwann cells (SCs). In vivo, ninety rabbits were equally and randomly divided into normal control, model, PRP-2.5×, PRP-4.5×, and PRP-6.5× groups. The neurological function and electrophysiological recovery evaluation, and the comparison of the multimodality ultrasound evaluation with the histological results of sciatic nerve crush injury were performed to investigate the regenerative effects of PRP at different concentrations on the sciatic nerve crush injury. Our results showed that the PRP with a 4.5-fold concentration of whole blood platelets could significantly stimulate the proliferation and secretion of SCs and nerve repair. The changes in stiffness and blood perfusion were positively correlated with the collagen area percentage and VEGF expression in the injured nerve, respectively. Thus, serial ultrasound-guided PRP injections at an appropriate concentration accelerates the recovery of axonal function. Multimodality ultrasound techniques provide a clinical reference for prognosis by allowing the stiffness and microcirculation perfusion of crush-injured peripheral nerves to be quantitatively evaluated.

Sonoelastographic Evaluation of the Achilles Tendon in Patients With Type 2 Diabetes Mellitus

Diabetic foot is one of the dreaded complications of diabetes mellitus (DM). Alterations of the Achilles tendon (AT) may contribute to development of foot ulcers in diabetic patients. We evaluated the sonoelastographic abnormalities of the AT in 61 healthy volunteers and 81 patients with type 2 DM. The patients were further divided into those with and without peripheral neuropathy (PN). The AT thickness was measured in the proximal, middle and distal portions. Alterations in echo pattern were noted. The patients were found to have thicker tendons than the healthy volunteers (p < 0.01). Alterations in the echo pattern of the AT were more common in patients compared with healthy volunteers (p < 0.01). The shear wave velocity in the distal one-third of the AT was measured using shear wave elasticity imaging. Mean shear wave velocity values obtained were lower in patients compared with healthy volunteers (p < 0.001). No significant difference was found in the sonoelastographic findings of the AT in patients with and without PN. We conclude that there is softening, thickening and alterations in echo pattern of the AT in the form of hypoechogenicity, loss of fibrillar pattern and calcification at insertion in patients with type 2 DM, and these alterations could occur independent of onset of PN.

Shear wave elastography for treatment monitoring of plantar fasciitis

BACKGROUND

Plantar fasciitis is a common cause of heel pain. Monitoring therapy effects is challenging with conventional B-mode ultrasound. Shear wave elastography (SWE) provides important diagnostic information beyond B-mode, with typically lower tissue stiffness in symptomatic plantar fascia. Up to now little is known about SWE features for therapy monitoring in plantar fasciitis. We evaluated the clinical effects of a 3-month physical therapy based treatment and its influence on B-mode and SWE ultrasound findings in patients suffering from plantar fasciitis, correlating ultrasound findings to score-based symptom development.

METHODS

Prospective, IRB-approved clinical study in plantar fasciitis patients undergoing a 3-month physical therapy based treatment. Measurement time points were before (T0), after 1 (T1) and 3 (T2) months of treatment, consisting of clinical orthopedic (FFI, AOFAS-Score) and multimodal radiologic sonographic examinations (B-mode/SWE) using a high-resolution linear 18-MHz probe.

RESULTS

A total of 33 patients with 43 symptomatic plantar fascia were included. We found a significant (P<0.001) clinical score improvement (AOFAS +14, FFI-Pain -21, FFI-Function -18) between T0 and T2. Mean initial thickness (T0) of symptomatic plantar fascia was 4.2 (±1.2) mm, compared to 3.2 (±0.7) mm at the asymptomatic contralateral side (P<0.001). No significant thickness changes were seen at T1 (4.2±1.1 mm) and T2 (4.5±1.3 mm), even though clinical scores improved significantly. Mean initial stiffness (T0) of symptomatic plantar fascia was 59.57 (±43.3) kPa, compared to 83.23 (±47.3) kPa at the asymptomatic contralateral side (P<0.001). In contrast to B-mode ultrasound, SWE values increased significantly between T0 (59.6±43.3 kPa), T1 (82.6±47.3 kPa) and T2 (102.5±47.2 kPa) (P<0.001-0.009), with positive correlations for AOFAS/FFI-Pain/Function scores (r=0.285-0.473, P<0.001-0.002).

CONCLUSIONS

A physical therapy based treatment relieves plantar fasciitis symptoms during a 3-month period. In line with symptom reduction, stiffness (Young's-moduli) of plantar fascia increased significantly, while B-mode ultrasound revealed no measurable changes during the healing process. Shear wave elastography was able to quantify plantar fascia pathologies and their recovery under therapy.

Shear wave elastography accurately detects chronic changes in renal histopathology

AIM

Renal biopsy is the gold standard for the histological characterization of chronic kidney disease (CKD), of which renal fibrosis is a dominant component, affecting its stiffness. The aim of this study was to investigate the correlation between kidney stiffness obtained by shear wave elastography (SWE) and renal histological fibrosis.

