Shear wave velocity measurement of upper trapezius muscle by color Doppler shear wave imaging

Examination of rapid adjustment system based on screen score obtained using continuous shear wave elastography

PURPOSE

Continuous shear wave elastography (C-SWE) can be expected to be applied to portable muscle elasticity diagnosis. To establish diagnostic technology, it will be necessary to improve measurement techniques and quantitative measurement accuracy.

METHODS

In this study, we investigated two screen scores: the quality index (Q-index), which determines whether the intensity of a power Doppler image is appropriate, and the shear wave propagation direction index (SWDI), which determines the uniformity of shear wave propagation.

RESULTS

First, we performed numerical simulations with white noise and found that the coefficient of variation of shear wave velocity estimation was less than 5% when the normalized Q-index was greater than 0.27. Furthermore, regarding the SWDI, we clarified the relationship between the standard deviation in shear wave propagation direction and the SWDI. Next, the relationship between the Q-index and coefficient of variation of estimated shear wave velocity was evaluated through experiments using a tissue-mimicking phantom. The results showed that there was a negative correlation between the Q-index and the coefficient of variation, and the fluctuation of the propagation velocity could be inferred from the Q-index. Finally, we showed the results of applying the screen scores to muscle relaxation monitoring and confirmed its usefulness in clinical applications.

CONCLUSION

By applying the screen scores, we showed improved stability in speed estimation in C-SWE, and demonstrated the possibility of clinical applicability.

Continuous Shear Wave Elastography for Liver Using Frame-to-Frame Equalization of Complex Amplitude

This study addresses a crucial necessity in the field of noninvasive liver fibrosis diagnosis by introducing the concept of continuous shear wave elastography (C-SWE), utilizing an external vibration source and color Doppler imaging. However, an application of C-SWE to assess liver elasticity, a deep region within the human body, arises an issue of signal instability in the obtained data. To tackle this challenge, this work proposes a method involving the acquisition of multiple frames of datasets, which are subsequently compressed. Furthermore, the proposed frame-to-frame equalization method compensates discrepancies in the initial phase that might exist among multiple-frame datasets, thereby significantly enhancing signal stability. The experimental validation of this approach encompasses both phantom tests and in vivo experiments. In the phantom tests, the proposed technique is validated through a comparison with the established shear wave elastography (SWE) technique. The results demonstrate a remarkable agreement, with an error in shear wave velocity of less than 4.2%. Additionally, the efficacy of the proposed method is confirmed through in vivo tests. As a result, the stabilization of observed shear waves using the frame-to-frame equalization technique exhibits promising potential for accurately assessing human liver elasticity. These findings collectively underscore the viability of C-SWE as a potential diagnostic instrument for liver fibrosis.

Evaluation of skeletal muscle elasticity using color Doppler shear wave imaging

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Reliability of Continuous Shear Wave Elastography in the Pathological Patellar Tendon

OBJECTIVES

Patellar tendon injuries occur via various mechanisms such as overuse, or due to surgical graft harvest for anterior cruciate ligament reconstruction (ACLR). Quantified patellar tendon stiffness after injury may help guide clinical care. Continuous shear wave elastography (cSWE) allows for the assessment of viscosity and shear modulus in tendons. The reliability of the measure, however, has not been established in the patellar tendon. The purpose of this study was to investigate the interrater reliability, intrarater reliability, and between-day stability of cSWE in both healthy and pathological patellar tendons.

METHODS

Participants with patellar tendinopathy (n = 13), history of ACLR using bone-patellar tendon-bone autograft (n = 9), and with no history of patellar tendon injury (n = 13) were recruited. cSWE was performed 4 times by multiple raters over 2 days. Intraclass correlations (ICC) and minimum detectable change (MDC_95% ) were calculated.

RESULTS

Good to excellent between-day stability were found for viscosity (ICC = 0.905, MDC_95%  = 8.3 Pa seconds) and shear modulus (ICC = 0.805, MDC_95%  = 27.4 kPa). The interrater reliability measures, however, were not as reliable (ICC = 0.591 and 0.532).

CONCLUSIONS

cSWE is a reliable assessment tool for quantifying patellar tendon viscoelastic properties over time. It is recommended, however, that a single rater performs the measure as the interrater reliability was less than ideal.

