Measurement Of Tissue Strain Research Articles

Immediate Changes to Skin and Subcutaneous Tissue Strains Following Manual Lymph Drainage in Legs with Lymphedema.

To study the immediate impact of manual lymph drainage (MLD) on skin and subcutaneous tissue strains in legs with lymphedema using free-hand real-time tissue elastography (RTE). Skin and subcutaneous tissue strain measurements were taken at the middle of the inner thigh and calf by RTE in 20 legs with lymphedema of 18 patients (stage II: 11, late stage II: 7, stage III: 2) and in 70 legs of 35 normal subjects. In patients with lymphedema, the same measurements were repeated immediately following MLD. Significant negative correlations were found between pre-MLD strains and the MLD-induced changes in thigh and calf skin strains (thigh skin: p <0.01, calf skin: p = 0.05), but not in subcutaneous tissue strains. Pre-MLD intercepts of these regression lines were closer to normal values as compared to mean pre-MLD values (normal thigh skin: 0.54% ± 0.30%, calf skin: 0.25% ± 0.18%, Pre-MLD thigh skin: 0.39% ± 0.20%, calf skin: 0.17% ± 0.12%, Pre-MLD intercept of thigh skin: 0.48%, Pre-MLD intercept of calf skin: 0.31%). It appears that MLD did not simply soften the skin, but rather normalized it in terms of strain. However, this was not confirmed in the subcutaneous tissue.

Computational Models Predict Larger Muscle Tissue Strains at Faster Sprinting Speeds

Proximal biceps femoris musculotendon strain injury has been well established as a common injury among athletes participating in sports that require sprinting near or at maximum speed; however, little is known about the mechanisms that make this muscle tissue more susceptible to injury at faster speeds. This study aimed to quantify localized tissue strain during sprinting at a range of speeds. Biceps femoris long head (BFlh) musculotendon dimensions of 14 athletes were measured on magnetic resonance (MR) images and used to generate a finite-element computational model. The model was first validated through comparison with previous dynamic MR experiments. After validation, muscle activation and muscle-tendon unit length change were derived from forward dynamic simulations of sprinting at 70%, 85%, and 100% maximum speed and used as input to the computational model simulations. Simulations ran from midswing to foot contact. The model predictions of local muscle tissue strain magnitude compared favorably with in vivo tissue strain measurements determined from dynamic MR experiments of the BFlh. For simulations of sprinting, local fiber strain was nonuniform at all speeds, with the highest muscle tissue strain where injury is often observed (proximal myotendinous junction). At faster sprinting speeds, increases were observed in fiber strain nonuniformity and peak local fiber strain (0.56, 0.67, and 0.72 for sprinting at 70%, 85%, and 100% maximum speed). A histogram of local fiber strains showed that more of the BFlh reached larger local fiber strains at faster speeds. At faster sprinting speeds, peak local fiber strain, fiber strain nonuniformity, and the amount of muscle undergoing larger strains are predicted to increase, likely contributing to the BFlh muscle's higher injury susceptibility at faster speeds.

Quantitative elastography for cervical stiffness assessment during pregnancy.

Aim. Feasibility and reliability of tissue Doppler imaging-(TDI-) based elastography for cervical quantitative stiffness assessment during all three trimesters of pregnancy were evaluated. Materials and Methods. Prospective case-control study including seventy-four patients collected between the 12th and 42nd weeks of gestation. The tissue strain (TS) was measured by two independent operators as natural strain. Intra- and interoperator intraclass correlation coefficient (ICC) agreements were evaluated. Results. TS measurement was always feasible and exhibited a high performance in terms of reliability (intraoperator ICC-agreement = 0.93; interoperator ICC agreement = 0.89 and 0.93 for a single measurement and for the average of two measurements, resp.). Cervical TS showed also a significant correlation with gestational age, cervical length, and parity. Conclusions. TS measurement during pregnancy demonstrated high feasibility and reliability. Furthermore, TS significantly correlated with gestational age, cervical length, and parity.

ELASTOGRAPHIC CHARACTERISTICS OF THE METACARPAL TENDONS IN HORSES WITHOUT CLINICAL EVIDENCE OF TENDON INJURY

Tendon and ligament injuries are common causes of impaired performance in equine athletes. Gray-scale ultrasonography is the current standard method for diagnosing and monitoring these injuries, however this modality only provides morphologic information. Elastography is an ultrasound technique that allows detection and measurement of tissue strain, and may provide valuable mechanical information about equine tendon and ligament injuries. The purpose of this study was to determine the feasibility, reproducibility, and repeatability of elastography; and to describe elastographic characteristics of metacarpal tendons in sound horses. Nineteen legs for 17 clinically sound horses without evidence of musculoskeletal pathology were included. Elastographic images of the superficial and deep digital flexor tendons and the branches of the suspensory ligament (tendon of the interosseous muscle) were described quantitatively and qualitatively. There was no statistically significant difference between operators (P = 0.86) nor within operators (P = 0.93). For qualitative assessments, reproducibility (0.46) was moderate and repeatability (0.78) was good. Similar to human Achilles tendons, equine tendons were classified as predominantly hard using elastography. There was no statistically significant difference in stiffness of the flexor tendons (P = 0.96). No significant difference in stiffness was found with altered leg position during standing (P = 0.84) and while nonweight bearing (P = 0.61). The flexor tendons were softer when imaged in longitudinal versus transverse planes (P < 0.01) however, the suspensory branches were not (P = 0.67). Findings supported future clinical application of elastography as a noninvasive "stall-side" imaging modality for evaluation of the tendons and ligaments of the distal forelimb in horses.