METHODS

Shear wave elastography assessments were performed in 75 CKD patients who underwent renal biopsy. The SWE-derived estimates of the tissue Young's modulus (YM), given as kilopascals (kPa), were measured. YM was correlated to patients' renal histological scores, broadly categorized into glomerular, tubulointerstitial and vascular scores.

RESULTS

Young's modulus correlates significantly with tubulointerstitial score (ρ = 0.442, P < .001) and glomerular score (ρ = 0.375, P = .001). Patients with no glomerular sclerosis showed lower mean YM measurements compared to those with glomerular sclerosis. The mean YM increased as the percentage of interstitial fibrosis and tubular atrophy increased. The area under the receiver operating characteristic curve (ROC) for SWE in differentiating between mildly and moderately impaired kidneys was 0.702.

CONCLUSION

Shear wave elastography accurately detects chronic renal damage resulting from glomerular sclerosis, interstitial fibrosis and tubular atrophy, using the optimal cut-off YM value of ≥5.81 kPa.

Differences in Achilles tendon stiffness in people with gout: a pilot study

Background

Gout has been associated with weaker foot/leg muscles and altered gait patterns. There is also evidence of on-going foot pain and an increased risk of tendinopathy, with the Achilles and patella tendons most frequently affected in gout. Additionally, the inflammation associated with gout may change tissue elasticity. Ultrasound imaging utilising shear wave elastography (SWE) offers a non-invasive method of quantifying changes in tendon stiffness. SWE findings have not previously been reported in individuals with gout. We sought to determine differences in Achilles tendon stiffness in people with gout compared to controls (non-gout).

Methods

A cross sectional study comparing 24 people with gout and 26 age/sex-matched controls. Clinical and demographic data were collated, and US imaging used to determine tendon thickness, presence of gouty tophi and/or aggregates and levels of angiogenesis. Ten shear wave elastography (SWE) measures were taken along the centre of a longitudinal section of the mid-portion of each Achilles tendon. Prior to data collection, intra-observer error was good (>0.69). Data were summarised using descriptive statistics and a repeated measures ANCOVA was used to compare SWE measures between the two groups for the left and right foot separately after accounting for Body Mass Index (BMI).

Results

A small proportion of those with gout presented with intra-tendon aggregates and/or intra-tendon tophi in one or both tendons. There was no statistically significant difference in tendon thickness between groups. Neo-vascularity was present in a third of gout participants. SWE findings demonstrated significantly reduced tendon stiffness in those with gout compared to controls: right Achilles mdiff =1.04 m/s (95% CI (0.38 to 1.7) p = 0.003 and left Achilles mdiff = 0.7 m/s (95% CI 0.09 to 1.32) p = 0.025. No relationship between the presence of tophi and SWE values were detected.

Conclusion

Subjects with chronic gout show significantly reduced Achilles tendon stiffness compared to non-gout controls. From a clinical standpoint, our findings were similar to SWE measurements in subjects with Achilles tendinopathy and who did not have gout.

Subcutaneous tissue stiffness of cesarean incision scar by elastography as a predictor of intra-abdominal adhesions

AIM

This study aimed to investigate whether subcutaneous tissue stiffness of the previous cesarean section (CS) skin incision could predict the severity of the intra-abdominal adhesions at a repeat CS.

METHODS

In this prospective cross-sectional study, pregnant women with at least one prior cesarean delivery were included. The subcutaneous tissue stiffness of the previous CS skin scar was measured by shear wave elastography (SWE) on the day of the repeat CS and the intra-abdominal adhesions were recorded by an adhesion classification scheme specific for CS. Total adhesion score was classified as mild adhesion between 1 and 4, moderate adhesion between 5 and 12, and severe adhesion if ≥13.

RESULTS

Of the 102 women, 41 (40.2%) had no adhesions, 18 (17.6%) had mild adhesions, 26 (25.5%) had moderate adhesions and 17 (16.7%) had severe adhesions. The mean SWE measurements were significantly higher in the moderate and severe adhesion group than the non-adhesion and mild adhesion group (51.5 ± 25.3 vs 36.8 ± 22.6, P = 0.003). There was a statistically significant correlation between the preoperative SWE measurements and total adhesion scores (correlation coefficient [r] = 0.397, P < 0.001). In receiver-operator characteristics curve analysis, the cut-off value for moderate or severe adhesions was found to be 36.5 (area under curve = 0.710, %95 confidence interval 0.606-0.815; P < 0.001). With the cut-off point of ≥36.5, the sensitivity and specificity for the prediction of mild and severe adhesions were 74.4% and 40.5%, respectively.

CONCLUSION

Elastographic evaluation of the subcutaneous tissue stiffness of the cesarean incision scar might show the degree of intra-abdominal adhesions at a repeat CS.