Effects of Two Botulinum Toxin Type a Evaluated by Shear Wave Elastography and Electromyographic Measurements of Masseter Reduction

ABSTRACT

The purpose of this study was to evaluate the efficacy and safety of onabotulinumtoxin A and Chinese botulinum toxin type A (CBA) for masseter reduction using elastography and electromyographic measurement. Female subjects aged 21 to 38 years with benign masseter hypertrophy received 1 treatment of either 50 units onabotulinumtoxin A or 50 units CBA in a double-blind clinical trial. The study enrolled 102 subjects (204 sides of masseters); 51 subjects per group. The thickness and stiffness of the masseter muscle and the electromyographic changes were evaluated before and 1, 4, 12, and 24 weeks after injection. One week after injection, the thickness of the masseter muscle did not change significantly, but the stiffness was reduced by 5% to 9%. After 4 weeks of injection, masseter muscle thickness, stiffness and strength decreased significantly compared with before injection. The changes were significantly at 12 weeks. Muscle stiffness measured by Shear-wave elastography was significantly reduced by 20% to 32% in the relaxed state and 25% to 47% in the contractile state. The electromyography showed that masseter muscle strength changed consistently with Shear-wave elastography value before and after injection. Six months after injection, ultrasound and electromyography showed that the masseter muscle thickness and stiffness began to recover. Between the 2 groups, there are no significant difference in thickness, stiffness and muscle strength reduction of masseters after treatment (P > 0.05), as well as in side effects (P > 0.05). Onabotulinumtoxin A and CBA were comparable in the efficacy and safety for masseter reduction.

Visualization of Human Skeletal Muscle Anisotropy by Using Dual-Direction Shear Wave Imaging

OBJECTIVE

Ultrasound (US) shear wave elasticity imaging (SWEI) is a mature technique for diagnosing the elasticity of isotropic tissues. However, the elasticity of anisotropic tissues, such as muscle and tendon, cannot be diagnosed correctly using SWEI because the shear wave velocity (SWV) varies with tissue fiber orientations. Recently, SWEI has been studied for measuring the anisotropic properties of muscles by rotating the transducer; however, this is difficult for clinical practice.

METHODS

In this study, a novel dual-direction shear wave imaging (DDSWI) technique was proposed for visualizing the mechanical anisotropy of muscles without rotation. Longitudinal and transverse shear waves were created by a specially designed external vibrator and supersonic pushing beam, respectively; the SWVs were then tracked using ultrafast US imaging. Subsequently, the SWV maps of two directions were obtained at the same scanning cross section, and the mechanical anisotropy was represented as the ratio between them at each pixel.

RESULTS

The performance of DDSWI was verified using a standard phantom, and human experiments were performed on the gastrocnemius and biceps brachii. Experimental results of phantom revealed DDSWI exhibited a high precision of <0.81 % and a low bias of <3.88 % in SWV measurements. The distribution of anisotropic properties in muscle was visualized with the anisotropic ratios of 1.54 and 2.27 for the gastrocnemius and biceps brachii, respectively.

CONCLUSION

The results highlight the potential of this novel anisotropic imaging in clinical applications because the conditions of musculoskeletal fiber orientation can be easily and accurately evaluated in real time by DDSWI.

Shear wave imaging and classification using extended Kalman filter and decision tree algorithm

Shear wave ultrasound elastography is a quantitative imaging approach in soft tissues based on viscosity-elastic properties. Complex shear modulus (CSM) estimation is an effective solution to analyze tissues' physical properties for elasticity and viscosity based on the wavenumber and attenuation coefficient. CSM offers a way to detect and classify some types of soft tissues. However, CSM-based elastography inherits some obstacles, such as estimation precision and calculation complexity. This work proposes an approach for two-dimensional CSM estimation and soft tissue classification using the Extended Kalman Filter (EKF) and Decision Tree (DT) algorithm, named the EKF-DT approach. CSM estimation is obtained by applying EKF to exploit shear wave propagation at each spatial point. Afterward, the classification of tissues is done by a direct and efficient decision tree algorithm categorizing three types of normal, cirrhosis, and fibrosis liver tissues. Numerical simulation scenarios have been employed to illustrate the recovered quality and practicality of the proposed method's liver tissue classification. With the EKF, the estimated wave number and attenuation coefficient are close to the ideal values, especially the estimated wave number. The states of three liver tissue types were automatically classified by applying the DT coupled with two proposed thresholds of elasticity and viscosity: (2.310 kPa, 1.885 Pa.s) and (3.620 kPa 3.146 Pa.s), respectively. The proposed method shows the feasibility of CSM estimation based on the wavenumber and attenuation coefficient by applying the EKF. Moreover, the DT can automate the classification of liver tissue conditions by proposing two thresholds. The proposed EKF-DT method can be developed by 3D image reconstruction and empirical data before applying it in medical practice.