Shear wave velocity is a useful marker for managing nonalcoholic steatohepatitis

To investigate whether a noninvasive measurement of tissue strain has a potential usefulness for management of nonalcoholic steatohepatitis (NASH). In total 26 patients, 23 NASHs and 3 normal controls were enrolled in this study. NASH was staged based on Brunt criterion. At a region of interest (ROI), a shear wave was evoked by implementing an acoustic radiation force impulse (ARFI), and the propagation velocity was quantified. Shear wave velocity (SWV) could be reproducibly quantified at all ROIs in all subjects except for 4 NASH cases, in which a reliable SWV value was not calculated at several ROIs. An average SWV of 1.34 +/- 0.26 m/s in fibrous stage 0-1 was significantly slower than 2.20 +/- 0.74 m/s and 2.90 +/- 1.01 m/s in stages 3 and 4, respectively, but was not significantly different from 1.79 +/- 0.78 m/s in stage 2. When a cutoff value was set at 1.47 m/s, receiver operating characteristic analysis showed significance to dissociate stages 3 and 4 from stage 0-1 (P = 0.0092) with sensitivity, specificity and area under curve of 100%, 75% and 94.2%, respectively. In addition, the correlation between SWV and hyaluronic acid was significant (P < 0.0001), while a tendency toward negative correlation was observed with serum albumin (P = 0.053). The clinical implementation of ARFI provides noninvasive repeated evaluations of liver stiffness at an arbitrary position, which has the potential to shed new light on NASH management.

Displacement vector measurement using instantaneous ultrasound signal phase-multidimensional autocorrelation and Doppler methods

Two new methods of measuring a multidimensional displacement vector using an instantaneous ultrasound signal phase are described, i.e., the multidimensional autocorrelation method (MAM) and multidimensional Doppler method (MDM). A high measurement accuracy is achieved by combining either method with the lateral Gaussian envelope cosine modulation method (LGECMM) or multidirectional synthetic aperture method (MDSAM). Measurement accuracy is evaluated using simulated noisy echo data. Both methods yield accurate measurements comparable to that of our previously developed cross-spectrum phase gradient method (MCSPGM); however, they require less computational time (the order, MDM < MAM approximate, equals MCSPGM) and would provide realtime measurements. Moreover, comparisons of LGECMM and MDSAM performed by geometrical evaluations clarifies that LGECMM has potentials to yield more accurate measurements with less computational time. Both MAM and MDM can be applied to the measurement of tissue strain, blood flow, sonar data, and other target motions.

Spatially variant regularization for tissue strain measurement and shear modulus reconstruction.

Regarding the regularization of the displacement vector measurement and shear modulus reconstruction, we propose to properly set the regularization parameters, i.e., to use spatially variant regularization parameters at each point in the region of interest, because the measurement accuracies of the displacements and strains vary spatially. As the measurement accuracies of the strains can be evaluated using the correlation coefficient when using the cross-spectrum phase gradient method, preliminarily the regularization parameters were set proportional to the reciprocal of a power of the correlation coefficient. Such a regularization scheme realizes the spatially uniform stabilities of the strain measurement and shear modulus reconstruction. The effectiveness of this method was verified by showing the regularized results of the axial strain measurement and of one-dimensional (1-D) shear modulus reconstruction obtained in vivo from a human liver carcinoma (that was treated by interstitial microwave coagulation therapy) as well as by a 1-D shear modulus reconstruction obtained using an agar phantom.

Simultaneous Measurement of Three-Dimensional Joint Kinematics and Ligament Strains With Optical Methods

The objective of this study was to assess the precision and accuracy of a nonproprietary, optical three-dimensional (3D) motion analysis system for the simultaneous measurement of soft tissue strains and joint kinematics. The system consisted of two high-resolution digital cameras and software for calculating the 3D coordinates of contrast markers. System precision was assessed by examining the variation in the coordinates of static markers over time. Three-dimensional strain measurement accuracy was assessed by moving contrast markers fixed distances in the field of view and calculating the error in predicted strain. Three-dimensional accuracy for kinematic measurements was assessed by simulating the measurements that are required for recording knee kinematics. The field of view (190 mm) was chosen to allow simultaneous recording of markers for soft tissue strain measurement and knee joint kinematics. Average system precision was between +/-0.004 mm and +/-0.035 mm, depending on marker size and camera angle. Absolute error in strain measurement varied from a minimum of +/-0.025% to a maximum of +/-0.142%, depending on the angle between cameras and the direction of strain with respect to the camera axes. Kinematic accuracy for translations was between +/-0.008 mm and +/-0.034 mm, while rotational accuracy was +/-0.082 deg to +/-0.160 deg. These results demonstrate that simultaneous optical measurement of 3D soft tissue strain and 3D joint kinematics can be performed while achieving excellent accuracy for both sets of measurements.

Quantitative elasticity imaging with ultrasound

For the past 10 or so years, various researchers have proposed different ways to measure strain distributions in vivo. The measured strains result from various sources including external palpation, low frequency vibration, or internal motion. By examining the relative strains in adjacent tissues, it is thought that one can infer the relative distributions of tissue stiffness. In this presentation, we discuss the process of creating a quantitative stiffness image from a given measurement of tissue strain. We show that the strain image by itself is insufficient information to infer the elastic stiffness. By examining the well-posedness of the inverse problem, we determine what information is needed to supplement the strain image in order to quantitatively infer the elastic stiffness distribution. Methods for obtaining the required information in vivo are currently being developed. We show examples of incorrect and misleading stiffness reconstructions in the absence of the required data. [Work supported by BU, NIH, Fulbright Foundation, ICR, and NSF via CenSSIS ERC.]