Quantitative assessment of temporal skin elasticity using shear wave elastography in pediatric cochlear implant users

OBJECTIVE

To evaluate temporal skin thicknesses and stiffness values using shear wave elastography (SWE) in asymptomatic pediatric patients who underwent cochlear implantation.

SUBJECTS AND METHODS

Sixty-four deafened pediatric patients with unilateral cochlear implant (CI) who had no complications were enrolled. The age, sex, weight, height, body mass index (BMI), CI side, duration of CI use and CI device brand of all participants were noted. Temporal skin thickness and stiffness values were measured from implanted and contralateral unimplanted sides using SWE.

RESULTS

The mean skin thickness measurements of implanted and unimplanted sides were 11.87 ± 3.42 and 5.34 ± 1.56 mm, respectively. The mean skin stiffness measurements of implanted and unimplanted sides were 3.08 ± 0.7 and 1.29 ± 0.26 m/s, respectively. There were statistically significant differences in skin thickness and stiffness between implanted and unimplanted sides (P < .001, P < .001). The mean skin thickness and stiffness measurements did not differ among types of CI devices (P = .948, P = .362). Age had positive correlation with implanted (P < .001, P = .019) and unimplanted sides (P < .001, P < .001) skin thickness and stiffness. BMI had positive correlation with implanted (P < .001, P = .023) and unimplanted sides (P < .001, P < .001) skin thickness and stiffness. Duration of CI use had positive correlation with implanted side skin thickness (P < .001) and stiffness (P = .031).

CONCLUSION

Temporal skin thickness and stiffness increase after CI surgery. SWE has the potential to improve diagnostic accuracy, and our results may provide important data for evaluation of clinical entities that affect temporal skin structures.

Quantitative Musculoskeletal Ultrasound

Ultrasound (US) imaging plays a crucial role in the assessment of musculoskeletal (MSK) disorders. Several quantitative tools are offered by US systems and add information to conventional US imaging. This article reviews the quantitative US imaging tools currently available in MSK radiology, specifically focusing on the evaluation of elasticity with shear-wave elastography, perfusion with contrast-enhanced US and noncontrast superb microvascular imaging, and bone and muscle mass with quantitative US methods. Some of them are well established and already of clinical value, such as elasticity and contrast-enhanced perfusion assessment in muscles and tendons. MSK radiologists should be aware of the potential of quantitative US tools and take advantage of their use in everyday practice, both for clinical and research purposes.

Detection of early changes in the muscle properties of the pectoralis major in breast cancer patients treated with radiotherapy using a handheld myotonometer

OBJECTIVE

The primary aim was to investigate serial changes in the mechanical properties of the pectoralis major (PM), upper trapezius (UT), and sternoclavicular mastoid muscle (SCM) in breast cancer patients undergoing radiotherapy (RT) using a hand-held myotonometer. The secondary aims were to determine changes in subjective symptoms and to identify correlation with subjective results.

DESIGN

A total of 42 breast cancer patients were enrolled in this longitudinal prospective study. Muscle properties of the PM, UT, and SCM were evaluated before RT, immediately after RT, and 4 months post-RT. Subjective symptom scales of pain and stiffness at rest/stretch of each muscle were evaluated.

RESULTS

The PM showed significant side-to-side differences; the affected PM showed increased tone, stiffness, and decreased elasticity compared with the unaffected PM. The affected PM and UT showed significant time-dependent interactions. Stiffness of the affected PM at stretching was significantly higher 4 months post-RT than baseline. Only the tone and elasticity of the affected PM were correlated with subjective symptoms.

CONCLUSION

In breast cancer patients who received RT after surgery, increased tone, stiffness, and decreased elasticity were observed in the affected PM compared with the unaffected side, which sustained four months post-RT. Change in muscle properties immediately after RT preceded subjective stiffness, which worsened significantly 4 months post-RT compared with baseline.

Shear wave elastography of the saphenous nerve

The purpose of this study is to study sonoelastographic features of the saphenous nerve.The study included 72 saphenous nerves in 36 healthy subjects. High resolution ultrasound and Shearwave elastography were used to evaluate the saphenous nerve. Cross sectional area (CSA) and stiffness were measured.The mean CSA of the saphenous nerve was 5.7 mm. The mean shear elastic modulus of the saphenous nerve in the short axis was 29.5 kPa. The mean shear elastic modulus of the saphenous nerve in long axis was 29.9 kPa. The saphenous nerve elastic modulus also showed no correlation with CSA in neither the long axis nor short axis. Positive correlation between elasticity measurements in the long and short axes. Age, height, weight, and BMI showed no correlation with saphenous nerve elastic modulus in short or long axes.The elastic modulus of the saphenous nerve has been determined in healthy subjects and can serve as a reference for future assessment of the saphenous nerve before different procedures.