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 the novel estimation method by shear wave elastography using vibrator to human skeletal muscle

In recent years, non-invasive measurement of tissue stiffness (hardness) using ultrasound elastography has attracted considerable attention. It has been used to evaluate muscle stiffness in the fields of rehabilitation, sports, and orthopedics. However, ultrasonic diagnostic devices with elastography systems are expensive and clinical use of such devices has been limited. In this study, we proposed a novel estimation method for vibration-based shear wave elastography measurement of human skeletal muscle, then determined its reproducibility and reliability. The coefficient of variation and correlation coefficient were used to determine reproducibility and reliability of the method by measuring the shear wave velocities in konjac phantom gels and agar phantom gels, as well as skeletal muscle. The intra-day, day-to-day, and inter-operator reliabilities were good when measuring the shear wave velocities in phantom gels. The intra-day and day-to-day reliabilities were good when measuring the shear wave velocities in skeletal muscle. The findings confirmed adequate reproducibility and reliability of the novel estimation method for vibration-based shear wave elastography. Therefore, the proposed measurement method may be a useful tool for evaluation of muscle stiffness.

Determination of reference ranges for normal upper trapezius elasticity during different shoulder abduction using shear wave elastography: a preliminary study

The purpose of this study was to determine the reference ranges of normal upper trapezius (UT) elasticity during different shoulder abduction using shear wave elastography (SWE). Mean shear wave velocity (SWV) of UT elasticity in eighty healthy participants were measured at left and right shoulder 0° abduction and 90° passive abduction (L0°, R0°, L90°, R90°) with SWE. The effects of potential factors (gender, UT thickness, age, and body mass index) on UT elasticity were analyzed. The reference ranges of normal UT elasticity were calculated by using the normal distribution method. UT elasticity was significantly different among various shoulder abduction (P < 0.0001). UT elasticity was significantly higher in males at both L90° (P < 0.05) and R90° (P < 0.01) than in females. The reference ranges of normal UT elasticity were 2.90-4.01 m/s at L0° and 3.01-4.29 m/s at R0°, and were 4.90-6.40 m/s in males and 4.40-6.20 m/s in females at L90°, 5.20-7.02 m/s in males and 4.71-6.80 m/s in females at R90°. Our results suggest that gender should be considered when determining the reference ranges of normal UT elasticity at L90° and R90° with SWE. These values may provide quantitative baseline measurements for the assessment of UT muscle strain in the future.

Shear-wave elastography for assessment of trapezius muscle stiffness: Reliability and association with low-level muscle activity

Purpose

Shear-wave elastography has been recognized a useful tool for quantifying muscle stiffness, commonly reported as shear modulus, however the reports on reliability are often limited to test-retest correlations. In this study, we explored the reliability of shear-wave elastography for assessment of the trapezius muscle stiffness and its relationship with low-level muscle activity.

Methods

Twenty participants were included in a two-session experiment. Measurements of shear modulus and muscle activity were performed at rest and during low-level activity, induced by shoulder abduction without additional external resistance.

Results

Good to excellent intra-session repeatability (ICC > 0.80) and moderate inter-rater and inter-session reproducibility (ICC = 0.66–0.74) were observed. Typical errors were acceptable (7.6% of the mean value) only for intra-session measurements in resting conditions, but not acceptable for all conditions with low-level muscle activity (10.2–16.6% of the mean value). Inverse relationships between shear modulus and muscle activity at 40° and 60° of shoulder abduction (r = -0.53 and -0.57) were observed on a group level. We also found higher shear modulus in males compared to females, for the parallel probe position compared to the perpendicular position (in relation to muscle fiber orientation), and for the dominant side of the body compared to the non-dominant side.

Conclusions

This study showed an inverse relationship between muscle activity in low-level range and shear modulus on a group level, suggesting inherent passive stiffness could account for a larger portion of the variance (compared to muscle activity) in shear modulus when the muscle activity is low. Our results imply that shear-wave elastography can be used in research exploring muscle stiffness, however, caution is needed since only intra-session examination in resting conditions showed acceptable within-participant typical errors. The secondary analyses of the study showed higher shear modulus for males, for the non-dominant side of the body and for the parallel orientation of the ultrasound probe.